Method and apparatus for recovering C2—C4 components in methane-containing industrial gas

Patent metadata

Field	Value
Publication number	US-12110460-B2
Application number	US-202017755418-A
Country	US
Kind code	B2
Filing date	Sep 24, 2020
Priority date	Oct 28, 2019
Publication date	Oct 8, 2024
Grant date	Oct 8, 2024

Abstract

A method for recovering C2 components in a methane-containing industrial gas includes the steps of (1) cooling a compressed methane-containing industrial gas and performing gas-liquid separation; (2) absorbing C2 components in the gas phase by using an absorbent to obtain an absorption rich liquid; (3) returning the absorption rich liquid to the compression in step (1) or mixing the absorption rich liquid with the liquid phase obtained in step (1) to obtain a mixed liquid, and depressurizing the mixed liquid or the absorption rich liquid; (4) performing methane desorption on the depressurized stream to obtain a rich absorbent, or performing second gas-liquid separation on the depressurized stream, followed by methane desorption on the second liquid phase to obtain a rich absorbent; and (5) desorbing and separating the rich absorbent to obtain a lean absorbent and an enriched gas, and recycling and reusing the lean absorbent.

First claim

The invention claimed is:

1. Method for recovering C2 components in a methane-containing industrial gas, the method comprising the following steps:
(1) compressing the methane-containing industrial gas, cooling the obtained compressed gas prior to performing gas-liquid separation, to obtain a gas phase and a liquid phase;
(2) contacting the gas phase with an absorbent to absorb the C2 components to obtain an absorption tail gas and an absorption rich liquid, wherein,
the absorption rich liquid is returned and mixed into the compressed gas, or
a mixed liquid of the absorption rich liquid and the liquid phase obtained in step (1) or the absorption rich liquid is used as a first stream;
(3) depressurizing the liquid phase obtained in step (1) or the first stream obtained in step (2);
(4) subjecting the depressurized stream in step (3) to methane desorption to obtain a desorbed gas and a rich absorbent, and returning the desorbed gas to the compression in step (1) or discharging it externally, or
subjecting the depressurized stream in step (3) to a second gas-liquid separation to obtain a second gas phase and a second liquid phase, returning the second gas phase to the compression in step (1), subjecting the second liquid phase to methane desorption to obtain a desorbed gas and a rich absorbent, and returning the desorbed gas to the compression in step (1) or discharging it externally;
(5) subjecting the rich absorbent to desorption separation to obtain a lean absorbent and an enriched gas containing the C2 components, the lean absorbent being returned and mixed into the absorbent in step (2).

2. The method according to claim 1 , wherein the methane-containing industrial gas includes dry gas, cracked gas, natural gas, and shale gas.

3. The method according to claim 1 , wherein in step (2), the absorption rich liquid is returned and mixed into the compressed gas, and the liquid phase obtained in the step (1) is depressurized and then subjected to methane desorption to obtain a desorbed gas and a rich absorbent.

4. The method according to claim 3 , wherein a pressure of the compressed gas is 2.5-4.6 MPaG;
the compression is a multi-stage compression;
a temperature of the cooling is 5-40° C., the cooling uses a cooling medium having a temperature of 0° C. or higher, and the cooling medium is at least one selected from the group consisting of low-temperature water, circulating water, propylene, ammonia and liquid nitrogen.

5. The method according to claim 3 , wherein the absorption of the C2 components is carried out in an absorption tower;
parameters of the absorption tower include: a theoretical plate number of 15-30, an operation pressure of 2.5-4.6 MPaG, a tower top temperature of 10-60° C., and a tower kettle temperature of 10-70° C.

6. The method according to claim 3 , wherein the methane desorption is carried out in a methane desorption tower,
parameters of the methane desorption tower include: a theoretical plate number of 20-50, an operation pressure of 0.5-2.4 MPaG, a tower top temperature of 10-60° C., and a tower kettle temperature of 35-90° C.;
a pressure of the liquid phase after depressurization is 0.8-3 MPaG.

7. The method according to claim 3 , wherein the desorption separation is carried out in a desorption tower,
parameters of the desorption tower include: a theoretical plate number of 20-50, an operation pressure of 1-2.8 MPaG, a tower top temperature of 25-70° C., and a tower kettle temperature of 90-160° C.

8. The method according to claim 3 , wherein the lean absorbent is used as a heat source of the methane desorption, and at least a portion of the stream obtained after heat exchange is returned and mixed into the absorbent.

9. The method according to claim 1 , wherein the method further comprises recovering C3 components, and the C3 components comprise propane and/or propylene.

10. The method according to claim 1 , wherein the first stream obtained in step (2) is depressurized and then subjected to a second gas-liquid separation to obtain a second gas phase and a second liquid phase, and the second liquid phase is subjected to methane desorption to obtain a desorbed gas and a rich absorbent.

11. The method according to claim 10 , wherein a pressure of the compressed gas is 2.5-5 MPaG;
the compression is a multi-stage compression;
a temperature of the cooling is 5-45° C., the cooling uses a cooling medium having a temperature of 0° C. or higher, and the cooling medium is at least one selected from the group consisting of low-temperature water, circulating water, propylene, ammonia and liquid nitrogen.

12. The method according to claim 10 , wherein absorption of C2 and C3 components is carried out in an absorption tower;
parameters of the absorption tower include: a theoretical plate number of 15-30, an operation pressure of 2.5-5 MPaG, a tower top temperature of 10-30° C., and a tower kettle temperature of 10-60° C.;
a pressure of the first stream after depressurization is 0.5-2.4 MPaG;
before/after the depressurization of the first steam, said first stream is subjected to cooling treatment, and a temperature of said first stream after cooling is 5-40° C.

13. The method according to claim 10 , wherein the methane desorption is carried out in a methane desorption tower,
parameters of the methane desorption tower include: a theoretical plate number of 20-50, an operation pressure of 0.5-2.4 MPaG, a tower top temperature of 10-40° C., and a tower kettle temperature of 35-100° C.

14. The method according to claim 10 , wherein the desorption separation is carried out in a desorption tower,
parameters of the desorption tower include: a theoretical plate number of 20-50, an operation pressure of 1-2.8 MPaG, a tower top temperature of 15-70° C., and a tower kettle temperature of 90-200° C.

15. The method according to claim 10 , wherein the lean absorbent is used as a heat source of the methane desorption, and at least a portion of the second stream obtained after heat exchange is returned and mixed into the absorbent.

16. The method according to claim 6 , wherein the heat source of the tower kettle of the methane desorption tower is provided by a methane desorption tower reboiler, and a heat source of the methane desorption tower reboiler is a process stream; the process stream is at least one selected from the group consisting of the absorbent, the rich absorbent and the lean absorbent.

17. The method according to claim 1 , wherein the absorbent is selected from C4 fractions and/or C5 fractions, the C4 fractions comprise at least one selected from the group consisting of n-butane, isobutane and butene, and the C5 fractions comprise at least one selected from the group consisting of n-pentane, isopentane and neopentane.

18. The method according to claim 1 , wherein the method further comprises recovering C4 components, and the C4 components comprise butane and/or butene.

19. The method according to claim 5 , wherein a temperature of the absorbent entering the tower is 40-50° C., a temperature of the gas phase entering the tower is 40° C., the cooling medium in step (1) is circulating water, and the tower top temperature of the absorption tower is 40-60° C.

20. The method according to claim 5 , wherein a temperature of the absorbent entering the tower is 5-20° C., a temperature of the gas phase entering the tower is 5-20° C., the cooling medium in step (1) is low-temperature water, and the tower top temperature of the absorption tower is 10-30° C.

21. Apparatus for r

Assignees

• China Petroleum & Chem Corp
• Beijing Res Inst Chemical Ind China Petroleum & Chemical Corp

Inventors

• Shao Huawei
• Li Dongfeng
• Zou Yi
• Liu Zhixin
• Li Chunfang
• Guo Liang
• Zhang Jingsheng
• Hu Zhiyan

Classifications

• F25J2230/30

  Compression of the feed stream · CPC title

• F25J2210/04

  Mixing or blending of fluids with the feed stream · CPC title

• F25J2205/50

  using absorption, i.e. with selective solvents or lean oil, heavier CnHm and including generally a regeneration step for the solvent or lean oil · CPC title

• F25J2205/04

  in the feed line, i.e. upstream of the fractionation step · CPC title

• F25J3/064

  separation of CnHm with 2 carbon atoms or more · CPC title