Green electricity microwave discharge plasma methane cracking hydrogen-carbon co-production system and method

Abstract

The invention discloses a green electricity microwave discharge plasma methane cracking hydrogen-carbon co-production system and method, and belongs to the technical field of methane thermal cracking hydrogen production. The system comprises a green electricity power supply system, a gas supply system, a microwave discharge plasma cracking system, a carbon product separation and collection system, a gas circulation system and a gas separation and purification system. According to the method, gt can be obtained under low flow and low energy consumption; the methane conversion rate is 95%, and efficient cracking of methane is realized; directional controllable production of products can be realized by adjusting microwave power and gas composition in a gas supply system, and directional selection regulation and control of gaseous products such as ethane and pure hydrogen can be realized by changing gas circulation.

Description

Technical Field

[0001] The present invention belongs to the technical field of methane thermal cracking hydrogen production, and in particular relates to a green electricity microwave discharge plasma methane cracking hydrogen-carbon cogeneration system and method. Background Art

[0002] Microwave discharge plasma is one of the common plasma cracking technologies. It has the characteristics of high ionization and decomposition degree, high electron temperature and density, and high energy efficiency. It can be designed without electrodes and has the ability to increase the reaction rate and reduce the reaction activation energy. It can achieve efficient methane cracking to obtain low-carbon hydrogen and high-value by-products.

[0003] At present, the main microwave discharge plasma action mode is plasma torch, which ignites the plasma torch through high energy consumption and high gas velocity, and can realize the action of high-energy electrons on reactants to achieve the purpose of reactant conversion. This method requires huge energy to start and also requires high energy input to maintain the plasma state, which has problems such as high energy consumption, high gas velocity, and uncontrollable reaction.

[0004] Adding a catalyst can reduce the reaction activity in exchange for the methane conversion rate under low power and low flow, but the deactivation of the catalyst will lead to low stability of the reaction, and the impurity of the gaseous products will increase the cost of later separation. CN111085242B discloses a method and catalyst for microwave catalytic methane hydrogen production, using Ni / Mo2C / SBA-15 catalyst to catalyze the direct conversion of methane to produce hydrogen under microwave conditions, and by adjusting different catalyst parameters and reaction conditions, a certain degree of heating temperature increase and conversion rate improvement can be achieved, but the power consumption is still very high. CN116553525A discloses an application and application method of a non-thermal oxygen-free plasma methane cracking system, which needs to be carried out at a high power of 15-30KW and a high flow of 100-300L / min. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, the present invention provides a green electricity microwave discharge plasma methane cracking hydrogen and carbon co-production system and method. Compared with the traditional microwave discharge plasma methane cracking method, this method achieves a high methane conversion rate (>95%) at a low gas velocity (<0.02m / s, which is 30% of the traditional method) and low energy consumption (<400kJ / mol, which is 40% of the traditional method) without adding any catalyst, and at the same time achieves orderly and controllable conversion of gaseous products and the production of high-value carbon. This method can realize the industrial production of green hydrogen and high-value carbon from methane, with low investment and low operating expenses, no catalyst and water are required, low implementation difficulty, and low energy consumption.

[0006] In order to achieve the above technical objectives, the technical solution implemented by the present invention is: The first aspect of the present invention provides a green power microwave discharge plasma methane cracking hydrogen and carbon cogeneration system, comprising: Green electricity supply system, used for access to green electricity; A gas supply system for providing stable hydrocarbon compounds and discharge medium gas; Microwave discharge plasma cracking system, used for cracking hydrocarbon compounds to produce gas and carbon products; A carbon product separation and collection system, used to separate and collect carbon products from gases; A gas circulation system, used for circulating part of the cracked gas; Gas separation and purification system, used for separation and purification of hydrogen.

[0007] Preferably, the hydrocarbon compound is selected from methane, ethane, ethylene or acetylene.

[0008] In an embodiment of the present invention, a microwave discharge plasma cracking system is equipped with a filler and a microwave source, and the filler is made of an absorbing material with a curvature radius less than or equal to the tip length or radius; further, the filler material is selected from metal needles, metal wires, metal mesh or activated carbon.

[0009] Preferably, the discharge medium gas is selected from argon or nitrogen and other chemically stable gases that are easy to form discharge plasma.

[0010] A second aspect of the present invention provides a method for co-producing hydrogen and carbon by methane cracking using green power microwave discharge plasma, comprising the following steps: S1. placing the filler into the reaction area of ​​the microwave discharge plasma cracking system; S2. A discharge medium gas is introduced into the microwave reaction chamber of the microwave discharge plasma cracking system to provide a discharge environment for the reaction chamber; S3. Adjust the energy input of the microwave generator to input microwaves into the microwave reaction chamber, so that the filling in the microwave reaction chamber is continuously discharged, and a stable plasma field is formed around the filling; S4. Adjust the gas input of the gas supply system, introduce a mixture of hydrocarbon compound gas and discharge medium gas into the microwave reaction chamber, and start the microwave discharge plasma cracking reaction; S5. The reaction products are separated into gas and solid by passing through the separation and settling area of ​​the microwave discharge plasma cracking system; the carbon products are collected in the carbon product separation and collection system; and the gas products are collected after passing through the gas separation and purification system.

[0011] Furthermore, the gas circulation volume and frequency of the gas circulation system are regulated according to the product distribution of the gas separation and purification system to regulate the quality of the gas-solid products.

[0012] Preferably, in step S4, the conditions for the microwave discharge plasma cracking reaction include: a gas velocity of 0.003 m / s to 0.033 m / s; a content of hydrocarbon compound gas in a mixture of hydrocarbon compound gas and discharge medium gas of any value between 10% and 50%; and adjusting the energy input of the microwave generator, the power of which is calculated as hydrocarbon compound gas to any condition between 20 W / mol and 150 W / mol.

[0013] The present invention provides a cracking hydrogen production technology in a low flow mode, which uses a lower flow rate to achieve more precise control, more efficient mixing and reduced energy consumption. The present invention can control the composition of the product by controlling the reaction time; the product can be pumped back to the reaction area through the gas circulation system to achieve a second reaction and change the product composition.

[0014] Based on the alkane cracking theory, the high-energy particles in the plasma interact with the alkane molecules, causing the chemical bonds to break and generate small molecular products. Alkane cracking involves: 1. Microwave energy effect: Microwaves are high-frequency electromagnetic waves that can penetrate matter and interact with its molecules. In alkane cracking, microwave energy is absorbed and converted into heat energy, giving alkane molecules enough energy to crack.

[0015] 2. Plasma generation: Microwave energy can induce gas ionization under certain conditions (such as high-pressure or low-pressure gas environment) to form plasma. Plasma is the fourth state of matter, composed of free electrons, ions and neutral particles. It is highly active and can promote chemical reactions. The high-energy electrons and ions in the plasma can collide with alkane molecules and trigger cracking reactions.

[0016] 3. Cracking mechanism: High-energy electrons in the plasma collide with alkane molecules, transferring energy to the alkane molecules, breaking their chemical bonds and generating free radicals and small molecular products. These free radicals further react to generate smaller hydrocarbon molecules, such as olefins and hydrogen.

[0017] 4. Main reaction steps: Excitation and ionization: high-energy electrons collide with alkane molecules to excite or ionize them, generating free radicals and ions; bond breaking: excited or ionized alkane molecules undergo bond breaking to generate small molecule products; free radical reaction: the generated free radicals react further to generate stable products.

[0018] The plasma alkane cracking theory uses the interaction between high-energy particles in the plasma and alkane molecules to cause chemical bond breakage and generate small molecule products. This technology has the advantages of high efficiency, strong selectivity and environmental protection, and has broad application prospects in many fields.

[0019] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: 1. The present invention provides a green electricity microwave discharge plasma methane cracking hydrogen-carbon cogeneration system and method, which can achieve a methane conversion rate of >95% under low flow and low energy consumption, realize efficient cracking of methane, and reduce the energy consumption and cost of the entire reaction process.

[0020] 2. The present invention can achieve directional and controllable production of products through a gas circulation system, and achieve directional and selective regulation of gaseous products such as ethane and pure hydrogen by changing the gas circulation.

[0021] 3. This method can obtain high-value carbon products, such as low-layer graphene products, carbon nanotubes, carbon black, etc. At the same time, no carbon dioxide is produced in the process. It is a cost-effective and environmentally friendly method for producing high-value carbon by methane cracking.

[0022] 4. This method prepares hydrogen through methane cracking, avoiding the emission of a large amount of carbon dioxide in the traditional methane steam reforming method, helping to reduce greenhouse gas emissions and meeting the requirements of environmental protection and sustainable development.

[0023] 5. This system can be started and stopped at any time, and can match unstable electricity such as solar energy, wind energy, geothermal energy, tidal energy, etc. It can realize industrial methane production of green hydrogen and high-value carbon, with low investment and low operating expenses, no catalyst and water required, and low implementation difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0025] Figure 1 It is a schematic diagram of the structure of a green electricity microwave discharge plasma methane cracking hydrogen-carbon cogeneration system; wherein, 1-green electricity power supply system, 2-gas supply system, 3-microwave discharge plasma cracking system, 4-carbon product separation and collection system, 5-gas circulation system, 6-gas separation and purification system.

[0026] Figure 2 Figures 1 and 2 are XRD and Raman spectra of carbon products from different embodiments; (a) is the XRD image of carbon products from different embodiments, (b) is the Raman image of carbon products from different embodiments, (c) and (d) are the Raman spectra of carbon products from different embodiments. Figure 2 Lorentzian fit of the D peak.

[0027] Figure 3 A schematic structural diagram of the microwave discharge plasma cracking system provided by the present invention; wherein, 301-reactor, 302-microwave generating device, 303-reaction area, 304-filler, 305-separation and sedimentation area, 306-carbon product outlet, 307-air inlet, 308-air outlet, 309-sieve plate. DETAILED DESCRIPTION

[0028] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0029] The present invention realizes a method and system for hydrogen-carbon co-production by cracking methane using green electricity microwave discharge plasma. The system realizes controllable cracking of methane at low power consumption and low gas velocity, and simultaneously generates high value-added carbon products.

[0030] The system structure is as follows Figure 1 As shown, it includes a green power supply system 1, a gas supply system 2, a microwave discharge plasma cracking system 3, a carbon product separation and collection system 4, a gas circulation system 5 and a gas separation and purification system 6. The green power supply system 1 is used for the access of green power, the gas supply system 2 is used to provide stable methane and discharge medium gas, the microwave discharge plasma cracking system 3 is equipped with a filler 304 with a certain radius of curvature and a microwave source (microwave generating device 302), which is used for methane cracking to produce gas and carbon, the carbon product separation and collection system 4 is used to separate and collect carbon products from gas, the gas circulation system 5 is used to circulate part of the cracked gas, and the gas separation and purification system 6 is used to separate and purify hydrogen from the gas. The green power supply system 1 is connected to the microwave discharge plasma cracking system 3 through a circuit, the gas supply system 2, the carbon product separation and collection system 4, and the gas circulation system 5 are respectively connected to the microwave discharge plasma cracking system 3 through pipelines, and the outlet of the gas circulation system 5 is divided into two branches, one branch is connected to the gas separation and purification system 6, and the other branch is connected to the microwave discharge plasma cracking system 3 through the connecting pipeline between the gas supply system 2 and the microwave discharge plasma cracking system 3, and the opening and closing of the two branches are controlled by valves. An air pump is set in the gas circulation system 5 to pump the product back to the reaction area 303 to achieve re-reaction, thereby changing the product composition.

[0031] like Figure 3 As shown, the microwave discharge plasma cracking system 3 includes a reactor 301 and a microwave generator 302. The microwave generator 302 is connected to the green electricity power supply system 1 and is powered by the green electricity power supply system 1. The reaction conditions in the reactor 301 are regulated by the microwave generator 302. The top of the reactor 301 is provided with an air inlet 307 connected to the gas supply system 2, the bottom is provided with a carbon product outlet 306, and the side is provided with an air outlet 308 connected to the gas circulation system 5. The interior of the reactor 301 is a microwave reaction chamber, and a sieve plate 309 is provided above the air outlet 308. A filler 304 is placed on the sieve plate 309. The reaction area 303 is above the sieve plate 309, and the separation and sedimentation area 305 is below.

[0032] The gas supply system 2 is connected to the gas inlet 307 of the microwave discharge plasma cracking system 3, and includes two gas circuits, which respectively supply hydrocarbon compounds and discharge medium gas, and the two gas circuits are switched by valves.

[0033] The carbon product separation and collection system 4 is connected to the carbon product outlet 306, and can use conventional mechanical stripping methods to separate and collect carbon products such as graphene, and its structure is not limited.

[0034] The gas circulation system 5 includes a three-way valve and an air pump. The three-way valve is connected to the gas outlet 308, the gas inlet 307 and the gas separation and purification system 6 of the microwave discharge plasma cracking system 3. By adjusting the opening and closing of the three-way valve and driven by the air pump, the gas product is supplied to the gas separation and purification system 6 or circulated to the microwave discharge plasma cracking system 3.

[0035] The gas separation and purification system 6 is used for separation and purification of hydrogen. It can adopt the low-temperature separation method in the prior art to separate hydrogen from the mixed gas by utilizing the boiling points of different components, or adopt adsorbents to selectively adsorb the gas, or adopt membrane separation method, etc., which will not be elaborated here.

[0036] Calculate the gas velocity according to the formula Q=V / A.

[0037] Wherein, Q is the gas velocity, m / s; V is the flow rate, ml / min; in this embodiment, the cross-sectional radius of the reaction region 303 of the reactor 301 is 9 mm.

[0038] In one or more embodiments of the present invention, the flow rate is 50ml / min, 100ml / min, 200ml / min, 300ml / min, 400ml / min, 500ml / min or any condition between 50ml / min and 500ml / min, corresponding to a gas velocity of 0.00328m / s, 0.00657m / s, 0.0131m / s, 0.0197m / s, 0.0263m / s, 0.0328m / s or any condition between 0.00328m / s and 0.0328m / s, preferably the gas velocity is 0.003m / s to 0.033m / s, more preferably 0.006m / s to 0.02m / s, and further preferably 0.006m / s to 0.01m / s.

[0039] In one or more embodiments of the present invention, in the microwave discharge plasma cracking reaction conditions, the content of methane in the mixed gas of methane and the discharge medium gas is 10%, 30%, 50% or any value between 10% and 50%; the energy input of the microwave generating device 302 is adjusted, and the power is calculated as methane: 20W / mol, 30W / mol, 40W / mol, 50W / mol, 60W / mol, 150W / mol or any condition between 20W / mol and 150W / mol; the microwave power of the microwave generating device 302 is set to 200W, 300W, 400W, 500W, 600W or any condition between 200W and 600W.

[0040] In one or more embodiments of the present invention, in the microwave discharge plasma cracking reaction conditions, the temperature is room temperature and the pressure is normal pressure.

[0041] In this method, the gas supply system 2 is used to provide hydrocarbon compounds and discharge medium gas and ensure a stable flow rate.

[0042] The discharge medium gas in the method includes, but is not limited to, argon, nitrogen and other chemically stable gases that are easy to form discharge plasma.

[0043] In the present method, the filler 304 in the microwave discharge plasma cracking system 3 includes, but is not limited to, metal needles, metal wires, metal meshes, activated carbon and other absorbing materials whose curvature radius is less than or equal to the tip length or radius.

[0044] The operation flow of the method includes: 1. placing the filler 304 into the reaction area 303 of the microwave discharge plasma cracking system 3; 2. introducing a discharge medium gas into the microwave reaction chamber of the microwave discharge plasma cracking system 3 to provide a discharge environment for the reaction chamber; 3. adjusting the energy input of the microwave generator 302, inputting microwaves into the microwave reaction chamber, so that the filler 304 in the microwave reaction chamber is continuously discharged, and a stable plasma field is formed around the filler 304; 4. adjusting the gas input, introducing a mixed gas of methane gas and a discharge medium gas into the microwave reaction chamber, and starting a microwave discharge plasma cracking reaction; 5. the reaction products are separated from the gas by passing through the separation and sedimentation area 305 of the microwave discharge plasma cracking system 3; 6. regulating the gas circulation amount and number of times of the gas circulation system 5 according to the product distribution of the gas separation and purification system 6 to regulate the quality of the gas-solid products; 7. collecting the carbon products in the carbon product separation and collection system 4; 8. collecting the gas products after the gas passes through the gas separation and purification system 6.

[0045] Example 1 A pure tungsten needle with a diameter of 1 mm, a length of 51 mm, and a needle tip of 15° was selected, and the tungsten needle was assembled with a quartz plate with a through hole, and then placed in the reactor 301. After 99.999% argon was introduced at a flow rate of 100 ml / min (gas velocity of 0.00657 m / s) for 15 minutes, the microwave switch of the microwave generator 302 was turned on, and the microwave power was adjusted to 300 W (30 W / mol methane). After stable discharge for 15 minutes, the gas path was switched, and a mixed gas of 10% methane + 90% argon was introduced into the reactor 301 for reaction for 20 minutes. The working temperature was 300°C, and the reaction pressure was normal pressure.

[0046] Example 2 The same as Example 1, except that the microwave power was adjusted to 400 W (40 W / mol methane) and the gas flow rate was maintained at 100 ml / min.

[0047] Example 3 The same as Example 1, except that the microwave power was adjusted to 500 W (50 W / mol methane) and the gas flow rate was maintained at 100 ml / min.

[0048] Example 4 The same as Example 1, except that the microwave power was adjusted to 300 W and the gas flow rate was adjusted to 200 ml / min (gas velocity was 0.0131 m / s).

[0049] Example 5 The same as Example 1, except that the microwave power was adjusted to 300 W and the gas flow rate was adjusted to 300 ml / min (gas velocity was 0.0197 m / s).

[0050] Example 6 The same as Example 1, except that the gas composition of methane and argon was adjusted to 50% methane + 50% argon, the microwave power was maintained at 300 W (150 W / mol methane), and the gas flow rate was maintained at 100 ml / min.

[0051] Example 7 The same as Example 1, except that a reactor 301 with a smaller cross-sectional radius of the reaction area 303 was used, the reaction area 303 was reduced by 20%, the reaction time was reduced by 50%, the microwave power was maintained at 300 W (30 W / mol methane), and the gas flow rate was maintained at 100 ml / min.

[0052] Example 8 Coal-based activated carbon particles with a diameter of 2 mm were selected and placed in the reactor 301. After 99.999% argon was introduced at a flow rate of 100 ml / min (gas velocity of 0.007 m / s) for 15 minutes, the microwave switch of the microwave generator 302 was turned on, and the microwave power was adjusted to 300 W (30 W / mol methane). After stable discharge for 15 minutes, the gas path was switched, and a mixed gas of 10% methane + 90% argon was introduced into the reactor 301 for reaction for 20 minutes. The working temperature was 300°C and the reaction pressure was normal pressure.

[0053] Example 9 Select a block of foamed silicon carbide with a diameter of 18 mm, put the foamed silicon carbide into the reactor 301, introduce 99.999% argon at a flow rate of 100 ml / min (gas velocity of 0.007 m / s) for 15 minutes, turn on the microwave switch of the microwave generator 302, adjust the microwave power to 300 W (30 W / mol methane), and switch the gas path after stable discharge for 15 minutes, and introduce a mixed gas of 10% methane + 90% argon into the reactor 301 for reaction for 20 minutes. The working temperature is 300°C and the reaction pressure is normal pressure.

[0054] Example 10 The same as Example 1, except that the microwave power was adjusted to 300 W and the gas flow rate was adjusted to 500 ml / min (gas velocity was 0.0328 m / s).

[0055] Embodiment 11 The same as Example 1, except that the microwave power was adjusted to 300 W and the gas flow rate was adjusted to 50 ml / min (gas velocity was 0.00328 m / s).

[0056] Example 12 The same as Example 1, except that the microwave power was adjusted to 200 W (20 W / mol methane) and the gas flow rate was adjusted to 100 ml / min (gas velocity was 0.00657 m / s).

[0057] Embodiment 13 The same as Example 1, except that the microwave power was adjusted to 600 W (60 W / mol methane) and the gas flow rate was adjusted to 100 ml / min (gas velocity was 0.00657 m / s).

[0058] Embodiment 14 Same as Example 7, except that the reaction time is the same as Example 1.

[0059] Embodiment 15 The same as Example 1, except that the microwave power was adjusted to 300W (30W / mol ethylene), the gas path was switched after stable discharge for 15 minutes, and a mixed gas of 10% ethylene + 90% argon was introduced into the reactor 301 for reaction for 20 minutes. The operating temperature was 300°C and the reaction pressure was normal pressure.

[0060] Example 16 The same as Example 1, except that the microwave power was adjusted to 300W (30W / mol ethane), the gas path was switched after stable discharge for 15 minutes, and a mixed gas of 10% ethane + 90% argon was introduced into the reactor 301 for reaction for 20 minutes. The working temperature was 300°C and the reaction pressure was normal pressure.

[0061] The reaction results under the schemes provided in Examples 1 to 16 are shown in Table 1.

[0062] Energy consumed per mol of methane conversion / kJ*mol -1 The calculation formula is: ; ; Where SEI is the specific energy input, P is the input power, F is the flow rate of the feed gas, and 60 is the conversion from minutes to seconds.

[0063] SER is the specific energy requirement, which is the energy required to completely convert 1 mole of methane to produce 1 mole of hydrogen; is the conversion rate of methane or other reactants.

[0064] Table 1. Reaction results under different embodiments

[0065] As can be seen from Table 1, the present method and process achieves methane>95% efficient cracking under the conditions of low energy consumption and low gas velocity of 300W, 100ml / min, i.e. 30W / mol methane, and 0.007m / s, and at the same time achieves 42% ethane gaseous product methane controllable conversion and 1-2 layers of low-layer graphene preparation. As can be seen from the results of Example 15, ethane can be obtained using ethylene as a reactant. As can be seen from the results of Example 16, the hydrogen yield can be increased using ethane as a reactant; similarly, the hydrogen yield can be increased by using the gas circulation system 5 to pass a large amount of ethane products again into the microwave discharge plasma cracking system 3. At the same time, based on the present method, about 100% selectivity of hydrogen can be achieved in the control experiment stage.

[0066] Figure 2 300W, 400W, and 500W correspond to Examples 1, 2, and 3, respectively; 100ml / min, 200ml / min, and 300ml / min correspond to Examples 4, 5, and 6, respectively.

[0067] Figure 2 (a) is the XRD image of the carbon products of different embodiments. The image has peak characteristics at 2θ=26°, 42° and 54°, corresponding to the (002), (101) and (004) characteristic peaks of graphite, respectively, indicating that the material has a strong degree of graphitization.

[0068] Figure 2 (b) is the Raman image of the carbon product of different embodiments. As shown in the image, the Raman spectrum of the product is composed of D peak, G peak and 2D peak from left to right along the X-axis. The D peak is used for defect characterization, the G peak represents the degree of graphitization, and the peak shape of the 2D peak can be used to identify the layer thickness. The peak ratio of the D peak and the G peak is used to describe the degree of graphitization of the sample, and a lower ID / IG indicates a better degree of graphitization. The sharper the 2D peak and the higher the intensity, the lower the number of graphene layers. It can be seen that the degree of graphitization is higher and the number of layers is lower under 400W conditions.

[0069] Figure 2 (c) and (d) are Raman spectra Figure 2 Lorentz fitting of the D peak. The 2D peak of monolayer graphene presents a perfect single peak under Lorentz fitting. As shown in the figure, the fitting effect is good.

[0070] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A green power microwave discharge plasma methane cracking hydrogen and carbon cogeneration system, characterized in that: include: Green electricity supply system, used for access to green electricity; A gas supply system for providing stable hydrocarbon compounds and discharge medium gas; Microwave discharge plasma cracking system, used for cracking hydrocarbon compounds to produce gas and carbon products; A carbon product separation and collection system, used to separate and collect carbon products from gases; A gas circulation system, used for circulating part of the cracked gas; Gas separation and purification system, used for separation and purification of hydrogen.

2. The green electricity microwave discharge plasma methane cracking hydrogen and carbon cogeneration system according to claim 1 is characterized in that: The green electricity power supply system is connected to the microwave discharge plasma cracking system through a circuit, the gas supply system, the carbon product separation and collection system, and the gas circulation system are respectively connected to the microwave discharge plasma cracking system through pipelines, and the outlet of the gas circulation system is divided into two branches, one branch is connected to the gas separation and purification system, and the other branch is connected to the microwave discharge plasma cracking system through a connecting pipeline between the gas supply system and the microwave discharge plasma cracking system.

3. The green electricity microwave discharge plasma methane cracking hydrogen and carbon cogeneration system according to claim 2 is characterized in that: The microwave discharge plasma cracking system includes a reactor and a microwave generator, and the reaction conditions in the reactor are regulated by the microwave generator; the top of the reactor is provided with an air inlet connected to the gas supply system, the bottom is provided with a carbon product outlet, and the side is provided with an air outlet connected to the gas circulation system; the inside of the reactor is a microwave reaction chamber, a sieve plate is provided above the air outlet, a filler is placed on the sieve plate, the upper part of the sieve plate is a reaction area, and the lower part is a separation and sedimentation area; the microwave generator is connected to the green electricity power supply system.

4. The green electricity microwave discharge plasma methane cracking hydrogen and carbon cogeneration system according to claim 3 is characterized in that: The filler is made of a wave-absorbing material whose curvature radius is less than or equal to the tip length or radius.

5. The green electricity microwave discharge plasma methane cracking hydrogen and carbon cogeneration system according to claim 4, characterized in that: The filler material is selected from metal needles, metal wires, metal mesh or activated carbon.

6. The green electricity microwave discharge plasma methane cracking hydrogen and carbon cogeneration system according to claim 3, characterized in that: The discharge medium gas is argon or nitrogen.

7. The green electricity microwave discharge plasma methane cracking hydrogen and carbon cogeneration system according to claim 3, characterized in that: The hydrocarbon compound is selected from methane, ethane, ethylene or acetylene.

8. A method for co-production of hydrogen and carbon by methane cracking using green microwave discharge plasma, characterized in that: Based on the green microwave discharge plasma methane cracking hydrogen-carbon cogeneration system according to any one of claims 3 to 7, the method comprises the following steps: S1. placing the filler into the reaction area of ​​the microwave discharge plasma cracking system; S2. A discharge medium gas is introduced into the microwave reaction chamber of the microwave discharge plasma cracking system to provide a discharge environment for the reaction chamber; S3. Adjust the energy input of the microwave generator to input microwaves into the microwave reaction chamber, so that the filling in the microwave reaction chamber is continuously discharged, and a stable plasma field is formed around the filling; S4. Adjust the gas input of the gas supply system, introduce a mixture of hydrocarbon compound gas and discharge medium gas into the microwave reaction chamber, and start the microwave discharge plasma cracking reaction; S5. The reaction products are separated into gas and solid by the separation and settling area of ​​the microwave discharge plasma cracking system; the carbon products are collected in the carbon product separation and collection system; The gas products are collected after passing through the gas separation and purification system.

9. The method for co-production of hydrogen and carbon by methane cracking by green electricity microwave discharge plasma according to claim 8, characterized in that: In step S4, the microwave discharge plasma cracking reaction conditions include: a gas velocity of 0.003 m / s to 0.033 m / s.

10. The method for co-production of hydrogen and carbon by methane cracking by green electricity microwave discharge plasma according to claim 8, characterized in that: In step S4, the microwave discharge plasma cracking reaction conditions include: in the mixed gas of hydrocarbon compound gas and discharge medium gas, the content of hydrocarbon compound gas is any value between 10% and 50%; the energy input of the microwave generator is adjusted, and the power is any condition between 20W / mol and 150W / mol in terms of hydrocarbon compound gas.

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