A method for discharging steam from a slab continuous caster compartment type secondary cooling chamber

Abstract

The application discloses a slab continuous caster compartment type secondary cooling chamber steam exhaust method, which separates nine cooling zones of a casting flow into six relatively sealed single rooms on both sides of the casting flow, wherein the first zone is one room, the second / third zone is one room, the fourth / fifth zone is one room, the sixth / seventh zone is one room, the eighth zone is one room, and the ninth zone is one room, and the both sides of the casting flow are symmetrically designed; the rooms are communicated with each other and the pull doors are designed to reduce the space; the air exhaust main pipeline and branch pipelines adopt circular high-frequency welded pipe structures with different diameters; the welding of the connection position of the air exhaust branch pipeline and the air exhaust main pipeline adopts 120-degree inclined welding; the air exhaust main pipeline is directly connected to the upper end of the side surface of the opening of the fan-shaped section after entering the casting flow sealing wall; the air exhaust port is 300mm away from the side surface of the fan-shaped section and is made into a flat duckbill shape.

Description

Technical Field

[0001] This invention relates to a method for exhausting steam from a box-type secondary cooling chamber in a slab continuous casting machine. Background Technology

[0002] During slab continuous casting, molten steel is injected into the crystallizer and cooled to form a slab with a certain shape and thickness, consisting of a shell and a liquid core. As the slab descends, water (or air) is continuously sprayed onto its surface to cool it and accelerate shell solidification. This cooling process generates a large amount of water vapor. The larger the casting cross-section and the greater the water content, the more steam is generated. Furthermore, the colder the weather, the greater the steam production. If this large amount of steam is not released from the plant, it will cause significant damage. Steam overflowing onto the casting platform greatly increases the ambient temperature of the platform, especially in hot summers, raising it by more than 10°C. In winter, the large amount of steam overflowing into the casting area severely obstructs the vision of the steelworkers, creating a significant safety hazard. In addition, the secondary cooling water steam has a pH value of 7-9, which is weakly alkaline. After the steam condenses into water droplets, it adheres to the steel structure of the continuous casting machine, causing corrosion. The surface of the steel structure will be corroded and oxidized layer by layer and then peel off. After years of continuous oxidation, the steel structure will become thinner, greatly reducing the strength and service life of the casting machine's steel structure and creating safety hazards. Therefore, the presence of secondary cooling steam in the continuous casting machine is extremely harmful to production and equipment, and measures must be taken to remove as much steam as possible from the plant.

[0003] The layout of the secondary cooling steam unit of the continuous casting machine is to set up a steam extraction device on each side of the casting machine head, and the exhaust fan is arranged at the position of the main pipeline. The two sides of the fan-shaped section are almost enclosed corridors. Several exhaust flue openings are evenly arranged on the walls of the corridors. The pipes of each exhaust flue opening are connected to the main exhaust pipeline, and after being extracted by the fan, they are discharged into the air above the factory through the pipe that leads straight to the top of the factory building.

[0004] The secondary cooling steam exhaust system of a slab continuous casting machine is located at a high position and is prone to the following problems: 1. The main steam pipeline of the secondary cooling system is located above one side of the casting machine, and the fan is located in front of the main pipeline. The pipeline is usually made of steel plates welded into a square shape. When the fan is working, the negative pressure at the flue outlet closer to the fan is large, and the steam extraction effect is good. However, at the horizontal section at the end of the casting machine, where the pressure is further away, the negative pressure is small, and the steam extraction effect is very poor. It is difficult for the steam to be discharged. The steam rises and overflows onto the steel pulling platform, which increases the platform temperature in summer and creates a smoky landscape in winter. 2. To ensure efficient steam extraction, high-powered fans are typically used. These high-powered secondary cooling fans, while extracting steam, also carry protective slag particles and iron oxide scale particles from the surface of the cast billet into the exhaust duct. Due to pressure drops caused by right-angle bends in the branch pipes, some of these particles fall into the pipes and accumulate at the bends. Other particles mix with the steam to form cement-like sludge that adheres to the pipe walls and fan impeller. Over time, this sludge buildup increases air resistance, hindering ventilation and significantly reducing steam extraction efficiency. Furthermore, the sludge accumulated on the fan impeller... Mud can disrupt the dynamic balance of the blower, causing excessive vibration and automatic shutdown. In severe cases, it can deform the entire blower impeller, cause excessive vibration or even breakage of the reducer, resulting in significant losses. In such situations, replacing the blower requires more than 36 hours of emergency repairs. However, the continuous casting machine cannot stop production due to the failure of a single secondary cooling blower. In this case, production can only continue under the condition of steam exhaust from one side of the blower. Operators must endure the harsh environment of high ambient temperature and poor visibility caused by steam overflow. In addition, the protective slag is prone to moisture due to the large amount of steam, which can also affect the quality of the cast billet.

[0005] Therefore, the square-shaped steam exhaust duct, due to its multiple right-angled structural seams, suffers from drawbacks such as pressure loss during ventilation and the accumulation of particulate matter at corners and edges. This results in the secondary cooling steam exhaust efficiency only reaching about 70% of the theoretical value. The exhaust duct inlets are located on the walls on both sides of the streamlined sealed chamber, more than two meters away from the casting billet location where a large amount of steam is generated in the fan-shaped injection area, significantly weakening the steam extraction suction. Furthermore, the secondary cooling steam exhaust system layout involves one steam exhaust fan on each side of the casting machine head. When one fan malfunctions, only that fan can perform steam exhaust, halving the efficiency and forcing operators to work in a hot and humid environment with overflowing steam.

[0006] In summary, the existing layout of the exhaust steam fan, exhaust steam pipeline, and pipeline structure of slab continuous casting machines all have certain defects that affect the exhaust steam efficiency. Literature search: A patent, CN206001942U, titled "Secondary Cooling Steam Treatment Device for Continuous Casting Machines," was found. This invention is a device for collecting and recovering secondary cooling steam, while this article describes a highly efficient chamber layout for exhausting steam from the secondary cooling chamber; the two describe different aspects. Another patent, CN109812705A, titled "Energy-Saving and Environmentally Friendly Steam Exhaust Device and Method for Secondary Cooling Chamber of Continuous Casting Machines," was found. This patent describes an energy-saving and environmentally friendly method that uses a waste heat steam pipeline connected to a venturi tube, which is then connected to a secondary cooling steam pipeline. The negative pressure generated by the discharged waste heat steam draws the steam from the secondary cooling chamber into the steam pipeline for exhaust. This method is completely different from the method described in this article, which uses a fan to exhaust secondary cooling steam. Summary of the Invention

[0007] The purpose of this invention is to provide a steam exhaust method for the secondary cooling chamber of a slab continuous casting machine, aiming to solve the problem that the poor steam extraction effect and the impact on safe production caused by the existing steam exhaust pipeline structure and closed design of the secondary cooling zone of the slab continuous casting machine.

[0008] The technical solution adopted in this invention is a steam exhaust method for a slab continuous casting machine's box-type secondary cooling chamber. This method changes the previous design where the secondary cooling zone was relatively sealed on the outside but completely open from top to bottom, resulting in weak steam exhaust from the fan. Instead, the nine cooling zones of the casting flow are divided into six relatively sealed single chambers on both sides of the casting flow: Zone 1 is one chamber, Zones 2 / 3 are one chamber, Zones 4 / 5 are one chamber, Zones 6 / 7 are one chamber, Zone 8 is one chamber, and Zone 9 is one chamber. The design is symmetrical on both sides of the casting flow. To reduce space, sliding doors are used to connect the chambers. During maintenance, the doors are opened for easy personnel access; during production, the sliding doors are closed to enhance the sealing performance of the secondary cooling chamber, preventing steam from escaping and facilitating the complete extraction of steam by the corresponding pipes.

[0009] The main exhaust pipe and branch pipes adopt a circular high-frequency welded pipe structure with different diameters. The circular steel pipe structure reduces the pressure loss caused by the four corners of the cubic structure and eliminates the large reduction of negative pressure caused by the easy accumulation of slag at the corners, which seriously affects the steam exhaust effect of the fan.

[0010] The connection between the exhaust branch pipe and the exhaust main pipe is welded at a 120-degree bevel. The purpose is to reduce the pressure head loss caused by the original right-angle welding structure to the negative pressure inside the steam pipe, and also to reduce the accumulation of inhaled particles at the right-angle corner.

[0011] Previously, the openings of each steam extraction pipe were located in the wall, 2.5 meters away from the steam generation point of the fan-shaped section. This distance resulted in poor steam extraction efficiency. Now, the main exhaust pipe enters through the casting flow sealing wall and runs directly to the upper side of the opening of the fan-shaped section. The exhaust port is 300mm away from the side of the fan-shaped section. The steam generated after the cooling water is sprayed on the surface of the billet flows to both sides along the gap between the rollers. The upper two sides of the fan-shaped section are the steam accumulation areas, and the exhaust port is located in this area, which greatly improves the steam extraction efficiency. At the same time, the exhaust port is 300mm away from the upper side of the fan-shaped section, so it does not affect equipment maintenance.

[0012] To increase the air intake area of ​​the exhaust vent, the exhaust vent is made into a flat duckbill shape;

[0013] During the monthly maintenance period of the continuous casting machine, clean the slag inside the steam exhaust port. First, clean the slag on the protective metal mesh of the steam extraction port, and then open the metal mesh door to clean the slag inside the pipe.

[0014] The function of welding and fabricating operable metal mesh doors at each steam exhaust vent is as follows:

[0015] 1. It blocks the intake of lightweight materials such as plastic (cloth) bags; 2. It facilitates the agglomeration and accumulation of particulate matter such as damp protective slag on the grid, which can reduce the blockage of the pipeline caused by particulate matter in the intake pipe; 3. It reduces the impact of particulate matter being sucked in in large quantities and adhering to the impeller, which can cause the impeller dynamic balance to be disrupted, resulting in large vibrations and reduced service life of the fan.

[0016] The box-type structure design of the steam exhaust chamber increases the sealing of the secondary cooling steam chamber, preventing steam from flowing between the two chambers. This allows the generated steam to more easily form a positive pressure within the limited space of each chamber, facilitating the entry of large amounts of steam into the negative pressure areas created by the extraction of steam from each branch port. Therefore, it improves the steam exhaust efficiency of each sealed chamber. This method is applicable to similar steel enterprises, allowing the large amount of steam generated in the secondary cooling chamber of the heavy plate continuous casting machine to be exhausted to the outside of the plant as much as possible. This reduces the ambient temperature of the casting platform and eliminates the significant safety hazard posed by large amounts of overflowing steam in the casting area during winter, which severely impairs the visibility of the casting workers. Attached Figure Description

[0017] Figure 1 This is a steam exhaust layout diagram of the secondary cooling chamber for slab continuous casting involved in the method of the present invention. Detailed Implementation

[0018] A method for exhausting steam from the secondary cooling chamber of a slab continuous casting machine, such as... Figure 1As shown, the previous design of a relatively sealed secondary cooling zone with a completely open interior from top to bottom, resulting in weak steam exhaust by the fan, has been changed. Instead, isolation walls 7, 8, 9, 10, 11, and 12 divide the nine cooling zones of the casting flow into six relatively sealed single rooms on both sides of the casting flow. These are: Zone 1 as one room, Zones 2 / 3 as one room, Zones 4 / 5 as one room, Zones 6 / 7 as one room, Zone 8 as one room, and Zone 9 as one room. The two sides of the casting flow are symmetrically designed. To reduce space, sliding doors are used to connect the rooms. The doors are opened for easy personnel access during maintenance, and closed during production to enhance the sealing performance of the secondary cooling chamber, prevent steam from spreading, and facilitate the removal of all steam by the corresponding pipes.

[0019] The main exhaust pipe 1 and each branch pipe adopt a circular high-frequency welded pipe structure with different diameters. The circular steel pipe structure reduces the pressure loss caused by the four corners of the cubic structure and eliminates the serious weakening of negative pressure caused by the easy accumulation of slag at the corners, which seriously affects the steam exhaust effect of the fan.

[0020] The welding of exhaust branch pipes 2, 3, 4, 5, 6 and the connection between the exhaust branch pipes and the main exhaust pipe is done at a 120-degree bevel angle. The purpose of this is to reduce the pressure head loss caused by the original right-angle welding structure in the steam extraction pipe, and also to reduce the accumulation of inhaled particles at the right-angle corner. The welding of the connection between the exhaust branch pipes and the main exhaust pipe is done at a 120-degree bevel angle.

[0021] Previously, the openings of each steam extraction pipeline were located at position 12 on the wall, which was 2.5 meters away from the steam generation point of the fan-shaped section. The distance was too far and the steam extraction effect was poor. Now, the main exhaust pipeline 1 enters from the casting flow sealing wall and goes directly to the upper side of the opening of the fan-shaped section. The exhaust port is 300mm away from the side of the fan-shaped section. The steam generated after the cooling water is sprayed on the surface of the billet flows to both sides along the gap between the rollers. The upper two sides of the fan-shaped section are the steam accumulation area. The exhaust port is set in this area, which greatly improves the steam extraction effect. At the same time, the exhaust port is 300mm away from the upper side of the fan-shaped section, so it does not affect equipment maintenance.

[0022] To increase the air intake area of ​​the exhaust vent, it is made into a flat, duckbill shape.

Claims

1. A method for exhausting steam from a slab continuous casting machine's secondary cooling chamber, characterized in that... The nine cooling zones of the casting flow are divided into six relatively sealed single rooms on both sides of the casting flow: Zone 1 is one room, Zones 2 / 3 are one room, Zones 4 / 5 are one room, Zones 6 / 7 are one room, Zone 8 is one room, and Zone 9 is one room. The two sides of the casting flow are symmetrically designed. The rooms are interconnected, and a sliding door design is used to reduce space. The main exhaust pipe and each branch pipe adopt a circular high-frequency welded pipe structure with different diameters. The welding at the connection between the exhaust branch pipe and the main exhaust pipe adopts a 120-degree bevel welding. The main exhaust pipe enters from the sealed wall of the casting flow and goes straight to the upper end of the side opening of the fan-shaped section. The exhaust port is 300mm away from the side of the fan-shaped section. The steam generated after the cooling water is sprayed on the surface of the billet flows to both sides along the gap between the rollers. The upper two sides of the fan-shaped section are the steam enrichment area. The exhaust port is set in this area to improve the steam extraction effect. The exhaust port is made into a flat duckbill shape.

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