Characterisation of electrochemical pump cells

Ghoroghchian, Jamal (1978) Characterisation of electrochemical pump cells. University of Southampton, Doctoral Thesis.

Abstract

The hydrodynamic behaviour of electrochemical pump cells is even more complicated than can be inferred from mass transfer data.Study of space time histpries of electrogeneratad species have shown that the flow can be modelled as being composed of two phases, a slow phase creeping along the electrode in communication with a faster phase. It is shown the environment in the pump cells is coupled with the rate chemistry, and simple mechanical variables such as direction of flow or the rotation of electrode can significantly affect the cell environment. It is found that chemical reactions which require strong mixing in order to go to completion (such as the indirect oxidation of propylene) are favoured by the pump cell. Due to controlability of conditions in these cells the engineering environment can be tailored to suit the kinetic of the primary reaction. For example, in the production of propylene oxide, it is possible to match the rate of primary electrochemical step to subsequent chemical step. Where the reactions are residence time sensitive, such as production of chlorate in which short residence time is the most important factor to obtain high current efficiency, again the pump cell is favoured. In the pump cell the electrolyte in the interelectrode gap is well stirred tangentially, but in the raidal sense the cell approximate sa plug flow reactor. This leads to specificity of the reaction in those cases where mixing is beneficial or the transport is sensitive to in homogeniety of conditions. The cell is ideal for the processing of dispersion, emulsions and slurries.

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