Desulfurization and demineralization of miike coal by molten alkali hydroxides.

概要

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Pulverized Miike coal was treated in molten mixtures of sodium hydroxide and potassium hydroxide at 473-673K. The removal yield of total sulfur, organic sulfur and ash and the change in heating value and volatile matter content were evaluated as functions of coal size, alkali composition, reaction temperature, and reaction time.<BR>No effect of the coal size was observed when the coal was crushed under 300/μm. The rate of demineralization was faster than that of desulfurization. The optimum conditions of temperature and treatment time were 623K and 60min, respectively. The removal yields of sulfur and ash based on the mass of treated coal were not increased under more severe condi-tions because of the decomposition of coal. An increase in the KOH concentration resulted in a higher sulfur removal yield and a lower heating value. The best KOH concentration was about 50wt%.<BR>Under most suitable conditions, the removal yields of total sulfur and ash were 92% (sulfur residue 0.27wt%, db) and 96% (ash residue 0.58wt%, db), respectively. The heating value per dry mass of clean coal was increased by about 7% than the original coal.
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