Biodesulphurisation of coal
The emission of sulphur oxides during the combustion of coal is one of the causes of an environmental problem known as acid rain. Biodesulphurisation technology applied as a method to remove sulphur before coal combustion was investigated in this work. The desulphurisation abilities of three specific bacterial strains including Rhodococcus erythropolis IGTS8, R. erythropolis X309 and Shewanella putrefaciens strain NCIMB 8768 have been evaluated. R. erythropolis IGTS8 and X309 were found to be able to remove both inorganic and organic sulphur from model compounds and coal samples. Their abilities to remove sulphur from benzothiophene were observed for the first time. A novel desulphurising bacterium, S. putrefaciens was also found to be able to remove inorganic and organic sulphur from coal samples. The bacterium, however, lost its ability to remove organic sulphur from model compounds during the investigation. R. erythropolis IGTS8 presented the greatest desulphurisation efficiency among the three bacterial strains. Nevertheless, the desulphurisation activity of R. erythropolis IGTS8 was too low for an economical coal biodesulphurisation process as it removed only 32.0% of total sulphur in bituminous coal, and 21.1% of total sulphur in anthracite coal. Alternatively, coal biodesulphurisation can be carried out in inexpensive conditions by using the bacteria inherent in the coal itself. The type of coal has an important effect on desulphurisation efficiency since the sulphur reduction in bituminous coal, which is in a lower rank than anthracite, was greater than the sulphur reduction in anthracite coal. This work also developed and evaluated the analytical methods used in the field. A HPLC method was developed to detect the desulphurisation metabolites of model compounds. The techniques for measuring sulphur in coal were improved.