2. Evaporator/Crystallizer A 30wt% solution of sodium carbonate (Na2CO3) is fed to an evaporator/crystallizer system with a mass flow rate of 10,000 lb/hr, as shown below. The feed solution is mixed with recycle before entering an evaporator. The evaporator removes water, concentrating the solution and permitting crystallization to occur. The filter cake contains 3.5 lb of crystals per lb of entrained solution (liquid that is carried along with the filter cake). The entrained solution and the recycle solution both contain 0.177 lb of sodium carbonate per pound of solution. a) What is the production rate of the crystals? b) How much water is removed in the evaporator? c) If 40% of the water fed to the evaporator is evaporated, what is the ratio of recycled solution to fresh feed? d) What is the purity (% sodium carbonate; note that this includes both the solid crystals and the sodium carbonate in the entrained solution) of the product solution? e) The solubility of sodium carbonate is 17.7 lb/100 lb of solution. Use references to estimate the temperature of the crystallizer. f) Your boss notes that the evaporator has a maximum capacity of 7500 lb of water evaporated per hour. Assuming the entrainment remains the same (lb of entrained solution per pound of filter cake), and that sodium carbonate solubility is fixed at 17.7 lb/100 lb of solution, will changing the recycle ratio improve product purity? Explain. g) Suggest a process modification that could increase product purity and/or recovery. 3 W 3000 S 7000 W 2 S mixer evaporator crystallizer/filter crystals entrained solution SW