煤矸石及煤泥燃烧过程重金属排放特性

Emission characteristics of heavy metal during combustion of coal gangue and coal slime

煤矸石和煤泥是煤炭分选和开采过程中产生的固体废弃物,大量煤矸石、煤泥的堆存会产生一系列的环境和生态问题。燃烧发电是煤矸石、煤泥资源化利用的主要途径之一。煤矸石和煤泥中均含有一定量的重金属元素,如Hg、As、Pb等。在燃烧过程中这些有害元素的释放造成严重环境危害,因此研究煤矸石及煤泥燃烧过程重金属的排放特性意义重大。为考察煤矸石及煤泥在富氧气氛和空气气氛下燃烧时重金属的排放特性,研究了不同温度下平朔煤矸石和煤泥在O2/CO2气氛和空气气氛下燃烧时,As、Hg、Pb和Se的排放特性。采用Hydra-II测汞仪测量煤矸石、煤泥和灰中的Hg含量,采用ICP-AES测量煤矸石、煤泥和灰中的As、Pb和Se含量。研究结果表明,煤矸石及煤泥燃烧过程中,燃烧温度在500~1000℃、O2体积分数在20%~40%时,随着温度和O2体积分数升高,煤矸石、煤泥的成灰比例降低。此外,煤矸石在O2/CO2气氛下燃烧时,随温度和O2体积分数提高,As、Hg、Pb和Se在燃烧烟气中的占比升高,燃烧后所得灰占比降低。煤泥在O2/CO2气氛下燃烧时,随燃烧温度的升高,As、Hg、Pb更容易挥发到气相中;煤泥在空气气氛下燃烧时,As、Hg、Pb在烟气中的占比略高于相同温度、O2/CO2气氛下O2体积分数为20%时的比例。

Coal gangue and coal slime are solid wastes produced in the process of coal washing and mining.A large number of the coal gangue and coal slime will cause a series of environmental and ecological problems.Combustion for power generation is one of the main ways to utilize coal gangue and coal slime efficiently.It is well known that coal gangue and coal slime contain a certain amount of heavy metals,such as Hg,As,Pb,etc.These harmful elements are released in the combustion process,which will cause serious harm to the environment.Therefore,it is of great significance to study the emission characteristics of heavy metals from coal gangue and slime during combustion.In order to investigate the emission characteristics of heavy metals from coal gangue and coal slime burning in O2/CO2 atmosphere and air atmosphere,Pingshuo coal gangue and coal slime was used for experiment and the emission characteristics of As,Hg,Pb and Se during combustion in O2/CO2 atmosphere(20%,30%and 40%of O2 concentration,respectively)and air at different temperatures(500-1000℃)were studied;and the Hydra-II mercury meter was used to measure the Hg content in coal gangue,coal slime and ash,and the ICP-AES was used to measure As,Pb and Se content in coal gangue,coal slime and ash.The results show that during combustion of coal gangue and coal slime,the ash ratio of coal gangue and slime decreases with the increase of temperature and the O2 concentration,when the combustion temperature is 500-1000℃and the O2 concentration is 20%-40%,the proportion of As,Hg,Pb and Se in the combustion flue gas increases with the increase of temperature and volume fraction of O2,and the ash content decreases after combustion.The As,Hg and Pb are easier to volatilize into the gas phase with the increase of combustion temperature when coal slime is burned in O2/CO2 atmosphere.In addition,when the coal slime burns in air,the ratio of As,Hg and Pb in flue gas is slightly higher than that in flue gas in O2/CO2 atmosphere with the O2 concentration of 20%at the same temperature.