MAY 2022 CHE3102 3. EVAPORATION PROCESS A metal salt solution is concentrated in a forced circulation evaporator from a concentration of 1.0wt% to a final concentration of 40wt%. The feed solution entering the evaporator at 50C has a flow rate of 1.5kgs1. The evaporator is operating at 75kPa and has an overall heat transfer coefficient of 1200Wm2K1. The boiling point of the solution in the evaporator is 125C. The heat duty of the evaporator is satisfied by saturated steam supplied at 10 bar. Steam enters the heating tubes. Each tube has an outer diameter of 2cm and a length of 3m. Assume that the specific heat capacity of the liquid solutions at constant pressure is constant at 4.2kJkg1K1 and heat loss from the evaporator is negligible. Calculate, (a) The mass flow rate of vapour and final liquor produced; [4 MARKS] (b) The boiling point rise of the solution; [3 MARKS] (c) The heat transfer surface area required; [12 MARKS] (d) The steam economy of this evaporator; [2 MARKS] (e) The minimum number of tubes required. [4 MARKS]