Purification system and method for recovering methane from nitrogen-containing coal bed gas

Abstract

The purification system comprises a first tower body, a second tower body, a third tower body, a fourth tower body, a fifth tower body, a sixth tower body, a raw material gas storage tank, a reverse deflation gas mixing tank, a vacuum buffer tank and a product buffer tank, upper pipelines and lower pipelines are arranged on the six tower bodies; branches are arranged on the upper pipeline and the lower pipeline. A branch pipe is further arranged on the branch, gas to be treated can flow through different pipelines, branches and branch pipes and then flow into and out of the tower bodies in different states, and tail gas discharged by the adsorption tower in the pressure-drop-equalizing state and tail gas discharged by the adsorption tower in the clockwise-release state are respectively introduced into the adsorption tower in the pressure-rise-equalizing state and the adsorption tower in the clockwise-release pre-adsorption state. And the reversely discharged tail gas and the raw material gas are introduced into the adsorption tower in the adsorption state, so that the purity and the recovery rate of methane in the nitrogen-containing coal bed gas can be further improved.

Description

Technical Field

[0001] The present invention relates to the technical field of gas separation, and in particular to a purification system and method for recovering methane from nitrogen-containing coalbed methane. Background Art

[0002] Vacuum pressure swing adsorption technology usually uses high-efficiency solid adsorbents. Based on the difference in adsorption capacity between gas components, adsorption is performed under a specific pressure environment. This technology preferentially adsorbs gas components with stronger affinity, and the remaining gases are discharged from the top of the adsorption tower. Subsequently, by reducing the pressure, placing forward, reverse, and vacuuming, the adsorbed gas components are desorbed and the adsorbent is regenerated. The whole process is repeated to achieve separation and purification of the product gas. The vacuum pressure swing adsorption product gas can be a component that is difficult to adsorb by the adsorbent, and the product gas is extracted from the top of the adsorption tower through the adsorption step; it can also be a component that is efficiently adsorbed by the adsorbent, and the product gas is desorbed from the adsorption tower by vacuuming. At present, the vacuum pressure swing adsorption technology in which the product gas is a component that is efficiently adsorbed by the adsorbent is widely used, including: CCUS (carbon capture, utilization and storage technology) to separate and recover carbon dioxide from conversion gas; separation and recovery of oxygen and nitrogen from air; separation and recovery of carbon monoxide from carbon monoxide-rich gases such as steel plant converter gas; separation and recovery of methane from low-concentration coalbed methane, biogas, biogas, etc.; separation and recovery of mixed gases mainly composed of C2 and hydrocarbon components above C2 from catalytic cracking dry gas of refineries; separation of C1, C2, C3, C4 components from C4 mixed gases of catalytic reforming and hydrocracking of refineries, etc. However, if conventional vacuum pressure swing adsorption devices are used, the purity and recovery rate of the product gas cannot be improved after reaching a certain value, and there is a large consumption of raw gas, which leads to a high generation cost.

[0003] CN117965216B discloses a method for safely recovering and purifying methane from oxygen-containing coalbed methane, comprising the following steps: (1) nitrogen-doped oxygen dilution explosion-proof operation: adding a predetermined amount of nitrogen byproduct gas to the oxygen-containing coalbed methane to form nitrogen-doped low-oxygen coalbed methane; (2) methane recovery and deoxygenation operation, wherein the methane recovery and deoxygenation operation adopts a vacuum pressure swing adsorption process and uses at least three first-stage adsorption towers. The methane recovery and deoxygenation operation cycles through five steps of adsorption, pressure equalization and decompression, vacuum desorption, pressure equalization and pressure increase, and the nitrogen-doped low-oxygen coalbed methane is treated by the methane recovery and deoxygenation operation to obtain nitrogen-containing methane enriched gas; (3) methane concentration and purification operation, the methane concentration and purification operation adopts a pressure gradient simulated moving bed process and adopts at least five second-stage adsorption towers, at least five second-stage adsorption towers are connected in series through pipelines, and the methane concentration and purification operation includes: step ① multi-tower series pressurization and adsorption: the nitrogen-containing methane enriched gas obtained by the methane recovery and deoxygenation operation is directly introduced into the bottom of a second-stage adsorption tower performing an adsorption operation and introduced into at least one of the remaining second-stage adsorption towers performing an adsorption operation after adsorption, and the last second-stage adsorption tower performing an adsorption operation is pressurized. In this process, methane is Adsorption, part of the nitrogen is retained in the second-stage adsorption tower, and part of the nitrogen is discharged from the top of the second-stage adsorption tower that completes the pressurized adsorption operation to obtain nitrogen by-product gas, which is used as a nitrogen source for mixing with oxygen-containing coalbed methane; Step ② Multi-tower series replacement: methane product gas is introduced from the bottom of a second-stage adsorption tower that performs a nitrogen replacement operation and introduced into at least one of the remaining second-stage adsorption towers that performs a nitrogen replacement operation after replacement, and the methane product gas is replaced with the nitrogen retained in the second-stage adsorption tower, and the replaced nitrogen is discharged from the top of the second-stage adsorption tower that performs the nitrogen replacement operation last and flows through the second-stage adsorption tower that performs the adsorption operation. The second-stage adsorption tower is discharged centrally; step ③ single-tower vacuum desorption: the second-stage adsorption tower that performs vacuum desorption operation is subjected to nitrogen replacement operation and before vacuum desorption, and the adsorbent filling layer inside the second-stage adsorption tower adsorbs methane, and the second-stage adsorption tower that performs vacuum desorption operation is evacuated to desorb the adsorbed methane and discharge it from the bottom of the tower to obtain a methane product gas with a methane concentration higher than 95%; under vacuum conditions, nitrogen byproduct gas is introduced into the top of the second-stage adsorption tower after evacuation to purge the residual methane in the tower, and methane and nitrogen form recovery gas 2, which is discharged from the bottom of the tower and introduced into nitrogen-containing methane-enriched gas for circulation treatment;Step ④: All gas input and output objects are synchronously switched to the next second-stage adsorption tower in sequence along the gas flow direction, and then steps ① to ③ are circulated: the second-stage adsorption tower that is directly introduced with nitrogen-containing methane-enriched gas to perform adsorption operation before the cycle finally performs nitrogen replacement operation in the next cycle, the second-stage adsorption tower that is directly connected to the second-stage adsorption tower that is directly introduced with nitrogen-containing methane-enriched gas to perform adsorption operation before the cycle is directly introduced with nitrogen-containing methane-enriched gas to perform adsorption operation in the next cycle, the second-stage adsorption tower that is directly introduced with methane product gas to perform nitrogen replacement operation before the cycle performs vacuum desorption operation in the next cycle, the second-stage adsorption tower that is directly connected to the second-stage adsorption tower that is directly introduced with methane product gas to perform nitrogen replacement operation before the cycle is directly introduced with methane product gas to perform nitrogen replacement operation in the next cycle, and the second-stage adsorption tower that performs vacuum desorption operation before the cycle performs pressurized adsorption operation in the next cycle. Although the purity and recovery rate of methane in this method are improved to a certain extent, the purity and recovery rate of methane can still be further improved. ;

[0004] It can be seen that how to further improve the purity and recovery rate of methane in coalbed methane is a technical problem that needs to be solved urgently. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a purification system and method for recovering methane from nitrogen-containing coalbed methane. The system and method can further improve the purity and recovery rate of methane in nitrogen-containing coalbed methane by respectively passing the tail gas discharged from the equal pressure drop state adsorption tower and the tail gas discharged from the forward release state adsorption tower into the equal pressure rise state adsorption tower and the forward release pre-adsorption state adsorption tower, and passing the reverse release tail gas together with the raw gas into the adsorption state adsorption tower.

[0006] The present invention provides a purification system for recovering methane from nitrogen-containing coalbed methane, the system comprising: The first tower body, the second tower body, the third tower body, the fourth tower body, the fifth tower body and the sixth tower body are arranged in sequence, and, Raw gas storage tanks, reverse vent gas mixing tanks, vacuum buffer tanks and product buffer tanks; Each of the six towers is provided with an upper pipe and a lower pipe; The upper pipeline and the lower pipeline are both provided with branches; The branch road is also provided with a branch pipe. The gas to be treated can flow through the different pipelines, branches and branch pipes, and then flow into and out of the tower body in different states, so as to recover the methane in the nitrogen-containing coalbed methane.

[0007] Furthermore, the six tower bodies are each provided with an upper pipeline and a lower pipeline: The first tower body, the second tower body, the third tower body, the fourth tower body, the fifth tower body and the sixth tower body are all provided with upper pipes and lower pipes, which are respectively recorded as the first upper pipe, the first lower pipe, the second upper pipe, the second lower pipe, the third upper pipe, the third lower pipe, the fourth upper pipe, the fourth lower pipe, the fifth upper pipe, the fifth lower pipe, the sixth upper pipe and the sixth lower pipe. Wherein, the first lower pipeline, the second lower pipeline, the third lower pipeline, the fourth lower pipeline, the fifth lower pipeline and the sixth lower pipeline are collectively summarized as a total lower pipeline, and the total lower pipeline is connected to the raw gas storage tank; The first upper pipeline, the second upper pipeline, the third upper pipeline, the fourth upper pipeline, the fifth upper pipeline and the sixth upper pipeline are collectively summarized as a total upper pipeline.

[0008] Furthermore, the upper pipeline and the lower pipeline are both provided with branches: The first lower pipeline, the second lower pipeline, the third lower pipeline, the fourth lower pipeline, the fifth lower pipeline and the sixth lower pipeline are all provided with a first branch and a second branch, which are respectively recorded as the first branch of the first lower pipeline, the first branch of the second lower pipeline, the first branch of the third lower pipeline, the first branch of the fourth lower pipeline, the first branch of the fifth lower pipeline, the first branch of the sixth lower pipeline, the second branch of the first lower pipeline, the second branch of the second lower pipeline, the second branch of the third lower pipeline, the second branch of the fourth lower pipeline, the second branch of the fifth lower pipeline and the second branch of the sixth lower pipeline, and the first lower pipeline is also provided with a third branch, a fourth branch and a fifth branch, which are respectively recorded as the third branch of the first lower pipeline, the fourth branch of the first lower pipeline and the fifth branch of the first lower pipeline, Wherein, the first branch of the first lower pipeline, the first branch of the second lower pipeline, the first branch of the third lower pipeline, the first branch of the fourth lower pipeline, the first branch of the fifth lower pipeline and the first branch of the sixth lower pipeline are collectively connected to the third branch of the first lower pipeline, the third branch of the first lower pipeline is connected to the reverse venting mixing tank, and the other end of the reverse venting mixing tank is connected to the main lower pipeline; The second branch of the first lower pipeline, the second branch of the second lower pipeline, the second branch of the third lower pipeline, the second branch of the fourth lower pipeline, the second branch of the fifth lower pipeline and the second branch of the sixth lower pipeline are collectively connected to the fourth branch of the first lower pipeline, the fourth branch of the first lower pipeline is connected to the vacuum buffer tank, and the other end of the vacuum buffer tank is connected to the product buffer tank; The fifth branch of the first lower pipeline is connected to the product buffer tank.

[0009] Furthermore, the branch line is also provided with a branch pipe: The fifth branch of the first lower pipeline is provided with a first branch, a second branch, a third branch, a fourth branch, a fifth branch and a sixth branch in sequence, which are respectively recorded as the fifth branch of the first lower pipeline-the first branch, the fifth branch of the first lower pipeline-the second branch, the fifth branch of the first lower pipeline-the third branch, the fifth branch of the first lower pipeline-the fourth branch, the fifth branch of the first lower pipeline-the fifth branch, and the fifth branch of the first lower pipeline-the sixth branch. Among them, the fifth branch of the first lower pipeline-the first branch, the fifth branch of the first lower pipeline-the second branch, the fifth branch of the first lower pipeline-the third branch, the fifth branch of the first lower pipeline-the fourth branch, the fifth branch of the first lower pipeline-the fifth branch and the fifth branch of the first lower pipeline-the sixth branch are respectively connected to the first lower pipeline, the second lower pipeline, the third lower pipeline, the fourth lower pipeline, the fifth lower pipeline and the sixth lower pipeline.

[0010] Furthermore, the upper pipeline and the lower pipeline are both provided with branches: The first upper pipeline, the second upper pipeline, the third upper pipeline, the fourth upper pipeline, the fifth upper pipeline and the sixth upper pipeline are all provided with a first branch, a second branch and a third branch, which are respectively recorded as the first branch of the first upper pipeline, the first branch of the second upper pipeline, the first branch of the third upper pipeline, the first branch of the fourth upper pipeline, the first branch of the fifth upper pipeline, the first branch of the sixth upper pipeline, the second branch of the first upper pipeline, the second branch of the second upper pipeline, the second branch of the third upper pipeline, the second branch of the fourth upper pipeline, the second branch of the fifth upper pipeline, the second branch of the sixth upper pipeline, the third branch of the first upper pipeline, the third branch of the second upper pipeline, the third branch of the third upper pipeline, the third branch of the fourth upper pipeline, the third branch of the fifth upper pipeline and the third branch of the sixth upper pipeline.

[0011] Furthermore, the branch line is also provided with a branch pipe: The first upper pipeline first branch, the second upper pipeline first branch, the third upper pipeline first branch, the fourth upper pipeline first branch, the fifth upper pipeline first branch and the sixth upper pipeline first branch are collectively summarized as the upper pipeline first branch, the upper pipeline first branch continues to extend and is sequentially provided with a first branch, a second branch, a third branch, a fourth branch, a fifth branch and a sixth branch, respectively recorded as the upper pipeline first branch-first branch, the upper pipeline first branch-second branch, the upper pipeline first branch-third branch, the upper pipeline The first branch-fourth branch, the first branch of the upper pipeline-fifth branch and the first branch of the upper pipeline-sixth branch, the first branch of the upper pipeline-first branch, the first branch of the upper pipeline-second branch, the first branch of the upper pipeline-third branch, the first branch of the upper pipeline-fourth branch, the first branch of the upper pipeline-fifth branch and the first branch of the upper pipeline-sixth branch are respectively connected to the first lower pipeline, the second lower pipeline, the third lower pipeline, the fourth lower pipeline, the fifth lower pipeline and the sixth lower pipeline.

[0012] Furthermore, the branch line is also provided with a branch pipe: The first upper pipeline second branch, the second upper pipeline second branch, the third upper pipeline second branch, the fourth upper pipeline second branch, the fifth upper pipeline second branch and the sixth upper pipeline second branch are collectively summarized as the upper pipeline second branch, the upper pipeline second branch continues to extend and is sequentially provided with a first branch, a second branch, a third branch, a fourth branch, a fifth branch and a sixth branch, respectively recorded as the upper pipeline second branch-first branch, the upper pipeline second branch-second branch, the upper pipeline second branch-third branch, the upper pipeline The second branch-fourth branch, the second branch of the upper pipeline-fifth branch and the second branch of the upper pipeline-sixth branch, the second branch of the upper pipeline-first branch, the second branch of the upper pipeline-second branch, the second branch of the upper pipeline-third branch, the second branch of the upper pipeline-fourth branch, the second branch of the upper pipeline-fifth branch and the second branch of the upper pipeline-sixth branch are respectively connected to the first lower pipeline, the second lower pipeline, the third lower pipeline, the fourth lower pipeline, the fifth lower pipeline and the sixth lower pipeline.

[0013] Further, the third branch of the first upper pipeline, the third branch of the second upper pipeline, the third branch of the third upper pipeline, the third branch of the fourth upper pipeline, the third branch of the fifth upper pipeline and the third branch of the sixth upper pipeline are collectively summarized as the third branch of the upper pipeline, and the third branch of the upper pipeline continues to extend and connect to the main lower pipeline.

[0014] Furthermore, the pipeline, the branch and the branch pipe are all provided with control valves.

[0015] Further, the first lower pipeline, the second lower pipeline, the third lower pipeline, the fourth lower pipeline, the fifth lower pipeline, the sixth lower pipeline, the total lower pipeline, the first upper pipeline, the second upper pipeline, the third upper pipeline, the fourth upper pipeline, the fifth upper pipeline, the sixth upper pipeline and the total upper pipeline are all provided with control valves, which are respectively recorded as the first lower pipeline control valve, the second lower pipeline control valve, the third lower pipeline control valve, the fourth lower pipeline control valve, the fifth lower pipeline control valve, the sixth lower pipeline control valve, the total lower pipeline control valve, the first upper pipeline control valve, the second upper pipeline control valve, the third upper pipeline control valve, the fourth upper pipeline control valve, the fifth upper pipeline control valve, the sixth upper pipeline control valve and the total upper pipeline control valve; The first branch of the first lower pipeline, the first branch of the second lower pipeline, the first branch of the third lower pipeline, the first branch of the fourth lower pipeline, the first branch of the fifth lower pipeline, the first branch of the sixth lower pipeline, the second branch of the first lower pipeline, the second branch of the second lower pipeline, the second branch of the third lower pipeline, the second branch of the fourth lower pipeline, the second branch of the fifth lower pipeline and the second branch of the sixth lower pipeline are all provided with control valves, which are respectively recorded as the first branch control valve of the first lower pipeline, the first branch control valve of the second lower pipeline, the first branch control valve of the third lower pipeline, the first branch control valve of the fourth lower pipeline, the first branch control valve of the fifth lower pipeline, the first branch control valve of the sixth lower pipeline, the second branch control valve of the first lower pipeline, the second branch control valve of the second lower pipeline, the third branch control valve of the fourth lower pipeline, the second branch control valve of the fifth lower pipeline and the second branch control valve of the sixth lower pipeline. A control valve is also provided between the reverse venting mixing tank and the main lower pipeline, which is recorded as the reverse venting control valve; The fifth branch of the first lower pipeline-first branch, the fifth branch of the first lower pipeline-second branch, the fifth branch of the first lower pipeline-third branch, the fifth branch of the first lower pipeline-fourth branch, the fifth branch of the first lower pipeline-fifth branch and the fifth branch of the first lower pipeline-sixth branch are all provided with control valves, which are respectively recorded as the fifth branch of the first lower pipeline-first branch control valve, the fifth branch of the first lower pipeline-second branch control valve, the fifth branch of the first lower pipeline-third branch control valve, the fifth branch of the first lower pipeline-fourth branch control valve, the fifth branch of the first lower pipeline-fifth branch control valve and the fifth branch of the first lower pipeline-sixth branch control valve; The first branch of the first upper pipeline, the first branch of the second upper pipeline, the first branch of the third upper pipeline, the first branch of the fourth upper pipeline, the first branch of the fifth upper pipeline, the first branch of the sixth upper pipeline, the first branch of the upper pipeline-first branch, the first branch of the upper pipeline-second branch, the first branch of the upper pipeline-third branch, the first branch of the upper pipeline-fourth branch, the first branch of the upper pipeline-fifth branch, the first branch of the upper pipeline-sixth branch, the second branch of the first upper pipeline, the second branch of the second upper pipeline, the third second branch of the upper pipeline, the fourth second branch of the upper pipeline, the fifth second branch of the upper pipeline, the sixth The second branch of the upper pipeline, the second branch of the upper pipeline-the first branch, the second branch of the upper pipeline-the second branch, the second branch of the upper pipeline-the third branch, the second branch of the upper pipeline-the fourth branch, the second branch of the upper pipeline-the fifth branch, the second branch of the upper pipeline-the sixth branch, the third branch of the first upper pipeline, the third branch of the second upper pipeline, the third branch of the third upper pipeline, the third branch of the fourth upper pipeline, the third branch of the fifth upper pipeline and the third branch of the sixth upper pipeline are all provided with control valves, which are respectively recorded as the first upper pipeline first branch control valve, the second upper pipeline first branch control valve, the third upper pipeline first branch control valve, the fourth upper pipeline first branch control valve Branch control valve, fifth upper pipeline first branch control valve, sixth upper pipeline first branch control valve, upper pipeline first branch-first branch control valve, upper pipeline first branch-second branch control valve, upper pipeline first branch-third branch control valve, upper pipeline first branch-fourth branch control valve, upper pipeline first branch-fifth branch control valve, upper pipeline first branch-sixth branch control valve, first upper pipeline second branch control valve, second upper pipeline second branch control valve, third upper pipeline second branch control valve, fourth upper pipeline second branch control valve, fifth upper pipeline second branch control valve, sixth upper pipeline second branch control valve, upper pipeline second branch-first branch control valve, upper pipeline second Branch-second branch control valve, upper pipeline second branch-third branch control valve, upper pipeline second branch-fourth branch control valve, upper pipeline second branch-fifth branch control valve, upper pipeline second branch-sixth branch control valve, first upper pipeline third branch control valve, second upper pipeline third branch control valve, third upper pipeline third branch control valve, fourth upper pipeline third branch control valve, fifth upper pipeline third branch control valve and sixth upper pipeline third branch control valve. The first branch of the upper pipeline, the second branch of the upper pipeline and the third branch of the upper pipeline are all provided with control valves, which are respectively recorded as the upper pipeline first branch control valve, the upper pipeline second branch control valve and the upper pipeline third branch control valve.

[0016] The present invention provides a method for purifying methane recovered from nitrogen-containing coalbed methane, the method comprising the following steps: Step 1: Adsorption: the raw gas and the inverted tail gas are introduced into an adsorption state adsorption tower, the methane is adsorbed by the adsorbent in the adsorption state adsorption tower, and the weakly adsorbed impurities are discharged from the adsorption state adsorption tower; Step 2: pressure drop: connect the pressure drop state adsorption tower with the pressure increase state adsorption tower, and the gas flows from the pressure drop state adsorption tower to the pressure increase state adsorption tower, the pressure in the pressure drop state adsorption tower decreases, and the pressure in the pressure increase state adsorption tower increases, and the gas is recorded as pressure drop tail gas; Step 3: sequential release: the sequential release state adsorption tower is connected to the sequential release pre-adsorption state adsorption tower, and the gas flows from the sequential release state adsorption tower to the sequential release pre-adsorption state adsorption tower, and the gas is recorded as sequential release tail gas; Step 4: Reverse discharge: the adsorption tower in the reverse state exhausts gas in the reverse direction along the adsorption direction of the adsorbent, and the gas flows through the reverse discharge mixing tank and then flows to the raw gas pipeline. The gas is recorded as reverse discharge tail gas; Step 5: Vacuuming: vacuuming the adsorption tower in the vacuum state, wherein the methane is desorbed in the adsorption tower in the vacuum state and the adsorbent is regenerated; Step 6: pre-adsorption in a forward direction: passing the tail gas in the forward direction into the adsorption tower in the forward direction pre-adsorption state; Step 7: pressure increase: passing the tail gas in pressure decrease state into the adsorption tower in pressure increase state; Step 8: Final flushing: the feed gas is introduced into the adsorption tower in the final flushing state.

[0017] Furthermore, the adsorbent is one or a mixture of metal organic framework materials, activated carbon, molecular sieves, and silica gel.

[0018] Furthermore, based on the sum of the amounts of the various components in the gas to be treated as a percentage basis, the molar fraction of the adsorbable component of the adsorbent is 5%-96%.

[0019] Furthermore, the operating pressures of steps 1-8 are respectively 0.50-0.70 MPa for adsorption pressure, 0.35-0.50 MPa for equalizing pressure drop, 0.20-0.25 MPa for forward release, 0.15-0.17 MPa for reverse release, 0.04-0.06 MPa for vacuuming, 0.12-0.16 MPa for forward release pre-adsorption, 0.33-0.45 MPa for equalizing pressure rise, and 0.50-0.70 MPa for final flushing.

[0020] Furthermore, the purity of the methane is 95%-98%, and the recovery rate is 93%-98%.

[0021] Beneficial Effects of the Invention 1. The existing vacuum pressure swing adsorption technology generally focuses on the rise and fall of pressure in the adsorption tower, and does not pay much attention to the recovery of the exhaust gas discharged from the adsorption tower. The present invention unexpectedly passes the exhaust gas discharged from the adsorption tower in the pressure drop state and the exhaust gas discharged from the adsorption tower in the forward release state into the adsorption tower in the pressure rise state and the adsorption tower in the forward release pre-adsorption state, respectively, to recover the methane in the methane-depleted exhaust gas (the methane content in the exhaust gas is low and the content of weakly adsorbed impurities is high), thereby further improving the purity and recovery rate of methane in nitrogen-containing coalbed methane.

[0022] 2. The present invention unexpectedly introduces the reverse tail gas into the adsorption tower together with the raw gas in the adsorption state, so as to recover the methane in the methane-rich tail gas. At this time, the pressure in the reverse state adsorption tower is relatively low, and the desorption degree of methane in the adsorption tower is relatively large, that is, the methane content in the reverse tail gas is relatively high. Therefore, the recovery of the reverse tail gas can significantly improve the purity and recovery rate of methane in the nitrogen-containing coalbed methane.

[0023] 3. The purification system of the present invention cooperates with multiple pipelines, multiple branches, multiple branch pipes and multiple control valves. The connection relationship between adsorption towers in different states can be flexibly adjusted so that the entire purification process can be carried out continuously, with simple operation and strong practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The schematic diagram of the structure of the purification system for recovering methane from nitrogen-containing coalbed methane in the present invention is as follows: The first tower body T1; the second tower body T2; the third tower body T3; the fourth tower body T4; the fifth tower body T5; the sixth tower body T6; the first upper pipeline U1; the first lower pipeline D1; the second upper pipeline U2; the second lower pipeline D2; the third upper pipeline U3; the third lower pipeline D3; the fourth upper pipeline U4; the fourth lower pipeline D4; the fifth upper pipeline U5; the fifth lower pipeline D5; the sixth upper pipeline U6; the sixth lower pipeline D6; the total lower pipeline D7; the total upper pipeline U7; the raw gas storage tank connection G1; the reverse exhaust mixing tank G2; the vacuum buffer tank G3; the product buffer tank G4; the first branch of the first lower pipeline D1-Z1; the first branch of the second lower pipeline D2-Z1; the first branch of the third lower pipeline D3-Z1; the first branch of the fourth lower pipeline D4-Z1 ; The first branch of the fifth lower pipeline D5-Z1; The first branch of the sixth lower pipeline D6-Z1; The second branch of the first lower pipeline D1-Z2; The second branch of the second lower pipeline D2-Z2; The second branch of the third lower pipeline D3-Z2; The second branch of the fourth lower pipeline D4-Z2; The second branch of the fifth lower pipeline D5-Z2; The second branch of the sixth lower pipeline D6-Z2; The third branch of the first lower pipeline D1-Z3; The fourth branch of the first lower pipeline D1-Z4; The fifth branch of the first lower pipeline D1-Z5; The fifth branch of the first lower pipeline - the first branch pipe D1-Z5-1; The fifth branch of the first lower pipeline - the second branch pipe D1-Z5-2; The fifth branch of the first lower pipeline - the third branch pipe D1-Z5-3; The fifth branch of the first lower pipeline - the fourth branch pipe D1 -Z5-4; the fifth branch of the first lower pipeline - the fifth branch pipe D1-Z5-5; the fifth branch of the first lower pipeline - the sixth branch pipe D1-Z5-6; the first branch of the first upper pipeline U1-Z1; the first branch of the second upper pipeline U2-Z1; the first branch of the third upper pipeline U3-Z1; the first branch of the fourth upper pipeline U4-Z1; the first branch of the fifth upper pipeline U5-Z1; the first branch of the sixth upper pipeline U6-Z1; the second branch of the first upper pipeline U1-Z2; the second branch of the second upper pipeline U2-Z2; the second branch of the third upper pipeline U3-Z2; the second branch of the fourth upper pipeline U4-Z2; the second branch of the fifth upper pipeline U5-Z2; the second branch of the sixth upper pipeline U6-Z2; the third branch of the first upper pipeline U1-Z3; the second upper pipeline The third branch of the pipeline U2-Z3; the third branch of the third upper pipeline U3-Z3; the third branch of the fourth upper pipeline U4-Z3; the third branch of the fifth upper pipeline U5-Z3; the third branch of the sixth upper pipeline U6-Z3; the first branch of the upper pipeline U-Z1; the first branch of the upper pipeline-the first branch U-Z1-1; the first branch of the upper pipeline-the second branch U-Z1-2; the first branch of the upper pipeline-the third branch U-Z1-3; the first branch of the upper pipeline-the fourth branch U-Z1-4; the first branch of the upper pipeline-the fifth branch U-Z1-5; the first branch of the upper pipeline-the sixth branch U-Z1-6; the second branch of the upper pipeline U-Z2; the second branch of the upper pipeline-the first branch U-Z2-1; the second branch of the upper pipeline-the second branch U-Z2-2;The second branch of the upper pipeline - the third branch U-Z2-3; the second branch of the upper pipeline - the fourth branch U-Z2-4; the second branch of the upper pipeline - the fifth branch U-Z2-5; the second branch of the upper pipeline - the sixth branch U-Z2-6; the third branch of the upper pipeline U-Z3; The first lower pipeline control valve 1; the second lower pipeline control valve 2; the third lower pipeline control valve 3; the fourth lower pipeline control valve 4; the fifth lower pipeline control valve 5; the sixth lower pipeline control valve 6; the total lower pipeline control valve 7; the first upper pipeline control valve 8; the second upper pipeline control valve 9; the third upper pipeline control valve 10; the fourth upper pipeline control valve 11; the fifth upper pipeline control valve 12; the sixth upper pipeline control valve 13; the total upper pipeline control valve 14; the first branch control valve of the first lower pipeline 15; the first branch control valve of the second lower pipeline 16; the first branch control valve of the third lower pipeline 17; the first branch control valve of the fourth lower pipeline 18; the first branch control valve of the fifth lower pipeline 19; the first branch control valve of the sixth lower pipeline 20; the second branch control valve of the first lower pipeline valve 21; second branch control valve 22 of the second lower pipeline; second branch control valve 23 of the third lower pipeline; second branch control valve 24 of the fourth lower pipeline; second branch control valve 25 of the fifth lower pipeline; second branch control valve 26 of the sixth lower pipeline; reverse venting control valve 27; fifth branch-first branch control valve 28 of the first lower pipeline; fifth branch-second branch control valve 29 of the first lower pipeline; fifth branch-third branch control valve 30 of the first lower pipeline; fifth branch-fourth branch control valve 31 of the first lower pipeline; fifth branch-fifth branch control valve 32 of the first lower pipeline; fifth branch-sixth branch control valve 33 of the first lower pipeline; first branch control valve 34 of the first upper pipeline; first branch control valve 35 of the second upper pipeline; third branch control valve 36 of the third upper pipeline a branch control valve 36; a first branch control valve 37 of the fourth upper pipeline; a first branch control valve 38 of the fifth upper pipeline; a first branch control valve 39 of the sixth upper pipeline; a first branch control valve 40 of the upper pipeline; a first branch control valve 41 of the upper pipeline; a first branch control valve 42 of the upper pipeline; a first branch control valve 43 of the upper pipeline; a first branch control valve 44 of the upper pipeline; a first branch control valve 45 of the upper pipeline; a second branch control valve 46 of the first upper pipeline; a second branch control valve 47 of the second upper pipeline; a second branch control valve 48 of the third upper pipeline; a second branch control valve 49 of the fourth upper pipeline; a second branch control valve 50 of the fifth upper pipeline; a second branch control valve 51 of the sixth upper pipeline; a second branch control valve 52 of the sixth upper pipeline; a second branch control valve 53 of the first upper pipeline; a second branch control valve 54 of the first upper pipeline; a second branch control valve 55 of the first upper pipeline; a second branch control valve 56 of the first upper pipeline; a second branch control valve 57 of the second upper pipeline; a second branch control valve 58 of the third upper pipeline; a second branch control valve 59 of the fourth upper pipeline; a second branch control valve 50 of the fifth upper pipeline; a second branch control valve 51 of the sixth upper pipeline; a second branch control valve 52 of the first upper pipeline; a second branch control valve 53 of the first upper pipeline; a second branch control valve 54 of the first upper pipeline; a second branch control valve 55 of the first upper pipeline; a second branch control valve 56 of the first upper pipeline; a second branch control valve 57 of the second upper pipeline; a second branch control valve 58 of the third upper pipeline; a second branch control valve 59 of the fourth upper pipeline; a second branch control valve 50 of the fifth upper pipeline; a second branch control valve 50 of the fifth upper pipeline; a second branch control valve 51 of the fifth upper pipeline; a second branch control valve Branch control valve 51; upper pipeline second branch-first branch control valve 52; upper pipeline second branch-second branch control valve 53; upper pipeline second branch-third branch control valve 54; upper pipeline second branch-fourth branch control valve 55; upper pipeline second branch-fifth branch control valve 56; upper pipeline second branch-sixth branch control valve 57; first upper pipeline third branch control valve 58; second upper pipeline third branch control valve 59; third upper pipeline third branch control valve 60; fourth upper pipeline third branch control valve 61; fifth upper pipeline third branch control valve 62; sixth upper pipeline third branch control valve 63; upper pipeline first branch control valve 64; upper pipeline second branch control valve 65; upper pipeline third branch control valve 66. DETAILED DESCRIPTION

[0025] Example 1 Purification system for recovering methane from nitrogen-containing coalbed methane Figure 1 As shown: (1) Adsorption: Open the total lower pipeline control valve 7, the sixth lower pipeline control valve 6, the sixth upper pipeline control valve 13 and the total upper pipeline control valve 14, and the raw gas and the reverse tail gas flow into the sixth tower body T6 (adsorption state adsorption tower) through the total lower pipeline D7 and the sixth lower pipeline D6. Methane is adsorbed by the adsorbent in the sixth tower body T6, and impurities are discharged from the sixth upper pipeline U6 and the total upper pipeline U7. The adsorption pressure is 0.50 MPa; (2) Balanced pressure drop: open the fifth upper pipeline first branch control valve 38, the upper pipeline first branch control valve 64 and the upper pipeline first branch-first branch control valve 40, connect the fifth tower body T5 (balanced pressure drop state adsorption tower) and the first tower body T1 (balanced pressure increase state adsorption tower), and the balanced pressure drop tail gas flows from the fifth tower body T5 to the first tower body T1 along the fifth upper pipeline first branch U5-Z1, the upper pipeline first branch U-Z1 and the upper pipeline first branch-first branch U-Z1-1, the pressure in the fifth tower body T5 decreases, and the pressure in the first tower body T1 increases, and the balanced pressure drop pressure is 0.35 MPa; (3) Forward discharge: open the fourth upper pipeline second branch control valve 49, the upper pipeline second branch control valve 65, the upper pipeline second branch-second branch control valve 53, the second upper pipeline control valve 9 and the total upper pipeline control valve 14, connect the fourth tower body T4 (forward discharge state adsorption tower) with the second tower body T2 (forward discharge pre-adsorption state adsorption tower), and the forward discharge tail gas flows from the fourth tower body T4 to the second tower body T2 along the fourth upper pipeline second branch U4-Z2, the upper pipeline second branch U-Z2, and the upper pipeline second branch-second branch U-Z2-2, and the impurities are discharged from the second upper pipeline U2 and the total upper pipeline U7. The forward discharge pressure is 0.25MPa; (4) Reverse discharge: Open the first branch control valve 17 of the third lower pipeline and the reverse discharge control valve 27, and the third tower body T3 (the adsorption tower in the reverse state) exhausts in the reverse direction of the adsorbent adsorption. The reverse discharge tail gas flows along the first branch D3-Z1 of the third lower pipeline and the third branch D1-Z3 of the first lower pipeline through the reverse discharge mixing tank G2, and then flows to the total lower pipeline D7. The reverse discharge pressure is 0.15 MPa; (5) Pre-adsorption: The tail gas in step 3 is passed into the second tower body T2, and the pre-adsorption pressure is 0.13 MPa; (6) Pressure increase: The pressure-reduced tail gas in step 2 is passed into the first tower body T1, and the pressure increase is 0.33 MPa. In Example 1, the purity of methane in the nitrogen-containing coalbed methane is 95%, and the recovery rate is 98%.

[0026] Example 2 Purification system for recovering methane from nitrogen-containing coalbed methane Figure 1 As shown: (1) Adsorption: Open the total lower pipeline control valve 7, the first lower pipeline control valve 1, the first upper pipeline control valve 8 and the total upper pipeline control valve 14, and the raw gas and the reverse tail gas flow into the first tower body T1 (adsorption state adsorption tower) through the total lower pipeline D7 and the first lower pipeline D1. Methane is adsorbed by the adsorbent in the first tower body T1, and impurities are discharged from the first upper pipeline U1 and the total upper pipeline U7. The adsorption pressure is 0.60 MPa; (2) Balanced pressure drop: open the sixth upper pipeline first branch control valve 39, the upper pipeline first branch control valve 64 and the upper pipeline first branch-second branch control valve 41, connect the sixth tower body T6 (balanced pressure drop state adsorption tower) and the second tower body T2 (balanced pressure increase state adsorption tower), and the balanced pressure drop tail gas flows from the sixth tower body T6 to the second tower body T2 along the sixth upper pipeline first branch U6-Z1, the upper pipeline first branch U-Z1 and the upper pipeline first branch-second branch U-Z1-2, the pressure in the sixth tower body T6 decreases, and the pressure in the second tower body T2 increases, and the balanced pressure drop pressure is 0.43 MPa; (3) Forward discharge: open the fifth upper pipeline second branch control valve 50, the upper pipeline second branch control valve 65, the upper pipeline second branch-third branch control valve 54, the third upper pipeline control valve 10 and the total upper pipeline control valve 14, connect the fifth tower body T5 (forward discharge state adsorption tower) with the third tower body T3 (forward discharge pre-adsorption state adsorption tower), and the forward discharge tail gas flows from the fifth tower body T5 to the third tower body T3 along the fifth upper pipeline second branch U5-Z2, the upper pipeline second branch U-Z2, and the upper pipeline second branch-third branch U-Z2-3, and impurities are discharged from the third upper pipeline U3 and the total upper pipeline U7. The forward discharge pressure is 0.20MPa; (4) Reverse discharge: Open the first branch control valve 18 of the fourth lower pipeline and the reverse discharge control valve 27, and the fourth tower body T4 (the adsorption tower in the reverse state) exhausts in the reverse direction of the adsorbent adsorption. The reverse discharge tail gas flows along the first branch D4-Z1 of the fourth lower pipeline and the third branch D1-Z3 of the first lower pipeline through the reverse discharge mixing tank G2, and then flows to the total lower pipeline D7. The reverse discharge pressure is 0.17 MPa; (5) Pre-adsorption: The tail gas in step 3 is passed into the third tower body T3, and the pre-adsorption pressure is 0.12 MPa; (6) Pressure increase: The pressure-reduced tail gas in step 2 is passed into the second tower body T2, and the pressure increase is 0.40 MPa. In Example 2, the purity of methane in the nitrogen-containing coalbed methane is 97%, and the recovery rate is 95%.

[0027] Example 3 Purification system for recovering methane from nitrogen-containing coalbed methane Figure 1 As shown: (1) Adsorption: Open the main lower pipeline control valve 7, the sixth lower pipeline control valve 6, the sixth upper pipeline control valve 13 and the main upper pipeline control valve 14, and the raw gas and the reverse tail gas flow into the sixth tower body T6 (adsorption state adsorption tower) through the main lower pipeline D7 and the sixth lower pipeline D6. Methane is adsorbed by the adsorbent in the sixth tower body T6, and impurities are discharged from the sixth upper pipeline U6 and the main upper pipeline U7. The adsorption pressure is 0.70 MPa; (2) Balanced pressure drop: open the fifth upper pipeline first branch control valve 38, the upper pipeline first branch control valve 64 and the upper pipeline first branch-second branch control valve 41, connect the fifth tower body T5 (balanced pressure drop state adsorption tower) and the second tower body T2 (balanced pressure increase state adsorption tower), and the balanced pressure drop tail gas flows from the fifth tower body T5 to the second tower body T2 along the fifth upper pipeline first branch U5-Z1, the upper pipeline first branch U-Z1 and the upper pipeline first branch-second branch U-Z1-2, the pressure in the fifth tower body T5 decreases, and the pressure in the second tower body T2 increases, and the balanced pressure drop pressure is 0.50 MPa; (3) Forward discharge: open the third upper pipeline second branch control valve 48, the upper pipeline second branch control valve 65, the upper pipeline second branch-first branch control valve 52, the first upper pipeline control valve 8 and the total upper pipeline control valve 14, connect the third tower body T3 (forward discharge state adsorption tower) with the first tower body T1 (forward discharge pre-adsorption state adsorption tower), and the forward discharge tail gas flows from the third tower body T3 to the first tower body T1 along the third upper pipeline second branch U3-Z2, the upper pipeline second branch U-Z2, and the upper pipeline second branch-first branch U-Z2-1, and impurities are discharged from the first upper pipeline U1 and the total upper pipeline U7. The forward discharge pressure is 0.20MPa; (4) Reverse discharge: Open the first branch control valve 18 of the fourth lower pipeline and the reverse discharge control valve 27, and the fourth tower body T4 (the adsorption tower in the reverse state) exhausts in the reverse direction of the adsorbent adsorption. The reverse discharge tail gas flows along the first branch D4-Z1 of the fourth lower pipeline and the third branch D1-Z3 of the first lower pipeline through the reverse discharge mixing tank G2, and then flows to the total lower pipeline D7. The reverse discharge pressure is 0.15 MPa; (5) Pre-adsorption: The tail gas in step 3 is passed into the first tower body T1, and the pre-adsorption pressure is 0.16 MPa; (6) Pressure increase: The pressure-reduced tail gas in step 2 is passed into the second tower body T2, and the pressure increase is 0.45 MPa. In Example 3, the purity of methane in the nitrogen-containing coalbed methane is 98%, and the recovery rate is 93%.

[0028] Example 4 Purification system for recovering methane from nitrogen-containing coalbed methane Figure 1 As shown: (1) Adsorption: Open the total lower pipeline control valve 7, the first lower pipeline control valve 1, the first upper pipeline control valve 8 and the total upper pipeline control valve 14, and the raw gas flows into the first tower body T1 (adsorption state adsorption tower) through the total lower pipeline D7 and the first lower pipeline D1. Methane is adsorbed by the adsorbent in the first tower body T1, and impurities are discharged from the first upper pipeline U1 and the total upper pipeline U7. The adsorption pressure is 0.60 MPa; (2) Balanced pressure drop: open the sixth upper pipeline first branch control valve 39, the upper pipeline first branch control valve 64 and the upper pipeline first branch-second branch control valve 41, connect the sixth tower body T6 (balanced pressure drop state adsorption tower) and the second tower body T2 (balanced pressure increase state adsorption tower), and the balanced pressure drop tail gas flows from the sixth tower body T6 to the second tower body T2 along the sixth upper pipeline first branch U6-Z1, the upper pipeline first branch U-Z1 and the upper pipeline first branch-second branch U-Z1-2, the pressure in the sixth tower body T6 decreases, and the pressure in the second tower body T2 increases, and the balanced pressure drop pressure is 0.43 MPa; (3) Forward discharge: open the fifth upper pipeline second branch control valve 50, the upper pipeline second branch control valve 65, the upper pipeline second branch-third branch control valve 54, the third upper pipeline control valve 10 and the total upper pipeline control valve 14, connect the fifth tower body T5 (forward discharge state adsorption tower) with the third tower body T3 (forward discharge pre-adsorption state adsorption tower), and the forward discharge tail gas flows from the fifth tower body T5 to the third tower body T3 along the fifth upper pipeline second branch U5-Z2, the upper pipeline second branch U-Z2, and the upper pipeline second branch-third branch U-Z2-3, and impurities are discharged from the third upper pipeline U3 and the total upper pipeline U7. The forward discharge pressure is 0.20MPa; (4) Vacuuming: Open the control valve 24 of the second branch of the fourth lower pipeline to vacuum the fourth tower body T4 (the adsorption tower in the vacuum state). After methane is desorbed, it flows along the second branch D4-Z2 of the fourth lower pipeline and the fourth branch D1-Z4 of the first lower pipeline to the vacuum buffer tank G3 and the product buffer tank G4. The adsorbent in the fourth tower body T4 is regenerated, and the vacuum pressure is 0.04 MPa. (5) Pre-adsorption: The tail gas in step 3 is passed into the third tower body T3, and the pre-adsorption pressure is 0.12 MPa; (6) Pressure increase: The pressure-reduced tail gas in step 2 is passed into the second tower body T2, and the pressure increase is 0.40 MPa. In Example 4, the purity of methane in the nitrogen-containing coalbed methane is 90%, and the recovery rate is 91%.

[0029] Example 5 Purification system for recovering methane from nitrogen-containing coalbed methane Figure 1 As shown: (1) Adsorption: Open the total lower pipeline control valve 7, the sixth lower pipeline control valve 6, the sixth upper pipeline control valve 13 and the total upper pipeline control valve 14, and the raw gas and the reverse tail gas flow into the sixth tower body T6 (adsorption state adsorption tower) through the total lower pipeline D7 and the sixth lower pipeline D6. Methane is adsorbed by the adsorbent in the sixth tower body T6, and impurities are discharged from the sixth upper pipeline U6 and the total upper pipeline U7. The adsorption pressure is 0.50 MPa; (2) Balanced pressure drop: open the fifth upper pipeline first branch control valve 38, the upper pipeline first branch control valve 64 and the upper pipeline first branch-second branch control valve 41, connect the fifth tower body T5 (balanced pressure drop state adsorption tower) and the second tower body T2 (balanced pressure increase state adsorption tower), and the balanced pressure drop tail gas flows from the fifth tower body T5 to the second tower body T2 along the fifth upper pipeline first branch U5-Z1, the upper pipeline first branch U-Z1 and the upper pipeline first branch-second branch U-Z1-2, the pressure in the fifth tower body T5 decreases, and the pressure in the second tower body T2 increases, and the balanced pressure drop pressure is 0.35 MPa; (3) Reverse discharge: Open the first branch control valve 18 of the fourth lower pipeline and the reverse discharge control valve 27, and the fourth tower body T4 (the adsorption tower in the reverse state) exhausts in the reverse direction of the adsorbent adsorption. The reverse discharge tail gas flows along the first branch D4-Z1 of the fourth lower pipeline and the third branch D1-Z3 of the first lower pipeline through the reverse discharge mixing tank G2, and then flows to the total lower pipeline D7. The reverse discharge pressure is 0.15 MPa; (4) Vacuuming: Open the control valve 23 of the second branch of the third lower pipeline to vacuum the third tower body T3 (the adsorption tower in the vacuum state). After methane is desorbed, it flows along the second branch D3-Z2 of the third lower pipeline and the fourth branch D1-Z4 of the first lower pipeline to the vacuum buffer tank G3 and the product buffer tank G4. The adsorbent in the third tower body T3 is regenerated, and the vacuum pressure is 0.06 MPa. (5) Pressure increase: The pressure-reduced tail gas in step 2 is passed into the second tower body T2, and the pressure increase is 0.33 MPa. (6) Final flushing: Open the main lower pipeline control valve 7 and the first lower pipeline control valve 1. After the raw material gas flows through the raw material gas storage tank, it flows along the main lower pipeline D7 and the first lower pipeline D1 to the first tower body T1 (the adsorption tower in the final flushing state). The final flushing pressure is 0.50 MPa. In Example 5, the purity of methane in the nitrogen-containing coalbed methane is 93%, and the recovery rate is 86%.

[0030] The purity and recovery rate of methane in Examples 1-5 are shown in Table 1: Table 1 Comparison of purity and recovery rate of methane in Examples 1-5

[0031] Compared with Example 4, Examples 1-3 of the present invention can recover methane in methane-rich tail gas by passing the reverse tail gas together with the raw gas into an adsorption tower in an adsorption state, and the purity and recovery rate of methane are improved, especially the purity of methane is significantly improved; Compared with Example 5, Examples 1-3 of the present invention can recover methane in methane-lean tail gas by passing the tail gas discharged from the forward-discharged adsorption tower into a forward-discharged pre-adsorption tower, and the purity and recovery rate of methane are also improved, especially the recovery rate of methane is significantly improved. Therefore, the present invention can realize the recovery of multiple tail gases through a specific purification system and purification method, thereby improving the purity and recovery rate of methane in nitrogen-containing coalbed methane.

[0032] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification and / or equivalent changes made based on the technical essence of the present invention still fall within the scope of protection required by the present invention.

Claims

1. A purification system for recovering methane from nitrogen-containing coalbed methane, characterized in that: The system comprises: The first tower body (T1), the second tower body (T2), the third tower body (T3), the fourth tower body (T4), and the fifth tower body (T5) are arranged in sequence. and a sixth tower body (T6), as well as a raw gas storage tank (G1), a reverse venting mixing tank (G2), a vacuum buffer tank (G3) and a product buffer tank (G4); Each of the six towers is provided with an upper pipe and a lower pipe; The upper pipeline and the lower pipeline are both provided with branches; The branch road is also provided with a branch pipe. The gas to be treated can flow through the different pipelines, branches and branch pipes, and then flow into and out of the tower body in different states, so as to recover the methane in the nitrogen-containing coalbed methane.

2. The system according to claim 1, characterized in that The six tower bodies are each provided with an upper pipeline and a lower pipeline: The first tower body (T1), the second tower body (T2), the third tower body (T3), the fourth tower body (T4), the fifth tower body (T5) and the sixth tower body (T6) are all provided with upper pipelines and lower pipelines, which are respectively denoted as the first upper pipeline (U1), the first lower pipeline (D1), the second upper pipeline (U2), the second lower pipeline (D2), the third upper pipeline (U3), the third lower pipeline (D3), the fourth upper pipeline (U4), the fourth lower pipeline (D4), the fifth upper pipeline (U5), the fifth lower pipeline (D5), the sixth upper pipeline (U6) and the sixth lower pipeline (D6), wherein the first lower pipeline (D1), the second lower pipeline (D2), the third lower pipeline (D3), the fourth lower pipeline (D4), the fifth lower pipeline (D5) and the sixth lower pipeline (D6) are collectively combined into a total lower pipeline (D7), and the total lower pipeline (D7) is connected to the raw gas storage tank (G1); The first upper pipeline (U1), the second upper pipeline (U2), the third upper pipeline (U3), the fourth upper pipeline (U4), the fifth upper pipeline (U5) and the sixth upper pipeline (U6) are collectively aggregated into a total upper pipeline (U7).

3. The system according to claim 2, characterized in that The upper pipeline and the lower pipeline are both provided with branches: The first lower pipeline (D1), the second lower pipeline (D2), the third lower pipeline (D3), the fourth lower pipeline (D4), the fifth lower pipeline (D5) and the sixth lower pipeline (D6) are each provided with a first branch and a second branch, which are respectively denoted as the first branch (D1-Z1) of the first lower pipeline, the first branch (D2-Z1) of the second lower pipeline, the first branch (D3-Z1) of the third lower pipeline, the first branch (D4-Z1) of the fourth lower pipeline, the first branch (D5-Z1) of the fifth lower pipeline, and the first branch (D6-Z1) of the sixth lower pipeline. ), the second branch of the first lower pipeline (D1-Z2), the second branch of the second lower pipeline (D2-Z2), the second branch of the third lower pipeline (D3-Z2), the second branch of the fourth lower pipeline (D4-Z2), the second branch of the fifth lower pipeline (D5-Z2) and the second branch of the sixth lower pipeline (D6-Z2), and the first lower pipeline (D1) is also provided with a third branch, a fourth branch and a fifth branch, which are respectively recorded as the third branch of the first lower pipeline (D1-Z3), the fourth branch of the first lower pipeline (D1-Z4) and the fifth branch of the first lower pipeline (D1-Z5), wherein the first branch of the first lower pipeline (D1-Z1), the first branch of the second lower pipeline (D2-Z1), the first branch of the third lower pipeline (D3-Z1), the first branch of the fourth lower pipeline (D4-Z1), the first branch of the fifth lower pipeline (D5-Z1) and the first branch of the sixth lower pipeline (D6-Z1) are collectively connected to the third branch of the first lower pipeline (D1-Z3), the third branch of the first lower pipeline (D1-Z3) is connected to the reverse venting mixing tank (G2), and the other end of the reverse venting mixing tank (G2) is connected to the main lower pipeline (D7); The second branch of the first lower pipeline (D1-Z2), the second branch of the second lower pipeline (D2-Z2), the second branch of the third lower pipeline (D3-Z2), the second branch of the fourth lower pipeline (D4-Z2), the second branch of the fifth lower pipeline (D5-Z2) and the second branch of the sixth lower pipeline (D6-Z2) are collectively connected to the fourth branch of the first lower pipeline (D1-Z4), the fourth branch of the first lower pipeline (D1-Z4) is connected to the vacuum buffer tank (G3), and the other end of the vacuum buffer tank (G3) is connected to the product buffer tank (G4); The fifth branch (D1-Z5) of the first lower pipeline is connected to the product buffer tank (G4).

4. The system according to claim 3, characterized in that The branch road is also provided with a branch pipe: The fifth branch (D1-Z5) of the first lower pipeline is provided with a first branch, a second branch, a third branch, a fourth branch, a fifth branch and a sixth branch in sequence, which are respectively recorded as the fifth branch of the first lower pipeline-the first branch (D1-Z5-1), the fifth branch of the first lower pipeline-the second branch (D1-Z5-2), the fifth branch of the first lower pipeline-the third branch (D1-Z5-3), the fifth branch of the first lower pipeline-the fourth branch (D1-Z5-4), the fifth branch of the first lower pipeline-the fifth branch (D1-Z5-5), and the fifth branch of the first lower pipeline-the sixth branch (D1-Z5-6). Among them, the fifth branch of the first lower pipeline - the first branch (D1-Z5-1), the fifth branch of the first lower pipeline - the second branch (D1-Z5-2), the fifth branch of the first lower pipeline - the third branch (D1-Z5-3), the fifth branch of the first lower pipeline - the fourth branch (D1-Z5-4), the fifth branch of the first lower pipeline - the fifth branch (D1-Z5-5) and the fifth branch of the first lower pipeline - the sixth branch (D1-Z5-6) are respectively connected to the first lower pipeline (D1), the second lower pipeline (D2), the third lower pipeline (D3), the fourth lower pipeline (D4), the fifth lower pipeline (D5) and the sixth lower pipeline (D6).

5. The system according to claim 2, characterized in that The upper pipeline and the lower pipeline are both provided with branches: The first upper pipeline (U1), the second upper pipeline (U2), the third upper pipeline (U3), the fourth upper pipeline (U4), the fifth upper pipeline (U5) and the sixth upper pipeline (U6) are each provided with a first branch, a second branch and a third branch, which are respectively denoted as the first branch (U1-Z1) of the first upper pipeline, the first branch (U2-Z1) of the second upper pipeline, the first branch (U3-Z1) of the third upper pipeline, the first branch (U4-Z1) of the fourth upper pipeline, the first branch (U5-Z1) of the fifth upper pipeline, the first branch (U6-Z1) of the sixth upper pipeline, and the first branch (U6-Z1) of the first upper pipeline. The second branch of the pipeline (U1-Z2), the second branch of the second upper pipeline (U2-Z2), the second branch of the third upper pipeline (U3-Z2), the second branch of the fourth upper pipeline (U4-Z2), the second branch of the fifth upper pipeline (U5-Z2), the second branch of the sixth upper pipeline (U6-Z2), the third branch of the first upper pipeline (U1-Z3), the third branch of the second upper pipeline (U2-Z3), the third branch of the third upper pipeline (U3-Z3), the third branch of the fourth upper pipeline (U4-Z3), the third branch of the fifth upper pipeline (U5-Z3) and the third branch of the sixth upper pipeline (U6-Z3).

6. The system according to claim 5, characterized in that The branch road is also provided with a branch pipe: The first upper pipeline first branch (U1-Z1), the second upper pipeline first branch (U2-Z1), the third upper pipeline first branch (U3-Z1), the fourth upper pipeline first branch (U4-Z1), the fifth upper pipeline first branch (U5-Z1) and the sixth upper pipeline first branch (U6-Z1) are collectively summarized as the upper pipeline first branch (U-Z1), and the upper pipeline first branch (U-Z1) continues to extend and is provided with a first branch pipe, a second branch pipe, a third branch pipe, a fourth branch pipe, a fifth branch pipe and a sixth branch pipe in sequence, which are respectively recorded as the upper pipeline first branch-first branch pipe (U-Z1-1), the upper pipeline first branch-second branch pipe (U-Z1-2), the upper pipeline first branch-third branch pipe (U-Z1-3), the upper pipeline first branch-fourth branch pipe The first branch of the upper pipeline-the first branch (U-Z1-1), the first branch of the upper pipeline-the second branch (U-Z1-2), the first branch of the upper pipeline-the third branch (U-Z1-3), the first branch of the upper pipeline-the fourth branch (U-Z1-4), the first branch of the upper pipeline-the fifth branch (U-Z1-5) and the first branch of the upper pipeline-the sixth branch (U-Z1-6) are respectively connected to the first lower pipeline (D1), the second lower pipeline (D2), the third lower pipeline (D3), the fourth lower pipeline (D4), the fifth lower pipeline (D5) and the sixth lower pipeline (D6).

7. The system according to claim 5, characterized in that The branch road is also provided with a branch pipe: The first upper pipeline second branch (U1-Z2), the second upper pipeline second branch (U2-Z2), the third upper pipeline second branch (U3-Z2), the fourth upper pipeline second branch (U4-Z2), the fifth upper pipeline second branch (U5-Z2) and the sixth upper pipeline second branch (U6-Z2) are collectively summarized as the upper pipeline second branch (U-Z2), and the upper pipeline second branch (U-Z2) continues to extend and is sequentially provided with a first branch, a second branch, a third branch, a fourth branch, a fifth branch and a sixth branch, which are respectively recorded as the upper pipeline second branch-first branch (U-Z2-1), the upper pipeline second branch-second branch (U-Z2-2), the upper pipeline second branch-third branch (U-Z2-3), the upper pipeline second branch-fourth branch (U-Z2-4), the upper pipeline second branch-fifth branch (U-Z2-5) and the upper pipeline second branch-fifth and sixth pipes (U-Z2-6), the upper pipeline second branch-first branch (U-Z2-1), the upper pipeline second branch-second branch (U-Z2-2), the upper pipeline second branch-third branch (U-Z2-3), the upper pipeline second branch-fourth branch (U-Z2-4), the upper pipeline second branch-fifth branch (U-Z2-5) and the upper pipeline second branch-fifth and sixth pipes (U-Z2-6) are respectively connected to the first lower pipe (D1), the second lower pipe (D2), the third lower pipe (D3), the fourth lower pipe (D4), the fifth lower pipe (D5) and the sixth lower pipe (D6).

8. The system according to claim 5, characterized in that The first upper pipeline third branch (U1-Z3), the second upper pipeline third branch (U2-Z3), the third upper pipeline third branch (U3-Z3), the fourth upper pipeline third branch (U4-Z3), the fifth upper pipeline third branch (U5-Z3) and the sixth upper pipeline third branch (U6-Z3) are collectively aggregated into an upper pipeline third branch (U-Z3), and the upper pipeline third branch (U-Z3) continues to extend and connect to the total lower pipeline (D7).

9. The system according to any one of claims 1 to 8, characterized in that: The pipeline, the branch and the branch pipe are all provided with control valves.

10. A method for purification using the system according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: Step 1: Adsorption: The raw gas and the inverted tail gas are introduced into an adsorption state adsorption tower, the methane is adsorbed by the adsorbent in the adsorption state adsorption tower, and the weakly adsorbed impurities are discharged from the adsorption state adsorption tower; Step 2: pressure drop: connect the pressure drop state adsorption tower with the pressure increase state adsorption tower, and the gas flows from the pressure drop state adsorption tower to the pressure increase state adsorption tower, the pressure in the pressure drop state adsorption tower decreases, and the pressure in the pressure increase state adsorption tower increases, and the gas is recorded as pressure drop tail gas; Step 3: sequential release: the sequential release state adsorption tower is connected to the sequential release pre-adsorption state adsorption tower, and the gas flows from the sequential release state adsorption tower to the sequential release pre-adsorption state adsorption tower, and the gas is recorded as sequential release tail gas; Step 4: Reverse discharge: The adsorption tower in the reverse state exhausts gas in the reverse direction along the adsorption direction of the adsorbent, and the gas flows through the reverse discharge mixing tank (G2) and then flows to the raw gas pipeline. The gas is recorded as reverse discharge tail gas; Step 5: Vacuuming: vacuuming the adsorption tower in the vacuum state, wherein the methane is desorbed in the adsorption tower in the vacuum state and the adsorbent is regenerated; Step 6: pre-adsorption in a forward direction: passing the tail gas in the forward direction into the adsorption tower in the forward direction pre-adsorption state; Step 7: pressure increase: passing the tail gas in pressure decrease state into the adsorption tower in pressure increase state; Step 8: Final flushing: the feed gas is introduced into the adsorption tower in the final flushing state.

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