煤化工废水中硫酸钠-氯化钠-硝酸钠分离工艺研究

根据硫酸钠、氯化钠和硝酸钠溶解度曲线及Na+//Cl-、SO42--H2O三元水盐体系相图,制定了分盐结晶工艺方案,考察了一次蒸发率、冷冻温度、二次蒸发率等参数对分离效果的影响。实验结果表明:控制一次蒸发率为68%,冷冻温度为-5℃,二次蒸发率为70%,采用本方案得到了纯度为96.7%的硫酸钠、94.3%的氯化钠和98.4%的硝酸钠,产品都达到工业标准,解决了杂盐危废问题,消除了二次污染,真正实现了盐的资源化利用。

Study on separation process of sodium sulfate-sodium chloride-sodium nitrate in coal chemical wastewater

According to the solubility curves of sodium sulfate,sodium chloride and sodium nitrate and the phase dia-gram of Na+//Cl-and SO42--H2O ternary water-salt system,a salt separation crystallization process scheme was estab-lished.The effects of parameters such as primary evaporation rate,secondary evaporation rate and freezing tempera-ture on the separation effect were investigated.Experimental results showed that when the primary evaporation rate was controlled at 68%,the freezing temperature was-5℃,and the secondary evaporation rate was 70%,the separa-tion purities of sodium sulfate,sodium chloride and sodium nitrate reached 96.7%,94.3%and 98.4%,respectively,which all meet industrial standards.Therefore,this study solves the problem of hazardous salt waste,eliminates secon-dary pollution,and truly realizes the resource utilization of salt.