Electrolysis improved concepts

The committee s assessment of electrolysis improvements focused on PEM-based technologies rather than on advanced concepts. The effect is to offer a view of futures that are based on today s technology and do not rely on new technological breakthroughs that, should they occur, would only enhance the cost and performance picture. 

Improved next-generation ODC with a catalyst based on rhodium [6] promises an even more simplified plant concept. This is due to the fact that this type of ODC does not require polarisation during shut-down as an inert cathode is no longer necessary. The plant can simply be put at stand-by where the anode side, as well as the HC1 circuit, remains pressurised under chlorine saturation. Therefore, re-starting the operation is very simple and the chlorine supply is derived directly from the electrolysis and liquid chlorine evaporation is no longer necessary. Instead, with a liquid chlorine buffer, the system can be re-started from the hydrochloric acid storage tank. 

Abstract Ion-conducting materials are used as cell separators in electrolysis cells for the double purpose of carrying electric charges between electrodes and separating the products formed at each electrode. The purpose of this chapter is to provide an overview of chlor-alkali technology and associated cell separators. After a brief historical review of the chlor-alkali process, the main reaction characteristics (thermodynamics, cell reactions and kinetics) are detailed in Section 9.1. Main chlor-alkali technologies are described in Section 9.2. Main cell separators are described in Section 9.3 (diaphragm materials) and in Section 9.4 (membrane materials). Some improved electrolysis concepts are described in Section 9.5. 

Classical electrochemical reactor designs invariably evolved from direct scale-up of simple laboratory electrolysis experiments. The most common example of this concept is the tank cell where an array of electrodes is immersed in a plastic or metal tank. More sophisticated versions involve a variety of approaches to enhancing convection, by rapid stirring, rotating or moving electrodes or improving geometry with plate and frame or filter-press-type cells. 

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