The coking process involves cracking of heavy residual oils into more valuable gasoil, distillate, naphtha and LPG products. Coke is also produced. Normal feeds include vacuum bottoms, atmospheric bottoms, asphaltenes from ROSE and other types of solvent deasphalting units, bitumen and other heavy oils, thermal and pyrolsis tars, decant oils, visbreaker and thermal tars.
Delayed coking is a semi-batch thermal cracking process. The process is comprised of coker heaters, coke drums, fractionation, vapor recovery unit, hydraulic decoking, coke handling and blowdown systems. Feed is normally routed via coker fractionator to remove light fractions. Feed plus recycle from the fractionator are brought to coking temperature in a specially designed heater and then sent to the coke drum. The feed cracks into lighter fractions and coke in the coke drum. Cracked material exiting from the overhead is quenched and sent to the fractionator.
After the coke level in the drum has reached the maximum accepted level, the feed is directed to the second drum. The drum with coke is cooled, then cut with high-pressure water jets and removed to coke handling area. The drum is then heated and put back in service when the second drum fills up with coke.