Purification system for adjusting hydrogen-carbon ratio of feed gas at methane synthesis inlet

Abstract

The utility model relates to a purification system for adjusting hydrogen-carbon ratio of feed gas at a methane synthesis inlet, which is characterized in that a purification B series flash tank isolating valve and a purification B series third connecting pipe are arranged on a purification B series first connecting pipe, and a purification A / B series No.1 flash tank flash steam recovery valve is arranged on the purification B series third connecting pipe; the air outlet end of the purified A-series flash steam compressor is communicated with an external purified A-series flash steam recycling pipeline; and the gas outlet end of the purified B-series flash steam compressor is respectively communicated with a purified B-series flash steam recycling pipeline and is communicated with the desulfurization module and an external methane synthesis raw gas pipeline. The hydrogen-carbon ratio of the raw material gas at the methane synthesis inlet is accurately adjusted, and the hydrogen content index in the product natural gas is ensured to meet the requirement; maintaining the air inlet flow of the conversion furnace, stabilizing the temperature of the conversion furnace and ensuring the normal operation of the conversion furnace; the ratio of carbon dioxide in feed gas is increased, the carbon precipitation risk of the methane synthesis catalyst is reduced, and the service life of the methane synthesis catalyst is prolonged.

Description

Technical Field

[0001] The utility model relates to the technical field of methane synthesis, in particular to a purification system for adjusting the hydrogen-carbon ratio of raw material gas at a methane synthesis inlet. Background Art

[0002] In the field of coal-to-natural gas technology, the main processes in a plant can be divided into gasification, conversion, purification, and methanation. The gasification process provides the raw gas, and the conversion process adjusts the hydrogen-to-carbon ratio in the methane synthesis raw gas to a three-to-one ratio as much as possible. The hydrogen-to-carbon ratio, M, is calculated as follows: M = (H2-CO2) / (CO+CO2). Since the ratio of hydrogen to carbon monoxide in the carbon monoxide methanation reaction is three to one, and the ratio of hydrogen to carbon monoxide in the carbon dioxide methanation reaction is four to one, a hydrogen-to-carbon ratio of three to one fully meets the requirements of both methanation reactions and maximizes the methane conversion rate.

[0003] The raw gas is then purified to remove ineffective components such as sulfur and carbon dioxide, and is finally sent to a methane synthesis unit to synthesize methane.

[0004] In the shift process, part of the raw gas needs to be passed into the shift furnace equipped with a shift catalyst to convert the carbon monoxide in this part of the raw gas into hydrogen. Finally, the ratio of hydrogen to carbon monoxide in the raw gas leaving the shift device is adjusted to three to one. The shift reaction equation is as follows: CO + H2O <=> CO2 + H2

[0005] The amount of raw gas entering the conversion furnace is adjusted according to the hydrogen-carbon ratio of the raw gas at the outlet of the conversion device. If the hydrogen-carbon ratio is too high, the amount of raw gas entering the conversion furnace is reduced, otherwise the amount of raw gas entering the conversion furnace is increased.

[0006] The raw gas from the conversion system outlet contains components such as light hydrocarbons, carbon dioxide, and sulfur, requiring treatment through a purification system. The purification system is divided into two series, A and B, which utilize the light hydrocarbons in the raw gas and directly remove carbon dioxide and hydrogen sulfide. The purification system primarily operates on a low-temperature methanol wash, utilizing low-temperature methanol in countercurrent contact with the process gas in a methanol scrubber to absorb the light hydrocarbons, hydrogen sulfide, and carbon dioxide, thereby purifying the raw gas. In the methanol scrubber, the raw gas enters from the bottom and the low-temperature methanol enters from the top. Based on the components being removed, the scrubber is divided, from bottom to top, into a pre-wash section, a desulfurization section, and a decarbonization (carbon dioxide) section. The carbon-rich methanol from the lower section of the methanol scrubber's decarbonization section enters Flash Tank 1, where some of the gas components absorbed by the methanol are flashed off and recovered. This flash steam contains 70% carbon dioxide and approximately 6 ppm sulfur, with the remainder primarily consisting of methane, hydrogen, and carbon monoxide. The sulfur-rich methanol from the desulfurization section of the methanol scrubber enters Flash Tank 2, where some of the gas components absorbed by the methanol are flashed off and recovered. This flash steam contains 70% carbon dioxide and approximately 1500 ppm sulfur, with the remainder primarily consisting of methane, hydrogen, and carbon monoxide. The flash steam from Flash Tank 1 and Flash Tank 2 merges and enters the flash steam compressor for pressurization. This recovered gas is ultimately delivered to the purification system's feed gas inlet for recycling.

[0007] After purification, the raw gas is sent to the methane synthesis system. The methane synthesis process uses high carbon monoxide synthesis technology. This process has four reactors, each loaded with nickel-based catalysts, and the methane synthesis reaction is carried out in each reactor in sequence. The main methanation reaction equation occurring in the reactor is as follows:

[0008] (2)CO+3H2<=>CH4+H2O

[0009] (3)CO2+4H2<=>CH4+2H2O

[0010] At the same time, part of the CO will also undergo carbon deposition reaction (Boudouard reaction), the reaction equation is as follows:

[0011] (4) 2CO <=> CO2 + C

[0012] The above three chemical reactions are all reversible reactions, and the conversion rate of each component in the chemical reaction changes with the change of its partial pressure.

[0013] The carbon deposition reaction of CO produces elemental carbon, which adheres to the catalyst surface, covering the catalytically active sites and reducing its activity. Furthermore, due to the porous structure of the catalyst, the accumulation of elemental carbon can rupture the catalyst's micropores, leading to catalyst fragmentation and reduced catalyst bed permeability, affecting the reactor's air intake. During the 2020 methane synthesis unit overhaul, catalyst samples from Reactors 1 and 2 were analyzed, revealing carbon content as high as 48.2% across samples, indicating significant carbon deposition on the catalyst. This indicates that catalyst carbon deposition has become a key factor hindering the normal operation of the methane synthesis system.

[0014] Since CO2 has a stable structure and will not precipitate elemental carbon, in the methane synthesis feed gas, under the same hydrogen-carbon ratio conditions, appropriately increasing the proportion of carbon dioxide can reduce the risk of catalyst carbon deposition.

[0015] Disadvantages of existing technology:

[0016] 1. Since the catalyst used in the shift reaction is a cobalt-molybdenum-based wide-temperature sulfur-resistant shift catalyst, the operating temperature of the catalyst is 180-500°C. Therefore, during the production process, a certain amount of raw gas must be ensured to enter the shift furnace for the shift reaction to generate heat in order to maintain the temperature of the shift furnace. Generally, the gas volume entering the shift furnace is required to be no less than 50,000 Nm 3 / h, corresponding to a production system load of about 30%. If the operating conditions of the production system fluctuate again at this time, it will easily lead to an excessive amount of carbon monoxide conversion in the raw gas, resulting in an excessively high hydrogen-carbon ratio in the raw gas, and ultimately causing the hydrogen content in the product natural gas to exceed the standard.

[0017] 2. The raw gas composition at the outlet of the gasification system varies greatly due to factors such as coal quality and steam-oxygen ratio. The inlet gas composition of the conversion system is complex and contains a large amount of oil and dust. Currently, it is impossible to install an online gas composition monitoring instrument. Therefore, it is impossible to accurately adjust the CO flow rate to be converted according to the inlet raw gas composition, which can easily cause the hydrogen-carbon ratio in the inlet raw gas of methane synthesis to exceed the specification range.

[0018] 3. Since the carbon dioxide in the methane synthesis raw gas is completely removed by the purified low-temperature methanol washing, and under the current process conditions, the carbon dioxide content in the methane synthesis raw gas cannot be adjusted, resulting in an excessively high carbon monoxide content in the methane synthesis raw gas, which can easily lead to carbon deposition of the methane synthesis catalyst. Utility Model Content

[0019] The technical problem to be solved by the utility model is to study a purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis. The purification system is added to the inlet of the methane synthesis system, and the carbon dioxide in the flash gas is used to achieve precise adjustment of the hydrogen-carbon ratio of the raw gas at the inlet of the methane synthesis system, thereby ensuring that the hydrogen content index in the product natural gas meets the requirements.

[0020] The technical solution of the utility model to solve the above technical problems is as follows:

[0021] A purification system for adjusting the hydrogen-carbon ratio of raw gas at the inlet of methane synthesis, comprising an original purification A series pipeline, an original purification B series pipeline, a desulfurization module and a methane flash gas pipeline;

[0022] The original purification A series pipeline includes the purification A series No. 1 flash tank, the purification A series first connecting pipe, the purification A series No. 2 flash tank, the purification A series second connecting pipe and the purification A series flash gas compressor, which are connected in sequence; the original purification B series pipeline includes the purification B series No. 1 flash tank, the purification B series first connecting pipe, the purification B series No. 2 flash tank, the purification B series second connecting pipe and the purification B series flash gas compressor, which are connected in sequence;

[0023] The first connecting pipe of the purification series A is provided with an isolation valve for the purification series A flash tank. The first connecting pipe of the purification series A is connected to the end of the first connecting pipe of the purification series A near the No. 1 flash tank of the purification series A, and is connected to the third connecting pipe of the purification series A which is connected to the first connecting pipe of the purification series B. The third connecting pipe of the purification series A is provided with a connecting valve for the No. 1 flash tank of the purification series A / B.

[0024] The first connecting pipe of the purification B series is provided with an isolation valve for the purification B series flash tank. The first connecting pipe of the purification B series is close to the third connecting pipe of the purification A series and is connected to the third connecting pipe of the purification B series, which is connected to the flash gas compressor of the purification B series. The third connecting pipe of the purification B series is provided with a flash gas recovery valve for the No. 1 flash tank of the purification A / B series.

[0025] The outlet of the purified A series flash gas compressor is connected to the external purified A series flash gas recycling pipeline;

[0026] The outlet of the Purification B series flash gas compressor is divided into two routes, one of which is connected to the Purification B series flash gas return pipeline, and the other is connected to the desulfurization module;

[0027] The gas outlet of the desulfurization module is provided with a methane flash gas pipeline connected to the external methane synthesis raw gas pipeline.

[0028] The beneficial effects of the present invention are as follows: Since the methane synthesis catalyst is nickel-based, any form of sulfur can permanently poison the catalyst. Therefore, flash steam with a relatively low sulfur content must be thoroughly desulfurized before being added to the methane synthesis feed gas inlet pipeline. Laboratory analysis shows that the flash steam produced by flash tank No. 1 contains 70% carbon dioxide and approximately 6 ppm sulfur, with the remainder being effective components of methane, hydrogen, and carbon monoxide. The flash steam produced by flash tank No. 2 also contains 70% carbon dioxide and approximately 1500 ppm sulfur, significantly higher than that of flash tank No. 1. Therefore, the present invention uses the flash steam produced by flash tank No. 1 as the source of carbon dioxide added to the methane synthesis feed gas inlet.

[0029] In order to make full use of the existing equipment, the purification A series flash tank isolation valve 141 can isolate the flash gas of the original purification A series No. 1 flash tank from the flash gas of the purification A series No. 2 flash tank. The purification A series third connecting pipe and the purification A / B series No. 1 flash tank connecting valve can lead the flash gas of the purification A series No. 1 flash tank to the purification B series, and combine it with the flash gas of the purification B series No. 1 flash tank for utilization; the purification B series third connecting pipe and the purification A / B series No. 1 flash tank flash gas recovery valve can collect the flash gas of the two tanks to the purification B series flash gas compressor. After pressurization by the purification B series flash gas compressor, it is sent out in two ways, one way is connected to the purification B series flash gas return pipeline, and the other way is connected to the desulfurization module. After desulfurization treatment, it is sent to the methane synthesis inlet to adjust the hydrogen-carbon ratio.

[0030] By adding a purification system at the methane synthesis inlet and utilizing the carbon dioxide in the flash gas, precise adjustment of the hydrogen-carbon ratio of the methane synthesis inlet feed gas is achieved, ensuring that the hydrogen content index in the product natural gas meets the requirements; by adding a purification system at the methane synthesis inlet, when the production system is running at low load, the air intake flow of the conversion furnace of the conversion device is effectively maintained, the temperature of the conversion furnace is stabilized, and the normal operation of the conversion device is ensured; by adding a purification system at the methane synthesis inlet, under the condition that the hydrogen-carbon ratio of the methane synthesis inlet feed gas is the same, the carbon dioxide ratio in the methane synthesis inlet feed gas can be increased, thereby reducing the risk of carbon deposition of the methane synthesis catalyst and extending the service life of the methane synthesis catalyst.

[0031] On the basis of the above technical solution, the present invention can also be improved as follows.

[0032] Furthermore, the purified B series flash steam recycling pipeline is sequentially provided with a purified B series flash steam pipeline check valve and a purified B series flash steam pipeline isolation valve along the outlet extension direction.

[0033] Furthermore, the second connecting pipe of the purification B series is connected to the fourth connecting pipe of the purification B series, which is connected to the second connecting pipe of the purification A series. The fourth connecting pipe of the purification B series is provided with a purification A / B series No. 2 flash tank connecting valve; the second connecting pipe of the purification B series is provided with a purification B series flash gas recycling isolation valve near the end of the purification B series flash gas compressor.

[0034] Furthermore, the desulfurization module includes a first desulfurization pipeline, a desulfurization tank and a second desulfurization pipeline which are connected in sequence, and an online detector for gas at the outlet of the desulfurization tank is provided on the second desulfurization pipeline.

[0035] Furthermore, the methane flash gas pipeline includes a purified A series methane flash gas pipeline and a purified B series methane flash gas pipeline; the outlet end of the second desulfurization pipeline is respectively connected to the purified A series methane flash gas pipeline and the purified B series methane flash gas pipeline; the external methane synthesis raw gas pipeline includes a methane synthesis A series raw gas pipeline and a methane synthesis B series raw gas pipeline.

[0036] Furthermore, a methane synthesis A series flash gas flowmeter and a methane synthesis A series supplementary flash gas pipeline regulating valve are provided on the purified A series methane flash gas pipeline; the gas outlet of the purified A series methane flash gas pipeline is connected to the methane synthesis A series raw gas pipeline; a methane synthesis A series raw gas inlet component online analyzer and a methane synthesis A series raw gas flowmeter are sequentially provided on the methane synthesis A series raw gas pipeline along the air inlet direction.

[0037] Furthermore, a methane synthesis B series flash gas flowmeter and a methane synthesis B series supplementary flash gas pipeline regulating valve are provided on the purified B series methane flash gas pipeline; the gas outlet of the purified B series methane flash gas pipeline is connected to the methane synthesis B series raw gas pipeline; a methane synthesis B series raw gas inlet component online analyzer and a methane synthesis A series raw gas flowmeter are sequentially provided on the methane synthesis B series raw gas pipeline along the air inlet direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a pipeline schematic diagram of a purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis according to the present invention;

[0039] Figure 2 This is a schematic diagram of the purification A series pipeline of a purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis in the present invention;

[0040] Figure 3 This is a schematic diagram of the purification B series pipeline of a purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis in the utility model;

[0041] Figure 4 This is a schematic diagram of the original purification A series pipeline of a purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis in the utility model;

[0042] Figure 5 This is a schematic diagram of the original purification B series pipeline of a purification system for adjusting the hydrogen-carbon ratio of methane synthesis inlet raw gas in the utility model.

[0043] In the accompanying drawings, the components represented by the reference numerals are as follows:

[0044] 1. Original Purification A Series Pipeline; 11. Purification A Series Flash Tank No. 1; 12. Purification A Series Flash Tank No. 2; 13. Purification A Series Flash Gas Compressor; 14. Purification A Series First Connecting Pipe; 141. Purification A Series Flash Tank Isolation Valve; 15. Purification A Series Second Connecting Pipe; 16. Purification A Series Third Connecting Pipe; 161. Purification A / B Series Flash Tank No. 1 Connecting Valve; 2. Original Purification B Series Pipeline; 21. Purification B Series Flash Tank No. 1; 22. Purification B Series Flash Tank No. 2; 23. Purification B Series Flash Gas Compressor; 24. Purification B Series First Connecting Pipe; 241. Purification B Series Flash Tank Isolation Valve; 25. Purification B Series Second Connecting Pipe; 251. Purification B Series Flash Gas Recovery Isolation Valve; 26. Purification B Series Third Connecting Pipe; 261. Purification A / B Series Flash Tank No. 1 Flash Gas Recovery Valve; 27. Purification B Series Fourth Connecting Pipe; 271 , purification A / B series No. 2 flash tank connecting valve; 3. Purification B series flash gas recycling pipeline; 31. Purification B series flash gas pipeline isolation valve; 32. Purification B series flash gas pipeline check valve; 4. Desulfurization module; 41. First desulfurization pipeline; 42. Desulfurization tank; 43. Second desulfurization pipeline; 431. Desulfurization tank outlet gas online detector; 5. Purification A series methane flash gas pipeline; 51. Methane synthesis A series flash gas flow meter; 52. Methane synthesis A series supplementary flash gas pipeline regulating valve; 6. Purification B series methane flash gas pipeline; 61. Methane synthesis B series flash gas flow meter; 62. Methane synthesis B series supplementary flash gas pipeline regulating valve; 71. Methane synthesis A series raw gas inlet component online analyzer; 72. Methane synthesis A series raw gas flow meter; 81. Methane synthesis B series raw gas inlet component online analyzer; 82. Methane synthesis B series raw gas flow meter. DETAILED DESCRIPTION

[0045] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0046] like Figures 1 to 5 As shown, Example 1 of the present invention is a purification system for adjusting the hydrogen-carbon ratio of the raw gas inlet of methane synthesis, comprising an original purification A series pipeline 1, an original purification B series pipeline 2, a desulfurization module 4 and a methane flash gas pipeline;

[0047] The original purification A series pipeline 1 includes the purification A series No. 1 flash tank 11, the purification A series first connecting pipe 14, the purification A series No. 2 flash tank 12, the purification A series second connecting pipe 15 and the purification A series flash gas compressor 13, which are connected in sequence; the original purification B series pipeline 2 includes the purification B series No. 1 flash tank 21, the purification B series first connecting pipe 24, the purification B series No. 2 flash tank 22, the purification B series second connecting pipe 25 and the purification B series flash gas compressor 23, which are connected in sequence;

[0048] The first connecting pipe 14 of the purification series A is provided with a purification series A flash tank isolation valve 141. The first connecting pipe 14 of the purification series A is connected to the end of the purification series A flash tank No. 1 11 near the purification series A third connecting pipe 16 of the purification series A, which is connected to the first connecting pipe 24 of the purification series B. The third connecting pipe 16 of the purification series A is provided with a purification series A / B flash tank No. 1 connecting valve 161.

[0049] The purification B series first connecting pipe 24 is provided with a purification B series flash tank isolation valve 241. The purification B series first connecting pipe 24 is connected to the purification B series third connecting pipe 26 at one end thereof close to the purification A series third connecting pipe 16, which is connected to the purification B series flash gas compressor 23. The purification B series third connecting pipe 26 is provided with a purification A / B series No. 1 flash tank flash gas recovery valve 261.

[0050] The outlet end of the purified A series flash gas compressor 13 is connected to the external purified A series flash gas recycling pipeline;

[0051] The outlet of the purification B series flash gas compressor 23 is divided into two paths, one of which is connected to the purification B series flash gas recycling pipeline 3, and the other is connected to the desulfurization module 4;

[0052] The gas outlet of the desulfurization module 4 is provided with a methane flash gas pipeline connected to an external methane synthesis raw gas pipeline.

[0053] Because the methane synthesis catalyst is nickel-based, any form of sulfur can permanently poison the catalyst. Therefore, flash steam with a relatively low sulfur content is thoroughly desulfurized before being added to the methane synthesis feed gas inlet pipeline. Laboratory analysis shows that the flash steam produced by Flash Tank No. 1 contains 70% carbon dioxide and approximately 6 ppm sulfur, with the remainder being methane, hydrogen, and carbon monoxide. Flash Tank No. 2 also contains 70% carbon dioxide and approximately 1500 ppm sulfur, significantly higher than Flash Tank No. 1. Therefore, this utility model uses flash steam from Flash Tank No. 1 as the source of carbon dioxide for the methane synthesis feed gas inlet.

[0054] In order to make full use of the existing equipment, the purification A series flash tank isolation valve 141 can isolate the flash gas of the original purification A series No. 1 flash tank 11 from the flash gas of the purification A series No. 2 flash tank 12, and the purification A series third connecting pipe 16 and the purification A / B series No. 1 flash tank connecting valve 161 can lead the flash gas of the purification A series No. 1 flash tank 11 to the purification B series, and combine it with the flash gas of the purification B series No. 1 flash tank 21 for utilization; the purification B series third connecting pipe 26 and the purification A / B series No. 1 flash tank flash gas recovery valve 261 can collect the flash gas of the two tanks to the purification B series flash gas compressor 23, and after being pressurized by the purification B series flash gas compressor 23, it is sent out in two ways, one way is connected to the purification B series flash gas return pipeline 3, and the other way is connected to the desulfurization module 4. After desulfurization treatment, it is sent to the methane synthesis inlet to adjust the hydrogen-carbon ratio.

[0055] By adding a purification system at the methane synthesis inlet and utilizing the carbon dioxide in the flash gas, precise adjustment of the hydrogen-carbon ratio of the methane synthesis inlet feed gas is achieved, ensuring that the hydrogen content index in the product natural gas meets the requirements; by adding a purification system at the methane synthesis inlet, when the production system is running at low load, the air intake flow of the conversion furnace of the conversion device is effectively maintained, the temperature of the conversion furnace is stabilized, and the normal operation of the conversion device is ensured; by adding a purification system at the methane synthesis inlet, under the condition that the hydrogen-carbon ratio of the methane synthesis inlet feed gas is the same, the carbon dioxide ratio in the methane synthesis inlet feed gas can be increased, thereby reducing the risk of carbon deposition of the methane synthesis catalyst and extending the service life of the methane synthesis catalyst.

[0056] Example 2 of the present invention provides a purification system for adjusting the hydrogen-to-carbon ratio of the feed gas at the inlet of methane synthesis. Based on Example 1, the purification B series flash gas recycling pipeline 3 is provided with a purification B series flash gas pipeline check valve 32 and a purification B series flash gas pipeline isolation valve 31, sequentially along the outlet extension direction. If the methane flash gas pipeline flow rate is less than the total flash gas flow rate of the purification A / B series flash tank No. 1, the excess flash gas is transported to the purification B series flash gas recycling pipeline for recycling through the purification B series flash gas pipeline isolation valve 31 and the purification B series original flash gas pipeline check valve. During normal operation, the purification B series flash gas pipeline isolation valve 31 is fully open. When the amount of supplementary flash gas added to the methane synthesis inlet exceeds the total flash gas flow rate of the purification A / B series flash tank No. 1, the conversion device is promptly contacted to reduce the amount of carbon monoxide converted. At this time, the purification B series flash gas pipeline check valve 32 prevents the feed gas in the purification B series feed gas inlet pipeline from flowing back into the supplementary flash gas pipeline.

[0057] Example 3 of the present utility model is a purification system for adjusting the hydrogen-carbon ratio of the raw gas at the methane synthesis inlet. On the basis of Example 1 or 2, the second connecting pipe 25 of the purification B series is connected to the fourth connecting pipe 27 of the purification B series, which is connected to the second connecting pipe 15 of the purification A series. The fourth connecting pipe 27 of the purification B series is provided with a purification A / B series No. 2 flash tank connecting valve 271; the second connecting pipe 25 of the purification B series is provided with a purification B series flash gas recycling isolation valve 251 near the end of the purification B series flash gas compressor 23. The flash gas recycling isolation valve 251 of the purification B series isolates the flash gas of the purification B series No. 2 flash tank 22 from the purification B series flash gas compressor 23. The flash tank isolation valve 241 of the purification B series isolates the flash gas of the purification B series No. 1 flash tank 21 from the flash gas of the purification B series No. 2 flash tank 22. The fourth connecting pipe of the purification B series and the purification A / B series No. 2 flash tank connecting valve 271 can connect the purification A / B series No. 2 flash tank and collect the flash gas of the two tanks to the purification A series flash gas compressor 13. The gas volume is 17400Nm 3 / h, without exceeding the load of the flash gas compressor, the flash gas from the purified A / B series No. 2 flash tank is pressurized by the purified A series flash gas compressor 13 and then sent to the purified A series flash gas return pipeline for recycling.

[0058] Example 4 of the present invention is a purification system for adjusting the hydrogen-to-carbon ratio of the raw gas at the inlet of methane synthesis. Based on Example 1, the desulfurization module 4 includes a first desulfurization pipeline 41, a desulfurization tank 42, and a second desulfurization pipeline 43 connected in sequence. The second desulfurization pipeline 43 is provided with an online gas detector 431 for the desulfurization tank outlet. In order to remove sulfur from the flash gas in the No. 1 flash tank of the A / B series, a new desulfurization tank 42 is added. An effective desulfurizer (generally zinc oxide) is loaded into the desulfurization tank 42. The flash gas at the outlet of the purified B series flash gas compressor 23 enters the desulfurization tank 42 from top to bottom for desulfurization treatment. In order to monitor the composition of this flash gas, an online gas detector 431 for the desulfurization tank outlet is installed to detect the gas composition and sulfur content of the flash gas.

[0059] Example 5 of the present invention is a purification system for adjusting the hydrogen-carbon ratio of the methane synthesis inlet raw gas. On the basis of Example 4, the methane flash gas pipeline includes a purification A series methane flash gas pipeline 5 and a purification B series methane flash gas pipeline 6; the outlet end of the second desulfurization pipeline 43 is respectively connected to the purification A series methane flash gas pipeline 5 and the purification B series methane flash gas pipeline 6; the external methane synthesis raw gas pipeline includes a methane synthesis A series raw gas pipeline and a methane synthesis B series raw gas pipeline.

[0060] Example 6 of the present utility model is a purification system for adjusting the hydrogen-carbon ratio of the methane synthesis inlet raw gas. On the basis of Example 5, a methane synthesis A series flash gas flowmeter 51 and a methane synthesis A series supplementary flash gas pipeline regulating valve 52 are provided on the purification A series methane flash gas pipeline 5; the gas outlet of the purification A series methane flash gas pipeline 5 is connected to the methane synthesis A series raw gas pipeline; a methane synthesis A series raw gas inlet component online analyzer 71 and a methane synthesis A series raw gas flowmeter 72 are sequentially provided on the methane synthesis A series raw gas pipeline along the air inlet direction.

[0061] Example 7 of the present invention provides a purification system for adjusting the hydrogen-to-carbon ratio of methane synthesis inlet feed gas, based on Example 5. A methane synthesis B-series flash gas flowmeter 61 and a methane synthesis B-series supplementary flash gas pipeline regulating valve 62 are provided on the purified B-series methane flash gas pipeline 6; the gas outlet of the purified B-series methane flash gas pipeline 6 is connected to the methane synthesis B-series feed gas pipeline; and a methane synthesis B-series feed gas inlet component online analyzer 81 and a methane synthesis A-series feed gas flowmeter 82 are provided on the methane synthesis B-series feed gas pipeline in sequence along the gas inlet direction.

[0062] The methane synthesis A series flash steam flowmeter 51 and the methane synthesis B series flash steam flowmeter 61 can monitor the methane synthesis A / B series supplementary flash steam flow rate; the methane synthesis A series supplementary flash steam pipeline regulating valve 52 and the methane synthesis B series supplementary flash steam pipeline regulating valve 62 can control the methane synthesis supplementary flash steam flow rate; when the desulfurization tank outlet gas online detector 431 detects that the sulfur content is greater than 10ppb, the methane synthesis A series supplementary flash steam pipeline regulating valve 52 and the methane synthesis B series supplementary flash steam pipeline regulating valve 62 are interlocked and closed.

[0063] In specific implementation, taking the methane synthesis A series as an example, during the flash gas addition process, the methane synthesis A series raw gas inlet component online analyzer 71 will detect the raw gas components in real time. Assuming that the hydrogen proportion is H1, the carbon monoxide proportion is C1, and the carbon dioxide proportion is X1, the flash gas flow rate measured by the methane synthesis A series flash gas flowmeter 51 is F1; the desulfurization tank outlet gas online detector 431 measures the hydrogen proportion is H2, the carbon monoxide proportion is C2, and the carbon dioxide proportion is X2. Assuming that the methane synthesis A series needs to add flash gas flow F2, the methane synthesis inlet raw gas hydrogen-carbon ratio M is adjusted to 3.0, and the following calculation formula can be obtained:

[0064]

[0065] The flash steam flow rate F2 required for methane synthesis series A can be calculated by the following formula:

[0066]

[0067] The flow control signal of the flash gas flow F2 required for the methane synthesis A series is transmitted to the flash gas pipeline regulating valve 52 of the methane synthesis A series to accurately adjust the flash gas flow, so as to stabilize the hydrogen-carbon ratio of the raw gas at the methane synthesis inlet.

[0068] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A purification system for adjusting the hydrogen-carbon ratio of methane synthesis inlet feed gas, characterized in that: It includes the original purified A series pipeline (1), the original purified B series pipeline (2), the desulfurization module (4) and the methane flash steam pipeline; The original purification A series pipeline (1) includes a purification A series No. 1 flash tank (11), a purification A series first connecting pipe (14), a purification A series No. 2 flash tank (12), a purification A series second connecting pipe (15), and a purification A series flash gas compressor (13) that are connected in sequence; the original purification B series pipeline (2) includes a purification B series No. 1 flash tank (21), a purification B series first connecting pipe (24), a purification B series No. 2 flash tank (22), a purification B series second connecting pipe (25), and a purification B series flash gas compressor (23) that are connected in sequence; The purification A series first connecting pipe (14) is provided with a purification A series flash tank isolation valve (141); the purification A series first connecting pipe (14) is connected to a purification A series third connecting pipe (16) at one end close to the purification A series No. 1 flash tank (11) and connected to the purification B series first connecting pipe (24); the purification A series third connecting pipe (16) is provided with a purification A / B series No. 1 flash tank connecting valve (161); The purification B series first connecting pipe (24) is provided with a purification B series flash tank isolation valve (241); the purification B series first connecting pipe (24) is adjacent to one end of the purification A series third connecting pipe (16) and is connected to the purification B series third connecting pipe (26) in communication with the purification B series flash gas compressor (23); the purification B series third connecting pipe (26) is provided with a purification A / B series No. 1 flash tank flash gas recovery valve (261); The gas outlet of the purified A series flash gas compressor (13) is connected to an external purified A series flash gas recycling pipeline; The outlet of the purified B series flash gas compressor (23) is divided into two paths, one path is connected to the purified B series flash gas recycling pipeline (3), and the other path is connected to the desulfurization module (4); The gas outlet end of the desulfurization module (4) is provided with the methane flash gas pipeline which is in communication with the external methane synthesis raw gas pipeline.

2. A purification system for adjusting the hydrogen-carbon ratio of methane synthesis inlet feed gas according to claim 1, characterized in that: The purified B series flash steam recycling pipeline (3) is provided with a purified B series flash steam pipeline check valve (32) and a purified B series flash steam pipeline isolation valve (31).

3. A purification system for adjusting the hydrogen-carbon ratio of methane synthesis inlet feed gas according to claim 1, characterized in that: The purification B series second connecting pipe (25) is connected to the purification B series fourth connecting pipe (27) which is in communication with the purification A series second connecting pipe (15), and the purification B series fourth connecting pipe (27) is provided with a purification A / B series No. 2 flash tank connecting valve (271); and one end of the purification B series second connecting pipe (25) is provided with a purification B series flash gas recycling isolation valve (251).

4. A purification system for adjusting the hydrogen-carbon ratio of methane synthesis inlet feed gas according to claim 1, characterized in that: The desulfurization module (4) comprises a first desulfurization pipeline (41), a desulfurization tank (42) and a second desulfurization pipeline (43) which are connected in sequence, and the second desulfurization pipeline (43) is provided with a desulfurization tank outlet gas online detector (431).

5. A purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis according to claim 4, characterized in that: The methane flash gas pipeline includes a purified A series methane flash gas pipeline (5) and a purified B series methane flash gas pipeline (6); the outlet end of the second desulfurization pipeline (43) is connected to the purified A series methane flash gas pipeline (5) and the purified B series methane flash gas pipeline (6); the external methane synthesis raw gas pipeline includes a methane synthesis A series raw gas pipeline and a methane synthesis B series raw gas pipeline.

6. A purification system for adjusting the hydrogen-carbon ratio of methane synthesis inlet feed gas according to claim 5, characterized in that: The purified A-series methane flash gas pipeline (5) is provided with a methane synthesis A-series flash gas flowmeter (51) and a methane synthesis A-series supplementary flash gas pipeline regulating valve (52); the gas outlet of the purified A-series methane flash gas pipeline (5) is connected to the methane synthesis A-series raw gas pipeline; and the methane synthesis A-series raw gas pipeline is provided with a methane synthesis A-series raw gas inlet component online analyzer (71) and a methane synthesis A-series raw gas flowmeter (72) in sequence along the gas inlet direction.

7. A purification system for adjusting the hydrogen-carbon ratio of methane synthesis inlet feed gas according to claim 5, characterized in that: The purified B series methane flash gas pipeline (6) is provided with a methane synthesis B series flash gas flowmeter (61) and a methane synthesis B series supplementary flash gas pipeline regulating valve (62); the gas outlet of the purified B series methane flash gas pipeline (6) is connected to the methane synthesis B series raw gas pipeline; and the methane synthesis B series raw gas pipeline is provided with a methane synthesis B series raw gas inlet component online analyzer (81) and a methane synthesis A series raw gas flowmeter (82) in sequence along the gas inlet direction.

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