两种煤在热解过程中汞的析出和形态分布实验研究

在程序升温热解反应系统上,研究了大同煤和宝日希勒煤在N2气氛下热解过程中汞析出及形态分布规律。实验结果表明,温度是影响煤热解过程中汞释放的主要因素。煤中汞释放率随着温度的升高而明显升高,当热解温度为600℃时,煤中汞已基本逸出,汞释放率在92%以上。元素汞(Hg0)是气态汞释放的主要形态,随着热解温度的升高,大同煤释放的元素汞在气态汞中的质量分数先增加后减小,而宝日希勒煤中元素汞的质量分数逐渐降低。随着停留时间的延长,煤中汞释放率和元素汞的质量分数都呈增加趋势,宝日希勒煤的增幅较大同煤更为显著。较高的加热速率促进了煤中汞的释放,同时也在一定程度上提高了氧化汞的质量分数,其中宝日希勒煤的氧化汞增幅明显大于大同煤,达19.5%。

Experimental study on mercury release behavior and speciation during pyrolysis of two different coals

Mercury release behavior and speciation during pyrolysis of Datong and Baorixile coals were studied in a temperature-programmed tube furnace under N_2 atmosphere. The results showed that mercury emission from coal pyrolysis significantly depended on temperature. The release ratio of Hg in coal increased dramatically with increasing temperatures, and more than 92% mercury was released at 600℃. Elemental mercury was the dominant species in the gaseous mercury during coal pyrolysis. The percentage of Hg~0 of Datong coal increased firstly, and then decreased, while it reduced gradually for Baorixile coal. Both the rate of Hg release and the percentage of Hg~0 rose finitely through the time ranging from 0～60min, and Baorixile coal displayed more significant increase than Datong coal. Higher heating rate promoted the mercury release in coal and enhanced the proportion of Hg~(2+) in gas; especially for Baorixile coal it reached 19.5%, being apparently higher than that for Datong coal.