CN-122006429-A - Method for synchronously purifying natural gas lean in helium and ultra-lean in helium and extracting high-value substances

CN122006429ACN 122006429 ACN122006429 ACN 122006429ACN-122006429-A

Abstract

The application discloses a method for synchronously purifying natural gas lean in helium and ultra-lean in helium and extracting high-value substances, belonging to the field of membrane separation. The method comprises the steps of firstly completing helium extraction of the natural gas lean in helium and ultra-lean in helium through a helium extraction membrane block, then enabling the residual gas to enter a nitrogen removal membrane block for nitrogen removal, wherein a helium extraction membrane is used in the helium extraction membrane block, the helium extraction membrane preferentially permeates helium, the He/CH 4 selectivity is at least 40, a nitrogen removal membrane is used in the nitrogen removal membrane block, the nitrogen removal membrane preferentially permeates nitrogen, and the N 2 /CH 4 selectivity is at least 4. By the method disclosed by the application, the helium concentration in natural gas can be increased from 0.01% -0.1% to not lower than 1%, the nitrogen content is reduced to not higher than 4%, and the recovery rates of helium and methane are not lower than 90%.

Inventors

REN JIZHONG
ZHAO DAN
SUN JIAN

Assignees

中国科学院大连化学物理研究所

Dates

Publication Date: 20260512
Application Date: 20251224

Claims (9)

1. A method for simultaneous purification and high value extraction of helium-depleted, ultra-helium-depleted natural gas, the method comprising: helium extraction is firstly completed on the helium-lean and ultra-helium-lean natural gas through a helium extraction membrane block, and then the residual gas enters a nitrogen removal membrane block for nitrogen removal; helium extraction membranes are used in the helium extraction membrane blocks, the helium extraction membranes preferentially permeate helium, and the He/CH 4 selectivity is at least 40; The nitrogen removal membrane block uses a nitrogen removal membrane, and the nitrogen removal membrane preferentially permeates nitrogen, and the N 2 /CH 4 selectivity is at least 4.
2. The method of claim 1 wherein the helium extraction film has a He/CH 4 selectivity of at least 100; The nitrogen removal membrane has an N 2 /CH 4 selectivity of at least 6.
3. The method according to claim 1, wherein the helium gas extraction film is at least one of a cellulose acetate film, a polybenzimidazole film, a polyimide film, a polyetherimide film, a polymethyl methacrylate film, and a perfluorocopolymer film; the nitrogen removal membrane is at least one of polytetrafluoroethylene membrane, (1, 2-trifluoro vinyl) 1,1,2,2,3,4,4-heptafluoro-3-butene ether cyclized polymer membrane and perfluoro copolymer membrane.
4. The method according to claim 1, wherein the method is operated at a temperature of-50 to 150 ℃ and at a pressure of 10 to 150 bar.
5. The method of claim 1, wherein the helium extraction membrane block and/or the nitrogen removal membrane block are coupled by a multistage process, each block or block being coupled by a permeate, retentate or a return thereof.
6. The method of claim 5, wherein the helium extraction membrane block comprises a helium extraction membrane separation unit, the nitrogen removal membrane block comprises two nitrogen removal membrane separation units, and the method comprises the following process flows: The method comprises the steps that raw material gas I enters a helium extraction membrane separation unit to obtain permeation gas I and permeation residual gas I, wherein the permeation gas I is helium-rich gas; The residual gas I enters a nitrogen removal membrane separation unit I to obtain permeation gas II and residual gas II, wherein the residual gas II is purified gas; The permeation gas II enters a nitrogen removal membrane separation unit II after being compressed to obtain permeation gas III and permeation residual gas III, wherein the permeation gas III is high-nitrogen tail gas; and the residual gas III is mixed with the raw material gas I and then returned to enter the helium extraction membrane separation unit, or the residual gas III is mixed with the residual gas I and then returned to enter the nitrogen removal membrane separation unit I.
7. The method of claim 5, wherein the helium extraction membrane block comprises one helium extraction membrane separation unit and the nitrogen removal membrane block comprises three nitrogen removal membrane separation units, including process flow a, process flow b, or process flow c; The process flow a comprises the steps that raw gas I enters a helium extraction membrane separation unit to obtain permeation gas I and permeation residual gas I, wherein the permeation gas I is helium-rich gas; The residual gas I enters a nitrogen removal membrane separation unit I to obtain permeation gas II and residual gas II, wherein the residual gas II is purified gas; the permeate gas II enters a nitrogen removal membrane separation unit II after being compressed to obtain permeate gas III and permeate residual gas III, and the permeate residual gas III and the permeate residual gas I are mixed and then returned to enter the nitrogen removal membrane separation unit I; The permeate gas III enters a nitrogen removal membrane separation unit III after being compressed to obtain permeate gas IV and retentate gas IV, wherein the permeate gas IV is high-nitrogen tail gas; The residual gas IV and the residual gas I are mixed and then returned to enter a nitrogen removal membrane separation unit I; The process flow b comprises the steps that raw gas I enters a helium extraction membrane separation unit to obtain permeation gas I and permeation residual gas I, wherein the permeation gas I is helium-rich gas; The permeation residual gas I enters a nitrogen removal membrane separation unit I to obtain permeation gas II and permeation residual gas II; The permeation gas II enters a nitrogen removal membrane separation unit II after being compressed to obtain permeation gas III and permeation residual gas III, wherein the permeation gas III is high-nitrogen tail gas; The residual gas III and the residual gas I are mixed and then returned to enter a nitrogen removal membrane separation unit I; the residual gas II enters a nitrogen removal membrane separation unit III to obtain permeation gas IV and residual gas IV, wherein the residual gas IV is purified gas; The permeate gas IV is compressed and then mixed with the retentate gas I, and then returns to enter the nitrogen removal membrane separation unit I; The scheme c is that raw gas I enters a helium extraction membrane separation unit to obtain permeation gas I and permeation residual gas I, wherein the permeation gas I is helium-rich gas; The permeation residual gas I enters a nitrogen removal membrane separation unit I to obtain permeation gas II and permeation residual gas II; The permeation gas II enters a nitrogen removal membrane separation unit II after being compressed to obtain permeation gas III and permeation residual gas III, wherein the permeation gas III is high-nitrogen tail gas; mixing the permeation residual gas III and the permeation residual gas II, and then entering a nitrogen removal membrane separation unit III to obtain permeation gas IV and permeation residual gas IV, wherein the permeation residual gas IV is purified gas; the permeate gas IV is compressed and then mixed with the retentate gas I, and then returns to enter the nitrogen removal membrane separation unit I.
8. The method of claim 5, wherein the helium extraction membrane block comprises two helium extraction membrane separation units and the nitrogen removal membrane block comprises two nitrogen removal membrane separation units, comprising the following process flows: The method comprises the steps that raw gas I enters a helium extraction membrane separation unit I to obtain permeation gas I and permeation residual gas I, wherein the permeation gas I is helium-rich gas; the residual gas I enters a helium extraction membrane separation unit II to obtain permeation gas II and residual gas II; The permeate gas II is compressed and then mixed with the feed gas I, and then returned to enter the helium extraction membrane separation unit I; The residual gas II enters a nitrogen removal membrane separation unit I to obtain permeation gas III and residual gas III, wherein the residual gas III is purified gas; The permeate gas III enters a nitrogen removal membrane separation unit II after being compressed to obtain permeate gas IV and retentate gas IV, wherein the permeate gas IV is high-nitrogen tail gas; And the residual gas IV and the residual gas II are mixed and then returned to enter the nitrogen removal membrane separation unit I.
9. The method of claim 5, wherein the helium extraction membrane block comprises three helium extraction membrane separation units and the nitrogen removal membrane block comprises two nitrogen removal membrane separation units, comprising the following process flows: The raw material gas I enters a helium extraction membrane separation unit I to obtain permeation gas I and permeation residual gas I; The permeation gas I enters a helium extraction membrane separation unit II after being compressed to obtain permeation gas II and permeation residual gas II, wherein the permeation gas II is helium-rich gas; the residual gas I enters a helium extraction membrane separation unit III to obtain permeation gas III and residual gas III; The permeate gas III is compressed and then mixed with the feed gas I, and then returned to enter the helium extraction membrane separation unit I; Mixing the permeation residual gas II and the permeation residual gas III, and then entering a nitrogen removal membrane separation unit I to obtain permeation gas IV and permeation residual gas IV, wherein the permeation residual gas IV is purified gas; The permeation gas IV enters a nitrogen removal membrane separation unit II after being compressed to obtain permeation gas V and permeation residual gas V, wherein the permeation gas V is high-nitrogen tail gas; and the residual gas V, the residual gas II and the residual gas III are mixed and then returned to enter the nitrogen removal membrane separation unit I.

Description

Method for synchronously purifying natural gas lean in helium and ultra-lean in helium and extracting high-value substances Technical Field The application relates to a method for synchronously purifying natural gas lean in helium and ultra-lean in helium and extracting high-value substances, belonging to the field of membrane separation. Background For industrial helium extraction, helium comes primarily from helium-containing natural gas. Conventional helium extraction technology relies on multistage low-temperature condensation and pressure swing adsorption, and has the disadvantages of long process, huge investment and challenging economic extraction. Meanwhile, natural gas is used as an important clean energy source, and efficient purification and component extraction of the natural gas are important for resource utilization. With the development of unconventional natural gas (such as shale gas and coal bed gas), the nitrogen (N 2) content in raw gas is generally increased (chemical engineering report, 2010,61 (S2): 54-57). High levels of N 2 lead to reduced heating values and affect the pipe standard (U.S. 2019/0321780 A1 indicates that N 2 levels need to be less than 4%). Conventional denitrification techniques such as cryogenic rectification have high energy consumption and complex equipment, while adsorption has capacity limitation and regeneration problems, and development of efficient and low-cost denitrification processes is highly needed. The membrane separation technology has the advantages of low energy consumption, modularization, no phase change and the like, and has potential in the field of gas separation. In the prior art, polymer membranes have been used for CO 2/CH4 separation, but for CH 4-N2 systems, the kinetic diameters of the two are close to (CH 4:0.38nm;N2: 0.364 nm), and the selectivity of traditional membrane materials is insufficient. Rubbery materials such as Pebax have a CH 4/N2 selectivity of around 3 and preferentially permeate methane. For natural gas, methane is the major component thereof, and permeation of a large amount of the major component through the membrane requires more membrane area and energy consumption. Whereas the N 2/CH4 selectivity of glassy polymers such as polyimide is typically around 2, efficient separation is not achieved. Disclosure of Invention Based on the background technology, the invention provides a method for synchronously purifying helium-lean and ultra-helium-lean natural gas and extracting high-value substances. The method comprises a high value substance extraction block (namely a helium gas extraction membrane block) and a purification block (namely a nitrogen gas removal membrane block), wherein each block can adopt a multi-stage and multi-section membrane process, and the blocks or the blocks are connected and coupled through permeation gas, permeation residual gas or a reflux connection thereof. In particular, the present invention proposes a membrane process for simultaneous helium extraction and nitrogen removal for helium-depleted, ultra-helium-depleted natural gas. The separation membrane and the process can synchronously realize the denitrification and helium extraction of the natural gas, and compared with the traditional process of denitrification (such as low-temperature rectification) and helium extraction (such as pressure swing adsorption), the process is simple, the equipment investment is small, and the energy consumption is reduced. The membrane process for simultaneously denitrifying and extracting helium from natural gas provided by the invention preferentially completes helium extraction and then carries out nitrogen removal. Natural gas passes through the helium extraction membrane block, and the residual gas enters the nitrogen removal block. The application provides a method for synchronously purifying natural gas lean in helium and ultra-lean in helium and extracting high-value substances. The method comprises the following steps of 1) extracting a block containing high-value resources and a purifying block, 2) realizing each block by adopting a membrane technology method, 3) adopting a multistage and multistage technology, 4) extracting helium from the high-value resources by permeation gas, permeation residual gas or reflux connection coupling of the permeation gas and the residual gas in each block or block, and firstly completing helium extraction and then nitrogen removal. A method of simultaneous purification and high value extraction of helium-depleted, ultra-helium-depleted natural gas, the method comprising: helium extraction is firstly completed on the helium-lean and ultra-helium-lean natural gas through a helium extraction membrane block, and then the residual gas enters a nitrogen removal membrane block for nitrogen removal; helium extraction membranes are used in the helium extraction membrane blocks, the helium extraction membranes preferentially permeate helium, and the He/CH 4 selectivity is at