Feed to a cooling crystallizer is 2,000 kg/h of 30 wt% Na2SO4 in water at 40...

 

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Feed to a cooling crystallizer is 2,000 kg/h of 30 wt% Na2SO4 in water at 40 C. This solution is to be cooled to a temperature at which 50% of the solute crystallizes as decahydrate. Estimate the required heat-transfer area in m if an overall heat-transfer coefficient of 15 Btu/h-ft-F can be achieved. Assume a constant specific heat for the solution of 0.80 cal/g-C. Cooling water at 10 C flows counter-currently to the solution, and exits at a temperature that gives a log mean driving force of at least 10 C. Table 17.5 Solubility and Heat of Solution at Infinite Dilution of Some Inorganic Compounds in Water (a Positive Heat of Solution Is Endothermic) Heat of Solution of Stable Hydrate (at Room Temperature) Solubility (Hydrate-free Basis) g/100 g H2O at T, C kcal/mole Compound Compound 0 10 20 30 40 60 80 100 Stable Hydrate at Room Temperature NHC +3.8 29.7 33.4 37.2 41.4 45.8 55.2 65.6 77.3 (NH4)2SO4 +1.5 71.0 73.0 75.4 78.0 81.0 88.0 95.3 103.3 BaCl2 +4.5 31.6 33.2 35.7 38.2 40.7 46.4 52.4 58.3 CuSO4 +2.86 14.3 17.4 20.7 25.0 28.5 40.0 55.0 75.4 MgSO4 +3.18 22.3 27.8 33.5 39.6 44.8 55.3 56.0 50.0 MgCh -3.1 52.8 53.5 54.5 56.0 57.5 61.0 66.0 73.0 NiSO4 +4.2 26 32 37 43 47 55 63 - KCI +4.4 27.6 31.0 34.0 37.0 40.0 45.5 51.1 56.7 KNO +8.6 13.3 20.9 31.6 45.8 63.9 110 169 247 102576700 0 K2SO4 +6.3 7.4 9.3 11.1 13.1 14.9 18.3 21.4 24.2 AgNO3 +5.4 122 170 222 300 376 525 669 952 0 NaClO3 +5.4 80 89 101 113 126 155 189 233 NaCl +0.93 35.6 35.7 35.8 36.1 36.4 37.1 38.1 39.8 NaNO3 +5.0 72 78 85 92 98 133 163 0 NaSO4 +18.7 4.81 9.0 19.4 40.8 48.8 45.3 43.7 42.5 10 NaSO +11.4 52 61 70 84 103 207 250 266 Na3PO4 +15.0 1.5 4 11 20 31 55 81 108 52 12 Feed to a cooling crystallizer is 2,000 kg/h of 30 wt% Na2SO4 in water at 40 C. This solution is to be cooled to a temperature at which 50% of the solute crystallizes as decahydrate. Estimate the required heat-transfer area in m if an overall heat-transfer coefficient of 15 Btu/h-ft-F can be achieved. Assume a constant specific heat for the solution of 0.80 cal/g-C. Cooling water at 10 C flows counter-currently to the solution, and exits at a temperature that gives a log mean driving force of at least 10 C. Table 17.5 Solubility and Heat of Solution at Infinite Dilution of Some Inorganic Compounds in Water (a Positive Heat of Solution Is Endothermic) Heat of Solution of Stable Hydrate (at Room Temperature) Solubility (Hydrate-free Basis) g/100 g H2O at T, C kcal/mole Compound Compound 0 10 20 30 40 60 80 100 Stable Hydrate at Room Temperature NHC +3.8 29.7 33.4 37.2 41.4 45.8 55.2 65.6 77.3 (NH4)2SO4 +1.5 71.0 73.0 75.4 78.0 81.0 88.0 95.3 103.3 BaCl2 +4.5 31.6 33.2 35.7 38.2 40.7 46.4 52.4 58.3 CuSO4 +2.86 14.3 17.4 20.7 25.0 28.5 40.0 55.0 75.4 MgSO4 +3.18 22.3 27.8 33.5 39.6 44.8 55.3 56.0 50.0 MgCh -3.1 52.8 53.5 54.5 56.0 57.5 61.0 66.0 73.0 NiSO4 +4.2 26 32 37 43 47 55 63 - KCI +4.4 27.6 31.0 34.0 37.0 40.0 45.5 51.1 56.7 KNO +8.6 13.3 20.9 31.6 45.8 63.9 110 169 247 102576700 0 K2SO4 +6.3 7.4 9.3 11.1 13.1 14.9 18.3 21.4 24.2 AgNO3 +5.4 122 170 222 300 376 525 669 952 0 NaClO3 +5.4 80 89 101 113 126 155 189 233 NaCl +0.93 35.6 35.7 35.8 36.1 36.4 37.1 38.1 39.8 NaNO3 +5.0 72 78 85 92 98 133 163 0 NaSO4 +18.7 4.81 9.0 19.4 40.8 48.8 45.3 43.7 42.5 10 NaSO +11.4 52 61 70 84 103 207 250 266 Na3PO4 +15.0 1.5 4 11 20 31 55 81 108 52 12