Information required for gas-liquid reactor design

Once the type of reactor has been chosen, designing the reactor from basic principles (as opposed to pilot plant construction and development) first of all requires some tentative decisions about the size, shape and mechanical arrangement of the equipment in the light of knowledge of the flowrates to be used. These preliminary decisions will eventually be subject to confirmation or amendment as the design proceeds. Then there is a variety of other information that needs to be either estimated from the literature, or measured experimentally if the opportunity exists. Altogether the kind of information required may be considered under three headings  

The kinetics of the reaction need to be known or measured, in particular the rate constant and how it may be affected by temperature. Many gas-liquid reactions, like chemical reactions generally, are accompanied by the evolution or absorption of heat. Even if there are arrangements within the reactor for the removal of heat (e.g. cooling coils in a stirred tank reactor), it is unlikely that the temperature will be maintained constant at all stages in the process. Experimental methods for measuring the kinetics of reactions are considered in a later section. 

The two most important physical properties of the system are the solubility of the gas and its diffusivity in the liquid. 

The solubility of the gas is needed so that CAI the concentration of the reactant A at the interface, can be calculated. The solubility is often expressed through the Henry Law constant M, this is defined by PAe = 3KCA, where PAe is the partial pressure of the gas A at equilibrium with liquid in which the concentration of the dissolved gas is CA. This immediately raises a problem for many systems how can the solubility, which requires gas and liquid to be at equilibrium, be determined when the gas reacts with the liquid The answer is by one of several methods. 

A similar problem exists in determining the diffusivity of a gas in a liquid with which it reacts. Diffusivities are not easy to measure accurately, even under the best experimental circumstances. As in the case of solubility, the diffusivity DAB needed in the basic equations can be estimated from a semi-empirical correlation, and 

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