Coke drum quench process

Patent metadata

Field	Value
Publication number	US-9809753-B2
Application number	US-201313868877-A
Country	US
Kind code	B2
Filing date	Apr 23, 2013
Priority date	Apr 23, 2013
Publication date	Nov 7, 2017
Grant date	Nov 7, 2017

Abstract

Processes for quenching coke in a coke drum of a delayed coker unit that more thoroughly cool the coke, eliminate hot spots in the coke bed, and remove residual hydrocarbons from the coke prior to venting the coke drum may comprise a ramp quench phase and a pressure quench phase after the ramp quench phase. During the ramp quench phase, the coke drum internal pressure may rise to a maximum pressure level and then fall to a transitional pressure level. At least one control valve may be actuated at the transitional pressure level to increase the coke drum internal pressure from the transitional pressure level to a pulsed pressure level of the pressure quench phase.

First claim

What is claimed is:

1. A process for quenching coke in a coke drum of a delayed coker unit, the process comprising:
a) feeding quench water to the coke drum during an initial quench phase of the quenching process at an initial quench rate;
b) after step a), increasing the rate of feeding the quench water to the coke drum during a ramp quench phase of the quenching process to attain a maximum ramp quench rate, wherein during the ramp quench phase the coke drum internal pressure increases to a maximum pressure level and thereafter the coke drum internal pressure decreases to a transitional pressure level; and
c) at the time of the transitional pressure level, actuating at least one control valve in a blowdown system that receives overhead vapors from the coke drum, whereby the coke drum internal pressure increases from the transitional pressure level to a pulsed pressure level.

2. The process of claim 1 , wherein the pulsed pressure level is in the range from about 15 to 20 psig.

3. The process of claim 1 , further comprising:
d) during step a), recovering hydrocarbon vapors from the coke, wherein:

prior to step c) the recovery of hydrocarbon vapors from the coke has decreased, and
after step c) the increase in the coke drum internal pressure to the pulsed pressure level effects the release of residual hydrocarbons from the coke.

4. The process of claim 3 , wherein: prior to step c) the recovery of hydrocarbon vapors from the coke has decreased to zero.

5. The process of claim 1 , further comprising:
e) after actuating the at least one control valve to start a pressure quench phase of the quenching process, further increasing the rate of feeding the quench water to the coke drum during the pressure quench phase of the quenching process to attain a maximum pressure quench rate, wherein the maximum pressure quench rate is at least about 1.5 times (1.5×) the maximum ramp quench rate.

6. The process of claim 1 , further comprising:
f) after step c), actuating the at least one control valve to effect a decrease in the coke drum internal pressure from the pulsed pressure level to a vent pressure level; and
g) venting the coke drum to the atmosphere.

7. A process for quenching coke in a coke drum of a delayed coker unit, the process comprising:
a) feeding quench water to the coke drum during an initial quench phase;
b) increasing the rate of feeding the quench water to the coke drum during a ramp quench phase subsequent to the initial quench phase, wherein during the ramp quench phase the coke drum internal pressure increases to a maximum pressure level and thereafter the coke drum internal pressure decreases to a transitional pressure level;
c) while the coke drum internal pressure is at the transitional pressure level, actuating at least one control valve, in a blowdown system that receives overhead vapors from the coke drum, to effect an increase in the coke drum internal pressure to a pulsed pressure level greater than the transitional pressure level; and
d) after step c), actuating the at least one control valve to effect a decrease in the coke drum internal pressure from the pulsed pressure level to a vent pressure level.

8. The process of claim 7 , wherein during the initial quench phase the coke drum internal pressure is in the range from about 2 to 10 psig, and the maximum pressure level is in the range from about 20 to 30 psig.

9. The process of claim 8 , wherein the transitional pressure level is in the range from about 10 to 20 psig.

10. The process of claim 9 , wherein the pulsed pressure level is in the range from about 15 to 20 psig.

11. The process of claim 9 , wherein the pulsed pressure level is in the range from about 2 to 10 psig greater than the transitional pressure level.

12. The process of claim 7 , further comprising:
e) after step d) and prior to venting the coke drum, soaking the coke in the quench water for a time period in the range from about 5 to 30 minutes at a coke drum internal pressure in the range from about 1 to 4 psig.

13. The process of claim 7 , wherein:
prior to step c) a first flow of hydrocarbon vapors from the coke drum has decreased, and
after step c) residual hydrocarbons are released from the coke to provide a second flow of hydrocarbon vapors from the coke drum.

14. The process of claim 13 , wherein: prior to step c) the first flow of hydrocarbon vapors from the coke drum has decreased to zero.

15. A process for quenching coke in a coke drum of a delayed coker unit having a blowdown system, the process comprising:
a) feeding quench water to the coke drum to effect cooling of the coke;
b) during step a), removing a first portion of hydrocarbon vapors from the coke drum to the blowdown system until a first flow of hydrocarbon vapors from the coke drum has decreased;
c) during step a), actuating at least one control valve in the blowdown system to effect an increase in coke drum internal pressure;
d) releasing a second portion of hydrocarbon vapors from the coke via the increase in coke drum internal pressure;
e) after step c), actuating the at least one control valve to effect a decrease in coke drum internal pressure; and
f) recovering the second portion of hydrocarbon vapors from the coke drum.

16. The process of claim 15 , wherein prior to step c) the second portion of hydrocarbon vapors are trapped in the coke.

17. The process of claim 15 , wherein step c) is performed after step b).

18. The process of claim 15 , wherein:
the increase in coke drum internal pressure effected by step c) comprises an increase from a transitional pressure level to a pulsed pressure level, and
the increase in coke drum internal pressure from the transitional pressure level to the pulsed pressure level occurs over a time period in the range from about 2 to 20 minutes.

19. The process of claim 15 , further comprising:
g) after step f), venting the coke drum to the atmosphere at a coke drum internal pressure of not more than about 2 psig.

20. The process of claim 19 , wherein step g) comprises venting the coke drum to the atmosphere for a time period of less than 10 minutes.

21. The process of claim 15 , wherein the blowdown system comprises a blowdown drum, and the at least one control valve is disposed downstream from the blowdown drum.

22. The process of claim 21 , wherein the blowdown system further comprises at least one heat exchanger disposed downstream from the blowdown drum, and the at least one control valve is disposed upstream from the at least one heat exchanger.

23. The process of claim 15 , wherein: during step b) the first flow of hydrocarbon vapors from the coke drum has decreased to zero.

Assignees

• Wilborn Dale William
• Love Eileen Imelda
• Alvarado Mark Anthony
• Chevron Usa Inc

Inventors

• Wilborn Dale William
• Love Eileen Imelda
• Alvarado Mark Anthony

Classifications

• C10B39/06 Primary

  in the oven · CPC title

• C10B55/00

  Coking mineral oils, bitumen, tar, and the like or mixtures thereof with solid carbonaceous material (cracking oils C10G) · CPC title

• C10G9/005

  Coking (in order to produce liquid products mainly) · CPC title