XANES技术探究酸处理对义马煤中硫形态及其热变迁行为的影响

利用XANES技术研究了酸处理对义马煤的比表面积、体相及表面硫形态分布和热解过程中硫变迁行为的影响。结果表明,由于酸处理过程中部分镶嵌于有机质中的矿物质被脱除导致部分闭合孔打开,煤的比表面积有所增大。HCl-HF和HCl-HF-HNO_3处理脱除了煤中大部分矿物质和无机硫,由于HNO_3的强氧化性,YMN中亚砜和砜硫化物的相对含量均高于YMR和YMD。相比煤样体相,酸处理过程对表面形态硫的分布产生了更为明显的影响。酸处理煤样热解含硫气体释放量减少,但由于大部分碱性矿物质的脱除和煤中易分解形态硫相对含量的增加,含硫气体释放率增加。不同形态硫之间的内部转化使得酸处理煤焦中主要形态硫的分布更为均匀。通过HCl-HF-HNO_3处理可以有效地脱除煤中矿物质及无机硫,并改变煤中形态硫分布,从而为高灰分、富含黄铁矿的高硫煤的利用提供指导。

XANES study on effect of acid treatment on sulfur forms in Yima coal and their transformation behavior during pyrolysis

Effect of acid treatment on specific surface area, sulfur forms and their transformation during pyrolysis of Yima coal were investigated by XANES technique. Results show that the specific surface area of acid-treated coals is higher than that of raw coal due to removal of some mosaic minerals in coal matrix and opening of some pores. Most of the minerals and inorganic sulfur are removed by the acid treatment, the relative percentages of sulfide, sulfoxide and sulfone in YMN are higher than that of YMR and YMD due to the higher oxidability of HNO₃. Sulfur forms on the coal surface are more modified than that in the coal bulk by the acid treatment. The release amount of sulfur-containing gases during pyrolysis of acid-treated coals decreases, but the accumulated release yields increase due to removal of most alkaline minerals and the relative increase of thermally decomposable sulfur forms in coal. The main sulfur forms show a more even distribution in acid-treated coal chars due to the inter-conversions between different sulfur forms during pyrolysis. HCl-HF-HNO₃ process could remove most of the minerals and inorganic sulfur, and change distribution of sulfur forms, which provides a suitable guidance for utilization of high ash, pyrite-rich high-sulfur coals.