Primary coal liquids upgrading

Primary coal liquids must be upgraded in order to serve these markets. A logical route is to use current black oil conversion technology as practiced in the petroleum industry (2). An applicable UOP process is RCD Unibon (3). This comprises the direct processing of petroleum residues to reduce the sulfur and nitrogen content of heavy fuel oil or to combine desulfurization with conversion of residue to lighter, more valuable products. 

The stages of coal conversion to final products are referred to as the primary stage, in which coal is converted to primary liquid (soluble) products in two steps and a secondary or final stage in which the primary products are upgraded to the final distillate products. 

Solid/liquid separation is usually required at the interface of the primary and secondary stages to allow optional upgrading of the crude coal liquids of the primary liquefaction stage, by removing mineral matter, unreacted coal, heavy products, and catalysts (111, 112). Distillation, anti-solvent extraction, and centrifugation have been conventionally employed in liquefaction processes (113, 114). 

Since only relatively simple equipment is required, it should prove feasible to flash-pyrolyze the coal at the generating station or at the mine at which it is produced, and to transport the primary liquids from several operations to a large central upgrading facility. In Alberta alone, where coal consumption by electric utilities is expected to climb from an annual rate of 6.5 million tons In 1977 to 16-17 million tons in 1985 and... 

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