Production of a low mineral content fuel by a coal liquefaction process utilizing an asphaltene-free hydrogenated coal solvent which yields as the primary product a mixture of liquid and solids, a part of which is suspended in the liquid. The suspended solids are effectively removed with minimum loss...http://www.google.ca/patents/US3997425?utm_source=gb-gplus-sharePatent US3997425 - Process for the liquefaction of coal
