Chemical Process Calculations Lecture series - Lecture 40 41 Energy Balance in (Distillation) Unit operations

In this lecture, Introduction to the concepts of Distillation , Numerical on Energy balance in Distillation column is added Numerical on crystallizer, DETERMINATION OF HEAT TRANSFER AREA NUMERICAL in crystallizer are solved. -------------- A Swenson-Walker crystallizer is used to crystallize Na2SO4*10H2O crystals at the rate of 1000 kg/h by cooling a saturated solution of Na2SO4 from 313 K to 290 K. Cooling water enters the unit at 285 K and leaves at 300 K. Evaporation is negligible. The solubilities of anhydrous Na2SO4 in water are 49 parts and 15 parts of Na2SO4 per 100 parts of free water at 313 K and 290 K respectively. The mean specific heat of liquor is 3.8 kJ/kg K and the heat of crystallization is -243 kJ/kg. For the crystallizer , the available heat transfer area is 3 m2/m length and the overall coefficient of heat transfer is 0.2 KW/m2K. How many sections of the crystallizer ,each 3 m long , will be required ? ---------------- FeSO4 7H2O crystals are produced in a Swenson-Walker crystallizer by cooling the saturated solution at 323 to 303 K. Solubility are 48 parts and 32.9 parts of FeSO4 per 100 parts of free water at at 323 K and 303 K respectively. The Feed solution has an average specific heat of 2.93 kJ/kg K. Heat of solution of FeSO4 7 H2O at 303 K is 18.4 kJ /mol How much heat is evolved during the process per kg of FeSO4 7H2O ---------------- A Swenson-Walker crystallizer is isto cool a 23 % solution of Na3PO4 from 40 OC to 25 OC. During cooling. Na3PO4 12 H2O is crystallized. It is desired to produce 225 kg of product/ hour. The solubilities of anhydrous Na3PO4 at 25 oC is 15.5 parts and 15 parts of anhydrous salt per 100 parts of total water. The mean specific heat of solution is 0.77 kcal/kg oC and the heat of crystallization for 1 kg of product is 35 kcal. The cooling H2O is to enter the crystallizer jacket at 15 oC and is to leave at 20 oC. The overall heat transfer coefficent (U) = 120 kcal/m2 h oC. What is the HT area of the crystallizer. --------------------- Numercal to determine Overall HEAT TRANSFER COEFFICIENT Answers are subject to verification by the learners.