聚硅酸盐混凝剂处理压裂返排液的效果及影响因素

Effect and Influence Factors of Poly-silicic-cation Coagulant in Fracturing Flowback Fluids Treatment

为提高压裂返排液化学处理效率、降低后续深度处理工艺负荷,采用自制聚硅酸盐混凝剂(PSiC)对返排液进行混凝预处理,利用Box-Behnken设计建立连续变量曲面模型进行Si浓度、聚合pH、Si/(Al+Fe)摩尔比(Fe/Al摩尔比9∶1)3因素3水平实验设计,考察了这3种因素对PSiC混凝效果的影响,确定出合适的制备参数。进一步利用统计软件Design Expert对实验数据进行多元回归拟合,并通过三维立体图像揭示三种因素交互作用规律。研究结果表明,Si/(Al+Fe)摩尔比对PSiC混凝效果和稳定性影响较大,当Si浓度、Si/(Fe+Al)比和pH值分别取3.41%、1.3、1.8时,PSiC具有最佳的混凝性能,投加量为130 mg/L(以铁铝和计)时压裂返排液的浊度去除率和COD去除率分别为88.52%和70.35%。Si浓度、聚合pH、Si/(Al+Fe)摩尔比与处理效果之间的二次多项回归模型方程显著、可靠。Si浓度和Si/(Fe+Al)比交互作用不显著,Si浓度和pH有一定的交互作用,Si/(Fe+Al)比和pH交互作用较显著。

In order to improve the efficiency of chemical treatment of fracturing flowback fluids,and reduce the load of subsequent treatment process,the poly-silicic-cation coagulant（PSiC）was prepared to treat fracturing flowback fluids. Through Box-Behnken experiment design and response surface analysis,optimization grouping of Si concentration,polymerization pH,Si/（Al＋Fe）molar ratio was realized,a quadratic response surface model and optimum level values were obtained. The experimental data were multivariable regression fitting by the statistical software Design Expert. Three-dimensional images were used to reveal interaction between three factors. The results showed that coagulation performances and stability were significantly influenced by the Si/（Fe＋Al）molar ratio. It was found that the optimization grouping of the main influence factors for coagulation were as following：Si concentration,pH value and Si/（Al＋Fe）molar ratio being of 3.39%,1.3 and 1.8,respectively,and the removal rate of turbidity and COD were 88.52% and 70.35% ,respectively,with the active ingredient （Fe ＋ Al） dosage of 130 mg/L. The quadratic polynomial regression equation model of Si concentration,polymerization pH,Si/（Al＋Fe）molar ratio and treatment effect was significant and reliable. The interaction between Si concentration and Si/（Al＋Fe）molar ratio was not significant,and there was some kind of interaction between Si concentration and pH,while the interaction between Si/（Al ＋ Fe）molar ratio and pH was significant.