| 摘要 |
The present invention provides a process for the manufacture of sodium hydroxide and sodium chloride products from a waste brine stream containing sodium chloride, and at least sodium carbonate or sodium bicarbonate. The method of this invention comprises converting the sodium carbonate and/or sodium bicarbonate to sodium hydroxide through addition of lime to the brine, while simultaneously converting impurities to less soluble forms to facilitate their removal. The causticized brine is separated from unreacted lime, calcium carbonate and solid impurities to produce clean brine with reduced levels of impurities. The brine is then concentrated by evaporation, forming relatively pure sodium chloride crystals, which are extracted and rinsed to reduce alkali contaminants. The process continues until sodium hydroxide solution strength of about 46-50 % is reached, with cooling of the solution and separation of crystallised salts further reducing impurities to a comparable level to diaphragm cell derived industrial grade sodium hydroxide. |
