Biodesulphurization of mengen lignite by Rhodoccocus rhodochrous in a batch stirred and aerated tank fermenter

The biodesulphurization of Mengen lignite by a mesophilic bacterium, Rhodoc occus rhodochrous ATCC 53968, was investigated in a batch stirred and aerat ed reactor. The experiments were carried out at 28 degrees C with an inocul um percentage, initial pH, initial sodium acetate and lignite concentration of the biodesulphurization medium of 8% [v/v], 6.5 mM, 20 mM and 20 g/l, r espectively. Variations in the sulphur contents of the lignite relative to the biodesulphurization period were monitored. The effects of the stirring and aeration rates on the removal of different sulphur forms from coal were investigated in the ranges 450-1,200 rpm and 0.1-0.53 vvm and the optimum values were found to be 500 rpm and 0.18 vvm, respectively. An increase in the total sulphur reduction with increasing biodesulphurization time was ob served. The maximum total sulphur removal percentage was found to be 15.2% at 1,200 rpm after four days of incubation. The highest total sulphur remov al rate was calculated on the second day of microbial desulphurization for each run. The total and organic sulphur contents of the coal after biodesul phurization were correlated with the stirring and aeration rates by using t he non-linear least squares regression method. In the experimental runs las ting 8 days, the highest organic sulphur reducing percentage of 10.1% was o btained at a stirring rate of 500 rpm and an aeration rate of 0.40 vvm.