Brine Preparation and Treatment

By contrast, in the diaphragm-cell process, more than enough water will be removed in the evaporators. Therefore, one of the advantages of this process is its ability to accept a brine feed, which is usually cheaper than solid salt. 

FIGURE 6.1. Major components of electrolytic chlor-alkali process. 

There are other impurities that may have to be removed from the brine. Sulfate is a frequent example. The techniques used are varied and are applied at different areas of the flowsheet. Therefore, they are not shown as part of the normal sequence in this basic flow diagram. 

The final step in brine preparation is acidification. This is truly not a purification step and is not an essential part of the chlor-aUcali process, but it offers several improvements in cell performance. These are discussed in Section 7.5.6. The acid used is HCl, often produced by reacting together some of the chlorine and hydrogen produced in the plant. 

The circuit is completed when two electrons are consumed at the cathode in the electrolysis of water  

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