Chemical heating rotary kiln and control method thereof

Abstract

The application discloses a rotary kiln for chemical heating and a control method thereof, and relates to the technical field of kiln equipment, which comprises a feeding mechanism, a furnace core pipe assembly, a radiation combustion mechanism and a driving mechanism. The furnace core pipe assembly comprises an inner furnace core pipe and an outer furnace core pipe which are coaxially sleeved, and a heat radiation interlayer cavity is formed between the two pipes; one end of the heat radiation pipe is suspended and extended along the central axis of the inner furnace core pipe. The driving mechanism drives the inner and outer furnace core pipes to rotate at different rotating speeds and in opposite directions. The heat radiation interlayer cavity is provided with air inlets and outlets, and a spiral airflow channel is arranged in the cavity. The application realizes 360-degree omnibearing uniform heating and efficient three-dimensional mixing of the materials through bidirectional heating of the heat radiation pipe and the heat radiation interlayer cavity, cooperation of the multi-spiral synergistic effect generated by the differential counter-rotation of the inner and outer pipes, and accurate regulation and control of the material temperature gradient and the residence time through the radially-opposed temperature sensors, and decouples the coupling relationship between the mixing intensity and the residence time.

Description

Technical Field

[0001] This invention relates to the field of sintering equipment, specifically to a rotary kiln for chemical heating and its control method. Background Technology

[0002] Rotary kilns are core equipment in industrial production used for high-temperature heat treatment of materials. In high-tech fields such as new energy materials and specialty chemicals, the materials being processed often have characteristics such as high corrosivity, extremely high requirements for temperature uniformity, and the need to react under strict atmospheric protection.

[0003] Existing rotary kilns are typically single-tube structures, with external heating as the primary heating method. This traditional structure presents the following problems: First, when the kiln diameter is increased to enhance production capacity, the radial heat transfer path from the tube wall to the center becomes longer, leading to uneven heating of the material between the tube wall and the center, resulting in a significant radial temperature difference that severely affects product consistency and batch quality. Second, both the mixing and residence time of the material depend on the rotational speed and tilt angle of the core tube, creating a high degree of coupling. To improve mixing intensity and ensure temperature uniformity, the rotational speed must be increased, but this shortens the residence time of the material within the kiln, potentially causing incomplete reactions; conversely, extending the residence time sacrifices mixing efficiency, presenting a difficult-to-reconcile contradiction. Third, for materials containing corrosive elements such as fluorine, sulfur, and chlorine, direct contact between the combustion flame or flue gas and the material, or its penetration through the tube wall, can easily lead to safety accidents and equipment damage. Therefore, there is an urgent need to develop a new type of rotary kiln that can effectively address the radial temperature difference problem, decouple mixing and residence time, and achieve intrinsic isolation between the material and the heating atmosphere. Summary of the Invention

[0004] The purpose of this invention is to provide a rotary kiln for chemical heating and its control method, which aims to overcome the above-mentioned problems existing in the prior art.

[0005] To achieve the objective, the present invention provides the following technical solution: A rotary kiln for chemical heating includes a feeding mechanism, a core tube assembly, a drive mechanism, and a radiation combustion mechanism. The core tube assembly includes an outer core tube and an inner core tube, with the inner core tube coaxially sleeved inside the outer core tube, forming a thermal radiation interlayer cavity between them. The feeding mechanism is located at one end of the inner core tube, and the discharging mechanism is located at the other end of the inner core tube. The radiant combustion mechanism includes a radiant tube and a radiant interlayer cavity. One end of the radiant tube extends suspended inside the inner furnace core tube along the central axis of the inner furnace core tube. The two ends of the radiant interlayer cavity are respectively provided with an air inlet and an air outlet. The driving mechanism includes a first driving unit and a second driving unit. The first driving unit is used to drive the outer furnace core tube to rotate along a first direction at a first speed, and the second driving unit is used to drive the inner furnace core tube to rotate along a second direction at a second speed, wherein the first direction is opposite to the second direction.

[0006] Furthermore, the inner wall surface of the inner furnace core tube is provided with a first spiral structure, and the inner wall surface of the outer furnace core tube is provided with a second spiral structure with the opposite spiral direction to the first spiral structure.

[0007] Furthermore, the outer wall of the inner furnace core tube is provided with a third spiral structure in the thermal radiation interlayer cavity, and the third spiral structure is staggered from the second spiral structure and has the same direction of rotation, forming a spiral airflow channel connecting the air inlet and the air outlet.

[0008] Furthermore, a first temperature sensor is provided on the inner wall surface of the inner furnace core tube in the radial direction, and a second temperature sensor is provided on the outer wall surface of the heat radiation tube.

[0009] Furthermore, the outer furnace core tube is covered with an insulation layer, the outer furnace core tube is made of heat-resistant metal material, and the inner furnace core tube is made of phosphate refractory castable or recrystallized silicon carbide material.

[0010] A control method for a rotary kiln used for chemical heating, applicable to any one of the above, includes the following steps: Step S1: According to the process requirements of the material to be calcined, set the first rotation speed N1 of the inner furnace core tube and the second rotation speed N2 of the outer furnace core tube and the rotation direction, and the first rotation speed N1 ≠ the second rotation speed N2, and make the rotation direction corresponding to the first rotation speed N1 opposite to the rotation direction corresponding to the second rotation speed N2. Step S2: Start the first drive unit and the second drive unit to make the outer furnace core tube and the inner furnace core tube operate stably according to the parameters set in step S1. Step S3: Drive the feeding mechanism to continuously feed materials into the rotating inner furnace core tube. The materials are carried up, tumbled and conveyed forward under the action of friction between the inner wall of the inner furnace core tube and the materials themselves. Step S4: The heat radiation tube heats the central axis of the inner furnace core tube, while the heat radiation jacket cavity heats the outer wall of the inner furnace core tube. The heat is uniformly heated to the material inside the tube in the form of heat radiation and heat conduction in 360 degrees.

[0011] Furthermore, it also includes the following steps: Step S5: The temperature of the material inside the inner furnace core tube is monitored in real time by the first temperature sensor and the second temperature sensor, and the difference between the first rotation speed N1 and the second rotation speed N2 is dynamically adjusted according to the temperature measurement data to change the heating temperature, mixing intensity and residence time of the material until calcination is completed.

[0012] Furthermore, step S5 specifically includes: Step S51: Real-time acquisition of the first temperature value T1 measured by the first temperature sensor and the second temperature value T2 measured by the second temperature sensor, and calculation of the current radial temperature difference ΔT = |second temperature value T2 - first temperature value T1|; Step S52: Based on the target radial temperature difference allowable range preset in step S1, determine whether the current radial temperature difference ΔT exceeds the allowable range; Step S53: If the current radial temperature difference ΔT exceeds the upper limit of the target radial temperature difference allowable range, increase the difference between the first rotation speed N1 and the second rotation speed N2 to increase the mixing frequency of the material in the radial direction, strengthen the contact heat exchange between the material and the inner wall of the inner furnace core tube, and reduce the radial temperature difference. Step S54: If the current radial temperature difference ΔT is within the allowable range of the target radial temperature difference, maintain the current rotational speed difference or make minor adjustments according to the residence time requirement; Step S55: When it is necessary to extend the residence time of the material to complete the full reaction, reduce the absolute values ​​of the first rotation speed N1 and the second rotation speed N2, while keeping the difference between the two unchanged or adjusting according to step S53.

[0013] Furthermore, it also includes the following steps: Step S6: In the cooling section, turn off or reduce the power of the radiation combustion mechanism, while increasing the difference between the first rotation speed N1 and the second rotation speed N2, and use the airflow in the thermal radiation jacket cavity to cool the material at a controllable rate.

[0014] Compared with the prior art, the present invention has the following advantages: Firstly, this invention uses a bidirectional heating mode, combining the central axis heat radiation tube and the outer heat radiation interlayer cavity, to ensure that the material layer is heated synchronously from the center to the edge, greatly reducing the radial temperature difference in large-diameter kilns and achieving radial low temperature difference calcination.

[0015] Secondly, this invention uses an outer furnace core tube and an inner furnace core tube to form a dual-tube differential counter-rotating structure, which separates the key parameter affecting material mixing (rotational speed difference) from the key parameter affecting residence time (basic rotational speed), that is, decouples mixing intensity and residence time, opening up a new dimension for process control and enabling the equipment to flexibly match various complex reaction kinetic conditions.

[0016] Thirdly, the present invention uses a central axis heat radiation tube and an outer heat radiation interlayer cavity to radiate and conduct heat, ensuring zero contact with the potentially corrosive material and process atmosphere inside the inner tube, thereby fundamentally avoiding the pollution and safety risks of combustion products to the materials.

[0017] Fourthly, in this invention, the long-range spiral airflow channel constructed by multiple spiral structures in the thermal radiation interlayer cavity greatly extends the heat exchange time and area between the high-temperature hot gas and the inner furnace core tube, firmly locking the heat in the working area and maximizing thermal efficiency.

[0018] Fifth, the present invention utilizes a radially opposed first temperature sensor and a second temperature sensor to directly sense the radial thermal gradient and adjust the rotation speed difference in real time and quantitatively, thereby leading to intelligent and precise control of the temperature field uniformity of the inner furnace core tube. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of a rotary kiln for chemical heating in this invention.

[0020] Figure 2 for Figure 1 A magnified view of a portion of point A in the diagram.

[0021] Figure 3 This is a schematic diagram of the structure of the thermal radiation tube in this invention.

[0022] Wherein: 1-Inner furnace core tube; 11-First spiral structure; 12-Third spiral structure; 2-Outer furnace core tube; 21-Second spiral structure; 22-Insulation layer; 201-Sleeve component; 2011-Bearing; 2012-Sealing ring; 31-Heat radiation interlayer cavity; 301-Air inlet; 302-Air outlet; 32-Heat radiation tube; 321-Gas inlet; 322-Burnhead; 323-Exhaust gas outlet; 4-Feeding mechanism; 5-Discharge mechanism; 61-First drive unit; 62-Second drive unit; 71-First temperature sensor; 72-Second temperature sensor. Detailed Implementation

[0023] Specific embodiments of the present invention will now be described with reference to the accompanying drawings. Many details are described below to provide a comprehensive understanding of the invention; however, those skilled in the art will be able to implement the invention without these details.

[0024] like Figures 1 to 3 As shown, a rotary kiln for chemical heating mainly includes a feeding mechanism 4, a discharging mechanism 5, a furnace core tube assembly, a radiation combustion mechanism, a first drive unit 61, and a second drive unit 62.

[0025] like Figures 1 to 3 As shown, the furnace core tube assembly includes an inner furnace core tube 1 and an outer furnace core tube 2. The inner furnace core tube 1 is coaxially fitted inside the outer furnace core tube 2 and is rotatable relative to it. The annular space between the inner furnace core tube 1 and the outer furnace core tube 2 is the thermal radiation interlayer cavity 31. The two ends of the thermal radiation interlayer cavity 31 are respectively provided with an air inlet 301 and an air outlet 302.

[0026] like Figures 1 to 3As shown, in one specific embodiment, the inner furnace core tube 1 is integrally sintered from recrystallized silicon carbide material with excellent corrosion resistance and high-temperature strength, and its inner diameter is 600 mm and its length is 8 meters. The feeding mechanism 4 is located at one end of the inner furnace core tube 1, and the discharging mechanism 5 is located at the other end of the inner furnace core tube 1.

[0027] The feeding mechanism 4 is an existing screw feeder, and its specific structure will not be described in detail here. The outer furnace core tube 2 is made of heat-resistant stainless steel 310S rolled and welded, with an inner diameter of 800mm. The outer layer is tightly wrapped with a heat insulation layer 22, which is a ceramic fiber heat insulation layer.

[0028] A sleeve 201 is rotatably fitted between both ends of the inner furnace core tube 1 and the outer furnace core tube 2. The sleeve 201 is a fixed component and cannot rotate relative to the ground. Bearings 2011 and sealing rings 2012 are provided between the sleeve 201 and both the inner furnace core tube 1 and the outer furnace core tube 2 to achieve dynamic sealing. The two sleeves 201 are respectively provided with an air inlet 301 and an air outlet 302.

[0029] like Figures 1 to 3 As shown, a heat radiation tube 32 is installed inside the inner furnace core tube 1 along its central axis. This heat radiation tube is a recrystallized silicon carbide tube with an outer diameter of 150 mm. One end of the tube is closed, and it extends suspended inside the inner furnace core tube 1 along its central axis without contacting the rotating inner wall of the inner furnace core tube 1. The other end of the heat radiation tube 32 passes through the end cap of the inner furnace core tube 1 and connects to an existing fuel supply device (not shown in the figure) installed externally. More specifically, the heat radiation tube 32 is provided with a gas inlet 321 and an exhaust gas inlet 323, and has a burner 322 inside. The high-temperature flue gas generated by fuel combustion flows throughout the heat radiation tube 32 and is then led out from the exhaust gas inlet 323. While the radiant tube 32 is working, high-temperature air is introduced into the radiant jacket cavity 31 through the air inlet 301, so that it flows closely against the outer wall of the inner furnace core tube 1. The radiant tube 32 and the radiant jacket cavity 31 form a radiant combustion mechanism, establishing a bidirectional heating system between the inner center and the outer jacket.

[0030] like Figures 1 to 3 As shown, the above-mentioned driving mechanism includes a first driving unit 61 and a second driving unit 62. The first driving unit 61 is used to drive the outer furnace core tube 2 to rotate along the first direction at a first speed, and the second driving unit 62 is used to drive the inner furnace core tube 1 to rotate along the second direction at a second speed. The first direction is opposite to the second direction, and the first speed is different from the second speed.

[0031] In one specific embodiment, both the first drive unit 61 and the second drive unit 62 employ precision servo motors in conjunction with hardened gear reducers and open gear pairs for transmission. Their speeds and directions are independently and steplessly adjusted via a PLC central controller. The output gear of the first drive unit 61 meshes with the gear ring of the outer furnace core tube 2, and the output gear of the second drive unit 62 meshes with the gear ring of the inner furnace core tube 1.

[0032] like Figures 1 to 3 As shown, on the inner wall of the inner furnace core tube 1, a right-handed blade with a height of 15mm-25mm and a pitch of 400mm-500mm is integrally sintered from the feeding end to the discharging end, constituting the first spiral structure 11 of the present invention. On the inner wall of the outer furnace core tube 2, a left-handed spiral blade with a height of 15-20mm and a pitch of 350mm-400mm is welded, constituting the second spiral structure 21 of the present invention.

[0033] like Figures 1 to 3 As shown, on the outer wall of the inner furnace core tube 1, within the heat radiation interlayer cavity 31, a left-handed spiral blade with a height of 10mm-15mm and a pitch of 350mm-400mm is welded, forming the third spiral structure 12 of the present invention. This third spiral structure 12 has the same spiral direction as the second spiral structure 21, but is axially offset by half a pitch.

[0034] When the inner furnace core tube 1 is driven to rotate clockwise by the second drive unit 62 (viewed from the feed end), and the outer furnace core tube 2 is driven to rotate counterclockwise by the first drive unit 61, the second spiral structure 21 and the third spiral structure 12 form a "twin screw"-like pushing effect, which forces the hot air entering the thermal radiation jacket cavity 31 to be transported to the air outlet 302 along the spiral channel, significantly extending the heat exchange path and time of the high-temperature gas in the cavity, and due to its spiral propulsion effect, the heat exchange coefficient between the airflow and the tube wall is greatly improved.

[0035] like Figures 1 to 3 As shown, in the high-temperature zone located in the middle of the kiln's length, a first temperature sensor 71 is provided on the inner wall of the inner core tube 1 in the radial direction, and a second temperature sensor 72 is provided on the outer wall of the thermal radiation tube 32. Specifically, an armored K-type thermocouple is embedded in the inner wall of the inner core tube 1 as the first temperature sensor 71, with its measuring end flush with the tube wall and in contact with the material. A K-type thermocouple of the same specification is welded to the outer wall of the corresponding thermal radiation tube 32 as the second temperature sensor 72, with its measuring end exposed to the flue gas inside the tube. The two sensors are strictly aligned in the radial direction. The sensor signals are transmitted to the PLC central controller via a wireless slip ring.

[0036] like Figures 1 to 3 As shown, based on the above control method for rotary kilns, the specific steps are as follows: Step S1: According to the process requirements of the material to be calcined (such as the precursor of lithium-ion battery cathode material), set the first rotation speed N1 and rotation direction of the inner furnace core tube 1, the second rotation speed N2 and rotation direction of the outer furnace core tube 2, and the target radial temperature difference allowable range, and the first rotation speed N1 ≠ the second rotation speed N2, and make the rotation direction corresponding to the first rotation speed N1 opposite to the rotation direction corresponding to the second rotation speed N2.

[0037] According to the process requirements of the lithium-ion battery cathode material precursor to be calcined, the temperature curve (such as heating from room temperature to 900℃, holding at 900℃ for 3 hours, and then naturally cooling down) and speed parameters (such as setting the initial value of the first speed N1 of the inner furnace core tube 1 to 4 revolutions per minute (clockwise, from the feeding end), the initial value of the second speed N2 of the outer furnace core tube 2 to 3 revolutions per minute (counterclockwise), and the speed difference ΔN = |N1 - N2| = 1 revolution per minute) can be preset in the central controller through the human-machine interface.

[0038] Step S2: Start the first drive unit 61 and the second drive unit 62 to make the outer furnace core tube 2 and the inner furnace core tube 1 operate stably according to the direction and speed set in step S1. The first spiral structure 11 on the inner wall of the inner furnace core tube 1 begins to generate a forward conveying force on the material.

[0039] Step S3: Start the feeding mechanism 4 to uniformly feed powder material into the continuously rotating inner furnace core tube 1. Under the combined action of the friction force of the tube wall and the first spiral structure 11, the material is carried up, tumbled, and collapsed to form a dynamic material bed that propels forward.

[0040] Step S4: The heat radiation tube 32 heats the central axis of the inner furnace core tube 1, while the heat radiation jacket cavity 31 heats the outer wall of the inner furnace core tube 1. The heat is uniformly heated to the material inside the tube in the form of heat radiation and heat conduction in 360 degrees.

[0041] Specifically, the radiant heating tube 32 is activated, and the ratio of natural gas to preheated combustion air is adjusted to rapidly raise the outer wall temperature of the radiant heating tube 32 to 1050°C. Simultaneously, clean air at 800°C is introduced into the radiant heating jacket cavity 31 from the air inlet 301 at a certain flow rate. At this time, the central radiant heating tube 32 directly irradiates the central area of ​​the material bed with intense radiant heat, while the high-temperature gas in the radiant heating jacket cavity 31 heats the inner furnace core tube 1 through convection and radiation, with heat being conducted from the outside to the inside.

[0042] Step S5: The temperature of the material inside the inner furnace core tube 1 is monitored in real time by the first temperature sensor 71 and the second temperature sensor 72. The difference between the first rotation speed N1 and the second rotation speed N2 is dynamically adjusted according to the temperature measurement data to change the heating temperature, mixing intensity and residence time of the material until calcination is completed.

[0043] Step S5 specifically includes the following sub-steps: Step S51: The PLC central controller acquires the first temperature value T1 of the first temperature sensor 71 and the second temperature value T2 of the second temperature sensor 72 in real time.

[0044] For example, during the heating phase, the system detected T2=1020℃, T1=950℃, and the current radial temperature difference ΔT=70℃.

[0045] In step S52, the PLC central controller determines the target radial temperature difference allowable range preset in step S1. For example, the upper limit of the target radial temperature difference allowable range is 50°C.

[0046] Step S53: If the current radial temperature difference ΔT exceeds the upper limit of the target radial temperature difference allowable range, increase the difference between the first rotation speed N1 and the second rotation speed N2 to increase the mixing frequency of the material in the radial direction, enhance the contact heat exchange between the material and the inner wall of the inner furnace core tube 1, and reduce the radial temperature difference.

[0047] For example, the system automatically adjusts the rotational speed difference ΔN from 1 rpm to 3 rpm. Specifically, it instantly increases the first rotational speed N1 of the inner core tube 1 to 5.5 rpm, while keeping the second rotational speed N2 of the outer core tube 2 unchanged. This increase in speed immediately intensifies the rapid alternating tumbling of material from the center to the tube wall and from the tube wall to the center. A large amount of low-temperature material is displaced to the high-temperature tube wall region to absorb heat, while the high-temperature material returns to the center region, causing the first temperature value T1 to rise rapidly. After approximately 15 seconds, the first temperature value T1 reaches 984℃, the second temperature value T2 is 1015℃, and the current radial temperature difference ΔT shrinks to 31℃, returning to the target allowable radial temperature difference range. Step S54 is executed, and the system maintains the new rotational speed parameters.

[0048] Step S54: If the current radial temperature difference ΔT is within the allowable range of the target radial temperature difference, maintain the current rotational speed difference or make a fine adjustment according to the residence time requirement.

[0049] Step S55: When it is necessary to extend the residence time of the material to complete the full reaction, reduce the absolute values ​​of the first rotation speed N1 and the second rotation speed N2, while keeping the difference between the two unchanged or adjusting according to step S53.

[0050] Step S6: In the cooling section, turn off or reduce the power of the radiation combustion mechanism, while increasing the difference between the first rotation speed N1 and the second rotation speed N2, and use the airflow in the thermal radiation interlayer cavity 31 to cool the material at a controllable rate.

[0051] Specifically, after the heat preservation period ends, the cooling phase begins. The power of the heat radiation tube 32 is reduced to a minimum, and the hot air supply to the air inlet 301 of the heat radiation jacket cavity 31 is shut off. Simultaneously, the system automatically switches to circulate dried room temperature air into the heat radiation jacket cavity 31, and instantly increases the rotational speed difference ΔN to 5 revolutions per minute. The violent tumbling continuously throws the material against the already cooling tube wall, while the cold air in the heat radiation jacket cavity 31 carries away the heat from the tube wall, achieving rapid and controllable forced cooling of the material.

[0052] By combining the rotary kiln and control method described above, the calcined material was sampled and tested. The results showed that key indicators such as the crystallinity and uniformity of particle size distribution were significantly better than those of traditional single-tube rotary kiln products. Furthermore, the physicochemical properties of the products sampled from different locations across the entire cross section were highly consistent, which fully verified the superior performance of this invention in eliminating radial temperature differences and achieving precise process control.

[0053] The above are merely specific embodiments of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention using this concept shall be considered as infringing upon the protection scope of the present invention.

Claims

1. A rotary kiln for chemical heating, comprising a feeding mechanism (4), a furnace core tube assembly, a drive mechanism, and a radiant combustion mechanism, characterized in that, The furnace core tube assembly includes an outer furnace core tube (2) and an inner furnace core tube (1). The inner furnace core tube (1) is coaxially sleeved inside the outer furnace core tube (2), and a heat radiation interlayer cavity (31) is formed between the two. The feeding mechanism (4) is located at one end of the inner furnace core tube (1), and the discharging mechanism (5) is located at the other end of the inner furnace core tube (1). The radiant combustion mechanism includes a radiant tube (32) and a radiant interlayer cavity (31). One end of the radiant tube (32) extends suspended inside the inner furnace core tube (1) along the central axis of the inner furnace core tube (1). The two ends of the radiant interlayer cavity (31) are respectively provided with an air inlet (301) and an air outlet (302). The driving mechanism includes a first driving unit (61) and a second driving unit (62). The first driving unit (61) is used to drive the outer furnace core tube (2) to rotate along a first direction at a first speed, and the second driving unit (62) is used to drive the inner furnace core tube (1) to rotate along a second direction at a second speed, and the first direction is opposite to the second direction. The inner wall of the inner furnace core tube (1) is provided with a first spiral structure (11), and the inner wall of the outer furnace core tube (2) is provided with a second spiral structure (21) with the opposite spiral direction to the first spiral structure (11); the outer wall of the inner furnace core tube (1) is provided with a third spiral structure (12) in the thermal radiation interlayer cavity (31), and the third spiral structure (12) and the second spiral structure (21) are staggered and have the same spiral direction, forming a spiral airflow channel connecting the air inlet (301) and the air outlet (302); In the radial direction of the inner furnace core tube (1), the inner wall surface of the inner furnace core tube (1) is provided with a first temperature sensor (71), and the outer wall surface of the heat radiation tube (32) is provided with a second temperature sensor (72); the first temperature sensor (71) and the second temperature sensor (72) are used to monitor the temperature of the material inside the inner furnace core tube (1) in real time, and dynamically adjust the difference between the first rotation speed and the second rotation speed according to the temperature measurement data, so as to change the heating temperature, mixing intensity and residence time of the material.

2. The rotary kiln for chemical heating according to claim 1, characterized in that, The outer furnace core tube (2) is covered with a heat insulation layer (22). The outer furnace core tube (2) is made of heat-resistant metal material, and the inner furnace core tube (1) is made of phosphate refractory castable or recrystallized silicon carbide material.

3. A control method for a rotary kiln used for chemical heating as described in any one of claims 1 or 2, characterized in that, Includes the following steps: Step S1: According to the process requirements of the material to be calcined, set the first rotation speed N1 of the inner furnace core tube (1) and the second rotation speed N2 and rotation direction of the outer furnace core tube (2), and the first rotation speed N1 ≠ the second rotation speed N2, and make the rotation direction corresponding to the first rotation speed N1 opposite to the rotation direction corresponding to the second rotation speed N2; Step S2: Start the first drive unit (61) and the second drive unit (62) to make the outer furnace core tube (2) and the inner furnace core tube (1) operate stably according to the parameters set in step S1; Step S3: Drive the feeding mechanism (4) to continuously feed materials into the rotating inner furnace core tube (1). The materials are carried up, rolled and conveyed forward under the action of friction between the inner wall of the inner furnace core tube (1) and the materials themselves. Step S4: The central axis of the inner furnace core tube (1) is heated by the thermal radiation tube (32), and the outer wall of the inner furnace core tube (1) is heated by the thermal radiation jacket cavity (31). The heat is uniformly heated to the material inside the tube in the form of thermal radiation and thermal conduction in 360 degrees.

4. The control method according to claim 3, characterized in that, It also includes the following steps: Step S5: The temperature of the material inside the inner furnace core tube (1) is monitored in real time by the first temperature sensor (71) and the second temperature sensor (72), and the difference between the first rotation speed N1 and the second rotation speed N2 is dynamically adjusted according to the temperature measurement data to change the heating temperature, mixing intensity and residence time of the material until calcination is completed.

5. The control method according to claim 4, characterized in that, Step S5 specifically includes: Step S51: Real-time acquisition of the first temperature value T1 measured by the first temperature sensor (71) and the second temperature value T2 measured by the second temperature sensor (72), and calculation of the current radial temperature difference ΔT = |second temperature value T2 - first temperature value T1|; Step S52: Based on the target radial temperature difference allowable range preset in step S1, determine whether the current radial temperature difference ΔT exceeds the allowable range; Step S53: If the current radial temperature difference ΔT exceeds the upper limit of the target radial temperature difference allowable range, increase the difference between the first rotation speed N1 and the second rotation speed N2, increase the mixing frequency of the material in the radial direction, strengthen the contact heat exchange between the material and the inner wall of the inner furnace core tube (1), and reduce the radial temperature difference. Step S54: If the current radial temperature difference ΔT is within the allowable range of the target radial temperature difference, maintain the current rotational speed difference or make minor adjustments according to the residence time requirement; Step S55: When it is necessary to extend the residence time of the material to complete the full reaction, reduce the absolute values ​​of the first rotation speed N1 and the second rotation speed N2, while keeping the difference between the two unchanged or adjusting according to step S53.

6. The control method according to claim 3, characterized in that, It also includes the following steps: Step S6: In the cooling section, turn off or reduce the power of the radiation combustion mechanism, while increasing the difference between the first rotation speed N1 and the second rotation speed N2, and use the airflow in the thermal radiation interlayer cavity (31) to cool the material at a controllable rate.

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