[Transformation of Na, K, Pb and Mn during pyrolysis of coal]

Transformation of Na, K, Pb and Mn in char for Shenhua and Yima coals at pyrolysis temperatures of 300 degrees C-700 degrees C was reported. Effects of atmosphere (N2, H2 and CO2) and pressure on release of the elements in Shenhua coal were also studied. The pyrolysis experiment was carried out in a closed stainless steal reactor. Results show that the bleeding ratio of Na, K, Pb and Mn varied with coal type but all increased with pyrolysis temperature. For example, the bleeding ratio of Na, K, Pb and Mn at 700 degrees C for Shenhua coal was 3, 4.2, 1.4, and 2.4 times larger than that of Yima coal. The effect of pressure was small. Among the N2, H2 and CO2 environments, H2 resulted in the highest bleeding ratio and CO2 the least bleeding ratio. Thermodynamic calculation shows that Pb was the most volatile element among the four inorganic harmful elements.