Fly ash low temperature thermal degradation rotary kiln reactor

Abstract

The utility model discloses a fly ash low temperature thermal degradation rotary kiln reactor, including the casing of the cylinder and the sleeve set its outside, the inside constitution of cylinder is the combustion chamber, and its outer surface is equipped with a plurality of axial extension's special section and forms the recess, and the inside correspondence arrangement and the shell intercommunication's pipe bundle, the casing both ends are equipped with the gas inlet and the export of height difference setting, make the gas flow direction with the fly ash flow direction opposite, the utility model discloses the special shape design and the inside pipe bundle cooperation of cylinder outer wall, improve the heat transfer effect and improve material flow state, can effectively improve the efficiency and stability of fly ash low temperature thermal degradation.

Description

Technical Field

[0001] This utility model relates to the technical field of fly ash treatment devices, specifically to a rotary kiln reactor for low-temperature thermal degradation of fly ash. Background Technology

[0002] Low-temperature thermal degradation of fly ash is a technology for treating hazardous wastes such as fly ash from waste incineration. Its core principle is to thermally decompose organic pollutants (such as dioxins and furans) in the fly ash at a relatively low temperature of 300℃ to 500℃, thereby achieving harmless disposal. This method avoids the energy consumption associated with high-temperature melting and preserves as much of the fly ash's physicochemical properties as possible for subsequent resource utilization. Currently, the mainstream industrial equipment for implementing this process is the rotary kiln reactor, which can be mainly divided into two categories based on the heating method: internal heating and external heating.

[0003] Internally heated rotary kilns typically refer to devices where the heat source (such as high-temperature flue gas or flame) and fly ash material directly contact and exchange heat inside the kiln shell. For example, Chinese patent CN116025909A uses an inclined rotary kiln with a burner at the kiln head that injects flames into the kiln. Fly ash enters from the kiln tail, moves towards the kiln head as the kiln rotates, and is directly heated by the flames. Externally heated rotary kilns, on the other hand, use indirect heating. The combustion flue gas flows within a jacket or shell outside the kiln shell, and heat is indirectly transferred to the fly ash material flowing inside through the kiln wall. Chinese patent CN115351054A mentions a dioxin pyrolysis system using an indirectly heated rotary kiln. This type of structure isolates the heat source from the material, facilitates control of the reaction atmosphere inside the kiln, avoids contaminating the material with heat source flue gas, and also facilitates the separate collection and treatment of volatile organic compounds.

[0004] Existing rotary kiln structures face the problems of fly ash caking and wall adhesion when processing fly ash. Fly ash contains low-melting-point salts such as sodium chloride and potassium chloride, which easily soften and melt at operating temperatures of 300-500℃. In the relatively simple internal structure of existing rotary kilns, fly ash particles easily adhere to each other during tumbling due to the stickiness of the molten salts, gradually accumulating on the inner wall of the kiln to form caking. This caking layer hinders heat transfer from the wall to the material, significantly impacting the efficiency of externally heated rotary kilns.

[0005] Therefore, it is necessary to improve the existing reactor. Utility Model Content

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a rotary kiln reactor that has higher processing efficiency and can improve the problem of fly ash caking.

[0007] To achieve the above objectives, the technical solution provided by this utility model is as follows.

[0008] A rotary kiln reactor for low-temperature thermal degradation of fly ash includes a cylindrical body and a shell fitted over the cylindrical body. The ends of the cylindrical body are exposed outside the shell. The interior of the cylindrical body is configured as a combustion chamber. The fly ash flow direction is axially aligned with the cylindrical body. The cylindrical body is rotated within the shell via rollers at its outer periphery outside the shell. Each roller is equipped with a rolling ring. A gas inlet and a gas outlet are respectively located at both ends of the shell. The height of the gas inlet is lower than the height of the gas outlet, and the gas flow direction is opposite to the fly ash flow direction. The outer surface of the cylindrical body is configured with multiple irregularly shaped cross-sections extending axially along the cylindrical body. A groove is left between adjacent irregularly shaped cross-sections. Multiple tube bundles are circumferentially arranged inside the cylindrical body, corresponding to the irregularly shaped cross-sections. The ends of the tube bundles are fixedly disposed within the cylindrical body and communicate with the shell.

[0009] As a preferred technical solution, the irregular cross-section of the outer surface of the cylinder includes an arc-shaped surface, the convex surface of the arc-shaped surface is located on the outer surface of the cylinder, and the concave surface of the arc-shaped surface is concentrically arranged with the tube bundle.

[0010] As a preferred technical solution, the width of the groove increases progressively from the radial direction of the cylinder to the outer periphery.

[0011] As a preferred technical solution, the irregular cross-section of the outer surface of the cylinder includes a protruding structure extending along its axial direction, and the protruding structure is arranged in a spiral shape in the circumferential direction of the outer wall of the cylinder.

[0012] As a preferred technical solution, the spiral direction of the protrusion structure is opposite to the rotation direction of the cylinder during operation.

[0013] As a preferred technical solution, the distance between the center of the tube bundle and the inner surface of the cylinder is L, and the inner diameter of the tube bundle is r. L and r satisfy L=k1r, where 1.2≤k1≤5.

[0014] As a preferred technical solution, the inner diameter of the cylinder is R, and the inner diameter of the tube bundle is r, where R and r satisfy R=k2r, and 6≤k2≤20.

[0015] As a preferred technical solution, the ratio of the heat transfer coefficient λ1 of the cylinder to the heat transfer coefficient λ2 of the tube bundle is k3, where 0.8≤k3≤2; The values ​​of λ1 and / or λ2 range from 15 W / (m·K) to 50 W / (m·K).

[0016] As a preferred technical solution, the ratio of the wall thickness t1 of the cylinder to the wall thickness t2 of the tube bundle is k4, where 1.5≤k4≤4.

[0017] As a preferred technical solution, the end of the cylinder is also provided with an exhaust gas desorption port.

[0018] The advantages and beneficial effects of this invention are as follows: It enhances the efficiency and stability of the low-temperature thermal degradation process of fly ash by strengthening heat transfer. This invention employs an externally heated rotary kiln, where the combustion gas flows counter-currently to the fly ash within the shell, avoiding direct contact between the flue gas and the material, thus facilitating the independent collection and purification of volatile organic compounds. The outer surface of the cylinder is designed with an axially extending irregular cross-section, creating grooves that increase the heat transfer area. During rotation, this generates axial pushing and radial tumbling action on the fly ash, alleviating the problems of material caking and wall adhesion caused by low-melting-point salts.

[0019] The reactor shown in this invention achieves multi-path, high-efficiency heat transfer through the irregularly shaped structure on the outer wall of the cylinder and the internal tube bundle. The radially increasing groove width facilitates optimized gas flow distribution and reduces heat transfer dead zones. The dimensions of the tube bundle and the cylinder are matched with the heat transfer coefficient, ensuring structural strength while enabling more uniform and efficient heat transfer to the fly ash material layer. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the rotary kiln reactor for low-temperature thermal degradation of fly ash shown in this utility model.

[0021] Figure 2 This is a cross-sectional structural diagram of the cylinder and its internal structure in one embodiment of the present invention.

[0022] Figure 3 This is a cross-sectional structural diagram of the cylinder and its internal structure in another embodiment of the present invention.

[0023] Figure label: 1-Cylinder, 2-Shell, 3-Combustion chamber, 4-Support roller, 5-Rolling ring, 6-Gas inlet, 7-Gas outlet, 8-Groove, 9-Pipe bundle, 10-Arc-shaped surface, 11-Protruding structure, 12-Exhaust gas desorption interface. Detailed Implementation

[0024] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, it should be noted that, for ease of description, only the parts relevant to this application are shown in the accompanying drawings, not the entire structure. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0025] The terms “comprising” and “having”, and any variations thereof, used in this application are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to such process, method, product, or apparatus.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly or implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] This utility model provides a rotary kiln reactor for the low-temperature thermal degradation of fly ash. For example... Figure 1 As shown, the reactor includes a cylindrical body 1 and a shell 2 fitted outside the cylindrical body 1. The ends of the cylindrical body 1 protrude outside the shell 2 to provide inlet and outlet for fly ash and facilitate connection to an external drive and feed / discharge system. The interior of the cylindrical body 1 is configured as a combustion chamber 3 for containing and processing fly ash material. The cylindrical body 1 is rotatably mounted inside the shell 2 via rollers 4 on its outer periphery outside the shell 2. The rollers 4 are equipped with rolling rings 5 ​​to ensure stable and continuous rotation of the cylindrical body 1 within the shell. A gas inlet 6 and a gas outlet 7 are respectively provided at the two ends of the shell 2. The height of the gas inlet 6 is lower than the height of the gas outlet 7, and the flow direction of the gas is opposite to the flow direction of the fly ash within the cylindrical body, forming a countercurrent flow. Preferably, the gas inlet 6 and the gas outlet 7 are diagonally arranged.

[0028] The outer surface of the cylinder 1 is constructed with multiple irregular cross sections extending along the cylinder axis, and a groove 8 is left between two adjacent irregular cross sections. Multiple tube bundles 9 are arranged circumferentially inside the cylinder 1. The tube bundles 9 correspond to the irregular cross sections on the outer surface of the cylinder, and the ends of the tube bundles 9 are fixedly set inside the cylinder 1 and connected to the shell 2.

[0029] In the above structure, the cylinder 1 serves as the core reaction component, with its internal combustion chamber 3 providing a site for the thermal degradation of fly ash. The external shell 2 forms a jacket with the cylinder 1, providing external heating. The cylinder rotates through the cooperation of the support rollers 4 and the rolling rings 5, serving as the basic motion mode of the rotary kiln and effectively promoting the mixing, tumbling, and axial conveying of the internal materials. The gas inlet 6 is positioned lower than the gas outlet 7, combining the counter-current flow of gas and fly ash. After entering through the inlet, the cold gas flows upward along the outer wall of the cylinder within the shell, continuously absorbing heat transferred from the cylinder and heating up; while the material inside the cylinder moves from the high end to the low end, its temperature gradually increasing. This counter-current arrangement maximizes the logarithmic mean temperature difference between the fluids on both sides, enhancing the heat transfer driving force, thereby improving the overall heat utilization efficiency with the same total heat transfer area.

[0030] The axially extended irregular cross-section and groove 8 designed on the outer surface of the cylinder increase the actual contact area between the gas and the cylinder wall inside the shell, improving the convective heat transfer on the gas side. Furthermore, the groove structure disrupts the laminar boundary layer of the gas along the cylinder wall, promoting turbulence and thus enhancing heat transfer within the shell. The corresponding tube bundle 9 inside the cylinder not only serves as a structural reinforcement but also constitutes an additional internal heat transfer unit. The same heat medium (such as gas) as that inside the shell can be introduced into the tube bundle 9. The radiative and convective heat transfer of the internal tube bundle 9 can directly act on the material core region, effectively penetrating and weakening the obstruction of heat transfer by the externally formed slab layer, thereby improving the problem of deteriorated internal heat transfer commonly faced by externally heated rotary kilns.

[0031] In some embodiments, to optimize the structural strength and heat transfer performance of the cylinder and ensure stable installation and effective heat exchange of the internal tube bundle, the irregular cross-section of the outer surface of the cylinder 1 includes an arc-shaped surface 10. The convex surface of the arc-shaped surface 10 is located on the outer surface of the cylinder 1, while its concave surface is concentrically arranged with the corresponding tube bundle 9. The arc-shaped concave surface provides good circumferential coverage and support for the tube bundle, enhancing its fatigue and deformation resistance under cylinder rotation and material impact. The concentric arrangement of the arc-shaped concave surface and the tube bundle makes the heat flow path from the outer wall of the cylinder through the arc-shaped surface to the tube bundle more straight, reducing abrupt changes in heat flow direction and local thermal resistance, which is beneficial for the efficient conduction of heat from the cylinder wall to the tube bundle.

[0032] In some embodiments, to improve the flow distribution and heat transfer uniformity of the gas within the shell and avoid flow dead zones or localized overheating / underheating, the width of the groove 8 increases radially outward from the outer periphery of the cylinder. This wedge-shaped or trapezoidal cross-section groove allows the flow cross-sectional area of ​​the gas to gradually increase radially outward as it flows within the shell. With a constant flow rate, the increased flow area reduces the fluid velocity. Therefore, the flow velocity is relatively high near the cylinder wall (groove root), enhancing convective heat transfer near the wall; while the flow velocity decreases in areas far from the cylinder wall (groove opening), facilitating sufficient residence of the gas and completion of heat exchange in these areas.

[0033] In some embodiments, to enhance the mixing capacity of the cylinder for internal fly ash materials and suppress fly ash adhesion and caking, the irregular cross-section of the outer surface of the cylinder 1 includes a protruding structure 11 extending along its axial direction. This protruding structure 11 is arranged spirally in the circumferential direction of the outer wall of the cylinder 1. When the cylinder rotates, this spiral structure generates a continuous axial force on the material, propelling the material to move stably axially from the feed end to the discharge end, ensuring sufficient residence time for the material within the kiln.

[0034] During rotation, the protruding structure continuously lifts the material at the bottom, which then falls under the influence of gravity, forming radial mixing. This effectively disperses the fly ash particles that have initially bonded due to the action of molten salt, thus disrupting the foundation for the formation of the slab layer.

[0035] In some embodiments, the helical direction of the protrusion structure 11 is opposite to the rotational direction of the cylinder 1 during operation. For example, if the cylinder is designed to rotate clockwise (viewed from the drive end), the helical protrusion is designed to rotate counterclockwise. This counter-rotation configuration increases the relative velocity and the angle of approach of the protrusion towards the moving material, thereby enhancing the mixing intensity.

[0036] In some embodiments, to optimize the heat exchange area between the tube bundle 9 and the inner surface of the cylinder 1, and to balance the utilization of internal space and heat transfer effect, the distance between the center of the tube bundle 9 and the inner surface of the cylinder 1 is L, and the inner diameter of the tube bundle 9 is r. L and r satisfy L=k1r, where 1.2≤k1≤5. This ratio k1 defines the radial embedment depth of the tube bundle in the cylinder. If the value of k1 is too small, it means that the tube bundle is too close to the inner wall of the cylinder. From the perspective of heat transfer, although this shortens the radial distance of heat from the tube bundle to the material, it may excessively compress the flow space of the material between the tube bundle and the cylinder wall, which may easily lead to poor material flow or even blockage in this area, which is not conducive to the transfer of heat to the material body through convection and conduction. If the value of k1 is too large, the tube bundle is too deep into the center of the material area, which may cause the annular material area near the cylinder wall to heat up slowly due to the lack of a direct heat source, while the central area may experience local overheating due to excessive heat concentration.

[0037] In some embodiments, to ensure that the rotary kiln has a suitable processing capacity and matches the heat exchange capacity of the internal tube bundle, the inner diameter of the cylinder 1 is R, and the inner diameter of the tube bundle 9 is r. R and r satisfy R = k2r, where 6 ≤ k2 ≤ 20. The value of k2 reflects the coordination between the number and size of the tube bundles that can be arranged per unit cross-sectional area. If k2 is too small, it means that for a given R, the r of the tube bundle is relatively too large or the number is too large. Although heat exchange is enhanced, it will seriously encroach on the material flow space, reduce the processing capacity, and increase manufacturing complexity and cost. If k2 is too large, the tube bundles are relatively too thin or the number is too small, and their contribution to the overall heat exchange is reduced, making it difficult to effectively play the core role of improving internal heat transfer and preventing caking.

[0038] In some embodiments, to coordinate the heat transfer performance of the cylinder and tube bundle from the perspective of material thermophysical properties and achieve balanced heat transfer in the composite structure, the heat transfer coefficients of the two are matched. The ratio of the heat transfer coefficient λ1 of the cylinder 1 to the heat transfer coefficient λ2 of the tube bundle 9 is k3, where 0.8 ≤ k3 ≤ 2. Meanwhile, the values ​​of λ1 and / or λ2 range from 15 W / (m·K) to 50 W / (m·K). k3 close to 1 means that the cylinder wall and the tube bundle wall have similar thermal conductivity. If k3 is too large, heat will preferentially and rapidly transfer through the cylinder wall, while the tube bundle, due to its lower thermal conductivity, becomes a bottleneck, weakening its heat exchange effect and failing to effectively heat the internal materials. If k3 is too small, heat tends to transfer rapidly through the tube bundle, potentially resulting in a relatively low cylinder wall temperature, affecting its effectiveness as the main heat transfer surface, and possibly causing uneven thermal stress in the structure.

[0039] In some embodiments, the ratio of the wall thickness t1 of the cylinder 1 to the wall thickness t2 of the tube bundle 9 is k4, where 1.5 ≤ k4 ≤ 4. The cylinder, as the main pressure-bearing component bearing material loads, rotational torque, and external pressure, requires sufficient wall thickness to ensure rigidity and strength. The tube bundle mainly bears the internal medium pressure and thermal stress, and its wall thickness can be relatively thin to reduce thermal resistance. If k4 is too small, it may mean that the tube bundle wall is relatively too thick, which, while increasing the strength safety margin, unnecessarily increases its thermal resistance, hindering heat exchange; or it may mean that the cylinder wall is relatively thin, potentially posing a strength risk. If k4 is too large, the cylinder wall is too thick, which, while robust, increases the radial thermal resistance and manufacturing cost of the cylinder.

[0040] In some embodiments, in order to effectively collect and treat the gaseous products generated during the pyrolysis process, a tail gas desorption port 12 is also provided at the end of the cylinder 1. During the low-temperature thermal degradation of fly ash, organic pollutants are decomposed by heat, and some volatile substances may be generated. The tail gas desorption port 12 is usually located near the discharge end of the cylinder and is connected to subsequent tail gas treatment systems such as condensation, adsorption, filtration or incineration.

[0041] The working principle of this novel rotary kiln reactor for low-temperature thermal degradation of fly ash is as follows: Fly ash material is continuously fed into the rotating cylinder from the feed end. Simultaneously, combustion gas enters the shell through the low-level inlet and flows counter-currently upwards along the outer wall of the cylinder within the jacket space. During the combustion gas flow, the heat released is transferred to the fly ash material inside the cylinder through a composite heat transfer system composed of the cylinder wall and internal tube bundles, primarily via heat conduction and radiation. Under the action of the rotating cylinder and internal spiral protrusions, the fly ash is continuously lifted and scattered, achieving axial conveying and thorough radial mixing, ensuring uniform heating and low-temperature thermal degradation within the target temperature range of 300℃ to 500℃, thus decomposing organic pollutants (such as dioxins). The degraded solid residue is discharged from the discharge end for subsequent disposal or resource utilization; while the volatile gases generated by the reaction are discharged through the tail gas desorption port at the end of the cylinder for purification.

[0042] Example 1 This embodiment provides a rotary kiln reactor for low-temperature thermal degradation of fly ash, the structure of which is as follows: Figure 1-2 As shown, the reactor includes a cylindrical body 1 and a shell 2 fitted over the cylindrical body 1. The ends of the cylindrical body 1 protrude outside the shell 2. The interior of the cylindrical body 1 is configured as a combustion chamber 3. The cylindrical body 1 is rotatably mounted inside the shell 2 via rollers 4 at its outer periphery outside the shell 2. Rollers 4 are equipped with rings 5. Gas inlet 6 and gas outlet 7 are respectively provided at the two ends of the shell 2. The height of the gas inlet 6 is lower than the height of the gas outlet 7, and the flow direction of the gas is opposite to the flow direction of fly ash inside the cylindrical body. The outer surface of the cylindrical body 1 is constructed with multiple irregularly shaped cross-sections extending axially along the cylindrical body, with grooves 8 between adjacent irregularly shaped cross-sections. Multiple tube bundles 9 are circumferentially arranged inside the cylindrical body 1, corresponding to the irregularly shaped cross-sections. The ends of the tube bundles 9 are fixedly mounted inside the cylindrical body 1 and connected to the shell 2.

[0043] The irregular cross-section of the outer surface of the cylinder 1 includes an arc-shaped surface 10. The convex surface of the arc-shaped surface 10 is located on the outer surface of the cylinder 1, and the concave surface of the arc-shaped surface 10 is concentrically arranged with the tube bundle 9. The width of the groove 8 increases radially outward from the outer periphery of the cylinder 1. The distance L between the center of the tube bundle 9 and the inner surface of the cylinder 1 is 25 mm, the inner diameter r of the tube bundle 9 is 10 mm, the inner diameter R of the cylinder 1 is 500 mm, and an exhaust gas desorption port 12 is also provided at the end of the cylinder 1.

[0044] The rotary kiln reactor for low-temperature thermal degradation of fly ash in this embodiment is used to treat fly ash generated by a waste incineration plant. Testing showed that the reactor in this embodiment achieved a degradation rate of 99.2% for dioxin-like pollutants in the fly ash.

[0045] Example 2 This embodiment provides another rotary kiln reactor for low-temperature thermal degradation of fly ash. Its basic structure and the connection relationships between the cylinder, shell, support rollers, rolling ring, gas inlet, gas outlet, groove, and tube bundle are the same as in Embodiment 1. The irregular cross-section of the outer surface of the cylinder 1 includes protruding structures 11 extending along its axial direction. The protruding structures 11 are arranged spirally in the circumferential direction of the outer wall of the cylinder 1, and the spiral direction of the protruding structures 11 is opposite to the rotation direction of the cylinder 1 during operation. The heat transfer coefficient λ1 of the cylinder 1 is 30 W / (m·K), and the heat transfer coefficient λ2 of the selected tube bundle 9 is 25 W / (m·K).

[0046] The distance L between the center of tube bundle 9 and the inner surface of cylinder 1 is 15mm, the inner diameter r of tube bundle 9 is 8mm, and the inner diameter R of cylinder 1 is 300mm.

[0047] The reactor in this embodiment is used to treat another type of industrial hazardous waste, fly ash. Operating conditions: Testing showed that this embodiment achieved a comprehensive degradation rate of 98.8% for organic pollutants in the fly ash.

[0048] Example 3 This embodiment provides yet another rotary kiln reactor for low-temperature thermal degradation of fly ash. Its basic structure and the connection relationships of the cylinder, shell, support rollers, rolling ring, gas inlet, gas outlet, groove, and tube bundle are the same as in Embodiment 1.

[0049] The irregular cross-section of the outer surface of the cylinder 1 includes both an arc-shaped surface 10 and a protruding structure 11 extending along its axial direction. The protruding structure 11 is arranged spirally in the circumferential direction of the outer wall of the cylinder 1, and its spiral direction is opposite to the rotation direction of the cylinder 1 during operation. The width of the groove 8 increases radially outward from the outer circumference of the cylinder 1. The wall thickness of the cylinder 1 is 18 mm, the wall thickness of the tube bundle 9 is 6 mm, the distance L between the center of the tube bundle 9 and the inner surface of the cylinder 1 is 40 mm, the inner diameter r of the tube bundle 9 is 20 mm, the inner diameter R of the cylinder 1 is 600 mm, the heat transfer coefficient λ1 of the cylinder 1 is 40 W / (m·K), and the heat transfer coefficient λ2 of the selected tube bundle 9 is 20 W / (m·K).

[0050] This embodiment treats high-salinity, easily caking waste incineration fly ash. Tests show that the degradation rate of dioxins in the fly ash is as high as 99.5%.

[0051] Comparative Example 1 This comparative example uses a traditional, straight-walled externally heated rotary kiln without internal reinforcement structures to treat fly ash. This conventional rotary kiln consists only of a rotating cylinder with a smooth inner wall and an external heating jacket (shell). Gas flows within the jacket to heat the cylinder, which in turn heats the fly ash inside through heat conduction. There are no internal tube bundles, irregular cross-sections, or spiral protrusions within the cylinder. The fly ash moves and mixes primarily within the cylinder through simple rolling and sliding.

[0052] Using this conventional rotary kiln, the process was operated at a similar processing scale, fly ash type, and feed rate as in Example 1 (cylinder rotation speed 1.5 rpm, tilt angle 2°, gas inlet temperature 600°C). Testing showed that this conventional process could only achieve a maximum degradation rate of approximately 65%-66% for dioxins in fly ash.

[0053] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A rotary kiln reactor for low-temperature thermal degradation of fly ash, comprising a cylindrical body (1) and a shell (2) sleeved outside the cylindrical body (1), wherein the end of the cylindrical body (1) is exposed outside the shell (2), characterized in that: The cylinder (1) is internally configured as a combustion chamber (3). The cylinder (1) is rotatably disposed inside the shell (2) via a support roller (4) on the outer periphery of the outer end of the shell (2). The support roller (4) is equipped with a rolling ring (5). The two ends of the housing (2) are respectively provided with a gas inlet (6) and a gas outlet (7). The height of the gas inlet (6) is lower than the height of the gas outlet (7), and the flow direction of the gas is opposite to the flow direction of the fly ash. The outer surface of the cylinder (1) is constructed with multiple irregular cross sections extending along the axial direction of the cylinder (1). A groove (8) is left between two adjacent irregular cross sections. Multiple tube bundles (9) are arranged circumferentially inside the cylinder (1). The tube bundles (9) correspond to the irregular cross sections. The ends of the tube bundles (9) are fixedly installed inside the cylinder (1) and connected to the shell (2).

2. The rotary kiln reactor for low-temperature thermal degradation of fly ash according to claim 1, characterized in that: The irregular cross section of the outer surface of the cylinder (1) includes an arc surface (10), the convex surface of the arc surface (10) is located on the outer surface of the cylinder (1), and the concave surface of the arc surface (10) is concentrically arranged with the tube bundle (9).

3. The rotary kiln reactor for low-temperature thermal degradation of fly ash according to claim 1, characterized in that: The width of the groove (8) increases radially outward from the outer periphery of the cylinder (1).

4. The rotary kiln reactor for low-temperature thermal degradation of fly ash according to claim 1, characterized in that: The irregular cross-section of the outer surface of the cylinder (1) includes a protruding structure (11) extending along its axial direction, the protruding structure (11) being arranged in a spiral shape in the circumferential direction of the outer wall of the cylinder (1).

5. The rotary kiln reactor for low-temperature thermal degradation of fly ash according to claim 4, characterized in that: The spiral direction of the protruding structure (11) is opposite to the rotation direction of the cylinder (1) during operation.

6. The rotary kiln reactor for low-temperature thermal degradation of fly ash according to claim 1, characterized in that: The distance between the center of the tube bundle (9) and the inner surface of the cylinder (1) is L, and the inner diameter of the tube bundle (9) is r. L and r satisfy L=k1r, where 1.2≤k1≤5.

7. The rotary kiln reactor for low-temperature thermal degradation of fly ash according to claim 1 or 6, characterized in that: The inner diameter of the cylinder (1) is R, and the inner diameter of the tube bundle (9) is r. R and r satisfy R=k2r, where 6≤k2≤20.

8. The rotary kiln reactor for low-temperature thermal degradation of fly ash according to claim 1, characterized in that: The ratio of the heat transfer coefficient λ1 of the cylinder (1) to the heat transfer coefficient λ2 of the tube bundle (9) is k3, where 0.8≤k3≤2; the values ​​of λ1 and / or λ2 are between 15W / (m·K) and 50W / (m·K).

9. The rotary kiln reactor for low-temperature thermal degradation of fly ash according to claim 1, characterized in that: The ratio of the wall thickness t1 of the cylinder (1) to the wall thickness t2 of the tube bundle (9) is k4, where 1.5≤k4≤4.

10. The rotary kiln reactor for low-temperature thermal degradation of fly ash according to claim 1, characterized in that: The end of the cylinder (1) is also provided with an exhaust gas desorption port (12).

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