Method for quickly baking alloy by using converter flue gas

Abstract

The invention discloses a method for quickly baking an alloy by using converter flue gas. According to the layout that the high aluminum iron is laid on the outer ring, the silicon iron is laid on the bottom and the top, and the manganese metal is laid in the middle, the three kinds of alloy are added into a baking oven, converter smoke and air are introduced into a jacket outside the baking oven for low-temperature heating, and then the high aluminum iron, the silicon iron and the manganese metal are subjected to heat preservation; and then the air inlet amount is gradually reduced for medium-temperature heating, compressed air is introduced into the baking box for purging, the air inlet amount is continuously reduced for high-temperature heating, and the baked alloy is immediately fed into a steel ladle. According to the method, through the design of alloy laying, sectional type baking, compressed air blowing and drying of the alloy through low-temperature drainage, medium-temperature moisture removal and high-temperature drying, the alloy can be rapidly dried within 5-10 min, the problems that after the alloy material is added into molten steel, a large amount of heat is absorbed, and hydrogen is increased in the molten steel are solved, the average temperature of the molten steel in the steel ladle can be increased, and the service life of the molten steel is prolonged. And the tapping temperature is reduced, and the alloy yield is increased.

Description

Technical Field

[0001] This invention relates to the field of iron and steel smelting technology, and more specifically to a method for rapidly baking alloys using converter flue gas. Background Technology

[0002] Commonly used alloys in converter steelmaking include ferrosilicon, metallic manganese, and high-alumina ferroalloys. The moisture content of these bulk alloy materials at room temperature is a significant cause of hydrogen enrichment in molten steel, and even hydrogen embrittlement. There are two types of moisture in alloys: free water, which is adhering to the alloy surface and is relatively common. This water is generated during storage and transportation due to environmental humidity and can be removed by heating the alloy to 100°C; the other type is crystal water within the alloy molecules, which is chemically bound and cannot be observed on the surface. It can only be precipitated at temperatures above 200°C. Studies have shown that adding unbaked alloys to molten steel increases the hydrogen content in the steel by more than 50%, severely affecting the mechanical properties and durability of the steel. To address the problem of excessive heat absorption and hydrogen enrichment in molten steel after the alloy material is added, it is necessary to bake the alloy before adding it to the molten steel.

[0003] Alloy baking technology refers to a process of dehydrating and preheating alloy raw materials for steelmaking through heat treatment. The basic principle is to use heat energy to remove moisture (including free water and crystal water) from the alloy material, while simultaneously heating the alloy to a suitable temperature to reduce the temperature drop caused when added to molten steel and stabilize the smelting process. As a key link in modern metallurgical processes, alloy baking technology directly affects the quality of steel products and the level of production energy consumption. It is of great significance for improving steel quality and reducing energy consumption and is an indispensable part of modern steel production processes. However, the amount of various alloys added in modern steel production processes must be adjusted according to steelmaking requirements. Each heat of steel takes approximately 30 minutes to produce. Within this time, the required alloys must be weighed and baked according to the type of steel to be produced in the next heat. If the alloys are baked prematurely, their temperature will gradually decrease after baking. Adding a low-temperature alloy to high-temperature molten steel will cause the alloy to absorb a large amount of heat, leading to a loss of temperature in the molten steel. Therefore, the alloys must be added simultaneously with steelmaking, which limits the baking time to only 5-10 minutes between heats. For steelmaking processes that require the addition of large amounts of alloys, the free water and water of crystallization of the alloys must be removed within a very short time, requiring a large amount of heat energy and resulting in high energy consumption. Furthermore, different types of alloys vary in their water content and the locations of water-containing components, which poses an obstacle to the rapid baking of the alloys.

[0004] The temperature of the flue gas from the converter's secondary dust removal system can reach up to 1300℃. Collecting and utilizing the residual heat of the converter flue gas for alloy baking can solve the problem of high energy consumption. However, it cannot address the issue of varying alloy types leading to ineffective removal of free water and crystal water during rapid baking, nor can it achieve rapid baking within a short timeframe. Therefore, a method for rapidly baking alloys using converter flue gas is needed to solve these problems. Summary of the Invention

[0005] In view of the above-mentioned prior art, the purpose of this invention is to provide a method for rapidly baking alloys using converter flue gas. This invention, through alloy laying design and segmented baking with compressed air purging, utilizes low-temperature drainage, medium-temperature dehumidification, and high-temperature drying to dry the alloy, thereby increasing the average temperature of the molten steel in the ladle, reducing the tapping temperature, and improving the alloy yield.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A first aspect of the present invention provides a method for rapidly baking an alloy using converter flue gas, characterized in that the method comprises: High-alumina ferrosilicon, ferrosilicon, and metallic manganese and other alloys are arranged with high-alumina ferrosilicon on the outer ring, ferrosilicon on the bottom and top, and metallic manganese and other alloys in the middle. The three alloys are added to the baking oven, and converter flue gas and air are introduced into the jacket outside the baking oven for low-temperature heating. Then, the amount of air entering is gradually reduced for medium-temperature heating, and compressed air is introduced into the baking oven for purging. The amount of air entering is further reduced for high-temperature heating. The baked alloy is immediately sent into the ladle.

[0007] Preferably, other alloys are laid in the middle together with metallic manganese, with metallic manganese located below the other alloys; the other alloys are ferrochrome and / or low-carbon, low-phosphorus, high-aluminum ferrochrome alloys. The other alloys can be randomly mixed or laid sequentially.

[0008] Preferably, the low-temperature heating temperature is 180~220℃ and the time is 1~3min.

[0009] Preferably, the temperature of the medium-temperature heating is 400~500℃, and the time is 2~6 minutes.

[0010] Preferably, the high-temperature heating temperature is 600~700℃ and the time is 1~2 minutes.

[0011] Preferably, when the medium-temperature heating reaches halfway, compressed air is introduced for purging, and the compressed air is introduced for 20~40s at a pressure of 0.4MPa.

[0012] Preferably, the temperature of the compressed air is 400~500℃. The compressed air can be preheated to 400~500℃ using converter flue gas.

[0013] A second aspect of the present invention provides the application of the above method in any of the following 1) to 3): 1) Rapidly reduce moisture content in the alloy; 2) Increase the tapping temperature; 3) Improve alloy yield.

[0014] Preferably, the moisture in the alloy includes free water and water of crystallization.

[0015] The beneficial effects of this invention are: (1) This invention utilizes the heat exchange between the high-temperature flue gas from the secondary dust removal of the converter and the alloy to bake the alloy and remove the moisture in the alloy, effectively reducing the temperature drop caused by the alloy during the tapping process. The high-temperature alloy after baking accelerates the melting of the alloy in the molten steel during the tapping process, improving the alloy yield. At the same time, it is conducive to reducing the final temperature of the converter, effectively reducing the energy cost and process cost of the converter, and has significant economic and social benefits.

[0016] (2) The method of the present invention can achieve rapid drying of the alloy within 5 to 10 minutes, which solves the problem of large heat absorption and hydrogen increase in the molten steel after the alloy material is added to the molten steel. It can increase the average temperature of the molten steel in the ladle, reduce the tapping temperature, and increase the alloy yield. Attached Figure Description

[0017] Figure 1 : Schematic diagram of the laying of high-alumina iron, ferrosilicon, and metallic manganese; where 14-high-alumina iron, 15-ferrosilicon, 16-metallic manganese; Figure 2 : Schematic diagram of the baking oven, where 1-baking oven, 2-jacket, 3-feed inlet, 4-discharge outlet, 5-compressed air inlet, 6-compressed air outlet, 7-converter flue gas inlet, 8-converter flue gas outlet, 9-sealed flap valve, 10-electric vibrating screen, 11-alloy feeding chute, 12-alloy rotating device, 13-steel ladle. Detailed Implementation

[0018] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0019] As described in the background section, the baking time for the alloy is limited and can only be carried out during the interval between smelting a batch of steel. Including the work before and after baking, the actual baking time is only 5 to 10 minutes. The free water and crystal water of the alloy must be removed within this short time.

[0020] Based on this, the purpose of this invention is to provide a method for rapidly baking alloys using converter flue gas. This invention mainly focuses on three alloys: high-alumina ferroalloy, ferrosilicon, and metallic manganese. During the baking process, it was found that the dense ferrosilicon alloy blocks primarily contain surface free water and moisture absorbed during storage, requiring measures to prevent moisture regain. Metallic manganese mainly contains water on its porous surface layer; rapid heating can easily cause secondary dust re-entrainment. High-alumina ferroalloy tends to be dry on the outside but moist on the inside, thus primarily containing bound water. Considering the characteristics of these three alloys, high-alumina ferroalloy is placed in the outer ring, ferrosilicon at the bottom and top, and metallic manganese in the middle. Placing high-alumina ferroalloy in the outer ring accelerates internal heat transfer and better removes its bound water; placing ferrosilicon at the bottom and top prevents moisture regain and quickly removes surface free water; placing metallic manganese in the middle prevents excessively rapid heating. The alloys are then dried using low-temperature drainage, medium-temperature dehumidification, and high-temperature drying. Low-temperature drainage removes surface moisture from the alloy, preventing it from suddenly vaporizing and causing "cracking" or "splattering" during subsequent heating. Medium-temperature drying further removes bound water from the alloy's interior. Before the medium-temperature drying process ends, heated compressed air is introduced to strongly circulate and displace the alloy, thus removing moisture. If only baking is performed without moisture removal, the rising humidity will slow down the baking process. Introducing compressed air for circulation serves both as a turning mechanism and as a way to reduce humidity. Finally, high-temperature drying, followed by discharge at this temperature, increases the average temperature of the molten steel in the ladle, lowers the tapping temperature, and improves the alloy yield.

[0021] To enable those skilled in the art to better understand the technical solution of this application, the technical solution of this application will be described in detail below with reference to specific embodiments.

[0022] The test materials used in the embodiments of this invention are all conventional test materials in the art and can be purchased through commercial channels.

[0023] First, this invention designs a device for baking alloys (such as...). Figure 2 As shown, it includes a jacketed baking oven, with a feed inlet and a compressed air inlet at the top, and a discharge outlet and a compressed air outlet at the bottom; the jacketed part has a converter flue gas inlet at the top and a converter flue gas outlet at the bottom; the discharge outlet is connected to an alloy feeding chute, and a sealing flap valve is installed on the discharge outlet; an electric vibrating screen is installed below the sealing flap valve; and a ladle is installed below the alloy feeding chute.

[0024] Screens and valves are installed at the feed inlet, compressed air inlet, discharge outlet, and compressed air outlet. The mesh size of the screen is much smaller than that of the alloy particles, ranging from 30 to 100 mesh.

[0025] After the alloy is laid in the baking oven, a mixture of filtered converter flue gas and air is introduced into the converter flue gas inlet to heat the oven, initially at a low temperature. Then, the amount of converter flue gas and air is adjusted for medium-temperature heating, and finally, high-temperature heating. After medium-temperature heating is completed halfway, preheated compressed air is introduced into the compressed air inlet to purge the alloy in the baking oven. After baking is complete, the sealed flap valve is opened to discharge the alloy, and an electric vibrating screen vibrates the alloy normally into the alloy discharge chute, which is then added to the ladle.

[0026] Example 1 (1) The steel grade to be smelted is Q550D; the temperature of the molten iron entering the furnace is 1356℃, and the composition of the molten iron is C: 4.37%; Si: 0.38%; Mn: 0.56%; P: 0.073%; S: 0.023%; the amount of scrap steel and molten iron added is (200+42.5)t; the target of the blowing end point is [C]: 0.075% and T: 1650℃; the material balance calculation shows that the steel output of this furnace is 237t; the alloy addition amount is calculated according to the target composition requirements of each alloy element of the steel grade, and the addition amount of each required alloy is weighed according to the lower limit of the composition (see Table 1).

[0027] Table 1 The above alloy is prepared according to Figure 1 The alloy is laid out as shown. High-alumina ferroalloy is laid on the outer ring, ferrosilicon is laid at the bottom and top, and metallic manganese and ferrochrome are laid in the middle, with metallic manganese located below ferrochrome. The average particle size of the alloy is 4~5cm.

[0028] (2) First, introduce converter flue gas and air into the jacket outside the baking oven to maintain the heating temperature at 200±10℃ for 2 minutes of low-temperature heating. Then, gradually reduce the amount of air entering (within 20 seconds) to maintain the heating temperature of converter flue gas and air at 450±20℃ for 5 minutes of medium-temperature heating. After 2.5 minutes of medium-temperature heating, purge with compressed air preheated by converter flue gas for 30 seconds at a pressure of 0.4MPa. Finally, adjust the amount of converter flue gas and air to maintain the heating temperature at 650±10℃ for 2 minutes of heating.

[0029] (3) After the converter blowing is completed, the TSO result of the final auxiliary lance is: [C]: 0.072%, T: 1652℃. The final carbon content and the final temperature are both "double hits" in one go. The ladle car transports the ladle to the tapping position under the furnace. The bottom blowing argon gas of the ladle is turned on and the tapping begins. When tapping the converter, the sealing flap valve at the lower end of the discharge port is opened. The electric vibrating screen at the lower end of the discharge port is started as required to vibrate the alloy normally into the alloy feeding chute and then add it into the ladle to complete the deoxidation and alloying of the tapping. After all the alloys in this batch are added, the electric vibrating screen is turned off and the sealing flap valve at the lower end of the discharge port is closed. In the later stage of tapping, the slag detection and the slag blocking of the sliding plate are carried out normally.

[0030] Example 2 (1) The steel grade to be smelted is 590DP; the temperature of the molten iron entering the furnace is 1365℃, and the composition of the molten iron is C: 4.33%; Si: 0.53%; Mn: 0.65%; P: 0.076%; S: 0.037%; the amount of scrap steel and molten iron added is (190+50)t; the target of the blowing end point is [C]: 0.08% and T: 1648℃; the material balance calculation shows that the steel output of this furnace is 237.5t; the alloy addition amount is calculated according to the target composition requirements of each alloy element of the steel grade, the alloy addition amount is calculated according to the target composition requirements of each alloy element of the steel grade, and the addition amount of each required alloy is weighed according to the lower limit of the composition (see Table 2).

[0031] Table 2 The above alloy is prepared according to Figure 1 The alloy is laid out as shown. High-alumina ferrophosphate is laid on the outer ring, ferrosilicon is laid at the bottom and top, and metallic manganese, ferrochrome, and low-carbon, low-phosphorus high-alumina ferrophosphate alloy are laid in the middle; metallic manganese is located below ferrochrome, and ferrochrome is located below the low-carbon, low-phosphorus high-alumina ferrophosphate alloy. The average particle size of the alloy is 4~5cm.

[0032] (2) First, introduce converter flue gas and air into the jacket outside the baking oven to maintain the heating temperature at 210±10℃ for low-temperature heating for 1.5 min. Then, gradually reduce the amount of air entering (within 20 s) to maintain the heating temperature of converter flue gas and air at 480±20℃ for medium-temperature heating for 4 min. When the medium-temperature heating has been carried out for 2.5 min, introduce compressed air preheated by converter flue gas to purge for 30 s at a pressure of 0.4 MPa. Finally, adjust the amount of converter flue gas and air to maintain the heating temperature at 680±20℃ for heating for 1.5 min.

[0033] (3) After the converter blowing is completed, the TSO result of the final auxiliary lance is: [C]: 0.075%, T: 1662℃. The final carbon content and the final temperature are both "double hits" in one go. The ladle car transports the ladle to the tapping position under the furnace. The bottom blowing argon gas of the ladle is turned on and the tapping begins. When tapping the converter, the sealing flap valve at the lower end of the discharge port is opened. The electric vibrating screen at the lower end of the discharge port is started as required to vibrate the alloy normally into the alloy feeding chute and then add it into the ladle to complete the deoxidation and alloying of the tapping. After all the alloys in this batch are added, the electric vibrating screen is turned off and the sealing flap valve at the lower end of the discharge port is closed. In the later stage of tapping, the slag detection and the slag blocking of the sliding plate are carried out normally.

[0034] Comparative Example 1 The difference from Example 1 is that in step (1), high-aluminum iron, ferrosilicon, ferrochrome and metallic manganese are filled into the baking oven from top to bottom; In step (2), converter flue gas and air are introduced into the jacket outside the baking oven to maintain the heating temperature at 450±20℃ for 9 minutes.

[0035] Comparative Example 2 The difference from Example 2 is that in step (1), high-aluminum iron, ferrosilicon, low-carbon low-phosphorus high-aluminum iron alloy, ferrochrome and metallic manganese are filled into the baking oven from top to bottom; In step (2), converter flue gas and air are introduced into the jacket outside the baking oven to maintain the heating temperature at 450±20℃ for 9 minutes.

[0036] Comparative Example 3 The difference from Example 1 is that in step (1), high-aluminum iron, ferrosilicon, ferrochrome and metallic manganese are filled into the baking oven from top to bottom.

[0037] Comparative Example 4 The difference from Example 1 is that in step (2), converter flue gas and air are introduced into the jacket outside the baking oven to maintain the heating temperature at 450±20℃ for 9 minutes.

[0038] Comparative Example 5 The difference from Example 1 is that compressed air is not introduced in step (2).

[0039] The temperature of molten steel in the ladle after the steel strands were removed in Examples 1-2 and Comparative Examples 1-5 was measured, and the alloy yield was calculated based on the content of each element after alloying. The metal yields of high-aluminum ferrosilicon, high-metallic manganese, and ferrochromium are shown in Tables 3 and 4.

[0040] Table 3 Table 4 As shown in Table 3, the temperature of the molten steel in the ladle after tapping in Example 1 was 1578℃, which was 6℃ higher than the average temperature of 1572℃ in Comparative Example 1, meaning the tapping temperature drop was reduced by 6℃. Furthermore, the alloy yield was calculated based on the content of each element after alloying. In Comparative Example 1, the metal yields of high-alumina ferrophosphate, ferrosilicon, high-manganese ferrophosphate, and ferrochrome were 81.3%, 85.6%, 88.9%, and 93.3%, respectively, while in Example 1 they were 82.0%, 86.6%, 89.8%, and 94.0%, respectively. Example 1 showed improvements of 0.7%, 1.0%, 0.9%, and 0.7% compared to Comparative Example 1. This indicates that the alloy placement method in the baking oven, as well as the segmented baking and purging compressed air, all affect the molten steel temperature and alloy yield.

[0041] As shown in Table 4, the temperature of the molten steel in the ladle after tapping in Example 2 was 1581℃, which was 5℃ higher than the average temperature of 1576℃ in Comparative Example 2, meaning the tapping temperature drop was reduced by 5℃. Furthermore, based on the alloying element content, the alloy yields for Comparative Example 2 (high-alumina ferrosilicon, high-manganese, ferrochrome, and low-carbon, low-phosphorus, high-alumina ferrosilicon) were 81.6%, 87.7%, 88.7%, 93.6%, and 88.1%, respectively. The alloy yields for Example 2 were 82.4%, 88.6%, 89.5%, 94.3%, and 88.9%, respectively, representing increases of 0.6%, 0.9%, 0.8%, 0.7%, and 0.8% compared to Comparative Example 2. This demonstrates that the method of the present invention can significantly reduce the tapping temperature drop and improve the alloy yield.

[0042] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for rapidly baking alloys using converter flue gas, characterized in that, The method is as follows: High-alumina ferrosilicon and metallic manganese are arranged with high-alumina ferrosilicon on the outer ring, ferrosilicon on the bottom and top, and metallic manganese in the middle. The three alloys are added to the baking oven, and converter flue gas and air are introduced into the jacket outside the baking oven for low-temperature heating. Then, the amount of air entering is gradually reduced for medium-temperature heating, and compressed air is introduced into the baking oven for purging. The amount of air entering is further reduced for high-temperature heating. The baked alloy is immediately sent into the ladle.

2. The method according to claim 1, characterized in that, Other alloys are laid in the middle together with metallic manganese, with metallic manganese located below the other alloys; the other alloys are ferrochrome and / or low-carbon, low-phosphorus, high-aluminum ferrochrome alloys.

3. The method according to claim 1, characterized in that, The low-temperature heating is performed at a temperature of 180~220℃ for 1~3 minutes.

4. The method according to claim 1, characterized in that, The medium-temperature heating is performed at a temperature of 400~500℃ for 2~6 minutes.

5. The method according to claim 1, characterized in that, The high-temperature heating is performed at a temperature of 600~700℃ for 1~2 minutes.

6. The method according to claim 1, characterized in that, When the medium-temperature heating reaches halfway, compressed air is introduced for purging. The compressed air is introduced for 20-40 seconds at a pressure of 0.4 MPa. The compressed air is preheated to a temperature of 400-500°C using converter flue gas.

7. The method according to claim 7, characterized in that, The temperature of the compressed air is 400~500℃.

8. The application of the method according to any one of claims 1 to 7 in any one of the following 1) to 3): 1) Rapidly reduce moisture content in the alloy; 2) Increase the tapping temperature; 3) Improve alloy yield.

9. The application according to claim 8, characterized in that, The moisture in the alloy includes free water and water of crystallization.

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