Chapter 17 - Separation columns (distillation, absorption, and extraction)

Abstract

Multistage counter-current separation columns are widely used in the process industries as they are an energy and capital efficient way of separating mixtures. Distillation, absorption, stripping and liquid-liquid extraction are all carried out in multistage columns. Methods for the design of binary distillation and multicomponent distillation are given, including factors to consider in setting column pressure, calculating required minimum reflux ratio and actual reflux ratio, estimating the number of trays and the feed location and estimating the reboiler and condenser duties. The McCabe-Thiele method for binary distillation and the Fenske-Underwood-Gilliland method for multicomponent distillation are explained. Mass transfer limitations in distillation are discussed and it is shown how these can be allowed for by using stage efficiency methods such as O’Connell’s correlation and the AIChE method. Methods for sizing plate columns and packed columns are given, including factors to consider in choosing a column diameter and in sizing trays and packings. The design of absorption and stripping columns using Cornell’s method or Onda’s method to estimate the mass transfer parameters is described. An overview of the design of multistage extraction columns is given.