Cooling method for preheating zone of double-hearth kiln in non-empty state

Abstract

This invention discloses a method for cooling the preheating zone of a double-chamber kiln under non-venting conditions. After kiln shutdown, the gas compressor is stopped, the flue gas dust removal fan remains running, and all other fans are shut down. Material is discharged from the kiln to be repaired, exposing the area to be repaired, and then discharged downwards for 0.5–1 m. Limestone is added to the kiln to be repaired to form a 0.5–1 m layer of cold material, ensuring the area to be repaired is above the surface of the cold material layer. The kiln to be repaired is connected to the outside environment, via an intermediate channel and through the non-repaired kiln to the dust collector. The flue gas dust removal fan is adjusted to 250–350 rpm / min, drawing external air into the kiln to be repaired, cooling the preheating zone for 20–30 minutes. The temperature of the top of the kiln shell and the surface of the cold material layer are measured, along with the CO concentration. Once the conditions are met, repairs can proceed. This invention improves the kiln maintenance environment under non-venting conditions.

Description

Technical Field

[0001] This invention relates to the field of lime kiln technology, and in particular to a cooling method for the preheating zone of a double-chamber kiln in a non-venting state. Background Technology

[0002] A double-chamber kiln is a calcination equipment with advantages such as low energy consumption and high degree of automation. It has two kiln chambers, namely a calcination chamber and a heat storage chamber. Calcination is carried out by alternating between the two kiln chambers, kiln A and kiln B. Every 12-14 minutes, the calcination direction is reversed, and the functions of the two kiln chambers are also interchanged accordingly.

[0003] During production, when kiln A is used as the calcining chamber, combustion air enters the chamber from the top through a combustion air reversing valve. This combustion air flows downwards and is preheated after passing over the limestone. When the combustion air reaches the calcination zone, it mixes and burns with the gas supplied by the spray gun. The combusted flue gas moves downwards along with the limestone until combustion is complete at the end of the calcination zone. Next, cooling air exchanges heat with the generated lime product in the area below the channel. Afterwards, this heat-exchanged gas, along with the combustion flue gas, passes through the annular channel and the intermediate channel into the kiln chamber of kiln B. There, it preheats the newly entered stone material with the upward-flowing cooling air, and then is discharged into the flue gas dust collector from the top flue gas duct. The limestone in the kiln chamber of kiln B absorbs the residual heat from the flue gas, thus increasing its temperature.

[0004] After one cycle is completed, the pressure inside the kiln is released by opening the combustion air release valve and the cooling air release valve. At this time, various airflows and media, such as combustion air, lime cooling air, and pulverized coal, will stop being supplied to the kiln. Subsequently, the reversing valve device will activate to switch between the combustion chamber and the preheating chamber, preparing for the new calcination cycle.

[0005] The brick lining structure of the kiln can be divided into a preheating zone, a calcination zone, and a cooling zone from top to bottom. Within the preheating zone, the stone material surface just covers the spray gun box. The preheating zone extends from the kiln cylinder's closing cover to the spray gun head, and the operating temperature in this area is expected to be 100-400℃. The calcination zone extends from the spray gun head to the suspension cylinder of the double-chamber kiln. The cooling zone extends from the suspension cylinder's casting point to the unloading platform.

[0006] Kiln maintenance is a high-risk, confined-space operation due to the presence of residual CO gas, high temperatures, and dust within the kiln. During production, equipment problems may occur in the kiln preheating zone, such as damage to the kiln roof spray gun box or falling refractory material. These situations may necessitate a temporary production halt for maintenance.

[0007] To ensure safety during temporary maintenance and prevent personnel from entering the potentially hazardous kiln environment, it is necessary to invent a preheating cooling method for double-chamber kilns in a non-vented state. This method will improve the maintenance environment of the kiln in a non-vented state, thereby ensuring the safe entry of personnel for maintenance work. Summary of the Invention

[0008] The purpose of this invention is to provide a method for cooling the preheating zone of a double-chamber kiln under non-venting conditions, which can improve the kiln maintenance environment under non-venting conditions.

[0009] To solve the above problems, the technical solution adopted in this invention is as follows: In this non-evacuation state, double-chamber kiln preheating zone cooling method, after kiln shutdown, the gas compressor is stopped, the flue gas dust removal fan continues to operate, and the remaining fans are shut down. Before personnel enter the kiln, ensure that the combustion air release valve and cooling air release valve are closed; discharge material from the kiln section requiring cooling, exposing the section to be repaired, and continue discharging material downwards for 0.5–1 m; limestone raw material is added into the kiln section requiring repair through a rotating hopper to form a 0.5–1 m cold material layer, ensuring that the section to be repaired is above the surface of the cold material layer; the section to be repaired is then... Connect the kiln to the outside, close the combustion air reversing valve at the top of the kiln to be repaired, and open the combustion air reversing valve at the top of the kiln not under repair, so that the kiln to be repaired is connected to the dust collector through the intermediate channel via the kiln not under repair; adjust the flue gas dust removal fan to 250-350 rpm / min to draw external air into the kiln to be repaired, and cool the preheating zone of the kiln to be repaired for 20-30 minutes; use a temperature measuring gun to detect the temperature of the kiln shell at the top of the kiln to be repaired and the surface temperature of the cold material layer, and use a CO alarm to detect the CO concentration. After passing the test, personnel can enter the kiln to be repaired for maintenance.

[0010] In the above-mentioned technical solution for the cooling method of the preheating zone of a double-chamber kiln under non-venting conditions, a more specific technical solution could be: before adding the cold material layer, ensure that all inspection doors, unloading gates, and ash discharge devices of the unloading platform of the kiln to be repaired are closed.

[0011] Furthermore, after the kiln is shut down, the fuel system pipelines that supply fuel to the kiln body are sealed with blind flanges.

[0012] Furthermore, during the kiln maintenance process, the temperature of the preheating zone of the kiln cylinder is controlled within the range of 35℃.

[0013] Furthermore, when cooling a double-chamber kiln with a suspension cylinder, the suspension cylinder fan is kept running continuously after the kiln is stopped.

[0014] By adopting the above technical solution, the present invention has the following advantages compared with the prior art:

[0015] 1. In non-venting mode, the preheating zone of the kiln requiring maintenance is rapidly cooled by drawing in external air through the control of the flue gas dust removal fan, valves, and the kiln cover. Combined with the discharge and feeding operations of the material layer in the kiln under maintenance, this effectively avoids excessively high stone temperatures, allowing maintenance personnel to stand on the material surface for safe maintenance of the preheating zone. This significantly improves kiln maintenance efficiency. Maintenance in non-venting mode allows the kiln to return to normal operation more quickly, thereby accelerating the recovery of the production process. The range of discharge height and added cold material height avoids excessive discharge that could cause heat loss and affect the recovery speed. Because the limestone raw material layer is at room temperature, maintenance personnel can perform maintenance on the material surface, ensuring their safety and preventing burns.

[0016] 2. Before adding the cold material layer, ensure that all inspection doors, unloading gates, and ash discharge devices on the unloading platform of the kiln to be repaired are closed. This can reduce air leakage in the lower part of the kiln, thereby controlling the airflow direction and flow rate inside the kiln, ensuring the ventilation effect in the upper part of the kiln, and accelerating the cooling speed.

[0017] 3. Sealing the fuel system pipelines with blind flanges can effectively cut off the fuel source and improve the safety of maintenance.

[0018] 4. Controlling the maintenance temperature within 35℃ can prevent injury to maintenance personnel due to excessive temperature and improve the safety of maintenance work.

[0019] 5. When cooling a double-chamber kiln with a suspension cylinder, keep the suspension cylinder fan running continuously to prevent the refractory material of the suspension cylinder from deforming or falling off. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of a double-chamber kiln.

[0021] The following are the reference numerals: 1. Combustion air release valve; 2. Inspection door; 3. Ash discharge device on unloading platform; 4. First kiln; 5. Spray gun; 6. Kiln closing cover; 7. Rotary hopper; 8. Combustion air reversing valve; 9. Chimney reversing valve; 10. Spray gun protection box; 11. Dust collector; 12. Flue gas dust removal fan; 13. Second kiln; 14. Unloading gate; 15. Cooling air release valve; 16. Preheating zone; 17. Calcination zone; 18. Cooling zone. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0023] The double-hearth kiln for cooling and maintenance according to the present invention, such as Figure 1As shown, the double-chamber kiln includes a first kiln cylinder 4 and a second kiln cylinder 13 connected by a central channel. Several spray guns 5 and spray gun protection boxes 10 are installed inside the kiln cylinder. The inner cavity of the kiln cylinder consists of a preheating zone 16, a calcination zone 17 and a cooling zone 18 from top to bottom. A combustion air release valve 1 is installed on the gas pipeline connected to the first kiln cylinder 4. An inspection door 2 is installed on the upper side wall of the kiln cylinder. A kiln cylinder closing cover 6 is installed on the top of the kiln. A rotating hopper 7 is installed above the kiln cylinder. A combustion air reversing valve 8 and a chimney reversing valve 9 are installed on the pipeline between the upper part of the kiln cylinder and the dust collector 11. The dust collector 11 is connected to a flue gas dust removal fan 12. A discharge platform and ash discharge device 3 are installed at the lower part of the kiln cylinder. A discharge gate 14 and a cooling air release valve 15 are connected to the bottom of the kiln.

[0024] Example 1

[0025] Taking the first kiln cylinder as the kiln cylinder to be inspected, the spray gun protection box as the part to be inspected, and the second kiln cylinder as the non-inspection kiln cylinder as an example, the cooling method of the preheating zone of the double-chamber kiln in the non-venting state in this embodiment includes the following steps:

[0026] (1) After the kiln is shut down, stop the gas compressor, keep the flue gas dust removal fan running, shut down the other fans, and seal the fuel system pipeline that delivers fuel to the kiln body with blind flanges; check and ensure that the combustion air release valve and cooling air release valve are closed at any step before personnel enter the kiln.

[0027] (2) Operate the ash discharge device of the unloading platform to discharge the material from the first kiln that needs to be cooled. After the part of the spray gun protection box that needs to be repaired is exposed, continue to discharge the material down 0.5m.

[0028] (3) Ensure that all inspection doors, unloading gates, and ash discharge devices of the unloading platform of the first kiln are closed;

[0029] (4) Limestone raw material is added into the first kiln cylinder by rotating the hopper to form a 0.5m cold material layer, so that the part to be inspected is above the surface of the cold material layer;

[0030] (5) Check to ensure that the stone inside the rotating hopper has been emptied, the combustion air release valve and the cooling air release valve have been closed, open the inspection door above the first kiln spray gun protection box and the kiln closing cover, connect the first kiln to the outside, close the combustion air reversing valve at the top of the first kiln, open the combustion air reversing valve at the top of the second kiln, open the chimney reversing valve to the chimney, so that the first kiln is connected to the dust collector through the middle channel and the second kiln, so that the flue gas is connected to the dust collector.

[0031] (7) Adjust the flue gas dust removal fan to 250 rpm / min, and draw the external air into the first kiln from the maintenance door above the kiln cover and spray gun protection box to cool the preheating zone of the first kiln for 30 minutes; the cooled air after preheating passes through the middle channel, through the heat storage chamber, and into the kiln top dust collector.

[0032] (8) Use a temperature gun to detect the temperature of the kiln shell at the top of the first kiln and the surface temperature of the cold material layer. Use a CO alarm to detect the CO concentration. When the temperature is within 35℃ and the CO concentration is zero, it is considered qualified. After passing the test, personnel can enter the first kiln for maintenance. If it fails, extend the cooling time for the hot zone. During the maintenance process, adjust the speed of the dust removal fan according to the perceived airflow to ensure sufficient suction power.

[0033] Example 2

[0034] In the non-empty state of the double-chamber kiln preheating zone cooling method of this embodiment, after the part of the spray gun protection box that needs to be repaired is exposed, continue to discharge material down 0.8m; limestone raw material is added into the first kiln cylinder by rotating the hopper to form a 0.8m cold material layer; adjust the flue gas dust removal fan to 300rpm / min and cool the preheating zone of the first kiln cylinder for 25min; the remaining steps are the same as in embodiment 1.

[0035] Example 3

[0036] In the non-evacuation state of the double-chamber kiln preheating zone cooling method of this embodiment, the double kiln cylinders are equipped with a suspension cylinder and a suspension cylinder fan. In order to protect the suspension cylinder, after the kiln is stopped, the suspension cylinder fan is kept running continuously. After the part of the spray gun protection box that needs to be repaired is exposed, the material continues to be discharged downwards for 1m. Limestone raw materials are added into the first kiln cylinder through the rotating hopper to form a 1m cold material layer. The flue gas dust removal fan is adjusted to 350rpm / min to cool the preheating zone of the first kiln cylinder for 20min. The remaining steps are the same as in Embodiment 1.

[0037] This invention utilizes the effective coordination of flue gas dust removal fans, combustion air valves, kiln cylinder closing covers, and unloading gates to focus on changes in preheating zone temperature and wind speed, controlling the temperature within the 35°C range. By partially discharging material and adding cold material, a safe maintenance environment is created in the kiln preheating zone, enabling personnel to quickly enter the kiln for maintenance. From kiln shutdown to the completion of maintenance and resumption of normal production, only about 2 hours are required.

Claims

1. A method for cooling the preheating zone of a double-chamber kiln under non-venting conditions, characterized in that: After the kiln is shut down, stop the gas compressor, keep the flue gas dust removal fan running, and shut down the other fans. Before personnel enter the kiln, ensure that the combustion air release valve and cooling air release valve are closed. Discharge the material from the kiln section that needs to be cooled, and after exposing the part to be repaired, continue to discharge material downwards for 0.5 to 1 meter. Add limestone raw material into the kiln section to be repaired through a rotating hopper to form a 0.5 to 1 meter cold material layer, so that the part to be repaired is above the surface of the cold material layer. Connect the kiln to be repaired to the outside, close the combustion air reversing valve at the top of the kiln to be repaired, and open the combustion air reversing valve at the top of the kiln not under repair, so that the kiln to be repaired is connected to the dust collector through the intermediate channel via the kiln not under repair; adjust the flue gas dust removal fan to 250-350 rpm / min, draw external air into the kiln to be repaired, and cool the preheating zone of the kiln to be repaired for 20-30 minutes; use a temperature measuring gun to detect the temperature of the kiln shell at the top of the kiln to be repaired and the surface temperature of the cold material layer, and use a CO alarm to detect the CO concentration. After passing the test, personnel can enter the kiln to be repaired for maintenance.

2. The method for cooling the preheating zone of a double-chamber kiln under non-venting conditions according to claim 1, characterized in that: Before adding the cold material layer, ensure that all inspection doors, unloading gates, and ash discharge devices of the unloading platform of the kiln to be repaired are closed.

3. The method for cooling the preheating zone of a double-chamber kiln under non-venting conditions according to claim 2, characterized in that: After the kiln is shut down, the fuel system pipelines that supply fuel to the kiln body are sealed with blind flanges.

4. The method for cooling the preheating zone of a double-chamber kiln under non-venting conditions according to claim 3, characterized in that: During the kiln maintenance process, the temperature of the preheating zone of the kiln cylinder should be controlled within the range of 35℃.

5. The method for cooling the preheating zone of a double-chamber kiln under non-venting conditions according to any one of claims 1 to 4, characterized in that: When cooling a double-chamber kiln with a suspension cylinder, keep the suspension cylinder fan running continuously after the kiln is stopped.

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