make-up water for sodium hydroxide and chlorine production electrolytic systems

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Membrane cells develop current densities of up to 7 000 A·m–2 and, therefore, require very advanced qualities from the NaCℓ brine they receive, resulting in the following treatments :

  • sulphate removal by precipitating BaSO4 in Densadeg (injecting BaCO3 or Ba Cℓ2);
  • removing traces of Ca2+ from specific softening resins (down to below 50 mg · L–1 Ca2+);
  • vacuum dechlorination, often in sidestream mode and, if necessary, supplemented with bisulphite (figure 25).
Chemical purification brine electrolysis membrane cell - Aracruz plant Secured image
Figure 25. Chemical purification of brine for electrolysis using membrane cells. Schematic diagram of the Aracruz plant (Brazil)