粉煤灰在热处理过程中汞的逸出规律

文章研究了粉煤灰在热处理过程中汞的逸出规律,通过改变焙烧温度、焙烧时间和通气流量等条件,利用安大略水法,对逸出的零价汞(Hg0)和二价汞(Hg2+)以及总汞的含量进行了测定。结果表明:在加热温度达到400℃时,飞灰中的可挥发汞已基本完全释放,逸出量大约为0.2μg/g。当加热温度升高到600~1 000℃之间时,零价汞含量明显降低,而二价汞含量明显升高,可以观察到较为明显的零价汞氧化为二价汞的现象。汞的逸出量与氧化程度主要与加热温度有关,而加热时间与通气量的影响相对较小。在1 000℃,加热时间30 min,通气量0.5 L/min的条件下,可挥发汞将完全逸出并有部分零价汞被氧化。结合上述研究结果,在对粉煤灰进行加热处理时,需要对其中汞的二次释放现象加以重视并采取相应的控制措施。

Law of Mercury Emitted from Coal Fly Ash during Thermal Treatment

Law of mercury emitted from the coal fly ash during thermal treatment was studied.Element mercury(Hg0) and divalent mercury(Hg2+) were determined by Ontario Hydro Method(OHM),by changing the calcinations temperature,calcinations time and air flow.Results showed that when heating temperature rose to 400 ℃,most of the volatilizable mercury has been released,and emission amount was 0.2 μg/g.In the heating temperature ranged from 600 ℃ to 1 000 ℃,zero-valent mercury(Hg0) was observed be oxidized to divalent mercury(Hg2+) distinctly.The mercury emission amount and oxidization degree were mainly related to calcinations temperature,while the calcinations time and air flow had less influence.The volatilizable mercury would release and some of element mercury was oxidized at 1 000 ℃,0.5 L/min and 30 min.Attention should be paid on this issue and control measures should be taken.