A You are designing a process that requires tight control ov

A) You are designing a process that requires tight control over the concentration of the product.

You will use control the product concentration by varying the bypass mass flow rate. Initially the

aqueous feed to the process enters at 1000 kg/h with mass fraction xA=0.400. Part of the feed

stream enters an evaporator that removes 35.0% of the water. The remainder of the feed

bypasses the evaporator and combines with the concentrated stream leaving the evaporator to

form the final product stream.

A.1) What is the range of concentrations that you can achieve by varying the bypass ratio (mass

flow rate of bypass / mass flow rate into evaporator)?

A.2) What bypass ratio should you choose to achieve a product concentration of xA=0.460?

A.3) Due to a disturbance upstream from your process, the feed concentration changes to

xA=0.425. What should the new bypass ratio be to maintain a product concentration of

xA=0.460?.

Solution

Answer

(c.)Determine the feed rates of 20 % solution and diluting wa