Production of clean fuels by solvent skimming of coal at around 350 °C

The authors have recently presented a new coal extraction method by which various kinds of coals ranging from brown coals to bituminous coals could be extracted up to 80% of the parent coals in a flowing stream of tetralin or a coal derived oil, carbol oil, under 10 MPa at 350 °C. The extract obtained by this method was almost free from inorganic materials. In this study the effect of solvent recycling on the extraction behavior was examined to make the method practically applicable. The solvent recycling was found to be effective in enhancing the extraction yield and in decreasing further the inorganic fraction in the extract. The extract and residue obtained were characterized through various analyses. To examine how inorganic materials are removed by the extraction, the contents of inorganic elements, including harmful trace elements, in the extract were investigated. It was clarified that the presented method was effective in the removal of most of the inorganic elements including even harmful trace elements from coals, although the degree of removal was dependent on the kind of element.