Characterization of Cokes from Delayed Co-Coking of Decant Oil, Coal, Resid, and Cracking Catalyst

Abstract

The following focuses on the quality of coke produced from delayed coking blends of decant oil, coal, and resid, and it also examines the effect of adding a cracking catalyst to each blend. We also examine the role of coal, resid, and catalyst addition on the formation of green coke, calcined coke, and graphitized cokes. The overall goal was to see if use of lower quality feedstocks could produce marketable coke. The coal sample was cleaned using the best available technology to as low a level of ash yield (as determined by proximate analysis) as possible. Conversion and yield results from the delayed coking of DO, DO/coal, and DO/resid/coal as well as each reaction using catalyst are discussed. Gas products obtained from the delayed coking experiments were characterized, and results are discussed. Green cokes obtained from different delayed coking processes were evaluated using optical microscopy; the cokes were calcined and graphitized. X-ray diffraction, temperature-programmed oxidation, and proximate/ultimate analyses were used to characterize green coke, calcined coke, and graphitized coke. In general, the green coke generated from the various reaction conditions (DO and DO plus coal) produced a coke that is adequate as an anode grade coke and is suitable as a graphite filler, but because of either the sulfur and/or ash content is not suitable for nuclear graphite production or metallurgical coke. In general, adding catalyst increased the liquid yields, while decreasing the coke/gas yield, and improved the carbon quality, but added to the ash composition. For reactions of DO/coal/resid, the carbon is not suitable for anode grade coke, graphite, nuclear graphite, or metallurgical coke, and addition of catalyst actually decreased the quality of the coke.