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Reserve of quality coal mines has been getting decreased all over the world, as well as Turkey. Presently, there is a concentrated effort in academia conducting intensive studies aimed at enhancing the quality of low-rank coals for utilization. Turkish lignite, containing high sulfur and ash, can be treated to remove sulfur and ash from the coal using physical, chemical, and biological methods. In this study, chemical (humic acid) and biological (Pseudomonas putida) leaching methods were applied for removing of pyritic and organic sulfur from a high sulfur content lignite coal taken from Çan (Turkish Coal Enterprises (TKI), Çanakkale, Turkey) region. The experimental study consisted of the two main stages as (i) column chemical leaching and bioleaching, and (ii) a combination of chemical and biological process at atmospheric pressure on physically the treated/cleaned lignite coal by heavy media separation. A clean coal product with 4.40% ash and 2.09% S content was obtained by both using chemical and biological leaching to the lignite coal treated/washed (16.46% ash and 6.14% S). [ABSTRACT FROM AUTHOR]

Turkey coal reserves are mainly lignite (brown coal) and the majority of these reserves contain high-ash/sulfur coals, therefore, it is important to evaluate these low-quality lignite coals. Most of the produced lignite is utilized at the coal power stations in Turkey. The polluting gases containing sulfur dioxide after burning of low-quality coals are the main reason for air pollution, acid rain, and some respiratory systems diseases. In order to avoid these problems, high ash and sulfur-containing coal in our country need to be improved. In this study, the sink-float tests (heavy media separation) were applied to increase the quality of coal samples so that the ash and the impurities could be removed using a high ash-sulfur content coal sample (36.96% ash, 6.94% S and calorific value 3185 kcal.kg−1) taken from TKI (Turkish Coal Enterprises) Çan (Çanakkale, Turkey) lignite coalfield. The results of the float-sink tests showed that the most convenient washing operating density was 1.6 g/cm3, and the weight yield of the clean coal was 53.16%wt. (70.94% coal recovery) with 16.46% ash, 6.14% S with calorific value 5000 kcal.kg−1 using 10–0.5 mm size fraction of the coal. [ABSTRACT FROM AUTHOR]