Concentration of chlor-alkali membrane cell depleted brine

Abstract

This invention relates to methods, systems and installations for concentrating depleted brine produced by the electrolytic decomposition of concentrated brine in chlor-alkali membrane cells and to the efficient use of power, steam and brine. More particularly, this invention relates to the use of depleted brine directly into evaporation systems, which are used to concentrate the brine for reuse in membrane cells or other processes. This invention employs the phenomena that a week unsaturated brine boiling under reduced pressure has a lower boiling point rise (BPR) than a saturated brine boiling at the same or higher pressure. The concentration of depleted brine at a lower boiling point rise improves the operating efficiency of either mechanical vapor recompression and/or steam jet thermocompression. Further, this invention allows for concentrating the depleted brine at temperatures low enough to utilize plastic materials of construction. The use of plastic materials of construction in place of metals in the major components of the installation eliminates or minimizes the metal contamination of the brine being concentrated.

Dependencies are inferred from the claim text.