CN112943186B - Pressure swing adsorption concentration and yield increasing system and method for extracted gas in coal mine - Google Patents
Pressure swing adsorption concentration and yield increasing system and method for extracted gas in coal mine Download PDFInfo
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- 239000003245 coal Substances 0.000 title claims abstract description 72
- 238000000034 method Methods 0.000 title claims abstract description 25
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims abstract description 212
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- 229910001628 calcium chloride Inorganic materials 0.000 claims description 3
- HNPSIPDUKPIQMN-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Al]O[Al]=O HNPSIPDUKPIQMN-UHFFFAOYSA-N 0.000 claims description 3
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- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 claims description 3
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- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/16—Enhanced recovery methods for obtaining hydrocarbons
- E21B43/18—Repressuring or vacuum methods
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01D47/00—Separating dispersed particles from gases, air or vapours by liquid as separating agent
- B01D47/06—Spray cleaning
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/02—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography
- B01D53/04—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by adsorption, e.g. preparative gas chromatography with stationary adsorbents
- B01D53/047—Pressure swing adsorption
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- B01D53/26—Drying gases or vapours
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/26—Drying gases or vapours
- B01D53/263—Drying gases or vapours by absorption
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
- C10L3/101—Removal of contaminants
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- C10L3/00—Gaseous fuels; Natural gas; Synthetic natural gas obtained by processes not covered by subclass C10G, C10K; Liquefied petroleum gas
- C10L3/06—Natural gas; Synthetic natural gas obtained by processes not covered by C10G, C10K3/02 or C10K3/04
- C10L3/10—Working-up natural gas or synthetic natural gas
- C10L3/101—Removal of contaminants
- C10L3/106—Removal of contaminants of water
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- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
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Abstract
The invention discloses a pressure swing adsorption concentration-increasing and yield-increasing system and method for gas extracted from underground coal mines, wherein a methane adsorption tank filled with an adsorbent and a dehydration device which are vacuumized in advance are communicated with a gas extraction branch pipe in the underground coal mines, low-concentration gas enters the dehydration device and the methane adsorption tank in a negative pressure state through a dust removal device and a gas-water separator under the action of pressure difference, methane is preferentially adsorbed by the adsorbent, free nitrogen and oxygen in the free space in the methane adsorption tank are extracted by using the low-negative-pressure extraction system in the underground coal mines, the methane adsorption tank and the dehydration device are vacuumized by using the high-negative-pressure extraction system in the underground coal mines, the methane adsorbed on the adsorbent is desorbed to obtain high-concentration gas, and a water absorbent and the methane adsorbent are regenerated. The invention can greatly increase the gas concentration of the high-negative-pressure extraction system by utilizing the existing high-negative-pressure and low-negative-pressure extraction system of the coal mine without additionally increasing power equipment, and has flexible installation and wide application.
Description
Technical Field
The invention relates to the technical field of coal mine gas extraction and concentration, in particular to a pressure swing adsorption concentration increasing and yield increasing system and method for coal mine underground extracted gas.
Background
Coal mine gas is also called coal bed gas and is an important unconventional natural gas resource, the coal mine gas reserves in China are very rich, and the amount of shallow geological resources of 2000m reaches 36.8 trillion m3. However, because the occurrence conditions of coal mine gas in China are complex, the coal seam permeability is poor, and the ground extraction effect is not good, about 70% of coal mine gas is from underground gas extraction at present. Influenced by the excavation activity, wellA large amount of air leakage cracks exist in the lower coal seam, and a large amount of air enters the extraction drill hole along the cracks under the negative pressure extraction effect, so that the underground gas extraction concentration is generally low. At present, low-concentration gas with methane concentration higher than 8% can be utilized by an internal combustion engine power generation technology, but the gas with methane concentration lower than 8% is difficult to utilize and is directly discharged into the atmosphere, so that huge energy waste and atmospheric greenhouse effect are caused. In addition, low-concentration gas with methane concentration of 5% -16% has explosion danger, and has potential safety hazard of explosion in the gas extraction pipeline transmission process. The corresponding technical measures are adopted to improve the concentration of the underground extracted gas, which is beneficial to improving the utilization rate of the gas, thereby avoiding the waste of clean energy and the emission of methane greenhouse gas. In order to improve the utilization value of low-concentration gas, the concentration of methane in the gas is mainly improved by establishing a gas concentration system on the ground at present. For example, "a method for separating and purifying methane in coal bed gas in a mine area by using a pressure swing adsorption method" disclosed in chinese patent application CN103205297A, "a method for enriching methane in coal mine gas by using a pressure swing adsorption method" disclosed in chinese patent application CN85103557, "and" a method for pressure swing adsorption and fractional concentration of low-concentration gas "disclosed in chinese patent application CN101596391A both establish a large-scale centralized pressure swing adsorption system on the ground, and configure an additional booster pump or vacuum pump to provide pressure swing adsorption power.
Disclosure of Invention
The invention aims to provide a pressure swing adsorption concentration and yield increase system for extracting gas in a coal mine, which can be used for carrying out underground distributed gas concentration and yield increase by utilizing the existing high and low negative pressure extraction systems in the coal mine, and reducing the operation cost of gas concentration.
The invention also aims to provide a yield increasing method based on the pressure swing adsorption concentration increasing and yield increasing system for the extracted gas in the coal mine.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows: a pressure swing adsorption concentration and yield increasing system for extracted gas in an underground coal mine comprises a gas extraction branch pipe, a dust removal device, a gas-water separator, a dehydration device, a methane adsorption tank, a low negative pressure extraction system in the underground coal mine and a high negative pressure extraction system in the underground coal mine;
one end of the gas extraction branch pipe is connected with a gas extraction hole in a coal mine, the other end of the gas extraction branch pipe is sequentially connected with a dust removal device and a gas-water separator, the gas-water separator is connected with a vent hole at the bottom of a dehydration device through a control valve V1, the vent hole at the top of the dehydration device is divided into two paths, one path is connected with a first vent hole at the bottom of a methane adsorption tank through a control valve V2, the other path is connected with a vent hole at the top of the methane adsorption tank in parallel and then connected with a low negative pressure extraction system in the coal mine through a control valve V5, a control valve V3 is further arranged on a parallel connection pipeline between the vent hole at the top of the dehydration device and the vent hole at the top of the methane adsorption tank, the vent hole at the bottom of the dehydration device is connected with a second vent hole at the bottom of the methane adsorption tank in parallel and then connected with a high negative pressure extraction system in the coal mine through a control valve V4, a pressure gauge I is arranged at the top of the dehydration device, a water absorbent is filled in the dehydration device, and a pressure gauge II is arranged at the top of the methane adsorption tank, an adsorbent for selectively adsorbing methane is filled in the methane adsorption tank.
As a further improvement of the invention, the total flow of the gas in the gas extraction branch pipe is 0.5m3/min～5m3/min。
As a further improvement of the invention, the adsorbent for selectively adsorbing methane is activated carbon, molecular sieve, ionic liquid zeolite and the like.
As a further improvement of the invention, the volume of the dehydration device is 0.05-0.3 m3The volume of the methane adsorption tank is 0.1-1 m3And the height-diameter ratio of the methane adsorption tank is 1-3.
As a further improvement of the present invention, the dust removing device is a wet dust removing device such as spray dust removal.
As a further improvement of the invention, the water absorbent is alumina, silica gel, calcium chloride and the like.
The invention also provides a yield increasing method based on the pressure swing adsorption concentration increasing and yield increasing system for the underground extracted gas of the coal mine, which comprises the following steps of:
1) and (3) air inlet adsorption: opening a control valve V1 and a control valve V2, closing a control valve V3, a control valve V4 and a control valve V5, and communicating a methane adsorption tank and a dehydration device which are in a negative pressure state with an underground coal mine gas extraction hole, a gas extraction branch pipe, a dust removal device and a gas-water separator, wherein low-concentration gas in the gas extraction hole and the gas extraction branch pipe firstly and sequentially removes dust and liquid water through the dust removal device and the gas-water separator under the action of pressure difference, the volume concentration of methane in the low-concentration gas is less than 16 percent, and then the low-concentration gas enters the dehydration device and the methane adsorption tank from the bottom respectively, water vapor in the low-concentration gas in the dehydration device is firstly absorbed by a water absorbent, then the methane in the low-concentration gas in the methane adsorption tank is selectively adsorbed by an adsorbent, and oxygen and nitrogen mainly remain in a free space of the methane adsorption tank;
2) extracting free gas: when the relative pressure in the methane adsorption tank rises from negative pressure to zero, closing the control valve V1, the control valve V2 and the control valve V4, opening the control valve V3 and the control valve V5, and pumping out partial water vapor in the dehydration device and free gas in the free space of the methane adsorption tank from the top by using the underground coal mine low negative pressure extraction system, wherein the methane concentration in gas entering the underground coal mine low negative pressure extraction system is less than 5%;
3) extracting high-concentration methane gas: when the relative pressure in the methane adsorption tank is reduced to-1 kPa to-5 kPa, closing the control valve V1, the control valve V2, the control valve V3 and the control valve V5, opening the control valve V4, vacuumizing the dehydration device and the methane adsorption tank from the bottom by using the underground coal mine high negative pressure extraction system until the relative pressure in the methane adsorption tank is reduced to-20 kPa to-40 kPa, desorbing the methane adsorbed in the methane adsorption tank and the water vapor absorbed in the dehydration device into the high negative pressure extraction system, regenerating the water absorbent and the adsorbent, and enabling the methane concentration in the gas entering the underground coal mine high negative pressure extraction system to be more than 16%.
Compared with the prior art, the invention has the following advantages:
(1) by utilizing the existing high-low negative pressure extraction system (required in design standard GB 50471-2018 of coal mine gas extraction engineering) running in the underground coal mine, the concentration of the underground extracted gas can be realized without additionally adding power equipment, and the energy consumption cost of pressure swing adsorption concentration is reduced;
(2) because the extraction hole has a large number of air leakage channels, the extraction hole is directly vacuumized and difficult to reach a larger vacuum degree, and the method firstly vacuums the dehydration device and the methane adsorption tank which are tightly sealed to reach a larger vacuum degree, and then carries out negative pressure extraction on the gas extraction hole by utilizing the dehydration device and the vacuum cavity of the adsorption tank, so that a high negative pressure extraction effect in a short time is achieved, and the gas far away from the extraction hole can be extracted;
(3) the invention can realize the intermittent and periodic change of the drilling extraction negative pressure, the orifice negative pressure absolute value of the extraction hole in the gas inlet adsorption stage is gradually reduced to zero from a larger value, and the orifice negative pressure of the extraction hole in the stage of extracting free gas and extracting high-concentration methane gas is zero, thereby avoiding the serious air leakage of the drill hole caused by the long-term continuous high negative pressure extraction, providing conditions for the flowing enrichment of gas to the drill hole and being beneficial to improving the gas concentration of the orifice of the drill hole;
(4) when the gas is extracted in a conventional continuous extraction process, the concentration of the gas at an extraction orifice is less than 16%, the concentration of methane in the gas entering a high negative pressure extraction system after the gas is treated by the method is more than 16%, and the concentration of methane in the gas entering a low negative pressure extraction system is less than 5%, so that the gas in a conveying pipeline has no explosion risk, and the safety of gas conveying is ensured;
(5) dust and moisture are removed through a dust removal device, a gas-water separation device and a dehydration device, so that the influence of impurities on methane adsorption concentration is avoided, pressurization is not needed, and the safety of pressure swing adsorption is improved;
(6) the gas concentration system provided by the invention can be installed in different underground extraction areas, is flexible and reliable, avoids the difficult problems of high risk and high investment of an underground centralized gas concentration system, and can be applied to concentration and yield increase of extracted gas in coal mine underground bedding drilling, cross-layer drilling, goaf, high-position drilling, high-level pumping roadway and the like.
Drawings
FIG. 1 is a schematic diagram of a pressure swing adsorption concentration and production increase system for extracting gas in an underground coal mine, according to the invention;
in the figure: 1. gas extraction holes; 2. a gas extraction branch pipe; 3. a dust removal device; 4. a gas-water separator; 5. a dewatering device; 5.1, a pressure gauge I; 6. a methane adsorption tank; 6.1, a pressure gauge II; 7. a coal mine underground low negative pressure extraction system; 8. a high negative pressure extraction system for underground coal mines.
Detailed Description
The invention is described in further detail below with reference to the figures and specific examples.
As shown in figure 1, the invention provides a pressure swing adsorption concentration-increasing and yield-increasing system for extracting gas in an underground coal mine, which comprises a gas extraction branch pipe 2, a dust removal device 3, a gas-water separator 4, a dehydration device 5, a methane adsorption tank 6, a low negative pressure extraction system 7 in the underground coal mine and a high negative pressure extraction system 8 in the underground coal mine. In this embodiment, the dust removing device 3 is a spray dust-settling wet dust removing device, and the volume of the dewatering device 5 is 0.05-0.3 m3The volume of the methane adsorption tank 6 is 0.1-1 m3. In addition, reasonable selection of the height and the diameter ratio of the methane adsorption tank 6 has important influence on separation and concentration of low-concentration gas, and the height-diameter ratio of the methane adsorption tank 6 is 1-3 in the embodiment.
A large number of gas extraction holes 1 are arranged in a roadway of one working face of the underground coal mine, one end of each gas extraction branch pipe 2 is connected with the gas extraction holes 1 in the underground coal mine, and the total flow of gas in the gas extraction branch pipes 2 is 0.5m3/min～5m3And/min, the other end of the gas extraction branch pipe 2 is sequentially connected with the dust removal device 3 and the gas-water separator 4, the gas-water separator 4 is connected with a vent hole at the bottom of the dehydration device 5 through a control valve V1, vent holes at the top of the dehydration device 5 are divided into two paths, one path is connected with a first vent hole at the bottom of the methane adsorption tank 6 through a control valve V2, the other path is connected with a vent hole at the top of the methane adsorption tank 6 in parallel and then connected with the underground low-negative-pressure extraction system 7 of the coal mine through a control valve V5, a vent hole at the bottom of the dehydration device 5 is connected with a second vent hole at the bottom of the methane adsorption tank 6 in parallel and then connected with the underground high-negative-pressure extraction system 8 of the coal mine through a control valve V4, and the underground low-negative-pressure extraction system 7 of the coal mine and the underground high-negative-pressure extraction system 8 of the coal mine are respectively connected with a water ring vacuum pump on the ground in a matching manner.
Control valve V3 still is installed on the parallel connection pipeline between 5 top blow vents of dewatering device and the 6 top blow vents of methane adsorption tank, manometer I5.1 is installed at 5 tops of dewatering device, fills up the water absorbent in the dewatering device 5, for example activated alumina, silica gel, calcium chloride etc. manometer II 6.1 is installed at 6 tops of methane adsorption tank, fills up the adsorbent of selective adsorption methane in the methane adsorption tank 6, for example activated carbon, molecular sieve or ionic liquid zeolite etc..
The system can be installed in different underground extraction areas, and the underground distributed gas extraction concentration and yield increase is realized.
The method for extracting gas, concentrating and increasing yield based on the concentration and yield increasing system needs to circularly perform the following steps:
1) and (3) air inlet adsorption: opening a control valve V1 and a control valve V2, closing a control valve V3, a control valve V4 and a control valve V5, communicating a methane adsorption tank 6 and a dehydration device 5 which are in a negative pressure state with an underground coal mine gas extraction hole 1, a gas extraction branch pipe 2, a dust removal device 3 and a gas-water separator 4, sequentially removing dust and liquid water from low-concentration gas in the gas extraction hole 1 and the gas extraction branch pipe 2 through the dust removal device 3 and the gas-water separator 4 under the action of pressure difference, wherein the volume concentration of methane in the low-concentration gas is less than 16%, sequentially entering the dehydration device 5 and the methane adsorption tank 6 from the bottom, absorbing water vapor in the low-concentration gas in the dehydration device 5 by a water absorbent, selectively absorbing the methane in the low-concentration gas in the methane adsorption tank 6 by an absorbent, and mainly remaining oxygen and nitrogen in a free space of the methane adsorption tank 6;
2) extracting free gas: when the relative pressure in the methane adsorption tank 6 rises from negative pressure to zero, closing the control valve V1, the control valve V2 and the control valve V4, opening the control valve V3 and the control valve V5, and pumping out part of water vapor in the dehydration device 5 and free gas in the free space of the methane adsorption tank 6 from the top by using the underground coal mine low negative pressure extraction system 7, wherein the methane concentration in the gas entering the underground coal mine low negative pressure extraction system 7 is less than 5%;
3) extracting high-concentration methane gas: when the relative pressure in the methane adsorption tank 6 is reduced to-1 kPa to-5 kPa, closing the control valve V1, the control valve V2, the control valve V3 and the control valve V5, opening the control valve V4, vacuumizing the dehydration device 5 and the methane adsorption tank 6 from the bottom by using the underground coal mine high negative pressure extraction system 8 until the relative pressure in the methane adsorption tank 6 is reduced to-20 kPa to-40 kPa, desorbing the methane adsorbed in the methane adsorption tank 6 and the water vapor absorbed in the dehydration device into the underground coal mine high negative pressure extraction system 8, and regenerating the water absorbent and the adsorbent, wherein the methane concentration in the gas entering the underground coal mine high negative pressure extraction system 8 is more than 16%.
According to the method, the adsorption tank and the dehydration device are firstly vacuumized to reach a larger vacuum degree, and then the vacuum cavities of the adsorption tank and the dehydration device are utilized to perform negative pressure extraction on the gas extraction hole, so that high negative pressure extraction in a short time can be realized, and the gas far away from the extraction hole can be extracted. In addition, the method enables the orifice negative pressure of the gas extraction hole to periodically change, the absolute value of the orifice negative pressure of the gas extraction hole is gradually reduced to zero from a larger value in the gas inlet adsorption stage, the orifice negative pressure of the extraction hole is zero in the stages of extracting free gas and extracting high-concentration methane gas, and serious air leakage of the gas extraction hole caused by long-time continuous high-negative-pressure extraction can be avoided. The negative pressure is zero stage gas flow enrichment towards the extraction hole, and the gas enriched in a larger range around the extraction hole can be pumped into the hole by utilizing the high negative pressure extraction stage of the vacuum cavity, so that the gas concentration at the orifice of the drill hole and the gas extraction quantity are improved.
When the gas is extracted in a conventional continuous extraction process, the concentration of the gas at an extraction orifice is less than 16%, the concentration of methane in the gas entering the high-negative-pressure extraction system after being treated by the method is more than 16%, and the concentration of methane in the gas entering the low-negative-pressure extraction system is less than 5%, so that the gas in the pipeline has no explosion risk.
The method can be widely applied to concentration and yield increase of gas extraction in coal mine underground bedding drilling, cross-layer drilling, goaf, high-position drilling, high pumping roadway and the like.
Claims (6)
1. A pressure swing adsorption concentration-extraction yield-increase method for gas extracted from underground coal mines is characterized in that a system for realizing the method comprises a gas extraction branch pipe (2), a dust removal device (3), a gas-water separator (4), a dehydration device (5), a methane adsorption tank (6), an underground coal mine low negative pressure extraction system (7) and an underground coal mine high negative pressure extraction system (8),
one end of the gas extraction branch pipe (2) is connected with a gas extraction hole (1) in the underground coal mine, the other end of the gas extraction branch pipe (2) is sequentially connected with a dust removal device (3) and a gas-water separator (4), the gas-water separator (4) is connected with a vent hole at the bottom of a dehydration device (5) through a control valve V1, the vent hole at the top of the dehydration device (5) is divided into two paths, one path is connected with a first vent hole at the bottom of a methane adsorption tank (6) through a control valve V2, the other path is connected with a vent hole at the top of the methane adsorption tank (6) in parallel and then connected with a low negative pressure extraction system (7) in the underground coal mine through a control valve V5, a control valve V3 is further installed on a parallel connection pipeline between the vent hole at the top of the dehydration device (5) and the vent hole at the top of the methane adsorption tank (6), the vent hole at the bottom of the dehydration device (5) is connected with a second vent hole at the bottom of the methane adsorption tank (6) in parallel and then connected with a high negative pressure extraction system (8) in the underground coal mine through the control valve V4, the top of the dehydration device (5) is provided with a pressure gauge I (5.1), the dehydration device (5) is filled with a water absorbent, the top of the methane adsorption tank (6) is provided with a pressure gauge II (6.1), and the methane adsorption tank (6) is filled with an adsorbent for selectively adsorbing methane;
the following operation steps are circularly carried out:
1) and (3) air inlet adsorption: opening a control valve V1 and a control valve V2, closing a control valve V3, a control valve V4 and a control valve V5, communicating a methane adsorption tank (6) in a negative pressure state, a dehydration device (5) with a coal mine underground gas extraction hole (1), a gas extraction branch pipe (2), a dust removal device (3) and a gas-water separator (4), removing dust and liquid water from low-concentration gas in the gas extraction hole (1) and the gas extraction branch pipe (2) under the action of pressure difference by the dust removal device (3) and the gas-water separator (4), wherein the volume concentration of methane in the low-concentration gas is less than 16%, then entering the dehydration device (5) and the methane adsorption tank (6) from the bottom in sequence, absorbing water vapor in the low-concentration gas in the dehydration device (5) by a water absorbent, and then selectively adsorbing methane in the low-concentration gas in the methane adsorption tank (6) by an adsorbent, the methane adsorption tank (6) is mainly used for remaining oxygen and nitrogen in the free space;
2) extracting free gas: when the relative pressure in the methane adsorption tank (6) rises to zero from negative pressure, closing the control valve V1, the control valve V2 and the control valve V4, opening the control valve V3 and the control valve V5, pumping out part of water vapor in the dehydration device (5) and free gas in the free space of the methane adsorption tank (6) from the top by using the underground coal mine low negative pressure extraction system (7), and enabling the methane concentration in gas entering the underground coal mine low negative pressure extraction system (7) to be less than 5%;
3) extracting high-concentration methane gas: when the relative pressure in the methane adsorption tank (6) is reduced to-1 kPa to-5 kPa, closing the control valve V1, the control valve V2, the control valve V3 and the control valve V5, opening the control valve V4, vacuumizing the dehydration device (5) and the methane adsorption tank (6) from the bottom by using the underground coal mine high negative pressure extraction system (8) to the methane adsorption tank (6), reducing the relative pressure in the methane adsorption tank (6) to-20 kPa to-40 kPa, desorbing the methane adsorbed in the methane adsorption tank (6) and the water vapor absorbed in the dehydration device to enter the underground coal mine high negative pressure extraction system (8), regenerating the water absorbent and the adsorbent, and enabling the methane concentration in the gas entering the underground coal mine high negative pressure extraction system (8) to be more than 16%.
2. The method for pressure swing adsorption concentration and yield increase of extracted gas in a coal mine according to claim 1, wherein the total flow rate of the gas in the gas extraction branch pipe (2) is 0.5m3/min~5m3/min。
3. The method for pressure swing adsorption concentration and production increase of extracted gas in a coal mine according to claim 1, wherein the adsorbent for selectively adsorbing methane comprises one or more of activated carbon, molecular sieve or ionic liquid zeolite.
4. The method for pressure swing adsorption concentration and production increase of extracted gas in a coal mine according to claim 1, wherein the volume of the dehydration device (5) is 0.05-0.3 m3The volume of the methane adsorption tank (6) is 0.1-1 m3The height-diameter ratio of the methane adsorption tank (6) is 1-3.
5. The pressure swing adsorption concentration-extraction yield-increase method for the extracted gas in the coal mine according to claim 1, wherein the dust removal device (3) adopts a wet dust removal device.
6. The method for pressure swing adsorption concentration and production increase of extracted gas in a coal mine according to claim 1, wherein the water absorbent comprises one or more of activated alumina, silica gel and calcium chloride.
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