Transformation behavior of trace elements during coal pyrolysis

Transformation behavior of trace elements during pyrolysis of three Chinese coals at temperatures up to 1000 °C was studied. Effects of temperature, atmosphere (N2 and H2), and coal type on release of As, Pb, Cr, Cd and Mn were examined. Experiments were carried out in a fixed bed quartz reactor with a heating rate of 20 °C/min. Results show that bleeding ratios of As, Pb, Cr, Cd and Mn increase with increasing pyrolysis temperature. H2 atmosphere promotes the release of these elements. Among the trace elements studied, Pb is the most volatile element; Cr and Mn are relatively non-volatile. However, the volatility of these elements varies with coal type. This suggests that these elements are present in various compounds in the coals and the distribution of the element in the compounds is different. Distribution of the forms for these elements in Yima coal and char was analyzed.