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PRODUCTION OF 300,000 MTPA OF NITROPHOSPHATE FERTILIZER



Session 2015-2019



Supervised by Dr. Saleem Iqbal Mr. Fazeel Ahmad



Group Members Khawaja Rehan Ahmed Shaharyar Ahmed Abbasi Abubaker Sufyan Amjad Muhammad Mansoor



UW-15-Ch.E-BSc-016 UW-15-Ch.E-BSc-014 UW-15-Ch.E-BSc-034 UW-15-Ch.E-BSc-030



Department of Chemical Engineering, Wah Engineering College, University of Wah, Wah Cantt.



PRODUCTION OF 300,000 MTPA OF NITROPHOSPHATE FERTILIZER



This report is submitted to the Department of Chemical Engineering, Wah Engineering College, University of Wah for the partial fulfilments of the requirement for the



Bachelor of Science In Chemical Engineering



Internal Examiner: Name: _______________ Sign: ________________ External Examiner: Name: _______________ Sign: ________________



Department of Chemical Engineering, Wah Engineering College, University of Wah, Wah Cantt.



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



Table of Contents 1. Introduction ........................................................................................................................... 1 1.1. Fertilizer ........................................................................................................................... 2 1.2. Nitro-phosphate (NP) ....................................................................................................... 3 1.3. History of product ............................................................................................................ 4 1.4. Physical properties & thermodynamic data ....................................................................... 4 1.5. Chemical reactions ........................................................................................................... 5 1.6. Industrial applications ....................................................................................................... 5 1.7. Handling, storage & safety ............................................................................................... 5 1.7.1. Phosphate rock........................................................................................................ 5 1.7.2. Ammonia ................................................................................................................ 6 1.7.3. Nitric acid ............................................................................................................... 6 1.7.4. Nitro-phosphate ...................................................................................................... 6 1.8. Shipping of product .......................................................................................................... 6 1.9. World overview ................................................................................................................ 7 1.10. Nitro-phosphate in Pakistan ......................................................................................... 10 1.11. Market assessment ....................................................................................................... 11 1.12. Future trends................................................................................................................ 11 2. Manufacturing Process ....................................................................................................... 12 2.1. ODDA process ............................................................................................................... 13 2.1.1. Raw materials ....................................................................................................... 13 2.1.2. Process description ............................................................................................... 13 2.2. Mixed acid process ......................................................................................................... 15 2.2.1. Raw materials ....................................................................................................... 15 2.2.2. Process description ............................................................................................... 15 i



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER 2.3. Process comparison ........................................................................................................ 17 2.4. Process selection............................................................................................................. 18 2.5. Process description ......................................................................................................... 18 2.5.1. Raw materials ....................................................................................................... 18 2.5.2. Phosphate rock digestion ....................................................................................... 18 2.5.3. Removal of silica .................................................................................................. 18 2.5.4. Crystallization unit ................................................................................................ 19 2.5.5. CN crystals filter ................................................................................................... 19 2.5.6. Neutralization reactor............................................................................................ 19 2.5.7. Evaporation & prilling .......................................................................................... 19 2.5.8. Coating & packaging ............................................................................................ 19 2.6. Capacity selection........................................................................................................... 23 3. Material & Energy Balance ................................................................................................ 24 3.1. Material balance ............................................................................................................. 25 3.1.1. Plant capacity........................................................................................................ 25 3.1.2. Main reactions ...................................................................................................... 25 3.1.3. Phosphate rock analysis ........................................................................................ 25 3.1.4. Material balance on digester (R-101) .................................................................... 27 3.1.5. Material balance on centrifuge (F-101) ................................................................. 28 3.1.6. Material balance on crystallizer (CR-101) ............................................................. 29 3.1.7. Material balance on centrifuge (F-102) ................................................................. 30 3.1.8. Material balance on neutralizer (R-102) ................................................................ 31 3.1.9. Material balance on evaporator (E-101) ................................................................ 33 3.2. Energy Balance .............................................................................................................. 34 3.2.1. Energy balance on digester (R-101) ...................................................................... 34



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER 3.2.2. Energy balance on heat exchanger (H-101) …………………………………..….. 37 3.2.3. Energy balance on crystallizer (CR-101) ............................................................... 38 3.2.4. Energy balance on preheater (H-102) .................................................................... 39 3.2.5. Energy balance on preheater (H-103) .................................................................... 40 3.2.6. Energy balance on neutralizer (R-102) .................................................................. 41 3.2.7. Energy balance on evaporator (E-101) .................................................................. 43 4. Equipment Design ............................................................................................................... 45 4.1. Reactor (R-101) .............................................................................................................. 46 4.1.1. Selection of reactor ............................................................................................... 46 4.1.2. Design of reactor (R-101) ..................................................................................... 46 4.1.3. Design of cooling jacket........................................................................................ 50 4.1.4. Design of impeller ……… ………………………………………………………. 51 4.2. Reactor (R-102) .............................................................................................................. 57 4.3. Heat exchanger (H-101).................................................................................................. 58 4.3.1. Thermal design ..................................................................................................... 58 4.4. Preheater (H-102) ........................................................................................................... 63 4.5. Ammonia preheater (H-103) ........................................................................................... 64 4.6. Centrifuge (F-101) .......................................................................................................... 70 4.6.1. Selection ............................................................................................................... 70 4.6.2. Design .................................................................................................................. 71 4.7. Centrifuge (F-102) .......................................................................................................... 75 4.8. Crystallizer (CR-101) ..................................................................................................... 76 4.8.1. Selection ............................................................................................................... 76 4.8.2. Design .................................................................................................................. 76 4.9. Evaporator (E-101) ......................................................................................................... 79



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER 4.9.1. Selection ............................................................................................................... 79 4.9.2. Design .................................................................................................................. 79 4.10. Prilling tower (T-101) ................................................................................................... 85 4.10.1. Design ................................................................................................................ 85 5. Mechanical Design............................................................................................................... 87 5.1. Shell & tube heat exchanger ........................................................................................... 88 5.1.1. Design pressure ..................................................................................................... 88 5.1.2. Design temperature ............................................................................................... 88 5.1.3. Material selection .................................................................................................. 89 5.1.4. Design stress ......................................................................................................... 89 5.1.5. Thickness of shell ................................................................................................. 89 5.1.6. Thickness of head ................................................................................................. 89 5.1.7. Effective exchanger length .................................................................................... 90 5.1.8. Thickness of tube sheet ......................................................................................... 90 5.1.9. Nozzle inside diameter .......................................................................................... 90 5.1.10. Gasket ................................................................................................................ 90 5.1.11. Support .............................................................................................................. 90 6. Pumps & Compressors ........................................................................................................ 92 6.1. Pump .............................................................................................................................. 93 6.1.1. Types of pump ...................................................................................................... 93 6.1.2. Sizing of pump (P-101) ......................................................................................... 93 6.1.3. Sizing of Pump (P-102)......................................................................................... 98 7. Cost Estimation ................................................................................................................... 99 7.1. Introduction .................................................................................................................. 100 7.1.1. Classification of cost estimation .......................................................................... 100



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER 7.1.2. Classification of rapid capital cost estimation ...................................................... 100 7.1.3. Equipment Purchased Cost .................................................................................. 100 7.1.4. Direct cost........................................................................................................... 106 7.1.5. Indirect Cost ....................................................................................................... 107 7.1.6. Variable Cost ...................................................................................................... 107 7.1.7. Fixed Cost .......................................................................................................... 109 7.1.8. Selling Price........................................................................................................ 109 7.1.9. Profitability Analysis .......................................................................................... 110 7.1.10. Rate of Return .................................................................................................. 111 7.1.11. Payback Period ................................................................................................ 111 8. Instrumentation & Control ............................................................................................... 112 8.1. Objective ...................................................................................................................... 113 8.1.1. Production Rate .................................................................................................. 113 8.1.2. Product Quality ................................................................................................... 113 8.1.3. Cost .................................................................................................................... 113 8.2. Process Instrumentation ................................................................................................ 113 8.2.1. Temperature ………………………………………………………………….…. 113 8.2.2. Pressure .............................................................................................................. 114 8.2.3. Flow ................................................................................................................... 114 8.2.4. Concentration ..................................................................................................... 114 8.3.Control Loops................................................................................................................ 114 8.3.1. Feedback Control Loop ....................................................................................... 114 8.3.2. Feed forward Control Loop ................................................................................. 114 8.3.3. Cascade Control Loop ………………………………………………..…………. 115 8.4. Cascade Control Loop on Crystallizer........................................................................... 115



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER 8.4.1. Control Objective ................................................................................................ 116 8.4.2. Controlled Variable ............................................................................................. 116 8.4.3. Disturbance Variable .......................................................................................... 116 8.4.4. Manipulated Variable .......................................................................................... 116 8.4.5. Control Procedure ……………………………………………….…………….... 116 9. HAZOP Study ................................................................................................................... 117 9.1. Introduction .................................................................................................................. 118 9.1.1. Background ........................................................................................................ 118 9.2. Success or Failure ......................................................................................................... 118 9.3. HAZOP Characteristics ................................................................................................ 118 9.3.1. Design ................................................................................................................ 119 9.3.2. Physical and operational environments ................................................................ 119 9.3.3. Operational and procedural controls .................................................................... 119 9.4. Advantages ................................................................................................................... 119 9.5. Disadvantages .............................................................................................................. 119 9.6. Effectiveness ................................................................................................................ 119 9.7. Key Elements ............................................................................................................. 119 9.8. Guide Words .............................................................................................................. 121 9.9. HAZOP Study on Crystallizer .................................................................................... 122 10. Environmental Impact Assessment ................................................................................ 124 10.1. Overview .................................................................................................................... 125 10.2. Objectives................................................................................................................... 125 10.3. Advantages ................................................................................................................. 125 10.4. Ammonia .................................................................................................................... 125 10.4.1. Hazard .............................................................................................................. 125



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER 10.4.2. Protective measures .......................................................................................... 126 10.4.3. Spills and emergencies ...................................................................................... 126 10.5. Nitric acid ................................................................................................................... 126 10.5.1. Hazards ............................................................................................................. 126 10.5.2. Protective measures .......................................................................................... 127 10.5.3. Exposure Controls ............................................................................................. 127 10.6. Nitro-phosphate fertilizer ............................................................................................ 127 10.6.1. Environmental issues ........................................................................................ 128 10.6.2. Recommended measures ................................................................................... 128 11. Appendixes ...................................................................................................................... 130 Appendix A: Heat exchangers ............................................................................................. 131 Appendix B: Pumps ............................................................................................................ 136 Appendix C: Equipment cost ............................................................................................... 139 12. References ........................................................................................................................ 142



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



List of Figures Figure 1-1: Global nutrients (N+P2O5+K2O) consumption in world ……..........................……… 7 Figure 1-2: Regional share of world in N-fertilizers consumption (2014-18) …….…….……….. 7 Figure 1-3: Regional share of P2O5-fertilizers consumption (2014-18) …………………….…… 8 Figure 1-4: N & P production in different regions of world ………………….……….…………. 9 Figure 1-5: Production of NP in Pakistan (1990-2017) ……………………………….………... 10 Figure 1-6: Off-take of NP in Pakistan (1990-2017) …………………….……………………... 10 Figure 1-7: Comparison of NP offtake & production in Pakistan (1990-2017) ……………..…. 10 Figure 2-1: Effect of Crystallization temperature on P2O5 water solubility ……………..…….. 14 Figure 2-2: Process flow diagram of ODDA process …………………………...………………. 15 Figure 2-3: Process flow diagram of mixed acid process ……………………………….……… 16 Figure 2-4: Flow sheet of ODDA process ………………………………………….…………… 20 Figure 3-1: Digestion Reactor (R-101) ……………………………………….………………… 27 Figure 3-2: Inerts centrifuge (F-101) ………………………………………...………………….. 28 Figure 3-3: Calcium nitrate crystallizer ……………………………………..………………….. 29 Figure 3-4: CN centrifuge (F-102) ……………………………..……………………………….. 30 Figure 3-5: Neutralizer reactor (R-102) …………………………………..…………………….. 31 Figure 3-6: Evaporator (E-101) …………………………………..……………………………... 33 Figure 3-7: Digester (R-101) …………………………………………………………..………... 34 Figure 3-8: Heat exchanger (H-101) ……………………………………….…………………… 37 Figure 3-9: Crystallizer (CR-101) ……………………………………..………………………... 38 Figure 3-10: Preheater (H-102) …………………………………………..……………………... 39 Figure 3-11: Preheater (H-103) ………………………………………..………………………... 40 Figure 3-12: Neutralizer reactor (R-102) ………………………………..……………………… 41 Figure 3-13: Evaporator (E-101) ……………………………….………………………………. 43 Figure 4-1: Digestion reactor (R-101) ………………………………..…………………………. 46 Figure 4-2: Log-log graph of finite differential method ………………………….…………….. 49 Figure 4-3: Rushton turbine …………………………………………………………………….. 52 Figure 4-4: Dimensions of impeller …………………………………………………………….. 53 viii



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER Figure 4-5: Graph b/w Reynolds number & pumping number (a) ..…………………………….. 53 Figure 4-6: Graph b/w Reynolds number & pumping number (b) ……………………………… 54 Figure 4-7: Heat exchanger (H-101) ………………………………….………………………… 58 Figure 4-8: Ammonia preheater (H-103) …………………………………..…………………… 64 Figure 4-9: Solid bowl centrifuge ………………………………………………….…………… 70 Figure 4-10: Inerts removal centrifuge ……………………………………...…………………. 71 Figure 4-11: Particle trajectory in sedimentation centrifuge ……………………..…………….. 72 Figure 4-12: Cooling crystallizer with agitator ………………………………..………………. 76 Figure 4-13: Crystallizer (CR-101) …………………………………………..…………………. 76 Figure 4-14: Falling film evaporator (E-101) ……………………………..……………………. 79 Figure 4-15: Prilling tower (T-101) ……………………………………….……………………. 85 Figure 5-1: Heat exchanger (H-102) ……………………………………….…………………… 88 Figure 8-1: Instrumentation & control on crystallizer (CR-101) ………….…………………... 115 Figure A-1: Tube side heat transfer curve ………………………………………….………….. 131 Figure A-2: LMTD correction factor ………………………………………………..………… 131 Figure A-3: Tube side friction factor ……………………………………………...…………… 132 Figure A-4: Tube side return pressure losses …………………………………..………………. 132 Figure A-5: Shell side heat transfer curve ………………………………….…………………. 133 Figure B-1: Pump selection chart …………………………………………..………………….. 136 Figure C-1: Cost data of double pipe heat exchanger ……………….………………………… 139 Figure C-2: Cost data of shell and tube heat exchanger ……………………..………………… 139 Figure C-3: Cost data of dryers …………………………………………..……………………. 140 Figure C-4: Cost data of centrifuge …………………………………………..………………... 140



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



List of Tables Table 1-1: Classification of elements necessary for plant growth ………………………..……… 2 Table 1-2: Conversion factors for nutrients ………………………………………..…………….. 2 Table 1-3: Phosphate fertilizer production capacities by industries in Pakistan …………….…... 3 Table 1-4: Physical properties ……………………………………………………..……………... 4 Table 1-5: Thermodynamic data ………………………………………………………..………... 5 Table 1-6: World fertilizer primary nutrients demand (2014-18) ……………………..…………. 8 Table 1-7: World supply of fertilizer nutrients (2014-18) ……………………….………………. 8 Table 1-8: Global NP production & consumption by country ……………………..…………….. 9 Table 2-1: Production methods comparison ……………………………………..…………….... 17 Table 2-2: Stream table ……………………………………………………….………………… 21 Table 3-1: Composition of phosphate rock ……………………………………..………………. 25 Table 3-2: Phosphate rock components ………………………………………….……………... 26 Table 3-3: Overall balance on R-101 ……………………………………………..…………….. 28 Table 3-4: Overall balance on centrifuge (F-101) ………………………………...…………….. 29 Table 3-5: Overall balance on crystallizer …………………………………….………………... 30 Table 3-6: Overall balance on CN centrifuge (F-102) …………………………..……………… 30 Table 3-7: Reaction (e) analysis ………………………………………………..……………….. 31 Table 3-8: Reaction (f) analysis ……………………………………………..………………….. 32 Table 3-9: Reaction (g) analysis ……………………………………………………..………….. 32 Table 3-10: Overall balance on R-102 …………………………………….……………………. 32 Table 3-11: Overall balance on evaporator (E-101) ………………………….………………… 33 Table 3-12: Basis for energy balance …………………………………………..……………….. 34 Table 4-1: Types of impeller ……………………………………………………………………. 51 Table 4-2: Specification sheet of digestion reactor (R-101) ……………………….…………… 56 Table 4-3: Specification sheet of neutralizer reactor (R-102) ……………………..……………. 57 Table 4-4: Specification sheet of heat exchanger (H-101) ………………………..…………….. 62 Table 4-5: Specification sheet of preheater (H-102) ……………………………….…………… 63 Table 4-6: Specification sheet of ammonia preheater …………………………..………………. 69



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER Table 4-7: Design data for centrifuge ……………………………………………...……………. 71 Table 4-8: Specification sheet of centrifuge (F-101) …………………………...……………….. 74 Table 4-9: Specification sheet of centrifuge (F-102) ……………………………………..…….. 75 Table 4-10: Specification sheet of crystallizer (CR-101) ……………………………..………… 78 Table 4-11: Specification sheet of evaporator (E-101) ………………………….……………… 84 Table 4-12: Specification sheet of prilling tower (T-101) ………………………….…………... 86 Table 5-1: Mechanical design specification sheet ……………………………...……………….. 91 Table 6-1: Specification sheet of pump (P-101) ……………………………..…………………. 97 Table 6-2: Specification sheet of pump (P-102) ……………………………..…………………. 98 Table 7-1: Purchased equipment cost ………………………………………...…………….…. 106 Table 7-2: Direct cost …………………………………………………………..………….….. 106 Table 7-3: Indirect cost ……………………………………………………….…………….…. 107 Table 7-4: Fixed cost …………………………………………………………..………………. 109 Table 9-1: HAZOP study guide words ……………………………………..…………………. 121 Table 9-2: HAZOP study on crystallizer ……………………………………...……………….. 122 Table A-1: Dimensions of steel pipe …………………………………………..………………. 133 Table A-2: Overall design coefficients ……………………………………..…………………. 134 Table A-3: Tube sheet layout (triangular pitch) ……………………………….……………… 134 Table A-4: Heat exchanger tube data …………………………………………….……………. 134 Table A-5: Materials of construction for heat exchangers ……………………………………. 135 Table A-6: Nozzle inside diameter for S&T heat exchangers ……………………..………….. 135 Table A-7: Gasket factors ………………………………………………………….………….. 135 Table B-1: Location of process equipment …………………………………………….……… 136 Table B-2: Pressure drop across process equipment ……………………………..……………. 136 Table B-3: Pump characteristics ………………………………………………….…………… 137 Table B-4: Characteristics of pump drivers …………………………………..……………….. 137 Table B-5: Standard electric motor sizes ………………………………………..…………….. 138 Table C-1: Cost data of equipment ……………………………………………………………. 141



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



Dedication We would like to dedicate our work to our honorable parents and respected teachers, who supported and motivated us at every step. Their tremendous support and cooperation led us to this wonderful accomplishment.



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



Acknowledgement We would like to thank ALMIGHTY ALLAH, the Creator of universe, the most Beneficent the most Merciful, who gave us enough strength to accomplish this task. All respects are for His HOLY PROPHET (‫)ﷺ‬, whose teachings are the true source of knowledge & guidance for the whole mankind. We would like to thank our honorable Parents for devotion of their time. They support and encourage us whenever we need them. We are owing gratitude to our Dean of Engineering Prof. Dr. A. K. Salariya, Head of Department Dr. K. S. Baig and Project Supervisors Dr. Saleem Iqbal and Mr. Fazeel Ahmad for their worthy discussions, encouragement, keen interest, and remarkable suggestions which helped us to accomplish this thesis.



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



Abstract Nitro-phosphate (NP) is a complex acidic fertilizer which contains two macronutrients of plants, nitrogen (N) and phosphorous (P). NP is majorly used for rooting, blooming and fruit production of plants. Demand of nitro-phosphate is increasing day by day with increasing demand for food and population growth. Increasing demand of NP and alkalinity of soil in Pakistan motivates us to work on this project. The project report includes discussion of project feasibility, comparison of manufacturing processes and application of NP fertilizer. The selected process is ODDA process that consists of four sections first one is the digestion of phosphate rock with nitric acid, second one is the separation of calcium nitrate, third one is the neutralization section in which NP acid is neutralized by ammonia and last section is the prilling section in which prills of NP solution is formed in prilling tower. This report includes material and energy balance, designing along with HAZOP and EIA study. The designing of each equipment (reactors, crystallizer, heat exchangers, centrifuges, evaporator and prilling tower) with designing is discussed in detail. The cost estimation of this plant was a major and compulsory part of this report. The plant capital cost and operating cost are also determined along with payback period (1.4 years). The payback period of the project is 1.24 years.



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



Nomenclature NP NPK CN CNTH AN CAN MT MTPA MTPD TMT TMTA MMT P2O5 NOx SOx HF HCl CO2 FAO NFDC EFERT IFDC EIA



= = = = = = = = = = = = = = = = = = = = = = =



Nitro-phosphate Nitrogen phosphorous potassium Calcium nitrate Calcium nitrate tetra-hydrate Ammonium nitrate Calcium ammonium nitrate Metric ton Metric ton per annum Metric ton per day Thousand metric ton Thousand metric ton per annum Million metric ton Phosphorous pentoxide Nitrous oxides Sulfur oxides Hydrogen fluoride Hydrogen chloride Carbon dioxide Food and Agriculture Organization of United Nations National Fertilizer Development Centre Engro Fertilizer Company Limited International Fertilizer Development Centre Environmental Impact Assessment



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PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



CHAPTER # 1 Introduction



1



CHAPTER I



1.1.



Introduction



Fertilizer



A fertilizer is the compound material that includes two or more elements that are necessary for proper development and growth of plants. Important fertilizers are chemical or mineral fertilizers, plant residues and manures. They may be organic or inorganic materials absorbed by the roots of the plants to provide essential nutrients that are lost by harvesting of crops, leaching or gaseous exchange. [1] These nutrients are termed as plant nutrients. Carbon, hydrogen and oxygen are essential for plants but are not considered as nutrients in fertilizer industry, because they are obtained by carbon dioxide (CO2) in atmosphere and water (H2O). These three constitute up to 90-95% of the dry matter of all plants. Other major nutrients are categorized as primary nutrients (Nitrogen (N), Phosphorous (P) and Potassium (K)) and secondary nutrients (Calcium (Ca), Magnesium (Mg) and Sulfur (S)). [1] Table 1-1: Classification of elements necessary for plant growth



Air & Water Major elements (Macronutrients)



Primary Nutrients



Secondary Nutrients



Minor Elements (Micronutrients)



Carbon Hydrogen Oxygen Nitrogen Phosphorous Potassium Calcium Magnesium Sulfur Chlorine Boron Copper Molybdenum Zinc Manganese Iron



In many countries primary nutrients are expressed in forms of elemental nitrogen (N), phosphorous pentoxide (P2O5) and potassium oxide (K2O). Secondary nutrients and micronutrients are mostly expressed in elemental form although sometimes calcium and magnesium are sometimes expressed in oxide form. Conversion factors are used for conversion of nutrients from oxide to elemental form or vice versa. [1] Table 1-2: Conversion factors for nutrients



P2O5 x 0.44 = P K2O x 0.83 = K MgO x 0.60 = Mg SO3 x 0.40 = S



Mg x 1.66 = MgO S x 2.50 = SO3



2



CaO x 0.71 = Ca P x 2.29 = P2O5



CHAPTER I



Introduction



Commonly fertilizers are represented by a series of numbers separated by dashes. This set of numbers is termed as grade of fertilizer. These numbers represents the quantity of nutrients in that fertilizer in percentages. For example 20-22 Nitro-phosphate (NP) constitutes of 20% nitrogen (N) and 22% phosphorous (P2O5). Agriculture sector of Pakistan, backbone of Pakistan’s economy, has direct or indirect involvement with fertilizer sector. Currently, Pakistan has an estimated installed capacity of 3 million tons for the production of all phosphate fertilizers like Di-ammonium phosphate (DAP), Mono-ammonium phosphate (MAP), Single superphosphate (SSP) and Nitro-phosphate (NP). Table 1-3: Phosphate fertilizer production capacities by industries in Pakistan



Company name



Type of fertilizer



Fauji Fertilizer Bin Qasim Ltd.



Di-ammonium Phosphate (DAP) Di-ammonium Phosphate (DAP) Single Super Phosphate (SSP) Single Super Phosphate (SSP) Single Super Phosphate (SSP) Nitro-phosphate (NP) Nitro-phosphate (NP) Nitro-phosphate (NP) NPK



Al-Noor Fertilizers Agritech Ltd. Suraj Fertilizers Allah Din Group Pak Arab Fertilizers Fatima Fertilizers Engro Fertilizers



Installed annual capacity (MTPA) 768,000 390,000 100,000 150,000 90,000 350,000 350,000 40,000 100,000



This sector accounts for: 1. 2. 3. 4. 5.



21% of the country’s gross domestic product (GDP). 60% of employed labor in rural areas. 65% of total Pakistan’s exports earnings. 3% growth rate per annum Provide raw materials for industries like sugar, textile, etc.



1.2.



Nitro-phosphate (NP)



Nitro-phosphate (NP) is a complex granulated fertilizer majorly consists of nitrogen (N) and phosphorous (P2O5) with little amounts of calcium (Ca). Nitrogen is a primary nutrient necessary for proper growth of plants and phosphorous is beneficial for rooting, blooming and fruit production in plants. It is acidic in nature with pH of 3.5 and is suitable for soils of higher pH. 223



CHAPTER I



Introduction



20, 20-20 and 18-18 grades of nitro-phosphate are mostly used by farmers. Its molecular formula is NO6P-2 and molecular weight of 140.975 g/mol. Nitro-phosphate is also used as a term for fertilizers manufactured by the treatment of phosphate rock with nitric acid. Pakistan has installed capacity for production of Nitro-phosphate of 740,000 MTPA. Major producers of NP fertilizer in Pakistan are Pak Arab Fertilizer with capacity of 350,000 MTPA, Fatima Fertilizer with capacity of 350,000 MTPA and Engro fertilizer with capacity of 40,000 MTPA. Supply of phosphate fertilizers in Pakistan covers only 50% of the total domestic demand, which is increasing 10% annually. This estimated gap is fulfilled by imports of fertilizers.



1.3.



History of product



The first process for the manufacture of nitro-phosphate fertilizer from the treatment of phosphate rock with nitric acid was developed by Erling Johnson in 1928. The process was named as Odda Process because this invention was developed in the town of Odda, Norway. [1] After invention, he transferred his patent to a Norwegian company named Norsk Hydro, which developed it in 1930 and introduced their own technology in 1938. Norsk Hydro was the first company to manufacture multi-nutrients like NP & NPK via Nitro-phosphate process. [1] After few years sulfuric acid was used via mixed acid process to manufacture complex fertilizers (NP, NPK, etc.). Due to high emissions of H2S and gypsum as byproduct, mixed acid process was not much used on large scale.



1.4.



Physical properties & thermodynamic data Table 1-4: Physical properties



Property Molecular Formula Molecular Weight (g/mol) Appearance Smell Boiling Point Melting Point



Nitric acid



Ammonia



Phosphate rock



Nitro-phosphate



HNO3



NH3



Ca3(PO4)2



NH4H2PO4



63.02



17.03



310.18



115



Colorless liquid



Pungent 86 oC -41.59 oC 47.8 mmHg Vapor Pressure at 20 oC Density (g/cc) 1.529



Colorless Irritating -33.35 oC -77.7 oC 10.2 atm at 25 oC 0.77



4



Greyish Sedimentary rock -



White/grey granules or prills -



-



-



3.14



-



CHAPTER I



Introduction Table 1-5: Thermodynamic data



Nitric acid



Property



Standard Molar Enthalpy of formation -174.1 (∆H) at 298.15 K (KJ/mol) Standard Molar Gibbs energy of formation -80.7 (∆G) at 298.15 K (KJ/mol) Standard Molar Entropy 155.6 at 298.15 K (J/mol-K) Standard Molar heat capacity 109.9 at 298.15 K (J/mol-K)



1.5.



Ammonia



Phosphate rock Nitro-phosphate



-45.9



-



-



-16.4



-



-



192.8



-



-



80.8



-



-



Chemical reactions



Nitric acid is reacted with phosphate rock in first step by the following reaction, Ca3 (PO4 )2 + 6HNO3 → Ca(NO3 )2 + 2H3 PO4 + 22.25 kcal After removal of calcium nitrate crystals, nitro-phosphoric acid gets neutralized with ammonia to produce a fertilizer. H3 PO4 + 2NH3 → NH4 H2 PO4 + 66.67 kcal Calcium nitrate is further utilized either as a fertilizer or in the production of calcium ammonium nitrate (CAN). [2]



1.6.



Industrial applications



Nitro-phosphate can be applied on all types of soil, mostly on soils of high pH or alkaline in nature. It is applied at planting and early stages of growth of crops. Nitro-phosphate constitutes of equal amounts of nitrogen (N) and phosphorous (P) hence, nutrients are equally distributed throughout the field. Sometimes it is also used in explosives due to presence of ammonium nitrate (NH4NO3). If ammonium nitrate exceeds 70% by weight in the product then it becomes dangerous to use.



1.7.



Handling, storage & safety



1.7.1. Phosphate rock Phosphate rock is mined and conveyed to plant site via trucks and dumpers. Large lumps of rock pass through crushers for size reduction and get stored in huge yards. Due to presence of dust, conveyors are covered with shed and bag filters. Magnetic separators are also installed to remove metallic impurities. [2]



5



CHAPTER I



Introduction



1.7.2. Ammonia Handling of ammonia requires careful attention. It is rapidly soluble in water and reacts with body moisture to cause a severe damage. It should be used with proper safety precautions like safety gears. Metal containers are not suitable for ammonia storage because ammonia corrodes the metals like copper, zinc, etc. It is stored in under pressure containers to stay ammonia in liquid form and transported to plant site via pressurized tankers. 1.7.3. Nitric acid Handling of Nitric acid requires proper safety measures like chemical safety glasses, face cover and gloves because, it is corrosive and causes severe skin burns. Nitric acid is transported to plant site via cool and pressurized tankers and gets stored in cool, dry and properly ventilated containers. 1.7.4. Nitro-phosphate Nitro-phosphate (NP) contains ammonium nitrate to great extent (> 50%) as it is the main source of nitrogen (N) in the nitro-phosphate fertilizer. If ammonium nitrate amounts exceed 70% by weight then it acts as an oxidizer and product must be tested for detonation ability. Ammonium nitrate in fertilizer also attracts moisture therefore, it is packed in water tight bags to prevent clumping or caking. Granules of nitro-phosphate is packed in 50kg bags and delivered to the farmers. [2]



1.8.



Shipping of product



If test for ammonium nitrate is negative, then it is suitable for use and its bulk shipment takes place in special air tight vessels. For long distance bulk shipment, NP fertilizer is checked for high mechanical resistance and low caking tendency. High mechanical resistance prevents the breakage of granules during storage and transportation. Low caking tendency restricts fertilizer to form a cake during long time storage and shipment. Anticaking agents are also added to prevent caking and make fertilizer free flowing. Due to hygroscopic nature of the fertilizer, it absorbs moisture during the storage and shipment. That’s why hydrophobic coating has been developed on the granules of NP to prevent moisture attraction and ease the shipment. De-dusting equipment like bag filters should be used at every step of transportation and storage to prevent dust evolution.



6



CHAPTER I



World overview 210 200.522 200



193.882 197.19



186.895



190



MMT



1.9.



Introduction



190.732



180.079 180



183.175 170.845



170



176.784



161.829 160 150 2008



161.659



2009



2010



2011



2012



2013



2014



2015



2016



2017



2018



Year



Figure 1-1: Global nutrients (N+P2O5+K2O) consumption in world [3]



East Asia South Asia West Asia Central Europe West Europe East Europe & Central Asia North Africa North America Sub Saharian Africa Oceania Latin America & Caribbean



Figure 1-2: Regional share of world in N-fertilizers consumption (2014-18) [3]



7



CHAPTER I



Introduction



South Aisa East Asia



Central Europe West Europe East Europe & Central Asia Oceania North Africa Sub Saharian Africa North America Latin America & Caribbean West Asia



Figure 1-3: Regional share of P2O5-fertilizers consumption (2014-18)



Table 1-6: World fertilizer primary nutrients demand (2014-18) [3]



Year 2014 2015 2016 2017 2018



Nitrogen (N) 113 147 115 100 116 514 117 953 119 418



Demand (TMT) Phosphorous Potassium (P2O5) (K2O) 42 706 31 042 43 803 31 829 44 740 32 628 45 718 33 519 46 748 34 456



Total (N+P2O5+K2O) 186 895 190 732 193 882 197 190 200 522



Table 1-7: World supply of fertilizer nutrients (2014-18) [3]



Year 2014 2015 2016 2017 2018



Supply (TMT) Phosphorous (P2O5) 46,864 48,299 49,487 50,598 52,189



Nitrogen (N) 152,769 159,591 165,784 172,059 176,489



8



Potassium (K2O) 43,568 45,175 46,974 49,741 51,439



CHAPTER I



Introduction



18000 16000 14000



TMT



12000 10000 8000 6000 4000



2000 0 Africa



North Latin West Asia South America America Asia & Caribbean



East Asia Central Europe



West East Oceania Europe Europe & Central Asia



Regions of world N



P



Figure 1-4: N & P production in different regions of world [3]



Table 1-8: Global NP production & consumption by country [3]



Production (TMTA) Country NP Russia 87,803 China 28,624 Canada 27,094 USA 23,005 India 15,052 Belarus 8,842 Saudi Arabia 7,161 Morocco 6,485 Indonesia 6,249



Consumption (TMTA) Country NP China 59,444 India 26,939 USA 20,376 Brazil 16,597 Indonesia 5,805 Canada 3,975 Russia 3,252 France 3,043 Vietnam 2,747



9



CHAPTER I



Introduction



1.10. Nitro-phosphate in Pakistan 700 600



TMT



500 400



300 200 100 1990



1993



1996



1999



2002



2005



2008



2011



2014



2017



Year



Source: NFDC



Figure 1-5: Production of NP in Pakistan (1990-2017) 700



600



TMT



500 400 300 200 100 1990



1993



Source: NFDC



1996



1999



2002



2005



2008



2011



2014



2017



Year



Figure 1-6: Off-take of NP in Pakistan (1990-2017) 700 600



TMT



500 400 300



200 100



1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017



0



Year



Source: NFDC



NP Off-take



NP Production



Figure 1-7: Comparison of NP offtake & production in Pakistan (1990-2017)



10



CHAPTER I



Introduction



Major producers of Nitro-phosphate (NP) in Pakistan are Pak Arab Fertilizer Limited with installed capacity of 304,500 MTPA, Fatima Fertilizer Company Limited with capacity of 360,000 MTPA and Engro Fertilizer Limited with capacity of 40,000 MTPA.



1.11. Market assessment Nitro-phosphate is a complex fertilizer, manufactured by digestion of phosphate rock with nitric acid. Nitro-phosphate is available in market in a 50 kg bag, which costs PKR 2975. Largest producer of nitro-phosphate is Russia with production of 20% of total NP in the world. Russia has also secured a top position in export of NP fertilizer with 35% of the total exports of NP in the world. China is the major consumer of NP in the world with consumption of 45% of total consumption of NP in the world. In Pakistan there are three major producers of nitro-phosphate named as Fatima Fertilizer Company Limited, Pak Arab Fertilizer Limited and Engro Fertilizer Limited. Pak Arab fertilizer was the first NP producer in Pakistan, founded in 1973, with installed capacity of 304,000 MTPA. With the increase in population, demand for food is also increasing that requires higher crop yields. For better crop yields, fertilizers are required. In 2005, Engro Fertilizer Limited (EFERT) started production of NP with installed capacity of 40,000 MTPA. To further overcome the demand of NP, Fatima Fertilizer Company Limited started NP production with installed capacity of 360,000 MTPA in 2010. After 2010, Pakistan stopped importing nitro-phosphate (NP) because, production of NP fulfill its demand. Due to greater demand for food with the passage of time, fertilizer with greater amounts of macronutrients will come into use for better crop yields.



1.12. Future trends Due to rapid growth of population, demand of food is increasing which requires better crop yields. For better crop yields, demand of fertilizers is boosting day by day. Nitro-phosphate constitutes of two major plant nutrients, nitrogen (N) and phosphorous (P), that are required for proper growth of plants, rooting, blooming and fruits production. Top producer of NP is Russia whereas, top consumer of NP is China in the world. In Pakistan, NP demand is fulfilled by its production after 2010. Due to rapid population growth, demand of nitro-phosphate is increasing. Off take of nitro-phosphate in the year 2016 was 651,000 MT and in 2017 it reached 688,000 MT. As per previous trend, demand of NP is increasing day by day.



11



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



CHAPTER # 2 Manufacturing Process



12



CHAPTER II



Manufacturing Process



Nitro-phosphate is manufactured commercially by two processes: 1. ODDA Process 2. Mixed Acid Process



2.1.



ODDA process



This process was invented by Erling Johnson in 1928. It is called as “Odda” because it was invented by Johnson in the town of Odda, Norway. This process was commercially used for the first time in 1938 by Norsk Hydro Company (now Yara International) for the production of NP fertilizer. Then it was further used by BASF after some modifications. [2] 2.1.1. Raw materials 1. Phosphate rock 2. Nitric acid 3. Ammonia gas 2.1.2. Process description Dissolving reactor The process starts with the dissolution of phosphate rock in 60% nitric acid. This reaction is being carried out in a stainless steel vessel, equipped with agitator, at a temperature of 60-70oC by the following reaction: Ca3 (PO4 )2 + 6HNO3 → Ca(NO3 )2 + 2H3 PO4 + 22.25 kcal The rate of dissolution depends on: 1. Excess of nitric acid. 2. Surface area of phosphate rock particles. 3. Degree of agitation. Foaming occurs in the reactor due to greater CO2 content and is reduced by effective agitation or by adding anti-foaming agents like glycols, stearates, alcohols, etc. Urea is also used, amount required would be 0.1-0.3% of rock feed, to suppress the emissions of NO x and HF. Sand removal Sand particles are removed by washing slurry with water. Suspended solids (quartz) and inert diluents of nutrients are removed in centrifuge. Crystallization unit Slurry of Calcium nitrate and phosphoric acid move towards crystallizer unit, which consists of several batch crystallizers operated continuously. Aqueous solution of ammonia (25%) from evaporator of refrigeration system, acts as a coolant, flows through each crystallizer to cool the slurry to -5oC. As the temperature decreases, water solubility of P2O5 in final product increases. Higher water solubility of P2O5 in final product enables effective use of nutrients by the plants. Trend of P2O5 water solubility with temperature inside the crystallizer is shown in Figure 2-1



13



CHAPTER II



Manufacturing Process



Water Solubility, % of P2O5



Temperature (oC)



Figure 2-1: Effect of Crystallization temperature on P 2O5 water solubility



CN crystals filter After the formation of crystals, solution is passed through centrifuge to separate crystals from acid liquor. Calcium nitrate tetra hydrate crystals are separated and utilized either as a fertilizer or in the formation of calcium ammonium nitrate (CAN). Neutralization reactor Nitro-phosphoric (NP) acid is further neutralized with gaseous ammonia (NH3) in a pressurized reactor at pressure of 1.5-2.5 bar and temperature of 150-180oC. Heat of reaction released concentrates the solution to 75% by removing most of the water and ammonia. H3 PO4 + 2NH3 → (NH4 )2 HPO4 + 66.67 kcal Evaporation & prilling NP solution is discharged to evaporators under vacuum. Evaporator is operated at 175 oC to concentrate final product to 99.9%. Pure nitro-phosphate melt is passed towards prilling tower. In prilling tower air is passed from the bottom whereas, melt enters the tower from the top. [4] Coating & packaging Solid prills are removed from the bottom of the tower with scrapper at 95 oC. Prills are then cooled and conveyed to coating drum. Final coated NP prills are conveyed to packaging plant and are packaged in 50 kg bags. For shipping, air tight vessels are used to restrict moisture away from the product.



14



CHAPTER II



Manufacturing Process



Figure 2-2: Process flow diagram of ODDA process [2]



2.2.



Mixed acid process



2.2.1. Raw materials 1. 2. 3. 4. 5.



Phosphate rock Nitric acid Ammonia gas Phosphoric acid Sulfuric acid



2.2.2. Process description Digestion reactor Phosphate rock is digested by nitric acid in the first reactor at the temperature of 60-70oC by the following reaction: Ca3 (PO4 )2 + 6HNO3 → 3Ca(NO3 )2 + 2H3 PO4 + 22.25 kcal Acid gases like nitrous oxides and compounds of fluorine are formed during the digestion reaction, which are removed by scrubber. Calcium nitrate is not removed from the reactor, it stays in the reactor to provide two nutrients, calcium and nitrogen. [1]



15



CHAPTER II



Manufacturing Process



Second reactor Neutralization of acidic slurry is done in second reactor by using ammonia (NH 3). Sulfuric acid and phosphoric acid are also added to the reactor to increase P2O5 content in the product, increase P2O5 water solubility and remove calcium from the reactor as gypsum (CaSO4). HNO3 + NH3 → NH4 NO3 + 22.27 kcal H3 PO4 + 2NH3 → (NH4 )2 HPO4 + 33.52 kcal 2H3 PO4 + Ca(NO3 )2 + 4NH3 → CaHPO4 + (NH4 )2 HPO4 + 2NH4 NO3 Ca(NO)3 + H2 SO4 → 2HNO3 + CaSO4 + 9.37 kcal Third reactor Further neutralization of overflow of second reactor by ammonia takes place in this reactor. pH of the solution reaches 5-6 to avoid formation of HCl in the reactor and several by-products are formed like di-calcium phosphate, calcium sulfate, calcium hypophosphate, etc. Buffer tank & spherodizer Buffer tank acts as a feed tank for spherodizer. Water content in the slurry is 5-30% and temperature of 100-140oC. Spherodizer is the combination of drying and granulating. Scrubbing columns Scrubbers are installed to clean reactors off gases. Scrubber liquor is used to recover nutrients form off gases and discharged them to the third reactor to improve product quality. Evaporation and packaging Product granules enters the evaporator, where steam enters, remove moisture and concentrate the product. Final product reach packaging plant for bulk loading or bagging.



Figure 2-3: Process flow diagram of mixed acid process [2]



16



CHAPTER II



2.3.



Manufacturing Process



Process comparison Table 2-1: Production methods comparison



Process



ODDA Process



Mixed Acid Process Phosphate rock Nitric acid Sulfuric acid Phosphoric acid Ammonia gas



Raw materials



Phosphate rock Nitric acid Ammonia gas



By-products



Ammonium nitrate Calcium ammonium nitrate Calcium nitrate



Separation of CNTH crystals



This process separates the CNTH crystals, after digestion, for the production of AN & CAN.



By-products usage/disposal



In this process, by-products are upgraded to commercial products like CAN, AN, etc.



Waste disposal



This process involves no wastes except NOx, which is controlled by adding urea or scrubbing.



CO2 emissions



This process utilizes CO2 emissions from ammonia plant in the formation of ammonium carbonate for CAN plant.



H2S emissions Simplicity of process Dependence on sulfur Product quality



Calcium sulfate Calcium nitrate This process does not separates CNTH crystals, to utilize micronutrient (calcium). This process does not involves utilization of by-products thus, facing difficulty in the disposal of by-products like phosphor-gypsum, etc. This process involves solid waste like phosphor -gypsum, which is difficult to dispose. It also involves reactor gases like fluorides, NOx, SOx, etc.



No CO2 emissions.



Higher H2S emissions inside the reactors due to the presence of sulfuric acid.



No H2S emissions Oldest and simplest process



Complex process



Sulfur independent



Sulfur dependent



It yields higher product quality It yields low product quality due to removal of impurities. due to formation of many impurities.



17



CHAPTER II



2.4.



Manufacturing Process



Process selection



Selected process for the manufacture of nitro-phosphate is ODDA process because: 1. 2. 3. 4. 5. 6.



It’s the oldest, simplest and widely used process all over the world. By-products are upgraded to commercial and useful products like AN and CAN. Process is sulfur independent. No solid waste and disposal difficulty. Product quality is fine due to removal of impurities at every step CO2 emissions from ammonia plant are used in the absorption column for the formation of ammonium carbonate in CAN plant.



2.5.



Process description



2.5.1. Raw materials Phosphate rock Phosphate rock is imported from Morocco, Jordan and Algeria because phosphate rock in Pakistan is not of good quality because it has P2O5 content of less than required (32%). Ammonia and nitric acid Ammonia is used in large amounts for the production of nitro-phosphate and nitric acid as the main reactant, neutralizer and cooling medium. Nitric acid is the main raw material for the production of NP. 2.5.2. Phosphate rock digestion The process starts with the dissolution of phosphate rock in 60% nitric acid. This reaction is being carried out in a two stainless steel vessels, equipped with agitator, at a temperature of 70oC by the following reaction: Ca3 (PO4 )2 + 6HNO3 → Ca(NO3 )2 + 2H3 PO4 + 22.25 kcal The rate of dissolution depends on: 1. Excess of nitric acid. 2. External surface of phosphate rock. 3. Degree of agitation. Foaming occurs in the reactor due to greater CO2 content and is reduced by effective agitation or by adding anti-foaming agents like glycols, stearates, alcohols, etc. Urea is also used, amount required would be 0.1-0.3% of phosphate rock feed, to suppress the emissions of NO x and HF. Rock particle size of less than 8 mesh requires less than one hour for dissolution. Large lumps requires pre-grinding for fast reaction. [4] 2.5.3. Removal of silica Silica particles are removed in centrifuge by washing slurry with water. Suspended solids (quartz) and inert diluents of nutrients are removed.



18



CHAPTER II



Manufacturing Process



2.5.4. Crystallization unit Slurry of Calcium nitrate and phosphoric acid move towards crystallizer unit, which consists of several batch crystallizers operated continuously. Refrigeration system is installed for supply of coolant. Aqueous ammonia (25%) from refrigeration system flows through each crystallizer to cool the slurry to -5oC. As the temperature decreases, water solubility of P2O5 in final product increases. Higher water solubility of P2O5 in final product enables effective use of nutrients by the plants. 2.5.5. CN crystals filter After the formation of crystals of size 70 µm, solution is passed through centrifuge to separate crystals from acid liquor. Calcium nitrate tetra hydrate crystals are separated and move towards CAN plant. [4] 2.5.6. Neutralization reactor Nitro-phosphoric (NP) acid is further neutralized with gaseous ammonia (NH 3) in a pressurized reactor at pressure of 1.5-2.5 bar and temperature of 120oC. Heat of reaction released concentrates the solution to 75% by removing most of the water and ammonia. H3 PO4 + 2NH3 → NH4 H2 PO4 + 66.67 kcal 2.5.7. Evaporation & prilling NP solution is discharged to forced circulation evaporators under vacuum. Evaporator is operated at 175oC to concentrate final product to 99%. Pure nitro-phosphate melt is passed through prilling tower. In prilling tower air is passed from the bottom whereas, melt enters the tower from the top to form solid prills. 2.5.8. Coating & packaging Solid prills are removed from the bottom of the tower with scrapper at 95oC. Prills are then cooled and conveyed to coating drum. Final coated NP and CAN prills are conveyed to packaging plant and are packaged in 50 kg bags. For shipping, air tight vessels are used to restrict moisture away from the product.



19



CHAPTER II



Manufacturing Process



Figure 2-4: Flow sheet of ODDA process



20



CHAPTER II



Manufacturing Process Table 2-2: Stream table



Stream # T (⁰C) P (bar) Components Ca3(PO4)2 CaCO3 CaF2 HNO3 Inerts SiO2 H2 O Ca(NO3)2 H3PO4 CO2 NOx HF CaSiF6



1 25 1.01



2 25 1.01



3 25 1.01



4 70 1.01



Off gases 5 70 45 1.01 1.01 kg/hr.



6 25 1.01



7 70 1.01



8 70 1.01



9 25 1.01



17848.24 2163.73 1944.42 48850.93 487.92 468.88 238.01



Stream # T (⁰C) P (bar) Components Ca(NO3)2 H3PO4 H2 O HNO3 Ca(NO3)2.4H2O NH3/H20 25%



17468.87 487.92 38644.25



17468.87 487.92



12809.03 27025.60 11284.69



38644.25



10978.13



23787.18 27025.60 11284.69



71027.71



952.04 492.32 59.38 1422.27 10 45 1.01 27025.60 11284.69 23787.18 17468.87



11 40 1.01



71027.71



1422.27



12 45 1.01



13 45 2.01



14 0 2.01



27025.60 11284.69 23787.18 17468.87



27025.60 11284.69 23787.18 17468.87



21



Coolant in -15 1.01 kg/hr. 8107.68 11284.69 10978.13 17468.87 31726.97 57751.56



Coolant out 15 22 0 1.01 2.01 8107.68 11284.69 10978.13 17468.87 31726.97 57751.56



16 0 2.01 8107.68 11284.69 10978.13 17468.87



CHAPTER II Stream # T (⁰C) P (bar) Components Ca(NO3)2 H3PO4 H2 O HNO3 Ca(NO3)2.4H2O Steam NH3



Manufacturing Process 17 0 2.01



18 148 4



19 120 2.01



20 148 4



8107.68 11284.69 10978.13 17468.87



21 25 1.01



22 25 17 kg/hr.



23 19 2.01



24 148 4



25 120 2.01



26 148 4



40722.69



31726.97



Stream # T (⁰C) P (bar) Components Ca(NO3)2 H3PO4 H2O HNO3 NH3 Steam CaHPO4 NH4NO3 NH4H2PO4



5013.70



5013.70



3883.78 8352.23



27 120 2.01



Off gases 120 2.01



10978.13



28 45 1.01



29 201 16



30 201 16 kg/hr.



8352.23



3883.78 8352.23



34 175 0.3



35 175 1.01



37 95 1.01



6723.44 30092.62 5556.98



6723.44 30092.62 5556.98



6723.44 30092.62 5556.98



40722.69 840.47 6091.8



6723.44 30092.62 5556.98



22



6091.81



CHAPTER II



2.6.



Manufacturing Process



Capacity selection



Demand of nitro-phosphate fertilizer is increasing day by day due to increasing demand of food with population growth. After analyzing the consumption data of last 10 years, we concluded that the consumption is increasing with growth rate of 9.6%. Current consumption of NP in Pakistan is 688,000 MTPA and after five years it will reach 992,040 MTPA. The difference would be then 304,040 MTPA. So we selected the capacity of 300,000 MTPA to fulfill our country’s demand.



23



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



CHAPTER # 3 Material & Energy Balance



24



CHAPTER III



Material & Energy Balance



3.1 Material balance A balance on conserved quantity (mass, energy, momentum, etc.) in a system (single unit, multiple units or entire process) may be written in the following general way, Input + Generation − Output − Consumption = Accumulation. Steady state process is assumed hence, accumulation becomes zero. 3.1.1 Plant capacity 1,000 MTPD 1000 ton day



1000 kg 1 ton



1 day 24 h



= 44,373 kg/h = 125.88 kmol/h



3.1.2 Main reactions Ca3 (PO4 )2 + 6HNO3 → 3Ca(NO3 )2 + 2H3 PO4 H3 PO4 + 2NH3 → NH4 H2 PO4 Conversions = 99% 3.1.3 Phosphate rock analysis Table 3-1: Composition of phosphate rock



Component P2O5 CaO F CO2 SiO2 Moisture Inerts Total



Percentage 34.35% 52.65% 3.98% 4.00% 1.97% 1.00% 2.05% 100.00%



Flow rate = 23801 kg/hr. Possible compounds in rock are: CaO + CO2 → CaCO3 1 CaO + 2F → CaF2 + O2 2 3CaO + P2 O5 → Ca3 (PO4 )2 Flow rates can be determined as,



25



CHAPTER III CaCO3 =



100 44



Ca3(PO4)2 =



Material & Energy Balance



𝑥 0.04 𝑥 23801 = 2163.73 kg/hr. 310 142



𝑥 0.3435 𝑥 23801 = 17848.24 kg/hr.



78



CaF2 = 38 𝑥 0.0398 𝑥 23801 = 1944.42 kg/hr. SiO2 = 0.0197 x 23801 = 468.88 kg/hr. Moisture = 0.01 x 23801 = 238.01 kg/hr. Inerts = 0.0205 x 23801 = 487.92 kg/hr. Table 3-2: Phosphate rock components



Components Ca3(PO4)2 CaCO3 CaF2 SiO2 Inerts Water Total



Flow rate kg/hr. 17848.24 2163.73 1944.42 468.88 487.92 238.01 23801.01



26



kmol/hr. 57.57 21.64 24.93 7.81 13.22 125.18



CHAPTER III



Material & Energy Balance



3.1.4. Material balance on digester (R-101) Off gases 1503.74 kg/hr.



60% Nitric acid 48850.93 kg/hr.



Phosphate rock 23801.01 kg/hr. 01



02



Cooling water 03 25⁰C, 1 bar 04 05



Reactor product 70498.38 kg/hr.



Cooling water 45⁰C, 1 bar



Figure 3-1: Digestion Reactor (R-101) Theoretical nitric acid required 6 ∗ 63 2 ∗ 63 2 ∗ 63 2 ∗ 63 x (17848.24) + x (2163.73) + 𝑥 (1944.42) − 𝑥 (468.88) 310 100 78 60



Theoretical HNO3 = 26645.96 kg/hr. = 422.95 kmol/hr. With 10% excess 26645.96 + (26645.96 x 0.1) = 29310.56 kg/hr. = 465.25 kmol/hr. Fresh HNO3 required 29310.56 0.6



= 48850.93 kg/hr. = 1085.58 kmol/hr.



Water required 48850.93 – 29310.56 = 19540.37 kg/hr. = 434.23 kmol/hr. Reactions Ca3 (PO4 )2 + 6HNO3 → 3Ca(NO3 )2 + 2H3 PO4



(a)



CaCO3 + 2HNO3 → Ca(NO3 )2 + H2 O + CO2



(b)



CaF2 + 2HNO3 → Ca(NO3 )2 + 2HF



(c)



Ca(NO3 )2 + SiO2 + 6HF → CaSiF6 + 2HNO3 + 2H2 O



(d)



27



CHAPTER III



Material & Energy Balance Table 3-3: Overall balance on R-101



Components Ca3(PO4)2 CaCO3 CaF2 HNO3 Inerts SiO2 H2O Ca(NO3)2 H3PO4 CO2 NOx HF CaSiF6 Sub Total Total



Material in Stream 01 Stream 02



Material out Stream 04 Off gases kg/hr.



17848.24 2163.73 1944.42 48850.93 487.92 468.88 238.01



17468.87 487.92 12809.03 27025.60 11284.69 952.04 492.32 59.38



23801.01 48850.93 72002.12



1422.27 70498.38 1503.74 72002.12



3.1.5. Material balance on centrifuge (F-101) Inert material and silica is removed in centrifuge. Solid particles settles down and are separated. Water 10978.13 kg/hr. 06



Filtrate 68588.19 kg/hr.



Slurry 70498.34 kg/hr.



08



04



07



Sludge 1910.19 kg/hr.



Figure 3-2: Inerts centrifuge (F-101)



28



CHAPTER III



Material & Energy Balance Table 3-4: Overall balance on centrifuge (F-101)



Components HNO3 Inerts H2O Ca(NO3)2 H3PO4 CaSiF6 Sub Total Total



Material in Stream 04 Stream 06



Material out Stream 07 Stream 08 kg/hr. 17468.87 17468.87 487.92 487.92 12809.03 10978.13 23787.18 27025.60 27025.60 11284.69 11284.69 1422.27 1422.27 70498.38 10978.13 1910.19 79566.32 81476.51 81476.51



3.1.6. Material balance on crystallizer (CR-101) Inside the crystallizer, -50C is maintained to achieve 90% water solubility in the final NP product. Crystals of calcium nitrate will form inside the crystallizer. Crystallizer efficiency is 70%.



Inlet Slurry 79566.32 kg/hr.



Coolant in. -15⁰C



13



Coolant out 22⁰C



14



Figure 3-3: Calcium nitrate crystallizer



29



Crystals + liquor 79566.32 kg/hr.



CHAPTER III



Material & Energy Balance Table 3-5: Overall balance on crystallizer



Material in Stream 13



Components



Material out Stream 14 kg/hr.



HNO3 H2O Ca(NO3)2 H3PO4 Ca(NO3)2.4H2O Total



17468.87 23787.18 27025.60 11284.69



17468.87 10978.13 8107.68 11284.69 31726.97 79566.32



79566.32



3.1.7. Material balance on centrifuge (F-102) Calcium nitrate tetra hydrate crystals are removed and get stored. Calcium nitrate can further used either as a fertilizer or in the manufacturing of calcium ammonium nitrate (CAN). Mother liquor move towards further processing. Mother liquor 47839.37 kg/hr.



Crystals + liquor 79566.32 kg/hr.



16



15



17



Calcium nitrate crystals 31726.97 kg/hr.



Figure 3-4: CN centrifuge (F-102) Table 3-6: Overall balance on CN centrifuge (F-102)



Components



Material in Stream 15



HNO3 Ca(NO3)2.4H2O H2O Ca(NO3)2 H3PO4 Sub Total Total



17468.87 31726.97 10978.13 8107.68 11284.69 79566.32 79566.32



30



Material out Stream 17 Stream 16 kg/hr. 17468.87 31726.97 10978.13 8107.68 11284.69 31726.97 47839.37 79566.32



CHAPTER III



Material & Energy Balance



3.1.8. Material balance on neutralizer (R-102) Off gases 840.47 kg/hr. Mother liquor 47839.37 kg/hr.



Ammonia gas 8352.23 kg/hr.



19



25



Cooling water 21 25⁰C, 1 bar 27 28



NP solution 55351.57 kg/hr.



Cooling water 45⁰C, 1 bar



Figure 3-5: Neutralizer reactor (R-102)



Reactions HNO3 + NH3 → NH4 NO3



(e)



Ca(NO3 )2 + H3 PO4 + 2NH3 → CaHPO4 + 2NH4 NO3



(f)



H3 PO4 + NH3 → NH4 H2 PO4



(g)



Ammonia required 1 ∗ 17 1 ∗ 17 2 ∗ 17 x (17468.87) + x (11284.69) + 𝑥 (8107.68) 63 98 164



Ammonia required = 8352.23 kg/hr. Reactions analysis e). HNO3 + NH3 → NH4 NO3 Table 3-7: Reaction (e) analysis



Input, kg/hr. Unreacted, kg/hr. Generation, kg/hr. Consumption, kg/hr.



HNO3



17468.87



NH3 NH3



8352.27 3638.45



NH4NO3 HNO3 NH3



22182.69 17468.87 4713.82



25821.14 3638.45 22182.69 22182.69 25821.14



Output, kg/hr.



31



CHAPTER III



Material & Energy Balance



f). Ca(NO3 )2 + H3 PO4 + 2NH3 → CaHPO4 + 2NH4 NO3 Table 3-8: Reaction (f) analysis



Inputs, kg/hr.



Unreacted, kg/hr. Generation, kg/hr.



Consumption, kg/hr.



H3PO4 NH3 Ca(NO3)2 H3PO4 NH3 CaHPO4 NH4NO3 H3PO4 NH3 Ca(NO3)2



11284.69 3638.45 8107.68 6439.86 1957.59 6723.44 7909.93 4844.83 1680.86 8107.68



23030.82



8397.45 14633.37



14633.37 23030.82



Output, kg/hr. g). H3 PO4 + NH3 → NH4 H2 PO4 Table 3-9: Reaction (g) analysis



Input, kg/hr. Unreacted, kg/hr. Generation, kg/hr. Consumption, kg/hr.



H3PO4 NH3 NH3 NH4H2PO4 H3PO4 NH3



6439.86 1957.59 840.47 7556.98 6439.86 1117.12



8397.45 840.47 7556.98 7556.98 8397.45



Output, kg/hr. Table 3-10: Overall balance on R-102



Components Ca(NO3)2 HNO3 H2O H3PO4 NH3 CaHPO4 NH4NO3 NH4H2PO4 Sub Total Total



Material in Material out Stream 19 Stream 25 Stream 27 Off gases kg/hr. 8107.68 17468.87 10978.13 10978.13 11284.69 8352.23 840.47 6723.44 30092.62 5556.98 47839.37 8352.23 55351.17 840.47 56191.64 56191.64



32



CHAPTER III



Material & Energy Balance



3.1.9. Material balance on evaporator (E-101) Steam 201⁰C, 16 bar



32



29



Water evaporated 10978.13 kg/hr.



NP solution 55351.57 kg/hr.



27



Concentrated NP 44373.04 kg/hr. 31



30



Condensate 201⁰C, 16 bar



Figure 3-6: Evaporator (E-101) Table 3-11: Overall balance on evaporator (E-101)



Components CaHPO4 NH4NO3 H2O NH4H2PO4 Sub Total Total



Material in Stream 27 6723.44 30092.62 10978.13 5556.98 55351.17 55351.17



Material out Stream 32 Stream 31 kg/hr. 6723.44 30092.62 10978.13 5556.98 10978.13 44373.04 55351.17



33



CHAPTER III



Material & Energy Balance



3.2. Energy Balance Table 3-12: Basis for energy balance [5]



Basis



Ambient Temperature Time of Operation Ambient Pressures State of H20 at 25⁰C



25⁰C 1 hr. 1 atm Liquid



3.2.1. Energy balance on digester (R-101) Off gases 70⁰C, 1 bar 1503.74 kg/hr. 60% Nitric acid 25⁰C, 1 bar 48850.93 kg/hr.



Phosphate rock 25⁰C, 1 bar 23801.01 kg/hr. 01



02



Cooling water 25⁰C, 1 bar 03 38644.25 kg/hr. 04



05



Reactor product 70⁰C, 1 bar 70498.38 kg/hr.



Cooling water 45⁰C, 1 bar 38644.25 kg/hr.



Figure 3-7: Digester (R-101)



Following are the reactions: Ca3 (PO4 )2 + 6HNO3 → 3Ca(NO3 )2 + 2H3 PO4



(a)



CaCO3 + 2HNO3 → Ca(NO3 )2 + H2 O + CO2



(b)



CaF2 + 2HNO3 → Ca(NO3 )2 + 2HF



(c)



Ca(NO3 )2 + SiO2 + 6HF → CaSiF6 + 2HNO3 + 2H2 O



(d)



There are numerous methods to do energy balance on reactor but we have to follow the optimum path for our conditions. As there are multiple reactions involve in our process so we have two choices to do the energy balance. [6] 1. By heat of reaction method 2. By heat of formation method The heat of reaction method is good in case when there is a single reaction. If there are multiple reactions then it is better to follow the heat of formation method. Although both methods will give the same result but in heat of formation method there is less chance of error. So we will follow the heat of formation method for enthalpy calculation on our reactor. [6] Reaction temperature = 70⁰C = 343K. 34



CHAPTER III



Material & Energy Balance



Heat duty = Q = ∑outlet(Hi Fi ) − ∑inlet(Hj Fj ) Inlet streams T



Hi = Hr + ∫ Cp∆T Tref



Hf = Heat of formation Calcium phosphate H⁰ = Hf + Cp(T-Tref) H⁰ = -4.14E+06 + Cp(298-298) H⁰ = -4.14E+06 kJ/kmol H = H⁰ x molar flow rate of calcium phosphate = -2.38E+08 kJ/hr. Calcium carbonate H⁰ = Hf + Cp(T-Tref) H⁰ = -1.21E+06 + Cp(298-298) H⁰ = -1.21E+06 kJ/kmol H = H⁰ x molar flow rate of calcium carbonate = -2.61E+07 kJ/hr. Calcium fluoride H⁰ = Hf + Cp(T-Tref) H⁰ = -1.21E+06 + Cp(298-298) H⁰ = -1.21E+06 kJ/kmol H = H⁰ x molar flow rate of calcium fluoride = -3.02E+07 kJ/hr. Silicon dioxide H⁰ = Hf + Cp(T-Tref) H⁰ = -8.51E+05 + Cp(298-298) H⁰ = -8.51E+05 kJ/kmol H = H⁰ x molar flow rate of silicon dioxide = -6.65E+07 kJ/hr. Nitric acid H⁰ = Hf + Cp(T-Tref) H⁰ = -1.73E+05 + Cp(298-298) H⁰ = -1.73E+05 kJ/kmol H = H⁰ x molar flow rate of nitric acid = -1.34E+08 kJ/hr. 35



CHAPTER III



Material & Energy Balance



Total inlet enthalpy = ∑inlet(Hj Fj ) = -4.95E+08 kJ/hr. Outlet streams T



H⁰ = Hr + ∫T



ref



Cp∆T



Calcium nitrate H⁰ = (-9.37E+05) + 205.07(343-298) H⁰ = -9.27E+05 kJ/kmol H = H⁰ x flow rate of calcium nitrate = -1.96E+08 kJ/hr. Phosphoric acid H⁰ = (-1.29E+06) + 117.00(343-298) H⁰ = -1.29E+06 kJ/kmol H = H⁰ x flow rate of phosphoric acid = -1.48E+08 kJ/hr. Hydrogen fluoride H⁰ = (-2.68E+05) + 28.38(343-298) H⁰ = -2.67E+05 kJ/kmol H = H⁰ x flow rate of hydrogen fluoride = -7.93E+05 kJ/hr. Water H⁰ = (-2.86E+05) + 91.88(343-298) H⁰ = -2.82E+05 kJ/kmol H = H⁰ x flow rate of water = -2.00E+08 kJ/hr. Carbon dioxide H⁰ = (-3.94E+05) + 38.96(343-298) H⁰ = -3.92E+05 kJ/kmol H = H⁰ x flow rate of carbon dioxide = -8.48E+06 kJ/hr. Calcium hexafluorosilicate H⁰ = (-2.68E+06) + 88.66(343-298) H⁰ = -2.68E+06 kJ/kmol H = H⁰ x flow rate of calcium hexafluorosilicate = -2.09E+07 kJ/hr. Nitric acid H⁰ = (-1.73E+05) + 141.41(343-298)



36



CHAPTER III



Material & Energy Balance



H⁰ = -1.67E+05 kJ/kmol H = H⁰ x flow rate of calcium hexafluorosilicate = -2.61E+06 kJ/hr. Total outlet enthalpy = ∑outlet(Hi Fi ) = -5.78E+08 kJ/hr. Heat duty = Q = ∑outlet(Hi Fi ) − ∑inlet(Hj Fj ) = -8.22E+06 kJ/hr. Heat removed by coolant = 8.22E+06 kJ/hr. Inlet water temperature = 25⁰C = 298K Outlet water temperature = 45⁰C = 318K Cp of water = 4.18 kJ/kg-K [7] Mass flow rate of water = m = Q⁄Cp∆T = 38644.25 kg/hr. 3.2.2. Energy balance on heat exchanger (H-101) 08



Process liquid mixture 70⁰C 79566.32 kg/hr.



09



Cold water 25⁰C 71027.71 kg/hr.



Cold water 40⁰C 71027.71 kg/hr.



11



Process liquid mixture 45⁰C 79566.32 kg/hr. 10



Figure 3-8: Heat exchanger (H-101)



Component Ca(NO3)2 H3PO4 H2O HNO3 Total



Flow rate kg/hr. kmol/hr. 27025.60 164.79 11284.69 115.15 23787.16 1321.51 17468.87 277.28 79566.32 1878.73



Percentage % 33.97 14.18 29.90 21.96 100



37



Cp kJ/kmol-K 135.06 84.35 64.33 80.80



Actual Cp kJ/kmol-K 45.88 11.96 19.23 17.74 94.82



CHAPTER III



Material & Energy Balance



Heat duty = Q = mCp∆T Heat duty = Q = 1878.73*94.82*(318-343) = -4.45E+06 kJ/hr. Inlet temperature of cold water = 25⁰C = 298K Outlet temperature of cold water = 40⁰C = 313K Cp of water = 4.18 kJ/kg-K [7] Mass flow rate of water = m = Q/Cp∆T = 71027.71 kg/hr. 3.2.3. Energy balance on crystallizer (CR-101) Liquid mixture 45⁰C, 1 bar 79566.32 kg/hr.



Coolant in. -15⁰C, 1 bar 57751.16 kg/hr.



13



Coolant out 22⁰C, 1 bar 57751.16 kg/hr.



14



Crystals + liquor 0⁰C, 1 bar 79566.32 kg/hr.



Figure 3-9: Crystallizer (CR-101)



Liquid mixture enters at 45⁰C. Ammonia-water mixture is used as a coolant to crystallize calcium nitrate. Weighted Cp of liquid mixture at crystallizer input = 84.60 kJ/kmol-K Enthalpy of inlet stream = mCp(T-Tref) = 1878.73*84.60(318-298) = 3.09E+06 kJ/hr. Latent heat of crystallization of calcium nitrate = -21401.6 kJ/kmol [8] Flow rate of crystals = 31726.97 kg/hr. = 134.44 kmol.hr. Heat of crystallization =Hc = 134.44 x -21401.6 = -2.88E+06 kJ/hr. Component



Flow rate kg/hr. kmol/hr. Ca(NO3)2.4H2O 31726.97 134.44 Ca(NO3)2 8107.68 49.44 H3PO4 11284.69 115.15 H2O 10978.13 609.90 HNO3 17468.87 277.28 Total 79566.32 1186.20



38



Percentage % 39.87 10.19 14.18 13.80 21.96 100.00



Cp kJ/kmol-K 154.45 107.51 87.40 72.19 84.10



Actual Cp kJ/kmol-K 61.58 10.96 12.39 9.96 18.47 113.36



CHAPTER III



Material & Energy Balance



Total enthalpy of outlet stream = mCp∆T + Hc Enthalpy of outlet stream = 1186.20*113.36(273-298) + (-2.88E+06) Qout = -6.24E+06 kJ/hr. Heat removed by coolant = Q = Qout – Qin = -9.33E+06 kJ/hr. Inlet temperature of coolant = -15⁰C = 258K Outlet temperature of coolant = 22⁰C = 295K Cp of coolant = 4.37 kJ/kg-K [7] Mass flow rate of coolant = Q/Cp∆T = 57751.56 kg/hr. 3.2.4. Energy balance on preheater (H-102) 16



Process liquid mixture 0⁰C, 2 bar 47839.37 kg/hr.



18



Steam 148⁰C, 4 bar 5013.70 kg/hr.



Steam 148⁰C, 4 bar 5013.70 kg/hr.



20



Process liquid mixture 120⁰C, 2 bar 47839.37 kg/hr. 19



Figure 3-10: Preheater (H-102)



Component Ca(NO3)2 H3PO4 H2O HNO3 Total



Flow rate kg/hr. kmol/hr. 8107.68 49.44 11284.69 115.15 10978.13 609.90 17468.87 277.28 47839.37 1051.77



Heat duty = Q = mCp∆T 39



Percentage % 16.94 23.58 22.95 36.52 100



Cp kJ/kmol-K 95.06 86.38 75.45 84.73



Actual Cp kJ/kmol-K 16.10 20.37 17.32 30.94 84.73



CHAPTER III



Material & Energy Balance



Heat duty = Q = 1051.77*84.73*(393-273) = 1.07E+07 kJ/hr. Steam at 148⁰C and 4 bar Latent heat of condensation of steam = ⅄ = -2132.95 kJ/kg [7] Mass flow rate of steam = m = Q/⅄ = 5013.70 kg/hr. 3.2.5. Energy balance on preheater (H-103) 16



Ammonia 19⁰C, 2 bar 8352.23 kg/hr.



18



Steam 148⁰C, 4 bar 3883.78 kg/hr.



Steam 148⁰C, 4 bar 3883.78 kg/hr.



Ammonia 120⁰C, 2 bar 8352.23 kg/hr.



19



Figure 3-11: Preheater (H-103)



Cold fluid = ammonia Inlet temperature = 19⁰C = 292K Outlet temperature = 120⁰C = 393K Cp of ammonia at 69.5⁰C = 9.82 kJ/kg-K [8] Flow rate of ammonia = 8352.23 kg/hr. Heat duty = Q = mCp∆T Q = 8352.23*9.82(393-292) = 8.28E+06 kJ/hr. Latent heat of condensation of steam = ⅄ = -2132.95 kJ/kg [7] Mass flow rate of steam = Q/⅄ = 3883.78 kg/hr.



40



20



CHAPTER III



Material & Energy Balance



3.2.6. Energy balance on neutralizer (R-102) Reactions HNO3 + NH3 → NH4 NO3



(e)



H3 PO4 + NH3 → NH4 H2 PO4



(f)



Ca(NO3 )2 + H3 PO4 + 2NH3 → CaHPO4 + 2NH4 NO3



(g)



Off gases 120⁰C, 2 bar 840.47 kg/hr. Ammonia gas 120⁰C, 2 bar 8352.23 kg/hr.



Mother liquor 120⁰C, 2 bar 47839.37 kg/hr. 19



25



Cooling water 25⁰C, 1 bar 21 40722.69 kg/hr. 27



28



Cooling water 45⁰C, 1 bar 40722.69 kg/hr.



Figure 3-12: Neutralizer reactor (R-102)



Reactor temperature = 120⁰C = 393K Inlet streams T



Hi = Hr + ∫ Cp∆T Tref



Hf = Heat of formation Nitric acid H⁰ = Hf + Cp(T-Tref) H⁰ = -1.73E+05 + 86.61(343-298) H⁰ = 1.81E+05 kJ/kmol H = H⁰ x molar flow rate of nitric acid = 5.03E+07 kJ/hr. Phosphoric acid H⁰ = Hf + Cp(T-Tref) H⁰ = -1.29E+06 + 87.4(343-298) H⁰ = -1.29E+06 kJ/kmol H = H⁰ x molar flow rate of phosphoric acid = -1.48E+08 kJ/hr.



41



NP solution 120⁰C, 2 bar 55351.57 kg/hr.



CHAPTER III



Material & Energy Balance



Calcium nitrate H⁰ = Hf + Cp(T-Tref) H⁰ = -9.37E+05 + 32.27(343-298) H⁰ = -9.35E+05 kJ/kmol H = H⁰ x molar flow rate of calcium nitrate = -4.62E+07 kJ/hr. Ammonia H⁰ = Hf + Cp(T-Tref) H⁰ = -4.62E+04 + 8.12(343-298) H⁰ = -4.58E+04 kJ/kmol H = H⁰ x molar flow rate of ammonia = -2.25E+07 kJ/hr. Total inlet enthalpy = ∑𝑖𝑛𝑙𝑒𝑡 (𝐻𝑗 𝐹𝑗 ) = -1.67E+06 kJ/hr. Outlet streams 𝑇



H⁰ = 𝐻𝑟 + ∫𝑇



𝑟𝑒𝑓



𝐶𝑝∆𝑇



Ammonium nitrate H⁰ = (-3.39E+05) + 209.54(343-298) H⁰ = -3.30E+05 kJ/kmol H = H⁰ x flow rate of ammonium nitrate = -1.24E+08 kJ/hr. Calcium hypophosphate H⁰ = (-4.33E+05) + 122.23(343-298) H⁰ = -4.27E+05 kJ/kmol H = H⁰ x flow rate of calcium hypophosphate = -2.11E+07 kJ/hr. Ammonium biphosphate H⁰ = (-3.43E+05) + 169.16(343-298) H⁰ = -3.35E+05 kJ/kmol H = H⁰ x flow rate of ammonium biphosphate = -1.62E+07 kJ/hr. Water H⁰ = (-2.85E+05) + 75.6(343-298) H⁰ = -2.82E+05 kJ/kmol H = H⁰ x flow rate of water = -1.72E+08 kJ/hr.



42



CHAPTER III



Material & Energy Balance



Total outlet enthalpy = ∑outlet(Hi Fi ) = -3.33E+06 kJ/hr. Heat duty = Q = ∑outlet(Hi Fi ) − ∑inlet(Hj Fj ) = -1.67E+06 kJ/hr. Heat removed by coolant = 1.67E+06 kJ/hr. Inlet water temperature = 25⁰C = 298K Outlet water temperature = 45⁰C = 318K Cp of water = 4.18 kJ/kg-K [7] Mass flow rate of water = m = Q⁄Cp∆T = 40722.69 kg/hr. 3.2.7. Energy balance on evaporator (E-101) Steam 201⁰C, 16 bar 23430.19 kg/hr. 32



29



Water evaporated 10978.13 kg/hr.



NP solution 55351.57 kg/hr.



27



Concentrated NP 44373.04 kg/hr. 31



30



Condensate 201⁰C, 16 bar 23430.19 kg/hr.



Figure 3-13: Evaporator (E-101)



Operating temperature = 175⁰C = 448K Enthalpy of inlet stream = mCp(T-Tref) Enthalpy of inlet stream = 1083.81*166.85(393-298) = 1.72E+07 kJ/hr. Latent heat of steam = 3.47E+04 kJ/kmol [7] Enthalpy of outlet stream = mCp(T-Tref) + (m⅄)water 43



CHAPTER III



Material & Energy Balance



Enthalpy of outlet stream = 1083.81*198.38(448-298) + (10978.13*2256) = 6.24E+07 kJ/hr. Heat duty = Q = Hout - Hin = 4.52E+07 kJ/hr. Steam flow rate = Q/⅄ = 4.52E+07/3.47E+04 = 1301.68 kmol/hr. = 23430.19 kg/hr.



44



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



CHAPTER # 4 Equipment Design



45



CHAPTER IV



Equipment Design



4.1. Reactor (R-101) 4.1.1. Selection of reactor Selected reactor for dissolution of phosphate rock is “Continuous Stirred Tank Reactor (CSTR)” The main reasons supporting the logical selection of CSTR are, [9] 1. 2. 3. 4.



Large scale application Economical (reduced operation cost) Control of product quality Better temperature control



4.1.2. Design of reactor (R-101) Off gases 70⁰C, 1 bar 1503.74 kg/hr. 60% Nitric acid 25⁰C, 1 bar 48850.93 kg/hr.



Phosphate rock 25⁰C, 1 bar 23801.01 kg/hr. 01



02



Cooling water 25⁰C, 1 bar 03 38644.25 kg/hr. 04



05



Cooling water 45⁰C, 1 bar 38644.25 kg/hr.



Figure 4-1: Digestion reactor (R-101)



Design equation of CSTR



V=



FA0 X −rA



[9]



Main reaction Ca3 (PO4 )2 + 6HNO3 → 3Ca(NO3 )2 + 2H3 PO4 Conversion = 99% Let A = Calcium phosphate B = Nitric acid FA0 = 57.57 kmol/hr. FB0 = 1085.58 kmol/hr. VA0 =



mA0 17848.24 m3 = = 5.57 ρA0 3200 hr



46



Reactor product 70⁰C, 1 bar 70498.38 kg/hr.



CHAPTER IV VB0



Equipment Design



mB0 48850.93 m3 = = = 41.39 ρB0 1180 hr



V0 = VA0 + VB0 = 5.57 + 41.39 = 46.97 CA0 =



FA0 57.57 = = 1.225 kmol⁄m3 V0 46.97



CA0 =



FB0 1085.58 = = 23.18 kmol⁄m3 V0 46.97



m3 hr



For irreversible reactions, β



−rA = k A CAα CB



As HNO3 is in excess so CB = CB0 β



−rA = k A CAα CB0 −rA = K ′ CAα β



Where K ′ = k A CB0 Developing rate law Mole balance equation:



dNA dt



= −rA V



Rate law: −rA = k ′ CAα CA =



NA V0



Combining the equations dNA = −k ′ CAα V0 dt N d( VA ) 0



dt −



= −k ′ CAα



dCA = k ′ CAα dt



Taking ln on both sides, ln(−



dCA ) = ln(k ′ ) + αln(CA ) dt



47



CHAPTER IV



Equipment Design



Concentration-time data is given as: CA x 10-3 (mol/dm3) 1225 807.8 538.5 369.2 265.1 191.6



Time (min) 0 1 2 3 4 5 Using finite difference method [10] (



dCA ) dt t0



(



dCA



(



dCA



(



dCA



(



dCA



(



dCA



dt



dt



dt



dt



dt



=



−3𝐶𝐴0 +4𝐶𝐴1 +𝐶𝐴2 2∆𝑡



) t1 =



CA2 −CA0



) t2 =



CA3 −CA1



) t3 =



CA4 −CA2



) t4 =



CA5 −CA3



) t5 =



CA3 −4CA4 +3CA5



= −343.25 x 10−3



2∆t



2∆t



2∆t



2∆t



= −219.30 x 10−3 = −136.70x 10−3 = −88.80 x 10−3



2∆t



Time (min) 0 1 2 3 4 5



= −491.15 x 10−3



= −58.20 x 10−3



CA x 10-3 (mol/dm3) 1225 807.8 538.5 369.2 265.1 191.6



-(dCA/dt) x 10-3 (mol/dm3-min) 491.15 343.25 219.30 136.70 88.80 58.20



48



ln(CA)



ln(-(dCA/dt))



7.11 6.94 6.75 6.45 5.86 5.14



6.20 5.84 5.39 4.92 4.49 4.06



CHAPTER IV



Equipment Design 7 6



ln(-(dCA/dt))



5 4 3 2 1 0 0



1



2



3



4



5



6



7



8



ln(CA)



Figure 4-2: Log-log graph of finite differential method



From graph Order of reaction = slope of graph = 𝛼 = 1.04 = 1 Ln(k’) = y-intercept of graph = -1.495 k’ = 0.22 min-1 CB0 = 23.18 mol/dm3 k′



K=C



B0



dm3



0.22



= 23.18 = 0.009 mol.min



Rate of reaction = -rA = 0.009 CACB CA = CA0(1-X) CB = CA0(ƟB – 6X) ƟB =



𝐶𝐵0 ⁄𝐶 = 23.10⁄1.225 = 18.86 𝐴0



Rate law can be written as: -rA = CA0(1-X) x CA0(ƟB – 6X) -rA = 1.225 x (1-0.99) x 1.225 x (18.86 – (6 x 0.99)) = -0.0019 x 60 = 0.113 mol-dm-3-hr-1 Volume of reactor =



FA0 X⁄ 3 −rA = 48.92 m



Space time = V⁄V = 48.92⁄46.97 = 1.04 hr. 0



Optimum L/D ratio = 1.4, L = 1.4D [11]



49



CHAPTER IV



Equipment Design



2 πD2 (1.4D)⁄ Volume of reactor = V = πD L⁄4 = 4



Diameter of reactor = D = 3.54 m Length of reactor = L = 1.4D = 4.96 m 4.1.3. Design of cooling jacket Following are the cooling arrangements for continuous stirred tank reactors: 1. Jackets 2. Internal coils 5. External coils Selection of Jacket Jacket provides the optimum method of heating and cooling process vessel in terms of control, efficiency and product quality. [12] Now there are three main types of jackets available 1. Spiral baffle Jacket 2. Half pipe coil Jacket 3. Dimple jacket Jacket selection Factor to be consider when selecting the type of jacket use are listed below: [13] 1. Cost in the terms of cost the design can be ranked, form cheapest to cost expensive    



Simple no baffles Agitation nozzles Dimple Jacket Half-pipe jacket



2. Heat transfer rate required; select a spirally baffled or half-pipe jacket if high rate are required. 3. Pressure as a rough guide, the pressure rating of the designs can be taken as:  Jackets, up to 10bar.  Half-pipe up to 40bar.  Dimple jacket up to 70bar. So, dimple jackets would be used for high pressure. Dimple jacket is less expensive and give low pressure drop than spiral and half-pipe coil jacket. So the selected jacket is Dimple baffle jacket. Cooling Jacket Calculations Q = UA∆t U = 350 W/m2.⁰C [14] Assuming 80% area of CSTR is covered with jacket 50



CHAPTER IV



Equipment Design



Aj = 𝜋 D2/4+ 𝜋 DL(0.8) Aj = 55.4 m2 Q = -8220000 kJ For jacket ho Dt /k = 0.85(ρxD2/μ )0.33 (Cμ/k)0.66(μ/μs)0.14 Assume, (μ/μs) =1 ho = 425 W/m2C Tank side hD/λ = 0.73(ρD2/μ )0.33 (Cμ/k)0.66(μ/μs)0.1 h =1309 W/m2.⁰C U = (ho×h)/(ho+h) = 320W/m2-ºC Ud = Q/A∆t Ud = 340 W/m2-ºC 4.1.4. Design of impeller Impeller selection Table 4-1: Types of impeller



Factors/Types



Propellers



Paddles



Turbine



Viscosity



For low to moderate viscous liquids



For moderate viscous liquids



For low to high viscous liquids



Flow pattern



Types No. of blades RPM ranges



For axial flow



For tangential flow



Square pitched marine propellers 3-blade,4-blade toothed 400-800,11501750



Flat paddle, anchor agitator



For radial and tangential flow, sometimes axial flow Vertical flat curved, and pitched blade



2 and 4 bladed paddles



2-8 blades



20-150



50-250



51



CHAPTER IV



Equipment Design



The selected impeller is disk style flat blade turbine which is commonly referred as Ruhstan impeller, a radial flow impeller because, 1. The weighted viscosity of mixture at mixing temperature is 2.519 cP which lies in the range of impeller. 2. It can be operated at reasonable speed. 3. Wide range of applications. 4. Maximum radial flows no back mixing. 5. Less power requirement. 6. Promote heat transfer between the liquid and a coil or jacket 7. High mass transfer between phases



Figure 4-3: Rushton turbine



Diameter of reactor = 3.54 m Design calculations The listed standard proportions, nonetheless, are widely accepted and are the basis of many published correlations of agitator performance: Da Dt



= 1/3



Da=1.19m H Dt



=1



H= 3.58m J = 1/12 Dt J = 0.298m E Dt



= 1/3



E = 1.19m W Da



= 1/5



W = 0.238m L Da



= 1/4



L = 0.29m



52



CHAPTER IV



Equipment Design



Where, Da = Diameter of impeller Dt = Tank diameter H = Depth of liquid in tank J = Width of baffles E = Hight of impeller above vessel flow W = Impeller width L = Length of impeller blade



Figure 4-4: Dimensions of impeller



Speed of impeller For turbine vertical blade with four baffles, Pumping number= Nq = 0.70-0.85 [14] Power number = Np = 3-5 [14]



Figure 4-5: Graph b/w Reynolds number and pumping number (a)



53



CHAPTER IV



Equipment Design



Form graph taking Nq = 0.75 Reynolds number = 8000 Where, Re=Da2nρ/μ Form here, the speed of the impeller = n = 2.56rev/s =153 rev/min. Degree of mixing calculations The degree of mixing in any liquid mixing system is defined in terms of agitator’s tip speed, as given by the following formula: TS = πDa * rpm of impeller Where, TS = Tip speed of impeller Da = Diameter of impeller By putting the values, we are left with, TS = 571.69 m/min Power calculations



Figure 4-6: Graph b/w \Reynolds number and power number (b)



54



CHAPTER IV



Equipment Design



From graph, power number = Np = 3 Np = P⁄n3 ρD5 From here, Power = P = 2594 W = 2.6 kW



55



CHAPTER IV



Equipment Design Table 4-2: Specification sheet of digestion reactor (R-101)



Specification Sheet Identification Item



Reactor (R-101)



Type



Continuous Stirred Tank Reactor



Function: Digestion of phosphate rock by 60% nitric acid. Ca3 (PO4 )2 + 6HNO3 → 3Ca(NO3 )2 + 2H3 PO4 Operating Temperature



70℃



Operation Pressure



1 bar



Residence Time



1.04 hr.



Volume



48.92 m3



Diameter



3.54 m



Length



4.96 m



Impeller power



2.6 kW



56



CHAPTER IV



Equipment Design



4.2. Reactor (R-102) Table 4-3: Specification sheet of neutralizer reactor (R-102)



Specification Sheet Identification Item



Reactor (R-102)



Type



Continuous Stirred Tank Reactor



Function: Neutralization of NP acid by ammonia. HNO3 + NH3 → NH4 NO3 H3 PO4 + NH3 → NH4 H2 PO4 Ca(NO3 )2 + H3 PO4 + 2NH3 → CaHPO4 + 2NH4 NO3 Operating Temperature



120℃



Operation Pressure



2 bar



Residence Time



1.5 hr.



Volume



60.19 m3



Diameter



3.80 m



Length



5.32



57



CHAPTER IV



Equipment Design



4.3. Heat exchanger (H-101) 08



Process liquid mixture 70⁰C 79566.32 kg/hr.



Cold water 25⁰C 71027.71 kg/hr.



Cold water 40⁰C 71027.71 kg/hr.



09



11



10



Process liquid mixture 45⁰C 79566.32 kg/hr.



Figure 4-7: Heat exchanger (H-101)



4.3.1. Thermal design Hot fluid (Product slurry) inlet temperature = T1 = 700C = 154.40F Cold fluid (cold water) inlet temperature = t 1 = 250C = 770F Hot fluid (product slurry) outlet temperature = T2 = 450C = 1130F Cold fluid (cold water) outlet temperature = t 2 = 400C = 1040F Mass flow rate of hot fluid (slurry) = W1 = 79566.32 kg/hr. = 175045.90 lb/hr. Mass flow rate of cold fluid (water) = W2 = 71027.71 kg/hr. = 156260.96 lb/hr. Heat balance Heat inside the exchanger = Q = 4.45E+06 kJ/hr. = 4.22E+06 Btu/hr. Log mean temperature difference Hot fluid 154.4 Higher temp.(0F) 113 Lower temp (0F). 41.4 Difference (0F).



LMTD =



Cold fluid 104 77 45



(𝑇1 − 𝑡1 ) − (𝑇2 − 𝑡2 ) ⁄ 𝑇1−𝑡1 [12] 𝑙𝑛 ( ) 𝑇2−𝑡2



LMTD = 42.84℉



58



Difference (0F) 32.4 36 -3.6



CHAPTER IV



Equipment Design



Corrected LMTD (true temperature) 𝑇 − 𝑇2⁄ R= 1 𝑡2 − 𝑡1 = 1.53 S=



𝑡2 − 𝑡1 ⁄𝑇 − 𝑡 = 0.35 1 1



Temperature correction factor (FT) should be greater than 0.75. From appendix, LMTD correction factor = FT = 0.89 A 1-2 heat exchanger will be satisfactory for the specific conditions. Corrected LMTD = ∆t = 42.84 x 0.89 = 38.13℉. Caloric temperature There is negligible change in viscosity on the cold end of heat exchanger therefore, calculations for design can be done on true temperature. Surface area Value of UD should be in the range of 250-500 Btu/h-ft2-0F. It is always better to assume value of UD too high than too low, so that the final exchanger will just fulfil the requirements. [13] Place the viscous stream (product slurry) on the shell side and less viscous fluid (water) on the tube side. Assume overall heat transfer coefficient = UD = 250 Btu/h-ft2-0F. Area = A =Q⁄U∆t = 4.22E + 06⁄250 x 38.13 = 228.70 ft 2 . Tube Specifications Assume Outside diameter of tube = OD = 3/4 = 0.75ft. Length of tube = L = 16ft. BWG = 16 Surface/lin. ft. = a’ = 0.1963ft. Number of tubes = A⁄La′ = 228.70⁄16 x 0.1963 = 73 tubes Assume 1 in. triangular pitch, With 2 tube passes, 3/4 in. OD and 1 in. triangular pitch, Corrected number of tubes (nearest tube count) = NT = 82 (from appendix) Inside diameter of shell = Ds = 12 in. = 1ft. Corrected area Corrected area = A = NTLa’ = 82 x 16 x 0.1963 = 257.55ft2. 59



CHAPTER IV



Equipment Design



Corrected UD Corrected UD = Q⁄A∆t = 4.22E + 06⁄257.55 (38.13) = 221.99 Btu/h-ft2-0F Shell side (Hot fluid, product slurry)



Tube side (Cold fluid, cold water)



Baffle spacing Assume baffle spacing = 5 in. 1



1



(baffle spacing > 5 (ID) = 5 (12) = 2.4 in.) [12] Clearance = c’ = PT-OD = 1-0.75 = 0.25 ′ Area of shell = As = IDxc b⁄144n



Flow area per tube = a’’ = 0.302 in.2 Number of passes = n = 4 𝑁 𝑎′′ Area of tubes = At = 𝑇 ⁄144𝑛 At = 82x0.302⁄144x2 = 0.09 ft 2



Area of shell = As = 12x0.25x5⁄144x1 = 0.1041 ft 2 Mass Velocity W Gs = 1⁄A = 175045.90⁄0.1041 s = 850904.02 lb⁄ft 2 hr.



156260.96 W1 ⁄A = 0.09 s Gt = 892416.22 lb⁄ft 2 hr.



Gt =



Reynolds number 𝐷𝐺 Re = 𝑒 𝑠⁄𝜇 Equivalent diameter of shell = De = 0.73 in. = 0.061 ft. Fluid viscosity = 𝜇 = 3.13 lb/ft.hr. Re = 0.061𝑥850904.02⁄3.13 = 52583



𝐷𝐺𝑡⁄ 𝜇 Inner diameter = D = 0.620 in. D = 0.0516 ft. Fluid viscosity = 𝜇 = 1.62 Re = 0.0516𝑥892416.22⁄1.62 Re = 68132 Re =



Prandtl number k = 0.37 Btu/hr.ft 2.0F/ft. Cp = 0.646 Btu/lb.0F



k = 0.369 Btu/hr.ft 2.0F/ft.



Cpμ⁄ 1/3 (0.646𝑥3.13 ⁄0.37)1/3 k) = Cpμ⁄ 1/3 20 ( k) = 1.76 Btu/hr.ft . F/ft. (



jH factor jH = 180



jH = 145



60



CHAPTER IV



Equipment Design



Heat transfer coefficient (h) Cpμ⁄ 1/3 20 ho = 𝑗𝐻 𝑘⁄𝐷 ( k) = 1921.0 Btu/hr.ft . F 𝑒



Velocity = u =



𝐺𝑡 ⁄3600𝜌



u = 2.35 ft/s. hi = 700 Btu/hr.ft2.0F hio = ℎ𝑖 𝑥 𝐼𝐷⁄𝑂𝐷 hio = 578 Btu/hr.ft2.0F



Clean overall heat transfer coefficient = Uc = Dirt factor = Rd =



ℎ𝑖𝑜 ℎ0 ⁄ℎ + ℎ = 444 Btu/hr.ft2.0F 𝑖𝑜 0



𝑈𝐶 − 𝑈𝐷 ⁄𝑈 𝑈 = 0.0013 h.ft2.℉/Btu 𝐶 𝐷



Pressure drop calculations Re = 52583



Re = 68132



Friction factor = f = 0.0012



Friction factor = f = 0.00018



Number of crosses = N+1 = 12𝐿⁄𝐵 = 38.5 ∆P1 = De = 12 in. = 1 ft. Specific gravity = s = 1.55 fGs2 Ds (N + 1) ⁄5.22x1010 D s e ∆Ps = 7.47 psi ∆Ps =



fGt2 Ln ⁄5.22x1010 D = 3.84 psi t



v 2⁄ = 0.02 [12] 2g Number of passes = n = 2 Specific gravity = s = 1 2 ∆P2 = 4n⁄s v ⁄2g = 2.32 psi ∆P = 3.84 + 2.32 = 6.16 psi



61



CHAPTER IV



Equipment Design Table 4-4: Specification sheet of heat exchanger (H-101)



Specification Sheet Identification Item Heat Exchanger (H-101) Type 1-2 Shell and Tube Heat Exchanger Function: Cool the process liquid from 70⁰C to 45⁰C. Tube side Shell side Fluid: Cold (Water) Fluid: Hot (Process liquid) Flow rate: 156260.96 lb/hr Flow rate: 175045.90 lb/hr Temperature: 77℉ to 104℉ Temperature:154.4℉ to 113℉ Pressure drop: 6.16 psi Pressure drop: 7.47 psi Tubes: 3/4 in OD. 16 BWG Shell ID:10 inch 53 number of tubes each 16 ft long Baffles spacing: 5 in Passes: 02 Passes: 01 Pitch: 1 in Triangular UD calculated: 221.99 Btu/h.ft2.℉ UD assumed: 250 Btu/h.ft2.℉ Rd= 0.0013 h.ft2.℉/Btu Uc calculated: 444 Btu/h.ft 2.℉



62



CHAPTER IV



Equipment Design



4.4. Preheater (H-102) Table 4-5: Specification sheet of preheater (H-102)



Specification Sheet Identification Preheater (H-102) 1-2 Shell and Tube Heat Exchanger



Item Type



Function: To heat NP acid before entering to neutralizer Tube side



Shell side



Fluid: Hot (Steam)



Fluid: Cold (Process liquid)



Flow rate: 11030.14 lb/hr



Flow rate: 105246.61 lb/hr



Temperature: 298.4℉



Temperature: 32℉ to 248℉



Pressure drop: 2.08 psi



Pressure drop: 8.29 psi



Tubes: 3/4 in OD. 16 BWG



Shell ID: 12 inch



82 number of tubes each 16 ft long



Baffles spacing: 5 in



Passes: 02



Passes: 01



Pitch: 1 in Triangular



UD calculated: 271.19 Btu/h.ft 2.℉



UD assumed: 300 Btu/h.ft 2.℉



Rd: 0.0015 h.ft2.℉/Btu



Uc calculated: 453 Btu/h.ft 2.℉ Corrected area: 257.54 ft2



63



CHAPTER IV



Equipment Design



4.5. Ammonia preheater (H-103) Steam 148⁰C, 4 bar 3883.78 kg/hr. 18



Ammonia 19⁰C, 2 bar 8352.23 kg/hr.



16



Ammonia 19 120⁰C, 2 bar 8352.23 kg/hr.



20



Condensate 148⁰C, 4 bar 3883.78 kg/hr. Figure 4-8: Ammonia preheater (H-103)



Hot fluid (steam) inlet temperature = T1 = 148⁰C = 298.4⁰F Cold fluid (ammonia) inlet temperature = t1 = 19⁰C = 66.2⁰F Hot fluid (steam) outlet temperature = T2 = 148⁰C = 298.4⁰F Cold fluid (ammonia) outlet temperature = t2 = 120⁰C = 248⁰F Flow rate of ammonia = 8352.23 kg/hr. = 18374.91 lb/hr. Flow rate of steam = 3883.78 kg/hr. = 8544.32 lb/hr. Heat balance Heat duty = Q = 8.28E+06 kJ/hr. = 8.26E+06 Btu/hr. LMTD Hot fluid (℉) 298.4 298.4 0



Temperatures High temperature Low temperature Difference



64



Cold fluid (℉) 248 66.2 181.8



Difference (℉) 50.4 232.2 -181.8



CHAPTER IV



Equipment Design



Δt = (Δt2 - Δt1)/ln(Δt2/ Δt1) Δt = 119.14 ℉ Tc and tc: A check of both streams shows that none of the fluids is viscous at the cold end and the temperature difference and temperature ranges are moderate. The coefficients may accordingly be evaluated from properties at the average temperatures T mean and tmean. So we assume (μ/μw )0.14 =1, because the viscosities are not great enough to introduce an error. Hot Fluid: annulus (Steam)



Cold Fluid: Inner Pipe (ammonia)



Flow area



Flow area



D2 = 4.026’’



D = 3.068 in.



= 4.026’’/12



D = 3.068/12



= 0.33 ft.



D = 0.26 ft.



D1 = 3.50’’ = 3.50’’/12 = 0.29 ft. Area aa = ᴫ(D22-D12)/4



ap =



aa= 3.14*(0.332-0.292)/4 =



=0.02 ft2



πD2 4 3.14×0.252 4



= 0.05 ft 2



Equivalent diameter De=(D22-D12)/ D1 De=(0.342-0.292)/0.29 =0.09ft. Mass velocity



Mass velocity:



Ga = W/a



Gp = a



w p



=



18374.91 0.05



= 282476 lb/hr.ft2



Ga = 8544.32/0.02 = 70495 lb/hr.ft2 Reynolds number



Reynolds number:



At Tmean = 298.4 F



At 157.1⁰F



μ = 0.051 cP × 2.42



μ = 0.09 cP



μ = 0.09×2.42



65



CHAPTER IV



Equipment Design



µ = 0.123 lb/ft.hr Rea = De Ga/ μ



μ = 0.217 lb/ft.hr Rep =



Rea = 0.09*70495/0.123 Rep =



DGp μ 0.26×282476 0.217



= 53836



= 331588 jh = 390



jh = 620



Prandtl number



Prandtl number



At tmean = 298.4℉



At tmean = 157.1℉



c = 0.45 Btu/lb. ℉



c = 0.52 Btu/lb. ℉



k = 0.016 Btu/hr.ft. ℉



k = 0.045 Btu/hr.ft. ℉



3



cμ



3



√k = √



0.454×0.123 0.016



3



cμ



= 1.51 k 3 cμ



3



√k = √



0.52×0. 0.045



= 1.36 μ



hi = jh d √ k (μ )0.14 w



= 1500 Btu/hr.ft2.℉



k 3 cμ



μ



hi = jh d √ k (μ )0.14 w



hi = jh*(k/D)*(cμ/k)1/3*(μ/μw)0.14 hi =



620×0.045×1.36×1.0 0.26



= 148.44 Btu/hr.ft2.℉ Correct hi to the surface at the OD ID



hio = hi × OD =148.44 ×



3.068 3.50



= 130.12 Btu/hr.ft2.℉ Clean overall coefficient, Uc h ×h



Uc = hio +ho io



o



66



CHAPTER IV



Equipment Design



130.12×1500



Uc = 130.12+1500 = 119.73 Btu/hr.ft2.℉ Design overall coefficient, UD 1 1 = + Rd UD UC 1 1 = + 0.002 UD 120 UD = 96.60 Btu/hr.ft2.℉ Required surface:



A= A=



Q UD ×∆t



8.26E + 06 96.60 × 119.14



A = 110.07 ft2 For 3’’ IPS standard pipe there are 0.917 ft2 of external surface per foot length. Required length =



110.01 0.917



= 119.94 lin. ft.



This can be fulfilled by connecting three 20-ft hairpins in series (3× 40 = 120) ft. The surface supplied will actually be A’ = 120 × 0.917 = 110.04 ft2 Actual design coefficient is, UD =



Q A′ × ∆t



UD =



8260000 110.04 × 119



= 109.13 Btu/hr.ft2. ℉ Rd =



UC − UD UC × UD



Rd =



119.73 − 109.13 119.73 × 109.13



R d = 0.0031 hr.ft2.℉/Btu



67



CHAPTER IV



Equipment Design



Pressure Drop Calculations Annulus: Steam De = 0.09 ft. Rea ′ =



De′ Ga μ



= 53836 0.264



f = 0.0035 + Re0.42 a



0.264



f = 0.0035 + 538360.42 f = 0.0062 ρ = 61.23 lb/ft3 4fGa2 L 2gρ2 De ′ 4 × 0.0062 × 704952 × 120 ∆Fa = 2 × 4.18 × 108 × 61.232 × 0.04 ∆Fa = 3.21 G V= 3600ρ 70495 V= 3600 × 61.23 V = 0.320 fps V2 Fl = 3 × ( ) 2g′ 0.3202 Fl = 3 × ( ) 2 × 32.2 = 0.005 ft ρ ∆Pa = (∆Fa + Fl ) × 144 (6.09 + 0.207) × 27.5 ∆Pa = 144 ∆Fa =



Inner Pipe: ammonia For Rep = 331588 0.264 f = 0.0035 + 0.42 Rep 0.264 f = 0.0035 + 3315880.42 f = 0.0049 ρ = 20.16 lb/ft3 4fGp2 L ∆Fp = 2gρ2 D 4 × 0.0049 × 3315882 × 120 ∆Fp = 2 × 4.18 × 108 × 20.162 × 0.25 ∆Fp = 2.35 ∆Fp × ρ 144 2.35 × 20.16 ∆Pp = 144 ∆Pp =



∆Pp = 0.33 psi Allowable ∆Pp=10 psi



∆Pa = 0.026 psi Allowable ∆Pa = 10 psi



68



CHAPTER IV



Equipment Design Table 4-6: Specification sheet of ammonia preheater



Specification Sheet Identification Item: Preheater (H-103) Type: Double pipe heat exchanger Function: To heat ammonia gas before entering neutralizer reactor. Annulus Inner Pipe Fluid: Hot Fluid: Cold Utility: Steam Process Fluid: (ammonia) Flow rate: 8544.32 lb/hr Flow rate: 18374.91 lb/hr 0 0 Temperature: 298.40 F to 298.40 F Temperature: 66.20F to 2480F Nominal pipe size: 4in. IPS Nominal pipe size: 3in. IPS ID: 4.026 in. ID: 3.068 in. OD: 4.50 in OD: 3.50 in ∆Pa=0.026 psi ∆Pp: 0.33 psi 2 Area: 119.84 ft Number of 20ft hairpins: 3 Rd= 0.0031 hr.ft2.F/Btu



69



CHAPTER IV



Equipment Design



4.6. Centrifuge (F-101) 4.6.1. Selection Selected solid liquid separator is solid bowl sedimentation centrifuge (helical conveyor centrifuge) due to the following reasons: [15] Physical properties of a material The characteristics of the solids and liquid handled in a process will influence centrifuge selection Specific gravities of solids and liquids If the solids are lighter than the liquid, a decanting centrifuge is not an option. If the specific gravities are very close, but the solids are slightly higher, a decanting centrifuge may be considered, but if either the particle size or centrifugal force improves the settling of solids. Particle size Coarse solids with particle size greater than 100 µm are generally best suited for a filtering type centrifuge. The finer solids that measures less than 10 µm are best handled in sedimentation centrifuges.



Figure 4-9: Solid bowl centrifuge



70



CHAPTER IV



Equipment Design



4.6.2. Design Water 10978.13 kg/hr. 06



Filtrate 68588.19 kg/hr.



Slurry 70498.34 kg/hr.



08



04



07



Sludge 1910.19 kg/hr.



Figure 4-10: Inerts removal centrifuge Table 4-7: Design data for centrifuge



Density of solids Average Density of mother liquor leaving Mass Flow rate of feed (kg/hr) DOA leaving the centrifuge (kg/hr) Mother liquor leaving (kg/hr) Diameter of bowl RPM of centrifuge Average viscosity of liquid Minimum Particle diameter dp



1610 kg/m3 820 kg/m3 81476.51 1910.19 79566.32 0.635 m 50 1.29*10-3 Pas 5*10-6 m



Mass flow rate of slurry = 70498.34 kg/hr. Weighted density of slurry = 2450.51 kg/m3 Volumetric flow rate of slurry = v1 = 70498.34/2450.51 = 28.77 m3/hr. Mass flow rate of water = 10978.13 kg/hr. Density of water = 1000 kg/m3 Volumetric flow rate of water = v2 = 10.98 m3/hr. Total volumetric flow rate of feed = v0 = 39.75 m3/hr. = 0.011 m3/s. Length of centrifuge Length of centrifuge can be calculated as: L=



v0 μ ⁄3.5D2 (ρ − ρ )d2 N 2 s L 71



CHAPTER IV



Equipment Design



Where, L = length of centrifuge, m μ = average viscosity of liquid, Pas v0 = volumetric flow rate of feed, m3/s D = diameter of bowl, m d = diameter of solid particle, m N = rotor speed, rpm ρs = density of mother liquor, kg/m3 ρL = density of solid particles, kg/m3 Length of centrifuge = L = 2.16 m = 7.08 ft. L/D = 1.6 L = 1.6D [11] D = 1.35 m = 6.56 ft. Volume of bowl 2 2 Volume of bowl = V = πD L⁄4 = 3.1415x0.635 ⁄4 x 2.16 = 0.68 m3 = 24.13 ft 3



Residence time Residence time for slurry = τ =



Volume of liquid⁄ Volumetric flow rate



Volume of liquid in bowl = πL(r22 − r12 )



Figure 4-11: Particle trajectory in sedimentation centrifuge



r2 = D/2 = 0.635/2 = 0.318 m r1 = r2/2 = 0.318/2 = 0.159 m Volume of liquid in bowl = 0.514 m3 = 18.16 ft3.



72



CHAPTER IV



Equipment Design



Residence time = 0.514/39.75 = 0.013 hr. = 0.78 min. Relative centrifugal force F RCF = c⁄F = ω2 r2 /g g ω = 2πN = 2x3.1415x50 = 314.15 rad/s RCF = 3202.4 Settling velocity Settling velocity can be calculated as: ut =



d2 (ρs − ρL )ω2 r2⁄ 2 18μ = 0.027 m/s



73



CHAPTER IV



Equipment Design Table 4-8: Specification sheet of centrifuge (F-101)



Specification sheet Identification Item Centrifuge F-04 Type Solid bowl Centrifuge Function Continuous Length 2.16 m Diameter 1.35 m Residence time 0.78 min Settling velocity 0.027 m/sec2 Relative Centrifugal Force (RCF) 3202.4



74



CHAPTER IV



Equipment Design



4.7. Centrifuge (F-102) Table 4-9: Specification sheet of centrifuge (F-102)



Specification sheet Identification Item Type Function



Centrifuge F-102 Solid bowl Centrifuge Continuous 3.56 m 2.25 m 2.63 min 0.0071 m/sec2 2218.2



Length Diameter Residence time Settling velocity Relative Centrifugal Force (RCF)



75



CHAPTER IV



Equipment Design



4.8. Crystallizer (CR-101) 4.8.1. Selection Cooling scraped surface swenson walker crystallizer is selected. The selection of cooling scraped surface swenson walker crystallizer includes many aspects but primarily they may be summarized under the following points. [17] 1)



Crystals are produced by lowering the temperature from 45oC to -5oC



2)



Process is continuous



3)



Minimum fouling problems



4)



Minimum capital cost



5)



Maintain uniform temperature



6)



It is best for viscous materials



Figure 4-12: Cooling crystallizer with agitator



4.8.2. Design Liquid mixture 45⁰C, 1 bar 79566.32 kg/hr.



Coolant in. -15⁰C, 1 bar 57751.16 kg/hr.



13



Coolant out 22⁰C, 1 bar 57751.16 kg/hr.



14



Figure 4-13: Crystallizer (CR-101)



76



Crystals + liquor 0⁰C, 1 bar 79566.32 kg/hr.



CHAPTER IV



Equipment Design



Volume of Crystallizer Residence time = t = 8 hr. = 480 min [1] Mass flow rate of feed = 79566.32 kg/hr. Weighted density of feed = 1658 kg/m3 Volumetric flow rate of feed = V0 = 79566.32/1658 = 47.99 m3/hr. Volume of crystallizer = V = V0xt = 47.99x8 = 383.93 m3. Volume for one continuous crystallizer is too large. It is convenient to install 5 batch crystallizers in series. Hence Volume for one batch crystallizer = V/5 = 76.8 m3 Length and diameter For cylindrical crystallizer: 2 V = πD L⁄4 = 47.99 m3



L/D = 2.5 [11] L = 2.5D Length of crystallizer = L = 8.5 m Diameter of crystallizer = D = 3.4 m Heat transfer area It can be calculated by using general heat transfer equation: Q = UA∆T LMTD = ∆T = 33.730F = 0.960C = 273.98 K Q = 9.33E+06 kJ/hr. For typical Swenson walker Crystallizer U = 378 kJ/m2.hr.K Area = 16.38 m2



77



CHAPTER IV



Equipment Design Table 4-10: Specification sheet of crystallizer (CR-101)



Specification Sheet Identification Item Crystallizer (CR-101) Type Scraped surface Swenson walker Operation Batch Function Formation of calcium nitrate crystals Heat transfer area required 16.38 m2 Length 8.5 m Diameter 3.4 m Volume 76.8 m3 Residence time 480n



78



CHAPTER IV



Equipment Design



4.9. Evaporator (E-101) 4.9.1. Selection Falling film evaporator is selected due to following reasons: [12] [13] 1. 2. 3. 4.



Best product quality Simple process control and operation High energy efficient Less residence time



4.9.2 Design Water vapors 3654.01 kg/hr. 175⁰C 0.3 bar



Water vapors 7324.09 kg/hr. 175⁰C 0.3 bar



NP solution 52630.19 kg/hr. 118⁰C 1 bar



NP concentrated solution 48976.19 kg/hr. 175⁰C 0.3 bar



Steam 6091.81 kg/hr. 201⁰C 16 bar



Water vapors 3654.01 kg/hr. 175⁰C 0.3 bar



Water vapors 3654.01 kg/hr. 175⁰C 0.3 bar



NP concentrated solution 48976.19 kg/hr. 175⁰C 0.3 bar Condensate 6091.81 kg/hr. 201⁰C 16 bar



NP concentrated solution 41652.06 kg/hr. 175⁰C 0.3 bar



Figure 4-14: Falling film evaporator (E-101)



Total feed to the evaporator = 117891 lb/hr. Temperature of feed = 244.5⁰F Specific heat of feed = 0.675 Btu/lb-⁰F Temperature of steam = Ts = 398⁰F Pressure of steam = 16 bar Water need to be evaporated = 24152 lb/hr. In double effect evaporator: m1 + m2 = 24344 lb/hr Pressure inside the evaporator = 0.3 kgf/cm2 79



CHAPTER IV



Equipment Design



Equations for the heat balance are: For 1st effect: 𝑚𝑠𝜆𝑠 + 𝑚𝑓(𝑡𝑓 − 𝑡1) = 𝑚1𝜆1 For 2nd effect: 𝑚1𝜆1 + (𝑚𝑓 − 𝑚1)(𝑡1 − 𝑡2) = 𝑚2𝜆2 Here: ms = mass flow rate of steam m1 & m2 = water removed from effect c1 = specific heat capacity of liquor in effect 1 𝜆1 = Latent heat of vapors No of effects 1 2 Vapor to condenser



Pressure (kgf/cm2) 17 4 0.3



Temperature of steam (⁰F) 398 289 155.5



Applying heat balance on first effect: 𝑚𝑠𝜆𝑠 + 𝑚𝑓(𝑡𝑓 − 𝑡1) = 𝑚1𝜆1 Latent heat of steam = 828 lb/hr. [7] Latent heat in second effect = 918 lb/hr. [7] Temperature of vapors in effect 2 = t1 = 289⁰F By putting the values: 828𝑚𝑠 − 3541151 = 918𝑚1 Heat balance on second effect: 𝑚1𝜆1 + (𝑚𝑓 − 𝑚1)(𝑡1 − 𝑡2) = 𝑚2𝜆2 𝑚1839.24 + 9285684.6 = 𝑚21004.6 The total vaporization rate required is: 𝑚1 + 𝑚2 = 24344 𝑚2 = 24344 − 𝑚1 No by solving the equations simultaneously: 80



Latent heat (lb/hr.) 828 918 1004.6



CHAPTER IV



Equipment Design



m1 = 8231 lb/hr. m2 = 16113 lb/hr. ms = 13402 lb/hr. Area for first effect:



For second effect:



U1 and U2 are the designed factors which are unknown have the range of 200-700 we can calculate UD by the help of the method of shell and tube heat exchanger Assume UD = 550 Btu/hr-ft2-⁰F [12]



LMTD =



LMTD = 93℉ A = 117 ft2 Number of Tubes = Length of tube = L = 16ft. Select number of tubes, shell ID and passes at 0.75 inch, OD tubes on 1-inch triangular pitch Nt = 37 Corrected area = Nt*at*L Area per linear foot = 0.1963 ft2 Corrected area = 116.2 ft 2 Corrected UD = U1 = 534.3 Btu/hr-ft2-⁰F



81



CHAPTER IV



Equipment Design



Similarly, for U2: U2 = 300 Btu/hr-ft2-⁰F



A1 = 190 ft2



A2 = 188 ft2 So A1 is approximately equal to A2 Outer Diameter Let us select ¾ inch nominal pipe size schedule 40 and length of tube is 16ft. Length of tube = L = 16ft. = 4.87m Outer Diameter = do = 1.05 inch = 26.7mm Inner diameter = 21mm Surface area for each tube = π*do*L = 0.40 m2 Number of tubes Area = 20 m2 (with 10% over design) Nt = Area/Surface area of each tube No of tubes = 50 Select 1-inch triangular pitch Pt = 1.25*do Pt = 33.3 mm Total area occupied by tubes n = number of passes = 2 Area occupied by tubes = 0.024 m2 This area is generally divided by a factor which varies from 0.8 to 1 to find out the actual area. This allows for position adjustment of peripheral tubes as those can't be too close to tube sheet edge. 82



CHAPTER IV



Equipment Design



A = 0.024/.90 A = 0.0266 m2 Down comer Area The central down comer area is generally taken as 40 to 70% of the total cross sectional area of tubes.



A = 0.014 m2 Down comer diameter



D = 0.1335 m Area of tube sheet Total area of tube sheet in evaporator = Down comer area + area occupied by tube A = 0.014 + 0.0266 A = 0.0406 m2 Tube sheet Diameter



D = 0.227 m



83



CHAPTER IV



Equipment Design Table 4-11: Specification sheet of evaporator (E-101)



Specification Sheet Identification Item Evaporator (E-101) Type Falling film double effect evaporator Function: To concentrate the final product. Shell side Tube side Fluid: Cold (NP solution) Fluid: Hot (Steam) Flow rate: 117373.62 lb/hr. Flow rate: 13402 lb/hr. Temperature: 120⁰C to 175⁰C Temperature: 201⁰C st 2 Area of 1 effect = 190 ft Area of 2nd effect = 188 ft2 U1 = 534.3 Btu/hr-ft2-⁰F U2 = 300 Btu/hr-ft2-⁰F



84



CHAPTER IV



Equipment Design



4.10. Prilling tower (T-101) 29 Feed 42178.37 kg/hr. T = 175⁰ C P = 1.1 bar 33



Prills 42178.37 kg/hr. T = 95⁰ C P = 1.1 bar



Figure 4-15: Prilling tower (T-101)



4.10.1. Design Q = 6.24E+07 kJ/hr. = 17333 kW = 17333000 W Heat transfer is by convection, apply Newton’s law of cooling. Q = hA∆T Temperature difference = ∆T = 800C Convection heat transfer coefficient for air = h = 10 W/m2-0C [8] Area = Q/h∆T = 2625 m2 = 28240.8 ft2. Area = πDL = 2625 A/π = 835.99 DL = 835.99 Diameter of tower = D = 12 m Length of tower = L = 69.93 = 70 m



85



CHAPTER IV



Equipment Design Table 4-12: Specification sheet of prilling tower (T-101)



Specification Sheet Identification Item Tower (T-101) Type Prilling Tower Function: To make prills of NP solution. Inlet Temperature 175℃ Outlet Temperature 95℃ Operation Pressure 1 atm Area 2625 m2 Diameter 12 m Length 70 m



86



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



CHAPTER # 5 Mechanical Design



87



CHAPTER V



Mechanical Design



5.1. Shell & tube heat exchanger Process liquid mixture 0⁰C, 2 bar 47839.37 kg/hr.



Steam 148⁰C, 4 bar 5013.70 kg/hr.



Steam 148⁰C, 4 bar 5013.70 kg/hr.



Process liquid mixture 120⁰C, 2 bar 47839.37 kg/hr.



Figure 5-1: Heat exchanger (H-102)



5.1.1. Design pressure It is taken as 10% of maximum working pressure of material of construction for shell and tube heat exchanger. [13] Shell side Maximum Operating Pressure = 2 bar Maximum Operating Pressure = 0.2 N/mm2 Design pressure is 10% of operating pressure. So, Design pressure = 2 + 2(0.1) Design pressure = 2.2 bar Design pressure = 0.22 N/mm2 Tube side Maximum Operating Pressure = 4 bar Maximum Operating Pressure = 0.4 N/mm2 Design pressure is 10% of operating pressure. So, Design pressure = 4 + 4(0.1) Design pressure = 4.4 bar Design pressure = 0.44 N/mm2 5.1.2. Design temperature It is taken as 10% of maximum working temperature of material of construction for shell and tube heat exchanger. Shell side Maximum operating temperature = 120oC Design temperature is 10% of operating temperature. So, 88



CHAPTER V



Mechanical Design



Design temperature = 120 + 120(0.1) Design temperature = 132⁰C Tube side Maximum Operating Temperature = 148⁰C Design temperature is 10% of operating temperature. So, Design temperature = 148 + 148(0.1) Design temperature = 163⁰C 5.1.3. Material selection Following factors must be considered in selecting a suitable material of construction for the heat exchanger: [13] 1. Temperature and Pressure 2. Good for the environment 3. Corrosion resistance 4. Availability 5. Cost effectiveness Selection The selected material is Carbon steel. The reasons for selection are as follows: 1. It has great mechanical properties. 2. It is easily available. 3. Its cost is not very high. 4. Temperature and pressure are within range. 5.1.4. Design stress S = 100.6 N/mm² Joint Efficiency = 0.8 [13] 5.1.5. Thickness of shell ts =



P* Ds SE - 0.6 Pi



+C



Where: ts = Wall thickness Pi = Design Pressure = 2.2 bar D = Internal Diameter of Shell = 304.9 mm S = Design stress E = Joint Efficiency ts = 0.85 mm + 2 mm ts = 2.87 mm (because of corrosion allowance = 2mm). 5.1.6. Thickness of head tH =



P* Rc *W 2SE - 0.2Pi



Where: tH = Head thickness P = Design Pressure = 2.2 bar = 0.22 N/mm2 Rc = Di = Internal Diameter = 304.9 mm S = Design stress 89



+𝐶



CHAPTER V



Mechanical Design



E = Efficiency tH = 0.75 mm + 2 mm tH = 2.75 mm (because of corrosion allowance). Inside depth of head = hi = 40.77 mm 5.1.7. Effective exchanger length Le = Lt +



2*hi 1000



Length of tube = Lt = 16ft. Lt = 4.88 m Le = 4.96 m 5.1.8. Thickness of tube sheet



ts =



F*Gp 3



P 0.5



( ) kf



+C



Where: F = Fixed Tube Sheet = 1 Pt= 1 in.(triangular pitch) Do = 19.05 mm Gp = Ds = Internal Diameter of Shell = 304.9 mm k = 0.5



𝑘 =1−



0.907 𝑃 ( 𝑡 )2 𝑑0



tts = 9.66 mm = 0.31 ft. 5.1.9. Nozzle inside diameter Shell ID Range: 12 to 17.25 inch Nozzle ID = 3 inch 5.1.10. Gasket Inside Gasket Diameter, DiG = 305.15 mm Design Pressure, P = 0.22 N/mm2 Minimum design seating stress (Solid flat metal), y = 18.28 Gasket Factor, m = 6.5 DOG y − Pm =√ DIG y − p(m + 1) DOG/DIG = 1.09 Outside Gasket Diameter, DOG = 332.61 mm 5.1.11. Support For Horizontal shell and tube heat exchanger:, support mostly used is saddle support No of saddles = 2



90



CHAPTER V



Mechanical Design Table 5-1: Mechanical design specification sheet



Specification Sheet Item



Preheater



Item No



H-102



Number required



1



Type



1-2 shell & tube heat exchanger Mechanical design



Design temperature



Shell side: 132⁰C Tube side: 163⁰C



Design pressure



Shell side: 2.2 bar Tube side: 4.4 bar



Material of construction



Carbon steel



Stress factor



100.6 N/mm2



Shell thickness



2.87 mm



Torispherical head thickness



2.75 mm



Effective exchanger length



4960 mm



Tube sheet thickness



9.66 mm



Nozzle inside diameter



76.2 mm



Gasket inside diameter



305.15 mm



Gasket outside diameter



332.61 mm



No of saddle support



2



91



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



CHAPTER # 6 Pumps & Compressors



92



CHAPTER VI



6.1.



Pumps & Compressors



Pump



Pump is a device that imparts momentum and mechanical energy to the process fluid. Pumps are used to transfer fluid from one location to other. A pump is a device used to raise, compress, or transfer fluids. The motors that power most pumps can be the focus of many best practices. It is common to model the operation of pumps via pump and system curves. Pump curves offer the horsepower, head, and flow rate figures for a specific pump at a constant rpm. System curves describe the capacity and head required by a pump system. [18] 6.1.1. Types of pump Various types of pumps are used in the chemical industry, including centrifugal, reciprocating, and helical rotor pumps. [15] Centrifugal pump Centrifugal pumps operate by applying a centrifugal force to fluids, many times with the assistance of impellers. These pumps are typically used in moderate to high flow applications with lowpressure head, and are very common in chemical process industries. There are three types of centrifugal pumps—radial, mixed, and axial flow pumps. In the radial pumps, pressure is developed completely through a centrifugal force, while in axial pumps pressure is developed by lift generated by the impeller. Mixed flow pumps develop flow through a centrifugal force and the impeller. Reciprocating pump Reciprocating pumps compress liquid in small chambers via pistons or diaphragms. These pumps are typically used in low-flow and high-head applications. Piston pumps may have single or multiple stages and are generally not suitable for transferring toxic or explosive material. Diaphragm pumps are more commonly used for toxic or explosive materials. Helical rotor pump Helical rotor pumps use a rotor within a helical cavity to develop pressure. These pumps are useful for submersible and waste applications. 6.1.2. Sizing of pump (P-101) Selection criteria of pumps Many different factors can influence the final choice of the pump for a particular operation .The following list indicates the major factors that govern the pump selection 1. 2. 3. 4. 5. 6.



The amount of liquid that must be pumped out. The properties of the fluid. The increase in presence of the fluid due to work input of the pump. Types of the flow distributions. Types of the power supply. Cost and mechanical efficiency of the pump.



93



CHAPTER VI



Pumps & Compressors



Pump Selection Pump type is selected from appendix. Capacity = 79566.32 kg/hr = 166.82 gpm P(g) Head = sp.gr∗0.4367



Head = 30 ft. Hence, the Pump selected is centrifugal pump. Pump sizing calculation steps Pump sizing steps are as follows: [18] 1. Locate the process equipment 2. Estimate z1 and z2. 3. Estimate Frictional pressure losses ED and ES 4. Calculate Pump Work. 5. Calculate Pump shaft horsepower & estimate its Efficiency. 6. Calculate electric-motor horsepower & estimate its Efficiency. 7. Select a standard electric-motor horsepower. 8. Calculate NPSH Inlet and outlet pressures The inlet pressure is = P1 = 1 bar The outlet pressure is = P2 = 2 bar Locate the process equipment Locate the process equipment according to the rule of thumb listed in following table… As we need to pump the liquid in to the crystallizer so our process equipment is crystallizer which is supported by a skirt having skirt height of about 4 ft. or 1.22 m. Estimation of z1 & z2 z1 with respect to pump = 0 z2 = skirt height + height of column z2 = 1.22 + 8.5 z2 = 9.72 m z2 = 31.88 ft.



94



CHAPTER VI



Pumps & Compressors



Estimation frictional pressure losses ED and ES ES & ED is equal to 0.35 (from appendix) Calculate the pump work g P − P2 (z1 − z2 ) + 1 W= − (ES − ED ) gC ρ W = 9.8(0 − 9.72) + W = −176.20



(1 ∗ 105 − 2 ∗ 106 ) (0.35 + 0.35) ∗ 105 − 2100 2100



Nm Kg



Calculate the pump power Pump power is calculated as, mW ɳ



P=



Pump efficiency = 52% (from appendix) P=



79566.32 ∗ 176.20 0.52



P = 2.59*107 J/hr. P = 124.82 W P = 0.17 hp. Calculate electric motor horsepower & efficiency On the basis of horsepower the selected motor is squirrel cage Induction motor having power range of 1 to 5,000 hp. Efficiency of motor is selected to be = 0.80 (from appendix) The power of motor is calculated as = PE = PE = PE =



PP ɳ



0.17 0.80



PE = 0.22 hp. Select a standard electric motor horsepower Hence the selected motor is of ¼ (0.25) hp. (from appendix) Net positive suction head (NPSH) 1 Pa − Pv NPSH = ( − hfs ) − Za g ρ Absolute pressure at the surface of reservoir = P a = 1.2 bar = 1.2*105 Pa Vapor pressure of solution= Pv = 4.72E+04 Pa 95



CHAPTER VI



Pumps & Compressors



Friction losses in suction line = hfs = 0 Za = 0 1 1.2 ∗ 105 − 4.72E + 04 NPSH = ( − 0) − 0 9.8 2100 NPSH = 3.45 m



96



CHAPTER VI



Pumps & Compressors Table 6-1: Specification sheet of pump (P-101)



Specification sheet Identification Item Item no.



Pump P-101



No. required



1



Type



Centrifugal



Function: To increase pressure from 1 bar to 2 bar Feed flow rate Inlet pressure



79566.32 kg/hr. 1 bar



Outlet pressure



2 bar



Power of pump



0.17 hp.



Power of electric motor



0.25 hp.



NPSH



3.45m



97



CHAPTER VI



Pumps & Compressors



6.1.3. Sizing of Pump (P-102) Table 6-2: Specification sheet of pump (P-102)



Specification Sheet Identification Item Item no.



Pump P-102



No. required



1



Type



Centrifugal



Function: To increase pressure from 0.3 bar to 1.1 bar Feed flow rate Inlet pressure



42178.37 kg/hr. 0.3 bar



Outlet pressure



1.1 bar



Power of pump



1.21 hp.



Power of electric motor



2 hp.



NPSH



3.02 m



98



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



CHAPTER # 7 Cost Estimation



99



CHAPTER VII



7.1.



Cost Estimation



Introduction



Cost estimation is a specialized subject and a profession in its own right. The design engineer needs to be able to make quick, rough, cost estimates. Chemical plants are built to make a profit. [19] 7.1.1. Classification of cost estimation Capital cost estimates can be broadly classified in to 3 types: [19] 1. Preliminary (approximate) 2. Authorization (Budgeting) 3. Detailed (Quotation) Preliminary estimate has been used. 7.1.2. Classification of rapid capital cost estimation Rapid Capital cost estimates can be broadly classified in to 3 types: [19] 1. Historical Cost 2. Step Counting Method 3. Factorial Method Factorial Method has been used. 7.1.3. Equipment Purchased CostCost of Reactor (R-101) Stainless steel 304 CSTR Volume of reactor = 48.92 m3 Diameter = 3.54 m Length = 4.96 m Equipment exponent = n = 0.7 (from appendix) Cost constants, a = 14,000 & b = 15,400 (from appendix) Material factor = 1.3 Cost of reactor in 2006 = (a + bS n ) x Material factor Cost of reactor in 2006 = $ 323,063 Cost index in 2006 = 478.6 [20] Cost index in 2018 = 711.11 [20] Cost of reactor in 2018 = 𝐶𝑜𝑠𝑡 𝑖𝑛 2006 𝑥



𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2018 𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2006



Cost of reactor = $ 480,011



100



CHAPTER VII



Cost Estimation



Cost of Centrifuge (F-101) Bowl diameter = 0.635 m Material of Construction = Stainless steel Cost of centrifuge in 2002 = $ 69,500 Cost index in 2002 = 395.6 [20] Cost index in 2018 = 711.11 Cost of centrifuge in 2018 = 𝐶𝑜𝑠𝑡 𝑖𝑛 2002 𝑥



𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2018 𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2002



Cost of centrifuge = $ 124,930 Cost of Heat Exchanger (H-101) Hot fluid = Process fluid Cold fluid = Cold water Heat transfer area = 257.55 ft 2 = 23.93 m2 Pressure factor = 1.0 [13] Type head = 0.85 (U tube sheet) Material factor = 1 (carbon steel) Bare cost of shell and tube heat exchanger in 2004 = $ 18,000 Purchased cost = bare cost x pressure factor x type factor Purchased cost in 2004 = $ 15,300 Cost index in 2004 = 444.2 [20] Cost index in 2018 = 621.1 [20] Cost of exchanger in 2018 = 𝐶𝑜𝑠𝑡 𝑖𝑛 2004 𝑥



𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2018 𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2004



Cost of exchanger in 2018 = $ 21,393 Cost of Crystallizers (CR-101-5) Cooling type scraped surface crystallizer Length of crystallizer = 8.5 m Diameter of crystallizer = 3.4 m Volume of crystallizer = 76.8 m3 Capacity = 31.72 tons/hr. Cost for the year 2012 = $ 85,228 101



CHAPTER VII



Cost Estimation



Cost index for year 2012 = 584.6 Cost index for year 2018 = 711.11 Cost for year 2018 = 𝐶𝑜𝑠𝑡 𝑖𝑛 2012 𝑥



𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2018 𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2012



Cost for year 2018 = $ 103,672 Cost of 5 crystallizers in series = 5 x 103,672 = $ 518,359 Cost of Centrifuge (F-102) Bowl diameter = 0.72 m Material of Construction = Stainless steel Cost of centrifuge in 2002 = $ 80,000 Cost index in 2002 = 395.6 Cost index in 2018 = 711.11 Cost of centrifuge in 2018 = Cost in 2002 x



Index in 2018 Index in 2002



Cost of centrifuge = $ 143,804 Cost of Preheater (H-102) Hot fluid = Steam Cold fluid = Process liquid Heat transfer area = 257.54 ft 2 = 23.93 m2 Pressure factor = 1.0 Type head = 0.85 (U tube sheet) Bare cost of shell and tube heat exchanger in 2004 = $ 18,000 Purchased cost = bare cost x pressure factor x type factor Purchased cost in 2004 = $ 15,300 Cost index in 2004 = 444.2 Cost index in 2018 = 621.1 Cost of exchanger in 2018 = 𝐶𝑜𝑠𝑡 𝑖𝑛 2004 𝑥



𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2018 𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2004



Cost of exchanger in 2018 = $ 21,393 Cost of Preheater (H-103) Hot fluid = Steam 102



CHAPTER VII



Cost Estimation



Cold fluid = Ammonia gas Heat transfer area = 120.01 ft 2 = 11.15 m2 Cost of double pipe heat exchanger in 2004 = $ 3,950 Cost index in 2004 = 444.2 Cost index in 2018 = 621.1 Cost of exchanger in 2018 = 𝐶𝑜𝑠𝑡 𝑖𝑛 2004 𝑥



𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2018 𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2004



Cost of exchanger in 2018 = $ 5,523 Cost of Reactor (R-102) Volume of reactor = 60.19 m3 Diameter = 3.80 m Length = 5.32 m Equipment exponent = n = 0.7 Cost constants, a = 14,000 & b = 15,400 Material factor = 1.3 Cost of reactor in 2006 = (a + bS n ) x Material factor Cost of reactor in 2006 = $ 411,029 Cost index in 2006 = 478.6 Cost index in 2018 = 711.11 Cost of reactor in 2018 = 𝐶𝑜𝑠𝑡 𝑖𝑛 2006 𝑥



𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2018 𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2006



Cost of reactor = $ 610,712 Cost of Evaporator (E-101-2) Dual effect falling film evaporator Area of 1st effect = 190 ft2 = 17.7 m2 Area of 2nd effect = 188 ft2 = 17.5 m2 Hot fluid = Steam at 205⁰C & 16 bar Cold fluid = NP solution Use the following formula to calculate purchased cost Ce = CS n Where Ce = Purchased cost, $ 103



CHAPTER VII



Cost Estimation



S = Characteristic size parameter = 17.7 C = Cost constant, $ = 10,000 n = Index for that type of equipment = 0.52 Cost of 1st effect for year 2004 = $ 44,560 Cost index for year 2004 = 444.2 Cost index for year 2018 = 711.1 Cost of 1st effect for year 2018 = 𝐶𝑜𝑠𝑡 𝑖𝑛 2004 𝑥



𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2018 𝐼𝑛𝑑𝑒𝑥 𝑖𝑛 2004



Cost of 1st effect for year 2018 = $ 71,335 Area of 1st effect is approximately equal to the 2nd effect. Therefore, Cost of 2nd effect for year 2018 = $ 71,335 Total cost of evaporators (E-101-2) = $ 142,670 Cost of Prilling Tower (T-101) Length of tower = 70 m Diameter of tower = 12 m 𝜋



Volume of tower V = 𝐷2 𝐿 = 7917 m3 = 279372 ft3 4



Cost of tower for year 1987 = $ 260,000 Cost index for the year 1987 = 326 Cost index for the year 2018 = 711.11 Cost of tower for the year 2018 = Cost in 1987 x



Index in 2018 Index in 1987



Cost of tower for the year 2018 = $ 567,143 Cost of Pump (P-101) High speed centrifugal pump Inlet pressure = 1 bar Discharge pressure = 2 bar Pump work = -176.20 J/kg Capacity = 10.52 L/s Cost constants, a = 3300 & b = 48 Equipment exponent = n = 1.2 104



CHAPTER VII



Cost Estimation



Cost of pump in 2006 = a + bS n Cost of pump in 2006 = $ 5,562 Cost index in 2006 = 478.6 Cost index in 2018 = 1032.4 Cost of pump in 2018 = Cost in 2006 x



Index in 2018 Index in 2006



Cost of pump in 2018 = $ 11,998 Cost of pump (P-102) Centrifugal pump Inlet pressure = 0.30 bar Discharge pressure = 1 bar Pump work = -165.18 J/kg Capacity = 7.32 L/s Cost constants, a = 3300 & b = 48 Equipment exponent = n = 1.2 Cost of pump in 2006 = a + bS n Cost of pump in 2006 = $ 4,103 Cost index in 2006 = 478.6 Cost index in 2018 = 1032.4 Cost of pump in 2018 = Cost in 2006 x



Index in 2018 Index in 2006



Cost of pump in 2018 = $ 8,851



105



CHAPTER VII



Cost Estimation Table 7-1: Purchased equipment cost



Equipment Reactor (R-101) Centrifuge (F-101) Heat exchanger (H-101) Crystallizers (CR-101-5) Preheater (H-102) Preheater (H-103) Reactor (R-102) Evaporators (E-101-2) Prilling tower (T-101) Pump (P-101) Pump (P-102) Total



Cost ($) 480,011 124,930 21,393 518,359 21,393 5,523 610,712 142,670 567,143 11,998 8,851 2,512,983



7.1.4. Direct cost Table 7-2: Direct cost



Items Purchased equipment Installation Instrument and Control Piping Electricity Building Land Service facility Yard Improvement Insulation cost Total



Range ---



%



Cost ($)



100%



2,512,983



25-55% of purchased equipment cost



25%



628,246



6-30% of purchased equipment cost



6%



150,779



40-80% of purchased equipment cost 10-15% of purchased equipment cost 15% of purchased equipment cost 4-8% of purchased equipment cost 30-80% of purchased equipment cost 10-20% of purchase equipment cost 8-9% of purchased equipment cost ---



40% 10% 15% 4% 30% 10% 8% ---



1,005,193 251,298 376,947 100,519 753,895 251,298 201,039



106



6,232,197



CHAPTER VII



Cost Estimation



7.1.5. Indirect Cost Table 7-3: Indirect cost



Range



%



Cost ($)



8% of total direct cost



8%



498,576



2-8% of direct plant cost



2%



124,644



Items Engg. & supervision Contractor fee Construction Expenses



10% of Total direct plant cost 10%



Contingences



Direct plant cost



5%



---



Total



Fixed capital investment = direct cost + indirect cost = 6,232,197 + 1,558,050 = $ 7,790,247 Working capital = 15% of fixed capital cost = $ 1,168,537 Total capital investment = fixed capital investment + working capital = $ 8,958,784 = PKR 1.2 billion 7.1.6. Variable Cost Raw Material Cost Phosphate rock Flow rate of phosphate rock = 23801 kg/hr. Operating days per year = 300 Flow rate of rock = 171367200 kg/yr. = 171367 ton/yr. Rock price in Jan 2019 = $ 102.50/ton Cost of phosphate rock per year = 102.50 x 171367 = $ 17,565,118/yr. Nitric acid Flow rate of 60% nitric acid = 48850.93 kg/hr. Operating days per year = 300 Flow rate of 60% nitric acid = 351726696 kg/yr. = 351726 ton/yr. Price of nitric acid = $ 500/ton Cost of nitric acid = 500 x 351726 = $ 75,863,000/yr. Ammonia Flow rate of liquid ammonia = 6591.51 kg/hr. Operating days per year = 300



107



---



623,220 311,610 1,558,050



CHAPTER VII



Cost Estimation



Flow rate of liquid ammonia = 47458872 kg/yr. = 47458 ton/yr. Price of liquid ammonia = $ 200/ton Cost of liquid ammonia = 200 x 47458 = $ 9,491,600/yr. Total cost of raw materials = $ 102,919,718 Utilities Cost Cooling water Flow rate of cooling water = 21,993.85 kg/hr. Operating days = 300/yr. Flow rate of cooling water = 158355720 kg/yr. Price of cooling water = $ 0.00001/kg Cost of cooling water = $ 1584/yr. Steam Total flow rate of steam = 11319.9 kg/hr. Operating days = 300 days/yr. Flow rate of steam = 81503280 kg/yr. Price of steam = $ 0.014/kg Cost of steam = $ 1,141,046/yr. Total cost of utilities = $ 1,142,636 Miscellaneous Materials Cost Maintenance cost = 7% of FCI Maintenance cost = $ 545,317 Miscellaneous material = 10% of maintenance cost Miscellaneous cost = $ 54,532 Variable cost = raw materials cost + utilities cost + miscellaneous cost Variable cost = $ 104,116,886/yr.



108



CHAPTER VII



Cost Estimation



7.1.7. Fixed Cost Table 7-4: Fixed cost



Maintenance



7 % of FCI



545,317



1% of TPC



0.01(TPC)



Laboratory Cost



1.5% of TPC



0.015(TPC)



Supervision Cost



2% of TPC



0.02(TPC)



Plant Overheads



5% of TPC



0.05(TPC)



Capital Charges



10% of FCI



779,025



Insurance



1% of FCI



77,902



Local Taxes



2% of FCI



155,805



Royalties



1% of FCI



77,902



Fixed Cost



-



1,635,951 + 0.095(TPC)



Operating Cost of Labor



Direct production cost = variable cost + fixed cost = 104,116,886 + 1,635,951 + 0.095(TPC) = 105,752,837 + 0.095(TPC) Now Total production cost = variable cost + fixed cost TPC = 104,116,886 + 1,635,951 + 0.095(TPC) TPC – 0.095(TPC) = 105,752,837 0.905(TPC) = 105,752,837 TPC = total production cost = $ 116,853,964/yr. Total production rate = 300,000 MTPA (ton/yr.) Production cost ($/ton) = total production cost ($/yr.)/total production rate (ton/yr.) Production cost ($/ton) = $ 368/ton Below this, we cannot sale our product. 7.1.8. Selling Price Cost of NP fertilizer in Pakistan = PKR 2,975/50 kg bag = PKR 59,500/ton = $ 425/ton Selling price = $ 425/ton



109



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Cost Estimation



7.1.9. Profitability Analysis Production cost = $ 0.368/kg Selling price = $ 0.425/kg Profit = Selling price – production cost = 0.425 – 0.368 = $ 0.057/kg = $ 57/ton Total production per year = 300,000 ton/yr. Profit per year = 57 x 300,000 = $ 17,100,000/yr. Total Income Selling price of NP = $ 425/ton Total production per year = 300,000 ton/yr. Total income = 300,000 x 425 = $ 127,500,000/yr. Gross Profit Gross profit = Total income – Total production cost = 127,500,000 – 116,853,964 = $ 10,646,036/yr. Net Profit Assume that the fixed capital investment depreciate by straight line method for 20 years. Assuming 5% selvage value at the end of plant life. Depreciation = D =



𝑉 − 𝑉𝑆⁄ 𝑁



V = FCI = $ 7,790,247 Salvage value = VS = 0.05(FCI) = $ 389,512 Number of years = N = 20 years. Depreciation = D = $ 370,037 Net profit before taxation = Gross profit – Depreciation = $ 10,275,999/yr. Taxes = 30% of net profit before taxation Taxes = 0.3(10,275,999) = $ 3,082,800/yr. Net profit = Net profit before taxation – Taxes



110



CHAPTER VII



Cost Estimation



= $ 7,193,200/yr. 7.1.10. Rate of Return Rate of return = (Net Profit⁄Total Capital Investment) 𝑥 100 Rate of return = 80.20% 7.1.11. Payback Period Payback period = 1⁄Rate of return Payback period = 1.24 yr.



111



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



CHAPTER # 8 Instrumentation & Control



112



CHAPTER VIII



8.1.



Instrumentation & Control



Objective



The primary objectives of the instrumentation and control are: [21] 1. To help the process variables within safe operating limits. 2. To detect dangerous situations as they develop and to provide alarms and automatic shutdown systems. 3. To provide inter locks and alarms to prevent dangerous operating procedures. 8.1.1. Production Rate To achieve the desired product output. 8.1.2. Product Quality To maintain the product composition within specified quality standard. 8.1.3. Cost To operate at the lowest production cost, commensurate with the other objective. These are not separate objectives and must be considered together. Measurement is a fundamental requisite of process control either the control will be affected automatically, semi-automatically or manually. The quality of the control obtainable is a function of the accuracy, repeatable and reliability of the measuring devices employed. The objective of an automatic process control is to use the manipulated variable to maintain the controlled variable at its set point in spite of disturbances. Instruments are provided to monitor the key process variables during plant operations. Instruments monitoring critical process variables will be fitted with automatic alarms to alert, the operations to critical and hazardous situations. Pneumatic instruments are used in this plant. The main process parameters are all indicated in the control room where automatic or remote control is carried out centrally. The process parameters e.g. temperatures, pressure, flow, liquid level etc. are converted to signals with transducers and then indicated, recorded and controlled with secondary instruments.



8.2.



Process Instrumentation



No chemical plant can be operated unless it is adequately instrumented. The monitoring of flows, pressures, temperatures and levels is necessary in almost every process in order that plant operator can see that all part of plant functioning as required. Additionally, it may be necessary to record and display many other quantities which are more specific to the particular process in question. In many instances sensors forms an essential part of control system or strategy for a process. Process instrumentation may be quite complex and rely upon the performance and characteristics of a substantial number of different sensors. [22] 8.2.1. Temperature Measurement and control of temperature are possibly the most common operations in process control. The basic principles of temperature measurement are: [22] 1. Expansion of substance with temperature, which produces a change in length, volume, pressure in its simplest form this is the common mercury in glass thermometer. 113



CHAPTER VIII



Instrumentation & Control



2. Change in electric resistance with temperature used in resistance thermometers (RTD) and thermostats. 3. Change in contact potential between dissimilar metals with temperature thermocouples. 4. Change in radiant energy with temperature, optical and radiation pyrometers. 8.2.2. Pressure For measurement of pressure, all pressure transducers are concerned with measurement of static pressure e.g. pressure of the fluid at rest. The most common of pressure transducer is DP cell which is used in conjunction with a sensing device such as an orifice meter, any mechanism of outputted. Pneumatic, electrical or mechanical can be coupled with it for signal transmission. 8.2.3. Flow The measurement of flow is an essential part of almost every industrial process, and many techniques have been evolved for it. Measurement of flow usually employs the same principal as the measurement of pressure i.e. sensing device coupled with a DP cell. For special applications other flow meters may be employed e.g. for process no external disturbance in the fluid stream is required for magnetic flow meters. 8.2.4. Concentration Knowledge of composition of a process stream is often of major importance. Such information may be necessary to determine whether the particular product has the required specification or whether composition of a particular stream is changing. Frequently, variation in either will require some kind of control action to maintain plant. Property of material is usually employed for the measurement of concentration e.g. absorption of electromagnetic waves, refractive index, pH, density of components as in chromatography



8.3.



Control Loops



For instrumentation and control of different sections and equipment’s of plants, following control loops are most often used. [21] 1. Feedback control loop 2. Feed forward control loop 3. Cascade control loop 8.3.1. Feedback Control Loop A method of control in which a measured value of a process variable is compared with the desired value of the process variable and any necessary action is taken. Feedback control is considered as the basic control loops system. Its disadvantage lies in its operational procedure. For example if a certain quantity is entering in a process, then a monitor will be there at the process to note its value. Any changes from the set point will be sent to the final control element through the controller so that to adjust the incoming quantity according to desired value (set point). But in fact changes have already occurred and only corrective action can be taken while using feedback control system. 8.3.2. Feed forward Control Loop A method of control in which the value of disturbance is measured than action is taken to prevent the disturbance by changing the value of a process variable. This is a control method designed to prevent errors occurring in a process variable. This control system is better than feedback control 114



CHAPTER VIII



Instrumentation & Control



because it anticipates the change in the process variable before it enters the process and takes the preventive action. While in feedback control system action is taken after the change has occurred. 8.3.3. Cascade Control Loop This is a control in which two or more control loops are arranged so that the output of one controlling element adjusts the set point of another controlling element. This control loop is used where proper and quick control is difficult by simple feed forward or feed backward control. Normally first loop is a feedback control loop.



8.4.



Cascade Control Loop on Crystallizer



Let us discuss instrumentation and control on crystallizer. Calcium nitrate tetra-hydrate crystals are formed inside the crystallizer. Conditions should be maintained inside the crystallizer to form specific calcium nitrate tetra-hydrate crystal size (50µm). Set point



TT



Set point



TC



S-6



TC



T



TT



LT



Tc



Process liquid mixture (45⁰C, 2 bar)



Coolant in. -15⁰C



Coolant out 22⁰C



FC



LC Set point



Set point FT



Process liquid with CN crystals (0⁰C, 2 bar)



Figure 8-1: Instrumentation & control on crystallizer (CR-101)



Where TT = Temperature transmitter FT = Flow transmitter LT = Level transmitter FC = Flow controller LC = Level controller TC = Temperature controller T = Temperature inside the crystallizer, ⁰C 115



CHAPTER VIII



Instrumentation & Control



Tc = Temperature of coolant, ⁰C 8.4.1. Control Objective There are two main control objectives, 1. Maintain the temperature inside the crystallizer at -5⁰C. 2. Maintain the level inside the crystallizer at 75% of total volume. 8.4.2. Controlled Variable There are two controlled variables, 1. Temperature 2. Level 8.4.3. Disturbance Variable Disturbances can be caused by, 1. 2. 3. 4.



Inlet temperature of process liquid mixture Inlet temperature of coolant Inlet flow rate of the mixture Poor agitation



8.4.4. Manipulated Variable Manipulated variable is flow rate of the coolant. 8.4.5. Control Procedure Temperature inside the crystallizer is maintained by the flow rate of the coolant. Cascade control loop is applied to maintain the desired crystal size of calcium nitrate. When the temperature inside the crystallizer is high then flow rate of the coolant is increased. Similarly when the temperature inside the crystallizer is lower than set point then the flow rate of the coolant is decreased. Level is also maintained inside the crystallizer. Crystallizer should be 75% filled with process liquid to gain the desired crystal size and fulfill the capacity. When the level inside the crystallizer decreases, outlet valve get close to fill the vessel up to set point. Similarly when the level exceeds the set point, outlet valve gets open and allow the process liquid to flow.



116



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



CHAPTER # 9 HAZOP Study



117



CHAPTER IX



HAZOP Study



9.1. Introduction The HAZOP study is a formal procedure to identify hazards in a chemical process facility. The procedure is effective in identifying hazards and is well accepted by the chemical industry. The basic idea is to let the mind go free in a controlled fashion in order to consider all the possible ways that process and operational failures can occur. Before the HAZOP study is started, detailed information on the process must be available. This includes up-to-date process flow diagrams (PFDs), process and instrumentation diagrams (P&IDs), and detailed equipment specifications, materials of construction, and mass and energy balances. [19] The full HAZOP study requires a committee composed of a cross-section of experienced ' plant, laboratory, technical, and safety professionals. One individual must be a trained HAZOP leader and serves as the committee chair. This person leads the discussion and must be experienced with the HAZOP procedure and the chemical process under review. One individual must also be assigned the task of recording the results, although a number of vendors provide software to perform this function on a personal computer. The committee meets on a regular basis for a few hours each time. The meeting duration must be short enough to ensure continuing interest and input from all committee members. A large process might take several months of biweekly meetings to complete the HAZOP study. Obviously, a complete HAZOP study requires a large investment in time and effort, but the value of the result is well worth the effort. 9.1.1. Background A HAZOP study identifies hazards and operability problems. The concept involves investigating how the plant might deviate from the design intent. If, in the process of identifying problems during a HAZOP study, a solution becomes apparent, it is recorded as part of the HAZOP result; however, care must be taken to avoid trying to find solutions which are not so apparent, because the prime objective for the HAZOP is problem identification. Although the HAZOP study was developed to supplement experience based practices when a new design or technology is involved, its use has expanded to almost all phases of a plant's life. HAZOP is based on the principle that several experts with different backgrounds can interact and identify more problems when working together than when working separately and combining their results. The "Guide-Word" HAZOP is the most wellknown of the HAZOPs; however, several specializations of this basic method have been developed. [19]



9.2. Success or Failure The success or failure of the HAZOP depends on several factors. 1. The completeness and accuracy of drawings and other data used as a basis for the study. 2. The technical skills and insights of the team. 3. The ability of the team to use the approach as an aid to their imagination in visualizing deviations, causes, and consequences. 4. The ability of the team to concentrate on the more serious hazards which are identified.



9.3. HAZOP Characteristics HAZOP is best suited for assessing hazards in facilities, equipment, and processes and is capable of assessing systems from multiple perspectives: [19] 118



CHAPTER IX



HAZOP Study



9.3.1. Design Assessing system design capability to meet user specifications and safety standards. Identifying weaknesses in systems 9.3.2. Physical and operational environments Assessing environment to ensure system is appropriately situated, supported, serviced, contained, etc. 9.3.3. Operational and procedural controls Assessing engineered controls (ex: automation), sequences of operations, procedural controls etc. Assessing different operational modes start-up, standby, normal operation, steady & unsteady states, normal shutdown, emergency shutdown, etc.



9.4. Advantages 1. Helpful when confronting hazards that are difficult to quantify that is,  Hazards rooted in human performance and behaviors.  Hazards that are difficult to detect, analyze, isolate, count, predict, etc.  Methodology doesn’t force you to explicitly rate or measure deviation probability of occurrence, severity of impact, or ability to detect. 2. Built-in brainstorming methodology. 3. Systematic & comprehensive methodology. 4. More simple and intuitive than other commonly used risk management tools.



9.5. Disadvantages 1. No means to assess hazards involving interactions between different parts of a system or process. 2. No risk ranking or prioritization capability. Teams may optionally build-in such capability as required. 3. No means to assess effectiveness of existing or proposed controls (safeguards). May need to interface HAZOP with other risk management tools.



9.6. Effectiveness The effectiveness of a HAZOP will depend on: 1. 2. 3. 4. 5. 6. 7. 8. 9.



The accuracy of information (including P&IDs) available to the team information Should be complete and up-to-date The skills and insights of the team members How well the team is able to use the systematic method as an aid to identifying Deviations The maintaining of a sense of proportion in assessing the seriousness of a hazard The expenditure of resources in reducing its likelihood The competence of the chairperson in ensuring the study team rigorously follows Sound procedures.



9.7.



Key Elements



Key elements of a HAZOP are, [19]



119



CHAPTER IX 1. 2. 3. 4. 5. 6.



HAZOP Study



HAZOP team. Full description of process. Relevant guide words. Conditions conducive to brainstorming. Recording of meeting. Follow up plan.



120



CHAPTER IX



9.8.



HAZOP Study



Guide Words Table 9-1: HAZOP study guide words [19]



Guide Words



Meaning The complete No, Not, None negation of the intention More, Higher, Greater



Quantitative increase



Less, Lower



Quantitative decrease



As well as



Qualitative increase



Part of



Qualitative decrease



Reverse



The logical opposite of the intention



Other Than



Complete substitution



Comments No part of the design intention is achieved, but nothing else happens. Applies to quantities such as flow rate and temperature and to activities such as heating and reaction. Applies to quantities such as flow rate and temperature and to activities such as heating and reaction. All the design and operating intentions are achieved along with some additional activity, such as contamination of process streams. Only some of the design intentions are achieved, some are not. Most applicable to activities such as flow or chemical reaction. Also applicable to substances, for example, poison instead of antidote. No part of the original intention is achieved. The original intention is replaced by something else.



121



CHAPTER IX



9.9.



HAZOP Study



HAZOP Study on Crystallizer Table 9-2: HAZOP study on crystallizer



Guide



Deviation



Flow rate No Level Temperature



Cause No Feed to crystallizer vessel Feed pump rupture Supply pipe rupture Valve is closed Pump is off Blockage in line Valve is closed Fault in refrigeration cycle Coolant pipe rupture



Consequences



Less crystal formation



Less crystal formation Less crystal formation



Action Cleaning of line Level control system Maintenance of pipes Automatic valve Automatic pump Maintenance of pipes Automatic valve Maintenance of pipes & valves Automatic valve Check feed pump



Flow rate



More valve opening



Less crystal formation



Level



More valve opening



Overflow



Check feed pump Automatic feed inlet valve



Fault in refrigeration cycle



Less crystal formation Loss of water



Check coolant flow rate Check coolant temperature Check pipelines



Flow rate



Feed pump rupture Feed valve failure



Less crystal formation



Automatic valve Check feed pump



Level



Feed pump rupture Feed valve failure



Less crystal formation



Check feed valve Check feed pump



More Temperature



Less



122



CHAPTER IX



HAZOP Study Temperature



Over cooling of process liquid



As well as



Impurities in feed stream



Fault in centrifuge (F-101) Fouling in pipes



Part of



Higher or Lower percentage calcium nitrate crystals



High percent of calcium nitrate Less percent of calcium nitrate of Maintain optimum temperature Fail to maintain optimum temperature



Less crystal formation Temperature control system Failure of operation Decrease the coolant flow rate Decrease water solubility in product Check centrifuge conditions and working Less crystal formation Maintain reactor (R-101) Decreases product quality temperature to minimize side reactions



More or less crystals formation than intended



123



Quality control of feed and crystals formed



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



CHAPTER # 10 Environmental Impact Assessment



124



CHAPTER X



Environmental Impact Assessment



Environmental Impact Assessment (EIA) is the process of assessing the likely environmental impacts of a proposal and identifying options to minimize environmental damage. The main purpose of EIA is to inform decision makers of the likely impacts of a proposal before a decision is made. EIA provides an opportunity to identify key issues and stakeholders early in the life of a proposal so that potentially adverse impacts can be addressed before final approval decisions are made. The EIA also includes a description of the measures taken to avoid, reduce or remedy these effects. [22]



10.1. Overview The US Environmental Protection Agency Pioneered the use of pathway analysis to determine the likely human health impact of environmental factors. The technology for performing such analysis is properly called as environmental science. The principal phenomenon or pathways of impact are: [23] 1. 2. 3. 4. 5. 6.



Noise and health effects Water pollution impacts Ecology impacts including endangered species assessment Air pollution impacts Soil contamination impacts Geological hazards assessment



10.2. Objectives 1. Ensuring environmental factors are considered in the decision-making process. 2. Ensuring that possible adverse environmental impacts are identified and avoided or minimized. 3. Informing the public about the proposal.



10.3. Advantages 1. Allows people to examine the underlying need for a project. 2. Gives people the opportunity to identify problems. 3. Helps a developer to design a more publicly acceptable project.



10.4. Ammonia Ammonia is a compound of nitrogen and hydrogen with the formula NH 3. Ammonia is a colorless gas with a characteristic pungent smell. NH3 boils at −33.34 °C (−28.012 °F) at a pressure of one atmosphere, so the liquid must be stored under pressure or at low temperature. When mixed with oxygen, it burns with a pale yellowish-green flame. At high temperature and in the presence of a suitable catalyst, ammonia is decomposed into its constituent elements. 10.4.1. Hazard Fire hazards 1. Ammonia vapor in air is flammable and may explode when ignited. 2. Chemically stable under normal conditions. 3. Emits poisonous fumes when heated to decomposition temperature. 4. Increased risk of fire and explosion on contact with oxidizing agents.



125



CHAPTER X



Environmental Impact Assessment



Health hazards 1. Exposure by any route may be dangerous. Main routes of exposure are:  Inhalation (if Inhale it is very toxic, can cause death).  Skin contact (if skin contact occurs this gas irritates or burns the skin).  Eye contact (if eye contact occurs, this can cause permanent blindness or other severe diseases). 2. Ammonia is not considered to be carcinogenic to humans. 3. Ammonia is not considered to be a human reproductive or developmental toxicant. 4. Acute inhalation may result in irritation of eyes and nose with sore throat, cough, 5. Chest tightness, headache and confusion. 6. Acute skin exposure may result in deep burns. 7. Immediately report leaks, spills or failures of the safety equipment. 8. In event of a spill or leak, immediately put on escape-type respirator and exit the area. 9. Get medical attention for all exposures. 10.4.2. Protective measures PPE’s needed when working with ammonia: Eye/face protection Wear chemical safety goggles. A face shield (with safety goggles) may also be necessary. Skin protection Wear chemical protective clothing e.g. gloves, aprons, boots. In some operations wear a chemical protective, full-body encapsulating suit and self-contained breathing apparatus (SCBA). Respiratory protection Up to 250 ppm any chemical cartridge respirator with cartridge(s) providing protection against ammonia or any supplied-air respirator. 10.4.3. Spills and emergencies If employees are required to clean up spills, they must be properly trained and equipped. If ammonia is leaked, take the following steps: 1. Evacuate personnel and secure and control entrance to the area. 2. Ventilate area of the leak to disperse the gas. 3. Stop flow of gas, if source of leak is cylinder and leak cannot be stopped in place, remove the leaking cylinder to a safe place in open air, and repair leak or allow cylinder to empty. 4. Move cylinders away from the fire if there is risk. 5. The threshold limit value of ammonia is 25 to 35ppm.



10.5. Nitric acid Nitric acid (HNO3) is a highly corrosive mineral acid. When the solution contains more than 86% HNO3, it is referred to as fuming nitric acid. 10.5.1. Hazards 1. Inhalation may result in a burning sensation, cough, unconsciousness, and death. Symptoms may be delayed. 126



CHAPTER X 2. 3. 4. 5.



Environmental Impact Assessment



Skin contact may result in serious skin burns and pain. Eye contact may result in redness and pain. Ingestion may result in abdominal pain, burning sensation and shock and vomiting. Long-term exposure to concentrated vapors may cause lung damage.



10.5.2. Protective measures 1. If exposed through inhalation, bring victim out into fresh air. To prevent inhalation exposure use proper ventilation, use local exhaust, use breathing protection. Artificial respiration may be needed. Provide immediate medical attention. 2. If skin contact occurs, remove contaminated clothes. Rinse skin with plenty of water or shower. Refer for medical attention. To prevent skin exposure use protective gloves, protective clothing. 3. If eye contact occurs, flush with cool water for at least 15 minutes. Use face shield or eye protection in combination with breathing protection to prevent eye exposure. 10.5.3. Exposure Controls 1. Local exhaust ventilation or breathing protection is required. Secondary containment of all storage and use is required if an exposure risk to employees or the environment is present. 2. Depending upon quantities, certain regulatory permits and/or registrations may be required. Personnel working with the materials must receive detailed training on the hazards, safe use, and emergency procedures. 3. Avoid all contact with substance. Prevent skin/eye contact through the use of impervious gloves, clothing, boots, apron, eye goggles and full face shield. If the airborne exposure limit may be exceeded and engineering controls are not feasible, wear appropriate respiratory protection. 4. Material is disposed of as hazardous waste. Contact the Waste Management Group for specific disposal requirements and procedures. Containers and other materials that are contaminated with nitric acid must also be treated as hazardous waste. Collect leaking liquid in sealable containers. Cautiously neutralize remainder with sodium carbonate. Then wash away with plenty of water. 5. In the event of a significant release that poses a threat to employees and/or the environment, immediately evacuate the area and notify your supervisor. 6. Keep it separated from combustible materials, in cool and dry place. Keep it in well ventilated room. 7. The threshold limit value of nitric acid is 2 to 4ppm.



10.6. Nitro-phosphate fertilizer Nitro-phosphate (NP) is a complex granulated fertilizer majorly consists of nitrogen (N) and phosphorous (P2O5) with little amounts of calcium (Ca). It is acidic in nature with pH of 3.5 and is suitable for soils of higher pH.



127



CHAPTER X



Environmental Impact Assessment



10.6.1. Environmental issues Air emissions 1. Exhaust gas emissions produced by the combustion of gas or diesel in turbines, boilers, compressors, pumps and other engines for power and heat generation, are a source of air emissions from phosphate fertilizer manufacturing facilities. 2. Air emissions from NPK plant include ammonia emissions from the ammonization reactors; nitrogen oxides (NOX), mainly NO and NO2 with some nitric acid, from phosphate rock digestion in nitric acid; fluorides from the phosphate rock reactions; aerosol emissions, including ammonium nitrate (NH4NO3), ammonium fluoride (NH4F), and ammonium chloride (NH4Cl), formed in the gas-phase neutralization reaction between ammonia and acidic components, as well as by sublimation from the boiling reaction mixture; and fertilizer dust originating from drying and cooling drums, and from other sources (e.g. screens, crushers, and conveyors). 3. Fugitive emissions are primarily associated with operational leaks from tubing, valves, connections, flanges, packing, open ended lines, floating roof storage tank and pump seals, gas conveyance systems, compressor seals, pressure relief valves, tanks or open pits/containments, and loading and unloading operations of products. Waste water Effluent from NPK facilities employing the nitro-phosphate route may contain ammonia, nitrate, fluoride and phosphate. Ammonia is found in the effluents of the condensates of the ammonium nitrate evaporation or the neutralization of the nitro phosphoric acid solution. Solutions containing ammonium nitrate must be pumped with care to limit the risks of explosions. The main sources of nitrate and fluoride levels in effluent are the scrubber liquors from phosphate digestion and sand (removed from the process slurry) washing. Washing of sand also generates phosphate content in the effluent. Hazardous materials Phosphate fertilizer manufacturing plants use, store, and distribute significant amounts of hazardous materials (e.g. acids and ammonia). Wastes Non-hazardous solid wastes may be generated from some phosphate fertilizer manufacturing processes, including phosphor-gypsum from wet phosphoric acid production, and quartz sand from NPK production using the nitro-phosphate route. Quartz sand should be separated, washed, and recycled as a building material. There is limited hazardous waste generated from the phosphate fertilizer manufacturing processes. Noise Noise is generated from large rotating machines, including compressors and turbines, pumps, electric motors, air coolers, rotating drums, spherodizer, conveyors belts, cranes, fired heaters, and from emergency depressurization. 10.6.2. Recommended measures 1. Reduce NOX emission from nitric acid use in phosphate rock digestion by controlling the reactor temperature, optimizing the rock / acid ratio, and adding urea solution. 128



CHAPTER X



Environmental Impact Assessment



2. Treat gases from the digestion reactor in a spray tower scrubber to recover NO X and fluorine compounds. The pH may be adjusted by the addition of ammonia. 3. Fluoride emissions should be controlled through scrubbing systems. 4. Emissions to air from phosphate rock digestion, sand washing and CNTH filtration should be reduced by applying appropriate controls (e.g. multistage scrubbing, conversion into cyanides). 5. Selection of appropriate valves, flanges, fittings during design, operation, and maintenance. 6. Implementation of monitoring, maintenance, and repair programs, particularly in stuffing boxes on valve stems and seats on relief valves, to reduce or eliminate accidental releases. 7. Use of open vents in tank roofs should be avoided by installing pressure relief valves. All storages and unloading stations should be provided with vapor recovery units. Vapor processing systems may consist of different methods, such as carbon adsorption, refrigeration, recycling collecting and burning. 8. Treat waste water through a biological treatment with nitrification/de-nitrification and precipitation of phosphorous compounds.



129



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



Appendixes



130



Appendixes



Appendix A: Heat exchangers



Figure A-1: Tube side heat transfer curve



Figure A-2: LMTD correction factor



131



Appendixes



Figure A-3: Tube side friction factor



Figure A-4: Tube side return pressure losses



132



Appendixes



Figure A-5: Shell side heat transfer curve Table A-1: Dimensions of steel pipe



133



Appendixes Table A-2: Overall design coefficients



Table A-3: Tube sheet layout (triangular pitch)



Table A-4: Heat exchanger tube data



134



Appendixes Table A-5: Materials of construction for heat exchangers



Table A-6: Nozzle inside diameter for S&T heat exchangers



Table A-7: Gasket factors



135



Appendixes



Appendix B: Pumps



Figure B-1: Pump selection chart Table B-1: Location of process equipment



Table B-2: Pressure drop across process equipment



136



Appendixes Table B-3: Pump characteristics



Table B-4: Characteristics of pump drivers



137



Appendixes Table B-5: Standard electric motor sizes



138



Appendixes



Appendix C: Equipment cost



Figure C-1: Cost data of double pipe heat exchanger



Figure C-2: Cost data of shell and tube heat exchanger



139



Appendixes



Figure C-3: Cost data of dryers



Figure C-4: Cost data of centrifuge



140



Appendixes Table C-1: Cost data of equipment



141



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER



12. References [1]



International Fertilizer Development Centre, Fertilizer Manual, Kluwer Academic Publishers, 1998.



[2]



Francis T. Nielsson, Manual of Fertilizer Processing, 1987.



[3]



Food & Agriculture Organization of United Nations, World fertilizer trends & outlook to 2018, 2018.



[4]



Iltifat Hussain, "The Operating experience of Nitrophosphate Plant," Elsevier, 2011.



[5]



Richard M. Felder &. Ronald W. Rousseau, Elementary Principles of Chemical Processes, 2005.



[6]



David M. Himmelblau &. James B. Riggs, Basic Principles & Calculations in Chemical Engineering.



[7]



H. C. Van Ness, M. M. Abbott & James M. Smith, Introduction to Chemical Engineering Thermodynamics, 7th edition.



[8]



Robert H. Perry, Perry's Chemical Engineers Handbook.



[9]



H. Scott Fogler, Elements of Chemical Reaction Engineering.



[10]



Octave Levenspiel, Chemical Reaction Engineering.



[11]



James M. Douglas, Conceptual Design of Chemical Processes, McGraw Hill Book Company.



[12]



Donald Q. Kern, Process Heat Transfer.



[13]



R. K. Sinott, Chemical Engineering Design, Volume 6.



[14]



Stenlay M. Walas, Chemical Process Equipment Selection & Design.



[15]



Warren L. McCabe &. Jullian C. Smith, Unit Operations of Chemical Engineering, 5th Edition.



[16]



Allan S. Myerson, Handbook of Industrial Crystallization.



[17]



Harry Silla, Chemical Process Engineering Design & Economics.



[18]



Klaus D. Timmerhaus, Ronald E. West & Max S. Peter, Plant Design & Economics



142



PRODUCTION OF 1,000 MTPD NITROPHOSPHATE FERTILIZER for Chemical Engineers, 2003. [19]



"Chemical Engineering Plant Cost Index," [Online]. Available: https://www.chemengonline.com/pci-home.



[20]



George Stephanopoulos, Chemical Process Control.



[21]



Dale E. Seborg &. Thomas F. Edgar, Process Dynamics & Control.



[22]



Mackenzie L. Devis & David A. Cornwell, Introduction to Environmental Engineering.



[23]



Betty Bowers Marriott, Environmental Impact Assessment.



143