Process for the preparation of recarburizer coke

• US 5,059,301 A
• Filed: 03/20/1991
• Issued: 10/22/1991
• Est. Priority Date: 11/29/1988
• Status: Expired due to Fees

• Current Assignee: Conoco Incorporated (ConocoPhillips)
• Original Assignee: Conoco Incorporated (ConocoPhillips)
• Inventors: Shigley, John K., Roussel, Keith M.
• Primary Examiner(s): Davis, Curtis R.
• Assistant Examiner(s): DIEMLER, WILLIAM
• Application Number:
  US07/672,504
• Time in Patent Office: 216 Days
• Field of Search: 208/50, 208/57, 208/93, 208/131, 208/58
• US Class Current: 208/50
• 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 69/06 including at least one step of thermal cracking in the absence of hydrogen

Abstract

Recarburizer coke containing not more than 0.1 weight percent sulfur and not more than 0.1 weight percent nitrogen is prepared by severe catalytic hydrotreating, followed by thermal cracking, and delayed coking of vacuum gas oil obtained from the vacuum distillation of FCC decant oil.

Claims

1. A process for the production of low sulfur and low nitrogen coke which comprises:

(a) subjecting a decant oil containing substantial amounts of sulfur and nitrogen to vacuum distillation to obtain a vacuum gas oil fraction in which the sulfur and nitrogen is concentrated, wherein said vacuum gas oil fraction has a boiling point below about 1000°

F. and a residuum having a boiling point above about 1000°

F.,

(b) subjecting the vacuum gas oil to severe hydrotreating conditions to obtain a product containing reduced sulfur and nitrogen,

(c) subjecting the hydrotreated product to fractionation in a first fractionator to produce a light hydrocarbon fraction, a heavy gas oil fraction and a thermal tar fraction,

(d) combining the thermal tar from step (c) with overhead hydrocarbon vapors from a coke drum to produce a mixture and subjecting said mixture to fractionation in a second fractionator to produce a heavy coker gas oil fraction and a thermal tar fraction; and

(e) subjecting the thermal tar from step (d) to delayed coking to produce a coke product.

2. The process according to claim 1 wherein the heavy gas oil fraction from step (c) is subjected to thermal cracking and the effluent from the thermal cracker is recycled to the first fractionator.

3. The process according to claim 1 wherein the heavy coker gas oil from step (d) is recycled and combined with the vacuum gas oil fraction of step (a).

4. A process of claim 1 wherein the heavy coker gas oil from step (d) is recycled and combined with the hydrotreated product of step (b).

5. The process according to claim 1 wherein the coke product contains not more than 0.10 weight percent sulfur and not more than 0.10 weight percent nitrogen.

6. The process according to claim 1 wherein the hydrotreating in step (b) is conducted at a temperature of 600°

F. to about 850°

F. a pressure of about 1000 psig to about 2500 psig, a hydrogen to oil ratio of about 3000 to about 4000 SCFB and a LHSV of from about 0.2 to about 2.0.

7. The process according to claim 1, wherein the coke product from step (e) is calcined to obtain recarburizer coke product containing not more than 0.05 weight percent sulfur and not more than 0.05 weight percent nitrogen.

8. A process for the production of low sulfur and low nitrogen recarburizer coke which comprises:

(a) subjecting a decant oil containing more than 1.0 weight percent sulfur and more than 1.0 weight percent nitrogen to vacuum distillation to obtain a vacuum gas oil fraction having a boiling point below about 1050°

F. and a residuum having a boiling point above about 1000°

F.,

(b) subjecting the vacuum gas oil to severe hydrotreating conditions at a temperature of 700°

F. to 800°

F., a pressure of 1800 psig to 2400 psig, a hydrogen to oil ratio of 3000 to 4000 SCFB and a LHSV of 0.5 to 1.5 to obtain a product containing reduced sulfur and nitrogen,

(c) subjecting the hydrotreated product to fractionation in a first fractionator to produce a light hydrocarbon fraction, a heavy gas oil fraction and a thermal tar fraction,

(d) combining the thermal tar fraction from step (c) with overhead hydrocarbon vapors from a coke drum to produce a mixture and subjecting said mixture to fractionation in a second fractionator to produce a heavy coker gas oil fraction and a thermal tar fraction,

(e) subjecting the thermal tar from step (d) to delayed coking to produce a coke product; and

(f) recovering a coke product containing not more than 0.10 weight percent sulfur and not more than 0.10 weight percent nitrogen.

9. The process according to claim 8 wherein the heavy gas oil fraction from step (c) is subjected to thermal cracking and the efflent from the thermal cracker is recycled to the first fractionator.

10. The process according to claim 8 wherein the heavy coker gas oil from step (d) is recycled and combined with the vacuum gas oil fraction of step (a).

11. The process of claim 8 wherein the heavy coker gas oil from step (d) is recycled and combined with the hydrotreated product of step (b).

12. The process of claim 8 wherein the thermal cracking is conducted at a temperature of from about 900°

F. to about 1100°

F. and a pressure of from about 300 psig to about 800 psig.

13. The process according to claim 8 wherein the delayed coking is conducted at a temperature of from about 850°

F. to about 950°

F., a pressure of from about 15 psig to about 200 psig and a coking cycle of from about 16 hours to about 100 hours.

14. The process according to claim 8 wherein the effluent from the hydrotreating in step (b) contains less than about 0.10 weight percent sulfur and less than about 0.10 weight percent nitrogen.

15. The process of claim 8 wherein the vacuum gas oil of step (a) has a maximum boiling point of from about 850°

F. to about 1050°

F.