富氧气化是煤炭地下气化生产高品质合成气的重要工艺方法。煤炭地下气化作为一种煤炭原位化学开采方法，主要提取煤中的含能组分，而将气化灰渣等污染物留在地下，煤中有害微量元素随地下气化过程的进行，富集在煤气、飞灰及灰渣中，气化后地下气化灰渣经过地下水长期浸出作用，其中有害微量元素可能进入到地下水体中，造成地下水污染风险。研究煤炭地下气化灰渣的浸出特性对于理解灰渣中有害微量元素的迁移行为以及保护地下水具有重要的意义。以乌兰察布褐煤为研究对象，通过不同体积分数的富氧地下气化模拟实验制备了富氧气化灰渣，采用XRD检定了灰渣中的特征矿物质，利用SEM-EDS表征了灰渣的形貌。采用ICP-MS和全自动测汞仪(DMA 80)测定了不同富氧气化灰渣中有害微量元素Hg,As,Se,Cd,Pb,Ni,Be,Cr,Cu,Zn,Ba,Ag的含量以及在不同pH浸出液中的浸出质量浓度。研究结果表明，Hg在气化灰渣中的富集系数极低，地下气化过程中主要迁移到气相中，而Pb,Be,As和Se经历了富氧地下气化后在灰渣中发生了明显的富集。不同体积分数的富氧气化灰渣中有害微量元素的浸出水平均低于我国颁布的关于固体废弃物毒性浸出标准(GB5085.3—2007)规定值，这表明富氧地下气化灰渣不具备浸出毒性。此外，灰渣中有害微量元素在去离子水中的浸出质量浓度远低于危废浸出毒性标准规定值，而且能够达到灌溉用水的标准。

Oxygen-enriched gasification is an important method for underground coal gasification to produce high-quality syngas.Underground coal gasification (UCG),as an in-situ coal seam gasification,mainly extracts the energetic components from coal,and leaves the residue in the underground.The hazardous trace elements in coal are enriched in gas,ash with the UCG process.The pollutants in the UCG residue may permeate into the underground water through the long-term leaching,causing the pollution of underground water.Detailed leaching characteristics of hazardous trace elements (HTEs) of underground coal gasification (UCG) slag are essential to understand the migration behavior of HTEs far from the surface and protect the underground water.Ulanqab coal was investigated in this study.UCG slag was prepared through some simulation tests of oxygen-enriched gasification under different atmospheric conditions,and the typical minerals in the coal and slag were identified by XRD and the physical structure of the slag were characterized by the SEM-EDS.The leaching concentration of HTEs including As,Se,Cd,Pb,Ni,Be,Cr,Cu,Zn,Ba,and Ag were identified by ICP-MS and Hg was detected by the direct mercury analyzer DMA 80.Results show that Hg is mostly emitted in the gas and Pb,Be,As,and Se are enriched in the slag.The leaching concentration of gasification slag with different oxygen-enriched level in different pH leaching solution is lower than the relevant limits (GB5085.3—2007),which indicates that the oxygen-enriched underground gasification slag has no risk to the groundwater.Meanwhile,the leaching concentration of HTEs in deionized water is far below the toxicity standard of leaching,and the leaching concentration of slag can fully meet the standard of irrigation water,and will not affect the use of adjacent aquifers.The results can provide a scientific guidance for the control and management of late-stage residues of underground gasification.

1 实验部分

   1.1 实验煤样

   1.2 地下气化模拟试验系统

   1.3 煤层模拟

   1.4 实验方法

   1.5 样品分析与测试

2 结果与讨论

   2.1 富氧地下气化过程煤中矿物质的演变行为

   2.2 有害微量元素在原煤以及灰渣中的质量分数

   2.3 灰渣中有害微量元素在不同pH浸出液中的浸出质量浓度

   2.4 灰渣中有害微量元素在去离子水中的浸出质量浓度

   2.5 浸出液PH的变化

3 结论