煤制乙二醇浓盐水分盐结晶工艺探讨

Investigation on Fractional Crystallization for Brine from Coal-to-Ethylene Glycol Process

以煤制乙二醇含盐废水经预处理、中水回用、纳滤提浓后的纳滤浓水为研究对象,利用水溶液体系相图进行理论分析,选用两种典型的分质结晶工艺进行分析对比,分析表明:浓缩、冷冻结晶、芒硝热溶结晶工艺,硫酸钠的品质有保证,但能耗较高,硫酸钠提取率低;蒸发浓缩→蒸发结晶→蒸发母液冷冻结晶,蒸发析出硫酸钠+冷冻芒硝→溶解重结晶工艺,既保证了硫酸钠品质,且能耗低,硫酸钠提取率高。

Nanofiltration concentrated water from coal-to-ethylene glycol process were pre-treated,reused then treated via nanofiltration,this study focused on the nanofiltration concentrated water after these treatments.Based on phase diagrams of aqueous solution,two processes to separate sodium sulfate from nanofiltration concentrated water were compared.The results showed that sodium sulfate from a concentration-freeze crystallization-mirabilite hot melt crystallization was of high quality,But high energy consumpution and low sodium sulfate extraction efficiency;in evaporation-crystallization process,sodium sulfate was evaporation-crystallized first and mirabilite was freeze-crystallized from mother liquid,sodium sulfate and mirabilite was dissolved and re-crystallized.This protocol was able to maintain the quality of sodium sulfate,reduce energy consumption and high sodium sulfate extraction efficiency.