Evaluation of elemental sulphur in biodesulphurized low rank coals

A new procedure for elemental sulphur (Sel) determination in coal and its fractions is offered. It includes exhaustive CHCl3 extraction and subsequent quantitative analysis of the extracts by HPLC using C18 reversed phase column. Its application gives ground to achieve better sulphur balance and to specify the changes in the organic and elemental sulphur as a result of biotreatments. Two Bulgarian high sulphur containing coal samples, i.e. subbituminious (Pirin) and lignite (Maritza East), and one Turkish lignite (Cayirhan-Beypazari) are used. Prior to biotreatments, the samples are demineralized and depyritized. In the biodesulphurization processes, the applied microorganisms are: the white rot fungi “Phanerochaeta Chrysosporium” – ME446 and the thermophilic and acidophilic archae “Sulfolobus Solfataricus” – ATCC 35091. preliminary demineralized and depyritized coals, the highest presence of Sel is registered, which is explained by their natural weathering. As a result of the implemented biotreatments, the amount of Sel could be reduced in the range of 16.1–53.8%. The content of Sel is also assessed as part of the total sulphur and organic sulphur. The following range of Sel content is measured: 0.01–0.16 wt.% or 0.3–4.6% of total sulphur and 0.3–5.1% of organic sulphur. In this way, more precise information is obtained concerning the content of organic sulphur presence.