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A delayed coking process in which the coker furnace feed is free of conventional heavy recycle. Elimination of this material from the coker furnace feed produces, based on fresh feed to the process, increased liquids and decreased coke. Coker furnace feed is initially combined with a diluent hydroca

A delayed coking process in which the coker furnace feed is free of conventional heavy recycle. Elimination of this material from the coker furnace feed produces, based on fresh feed to the process, increased liquids and decreased coke. Coker furnace feed is initially combined with a diluent hydrocarbon having a lower boiling range than conventional heavy coker recycle and then transferred to the coker furnace. The hydrocarbon diluent is much lower in coke-forming components than the heavy recycle which is normally combined with the fresh feed and fed to the coker furnace.

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A process for improving the product yields from delayed coking of a heavy hydrocarbon oil feedstock in a coking unit comprising a coker furnace, a coking drum and a coker fractionator to produce delayed coke and cracked liquid and gaseous hydrocarbon products comprising the steps of: (a) delayed cok

A process for improving the product yields from delayed coking of a heavy hydrocarbon oil feedstock in a coking unit comprising a coker furnace, a coking drum and a coker fractionator to produce delayed coke and cracked liquid and gaseous hydrocarbon products comprising the steps of: (a) delayed coking said heavy hydrocarbon oil in said coking drum under conditions at which delayed coke having a volatile matter content of not more than 15 percent by weight is produced; (b) passing overhead vapors from said coking drum to said coker fractionator; (c) condensing the highest boiling fraction of said overhead vapors and removing said fraction from said process; and (d) adding a diluent hydrocarbon having a lower boiling range than said highest boiling fraction to said heavy hydrocarbon oil feedstock prior to heating said heavy hydrocarbon oil feedstock to coking temperature in said coker furnace, said diluent hydrocarbon being added in an amount sufficient to effectively prevent coke deposition in said coker furnace, whereby the yield of delayed coke having a volatile matter content of less than 15 percent by weight is lower, and the liquids yield is higher, than the yields which would be obtained if said highest boiling fraction of said overhead vapors were combined with said feedstock.