Chapter 4, Problem 4.6P

A liquid mixture of acetone and water contains 35 mole% acetone. The mixture is to be partially evaporated to produce a vapor that is 75 mole% acetone and leave a residual liquid that is 18.7 mole% acetone.

(a) Suppose the process is to be carried out continuously and at steady state with a feed rate of lO.Okmol/h. Let zi_v and zii be the flow rates of the vapor and liquid product streams, respectively. Draw and label a process flowchart, then write and solve balances on total moles and on acetone to determine the values of zz_v and zii. For each balance, state which terms in the general balance equation (accumulation = input + generation — output — consumption) can be discarded and why. (See Example 4.2-2.)

(b, Now* suppose the process is to be carried out in a closed container that initially contains 10.0 kmol of the liquid mixture. Let zi_v and zz, be the moles of final vapor and liquid phases, respectively. Draw' and label a process flowchart, then write and solve integral balances on total moles and on acetone. For each balance, state which terms of the general balance equation can be discarded and why.

(c) Returning to the continuous process, suppose the vaporization unit is built and started and the product stream flow' rates and compositions are measured. The measured acetone content of the vapor stream is 75 mole% acetone, and the product stream flow rates have the values calculated in Part (a). However, the liquid product stream is found to contain 22.3 mole% acetone. It is possible that there is an error in the measured composition of the liquid stream, but give at least five other reasons for the discrepancy. [Think about assumptions made in obtaining the solution of Part (a).]