正渗透技术浓缩氯碱阳极淡盐水

Concentration of diluted brine from chlor-alkali industry by forward osmosis

采用正渗透(FO)技术对离子膜法制烧碱中产生的阳极淡盐水进行浓缩,开发阳极淡盐水浓缩新工艺.以脱氯后的淡盐水为原料,饱和盐水为汲取液,研究了膜活性层朝向、膜面流速及原料液温度对FO过程纯水透过通量的影响,并对FO过程的淡盐水浓缩效果和膜污染情况进行了研究,验证了该浓缩工艺的可行性.结果表明,压力延迟渗透(PRO)模式水通量要高于FO模式,在处理高浓度料液时,外浓差极化和内浓差极化均对水通量有较明显的影响;提高进料膜面错流流速,水通量增加,且对PRO模式比对FO模式影响更明显;进料温度升高,膜的水通量提高.两种运行模式下均能将淡盐水浓缩至300g/L以上,满足盐水循环使用要求.浓缩过程中未见明显盐结晶导致的膜污染发生.用工艺液体饱和盐水作汲取液,避免了稀释后汲取液的回收问题,实现了FO过程中真正的低能耗,为FO过程在工业中的大规模推广应用提供了新思路.

Forward osmosis(FO)process was used to concentrate the diluted brine from the production of caustic soda with ion-exchange membrane electrolysis.The effect of membrane orientation,flow velocity,and feed temperature on the water flux of FO process was studied with the diluted brine as feed and saturated brine as draw solution.The concentration effect and the membrane fouling during this process were also investigated.The results show that the water flux in PRO mode is higher than that of FO mode.Both the internal concentration polarization and external polarization concentration polarization had obvious effects on water flux of the high concentration system.The water flux of the FO membrane increased with the brine flow velocity and temperature.The water flux of PRO mode increased more than that of FO mode with the increase of flow velocity.In both FO mode and PRO mode,the diluted brine could be concentrated to more than 300 g/L,which meets the requirements of brine recycling.Membrane fouling caused by salt crystallization was not observed after concentration.The process of the diluted solution recovery was avoided with saturated brine as draw solution,thus low energy consumption of FO process is realized.This study provided a new idea for the popularization and application of FO process in industry.