Mild coal extraction for the production of anode coke from Blue Gem coal

The quality and availability of petroleum coke used in the manufacture of carbon anodes for aluminum production is a growing concern to the industry. Coke quality and yields have progressively declined as changes in refinery practice and the move towards processing an increasing proportion of heavier sour crudes have affected coke properties, resulting in an increase in the metal impurities and sulfur content of the coke. An alternative supply of anode coke is required to supplement or eventually replace calcined petroleum coke. The significant domestic reserves of coal could represent a viable carbon resource for anode production, provided defined coke specifications can be met and at a cost that is economically viable.The principal objective of this study was to examine the feasibility of producing anode grade coke by the UKCAER process for the mild solvent extraction of coal. Blue Gem coal from Eastern Kentucky was dissolved in a high boiling point solvent, the mineral matter and unreacted products removed by filtration, and the clean coal liquid converted to coke. The performance of the coal in solvent extraction was compared to a very reactive coal from Western Kentucky. A simple solvent-extraction screening test was established to assess potential candidate materials and process variables without the need for prolonged and complex routines. The coals were assessed in more detail to determine the optimum process conditions by conducting larger scale extraction tests to yield sufficient material for conversion to coke. The green cokes were calcined and the products characterized. The composition and structure of the calcined cokes were compared to typical petroleum coke and assessed for their use in the fabrication of carbon anodes.