Most refiners dispose of slurry oil in the coker because there is nowhere else to go with it. Some use slurry oil to control or avoid shot coke – especally in the cone section of the drum. Finally, a few use slurry oil to control the metals and sulfur in anode grade coke.
FCC slurry oil boils in the same range as heavy coker gas oil – approximately. So when the slurry oil is fed to the coker most of the slurry oil vaporizes out of the coke drum and reports to the gas oil product. This is highly dependent on the pressure/temperature of the coke drums.
KBC, the company I work for, has done this type of analysis many times. The economics of sending FCC slurry oil to the coker gets complicated with the gas oil yields in the Hydrotreater(HT) and then the FCC. A low pressure HT will send aromatic (due to the slurry oil) coker heavy gas oil to the FCC which then will yield higher amounts of slurry oil. The net results is an increase in slurry oil, poor utilization of the coker, the hydrotreater and the FCC. However if the HT operates at sufficient pressures to breakup the polynuclear aromatics in the coker gas oil then this might work well. Bottom line is this is not a simple issue.