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Show 1 Introduction This paper describes a series of experimental investigations of the release of iron during the combustion of Illinois #6 (PSOC-1493d) coal. More than 95 % of the iron in the coal used in this study occurs in the form of pyrite. The experimental observation is that a large fraction of this iron, that is, 40-70 %, is released from the coal/char particle. The mechanism of release cannot satisfactorily be attributed to a vaporization process. All of the experimental evidence shows that it is related to the thermal decomposition and chemical reaction of pyrite and its decomposition products. The large and rapid release of iron was not an anticipated result, and thorough statistical analyses have been performed to quantify the degree of uncertainty in the data. The decomposition of pyrite in combustion environments has been the subject of many papers. A comprehensive review of these studies is given by Watt [1969], with more recent discussions by Reid [1981]' Raask [1985] and Groves et al. [1987]. These papers conclude that pyrite, when heated in an inert environment, decomposes at temperatures of 450-550 °c to form pyrrhotite. Pyrrhotite is a highly porous complex which does not have a definite crystalline structure. Its approximate chemical composition is Fe7Ss. The decomposition of pyrite to form pyrrhotite is accompanied by an increase in the porosity and some channeling and rupturing of the mineral grain. Pyrrhotite begins to melt in an inert atmosphere at temperatures between 800 and 1050 K, depending on the means by which it is formed. At high temperatures, the pyrrhotite can further decompose to form metallic iron. Pyrite and all of its decomposition products are reactive to oxygen. The oxidation reactions are strongly exothermic and are often more rapid than the oxidation of carbon under similar conditions. This paper briefly describes the experimental conditions under which the data were obtained. The data will then be presented, with statistical analyses. Finally, a mechanistic interpretation of the data will be suggested. 2 Experimental Conditions Samples of Illinois #6 (PSOC-1493d) coal were entrained in a laminar flow reactor in two different post flame environments. The laminar flow reactor and associated optical diagnostics have been previously reported [Mitchell, 1987] . The mole fractions of water and carbon dioxide and the gas temperatures were approximately 0.16, 0.02, and 1600 K, respectively, in both environments. The mole fractions of oxygen and nitrogen were approximately 0.06 and 0.76, respectively, in the first environment and 0.12 and 0.70, respectively, in the second environment. Particles with two different 2 |