A microwave plasma co2 cracking apparatus and method for product recycle separation

Abstract

This invention discloses a microwave plasma CO2 pyrolysis device and method with product recycling and separation, comprising four parts: a microwave plasma power supply unit, a gas supply and reactor unit, a post-processing and circulation unit, and a signal acquisition and control unit. A solid-state power supply generates microwaves via a magnetron, which, through a waveguide, form microwave plasma within the reactor, pyrolyzing CO2 into CO and O2. A contraction-expansion nozzle creates eddies and a more optimized temperature distribution within the microwave reactor, achieving a higher CO2 conversion rate. A constant-temperature chamber and a carbon bed remove O2 from the products to increase the CO concentration. A pressure swing adsorption device separates and collects the CO, and a vacuum pump circulates the unreacted raw material gas, thus achieving complete CO2 pyrolysis. This invention features novel functional integration, enabling highly efficient CO2 pyrolysis and conversion. It can also be extended to other microwave plasma-based gaseous product conversion processes, facilitating industrial application.

Description

Technical Field

[0001] This invention belongs to the field of greenhouse gas conversion technology, specifically relating to a microwave plasma CO2 pyrolysis device and method for product recycling and separation. Background Technology

[0002] Capture, utilization, and storage of greenhouse gases, primarily CO2, is a key technological approach. Among these, the cracking of CO2 to produce CO and O2, followed by the Fischer-Tropsch process to convert CO into high-value chemicals, is a widely studied utilization route. However, due to the high bond energy of CO2 molecules (803 kJ / mol), traditional thermochemical CO2 cracking suffers from high energy consumption, low activity, and requires further improvement in selectivity and stability. Plasma technology, on the other hand, can utilize high-energy electrons and reactive species generated by high-voltage discharge to activate small energy molecules, breaking inert chemical bonds and lowering the catalytic reaction energy barrier, thus reducing reaction energy consumption and offering a new approach for CO2 emission reduction and high-value utilization.

[0003] Among different types of plasma sources, microwave (MW) plasma has high CO2 dissociation energy efficiency due to its effective vibrational excitation (effective channel for dissociation) process; its relatively high internal heavy particle temperature also promotes the thermal decomposition of CO2. Using a microwave plasma reactor to achieve CO2 dissociation to generate CO can achieve a conversion rate close to the thermodynamic limit of 50% (Chemical Society Reviews, 2017, 46: 5805–63).

[0004] However, the core gas temperature of microwave plasma can reach 5000K or even higher, and the temperature in the surrounding area can exceed 3000K. Excessively high temperatures can lead to a reverse recombination reaction between CO and O, and there is also a risk of explosion if the CO and O2 concentrations in the products reach a certain range. Therefore, the key to overcoming thermodynamic limitations and achieving efficient microwave plasma CO2 pyrolysis lies in controlling the temperature distribution inside the reactor and removing O2 from the product gas mixture. Improving the reactor system to meet these requirements is fundamental to the large-scale industrial application of microwave plasma CO2 pyrolysis.

[0005] Chinese patent application CN201910449663.4 discloses a device for microwave plasma pyrolysis hydrogen production. The device includes a microwave energy supply unit, a plasma torch supply unit, and a pyrolysis chamber connected in sequence, achieving low loss, high pyrolysis efficiency, and safety and reliability. This invention addresses the shortcomings of existing inexpensive and efficient pure hydrogen production technologies, the easy wear and short service life of electrodes used to generate plasma via arc discharge, and the incomplete fuel pyrolysis. It provides a device for microwave plasma pyrolysis hydrogen production that solves the problem of incomplete fuel combustion during hydrogen production. However, it does not address the corresponding treatment of reaction products, posing a problem of product separation.

[0006] Chinese patent application CN200580022852.X discloses a microwave plasma nozzle with higher plume stability and heating efficiency, and provides various systems and methods for generating relatively cool microwave plasma using atmospheric pressure. These systems have lower unit costs and operate at atmospheric pressure with lower operating costs, lower energy consumption, and shorter sterilization turnaround times. The relatively cool microwave plasma is generated by the nozzle, which, unlike existing plasma generation systems, operates at atmospheric pressure with higher operating efficiency. However, the addition of the nozzle limits the reactor temperature, and a matching design for the corresponding post-treatment process is still lacking.

[0007] In summary, traditional thermocatalytic CO2 cracking and conversion often requires high temperature, high pressure, and a suitable catalyst to achieve large-scale utilization. Microwave plasma technology provides a sustainable and energy-saving application solution for rapid and efficient CO2 cracking and conversion. However, there is still a lack of exploration into the control of temperature distribution in microwave plasma reactors and the design of post-treatment devices. Summary of the Invention

[0008] To address the aforementioned technical problems, this invention proposes a microwave plasma CO2 pyrolysis device and method for product recycling and separation. This device utilizes a contraction-expansion nozzle to achieve a reasonable temperature distribution inside the reactor and timely extraction of products. Simultaneously, the post-treatment carbon bed and recycling separation device, in conjunction with a signal transmission line and a host computer, can achieve the production of high-purity CO and the recycling of CO2 feed gas, thereby improving the automation level of the CO2 pyrolysis process.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A microwave plasma CO2 pyrolysis device for product recycling and separation, characterized in that it includes a microwave plasma power supply unit, a gas supply and reactor unit, a post-processing and circulation unit, and a signal acquisition and control unit.

[0011] The microwave plasma power supply unit includes a solid-state power supply, a high-voltage transmission line, a magnetron, a rectangular waveguide, a tapered waveguide, a tungsten rod electrode, a circulating water system, and circulating water pipelines. The solid-state power supply generates microwaves by connecting to the magnetron through the high-voltage transmission line. After multiple reflections in the rectangular and tapered waveguide cavities, standing waves are formed, generating a stable microwave field strength. This field strength leads to gas discharge at the electrode tip, initiating microwave plasma. The circulating water system achieves cooling by connecting to the inlet and outlet of the magnetron through the circulating pipelines.

[0012] The gas supply and reactor unit includes a high-pressure steel cylinder, stainless steel pipeline, solenoid valve, flow meter, insulating pipeline, cylindrical quartz tube, connector sleeve, and arc-shaped quartz tube; the high-pressure steel cylinder, solenoid valve, and flow meter are connected through the stainless steel pipeline; the cylindrical quartz tube passes through the center of the conical waveguide, and the gas enters the gas inlet of the cylindrical quartz tube through the insulating pipeline; the arc-shaped quartz tube is connected to the gas outlet of the cylindrical quartz tube through the connector sleeve.

[0013] The post-processing and circulation unit includes a constant temperature chamber, a resistance heating system, flange connectors, a contraction-expansion nozzle, a permeable plate, a carbon bed, a feed trough, a conical tube, a pressure swing adsorption (PSA) unit, a gas storage tank, a vacuum pump, and a barometer. The constant temperature chamber is heated and maintained at its temperature by the resistance heating system, and its inlet is connected to an arc-shaped quartz tube. The air inlet of the contraction-expansion nozzle is connected to the arc-shaped quartz tube via a flange connector, and its outlet is connected to the carbon bed. The feed trough penetrates the constant temperature chamber and is connected to the carbon bed, with the carbon bed's air inlet... The gas outlet is separated from the contraction-expansion nozzle by a vent plate, and the gas inlet is connected to the carbon bed outlet. The gas outlet is also connected to the constant temperature chamber. The pressure swing adsorption (PSA) instrument is connected to the outlet of the conical tube, which separates CO from the mixed gas product and injects it into the gas storage tank through a stainless steel pipeline. Its built-in barometer can monitor the internal gas pressure in real time. The vacuum pump inlet is connected to the PSA instrument, and the outlet is connected to a cylindrical quartz tube to achieve gas circulation under conditions of less than one standard atmosphere.

[0014] The signal acquisition and control unit includes a thermocouple, a host computer, and a signal transmission line; the thermocouple is inserted into the carbon bed through the constant temperature cavity and connected to the host computer through the signal transmission line; the host computer establishes communication connections with the solid-state power supply, solenoid valve, thermocouple, resistance heating system, and barometer.

[0015] Furthermore, the solid-state power supply is used to drive the magnetron to generate uniform microwaves in the waveguide at a frequency of 915MHz or 2.45GHz.

[0016] Furthermore, both the rectangular waveguide and the tapered waveguide are hollow structures, with their inner sides made of a metallic material, which is either copper or aluminum; and their outer sides made of an insulating material, which is polytetrafluoroethylene.

[0017] Furthermore, the tip of the tungsten rod electrode is located at the center of the tapered waveguide and is fixed to the air inlet of the cylindrical quartz tube; the air outlet of the cylindrical quartz tube is connected to the arc-shaped quartz tube through a connector sleeve, the material of which is polytetrafluoroethylene.

[0018] Furthermore, the constant temperature chamber has four openings: one connected to the arc-shaped quartz tube, one connected to the feed trough, one connected to the conical tube, and one connected to the thermocouple. Each opening is sealed to the constant temperature chamber with high-temperature adhesive.

[0019] Furthermore, the contraction-expansion nozzle has a smaller diameter in the middle compared to the sides, ensuring that the flow velocity changes as the airflow passes through, thereby forming a vortex. The material used is stainless steel.

[0020] Furthermore, the carbon bed is a hollow cuboid cavity with an opening on the upper side connected to a feed trough. The interior is filled with carbon particles with a diameter of 0.1 to 2 mm. The feed trough remains sealed during the reaction process.

[0021] Furthermore, the probe of the thermocouple is inserted into the carbon bed to measure its temperature in real time, and communicates with the host computer through a signal transmission line. The host computer controls the resistance heating system to adjust the temperature of the constant temperature cavity based on the temperature information via the signal transmission line.

[0022] The present invention also provides a conversion method for a microwave plasma CO2 pyrolysis device with product recycling and separation, comprising the following steps:

[0023] Step (1): The solid-state power supply drives the magnetron to generate microwaves, forming standing waves in the rectangular waveguide and the tapered waveguide, and generating microwave plasma by discharging at the tungsten rod electrode.

[0024] Step (2): The raw material gas in the high-pressure steel cylinder passes through the solenoid valve and flow meter in sequence and enters the cylindrical quartz tube at a fixed flow rate. At the same time, the vacuum pump is started to form a gas circulation flow.

[0025] Step (3): After passing through the cylindrical quartz tube, the raw gas enters the constant temperature chamber through the arc-shaped quartz tube and then enters the carbon bed through the contraction-expansion nozzle.

[0026] Step (4): The thermocouple monitors the internal temperature of the carbon bed in real time and sends it to the host computer. The host computer controls the resistance heating system to adjust the temperature of the constant temperature chamber so that the temperature of the carbon bed is suitable for the reaction of O2 and carbon in the product to convert into CO.

[0027] Step (5): The CO in the mixed product is extracted by pressure swing adsorption and injected into the gas storage tank. The remaining gas is re-entered into the inlet of the cylindrical quartz tube by a vacuum pump.

[0028] Step (6): When the barometer reading reaches the set maximum pressure value of the gas storage tank or the carbon bed needs to be replaced with carbon particles, the host computer controls the solid-state power supply and solenoid valve to close via the signal transmission line, and further sends a signal to control the resistance heating system, vacuum pump and pressure swing adsorption instrument to stop running.

[0029] Step (7): After the gas in the gas storage tank is emptied or the carbon particles are replaced, the barometer transmits the data to the host computer, which controls the solenoid valve, vacuum pump and resistance heating system to start. After running for a period of time to empty the air, it further controls the solid power supply and pressure swing adsorption instrument to run. Steps (1)-(7) are repeated to achieve unattended operation around the clock.

[0030] The beneficial effects of this invention are as follows:

[0031] (1) The device of the present invention can make full use of microwave plasma technology to significantly reduce reaction energy consumption and improve the conversion efficiency of greenhouse gases;

[0032] (2) The present invention combines the shrink-expansion nozzle, the post-treatment carbon bed, and the circulation device with the microwave plasma reactor to promote a significant increase in CO2 cracking conversion rate and can directly obtain high-purity CO products.

[0033] (3) The present invention utilizes a host computer for data processing, signal transmission and equipment control to realize automated control of the device;

[0034] (4) The present invention has the advantages of simple structure, high degree of automation, controllable discharge intensity, large processing capacity and good CO2 cracking effect. Attached Figure Description

[0035] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments of this application and their descriptions are used to explain this application and do not constitute a limitation thereof.

[0036] Figure 1 This is a front view of the overall structure of the microwave plasma CO2 pyrolysis device for product recycling and separation in an embodiment of the present invention.

[0037] Figure 2 These are a cross-sectional schematic diagram and a perspective view of the combined structure of the tapered waveguide, cylindrical quartz tube, and tungsten rod electrode of the present invention;

[0038] Figure 3This is a cross-sectional view of the arc-shaped quartz tube, the shrink-expansion nozzle, the constant temperature chamber, the flange connector, the vent plate, the carbon bed, the feed trough, and the conical tube combination structure of the present invention, as well as a perspective view of the shrink-expansion nozzle and the vent plate.

[0039] Figure 4 This is a flowchart of the microwave plasma CO2 cyclic pyrolysis process of the present invention;

[0040] Figure 1 The reference numerals in the accompanying drawings are as follows:

[0041] Solid-state power supply 1, grounding 2, high-voltage connection line 3, magnetron 4, magnetron outlet 5, magnetron inlet 6, circulating water pipeline 7, circulating water machine 8, rectangular waveguide 9, tapered waveguide 10, tungsten rod electrode 11, cylindrical quartz tube 12, connector sleeve 13, arc-shaped quartz tube 14, flange connector 15, constant temperature chamber 16, contraction-expansion nozzle 17, carbon bed 18, feed trough 19, carbon particles 20, permeable plate 21, tapered tube 22, stainless steel pipeline 23, pressure swing adsorption instrument 24, gas storage and transportation tank 25, barometer 26, insulated pipeline 27, host computer 28, thermocouple 29, signal transmission line 30, resistance heating system 31, vacuum pump 32, flow meter 33, solenoid valve 34, high-pressure cylinder 35.

[0042] Figure 3 The reference numerals in the accompanying drawings are as follows:

[0043] Bolt 36, flange 37, nut 38, O-ring 39, circular opening 40. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0045] Example 1

[0046] In a typical embodiment of the present invention, such as Figure 1 As shown, the microwave plasma CO2 pyrolysis device for product recycling separation of the present invention comprises a microwave plasma power supply unit, a gas supply and reactor unit, a post-processing and circulation unit, and a signal acquisition and control unit, totaling four units.

[0047] The microwave plasma power supply unit comprises a solid-state power supply 1, a grounding 2, a high-voltage connection line 3, a magnetron 4, a magnetron outlet 5, a magnetron inlet 6, a circulating water pipeline 7, and a circulating water machine 8. The solid-state power supply 1 is connected to the grounding 2 and to the magnetron 4 via the high-voltage connection line 3. The magnetron outlet 5 and the magnetron inlet 6 are respectively connected to the circulating water machine 8 via the circulating water pipeline 7 to achieve temperature control.

[0048] A gas supply and reactor unit is composed of a rectangular waveguide 9, a tapered waveguide 10, a tungsten rod electrode 11, a cylindrical quartz tube 12, a connector sleeve 13, an arc-shaped quartz tube 14, a stainless steel pipe 23, an insulating pipe 27, a flow meter 33, a solenoid valve 34, and a high-pressure gas cylinder 35. The hollow rectangular waveguide 9 is connected to the hollow tapered waveguide 10. The tungsten rod electrode 11 is fixed to the inlet side of the cylindrical quartz tube 12. The cylindrical quartz tube 12 passes through the center of the tapered waveguide 10, and its outlet side is connected to the arc-shaped quartz tube 14 through the connector sleeve 13. The high-pressure gas cylinder 35 is connected to the solenoid valve 34 and the flow meter 33 in sequence through the stainless steel pipe 23, and then connected to the inlet of the cylindrical quartz tube 12 through the insulating pipe 27.

[0049] The following components constitute the post-processing and circulation unit: 14. Arc-shaped quartz tube; 15. Flange connector; 16. Constant temperature chamber; 17. Shrink-expand nozzle; 18. Carbon bed; 19. Feed trough; 20. Carbon particles; 21. Air permeable plate; 22. Conical tube; 23. Stainless steel pipeline; 24. Pressure swing adsorption instrument; 25. Gas storage and transportation tank; 26. Barometer; 27. Insulated pipeline; 30. Signal transmission line; 31. Resistance heating system; 32. Vacuum pump; and 33. Flow meter. The arc-shaped quartz tube 14 is connected to the contraction-expansion nozzle 17 via a flange connector 15 and is fixed at the inlet opening of the constant temperature chamber 16. The resistance heating system 31 controls the temperature of the constant temperature chamber 16 via a signal transmission line 30. The contraction-expansion nozzle 17 is connected to the carbon bed 18, separated by a vent plate 21. The carbon bed 18 is filled with carbon particles 20 and continuously replenished via a feed trough 19. The outlet of the carbon bed 18 is connected to a conical tube 22 and separated by a vent plate 21. The outlet of the conical tube 22 is fixed to the outlet opening of the constant temperature chamber 16 and is connected to the pressure swing adsorption unit 24 via a stainless steel pipe 23. One end of the outlet of the pressure swing adsorption unit 24 is connected to a gas storage tank 25 with a built-in barometer 26 via an insulating pipe 27, and the other end is connected to the inlet of the vacuum pump 32 via an insulating pipe 27. The outlet of the vacuum pump 32 is connected to the inlet of the cylindrical quartz tube 12 via an insulating pipe 27 and a flow meter 33, thereby realizing gas circulation.

[0050] The host computer 28, thermocouple 29, and signal transmission line 30 constitute a signal acquisition and control unit. The host computer 28 establishes a communication connection with the thermocouple 29 through the signal transmission line 30 to monitor the internal temperature of the carbon bed in real time. In addition, it also establishes communication connections with the barometer 26, resistance heating system 31, vacuum pump 32, flow meter 33, and solenoid valve 34 through the signal transmission line 30.

[0051] like Figure 1 As shown, the solid-state power supply 1 is used to provide power to the magnetron 4, with a power of 2000W and a frequency of 915MHz or 2.45GHz.

[0052] like Figure 2 As shown, the tapered waveguide 10 has a central opening through which a cylindrical quartz tube 12 passes, and a tungsten rod electrode 11 is fixed at its bottom.

[0053] like Figure 3 As shown, the flange 37 has an O-ring rubber ring 39 in the middle, and the two ends are fixed by bolts 36 and nuts 38; the vent plate 21 has through circular openings 40, the diameter of which is smaller than the diameter of the carbon particles 20.

[0054] Example 2

[0055] like Figure 4 As shown, the present invention also provides a microwave plasma CO2 pyrolysis conversion method with product recycling and separation, comprising the following steps:

[0056] Step (1): Solid-state power supply 1 drives magnetron 4 to generate microwaves, forming standing waves in rectangular waveguide 9 and tapered waveguide 10, and generating microwave plasma by discharging at tungsten rod electrode 11.

[0057] Step (2): The raw material gas in the high-pressure steel cylinder 35 passes through the solenoid valve 34 and the flow meter 33 in sequence and enters the cylindrical quartz tube 12 at a fixed flow rate. At the same time, the vacuum pump 32 is started to form a gas circulation flow.

[0058] Step (3): After passing through the cylindrical quartz tube 12, the raw gas enters the constant temperature chamber 16 through the arc-shaped quartz tube 14, and then enters the carbon bed 18 through the contraction-expansion nozzle 17.

[0059] Step (4): Thermocouple 29 monitors the internal temperature of carbon bed 18 in real time and sends it to host computer 28. Host computer 28 controls resistance heating system 31 to adjust the temperature of constant temperature chamber 16 so that the temperature of carbon bed 18 is suitable for O2 in the product to react with carbon and be converted into CO.

[0060] Step (5): The CO in the mixed product is extracted by the pressure swing adsorption instrument 24 and injected into the gas storage tank 25. The remaining gas is re-entered into the gas inlet of the cylindrical quartz tube 12 by the vacuum pump 32.

[0061] Step (6): When the value of the barometer 26 reaches the set maximum pressure value of the gas storage tank 25 or the carbon bed 18 needs to replace the carbon particles 20, the host computer 28 controls the solid power supply 1 and the solenoid valve 34 to close through the signal transmission line 30, and further sends a signal to control the resistance heating system 31, the vacuum pump 32 and the pressure swing adsorption instrument 24 to stop running.

[0062] Step (7): After the gas in the gas storage tank 25 is emptied or the carbon particles 20 are replaced, the barometer 26 transmits the data to the host computer 28, which controls the solenoid valve 34, vacuum pump 32 and resistance heating system 31 to open. After running for a period of time to empty the air, it further controls the solid power supply 1 and pressure swing adsorption instrument 24 to run, repeating steps (1)-(7) to achieve unattended operation around the clock.

[0063] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A microwave plasma CO2 pyrolysis device for product recycling and separation, characterized in that: It includes a microwave plasma power supply unit, a gas supply and reactor unit, a post-processing and circulation unit, and a signal acquisition and control unit; The microwave plasma power supply unit includes a solid-state power supply, a high-voltage transmission line, a magnetron, a rectangular waveguide, a tapered waveguide, a tungsten rod electrode, a circulating water system, and circulating water pipelines. The solid-state power supply generates microwaves by connecting to the magnetron through the high-voltage transmission line. After multiple reflections within the cavities of the rectangular and tapered waveguides, standing waves are formed, generating a stable microwave field strength. This field strength leads to gas discharge at the electrode tips, triggering microwave plasma. The circulating water system achieves cooling by connecting to the inlet and outlet of the magnetron through circulating water pipelines. The gas supply and reactor unit includes a high-pressure steel cylinder, stainless steel pipeline, solenoid valve, flow meter, insulating pipeline, cylindrical quartz tube, connector sleeve, and arc-shaped quartz tube; the high-pressure steel cylinder, solenoid valve, and flow meter are connected through the stainless steel pipeline; the cylindrical quartz tube passes through the center of the conical waveguide, and the gas enters the inlet of the cylindrical quartz tube through the insulating pipeline; the arc-shaped quartz tube is connected to the outlet of the cylindrical quartz tube through the connector sleeve. The post-processing and circulation unit includes a constant temperature chamber, a resistance heating system, flange connectors, a contraction-expansion nozzle, a permeable plate, a carbon bed, a feed trough, a conical tube, a pressure swing adsorption (PSA) unit, a gas storage tank, a vacuum pump, and a barometer. The constant temperature chamber is heated and maintained at its temperature by the resistance heating system, and its inlet is connected to an arc-shaped quartz tube. The air inlet of the contraction-expansion nozzle is connected to the arc-shaped quartz tube via a flange connector, and its outlet is connected to the carbon bed. The feed trough penetrates the constant temperature chamber and connects to the carbon bed, allowing air to enter the carbon bed. The inlet is separated from the contraction-expansion nozzle by a vent plate, and the outlet is separated from the conical tube by a vent plate. The inlet of the conical tube is connected to the outlet of the carbon bed, and the outlet is connected to the constant temperature chamber. The pressure swing adsorption (PSA) instrument is connected to the outlet of the conical tube, which separates CO from the mixed gas products and injects it into the gas storage tank through a stainless steel pipeline. Its built-in barometer monitors the internal gas pressure in real time. The inlet of the vacuum pump is connected to the PSA instrument, and the outlet is connected to a cylindrical quartz tube to achieve gas circulation under conditions of less than one standard atmosphere. The signal acquisition and control unit includes a thermocouple, a host computer, and a signal transmission line; the thermocouple is inserted into the carbon bed through the constant temperature cavity and connected to the host computer through the signal transmission line; the host computer establishes communication connections with the solid-state power supply, solenoid valve, thermocouple, resistance heating system, and barometer.

2. The microwave plasma CO2 pyrolysis device for product recycling and separation according to claim 1, characterized in that: The solid-state power supply is used to drive the magnetron to generate uniform microwaves in the waveguide at a frequency of 915 MHz or 2.45 GHz.

3. The microwave plasma CO2 pyrolysis device for product recycling and separation according to claim 1, characterized in that: Both the rectangular and tapered waveguides are hollow structures, with their inner sides made of a metallic material, either copper or aluminum; and their outer sides made of an insulating material, which is polytetrafluoroethylene (PTFE).

4. The microwave plasma CO2 pyrolysis device for product recycling and separation according to claim 1, characterized in that: The tip of the tungsten rod electrode is located at the center of the tapered waveguide and is fixed to the air inlet of the cylindrical quartz tube; the air outlet of the cylindrical quartz tube is connected to the arc-shaped quartz tube through a connector sleeve, the material of which is polytetrafluoroethylene.

5. The microwave plasma CO2 pyrolysis device for product recycling and separation according to claim 1, characterized in that: The constant temperature chamber has four openings: one connected to the arc-shaped quartz tube, one connected to the feed trough, one connected to the conical tube, and one connected to the thermocouple. Each opening is sealed to the constant temperature chamber with high-temperature adhesive.

6. The microwave plasma CO2 pyrolysis device for product recycling and separation according to claim 1, characterized in that: The contraction-expansion nozzle has a smaller diameter in the middle compared to the sides, ensuring that the flow velocity changes as the airflow passes through, thereby forming a vortex. The material used is stainless steel.

7. The microwave plasma CO2 pyrolysis device for product recycling and separation according to claim 1, characterized in that: The carbon bed is a hollow cuboid cavity with an opening on the upper side connected to a feed trough. The interior is filled with carbon particles with a diameter of 0.1 to 2 mm. The feed trough is kept sealed during the reaction.

8. The microwave plasma CO2 pyrolysis device for product recycling and separation according to claim 1, characterized in that: The inlet and outlet of the magnetron are connected to the circulating water machine through circulating water pipelines; the circulating water is tap water with a flow rate of 5~15 L / min; the inlet of the vacuum pump is connected to the outlet of the pressure swing adsorption instrument, and its outlet is connected to the cylindrical quartz tube through a flow meter.

9. The microwave plasma CO2 pyrolysis device for product recycling and separation according to claim 1, characterized in that: The thermocouple probe is inserted into the carbon bed to measure its temperature in real time and communicates with the host computer through a signal transmission line. The host computer controls the resistance heating system to adjust the temperature of the constant temperature cavity based on the temperature information via the signal transmission line.

10. A pyrolysis and conversion method for a microwave plasma CO2 pyrolysis apparatus with product recycling and separation according to any one of claims 1-9, characterized in that, Includes the following steps: Step (1): The solid-state power supply drives the magnetron to generate microwaves, forming standing waves in the rectangular waveguide and the tapered waveguide, and generating microwave plasma by discharging at the tungsten rod electrode; Step (2): The raw material gas in the high-pressure steel cylinder passes through the solenoid valve and flow meter in sequence and enters the cylindrical quartz tube at a fixed flow rate. At the same time, the vacuum pump is started to form a gas circulation flow. Step (3): After passing through the cylindrical quartz tube, the raw gas enters the constant temperature chamber through the arc-shaped quartz tube and then enters the carbon bed through the contraction-expansion nozzle; Step (4): The thermocouple monitors the internal temperature of the carbon bed in real time and sends it to the host computer. The host computer controls the resistance heating system to adjust the temperature of the constant temperature chamber so that the temperature of the carbon bed is suitable for the O2 in the product to react with the carbon and be converted into CO. Step (5): The CO in the mixed product is extracted by pressure swing adsorption and injected into the gas storage tank. The remaining gas is re-entered into the inlet of the cylindrical quartz tube by a vacuum pump. Step (6): When the barometer reading reaches the set maximum pressure value of the gas storage tank or the carbon bed needs to be replaced with carbon particles, the host computer controls the solid-state power supply and solenoid valve to close through the signal transmission line, and further sends a signal to control the resistance heating system, vacuum pump and pressure swing adsorption instrument to stop running. Step (7): After the gas in the gas storage tank is emptied or the carbon particles are replaced, the barometer transmits the data to the host computer, which controls the solenoid valve, vacuum pump and resistance heating system to start. After running for a period of time to empty the air, it further controls the solid power supply and pressure swing adsorption instrument to run, repeating steps (1) to (7) to achieve unattended operation around the clock.

Images