Effect Of Metal Compound On The Transformation Of Coal-N And Coal-S During Coal Pyrolysis

In this paper, three coals from Xiaolongtan, Pingshuo and Shendong mines in China were selected, the pyrolysis experiment was carned out under Ar atmosphere. It is discussed that the effect of several factors on distrbution of nitrogend and sulfur during coal pyrolysis. The main factors concerned are coal type, temperature, additives included its type and the content of metal compound of Na,Fe and Ca, holding times and coal particle sizes and so on. The gaseous and solid products from coal pyrolysis were detected by ion chromatography and element analyzer, respectively, in order to syudy the role of additives in the transformation of nitrogen and surful. Some useful results are acquired as follows:(1) The additives of metal compound play an important role in the formation of NH₃, HCN and H₂S.(2) Effect of additives on XLT coal: Yields of NH₃,HCN and H₂S were decreased during XLT coal pyrolysis with additive of Na-containing. Additive that content of 0.03wt% Fe promoted the formation of NH₃, but with the content of Fe increasing that reaction is restrained. It increased the release of HCN but reduce the released of H₂S. Loaded of Na/Ca in XLT coal made the yiled of NH₃ and H₂S decrease, but increased the yield of HCN.(3) Effect of additives on PS coal: Content of 5wt% Na restrained the formation of NH₃ but promoted the formation HCN and H₂S during PS coal pyrolysis. Fe made the yields of NH₃ and HCN were reduced and increase, respectively. Content of Fe under or above 0.03wt% made the release of H₂S increased. The yields of NH₃,HCN and H₂S increased during PS coal with Na/Ca pyrolysis.(4) Effect of additives on SD coal: The yield of NH₃ and HCN increased during SD coal with Na-containing pyrolysis. With content of Na increasing, the effect of Na on the formation of NH₃ did not show clear corresponding relation. Content of Na above lwt% made the yield of H₂S reduced. The formation of NH₃, HCN and H₂S were restrained because of Fe in SD coal. Na/Ca additive promoted the release of NH₃, but the promoting or suppressing the formation of HCN and H₂S were changed with the change of its content in the bulk.(5) Effect of additives on the formation of Char-N and Char-S at 1073K: For XLT coal, Na and Fe made the yields of Char-N and Char-S increased, respectively, while the effect of Na/Ca was opposite. Three additives in PS coal made yield of Char-N decreased and yield of Char-S increased. For SD coal, the effect of Na on formation of Char-N changed with content of Na. Fe and Na/Ca decreased the yiled of Char-N. Rule of yield of Char-S changed with content of three additives, respectively.(6) Release of NH₃ and HCN all occurred mainly during the temperature-programmed period for the three coals pyrolysis. The different coal type and content of additives caused the different proportion of yield of NH₃ and HCN in heating and holding period.