Question

FULL SOLUTION PLEASE

Fifty mol% methanol in water at 101 kPa is continuously distilled in a seven-plate, perforated-tray column, with a total condenser and a partial reboiler heated by steam. Normally 100 kmol/h of feed is introduced on the third plate from the bottom. The overhead product contains 90 mol% methanol, and the bottoms 5 mol%. One mole of reflux is returned for each mole of overhead product. Recently it has been impossible to maintain the product purity in spite of an increase in the reflux ratio. The following test data were obtained:

Stream	Kmol/h	Mol% alcohol
Feed	100	51
Waste	62	12
Product	53	80
Reflux	94	-

What is the most probable cause of this poor performance? What further tests would you conduct to establish the reason for the trouble? VLE data at 1 atm for methanol-water is:

x	0.0321	0.0523	0.075	0.154	0.225	0.349	0.813	0.918
y	0.1900	0.2940	0.352	0.516	0.593	0.703	0.918	0.963

Answer 1