System and method for coal mine gas deoxidization and cracking hydrogen and carbon material

Abstract

This invention relates to the field of coal mine gas resource utilization technology, and particularly to a system and method for coal mine gas deoxygenation and cracking to produce hydrogen and carbon materials. The system includes a gas circulation deoxygenation unit, a high-temperature methane cracking unit for cracking the deoxygenated mixed gas, a safety intelligent monitoring unit for detecting the oxygen content of the mixed gas entering the high-temperature methane cracking unit, an intelligent pulse purging unit for pulse purging the carbon materials produced by methane cracking, and a unit for collecting and processing the carbon materials produced by methane cracking. This invention establishes an integrated technical solution from safe deoxygenation of low-concentration gas to efficient methane cracking, achieving efficient co-production of hydrogen and carbon products. It also effectively avoids problems commonly found in existing reactors, such as easy accumulation of carbon products, easy blockage of flow channels, uneven heat transfer, insufficient gas-liquid contact, insufficient stability in continuous operation, and safety issues in the cracking reaction. It has significant theoretical value and promising engineering applications.

Description

Technical Field

[0001] This invention relates to the field of coal mine gas resource utilization technology, and in particular to a system and method for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials, for use in the research of coal mine gas resource utilization. Background Technology

[0003] Against the backdrop of the "dual-carbon" strategy and the large-scale application of hydrogen energy, green and low-carbon hydrogen production has become a key development direction in the energy sector. Traditional methane-to-hydrogen processes often employ steam reforming, carbon dioxide reforming, and partial oxidation, generating large amounts of CO and CO2 during the reaction. These processes are complex, have high carbon emission intensity, and contradict the goals of low-carbon and clean development. Molten medium catalytic cracking of methane offers significant advantages over traditional methane cracking technologies. It utilizes a molten catalytic medium to promote methane cracking, producing carbon and hydrogen without generating carbon dioxide, aligning with the direction of green hydrogen development. The density difference between carbon and the catalytic medium causes the generated carbon material to automatically float on the surface of the catalytic medium, effectively avoiding carbon buildup and deactivation. Furthermore, it allows for effective separation of the carbon material for further processing into high-value carbon.

[0004] Existing molten medium cracking technology for hydrogen production from methane can achieve efficient methane cracking by utilizing the thermal conductivity of the molten medium and achieve automatic separation of carbon materials by relying on the density difference between carbon and the molten medium, thus alleviating the problem of catalyst deactivation due to carbon buildup. However, the related technologies and devices only focus on the single stage of pure methane cracking and have not paid sufficient attention to the regeneration and utilization of low-concentration methane and other resources emitted in large quantities during industrial production and energy extraction as feedstock gases for cracking.

[0005] Therefore, existing reactors commonly suffer from problems such as easy accumulation of carbon products, easy blockage of flow channels, insufficient gas-liquid contact, insufficient stability of continuous operation, and safety of the pyrolysis reaction when safely deoxygenating and cracking low-concentration methane to produce hydrogen and carbon products. Summary of the Invention

[0006] The purpose of this invention is to provide a system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials, solving the problems of easy accumulation of carbon products, easy blockage of flow channels, insufficient gas-liquid contact, insufficient stability of continuous operation, and safety of cracking reaction in existing reactors.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention provides a system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials, including a gas circulation deoxygenation unit for deoxygenating low-concentration coal mine gas, a high-temperature methane cracking unit for cracking reaction of deoxygenated mixed gas, and a safety intelligent monitoring unit for detecting the oxygen content of the mixed gas entering the high-temperature methane cracking unit. The gas circulation deoxygenation unit includes a gas supply pipe, a first deoxygenation reactor and a second deoxygenation reactor connected in parallel between the gas outlet end of the gas supply pipe and the safety intelligent monitoring unit, and a gas component detection device for detecting the oxygen content of the tail gas of the first deoxygenation reactor and the second deoxygenation reactor. The methane high-temperature cracking unit includes a cracking reactor that is connected to the gas outlet of the first deoxygenation reactor and the second deoxygenation reactor respectively, a first porous ceramic membrane disposed at the bottom of the cracking reactor, a second porous ceramic membrane disposed at the top of the cracking reactor, and a cracking tail gas collection device disposed above and connected to the second porous ceramic membrane. Deoxidizers are respectively provided in the first deoxidation reactor and the second deoxidation reactor; the pyrolysis tail gas collection device is connected in parallel between the gas outlet of the gas transmission pipe and the safety intelligent monitoring unit, and collects hydrogen gas for regenerating the deoxidizers. The safety intelligent monitoring unit includes a gas collection hood connected to the gas path of the pyrolysis reactor and an oxygen concentration alarm installed inside the gas collection hood.

[0008] Furthermore, a first gas supply valve is provided on the gas transmission pipe connecting to the first deoxygenation reactor; a second gas supply valve is provided on the gas transmission pipe connecting to the second deoxygenation reactor. A first detection pipeline regulating valve and a tail gas regulating valve are installed on the connecting pipeline between the gas component detection device and the first deoxygenation reactor, and a second detection pipeline regulating valve and a tail gas regulating valve are installed on the connecting pipeline between the gas component detection device and the second deoxygenation reactor.

[0009] Furthermore, it also includes a gas supply unit; the gas supply unit includes a simulated coal mine gas source and a nitrogen cylinder respectively connected to the gas transmission pipe; a gas cylinder valve and a first mass flow meter are installed on the pipeline between the simulated coal mine gas source and the gas transmission pipe, and a nitrogen cylinder valve and a mass flow meter are installed on the pipeline between the nitrogen cylinder and the gas transmission pipe.

[0010] Furthermore, the first deoxygenation reactor introduces deoxygenated gas into the molten medium inside the pyrolysis reactor through a pipeline equipped with a first deoxygenation outlet valve; the second deoxygenation reactor introduces deoxygenated gas into the molten medium inside the pyrolysis reactor through a pipeline equipped with a second deoxygenation outlet valve; the first deoxygenation reactor and the second deoxygenation reactor serve as backups for each other, and the two alternately operate in the regeneration and deoxygenation process stages.

[0011] Furthermore, a first heating furnace is installed outside the first deoxygenation reactor, and a second heating furnace is installed outside the second deoxygenation reactor; the gas component detection device is an online mass spectrometer.

[0012] Furthermore, a pyrolysis tail gas regulating valve, a deoxygenated tail gas dryer, and a tail gas regulating valve are sequentially installed on the pipeline between the gas inlet of the pyrolysis tail gas collection device and the gas outlet of the pyrolysis reactor; a hydrogen collector is also connected to the pipeline between the tail gas regulating valve and the pyrolysis tail gas collection device through a pipeline with a hydrogen collection valve. The outlet of the pyrolysis tail gas collection device is equipped with a hydrogen output regulating valve that controls the supply of regenerated hydrogen to the first deoxygenation reactor and the second deoxygenation reactor, respectively, so as to realize the function of deoxygenating agent reduction and achieve cyclic deoxygenation.

[0013] Furthermore, a pyrolysis furnace is provided outside the pyrolysis reactor; the first porous ceramic membrane is a micron-sized porous distributor used to convert the incoming methane into microbubbles, increase the gas-liquid contact area, improve the methane conversion rate, enhance the production quality of hydrogen and carbon materials, and strengthen the mass transfer process; the second porous ceramic membrane is a micron-sized ceramic membrane used to initially collect the carbon materials produced by methane pyrolysis, while preventing the overflow of extremely small carbon materials that could cause blockage of the reactor inlet pipe; through intelligent pulse purging, some of the carbon materials collected by the porous ceramic membrane can be purged onto the molten medium in the pyrolysis reactor, and some carbon materials are purged into the filter chamber for easy collection and utilization of carbon materials.

[0014] Furthermore, it also includes a carbon material collection and processing unit for receiving the products of the methane high-temperature cracking unit; the carbon material collection and processing unit includes a filter chamber communicating with the bottom of the cracking reactor, a carbon collection chamber disposed below the filter chamber, a waste liquid collection chamber communicating with the filter chamber and used for collecting the cracking catalyst, and a vacuum pump providing a negative pressure for collecting the carbon collection chamber. A carbon collection chamber valve is provided between the filter chamber and the carbon collection chamber; a waste liquid channel valve is provided between the filter chamber and the waste liquid collection chamber; and a vacuum regulating valve is provided between the negative pressure pipeline of the vacuum pump and the carbon collection chamber.

[0015] Furthermore, it also includes an intelligent pulse purging unit; the intelligent pulse purging unit includes a pulse pipeline disposed in the pyrolysis reactor and located above the second porous ceramic membrane, a purging gas cylinder for supplying gas to the pulse pipeline, a purging gas cylinder regulating valve disposed on the gas supply pipe between the purging gas cylinder and the pulse pipeline, a second mass flow meter, an electromagnetic pulse valve, and a programmable pulse controller for controlling the electromagnetic pulse valve.

[0016] This embodiment provides a method for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials, including the following steps: Includes the following steps: S1. Open the nitrogen cylinder valve, the first gas supply valve, the first detection pipeline regulating valve, and the tail gas regulating valve. Purge the first deoxygenation reactor with nitrogen through the tee and gas supply pipe to replace the internal air of the first deoxygenation reactor. Use the gas component detection device to monitor in real time and completely replace oxygen, carbon dioxide and other gases. S2. Open the gas cylinder valve and the first gas supply valve to introduce simulated low-concentration coal mine gas into the first deoxygenation reactor; open the first detection pipeline regulating valve and the tail gas regulating valve to program the temperature of the first deoxygenation reactor at a rate of 2℃ / min. Monitor the changes in oxygen, methane, and nitrogen signals in the online mass spectrometer in real time. The Fe-Na2S / AC deoxygenator achieves deoxygenation at approximately 356℃, meaning the remaining oxygen detected in the online mass spectrometer reaches its minimum value (oxygen concentration less than 0.1%) and the oxygen signal no longer decreases, indicating deoxygenation. Maintain a constant temperature of 356℃ for approximately 23 hours. During this period, deoxygenated gas feedstock gas can be continuously supplied to the pyrolysis unit for the next deoxygenated gas pyrolysis reaction. After deoxygenation, the deoxygenator turns into a reddish-brown substance, mainly composed of Fe2O3. S3. Based on S2, open the first deoxygenation outlet valve, the pyrolysis tail gas regulating valve, the tail gas regulating valve, and the inlet valve connected to the pyrolysis tail gas collection device. During this process, the oxygen concentration alarm monitors the oxygen situation in real time. If oxygen is detected, it will immediately alarm and shut off the first deoxygenation outlet valve and the pyrolysis tail gas regulating valve to stop the reaction. The reaction proceeds to the methane cracking unit. The molten medium in the cracking reactor consists of Sn-Cu metal and NaBr as catalysts for deoxidized gas cracking, with a Sn:Cu mass ratio of 5:1 and a total mass of 100g. NaBr is added to the cracking reactor at a mass of 40g. The cracking furnace is programmed to increase in temperature at a rate of 10℃ / min. After reaching 650℃, the temperature is increased by 50℃ and then held for 30 minutes. The gas composition is analyzed using a gas chromatograph. The deoxidized mixed gas pipeline is then opened, and the deoxidized gas is introduced into the cracking reactor. When the temperature reaches 950℃, the methane conversion rate is 95%, and the hydrogen selectivity is over 95%. S4. Some of the carbon materials generated by the pyrolysis reaction float on the molten salt due to the density difference, while some tiny particles float and accumulate on the second porous ceramic membrane in the pyrolysis furnace. The purge gas cylinder is opened, and the electromagnetic pulse valve and programmable pulse controller are set to adjust the pulse frequency and time. The electromagnetic pulse tube is used to purge the carbon materials generated by pyrolysis. Some of the carbon materials can be purged onto the molten salt in the pyrolysis reactor, and some of the carbon materials are purged into the filter chamber. S5. The filter chamber is kept heated by heating, and the channel with the waste liquid channel valve is also heated by heating jacket to keep the molten medium (mainly NaBr salt) in a liquid state, facilitating the separation of carbon material from the molten medium. The waste liquid channel valve is opened to filter a trace amount of molten medium waste liquid through filter screen θ into the waste liquid collection chamber. The carbon collection chamber valve is opened to collect carbon material into the carbon collection chamber. When the carbon material in the carbon collection chamber reaches the limit, the carbon collection chamber valve is closed, and the carbon material in the carbon collection chamber is poured out for cleaning and drying. XRD and SEM characterization are performed, and the main component is graphite carbon material. The cleaned carbon collection chamber is reinstalled in the corresponding position, and the vacuum regulating valve is opened to perform vacuum treatment. When collecting carbon material again, the negative pressure in the chamber facilitates the flow and collection of carbon material. When the waste liquid collection chamber is full, the waste liquid can be poured out by closing the waste liquid channel valve, and then the vacuum assembly is used to provide negative pressure to the waste liquid collection chamber. Then, the waste liquid channel valve is opened to continue collecting waste liquid. S6. Close the regulating valve of the first detection pipeline and the inlet valve of the gas component detection device, open the regulating valve of the pyrolysis tail gas, the tail gas regulating valve, and the inlet valve of the pyrolysis tail gas collection device, collect the hydrogen produced by the deoxygenated gas pyrolysis, and the gas collected into the pyrolysis tail gas collection device is a small amount of incompletely pyrolyzed methane and hydrogen produced by pyrolysis. When the gas collection volume reaches the upper limit, open the hydrogen collection valve and use the hydrogen collector to collect it. S7. When the deoxidizer in the first deoxygenation reactor is exhausted, the oxygen signal in the online mass spectrometer begins to rise. When the oxygen concentration is greater than or equal to 0.1%, the oxygen curve reaches the breakthrough state, the deoxygenation reaction ends, the first deoxygenation outlet valve is closed, and the nitrogen cylinder valve, the first gas supply valve, the first detection pipeline regulating valve, and the tail gas regulating valve are opened to purge with nitrogen and replace the air in the reactor. After the replacement is completed, the gas in the tail gas collection device, namely hydrogen and a small amount of methane, is introduced into the first deoxygenation reactor by opening the hydrogen output regulating valve and the pipeline of the first gas supply valve to reduce the deoxidizer Fe-Na2S / AC. When the deoxidizer in the first and second deoxygenation reactors can no longer deoxygenate after the active sites are exhausted, the hydrogen in the hydrogen collector reduces the deoxidizer to restore its deoxygenation function, so that the deoxidizer in the first and second deoxygenation reactors achieves a cyclic deoxygenation effect.

[0017] Compared with the prior art, the beneficial technical effects of the present invention are as follows: This invention develops an integrated technical solution for the efficient co-production of hydrogen and carbon products, from safe deoxygenation of low-concentration methane to efficient methane cracking. It also effectively avoids problems commonly found in existing reactors, such as easy accumulation of carbon products, easy blockage of flow channels, uneven heat transfer, insufficient gas-liquid contact, insufficient stability of continuous operation, and safety of cracking reaction. It has significant theoretical value and promising engineering applications. Attached Figure Description

[0018] The present invention will be further described below with reference to the accompanying drawings. Figure 1 This is a schematic diagram of the system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials according to the present invention; Figure 2 This is a schematic diagram of the pyrolysis reactor design of the present invention.

[0019] Explanation of reference numerals in the attached diagram: 11. Simulated coal mine gas source; 111. Gas cylinder valve; 112. First mass flow meter; 12. Nitrogen cylinder; 121. Nitrogen cylinder valve; 13. Tee; 14. Gas supply pipe; 141. First gas supply valve; 142. Second gas supply valve; 21. First deoxygenation reactor; 211. First heating furnace; 212. First deoxygenation outlet valve; 213. First detection pipeline regulating valve; 22. Second deoxygenation reactor; 221. Second deoxygenation outlet valve; 222. Second detection pipeline regulating valve; 223. Second heating furnace; 23. Gas component detection device; 31. Gas collection hood; 32. Oxygen concentration alarm; 41. Purge gas cylinder; 411. Purge gas cylinder 42. Gas cylinder regulating valve; 43. Second mass flow meter; 44. Electromagnetic pulse valve; 45. Programmable pulse controller; 56. Pulse pipeline; 57. Pyrolysis furnace; 58. Pyrolysis reactor; 59. First porous ceramic membrane; 50. Second porous ceramic membrane; 51. Pyrolysis tail gas collection device; 52. Hydrogen output regulating valve; 53. Tail gas dryer; 54. Hydrogen collector; 55. Hydrogen collection valve; 56. Pyrolysis tail gas regulating valve; 57. Tail gas regulating valve; 68. Filter chamber; 69. Filter chamber heater; 60. Carbon collection chamber; 61. Carbon collection chamber valve; 62. Vacuum pump; 63. Vacuum regulating valve; 64. Waste liquid collection chamber; 65. Waste liquid channel valve. Detailed Implementation

[0020] Example 1 In this embodiment, the deoxidizer is made from coconut shell activated carbon (AC), Fe(NO3)3·9H2O, and Na2S·9H2O, wherein Fe 3+ The mass of Fe is 3% of the mass of AC, and the mass of Na2S is 20% of the mass of AC. Fe is removed by physical grinding. 3+ Na2S is fully loaded onto AC to create a composite deoxidizer (Fe-Na2S / AC).

[0021] The main principle of deoxygenation is: 2Na2S + 4O2 = 2Na2SO4 (1) 3Fe + 2O₂ = Fe₃O₄ (2) 4Fe3O4 + O2 = 6Fe2O3 (3) The simulated low-concentration coal mine methane gas 11 consists of CH4, O2, and N2, with CH4 comprising 30% by volume, O2 comprising 14% by volume, and N2 comprising 56% by volume. A quartz glass tube with an inner diameter of 8 mm is placed in the first deoxidation reactor 21 as the reactor, with a built-in thermocouple. 3g of deoxidizer (Fe-Na2S / AC) is placed in the middle of the quartz glass tube, and the top and bottom are fixed and sealed with quartz wool. The gas inlet is located at the top of the reactor.

[0022] Deoxygenation is performed on one side at a time, starting from the first deoxygenation reactor 21. The deoxygenating agent is the same on both sides of the first deoxygenation reactor 21 and the second deoxygenation reactor 22.

[0023] S1, Reference Figure 1 Open the nitrogen cylinder valve 121, the first gas supply valve 141, the first detection pipeline regulating valve 213, and the tail gas regulating valve 57. Purge the first deoxygenation reactor 21 with nitrogen gas at a rate of 60 mL / min through the three-way valve 13 and the gas supply pipe 14 to replace the internal air of the first deoxygenation reactor 21. Use an online mass spectrometer (gas component detection device 23) to monitor in real time and completely replace gases such as oxygen and carbon dioxide.

[0024] S2. Open the gas cylinder valve 111 and the first gas supply valve 141 to introduce simulated low-concentration coal mine gas into the first deoxygenation reactor 21 at a total flow rate of 20 mL / min. Open the first detection pipeline regulating valve 213 and the tail gas regulating valve 57 to program the temperature of the first deoxygenation reactor 21 at a rate of 2℃ / min. Observe the changes in oxygen, methane, and nitrogen signals in the online mass spectrometer in real time. The Fe-Na2S / AC deoxygenator achieves the deoxygenation effect at approximately 356℃, that is, the remaining oxygen detected in the online mass spectrometer reaches the minimum value (oxygen concentration less than 0.1%) and the oxygen signal no longer decreases, indicating that the deoxygenation state has been reached. Maintain a constant temperature of 356℃ for approximately 23 hours. During this period, deoxygenated gas feedstock gas can be continuously supplied to the pyrolysis unit for the next deoxygenated gas pyrolysis reaction. After deoxygenation, the deoxygenator turns into an iron-red substance, the main component of which is Fe2O3.

[0025] S3, based on S2, open the first deoxygenation outlet valve 212, the pyrolysis tail gas regulating valve 56, the tail gas regulating valve 57, and the inlet valve connected to the pyrolysis tail gas collection device 54; during this process, the oxygen concentration alarm 32 monitors the oxygen status in real time, and if oxygen is detected, it will immediately alarm and shut off the first deoxygenation outlet valve 212 and the pyrolysis tail gas regulating valve 56 to stop the reaction.

[0026] The reaction proceeds to the methane cracking unit, such as... Figure 2As shown, the molten medium in the pyrolysis reactor 52 is Sn-Cu metal and NaBr as catalysts for deoxygenated gas pyrolysis, with a Sn:Cu mass ratio of 5:1 and a total mass of 100g, and NaBr mass of 40g, which are filled into the pyrolysis reactor 52. The pyrolysis reactor 52 adopts a U-shaped design and is made of quartz glass tube, with the following lengths: U1 section 180mm, U2 section 160mm, U3 section 240mm, U4 section 45mm, U5 section 120mm, U6 section 180mm, and U7 section 270mm. The first porous ceramic membrane 521 is a porous distributor with a pore size of 50μm, which converts the incoming deoxygenated gas into microbubbles, increases the gas-liquid contact area, improves the methane conversion rate, enhances the production quality of hydrogen and carbon materials, and strengthens the mass transfer process. The pyrolysis furnace 51 is programmed to increase in temperature at a rate of 10°C / min. After the temperature reaches 650°C, it is kept at a constant temperature for 30 minutes after each 50°C increase. The gas composition is analyzed by gas chromatography. The deoxygenated mixed gas pipeline is opened, and the deoxygenated gas is introduced into the pyrolysis reactor 52. When the temperature reaches 950°C, the methane conversion rate is 95%, and the hydrogen selectivity is over 95%.

[0027] S4. Some of the carbon material generated by the pyrolysis reaction floats on the molten salt due to the density difference, while some tiny particles float and accumulate on the second porous ceramic membrane 53 in the pyrolysis furnace. The purge gas bottle is opened, and the electromagnetic pulse valve 43 and the programmable pulse controller 44 are set to adjust the pulse frequency and time. The electromagnetic pulse tube 45 is used to purge the carbon material generated by pyrolysis. Some of the carbon material can be purged onto the molten salt in the pyrolysis reactor 52, and some of the carbon material is purged into the filter chamber 61.

[0028] S5. The filter chamber 61 is kept in a heated state by the filter chamber heating 611. In addition, the channel with waste liquid channel valve 641 is heated by the heating jacket, so that the molten medium (mainly NaBr salt) is kept in a liquid state, which facilitates the separation of carbon materials from the molten medium. The waste liquid channel valve is opened to filter a small amount of molten medium waste liquid through the filter screen θ into the waste liquid collection chamber 64. Open the carbon collection chamber valve 621 to collect carbon material into the carbon collection chamber 62. When the carbon material in the carbon collection chamber 62 reaches the limit, close the carbon collection chamber valve 621, pour out the carbon material in the carbon collection chamber 62 for cleaning and drying, and perform XRD and SEM characterization. The main component is graphite carbon material. Reinstall the cleaned carbon collection chamber 62 in the corresponding position, open the vacuum regulating valve 631, and perform vacuum treatment. When collecting carbon material again, the negative pressure in the chamber can facilitate the flow and collection of carbon material. When the waste liquid collection chamber 64 is full of waste liquid, the waste liquid can be poured out by closing the waste liquid channel valve 641, and then the vacuum assembly can be used to provide negative pressure to the waste liquid collection chamber 64. Then, the waste liquid can be collected again by opening the waste liquid channel valve 641.

[0029] S6. Close the inlet valve of the first detection pipeline regulating valve 213 and the gas component detection device 23, and open the inlet valve of the pyrolysis tail gas regulating valve 56, the tail gas regulating valve 57, and the pyrolysis tail gas collection device 54 to collect the hydrogen produced by the deoxygenated gas pyrolysis. The gas collected in the pyrolysis tail gas collection device 54 is a small amount of incompletely pyrolyzed methane and hydrogen produced by pyrolysis. When the gas collection volume reaches the upper limit, open the hydrogen collection valve 551 and use the hydrogen collector 55 to collect it.

[0030] S7. When the deoxidizer in the first deoxygenation reactor 21 is exhausted, the oxygen signal in the online mass spectrometer begins to rise. When the oxygen concentration is greater than or equal to 0.1%, the oxygen curve reaches the breakthrough state, the deoxygenation reaction ends, the first deoxygenation outlet valve 212 is closed, and the nitrogen cylinder valve 121, the first gas supply valve 141, the first detection pipeline regulating valve 213, and the tail gas regulating valve 57 are opened to purge with nitrogen and replace the air in the reactor. After the replacement is completed, the gas in the tail gas collection device 54, namely hydrogen and a small amount of methane, is introduced into the first deoxygenation reactor 21 by opening the pipeline of the hydrogen output regulating valve 541 and the first gas supply valve 141 to reduce the deoxidizer Fe-Na2S / AC. When the deoxidizer in the first deoxygenation reactor 21 and the second deoxygenation reactor 22 can no longer deoxygenate after the active sites are exhausted, the hydrogen in the hydrogen collector 54 reduces the deoxidizer to restore its deoxygenation function, so that the deoxidizer in the first deoxygenation reactor 21 and the second deoxygenation reactor 22 achieves a cyclic deoxygenation effect.

[0031] The main principle of the reaction is: Fe2O3 + 3H2 = 2Fe + 3H2O (4) Fe3O4+ 4H2= 3Fe + 4H2O (5) Na2SO4+ 4H2= Na2S + 4H2O (6) The first heating furnace 211 is turned on and programmed to heat at a rate of 10℃ / min. At a reduction temperature of 650℃ and a total gas flow rate of 40mL / min, the reduction time is approximately 120 minutes. If a leak occurs in the pyrolysis unit and oxygen is generated, the oxygen concentration alarm 32 will sound an alarm, closing the first deoxygenation outlet valve 212 and the pyrolysis tail gas regulating valve 56 to cut off the pyrolysis reaction and prevent an explosion. Changes in hydrogen and methane gases are monitored using an online mass spectrometer. Reduction ends when the hydrogen concentration stabilizes at the initial inlet level and the methane concentration remains stable for more than 30 minutes. The second deoxygenation reactor 22 is started in the same manner to deoxygenate and pyrolyze low-concentration coal mine gas, achieving uninterrupted supply of deoxygenated gas from both sides, providing raw material gas for pyrolysis, and forming an integrated reaction device with low-concentration gas circulation deoxygenation—high-temperature pyrolysis of deoxygenated gas—automatic collection of carbon materials—effective utilization of hydrogen.

[0032] Example 2 like Figures 1-2 As shown, based on Example 1, the structure, parameters and connection relationships of this example are consistent with those of Example 1, with only the parameters of the deoxidizer and the molten medium material changing.

[0033] In this embodiment, the deoxidizer is made from coconut shell activated carbon (AC), Fe(NO3)3·9H2O, and Na2S·9H2O, wherein Fe 3+ The mass of Fe is 1% of the mass of AC, and the mass of Na2S is 20% of the mass of AC. Fe is removed by physical grinding. 3+ Na2S is fully loaded onto AC to create a composite deoxidizer (Fe-Na2S / AC).

[0034] First, deoxygenation is carried out on one side of the second deoxygenation reactor 22. The deoxygenating agent is the same on the first deoxygenation reactor 21 and the second deoxygenation reactor 22. After the deoxygenation on the second deoxygenation reactor 22 is completed, the deoxygenation on the first deoxygenation reactor 21 is carried out to achieve a continuous supply of deoxygenated gas.

[0035] like Figure 1 As shown, open nitrogen cylinder valve 121, second gas supply valve 142, second detection pipeline regulating valve 222, and tail gas regulating valve 57 to purge the second deoxygenation reactor 22 with nitrogen gas at a rate of 60 mL / min to replace the internal air. Monitor the process in real time using an online mass spectrometer. After the oxygen, carbon dioxide, and other gases have been completely replaced, open gas cylinder valve 111 and second gas supply valve 143 to purge the second deoxygenation reactor 22 with simulated low-concentration coal mine methane gas at a total flow rate of 20 mL / min. Open the second gas supply valve 142, the second detection pipeline regulating valve 222, the tail gas regulating valve 57, and the inlet valve of the gas component detection device 23. The second deoxygenation reactor 22 is programmed to heat up at a rate of 2℃ / min. The changes in the concentrations of oxygen, methane, and nitrogen in the online mass spectrometer are observed in real time. The Fe-Na2S / AC deoxygenating agent achieves the deoxygenation effect at about 363℃, that is, oxygen cannot be detected in the online mass spectrometer. Maintain a constant temperature of 363℃. The deoxygenation duration is about 23.5 hours. During this period, deoxygenated gas feedstock gas can be continuously supplied to the pyrolysis unit for the next deoxygenated gas pyrolysis reaction.

[0036] Open the second deoxygenation outlet valve 221, the pyrolysis tail gas regulating valve 56, the tail gas regulating valve 57, and the inlet valve of the pyrolysis tail gas collection device 54. The oxygen concentration alarm 32 monitors the oxygen status in real time. If oxygen is detected, it will immediately alarm and shut off the second deoxygenation outlet valve 221 and the pyrolysis tail gas regulating valve 56 to stop the reaction.

[0037] The reaction proceeds to the methane cracking unit. The molten medium in the cracking reactor 52 is Sn-Cu metal and NaBr, with a Sn:Cu mass ratio of 4:1 and a total mass of 100g. The NaBr mass is 40g. The cracking furnace 51 is programmed to increase the temperature at a rate of 10℃ / min. After the temperature reaches 650℃, it is held at a constant temperature for 30min after each 50℃ increase. The gas composition is analyzed by gas chromatography. The deoxygenated mixed gas pipeline is opened, and the deoxygenated gas is introduced into the cracking reactor 52. When the temperature reaches 950℃, the methane conversion rate is approximately 94.59%, and the hydrogen selectivity is over 95%.

[0038] The carbon materials generated by the pyrolysis reaction were collected, cleaned, dried, and characterized by XRD and SEM. The main components were graphite carbon materials.

[0039] Close the inlet valves of the second detection pipeline regulating valve 222 and the gas component detection device 23, and open the inlet valves of the pyrolysis tail gas regulating valve 56, the tail gas regulating valve 57, and the pyrolysis tail gas collection device 54 to collect the hydrogen produced by the deoxygenated gas pyrolysis. The gas collected in the pyrolysis tail gas collection device is a small amount of incompletely pyrolyzed methane and hydrogen produced by pyrolysis. When the gas collection volume reaches the upper limit, open the hydrogen collection valve 551 and use the hydrogen collector 55 to collect the gas. After the deoxidizer in the second deoxidation reactor 22 is exhausted, the second deoxidation outlet valve 221 is closed, and nitrogen is introduced to purge and replace the air in the reactor. After the replacement is completed, the hydrogen output regulating valve 541 and the second gas supply valve 142 are opened to introduce hydrogen into the second deoxidation reactor 22. The heating furnace 223 is turned on, and the temperature is programmed to rise at a rate of 10℃ / min. At a reduction temperature of 530℃ and a total gas flow rate of 40mL / min, the reduction time is approximately 150min. If a leak occurs in the pyrolysis unit and oxygen is generated, the oxygen concentration alarm 32 will sound an alarm in time, and the second deoxidation outlet valve 221 and the pyrolysis tail gas regulating valve 56 will be closed to cut off the pyrolysis reaction and prevent an explosion. The changes in hydrogen, methane, and other gases are monitored by an online mass spectrometer. The reduction ends when the hydrogen concentration stabilizes at the initial inlet level and the methane concentration remains stable and above 30min.

[0040] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials, characterized in that: It includes a gas circulation deoxygenation unit for deoxygenating low-concentration coal mine gas, a high-temperature methane cracking unit for cracking reaction of deoxygenated mixed gas, and a safety intelligent monitoring unit for detecting the oxygen content of the mixed gas entering the high-temperature methane cracking unit. The gas circulation deoxygenation unit includes a gas supply pipe (14), a first deoxygenation reactor (21) and a second deoxygenation reactor (22) connected in parallel between the gas outlet end of the gas supply pipe (14) and the safety intelligent monitoring unit, and a gas component detection device (23) for detecting the oxygen content of the tail gas of the first deoxygenation reactor (21) and the second deoxygenation reactor (22). The methane high-temperature cracking unit includes a cracking reactor (52) that is connected to the gas outlet of the first deoxygenation reactor (21) and the second deoxygenation reactor (22) respectively, a first porous ceramic membrane (521) disposed at the bottom of the cracking reactor (52), a second porous ceramic membrane (53) disposed at the top of the cracking reactor (52), and a cracking tail gas collection device (54) disposed above the second porous ceramic membrane (53). Deoxidizers are respectively provided in the first deoxidation reactor (21) and the second deoxidation reactor (22); the pyrolysis tail gas collection device (54) is connected in parallel between the gas outlet of the gas transmission pipe (14) and the safety intelligent monitoring unit, and collects hydrogen gas for regenerating the deoxidizers. The safety intelligent monitoring unit includes a gas collection hood (31) that is connected to the gas path of the pyrolysis reactor (52) and an oxygen concentration alarm (32) installed in the gas collection hood (31).

2. The system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials according to claim 1, characterized in that: A first gas supply valve (141) is provided on the gas transmission pipe (14) connecting to the first deoxygenation reactor (21); a second gas supply valve (142) is provided on the gas transmission pipe (14) connecting to the second deoxygenation reactor (22). The gas component detection device (23) is connected to the first deoxygenation reactor (21) by a first detection pipeline regulating valve (213) and a tail gas regulating valve (57), and the gas component detection device (23) is connected to the second deoxygenation reactor (22) by a second detection pipeline regulating valve (222) and a tail gas regulating valve (57).

3. The system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials according to claim 2, characterized in that: It also includes a gas supply unit; the gas supply unit includes a simulated coal mine gas source (11) and a nitrogen cylinder (12) respectively connected to the gas transmission pipe (14); a gas cylinder valve (111) and a first mass flow meter (112) are installed on the pipeline between the simulated coal mine gas source (11) and the gas transmission pipe (14), and a nitrogen cylinder valve (121) and a mass flow meter are installed on the pipeline between the nitrogen cylinder (12) and the gas transmission pipe (14).

4. The system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials according to claim 1, characterized in that: The first deoxygenation reactor (21) introduces deoxygenated gas into the molten medium in the pyrolysis reactor (52) through a pipeline with a first deoxygenation outlet valve (212); the second deoxygenation reactor (22) introduces deoxygenated gas into the molten medium in the pyrolysis reactor (52) through a pipeline with a second deoxygenation outlet valve (221); the first deoxygenation reactor (21) and the second deoxygenation reactor (22) serve as backups for each other, and the two alternately operate in the regeneration and deoxygenation process stages.

5. The system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials according to claim 1, characterized in that: A first heating furnace (211) is provided outside the first deoxygenation reactor (21), and a second heating furnace (223) is provided outside the second deoxygenation reactor (22); the gas component detection device (23) is an online mass spectrometer.

6. The system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials according to claim 1, characterized in that: A pyrolysis tail gas regulating valve (56), a deoxygenated tail gas dryer (542), and a tail gas regulating valve (57) are sequentially installed on the pipeline between the gas inlet of the pyrolysis tail gas collection device (54) and the gas outlet of the pyrolysis reactor (52). A hydrogen collector (55) is also connected to the pipeline between the tail gas regulating valve (57) and the pyrolysis tail gas collection device (54) through a pipeline with a hydrogen collection valve (551). The outlet of the pyrolysis tail gas collection device (54) is equipped with a hydrogen output regulating valve (541) for controlling the supply of regenerated hydrogen to the first deoxygenation reactor (21) and the second deoxygenation reactor (22) respectively, so as to realize the function of deoxygenating agent reduction and realize cyclic deoxygenation.

7. The system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials according to claim 6, characterized in that: The pyrolysis reactor (52) is externally equipped with a pyrolysis furnace (51); the first porous ceramic membrane (521) is a micron-sized porous distributor used to convert the incoming methane into tiny bubbles, increase the gas-liquid contact area, improve the methane conversion rate, improve the production quality of hydrogen and carbon materials, and enhance the mass transfer process; the second porous ceramic membrane (53) is a micron-sized ceramic membrane used to initially collect the carbon materials produced by methane pyrolysis, while preventing the overflow of extremely small carbon materials that could cause blockage of the reactor inlet pipe; Through intelligent pulse purging, some of the carbon material collected by the porous ceramic membrane can be purged onto the molten medium in the pyrolysis reactor, while some carbon material is purged into the filter chamber, facilitating the collection and utilization of carbon material.

8. The system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials according to claim 7, characterized in that: It also includes a carbon material collection and processing unit for receiving the products of the methane high-temperature cracking unit; the carbon material collection and processing unit includes a filter chamber (61) connected to the bottom of the cracking reactor (52), a carbon collection chamber (62) disposed below the filter chamber (61), a waste liquid collection chamber (64) connected to the filter chamber (61) and used for collecting the cracking catalyst, and a vacuum pump (63) for providing a collection negative pressure to the carbon collection chamber (62). A carbon collection chamber valve (621) is provided between the filter chamber (61) and the carbon collection chamber (62); a filter chamber heater (611) is provided outside the filter chamber (61); a waste liquid channel valve (641) is provided between the filter chamber (61) and the waste liquid collection chamber (64); and a vacuum regulating valve (631) is provided between the negative pressure pipeline of the vacuum pump (63) and the carbon collection chamber (62).

9. The system for safe deoxygenation and cracking of coal mine gas to produce hydrogen and carbon materials according to claim 8, characterized in that: It also includes an intelligent pulse purging unit; the intelligent pulse purging unit includes a pulse pipeline (45) disposed in the pyrolysis reactor (52) and located above the second porous ceramic membrane (53), a purging gas cylinder (41) for supplying gas to the pulse pipeline (45), a purging gas cylinder regulating valve (411) disposed on the gas supply pipe between the purging gas cylinder (41) and the pulse pipeline (45), a second mass flow meter (42), an electromagnetic pulse valve (43), and a programmable pulse controller (44) for controlling the electromagnetic pulse valve (43).

10. A method for safe deoxygenation and pyrolysis of coal mine gas to produce hydrogen and carbon materials, the system for safe deoxygenation and pyrolysis of coal mine gas to produce hydrogen and carbon materials according to any one of claims 1-9, characterized in that: Includes the following steps: S1. Open the nitrogen cylinder valve (121), the first gas supply valve (141), the first detection pipeline regulating valve (213), and the tail gas regulating valve (57). Purge the first deoxygenation reactor (21) with nitrogen through the three-way valve (13) and the gas supply pipe (14) to replace the internal air of the first deoxygenation reactor (21). Use the gas component detection device (23) to monitor in real time and completely replace the oxygen, carbon dioxide and other gases. S2. Open the gas cylinder valve (111) and the first gas supply valve (141) to introduce simulated low-concentration coal mine gas into the first deoxygenation reactor (21); open the first detection pipeline regulating valve (213) and the tail gas regulating valve (57) to program the temperature of the first deoxygenation reactor (21) at a rate of 2℃ / min, and observe the changes in oxygen, methane and nitrogen signals in the online mass spectrometer in real time. When the remaining oxygen detected in the online mass spectrometer reaches the minimum value (oxygen concentration less than 0.1%) and the oxygen signal no longer decreases, the deoxygenation state is reached. Maintain the set constant temperature. During this period, the deoxygenated gas feedstock gas can be continuously supplied to the cracking unit for the next deoxygenated gas cracking reaction. S3. Based on S2, open the first deoxygenation outlet valve (212), the pyrolysis tail gas regulating valve (56), the tail gas regulating valve (57), and the inlet valve connected to the pyrolysis tail gas collection device (54). During this process, the oxygen concentration alarm (32) monitors the oxygen situation in real time. If oxygen is present, it will immediately alarm and cut off the first deoxygenation outlet valve (212) and the pyrolysis tail gas regulating valve (56) to stop the reaction. The reaction proceeds to the methane cracking unit. The molten medium in the cracking reactor (52) is Sn-Cu metal and NaBr, which serve as catalysts for deoxygenated gas cracking. The molten medium is filled into the cracking reactor (52). The cracking furnace (51) is programmed to increase the temperature at a rate of 10°C / min. After the temperature reaches 650°C, it is kept constant for 30 min after each 50°C increase. The gas composition is analyzed by gas chromatography. The deoxygenated mixed gas pipeline is opened, and the deoxygenated gas is introduced into the cracking reactor (52). When the temperature reaches 950°C, the methane conversion rate is 95%, and the hydrogen selectivity is over 95%. S4. Some of the carbon materials generated by the pyrolysis reaction float on the molten salt due to the density difference, and some tiny particles float and accumulate on the second porous ceramic membrane (53) in the pyrolysis furnace. The purge gas bottle is opened, and the electromagnetic pulse valve (43) and the programmable pulse controller (44) are set to adjust the pulse frequency and time. The carbon materials generated by the pyrolysis are pulse-purged through the electromagnetic pulse tube (45). Some of the carbon materials can be purged onto the molten salt in the pyrolysis reactor (52), and some of the carbon materials are purged into the filter chamber (61). S5. The filter chamber (61) is kept in a heated state by heating the filter chamber (611). In addition, the channel with waste liquid channel valve (641) is heated by heating the heating jacket to keep the molten medium in a liquid state, so as to facilitate the separation of carbon material from the molten medium. The waste liquid channel valve is opened to filter a small amount of molten medium waste liquid through the filter screen θ into the waste liquid collection chamber (64). Open the carbon collection chamber valve (621) to collect carbon material into the carbon collection chamber (62). When the carbon material in the carbon collection chamber (62) reaches the limit, close the carbon collection chamber valve (621) and take out the carbon material from the carbon collection chamber (62). Then, reinstall the cleaned carbon collection chamber (62) into the corresponding position, open the vacuum regulating valve (631) to perform vacuum treatment. When collecting carbon material again, the negative pressure in the chamber will facilitate the flow and collection of carbon material. When the waste liquid collection chamber (64) is full of waste liquid, the waste liquid in the waste liquid collection chamber (64) can be poured out by closing the waste liquid channel valve (641). Then, the vacuum assembly will provide negative pressure to the waste liquid collection chamber (64). Then, the waste liquid will continue to be collected by opening the waste liquid channel valve (641). S6. Close the inlet valve of the first detection pipeline regulating valve (213) and the gas component detection device (23), open the inlet valve of the cracking tail gas regulating valve (56), the tail gas regulating valve (57) and the cracking tail gas collection device (54), collect the hydrogen produced by deoxygenated gas cracking, and the gas collected in the cracking tail gas collection device (54) is a small amount of incompletely cracked methane and cracked hydrogen. When the gas collection amount reaches the upper limit, open the hydrogen collection valve (551) and use the hydrogen collector (55) to collect it. S7. When the deoxygenating agent in the first deoxygenation reactor (21) is exhausted, the oxygen signal in the online mass spectrometer begins to rise. When the oxygen concentration is greater than or equal to 0.1%, the oxygen curve reaches the breakthrough state, the deoxygenation reaction ends, the first deoxygenation outlet valve (212) is closed, and the nitrogen cylinder valve (121), the first gas supply valve (141), the first detection pipeline regulating valve (213), and the tail gas regulating valve (57) are opened to purge with nitrogen and replace the air in the reactor. After the replacement is completed, the hydrogen output regulating valve (541) is opened. The pipeline of the first gas supply valve (141) introduces the gas in the tail gas collection device (54), namely hydrogen and a small amount of methane, into the first deoxygenation reactor (21) to reduce the deoxygenator; when the deoxygenator in the first deoxygenation reactor (21) and the second deoxygenation reactor (22) can no longer deoxygenate after the active sites are exhausted, the hydrogen in the hydrogen collector (54) reduces the deoxygenator to restore its deoxygenation function, so that the deoxygenator in the first deoxygenation reactor (21) and the second deoxygenation reactor (22) can achieve a cyclic deoxygenation effect.

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