Experimental study on mercury release behavior during coal pyrolysis with calcium chloride addition

Mercury release and speciation behavior during coal pyrolysis with the addition of calcium chloride in different chlorine contents of 0.1%,0.3% and 0.5% in mass was studied in a temperature-programmed tube furnace. The concentration of gaseous mercury was monitored online with an online mercury analyzer. The results show that the temperature is a key factor for the mercury releasing during coal pyrolysis. With the rising of calcium chloride addition in coal, the percentage of Hg²⁺ increases, while the temperature of maximum mercury releasing and the release of total mercury decrease. The percentage of Hg²⁺ also increases to some degrees with the increase of O₂ percentage raised. Higher heating rate can promote the mercury release in coal and enhance the proportion of Hg²⁺ in flue gas. The study indicates that the calcium chloride addition into the low-chlorine coal can enhance the oxidation of Hg⁰.