膜法冷冻脱硝工艺在氯碱联产氯酸钠中的应用

Application of combined membrane and freezing process for sulfate removal in combined chlor-alkali and sodium chlorate production

介绍了在氯碱联产氯酸钠过程中的淡盐水脱硝工艺。将氯碱生产中的淡盐水通过氯碱生产系统纳滤膜和氯酸钠生产系统纳滤膜二次脱硝后,送入氯酸钠电解系统。电解液中硫酸钠质量浓度≤6 g/L,氯化钠质量浓度提高至100-120 g/L,电解效率提高至91%-92%;氯酸钠产品中芒硝质量分数≤0.02%,芒硝产品中氯酸钠含量≤5 mg/kg,纳滤膜使用寿命延长至3年。该工艺适合北方干燥地区用卤水制烧碱企业,将氯碱生产系统的淡盐水通过管道直接供给氯酸钠电解系统,低品位电解液热量也得到充分利用。

The process for sulfate removal from the dilute brine formed in combined chlor-alkali and sodium chlorate production was introduced.The dilute brine formed in chlor-alkali production was sent to nanofiltration membrane in chlor-alkali system and to nanofiltration membrane in sodium chlorate system to remove sulfate twice,then was sent to the chlorate electrolytic system.The mass concentration of sodium sulfate in electrolyte was ≤6 g/L.The mass concentration of sodium chloride was increased to 100-120 g/L.The electrolysis efficiency was increased to 91%-92%.The mass fraction of mirabilite in sodium chlorate products was≤0.02%.The sodium chlorate content in mirabilite products was ≤5 mg/kg.The service life of nanofiltration membrane was extended to 3 years.The process was suitable for the caustic soda production enterprises using bittern as raw material in northern dry areas.The dilute brine formed in the chlor-alkali production system was directly supplied to the electrolytic system for producing sodium chlorate through the pipeline,and the low-grade heat of the electrolyte was also fully utilized.