A heat recovery device for hot air exhaust at the kiln head

Abstract

This utility model provides a heat recovery device for exhaust hot air from a kiln head, including a grate cooler. The grate cooler contains a first-stage grate bed and a second-stage grate bed. A wind box is fixedly connected below the first-stage and second-stage grate beds. An air chamber is located inside the air box. Side pipes of the air chamber are connected to the outlets of a first, second, third, fourth, and fifth fan. The first, second, third, and fifth fans are connected to a circulating air duct assembly. This utility model, by connecting the exhaust fan chimney of the rotary kiln head to the fans of the grate cooler via the circulating air duct assembly, increases the initial temperature of the cooling air. This, in turn, increases the inlet flue gas temperature entering the AQC furnace after heat exchange in the grate cooler, thereby increasing the main steam temperature of the AQC furnace. This improves the operational stability of the waste heat generator unit, increases the usable calorific value of the AQC furnace, reduces the coal input required to maintain steam parameters, and saves costs while reducing energy consumption.

Description

Technical Field

[0001] This utility model relates to the field of cement clinker cooling heat recovery technology, specifically a kiln head exhaust hot air heat recovery device. Background Technology

[0002] The grate cooler is a crucial piece of equipment in the cement clinker calcination system. Its main function is to rapidly cool the high-temperature clinker discharged from the rotary kiln, while simultaneously recovering the heat carried by the clinker to improve the system's thermal efficiency. In the cement production process, the grate cooler propels the clinker forward through the reciprocating motion of the grate bed. Simultaneously, a fan delivers cooling air into the air box and air chamber, penetrating the clinker layer to achieve heat exchange. The cooled clinker temperature can be reduced to below 100℃, while the heat-absorbing air is introduced into equipment such as the AQC furnace (grate cooler waste heat boiler) for power generation or heating, making it a key link in achieving waste heat recovery.

[0003] In current cement production kiln systems, the inlet flue gas temperature of the AQC boiler is normally only 320-360℃, and fluctuates significantly due to cost reduction, coal consumption reduction, electricity consumption reduction and the addition of the SCR system. It is often shut down due to unqualified steam quality caused by excessively low flue gas temperature. Especially after the addition of the SCR system at the kiln tail, the inlet flue gas temperature of the SP boiler drops to 295-310℃, and the steam temperature is only 270-295℃. This requires the use of high-temperature steam from the AQC boiler for neutralization. Otherwise, if the steam temperature is below 275℃, water will be carried in the steam, which will cause the turbine to shut down. The outlet temperature of the hot air discharged from the kiln head exhaust fan is about 85-90℃. This part of the hot air is directly discharged, and the waste heat is not effectively utilized, resulting in energy waste. Utility Model Content

[0004] The purpose of this invention is to provide a heat recovery device for the external exhaust air of a kiln to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, this utility model provides the following technical solution:

[0006] A heat recovery device for hot air exhaust at the kiln head includes:

[0007] The grate cooler has its inlet connected to the discharge pipe of the rotary kiln head. A return air pipe is connected to the top of the grate cooler and is connected to the AQC furnace pipe. The grate cooler contains a first-stage grate bed and a second-stage grate bed. The end of the second-stage grate bed extends to the discharge section of the grate cooler. A wind box is fixedly connected below the first-stage and second-stage grate beds. An air chamber is located inside the wind box. A side pipe of the air chamber is connected to the air outlets of a first, second, third, fourth, and fifth fan. The first, second, third, and fifth fans are connected to a circulating air duct assembly for waste heat recovery and reuse.

[0008] Preferably, the circulating air duct assembly includes a main air duct, the air inlet of which is connected to the chimney of the kiln head exhaust fan of the rotary kiln, and a louvered valve is flanged between the main air duct and the chimney of the kiln head exhaust fan.

[0009] Preferably, when the main air duct approaches the grate cooler, it is divided into a left branch pipe and a right branch pipe by a tee pipe. The diameter of the main air duct is Φ3500, and the diameters of the left branch pipe and the right branch pipe are Φ2500.

[0010] Preferably, the left branch pipe is connected to the air inlet pipes of the first fan and the fifth fan, and an air inlet valve is flanged between the air inlet pipes of the first fan and the fifth fan and the left branch pipe, and a cold air valve is flanged on the air inlet pipes of the first fan and the fifth fan.

[0011] Preferably, the right branch pipe is connected to the air inlet pipes of the second and third fans, and an air inlet valve is flanged between the air inlet pipes of the second and third fans and the right branch pipe. A cold air valve is flanged on the air inlet pipes of the first and fifth fans.

[0012] Preferably, the air inlet of the fourth fan is in contact with the outside air, the air outlet of the fourth fan is located below the hydraulic cylinder and position detection switch of the grate bed, the air outlets of the first, second and third fans are located below the first section of the grate bed, and the air outlet of the fifth fan is located below the crushing roller at the end of the second section of the grate bed.

[0013] Preferably, the heat generated inside the grate cooler is directed to the AQC furnace through a return air duct.

[0014] Compared with the prior art, the beneficial effects of this utility model are:

[0015] This invention connects the rotary kiln head exhaust fan chimney to the grate cooler fan by setting up a circulating air duct assembly, and uses louvered valves to regulate the hot air volume, thereby increasing the initial temperature of the cooling air. This, in turn, increases the inlet flue gas temperature entering the AQC furnace after heat exchange in the grate cooler, thereby increasing the main steam temperature of the AQC furnace, improving the operational stability of the waste heat generator set, increasing the usable calorific value of the AQC furnace, reducing the coal input required to maintain steam parameters, saving costs and reducing energy consumption.

[0016] This invention improves the temperature of the hot air blown onto the grate by introducing hot air into the fans below the first and second grate beds of the grate cooler. This causes the temperatures of the secondary air (kiln head combustion air) and the tertiary air (decomposition furnace air) to rise simultaneously, thereby optimizing the combustion efficiency of the rotary kiln and the heat exchange efficiency of the decomposition furnace, and enhancing the thermal circulation of the kiln system.

[0017] This utility model divides the main air duct into left and right branches and equips them with air inlet valves and cold air valves. It can adjust the hot air volume and air temperature according to the different cooling requirements of the grate bed of the grate cooler to avoid uneven cooling. At the same time, by mixing room temperature air into the cold air valve, the inlet air temperature of the fan is controlled to be ≤100℃, thus protecting the safety of the equipment. Attached Figure Description

[0018] Figure 1 This is a three-dimensional schematic diagram of the overall structure of this utility model;

[0019] Figure 2 This is a top view of the grate cooler of this utility model;

[0020] Figure 3 This is a front view of the grate cooler of this utility model;

[0021] Figure 4 This is a schematic diagram showing the connection between the circulating air duct of the grate cooler, the kiln head exhaust duct, the fan, and the grate cooler of this utility model.

[0022] In the diagram: 1. Grate cooler; 101. First-stage grate bed; 102. Second-stage grate bed; 2. Air box; 3. Rotary kiln head discharge pipe; 4. Return air pipe; 5. Discharge section; 6. First fan; 7. Second fan; 8. Third fan; 9. Fourth fan; 10. Fifth fan; 11. Main air pipe; 12. Right branch pipe; 13. Left branch pipe; 14. Air inlet valve; 15. Cold air valve. Detailed Implementation

[0023] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0024] The grate cooler is a key cooling device in cement production. Installed at the outlet of the rotary kiln, it pushes high-temperature clinker through reciprocating grate plates while simultaneously blowing in cold air to rapidly cool it, causing the clinker temperature to drop below 100°C. Its core functions include: stabilizing clinker quality (preventing β-C2S crystal transformation), recovering waste heat, crushing large pieces of clinker and providing suitable particle size for subsequent conveying, making it an important link in the high-efficiency and energy-saving process of modern cement plants.

[0025] Example 1:

[0026] Please see Figures 1 to 3 This utility model provides a technical solution:

[0027] A heat recovery device for hot air exhaust at the kiln head, used to recover heat from a rotary kiln and increase the inlet flue gas temperature of the AQC furnace, comprising:

[0028] A grate cooler 1 is provided, with its inlet connected to the rotary kiln head discharge pipe 3. A return air pipe 4 is connected to the upper part of the grate cooler 1 and is connected to the AQC furnace pipe. The grate cooler 1 contains a first grate bed 101 and a second grate bed 102. The end of the second grate bed 102 extends to the discharge section 5 of the grate cooler 1. A wind box 2 is fixedly connected below the first grate bed 101 and the second grate bed 102. An air chamber is provided inside the wind box 2. The side pipes of the air chamber are connected to the air outlets of a first fan 6, a second fan 7, a third fan 8, a fourth fan 9, and a fifth fan 10. The first fan 6, the second fan 7, the third fan 8, and the fifth fan 10 are connected to a circulating air duct assembly for waste heat recovery and reuse.

[0029] Specifically, the AQC boiler (Air Quenching Cooler Boiler) is a key piece of equipment in cement production lines for recovering the high-temperature waste heat from the grate cooler. It converts the heat from the waste gas into steam (typically 0.8-2.5 MPa) through a heat exchange device for power generation or production heating. A typical structure includes a settling chamber, superheater, evaporator, and economizer, with an operating temperature range of 300-400℃.

[0030] Specifically, a rotary kiln is a large cylindrical high-temperature calcining device that uses the slow rotation and tilting of the cylinder to allow materials to undergo physical or chemical reactions at high temperatures (up to 1600℃). It is widely used in cement clinker calcination, metallurgical ore roasting, and hazardous waste treatment. It features high thermal efficiency and large processing capacity (up to 10,000 t / d). Its structure mainly includes the kiln cylinder, support belt, transmission device, and combustion system.

[0031] Specifically, the circulating air duct assembly includes a main air duct 11, the air inlet of which is connected to the chimney of the kiln head exhaust fan of the rotary kiln, and a louvered valve is flanged between the main air duct 11 and the chimney of the kiln head exhaust fan.

[0032] Specifically, when the main air duct 11 approaches the grate cooler 1, it is divided into a left branch duct 13 and a right branch duct 12 by a three-way pipe. The diameter of the main air duct 11 is Φ3500, and the diameters of the left branch duct 13 and the right branch duct 12 are Φ2500.

[0033] Specifically, the left branch pipe 13 is connected to the air inlet pipes of the first fan 6 and the fifth fan 10.

[0034] Specifically, the right branch pipe 12 is connected to the air inlet pipes of the second fan 7 and the third fan 8.

[0035] In this embodiment, the kiln head exhaust fan chimney of the rotary kiln is connected to the main air duct 11 flange via a louvered valve, which transports the hot air of about 80°C generated during the kiln production process along the main air duct 11. Near the grate cooler 1, it is divided into a left branch pipe 13 and a right branch pipe 12 through a three-way pipe. The left branch pipe 13 is connected to the first fan 6 and the fifth fan 10, and the right branch pipe 12 is connected to the second fan 7 and the third fan 8. After the fans are started, the hot air is pressurized by the impeller and blown evenly to the first grate bed 101 and the second grate bed 102 through the air chamber in the air box 2. When it penetrates the high-temperature clinker layer, it absorbs heat and reduces the clinker temperature.

[0036] After the cooling air exchanges heat with the high-temperature clinker through the first and second grate beds 102 of the grate cooler 1, it enters the AQC furnace for reuse through the return air duct 4. Compared with the existing technology, since the fan uses hot air introduced from the rotary kiln, the temperature of the hot air is about 60°C higher than the room temperature. The higher the initial temperature of the cooling air, the smaller the temperature difference with the high-temperature clinker, and the less heat loss of the clinker during heat exchange. More heat is retained in the cooling air. The high-temperature gas generated after heat exchange has a higher temperature than the high-temperature gas generated using room temperature, thereby increasing the flue gas temperature at the inlet of the AQC furnace. The higher the inlet flue gas temperature, the higher the temperature of the main steam generated by the AQC furnace, which can directly reduce the amount of coal required for heating, thereby reducing coal consumption and saving energy in the cement production process.

[0037] Specifically, the air inlet of the fourth fan 9 is in contact with the outside air, the air outlet of the fourth fan 9 is located below the hydraulic cylinder and position detection switch of the grate bed, the air outlets of the first fan 6, the second fan 7 and the third fan 8 are located below the first section grate bed 101, and the air outlet of the fifth fan 10 is located below the end crushing roller of the second section grate bed 102.

[0038] To ensure the safety of the hydraulic cylinder and position detection switch, the fourth fan 9 does not connect to hot air, but directly introduces ambient air (around 20℃). Because the hydraulic cylinder and position detection switch have poor temperature resistance (usually ≤60℃), if 80℃ hot air is connected, it will easily cause the hydraulic oil viscosity to decrease and the detection element to malfunction. Therefore, the fourth fan 9 supplies ambient air separately to avoid equipment failure caused by high temperature.

[0039] The outlet of the fifth blower 10 is located below the crushing roller at the end of the second-stage grate 102. After the clinker below the crushing roller is crushed, the size of the clinker is reduced and the surface area is increased, which will release more heat. The introduction of hot air by the fifth blower 10 can enhance the heat exchange efficiency of this area. When the hot air comes into contact with the crushed clinker, it can absorb heat more fully, so that the air temperature rises rapidly. Moreover, the location is close to the return air pipe 4 of the AQC furnace, and the rapidly heated cooling air can directly enter the return air pipe 4.

[0040] Specifically, the preferred fan is a common centrifugal fan on the market, with a wind pressure of 5000-10000Pa, which overcomes the resistance of the high-temperature clinker layer and ensures that the cooling air penetrates the material layer. The centrifugal fan drives the impeller to rotate through the motor, transmission belt, pulley and other connecting parts.

[0041] Specifically, the heat generated inside the grate cooler 1 is directed to the AQC furnace through the return air duct 4.

[0042] Example 2:

[0043] Please see Figure 4 This utility model provides a technical solution that is basically the same as that in Embodiment 1, with slight differences:

[0044] A heat recovery device for hot air exhaust at the kiln head, used to recover heat from a rotary kiln and increase the inlet flue gas temperature of the AQC furnace, comprising:

[0045] Specifically, the circulating air duct assembly includes a main air duct 11, the air inlet of which is connected to the chimney of the kiln head exhaust fan of the rotary kiln, and a louvered valve is flanged between the main air duct 11 and the chimney of the kiln head exhaust fan.

[0046] The louvered valve is installed between the chimney and the main air duct 11. It can control the amount of hot air in the main air duct 11 and can also cut off the source of hot air during system maintenance to ensure the safety of maintenance personnel.

[0047] Specifically, when the main air duct 11 approaches the grate cooler 1, it is divided into a left branch duct 13 and a right branch duct 12 by a three-way pipe. The diameter of the main air duct 11 is Φ3500, and the diameters of the left branch duct 13 and the right branch duct 12 are Φ2500.

[0048] Specifically, the left branch pipe 13 is connected to the air inlet pipes of the first fan 6 and the fifth fan 10. An air inlet valve 14 is flanged between the air inlet pipes of the first fan 6 and the fifth fan 10 and the left branch pipe 13. A cold air valve 15 is flanged on the air inlet pipes of the first fan 6 and the fifth fan 10.

[0049] Specifically, the right branch pipe 12 is connected to the air inlet pipes of the second fan 7 and the third fan 8, and an air inlet valve 14 is flanged between the air inlet pipes of the second fan 7 and the third fan 8 and the right branch pipe 12. A cold air valve 15 is flanged on the air inlet pipes of the first fan 6 and the fifth fan 10.

[0050] The inlet valve 14 is used to regulate the amount of hot air entering the blower. The opening can be adjusted in real time according to the clinker temperature of the grate to ensure that the cooling air matches the heat exchange requirements. When the flue gas temperature at the AQC furnace inlet is too high, the inlet valve is closed to reduce the amount of hot air and prevent the steam parameters of the AQC furnace from exceeding the standard. The cold air valve 15 introduces ambient air and mixes it with the hot air. When the hot air temperature is too high or the production requires a reduction in air temperature, the cold air valve 15 is opened to draw in ambient air (20°C) and mix it with the hot air to control the blower inlet air temperature within a safe range (e.g., ≤100°C).

[0051] The left branch pipe 13 connects to the first fan 6 and the fifth fan 10, leading to the front end of the first grate bed 101 and the crushing roller area of ​​the second grate bed 102. The cement clinker in these areas has a high temperature and concentrated heat release, so it is necessary to prioritize the hot air volume to enhance cooling and waste heat recovery. The right branch pipe 12 connects to the second and third fans 8, covering the middle area of ​​the first grate bed 101. The air volume can be flexibly adjusted according to the clinker layer thickness and temperature distribution to avoid uneven cooling.

[0052] Specifically, the valve is preferably an electrically adjustable butterfly valve, which is linked with the PLC control system. The PLC acquires key data through a sensor network: temperature sensors (such as K-type thermocouples) are arranged in each section of the grate to monitor the clinker layer temperature; pressure sensors (such as diffused silicon transmitters) are installed in the air ducts and air chambers to provide feedback on the air pressure value; the actual air volume is collected through flow sensors (such as vortex flow meters); and the grate operating status signal is received from the position detection switch. The data is converted into electrical signals by the PLC's analog input module (AI) and digital input module (DI) and then entered into the CPU for calculation.

[0053] Specifically, the air inlet of the fourth fan 9 is in contact with the outside air, the air outlet of the fourth fan 9 is located below the hydraulic cylinder and position detection switch of the grate bed, the air outlets of the first fan 6, the second fan 7 and the third fan 8 are located below the first section grate bed 101, and the air outlet of the fifth fan 10 is located below the end crushing roller of the second section grate bed 102.

[0054] Specifically, the heat generated inside the grate cooler 1 is directed to the AQC furnace through the return air duct 4.

[0055] Example 3:

[0056] This utility model provides a technical solution:

[0057] A heat recovery device for hot air exhaust at the kiln head, used to recover heat from a rotary kiln and increase the inlet flue gas temperature of the AQC furnace, comprising:

[0058] The grate cooler 1 has its inlet connected to the rotary kiln head discharge pipe 3 of the rotary kiln. A return air pipe 4 is connected to the upper part of the grate cooler 1 and is connected to the AQC furnace pipe. The grate cooler 1 contains a first grate bed 101 and a second grate bed 102. The end of the second grate bed extends to the discharge section 5 of the grate cooler 1. A wind box 2 is fixedly connected below the first and second grate beds. An air chamber is provided inside the wind box 2. The side pipes of the air chamber are connected to the air outlets of a first fan 6, a second fan 7, a third fan 8, a fourth fan 9, and a fifth fan 10. The first fan 6, the second fan 7, the third fan 8, and the fifth fan 10 are connected to a circulating air duct assembly for waste heat recovery and reuse.

[0059] In this embodiment, the exhaust gas temperature at the kiln head exhaust fan outlet of the rotary kiln is approximately 85-90°C. This gas is introduced into the inlet of the grate cooler 1 fan, increasing the initial temperature of the cooling air. The higher the initial temperature, the smaller the temperature difference between the cooling air and the high-temperature clinker (1000-1450°C), resulting in less heat loss from the clinker during heat exchange. More heat is retained in the cooling air. When ambient temperature air (20°C) is introduced, the cooling air absorbs heat and its temperature rises to approximately 300°C (entering the AQC furnace). After introducing exhaust gas at 85°C, the initial temperature of the cooling air increases by approximately 65°C. After heat exchange with the clinker, the temperature can rise to approximately 350°C, directly increasing the inlet flue gas temperature of the AQC furnace by approximately 50°C, thereby directly increasing the inlet flue gas temperature of the AQC furnace.

[0060] In use, the hot air generated by the rotary kiln is first drawn out through the chimney by the kiln head exhaust fan, and the hot air volume is controlled by the louvered valve between the chimney and the main air duct 11. The hot air in the main air duct 11 is split into left and right branch pipes 12 through a three-way pipe. The left branch pipe 13 delivers the hot air to the first fan 6 and the fifth fan 10, corresponding to the front end of the first grate bed 101 and the crushing roller area of ​​the second grate bed 102, respectively. The right branch pipe 12 sends the hot air to the second and third fans 8, covering the middle area of ​​the first grate bed 101. The hot air, pressurized by the fans, is evenly blown onto the grate bed through the air chamber, penetrates the high-temperature clinker layer to absorb heat, and the hot air after absorbing heat enters the AQC furnace through the return air duct 4 to increase the inlet flue gas temperature of the AQC furnace.

[0061] All other parts of this utility model not described herein are the same as existing technologies, or are known technologies, or can be implemented using existing technologies, and will not be described in detail here.

[0062] Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A heat recovery device for hot air exhaust at the kiln head, characterized in that, include: A grate cooler (1) is provided, the inlet of which is connected to the rotary kiln head discharge pipe (3) of the rotary kiln. A return air pipe (4) is connected to the upper pipe of the grate cooler (1), and the return air pipe (4) is connected to the AQC furnace pipe. The grate cooler (1) is provided with a first grate bed (101) and a second grate bed (102). The end of the second grate bed (102) extends to the discharge section (5) of the grate cooler (1). The first grate bed (101) is provided with a first grate bed (101) and a second grate bed (102). A wind box (2) is fixedly connected to the bottom of the second-stage grate bed (102). The wind box (2) is equipped with a wind chamber. The side pipe of the wind chamber is connected to the air outlet of the first fan (6), the second fan (7), the third fan (8), the fourth fan (9) and the fifth fan (10). The first fan (6), the second fan (7), the third fan (8) and the fifth fan (10) are connected to the circulating air duct assembly for the purpose of recovering waste heat for reuse.

2. The heat recovery device for external exhaust air at the kiln head according to claim 1, characterized in that: The circulating air duct assembly includes a main air duct (11), the air inlet of which is connected to the chimney of the kiln head exhaust fan of the rotary kiln, and a louvered valve is flanged between the main air duct (11) and the chimney of the kiln head exhaust fan.

3. The heat recovery device for external exhaust air at the kiln head according to claim 2, characterized in that: When the main air duct (11) reaches the grate cooler (1), it is divided into a left branch pipe (13) and a right branch pipe (12) through a three-way pipe.

4. The kiln head exhaust hot air heat recovery device according to claim 3, characterized in that: The left branch pipe (13) is connected to the air inlet pipes of the first fan (6) and the fifth fan (10). An air inlet valve (14) is flanged between the air inlet pipes of the first fan (6) and the fifth fan (10) and the left branch pipe (13). A cold air valve (15) is flanged on the air inlet pipes of the first fan (6) and the fifth fan (10).

5. The heat recovery device for external exhaust air at the kiln head according to claim 3, characterized in that: The right branch pipe (12) is connected to the air inlet pipes of the second fan (7) and the third fan (8). An air inlet valve (14) is flanged between the air inlet pipes of the second fan (7) and the third fan (8) and the right branch pipe (12). A cold air valve (15) is flanged on the air inlet pipes of the first fan (6) and the fifth fan (10).

6. The heat recovery device for external exhaust air at the kiln head according to claim 3, characterized in that: The air inlet of the fourth fan (9) is in contact with the outside air. The air outlet of the fourth fan (9) is located below the hydraulic cylinder and position detection switch of the grate. The air outlets of the first fan (6), the second fan (7) and the third fan (8) are located below the first grate (101). The air outlet of the fifth fan (10) is located below the crushing roller at the end of the second grate (102).

7. The heat recovery device for external exhaust air at the kiln head according to claim 1, characterized in that: The heat generated in the grate cooler (1) is transmitted to the AQC furnace through the return air duct (4).

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