Delayed coking process
Petroleum cokes derived from extra-heavy crude sources can be made more amenable to quenching by adding water or a water/light oil mixture to the coker feed downstream of the furnace. The coke product resulting from this addition of normally volatile liquids to the hot coker feed is still relatively dense but is more friable and usually is in a compact, relatively free-flowing, granular form. The coke is more amenable to uniform quenching in the drum and so can be cut and discharged with a reduced risk of eruptions and a reduced risk of fires in the coke pit or when the coke is subsequently handled and transported.
1. A delayed coking method comprising:
(a) heating a petroleum resid feed derived from a heavy crude having a gravity of 5 to 9° API in a first heating zone, to a temperature at which the resid is a pumpable liquid;
(b) heating the resid further in a furnace to a coking temperature of up to 520° C.;
(c) conducting the heated resid from the furnace in a transfer line to a delayed coking drum;
(d) injecting a volatile liquid comprising water and a naphtha having an end point up to 150° C. into the heated resid in the transfer line in an amount from 0.5 to 2 v/v percent volatile liquid to feed;
(e) subjecting the heated resid in the coking drum to coking at a coking temperature up to 520° C. and at 100 to 550 kPag coking drum pressure and removing the vapor products produced in the coking as overhead and forming a quenchable coke product as a mass in the drum
(f) quenching the coke mass in the drum to produce a solid coke product;
(g) removing the quenched coke product from the drum.
2. A process according to claim 1 in which the resid feed comprises an atmospheric or vacuum resid derived from an Orinoco Heavy Oil crude.
3. A process according to claim 2 in which the temperature of the drum is from 400 to 500° C.
4. A process according to claim 2 in which the resid feed comprises an atmospheric vacuum resid derived from an Orinoco Heavy Oil crude.
5. A process according to claim 2 in which the amount of the volatile liquid injected into the heated feed is about 1.3 v/v percent volatile liquid to feed.
6. A process according to claim 1 in which the volatile liquid comprises water and a light hydrocarbon oil having an end point up to 400° C.
7. A process according to claim 1 in which the amount of naphtha relative to water in the volatile liquid is from 10 to 50 percent v/v of the liquid.