A rotary kiln surface waste heat recycling device and utilization method thereof

Abstract

The present invention discloses a device for recycling waste heat on the surface of a rotary kiln, comprising a heat absorbing device, a plate air inlet, a fan and a burner; the heat absorbing device is used to recover waste heat at the baffle belt, and is symmetrically arranged on both sides of the baffle belt; the plate air inlet is used to recover waste heat on the surface of the rotary kiln, and can move to the highest temperature point on the surface of the rotary kiln; the heat absorbing device is connected to the fan through a fixed air duct, and the plate air inlet is connected to the fan through an adjustable air duct; the fan is connected to the burner; the heat absorbing device comprises a flow guide, a heat pipe flow guide and a baffle, the flow guide is used to guide the hot air in the tangential direction of the rotary kiln into the heat absorbing device, the heat pipe flow guide is used to absorb the radiant heat from the surface of the rotary kiln and heat the passing air, and the baffle is provided with barbs that can block the entry of low-temperature air. The present invention also discloses a method for recycling waste heat on the surface of a rotary kiln. The present invention has a simple structure, is easy to install and maintain, has a low cost, has a high waste heat utilization rate, and is suitable for popularization and application.

Description

Technical Field

[0001] The invention relates to a waste heat utilization device and method, in particular to a rotary kiln surface waste heat recycling device and a utilization method thereof. Background Art

[0002] For the dry second-generation cement production line, the temperature of the rotary kiln cylinder is generally 200℃~350℃, and the heat dissipation on the cylinder surface accounts for about 3%~4% of the burning heat consumption. The area between the kiln head and the second belt of the rotary kiln is in the high-temperature area of ​​the rotary kiln, and the surface temperature of the cylinder is relatively high. The gap between the rotary kiln belt and the rotary kiln cylinder is strictly required, and it needs to be cooled to prevent local overheating and damage to mechanical parts. At present, most cement plants generally use centrifugal fans to cool the gap between the belt and the rotary kiln cylinder, and the heat is directly discharged into the environment, causing heat loss. In addition, for the waste heat on the surface of the rotary kiln cylinder, some cement production lines use a heat collection system to collect it for domestic water or waste heat power generation. Due to its large structure, low heat utilization rate, and difficulty in recovery, it has not yet been fully popularized.

[0003] The theoretical air required for normal combustion of the kiln head burner comes from high-temperature secondary air and normal-temperature primary air. The primary air comes from the natural environment and has a low temperature. The amount of air used is about 7% to 10% of the theoretical air required for kiln head coal combustion. If the residual heat on the surface of the rotary kiln cylinder is used to increase the primary air temperature, it will not only be beneficial to the full combustion of kiln head coal, reduce the heat consumption of burning, save fuel resources, and reduce operating costs, but also improve energy utilization and help reduce carbon emissions.

[0004] Heat pipe is a kind of high-efficiency heat transfer element. Under different temperature difference conditions, it uses the evaporation heat absorption and condensation heat release of the working fluid in the pipe to achieve heat transfer without the need for additional power. Heat pipe has high thermal conductivity, excellent isothermal, constant temperature characteristics, environmental adaptability and other characteristics, and is widely used in aerospace, chemical industry, electronics, metallurgy, power and many other fields.

[0005] At present, some cement production lines use heat collection systems to recover waste heat from the surface of the rotary kiln cylinder for domestic water or waste heat power generation. The heat collection system mainly installs an arc-shaped heat collection cover on the rotary kiln cylinder, and uses water as the working medium. The circulating water pump sends it to the heat collection cover. The hot water from the heat collection cover is first exchanged with the kiln head boiler feed water to improve the thermal efficiency of the waste heat power generation system, and then exchanged with tap water for bathing in the bathhouse. Finally, a booster pump is added to provide heating for the production office area in winter, and the cooled water is returned to the circulating water tank. However, the heat collection system is used to recover the waste heat from the surface of the rotary kiln cylinder. The heat collection system has a large structure, a large footprint, and a high cost. The heat collection system is a static device and is installed in the air, while the rotary kiln is a rotating device, which is inconvenient to install and maintain. The recovered heat is reused after multiple heat exchanges, resulting in a low waste heat utilization rate. Summary of the invention

[0006] Purpose of the invention: In order to overcome the deficiencies in the prior art, the purpose of the present invention is to provide a waste heat recycling device with simple structure, low cost and high utilization rate. Another purpose of the present invention is to provide a method for utilizing waste heat on the surface of a rotary kiln with stable temperature and high heat transfer efficiency.

[0007] Technical solution: A rotary kiln surface waste heat recycling device described in the present invention includes a heat absorption device, a plate air inlet, a fan and a burner; the heat absorption device is used to recover the waste heat at the baffle belt and is symmetrically arranged on both sides of the baffle belt; the plate air inlet is used to recover the waste heat on the rotary kiln surface and can move to the highest temperature point on the rotary kiln surface; the heat absorption device is connected to the fan through a fixed air duct, and the plate air inlet is connected to the fixed air duct through an adjustable air duct; the fan is connected to the burner; the heat absorption device includes a guide, a heat pipe guide and a baffle, the guide is used to guide the hot air in the tangential direction of the rotary kiln into the heat absorption device, the heat pipe guide is used to absorb the radiant heat from the rotary kiln surface and heat the passing air, and the baffle is provided with barbs that can block the entry of low-temperature air to ensure the temperature of the air inlet.

[0008] Furthermore, the heat pipe deflector includes an air channel, a working fluid cavity and a liquid wick, the inside of the liquid wick is the air channel, and the outside is the working fluid cavity. The air channel is circular, equilateral triangle, square or regular hexagonal. The working fluid cavity is an interconnected enclosed space filled with water working fluid with a filling rate of 50%. The heat pipe deflector is a honeycomb type heat pipe deflector, which can store heat, ensure the temperature of the primary air is stable, and has a higher heat transfer efficiency. After the air blown out by the cooling fan passes through the rotary kiln for heat exchange, the speed direction of the hot air is different, which will generate vortexes and cause kinetic energy loss. The air channel can guide the air into the fixed air duct to avoid air vortexes and reduce kinetic energy loss.

[0009] Furthermore, a valve capable of preventing hot air from generating vortex is arranged on the flow diverter, and the flow diverter has a one-way guiding property. The flow diverter is an arc-shaped flow diverter.

[0010] Furthermore, a temperature sensor is arranged on the fixed air duct. The relationship between the distance between the plate air inlet and the outer surface of the rotary kiln and the temperature measured by the temperature sensor is as follows: when the area A of the plate air inlet remains unchanged, the larger the distance d from the outer surface of the rotary kiln, the larger the radiation area A of the rotary kiln. fThe larger the value, the less radiant heat absorbed by the plate air inlet, the less heat absorbed by the air in the tube, and the lower the temperature. The plate air inlet is a polygonal channel, and the distance from the outer surface of the rotary kiln is 50mm to 100mm. A honeycomb heat pipe deflector is arranged in the plate air inlet, which also includes an air channel, a working fluid cavity, and a liquid absorption core. The cross-sectional area and height of its air channel are large, and the size of the plate air inlet close to the rotary kiln is large, which is conducive to absorbing more radiant heat, and then heating the inlet air in the form of convection. There is a certain distance between the upper surface of the honeycomb deflector and the top surface of the plate air inlet, which is conducive to the convergence of air from different channels of the honeycomb heat pipe deflector and entering the pipeline.

[0011] Furthermore, the distance between the heat absorbing device and the outer surface of the rotary kiln and the retaining wheel belt is 80 mm to 150 mm. The setting of this distance is related to the deformation of the rotary kiln, the primary air volume, the primary air temperature, the heat transfer efficiency, the resistance of the pipeline, the wind speed of the air and other factors, and is optimized based on multiple cement production lines and theoretical knowledge.

[0012] Furthermore, the outer surfaces of the heat absorbing device, the fixed air duct and the adjustable air duct are all provided with a thermal insulation layer.

[0013] Furthermore, the surfaces of the guider and the heat pipe guider are coated with black light-absorbing material, and the radiated light is reflected multiple times, and its light-absorbing performance is close to that of a black body, and the absorbed radiant heat heats the inlet air in the form of convection.

[0014] Furthermore, the lower end baffle of the baffle is always vertically downward, and the upper end height does not exceed the height of the heat pipe deflector, which is conducive to air collection.

[0015] The method for utilizing waste heat by the above-mentioned rotary kiln surface waste heat recycling device comprises the following steps:

[0016] Step 1: The temperature of the baffle belt of the rotary kiln is 300-350°C, the baffle belt is connected to the cooling fan, and the hot air enters the fixed air duct along the heat absorption device;

[0017] Step 2: Measure the point with the highest temperature in the rotary kiln, move the plate air inlet to this position, and let the hot air enter the adjustable air duct along the plate air inlet and merge into the fixed air duct; in this way, the temperature inside the rotary kiln can also be controlled at 1300-1450°C, which is beneficial to the formation of the kiln skin on the inner surface of the rotary kiln, prolong the service life of the refractory bricks, reduce the deformation of the rotary kiln, and reduce the temperature of the outer surface of the rotary kiln, which is beneficial to the stable and safe operation of the cement production line;

[0018] Step three, the temperature in the fixed air duct is measured by a temperature sensor, and then the adjustable air duct is adjusted according to the temperature, and the distance between the plate air inlet and the rotary kiln is changed so that the temperature of the hot air at the fan is 150-200°C before entering the burner.

[0019] Working principle: After the air and the rotary kiln transfer heat by convection, they enter the heat absorber and the plate air inlet respectively. Under the action of the guide and baffle, the kinetic energy loss of the air is reduced and the entry of low-temperature air in the environment is blocked; and under the action of the heat pipe guide, the radiant heat on the surface of the rotary kiln is absorbed and stored, and the passing air is heated at a constant temperature to ensure the stability of the inlet air temperature. At the same time, the air temperature in the pipe is measured by the temperature sensor, and the distance between the plate air inlet and the rotary kiln is adjusted to ensure that the temperature of the air in the pipe is stable at 150-200℃. The metal barbs make the passage between the tube shell and the baffle tortuous, which can prevent low-temperature air from entering the fixed air duct and ensure the temperature of the air inlet of the heat absorber. The valve guides the hot air in one direction, reduces the vortex, and reduces the kinetic energy loss of the hot air at the guide. The heated air enters the burner under the action of the fan, and is used as the primary air to provide fuel combustion. The recovered waste heat is directly returned to the cement production system, which improves the thermal efficiency of the system and is conducive to carbon emission reduction.

[0020] Beneficial effects: Compared with the prior art, the present invention has the following significant features:

[0021] 1. Simple structure, easy installation and maintenance, low cost, high waste heat utilization rate of more than 95%, suitable for promotion and application;

[0022] 2. The air exchanged with the rotary kiln is used as primary air, which reduces indirect heat exchange, effectively improves the waste heat recovery efficiency, helps to fully burn the pulverized coal at the kiln head, reduces the amount of pulverized coal, reduces the heat consumption of the firing system, reduces the thermal pollution to the environment, and is conducive to carbon emission reduction;

[0023] 3. The axial cooling fan on the surface of the rotary kiln can be eliminated or reduced, which helps to reduce the comprehensive power consumption of cement clinker. At the same time, the device evenly recovers the waste heat on the surface of the rotary kiln, which helps to form a stable kiln skin in the rotary kiln, and promotes the stabilization of the kiln condition and production operation.

[0024] 4. The arc-shaped flow guide and baffle are set to effectively ensure that hot air enters the heat absorption device, reduce the entry of low-temperature air in the environment, and improve the waste heat efficiency;

[0025] 5. The honeycomb heat pipe deflector is set, which not only plays the role of guiding and reducing resistance, but also the black light-absorbing material is set in the lower part of the honeycomb structure. The radiation light on the surface of the rotary kiln is reflected multiple times on the wall of the honeycomb channel. Its light absorption performance is close to that of a black body, and the absorbed radiation heat heats the inlet air in the form of convection;

[0026] 6. It has high heat transfer efficiency and excellent isothermal characteristics, ensuring that the temperature of the burner's inlet air is stable within a certain range. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1It is a schematic diagram of the structure of the present invention;

[0028] Figure 2 It is a schematic structural diagram of the heat absorption device 1 of the present invention;

[0029] Figure 3 is a view of the heat absorbing device 1 of the present invention taken along the direction of A;

[0030] Figure 4 is a B-direction view of the heat absorbing device 1 of the present invention;

[0031] Figure 5 It is a schematic structural diagram of the flow diverter 11 of the present invention;

[0032] Figure 6 1 is a schematic structural diagram of the baffle 13 of the present invention;

[0033] Figure 7 is a schematic structural diagram of the heat pipe deflector 12 of the present invention;

[0034] Figure 8 It is a partial enlarged view of the C portion of the present invention;

[0035] Fig. 9 It is a DD-plane cross-sectional view of the present invention;

[0036] Fig.10 It is a partial enlarged view of E of the present invention;

[0037] Fig.11 It is a partial enlarged view of the plate-type air inlet 2 of the present invention;

[0038] Fig.12 It is a view of the plate-type air inlet 2 of the present invention taken along the direction F. DETAILED DESCRIPTION

[0039] like Figure 1There are multiple groups of baffle belts 5 on the rotary kiln 6, and the baffle belts 5 are connected to the cooling fan 10. The air blown out by the cooling fan 10 passes through the rotary kiln 6 for heat exchange, that is, after cooling the baffle belts 5, the cooled hot air is blown to the heat absorbing device 1 inclined on both sides of the baffle belts 5, and the heat absorbing device 1 is fixedly connected to the fixed air duct 7. The plate-type air inlet 2 is close to the surface of the rotary kiln 6 between the baffle belts 5, and is fixedly connected to the adjustable air duct 8, and the adjustable air duct 8 is also fixedly connected to the fixed air duct 7. The adjustable air duct 8 can be moved to the point with the highest temperature on the surface of the rotary kiln 6 according to the needs of use, and take away part of the heat, so as to form the kiln skin on the inner surface of the rotary kiln 6, extend the service life of the refractory bricks, reduce the deformation of the rotary kiln, and reduce the temperature of the outer surface of the rotary kiln, which is conducive to the stable and safe operation of the cement production line. The fixed air duct 7 is provided with a temperature sensor 9 for detecting the temperature inside the duct. The relationship between the distance between the plate air inlet 2 and the outer surface of the rotary kiln 6 and the temperature measured by the temperature sensor 9 is as follows: when the area A of the plate air inlet 2 remains unchanged, the larger the distance d from the outer surface of the rotary kiln 6, the larger the radiation area A of the rotary kiln 6. f The larger the value, the smaller the radiation heat absorbed by the plate air inlet 2, the smaller the heat absorption of the air in the tube, and the lower the temperature. The fixed air duct 7 is connected to the fan 3, and the temperature is reduced to below 200°C before entering the burner 4 to participate in the combustion of coal powder. The outer surfaces of the heat absorption device 1, the fixed air duct 7, and the adjustable air duct 8 are all provided with a heat preservation layer.

[0040] The adjustable air duct 8 is made of a metal hose, and a heat-insulating material is arranged on the outer surface for heat preservation. The positions of the plate-type air inlet 2 and the rotary kiln 6 are changed by moving the adjustable air duct 8. After the position of the plate-type air inlet 2 is determined, the fixed element can be maintained. The fixed air duct 7 is a round tube made of metal, and a heat-insulating material is arranged on the outer surface for heat preservation.

[0041] According to the output of the cement production line, the size of the rotary kiln 6, the cooling air volume of the belt 5, and the air volume output by the fan 3 are obtained, and 50% to 80% of the cooling air volume is selected. Considering that the cooling air volume flows into the environment and that the low-temperature air in the environment is not allowed to enter, the specific value can be adjusted according to production. As the air intake of the heat absorber 1, the required air volume (the air volume output by the fan 3 minus the air volume of the heat absorber 1) is used as the air volume of the plate air inlet 2, so that the temperature of the air output by the fan 3 can be effectively guaranteed.

[0042] like Figures 2 to 4The heat absorbing device 1 includes a flow guide 11, a heat pipe flow guide 12 and a baffle 13. The arc-shaped flow guide 11 is used to guide the hot air in the tangential direction of the rotary kiln 6 into the heat absorbing device 1, and the honeycomb heat pipe flow guide 12 is used to absorb the air heated by the radiant heat on the surface of the rotary kiln 6 and guide the hot air into the pipe. The baffle 13 is provided with barbs 14 that can block the entry of low-temperature air to ensure the temperature of the air inlet of the heat absorbing device 1. The shell of the heat absorbing device 1 changes according to the size of the rotary kiln 6 and the baffle belt 5. The distance between the heat absorbing device 1 and the outer surface of the rotary kiln 6 and the baffle belt 5 is 80mm to 150mm. The specific distance can be adjusted according to production to ensure that the air inlet of the heat absorbing device 1 does not collide with the rotary kiln 6. The setting of this distance is related to the deformation of the rotary kiln 6, the primary air volume, the primary air temperature, the heat transfer efficiency, the resistance of the pipeline, the wind speed of the air and other factors, and is optimized based on multiple cement production lines and theoretical knowledge. The shell of the heat absorbing device 1 is made of metal material and is provided with heat-insulating material for heat preservation.

[0043] like Figure 5 The arc-shaped flow guide 11 is made of metal material, and the surface is coated with black light-absorbing material. It absorbs the radiant heat from the surface of the rotary kiln 6 cylinder, and then heats the inlet air in the form of convection. The arc of the flow guide 11 is tangent to the surface of the rotary kiln 6. Its main function is to guide the hot air in the tangential direction of the rotary kiln 6 into the new air inlet, reduce the flow of hot air into the environment, and reduce the kinetic energy loss. Multiple flow guides 11 are parallel to each other and welded with valves 15 made of metal materials. The valve 15 adopts an eight-shaped structure, and the diameter gradually decreases along the direction of air flow, which is equivalent to a small nozzle. When the airflow passes through the valve 15, it can play a role in speeding up. Its main function is to guide the hot air in one direction, reduce eddy currents, and reduce the kinetic energy loss of the hot air. The number of flow guides 11 can be adjusted according to production.

[0044] like Figure 6 The baffle 13 is made of metal material. The lower end of the baffle 13 is always vertically downward, and the upper end height does not exceed the height of the heat pipe deflector 12, which is conducive to air collection. Metal barbs 14 are staggered between the baffle 13, the tube shell and the baffle 13. The metal barbs 14 can be a rough curved structure, so that the channel between the tube shell and the baffle 13 becomes tortuous, ensuring that the pressure of the heat absorber 1 and the environment is relatively stable, and at the same time, it can prevent low-temperature air from entering the fixed air duct 7, ensuring the temperature of the air inlet of the heat absorber 1.

[0045] like Figures 7-10The heat pipe guide 12 includes an air channel 121, a working fluid cavity 122 and a liquid wick 123. The inner side of the liquid wick 123 is the air channel 121, and the outer side is the working fluid cavity 122. The air channel 121 is circular, equilateral triangle, square or regular hexagonal. The shape of the working fluid cavity 122 is determined according to the air channel 121. The working fluid cavity 122 is an interconnected enclosed space filled with a water working fluid with a filling rate of 50%. The liquid wick 123 is tightly attached to the inner wall of the working fluid cavity 122. The heat pipe guide 12 is a honeycomb heat pipe guide 12, which is made of copper metal material. It can store heat, ensure the temperature of the primary air is stable, and have higher heat transfer efficiency. Due to the different speed directions of the hot air, eddy currents will be generated, resulting in kinetic energy loss. The air channel 121 can guide the air into the fixed air duct 7 to avoid eddy currents in the air and reduce kinetic energy loss. The lower part of the honeycomb heat pipe deflector 12 is provided with a black light-absorbing material. The radiation light on the surface of the rotary kiln 6 is reflected multiple times on the wall of the honeycomb channel. Its light-absorbing performance is close to that of a black body. The absorbed radiation heat heats the inlet air in the form of convection. The part of the black light-absorbing material is equivalent to the evaporation section of the heat pipe, and the upper end is equivalent to the condensation section of the heat pipe. In the evaporation section, the water medium in the pipe absorbs the radiation heat on the surface of the rotary kiln 6 and evaporates and vaporizes, moving upward. In the condensation section, the water vapor in the pipe exchanges heat with the air outside the pipe by convection. The condensed water medium is transferred to the evaporation section through the liquid absorption core 123 to complete the heat transfer. The honeycomb heat pipe deflector 12 can store heat, ensure the temperature of the primary air is stable, and have a higher heat transfer efficiency.

[0046] like Figures 11-12 The plate air inlet 2 is a polygonal channel. The outer shell changes according to the size of the rotary kiln 6, but always ensures that the distance from the outer surface of the rotary kiln 6 is 50mm to 100mm. The specific distance can be adjusted according to production to ensure that the plate air inlet 2 does not collide with the rotary kiln 6. The outer shell is made of metal material, and thermal insulation material is provided for heat preservation. A honeycomb-type heat pipe deflector 12 is provided in the plate air inlet 2, which also includes an air channel 121, a working medium cavity 122, and a liquid wick 123. The cross-sectional area and height of its air channel 121 are large, and the size of the plate air inlet 2 close to the rotary kiln 6 is large, which is conducive to absorbing more radiant heat, and then heating the inlet air in the form of convection. The upper surface of the honeycomb deflector is at a certain distance from the top surface of the plate air inlet 2, which is conducive to the convergence of air from different channels of the honeycomb heat pipe deflector 12 and entering the pipeline.

[0047] The method for utilizing the above-mentioned rotary kiln surface waste heat recycling device comprises the following steps:

[0048] Step 1: The temperature at the baffle belt 5 of the rotary kiln 6 is generally 300-350°C, the baffle belt 5 is connected to the cooling fan 10, and the hot air enters the fixed air duct 7 along the heat absorption device 1;

[0049] Step 2: Measure the point with the highest temperature in the rotary kiln 6, move the plate-type air inlet 2 to this position, and let the hot air enter the adjustable air duct 8 along the plate-type air inlet 2 and merge into the fixed air duct 7;

[0050] Step 3: The temperature in the fixed air duct 7 is measured by the temperature sensor 9, and then the adjustable air duct 8 is adjusted according to the temperature, and the distance between the plate air inlet 2 and the rotary kiln 6 is changed, so that the temperature of the hot air at the fan 3 is 150-200°C, and then enters the burner 4. The waste heat utilization rate is high, reaching more than 95%.

Claims

1. A device for recycling waste heat from the surface of a rotary kiln, characterized in that: The invention comprises a heat absorbing device (1), a plate-type air inlet (2), a fan (3) and a burner (4); the heat absorbing device (1) is used to recover waste heat at the retaining wheel belt (5) and is symmetrically arranged on both sides of the retaining wheel belt (5); the plate-type air inlet (2) is used to recover waste heat from the surface of the rotary kiln (6) and can be moved to the highest temperature point on the surface of the rotary kiln (6); the heat absorbing device (1) is connected to the fan (3) via a fixed air duct (7), and the plate-type air inlet (2) is connected to the fixed air duct (7) via an adjustable air duct (8); the fan ( 3) connected to the burner (4); the heat absorbing device (1) comprises a flow guide (11), a heat pipe flow guide (12) and a baffle (13); the flow guide (11) is used to guide hot air in a tangential direction of the rotary kiln (6) into the heat absorbing device (1); the heat pipe flow guide (12) is used to absorb radiant heat from the surface of the rotary kiln (6) and heat the passing air; the baffle (12) is provided with barbs (14) capable of blocking the entry of low-temperature air; a honeycomb-shaped heat pipe flow guide (12) is provided in the plate-type air inlet (2); The heat pipe guide (12) comprises an air channel (121), a working fluid cavity (122) and a liquid wick (123); the inside of the liquid wick (123) is the air channel (121), and the outside of the liquid wick (123) is the working fluid cavity (122).

2. The rotary kiln surface waste heat recycling device according to claim 1, characterized in that: The air channel (121) is in the shape of a circle, a regular triangle, a square or a regular hexagon.

3. The rotary kiln surface waste heat recycling device according to claim 1, characterized in that: The working medium cavity (122) is a communicating closed space filled with water working medium with a filling rate of 50%.

4. The rotary kiln surface waste heat recycling device according to claim 1, characterized in that: The flow guider (11) is provided with a valve (15) capable of preventing hot air from generating vortices.

5. The rotary kiln surface waste heat recycling device according to claim 1, characterized in that: A temperature sensor (9) is provided on the fixed air duct (7).

6. The rotary kiln surface waste heat recycling device according to claim 1, characterized in that: The distance between the heat absorbing device (1) and the outer surface of the rotary kiln (6) and the retaining wheel belt (5) is 80 mm to 150 mm.

7. The rotary kiln surface waste heat recycling device according to claim 1, characterized in that: The outer surfaces of the heat absorbing device (1), the fixed air duct (7), and the adjustable air duct (8) are all provided with a thermal insulation layer.

8. The device for recycling waste heat from the surface of a rotary kiln according to claim 1, characterized in that: The surfaces of the flow guide (11) and the heat pipe flow guide (12) are both coated with black light-absorbing material.

9. A method for utilizing waste heat from a rotary kiln surface waste heat recycling device according to any one of claims 1 to 8, characterized in that: The following steps are involved: Step 1: The temperature at the baffle belt (5) of the rotary kiln (6) is 300-350° C., the baffle belt (5) is connected to the cooling fan (10), and the hot air enters the fixed air duct (7) along the heat absorption device (1); Step 2: Measure the point with the highest temperature in the rotary kiln (6), move the plate-type air inlet (2) to this position, and let the hot air enter the adjustable air duct (8) along the plate-type air inlet (2) and then flow into the fixed air duct (7); Step three, the temperature in the fixed air duct (7) is measured by the temperature sensor (9), and then the adjustable air duct (8) is adjusted according to the temperature, and the distance between the plate air inlet (2) and the rotary kiln (6) is changed so that the temperature of the hot air at the fan (3) is 150-200°C, and then enters the burner (4).

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