Cocarbonization properties of dewaxed FCC decant oils with low sulfur vacuum residue leading to production of needle coke.

Abstract

Cocarbonization properties of a particular FCC decant oil (FCC-DO) of paraffinic nature with low sulfur vacuum residue (LSVR) were studied in an attempt to find guiding principles of its thermal modification for production of better quality needle coke, using a tube bomb, as these oils do not always make excellent coke of homogeneous quality because of difference existing in the oils properties. FCC-DO was heattreated under some conditions of temperature and residence time before cocarbonization with LSVR, to eliminate the unfavorable bottom mosaic coke. The heattreatment of FCC-DO removed paraffins and alkyl groups of longer chains on aromatic ring, which increased the aromaticity. Highly aromatized FCC-DOs increased solvency, at early stage cocarbonization, dissolving viscous mesophase derived from the most reactive portion in LSVR which is believed to cause bottom mosaic structure. The coefficient of thermal expansion (CTE) of the coke was maintained at optimum range for graphite electrodes by selecting adequate carbonization conditions for the particular feed.