Porous carbon preparation method and continuous fluidized bed system

Abstract

The invention discloses a porous carbon preparation method and a continuous fluidized bed system.The porous carbon preparation method comprises the steps that rice husks and bamboo fibers are mixed and smashed, the smashed rice husks and bamboo fibers are dried and then mixed with a composite activating agent solution to be steeped, and a pretreated material is formed; feeding the pretreated material into a first-stage fluidized bed, and carbonizing the pretreated product in a nitrogen atmosphere to obtain a carbonized product; feeding the carbonized product into a second-stage fluidized bed, introducing saturated steam and CO2 gas into the second-stage fluidized bed in stages, and activating the carbonized product to obtain an activated product; feeding the activated product into a third-stage fluidized bed, introducing methane gas into the third-stage fluidized bed in an inert gas atmosphere, and performing micropore surface modification on the activated product to obtain a modified product; and washing the modified product with a hydrochloric acid solution and deionized water in sequence, and carrying out vacuum drying to obtain a porous carbon product. According to the preparation method of the porous carbon, the micropore development efficiency is improved, and continuous production of the porous carbon with high specific surface area and high micropore proportion is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of carbon preparation, and in particular to a porous carbon preparation method and a continuous fluidized bed system. BACKGROUND

[0002] Porous carbon materials have a wide range of applications in energy storage, gas adsorption and catalysis due to their excellent specific surface area and pore structure. Among them, porous carbon materials with high specific surface area (>2000 m² / g) and micropore ratio >90% have unique advantages in supercapacitors and gas separation. Continuous fluidized bed activation technology has become the preferred process for large-scale preparation of porous carbon due to its high mass transfer efficiency, large processing capacity and easy industrialization.

[0003] In the prior art, the method for preparing porous carbon by a continuous fluidized bed uses single raw materials such as catalytic diesel, which limits the control of pore structure and makes it difficult to achieve high specific surface area and high micropore ratio at the same time. In addition, single gas activator such as CO2 or steam is used in the activation process, which has low activation efficiency and imperfect micropore development. Some existing preparation methods can obtain a high micropore ratio of ≥95%, but they use a batch preparation process, which has low production efficiency. SUMMARY

[0004] The embodiments of the present application provide a porous carbon preparation method and a continuous fluidized bed system, which solve the above technical problems, improve the micropore development efficiency, and realize the continuous production of porous carbon with high specific surface area and high micropore ratio.

[0005] In a first aspect, the embodiments of the present application provide a porous carbon preparation method, which includes: mixing and crushing rice husks and bamboo fibers, and then mixing and impregnating the dried mixture with a composite activator solution to form pretreated material; wherein the composite activator includes magnesium tartrate and diammonium hydrogen phosphate; feeding the pretreated material into a first fluidized bed, carbonizing the pretreated product in a nitrogen atmosphere to obtain carbonized product; feeding the carbonized product into a second fluidized bed, and introducing saturated steam and CO2 gas into the second fluidized bed in stages to activate the carbonized product and obtain activated product; feeding the activated product into a third fluidized bed, introducing methane gas into the third fluidized bed in an inert gas atmosphere to modify the microporous surface of the activated product and obtain modified product; and washing the modified product with hydrochloric acid solution and deionized water in sequence, and then vacuum drying to obtain porous carbon product.

[0006] In combination with the first aspect, in a possible implementation manner, the solution concentration of the composite activator is 15-25wt%, and the mass ratio of the magnesium tartrate to the diammonium hydrogen phosphate is 2:1-3:1.

[0007] In conjunction with the first aspect, in one possible implementation, microwave-assisted heating is used during the activation of the carbonized product, and the microwave-assisted heating employs an intermittent pulse mode.

[0008] In conjunction with the first aspect, in one possible implementation, the mass ratio of saturated steam flow rate to the carbonization product in the saturated steam activation stage is 0.5:1 to 0.8:1, and the mass ratio of CO2 gas flow rate to the carbonization product in the CO2 activation stage is 1:1 to 1.2:1.

[0009] Secondly, embodiments of this application provide a continuous fluidized bed system for implementing the aforementioned porous carbon preparation method. The continuous fluidized bed system includes: a raw material pretreatment mechanism configured to mix and pulverize rice husks and bamboo fibers, and then dry the rice husks and bamboo fibers before mixing and impregnating them with a composite activator solution; a primary fluidized bed, the inlet of which is connected to the raw material pretreatment mechanism, the primary fluidized bed including a first bed body, a gas distributor installed at the bottom of the first bed body, multiple gas outlet pipes installed in the middle of the first bed body, and a cyclone separator installed at the top of the first bed body; the sidewalls of the gas outlet pipes are provided with multiple vent holes; and a secondary fluidized bed, the secondary fluidized bed including a second bed body and a temperature sensor array disposed on the inner wall of the secondary fluidized bed; and the second bed body including a axially arranged... The system comprises an upper fluidized bed and a lower fluidized bed, the lower fluidized bed having a steam inlet and the upper fluidized bed having a CO2 inlet; a three-stage fluidized bed, the three-stage fluidized bed including a third bed, a gas mixer installed at the bottom of the third bed, and a tail gas treatment device installed at the top of the bed; the gas mixer is used to introduce a mixture of inert gas and methane; a pressure gradient control system, the pressure gradient control system including pressure sensors and automatic regulating valves installed between the first-stage fluidized bed, the second-stage fluidized bed and the third-stage fluidized bed, configured to maintain a first pressure difference between the first-stage fluidized bed and the second-stage fluidized bed, and a second pressure difference between the second-stage fluidized bed and the third-stage fluidized bed; and a material conveying mechanism connected between the first-stage fluidized bed, the second-stage fluidized bed and the third-stage fluidized bed, configured to drive the sealed conveying of material in different pressure ranges.

[0010] In conjunction with the second aspect, in one possible implementation, the raw material pretreatment mechanism includes a pretreatment tank, two screw feeders, and two metering pumps; the inlets of the two metering pumps are respectively connected to the outlets of the two screw feeders, and the outlets of the two metering pumps are both connected to the pretreatment tank; the pretreatment tank is configured to crush and dry the rice husks and bamboo fibers, and to stir them after the addition of the composite activator solution, and the outlet of the pretreatment tank is connected to the primary fluidized bed.

[0011] In conjunction with the second aspect, in one possible implementation, the porosity of the plurality of gas outlet tubes increases in a gradient with height.

[0012] In conjunction with the second aspect, in one possible implementation, the diameter of the gas outlet pipe is 30-50 mm, and the diameter of the vent opening on the side wall of the gas outlet pipe is 2-5 mm.

[0013] In conjunction with the second aspect, in one possible implementation, the secondary fluidized bed further includes a microwave generator wound around the outer wall of the second bed.

[0014] In conjunction with the second aspect, in one possible implementation, the microwave generator has 6-8 magnetrons arranged in a ring around the second bed, and the magnetrons operate at a frequency of 2450±50MHz.

[0015] This application provides a method for preparing porous carbon. The porous carbon prepared by this method has a specific surface area of ​​1800-2000 m² / g, a micropore ratio of >85%, and a pore size distribution concentrated in the 0.44-2 nm range. Rice husk and bamboo fiber are used as composite biomass raw materials, and in synergy with a composite activator, the complementary components of rice husk and bamboo fiber and the synergistic etching effect of the activator are utilized to significantly improve the micropore development efficiency. A staged activation process using saturated steam and CO2 is adopted, which shortens the activation time by 40% compared with traditional methods and improves the activation efficiency. Continuous production using a primary fluidized bed, a secondary fluidized bed, and a tertiary fluidized bed achieves seamless connection from carbonization to activation, has high production efficiency, and ensures the stability of product batches. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments of this application or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1Flowcharts of methods for preparing porous carbon provided for some embodiments of this application; Figure 2 A schematic diagram showing the results of density functional theory analysis (calculated based on adsorption isotherms) of porous carbon products provided in Example 1 of this application; Figure 3 A schematic diagram showing the results of density functional theory analysis (calculated based on adsorption isotherms) of porous carbon products provided in Example 2 of this application; Figure 4 Schematic diagrams of a continuous fluidized bed system provided for some embodiments of this application; Figure 5 Schematic diagrams of the raw material pretreatment mechanism provided for some embodiments of this application; Figure 6 Schematic diagrams of the structure of a primary fluidized bed provided for some embodiments of this application; Figure 7 Schematic diagrams of a secondary fluidized bed provided for some embodiments of this application; Figure 8 A schematic diagram of a three-stage fluidized bed provided for some embodiments of this application.

[0018] Reference numerals: 100-Primary fluidized bed; 110-First bed; 120-Gas distributor; 130-Gas outlet pipe; 140-Cyclone separator; 200-Secondary fluidized bed; 210-Second bed; 211-Upper bed; 212-Lower bed; 220-Temperature sensor array; 230-Microwave generator; 300-Tertiary fluidized bed; 310-Third bed; 320-Gas mixer; 330-Tail gas treatment device; 400-Raw material pretreatment mechanism; 410-Pretreatment storage tank; 420-Screw feeder; 430-Metering pump; 500-Pressure gradient control system; 600-Material conveying mechanism. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0020] In the description of the embodiments of this application, it should be noted that the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0021] This application provides a method for preparing porous carbon, such as Figure 1 As shown, the porous carbon preparation method includes steps S101 to S105.

[0022] S101. Rice husks and bamboo fibers are mixed and crushed, dried, and then mixed and impregnated with a composite activator solution to form a pretreated material; wherein, the composite activator includes magnesium tartrate and diammonium hydrogen phosphate.

[0023] For example, the mass ratio of rice husk to bamboo fiber is 3:1-5:1, the particle size of rice husk and bamboo fiber is 50-100 mesh, and they are dried at 105℃ for 8-12 hours; the dried rice husk and bamboo fiber are mixed with the composite activator solution at a solid-liquid ratio of 1:2-1:3 and impregnated for 24-36 hours.

[0024] Rice husks and bamboo fiber are used as composite biomass raw materials. Both are rich in cellulose and lignin, and their ash compositions are complementary. The silicon in rice husks and the potassium in bamboo fiber can synergistically promote micropore formation. This composite biomass raw material, combined with a composite activator, utilizes the self-activation effect of magnesium tartrate (high-temperature decomposition to produce CO2 and MgO) and the catalytic etching effect of diammonium hydrogen phosphate to lay the foundation for subsequent micropore development.

[0025] S102. The pretreated material is fed into a primary fluidized bed, and the pretreated product is carbonized under a nitrogen atmosphere to obtain a carbonized product.

[0026] For example, during the carbonization process of the pretreated material, the temperature is controlled at 500-600℃, the pressure at 0.05-0.1MPa, the apparent gas velocity at 0.1-0.2m / s, and the residence time at 1-2h.

[0027] The pretreated material undergoes carbonization in the primary fluidized bed. The nitrogen atmosphere in the primary fluidized bed can suppress excessive cracking, allowing the carbonized product to retain more of the reactivatable carbon skeleton.

[0028] S103. The carbonized product is fed into a secondary fluidized bed, and saturated steam and CO2 gas are introduced into the secondary fluidized bed in stages to activate the carbonized product and obtain the activated product.

[0029] For example, saturated steam is first introduced into the secondary fluidized bed for 1-1.5 hours, with the temperature controlled at 700-750°C and the pressure at 0.15-0.2 MPa; then, CO2 gas is introduced into the secondary fluidized bed for 1-1.5 hours, with the temperature rising to 750-800°C and the pressure maintained at 0.15-0.2 MPa.

[0030] Step S103 employs a two-step method of "saturated steam pre-activation - CO2 deep activation": saturated steam activation can preferentially etch the surface of carbonized products to form initial micropores; CO2 activation can further expand the pore depth and increase the specific surface area.

[0031] S104. The activated product is fed into a three-stage fluidized bed, and methane gas is introduced into the three-stage fluidized bed under an inert gas atmosphere to modify the microporous surface of the activated product and obtain the modified product.

[0032] For example, methane gas with a volume fraction of 5-10% is introduced into a three-stage fluidized bed under an inert gas atmosphere, with the temperature controlled at 600-650°C and the pressure at 0.1-0.15 MPa, and maintained for 30-60 minutes.

[0033] In step S103, methane gas is introduced into the three-stage fluidized bed to seal the entrances of overdeveloped mesopores through vapor deposition, while forming a carbon-rich layer on the surface of the micropores. This ensures a high proportion of micropores and improves the conductivity of the material.

[0034] S105. The modified product is washed sequentially with hydrochloric acid solution and deionized water, and then vacuum dried to obtain a porous carbon product.

[0035] For example, firstly, the modified product is washed 2-3 times with a 1 mol / L hydrochloric acid solution, then washed with deionized water until neutral, and dried at a temperature of 80-100℃ under vacuum for 12-24 hours to obtain a porous carbon product with a specific surface area of ​​2000-2300 m² / g and a micropore ratio of >90%.

[0036] Hydrochloric acid solution can remove residual composite activators and impurities, while deionized water can adjust the pH of porous carbon products to neutral.

[0037] Specifically, the concentration of the composite activator solution is 15-25wt%. This concentration range can balance the permeability and reaction efficiency of the composite activator. Too low a concentration (<15wt%) may lead to uneven impregnation, while too high a concentration (>25wt%) may easily cause excessive etching and collapse of the pore structure. Furthermore, the mass ratio of magnesium tartrate to diammonium hydrogen phosphate is 2:1-3:1.

[0038] In step S103, microwave-assisted heating is used during the activation of the carbonized product, and the microwave-assisted heating adopts an intermittent pulse mode.

[0039] Microwave-assisted heating has selective heating characteristics, which increases the reaction rate between the composite activator and the surface of the carbonized product by 30% and significantly shortens the activation time.

[0040] Furthermore, in step S103, the mass ratio of steam flow rate to carbonized product in the saturated steam activation stage is 0.5:1-0.8:1. This ratio ensures that steam fully penetrates the interior of the carbonized product, preferentially etching the surface amorphous carbon to form initial micropores, while avoiding excessive steam causing pore wall collapse. The mass ratio of CO2 gas flow rate to carbonized product in the CO2 activation stage is 1:1-1.2:1. This ratio allows the CO2 diffusion rate to match the reaction rate, avoiding pore blockage.

[0041] The activator flow gradient design in the two activation stages (low steam flow → high CO2 flow) conforms to the pore development law of "preferential surface etching - deep pore expansion", and the microporosity is significantly improved compared with single-stage activation.

[0042] The porous carbon preparation method provided in this application will be described in detail below through examples and comparative examples.

[0043] Example 1 Step 1: First, mix rice husks and bamboo fiber at a mass ratio of 3:1, pulverize to 80 mesh, and dry at 105℃ for 10 hours. Then, add a 20wt% composite activator solution at a solid-liquid ratio of 1:2 and impregnate for 30 hours to obtain the pretreated material. The composite activator solution includes magnesium tartrate and diammonium hydrogen phosphate, with a mass ratio of magnesium tartrate to diammonium hydrogen phosphate of 2:1.

[0044] The second step involves feeding the pretreated material into a primary fluidized bed, introducing nitrogen gas into the bed, and maintaining the temperature at 550℃, pressure at 0.08MPa, and apparent gas velocity at 0.15m / s under a nitrogen atmosphere for 1.5 hours to obtain the carbonized product. The primary fluidized bed is equipped with four 40mm diameter ceramic gas outlet pipes. The lower end of each gas outlet pipe is 250mm from the distributor at the bottom of the primary fluidized bed, and the opening ratio of the gas outlet pipes increases from 1% at the bottom to 3% at the top.

[0045] The third step involves feeding the carbonized product into a secondary fluidized bed. First, saturated steam is introduced at a flow rate to product mass ratio of 0.6:1, with the temperature controlled at 720℃ and the pressure at 0.18MPa for 1.2 hours. Then, CO2 gas is introduced at a flow rate to product mass ratio of 1.1:1, and the temperature is raised to 780℃ for another 1.2 hours under the same pressure. Microwave-assisted activation uses a frequency of 2450MHz with a pulse period of 30s (20s irradiation followed by a 10s interval).

[0046] Step 4: The carbonized product is fed into a three-stage fluidized bed, and a nitrogen mixture containing 8% methane is introduced. The temperature is controlled at 620℃ and the pressure at 0.12MPa for 45 minutes.

[0047] Step 5: First, wash the modified product three times with 1 mol / L hydrochloric acid solution, then wash with deionized water until neutral, and dry in vacuum at 90°C for 18 hours to obtain porous carbon product.

[0048] Product performance test: Specific surface area 2298m² / g, total pore volume 0.9884cm³ / g, of which micropore volume is 0.9350cm³ / g (accounting for 94.59%), and average pore size is 1.6955nm.

[0049] The results of density functional theory analysis (calculated based on adsorption isotherms) on porous carbon products, such as... Figure 2 As shown.

[0050] The pore volume of porous carbon was statistically analyzed, and the results are shown in Table 1.

[0051] Table 1 Pore size range / nm 0.3-2 2-5 5-50 ＞50 / / / ΔVi / ∑Vi / (%) 94.65 3.87 1.17 0.30 / / / Example 2 Based on Example 1, the ratio of rice husk to bamboo fiber was changed to 5:1, the ratio of composite activator and the rest of the process were the same as in Example 1.

[0052] Product performance: Specific surface area is 2162.12 m² / g, total pore volume is 0.9254 cm³ / g, micropore volume is 0.8728 cm³ / g, micropore ratio is 94.38%, and average pore size is 1.71 nm.

[0053] The results of density functional theory analysis (calculated based on adsorption isotherms) on porous carbon products, such as... Figure 3 As shown.

[0054] The pore volume of porous carbon was statistically analyzed, and the results are shown in Table 2.

[0055] Table 2 Pore size range / nm 0.3-2 2-5 5-50 ＞50 / / / ΔVi / ∑Vi / (%) 94.38 4.06 1.22 0.34 / / / Comparative Example 1 Using only rice husk as raw material, the rest is the same as in Example 1.

[0056] Product performance: Specific surface area is 1650m² / g, and micropores account for 78.5%.

[0057] Comparative Example 2 With microwave assistance, the rest is the same as in Example 1.

[0058] Product performance: Specific surface area is 1720m² / g, and micropores account for 82.3%.

[0059] This application also provides a continuous fluidized bed system, such as Figure 4 As shown, the continuous fluidized bed system is used to realize the above-mentioned porous carbon preparation method. The continuous fluidized bed system includes a raw material pretreatment mechanism 400, a primary fluidized bed 100, a secondary fluidized bed 200, a tertiary fluidized bed 300, a pressure gradient control system 500, and a material conveying mechanism 600.

[0060] The raw material pretreatment unit 400 is configured to mix and crush rice husks and bamboo fibers, and then dry the rice husks and bamboo fibers before mixing and impregnating them with a composite activator solution.

[0061] like Figure 6 As shown, the inlet of the primary fluidized bed 100 is connected to the raw material pretreatment mechanism 400. The primary fluidized bed 100 includes a first bed body 110, a gas distributor 120 installed at the bottom of the first bed body 110, multiple gas outlet pipes 130 installed in the middle of the first bed body 110, and a cyclone separator 140 installed at the top of the first bed body 110. Multiple air vents are provided on the side wall of the gas outlet pipes 130. Gas enters the first bed body 110 through the multiple air vents, which can effectively eliminate the bubble effect in the carbonization process and make the particle size distribution deviation of the carbonization product smaller.

[0062] like Figure 7 As shown, the secondary fluidized bed 200 includes a second bed body 210 and a temperature sensor array 220 disposed on the inner wall of the secondary fluidized bed 200. The second bed body 210 includes an upper bed body 211 and a lower bed body 212 arranged axially. The lower bed body 212 is provided with a steam inlet, and the upper bed body 211 is provided with a CO2 inlet. The secondary fluidized bed 200 is used to activate the carbonized products generated by the primary fluidized bed 100. First, saturated steam is introduced through the lower bed body 212 to form initial micro-controls on the surface of the carbonized products. Then, CO2 is introduced through the upper bed body to further expand the pore depth and increase the specific surface area.

[0063] like Figure 8As shown, the three-stage fluidized bed 300 includes a third bed body 310, a gas mixer 320 installed at the bottom of the third bed body 310, and a tail gas treatment device 330 installed at the top of the bed body; the gas mixer 320 is used to introduce a mixture of inert gas and methane. The methane gas can perform microporous modification on the activation products generated by the secondary fluidized bed 200. Specifically, the methane gas blocks the inlets of overdeveloped mesopores through vapor deposition, while forming a carbon-rich layer on the surface of the micropores, ensuring a high micropore ratio and improving the conductivity of the material.

[0064] The pressure gradient control system 500 includes pressure sensors and automatic regulating valves installed between the primary fluidized bed 100, the secondary fluidized bed 200, and the tertiary fluidized bed 300. It is configured to maintain a first pressure difference between the primary fluidized bed 100 and the secondary fluidized bed 200, and a second pressure difference between the secondary fluidized bed 200 and the tertiary fluidized bed 300, in order to ensure smooth material transport and provide a reasonable pressure environment for different stages of the reaction.

[0065] The material conveying mechanism 600 is connected between the primary fluidized bed 100, the secondary fluidized bed 200, and the tertiary fluidized bed 300, and is configured to drive the sealed conveying of materials in different pressure ranges. Exemplarily, the material conveying mechanism 600 includes a sealed tube for connecting two adjacent fluidized beds, and a screw propeller disposed on the sealed tube.

[0066] In some embodiments of this application, such as Figure 5 As shown, the raw material pretreatment mechanism 400 includes a pretreatment tank 410, two screw feeders 420, and two metering pumps 430. The inlets of the two metering pumps 430 are respectively connected to the outlets of the two screw feeders 420, and the outlets of the two metering pumps 430 are both connected to the pretreatment tank 410. The pretreatment tank 410 is configured to crush and dry rice husks and bamboo fibers, and to agitate them after the addition of a composite activator solution. The outlet of the pretreatment tank 410 is connected to the primary fluidized bed 100.

[0067] When the raw material pretreatment unit 400 is working, the staff adds rice husks and bamboo fibers to the two screw feeders 420 respectively. The two screw feeders 420 feed the rice husks and bamboo fibers into the two metering pumps 430 respectively. After the two metering pumps 430 weigh the rice husks and bamboo fibers respectively, they are added to the pretreatment storage tank 410 according to the preset mass ratio. The staff adds a composite activator to the pretreatment storage tank 410 and stirs the rice husks and bamboo fibers in the pretreatment storage tank 410 so that the composite activator evenly impregnates the rice husks and bamboo fibers.

[0068] Specifically, the opening ratio of the multiple gas outlet pipes 130 increases gradually with height, thereby achieving gas diversion, reducing bed density fluctuations, and significantly improving fluidization quality. For example, the opening ratio of the multiple gas outlet pipes 130 increases gradually from 1% to 3%.

[0069] Furthermore, the diameter of the gas outlet pipe 130 is 30-50mm, and the diameter of the vent opening on the side wall of the gas outlet pipe 130 is 2-5mm.

[0070] In some embodiments of this application, such as Figure 7 As shown, the secondary fluidized bed 200 also includes a microwave generator 230 wound around the outer wall of the second bed body 210. The microwave generator 230 is capable of rapidly raising the internal temperature of the second fluidized bed to the activation temperature.

[0071] The microwave generator 230 has 6-8 magnetrons arranged in a ring around the second bed 210 to achieve uniform distribution of microwave energy. Combined with the temperature sensor array 220 (accuracy ±2℃), this ensures the activation temperature remains stable within a reasonable range of 700-800℃. Furthermore, the magnetrons operate at a frequency of 2450±50MHz.

[0072] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0073] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A method for preparing porous carbon, characterized in that, include: Rice husks and bamboo fibers are mixed and crushed, dried, and then mixed with a composite activator solution for impregnation to form a pretreated material; wherein the composite activator includes magnesium tartrate and diammonium hydrogen phosphate. The pretreated material is fed into a primary fluidized bed, and the pretreated product is carbonized under a nitrogen atmosphere to obtain a carbonized product. The carbonized product is fed into a secondary fluidized bed, and saturated steam and CO2 gas are introduced into the secondary fluidized bed in stages to activate the carbonized product and obtain an activated product. The activated product is fed into a three-stage fluidized bed, and methane gas is introduced into the three-stage fluidized bed under an inert gas atmosphere to perform microporous surface modification on the activated product to obtain a modified product. The modified product was washed sequentially with hydrochloric acid solution and deionized water, and then vacuum dried to obtain a porous carbon product.

2. The method for preparing porous carbon according to claim 1, characterized in that, The concentration of the composite activator solution is 15-25 wt%, and the mass ratio of magnesium tartrate to diammonium hydrogen phosphate is 2:1-3:

1.

3. The method for preparing porous carbon according to claim 1, characterized in that, Microwave-assisted heating is used during the activation of the carbonized product, and the microwave-assisted heating adopts an intermittent pulse mode.

4. The method for preparing porous carbon according to claim 1, characterized in that, The mass ratio of saturated steam flow rate to carbonization product in the saturated steam activation stage is 0.5:1-0.8:1, and the mass ratio of CO2 gas flow rate to carbonization product in the CO2 activation stage is 1:1-1.2:

1.

5. A continuous fluidized bed system, characterized in that, The continuous fluidized bed system is used to implement the porous carbon preparation method according to any one of claims 1-4, wherein the continuous fluidized bed system comprises: The raw material pretreatment unit is configured to mix and crush the rice husk and the bamboo fiber, and then dry the rice husk and the bamboo fiber and impregnate them with a composite activator solution; A primary fluidized bed, the inlet of which is connected to the raw material pretreatment mechanism, the primary fluidized bed including a first bed body, a gas distributor installed at the bottom of the first bed body, a plurality of gas outlet pipes installed in the middle of the first bed body, and a cyclone separator installed at the top of the first bed body; the side wall of the gas outlet pipes is provided with a plurality of air vents. A secondary fluidized bed, comprising a second bed body and a temperature sensor array disposed on the inner wall of the secondary fluidized bed; and the second bed body comprising an upper bed body and a lower bed body disposed along the axial direction, the lower bed body being provided with a steam inlet and the upper bed body being provided with a CO2 inlet; The three-stage fluidized bed includes a third bed body, a gas mixer installed at the bottom of the third bed body, and an exhaust gas treatment device installed at the top of the bed body; the gas mixer is used to introduce a mixture of inert gas and methane. A pressure gradient control system, comprising a pressure sensor and an automatic regulating valve installed between the primary fluidized bed, the secondary fluidized bed and the tertiary fluidized bed, configured to maintain a first pressure difference between the primary fluidized bed and the secondary fluidized bed, and a second pressure difference between the secondary fluidized bed and the tertiary fluidized bed; A material conveying mechanism is connected between the primary fluidized bed, the secondary fluidized bed, and the tertiary fluidized bed, and is configured to drive the sealed conveying of materials in different pressure ranges.

6. The continuous fluidized bed system according to claim 5, characterized in that, The raw material pretreatment mechanism includes a pretreatment storage tank, two screw feeders, and two metering pumps; The inlets of the two metering pumps are respectively connected to the outlets of the two screw feeders, and the outlets of the two metering pumps are both connected to the pretreatment storage tank. The pretreatment tank is configured to crush and dry the rice husks and bamboo fibers, and to stir them after adding the composite activator solution, and the outlet of the pretreatment tank is connected to the primary fluidized bed.

7. The continuous fluidized bed system according to claim 5, characterized in that, The porosity of the multiple gas outlet tubes increases gradually with height.

8. The continuous fluidized bed system according to claim 5 or 7, characterized in that, The diameter of the gas outlet pipe is 30-50mm, and the diameter of the ventilation opening on the side wall of the gas outlet pipe is 2-5mm.

9. The continuous fluidized bed system according to claim 5, characterized in that, The secondary fluidized bed also includes: A microwave generator wrapped around the outer wall of the second bed.

10. The continuous fluidized bed system according to claim 5, characterized in that, The microwave generator has 6-8 magnetrons arranged in a ring around the second bed, and the operating frequency of the magnetrons is 2450±50MHz.

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