Automatic device and method for preparing graphite from methane in atmosphere

Abstract

The invention discloses an automatic device and method for preparing graphite from methane in atmosphere, and relates to the field of atmospheric chemistry and isotope geochemistry. The device comprises a vacuum pump, a flow meter, an electromagnetic valve, a pressure gauge, a reaction tube, an electric heating jacket, a liquid nitrogen cold trap, magnesium perchlorate hydrazine hydrate, a CuO high-temperature furnace, soda lime / magnesium perchlorate composite hydrazine, water-cooled hydrazine, a sample gas bag, a helium steel cylinder and the like. The method comprises the following steps: removing water from gas in a sample gas bag through water-cooled hydrazine, removing carbon dioxide from the gas through soda lime / magnesium perchlorate composite hydrazine, purifying the gas, enabling the gas to pass through a high-temperature furnace containing CuO particles, reacting methane with CuO at high temperature to oxidize the gas into carbon dioxide, further removing water from the gas through magnesium perchlorate hydrazine, and gathering the gas through a liquid nitrogen cold trap to realize enrichment; then the carbon dioxide gas is released and enters a reaction tube, the reaction tube is filled with a catalyst, and graphite is prepared through a reduction reaction at the high temperature.

Description

Technical Field

[0001] The invention relates to the fields of atmospheric chemistry and isotope geochemistry, and in particular to an automated device and method for preparing graphite from methane in the atmosphere, which can automatically purify, oxidize, enrich and reduce trace methane in the atmosphere into graphite. Background Art

[0002] Radiocarbon ( 14 C) Dating technology is known as an important chronological method and a unique tracer that can provide the age of CH4 and serve as a tool for source identification of CH4 emissions, improve the understanding of carbon cycling in ecosystems (Levin and Hesshaimer, 2000), and reveal the sources and pathways of greenhouse gases. 14 The main principle of C dating technology is 14 C and 12 The ratio of C remains basically unchanged in nature (including the atmosphere and biosphere). When an organism dies, its metabolism stops and it no longer absorbs C. 14 C, and 14 C continues to decay, and because the ratio continues to decrease, the age of the organism's death can be calculated by measuring this ratio. 14 The measurement of C can help us understand the "carbon cycle" laws of the atmosphere, biosphere, ocean, and rocks, and conduct research on ocean material flux and the global carbon cycle.

[0003] Existing methane dating studies have shown an unusually wide range of 14 C ages range from modern to 40,000 years BP (Walter et al., 2006). CH4 from modern biogenic activities contains modern 14 C signature (called “new carbon”), while thermogenic (fossil fuel, geological methane) CH4 has a long history. 14 C levels are very low (called “old carbon”), so CH4 14 The level of C can be used to determine the biogas content in natural gas (Palonen et al., 2017). 14 C dating techniques provide new evidence for the contribution of ancient CH4 release to contemporary carbon reservoirs in peatlands (Cooper et al., 2017) and marine environments (Sparrow et al., 2018). 14 CH4 and δ 13 C can be further used together with D-CH4 to elucidate the methane generation pathway (e.g. Negandhi et al., 2013). 14C has also been used as a tracer in wastewater studies (Law et al., 2013) and can be an effective tracer of methane gas migration in landfills (Palstra and Meijer, 2014).

[0004] and other 14 Like samples of C, CH4 also needs to be converted into CO2 first, then the CO2 is converted into graphite, and then the target is made for accelerator mass spectrometry (AMS) measurement and dating. The CH4 concentration range of environmental samples is very large, ranging from 2ppm in the atmosphere to several tens of percent. 14 CH4 research has mainly focused on the CH4 bubbling region (Negandhi et al., 2013; Walter Anthony et al., 2016), because CH4 is usually present in high concentrations in bubbles (Walter Anthony et al., 2010), making it easier to obtain sufficient samples for analysis. 14 However, CH4 dissolved in water or methane in the atmosphere usually exists only at very low concentrations (Holgerson and Raymon, 2016; Dean et al., 2016). 14 The main reason why C dating technology is not used in areas with low CH4 concentration is that the concentration is too low to provide sufficient 14 Sample C was used for subsequent analysis on an AMS instrument. Summary of the invention

[0005] The purpose of the present invention is to provide an efficient and convenient automated device for preparing methane in the atmosphere into graphite. The device integrates multiple functional modules such as water vapor and carbon dioxide removal, methane oxidation, carbon dioxide capture and carbon dioxide reduction to achieve a one-stop conversion process from methane to graphite.

[0006] Another object of the present invention is to provide an automated method for preparing methane from the atmosphere into graphite, which is used to enrich and purify low-concentration methane in the outdoor atmosphere or water to prepare pure carbon dioxide gas, effectively remove the interference of carbon dioxide gas in the gas sample and the pollution of the external atmosphere, and then reduce the carbon dioxide gas to graphite, and carry out the target on the accelerator mass spectrometer. 14 C dating test.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions:

[0008] An automated device for preparing graphite from methane in the atmosphere, comprising:

[0009] The vacuum system is used to evacuate the entire pipeline to ensure the sealing of the pipeline and provide power for the sample gas to flow in the methane sample bag;

[0010] Water and carbon dioxide absorption and removal system, including water-cooled hydrazine, soda lime / magnesium perchlorate composite hydrazine and magnesium perchlorate dehydrated hydrazine, is used to remove impurities such as water vapor and carbon dioxide from the sample gas;

[0011] a methane oxidation system, including a CuO high temperature furnace filled with CuO pellets, for oxidizing methane into carbon dioxide;

[0012] a carbon dioxide capture system, comprising at least one liquid nitrogen cold trap for capturing and condensing carbon dioxide in the gas flowing out of the outlet of the CuO high temperature furnace;

[0013] The carbon dioxide reduction system includes a reaction tube and an electric heating jacket. The reaction tube is a glass reaction tube with an inner and outer tube-tube structure. The inner tube is filled with iron powder as a catalyst, and the outer tube is filled with zinc powder as a reducing agent. The electric heating jacket provides a high temperature environment for reducing the captured carbon dioxide into graphite.

[0014] The solenoid valve control system includes a plurality of solenoid valve switches, which are used to control the connection or disconnection between various systems and control the on and off of the gas circuit;

[0015] When carbon dioxide needs to be captured, the reaction tube is immersed in a liquid nitrogen cold trap. After the carbon dioxide is captured, the solenoid valve is switched to make the carbon dioxide capture system independent of other gas paths, the liquid nitrogen cold trap is removed, and the electric heating jacket provides high temperature, and the carbon dioxide is reduced to graphite under the action of the catalyst.

[0016] The device also includes a pressure meter and a flow meter, the pressure meter is connected to the carbon dioxide reduction system, the pressure meter is used to monitor the capture of carbon dioxide in the pipeline and the pressure change in the reaction tube, and the flow meter is used to control the flow rate of the sample gas;

[0017] The methane sample gas bag is connected to the water-cooled hydrazine through a solenoid valve, the water-cooled hydrazine is connected to the soda lime / magnesium perchlorate composite hydrazine, the soda lime / magnesium perchlorate composite hydrazine is connected to the CuO high-temperature furnace through a solenoid valve, the outlet of the CuO high-temperature furnace is connected to magnesium perchlorate hydrazine water, the outlet of magnesium perchlorate hydrazine water is connected to a liquid nitrogen cold trap through a solenoid valve, and the outlet of the liquid nitrogen cold trap is connected to a carbon dioxide reduction system, a pressure gauge and a vacuum pump through a solenoid valve;

[0018] The entire device automates the entire process by controlling the opening and closing of the solenoid valve, including vacuum extraction, sample gas purification, methane oxidation, carbon dioxide capture, carbon dioxide reduction, and calculation of graphite production.

[0019] Furthermore, the vacuum system components include a vacuum pump, a pressure gauge, a 1 / 8” stainless steel pipeline, a Swagelok connector (1 / 8”, 1 / 4”), and a solenoid valve; the vacuum pump is used to evacuate the entire vacuum system and serve as a power source for the flow of sample gas. A flow meter is also set at the connection between the vacuum pump and the gas line to maintain a flow rate of about 100 ml / min to draw the sample gas into the vacuum system. The pressure gauge records the vacuum degree in the entire pipeline to ensure that the vacuum pressure of the entire system is <1×10 -3 mbar, the switch of the solenoid valve can be completely controlled by software to realize the automation program, and the required gas circuit can be controlled according to the experimental process.

[0020] Further, the water and carbon dioxide absorption and removal system includes hydrazine water, soda lime magnesium perchlorate composite hydrazine, and magnesium perchlorate dehydrated hydrazine prepared by mixing anhydrous ethanol / liquid nitrogen; the anhydrous ethanol and liquid nitrogen are mixed and prepared into a viscous state, and the temperature is about -85°C, which can effectively remove the water vapor passing through the gas path, and then the soda lime magnesium perchlorate composite secondary hydrazine can remove the remaining water vapor and carbon dioxide in the gas path again, and as the absorption of carbon dioxide increases, the color of the soda lime will turn white, and when 1 / 3 of the soda lime turns white, the soda lime can be replaced to avoid carbon dioxide penetration and enter the next link of the gas path. Magnesium perchlorate hydrazine water is used to further remove the water vapor generated after the oxidation of methane from the pipeline.

[0021] Furthermore, the methane oxidation system uses a high-temperature furnace filled with CuO particles, the temperature of the high-temperature furnace is set at 850° C. When the methane in the gas passes through the high-temperature furnace, the methane reacts with CuO at high temperature and is oxidized into carbon dioxide.

[0022] Furthermore, the carbon dioxide capture system uses liquid nitrogen as a low temperature source externally. After being submerged in liquid nitrogen (-196°C atmosphere), pure carbon dioxide gas oxidized by methane is captured in a stainless steel pipeline.

[0023] Furthermore, the carbon dioxide reduction system includes a glass reaction tube, the reaction tube is designed with an inner tube and an outer tube, the inner tube is filled with iron powder and the outer tube is filled with zinc powder, the reaction tube is wrapped with an electric heating jacket, and the temperature can be set to 550°C. After all the carbon dioxide is captured, the capture system is independent of other gas lines by switching the solenoid valve, the liquid nitrogen dewar tank is evacuated, and the electric heating jacket starts heating. After about 4 hours, the carbon dioxide can be reduced to graphite. The pressure gauge above the glass pipeline is used to monitor whether all the carbon dioxide in the pipeline is captured.

[0024] An automated method for preparing graphite from atmospheric methane comprises the following steps:

[0025] 1) System initialization and pipeline vacuuming: Close all solenoid valves and use a high vacuum pump to deeply vacuum the entire reaction pipeline to ensure that the internal pressure of the pipeline is less than 1×10 -3 mbar, verify and ensure good sealing of the pipeline;

[0026] 2) Sample gas pretreatment: Use water and carbon dioxide absorption removal system to remove impurities such as water vapor and carbon dioxide in the sample gas;

[0027] 3) Methane oxidation: The gas in the methane sample bag is regulated by a flow meter and then passed into a methane oxidation system. A CuO high-temperature furnace filled with CuO particles is used to oxidize methane into carbon dioxide, and then magnesium perchlorate hydrazine is used to further remove water.

[0028] 4) Carbon dioxide capture and condensation: The carbon dioxide gas produced by oxidation passes through the carbon dioxide capture system, and the liquid nitrogen cold trap (-196°C) is used to condense the carbon dioxide into a solid state and capture it for enrichment; the pressure gauge monitors whether all the carbon dioxide in the pipeline is captured;

[0029] 5) Carbon dioxide is reduced to graphite: After confirming that all carbon dioxide has been captured, the capture system is isolated from other gas paths by switching the solenoid valve; the liquid nitrogen cold trap is evacuated, allowing the solid carbon dioxide to heat up and convert into gas, and the carbon dioxide gas is released into the reaction tube; at this time, the electric heating jacket is started to heat the reaction tube containing the catalyst (such as iron powder or nickel powder) and the reducing agent (such as zinc powder or magnesium powder) to a suitable temperature (such as 500°C to 600°C), and the carbon dioxide is reduced to graphite under a reducing atmosphere;

[0030] 6) Calculation of graphite production: The pressure change in the reaction tube is continuously monitored by a pressure gauge. By recording the pressure gauge readings before and after the reaction, the production of reduced graphite is calculated based on the volume of the reaction tube and the pressure difference before and after the reaction.

[0031] In step 2), the operation of removing impurities such as water vapor and carbon dioxide from the sample gas using a water and carbon dioxide absorption removal system includes: passing the sample gas through water-cooled hydrazine to remove water, passing through soda lime / magnesium perchlorate composite hydrazine to purify carbon dioxide, and passing through magnesium perchlorate dehydration hydrazine to remove water.

[0032] In step 4), the operation of capturing and condensing the carbon dioxide produced by oxidation using a carbon dioxide capture system includes: the gas produced by oxidation is further treated by magnesium perchlorate dehydration hydrazine and then enters a liquid nitrogen cold trap. Due to the extremely low temperature of the liquid nitrogen, the carbon dioxide is condensed and captured in the cold trap.

[0033] In step 5), the operation of reducing carbon dioxide to graphite includes: after all carbon dioxide is captured, the capture system is made independent of other gas lines by a specific electromagnetic valve switch, the liquid nitrogen cold trap is evacuated, the electric heating jacket is started to heat the reaction tube, and the reduction reaction is first carried out at a certain temperature (such as 500°C) for a period of time (such as 3 hours), and then the temperature is raised to a higher temperature (such as 550°C) for a period of time (such as 4 hours) to obtain a graphite sample; the progress is judged by observing the pressure gauge reading. When capturing carbon dioxide, if the reading no longer changes, it is considered that all carbon dioxide is captured; when reducing carbon dioxide, the output of reduced graphite is calculated according to the volume of the reaction tube and the pressure difference before and after the reaction by recording the pressure gauge readings before and after the reaction.

[0034] Compared with the prior art, the present invention has the following outstanding technical effects and advantages:

[0035] The present invention realizes efficient capture and separation of carbon dioxide through multiple purification treatments and liquid nitrogen cold trap capture. The solenoid valve can be software-controlled to realize an automated program, and accurately control the on and off of the gas path according to the experimental process. The present invention reduces carbon dioxide to graphite, thereby realizing efficient utilization of carbon dioxide and recycling of resources. The system of the present invention is reasonably designed, and the components are compact in structure, easy to maintain and maintain, ensuring the safety and reliability of the experiment. The present invention is efficient, flexible, and environmentally friendly, and has broad application prospects and potential economic value. The method of the present invention integrates advanced automation control technologies, including gas flow control, temperature and pressure monitoring, solenoid valve switch logic control, etc., to realize efficient, accurate, and continuous production from methane to graphite. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The present invention is a schematic structural diagram of an automated device embodiment for preparing graphite from methane in the atmosphere.

[0037] Figure numerals: 1, helium cylinder; 2, first solenoid valve switch; 3, second solenoid valve switch; 7, third solenoid valve switch; 10, fourth solenoid valve switch; 12, fifth solenoid valve switch; 14, sixth solenoid valve switch; 17, seventh solenoid valve switch; 4, methane sample gas bag; 5, water-cooled hydrazine; 6, soda lime / magnesium perchlorate composite hydrazine; 8, CuO high-temperature furnace; 9, magnesium perchlorate hydrazine; 11, first liquid nitrogen cold trap; 20, second liquid nitrogen cold trap; 13, pressure gauge; 15, electric heating jacket; 16, reaction tube; 18, flow meter; 19, vacuum pump. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the following embodiments will further illustrate the present invention in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. On the contrary, the present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention as defined by the claims.

[0039] Reference Figure 1 The automated device for preparing graphite from methane in the atmosphere according to the embodiment of the present invention comprises a vacuum system, a water and carbon dioxide absorption and removal system, a methane oxidation system, a carbon dioxide capture system, and a carbon dioxide reduction system. Specifically, the device is provided with a vacuum pump 19, a flow meter 18, a solenoid valve, a pressure gauge 13, a reaction tube 16, an electric heating jacket 15, a first liquid nitrogen cold trap 11, a second liquid nitrogen cold trap 20, magnesium perchlorate hydrazine 9, a CuO high temperature furnace 8, soda lime / magnesium perchlorate composite hydrazine 6, a water-cooled hydrazine 5, a methane sample gas bag 4, a helium cylinder 1, and the like. The entire pipeline adopts 1 / 8" stainless steel pipeline, and the joint adopts Swagelok joints (1 / 8", 1 / 4").

[0040] The solenoid valve switch includes a first solenoid valve switch 2, a second solenoid valve switch 3, a third solenoid valve switch 7, a fourth solenoid valve switch 10, a fifth solenoid valve switch 12, a sixth solenoid valve switch 14, and a seventh solenoid valve switch 17;

[0041] The first solenoid valve switch 2 is used to control the connection or disconnection of the methane sample gas bag 4 with the entire system.

[0042] The second solenoid valve switch 3 is used to control the connection between the methane sample gas bag 4 and the water-cooled hydrazine 5; when the second solenoid valve switch 3 is turned on, the sample gas is allowed to flow from the methane sample gas bag 4 into the water-cooled hydrazine 5 for preliminary treatment (such as cooling and removing some impurities).

[0043] The third solenoid valve switch 7 is used to control the connection between the soda lime / magnesium perchlorate composite hydrazine 6 and the CuO high temperature furnace 8; when the third solenoid valve switch 7 is turned on, the purified gas (which has been treated by the water-cooled hydrazine 5 and the soda lime / magnesium perchlorate composite hydrazine 6) can flow into the CuO high temperature furnace 8 for the oxidation reaction of methane.

[0044] The fourth solenoid valve switch 10 is used to control the connection between the outlet of the CuO high temperature furnace 8, the magnesium perchlorate hydrazine 9 and the subsequent first liquid nitrogen cold trap 11. When the fourth solenoid valve switch 10 is turned on, the gas (including carbon dioxide and other gases) produced by the oxidation reaction can flow into the magnesium perchlorate hydrazine 9 for further treatment (such as removing water vapor), and then be sent to the first liquid nitrogen cold trap 11 for freezing and capturing carbon dioxide.

[0045] The fifth solenoid valve switch 12 and the sixth solenoid valve switch 14 are used to control the connection between the first liquid nitrogen cold trap 11 and the carbon dioxide reduction system, or to control the isolation of the path from other gas paths. When capturing carbon dioxide, it may remain closed until all carbon dioxide is captured and ready for reduction reaction. After the capture is completed, the sixth solenoid valve switch 14 works in conjunction with the fifth solenoid valve switch 12 to ensure that carbon dioxide can be smoothly transferred from the liquid nitrogen cold trap to the reaction tube 16 for reduction reaction. The sixth solenoid valve switch 14 is also used to maintain the sealing of the system during the reduction reaction.

[0046] The seventh solenoid valve switch 17 is used to control the connection between the carbon dioxide reduction system and the pressure gauge 13 and the vacuum pump 19 .

[0047] The purification (dehydration and carbon dioxide removal) of the sample gas in the methane sample gas bag 4 is achieved by water-cooled hydrazine 5 and soda lime / magnesium perchlorate composite hydrazine 6; the methane sample gas bag 4 is connected to the water-cooled hydrazine 5 through the second solenoid valve switch 3, the water-cooled hydrazine 5 is connected to the soda lime / magnesium perchlorate composite hydrazine 6, the soda lime / magnesium perchlorate composite hydrazine 6 is connected to the CuO high-temperature furnace 8 filled with CuO particles through the third solenoid valve switch 7, and the oxidation of methane is achieved by the CuO high-temperature furnace 8; the outlet of the CuO high-temperature furnace 8 is connected to the magnesium perchlorate hydrazine 9, the outlet of the magnesium perchlorate hydrazine 9 is connected to the first liquid nitrogen cold trap 11 through the fourth solenoid valve switch 10, and the outlet of the first liquid nitrogen cold trap 11 is connected to the carbon dioxide reduction system through the fifth solenoid valve switch 12 and the sixth solenoid valve switch 14;

[0048] The water and carbon dioxide absorption and removal system includes a water-cooled hydrazine 5, a soda lime / magnesium perchlorate composite hydrazine 6, and a magnesium perchlorate dehydrated hydrazine 9, which are mixed and modulated by anhydrous ethanol / liquid nitrogen; the anhydrous ethanol and liquid nitrogen in the water-cooled trap 5 are mixed and modulated into a viscous state, and the temperature is about -85°C, which can effectively remove the water vapor passing through the gas path, and then the soda lime / magnesium perchlorate composite secondary hydrazine 6 can remove the remaining water vapor and carbon dioxide in the gas path again, and as the absorption of carbon dioxide increases, the color of the soda lime will turn white. When 1 / 3 of the soda lime turns white, the soda lime can be replaced to avoid carbon dioxide penetration and enter the next link of the gas path. The magnesium perchlorate hydrazine 9 is used to further remove the water vapor generated after the oxidation of methane from the pipeline.

[0049] The methane oxidation system includes a third solenoid valve switch 7, a CuO high-temperature furnace 8 filled with CuO particles, magnesium perchlorate hydrazine 9, and a fourth solenoid valve switch 10; the oxidation of methane is achieved by the high-temperature furnace filled with CuO particles, the temperature of the CuO high-temperature furnace 8 is set at 850°C, and when the methane in the gas passes through the CuO high-temperature furnace 8, the methane reacts with CuO at high temperature and is oxidized into carbon dioxide.

[0050] The first liquid nitrogen cold trap 11 is used to capture and condense carbon dioxide in the gas flowing out of the outlet of the CuO high temperature furnace 8. When the methane sample is oxidized in the CuO high temperature furnace, carbon dioxide and other gases are produced. These gases are further treated by magnesium perchlorate hydrazine 9 and enter the first liquid nitrogen cold trap 11. Due to the extremely low temperature of liquid nitrogen, carbon dioxide is condensed and captured in the cold trap, thereby achieving separation from other gases. The first liquid nitrogen cold trap 11 ensures that only pure carbon dioxide is sent to the subsequent carbon dioxide reduction system.

[0051] The second liquid nitrogen cold trap 20 is used to provide a low temperature environment for the carbon dioxide reduction system (especially the reaction tube 16) before capturing carbon dioxide. When carbon dioxide needs to be captured, the reaction tube 16 is immersed in the second liquid nitrogen cold trap 20. This has two purposes: first, to ensure that during the capture process, the reaction tube 16 and the catalyst and reducing agent inside it will not be affected by external heat; second, if a small amount of carbon dioxide or other gases escape during the capture process, they can be further condensed and captured in the second liquid nitrogen cold trap 20, thereby preventing these gases from entering the experimental environment or interfering with other steps.

[0052] The carbon dioxide capture system includes a second liquid nitrogen cold trap 20, a reaction tube 16 and a sixth solenoid valve switch 14. The capture of carbon dioxide is achieved by the liquid nitrogen cold trap. Liquid nitrogen is used externally as a low temperature source. When carbon dioxide needs to be captured, the reaction tube 16 is immersed in a liquid nitrogen dewar tank. After being submerged in liquid nitrogen (-196°C atmosphere), pure carbon dioxide gas oxidized by methane is captured in a stainless steel pipeline.

[0053] The carbon dioxide reduction system includes a reaction tube 16, an electric heating jacket 15 and a sixth solenoid valve switch 14. The reaction tube 16 is a glass reaction tube with an inner and outer tube structure. The reaction tube 16 is provided with an inner tube and an outer tube. The inner tube of the reaction tube 16 is filled with iron powder as a catalyst, and the outer tube of the reaction tube 16 is filled with zinc powder as a reducing agent. The reaction tube 16 is wrapped with an electric heating jacket 15 to provide a high temperature environment. The temperature can be set to 550°C. After all carbon dioxide is captured, the capture system is independent of other gas circuits by switching the sixth solenoid valve switch 14, the liquid nitrogen dewar tank is evacuated, and the electric heating jacket starts heating. After about 4 hours, carbon dioxide can be reduced to graphite. The pressure gauge above the glass pipeline is used to monitor whether all carbon dioxide in the pipeline is captured.

[0054] After all the carbon dioxide is captured, the capture system is made independent of other gas lines by switching the electromagnetic valve, the liquid nitrogen dewar is evacuated, and the electric heating jacket 15 starts heating. After about 4 hours, the carbon dioxide is reduced to graphite under the action of the catalyst (iron powder filled in the inner tube). The pressure gauge 13 above the glass pipeline is used to monitor whether all the carbon dioxide in the pipeline is captured. The progress of the experiment can be judged by observing the reading of the pressure gauge 13. For example, when capturing carbon dioxide, if the reading no longer changes, it can be considered that all the carbon dioxide is captured; when reducing carbon dioxide, the output of reduced graphite can be calculated by recording the reading of the pressure gauge 13 before and after the reaction.

[0055] The vacuum pump 19, the pressure gauge 13, 1 / 8", stainless steel pipeline, Swagelok connector (1 / 8", 1 / 4"), and the seventh solenoid valve switch 17 constitute a vacuum system component; the vacuum pump 19 is not only used to evacuate the entire vacuum system to ensure the required vacuum in the pipeline and prevent the sample gas from being contaminated by carbon in the outside air, but also provides a power source for the flow of the sample gas in the methane sample gas bag 4. A flow meter 18 is provided at the connection between the vacuum pump and the gas path, and the flow rate is stabilized by the flow meter 18. In this embodiment, the sample gas is pumped into the vacuum system at a flow rate of about 100 ml / min. The pressure gauge 13 is used to record the vacuum degree in the entire pipeline to ensure that the vacuum pressure of the entire system is <1×10 -3 mbar, the switches of all solenoid valves can be controlled manually or by control software to realize an automated program, and the required gas circuit can be controlled according to the experimental process. The control software receives data from the pressure gauge 13, etc., and controls the switch of the solenoid valve according to the preset logic or user-defined program. The control software that can be used includes PLC (programmable logic controller) programming software, LabVIEW, MATLAB / Simulink, etc. The specific selection depends on the complexity of the system and the existing resources of the laboratory. It is sufficient to realize the relevant functions described in the present invention. The control software can also have monitoring and alarm functions. If any abnormal situation occurs (such as abnormal pressure, solenoid valve failure, etc.), the system can immediately issue an alarm and take corresponding measures (such as stopping the experiment, closing the dangerous source, etc.).

[0056] The embodiment of the present invention provides an automated method for preparing graphite from methane in the atmosphere. The gas in the sample gas bag is first dehydrated by water-cooled hydrazine, purified by soda lime / magnesium perchlorate composite hydrazine to remove carbon dioxide, and then passed through a high-temperature furnace containing CuO particles. At high temperature, methane reacts with CuO to oxidize into carbon dioxide, and further dehydrated by magnesium perchlorate hydrazine water. The gas is enriched by being captured by a liquid nitrogen cold trap, and then the carbon dioxide gas is released into a reaction tube filled with a catalyst, and is prepared into graphite by a reduction reaction at high temperature. Specifically, the following steps are included:

[0057] 1. Install a water-cooled trap 5, prepare anhydrous ethanol and liquid nitrogen, mix and stir evenly until a slurry state with a temperature of about -85°C, install a first liquid nitrogen cold trap 11 and a second liquid nitrogen cold trap 20, and start heating the combustion furnace 8 containing CuO particles to 850°C to oxidize methane.

[0058] 2. Open all solenoid valves except the first solenoid valve switch 2, and use a vacuum pump to evacuate the entire pipeline until the vacuum pressure is <1×10 -3 mbar, and keep it for a while. If the vacuum pressure value does not increase, it means that the vacuum pipeline is not leaking, ensuring the pipeline sealing; then open the valve of the helium cylinder, open all solenoid valves except the seventh solenoid valve switch 17, fill the entire gas circuit with helium, close the helium cylinder, open the seventh solenoid valve switch 17, close the first solenoid valve switch 2, and use a vacuum pump to evacuate the entire pipeline. This step is performed twice to remove all impurity gases and water vapor in the gas circuit.

[0059] 3. Connect the methane sample bag 4 to the vacuum pipeline through the side hole needle, close the first solenoid valve switch 2, open all other solenoid valves, and keep the flow rate at about 100 mL / min at the flowmeter 18. The sample gas in the methane sample bag 4 first passes through the water-cooled trap 5 and the soda lime / magnesium perchlorate composite hydrazine 6 mixed with anhydrous ethanol / liquid nitrogen to remove impurities such as water vapor and carbon dioxide in the sample gas; then the trace methane in the sample gas passes through the CuO high-temperature furnace 8 containing CuO particles, where the methane is oxidized into carbon dioxide, the generated water vapor is removed in the magnesium perchlorate hydrazine 9, and the carbon dioxide is frozen in the pipeline of the first liquid nitrogen cold trap 11; other gases such as nitrogen and oxygen pass through the first liquid nitrogen cold trap 11 and are finally pumped into the atmosphere by the vacuum pump 19.

[0060] 4. Wait for all the gas samples in the methane sample air bag 4 to react completely. At this time, all the methane is oxidized to carbon dioxide and is completely frozen in the pipeline of the first liquid nitrogen cold trap 11. Close the fourth solenoid valve switch 10, the seventh solenoid valve switch 17, open the sixth solenoid valve switch 14, remove the first liquid nitrogen cold trap 11, and the carbon dioxide will become gas and enter the reaction tube 16 through the sixth solenoid valve switch 14. The carbon dioxide is re-frozen inside the reaction tube 16 under the liquid nitrogen atmosphere. By observing the changes in the readings of the pressure gauge 13, it can be considered that all the carbon dioxide has been transferred to the inside of the reaction tube 16 when the value no longer changes.

[0061] 5. Close the fifth solenoid valve switch 12 and the seventh solenoid valve switch 17, open the sixth solenoid valve switch 14, and remove the second liquid nitrogen cold trap 20. At this time, the carbon dioxide returns to a gaseous state, and the pressure gauge 13 reading at this time is recorded. The reaction tube 16 is designed as an outer tube and an inner tube structure. The inner tube is filled with 5 mg of iron powder and the outer tube is filled with 15 mg of zinc powder. The reaction tube 16 is heated by the electric heating jacket 15. The reduction reaction is first carried out at 500°C for 3 hours, and then the temperature is raised to 550°C for graphitization reaction for 4 hours to obtain a graphite sample. After the reaction is completed, the value of the pressure gauge 13 is recorded. When the volume of the reaction tube 16 is known, the yield converted into graphite can be calculated according to the volume of the reaction tube 16 and the pressure difference before and after the reaction, and the gas state equation.

[0062] The gas state equation is pV=nRT, where p is the pressure of the gas (unit: Pascal, Pa); V is the volume of the gas (unit: cubic meter, m³); n is the amount of substance in the gas (unit: mole, mol); R is the ideal gas constant (unit: joule per mole per Kelvin, J / (mol·K)), and the value of R is different for different gases. For air or most diatomic gases, R ≈ 8.314 J / (mol·K); T is the thermodynamic temperature of the gas (unit: Kelvin, K)

[0063] At the same time, analytical methods such as X-ray diffraction (XRD) and scanning electron microscopy (SEM) can be used to control the quality of graphite products to ensure that their purity, crystal form and physical properties meet expectations.

[0064] In summary, the present invention can efficiently capture carbon dioxide flowing out of the CuO high temperature furnace 8 through the first liquid nitrogen cold trap 11. The extremely low temperature of liquid nitrogen ensures the full condensation and capture of carbon dioxide, thereby achieving effective separation from other gases. Before the methane sample enters the CuO high temperature furnace, water vapor and other impurities in the sample are removed through multiple purification treatments of water-cooled hydrazine 5 and soda lime / magnesium perchlorate composite hydrazine 6 to ensure the quality of the gas entering the high temperature furnace.

[0065] The entire device achieves flexible gas control and operation through multiple solenoid valve switches. These solenoid valve switches can accurately control the flow direction and on-off of the gas, thereby ensuring the smooth progress of the experiment and the efficient use of gas.

[0066] The present invention adopts an innovative carbon dioxide reduction system, which reduces the captured carbon dioxide to graphite through the catalytic reduction of iron powder and zinc powder. It not only achieves efficient utilization of carbon dioxide, but also reduces greenhouse gas emissions, which is in line with the concept of environmental protection and sustainable development.

[0067] The device of the present invention has reasonable design, compact structure and is easy to carry out daily maintenance and upkeep. It has significant advantages such as efficient capture and separation, flexible control and operation, innovation and environmental protection, safety and reliability. It has broad application prospects and potential economic value in the fields of methane treatment and carbon dioxide reduction.

[0068] The above embodiments are only preferred embodiments of the present invention and cannot be considered to limit the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. An automated device for preparing graphite from methane in the atmosphere, characterized in that: include: The vacuum system is used to evacuate the entire pipeline to ensure the sealing of the pipeline and provide power for the sample gas to flow in the methane sample bag; Water and carbon dioxide absorption and removal system, including water-cooled hydrazine, soda lime / magnesium perchlorate composite hydrazine and magnesium perchlorate dehydrated hydrazine, is used to remove impurities such as water vapor and carbon dioxide from the sample gas; a methane oxidation system, including a CuO high temperature furnace filled with CuO pellets, for oxidizing methane into carbon dioxide; a carbon dioxide capture system, comprising at least one liquid nitrogen cold trap for capturing and condensing carbon dioxide in the gas flowing out of the outlet of the CuO high temperature furnace; The carbon dioxide reduction system includes a reaction tube and an electric heating jacket. The reaction tube is a glass reaction tube with an inner and outer tube-tube structure. The inner tube is filled with iron powder as a catalyst, and the outer tube is filled with zinc powder as a reducing agent. The electric heating jacket provides a high temperature environment for reducing the captured carbon dioxide into graphite. The solenoid valve control system includes a plurality of solenoid valve switches, which are used to control the connection or disconnection between various systems and control the on and off of the gas circuit; When carbon dioxide needs to be captured, the reaction tube is immersed in a liquid nitrogen cold trap. After the carbon dioxide is captured, the solenoid valve is switched to make the carbon dioxide capture system independent of other gas paths, the liquid nitrogen cold trap is removed, and the electric heating jacket provides high temperature, and the carbon dioxide is reduced to graphite under the action of the catalyst. The device also includes a pressure meter and a flow meter, the pressure meter is connected to the carbon dioxide reduction system, the pressure meter is used to monitor the capture of carbon dioxide in the pipeline and the pressure change in the reaction tube, and the flow meter is used to control the flow rate of the sample gas; The methane sample gas bag is connected to the water-cooled hydrazine through a solenoid valve, the water-cooled hydrazine is connected to the soda lime / magnesium perchlorate composite hydrazine, the soda lime / magnesium perchlorate composite hydrazine is connected to the CuO high-temperature furnace through a solenoid valve, the outlet of the CuO high-temperature furnace is connected to magnesium perchlorate hydrazine water, the outlet of magnesium perchlorate hydrazine water is connected to a liquid nitrogen cold trap through a solenoid valve, and the outlet of the liquid nitrogen cold trap is connected to a carbon dioxide reduction system, a pressure gauge and a vacuum pump through a solenoid valve; By controlling the opening and closing of the solenoid valve, the entire process is automated, including vacuuming, sample gas purification, methane oxidation, carbon dioxide capture, carbon dioxide reduction, and calculation of graphite production.

2. An automated device for preparing graphite from methane in the atmosphere according to claim 1, characterized in that: The anhydrous ethanol and liquid nitrogen in the water-cooled hydrazine are mixed and prepared into a viscous state with a temperature of about -85°C, which is used to effectively remove water vapor passing through the gas path.

3. The automated device for preparing graphite from methane in the atmosphere according to claim 1, characterized in that: The soda lime / magnesium perchlorate composite hydrazine is used to remove the remaining water vapor and carbon dioxide in the gas path. As the absorption of carbon dioxide increases, the soda lime turns white. When 1 / 3 of the soda lime turns white, the soda lime is replaced to avoid carbon dioxide penetration.

4. The automated device for preparing graphite from methane in the atmosphere according to claim 1, characterized in that: The temperature of the CuO high temperature furnace in the methane oxidation system is set at 850° C. to ensure that methane reacts with CuO at high temperature and is oxidized to carbon dioxide.

5. The automated device for preparing graphite from methane in the atmosphere according to claim 1, characterized in that: The liquid nitrogen cold trap in the carbon dioxide capture system uses liquid nitrogen as a low temperature source outside. When carbon dioxide needs to be captured, the reaction tube is immersed in liquid nitrogen to achieve condensation and capture of carbon dioxide.

6. The automated device for preparing graphite from methane in the atmosphere according to claim 1, characterized in that: The reaction tube in the carbon dioxide reduction system adopts a glass reaction tube with an inner and outer tube structure. The inner tube is filled with iron powder as a catalyst, and the outer tube is filled with zinc powder as a reducing agent. The electric heating jacket provides a high temperature environment, and the temperature can be set to 550°C.

7. An automated method for preparing graphite from methane in the atmosphere, characterized in that: An automated device for preparing graphite from methane in the atmosphere as claimed in any one of claims 1 to 6 is used, wherein the method comprises the following steps: 1) System initialization and pipeline vacuuming: Close all solenoid valves and use a high vacuum pump to deeply vacuum the entire reaction pipeline to ensure that the internal pressure of the pipeline is less than 1×10 -3 mbar, verify and ensure good sealing of the pipeline; 2) Sample gas pretreatment: Use water and carbon dioxide absorption removal system to remove impurities such as water vapor and carbon dioxide in the sample gas; 3) Methane oxidation: The gas in the methane sample bag is regulated by a flow meter and then passed into a methane oxidation system. A CuO high-temperature furnace filled with CuO particles is used to oxidize methane into carbon dioxide, and then magnesium perchlorate hydrazine is used to further remove water. 4) Carbon dioxide capture and condensation: The carbon dioxide gas produced by oxidation passes through the carbon dioxide capture system, and the liquid nitrogen cold trap (-196°C) is used to condense the carbon dioxide into a solid state and capture it for enrichment; the pressure gauge monitors whether all the carbon dioxide in the pipeline is captured; 5) Carbon dioxide reduction to graphite: After confirming that all carbon dioxide has been captured, the capture system is isolated from other gas paths by the solenoid valve switch; the liquid nitrogen cold trap is evacuated, allowing the solid carbon dioxide to heat up and convert into gas, and the carbon dioxide gas is released into the reaction tube; at this time, the electric heating jacket is started to heat the reaction tube containing the catalyst and the reducing agent to a suitable temperature, and the carbon dioxide is reduced to graphite in a reducing atmosphere; 6) Calculation of graphite production: The pressure change in the reaction tube is continuously monitored by a pressure gauge. By recording the pressure gauge readings before and after the reaction, the production of reduced graphite is calculated based on the volume of the reaction tube and the pressure difference before and after the reaction.

8. An automated method for preparing graphite from methane in the atmosphere according to claim 7, characterized in that: In step 2), the operation of removing impurities such as water vapor and carbon dioxide from the sample gas using a water and carbon dioxide absorption removal system includes: passing the sample gas through water-cooled hydrazine to remove water, passing through soda lime / magnesium perchlorate composite hydrazine to purify carbon dioxide, and passing through magnesium perchlorate dehydration hydrazine to remove water.

9. An automated method for preparing graphite from methane in the atmosphere according to claim 7, characterized in that: In step 4), the operation of capturing and condensing the carbon dioxide produced by oxidation using a carbon dioxide capture system includes: the gas produced by oxidation is further treated by magnesium perchlorate dehydration hydrazine and then enters a liquid nitrogen cold trap. Due to the extremely low temperature of the liquid nitrogen, the carbon dioxide is condensed and captured in the cold trap.

10. An automated method for preparing graphite from methane in the atmosphere according to claim 7, characterized in that: In step 5), the operation of reducing carbon dioxide to graphite includes: after all the carbon dioxide is captured, the capture system is made independent of other gas lines by a specific electromagnetic valve switch, the liquid nitrogen cold trap is evacuated, the electric heating jacket is started to heat the reaction tube, a reduction reaction is carried out, and then the temperature is raised to a higher temperature to carry out a graphitization reaction to obtain a graphite sample; the progress is judged by observing the pressure gauge reading, and when capturing carbon dioxide, if the reading no longer changes, it is considered that all the carbon dioxide is captured; when reducing carbon dioxide, the output of reduced graphite is calculated according to the volume of the reaction tube and the pressure difference before and after the reaction by recording the pressure gauge readings before and after the reaction.

Images