Coprocessing of Pyrolytic Nitrogen Removal of Low-Rank Coals and Reduction of Limonite Ore

Temperature-programmed pyrolysis of low-rank coals physically mixed with goethite-rich limonite ore has been studied with a fixed-bed quartz reactor for the purpose of developing a novel coprocessing method for the removal of coal-bound nitrogen and the reduction of goethite. Limonite at loadings of 5-40 mass % promotes the formation of N₂ from brown coal at 650-1000°C and the consequent nitrogen removal, although the effect levels off beyond 20 mass % and thus seems to be limited. X-ray diffraction (XRD) measurements after pyrolysis showed that goethite can readily be reduced to metallic iron (α-Fe), irrespective of the limonite loading and the type of coexisting coal, and that part of the α-Fe reacts with a small amount of carbon to form cementite, a solid solution of iron and carbon. This method might have potential for the simultaneous production of low-nitrogen chars and reduced iron materials by utilizing low-value coals and limonite ores.