High pressure ethane cracking with small diameter furnace tubes

Patent metadata

Field	Value
Publication number	US-12024685-B2
Application number	US-201917299878-A
Country	US
Kind code	B2
Filing date	Dec 13, 2019
Priority date	Dec 20, 2018
Publication date	Jul 2, 2024
Grant date	Jul 2, 2024

Abstract

Systems and methods are provided for performing ethane steam cracking at elevated coil inlet pressures and/or elevated coil outlet pressures in small diameter furnace coils. Instead of performing steam cracking of ethane at a coil outlet pressure of ˜22 psig or less (˜150 kPa-g or less), the steam cracking of ethane can be performed in small diameter furnace coils at a coil outlet pressure of 30 psig to 75 psig (˜200 kPa-g to ˜520 kPa-g), or 40 psig to 75 psig (˜270 kPa-g to ˜520 kPa-g). In order to achieve such higher coil outlet pressures, a correspondingly higher coil inlet pressure can also be used, such as a pressure of 45 psig (˜310 kPa-g) or more, or 50 psig (˜340 kPa-g) or more.

First claim

What is claimed is:

1. A method for performing steam cracking, comprising:
pre-heating a mixture of steam and a feed comprising 50 vol % or more of ethane to a first temperature;
passing the mixture into a plurality of radiant coils at a coil inlet pressure via a plurality of critical flow nozzles, wherein each of the furnace coils has an inner diameter of 6.0 cm or less; and
exposing the mixture in the plurality of radiant coils to steam cracking conditions which include a cracking temperature of 800° C. or more and a coil outlet pressure of 200 kPa-g to 520 kPa-g for a residence time to produce a steam cracked effluent.

2. The method of claim 1 , wherein the coil outlet pressure is in a range of from 270 kPa-g to 520 kPa-g.

3. The method of claim 1 , wherein the residence time is in a range of from 0.1 second to 1.0 second.

4. The method of claim 1 , wherein the coil inlet pressure is 310 kPa-g or more.

5. The method of claim 1 , wherein the residence time is in a range of from 0.1 to 0.3 seconds.

6. The method of claim 1 , wherein the first temperature is 675° C. or more.

7. The method of claim 1 , wherein the first temperature is in a range of from 760° C. to 775° C.

8. The method of claim 1 , wherein each of the furnace coils has an inner diameter in a range of from 2.5 cm to 5.0 cm.

9. The method of claim 1 , wherein each of the furnace coils has substantially the same inner diameter, the inner diameter being in a range of from 3.0 cm to 6.0 cm.

10. The method of claim 1 , wherein an inner surface of the radiant coils comprises a coke-resistant inner surface.

11. The method of claim 10 , wherein the coke-resistant inner surface is a material selected from the group consisting of a nickel chrome alloy, an alumina barrier layer, or a combination thereof.

12. The method of claim 1 , further comprising separating an ethylene-containing fraction from the steam cracked effluent.

13. The method of claim 1 , wherein the coil inlet pressure is 340 kPa-g or more.

14. The method of claim 1 , wherein the steam cracking conditions further comprise a once-through ethane conversion of 60% or more.

15. The method of claim 1 , wherein the steam cracking conditions further comprise an ethylene selectivity, relative to an amount of converted ethane, of 50% or more.

16. The method of claim 1 , wherein the cracking temperature is in a range of from 800° C. to 920° C.

17. A system for performing steam cracking, comprising:
a steam cracker furnace comprising a pre-heating section and a radiant section, the radiant section comprising a plurality of radiant coils having an inner diameter ≤6.0 cm, the pre-heating section being in fluid communication with a coil inlet of the plurality of radiant coils via a plurality of critical flow nozzles;
a separation stage, in fluid communication with a coil outlet of the plurality of radiant coils, for separating H 2 and C 1 -C 4 hydrocarbons from an effluent generated by the plurality of radiant coils; and
a compressor comprising a compressor inlet, a compressor outlet, and three or less compression stages, the separation stage being in fluid communication with the compressor via the compressor inlet.

18. The system of claim 17 , wherein the separation stage comprises a water quench tower.

19. The system of claim 17 or 18 , wherein the coil outlet of the plurality of radiant coils comprises the effluent generated by the plurality of radiant coils at a pressure in a range of from 270 kPa-g to 520 kPa-g.

Assignees

• Exxonmobil Chemical Patents Inc

Inventors

• Stephens George
• Spicer David
• Yeo Gregory E
• Phillips Stephen R

Classifications

• C10G2400/20

  C2-C4 olefins · CPC title

• C10G2300/807

  Steam · CPC title

• C10G2300/4031

  Start up or shut down operations · CPC title

• C10G2300/4012

  Pressure · CPC title

• C10G2300/4006

  Temperature · CPC title