膜蒸馏处理页岩气井压裂返排液

Treatment of fracturing flowback fluids of shale gas wells by membrane distillation

页岩气压裂返排液的有效处理是页岩气开发急需解决的关键环保问题之一。针对新页HF-1井页岩气压裂返排液经预氧化结合湿式氧化(PO-WAO)工艺处理的出水COD不达标、含盐量高等技术难题,采用膜蒸馏处理技术对工艺的出水进行深度处理。通过膜蒸馏单因素和正交实验表明料液温度和冷凝温度对膜蒸馏处理效果影响较大,在料液温度、冷凝液温度、真空度、运行时间分别为80℃、8℃、0.090 MPa和60 min的最佳工艺条件下,膜通量可达1.750 L·(m2·h)-1,出水COD浓度为95.8 mg·L^(-1),出水水质可满足《污水综合排放标准》(GB 8978-1996)中一级排放的要求。膜蒸馏出水中电导率为63μS·cm-1,氯化钠的质量浓度为1.168 0 mg·L^(-1),可有效降低处理后的压裂废液对周围土壤的盐碱化伤害。

The treatment of fracturing flowback fluids from shale gas wells is crucial for the development of shale gas. Water containing fracturing flowback fluids obtained from the Xinye HF-1 shale gas well is characterized by a non-compliant COD and salinity after pre-oxidation combined with wet oxidation（ PO-WAO）. Advanced treatment using membrane distillation technology is effective for treating high-salinity wastewater. For membrane distillation processing,single-factor and orthogonal tests indicate that the temperature of the feed liquid and condensation significantly affected the processing effort. The tests also revealed that the effluent quality eventually satisfied the first-grade criteria of the Integrated Wastewater Discharge Standard（ GB 8978-1996） under the optimum technological conditions： a feed liquid temperature of 80 ℃,condensation temperature of 8 ℃,vacuum of 0. 090 MPa,reaction time of 60 min,membrane flux of up to 1. 750 L·（ m2·h）- 1,and COD concentration in the membrane distillation effluent of 95. 8 mg·L^-1. The conductivity and sodium chloride concentration were 63 μS·cm- 1and1. 168 0 mg·L^（-1）,respectively,which implied low levels of salinization damage to the surrounding soil.