EXP-10 Pressure Drop in Packed Bed [PDF]

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CDB2052 Chemical Engineering Lab I September 2018 Experiment



:



10 - Pressure Drop in Packed Bed



Group



:



B10



Group Members



:



Muhammad Amirul Akmal Bin Mohd Kamal



24460



Aimal 'Aqillah Binti Mohamed Hanif



23795



Rashween Kaur A/P Jagjit Singh



24260



Muhammad Noor Firdaus Bin Sulaiman



24285



Awang Harun Al Rashid Bin Hamzah



Lab Instructor



:



Wegik Dwi Prasetyo



Date of Experiment



:



25th October 2018



18003028



CHAPTER 1 (ABSTRACT) In industry, packed bed reactor is a type of reactor that is commonly used for chemical process that requires catalyst. These reactors are tubular and are filled with solid catalyst particles, most often used to catalyze gas reactions.The chemical reaction takes place on the surface of the catalyst. The advantage of using a packed bed reactor is the higher conversion per weight of catalyst than other catalytic reactors. The conversion is based on the amount of the solid catalyst rather than the volume of the reactor. However, there will be pressure drop packed take place when these reactor is used. The aim for this experiment is to determine the pressure and height variation with flow rate for water system, determine the pressure and height variation with flow rate for air system, verify the friction factor for water system and verify the friction factor for air system. The experiment will be conducted by using the packed bed unit. The fluid that will be used for this packed bed unit is air and water. The packed bed will be tested by using sand, carbon grains, ballotini, ceramic spheres and acrylic pellets. The height of the packed bed and the pressure drop in packed bed unit will be recorded for each conditions. From this experiment, we can observed that in water system at the volumetric flow rate of 5.3 L/m ,as the diameter of the packed material is at the lowest (5mm), the pressure drop will be the highest (1569 Pa). While for the air system, we can observed at volumetric flow rate of 0.04 m3/s, acrylic pellets have the highest pressure drop which is 264.78 Pa. The change in the size of packed bed affects the Reynold’s number (RE) of the flow and RE will affects the friction factor



(f) in the system. Frictional loss is calculated from the formula F =



As the conclusion, the frictional loss is directly proportional to the superficial velocity while inversely proportional to the diameter of particles. As the diameter of the packed bed material is decrease, the frictional loss will become higher and as the superficial velocity increase, the frictional loss will increase. . The type of flow also seems to affect the frictional loss in a pipe system which is transitional flow will have the highest frictional loss compare to laminar and turbulent flow.



CHAPTER 2 (METHODOLOGY/EXPERIMENTAL PROCEDURES) Determination of pressure and height variation with flow rate for water system.



Determination of pressure and height variation with flow rate for air system.



CHAPTER 3 (RESULTS & DISCUSSIONS) Calculation Vs = Q Apipe



= 0.000016666667 π (0.046)2



= 0.010028667



4 The rest of the values of the Vs are calculated by using the same step and tabulated in the Appendices.. RePM = ρVsDP μ(1- ε) = (1000)(0.010028667)(0.0031) (9.107E-4)(1- 0.3584) = 532.07



Laminar Flow RePM < 10 Friction Factor: fPM = 150 RePM



from equation 7



= 0.2819



Friction Loss: F



=150 (0.010028667)(9.107E-4) (1- 0.3584)2 (0.04) (0.031)2 (0.3584)3 (1000)



Turbulent Flow RePM < 1000 Friction Factor: FPM = 1.75



= 2841.99



from equation 9



Friction Loss : F = 1.75 (0.020057333)2(0.04)



= (0.031) Transition Flow 10< RePM < 1000 Friction Factor: FPM = 1.75 + 150 RePM



(1-0.3584) = 0.1266



3



(0.3584)



from equation 11



Friction Loss, F, =



= 1.75 (0.000016666667)2(0.04) (1-0.3584) + 150 (0.000016667)(9.107E-4) (1-0.3584)2 (0.04) (0.031) (0.3584)3 (0.031)2 (0.3584)3 (1000) = 2842.02 For a packed bed of spherical particles, the friction factor: f=



= (137.2931) (0.04)



(0.031) (0.3584)3 = 5.96 (1000)( 0.010028667)2 (1-0.3584)



from equation 13



f = 1.24 + 368 RePM = 1.24 + 368 = 1.93 532.07



from equation 14



f = 2.87Rep-0.1 + 180 Rep



-0.1



= 2.87(532.07)



+ 180



= 1.87



from equation 15



532.07



The value of friction factors, f and friction loss, F for all type of materials are calculated based on the value of Reynold, and are calculated from different equations and are tabulated as per attached in the appendices.



WATER SYSTEM



Figure 1 Figure 2 In the experiment that we conducted, there was no changes in packed bed height for (ballotini) while we increased the flow rate which also increase in Vs of the water and maintained to 0.04 m for all of the flow rates. While the pressure difference, ΔP increased linearly with respect to the increasing in the flow rates with superficial velocity. For material used (sand), the packed bed began to change its behaviour (slight movement) when we increased the flow rate, at Vs: 0.015043 m/s, there was a slight movement in the packed bed and also its bed height began to increase as well means it shows its fluidization.



Figure 3 Figure 4 From the graphs above, (sand) we can see that both graphs show a pattern of inversely proportional when we plotted them with Reynold against the friction factor, f from various equations of friction factor. The entire graph did not fall on the same line for Figure 3 because of the value of the friction factor calculated are difference while Figure 4 falls under the same line because of value of friction factor calculated from equation (7) or (9) are pretty similar. Both graphs are indeed follow the trend of the friction factor diagram for packed bed.



Figure 5 Figure 6 The graphs show an inversely proportional pattern in the water system for material used, sand,



when the values of Reynold were plotted against the value of Friction Loss, F. When the is an increase in friction loss values, the values of friction factor should decrease theoretically. From the graphs that we obtained, it is proved that friction factor is inversely proportional to the value of friction loss.



Figure 7 Figure 8 From the graphs above, (ballotini) we can see that both graphs show a pattern of inversely proportional when we plotted them with Reynold against the friction factor, f from various equations of friction factor. The entire graphs did not fall on the same line for Figure 7 as well as Figure 4 because of the value of the friction factor calculated are difference from using different equations.



Figure 9



Figure 10



The graph in Figure 9 shows a sudden drop in the value of Friction factor, f from 2.03 to 1.75 because of the value of Reynold for both flow rate 1 and 2 in water system for material used, ballotini, are transitional while the rest of them are turbulent flow. So the value of friction factor for turbulent flow should be 1.75 and it maintained until the rest of the flow rates. While in Figure 10 the graph shows an inversely proportional pattern, which if there is an increase in friction loss, the value of frictional factor shall decrease.



Figure 11



Figure 12



In Figure 11, the friction loss against Reynold number graph (Sand) shows that it is directly proportional to each other which indicate that if there is any increase in the value of friction loss, F, the value of Reynold will also increase. While in Figure 12, the friction loss value increased from 2842.02 to 4263.05 and suddenly decreased to the values as tabulated in the Table in the Appendices.



AIR SYSTEM



For air system, there was no changes in packed bed height for these 3 materials which is carbon grains, acrylic pellets and also ceramic sphere when we increased the flow rate which also increase in Vs of the water and bed height still maintained at 0.045 m for all of the flow rates. While the pressure difference, ΔP increased linearly with respect to the increasing in the flow rates and superficial velocity. There are also no slight movements for all these 3 materials that we used in air system that shows packed bed does not change its behavior.



From the graphs above, for carbon grains we can see that the all the plots are decreasing linearly except for the plot of friction factor using laminar or turbulent flow which is increasing linearly and for equation 13 ( friction factor for a packed bed of spherical particles) the graph is constant. Since the flow for carbon grains are laminar flow, the friction factor decreases as the Reynolds number increases. From the second graph we can observe that for both laminar or transition flow, the friction factor decreases linearly as the Reynolds number increases.



For ceramic sphere, according to the Reynolds number, there is transition and turbulent flow in the columns. That is why there is a gap between equations 7 or 9, and 13 with equations 14 and 15. The same concept applies on the second graph. For both the graphs, as Reynolds number increases, the friction factor decreases.



From the above graphs of friction loss against friction factor, the plot for carbon grains decreases linearly but for ceramic spheres and acrylic pellets, the plot is constant. Therefore, as friction factor (using equation 7 or 9 and 11) for carbon grains increases, the friction loss decreases. Both the graphs have the same plot because the flow in the column for carbon grains, ceramic spheres and acrylic pellets are in transition flow.



From the above graphs, we can see that the graph increases linearly for all the three different packed bed materials. Thus, is it proven, the higher the Reynolds number of a porous medium,



the higher the friction factor of the packed bed. This is because friction factor depends on the Reynolds number which differs from laminar to transition and turbulent flow.



CHAPTER 4 (CONCLUSION)



In this pressure drop in packed bed experiment, the most significant elements in this analysis are the continuity and energy conservation. In order to have continuity and energy conservation, the effect of different material of packed bed towards the pressure drop must be studied. If this phenomenon of pressure drop in packed bed is not studied, then we will not have the exact amount of product that we want to produce later in which packed bed reactor is required to produce the product. We can see that different material will cause different pressure drop at the same



volumetric flow rate. From the equation RePM = ρVsDP ,it clearly show us that the diameter and μ(1- ε) porosity of the material will affect the the reynold number of the flow that will determine whether the flow is laminar, turbulent or transitional. This reynolds number will then effect the friction factor from the formula fPM = 150 . As the Reynold’s number increase the friction factor RePM will decrease.



From the formula, F



, frictional loss is depends on the diameter



of the particle,the superficial velocity and the porosity of the material. The frictional loss is directly proportional to the superficial velocity while inversely proportional to the diameter of particles. As the diameter of the packed bed material is decrease, the frictional loss will become higher and as the superficial velocity increase, the frictional loss will increase.



REFERENCES 1. Foley, A. (2018). What Is a Packed Bed Reactor?. Retrieved from https://www.comsol.com/blogs/packed-bed-reactor/ 2. Chaplin, M. (2018). Packed bed reactors. Retrieved from



http://www1.lsbu.ac.uk/water/enztech/pbr.html 3. Itt, M. (2018). NPTEL Chemical Reaction Engineering 2 (Heterogeneous Reactors). Retrieved from https://nptel.ac.in/courses/103106117/33 4. Martin, JJ, WL McCabe and CC Monrad: Chem. Eng. Prog. , 47 , 91-94 (1951) 5. Lee, S. J, Ogawa, K. (1994) Journal of Chemical Engineering of Japan, 25(5), p. 691-693.



APPENDICES



Water System (Sand)



Water System (Ballotini)



Air System (Carbon Grains)



Air System (Acrylic Pellets)



Air System (Ceramic Sphere)



(Sand, Ballotini, Carbon Grain, Acrylic Pellets, Ceramic Sphere)



(Pipe)



(Water Switch, Water Flow, Water Pressure)



(Air Switch, Air Flow, Air Pressure)



(Water Tank)



(Main Power Switch)



(Control Valve)



(Air Compressor)