MICROBIAL REMOVAL OF PYRITE FROM COAL USING A PERCOLATION BIOREACTOR

To compare the suspension and the percolation process system for the microbial desulphurization of coal the microbial pyrite oxidation in coal during storage in dumps was investigated in laboratory experiments with Thiobacillus ferrooxidans using a percolation bioreactor and results in a removal of 75 % of pyrite within 70 days. In the initial desulphurization phase 450 mg pyritic-S/kg coal per day were oxidized at maximum rate, while the overall rate was determined to 130 mg pyritic-S/kg coal per day. During the desulphurization the mean particle size of the coal was reduced from 0.55 mm to 0.175 mm. As shown by microscopy and elemental analyses of the coal the pyrite was completely removed from small coal particles, whereas parts of it remained in the core of the greater particles.