Rotary kiln

Abstract

A rotary kiln comprises: a cylinder; the pipe frame plate is arranged in the cylinder body and is provided with a through hole; the supporting pipe penetrates through the through hole and is connected to the pipe frame plate; the protection pipe is arranged in the supporting pipe and connected to the supporting pipe, and the length of the protection pipe is smaller than that of the supporting pipe; the heat exchange tube is arranged in the protection tube in a penetrating manner; the annular space between the supporting pipe and the heat exchange pipe is filled with the sealing filler, and the sealing filler is located on one side of the protection pipe. The rotary kiln is high in energy utilization rate, low in production energy consumption and high in production efficiency.

Description

Technical Field

[0001] The present invention relates to the field of gypsum board production technology, and in particular to a rotary kiln. Background Art

[0002] When producing building plaster, a rotary kiln is usually used to calcine the desulfurized gypsum to remove most of the crystal water in the desulfurized gypsum, thereby converting the desulfurized gypsum into building plaster. Building plaster can be used as a raw material for wall gypsum products, such as gypsum board.

[0003] The rotary kiln includes a cylinder, a plurality of heat exchange tubes and a tube rack plate. The heat exchange tubes and the tube rack plate are both arranged in the cylinder. The tube rack plate is connected to the cylinder, and a through hole is arranged on the tube rack plate, through which the heat exchange tubes pass and are supported by the tube rack plate. The cylinder, the tube rack plate and the heat exchange tubes can rotate synchronously around the axis of the cylinder. The rotary kiln uses steam as a heat source, inputs steam from one end of the heat exchange tube, and outputs from the other end of the heat exchange tube after passing through the heat exchange tube. The steam transfers heat to the heat exchange tube so that the heat exchange tube can maintain a high temperature state. Desulfurized gypsum is input into the cylinder from one end of the cylinder. As the cylinder rotates, the desulfurized gypsum can move to the other end of the cylinder. The desulfurized gypsum contacts the heat exchange tube in the cylinder to achieve the purpose of being calcined, thereby being converted into building gypsum with low crystalline water content and output from the other end of the cylinder.

[0004] A plurality of heat exchange tubes are arranged in a multi-layer structure in sequence along the radial direction of the cylinder. In addition to supporting the heat exchange tubes, the tube rack plate also blocks the desulfurized gypsum from moving along the axial direction of the cylinder to a certain extent so that the height of the desulfurized gypsum stacking reaches a level that can contact the innermost heat exchange tube, so that the desulfurized gypsum can contact the innermost heat exchange tube to fully utilize the heat emitted by the innermost heat exchange tube. However, in order to facilitate the assembly of the heat exchange tubes on the tube rack plate and reserve a large enough space for the heat exchange tubes to expand and contract, it is necessary to set a large assembly gap around the heat exchange tubes, which will allow the desulfurized gypsum to pass through the tube rack plate from the assembly gap, resulting in the height of the desulfurized gypsum stacking not actually reaching the height that can contact the innermost heat exchange tube, thereby resulting in a decrease in energy utilization, an increase in production energy consumption, and a decrease in production efficiency. Summary of the invention

[0005] In order to solve the above technical problems, the present application provides a rotary kiln, which includes: Cylinder; A tube rack plate is arranged in the cylinder and is provided with a through hole; A support pipe, passing through the through hole and connected to the pipe rack plate; A protection tube, disposed in the support tube and connected to the support tube, wherein the length of the protection tube is shorter than the length of the support tube; a heat exchange tube, passing through the protection tube; and The sealing filler is filled in the annular space between the support tube and the heat exchange tube and is located on one side of the protection tube.

[0006] In an illustrative embodiment, a feed port is provided at one end of the cylinder, and a discharge port is provided at the other end of the cylinder; The sealing filler is arranged on a side of the protection tube close to the feed port.

[0007] In an illustrative embodiment, the rotary kiln further comprises a sealant layer; The sealant layer is filled in the annular space between the support tube and the heat exchange tube, and is located on a side of the sealing filler facing away from the protection tube.

[0008] In an illustrative embodiment, the sealant layer is formed by condensing a high-temperature sealant.

[0009] In an illustrative embodiment, the sealing filler includes asbestos tape and asbestos packing; The asbestos tape fills the area between the sealant layer and the protection tube and close to the protection tube, and the asbestos packing fills the area between the asbestos tape and the sealant layer.

[0010] In an exemplary embodiment, the heat exchange tube is provided with multiple layers, each layer of the heat exchange tube is composed of multiple heat exchange tubes arranged in sequence along the circumference of the cylinder, and the multiple layers of heat exchange tubes are arranged in sequence along the radial direction of the cylinder; The tube rack plate is provided with through holes having the same number as the heat exchange tubes, each of the through holes is penetrated by the support tube, and each of the support tubes is provided with the sealing filler and the protection tube; The plurality of heat exchange tubes are respectively passed through a plurality of protection tubes.

[0011] In an illustrative embodiment, a plurality of the tube rack plates are provided, and the plurality of the tube rack plates are sequentially arranged along the axial direction of the cylinder and spaced apart from each other.

[0012] In an illustrative embodiment, the difference between the inner diameter of the support tube and the outer diameter of the heat exchange tube is greater than or equal to 2 cm.

[0013] In an illustrative embodiment, the tube rack plate is a circular flat plate.

[0014] In an illustrative embodiment, the length of the protection tube is 250 mm.

[0015] In the technical solution of the present application, the cylinder rigidly supports the heat exchange tube through the tube rack plate, the support tube and the protection tube, which can firmly fix the heat exchange tube relative to the cylinder, reduce the shaking of the heat exchange tube, and prevent the sealing filler from being damaged by excessive pressure. At the same time, since the heat exchange tube is supported by the protection tube, the contact area between the protection tube and the heat exchange tube is large, which can prevent the heat exchange tube from being worn. The sealing filler is filled in the annular space between the support tube and the heat exchange tube, which can block the gap between the support tube and the heat exchange tube, and prevent the desulfurized gypsum from passing through the tube rack plate from the gap between the support tube and the heat exchange tube. The height of the desulfurized gypsum stacked in the cylinder can reach the extent of contacting the innermost heat exchange tube, thereby improving energy utilization, reducing production energy consumption, and improving production efficiency.

[0016] Other features and advantages of the present application will be described in the following description, and partly become apparent from the description, or be understood by implementing the present application. Other advantages of the present application can be realized and obtained by the schemes described in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings are used to provide an understanding of the technical solution of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of the present application and do not constitute a limitation on the technical solution of the present application.

[0018] Figure 1 A schematic diagram of a main view of a rotary kiln in an embodiment of the present application; Figure 2 A cross-sectional schematic diagram of a rotary kiln in an embodiment of the present application; Figure 3 It is a partial cross-sectional schematic diagram of a rotary kiln in an embodiment of the present application. DETAILED DESCRIPTION

[0019] The present application describes multiple embodiments, but the description is exemplary rather than restrictive, and it is obvious to those skilled in the art that there may be more embodiments and implementations within the scope of the embodiments described in the present application. Although many possible feature combinations are shown in the drawings and discussed in the specific embodiments, many other combinations of the disclosed features are also possible. Unless specifically limited, any feature or element of any embodiment may be used in combination with any other feature or element in any other embodiment, or may replace any other feature or element in any other embodiment.

[0020] like Figure 1 , 2 As shown, Figure 1 , 2The structure of a rotary kiln 100 in an embodiment of the present application is shown. The rotary kiln 100 includes a cylinder 1, a supporting device (not shown in the figure), a driving device (not shown in the figure), a tube rack plate 3, a supporting tube 4, a protective tube 5, a heat exchange tube 2 and a sealing filler 6.

[0021] The cylinder 1 is cylindrical in structure. The cylinder 1 is usually made of high-quality heat-resistant steel or other high-temperature resistant and wear-resistant alloy materials, such as manganese steel, and can withstand high temperature environment and friction and impact of materials. The cylinder 1 is the core component of the rotary kiln 100, providing space for the calcination of gypsum. A feed port is provided at one end of the cylinder 1, and a discharge port is provided at the other end of the cylinder 1. There is a certain inclination inside the cylinder 1, and when the rotary kiln 100 rotates, the material in the cylinder 1 can move slowly from the feed port to the discharge port, ensuring that the material has enough residence time in the cylinder 1 for calcination.

[0022] The supporting device includes a plurality of supporting wheels and rollers. The roller is in a circular shape and is sleeved on the outside of the cylinder 1. The supporting wheels are evenly distributed below the cylinder 1 and are against the outer circumference of the rollers. The weight of the cylinder 1 is transferred to the supporting wheels through the rollers. The supporting wheels jointly support the weight of the cylinder 1 and ensure that the cylinder 1 can rotate around the axis of the cylinder 1. The supporting wheels are usually made of high-strength alloy steel and have good load-bearing capacity and wear resistance.

[0023] The driving device includes a motor and a reducer. The reducer is connected to the motor and the cylinder 1. The motor transmits torque to the reducer, the reducer decelerates and increases the torque transmitted by the motor, and transmits the torque to the cylinder 1 to drive the cylinder 1 to rotate.

[0024] like Figure 2 , 3 As shown, the tube rack plate 3 is made of metal. The tube rack plate 3 is constructed as a flat plate, and the tube rack plate 3 can be a flat plate constructed as a circular ring. The tube rack plate 3 is arranged in the cylinder 1, and the tube rack plate 3 is perpendicular to the cylinder 1. The outer edge of the tube rack plate 3 is connected to the inner wall of the cylinder 1. The outer edge of the tube rack plate 3 and the inner wall of the cylinder 1 can be welded. The tube rack plate 3 is provided with a through hole 31, and the through hole 31 vertically penetrates the tube rack plate 3.

[0025] The support tube 4 is made of metal. The support tube 4 is a round tube, and the support tube 4 is passed through the through hole 31 on the tube rack plate 3. The outer diameter of the support tube 4 is the same as the inner diameter of the through hole 31 on the tube rack plate 3, and the outer diameter of the support tube 4 may also be slightly larger than the inner diameter of the through hole 31 of the tube rack plate 3. The support tube 4 is fixedly connected to the tube rack plate 3. The support tube 4 and the tube rack plate 3 may be welded. The axial direction of the support tube 4 is parallel to the axial direction of the cylinder 1.

[0026] The protection tube 5 is made of metal material. The protection tube 5 is configured as a round tube. The outer diameter of the protection tube 5 is less than or equal to the inner diameter of the support tube 4. The protection tube 5 is disposed inside the support tube 4. The protection tube 5 is connected to the support tube 4. The protection tube 5 may be welded to the support tube 4. The length of the protection tube 5 is less than the length of the support tube 4.

[0027] The heat exchange tube 2 is made of metal material. The heat exchange tube 2 is a round tube. The heat exchange tube 2 is inserted into the protective tube 5. The outer diameter of the heat exchange tube 2 is smaller than the outer diameter of the protective tube 5. The heat exchange tube 2 extends from one end of the cylinder 1 to the other end of the cylinder 1. The heat exchange tube 2 is inserted into the protective tube 5.

[0028] The sealing filler 6 is used to seal the gap between the support tube 4 and the heat exchange tube 2. There is an annular space between the inner wall of the support tube 4 and the outer wall of the heat exchange tube 2, and the sealing filler 6 is filled in the annular space between the support tube 4 and the heat exchange tube 2. The sealing filler 6 is flexible. The sealing filler 6 is annular as a whole and fills the annular space. The sealing filler 6 is located on one side of the protection tube 5.

[0029] The rotary kiln 100 uses steam as a heat source, and inputs steam from one end of the heat exchange tube 2. After the steam flows through the heat exchange tube 2, it is output from the other end of the heat exchange tube 2. The steam transfers heat to the heat exchange tube 2 so that the heat exchange tube 2 can maintain a high temperature state. The driving device drives the cylinder 1 to rotate. The desulfurized gypsum 200 is input into the cylinder 1 from the feed port of the cylinder 1. As the cylinder 1 rotates, the desulfurized gypsum 200 can move toward the discharge port of the cylinder 1. The desulfurized gypsum 200 contacts the heat exchange tube 2 in the cylinder 1 to achieve the purpose of being calcined, thereby being converted into building gypsum with low crystalline water content, and output from the discharge port of the cylinder 1. When the desulfurized gypsum 200 moves in the cylinder 1, the desulfurized gypsum 200 is blocked by the pipe rack plate 3 and is stacked in the cylinder 1. When the stacking height reaches the middle circular hole 32 of the pipe rack plate 3, the desulfurized gypsum 200 can pass through the pipe rack plate 3 through the middle circular hole 32 of the pipe rack plate 3.

[0030] The cylinder 1 rigidly supports the heat exchange tube 2 through the tube rack plate 3, the support tube 4 and the protection tube 5, which can firmly fix the heat exchange tube 2 and the cylinder 1 relative to each other, reduce the shaking of the heat exchange tube 2, and prevent the sealing filler 6 from being damaged by excessive pressure. At the same time, since the protection tube 5 is used to support the heat exchange tube 2, the contact area between the protection tube 5 and the heat exchange tube 2 is large, which can prevent the heat exchange tube 2 from being worn. The sealing filler 6 is filled in the annular space between the support tube 4 and the heat exchange tube 2, which can block the gap between the support tube 4 and the heat exchange tube 2, and prevent the desulfurized gypsum 200 from passing through the tube rack plate 3 from the gap between the support tube 4 and the heat exchange tube 2. The height of the stacking of the desulfurized gypsum 200 in the cylinder 1 can reach the extent of contacting the innermost heat exchange tube 2, thereby improving energy utilization, reducing production energy consumption, and improving production efficiency.

[0031] During assembly, the support tube 4 can be welded to the tube rack plate 3 first, and then the heat exchange tube 2 can be passed through the support tube 4. Since the difference between the inner diameter of the support tube 4 and the outer diameter of the heat exchange tube 2 is large, the heat exchange tube 2 can be easily passed through the support tube 4. Then, the protection tube 5 is sleeved on the heat exchange tube 2, and then the protection tube 5 is slid along the heat exchange tube 2 into the support tube 4, and then the protection tube 5 and the support tube 4 are welded together, and finally, the sealing filler 6 is filled between the support tube 4 and the heat exchange tube 2. The rotary kiln 100 of this structure is easy to assemble.

[0032] In an illustrative embodiment, the sealing filler 6 is disposed on a side of the protection tube 5 close to the feed port of the cylinder 1 .

[0033] Since the desulfurized gypsum 200 in the cylinder 1 moves from the feed port to the discharge port, the sealing filler 6 is arranged on the side of the protective tube 5 close to the feed port of the cylinder 1. The protective tube 5 can support the sealing filler 6 to prevent the sealing filler 6 from being squeezed by the desulfurized gypsum 200 and moving toward the discharge port.

[0034] In an illustrative embodiment, the rotary kiln 100 further includes a sealant layer 7. The sealant layer 7 is filled in the annular space between the support tube 4 and the heat exchange tube 2, and the sealant layer 7 seals the gap between the support tube 4 and the heat exchange tube 2. The sealant layer 7 adheres to the heat exchange tube 2 and the support tube 4. The sealant layer 7 is located on the side of the sealing filler 6 facing away from the protection tube 5. The sealant layer 7 can be formed by condensing a high-temperature sealant, so that the sealant layer 7 is resistant to high temperatures.

[0035] The sealant layer 7 can not only further enhance the sealing performance between the support tube 4 and the heat exchange tube 2 , but also prevent the sealing filler 6 from escaping from the gap between the support tube 4 and the heat exchange tube 2 .

[0036] In an illustrative embodiment, the support tube 4 is a split structure. The support tube 4 includes a tube ring 41 and a sleeve 42. The tube ring 41 and the sleeve 42 are both constructed as round tubes and are coaxially arranged. The inner diameter of the tube ring 41 is the same as the inner diameter of the sleeve 42. One end of the tube ring 41 is welded to one end of the sleeve 42. The tube ring 41 is inserted into the through hole 31 of the tube rack plate 3 and is welded to the tube rack plate 3. The sleeve 42 is arranged on one side of the tube ring 41 close to the feed port of the cylinder 1. The length of the sleeve 42 is 250 mm. The protective tube 5 is arranged in the tube ring 41, and the sealing filler 6 and the sealant layer 7 are arranged in the sleeve 42.

[0037] In an exemplary embodiment, the sealing filler 6 includes an asbestos tape 61 and an asbestos packing 62. The asbestos tape 61 fills the area between the sealant layer 7 and the protection tube 5 and close to the protection tube 5. The asbestos packing 62 fills the area between the asbestos tape 61 and the sealant layer 7.

[0038] The asbestos tape 61 is resistant to high temperature and corrosion. The asbestos tape 61 is in the shape of a strip, and is made of asbestos fibers woven or pressed into a long strip. The shape is relatively regular, and the width and thickness are relatively uniform. The asbestos tape 61 is like a long, flat belt, which is wrapped around the heat exchange tube 2 to have the functions of heat insulation and sealing, and can wrap the heat exchange tube 2 in a surrounding manner.

[0039] The asbestos packing 62 is resistant to high temperature and corrosion. The asbestos packing 62 is in the shape of a packing. The asbestos packing 62 is a flat rope woven from asbestos fibers. The asbestos packing 62 can not only resist wear and extrusion, but also does not deform when the temperature rises, thereby reducing the adjustment of the asbestos packing 62 and effectively reducing the leakage of the desulfurized gypsum 200.

[0040] In an illustrative embodiment, the heat exchange tubes 2 are provided with multiple layers. Each layer of heat exchange tubes 2 is composed of multiple heat exchange tubes 2 arranged in sequence along the circumference of the cylinder 1, and the distance between two adjacent heat exchange tubes in each layer of heat exchange tubes 2 is the same. All heat exchange tubes 2 in each layer of heat exchange tubes 2 are arranged in a circular ring coaxial with the cylinder 1. The multiple layers of heat exchange tubes 2 are arranged in sequence along the radial direction of the cylinder 1, and the distances between the multiple layers of heat exchange tubes 2 and the axis of the cylinder 1 are different.

[0041] The number of through holes 31 of the tube rack plate 3 is the same as the number of heat exchange tubes 2. Each through hole 31 on the tube rack plate 3 is penetrated by a support tube 4, and the support tube 4 is welded to the through hole 31. A sealing filler 6 and a protective tube 5 are arranged in each support tube 4. Multiple heat exchange tubes 2 are respectively penetrated by multiple protective tubes 5.

[0042] The heat exchange tubes 2 are arranged in multiple layers. During the rotation of the cylinder 1 , multiple heat exchange tubes 2 in each layer of heat exchange tubes 2 contact the desulfurized gypsum 200 in turn, thereby achieving uninterrupted calcination of the desulfurized gypsum 200 .

[0043] In an exemplary embodiment, a plurality of tube rack plates 3 are provided, and the plurality of tube rack plates 3 are sequentially arranged and spaced apart from each other along the axial direction of the cylinder 1. The through holes 31 of all tube rack plates 3 are provided with a sealing rubber layer 7, a support tube 4, a protection tube 5 and a sealing filler 6.

[0044] The plurality of tube rack plates 3 jointly support the plurality of heat exchange tubes 2 , so that the heat exchange tubes 2 can be installed more stably.

[0045] In an illustrative embodiment, the difference between the inner diameter of the support tube 4 and the outer diameter of the heat exchange tube 2 is greater than or equal to 2 cm.

[0046] In this way, the inner diameter of the support tube 4 is large enough, and the heat exchange tube 2 can pass through the support tube 4 more easily during assembly, and it is also convenient to insert the sealing filler 6 into the gap between the support tube 4 and the heat exchange tube 2.

[0047] In an illustrative embodiment, the length of the protection tube 5 is greater than the thickness of the tube rack plate 3 , and the contact area between the protection tube 5 and the heat exchange tube 2 is large enough to reduce the wear of the heat exchange tube 2 .

[0048] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0049] In addition, the terms "first", "second", etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include at least one of the features.

[0050] In the description of the present application, “plurality” means at least two, for example, two, three, etc., unless otherwise clearly and specifically defined.

[0051] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0052] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0053] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0054] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A rotary kiln, characterized in that: include: Cylinder; A tube rack plate is arranged in the cylinder and is provided with a through hole; A support pipe, passing through the through hole and connected to the pipe rack plate; A protection tube, disposed in the support tube and connected to the support tube, wherein the length of the protection tube is shorter than the length of the support tube; a heat exchange tube, passing through the protection tube; and The sealing filler is filled in the annular space between the support tube and the heat exchange tube and is located on one side of the protection tube.

2. The rotary kiln according to claim 1, characterized in that: A feed port is provided at one end of the cylinder, and a discharge port is provided at the other end of the cylinder; The sealing filler is arranged on a side of the protection tube close to the feed port.

3. The rotary kiln according to claim 2, characterized in that: The rotary kiln also includes a sealing rubber layer; The sealant layer is filled in the annular space between the support tube and the heat exchange tube, and is located on a side of the sealing filler facing away from the protection tube.

4. The rotary kiln according to claim 3, characterized in that: The sealant layer is formed by condensing high-temperature sealant.

5. The rotary kiln according to claim 3, characterized in that: The sealing filler includes asbestos tape and asbestos packing; The asbestos tape fills the area between the sealant layer and the protection tube and close to the protection tube, and the asbestos packing fills the area between the asbestos tape and the sealant layer.

6. The rotary kiln according to any one of claims 1 to 5, characterized in that: The heat exchange tubes are provided with multiple layers, each layer of the heat exchange tubes is composed of multiple heat exchange tubes arranged in sequence along the circumferential direction of the cylinder, and the multiple layers of heat exchange tubes are arranged in sequence along the radial direction of the cylinder; The tube rack plate is provided with through holes having the same number as the heat exchange tubes, each of the through holes is penetrated by the support tube, and each of the support tubes is provided with the sealing filler and the protection tube; The plurality of heat exchange tubes are respectively passed through a plurality of protection tubes.

7. The rotary kiln according to claim 6, characterized in that: A plurality of the tube rack plates are provided, and the plurality of the tube rack plates are arranged in sequence along the axial direction of the cylinder and are spaced apart from each other.

8. The rotary kiln according to any one of claims 1 to 5, characterized in that: The difference between the inner diameter of the support tube and the outer diameter of the heat exchange tube is greater than or equal to 2 cm.

9. The rotary kiln according to any one of claims 1 to 5, characterized in that: The pipe rack plate is a circular flat plate.

10. The rotary kiln according to any one of claims 1 to 5, characterized in that: The length of the protection tube is greater than the thickness of the tube rack plate.

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