Hydrotreating decant oils for needle coke production in delayed coking

Needle coke used in the production of graphite electrodes must possess high mechanical strength, low coefficient of thermal expansion (CTE), low porosity and low levels of impurities such as sulfur. When sulfur is present in sufficient quantities it can result in irreversible thermal expansion during graphitization. This expansion decreases the graphite's bulk density, strength and electrical conductivity. Hydrotreating of decant oils used as feedstock for needle coke production was evaluated as a technique for reducing the sulfur content. A bench-scale hydrotreating flow reactor was constructed and used to study the effect of catalyst temperature, hydrogen pressure, and liquid hourly space velocity on sulfur reduction. Hydrotreated oils were analyzed by GC/MS and GC-PFPD. Semi-coke produced from selected decant oils was subjected to a microscopic optical texture examination.