Safe and automatic method for preparation of coke for removal from a coke vessel

• US 20040118746A1
• Filed: 12/18/2002
• Published: 06/24/2004
• Est. Priority Date: 12/18/2002
• Status: Active Grant

• Current Assignee: Chevron USA Incorporated (Chevron Corp.)
• Original Assignee: Chevron USA Incorporated (Chevron Corp.)
• Inventors: Stewart, Gary D., DiPadua, Ronald R., Fitzgerald, Christopher I., Wilborn, Dale W.
• Granted Patent: US 7,037,408 B2
• Time in Patent Office: Days
• US Class Current: 208/131
• CPC Class Codes: C10B 1/04 Vertical retorts
• CPC Class Codes: C10B 25/10 for ovens with vertical chambers
• CPC Class Codes: C10B 33/00 Discharging devices; Coke guides
• CPC Class Codes: C10B 55/00 Coking mineral oils, bitumen, tar, and the like or mixtures thereof with solid carbonaceous material cracking oils C10G
• CPC Class Codes: C10G 9/14 in pipes or coils with or without auxiliary means, e.g. digesters, soaking drums, expansion means
• CPC Class Codes: C10G 9/18 Apparatus

Abstract

A safe, efficient and repetitively operable coke vessel decoking system is disclosed. In a preferred embodiment the closed system comprises a coker vessel pressure-tightly sealed to a top head system, which includes a closure housing with a laterally moveable horizontal closure member therein and a cutting head enclosure, which further comprises a drill stem guide, an access door, and a cutting assembly mounted therein. A novel feature of the invention is a steam purge/blocking system whereby steam pressure is maintained in the closure housing during the coking cycle to maintain seal integrity. Personnel safety during decoking operations is greatly enhanced by eliminating dangerous manual tasks associated with the prior art such as unbolting and removing top head devices. The system can be remotely and repetitively operated through numerous coking/decoking cycles without removal of any system element.

Claims

1. A process for repetitively producing and removing coke from a delayed coker vessel, wherein the coker vessel has a top portion defining an aperture through which a coke cutting drill is vertically inserted to cut and remove coke from the vessel, comprising:

a) sealing an aperture closure housing to the top portion of the coker vessel;

b) sealing a cutting head enclosure to the aperture closure housing;

c) inserting a cutting head into said enclosure wherein said cutting head is attached to the distal end of a vertically rotatable shaft;

d) moving a horizontal closure member within the closure housing to open the aperture of the coker vessel top;

e) rotatably lowering the cutting head by means of the shaft through the vessel aperture into and through coke contained in the vessel;

f) injecting a fluid through a plurality of nozzles attached to the cutting head at a pressure sufficient to cut and dislodge coke from the vessel;

g) raising the cutting head to the position of step (c);

h) moving the horizontal closure member within the closure housing to close the aperture to the coker drum; and

i) repeating steps (c) through (h) through successive coking/decoking cycles.

2. The process of claim 1 wherein step (a) further comprises interposing and sealing a spool adapter between the coker vessel top and the closure housing.

3. The process of claim 1 wherein step (a) further comprises forming a seal between the aperture closure housing and the top portion of the coker vessel wherein the seal withstands pressure within the coker vessel from atmospheric to about 500 psi.

4. The process of claim 3 wherein step (a) further comprises forming a seal between the aperture closure housing and the top portion of the vessel wherein the seal withstands vessel temperatures ranging from about −

50°

F. to about 1000°

F. through repetitive coking/decoking cycles.

5. The process of claim 1 wherein the cutting head enclosure of step (b) further comprises a blow-back prevention barrier fixedly attached within the cutting head enclosure above the cutting head.

6. The process of claim 1 wherein step (a) further comprises placing a gasket between the top portion of the coker vessel and the closure unit and pressure-tightly joining the coker vessel top, the gasket and the closure unit.

7. The process of claim 5 wherein step (b) further comprises placing a gasket between the top of the closure housing and the cutting head enclosure and pressure-tightly joining the closure housing, the gasket and the cutting head enclosure.

8. The process of claim 6 or 7 wherein the gasket comprises an annular corrugated metal bonded to a graphite material.

9. The process of claim 5 wherein the cutting head enclosure comprises a first half and a second half joined at a vertical seam.

10. The process of claim 5 wherein the blowback prevention barrier further comprises a centered drill stem guide.

11. The process of claim 9 wherein at least one of the cutting head enclosure halves comprises at least one cutting head access door.

12. A process in accordance with claim 1 wherein steps (d) and (h) further comprises moving the horizontal closure member by a powered actuator or a plurality of powered actuators.

13. The process of claim 12 wherein said powered actuators are remotely actuated.

14. A process in accordance with claim 1 wherein the opening step (d) is carried out at a temperature between −

50°

F. and 110°

F. from a prior temperature of between 900°

F. and 1100°

F., and the valve is selected to withstand repeated operations at the above operating temperatures.

15. A process in accordance with claim 1 wherein the horizontal closure member of steps (d) and (h) is a valve.

16. A process in accordance with claim 15 wherein the valve is selected from a slide valve, a knife valve or a wedge plug valve.

17. A process in accordance with claim 1 wherein the aperture opens to a diameter between 24 and 48 inches.

18. A process in accordance with claim 1 wherein the closure unit is mounted to a weight bearing structure selected from the group consisting of a gantry system and a trolley system.

19. The process of claim 18 wherein the closure unit is laterally removable from the coker vessel by means of said weight bearing structure.

20. A coker vessel comprising:

(a) a vessel having a flanged top aperture;

(b) an aperture closure unit fitted and sealed to said top aperture;

(c) a horizontal closure member moveable within said closure unit;

(d) a cutting head enclosure assembly sealed to the top portion of the closure unit for containing coke particulant;

(e) a blowback/cutting guide assembly attached to the top portion of the cutting head enclosure for preventing blowback of hydrocarbon vapor emissions; and

(f) a cutting assembly to cut and dislodge the coke;

21. The coker vessel of claim 20 wherein the horizontal closure member comprises a valve.

22. The coker vessel of claim 20 wherein the cutting head enclosure assembly houses a coke cutting apparatus including a portion of a moveable shaft.

23. The coker vessel of claim 21 wherein the valve is a slide valve, a knife valve or a wedge plug valve.

24. The coker vessel of claim 21 wherein the valve further comprises a power actuated valve.

25. The coker vessel of claim 21 wherein the top aperture diameter is from 28 to 36 inches.

26. The coke vessel of claim 22 wherein the moveable shaft extends through the blowback/cutting guide assembly.

27. The coke vessel of claim 22 wherein the moveable shaft is maintained in alignment by the blowback/cutting guide assembly.

28. The coke vessel of claim 20 wherein the coke cutting apparatus is selected from the group consisting of hydraulic drill systems, rotating cutting heads with water jets, screw augers, diamond head cutters and water jets.