This study has two aims: to improve the biodesulphurization of a semi-anthracite by packed-column leaching by reducing the insoluble sulphate on the coal surface, and to determine whether after the combustion of treated and untreated coal, sulphate sulphur is transformed completely into sulphur dioxide or part remains in the ashes without reacting. Combustion tests were analysed by TG-MS. To reduce the precipitation of salts, two parameters are worked on: solution pH, which is reduced to 1.3, and the idle time between washes (ITBW), which is altered. After 125 days of treatment, comparison with the results of previous studies showed that the precipitated salt content was reduced pyritic desulphurization was increased up to 43%, and total desulphurization to 24%.