Delayed coking is a thermal process in which the vacuum residue from crude distillation is heated in a furnace then confined in a reaction zone or coke drum under proper operating conditions of temperature and pressure until the unvaporized portion of the furnace effluent is converted to vapor and coke.
Delayed coking is an endothermic reaction, with the furnace supplying the necessary heat for the coking reactions. The reactions in the delayed coking are complex. In the initial phase, the feed is partially vaporized and cracked as it passes through the furnace. In the next step, cracking of the vapor occurs as it passes through the drum. In the final step, successive cracking and polymerization of the liquid confined in the drum takes place at high temperatures, until the liquid is converted into vapor and coke.
The coke produced in the delayed coker is almost pure carbon containing some of the impurities of the feed, such as sulfur and metals.
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