Extraction of low rank coals by coal derived oils at 350°C for producing clean fuels

We have recently presented a new coal solvent extraction method that enhances the extraction yield dramatically. The method extracts coal using a flowing stream of either tetralin or 1-methyinaphthalene under 10 MPa at 200 to 400degreesC. The extract yield reached 65 to 80% for bituminous coals at 350degreesC, and the extract was almost free from mineral matters. Thus, this method was found to be effective to recover clean fuels from bituminous coals under rather mild conditions. To extend the extraction method to low rank coals and to make the method practically applicable, coal derived oils, carbol oil and creosote oil, were used in addition to tetralin in this study. Twenty kinds of coals were subjected to the extraction by tetralin and the coal derived oils at 350degreesC. Almost all sub-bituminous coals and brown coals examined were surprisingly extracted by 80% in the carbol oil at 350degreesC. It was also found that the extract was almost free from mineral matters and that most of sulfur was retained in the coal through the extraction by tetralin, whereas most of sulfur including pyritic sulfur was transferred into the soluble fraction through the extraction by the carbol oil. Thus, it was clarified that the proposed method was effective to produce a large amount of clean fuels from low rank coals under rather mild conditions.