A rotary kiln outer ring particle jacket waste heat recovery system and a method for operating the same

Abstract

This invention discloses a rotary kiln outer annular particle jacket waste heat recovery system and its operation method. The rotary kiln includes layers A and B from the inside out. A layer C, rotating synchronously with the rotary kiln, is set outside layer B. Layer C is connected to the rotary kiln through discrete support members spaced apart circumferentially, forming an annular particle jacket flow channel between layers B and C. Multiple segmented spiral flow guiding components are arranged at intervals circumferentially within the flow channel. The system uses high-temperature resistant solid particles as the heat transfer medium. A high-end annular feeding chamber is set at the high end of the rotary kiln, and a low-end annular receiving chamber is set at the low end. Under the influence of the rotary kiln's tilt angle, the guidance of the segmented spiral flow guiding components, and gravity, the solid particles undergo a net axial displacement from the high end to the low end and absorb heat from layer B. The high-temperature solid particles are introduced through a particle circulation loop into a stationary external heat exchange component set outside the rotary kiln, where they exchange heat with the working fluid to generate steam and / or high-temperature hot water before returning to the high-end annular feeding chamber. This invention replaces the fluid working medium with a solid particle moving bed medium, reducing the reliance on dynamic sealing of rotating pressurized fluids and facilitating the stable, long-life industrial recycling of waste heat from the rotary kiln shell.

Description

Technical Field

[0001] This invention relates to the field of industrial kiln waste heat recovery technology, and in particular to an annular particle jacket waste heat recovery system installed outside a rotary kiln and using solid particles as a heat transfer medium, and its operation method. Background Technology

[0002] Rotary kilns are widely used in industries such as cement, metallurgy, and chemicals. During normal operation, the heat from the kiln lining is transferred outward through the refractory layer and the kiln shell, but the surface of the outer steel shell of the kiln still has a high temperature, resulting in continuous heat loss and environmental thermal pollution.

[0003] Existing waste heat recovery schemes for rotary kiln shells typically use air, water, or other fluids to remove heat. When using a gaseous working medium, the heat-carrying capacity per unit volume is limited due to the low volumetric heat capacity of gases, resulting in a limited heat-carrying capacity per unit volume under the same external surface temperature constraint, and the temperature of the external usable heat source is often low. When using a liquid working medium, issues such as fluid cavities, rotary joints, dynamic sealing, leakage, pressure drop, and vapor-liquid phase change control need to be addressed around the rotating equipment, which limits the reliability of long-term industrial operation.

[0004] Other solutions reduce heat dissipation from the outer surface of the kiln by adding an insulation layer, but these solutions mainly aim to reduce heat loss and cannot stably remove and further utilize the heat from the outer wall of the kiln.

[0005] Therefore, a new waste heat recovery system for the outer wall of a rotary kiln is needed to reduce the dependence on the dynamic sealing of the rotating pressurized fluid without significantly changing the original thermal state of the outer steel shell of the rotary kiln, and to achieve stable, reliable, and industrially sustainable heat extraction and utilization. Summary of the Invention

[0006] The purpose of this invention is to provide a rotary kiln outer annular particle jacket waste heat recovery system and its operation method, so as to solve the problems of complex dynamic sealing, insufficient long-term operational reliability and poor heat output stability in existing fluid working fluid waste heat recovery schemes.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A rotary kiln outer annular particle jacket waste heat recovery system includes an inclined rotary kiln body, a particle circulation loop, an external heat exchange assembly, and a control assembly. The rotary kiln body comprises at least layer A and layer B from the inside out. A layer C, coaxial with the rotary kiln body and rotating synchronously with it, is spaced apart on the outer side of layer B. Layer C is connected to the rotary kiln body via discrete supports spaced apart circumferentially, and these discrete supports are separate from the flow guiding assembly. An annular particle jacket flow channel with a radial thickness of 20-80 mm is formed between layers B and C. Multiple segmented spiral flow guiding assemblies, spaced apart circumferentially and extending axially along the rotary kiln, are arranged within the annular particle jacket flow channel to divide it into multiple particle flow channels. The system uses high-temperature resistant solid particles as the heat transfer medium. The rotary kiln has a high... The rotary kiln is equipped with a high-end annular feeding chamber communicating with each particle flow channel, and the high-end annular feeding chamber is equipped with a high-end labyrinth-type sealing structure; the rotary kiln is equipped with a low-end annular receiving chamber communicating with each particle flow channel, and the low-end annular receiving chamber is equipped with a low-end labyrinth-type sealing structure; the solid particles form a net axial displacement from the high end to the low end under the guidance of the rotary kiln tilt angle, the segmented spiral guide component, and gravity, and absorb heat from the B layer; the particle circulation loop includes at least a lifting device and a return conveying device, used to transport the high-temperature solid particles discharged from the low end to a stationary external heat exchange component located outside the rotary kiln and return them to the high-end annular feeding chamber after heat exchange; the control component is configured to adjust the solid particle circulation volume according to the B layer temperature and / or the solid particle inlet and outlet temperature, so that the B layer temperature is maintained within a preset range.

[0008] Preferably, the radial thickness of the annular particle jacket flow channel is 35~50mm.

[0009] Preferably, the segmented spiral guide assembly has a single segment length of 300~1500mm, a thickness of 0.8~3.0mm, and an axial guide angle of 5°~45° relative to the rotary kiln axis.

[0010] Preferably, an overlap section and / or a thermal expansion release gap are provided between adjacent segmented spiral guide components.

[0011] Preferably, the segmented spiral flow guide assembly is connected to layer B and / or layer C via an ear seat, the ear seat is a carbon steel ear seat, the segmented spiral flow guide assembly is a stainless steel or heat-resistant steel component, and a dissimilar steel transition weld connection is provided between the ear seat and the segmented spiral flow guide assembly.

[0012] Preferably, the segmented spiral guide assembly is a 304 stainless steel sheet component, the lug is a 20# carbon steel lug, and the transition weld connection is formed using 309L welding material and / or 312 welding material.

[0013] Preferably, the high-temperature resistant solid particles are high-temperature resistant ceramic particles, which are selected from one or more of high-alumina ceramic balls, corundum particles, mullite particles, sintered bauxite particles, and silicon carbide particles. The particle size of the solid particles is 1~10mm, preferably 2~6mm.

[0014] Preferably, the solid particles have a running filling rate of 0.30~0.75 in the particle flow channel, more preferably 0.40~0.60.

[0015] Preferably, the tilt angle of the rotary kiln body is 1°~15°, and more preferably 3°~12°.

[0016] Preferably, the particle circulation rate is 10~60 kg / s.

[0017] Preferably, the external heat exchange component includes a particle-water heat exchanger and a steam generation component, wherein the steam generation component is used to convert the working fluid heated by the particle-water heat exchanger into steam; or, the external heat exchange component is used to output high-temperature hot water.

[0018] Preferably, a D layer is provided outside the C layer, and the D layer includes at least a reflective layer, a heat insulation layer and a protective layer; the reflective layer is provided on the side close to the C layer, the heat insulation layer is provided outside the reflective layer, and the protective layer is provided outside the heat insulation layer.

[0019] Preferably, the reflective layer is an aluminum foil layer, the heat insulation layer is an aerogel heat insulation felt layer, and the protective layer is an aluminum protective plate layer; the thickness of the heat insulation layer is 5~50mm, preferably 15~35mm.

[0020] Preferably, the control component uses the temperature of layer B as the main control variable, and adjusts the circulation rate of solid particles according to the direction and magnitude of the deviation of the temperature of layer B from the target value.

[0021] This invention also provides a method for recovering waste heat from the outer annular particle jacket of a rotary kiln based on the above system, comprising the following steps: introducing low-temperature solid particles into the annular particle jacket flow channel between layers B and C through the high-end annular feeding chamber at the high end of the rotary kiln; allowing the solid particles to move towards the lower end along the particle flow channel under the guidance of the rotary kiln tilt angle, the segmented spiral guide assembly, and gravity, and absorbing heat from layer B during the movement; exporting the solid particles at the lower end through the low-end annular receiving chamber and conveying them to a stationary external heat exchange assembly outside the rotary kiln; exchanging heat between the solid particles and the working fluid in the stationary external heat exchange assembly to obtain steam and / or high-temperature hot water; re-conveying the cooled solid particles to the high-end annular feeding chamber through a particle circulation loop; adjusting the solid particle circulation rate according to the layer B temperature and / or the inlet and outlet temperatures of the solid particles to maintain the layer B temperature within a preset range.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects: First, the present invention uses a solid particle moving bed medium in the rotating recovery section, which eliminates the need to establish a long-distance pressurized fluid dynamic sealed heat exchange chamber, thereby reducing the risks of leakage, pressure drop and phase change instability, and making it more suitable for long-term industrial operation.

[0023] Second, compared with gaseous media recovery schemes, solid particles typically have higher volumetric heat capacity and sensible heat carrying capacity, which is beneficial for obtaining higher particle outlet temperatures and higher quality available heat sources under the same B-layer temperature control conditions.

[0024] Third, compared with liquid medium recovery schemes, this invention avoids directly handling the flow of pressurized liquid and the control of vapor-liquid phase change in the rotating jacket, which is beneficial to achieving stable high-temperature heat removal with lower dynamic sealing risk.

[0025] Fourth, the high-end annular feeding chamber, the low-end annular receiving chamber, and the static external heat exchange components enable high-temperature particles to exchange heat stably outside the rotary kiln, facilitating the production of steam or high-temperature hot water.

[0026] Fifth, the separate arrangement of discrete support components and segmented spiral flow guide components helps to reduce thermal bridges caused by continuous large-area metal connections.

[0027] Sixth, the D layer reduces heat leakage from the C layer to the environment with a lower added weight and lowers the external surface temperature. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall system structure of the present invention.

[0029] Figure 2 This is a schematic diagram of the radial cross-section of the middle part of the rotary kiln of the present invention.

[0030] Figure 3 This is a schematic diagram of the flow guiding component and connection node of the present invention.

[0031] In the diagram: 1. Rotary kiln body; 11. Layer A; 12. Layer B; 13. Layer C; 14. Layer D; 2. Annular particle jacket flow channel; 21. Particle flow channel; 22. Segmented spiral guide assembly; 23. Ear seat; 24. Transition weld connection; 25. Discrete support component; 3. High-end annular feeding chamber; 31. High-end labyrinth seal structure; 4. Low-end annular receiving chamber; 41. Low-end labyrinth seal structure; 5. Particle circulation loop; 51. Lifting equipment; 52. Return material conveying equipment; 53. Buffer silo; 6. Static external heat exchange assembly; 61. Particle-water heat exchanger; 62. Steam generation assembly; 7. Control assembly. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings. It should be understood that the following embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention.

[0033] like Figure 1 and Figure 2 As shown, the rotary kiln body 1 is an inclined rotary kiln. From the inside out, the rotary kiln body 1 includes layer A 11 and layer B 12. Layer A 11 is the hot surface layer in contact with the raw materials in a traditional refractory brick or insulating brick layer, and layer B 12 is the original outer steel shell layer of the rotary kiln. A layer C 13, coaxial with the rotary kiln body 1, is disposed outside layer B 12. Layer C 13 is connected to the rotary kiln body 1 via a connecting structure and rotates synchronously with the rotary kiln body 1.

[0034] Layer C 13 is connected to the rotary kiln body 1 via discrete support members 25 spaced circumferentially. In this embodiment, the discrete support members 25 are separately arranged from the segmented spiral flow guide assembly 22, thereby reducing thermal bridges caused by continuous large-area metal connections. An annular gap is left between layer B 12 and layer C 13, which forms an annular particle jacket flow channel 2. The radial thickness of the annular particle jacket flow channel 2 is preferably 20~80mm, more preferably 35~50mm, and in one embodiment 40mm.

[0035] Multiple segmented spiral guide components 22 are arranged within the annular particle jacket flow channel 2. These segmented spiral guide components 22 are spaced apart circumferentially to divide the annular particle jacket flow channel 2 into multiple particle flow channels 21. The length of a single segment of each segmented spiral guide component 22 is preferably 300~1500mm, more preferably 600~1000mm, the thickness is preferably 0.8~3.0mm, and the axial guide angle relative to the rotary kiln axis is preferably 5°~45°. An overlapping section and a thermal expansion release gap are preferably provided between adjacent segments.

[0036] like Figure 3 As shown, the segmented spiral flow guide assembly 22 is connected to layer B 12 and / or layer C 13 via lug 23. Lug 23 is preferably a 20# carbon steel lug, and the segmented spiral flow guide assembly 22 is preferably a 304 stainless steel sheet component. A transition weld connection 24 is provided between lug 23 and the segmented spiral flow guide assembly 22, and the transition weld connection 24 can be formed using 309L or 312 welding material.

[0037] The system uses solid particles as the heat transfer medium in the rotating recovery section. The solid particles are preferably high-alumina ceramic spheres, corundum particles, mullite particles, sintered bauxite particles, or other high-temperature resistant ceramic particles. The particle size is preferably 1-10 mm, more preferably 2-6 mm, and in one embodiment, 3-4 mm. The particle filling rate in the particle flow channel 21 is preferably 0.30-0.75, more preferably 0.40-0.60.

[0038] The rotary kiln body 1 has a high-end annular feeding chamber 3 at its high end and a low-end annular receiving chamber 4 at its low end. The high-end annular feeding chamber 3 is used to guide low-temperature solid particles from the particle circulation loop 5 into each particle flow channel 21; the low-end annular receiving chamber 4 is used to discharge high-temperature solid particles after heat absorption from each particle flow channel 21. The high-end annular feeding chamber 3 is equipped with a high-end labyrinth seal structure 31, and the low-end annular receiving chamber 4 is equipped with a low-end labyrinth seal structure 41.

[0039] In this invention, the movement of particles in the particle flow channel 21 is not a simple free fall, but rather a net axial displacement from the high end to the low end, formed by the combined effects of the rotary kiln tilt angle, the axial guiding effect of the segmented spiral flow guide assembly 22, and the gravity of the particles. As the C layer 13 rotates synchronously with the rotary kiln body 1, the particles undergo follow-up motion, rolling, and partial tumbling in the circumferential direction; the segmented spiral flow guide assembly 22 converts part of the circumferential motion into axial guiding motion, thereby enabling the particles to form a stable axially downward moving bed under continuous rotation conditions.

[0040] High-temperature solid particles discharged from the lower end enter the particle circulation loop 5. The particle circulation loop 5 includes a lifting device 51, a return conveying device 52, and a buffer hopper 53. The lifting device 51 can be a bucket elevator, and the return conveying device 52 can be a screw conveyor or a scraper conveyor. The high-temperature solid particles are fed into the stationary external heat exchange assembly 6 located outside the rotary kiln, where they exchange heat with the working fluid before returning to the upper-end annular distribution chamber 3, forming a closed loop.

[0041] The static external heat exchange assembly 6 includes a particle-water heat exchanger 61 and a steam generation assembly 62. The particle-water heat exchanger 61 transfers the sensible heat carried by the solid particles to the feed water, and the steam generation assembly 62 converts the heated working fluid into steam. In other embodiments, the static external heat exchange assembly 6 may also output only high-temperature hot water.

[0042] A layer D 14 is disposed outside layer C 13. Layer D 14 includes at least a reflective layer near layer C 13, an insulating layer disposed outside the reflective layer, and a protective layer disposed outside the insulating layer. Preferably, the reflective layer is an aluminum foil layer, the insulating layer is an aerogel insulating felt layer, and the protective layer is an aluminum protective plate layer. The thickness of the insulating layer is preferably 5~50mm, more preferably 15~35mm.

[0043] Control component 7 is used to adjust the solid particle circulation rate based on temperature parameters. Preferably, control component 7 uses the temperature of layer B 12 as the primary controlled variable. When the temperature of layer B 12 is higher than the target value, the solid particle circulation rate is increased; when the temperature of layer B 12 is lower than the target value, the solid particle circulation rate is decreased. Control component 7 can also be used in conjunction with parameters such as solid particle inlet and outlet temperatures, steam pressure, and steam flow rate for coordinated control.

[0044] In one embodiment, the rotary kiln has an inclination angle of 10°, the annular particle jacket flow channel has a thickness of 40 mm, the segmented spiral guide assembly has a single segment length of 800 mm, the solid particles are high-alumina ceramic balls with a particle size of 3~4 mm, the particle circulation rate is about 25 kg / s, and the static external heat exchange assembly is used to generate low-pressure steam.

[0045] In comparison, if air is used as the direct heat exchange medium in the rotating section, a large volumetric airflow needs to be organized in the outer jacket. Due to the limitation of air volumetric heat capacity, the quality of the usable heat source extracted is usually low. If liquid is used as the direct heat exchange medium in the rotating section, the flow of pressurized liquid and dynamic sealing issues need to be addressed in the rotating jacket. This invention adopts a solid particle moving bed route, which is beneficial for achieving stable high-temperature sensible heat extraction with lower dynamic sealing risks.

[0046] The above embodiments are merely preferred embodiments of the present invention. Those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements should also be considered to fall within the protection scope of the present invention.

Claims

1. A rotary kiln outer annular particle jacket waste heat recovery system, comprising an inclined rotary kiln body, a particle circulation loop, an external heat exchange assembly, and a control assembly, characterized in that: The rotary kiln body includes at least layer A and layer B from the inside out, where layer A is the inner lining layer and layer B is the outer steel shell layer; The outer side of the B layer is provided with a C layer that is coaxial with the rotary kiln body and rotates synchronously with the rotary kiln body. The C layer is connected to the rotary kiln body through discrete support members that are spaced apart along the circumference. The B layer and the C layer form an annular particle jacket flow channel with a radial thickness of 20~80mm. The annular particle jacket flow channel is provided with a plurality of segmented spiral flow guiding components arranged at intervals along the circumference of the rotary kiln and extending along the axial direction of the rotary kiln, so as to divide the annular particle jacket flow channel into a plurality of particle flow channels, and the discrete support is separately provided from the segmented spiral flow guiding components. The system uses high-temperature resistant solid particles as the heat transfer medium; The rotary kiln is provided with a high-end annular feeding chamber that communicates with each particle flow channel at its high end, and the high-end annular feeding chamber is provided with a high-end labyrinth-type sealing structure; the rotary kiln is provided with a low-end annular receiving chamber that communicates with each particle flow channel at its low end, and the low-end annular receiving chamber is provided with a low-end labyrinth-type sealing structure. The solid particles undergo a net axial displacement from the high end to the low end under the guidance of the rotary kiln tilt angle, the segmented spiral flow guide assembly, and gravity, and absorb heat from layer B during their movement within the particle flow channel. The particle circulation loop includes at least a lifting device and a return conveying device, used to convey the high-temperature solid particles exported from the lower end to a stationary external heat exchange component located outside the rotary kiln, and to return the solid particles after heat exchange by the stationary external heat exchange component to the high-end annular feeding chamber. The control component is configured to adjust the solid particle circulation rate based on the B layer temperature and / or the solid particle inlet and outlet temperatures, so that the B layer temperature is maintained within a preset range.

2. The system according to claim 1, characterized in that, The radial thickness of the annular particle jacket flow channel is 35~50mm; and / or the running filling rate of the solid particles in the particle flow channel is 0.30~0.75, preferably 0.40~0.

60.

3. The system according to claim 1, characterized in that, The segmented spiral guide assembly has a single segment length of 300~1500mm, a thickness of 0.8~3.0mm, and an axial guide angle of 5°~45° relative to the rotary kiln axis.

4. The system according to claim 1 or 3, characterized in that, An overlap section and / or a thermal expansion release gap are provided between adjacent segmented spiral guide components.

5. The system according to claim 1, characterized in that, The segmented spiral guide assembly is connected to the B layer and / or C layer via an ear seat. The ear seat is made of carbon steel, and the segmented spiral guide assembly is made of stainless steel or heat-resistant steel. A dissimilar steel transition weld connection is provided between the ear seat and the segmented spiral guide assembly.

6. The system according to claim 5, characterized in that, The segmented spiral guide assembly is a 304 stainless steel sheet component, the lug is a 20# carbon steel lug, and the transition weld connection is formed using 309L welding material and / or 312 welding material.

7. The system according to claim 1, characterized in that, The solid particles are high-temperature resistant ceramic particles, which are selected from one or more of high-alumina ceramic balls, corundum particles, mullite particles, sintered bauxite particles, and silicon carbide particles, and the particle size of the solid particles is 1~10mm, preferably 2~6mm.

8. The system according to claim 1, characterized in that, The external heat exchange assembly includes a particle-water heat exchanger and a steam generation assembly. The steam generation assembly is used to convert the working fluid heated by the particle-water heat exchanger into steam; or, the external heat exchange assembly is used to output high-temperature hot water.

9. The system according to claim 1, characterized in that, A layer D is provided on the outside of layer C. Layer D includes at least a reflective layer, a heat insulation layer, and a protective layer. The reflective layer is disposed on the side close to layer C, the heat insulation layer is disposed on the outside of the reflective layer, and the protective layer is disposed on the outside of the heat insulation layer. Preferably, the reflective layer is an aluminum foil layer, the heat insulation layer is an aerogel heat insulation felt layer, and the protective layer is an aluminum protective plate layer.

10. A method for recovering waste heat from the outer annular particle jacket of a rotary kiln based on the system described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Low-temperature solid particles are introduced into the annular particle jacket flow channel between layer B and layer C through the high-end annular feeding cavity at the high end of the rotary kiln. S2. The solid particles are subjected to net axial displacement towards the lower end of the particle flow channel under the guidance of the rotary kiln tilt angle, the segmented spiral flow guide assembly and gravity, and absorb heat from layer B during the movement. S3. The solid particles are discharged from the lower end through the lower end annular receiving chamber and transported to the stationary external heat exchange assembly outside the rotary kiln. S4. In the static external heat exchange assembly, the solid particles are exchanged with the working fluid to obtain steam and / or high-temperature hot water; S5. The cooled solid particles are transported back to the high-end annular fabric chamber through the particle circulation loop. S6. Adjust the solid particle circulation rate according to the temperature of layer B and / or the inlet and outlet temperatures of solid particles to keep the temperature of layer B within the preset range.

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