CaCl2添加对煤热解过程中汞形态转化影响的实验

基于单质汞是煤热解烟气中主要汞存在形态,提出煤中添加CaCl2并协同SCR催化剂促进热解烟气中单质汞的转化。利用程序升温热解实验台研究煤在热解时汞析出速率及累积释放率,通过积分各形态汞的总析出量分析汞的形态转化,考察煤中添加CaCl2以及与SCR催化剂协同作用对汞的形态转化的影响。结果表明,温度是影响汞析出速率的关键因素,低于430℃时析出速率随温度升高而升高,之后随温度升高而降低;总汞累积释放率在400~500℃随温度呈明显线性正相关关系,600℃时累积释放率达90％左右。随着氯添加量的增加,Hg2+比例明显提高,在催化剂协同作用下,绝大部分单质汞被氧化成氧化态汞,有利于汞的脱除。

Experiment on mercury speciation transformation during coal pyrolysis with calcium chloride addition

Adding CaCl2 cooperating with SCR catalyst to accelerate the transformation of Hg0 during coal pyrolysis was proposed based on the fact that elemental mercury was the dominant species in the coal pyrolysis gas. A temperature-programmed tube furnace was set up to investigate the mercury release rate and cumulative release rate during coal pyrolysis. The mercury speciation transformation was determined by integration of the total released amount of various forms of mercury. The effect of different chlorine content and synergy of chlorine and catalyst on mercury transformation was investigated. The results showed that mercury emission from coal pyrolysis significantly depended on temperature. The release rate of Hg in coal increased with increasing temperature before 430℃, and it decreased subsequently with increasing temperature; Cumulative release rate of mercury showed significant positive linear correlation between 400~500℃, and about 90％ mercury was released at 600℃. With the amount of chloride was increased, percentage of Hg2+in gas increased dramatically, most of element mercury was oxidized forming Hg2+ under the synergy of catalyst.