ABSTRACT
Many chemical and biochemical reactions are heterogeneous in nature, involving all three phases of solid, liquid and gas. Filtration, sedimentation and dispersion of solids in a liquid involve two phases. One phase is fluid, and the other phase is solid particles. The solid particles may be stationary as in fixed beds, or it may be moving as in fluidised beds or mechanically stirred vessels. Gas-liquid contactors involve the gas phase in the form of bubbles dispersed in liquid or liquid dispersed as droplets in gases. Many processes are carried out in which all three phases (solid, liquid and gas) are present (e.g. slurry bubble column, three-phase fluidised beds and slurry reactors). In bioprocesses, microorganisms or enzymes supported on solids may be present as the solid phase in bioreactors. Some multiphase contactors are presented in Figure 5.1.
