开展了使用真空多效膜蒸馏处理页岩气压裂返排液的现场试验研究,考察了处理前后原水、浓缩液、淡水产水的TDS、COD、氯化物等11项指标的变化情况及进水含盐量变化对膜蒸馏处理的影响,运行过程中对装置进行30 d的热端及冷端压力监测。结果表明,膜蒸馏具有较好的离子及有机物截留效果,运行较为稳定,随着试验进程推进,膜与物料接触侧发生结垢现象,由于其耐酸碱的特性,经过化学清洗,热端及冷端压力差得以有效恢复。优化运行参数,收水率最高达87.8%,浓缩液最高含盐量可达到29%。装置处理后的淡水水质较好,出水COD、氯化物浓度分别为5、102 mg/L,满足外排标准中对应指标的要求。

A field test is performed to treat with shale gas fracturing flow-back fluid by vacuum multi-effect membrane distillation.The changes of 11 indicators including TDS,COD,and chlorides in raw water,concentrated solution,and permeate solution are examined before and after treatment.The effect of salt concentration in raw water on membrane distillation treatment are investigated.Pressure at the feed and permeate sections of the unit has been monitored for 30 days during operation.It is demonstrated that membrane distillation has a significant retention effect on ions and organic matters,and runs stably.Scaling develops on the interface between the membrane and the feed as the experiment proceeds.Because the membrane has resistance to acid and alkali,the pressure differential between the feed and permeate sections can be effectively recovered after chemical cleaning.The recovery rate of water can reach 87.8% under the optimized operating conditions,while the maximum salt concentration of the concentrate can reach 29%.Fresh water after being treated by the unit has a better quality,containing 5 mg·L^-1 of COD and 102 mg·L^-1 of chlorides,which can satisfy the requirements of China's national standard for the related indicators.