Abstract: Hydrocarbon liquids are recovered from run-of-mine oil-bearing rock composed primarily of limestone by separating the rock into a low-density fraction and a high-density fraction, contacting the low-density fraction with an organic solvent in an extraction zone thereby extracting the oil from the low-density fraction, and recovering the extracted oil from the organic solvent.

Abstract: A size fraction of oil shale is upgraded by separating the shale into a first low density fraction containing particles relatively rich in kerogen and a first high density fraction containing particles relatively lean in kerogen, crushing the first low density fraction to produce smaller particles, separating the smaller particles into a second low density fraction and a second high density fraction and recovering the second low density fraction as high grade oil shale rich in kerogen.

Abstract: A size fraction of coal is physically cleaned by separating the coal into a low density fraction containing relatively small amounts of inorganic constituents and a high density fraction containing relatively large amounts of inorganic constituents, crushing the low density fraction to produce smaller particles, separating the smaller particles into a low density fraction and a high density fraction and recovering the low density fraction as clean coal product.

Abstract: A staged air burner having a swirl chamber for providing a swirl flow path for primary combustion air, a tangential duct system for providing a tangential flow path for primary combustion air flowing toward the swirl flow path, and a converging passage structure for providing a converging flow path for secondary air which flows along the converging flow path inwardly toward an axis of the swirl chamber downstream of the latter. At least two fuel supply systems are respectively situated at two of the above flow paths for supplying combustible fuel thereto so that it is possible to fire fuel simultaneously at least at two of the flow paths.