Apparatus and method for preparing nano-iron-carbon composite material by rotary pyrolysis

Abstract

The application relates to the technical field of nano iron-carbon composite material preparation, and discloses a device and a method for preparing nano iron-carbon composite material through rotary pyrolysis. The device comprises a temperature control furnace which is provided with a hearth and a heating element in the hearth; a rotary reaction tube which is rotatably arranged in the hearth and used for containing a mixture of an iron precursor and a biomass carbon source; a driving system which is connected with the rotary reaction tube and used for driving the rotary reaction tube to rotate around a central axis; and a spraying system which can spray a coating liquid to the surface of the mixture in the rotary reaction tube through a fluid passage interface. The device can solve the technical problems of uneven heat and mass transfer and different product quality caused by static accumulation of materials in a traditional static pyrolysis process, ensures that the heating, carbonization and reduction processes of the materials are highly uniform, and thus the composite material with narrow nano iron particle size distribution and uniform dispersion on the carbon carrier is obtained, and the batch stability of the product is greatly improved.

Description

Technical Field

[0001] This invention relates to the field of nano-iron-carbon composite material preparation technology, and more specifically, to an apparatus for preparing nano-iron-carbon composite materials by rotational pyrolysis and a method for preparing nano-iron-carbon composite materials by rotational pyrolysis. Background Technology

[0002] Nano-iron-carbon composites, due to their high specific surface area, abundant active sites, and synergistic effect between iron and carbon supports, show broad application prospects in environmental remediation (such as wastewater treatment and soil improvement), catalysis, and energy fields. The core of preparing high-performance nano-iron-carbon materials lies in achieving uniform dispersion and stable fixation of nano-zero-valent iron particles on a carbon support, and effectively preventing oxidative deactivation of their highly active surfaces during preparation and storage. Currently, mainstream preparation technologies mainly follow two paths: "liquid-phase reduction" and "solid-phase pyrolysis," but both have significant limitations.

[0003] Liquid-phase reduction typically uses soluble iron salts as precursors, which are converted into zero-valent iron nanoparticles in a liquid environment by a reducing agent and then loaded onto carbon materials. Although this method is mild and combines reduction and coating effects, its inherent drawbacks limit its large-scale application: such as discontinuous reactions, mostly batch operations, low production efficiency, poor product consistency, and limited stability.

[0004] To overcome the shortcomings of the liquid phase method, the atmosphere furnace pyrolysis method was developed. This method mixes organic iron salts with biomass carbon sources (such as straw and sawdust) and pyrolyzes them at high temperature in an inert or reducing atmosphere, thereby achieving the formation of carbon carriers and the reduction of iron salts in one step. This approach has potential advantages such as a wide range of raw material sources, no wastewater in the process, and easy scale-up. However, the traditional static or tubular fixed bed pyrolysis process has the following bottleneck problems: (1) Uneven heat and mass transfer: The static accumulation of materials leads to a large gradient in heat and atmosphere distribution during pyrolysis, resulting in uneven carbonization and iron reduction of products in the same batch, and wide size distribution of nano-iron particles, which are easy to agglomerate; (2) Oxidation risk throughout: Especially in the cooling and material removal stage after the high-temperature reaction, the material is very easy to be violently oxidized or even spontaneously combusted due to exposure to air, resulting in the loss of all previous efforts. Summary of the Invention

[0005] The present invention aims to overcome at least one of the defects of the prior art and provide an apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis, which solves the technical problems of uneven heat and mass transfer and inconsistent product quality caused by static accumulation of materials in traditional static pyrolysis processes.

[0006] The technical solution adopted in this invention is an apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis, comprising: a temperature-controlled furnace having a furnace chamber and a heating element inside; a rotary reaction system including a rotary reaction tube rotatably disposed within the furnace chamber for containing a mixture of iron-containing precursor and biomass carbon source; a sealing component disposed on the rotary reaction tube for sealing the rotary reaction tube during rotation, and having several fluid channel interfaces thereon; a drive system connected to the rotary reaction tube for driving the rotary reaction tube to rotate around its central axis; a spraying system capable of spraying a coating liquid onto the surface of the mixture inside the rotary reaction tube through the fluid channel interfaces; a control system electrically connected to the heating element and the drive system for controlling the pyrolysis temperature and the rotational speed of the rotary reaction tube; and a cooling protection system connected to the fluid channel interfaces through pipelines for condensing and recovering the pyrolysis tail gas.

[0007] By driving a rotating reaction tube to dynamically tumble the material, the problems of uneven heat and mass transfer and inconsistent product quality in traditional static pyrolysis are solved.

[0008] Furthermore, the temperature-controlled furnace has inlets on both sides that communicate with the furnace chamber; the middle section of the rotating reaction tube is a material-bearing section with a larger diameter, which is located inside the furnace chamber, while its two smaller diameter ends pass through the inlets on both sides and are located outside the temperature-controlled furnace. The middle material-bearing section is completely located inside the heating furnace chamber to ensure efficient heating, while the two ends extend outside the furnace, providing physical space for subsequent connection of transmission, sealing, and piping systems.

[0009] Furthermore, the sealing component includes: a sealing end cap, with sealing end caps fixed on both sides of the temperature-controlled furnace, and the two ends of the rotary reaction tube respectively connected to the sealing end caps on both sides; the fluid channel interface includes: a connecting pipe, ball valve a, ball valve b, and ball valve c, with at least one connecting pipe on each sealing end cap; the rotary reaction tube has a first end and a second end opposite to each other, with ball valve a on the connecting pipe of the sealing end cap at the first end for connecting to the spray system, and ball valve c connected to another connecting pipe on the sealing end cap at the first end for venting; ball valve b on the connecting pipe of the sealing end cap at the second end of the rotary reaction tube for connecting to an inert gas source. Dynamic sealing is achieved by fixing the sealing end caps, and by setting different valves at both ends, the functions of inert gas intake, exhaust gas emission, and spray system intervention are separated and precisely controlled, ensuring a pure atmosphere and orderly operation during the process.

[0010] Furthermore, the rotary reaction system also includes a second thermocouple. A second thermocouple extending into the sealed end cap of either end of the rotary reaction tube is installed, and this second thermocouple is electrically connected to the control system. By setting a second thermocouple directly inside the rotary reaction tube, real-time monitoring of the material's actual temperature is achieved, and the signal is fed back to the control system. This provides crucial data for achieving precise programmed temperature control and avoids temperature control deviations caused by relying solely on furnace temperature monitoring.

[0011] Furthermore, the inner circumferential surface of the sealing end cap is provided with an annular groove, and a spring sealing ring is disposed within the annular groove. The spring sealing ring is in pressure contact with the outer circumferential surface of the end of the rotating reaction tube. The spring sealing ring provides continuous clamping force within the annular groove, ensuring a reliable seal between its end and the fixed end cap when the reaction tube rotates, effectively preventing air infiltration and reaction gas leakage, which is crucial for maintaining an inert atmosphere.

[0012] Furthermore, the spraying system includes a spray pipe and a sealing structure located at the end of ball valve a. The spray pipe has a spray section with several nozzles. The spray pipe can pass through the sealing structure and ball valve a sequentially and extend into the rotating reaction tube. Through the design of the penetrable spray pipe and the spray section with nozzles, the coating solution can be directly and uniformly sprayed onto the surface of the rotating material without disrupting the reaction atmosphere, thus achieving in-situ coating operation.

[0013] Furthermore, the sealing structure is a sealing plug with a through hole in the center for the spray pipe to pass through and form a sealing fit with the outer wall of the spray pipe. The sealing plug has a simple and effective structure. Its through hole allows the spray pipe to be inserted while tightly wrapping the outer wall of the spray pipe, preventing external air from entering the reaction tube during spraying. Moreover, it is directly inserted into the end of ball valve a, and the space between it and the valve core of ball valve a is limited. The amount of air stored in this space is negligible and its impact on the entire experiment can be ignored.

[0014] A method for preparing nano-iron-carbon composite materials by rotational pyrolysis, using the aforementioned apparatus for preparing nano-iron-carbon composite materials by rotational pyrolysis, includes the following steps:

[0015] S1. Place the mixture of iron-containing precursor and biomass carbon source in the rotary reaction tube of the rotary reaction system, operate the sealing component to seal the rotary reaction tube, and introduce inert gas through the fluid channel interface to replace the internal air.

[0016] S2. Start the drive system to rotate the rotary reaction tube, and at the same time control the heating element to raise the temperature through the control system, so as to carry out the pyrolysis reduction reaction under an inert atmosphere;

[0017] S3. After the reaction is complete, the rotating reaction tube and the material inside it are cooled to a predetermined temperature under an inert atmosphere.

[0018] S4. While maintaining an inert atmosphere and rotating the rotary reaction tube, activate the spray system and spray the coating liquid onto the surface of the rotating mixture via the fluid channel interface;

[0019] S5. Low-temperature drying solidifies the coating layer formed on the material surface by the coating solution, yielding a nano-iron-carbon composite material. Combining dynamic rotary pyrolysis with in-situ spray coating under an inert atmosphere not only ensures the uniformity of material synthesis but also actively constructs a protective layer before the material cools and exits the furnace, systematically solving the oxidation resistance problem throughout the entire process from preparation to storage.

[0020] Furthermore, the specific conditions for the pyrolysis-reduction reaction described in step S2 are as follows: under an inert atmosphere, the temperature is increased to 750–800°C at a preset heating rate, and maintained at this temperature for 1–2 hours. This temperature and time range is the optimal condition to ensure that the plant debris is fully carbonized to form a porous carrier, while simultaneously allowing the organic iron salt to be fully reduced to nano-zero valent iron, and obtaining a highly reactive product.

[0021] Furthermore, the coating solution in step S4 is at least one of a 1%–10% aqueous solution of polyvinyl alcohol or a polyvinylpyrrolidone aqueous solution; the solute contained in the coating solution is added at 0.05%–1% of the total mass of the initial mixture in step S1. The selected solvent and concentration range can form an effective protective film; the dosage range (0.05%–1%) ensures the formation of a complete, dense but not excessively thick coating layer.

[0022] Compared with existing technologies, the advantages of this invention are as follows: by driving a rotating reaction tube to dynamically tumble the material, the problem of uneven heat and mass transfer in traditional static pyrolysis is completely solved. This design ensures highly uniform material heating, carbonization, and reduction processes, thereby obtaining a composite material with a narrow size distribution of nano-iron particles and uniform dispersion on a carbon support, improving batch stability of the product.

[0023] By using a spray system to seal and coat the rotating reaction tube with a film, a continuous "pyrolysis-cooling-coating" operation was achieved under an inert atmosphere throughout the process. A dense protective layer was actively constructed before the material came into contact with air, blocking secondary oxidation pathways during cooling, material handling, and storage, thus ensuring the long-term stable preservation of highly active nano-zero-valent iron. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0025] Figure 2 This is a schematic diagram of the rear structure of the temperature-controlled furnace of the present invention.

[0026] Figure 3 This is a cross-sectional view of the present invention.

[0027] Figure 4 This is a schematic diagram of the drive system at the end of the temperature-controlled furnace of the present invention.

[0028] Figure 5 This is a longitudinal sectional view of the present invention.

[0029] In the diagram: 1. Temperature-controlled furnace; 11. Upper furnace body; 12. Lower furnace body; 13. Hinge; 14. Heating element; 15. Furnace chamber; 16. Thermocouple 1; 17. Inlet; 18. Top cover handle; 19. Electrical protection cover; 110. Furnace body support leg; 2. Rotary reaction system; 21. Rotary reaction tube; 22. Sealing end cap; 23. Spring sealing ring; 24. Connecting pipe; 25. Ball valve a; 26. Ball valve b; 27. Ball valve c; 28. Thermocouple 2 29. Pipe clamp; 210. Pipe rack; 3. Drive system; 31. Fixed bracket; 32. Bearing housing a; 33. Bearing housing b; 34. Bearing housing c; 35. Gear motor; 36. Drive shaft; 37. Drive sprocket; 38. Driven sprocket; 39. Transmission chain; 310. Active friction wheel; 311. Passive friction wheel; 312. Friction ring; 4. Spray system; 41. Spray pipe; 42. Nozzle; 43. Spray section; 44. Sealing plug. Detailed Implementation

[0030] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the invention. To better illustrate the following embodiments, some parts in the drawings may be omitted, enlarged, or reduced, and do not represent the actual product dimensions; it is understandable to those skilled in the art that some well-known structures and their descriptions may be omitted in the drawings.

[0031] Example 1

[0032] like Figures 1-5 As shown, this scheme discloses an apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis. The apparatus mainly includes a temperature-controlled furnace 1, a rotary reaction system 2, a drive system 3, a spray system 4, a control system, and a cooling and protection system.

[0033] The temperature-controlled furnace 1 includes an upper furnace body 11 and a lower furnace body 12 connected by a hinge 13, forming an openable furnace chamber 15 for easy insertion and removal of the rotating reaction tube 21. Heating elements 14 (such as heating tubes, heating wires, etc.) are evenly arranged on the inner wall of the furnace chamber 15. A thermocouple 16 electrically connected to the control system is located at the lower part of the furnace chamber 15 for monitoring and precise control of the furnace temperature. Inlets 17 are located at both ends of the furnace chamber 15 for installing the rotating reaction tube 21. The upper furnace body 11 has a top cover handle 18 and is externally covered by an electrical protection cover 19. The entire furnace body is supported by furnace body legs 110.

[0034] The rotary reaction system 2 is the core reaction vessel, mainly consisting of an integrated tube made of high-temperature resistant quartz, namely the rotary reaction tube 21, with a larger diameter material-bearing section in the middle. Both ends of the tube are sealed by end caps 22. The inner circumference of the end caps has an annular groove containing a spring sealing ring 23, which enables rotational connection and dynamic sealing with the ends of the rotary reaction tube 21. A thermocouple 28 is embedded in one end cap for monitoring the temperature within the material-bearing section. Both end caps 22 are equipped with connecting pipes 24. One connecting pipe 24 connects to ball valve a25, and also has a branch connecting pipe 24 connected to ball valve c27. The other connecting pipe 24 connects to ball valve b26, used for connecting to the spray system, discharging waste gas, and introducing gas, respectively. The connecting pipes on both sides are clamped by pipe clamps 29, which are supported by a pipe rack 210 to suspend the entire tube within the furnace 15.

[0035] The spray system 4 is used to spray the coating liquid and includes a spray pipe 41, nozzles 42, a spray section 43, and a sealing plug 44. The sealing plug 44 is fixed to the inlet of the ball valve a25 and is made of high-temperature resistant fluororubber. It has a through hole in its center that matches or is smaller than the outer diameter of the spray pipe 41 to ensure a seal when the spray pipe 41 is inserted into the central through hole of the sealing plug 44. The spray section 43 at the tail end of the spray pipe 41 is equipped with several nozzles 42. The length of the spray section 43 is set according to the length of the material receiving section so that, during insertion, the spray section can reach the material receiving section with the larger diameter in the middle section.

[0036] The drive system 3 is located below the rotating reaction tube 21 and includes two fixed supports 31, multiple bearing seats (bearing seat a32, bearing seat b33, bearing seat c34), a geared motor 35, a drive shaft 36, a sprocket mechanism (drive sprocket 37, driven sprocket 38, transmission chain 39), an active friction wheel 310, and a passive friction wheel 311. The two fixed supports 31 are located on opposite sides below the rotating reaction tube 21. Each fixed support 31 has a bearing seat a32 mounted at its bottom and bearing seats b33 and c34 mounted side-by-side at its top. The active friction wheel 310 is rotatably mounted on bearing seat b33, and the passive friction wheel 311 is rotatably mounted on bearing seat c34. The axle of the active friction wheel 310 is fixedly connected to the driven sprocket 38. A friction ring 312 is fixedly fitted onto the outer circumferential surface of each end of the rotating reaction tube 21. The friction rings 312 at both ends are supported and in close contact by the corresponding active friction wheel 310 and passive friction wheel 311, thereby driving the rotating reaction tube 21 to rotate through friction. A drive shaft 36 is installed between the bearing seats a32 of the two fixed supports 31. A drive sprocket 37 is fixed to each end of the drive shaft 36, one end of which is connected to the output shaft of the geared motor 35 via a coupling. Two transmission chains 39 connect the drive sprockets 37 on both sides to the driven sprockets 38 on the same side, thereby transmitting the power of the geared motor 35 to the active friction wheel 310. Thus, the system constitutes a stable support and power transmission structure, ensuring that the rotating reaction tube 21 can rotate smoothly and at a uniform speed at high temperatures.

[0037] The control system is used to control the operation of the entire device. Specifically, a microcontroller (such as the STC series, STM32 series, etc.), PLC, or industrial computer can be selected as the control core, integrating peripheral circuits such as temperature control modules, motor drive modules, solenoid valves, and sensors corresponding to other components in this solution. This system is also responsible for receiving signals from thermocouple 16 and thermocouple 28 for precise temperature control; controlling the inert gas source, each ball valve, and oxygen content monitoring to achieve the replacement and maintenance of the atmosphere inside the furnace; and controlling the start, stop, and speed of the geared motor 35. These are technologies well-known to those skilled in the art and will not be detailed here.

[0038] The cooling protection system includes a condenser, an exhaust gas treatment unit, and a cooling medium circulation device, which are used to recover pyrolysis volatiles, purify exhaust gas, and control the cooling process.

[0039] Example 2

[0040] Based on the above-mentioned apparatus, the present invention also discloses a method for preparing nano-iron-carbon composite materials by rotational pyrolysis, comprising the following steps:

[0041] S1, place the mixture of iron-containing precursor and biomass carbon source in the receiving section of the rotary reaction tube 21, install the rotary reaction tube 21 into the furnace 15 and connect the pipeline and gas source.

[0042] S2, nitrogen gas is introduced through ball valve b26, while internal air is discharged through ball valve c, so as to replace the air inside the rotating reaction tube 21 and ultimately make the oxygen content lower than 100ppm (corresponding detection equipment can be installed on the exhaust gas pipeline).

[0043] S3, start heating element 14 and drive system 3 to make rotating reaction tube 21 rotate, and carry out pyrolysis reduction according to program temperature rise, and keep the temperature at 750~800℃ for 1~2 hours.

[0044] S4, after the reaction is complete, cool under nitrogen protection;

[0045] S5. When the temperature drops below 60°C, insert the spray pipe 41 into the sealing plug 44, open the ball valve a25, and continue to insert it forward until the spray section 43 is above the mixture. The coating liquid is atomized and sprayed onto the rotating material surface by the metering pump connected to the spray pipe 41.

[0046] S6. After spraying is completed, remove the spray pipe 41 to the outside of the ball valve a25, close the ball valve a25 first, and then remove the sealing plug 44.

[0047] S7, heat to 100-105℃ and dry to cure the coating layer;

[0048] S8. After cooling to room temperature, the product is removed to obtain a nano-iron-carbon composite material.

[0049] The mass ratio of plant debris (i.e., the aforementioned biomass carbon source) to iron salt (i.e., the aforementioned iron-containing precursor) is 1:1 to 4:1; the coating solution is at least one of polyvinyl alcohol, polyvinylpyrrolidone, etc., with a concentration of 1% to 10% (by mass); the spraying amount is added at 0.05% to 1% (by solid content) of the total mass of the initial mixture in step S1; and the solvent is deionized water or ethanol.

[0050] To verify the beneficial effects of the coating treatment of the present invention, the following comparative examples were set up:

[0051] The comparative operation followed the same steps as S1 to S4, but after cooling to room temperature, the coating process was skipped (i.e., S5 to S7 were skipped), and the nitrogen gas was directly shut off before exiting the furnace. Analysis showed that the obtained product contained virtually no zero-valent iron (Fe). 0 The uncoated material mainly consists of oxidized phases such as Fe2O3 and Fe3O4, indicating that it is highly susceptible to environmental oxidation during furnace operation and storage, resulting in poor stability. In contrast, the material treated with the coating method of this invention effectively blocks the penetration of external oxygen molecules, maintaining the active component Fe.0 The reduced structure of the iron-carbon composite material. In actual wastewater treatment tests, the coating of the iron-carbon composite material achieved removal rates of 98.5% and 92.3% for methylene blue and phenol, respectively, significantly outperforming the uncoated material. After 90 days of storage under simulated humid and hot conditions, the Fe content in the coated sample decreased. 0 The content retention rate exceeded 90%, while the uncoated sample contained no Fe. 0 These comparative data fully demonstrate the crucial role of the coating process employed in this invention in enhancing the antioxidant stability of nano-iron-carbon composite materials and maintaining their high reactivity.

[0052] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solution of the present invention, and are not intended to limit the specific implementation of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the claims of the present invention should be included within the protection scope of the claims of the present invention.

Claims

1. An apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis, characterized in that, include: Temperature-controlled furnace (1), which has a furnace chamber (15) and a heating element (14) inside; The rotary reaction system (2) includes a rotary reaction tube (21), which is rotatably disposed in the furnace (15) for containing a mixture of iron precursor and biomass carbon source; and a sealing component disposed on the rotary reaction tube (21) for sealing the rotary reaction tube (21) during rotation, and having several fluid channel interfaces disposed thereon. The drive system (3), which is connected to the rotating reaction tube (21), is used to drive the rotating reaction tube (21) to rotate around its central axis; The spraying system (4) can spray coating liquid onto the surface of the mixture in the rotating reaction tube (21) through the fluid channel interface; The control system is electrically connected to the heating element (14) and the drive system (3) to control the pyrolysis temperature and the rotation speed of the rotating reaction tube (21); The cooling protection system, connected to the fluid channel interface via pipelines, is used to condense and recover the pyrolysis exhaust gas.

2. The apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis according to claim 1, characterized in that, The temperature-controlled furnace (1) has inlet ports (17) on both sides that communicate with the furnace chamber (15); the middle section of the rotating reaction tube (21) is a material-bearing section with a larger diameter. The material-bearing section is located inside the furnace chamber (15), and its two ends with smaller diameters pass through the inlet ports (17) on both sides and are located outside the temperature-controlled furnace (1).

3. The apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis according to claim 1, characterized in that, The enclosed component includes: Sealed end caps (22), the temperature control furnace (1) is fixedly provided with sealed end caps (22) on both sides respectively, and the two ends of the rotating reaction tube (21) are respectively sleeved with the sealed end caps (22) on both sides; The fluid channel interface includes: a connecting pipe (24), ball valve a (25), ball valve b (26), and ball valve c (27). Each sealing end cap (22) is provided with at least one connecting pipe (24); the rotary reaction tube (21) has a first end and a second end opposite to each other. A ball valve a (25) is provided on the connecting pipe (24) of the first end sealing end cap (22) for connecting to the spray system (4), and another ball valve c (27) is also connected to the other connecting pipe (24) of the first end sealing end cap (22) for venting; a ball valve b (26) is provided on the connecting pipe (24) of the second end sealing end cap (22) of the rotary reaction tube (21) for connecting to an inert gas source.

4. The apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis according to claim 3, characterized in that, The rotary reaction system (2) also includes a second thermocouple (28). The second thermocouple (28) is installed on the sealing end cap (22) at either end of the rotary reaction tube (21) and extends into it. The second thermocouple (28) is electrically connected to the control system.

5. The apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis according to claim 3, characterized in that, The inner circumferential surface of the sealing end cap (22) is provided with an annular groove, and a spring sealing ring (23) is provided in the annular groove. The spring sealing ring (23) is in contact with the outer circumferential surface of the end of the rotating reaction tube (21).

6. The apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis according to claim 3, characterized in that, The spray system (4) includes a spray pipe (41) and a sealing structure provided at the end of the ball valve a (25). The spray pipe (41) is provided with a spray section (43) and a plurality of nozzles (42) are provided on the spray section (43). The spray pipe (41) can pass through the sealing structure and the ball valve a (25) in sequence and extend into the interior of the rotating reaction tube (21).

7. The apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis according to claim 6, characterized in that, The sealing structure is a sealing plug (44), and the sealing plug (44) has a through hole in the middle so that the spray pipe (41) can pass through and form a sealing fit with the outer wall of the spray pipe (41).

8. A method for preparing nano-iron-carbon composite materials by rotational pyrolysis, characterized in that, The apparatus for preparing nano-iron-carbon composite materials by rotary pyrolysis according to any one of claims 1 to 7 includes the following steps: S1. Place the mixture of iron-containing precursor and biomass carbon source in the rotary reaction tube (21) of the rotary reaction system (2), operate the sealing component to seal the rotary reaction tube (21), and introduce inert gas through the fluid channel interface to replace the internal air; S2. Start the drive system (3) to rotate the rotating reaction tube (21), and at the same time control the heating element (14) to heat up under the control system to carry out the pyrolysis reduction reaction under an inert atmosphere; S3. After the reaction is completed, the rotating reaction tube (21) and the material inside it are cooled to a predetermined temperature under an inert atmosphere. S4. While maintaining an inert atmosphere and rotating the rotating reaction tube (21), activate the spray system (4) and spray the coating liquid onto the surface of the rotating mixture through the fluid channel interface; S5. Low-temperature drying is performed to solidify the coating layer formed on the material surface by the coating liquid, thereby obtaining a nano-iron-carbon composite material.

9. The method for preparing nano-iron-carbon composite materials by rotary pyrolysis according to claim 8, characterized in that, The specific conditions for the pyrolysis-reduction reaction described in step S2 are as follows: under the protection of an inert atmosphere, the temperature is raised to 750-800°C at a preset heating rate, and then kept at this temperature for 1-2 hours.

10. The method for preparing nano-iron-carbon composite materials by rotary pyrolysis according to claim 8 or 9, characterized in that, In step S4, the coating solution is at least one of a 1% to 10% aqueous solution of polyvinyl alcohol or a polyvinylpyrrolidone aqueous solution; the solute contained in the coating solution is added at 0.05% to 1% of the total mass of the initial mixture in step S1.

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