COMPCOAL(trademark): A profitable process for production of a stable high-Btu fuel from Powder River Basin coal

摘要

Western Research Institute (WRI) is developing a process to produce a stable, clean-burning, premium fuel from Powder River Basin (PRB) coal and other low-rank coals. This process is designed to overcome the problems of spontaneous combustion, dust formation, and readsorption of moisture that are experienced with PRB coal and with processed PRB coal. This process, called COMPCOAL(trademark), results in high-Btu product that is intended for burning in boilers designed for midwestern coals or for blending with other coals. In the COMPCOAL process, sized coal is dried to zero moisture content and additional oxygen is removed from the coal by partial decarboxylation as the coal is contacted by a stream of hot fluidizing gas in the dryer. The hot, dried coal particles flow into the pyrolyzer where they are contacted by a very small flow of air. The oxygen in the air reacts with active sites on the surface of the coal particles causing the temperature of the coal to be raised to about 700 F (371 C) and oxidizing the most reactive sites on the particles. This ''instant aging'' contributes to the stability of the product while only reducing the heating value of the product by about 50 Btu/lb. Less than 1 scf of air per pound of dried coal is used to avoid removing any of the condensible liquid or vapors from the coal particles. The pyrolyzed coal particles are mixed with fines from the dryer cyclone and dust filter and the resulting mixture at about 600 F (316 C) is fed into a briquettor. Briquettes are cooled to about 250 F (121 C) by contact with a mist of water in a gas-tight mixing conveyor. The cooled briquettes are transferred to a storage bin where they are accumulated for shipment.