DESULFURIZATION OF PITTSBURGH COAL BY MICROBIAL COLUMN FLOTATION

Microbial column flotation using Thiobacillus ferrooxidans was applied for desulfurization of Pittsburgh coal of CWM (Coal-Water Mixture) si ze between 38 mu m and 75 mu m. The coal contained ferrous ion which w ould interfere separation of pyrite from coal by microbial flotation. The wash-out of ferrous ion with 0.5N HCl solution enabled pyrite remo val from coal. The coal was divided into two parts, the small-size coa l between 38 mu m and 53 mu m, and the large-size coal between 53 mu m and 75 mu m. The pyritic sulfur content was decreased from 2.88% of t he feed coal to 0.98% of the product coal for the large-size coal and from 2.77% of the feed coal to 1.12% of the product coal for the small -size coal by microbial flotation. The decrease was based on removal o f liberated pyrite particles (between 20 mu m and 70 mu m). However, t he fine particles (less than 20 mu m) could not be removed even though the pyrite particles were liberated from coal particles. The microbia l column flotation was more effective for desulfurization of the large liberated pyrite particle than that of the small. It was not effectiv e for desulfurization of the locked pyrite particles that were buried in coal particles. Both the pyrite liberation from coal and its partic le size are important factors for the pyrite removal by microbial colu mn flotation.