摘要
本研究选用两种煤(白音华褐煤和鄂州煤),研究了煤中重金属砷、硒、铅的赋存形态及其在灰化过程的释放规律,并结合煤中矿物质的变化,研究了灰化条件对矿物质转化的影响。通过外推法从热失重曲线确定了煤样的燃尽温度,以此为基准并结合国标法分别对煤样进行低温和高温灰化,对所制备的灰样采用XRD、XRF、TG-DTG等方法进行表征,分析煤中矿物质在不同灰化温度下的变化特征;采用逐级化学提取法分析煤样中As、Se、Pb的形态及含量,同时利用HNO_(3)+HF一步法提取煤样中的重金属,提取液中重金属含量均采用电感耦合等离子体质谱法(ICP-MS)检测。研究结果表明,白音华煤中重金属主要以硫化物结合态形式存在的As为主,且As的挥发性随温度升高而增大;鄂州煤中重金属主要为硫化物结合态的Pb,其挥发性同样极易随温度变化而改变;煤中Se主要以有机结合态和硫化物结合态形式存在。煤在灰化过程中矿物质发生了一系列的变化:如高岭土逐渐脱羟基变成偏高岭土,最终转变成莫来石;黄铁矿氧化形成赤铁矿;石膏脱水形成硬石膏。灰化过程各重金属的释放率受燃烧温度的影响较大,其硫化物结合态含量越高,释放率随温度升高增加的程度越大。
In this paper,two kinds of coal(Baiyinhua lignite and coal using in Ezhou Power Plant)were selected to study the occurrence of heavy metals including arsenic(As),selenium(Se)and lead(Pb)in coal and their release behaviors during the ashing process.The influence of ashing conditions on the mineral conversion was also examined by the combination with the changes of minerals in coal.The burn-out temperature of the coal was determined from the thermal weight loss curve by extrapolation method,and then the coal sample was ashed according to the National Standard Method of China.The obtained ash samples were characterized by XRD,XRF,and TG-DTG to analyze the change characteristics of coal minerals at different ashing temperatures.The content and occurrence of As,Se and Pb in coal samples were extracted by sequential chemical extraction method.The heavy metals in the ash sample were extracted by HNO_(3)+HF,and the heavy metal content in the extract was detected by Inductively Coupled Plasma Mass Spectrometer(ICP-MS).The results show that the heavy metal in BYH coal is mainly As in the form of sulfide bound state,which leads to the increasing volatility of As with temperature easily.However,the heavy metal in EZ is mainly sulfide-bound Pb,which makes it easy to release with temperature.Se in coal mainly exists in the form of organic bound state and sulfide bound state.During coal ashing,kaolin is gradually dehydroxylated into metakaolin and finally converted into mullite;pyrite is oxidized to form hematite;gypsum is dehydrated to form anhydrite.The release rate of heavy metals is greatly affected by the combustion temperature during the ashing process.High content of heavy metals in the sulfide bound state results in high release rate with increasing the temperature.
作者
李扬
鲁子龙
杨赫
靳立军
胡浩权
LI Yang;LU Zi-long;YANG He;JIN Li-jun;HU Hao-quan(State Key Laboratory of Fine Chemicals,Institute of Coal Chemical Engineering,School of Chemical Engineering,Dalian University of Technology,Dalian 116024,China)
出处
《燃料化学学报》
EI
CAS
CSCD
北大核心
2022年第1期11-18,共8页
Journal of Fuel Chemistry and Technology
基金
国家重点研发计划(2018YFB0605104)
国家自然科学基金(21776039)
中央高校基本科研业务费(DUT2018TB0)资助。
关键词
煤
重金属
逐级提取
灰化方法
矿物质
coal
heavy metal
sequential chemical extraction
ashing method
mineral
