高盐废水中硫酸铵和硫酸钠的分质结晶工艺研究

Study on fractional crystallization process of ammonium sulfate and sodium sulfate in high salt wastewater

处理高盐废水并回收其中的盐资源是许多生产企业废水综合治理的难题。采用等温溶解平衡法测定了10、15、60、80℃下Na_(2)SO_(4)-(NH_(4))_(2)SO_(4)-H_(2)O的液固相平衡数据,基于相平衡数据划分了结晶区域。根据高盐废水的组成和液固相平衡数据,提出了分质结晶分离(NH_(4))_(2)SO4和Na_(2)SO_(4)的工艺路线,设计了结晶过程工艺参数并进行了实验验证。结果表明,废水经3步结晶回收得到的(NH4)2SO4纯度达到了99.2%、Na_(2)SO_(4)纯度达到了98.9%,满足GB/T 535—2020《肥料级硫酸铵》和GB/T 6009—2014《工业无水硫酸钠》的纯度指标要求。该研究可为高盐废水中(NH_(4))_(2)SO_(4)和Na_(2)SO_(4)的回收利用提供参考。

The treatment of high salinity wastewater and the recycling of salt resources in wastewater are challenging task faced by enterprises.The liquid⁃solid equilibrium data of Na_(2)SO_(4)-(NH_(4))_(2)SO_(4)-H_(2)O at 10,15,60 and 80℃were determined by isothermal solution equilibrium method,and the crystallization regions were divided based on phase equilibrium data.A fractional crystallization process was then proposed for the separation and recovery of(NH_(4))_(2)SO_(4)and Na_(2)SO_(4)based on the composition of the high salinity wastewater and the liquid-solid equilibrium data.The technological parameters of the crys⁃tallization process were designed and experimentally verified.The results showed that the purity of(NH_(4))_(2)SO_(4)and Na_(2)SO_(4)by three⁃step crystallization reached 99.2%and 98.9%respectively,which met the purity index of national standard of GB/T 535—2020 and GB/T 6009—2014.This study provided valuable reference for the recovery of(NH_(4))_(2)SO_(4)and Na_(2)SO_(4)from high salinity wastewater.