Abstract

Fluid mixing is a unit operation carried out to homogenize fluids in terms of concentrations, physical properties, and temperature, and create dispersions of mutually insoluble phases. It is frequently encountered in process industries such as petroleum, chemical, food, pharmaceutical, paper, and mining. Applications range from 0.01-m³ reactors to 20,000-m³ product storage tanks and continuous in-line mixers. The fundamental mechanism of mixing involves physical movement of material between various parts of the whole mass by transmitting mechanical energy. Adequate mixing is a prerequisite for the success of chemical processes for minimizing investment and operating costs. In addition, chemical reactions with mass-transfer limitation can be enhanced to provide high yields. Good mixing, therefore, plays a significant role in the profitability of the process industry.

Mixing systems are broadly divided into single-phase systems involving blending of miscible liquids; and multiphase systems such as solid–liquid, mutually insoluble liquids, gas–liquid. Fundamental mixing concepts and suitable mixer types, design, and scale-up issues for these mixing classes are discussed. The mixing equipment described includes agitated tanks, jets, static mixers, unique designs for powders and pastes, and devices for transferring heat. Blending of low and high viscosity liquids and suspension of sinking and floating solids are covered in more detail.