System and method for co-producing graphite carbon and hydrogen through two-stage pyrolysis of biomass

Abstract

The invention discloses a system and a method for co-producing graphite carbon and hydrogen through biomass two-stage pyrolysis, and belongs to the technical field of biomass pyrolysis. The system comprises a low-temperature pyrolysis module and a continuous Joule thermal pyrolysis module. The Joule pyrolysis reactor is designed into a wheel disc type, so that biomass pyrolysis reactions can be linked into a whole, the reactions are continuously carried out, the starting and stopping time of a pyrolysis module is shortened, the economical efficiency of the whole system is improved, and graphite carbon and hydrogen are more efficiently obtained. By utilizing the system, firstly, biomass is subjected to low-temperature pyrolysis and condensation to obtain pyrolytic carbon and bio-oil, then the pyrolytic carbon is subjected to Joule thermal pyrolysis, condensation and purification to obtain graphite carbon, bio-oil and hydrogen-rich synthesis gas, the low-cost biomass is used as a raw material to prepare graphite carbon and hydrogen, and fossil resources used in traditional graphite carbon preparation are saved. The system can be better used for industrial production, and co-production of graphite carbon and hydrogen is achieved.

Description

Technical Field

[0001] The 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 the 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 a person skilled in the art.

[0003] High-quality graphite carbon materials are widely used in many fields such as batteries, brushes, lubricants, thermal conductive materials, etc., which can significantly improve the performance and service life of related products. At the same time, hydrogen, as a clean and efficient energy source, is widely regarded as an important part of the future energy structure. Biomass, as a widely available and only renewable carbon-containing resource, has huge 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 the use of fossil fuels and carbon dioxide emissions, achieving a win-win situation for environmental and economic benefits.

[0004] Currently, these two high-value products mainly come from fossil resources, and the production process requires huge energy and causes environmental pollution. Traditional biomass pyrolysis technology faces many challenges in practical applications. First, the composition of biomass is extremely complex and contains a high level of oxygen, which leads to low purity and quality of pyrolysis products, especially carbon products that are difficult to meet high graphitization requirements. Secondly, the gas composition produced by the pyrolysis process is complex, the selectivity of hydrogen is low, and it is difficult to efficiently separate it from the mixed gas.

[0005] Patent CN114989844A discloses a method for the catalytic pyrolysis of biomass and polyolefin plastics to produce high-quality bio-oil and porous graphite carbon. The method first pre-treats the biomass with FeCl3, then adds polyolefin plastics for uniform mechanical mixing, uses a fixed bed reactor to perform a rapid pyrolysis reaction under a nitrogen atmosphere, then performs a slow pyrolysis to increase the degree of modification of the biochar, and then collects the solid product and washes and dries it to obtain porous graphite carbon. This method has high energy consumption, and it is difficult to remove metal impurities, which increases the process complexity and cost.

[0006] Patent CN115974058A discloses a method and system for preparing graphene. First, the biomass is pyrolyzed and condensed to obtain activated carbon, oil phase products and gas phase products, and then part of the activated carbon is pyrolyzed and condensed to obtain graphite carbon and gas and liquid two-phase products, and the two-stage gas phase products are passed into the remaining activated carbon for vapor deposition to obtain graphene-loaded activated carbon and a first mixed gas. This method has high energy consumption and low efficiency, and it is difficult to efficiently separate hydrogen from the mixed gas.

[0007] Patent CN117304955A discloses a tar catalytic cracking device based on a Joule heat reactor and a product processing method. The biomass pyrolysis, tar catalytic cracking, bio-oil condensation and hydrogen-rich combustible gas collection system are separated. However, the process is complicated, the degree of graphitization of the obtained biochar is low, and the catalyst cost required for the catalytic cracking reaction is high.

[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 in the prior art, the object 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 complex existing biomass pyrolysis process, 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 comprises a first pyrolysis reactor, a first condenser and a first oil storage tank which are connected in sequence;

[0013] The continuous Joule heat pyrolysis module includes a mixing device, a tablet press, a wheel-disk Joule heat pyrolysis reactor and a carbon storage tank which are connected in sequence; the material inlet of the mixing device is connected to the material outlet of the first pyrolysis reactor; the wheel-disk Joule heat pyrolysis reactor includes a bottom plate, a wheel, a sieve plate electrode plate and a motor, the wheel is fixed on the bottom plate and rotates on the bottom plate driven by the motor; a reaction tube is arranged inside the wheel disk, and the tablet press presses the raw material into the reaction tube; the sieve plate electrode plate moves up and down relative to the wheel disk and does not rotate with the wheel disk; 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, and 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, whose material outlet is connected to the material inlet of the mixing device;

[0023] The first oil storage tank is connected to the material 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, and the positive and negative electrodes of the power control system are respectively connected to the sieve plate electrode plate and the metal electrode plate.

[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 also 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 disposed 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 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 pyrolysis carbon obtained by pyrolysis enters the mixing device, and enters the reaction tube after being pressed and formed by the tablet press. 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 >3000K, and the raw material is instantly converted into graphite carbon; after the end, 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 roulette type, so that the biomass pyrolysis reaction can be linked as a whole, the reaction is carried out continuously, the start-up and stop time of the pyrolysis module is reduced, and the economy of the entire system is improved, so that graphite carbon and hydrogen are obtained 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. The system uses cheap biomass as raw materials to prepare graphite carbon and hydrogen, saving 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 in the biomass, improves the H / O ratio and conductivity of the solid product, and optimizes the selectivity and yield of hydrogen. The gas produced during the low-temperature pyrolysis process is recycled to provide an inert atmosphere for the pyrolysis reaction, and bio-oil is used as a binder for the rapid pressing of a mixture of biomass pyrolysis carbon and conductive carbon black. This process makes full use of by-products and is highly economical and environmentally friendly.

[0037] Through the flash Joule heat pyrolysis, the efficient pyrolysis graphitization reaction is carried out, and the conductive material's own resistance thermal effect is used to reach ultra-high temperature (>3000K) at the moment of power on, which greatly improves the energy conversion efficiency and reduces the reaction energy consumption. The Joule heat pyrolysis reactor is designed as a roulette type, so that the biomass pyrolysis reaction can be linked as a whole, the reaction is carried out continuously, the start-up and stop time of the pyrolysis module is reduced, and the economy of the entire system is improved, so that graphite carbon and hydrogen can be obtained more efficiently. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] 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.

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

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

[0041] Figure 3 It is a side view of a wheel-disk type 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 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 is a change diagram of 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 invention discloses a system and method for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass. The system can solve the problems of complex existing biomass pyrolysis process, high reaction energy consumption, low efficiency, low degree of graphitization of pyrolytic carbon, poor hydrogen selectivity, etc.

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0048] In the description of the present invention, it is necessary to understand that the orientations or positional relationships indicated by the terms "upper", "lower", "top", "bottom", etc. 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 As shown, the present invention discloses 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. The low-temperature pyrolysis module is used to perform low-temperature pyrolysis deoxidation and condensation on biomass to obtain 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 used to perform Joule heat pyrolysis and condensation on the pyrolytic carbon produced by the low-temperature pyrolysis module to obtain 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 action 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 can also be 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 connected in sequence. Specifically, the material inlet of the mixing device 7 is connected to the material outlet of the first pyrolysis reactor 2, and a tablet press 6 is provided above the material outlet of the mixing device 7, and the tablet press 6 is used to press the raw material output by the mixing device 7 into the wheel-disk Joule heat pyrolysis reactor 8. The wheel-disc type Joule heat pyrolysis reactor 8 comprises a bottom plate 801, a wheel disc 802, a sieve plate electrode plate 803 and a motor 10, wherein 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 arranged 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, and 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 arranged on the upper surface of the wheel disc, and ventilation holes 806 are arranged 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, and 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 bottom plate 801 directly below the sieve plate electrode plate 803 is a metal electrode plate 808. The bottom plate 801 is also provided with 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, and 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 extruded for the first time into the reaction tube 804 connected to the bottom of the tablet press 6, and enter the next continuous Joule heat pyrolysis module.

[0054] The reaction tube 804 filled with raw materials rotates with the wheel disc 802 to the bottom of the sieve plate electrode plate 803. The sieve plate electrode plate 803 moves downward and squeezes the raw materials together with the metal electrode plate 808 fixed on the bottom plate 801 to fix them in the reaction tube 804. The voltage is applied by an external power supply to form a conductive circuit, thereby quickly heating the raw materials and converting the raw materials into graphite carbon instantly. After the voltage is applied, the sieve plate electrode plate 803 moves upward to the top of the wheel disc 802 to avoid affecting the rotation of the wheel disc 802. As the wheel disc 802 rotates, the fan 805 starts to work, and the graphite carbon in the reaction tube 804 is cooled by air flow. When the reaction tube 804 containing graphite carbon rotates to the circular discharge port 809, the graphite carbon falls into the carbon storage tank 9 through the circular discharge port 809. As the wheel disc 802 rotates, the reaction tube 804 continues to rotate to the bottom of the tablet press 6, and the raw materials extruded by the tablet press 6 are collected again, and the entire Joule heat pyrolysis process forms a closed loop. The continuous Joule heat pyrolysis module can carry out multiple reactions at the same time, and each reaction tube 804 repeats the reaction process of the previous reaction tube 804. If the wheel is large enough and the designed chambers are sufficient, the reaction efficiency can be greatly improved.

[0055] In order to improve production efficiency and fully cool the reaction tube 804, the orthographic projection of the tablet press 6 on the bottom plate 801 and 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 that does not pass 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 pyrolysis reactor 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. The spiral pyrolysis reactor has the advantages of simple structure, precise control of reaction temperature, small device wear, and no need for additional carrier gas, and is currently the mainstream type of organic solid waste pyrolysis device.

[0060] The continuous Joule heat pyrolysis module further includes a power control system 11, the positive and negative electrodes of which are respectively connected to the sieve plate electrode plate 803 and the metal electrode plate 808. The power control system 11 can apply voltage to both sides of the conductive raw material in the reaction tube 804 and control the power-on time, so that the conductive raw material undergoes Joule heat pyrolysis reaction, and the pyrolysis carbon is converted into graphite carbon.

[0061] It should be noted that, in order to ensure safety, the reaction tube 804 is made of insulating material, which can be a quartz tube, a corundum tube, etc. The wheel 802 around the top of the reaction tube 804 is made of insulating material, and the bottom plate 801 around the metal electrode plate 808 is made of 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 can ensure the 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 inside. The metal electrode plate 808, the raw materials and the sieve plate electrode plate 803 form a circuit with an external power supply, and the raw materials are heated by the resistive thermal effect of the raw materials themselves, so as to convert the biomass low-temperature pyrolysis carbon 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 is stored in the conductive carbon black silo 4, 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 storage tank 5 is connected to the mixing device 7, and is used to add the bio-oil in the first oil storage tank 5 into the mixing device 7, so that the conductive carbon black, pyrolytic carbon and bio-oil are fully mixed. To improve the mixing uniformity, the bio-oil can be introduced into the mixing device in the form of spray.

[0064] It should be noted that the mixing device 7 is a mixing auger, and the first oil storage tank 5 is connected to the bio-oil inlet on the mixing auger pipe wall. In order to improve the mixing effect, multiple bio-oil inlets are provided. The pyrolytic carbon and conductive carbon black obtained by low-temperature pyrolysis enter the mixing auger, and at the same time, the bio-oil in the first oil storage tank 5 also enters the mixing auger (connected to the tablet press 6) in the form of spray. After the three substances are fully mixed, they enter the tablet press 6 under the action of the spiral propulsion shaft.

[0065] In order to facilitate the collection of hydrogen-rich gas, the sieve plate electrode plate 803 is provided with a through hole for gas to pass through. 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 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, and the bio-oil is stored in the second oil storage tank 16 through the condensation effect of the second condenser 12, and the hydrogen-rich synthesis gas is collected in the gas storage tank 15.

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

[0067] In order to ensure normal discharge and prevent graphite carbon from being stuck in the reaction tube 804, the continuous Joule heat pyrolysis module further includes a pressing plate 17, which is arranged above the wheel disc 802 and directly above the circular discharge port 809, moves up and down and does not rotate with the wheel disc 802. When the reaction tube 804 containing graphite carbon rotates to the circular discharge port 809, the pressing plate 17 moves down to push the graphite carbon into the carbon storage tank 9.

[0068] In order to improve production efficiency, a plurality of reaction tubes 804 are arranged inside the wheel 802, and the center of the wheel 802 is used as the vertex, and the plurality of independent spaces are evenly divided, and the spaces are not connected; a reaction tube 804 is arranged in each space, and a fan 805 (used to cool the quartz tube after the reaction is completed) is arranged on the upper surface of the wheel 802 in each space, and a ventilation hole 806 is arranged on the outer wall of the wheel 802 in each space. As the wheel 802 rotates, each reaction tube 804 performs injection-reaction-cooling-discharging in sequence, forming a closed loop, and each reaction tube 804 repeats the reaction process of the previous reaction tube 804, greatly improving the 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, and 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 playing a role in 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 on biomass to obtain pyrolytic carbon and bio-oil, and then performs Joule heat pyrolysis and condensation and purification on the pyrolytic carbon to obtain graphite carbon, bio-oil and hydrogen-rich synthesis gas. Therefore, the above scheme uses cheap biomass as raw materials to prepare graphite carbon and hydrogen, which can save fossil resources used in traditional preparation of graphite carbon.

[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 system and comprises the following steps:

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

[0073] The biomass enters the first pyrolysis reactor 2 (i.e., the spiral pyrolysis reactor) and is pyrolyzed at a temperature of 300°C to 600°C. This process can remove most of the oxygen in the biomass in the form of volatiles. The volatiles flow out of the outlet of the spiral pyrolysis reactor and enter the first condenser 3 for condensation. A portion of the uncondensed pyrolysis gas (mainly carbon dioxide, carbon monoxide, and methane) is circulated back to the spiral pyrolysis reactor to provide an inert environment for it, and 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), and at the same time, the bio-oil in the first oil storage tank 5 also enters the mixing auger in the form of spray. After the three substances are fully mixed, they enter the tablet press 6 under the action of the spiral propulsion shaft. The operation procedure of the tablet press 6 is designed in advance. When the tablet press 6 operates for the first time, the mixed raw materials are squeezed into shape. Then, while the tablet press 6 moves upward, the pressing plate below is opened. The distance of the second squeezing is greater than the first time, and the raw materials formed for 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), and the sieve plate electrode plate 803 (copper electrode) on the upper part of the wheel 802 moves down to cooperate with the metal electrode plate 808 and squeezes the raw materials to the target initial resistance (5Ω~50Ω) through the power supply 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, using the material's own resistance thermal effect to heat it, with a heating rate of >10 4K / s, final temperature>3000K, converting biomass low-temperature pyrolysis carbon into graphite carbon in a very short time (>100ms). At the same time, the sieve plate electrode plate 803 is connected to the outlet pipe 807, and the non-condensable gas produced by the reaction is condensed by the second condenser 12 and purified by the purifier 13 before being collected in the gas storage tank 15, most of which is hydrogen mixed with a small amount 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 up to the top of the wheel disc, and the fan 805 works, which absorbs the outside air from the side wall ventilation holes 806 and flows through the reaction tube 804 and then is discharged from the top, thereby playing a role in reducing the temperature of the reaction tube 804. The reaction tube containing graphite carbon rotates with the wheel disc 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 disc 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 biomass pyrolysis carbon directly produced by Joule heat is very low, while the graphitization degree of biomass pyrolysis carbon obtained by the two-stage pyrolysis system of the present invention is significantly improved, reaching more than 85%.

[0076] The changes of 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 figure, in the first stage of low-temperature pyrolysis (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 stage of flash Joule thermal pyrolysis, the H2 selectivity increases significantly to more than 80%, and the contents of CO, CO2 and CH4 decrease significantly. In contrast, the hydrogen selectivity of direct Joule thermal pyrolysis of biomass is less than 40%.

[0077] 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 system for co-producing graphite carbon and hydrogen by two-stage pyrolysis of biomass, characterized in that: It includes a low-temperature pyrolysis module and a continuous Joule heat pyrolysis module; The low-temperature pyrolysis module comprises a first pyrolysis reactor, a first condenser and a first oil storage tank which are connected in sequence; The continuous Joule heat pyrolysis module includes a mixing device, a tablet press, a wheel-disk Joule heat pyrolysis reactor and a carbon storage tank which are connected in sequence; the material inlet of the mixing device is connected to the material outlet of the first pyrolysis reactor; the wheel-disk Joule heat pyrolysis reactor includes a bottom plate, a wheel, a sieve plate electrode plate and a motor, the wheel is fixed on the bottom plate and rotates on the bottom plate driven by the motor; a reaction tube is arranged inside the wheel disk, and the tablet press presses the raw material into the reaction tube; the sieve plate electrode plate moves up and down relative to the wheel disk and does not rotate with the wheel disk; 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, characterized in that 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; 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; 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.

3. The system according to claim 1, characterized in that 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; The feeding device is preferably a ball mill; Preferably, the first pyrolysis reactor is a spiral pyrolysis reactor; Preferably, the reaction tube comprises a quartz tube or a corundum tube; Preferably, the gas outlet of the first condenser is connected to the material inlet of the first pyrolysis reactor.

4. The system according to claim 1, characterized in that The continuous Joule heat pyrolysis module also includes a conductive carbon black material bin, whose material outlet is connected to the material inlet of the mixing device; The first oil storage tank is connected to the mixing device; 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.

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

6. 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 also includes an outlet pipe, a second condenser, a second oil storage tank and an air storage tank connected in sequence; the outlet pipe is connected to the sieve plate electrode plate; Preferably, a purifier is provided between the second condenser and the gas storage tank.

7. The system according to claim 1, characterized in that The continuous Joule heat pyrolysis module also 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.

8. The system of claim 1, wherein: The inside 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 arranged in each space, a fan is arranged on the upper surface of the wheel in each space, and ventilation holes are arranged on the outer wall of the wheel in each space.

9. 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 8 comprises the following steps: 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 pyrolysis carbon obtained by pyrolysis enters the mixing device, and enters the reaction tube after being pressed and formed by the tablet press. 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 >3000K, and the raw material is instantly converted into graphite carbon; after the end, 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.

10. The method according to claim 9, characterized in that The gas generated during the instantaneous conversion of the 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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