FE-MINERAL TRANSFORMATIONS DURING THE INITIAL STAGES OF ENTRAINED-FLOW COAL GASIFICATION

摘要

Fe-minerals in coals, which are primarily pyrite (FeS_2) in deposits from the Northern Hemisphere, undergo the following sequence of transfonnations when the coals are heated rapidly under reducing atmospheres, as during entrained flow gasification: Excluded solid pyrite decomposes into pyrrhotite, another S-rich liquid phase, and S_2 vapor at the incongruent melting point of 743°C. The proportions of sulfur to iron in pyrrhotite are functions of pressure, and increase for progressively higher pressures. Pyrrhotite is then converted at a slower rate into troilite, which melts when the temperature reaches 1083°C. Production rates for troilite may be estimated from the times required to accumulate the latent heats of melting for FeS_2 and FeS_x at the local heat transfer rates.