Method and system for preparing porous graphite carbon through biomass pyrolysis

Abstract

The invention discloses a method and a system device for preparing porous graphite carbon through biomass pyrolysis. Iron salt and plastic are added in the process of preparing biomass coke through biomass pyrolysis. The ferric salt plays a catalytic role in the biomass pyrolysis process, promotes the carbon material to form an ordered layered graphite structure and adjusts the pore structure of the carbon material. The plastic promotes release of volatile substances during biomass pyrolysis, and the pore structure of the carbon material is improved. The iron salt and the plastic have a synergistic effect in the pyrolysis process. Hydrocarbon generated by plastic pyrolysis is combined with iron generated by Fe < 3 + > carbonization reduction to form a graphite carbon structure, so that the graphitization degree of the carbon material is remarkably improved. A pyrolysis device is designed according to a method for preparing porous graphite carbon through biomass pyrolysis. Biomass oil and gas generated in the preparation process of porous graphite carbon are fully utilized as a heat source of the pyrolyzing furnace. The whole system is high in energy efficiency, low in operation cost and excellent in product performance, and efficiently and cleanly treats biomass and plastic waste.

Description

Technical Field

[0001] The present invention belongs to the field of biomass and plastic processing, in particular to a method and system for preparing porous graphite carbon by pyrolyzing biomass. Background Art

[0002] In recent years, with the gradual strengthening of my country's environmental protection policies and the increasing demand for sustainable energy, the development and utilization of biomass energy has become an important research direction. The preparation of graphitic carbon materials using biomass catalytic pyrolysis not only meets the strategic goal of green and low-carbon development, but also provides innovative technical support for energy storage, environmental protection and other fields.

[0003] Graphite carbon produced by catalytic pyrolysis of biomass is of great value in resource utilization, environmental protection, and energy storage. Graphite carbon produced by catalytic pyrolysis of biomass has a high specific surface area and chemical stability, giving it excellent adsorption properties in environmental management. It can effectively remove pollutants such as heavy metals and harmful substances from soil and water, improving environmental quality. The conductivity and stability of graphite carbon make it an ideal electrode material for batteries and supercapacitors. It is widely used in energy storage technologies and has good market prospects. Biomass graphite carbon has carbon sequestration capabilities, which can help reduce greenhouse gas emissions and has the potential to address climate change.

[0004] During the catalytic pyrolysis of biomass, catalysts promote the decomposition of biomass under high-temperature, oxygen-free conditions, generating solid char, gaseous, and liquid products. Under the action of the catalyst, biomass feedstock undergoes chemical reactions such as cracking and rearrangement to produce carbon materials. In this process, the catalyst reduces the activation energy of the reaction, promoting the decomposition of macromolecules in the biomass and allowing more carbon elements to aggregate into a stable carbon structure. Compared with traditional pyrolysis technology, catalytic pyrolysis technology can more effectively control the quality and quantity of carbon products, especially in terms of pore structure and specific surface area. Carbon materials prepared by catalytic pyrolysis have superior properties. Adding plastics to the process of preparing graphite carbon from biomass catalytic pyrolysis can further improve the pore structure and degree of graphitization of the carbon material. Furthermore, by converting agricultural and forestry waste and waste plastics into high-value graphite carbon, waste can be recycled and environmental pollution can be reduced. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for producing porous graphite carbon by pyrolysis of biomass, which can systematically, efficiently and cleanly dispose of plastic waste and biomass resources and realize their energy utilization.

[0006] The technical solutions for achieving the purpose of the present invention are:

[0007] A method for preparing porous graphite carbon by pyrolysis of biomass, comprising:

[0008] 1) stirring the biomass and the iron salt solution to form a uniformly dispersed suspension;

[0009] 2) drying the suspension to obtain an iron salt-loaded biomass raw material with a moisture content of 5% to 10%;

[0010] 3) Pyrolyzing the iron salt-loaded biomass raw material and the plastic at 900-1200° C. under an inert atmosphere, the iron salt is converted into elemental iron under the action of carbon and reducing gas generated by the pyrolysis of the plastic and biomass, and the elemental iron interacts with hydrocarbons generated by the pyrolysis of the plastic. The hydrocarbons aggregate on the surface of the elemental iron to form Fe3C, and a graphite carbon structure is formed with Fe3C as the center, thereby obtaining a porous graphite carbon material containing iron salt.

[0011] A system for producing porous graphite carbon by pyrolysis of biomass, comprising:

[0012] The pretreatment system is used to stir the biomass and the iron salt solution to form a uniformly dispersed suspension, and then dry the biomass raw material loaded with iron salt to a moisture content of 5% to 10%;

[0013] The pyrolysis system is used to pyrolyze biomass raw materials and plastics loaded with iron salts at 900-1200°C under an inert atmosphere. The iron salt is converted into elemental iron under the action of carbon and reducing gas produced by the pyrolysis of plastics and biomass. The elemental iron interacts with hydrocarbons produced by the pyrolysis of plastics. The hydrocarbons aggregate on the surface of the elemental iron to form Fe3C, and a graphite carbon structure is formed with Fe3C as the center, thereby obtaining a porous graphite carbon material containing iron salts.

[0014] Compared with the prior art, the present invention has the following significant advantages:

[0015] (1) The addition of plastics during the iron-catalyzed pyrolysis of biomass to prepare graphite carbon optimizes the pore structure and degree of graphitization of the graphite carbon. During the pyrolysis process, the plastics produce a large amount of hydrocarbon vapor that is deposited on the biomass carbon and adsorbed on the surface of elemental iron, growing into a graphite carbon structure. This increases the degree of graphitization of the resulting pyrolytic carbon and optimizes the pore structure of the pyrolytic carbon, thereby improving the quality of the resulting graphite carbon.

[0016] (2) It provides an effective way to recycle plastic waste and has obvious environmental value. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a structural diagram of the method and system for producing porous graphite carbon by pyrolysis of biomass according to the present invention.

[0018] In the figure: 1- iron salt solution silo, 2- liquid feed pump, 3- screw feeder feed port, 4- iron salt solution feed port, 5- screw feeder, 6- screw feeder outlet, 7- dryer, 8- dryer feed port, 9- dryer outlet, 10- flow meter, 11- thermometer, 12- plastic silo, 13- screw feeder 2, 14- pyrolysis furnace feed port, 15- pyrolysis furnace, 16- condenser , 17-pyrolysis gas inlet, 18-pyrolysis gas collecting tank, 19-pyrolysis oil collecting tank, 20-pickling and water washing tower, 21-acid tank, 22-valve one, 23-pickling liquid pump, 24-valve two, 25-valve three, 26-valve four, 27-water washing liquid pump, 28-water washing liquid tank, 29-pyrolysis carbon collecting tank, 30-valve 5, 31-pyrolysis gas outlet, 32-burner, 33-drying device.

[0019] Figure 2 TEM image of porous graphitic carbon produced by biomass pyrolysis.

[0020] Figure 3 XRD pattern of porous graphitic carbon prepared by biomass pyrolysis.

[0021] Figure 4 BET image of porous graphitic carbon prepared by biomass pyrolysis. DETAILED DESCRIPTION

[0022] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0023] The present invention provides a method for producing porous graphite carbon by biomass pyrolysis, which is used to prepare high-quality graphite carbon. The method is characterized by adding plastic during the pyrolysis process, based on the method for producing graphite carbon by iron-catalyzed biomass pyrolysis. The addition of plastic improves the pore structure of the carbon material. The iron salt and plastic interact during the process of producing coke by biomass pyrolysis, significantly increasing the degree of graphitization of the carbon material. This is achieved by:

[0024] 1) The biomass and the iron salt solution are fed into a rotary feeder and stirred thoroughly to form a uniformly dispersed suspension A.

[0025] In step 1), the biomass is one or more of corn stalks, corn cobs, rice straw, cotton straw, wheat straw, peanut straw, peanut shells, wheat shells, coconut shells, husks, rice husks, walnut shells, hazelnut shells, bagasse, wood, sawdust, bamboo, and weeds.

[0026] In step 1), the iron salt solution can be FeCl3 solution, Fe(NO3)3 solution, Fe2(SO4)3 solution, etc.

[0027] In step 1), the iron salt solution contains Fe 3+ The concentration is 0.25mol / L.

[0028] In step 1), the biomass and the iron salt solution are stirred and mixed at a ratio of 6 to 10 ml of iron salt solution per 1 g of biomass to obtain a uniformly dispersed suspension A.

[0029] 2) sending the suspension into a dryer to evaporate the solvent and dry it to a moisture content of 5% to 10%, and the resulting solid mixture is the biomass raw material B loaded with iron salt;

[0030] 3) The biomass raw material B loaded with iron salts and plastic are fed into a pyrolysis furnace, uniformly mixed, and pyrolyzed at 900-1200°C under an inert atmosphere. The iron salts promote the structuring of the carbon material during the pyrolysis process to form an ordered layered graphite structure. The addition of plastics promotes the release of volatile substances during biomass pyrolysis and improves the pore structure of the co-pyrolysis carbon. The iron salts are converted into elemental iron under the action of carbon and reducing gases produced by the pyrolysis of plastics and biomass. The elemental iron interacts with the hydrocarbons produced by the pyrolysis of the plastic. The hydrocarbons aggregate on the surface of the elemental iron to form Fe3C. As the carbon thermal reduction process proceeds, the hydrocarbons produced by the pyrolysis of the plastic form a graphite carbon structure with Fe3C as the center. A porous graphite carbon material C containing iron salts is obtained during the pyrolysis process.

[0031] The type of plastic is one of polyethylene (PE), polypropylene (PP), and polystyrene (PS).

[0032] The mass ratio of the iron salt-loaded biomass raw material B to the plastic is 1:0.1-0.2.

[0033] The pyrolysis conditions are: heating from room temperature (10-40 degrees Celsius) to 900-1200 degrees Celsius at a rate of 5-10 degrees Celsius / min, with a holding time of 0.5-1 hour. The inert gas can be one or more of nitrogen, argon, and helium, with a gas flow rate of 50-500 ml / min.

[0034] 4) The porous graphite carbon material C containing iron salt is acid-washed, water-washed, and dried to obtain a porous graphite carbon material D.

[0035] The acid washing process is as follows: the porous graphite carbon material C containing iron salt is added to a 1M HCl solution and acid washed until the iron in the carbon material is completely removed. A small amount of the carbon material sample is calcined at 800°C for 1 hour. After calcination, no red ash remains, indicating that the iron has been completely removed. The acid washing is then stopped to obtain the acid-washed porous graphite carbon material E.

[0036] The conditions for the water washing operation are as follows: the porous graphite carbon material E after acid washing is washed with deionized water until the pH value reaches 7. The washing is stopped, and the porous graphite carbon material D is obtained after drying.

[0037] The system for preparing porous graphite carbon by pyrolysis of biomass of the present invention comprises: a pretreatment system, a pyrolysis system, an acid washing system, a product collection system, and an exhaust gas treatment system.

[0038] The pretreatment system includes a biomass raw material inlet 3, an iron salt solution silo 1, a liquid feed pump 2, a screw feeder 5, and a dryer 7. The outlet of the iron salt solution silo 1 is connected to the iron salt solution feed port 4 of the screw feeder 5 via the liquid feed pump 2. The screw feeder 5 is provided with a biomass raw material inlet 3, where the iron salt solution and biomass are mixed. The screw feeder 5 discharge port 6 is connected to the dryer feed port 8. The dryer 7 dries the suspension formed by the mixing of the biomass and iron salt solution to obtain a solid mixture of biomass and iron salt with a moisture content of 5% to 10%.

[0039] The pyrolysis system is connected to the dryer discharge port 9, and includes a flow meter 10, a thermometer 11, a pyrolysis furnace 15, a second screw feeder 13, and a plastic silo 12; the dryer discharge port 9 is connected to the pyrolysis furnace 15; the plastic silo 12 is connected to the second screw feeder 13, and the second screw feeder 13 is connected to the pyrolysis furnace feed port 14. Plastic enters the pyrolysis furnace 15 through the pyrolysis furnace feed port 14, and the solid mixture of biomass and iron salt enters the pyrolysis furnace 15 through the dryer discharge port 9. Both are pyrolyzed in the pyrolysis furnace 15. A flow meter 10 and a thermometer 11 are provided on the pyrolysis furnace 15, which are used to monitor the inert gas flow rate and the temperature inside the pyrolysis furnace 15 respectively.

[0040] The pickling and water washing system is connected to the solid product discharge port of the pyrolysis system and includes an acid washing pump 23, a water washing pump 27, an acid washing tower 20, an acid tank 21, a water washing tank 28, and a pyrolytic carbon collection tank 29. The porous carbon product obtained by pyrolysis enters the acid washing tower 20. The acid washing tower 20 is connected to the acid tank 21 through valve 24 on one side. The acid tank 21 is connected to the acid washing pump 23 through valve 1. The acid washing tower 20 is connected to the water washing tank 28 on another side through valve 3. The water washing tank 28 is connected to the water washing pump 27 through valve 4 26. The third side of the acid washing tower 20 is connected to the pyrolytic carbon collection tank 29 through valve 5 30 and a drying device 33 to collect the dried porous graphite carbon material. Acid enters the acid washing tower 20 from the acid tank 21 through the acid washing pump 23 for pickling. During water washing, the water washing liquid enters the acid washing tower 20 from the water washing tank 28 through the water washing liquid pump 27. After acid washing and water washing, the material enters the drying device 33 and is dried at 105° C. for 12 hours to obtain the porous graphite carbon material.

[0041] The product collection system is connected to the gas and liquid product outlet of the pyrolysis system and includes a condenser 16, a pyrolysis gas collection tank 18, and a pyrolysis oil collection tank 19. The condenser 16 is connected to the gas and liquid product outlet of the pyrolysis system. The gas and liquid products obtained by pyrolysis are separated by the condenser 16, the pyrolysis oil enters the pyrolysis oil collection tank 19, and the pyrolysis gas enters the pyrolysis gas collection tank 18.

[0042] The exhaust gas treatment system is connected to the outlet of the pyrolysis gas collection tank 18 and includes a burner 32. The pyrolysis gas is burned in the burner 32 to provide heat for the pyrolysis furnace 15. After heat exchange in the pyrolysis furnace, it is discharged through the pyrolysis gas outlet 31 and serves as a heat source for the dryer 7.

[0043] During implementation, the iron salt solution is placed in the iron salt solution silo 1 and fed into the screw feeder 5 via the liquid feed pump 2. The biomass raw material enters the screw feeder 5 through the screw feeder inlet 3 and mixes with the iron salt solution to form a uniformly dispersed suspension. The suspension is then fed into the dryer 7 to evaporate the solvent at a drying temperature of 150-200°C, drying to a moisture content of 5% to 10%. The dried raw material enters the pyrolysis furnace 15. The plastic raw material is fed into the screw feeder 2 13 through the plastic silo 12 and mixed with the biomass raw material through the pyrolysis furnace inlet 14 for a carbon thermal reduction reaction. The pyrolysis temperature is controlled at 900-1200°C and the holding time is 0.5-1.5 hours. The resulting solid product enters the acid washing tower 20 for acid washing and water washing, and is then collected in the pyrolysis carbon collection tank 29. The gas-liquid mixed product generated enters the condenser 20 and is separated. The resulting pyrolysis oil enters the pyrolysis oil collection tank 19 for collection. The resulting pyrolysis gas enters the pyrolysis gas collection tank 18 for collection and then is burned to provide heat for the pyrolysis furnace 15. The pyrolysis gas temperature range is 800-950°C. The exhaust gas is discharged and used as a heat source for the dryer 7. At this time, the temperature drops to 250-350°C, and the biomass raw material is dried before being discharged.

[0044] Example

[0045] In this embodiment, bamboo powder is used as the biomass raw material and polystyrene is used as the plastic raw material. Iron salt is selected from FeCl3, the solution concentration is 0.25 mol / L, and the pickling solution uses hydrochloric acid with a concentration of 1 mol / L. After the bamboo powder and FeCl3 solution are fully mixed, they are put into a dryer and dried at 105°C for 24 hours. Then, they are put into a pyrolysis furnace and polystyrene plastic is added for pyrolysis. The pyrolysis operating conditions are heating to 900°C at a heating rate of 10°C / min and keeping the temperature for 30 minutes. Afterwards, the pyrolytic carbon is washed with hydrochloric acid to remove FeCl3 and then collected. Figure 2The XRD images of the carbon obtained by pyrolysis of FeCl3-loaded bamboo powder alone (BM) and the carbon obtained by pyrolysis of FeCl3-loaded bamboo powder with 10% wt.% polystyrene added (BM+10% PS) are shown. The characterization results show that the carbon obtained by pyrolysis of BM+10% PS has a significant graphite peak (002) at 2θ=26°, indicating that the addition of polystyrene improves the degree of graphitization of the pyrolytic carbon and promotes the graphitization process of the pyrolytic carbon. The obtained pyrolytic carbon has a good degree of graphitization. At the same time, by comparing the carbon obtained by pyrolysis of FeCl3-loaded bamboo powder alone, it can be found that the carbon obtained by the present invention significantly improves the degree of graphitization of the pyrolytic carbon. Figure 3 The BET images show that the pore size of the carbon material is enlarged after the addition of plastic. This may be because the PS pyrolysis volatiles interact with the iron in the bamboo pyrolysis coke to form a porous graphitic carbon structure. The stacked graphitic carbon structure expands the pore structure of the co-pyrolysis carbon. The surface of the pyrolysis coke obtained by pyrolysis of bamboo powder loaded with FeCl3 is evenly distributed with gray-black particles. The stripes with characteristic crystal plane spacing of 0.203nm and 0.21nm correspond to the (110) crystal plane of Fe and the corresponding crystal plane of Fe3C. The elemental iron and Fe3C are surrounded by amorphous carbon in the coke. The carbon obtained by pyrolysis of BM + 10% PS shows obvious graphitization stripes near the Fe / Fe3C, with a characteristic crystal plane spacing of 0.342nm. This shows that the surface of the pyrolysis coke produced by pyrolysis of bamboo powder loaded with FeCl3 is mainly amorphous carbon, while the surface of the co-pyrolysis coke produced by BM + 10% PS undergoes a strong graphitization reaction. This is because the PS pyrolysis volatiles dissolve on the iron surface and grow in the form of graphitic carbon. The main product of PS pyrolysis is styrene, which has a benzene ring and is the basic unit structure of deposited carbon. Components such as styrene containing a benzene ring are conducive to the growth of graphitic carbon structures. Furthermore, the volatiles produced during PS pyrolysis contain a relatively high number of aromatic hydrocarbons, which are relatively easy to aggregate on the surface of the Fe catalyst and form graphitic carbon through further polymerization and induced graphitization. The above shows that the porous graphitic carbon obtained by biomass pyrolysis according to the method of the present invention has excellent properties such as a high degree of graphitization and abundant porosity, making it a high-value-added carbon material.

Claims

1. A method for preparing porous graphite carbon by pyrolysis of biomass, characterized in that: include: 1) Stirring the biomass and the iron salt solution to form a uniformly dispersed suspension; 2) drying the suspension to obtain an iron salt-loaded biomass raw material with a moisture content of 5% to 10%; 3) Pyrolyzing the iron salt-loaded biomass raw material and the plastic at 900-1200° C. under an inert atmosphere, the iron salt is converted into elemental iron under the action of carbon and reducing gas produced by the pyrolysis of the plastic and biomass. The elemental iron interacts with hydrocarbons produced by the pyrolysis of the plastic, and the hydrocarbons aggregate on the surface of the elemental iron to form Fe3C, and a graphite carbon structure is formed with the Fe3C as the center, thereby obtaining a porous graphite carbon material containing iron salt.

2. The method for preparing porous graphite carbon by pyrolysis of biomass according to claim 1, characterized in that: The mass ratio of the biomass raw material loaded with iron salt to the plastic is 1:0.1-0.

2.

3. The method for preparing porous graphite carbon by pyrolysis of biomass according to claim 1, characterized in that: The heating rate of pyrolysis is 5-10°C / min, and the holding time is 0.5-1h.

4. The method for preparing porous graphite carbon by pyrolysis of biomass according to claim 1, characterized in that: The method further includes acid washing, water washing and drying the porous graphite carbon material containing iron salt to obtain a final porous graphite carbon material.

5. The method for preparing porous graphite carbon by pyrolysis of biomass according to claim 1, characterized in that: The test standard for pickling is: burning at 800℃ for 1h, and there is no red residue in the ash after burning.

6. The method for preparing porous graphite carbon by pyrolysis of biomass according to claim 1, characterized in that: The conditions for the water washing operation are to rinse the acid-washed porous graphite carbon material with deionized water until the pH value reaches 7.

7. A system for producing porous graphite carbon by pyrolysis of biomass, characterized in that: include: The pretreatment system is used to stir the biomass and the iron salt solution to form a uniformly dispersed suspension, and then dry the biomass raw material loaded with iron salt to a moisture content of 5% to 10%; The pyrolysis system is used to pyrolyze biomass raw materials and plastics loaded with iron salts at 900-1200°C under an inert atmosphere. The iron salt is converted into elemental iron under the action of carbon and reducing gas produced by the pyrolysis of plastics and biomass. The elemental iron interacts with hydrocarbons produced by the pyrolysis of plastics. The hydrocarbons aggregate on the surface of the elemental iron to form Fe3C, and a graphite carbon structure is formed with Fe3C as the center, thereby obtaining a porous graphite carbon material containing iron salts.

8. The system for producing porous graphite carbon by pyrolysis of biomass according to claim 7, characterized in that: The pretreatment system includes an iron salt solution silo, a liquid feed pump, a screw feeder and a dryer; The iron salt solution silo is used to contain the iron salt solution, which is fed into a first screw feeder via a liquid feed pump. The first screw feeder is provided with a biomass raw material inlet, and the iron salt solution and the biomass are mixed in the screw feeder to form a uniformly dispersed suspension. The first discharge port of the screw feeder is connected to a dryer, which dries the suspension to a biomass raw material loaded with iron salt with a moisture content of 5% to 10%.

9. The system for producing porous graphite carbon by pyrolysis of biomass according to claim 7, characterized in that: The pyrolysis system includes a flow meter, a thermometer, a pyrolysis furnace, a second screw feeder, and a plastic silo; the plastic silo is connected to the pyrolysis furnace through the second screw feeder, and the pyrolysis furnace is used to pyrolyze biomass raw materials loaded with iron salts and plastics at 900-1200°C under an inert atmosphere; the pyrolysis furnace is provided with a flow meter and a thermometer, which are used to monitor the inert gas flow and the temperature inside the pyrolysis furnace, respectively.

10. The system for producing porous graphite carbon by pyrolysis of biomass according to claim 7, characterized in that: The method also includes an acid washing and water washing system for acid washing, water washing and drying the porous graphite carbon material containing iron salt.

11. The system for producing porous graphite carbon by pyrolysis of biomass according to claim 7, characterized in that: It also includes product collection systems and waste gas treatment systems; The product collection system is connected to the gas-liquid product outlet of the pyrolysis system, and includes a condenser, a pyrolysis gas collection tank, and a pyrolysis oil collection tank; the condenser is connected to the gas-liquid product outlet of the pyrolysis system, and the gas and liquid products obtained by pyrolysis are separated by the condenser, the pyrolysis oil enters the pyrolysis oil collection tank, and the pyrolysis gas enters the pyrolysis gas collection tank; The waste gas treatment system is connected to the outlet of the pyrolysis gas collection tank and includes a burner; the pyrolysis gas is burned by the burner to provide heat for the pyrolysis furnace, and is discharged through the pyrolysis gas outlet after heat exchange in the pyrolysis furnace to serve as a heat source for the dryer.

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