Inside a distillation column (Problem 4.8), a downward-flowing liquid and an upward-flowing vapor maintain contact with each other. For reasons we will discuss in greater detail in Chapter 6, the vapor stream becomes increasingly rich in the more volatile components of the mixture as it moves up the column, and the liquid stream is enriched in the less volatile components as it moves down. The vapor leaving the top of the column goes to a condenser. A portion of the condensate is taken off as a product (the overhead product), and the remainder (the reflux) is returned to the top of the column to begin its downward journey as the liquid stream. The condensation process can be represented as shown below:

A distillation column is being used to separate a liquid mixture of ethanol (more volatile) and water (less volatile). A vapor mixture containing 89.0 mole% ethanol and the balance water enters the overhead condenser at a rate of 100 lb-mole/h. The liquid condensate has a density of 49.0 lbm/ft3, and the reflux ratio is 3 lbm reflux/lbm overhead product. When the system is operating at steady state, the tank collecting the condensate is half full of liquid and the mean residence time in the tank (volume of liquid/volumetric flow rate of liquid) is 10.0 minutes. Determine the overhead product volumetric flow rate (ft3/min) and the condenser tank volume (gal).

CONDENSER Vapor Condensate CONDENSATE TANK TOP OF Overhead Product DISTILLATION COLUMN Reflux