石嘴山电厂煤中微量元素的迁移释放行为

摘要

应用电感耦合等离子体质谱(ICP-MS)和原子荧光光谱(AFS)对中国西北部石嘴山电厂的原煤、底灰和飞灰中Hg、As、Se、Pb、Cr、Cd、Mo、Ni、Co、U和Th 11种微量元素的含量进行了测定.根据底灰和飞灰的产率,结合微量元素在底灰和飞灰中的含量计算了电厂燃煤过程中微量元素的挥发性.结果表明,Hg、Cd、Se、As四种元素在燃煤过程的挥发率均在50%以上,最高可达70%.通过对底灰和飞灰在酸性介质下的柱淋滤实验研究了底灰和飞灰中微量元素在60h内的迁移释放行为.Mn、Ni、Co、As四种元素的最大淋出率均超过2.0%,最高接近10.0%,并且还未达到淋滤平衡.根据微量元素的挥发和淋滤释放特性建立了电厂煤中有害微量元素在燃烧和淋滤过程中的释放分配模型.结果显示,燃煤过程中的挥发是微量元素释放的主要形式,部分元素的淋滤释放也可对周围水环境造成污染.%The volatility and mobility of eleven trace elements (Hg, As, Se, Ph, Cr, Cd, Mo, Ni, Co, U and Th) in coal from Shizuishan Power Plant were investigated.Column leaching tests on bottom ash and fly ash by sulfuric acid for 60 h were conducted.The contents of trace elements in input coal, bottom ash, fly ash and leaching solutions were determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic fluorescence spectroscopy (AFS).The volatility of trace elements during coal combustion was calculated based on the trace elements concentration in coal, ash and the ash yield of the raw coal.The results demonstrate that over 50％ of As, Pb, and Hg volatilize to the atmosphere, leaching test results indicate that the maximum leaching proportion of As, Cd, Ni, and Mo is 1.8％ ～ 6.2％.Based on the volatility and leaching characteristics, the volatilization and migration model of trace elements in the process of combustion and leaching was established.The results show that volatility of trace elements is the main pollution sources on environment in Shizuishan Power Plant.The concentration of Ph, Cd, Mo, Co, Ni, and Cr in leachate is extremely high and they are potential harmful elements to the environment.