乌兰图嘎富锗煤中微量元素在不同密度级煤中的分布特征

Distribution characteristics of trace elements in different density fractions of high-germanium coal from Wulantuga,Inner Mongolia,China

煤系关键金属的开发利用对于缓解我国战略性矿产资源紧缺具有重要意义。内蒙古胜利煤田乌兰图嘎低阶煤中除富集关键金属Ge以外,同时富集有害元素Be、F、As、Hg、Sb和W,出于对关键金属的提取利用及环境保护2个方面考虑,须对研究区煤炭进行洗选处理。基于前期研究认识,浮选对于乌兰图嘎煤中As、Sb和W脱除效果相对较好,对于F和Hg的脱除效果较差,基于此,采用浮沉实验(重选法)以及XRD、XRF、SEM-EDS和EMPA等实验方法和测试手段,研究关键金属Ge以及Be、F、As、Hg等有害元素在不同密度级煤中的分布特征,结果表明:(1)乌兰图嘎煤中矿物主要包括石膏、石英、黄铁矿、高岭石等,矿物含量随煤密度级增大而增加,电子探针分析结果表明,Co、As、Sb和Hg赋存在黄铁矿中。(2)经过重选,低密度精煤中Ge元素富集,表明Ge主要以有机态存在,Be、F、As等可能与有机质相关,或者赋存在嵌布于有机质中的微细粒矿物中,煤中Hg和大部分亲石性元素在高密度级煤中含量较高,表明其赋存在矿物中。(3)重选对于Hg元素的脱除效果较好,对Be、F、As和一些亲硫或亲铁性元素浮选脱除效果优于重选。建议乌兰图嘎低阶煤使用重选-浮选联合脱除法进行有害元素的脱除。

The exploitation and utilization of critical metals in coal measures is of great significance to alleviate the shortage of strategic mineral resources in China.In addition to the critical metal germanium(Ge),the low-rank coal from Wulantuga Coal Mine of Shengli Coalfield in Inner Mongolia,China is enriched with the toxic elements Be,F,As,Hg,Sb and W.Considering the extraction and utilization of key metals and environmental protection,the coal in the study area must be washed.As shown in the previous study,flotation is relatively good for the removal of As,Sb and W inWulantuga coal,but relatively poor for the removal of F and Hg.Hence,the distribution characteristics of the critical metal Ge and the toxic elements,such as Be,F,As and Hg,in different density fractions of coal were studied with the experiment and test methods,including floating-sinking experiment(the gravity separation),XRD,XRF,SEM-EDS and EMPA.The results show the following:(1)The minerals in Wulantuga coal mainly include gypsum,quartz,pyrite and kaolinite,the mineral content increases with the increasing of coal density fraction,and the Co,As,Sb and Hg occurs in pyrite according to the results of electron probe analysis.(2)After gravity separation,Ge is enriched in the low-density cleaned coal,indicating that Ge mainly exists in organic state,and Be,F,and As may be associated with the organic matter or occur in the fine grained minerals embedded in organic matter.Hg and most lithophile elements have higher concentrations in coals at higher density fractions,which indicates they occur in minerals.(3)Gravity separation is good for the removal of Hg,and flotation has a better effect for the removal of Be,F,As and some sulfurophilic or siderophile elements than gravity separation.Therefore,the gravity separation and flotation combined process is recommended for the removal of toxic elements in Wulantuga low-rank coal.