淖毛湖煤中有害微量元素的赋存特征研究

Study on occurrence characteristics of harmful trace elements for Naomaohu coal

煤中存在的微量有害元素会在煤炭加工利用过程中造成环境污染,对属优质直接加氢液化用煤的淖毛湖煤中的有害微量元素迁移特性和演变规律进行研究,可揭示加氢液化过程中的迁移机理并对淖毛湖煤的直接转化利用提供指导。为探明淖毛湖煤中5种有害微量元素As、Cr、Cd、Pd、Hg在直接加氢液化工艺中的迁移行为,采用逐级提取试验为主要手段,研究原样和液化残渣样中各种元素赋存状态的变化规律。淖毛湖煤中5种元素整体含量不高,但Hg和Cd元素含量远超过全国均值。加氢液化工艺之后对水样、油样和液化残渣样进行元素含量测试,发现5种元素几乎不在水样和油样中分布,迁移程度按挥发性大小排序为:Cd>Hg>As>Pb>Cr。硫化物结合态和有机结合态是淖毛湖煤中5种有害微量元素最主要的赋存状态,但在各元素中占比有所差异,Pb、Cr和Hg元素的残渣态占比较高。经过加氢液化之后,几乎不迁移的Cr元素的赋存状态变化不大,其他元素的不稳定状态发生迁移,含量大幅度下降。有机质的反应使得与其赋存的As和Cd也发生大量挥发,导致残渣态在液化残渣中的占比变高;Hg的所有赋存状态均降低,在液化残渣的剩余量中与微量有机质和硫化物共存的Hg含量相对较高。

Harmful trace elements in coal can cause environmental pollution in the process of coal processing and utilization.The study on the migration characteristics and evolution law of harmful trace elements in Nuomahu coal,which is a high-quality direct hydro-liquefaction coal,can reveal the migration mechanism in the process of hydro-liquefaction and provide guidance for direct conversion and utilization of Nuomahu coal.In order to investigate the migration behavior of five harmful trace elements As,Cr,Cd,Pd and Hg in Nuomaohu coal during the direct hydro-liquefaction process,the sequential chemical extract was used to study the change of the occurrence state of various elements in the original samples and the liquefied residue samples.The overall contents of five elements in Nuomaohu coal are not high,but the contents of Hg and Cd are far higher than the national average.After hydro-liquefaction,the contents of five elements were measured in water samples,oil samples and liquefaction residue samples.It is found that the five elements are almost not distributed in water samples or oil samples,the migration degree according to volatile order is Cd>Hg>As>Pb>Cr.The main occurrence states of five harmful trace elements in Nuomaohu coal are bound to organic matter and bound-state sulfide,but the proportion of each element is different,and Pb,Cr and Hg exist in the form of residual state.After hydrogenation and liquefaction,the content and the occurrence state of Cr element are almost no changes,while the unstable states of other elements decrease greatly.The reaction of organic matter release the As and Cd in it,which results in a higher proportion of residual state in the liquefaction residue.All the occurrence states of Hg decrease,and the content in the bound to organic matter and bound-state sulfide Hg is relatively high in the hydrogenation liquefaction residue.