Comparison of Pyrolysis Products between Coal, Coal/CaO, and Coal/Ca(OH)₂ Materials

Products from coal, coal/CaO, and coal/Ca(OH)2 pyrolysis under various pressures were examined and compared experimentally. A high-pressure flow-type reactor with a rapid cooling system was used for the pyrolysis experiment, and it was found that the amount of gas products increased in response to CaO and Ca(OH)2 addition. The total volume of gas product from pyrolysis was in the order of coal/Ca(OH)2 > coal/CaO > coal at extremely high pressure. H2 products in coal/CaO and coal/Ca(OH)2 pyrolysis peaked in the temperature range of 923−973 K. At this H2 peak temperature, the H2 content in product gas was approximately 80%, while there were little CO, CO2, and CH4. One reason for this is that the H2O contained in coal can be brought to a higher temperature by the reactions of Ca(OH)2 formation and decomposition. H2O reacted with coal at high temperature, producing H2 and CO. It was also found that CO can shift to CO2, and that CO2 can be fixed by CaO to CaCO3 in the temperature range of the H2 peak.