The concept of a trickle tower, using ordered bipolar electrode elements stacked in (10 to 80) similar layers of porous, 3D electrodes separated by insulating separator meshes is described and key features of electrochemical reactors based on the bipolar trickle tower reactor (BTTR) geometry are reviewed. Fluid flow, mass transfer, active area and bypass current are considered in detail, since they affect the reaction environment. Modified reactor designs have resulted from the process of electrode selection and tower construction. The performance of BTTRs is illustrated by examples from laboratory and industry, including electrosynthesis and environmental treatment. Experimental data are used to rationalise reaction environment and simulate performance. Operational factors such as electrolyte flow, mass transfer rates and volumetric electrode area are highlighted as important factors in achieving high efficiency; minimisation of internal bypass currents is critical. Developments have enabled improvements in reactor construction and a wider choice of electrode material. Future R & D needs are highlighted.
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