Extractive distillation (Figure 8-14) is used to separate ethanol from water with ethylene glycol as solvent. The A product will be ethanol and the B product water. Stages are counted with condenser \(=1\) and reboiler \(=\mathrm{N}\). The feed plate for the solvent recycle in column 1 is = NS. The feed stages are NF1 in column 1 and NF2 in column 2. Pick the best solution of the listed items. Hint: Sketch the process.

1. If too much solvent is found in the water product:

a. Increase L/D in column 1.

b. Increase the value of NS.

c. Increase the number of stages in the stripping section of column 1 .

d. Increase the number of stages in the stripping section of column 2.

e. Increase the number of stages in the enriching section of column 2.

2. If excessive water is in the ethanol product when fresh solvent is added (no solvent recycle):

a. Increase L/D in column 1.

b. Increase the solvent rate.

c. Increase the value of NS.

d. Increase the number of stages in the stripping section of column 1.

3. If excessive water is in the ethanol product with solvent recycle but was not with the fresh solvent:

a. Increase L/D in column 1.

b. Increase the value of NS.

c. Increase the number of stages in the stripping section of column 1 .

d. Reduce the water in the bottoms of column 2.

4. If excessive ethanol is found in the water product:

a. Increase L/D in column 1.

b. Increase the value of NS.

c. Increase the number of stages in the stripping section of column 1 .

d. Reduce the water in the bottoms of column 2.

e. Increase the number of stages in the enriching section of column 2. 5. If too much solvent is in the ethanol product:

a. Increase L/D in column 1.

b. Increase the value of NF1.

c. Increase the number of stages in the stripping section of column 1 .

d. Reduce the water in the bottoms of column 2.

Transcribed Image Text:

A Product Feed- Solvent Recycle Cooler B B Make up Solvent 2 B Product