The selective oxidation desulfurization process: bench-scale studies: Final report

Five high-sulfur caking coals were desulfurized, under bench-scale conditions, using a fluidized-bed selective oxidation process. Earlier work with this selective oxidation process (EPRI report AP-4873) had shown very promising sulfur removal results under batch operating conditions. For this current work, the bench-scale unit was modified is that it could simulate continuous operation under more realistic conditions: the collection and recycle of fines, addition of SO/sub 2/ to the fluidizing gas, and semi-continuous feed. Under batch conditions, the reductions in sulfur achieved were generally equivalent to at least the pyritic sulfur content of each coal. The simulated continuous-operation experiments indicated that continuous operation might give slightly reduced sulfur-removal efficiencies. Temperatures of 725-775/degree/F and residence times of 2-4 hours are required for near optimum sulfur removal. Gas compositions of 8-26% air (92 to 74% steam) were used. For Pittsburgh No. 8 seam coal, 70% reduction in total sulfur was achieved. Kentucky No. 9 seam coal had a sulfur reduction of over 60% and the two Illinois No. 6 coals were desulfurized by over 50%. Heating value losses from the coals during processing ranged from 5 to 40 percent. 11 figs., 7 tabs.