A system and method for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass

Abstract

The present invention discloses a system and method for the co-production of graphite carbon and hydrogen by two-stage pyrolysis of biomass, belonging to the field of biomass pyrolysis technology. The system includes a low-temperature pyrolysis module and a continuous Joule heat pyrolysis module. The Joule heat pyrolysis reactor is designed as a wheel type, so that the biomass pyrolysis reaction can be linked as a whole, and the reaction is carried out continuously, which reduces the start-up and shutdown time of the pyrolysis module and improves the economy of the entire system, thereby obtaining graphite carbon and hydrogen more efficiently. Using this system, the biomass is first subjected to low-temperature pyrolysis and condensation to obtain pyrolytic carbon and bio-oil, and then the pyrolytic carbon is subjected to Joule heat pyrolysis, condensation, and purification to obtain graphite carbon, bio-oil and hydrogen-rich synthesis gas. Graphite carbon and hydrogen are prepared using cheap biomass as raw material, saving fossil resources used in the traditional preparation of graphite carbon. This system can be better used for industrial production to achieve the co-production of graphite carbon and hydrogen.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomass pyrolysis, and in particular relates to a system and method for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] High-quality graphite carbon materials are widely used in a variety of fields, including batteries, brushes, lubricants, and thermal conductive materials, significantly improving the performance and service life of related products. Furthermore, hydrogen, as a clean and efficient energy source, is widely considered a crucial component of the future energy mix. Biomass, as a widely available and only renewable carbon resource, holds enormous development potential. Converting biomass into high-value-added graphite carbon materials and hydrogen through pyrolysis technology can not only effectively alleviate the energy crisis but also reduce fossil fuel use and CO2 emissions, achieving a win-win situation for both the environment and the economy.

[0004] Currently, these two high-value products are primarily derived from fossil resources, requiring enormous amounts of energy and causing environmental pollution during production. Traditional biomass pyrolysis technology faces numerous challenges in practical application. First, the composition of biomass is extremely complex and contains a high level of oxygen, resulting in low purity and quality of the pyrolysis products. In particular, carbonaceous products struggle to meet high graphitization requirements. Second, the gases produced during the pyrolysis process are complex in composition, with low hydrogen selectivity and difficulty in efficient separation from the gas mixture.

[0005] Patent CN114989844A discloses a method for the co-production of high-quality bio-oil and porous graphite carbon through catalytic pyrolysis of biomass and polyolefin plastics. This method involves pretreating the biomass with FeCl3, then adding the polyolefin plastic and mechanically mixing it uniformly. Rapid pyrolysis is then carried out in a fixed-bed reactor under a nitrogen atmosphere. This is followed by a slow pyrolysis to increase the degree of biochar modification. The solid product is then collected, washed, and dried to produce porous graphite carbon. This method has high energy consumption, makes metal impurity removal difficult, and increases process complexity and cost.

[0006] Patent CN115974058A discloses a method and system for preparing graphene. First, biomass undergoes primary pyrolysis and condensation to produce activated carbon, an oil-phase product, and a gas-phase product. Then, a portion of the activated carbon undergoes secondary pyrolysis and condensation to produce graphite carbon and a gas-liquid two-phase product. The two-stage gas-phase product is then passed through the remaining activated carbon for vapor deposition to produce graphene-loaded activated carbon and a first mixed gas. This method suffers from high energy consumption, low efficiency, and difficulty in efficiently separating hydrogen from the mixed gas.

[0007] Patent CN117304955A discloses a tar catalytic cracking device and product processing method based on a Joule heat reactor. This method separates the biomass pyrolysis, tar catalytic cracking, bio-oil condensation, and hydrogen-rich combustible gas collection systems. However, this process is complex, resulting in a low degree of graphitization of the biochar, and the catalyst required for the catalytic cracking reaction is expensive.

[0008] In summary, the existing biomass pyrolysis technology has a series of disadvantages such as complex process, high reaction energy consumption, low energy conversion efficiency, low degree of graphitization of pyrolytic carbon, and poor hydrogen selectivity. Summary of the Invention

[0009] In order to address the deficiencies of the prior art, the purpose of the present invention is to provide a system and method for the co-production of graphite carbon and hydrogen by two-stage pyrolysis of biomass. The system provided by the present invention can solve the problems of the existing biomass pyrolysis process being complex, high reaction energy consumption, low efficiency, low degree of graphitization of pyrolytic carbon, and poor hydrogen selectivity.

[0010] In order to achieve the above object, the technical solution of the present invention is:

[0011] In a first aspect, the present invention provides a system for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass, comprising a low-temperature pyrolysis module and a continuous Joule heat pyrolysis module;

[0012] The low-temperature pyrolysis module includes a first pyrolysis reactor, a first condenser and a first oil storage tank connected in sequence;

[0013] The continuous Joule heat pyrolysis module includes a mixing device, a tablet press, a wheel-disc Joule heat pyrolysis reactor and a carbon storage tank connected in sequence; the material inlet of the mixing device is connected to the material outlet of the first pyrolysis reactor; the wheel-disc Joule heat pyrolysis reactor includes a bottom plate, a wheel disc, a sieve plate electrode plate and a motor, the wheel disc is fixed to the bottom plate and rotates on the bottom plate driven by the motor; a reaction tube is provided inside the wheel disc, and the tablet press presses the raw materials into the reaction tube; the sieve plate electrode plate moves up and down relative to the wheel disc and does not rotate with the wheel disc; the bottom plate position directly below the sieve plate electrode plate is a metal electrode plate; the bottom plate is also provided with a circular discharge port, and the carbon storage tank is connected below the circular discharge port.

[0014] In some embodiments of the present invention, the distance between the center of the reaction tube and the center of the wheel disc is equal to the distance between the center of the tablet press and the center of the wheel disc.

[0015] Preferably, the distance between the center of the sieve plate electrode plate and the center of the wheel disc is equal to the distance between the center of the reaction tube and the center of the wheel disc.

[0016] Preferably, the distance between the center of the circular discharge port and the center of the wheel disc is equal to the distance between the center of the reaction tube and the center of the wheel disc.

[0017] In some embodiments of the present invention, the low-temperature pyrolysis module further comprises a feeding device, wherein a material outlet of the feeding device is connected to an inlet of the first pyrolysis reactor;

[0018] The feeding device is preferably a ball mill.

[0019] Preferably, the first pyrolysis reactor is a spiral pyrolysis reactor.

[0020] Preferably, the reaction tube includes but is not limited to a quartz tube and a corundum tube.

[0021] In some embodiments of the present invention, the gas outlet of the first condenser is connected to the material inlet of the first pyrolysis reactor.

[0022] In some embodiments of the present invention, the continuous Joule heat pyrolysis module further comprises a conductive carbon black silo, the material outlet of which is connected to the material inlet of the mixing device;

[0023] The first oil storage tank is connected to the mixing device.

[0024] Preferably, the mixing device is a mixing auger, and the first oil storage tank is connected to the bio-oil inlet on the pipe wall of the mixing auger.

[0025] In some embodiments of the present invention, the continuous Joule heat pyrolysis module further includes a power control system, wherein the positive and negative poles of the power control system are connected to the sieve plate electrode plate and the metal electrode plate, respectively.

[0026] In some embodiments of the present invention, the sieve plate electrode plate is provided with through holes for gas to pass through;

[0027] The continuous Joule heat pyrolysis module further includes an outlet pipe, a second condenser, a second oil storage tank and an air storage tank which are connected in sequence; the outlet pipe is connected to the sieve plate electrode plate.

[0028] Preferably, a purifier is provided between the second condenser and the gas storage tank.

[0029] In some embodiments of the present invention, the continuous Joule heat pyrolysis module further includes a pressure plate, which is arranged above the wheel disc and directly above the circular discharge port, moves up and down and does not rotate with the wheel disc.

[0030] In some embodiments of the present invention, the interior of the wheel disc is evenly divided into multiple independent spaces with the center of the wheel disc as the vertex, and the spaces are not connected to each other; a reaction tube is provided in each space, a fan is provided on the upper surface of the wheel disc in each space, and ventilation holes are provided on the outer wall of the wheel disc in each space.

[0031] A second aspect of the present invention provides a method for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass, using the above-mentioned system, comprising the following steps:

[0032] The biomass enters the first pyrolysis reactor and is pyrolyzed at a temperature of 300℃ to 600℃. The volatile matter enters the first condenser for condensation, and the condensate enters the first oil storage tank. The pyrolytic carbon obtained by pyrolysis enters the mixing device, is pressed into shape by the tablet press, and then enters the reaction tube. The reaction tube rotates to the bottom of the sieve plate electrode plate, and the sieve plate electrode plate moves downward to press the raw material to a resistance of 5 to 50Ω. A voltage is applied to the sieve plate electrode plate and the metal electrode plate, and the raw material is heated by the resistance thermal effect of the raw material itself. The heating rate is >10 4 K / s, the final temperature is greater than 3000K, and the raw materials are instantly converted into graphite carbon; after completion, the sieve plate electrode plate moves up, and the reaction tube rotates to the circular discharge port. During the rotation, the fan works to cool the reaction tube; at the circular discharge port, the graphite carbon falls into the carbon storage tank; the reaction tube continues to rotate, and the above process is repeated.

[0033] In some embodiments of the present invention, the gas generated during the instantaneous conversion of the raw material into graphite carbon enters the second condenser through the gas outlet pipe, the non-condensable gas enters the gas storage tank, and the condensate enters the second oil storage tank.

[0034] The beneficial effects of the present invention are:

[0035] The present invention provides a system and method for the co-production of graphite carbon and hydrogen by two-stage pyrolysis of biomass. The Joule heat pyrolysis reactor is designed as a wheel-type, so that the biomass pyrolysis reaction can be linked as a whole, and the reaction is carried out continuously, which reduces the start-up and shutdown time of the pyrolysis module and improves the economic efficiency of the entire system, thereby more efficiently obtaining graphite carbon and hydrogen. Using this system, the biomass is first subjected to low-temperature pyrolysis and condensation to obtain pyrolytic carbon and bio-oil, and then the pyrolytic carbon is subjected to Joule heat pyrolysis, condensation, and purification to obtain graphite carbon, bio-oil, and hydrogen-rich synthesis gas. The system uses cheap biomass as raw material to produce graphite carbon and hydrogen, saving the fossil resources used in the traditional preparation of graphite carbon. The system can be better used in industrial production to achieve the co-production of graphite carbon and hydrogen.

[0036] Low-temperature pyrolysis pretreatment removes most of the oxygen from the biomass, improving the H / O ratio and electrical conductivity of the solid product, thereby optimizing hydrogen selectivity and yield. The gases produced during the low-temperature pyrolysis process are recycled to provide an inert atmosphere for the pyrolysis reaction, while bio-oil is used as a binder for the rapid pressing of a mixture of biomass pyrolysis carbon and conductive carbon black. This process fully utilizes byproducts, making it highly economical and environmentally friendly.

[0037] The highly efficient pyrolysis and graphitization reaction is achieved through flash Joule heating, leveraging the inherent resistive thermal effect of the conductive material to reach ultra-high temperatures (>3000K) the moment power is applied, significantly improving energy conversion efficiency and reducing reaction energy consumption. The Joule heating pyrolysis reactor is designed as a disc, allowing the biomass pyrolysis reaction to be linked as a whole, allowing for continuous reaction. This reduces the start-up and shutdown time of the pyrolysis module, improving the economic efficiency of the entire system, and resulting in more efficient production of graphite carbon and hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, 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.

[0039] Figure 1 This is a schematic diagram of the system structure of the two-stage pyrolysis of biomass for co-production of graphite carbon and hydrogen according to the present invention;

[0040] Figure 2 1. It is a top view of a wheel in the system for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass according to the present invention;

[0041] Figure 3 1 is a side view of a wheel-disc Joule heat pyrolysis reactor in a system for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass according to the present invention;

[0042] Figure 4 1. It is a top view of the bottom plate of the system for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass according to the present invention;

[0043] Figure 5 XRD patterns of graphite carbon obtained by direct Joule pyrolysis of biomass and two-stage pyrolysis using the system provided by the present invention;

[0044] Figure 6 The diagram shows the changes in gas products during direct Joule heat pyrolysis of biomass and two-stage pyrolysis using the system provided by the present invention.

[0045] Markings in the figure: 1. Feeding device (i.e. ball mill); 2. First pyrolysis reactor; 3. First condenser; 4. Conductive carbon black silo; 5. First oil storage tank; 6. Tablet press; 7. Mixing device (i.e. mixing auger with a spiral propulsion shaft); 8. Disc-type Joule heat pyrolysis reactor; 801. Bottom plate; 802. Disc; 803. Sieve plate electrode plate; 804. Reaction tube; 805. Fan; 806. Ventilation hole; 807. Exhaust pipe; 808. Metal electrode plate; 809. Circular discharge port; 9. Carbon storage tank; 10. Motor; 11. Power control system; 12. Second condenser; 13. Purifier; 14. Second fan; 15. Gas storage tank; 16. Second oil storage tank; 17. Press plate. DETAILED DESCRIPTION

[0046] The present invention discloses a system and method for the co-production of graphite carbon and hydrogen by two-stage pyrolysis of biomass. The system can solve the problems of the existing biomass pyrolysis process, such as complex process, high reaction energy consumption, low efficiency, low degree of graphitization of pyrolytic carbon, and poor hydrogen selectivity.

[0047] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0048] In the description of the present invention, it should be understood that the terms "upper", "lower", "top", "bottom", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0049] like Figure 1 The present invention discloses a system for co-producing graphite carbon and hydrogen through two-stage pyrolysis of biomass, comprising a low-temperature pyrolysis module and a continuous Joule-heat pyrolysis module. The low-temperature pyrolysis module is configured to perform low-temperature pyrolysis deoxidation and condensation on the biomass to produce pyrolytic carbon with a certain conductivity and oxygen-rich bio-oil. The continuous Joule-heat pyrolysis module is connected to the low-temperature pyrolysis module and is configured to perform Joule-heat pyrolysis and condensation on the pyrolytic carbon produced by the low-temperature pyrolysis module to produce graphite carbon, bio-oil, and hydrogen-rich synthesis gas.

[0050] The low-temperature pyrolysis module includes a first pyrolysis reactor 2, a first condenser 3, and a first oil storage tank 5, which are connected in sequence. Specifically, the gas outlet of the first pyrolysis reactor 2 is connected to the gas inlet of the first condenser 3, and the liquid outlet of the first condenser 3 is connected to the first oil storage tank 5. The pyrolysis gas generated in the first pyrolysis reactor 2 enters the first condenser 3 through a pipeline, and the bio-oil is condensed by the condensation effect of the first condenser 3 and stored in the first oil storage tank 5. The non-condensable hydrogen-rich gas (mainly carbon monoxide and carbon dioxide) can be collected and returned to the beginning of the first pyrolysis reactor through a pipeline to provide an inert atmosphere for the pyrolysis reaction.

[0051] In order to improve the purity and yield of the hydrogen-rich gas, the gas outlet of the first condenser 3 is connected to the material inlet of the first pyrolysis reactor 2, and the non-condensable hydrogen-rich gas returns to the first pyrolysis reactor 2 through a pipeline to provide an inert atmosphere for the pyrolysis reaction.

[0052] The continuous Joule heat pyrolysis module includes a mixing device 7, a tablet press 6, a wheel-disk Joule heat pyrolysis reactor 8, and a carbon storage tank 9, which are connected in sequence. Specifically, the material inlet of the mixing device 7 is connected to the material outlet of the first pyrolysis reactor 2. The tablet press 6 is provided above the material outlet of the mixing device 7. The tablet press 6 is used to press the raw materials output by the mixing device 7 into the wheel-disk Joule heat pyrolysis reactor 8. The wheel-disc type Joule heat pyrolysis reactor 8 includes a bottom plate 801, a wheel disc 802, a sieve plate electrode plate 803 and a motor 10. The wheel disc 802 is fixed on the bottom plate 801 and rotates on the bottom plate 801 driven by the motor 10; a reaction tube 804 is provided inside the wheel disc 802, and the distance between the center of the reaction tube 804 and the center of the wheel disc 802 is equal to the distance between the center of the tablet press 6 and the center of the wheel disc 802. When the reaction tube 804 is rotated to the bottom of the tablet press 6, the tablet press 6 presses the material output by the mixing device 7 into the reaction tube 804; a fan 805 is provided on the upper surface of the wheel disc, and ventilation holes 806 are provided on the side wall; the sieve plate electrode plate 803 moves up and down relative to the wheel disc 802 and does not rotate with the wheel disc 802. The distance between the center of the sieve plate electrode plate 803 and the center of the wheel disc 802 is equal to the distance between the center of the reaction tube 804 and the center of the wheel disc 802, that is, the sieve plate electrode plate 803 can seal the reaction tube 804 by moving up and down. The metal electrode plate 808 is located on the bottom plate 801 directly below the sieve plate electrode plate 803. The bottom plate 801 also has a circular discharge port 809. The distance between the center of the circular discharge port 809 and the center of the wheel disc 802 is equal to the distance between the center of the reaction tube 804 and the center of the wheel disc 802. The carbon storage tank 9 is connected below the circular discharge port 809.

[0053] It should be noted that the pyrolytic carbon produced by the first pyrolysis reactor 2 is fully mixed with other raw materials in the mixing device 7 and then output to the bottom of the tablet press 6. The tablet press 6 performs the first operation to extrude the mixed raw materials into a shape that can be filled into the reaction tube 804. The bottom of the tablet press 6 is designed to be open. After the first extrusion is completed, the bottom is opened, and then the distance of the second extrusion is greater than the first, in order to press the raw materials formed by the first extrusion into the reaction tube 804 connected to the bottom of the tablet press 6 and enter the next continuous Joule heat pyrolysis module.

[0054] Reactor tube 804, filled with raw material, rotates with disc 802 to below sieve electrode plate 803. Sieve electrode plate 803 moves downward and, together with metal electrode plate 808 fixed to base plate 801, squeezes and secures the raw material within reaction tube 804. Voltage is applied via an external power supply, forming a conductive circuit that rapidly heats the raw material and instantly converts it into graphite carbon. After the voltage application ends, sieve electrode plate 803 moves upward above disc 802 to avoid interfering with its rotation. As disc 802 rotates, fan 805 begins operating, cooling the graphite carbon within reaction tube 804 through airflow. When reaction tube 804, filled with graphite carbon, rotates to circular discharge port 809, the graphite carbon falls through this port into carbon storage tank 9. As disc 802 rotates, reaction tube 804 continues to rotate to directly below tablet press 6, where the extruded raw material is collected again, forming a closed-loop Joule heat pyrolysis process. The continuous Joule heat pyrolysis module can carry out multiple reactions simultaneously, and each reaction tube 804 repeats the reaction process of the previous reaction tube 804. If the wheel is large enough and the number of chambers is sufficient, the reaction efficiency can be greatly improved.

[0055] To improve production efficiency and fully cool the reaction tube 804, the orthographic projection of the tablet press 6 on the bottom plate 801, the orthographic projection of the sieve plate electrode plate 803 on the bottom plate 801, and the circular discharge port 809 should be as close as possible, and the circumferential distance between the orthographic projection of the sieve plate electrode plate 803 on the bottom plate 801 and the circular discharge port 809 should be as large as possible. That is, the orthographic projection of the tablet press 6 on the bottom plate 801, the orthographic projection of the sieve plate electrode plate 803 on the bottom plate 801, and the circular discharge port 809 are on the same circle, and the orthographic projection of the tablet press 6 on the bottom plate 801 is located between the orthographic projection of the sieve plate electrode plate 803 on the bottom plate 801 and the circular discharge port 809.

[0056] It should be noted that the term circumferential distance refers to the length of the circumference of the orthographic projection of the sieve plate electrode plate 803 on the bottom plate 801 and the circular discharge port 809 , not passing through the orthographic projection of the tablet press 6 on the bottom plate 801 .

[0057] In a specific embodiment of the present invention, the low-temperature pyrolysis module further includes a feeding device 1 , and a material outlet of the feeding device 1 is connected to an inlet of the first pyrolysis reactor 2 .

[0058] In a specific embodiment of the present invention, the feeding device 1 is a ball mill, which is connected to the 2 inlets of the first pyrolyzer and is used to crush the biomass raw materials through the ball mill and then feed them into the first pyrolysis reactor for low-temperature pyrolysis.

[0059] In a specific embodiment of the present invention, the first pyrolysis reactor 2 is a spiral pyrolysis reactor. Spiral pyrolysis reactors have the advantages of simple structure, precise reaction temperature control, low device wear, and no need for additional carrier gas. They are currently the mainstream type of organic solid waste pyrolysis device.

[0060] The continuous Joule heat pyrolysis module also includes a power control system 11, the positive and negative electrodes of which are connected to the sieve plate electrode plate 803 and the metal electrode plate 808, respectively. The power control system 11 applies a voltage to both sides of the conductive material in the reaction tube 804 and controls the duration of the power supply, causing the conductive material to undergo Joule heat pyrolysis, converting the pyrolytic carbon into graphite carbon.

[0061] It should be noted that, to ensure safety, the reaction tube 804 is made of an insulating material, such as a quartz tube or a corundum tube. The wheel 802 surrounding the top of the reaction tube 804 is also made of an insulating material, and the bottom plate 801 surrounding the metal electrode plate 808 is also made of an insulating material. The metal electrode plate 808 and the sieve plate electrode plate 803 are both made of metal materials, such as copper plates. Quartz is an insulating material that ensures safe Joule heat pyrolysis. The metal electrode plate 808 is located at the bottom of the reaction tube 804, and the sieve plate electrode plate 803 is located at the top of the reaction tube 804, in contact with the raw materials within. The metal electrode plate 808, the raw materials, and the sieve plate electrode plate 803 form an electrical circuit with an external power source, utilizing the raw materials' own resistive heating effect to heat the biomass low-temperature pyrolysis carbon, thereby converting it into graphite carbon.

[0062] In a specific embodiment of the present invention, the continuous Joule heat pyrolysis module further includes a conductive carbon black silo 4, whose material outlet is connected to the material inlet of the mixing device 7. The conductive carbon black silo 4 stores conductive carbon black, and the conductive carbon black and pyrolytic carbon are fully mixed in the mixing device 7 to improve the conductivity of the raw materials and facilitate the Joule heat pyrolysis reaction.

[0063] The first oil tank 5 is connected to a mixing device 7, which is used to add the bio-oil in the first oil tank 5 to the mixing device 7, thereby thoroughly mixing the conductive carbon black, pyrolytic carbon, and bio-oil. To improve mixing uniformity, the bio-oil can be introduced into the mixing device in the form of a spray.

[0064] It should be noted that the mixing device 7 is a mixing auger. The first oil storage tank 5 is connected to a bio-oil inlet on the mixing auger's wall. To improve mixing efficiency, multiple bio-oil inlets are provided. The pyrolytic carbon and conductive carbon black obtained by low-temperature pyrolysis enter the mixing auger. Simultaneously, the bio-oil in the first oil storage tank 5 is sprayed into the mixing auger (connected to the tablet press 6). After the three substances are thoroughly mixed, the auger is fed into the tablet press 6 by the propeller.

[0065] To facilitate the collection of hydrogen-rich gas, the sieve plate electrode plate 803 is provided with a through hole for gas passage. The continuous Joule heat pyrolysis module also includes an outlet pipe 807, a second condenser 12, a second oil storage tank 16, and a gas storage tank 15, which are connected in sequence. Specifically, one end of the outlet pipe 807 is connected to the sieve plate electrode plate 803, and the other end is connected to the gas inlet of the second condenser 12. The gas generated during the Joule heat pyrolysis process enters the second condenser 12 through the sieve plate electrode plate 803 and the outlet pipe 807. The bio-oil is stored in the second oil storage tank 16 through the condensation effect of the second condenser 12, while the hydrogen-rich synthesis gas is collected in the gas storage tank 15.

[0066] Preferably, a purifier 13 and a second blower 14 are provided between the gas outlet of the second condenser 12 and the gas storage tank 15. The non-condensable gas produced by the Joule heat pyrolysis reaction is cooled by the second condenser 12, purified by the purifier 13, and then collected. Most of the gas is hydrogen mixed with a small amount of CH4 and CO.

[0067] To ensure proper discharge and prevent the graphite carbon from becoming stuck in the reaction tube 804, the continuous Joule heat pyrolysis module further includes a pressure plate 17, which is positioned above the wheel disc 802 and directly above the circular discharge port 809. The pressure plate 17 moves up and down without rotating with the wheel disc 802. When the reaction tube 804 containing the graphite carbon rotates to the circular discharge port 809, the pressure plate 17 moves downward, pushing the graphite carbon into the carbon storage tank 9.

[0068] To improve production efficiency, the interior of the wheel 802 is equipped with multiple reaction tubes 804. The center of the wheel 802 serves as the vertex, evenly dividing the space into multiple independent compartments. Each compartment houses a reaction tube 804. A fan 805 is installed on the upper surface of the wheel 802 in each compartment (to cool the quartz tube after the reaction is complete). Ventilation holes 806 are also located on the outer wall of the wheel 802 in each compartment. As the wheel 802 rotates, each reaction tube 804 undergoes a cycle of injection, reaction, cooling, and discharge, forming a closed loop. Each reaction tube 804 repeats the reaction cycle of the previous tube 804, significantly improving reaction efficiency.

[0069] It should be noted that the fan 805 is arranged on the upper surface of the wheel 802, which draws out the air in the independent space. The outside air enters from the ventilation holes 806 on the side wall, flows through the reaction tube 804 and is then discharged from the top, thereby reducing the temperature of the reaction tube 804.

[0070] The system for co-producing graphite carbon and hydrogen provided by the present invention first performs low-temperature pyrolysis and condensation of biomass to produce pyrolytic carbon and bio-oil. The pyrolytic carbon is then subjected to Joule-heat pyrolysis, condensation, and purification to produce graphite carbon, bio-oil, and hydrogen-rich syngas. This system uses inexpensive biomass as a raw material to produce graphite carbon and hydrogen, conserving fossil resources typically used in traditional graphite carbon production.

[0071] The present invention also discloses a method for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass, which adopts the above-mentioned system and includes the following steps:

[0072] After being dried and crushed to a specified particle size in the ball mill 1, the biomass continuously enters the first pyrolysis reactor 2 under the action of a rotating propeller shaft.

[0073] The biomass enters the first pyrolysis reactor 2 (i.e., the spiral pyrolysis reactor) and undergoes pyrolysis at a temperature of 300°C to 600°C. This process removes most of the oxygen from the biomass in the form of volatiles. The volatiles flow out of the spiral pyrolysis reactor outlet and enter the first condenser 3 for condensation. A portion of the uncondensed pyrolysis gas (primarily carbon dioxide, carbon monoxide, and methane) is recycled back to the spiral pyrolysis reactor to provide an inert environment. The condensed bio-oil is stored in the first oil storage tank 5.

[0074] The pyrolytic carbon and conductive carbon black obtained by low-temperature pyrolysis enter the mixing device 7 (i.e., the mixing auger). At the same time, the bio-oil in the first oil storage tank 5 also enters the mixing auger in the form of a spray. After the three substances are fully mixed, they enter the tablet press 6 under the action of the spiral propulsion shaft. The operating procedure of the tablet press 6 is designed in advance. During the first operation of the tablet press 6, the mixed raw materials are squeezed into shape. Then, as the tablet press 6 moves upward, the lower pressure plate opens. The second squeezing distance is greater than the first, and the raw materials formed in the first time are pressed into the reaction tube 804 of the wheel-type Joule heat pyrolysis reactor 8 connected to the tablet press. As the wheel 802 rotates, the reaction tube 804 reaches the metal electrode plate 808 (copper electrode). The sieve plate electrode plate 803 (copper electrode) on the upper part of the wheel 802 moves downward to cooperate with the metal electrode plate 808 and squeezes the raw materials to the target initial resistance (5Ω to 50Ω) through the power control system 11. The power control system 11 applies voltage to both sides of the conductive material in the reaction tube 804 and controls the power-on time, heating the material by using its own resistance thermal effect. The heating rate is >10 4K / s, with a final temperature >3000K, converting biomass low-temperature pyrolysis carbon into graphite carbon in a very short time (>100ms). Simultaneously, an outlet pipe 807 is connected above the sieve plate electrode plate 803. The non-condensable gases produced by the reaction are condensed by the second condenser 12 and purified by the purifier 13 before being collected in the gas storage tank 15. Most of the non-condensable gases are hydrogen, mixed with small amounts of methane and carbon monoxide. The bio-oil in the second condenser 12 is collected in the second oil storage tank 16. After the reaction is completed, the sieve plate electrode plate 803 moves upward to above the wheel disc, and the fan 805 operates, drawing in external air that flows through the sidewall vents 806 through the reaction tube 804 and is then discharged from the top, thereby reducing the temperature of the reaction tube 804. The reaction tube containing graphite carbon rotates with the wheel 802 to the circular discharge port 809, and the pressing plate 17 moves downward to press the graphite carbon in the reaction tube 804 into the carbon storage tank 9. Then the wheel continues to rotate, and the empty reaction tube 804 rotates to the bottom of the tablet press 6. The above process is repeated to form a closed loop.

[0075] The XRD patterns of graphite carbon obtained by direct Joule pyrolysis of biomass and two-stage pyrolysis using the system provided by the present invention are as follows: Figure 5 The graphitization degree of carbon produced by direct Joule heat pyrolysis of biomass is very low, while the graphitization degree of carbon produced by pyrolysis of biomass using the two-stage pyrolysis system of the present invention is significantly improved, reaching more than 85%.

[0076] The changes in gas products (H2, CH4, CO, CO2) during direct Joule pyrolysis of biomass and two-stage pyrolysis using the system provided by the present invention are as follows: Figure 6 As shown in the first low-temperature pyrolysis stage (500°C), a large amount of oxygen is removed in the form of CO and CO2, and the process produces very little hydrogen. In the second flash Joule pyrolysis stage, the H2 selectivity increases significantly to over 80%, and the CO, CO2, and CH4 contents decrease significantly. In contrast, the hydrogen selectivity of direct Joule heating of biomass is less than 40%.

[0077] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A system for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass, characterized in that: Including low-temperature pyrolysis module and continuous Joule heat pyrolysis module; The low-temperature pyrolysis module includes a first pyrolysis reactor, a first condenser and a first oil storage tank connected in sequence; The continuous Joule heat pyrolysis module includes a mixing device, a tablet press, a wheel-disc Joule heat pyrolysis reactor and a carbon storage tank connected in sequence; the material inlet of the mixing device is connected to the material outlet of the first pyrolysis reactor; the wheel-disc Joule heat pyrolysis reactor includes a bottom plate, a wheel disc, a sieve plate electrode plate and a motor, the wheel disc is fixed to the bottom plate and rotates on the bottom plate driven by the motor; a reaction tube is provided inside the wheel disc, and the tablet press presses the raw materials into the reaction tube; the sieve plate electrode plate moves up and down relative to the wheel disc and does not rotate with the wheel disc; the bottom plate position directly below the sieve plate electrode plate is a metal electrode plate; the bottom plate is also provided with a circular discharge port, and the carbon storage tank is connected below the circular discharge port.

2. The system according to claim 1, wherein The distance between the center of the reaction tube and the center of the wheel is equal to the distance between the center of the tablet press and the center of the wheel; The distance between the center of the sieve plate electrode and the center of the wheel is equal to the distance between the center of the reaction tube and the center of the wheel; The distance between the center of the circular discharge port and the center of the wheel is equal to the distance between the center of the reaction tube and the center of the wheel.

3. The system according to claim 1, wherein: The low-temperature pyrolysis module further includes a feeding device, wherein a material outlet of the feeding device is connected to an inlet of the first pyrolysis reactor.

4. The system according to claim 3, wherein: The feeding device is a ball mill.

5. The system according to claim 1, wherein: The first pyrolysis reactor is a spiral pyrolysis reactor.

6. The system according to claim 1, wherein: The reaction tube is a quartz tube or a corundum tube.

7. The system according to claim 1, wherein: The gas outlet of the first condenser is connected to the material inlet of the first pyrolysis reactor.

8. The system according to claim 1, wherein: The continuous Joule heat pyrolysis module further includes a conductive carbon black silo, the material outlet of which is connected to the material inlet of the mixing device; The first oil storage tank is connected to the mixing device.

9. The system according to claim 1, wherein: The mixing device is a mixing auger, and the first oil storage tank is connected to the bio-oil inlet on the pipe wall of the mixing auger.

10. The system according to claim 1, wherein: The continuous Joule heat pyrolysis module further includes a power supply control system, wherein the positive and negative electrodes of the power supply control system are connected to the sieve plate electrode plate and the metal electrode plate respectively.

11. The system according to claim 1, wherein: The sieve plate electrode plate is provided with through holes for gas to pass through; The continuous Joule heat pyrolysis module further includes an outlet pipe, a second condenser, a second oil storage tank and an air storage tank which are connected in sequence; the outlet pipe is connected to the sieve plate electrode plate.

12. The system according to claim 11, wherein A purifier is provided between the second condenser and the gas storage tank.

13. The system of claim 1, wherein: The continuous Joule heat pyrolysis module further includes a pressing plate, which is arranged above the wheel disc and directly above the circular discharge port, moves up and down and does not rotate with the wheel disc.

14. The system of claim 1, wherein: The interior of the wheel is evenly divided into multiple independent spaces with the center of the wheel as the vertex, and the spaces are not connected. A reaction tube is provided in each space, a fan is provided on the upper surface of the wheel in each space, and ventilation holes are provided on the outer wall of the wheel in each space.

15. A method for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass, characterized in that: The system according to any one of claims 1 to 14 comprises the following steps: The biomass enters the first pyrolysis reactor and undergoes pyrolysis at a temperature of 300°C to 600°C. The volatile matter enters the first condenser for condensation, and the condensate enters the first oil storage tank. The pyrolytic carbon obtained by pyrolysis enters the mixing device, is pressed into shape by the tablet press, and then enters the reaction tube. The reaction tube is rotated to the bottom of the sieve plate electrode plate, and the sieve plate electrode plate is moved down to pressurize the raw material to a resistance of 5~50Ω. Voltage is applied to the sieve plate electrode plate and the metal electrode plate, and the raw material is heated by its own resistance thermal effect. The heating rate is >10 4 K / s, the final temperature is greater than 3000 K, and the raw materials are instantly converted into graphite carbon. After completion, the sieve plate electrode plate moves up, and the reaction tube rotates to the circular discharge port. During the rotation, the fan works to cool the reaction tube. At the circular discharge port, the graphite carbon falls into the carbon storage tank. The reaction tube continues to rotate and the above process is repeated.

16. The method according to claim 15, wherein The gas generated during the instantaneous conversion of raw materials into graphite carbon enters the second condenser through the outlet pipe, the non-condensable gas enters the gas storage tank, and the condensate enters the second oil storage tank.

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