M Bubble Column Reactors

The processes involving reactions between liquid and gas phases are technologically important in many industries. In a bubble column reactor, reactant gas itself (along with an inert gas, if present) provides the required stirring action. It offers an attractive way to carry out gas-liquid and gas-liquid-solid reactions because of its simple construction and operation. However, because of the simple construction, bubble column reactors also have an inherent limitation of having fewer degrees of freedom available to tailor performance characteristics. In a bubble column reactor, local flow, turbulence and gas hold-up distribution are interrelated in a complex way with the operating and design variables. Fluid dynamics of bubble columns may change considerably with variations in physicochemical properties and scale of operation. This causes problems in efficient design and scale-up of bubble column reactors and often results in oversizing of these reactors. Oversizing does not always reduce unreliability and may often cause additional problems concerning product quality and stable reactor operation at varying loads. Development of a detailed fluid dynamic model is therefore essential to understand of the complex interaction between multiphase fluid dynamics and the design and operating variables. Such a model can be used to reduce the number of experiments and to interpret the experimental results with more confidence. The detailed predicted flow field can give an accurate insight and may sometimes give information that cannot be obtained from experiments. This chapter reviews and discusses the application of computational fluid dynamics based models to bubble column reactors.

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