基于水凝胶界面光蒸发的压裂返排液脱盐降污处理

Desalination and pollution treatment of fracturing flow-back fluid based on interfacial solar evaporation of hydrogel

压裂返排液的无害化处理是页岩气绿色开发中亟待解决的问题之一,也是实现“双碳”目标的重要组成部分。本文以天然高分子材料假酸浆胶(NPG)、聚乙烯醇(PVA)为原料,聚吡咯(Ppy)为光吸收剂,制备了具有双网络套孔结构的超亲水性水凝胶(SH)。以太阳能为驱动力,将基于该水凝胶的界面光蒸发技术用于压裂返排液的核心脱盐降污处理,实现了压裂返排液的低能耗达标外排处理。实验结果表明:在1个标准太阳光强度下(1kW/m^(2)),SH处理压裂返排液的界面光蒸发速率最高为3.59kg/(m^(2)·h),平均光蒸发效率高达96%以上。经脱盐降污处理后的返排液总溶解固体量低于150mg/L,各类盐离子浓度显著降低3~4个数量级,TOC含量去除率高达87.1%。同时水凝胶具有良好的抗盐性和自洁功能,能确保其长期、持续使用。

The harmless treatment of fracturing flow-back fluid is one of the urgent problems to be solved in the green development of shale gas, which is also an important part of realizing the goal of “carbon peaking and carbon neutrality”. In this paper, the hydrophilic hydrogel with double network pore structure was prepared from natural polymer material NPG and polyvinyl alcohol(PVA), with polypyrrole(Ppy) as solar absorber. Taking solar energy as driving force, the interface solar evaporation technology based on the hydrogel was applied to core desalination and pollution reduction of fracturing flow-back fluid,achieving the low energy consumption and standard discharge treatment of fracturing flow-back fluid. The experimental results showed that under a standard solar intensity(1kW/m^(2)), the maximum evaporation rate of fracturing flow-back fluid treated with SH was 3.59kg/(m^(2)·h), and the average solar evaporation efficiency was more than 96%. After desalination and sewage treatment, the total dissolved solids of the flow-back fluid was less than 150mg/L, the concentration of various salt ions was significantly reduced by 3—4 orders of magnitude, and the removal efficiency of TOC content was as high as 87.1%. At the same time, hydrogel had good salt resistance and self-cleaning function, which can ensure its long-term and continuous use.