Electrochemical Reactors

Abstract

The article contains sections titled: 1. Reactors with Gas‐Evolving Electrodes 1.1. Effects of Gas Evolution on Cell Operation 1.2. Bubble Nucleation, Growth, and Detachment 1.3. Bubble Coverage 1.4. Product Release 1.5. Ohmic Resistance of the Interelectrode Gap 1.6. Mass Transfer at Gas‐Evolving Electrodes 1.7. Heat Transfer 1.8. Overpotential of Gas‐Evolving Electrodes 1.9. Limiting Current Density at Gas‐Evolving Electrodes 1.10. Electrodes 1.11. Gas‐Lift Systems 2. Reactors with Superficial Electrodes 3. Reactors with Three‐Dimensional Electrodes 4. Special Reactor Designs The operating modes of electrochemical reactors vary as widely as the designs of the reactors. This is determined not only by the chemical behavior of the different electrolytes, especially their corrosivity, but also by the very different products. These can be formed as solids, as in electrodeposition, in liquid form, as in the case of many substances that react further in the liquid phase, or as a gaseous phase, for example, in the electrolysis of water. Operating temperatures cover a wide range, from room temperature to 1000 °C. In most cases the electrolytes are liquid solutions or melts, but more recently also solids (e.g., solid polymer electrolytes) and in special cases gases, as in high‐temperature water electrolysis, or plasmas in glow‐discharge electrolysis. Accordingly, the materials and shapes of the electrodes also very diverse. The simplest electrodes are those with flat surfaces. Two such electrodes face each other a few millimeters apart in order to minimize the ohmic potential drop across the gap, or they are divided by a liquid‐permeable diaphragm or gas‐permeable membrane, which also separates the electrolyte chambers from one another. In many cases specially shaped electrodes are used that better meet the requirements of a process. Their influence on the design and operation of the reactors are the subject of this article. In particular, these are reactors with gas‐evolving electrodes and special reactor designs to meet specific requirements.

Tertiary Current and Potential Distribution Including Laminar/Turbulent Convection, Diffusion, and Migration by the Finite Volume Method Using OpenFOAM

“…4 However, the working conditions for electro-synthesis of some products in special electrochemical reactors can deviate from the previous situation and the masstransfer could be influenced by migration, affecting the reactor performance. This situation occurs in the production of periodate from iodate, 16 persulfate, 17 electrodeposition of manganese, 18 organic electrochemistry, 19 electrophoresis, 20 electrodialysis, 21 electrochemical treatment of wastes and effluents, or molten salt electrochemical process. 22 In all these cases, the reactor behavior may be influenced by migration.…”