Improving the effectiveness of delayed coking by its combination with viscosity breaking

Delayed coking plants (DCP) performance can be improved by combining viscosity breaking process, which can be employed in a number of refineries to produce boiler fuel oil from vacuum resids, and can be specified as a stage of preliminary heat treatment. The carbon residue in viscosity breaking is greater, and its increased content of polycyclic aromatic hydrocarbons contributes to an increase in coke yield in the DCP. The normal strength of the coke and its content of volatile substances are attained during 24-h coking, and at a furnace outlet temperature 3-4° lower. As a result of preliminary cracking of the feedstock and heavy bleed-off of distillates during viscosity breaking, the output of light distillates is reduced during coking of the heavy viscosity-breaking resid, and, consequently, the load on the DCP tower is reduced. The combination of viscosity-breaking and coking processes ensures an appreciable increase in the depth of crude refining, and also an increase in the volume of quality low-sulfur coke produced without significant capital expenditures.