反渗透浓水诱导结晶法除硬技术开发与应用

Development and Application of Induced Crystallization Method in Hardness Removal from Reverse Osmosis Concentrate

针对化纤类工业园区反渗透浓水除硬难题,研发了硫酸钙诱导结晶除硬优化技术,设计了结晶器并开展中试研究,同时对优化技术进行评价,并进一步将中试成果应用于示范工程,实现了资源化回收硫酸钙产品。对结晶产物进行扫描电镜-能谱(SEM-EDS)分析和热重分析,明确了结晶产物主要为CaSO_(4)·2H_(2)O,当硫酸钙结晶器的水力停留时间为60 min、絮凝剂(含量为11%的聚合氯化铝)投加量为100 mg/L时,硬度去除率较高,同时也可控制运行成本。示范工程运行结果表明,反渗透浓水中的钙离子和硫酸根离子得到了充分回收,CaSO_(4)·2H_(2)O的生成量为51~81 t/d。该诱导结晶除硬技术不仅可以克服传统双碱法的不足(药剂使用量大、运行成本高),还可以减少污泥产量,实现硫酸钙的资源化回收。

This paper developed the optimized technology of calcium sulfate induced crystallization for hardness removal,so as to address the challenge of hardness removal from reverse osmosis concentrate in chemical fiber industrial parks.A crystallizer was designed and applied in a pilot test,while the optimized technique was evaluated.The achievements of the pilot test were further applied in a demonstration project,in which the recovery of calcium sulfate products was realized.The crystal products were analyzed by scanning electron microscopy-energy dispersion spectroscopy(SEM-EDS)and thermogravimetric analysis,which conformed that the crystal products were mainly CaSO_(4)·2H_(2)O.When the hydraulic retention time of calcium sulfate crystallizer was 60 min and the dosage of flocculant(11%polyaluminum chloride)was 100 mg/L,higher hardness removal efficiency was obtained,while the operating cost could be controlled.The operational results of the demonstration project showed that the calcium ions and sulfate ions in the reverse osmosis concentrate were fully recovered,and the yield of CaSO_(4)·2H_(2)O was 51-81 t/d.The induced crystallization technology for hardness removal overcame the shortcomings such as large chemical dosage and high operating cost of the traditional double‑alkali method,reduced the yield of sludge and realized the recovery of calcium sulfate.