Abstract: 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.

Key words: calcium chloride, coal pyrolysis, mercury species, catalyst;mercury removal