Method for Reducing Fouling of Coker Furnaces

• US 20090266742A1
• Filed: 04/28/2008
• Published: 10/29/2009
• Est. Priority Date: 04/28/2008
• Status: Active Grant

• Current Assignee: Bechtel Energy Technologies & Solutions Incorporated
• Original Assignee: Conocophillips Company (ConocoPhillips)
• Inventors: Hughes, Gary C., Roth, James R., Newman, Bruce A., Alexander, Keith D.
• Granted Patent: US 7,922,896 B2
• Time in Patent Office: Days
• US Class Current: 208/131
• CPC Class Codes: C10B 57/045 containing mineral oils, bitumen, tar or the like or mixtures thereof
• CPC Class Codes: C10G 75/04 by addition of antifouling agents
• CPC Class Codes: C10G 9/16 Preventing or removing incrustation

Abstract

A method for reducing furnace fouling in a delayed coking process comprising (a) supplying at least one feed to a delayed coking unit comprised of coker furnace, at least two coke drums and a coker fractionator, (b) increasing the aromaticity of the feed to produce a modified stream by combining with the feed upstream of the coker furnace at least one added stream selected from the group consisting of an aromatic gas oil, a hydrotreated aromatic gas oil and combinations thereof, (c) introducing the modified feed stream into the coker furnace, d) heating the modified feed stream to a coking temperature in the coker furnace to produce a heated modified stream, and e) transferring the heated modified stream from the coker furnace to a coke drum.

Claims

1. A method for reducing furnace fouling in a delayed coking process wherein at least one coker feed is supplied to a delayed coking unit comprised of a coker furnace, at least two coke drums and a coker fractionator comprising

(a) increasing the aromaticity of the feed to produce a modified stream by combining with the feed upstream of the coker furnace at least one added stream selected from the group consisting of an aromatic gas oil, a hydrotreated aromatic gas oil and combinations thereof, said aromatic gas oil having an aromatic carbon content of at least about 40% as measured by ¹³C NMR based on the total carbon content of the added stream and said hydrotreated aromatic gas oil having an aromatic carbon content of at least about X % according to the formula

X=(A %)−

[(0.02)·

(hydrogen uptake in the hydrotreater)]

 

where X is as least about 20% as measured by ¹³C NMR based on the total carbon content of the hydrotreated aromatic gas oil and A is the aromaticity of the unhydrotreated aromatic gas oil as measured by ¹³C NMR and is at least about 40%, hydrogen uptake is [ρ

·

659.5·

(Δ

hydrogen content (wt %) of the hydrotreater product and feed)] and ρ

is the density (grams/cc) of the hydrotreater feed;

(b) introducing the modified stream into the coker furnace;

(c) heating the modified stream to a coking temperature in the coker furnace to produce a heated modified stream; and

(d) transferring the heated modified stream from the coker furnace to a coke drum.

2. The method of claim 1 wherein the at least one added stream has an aromatic carbon content of at least about 50% as measured by as measured by ¹³C NMR based on the total carbon content.

3. The method of claim 1 wherein the at least one added stream has an aromatic carbon content of at least about 60% as measured by as measured by ¹³C NMR based on the total carbon content.

4. The method of claim 1 wherein step (a) is carried out such that the amount of added stream in the modified stream is between about 1 wt % up to about 50 wt % of the modified stream.

5. The method of claim 1 wherein step (a) is carried out such that the amount of added stream in the modified stream is between about 20 wt % to about 40 wt % of the weight of the modified stream.

6. The method of claim 1 wherein the at least one added stream has a boiling point in a range of about 650 to about 1,000°

F.

7. The method of claim 1 wherein the at least one added stream has a boiling point in a range of about 750 to about 850°

F.

8. The method of claim 1 wherein the at least one added stream comprises an aromatic gas oil selected from the group consisting of heavy premium coker gas oil, light premium coker gas oil, cycle oil from a fluid catalytic cracking process, and combinations thereof.

9. The method of claim 1 wherein the at least one added stream comprises a decant oil fraction.

10. The method of claim 1 wherein at least a portion of the at least one added stream is hydrotreated and wherein the hydrotreated portion of the at least one added stream has an aromatic carbon content of at least about 30% as measured by as measured by ¹³C NMR based on the total carbon content.

11. The method of claim 1 wherein at least a portion of the at least one added stream is hydrotreated and wherein the hydrotreated portion of the at least one added stream has an aromatic carbon content of at least about 40% as measured by as measured by ¹³C NMR based on the total carbon content.

12. The method of claim 10 wherein the hydrogen uptake of the hydrotreated portion of the at least one added stream is at least about 150 SCFB.

13. The method of claim 10 wherein the hydrogen uptake of the hydrotreated portion of the at least one added stream is at least about 500 SCFB.

14. The method of claim 10 wherein the hydrogen uptake of the hydrotreated portion of the at least one added stream is at least about 1000 SCFB.

15. A method for reducing furnace fouling in a delayed coking process wherein at least one coker feed is supplied to a delayed coking unit comprised of a coker furnace, at least two coke drums and a coker fractionator comprising

(a) supplying the feed to the bottom of the fractionator to produce an overhead stream, a bottoms stream and at least one intermediate stream from the fractionator;

(b) increasing the aromaticity of the bottoms stream to produce a modified stream by combining with the bottoms stream upstream of the coker furnace at least one added stream selected from the group consisting of an aromatic gas oil, a hydrotreated aromatic gas oil and combinations thereof, said aromatic gas oil having an aromatic carbon content of at least about 40% as measured by ¹³C NMR based on the total carbon content of the added stream and said hydrotreated aromatic gas oil having an aromatic carbon content of at least about X % according to the formula

X=(A %)−

[(0.02)·

(hydrogen uptake in the hydrotreater)]

 

where X is as least about 20% as measured by ¹³C NMR based on the total carbon content of the hydrotreated aromatic gas oil and A is the aromaticity of the unhydrotreated aromatic gas oil as measured by ¹³C NMR and is at least about 40%, hydrogen uptake is [ρ

·

659.5·

(Δ

hydrogen content (wt %) of the hydrotreater product and feed)] and ρ

is the density (grams/cc) of the hydrotreater feed;

(c) introducing the modified stream into the coker furnace;

(d) heating the modified stream to a coking temperature in the coker furnace to produce a heated modified stream; and

(e) transferring the heated modified stream from the coker furnace to a coke drum.

16. The method of claim 15 wherein the at least one added stream comprises a decant oil fraction obtained by supplying a decant oil stream to the fractionator just above the FZGO tray.

17. The method of claim 16 wherein the decant oil stream is hydrotreated.

18. The method of claim 16 wherein the at least one added stream further comprises an aromatic gas oil stream added to the bottoms stream.

19. The method of claim 18 wherein a portion of the aromatic gas oil stream is added to the decant oil stream supplied to the fractionator just above the FZGO tray.

20. The method of claim 15 further comprising the step of adding at least a portion of at least one intermediate stream to the bottoms stream.

21. The method of claim 20 wherein the at least one intermediate stream is selected from the group consisting of a light coker gas oil stream, a heavy coker gas oil stream, and combinations thereof exiting the fractionator.

22. The method of claim 20 wherein at least a portion the at least one intermediate stream is hydrotreated.

23. A method for reducing furnace fouling in a delayed coking process wherein at least one coker feed is supplied to a delayed coking unit comprised of a coker furnace, at least two coke drums and a coker fractionator comprising

(a) supplying the feed to the coker furnace without first passing the feed through the fractionator,

(b) increasing the aromaticity of the feed to produce a modified stream by combining with the feed upstream of the coker furnace at least one added stream selected from the group consisting of an aromatic gas oil, a hydrotreated aromatic gas oil and combinations thereof, said aromatic gas oil having an aromatic carbon content of at least about 40% as measured by ¹³C NMR based on the total carbon content of the added stream and said hydrotreated aromatic gas oil stream having an aromatic carbon content of at least about X % according to the formula

X=(A %)−

[(0.02)·

(hydrogen uptake in the hydrotreater)]

 

where X is as least about 20% as measured by ¹³C NMR based on the total carbon content of the hydrotreated aromatic gas oil and A is the aromaticity of the unhydrotreated aromatic gas oil as measured by ¹³C NMR and is at least about 40%, hydrogen uptake is [ρ

·

659.5·

(Δ

hydrogen content (wt %) of the hydrotreater product and feed)] and ρ

is the density (grams/cc) of the hydrotreater feed;

(c) introducing the modified stream into the coker furnace;

(d) heating the modified stream to a coking temperature in the coker furnace to produce a heated modified stream; and

(e) transferring the heated modified stream from the coker furnace to a coke drum.

24. The method of claim 23 further comprising the step of combining with the feed upstream of the coker furnace at least a portion of at least one intermediate stream exiting the fractionator.

25. The method of claim 24 wherein the at least one intermediate stream is selected from the group consisting of a light coker gas oil stream, a heavy coker gas oil stream, and combinations thereof exiting the fractionator.

26. The method of claim 24 wherein at least a portion the at least one intermediate stream is hydrotreated.