Perhitungan Evaporator [PDF]

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BAB III HASIL DAN PEMBAHASAN



Data-data yang diketahui sebagai berikut : -



Jumlah Nira Encer Densitas Nira Encer % Nira Encer % Nira Kental 1 % Nira Kental II



Rate Nira Encer



= 124,33095 m3/hari = 1587 kg/m3 = 12,12 = 57,97 = 58,89 = 85% nira encer x jumlah niira encer x densitas nira encer = 85% x 124,33095 m3/hari x 1.587 kg/m3 = 167.716,23 kg/hari



Neraca Massa



Menghitung Neraca Massa per Badan Evaporator 1. Evaporator I



Nira Encer



Massa Masuk - Nira Encer - Brix - Air



Nira Pekat Evap I



= 12,12% x 167.716,23 = 167.716,23 – 20.327,21 H2O



= 20.327,21 = 147.389,02 167.716,23 kg/hari



Massa Keluar -



H2O yang diuapkan



=



=



( ( ( ( 1-



% Brix Nira Encer % Brix Nira Evap I



1-



12,12 % 20,32 %



))



))



x 167.716,23



x 167.716,23



= 67.680,76 -



Nira Pekat Evaporator I - Brix = 20,32 % x (167.716,23 – 67.680,76) - Air = 167.716,23 – 67.680,76 – 20.327,21



= 20.327,21 = 79.708,26 167.716,23 kg/hari



 Brix keluar Evaporator I rate nira encer = rate nira keluar x brix nira encer =



(



)



(167.716,23 100 .035,47 )



x 12,12



= 20,32 % 2. Evaporator II



Nira Pekat Evap I



Nira Pekat Evap II



H2O



Massa Masuk - Nira Pekat Evap I - Brix = 20,32 % x (167.716,23 – 67.680,76) - Air = 167.716,23 – 67.680,76 – 20.327,21



= 20.327,21 = 79.708,26 100.035,47 kg/hari



Massa Keluar -



-



H2O yang diuapkan



=



% Brix Nira Evap encer ( ( % Brix Nira Evap I ))



=



12,12 % ( ( 20,32 % ))



1-



1-



x 100.035,47



x 100.035,47



= 40.368,64 Nira Pekat Evaporator II - Brix = 20,32 % x (100.035,47 – 40.368,64) - Air = 100.035,47 – 40.368,64 – 12124,29



= 12124,29 = 47.542,54 100.035,47 kg/hari



 Brix keluar Evaporator II rate nira encer = rate nira keluar x brix Evaporator I =



(



)



(100.035,47 59.666,83 )



x 20,32



= 34,06 % 3. Evaporator III



Nira Pekat Evap II



Massa Masuk H2O - Nira Pekat Evaporator II - Brix = 20,32 % x (100.035,47 – 40.368,64) - Air = 100.035,47 – 40.368,64 – 12.124,29 Massa Keluar



Nira Pekat Evap III



= 12.124,29 = 47.542,54 59.666,83 kg/hari



-



H2O yang diuapkan



=



=



( ( ( ( 1-



% Brix Nira Evap I % Brix Nira Evap I I



1-



20,32 % 34,06 %



))



))



x 59.666,83



x 59.666,83



= 24.069,94 -



Nira Pekat Evaporator III - Brix = 34,06 % x (59.666,83 – 24.069,94) - Air = 59.666,83 – 24.069,94 – 12.124,30



= 12.124,30 = 23.472,59 59.666,83 kg/hari



 Brik keluar Evaporator III rate nira encer = rate nira keluar x brik Evaporator II



(



=



(59.666,83 35.596,89 )



)



x 34,06



= 57,09 % 4. Evaporator IV



Nira Pekat Evap III



Nira Pekat Evap IV



H2O Massa Masuk -



Nira Pekat Evaporator III - Brix = 34,06 % x (59.666,83 – 24.069,94) - Air = 59.666,83 – 24.069,94 – 12.124,30



= 12.124,30 = 23.472,59 35.596,89 kg/hari



Massa Keluar -



H2O yang diuapkan



=



( ( 1-



% Brix Nira Evap I II % Brix Nira Evap I V



))



x 35.596,89



=



( ( 1-



57,09 % 58,89 %



))



x 35.596,89



= 1088,03 -



Nira Pekat Evaporator IV - Brix = 58,89 % x (35.596,89 – 1088,03) - Air = 35.596,89 – 1088,03 – 20.322,27



= 20.322,27 = 14.186,59 35.596,89 kg/hari



 Brix keluar Evaporator IV rate nira encer = rate nira keluar x brix Evaporator III



(



=



)



(35.596,89 34.508,86 )



x 57,09



= 58,89 % Neraca Massa Overall Evaporator



Nira Encer



Massa Masuk - Nira Encer - Brix - Air



Nira Pekat Evap IV



= 12,12 % x 167.716,23 H2O = 167.716,23 – 20.327,21



= 20.327,21 = 147.389,02 167.716,23 kg/hari



Massa Keluar -



H2O yang diuapkan



=



= -



( ( ( ( 1-



% Brix Nira Encer % Brix Nira Evap I V



1-



12,12 % 58,89 %



))



x 167.716,23



x 167.716,23



= 133.198,98 Nira Pekat Evaporator IV - Brix = 58,89 % x (167.716,23 – 133.198,98) - Air = 167.716,23 – 133.198,98 – 20.327,21



 Brix keluar Evaporator IV



))



= 20.327,21 = 14.190,04 167.716,23 kg/hari



=



nira encer (rate rate nira keluar )



=



(167.716,23 34.517,25 )



x brix nira encer



x 12,12



= 58,89 % Data brix keseluruhan yang di dapatkan pada Stasiun Penguapan Uraian Bahan Nira Encer Evaporator I Evaporator II Evaporator III Evaporator IV



%Brix 12,12 20,32 34,06 57,09 58,89



Neraca Panas Distribusi tekanan menurut Hugot Tekanan uap bekas = 0,8 kg/cm2



76 cmHg = 1,8332 kg/cm2 abs x 1,0332 kg/ cm 2



= 134,846 cmHg abs Dari hasil Interpolasi pada P = 1,8332 kg/cm2 abs diperoleh : T Evaporator = 116,89oC (Sumber : Tabel 41.1A, “Properties of Dry Saturated Steam, Hugot, 3rd edition, hlm. 1034)



Vacum Evaporator IV



= 57 cmHg = 76 cmHg – 57 cmHg = 19 cmHg abs ΔP (Pressure Drop) Evaporator I sampai Evaporator IV



= 134,846 – 19 = 115,846 cmHg abs



Perbandingan distribusi ΔP tiap Evaporator (Sumber : Tabel 32.23, “Distribution of Pressure Drop between Vessels, Hugot, 3rd edition, hlm. 579)



 Evaporator I  Evaporator II  Evaporator III  Evaporator IV Tekanan Evaporator I



= 11/40 = 10,3/40 = 9,7/40 = 9/40 = 134,846 – (11/40 x 115,846) = 102,988 cmHg abs = 1,400 kg/cm2 abs Dari hasil Interpolasi pada P = 1,400 kg/cm2 abs diperoleh Tuap = 108,73oC (Sumber : Tabel 41.1A, “Properties of Dry Saturated Steam, Hugot, 3rd edition, hlm. 1034)



Tekanan Evaporator II



= 102,988 – (10,3/40 x 115,846) = 73,158 cmHg abs = 0,9946 kg/cm2 abs Dari hasil Interpolasi pada P = 0,9946 kg/cm2 abs diperoleh Tuap = 98,93oC (Sumber : Tabel 41.1A, “Properties of Dry Saturated Steam, Hugot, 3rd edition, hlm. 1034)



Tekanan Evaporator III



= 73,158 – (9,7/40 x 115,846) = 45,065 cmHg abs = 0,6127 kg/cm2 abs Dari hasil Interpolasi pada P = 0,6127 kg/cm2 abs diperoleh Taup = 85,99oC (Sumber : Tabel 41.1A, “Properties of Dry Saturated Steam, Hugot, 3rd edition, hlm. 1034)



Tekanan Evaporator IV



= 45,065 – (9/40 x 115,846) = 18,999 cmHg abs = 0,2583 kg/cm2 abs Dari hasil Interpolasi pada P = 0,2583 kg/cm2 abs diperoleh Tuap = 65,28oC (Sumber : Tabel 41.1A, “Properties of Dry Saturated Steam, Hugot, 3rd edition, hlm. 1034)



Perhitungan kalor jenis (Cp) nira pada tiap badan Evaporator Rumus :Cp = 1 – (0,006 . X) kkal/kg oC ………………………………………………(1) X = % Brix nira a. Kalor jenis (Cp) nira encer : Cp0 = 1 – (0,006 x 12,12) b. Kalor jenis (Cp) nira pekat : - Cp1 = 1 – (0,006 x 20,32) - Cp2 = 1 – (0,006 x 34,06) - Cp3 = 1 – (0,006 x 57,09) - Cp4 = 1 – (0,006 x 58,89)



= 0,92728 kkal/kg oC = 0,87808 kkal/kg oC = 0,79564 kkal/kg oC = 0,65746 kkal/kg oC = 0,64666 kkal/kg oC



Data-data yang dibutuhkan untuk menghitung neraca panas Komponen



P (kg/cm2)



T (oC)



Uap bekas Nira pekat evaporator I Nira pekat evaporator II Nira pekat evaporator III Nira pekat evaporator IV



0,8 1,400 0,9946 0,6127 0,2583



118,89 108,73 98,93 85,99 65,28



λ (kkal/kg) 644,96 641,99 638,48 633,59 625,31



q (kkal/kg) 117,09 108,63 98,93 85,99 65,18



λ dan q diperoleh dari interpolasi terhadap suhu (Sumber : Tabel 41.1A, “Properties of Dry Saturated Steam, Hugot, 3rd edition, hlm. 1034)



Perhitungan Neraca Panas pada Evaporator Nira Encer (F)



Nira Pekat (L)



Uap (S)



Kondensat (C)



Persamaan yang digunakan : F h f + S h s = L h l + V hv + C h c Panas masuk -



Uap Nira



H2O (V)



= mv1 x λ1 = mN1 x Cp1 x T1



Panas keluar -



Kondensat = mv2 x q2 H2O yang diuapkan = mv2 x λ2 Nira = mN2 x Cp1 x T2 Dimana :



mv



= Rate massa uap (kg/jam)



mN



= Rate massa nira (kg/jam)



λ



= Total heat (kkal/kg)



q



= Sensibel heat (kkal/kg)



Cp



= kalor jenis (kkal/kg oC)



T



= Suhu (oC)



Notasi 1 = menyatakan keadaan masuk Notasi 2 = menyatakan keadaan keluar



Menghitung Neraca Panas tiap badan Evaporator : 1. Evaporator I Panas Masuk - Uap - Nira



= mv x 644,96 = 167.716,23 x 0,92728 x 116,89



Panas Keluar - Kondensat = mv x 117,09 - H2O diaupkan = 67.680,76 x 641,99 - Nira = 100.035,47 x 0,87808 x 108,73



= 644,96 mv = 18.178.721,78 18.178.721,78 + 644,96 mv = 117,09 mv = 43.450.371,11 = 9.550.750,29 53.001.121,4 + 117,09 mv



Persamaan Neraca Panas Overall 18.178.721,78 + 644,96 mv = 53.001.121,4 + 117,09 mv 527,87 mv = 34.822.396,62 mv = 65.967,76 2. Evaporator II Panas Masuk - Uap = mv x 641,99 = 641,99 mv - Nira = 100.035,47 x 0,87808 x 108,73 = 9.550.750,29 9.550.750,29 + 641,99 mv Panas Keluar -



Kondensat = mv x 108,63 H2O diuapkan = 40.368,64 x 638,48 Nira = 59.666,83 x 0,79564 x 98,93



= 108,63 mv = 25.774.569,27 = 4.696.535,21 30.471.104,48 + 108,63 mv



Persamaan Neraca Panas Overall 9.550.750,29 + 641,99 mv = 30.471.104,48 + 108,63 mv 533,36 mv = 20.920.354,19 mv = 39.223,70



3. Evaporator III Panas Masuk -



Uap Nira



Panas Keluar



= mv x 638,48 = 59.666,83 x 0,79564 x 98,93



= 638,48 mv = 4.696.535,21 4.696.535,21 + 638,48 mv



-



Kondensat H2O duapkan Nira



= mv x 98,93 = 24.069,94 x 633,59 = 35.596,89 x 0,65746 x 85,99



= 98,93 mv = 15.250.473,28 = 2.012.469,66 17.262.942.94 + 98,93 mv



Persamaan Neraca Panas Overall 4.696.535,21 + 638,48 mv = 17.262.942,94 + 98,93 mv 539,55 mv = 12.566.407,73 mv = 23.290,53 4. Evaporator IV Panas Masuk - Uap = mv x 633,59 = 633,59 mv - Nira = 35,596,89 x 0,65746 x 85,99 = 2.012.469,66 2.012.469,66 + 633,59 mv Panas Keluar -



Kondensat = mv x 85,99 H2O diuapkan = 1.088,03 x 625,31 Nira ` = 34.508,86 x 0,64666 x 65,28



= 85,99 mv = 680.356,04 = 1.456.755,80 2.137.111,84 + 85,99 mv



Persamaan Neraca Panas Overall 2.012.469,66 + 633,59 mv = 2.137.111,84 + 85,99 mv 547,6 mv = 124.642,18 mv = 227,61



Masuk Uap Nira Total (kcal/jam) Uap Nira Total (kcal/jam) Uap Nira Total (kcal/jam) Uap



Jumlah



Keluar Evaporator I 42.546.566,49 Kondensat H2O yang diuapkan 18.178.721,78 Nira 60.725.288,27 Total (kcal/jam) Evaporator 1I 25.181.223,16 Kondensat H2O yang diuapkan 9.550.750,29 Nira 34.731.973,45 Total (kcal/jam) Evaporator III 14.870.537,59 Kondensat H2O yang diuapkan 4.696.535,21 Nira 19.567.072,8 Total (kcal/jam) Evaporator IV 144.211,42 Kondensat



Jumlah 7.724.165,02 43.450.371,11 9.550.750,29 60.725.286,42 4.260.870,53 25.774.569,27 4.696.535,21 34.731.975,01 2.304.132,13 15.250.473,28 2.012.469,66 19.567.075,07 19.572,18



Nira



2.012.469,66



Total (kcal/jam)



2.156.681,08



H2O yang diuapkan Nira Total (kcal/jam)



680.356,04 1.456.755,80 2.156.684,02