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

Abstract

The invention relates to a purification system for adjusting the hydrogen-carbon ratio of feed gas at a methane synthesis inlet, a purification B series flash tank isolation 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 invention relates to the technical field of methane synthesis, and in particular to a purification system for adjusting the hydrogen-carbon ratio of raw material gas at an inlet of methane synthesis. Background Art

[0002] In the field of coal-to-natural gas technology, the main processes of the whole plant can be divided into gasification, transformation, purification and methanation. The gasification process provides raw gas, and the hydrogen-carbon ratio in the methane synthesis raw gas is adjusted to three to one as much as possible through the transformation process. The calculation formula of the hydrogen-carbon ratio M is 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, the hydrogen-carbon ratio of three to one is a component ratio that fully meets the requirements of the two methanation reactions, which can maximize 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 conversion process, part of the raw gas needs to be passed into the conversion furnace equipped with a conversion 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 conversion device is adjusted to three to one. The conversion 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 at the outlet of the conversion system contains components such as light hydrocarbons, carbon dioxide and sulfur, which need to be processed by the purification system. The purification system is divided into two series, A / B, which utilize the light hydrocarbons in the raw gas and directly remove carbon dioxide and hydrogen sulfide. The main working principle of the purification system is low-temperature methanol washing, which uses low-temperature methanol to countercurrently contact with the process gas in the methanol washing tower to absorb the light hydrocarbons, hydrogen sulfide and carbon dioxide components in it, so as to purify the raw gas. In the methanol washing tower, the raw gas enters from the bottom and the low-temperature methanol enters from the top. According to the different components to be removed, it is divided from bottom to top into pre-washing section, desulfurization section, and decarbonization (carbon dioxide) section. The carbon-rich methanol from the lower section of the methanol scrubber decarbonization section enters the No. 1 flash tank, where some of the gas components absorbed by the methanol are flashed out and recovered. The carbon dioxide in this flash steam accounts for 70%, the sulfur accounts for about 6ppm, and the rest are mainly methane, hydrogen and carbon monoxide; the sulfur-rich methanol from the desulfurization section of the methanol scrubber enters the No. 2 flash tank, where some of the gas components absorbed by the methanol are flashed out and recovered. The carbon dioxide in this flash steam accounts for 70%, the sulfur accounts for about 1500ppm, and the rest are mainly methane, hydrogen and carbon monoxide. The flash gas from the No. 1 flash tank merges with the flash gas from the No. 2 flash tank and enters the flash gas compressor for pressurization, and finally this part of the recovered gas is sent to the raw gas inlet of the purification system for recycling.

[0007] After purification, the raw gas is sent to the methane synthesis system. The methane synthesis process adopts high carbon monoxide synthesis methane technology. There are 4 reactors in the process, each loaded with nickel-based catalysts, and the methane synthesis reaction is carried out in each reactor in turn. The main methanogenic reaction equation occurring in the furnace 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] Among them, the carbon deposition reaction of CO can generate elemental carbon and attach to the surface of the catalyst, covering the active sites in the catalyst that play a catalytic role, reducing the activity of the catalyst; in addition, since the catalyst has a porous structure, the elemental carbon generated by the reaction accumulates to a certain extent, which can break the micropores in the catalyst, thereby causing the catalyst to break, resulting in poor permeability of the catalyst bed, affecting the air intake of the reactor. During the maintenance of the methane synthesis unit in 2020, the results of sampling and analysis of the catalysts in the No. 1 and No. 2 reactors showed that the carbon content in different samples was as high as 48.2%, and the catalyst showed obvious carbon deposition. It can be seen that catalyst carbon deposition has become a key factor restricting the normal operation of the methane synthesis system.

[0014] Since CO2 has a stable structure and will not react to 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 working 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 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, causing the hydrogen-carbon ratio in the raw gas to be too high, 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 component 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 index 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 excessively high carbon monoxide content in the methane synthesis raw gas, which can easily lead to carbon deposition of the methane synthesis catalyst. Summary of the invention

[0019] The technical problem to be solved by the present invention 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 at 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 present invention 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 steam pipeline;

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

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

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

[0025] The outlet end 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 steam compressor is divided into two routes, one of which is connected to the Purification B series flash steam recycling pipeline, and the other is connected to the desulfurization module;

[0027] A methane flash gas pipeline connected to an external methane synthesis raw gas pipeline is provided at the gas outlet of the desulfurization module.

[0028] The beneficial effect of the present invention is that since the methane synthesis catalyst is a nickel-based catalyst, any form of sulfur can cause permanent poisoning of the catalyst, so it is necessary to quote flash gas with a relatively low sulfur content and add it to the methane synthesis raw gas inlet pipeline after thorough desulfurization. According to the laboratory analysis, the proportion of carbon dioxide in the flash gas produced by the No. 1 flash tank is 70%, the proportion of sulfur is about 6ppm, and the rest are effective components of methane, hydrogen, and carbon monoxide; the proportion of carbon dioxide in the flash gas produced by the No. 2 flash tank is also 70%, and the proportion of sulfur is about 1500ppm, which is significantly higher than that of the No. 1 flash tank. Therefore, the present invention uses the flash gas produced by the No. 1 flash tank as the source of carbon dioxide added to the inlet of the methane synthesis raw gas.

[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, which is pressurized by the purification B series flash gas compressor and 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, the 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 can be effectively maintained, the temperature of the conversion furnace can be stabilized, and the normal operation of the conversion device can be 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] Based on the above technical solution, the present invention can also be improved as follows.

[0032] Furthermore, the purified B series flash steam recycling pipeline is provided with a purified B series flash steam pipeline check valve and a purified B series flash steam pipeline isolation valve in sequence 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, and 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 steam recovery isolation valve at one end close to the purification B series flash steam 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 arranged on the second desulfurization pipeline.

[0035] Furthermore, the methane flash steam pipeline includes a purified A series methane flash steam pipeline and a purified B series methane flash steam pipeline; the outlet end of the second desulfurization pipeline is respectively connected to the purified A series methane flash steam pipeline and the purified B series methane flash steam 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 with 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 steam flowmeter and a methane synthesis B series supplementary flash steam pipeline regulating valve are provided on the purified B series methane flash steam pipeline; the gas outlet of the purified B series methane flash steam pipeline is connected with 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 raw gas at the inlet of methane synthesis according to the present invention;

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

[0040] Figure 3 A schematic diagram of a purification B series pipeline of a purification system for adjusting the hydrogen-carbon ratio of raw gas at an inlet of methane synthesis according to the present invention;

[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 according to the present invention;

[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 of the present invention.

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

[0044] 1. Original purification A series pipeline; 11. Purification A series No. 1 flash tank; 12. Purification A series No. 2 flash tank; 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 No. 1 flash tank connecting valve; 2. Original purification B series pipeline; 21. Purification B series No. 1 flash tank; 22. Purification B series No. 2 flash tank; 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 recycling isolation valve; 26. Purification B series third connecting pipe; 261. Purification A / B series No. 1 flash tank 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 steam recycling pipeline; 31, purification B series flash steam pipeline isolation valve; 32, purification B series flash steam 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 steam pipeline; 51, methane synthesis A series flash steam flowmeter; 52, methane synthesis A series supplementary flash steam pipeline regulating valve; 6, purification B series methane flash steam pipeline; 61, methane synthesis B series flash steam flowmeter; 62, methane synthesis B series supplementary flash steam pipeline regulating valve; 71, methane synthesis A series raw gas inlet component online analyzer; 72, methane synthesis A series raw gas flowmeter; 81, methane synthesis B series raw gas inlet component online analyzer; 82, methane synthesis B series raw gas flowmeter. 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 Figure 1 to Figure 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 steam 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 connection pipe 14 of the purification series A is provided with a purification series A flash tank isolation valve 141, and the first connection 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 connection pipe 16 of the purification series A connected with the first connection pipe 24 of the purification series B, and the third connection 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, and 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 connected to the purification B series flash gas compressor 23, and 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 gas outlet of the purified A series flash gas compressor 13 is connected to an external purified A series flash gas recycling pipeline;

[0051] The outlet of the purified B series flash gas compressor 23 is divided into two paths, one of which is connected to the purified 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 which is connected to an external methane synthesis raw gas pipeline.

[0053] Since the methane synthesis catalyst is a nickel-based catalyst, any form of sulfur can cause permanent poisoning of the catalyst, so it is necessary to quote flash gas with a relatively low sulfur content and add it to the methane synthesis raw gas inlet pipeline after thorough desulfurization. According to laboratory analysis, the proportion of carbon dioxide in the flash gas produced by the No. 1 flash tank is 70%, the proportion of sulfur is about 6ppm, and the rest are effective components of methane, hydrogen, and carbon monoxide; the proportion of carbon dioxide in the flash gas produced by the No. 2 flash tank is also 70%, and the proportion of sulfur is about 1500ppm, which is significantly higher than that of the No. 1 flash tank. Therefore, the present invention uses the flash gas produced by the No. 1 flash tank as the source of carbon dioxide added to the inlet of the methane synthesis raw gas.

[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, 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 combined use; 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, and 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, the 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 can be effectively maintained, the temperature of the conversion furnace can be stabilized, and the normal operation of the conversion device can be 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] Embodiment 2 of the present invention is a purification system for adjusting the hydrogen-carbon ratio of raw gas at the inlet of methane synthesis. On the basis of embodiment 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 in sequence along the outlet extension direction. If the methane flash gas pipeline flow is less than the total flash gas flow of the purification A / B series No. 1 flash tank, the excess flash gas is sent to the purification B 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 in a fully open state. When the amount of flash gas added to the inlet of methane synthesis is greater than the total flash gas flow of the purification A / B series No. 1 flash tank, the conversion device is contacted in time to reduce the carbon monoxide conversion amount. At this time, the purification B series flash gas pipeline check valve 32 can prevent the raw gas in the purification B series raw gas inlet pipeline from flowing back to the flash gas supplement pipeline.

[0057] Embodiment 3 of the present invention is a purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis. On the basis of Embodiment 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, and 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 steam recovery isolation valve 251 at one end close to the purification B series flash steam 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] Embodiment 4 of the present invention is a purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis. On the basis of embodiment 1, the desulfurization module 4 includes a first desulfurization pipeline 41, a desulfurization tank 42 and a second desulfurization pipeline 43 which are connected in sequence, and an online detector 431 for gas at the outlet of the desulfurization tank is provided on the second desulfurization pipeline 43. 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, and an effective desulfurizer (generally zinc oxide) is loaded into the desulfurization tank 42, so that 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 detector 431 for gas at the outlet of the desulfurization tank is installed to detect the gas composition and sulfur content of the flash gas.

[0059] Embodiment 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 Embodiment 4, the methane flash steam pipeline includes a purified A series methane flash steam pipeline 5 and a purified B series methane flash steam pipeline 6; the outlet end of the second desulfurization pipeline 43 is respectively connected to the purified A series methane flash steam pipeline 5 and the purified B series methane flash steam 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] Embodiment 6 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 Embodiment 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 purified A series methane flash gas pipeline 5; the gas outlet of the purified 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] Embodiment 7 of the present invention is a purification system for adjusting the hydrogen-carbon ratio of the raw gas inlet of methane synthesis, based on Embodiment 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 raw gas pipeline; and a methane synthesis B series raw gas inlet component online analyzer 81 and a methane synthesis A series raw gas flowmeter 82 are sequentially provided on the methane synthesis B series raw gas pipeline 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; 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; 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 process of adding flash gas, the methane synthesis A series raw gas inlet component online analyzer 71 will detect the raw gas components in real time. Assuming that the proportion of hydrogen is H1, the proportion of carbon monoxide is C1, and the proportion of carbon dioxide 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 proportion of hydrogen to be H2, the proportion of carbon monoxide to be C2, and the proportion of carbon dioxide to be X2. Assuming that the methane synthesis A series needs to add flash gas flow F2, the hydrogen-carbon ratio M of the methane synthesis inlet raw gas 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 steam flow F2 required for the methane synthesis A series is transmitted to the flash steam pipeline regulating valve 52 of the methane synthesis A series to accurately adjust the flash steam flow, so as to stabilize the hydrogen-carbon ratio of the raw gas at the inlet of the methane synthesis.

[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 substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis, 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) comprises 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) which are connected in sequence; the original purification B series pipeline (2) comprises 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) which 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 the purification A series No. 1 flash tank (11) at one end thereof close to the purification A series No. 1 flash tank (11); the purification A series third connecting pipe (16) is 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 connected to a purification B series third connecting pipe (26) in communication with the purification B series flash gas compressor (23) at one end close to the purification A series third connecting pipe (16); 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 end of the purified A series flash gas compressor (13) is connected to an external purified A series flash gas recycling pipeline; The gas outlet of the purified B series flash gas compressor (23) is divided into two paths, one of which is connected to the purified B series flash gas recycling pipeline (3), and the other 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 connected to the external methane synthesis raw gas pipeline.

2. A purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis 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) in sequence along the outlet extension direction.

3. A purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis according to claim 1, characterized in that: The purification B series second connecting pipe (25) is connected to a purification B series fourth connecting pipe (27) which is in communication with the purification A series second connecting pipe (15); the purification B series fourth connecting pipe (27) is provided with a purification A / B series No. 2 flash tank connecting valve (271); and a purification B series flash steam recycling isolation valve (251) is provided at one end of the purification B series second connecting pipe (25) close to the purification B series flash steam compressor (23).

4. A purification system for adjusting the hydrogen-carbon ratio of the raw gas at the inlet of methane synthesis 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 an online detector (431) for gas at the outlet of the desulfurization tank.

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 steam pipeline comprises a purified A series methane flash steam pipeline (5) and a purified B series methane flash steam pipeline (6); the outlet end of the second desulfurization pipeline (43) is respectively connected to the purified A series methane flash steam pipeline (5) and the purified B series methane flash steam pipeline (6); the external methane synthesis raw gas pipeline comprises 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 the raw gas at the inlet of methane synthesis 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 the raw gas at the inlet of methane synthesis 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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