Yu Xingjun
Abstract : Combining with the production practice, this paper analyzes the causes of the explosion caused by the ignition of the lime furnace, finds out the problems existing in the traditional lime furnace ignition production mode, proposes a new ignition method, and illustrates the method using actual cases. Advanced nature.
Keywords: lime stove remote ignition explosion
1 Introduction
In the alumina production process, the lime furnace is responsible for providing qualified lime for the sintering process to supply raw slurry ingredients, providing high concentration of carbon dioxide gas for carbonation decomposition, and providing high-quality lime for the Bayer process for desilication and caustic alkali liquor. task. After the new or lime furnace overhaul, it is necessary to conduct trial ignition and use the traditional lime furnace ignition method. This can easily cause explosions, which seriously endangers the lives of employees and equipment safety. It is a major safety hazard for lime stoves. At the same time, this conventional lime furnace ignition method has a poor fire after ignition, and has a great influence on subsequent ovens, gas generation, and production. For this reason, it is imperative to improve the ignition method and optimize the starting process of the lime furnace process.
2. The disadvantages of traditional lime furnace ignition methods
The traditional lime furnace ignition method is: firstly lay a layer of 300mm protective coal above the lime stove hood at the bottom of the furnace, and then apply about 500mm limestone as the heat insulation layer, adding a certain amount of large pieces of wood and small pieces of wood in sequence. Such as pilots, poured about 50kg of kerosene, close all the inlet door of the bottom of the lime furnace, open the stove top chimney and bell, manhole, ignited the torch, the torch slowly from the top of the furnace with the artificial slowly to the bottom of the furnace, lit kerosene And igniters. After the ignition, the personnel quickly evacuated the top of the furnace. This ignition method mainly has the following drawbacks:
(1) Kerosene is highly volatile. Volatile kerosene gas accumulates at the top of the furnace and mixes with the air to reach the explosion limit. Different levels of explosion will occur after encountering an open flame. In severe cases, the top equipment will be damaged and even cause personal injury. . In 2004, a factory #4 lime stove exploded and caused damage to the top distributor and clock. At the moment of explosion, the shock wave directly extinguished the torch, which greatly affected the production. Fortunately, no personal injury was caused.
(1) Kerosene is highly volatile. Volatile kerosene gas accumulates at the top of the furnace and mixes with the air to reach the explosion limit. Different levels of explosion will occur after encountering an open flame. In severe cases, the top equipment will be damaged and even cause personal injury. . In 2004, a factory #4 lime stove exploded and caused damage to the top distributor and clock. At the moment of explosion, the shock wave directly extinguished the torch, which greatly affected the production. Fortunately, no personal injury was caused.
(2) Due to the poor air permeability of the protective material for bottoming, resulting in poor ventilation after successful ignition, the fire is not prosperous, and the effect of the oven is poor. Therefore, it is forced to open the blower for forced ventilation in advance. The presence of a large amount of gas mixture in the furnace chamber will cause a new round of explosion during forced ventilation, which will have a greater impact on the subsequent gasifier operation.
2. The improvement of the traditional lime furnace ignition method is as follows
2.1 The main reason for the poor permeability of the protective material is that the strength of lime and lump coal is small and the porosity is low. Therefore, the use of lime to be added in advance, to achieve higher than the wind cap 300mm standard requirements and then add a larger particle size, better permeability limestone replacement, after replacement limestone 500-800mm higher than the hood. The use of limestone to cover the bottom is better than that of lime and coal, which is conducive to the post-ignition oven and gas operation.
2.2 The main reason for the explosion at the moment of ignition is that the ignited kerosene added has a high volatility. Therefore, it is changed to a mechanical oil with poorer volatility to avoid the explosion limit of combustible gas as much as possible so as to avoid explosion.
2.3 Open the bottom air intake door before ignition.
2.4 Make long-range ignition devices to achieve remote ignition, and prevent the operator from forming explosive damage once firing.
3. Specific implementation plan
3.1 Replace volatile kerosene with less volatile mechanical oil. Only use a small amount of kerosene to soak the igniter to prevent explosion during ignition.
3.2 All of the bottom material shall be replaced with limestone with good breathability to ensure that the igniter ignites the igniter smoothly.
3.3 Open the air intake door before ignition to facilitate ventilation and combustion.
3.4 Make a remote ignition device. The ignition personnel ignites in real time other than 100M from the site.
3.5 lime stove remote ignition device includes: (1) lime furnace body (2) heating resistor (3) ignition switch (4) wire (5) 220V AC Power Supply.
4. How to use lime stove remote ignition device
4.1 Lime Furnace Preservation Material Lime is used, lime is then used to displace the lime, and after passing the measurement, the blower is turned on with full pressure for 2-4 hours to blow through the primer.
4.2 Make and install remote ignition after adding the wood.
4.3 When the remote ignition device is in place, evenly spread about 50kg of mechanical oil into the furnace.
4.4 Open the bottom air intake door.
4.5 After all the workers have evacuated from the scene, turn on the ignition switch and perform remote ignition.
5. Practical examples:
The Zhongzhou branch currently has 6 sets of ¢5*26M lime stoves. In April 2005, the 1# lime stove overhaul after commissioning was adopted as follows:
(1) On April 17th, 1# Lime Furnace started to add protection material after the joint test run. First add 30t lime, then use 50t limestone to replace lime. After passing the measurement, turn on the blower to fully blow the blower for 2-4 hours.
The Zhongzhou branch currently has 6 sets of ¢5*26M lime stoves. In April 2005, the 1# lime stove overhaul after commissioning was adopted as follows:
(1) On April 17th, 1# Lime Furnace started to add protection material after the joint test run. First add 30t lime, then use 50t limestone to replace lime. After passing the measurement, turn on the blower to fully blow the blower for 2-4 hours.
(2)After 10 tons of wood was added on April 18, a remote ignition device was built and installed.
(3) After the ignition device was installed in place on April 19, about 50kg of mechanical oil was evenly thrown into the furnace.
(4) Open the bottom air intake door, and all the workers are evacuated from the site.
(5) At 9:00 on April 19th, the ignition switch was turned on at a distance of 150m from the 1# lime oven to remotely ignite. After 30 seconds, the smoke blew up and the ignition was successful. No explosion occurred.
(6) April 19, 9:00 - April 24, 21:00 oven, add the mixture.
(7) On April 24th, 21:00, the gas concentration at the top of the lime furnace #1 reached 36%, and the gas was ignited. The ignition was successful.
6 Conclusion
The remote ignition device solves the disadvantages of the traditional ignition method, limestone replacement and bottom ventilation measures, and optimizes the lime furnace process startup process. This kind of lime furnace ignition control method has been successfully applied to 1#, 3#, 4# and 6# lime furnaces. Practice has proved that it minimizes the probability of an explosion and completely eliminates damage to workers. At the same time, the fire is good after ignition, the oven time is shortened, and the oven cost is reduced, which is worth promoting.
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