Assignment 2. Mass Balance Problems Carefully read and solve the mass problems. Include flow diagram and all the procedure and equations used to solve each problem. 1. (10 pts) How much dry sugar needs to be added to 250 kg of aqueous sugar solution in order to increase its concentration from 35% to 75%? 2. (20 pts) You are assigned to design a concentrated orange juice production plant. Fresh orange juice with 10% soluble solids content is concentrated to 50% in a multiple effect evaporator. To improve the quality of the final product the concentrated juice is mixed with an amount of fresh juice (cut back) so that the concentration of the mixture is 38%. Calculate: How much final product will be produced if the inlet feed flow rate is 14,000 kg/h fresh juice. Assume steady state. 3. (20 pts) A continuously operated rotary drier is used to dry 20 kg/min of a starch-based food containing 30% moisture (wet weight basis) to give a product with 15% moisture. The drier cannot handle feed material with a moisture content greater than 20% and therefore a proportion of dry product must be recycled and mixed with the fresh feed. Calculate the evaporation rate and the recycle ratio (ratio of stream recycled/stream it leaves). 4. (Extra credit, 10 pts) Milk with 3.8% fat and 8.1% fat-free solids (FFS) is used to produce canned concentrated milk. The process includes separation of the cream in a centrifuge and concentration of the partially defatted milk in an evaporator. If the cream that is produced in the centrifuge contains 55% water, 40% fat, and 5% fat-free solids, calculate how much milk is necessary in order to produce a can of concentrated milk that contains 410 g milk with 7.8% fat and 18.1% fat-free solids. How much cream and how much water must be removed in the centrifuge and the evaporator respectively? Assume steady state.

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