Extracting sodium chloride from seawater, using nanofiltration

摘要

Seawater is pretreated to make it suitable for nanofiltration. The nanofiltered seawater is sent to a thermal desalination plant, 14 which operates as a sodium chloride concentrator and a distilled water producer. The concentrated sodium chloride solution is then crystallised (e.g. in a forced circulation crystalliser 21). The crystallised sodium chloride is dewatered 25. This process should provide a high purity sodium chloride product salt suitable for many industries. The salt produced should eliminate many of the requirements of the primary and secondary brine pre-treatment for the chlor-alkali salt electrolysis industry. The nano-filtration process 4 has a higher rejection rate for calcium, magnesium and sulphate ions, than for Na or Cl ions.