Raw material recovery from hydraulic fracturing residual solid waste with implications for sustainability and radioactive waste disposal
Raw material recovery from hydraulic fracturing residual solid waste with implications for sustainability and radioactive waste disposal
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从水力压裂残余固体废物中回收原材料对可持续性和放射性废物处置的影响
DOI：
10.1039/c8em00248g
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发表时间：
2019
期刊：
影响因子：
--
通讯作者：
Warner, Nathaniel R.
中科院分区：
文献类型：
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作者：
Ajemigbitse, Moses A.;Cannon, Fred S.;Klima, Mark S.;Furness, James C.;Wunz, Chris;Warner, Nathaniel R.
非常规油气残余固体废物通常被处理在城市垃圾填埋场（RCRA Subtitle D），但它们含有宝贵的原料，如支撑剂砂。提出了一种从水力压裂废渣中回收原料的新工艺。具体来说，一种新型的水声空化系统与物理分离装置相结合，通过空化的色散能量与超声波、臭氧和过氧化氢相结合，可以从剩余的固体废物中产生一种不同的高浓度砂流和另一种不同的粘土流。这种组合通过清除砂表面先前聚集的粘土和残留物来清洁砂粒。当这些单元操作之后是水力旋流器和螺旋分离器时，可以根据颗粒大小分离固体，在一次流动中产生主要清洗过的砂；另一种是粘土和细颗粒；又淤积了第三条小溪。因此，粒度的分离也影响了镭的分布——沙粒的镭活度很低，低至0.207 Bq g−1 （5.6 pCi g−1）。相比之下，粘土的镭活性升高，高达1.85-3.7 Bq g−1 (50-100 pCi g−1)，其中大部分镭与可以从粘土中分离出来的有机物和盐类有关。建议再生砂可作为水力压裂支撑剂重复利用。砂与淤泥和粘土的分离可以减少垃圾填埋场处理的体积和镭质量。这可以为处理石油和天然气废物的设施节省大量资金，每年可节省10万至30万美元。在井下处理富镭盐和有机物将减少镭向地表的释放。此外，再生砂可能具有市场价值，这可以节省多达三分之一的成本。采用毒性特征浸出方案（TCLP）对这些分离固体流进行的测试表明，这种新型处理方法降低了再生砂、粘土或处置材料的镭迁移风险，使其更适合填埋。
Unconventional oil and gas residual solid wastes are generally disposed in municipal waste landfills (RCRA Subtitle D), but they contain valuable raw materials such as proppant sands. A novel process for recovering raw materials from hydraulic fracturing residual waste is presented. Specifically, a novel hydroacoustic cavitation system, combined with physical separation devices, can create a distinct stream of highly concentrated sand, and another distinct stream of clay from the residual solid waste by the dispersive energy of cavitation conjoined with ultrasonics, ozone and hydrogen peroxide. This combination cleaned the sand grains, by removing previously aggregated clays and residues from the sand surfaces. When these unit operations were followed by a hydrocyclone and spiral, the solids could be separated by particle size, yielding primarily cleaned sand in one flow stream; clays and fine particles in another; and silts in yet a third stream. Consequently, the separation of particle sizes also affected radium distribution – the sand grains had low radium activities, as lows as 0.207 Bq g−1 (5.6 pCi g−1). In contrast, the clays had elevated radium activities, as high as 1.85–3.7 Bq g−1 (50–100 pCi g−1) – and much of this radium was affiliated with organics and salts that could be separated from the clays. We propose that the reclaimed sand could be reused as hydraulic fracturing proppant. The separation of sand from silt and clay could reduce the volume and radium masses of wastes that are disposed in landfills. This could represent a significant savings to facilities handling oil and gas waste, as much as $100 000–300 000 per year. Disposing the radium-enriched salts and organics downhole will mitigate radium release to the surface. Additionally, the reclaimed sand could have market value, and this could represent as much as a third of the cost savings. Tests that employed the toxicity characteristic leaching protocol (TCLP) on these separated solids streams determined that this novel treatment diminished the risk of radium mobility for the reclaimed sand, clays or disposed material, rendering them better suited for landfilling.