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 N2 atmosphere. The results showed that mercury emission from coal pyrolysis significantly depended on temperature. The ratio of Hg release in coal increased dramatically with increasing temperatures, and more than 92% mercury was released at 600°C. Elemental mercury was the dominant species in the gaseous mercury during coal pyrolysis. The percentage of Hg0 of Datong coal increased first, and then decreased, while it reduced gradually for Baorixile coal. Both the rate of Hg release and the percentage of Hg0 rose finitely through the time ranging from 0 to 60 min, and Baorixile coal displayed more significant increase than Datong coal. Higher heating rate promoted the mercury release in coal and enhanced the proportion of Hg2+ in gas; especially for Baorixile coal it reached 19.5%, being apparently higher than that for Datong coal.