Introduction

Distillation is the oldest separation process and the most widely used unit operation in industry. Distillation began as a simple still in a laboratory. Figure 1.1 shows a schematic illustration of such a still initially lled with a feed mixture which evaporates and leaves the liquid. The vapor, which is richer in the more volatile component, is collected in the condenser at the top. The simple distillation still is an example of a batch operation. The concept of re ux and the use of accessories such as packings or plates to increase the mass transfer convert this simple still into a batch distillation column.