A method for efficiently quenching desulfurization slag to reduce large pieces of slag and iron

Abstract

The present invention relates to a method for efficiently quenching desulfurized slag to reduce large pieces of slag and iron. The method comprises the following steps: Step 1: adding lime powder during the hot metal desulfurization process; Step 2: the slag skimming speed is 9 - 13 seconds, and it is required to control the molten iron entrained during the slag skimming process, and the molten iron content in the desulfurized slag during the slag skimming process is required to be controlled below 30%; Step 3: uniformly spraying a certain thickness of dry steel slag powder, with a thickness of 3 - 5 mm, on the surface of the desulfurized slag removed between each ladle and the next ladle. The particle size of the dry slag is required to be less than 3 mm and the moisture content is less than 3%; Step 4: after the slag skimming is completed, quenching is carried out. Control the temperature of the slag before quenching and the amount of water, strengthen stirring, and keep the slag temperature above 300°C; perform a water injection operation on the desulfurized slag, and use a hydraulic drill rod to stir the slag, so that the slag at the bottom layer of the ladle can be fully mixed and contacted with water, promoting the chemical reaction inside the desulfurized slag.

Description

Technical Field

[0001] The present invention relates to a method, specifically to a method for efficiently quenching desulfurized slag to reduce large pieces of slag iron, belonging to the technical field of metallurgy. Background Art

[0002] Before hot metal is charged into a converter for smelting, it must go through the processes of desulfurization and slag skimming. Different slag skimming control methods and quenching technologies have a great impact on the treatment of desulfurized slag. Currently, most slag skimming and quenching controls mainly involve removing the desulfurized slag in the hot metal ladle after desulfurizing the hot metal, and then controlling the amount of slag skimmed into the slag pot to a certain height along the pot edge, after which the slag skimming operation for this slag pot batch is ended, and then water quenching is carried out, with a quenching time of 12 - 20 hours. The quenching time is long, the efficiency is low, the desulfurized slag and metallic iron cannot be well separated, the desulfurized slag iron after quenching has a high slag content, and the size of the slag iron is large, reaching more than 1 meter, and it must be cut before it can be recycled. Cutting requires a large amount of processing costs. At the same time, the large pieces of slag iron cut contain a certain amount of desulfurized slag. Because the sulfur content in the slag is high, a considerable number of steel grades cannot be added back to the steelmaking process. Therefore, there is an urgent need for a new solution to solve the above technical problems. Summary of the Invention

[0003] The present invention precisely aims at the problems existing in the prior art and provides a method for efficiently quenching desulfurized slag to reduce large pieces of slag iron. This technical solution improves the quenching efficiency, reduces large pieces of slag iron in the desulfurized slag, thereby reducing the company's processing costs, and at the same time increases the recovery rate of metallic iron in the slag iron.

[0004] To achieve the above object, the technical solution of the present invention is as follows. A method for efficiently quenching desulfurized slag to reduce large pieces of slag iron, the method comprising the following steps:

[0005] Step 1: By adding lime powder during the hot metal desulfurization process, the lime content in the desulfurized slag is increased. The injection amount of pre-injected lime powder is 8 - 10 kg per ton of hot metal, which is beneficial to the subsequent quenching operation of the desulfurized slag. The principle is that a high lime content in the slag is beneficial to quenching, and its chemical equation is CaO + H2O = Ca(OH)2. During the injection process, the lime powder and desulfurizer are mixed and injected in a ratio of 5 - 6:1. The main purpose is to increase the calcium oxide content in the desulfurized slag, which is beneficial to the subsequent quenching operation of the desulfurized slag.

[0006] Step 2: After desulfurization is completed, slag skimming control is carried out to reduce the slag skimming speed and the iron content in the desulfurized slag carried away. The slag skimming speed is 9 - 13 seconds. It is required to control the metallic iron carried during the slag skimming process, and the metallic iron content in the desulfurized slag during the slag skimming process is required to be controlled below 30%. When slag skimming, it is required that the height difference between the hot metal liquid level and the ladle edge of the hot metal ladle is greater than 250 mm. When slag skimming reaches the ladle mouth, the slag skimmer should stay for 1 - 2 seconds to allow the hot metal in the desulfurized slag to fully settle.

[0007] Step 3: To prevent the molten iron in the slag from penetrating to the bottom layer of the slag pot and sticking together during the slag skimming of the next furnace. During the interval between each pot and the next pot for slag skimming, a certain thickness of dry steel slag powder is evenly sprayed on the surface of the desulfurized slag being skimmed off. The thickness is generally 3 - 5 mm. The particle size of the dry slag is required to be less than 3 mm, and the moisture content is less than 3%. Since the properties of the steel slag powder and the desulfurized slag are different, the iron in the desulfurized slag is naturally blocked and separated, reducing the formation of large chunks of slag and iron. At the same time, since the iron in the desulfurized slag contains a certain amount of carbon and the steel slag contains iron oxide, a chemical reaction will occur when the two combine. The chemical equation is FeO + C = Fe + CO, which can improve the metal yield rate, modify the slag, make the slag more brittle, thereby reducing the cutting amount of the company, reducing the processing cost, and increasing the proportion of slag and iron returned to production. Since the properties of the steel slag powder and the desulfurized slag are different, the iron in the desulfurized slag is naturally blocked and separated, providing convenience for the subsequent process treatment.

[0008] Step 4: After the slag skimming is completed, quenching is carried out. Control the temperature of the furnace slag and the amount of water before quenching, and at the same time strengthen stirring, and try to keep the furnace slag temperature above 300 °C; carry out a water injection operation on the desulfurized slag. The amount of water must be controlled to the edge of the pot. Use a hydraulic drill rod to stir the furnace slag so that the furnace slag at the bottom layer of the pot can fully mix and contact with water, effectively shortening the quenching time, and at the same time promoting the chemical reaction inside the desulfurized slag.

[0009] As a further improvement of the present invention, the number of slag skimming furnaces is controlled at 2 - 3 furnaces. At the same time, it is required that the height of the furnace slag in the slag pot does not exceed 50% of the depth of the slag pot, and the weight of the slag skimming is less than 10 tons. The purpose of controlling the number of slag skimming furnaces and the weight is mainly to ensure that the total amount of furnace slag in the slag pot is beneficial to quenching.

[0010] As a further improvement of the present invention, in Step 4, quenching must be carried out within 1 hour after the slag skimming of the slag pot to minimize the temperature loss of the furnace slag. It is required that the temperature of the furnace slag before quenching is greater than 300 °C. After the slag skimming of the slag pot is completed, quenching control is carried out, and a water injection operation is carried out on the desulfurized slag. The amount of water must be controlled to the edge of the pot.

[0011] As a further improvement of the present invention, in Step 4, after the water injection is in place, a stirring operation is carried out on the desulfurized slag in the pot. Use a hydraulic drill rod to strike and stir the furnace slag, stir once every 2 hours, and stir a total of three times. The quenching time is controlled within 6 - 8 hours. By using the hammering and stirring of the hydraulic drill rod, the furnace slag at the bottom layer of the pot can fully mix and contact with water, effectively shortening the quenching time. At the same time, since the furnace slag is fully broken under the action of mechanical external force, the purpose of reducing the size of the desulfurized slag iron is achieved.

[0012] Compared with the prior art, the present invention has the following advantages: 1) In this technical solution, large chunks of slag and iron are significantly reduced, and the generation ratio of slag and iron chunks with a size greater than 1 meter is reduced from the original 50% to less than 10%; 2) The time required for quenching is greatly reduced, from 12 - 20 hours of quenching time to 6 - 8 hours, greatly improving the operating efficiency; 3) This technical solution can increase the recovery rate of metallic iron and increase the content of metallic iron by 1 - 3%; 4) The slag treated by this method becomes more brittle and is easier to process. Through the comprehensive control of the desulfurization, slag skimming, and quenching processes, the size of the desulfurized slag after quenching meets the standard for direct recycling, and the size of the large chunks of desulfurized slag iron is basically below 500 mm, and more than 90% is powder slag with a particle size below 200 mm. Detailed implementation manners

[0013] To deepen the understanding of the present invention, the following embodiments are described in detail.

[0014] Embodiment 1: A method for efficiently quenching desulfurized slag to reduce large chunks of slag and iron, the method comprising the following steps: Step 1: By adding lime powder during the hot metal desulfurization process, the lime content in the desulfurized slag is increased. The injection amount of pre-injected lime powder is 8 - 10 kg per ton of hot metal, which is beneficial to the subsequent quenching operation of the desulfurized slag. The principle is that a high lime content in the slag is beneficial to quenching, and its chemical equation is CaO + H2O = Ca(OH)2. During the injection process, the lime powder and desulfurizer are mixed and injected in a ratio of 5 - 6:1, mainly aiming to increase the calcium oxide content in the desulfurized slag, which is beneficial to the subsequent quenching operation of the desulfurized slag.

[0015] Step 2: After desulfurization, slag skimming control is carried out to reduce the slag skimming speed and the iron content in the desulfurized slag. The slag skimming speed is 9 - 13 seconds. It is required to control the metallic iron entrained during the slag skimming process, and the metallic iron content in the desulfurized slag during the slag skimming process is required to be controlled below 30%. When skimming the slag, it is required that the height difference between the hot metal surface and the lip of the hot metal ladle is greater than 250 mm. When skimming the slag to the ladle mouth, the slag skimmer should stay for 1 - 2 seconds to allow the hot metal in the desulfurized slag to fully settle.

[0016] Step 3: To prevent the molten iron in the slag from penetrating to the bottom layer of the slag pot and sticking together during the slag skimming of the next furnace. During the interval between each pot and the next pot for slag skimming, dry steel slag powder with a certain thickness is evenly sprayed on the surface of the desulfurized slag being skimmed off. The thickness is generally 3 - 5 mm. The particle size of the dry slag is required to be less than 3 mm, and the moisture content is less than 3%. Since the properties of the steel slag powder and the desulfurized slag are different, the iron in the desulfurized slag is naturally blocked and separated, reducing the formation of large chunks of slag and iron. At the same time, since the iron in the desulfurized slag contains a certain amount of carbon and the steel slag contains iron oxide, a chemical reaction will occur when the two combine. The chemical equation is FeO + C = Fe + CO, which can improve the metal recovery rate, modify the slag, make the slag more brittle, thereby reducing the cutting amount of the company, reducing the processing cost, and increasing the proportion of slag and iron returned to production. Since the properties of the steel slag powder and the desulfurized slag are different, the iron in the desulfurized slag is naturally blocked and separated, providing convenience for the subsequent process treatment.

[0017] Step 4: After the slag skimming is completed, quenching is carried out. Control the temperature and water volume of the slag before quenching, and at the same time strengthen stirring to keep the slag temperature greater than 300 °C as much as possible; carry out a water injection operation on the desulfurized slag, and the water volume must be controlled to the edge of the pot. Use a hydraulic drill rod to stir the slag, so that the slag at the bottom layer of the pot can fully mix and contact with water, effectively shortening the quenching time, and at the same time promoting the chemical reaction inside the desulfurized slag.

[0018] Among them, the number of slag skimming furnaces is controlled at 2 - 3 furnaces. At the same time, it is required that the height of the slag in the slag pot does not exceed 50% of the depth of the slag pot, and the weight of the slag skimming is less than 10 tons. The purpose of controlling the number of slag skimming furnaces and the weight is mainly to ensure that the total amount of slag in the slag pot is beneficial to quenching.

[0019] Among them, in Step 4, quenching must be carried out within 1 hour after the slag skimming of the slag pot to minimize the temperature loss of the slag. It is required that the temperature of the slag before quenching is greater than 300 °C. After the slag skimming of the slag pot is completed, quenching control is carried out, and a water injection operation is carried out on the desulfurized slag, and the water volume must be controlled to the edge of the pot.

[0020] Among them, in Step 4, it is required to carry out a stirring operation on the desulfurized slag in the pot after the water injection is in place. Use a hydraulic drill rod to strike and stir the slag, stir once every 2 hours, and stir a total of three times. The quenching time is controlled within 6 - 8 hours. By using the hammering and stirring of the hydraulic drill rod, the slag at the bottom layer of the pot can fully mix and contact with water, effectively shortening the quenching time. At the same time, since the slag is fully broken under the action of mechanical external force, the purpose of reducing the size of the desulfurized slag and iron is achieved.

[0021] Specific Embodiment: A method for efficiently quenching desulfurization slag to reduce large pieces of slag and iron. The method includes the following steps: quenching time, controlling the size of the quenched product. In the present invention, from the desulfurization process, slag skimming, and quenching process control, the quenching time is shortened to 6 - 8 hours. After quenching, there are only a small amount of large pieces of desulfurization slag and iron, and it can be recycled with almost no need for cutting. The generation ratio of large pieces of slag and iron with a size greater than 1 meter is within 10%.

[0022] Step 1: By adding lime powder during the hot metal desulfurization process, the injection amount of pre-injected lime powder is 8 - 10 kg per ton of hot metal, thereby increasing the lime content in the desulfurization slag, which is beneficial to the subsequent quenching operation of the desulfurization slag. The principle is that a high lime content in the slag is beneficial to quenching, and its chemical formula is CaO + H2O = Ca(OH)2.

[0023] Step 2: Reduce the slag skimming speed to reduce the iron content in the desulfurization slag. The slag skimming speed is 9 - 13 seconds. When skimming the slag to the ladle mouth, the slag skimmer should stay for 1 - 3 seconds to allow the hot metal in the desulfurization slag to fully flow out into the hot metal ladle, reducing iron loss.

[0024] Step 3: To prevent the hot metal in the slag from penetrating to the bottom layer of the slag pot and sticking together during the slag skimming of the next furnace. During the interval between skimming each pot and the next pot, evenly spray a certain thickness of dry steel slag powder on the surface of the desulfurized slag that has been skimmed off. The thickness is generally 3 - 5 mm. The particle size requirement of the dry slag is less than 3 mm, and the moisture content is less than 3%. Due to the different properties of the steel slag powder and the desulfurization slag, the iron in the desulfurization slag is naturally blocked and separated, reducing the formation of large pieces of slag and iron. At the same time, since the iron in the desulfurization slag contains a certain amount of carbon and the steel slag contains iron oxide, a chemical reaction will occur when the two combine. Its chemical formula is FeO + C = Fe + CO, which can improve the metal recovery rate, modify the slag, make the slag more brittle, thereby reducing the cutting amount of the company, reducing the processing cost, and increasing the return production ratio of slag and iron.

[0025] Step 4: After slag skimming, perform quenching, control the temperature and water volume of the slag before quenching, and strengthen stirring at the same time. Try to keep the slag temperature above 300 °C; perform water injection on the desulfurization slag, and the water volume must be controlled to the ladle edge. Use a hydraulic drill rod to stir the slag once every 2 hours, for a total of three times. The slag at the bottom layer of the ladle can be fully mixed and contacted with water, effectively shortening the quenching time and promoting the chemical reaction inside the desulfurization slag.

[0026] According to this method, 5 operation verifications were carried out. The generation ratios of slag-iron lumps with sizes greater than 1 meter in the desulfurized slag were 5%, 6%, 3%, 0%, and 1% respectively; the required quenching times were 6 hours, 8 hours, 6 hours, 6 hours, and 7 hours; compared with the metallic iron in the desulfurized slag of the traditional method, the metal iron recovery rates of the 5 cases of the present invention were increased by 3%, 2%, 3%, 3%, and 2% respectively. Due to the significant reduction of slag-iron lumps, the treatment cost of the company was reduced, and the increase in the metal iron recovery rate increased the company's benefits.

[0027] It should be noted that the above embodiments are not used to limit the protection scope of the present invention. Equivalent transformations or substitutions made on the basis of the above technical solutions all fall within the scope protected by the claims of the present invention.

Claims

1. A method for efficiently quenching desulfurization slag to reduce large chunks of slag and iron, characterized in that The method includes the following steps: Step 1: By adding lime powder during the hot metal desulfurization process, the lime content in the desulfurized slag is increased. The injection amount of pre-injected lime powder is 8-10 kg per ton of hot metal, which is beneficial to the subsequent quenching operation of the desulfurized slag; Step 2: The slag skimming speed is 9-13 seconds. It is required to control the molten iron entrained during the slag skimming process. The molten iron content in the desulfurized slag during the slag skimming process should be controlled below 30%. When skimming the slag, it is required that the height difference between the molten iron surface and the ladle lip is greater than 250 mm. When skimming the slag to the ladle mouth, the slag skimmer should stay for 1-2 seconds to allow the molten iron in the desulfurized slag to fully settle; Step 3: During the interval between skimming each ladle and the next ladle, a certain thickness of dry steel slag powder is evenly sprayed on the surface of the desulfurized slag that has been skimmed off. The thickness is 3-5 mm. The particle size of the dry slag is required to be less than 3 mm, and the moisture content is less than 3%; Step 4: After the slag skimming is completed, quenching is carried out. Control the slag temperature and water volume before quenching, strengthen stirring, and keep the slag temperature above 300 °C; perform a water injection operation on the desulfurized slag. Use a hydraulic drill rod to stir the slag so that the slag at the bottom layer of the ladle can fully mix and contact with water, promoting the chemical reaction inside the desulfurized slag.

2. The method for efficiently quenching desulfurized slag to reduce large lumps of slag and iron according to claim 1, wherein The number of slag skimming furnaces is controlled at 2-3 furnaces. At the same time, it is required that the height of the slag in the slag pot does not exceed 50% of the depth of the slag pot, and the slag skimming weight is less than 10 tons.

3. The method for efficiently quenching desulfurized slag to reduce large lumps of slag and iron according to claim 2, characterized in that, In Step 4, quenching is carried out within 1 hour after the slag skimming of the slag pot is completed. The slag temperature before quenching is greater than 300 °C. After the slag skimming of the slag pot is completed, quenching control is carried out, and a water injection operation is performed on the desulfurized slag. The water volume is controlled to the ladle lip.

4. The method for efficiently quenching desulfurized slag to reduce large chunks of slag and iron according to claim 3, characterized in that, In Step 4, it is required to stir the desulfurized slag in the ladle after the water injection is in place. Use a hydraulic drill rod to strike and stir the slag, stir once every 2 hours, for a total of three times. The quenching time is controlled at 6-8 hours. Through the hammering and stirring of the hydraulic drill rod, the slag at the bottom layer of the ladle can fully mix and contact with water.