A feeding method for disposing iron-rich red mud in a molten iron pretreatment process

Abstract

The present application relates to the technical field of comprehensive utilization of steel smelting resources, and particularly relates to a feeding method for disposing iron-rich red mud in a molten iron pretreatment process, which comprises the following steps: step one: uniformly mixing the iron-rich red mud, LT dry dedusting ash and limestone by using a feeding device to obtain a mixture; step two: spraying the mixture into the molten iron by using a nitrogen gas flow, and then lowering a stirring head to stir the molten iron for the first time; after the first stirring is completed, the stirring head is lifted to a waiting position; step three: lowering the stirring head to stir the molten iron for the second time; after the second stirring is completed, the stirring head is lifted to the waiting position; and step four: transporting the molten iron to a converter, and then adding scrap steel and blowing. The present application utilizes the iron-rich red mud, LT dry dedusting ash and limestone to pretreat the molten iron, realizes the recycling of the iron resources and valuable minerals in the solid waste such as the iron-rich red mud and LT dry dedusting ash, and simultaneously reduces the consumption of the pretreatment agent.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization technology of iron and steel smelting resources, specifically to a method for adding iron-rich red mud to the hot metal pretreatment process. Background Technology

[0002] Converter dust generally refers to the fine dust obtained after dry dust removal of the flue gas generated during the converter blowing process. Converter dust contains a large amount of alkaline oxides such as CaO, and is characterized by high iron content, fine particle size, and large specific surface area. The iron element mainly exists in the form of Fe3O4 and Fe2O3. Converter dust is a high-quality iron-containing resource, but due to its high alkaline oxide content and fine particle size, it is not only corrosive but also prone to spontaneous combustion.

[0003] Red mud is a byproduct of alumina production from bauxite. It is reddish-brown due to its high hematite content, hence the name. Red mud is produced in large quantities and has high alkalinity. If traditional treatment methods are used to discharge it into the ocean and / or store it on land, it will severely pollute seawater, air, and soil. This not only occupies a large amount of space but also poses serious ecological and environmental safety risks, and is also a waste of resources.

[0004] Hot metal pretreatment refers to a process that removes impurities or recovers valuable elements from molten iron before it is added to the steelmaking furnace. Hot metal pretreatment processes can be divided into two main categories: ordinary hot metal pretreatment and special hot metal pretreatment. Ordinary hot metal pretreatment includes desulfurization, desiliconization, and dephosphorization of hot metal. Special hot metal pretreatment is generally a process for purifying, refining, or comprehensively utilizing special elements contained in hot metal, such as vanadium extraction, niobium extraction, tungsten extraction, and chromium removal pretreatment processes.

[0005] Hot metal pretreatment is an important process before steelmaking, aiming to improve hot metal quality and increase smelting efficiency. The main methods of hot metal pretreatment include the trough pretreatment method, the ladle injection method, and the mechanical stirring method. The trough pretreatment method involves distributing a pretreatment agent onto the molten iron in the trough during tapping from the blast furnace. The turbulent flow of the molten iron mixes the agent with the pretreatment agent. This method is simple and easy to implement, but the removal efficiency of harmful elements fluctuates greatly and it causes serious environmental pollution. The ladle injection method involves spraying the pretreatment agent into the molten iron in the ladle using a spray gun, allowing it to react fully with the molten iron. This method ensures good contact between the pretreatment agent and the molten iron, resulting in a higher removal efficiency of harmful elements, but it leads to a greater temperature drop in the molten iron and higher operating costs. The KR method is a method that uses stirring to bring a pretreatment agent placed on the surface of molten iron into effective contact with the molten iron. The KR method can be used for deep purification of molten iron, effectively improving the removal efficiency of harmful elements and has low operating costs. It is widely used at home and abroad, but it also has the problems of large temperature drop of molten iron and large consumption of pretreatment agent. Summary of the Invention

[0006] To address the problem of high pretreatment agent consumption in existing technologies using mechanical stirring for molten iron pretreatment, this invention provides a feeding method for incorporating iron-rich red mud in the molten iron pretreatment process. This method utilizes iron-rich red mud, LT dry dust, and limestone to pretreat the molten iron, achieving the recovery and utilization of iron resources and valuable minerals from solid wastes such as iron-rich red mud and LT dry dust, while simultaneously reducing the consumption of pretreatment agents.

[0007] The technical solution of this invention is as follows: A method for adding iron-rich red mud during the hot metal pretreatment process includes the following steps: Step 1: Use a feeding device to mix the iron-rich red mud, LT dry dust, and limestone evenly to obtain a mixture. Step 2: Use nitrogen gas flow to spray the mixture into the molten iron, lower the stirring head to stir the molten iron for the first time, and after the first stirring is completed, raise the stirring head to the waiting position; Step 3: Lower the stirring head to stir the molten iron a second time. After the second stirring is completed, raise the stirring head to the waiting position. Step 4: Transport the molten iron to the converter, add scrap steel, and then blow it.

[0008] Furthermore, in the mixture, the mass ratio of iron-rich red mud, LT dry dust, and limestone is 4-5:2-2.5:1.

[0009] Furthermore, in the mixture, the total content of CaO is 15wt%-25wt%; and the total content of SiO2 is 2wt%-2.5wt%.

[0010] Furthermore, in step two, the amount of the mixture added per ton of steel is calculated according to the following formula: , G represents the amount of steel added per ton of the mixture, expressed in kg / t. G0 represents the historical average of the amount of mixed materials added per ton of steel in the current year, expressed in kg / t. T represents the temperature of the molten iron in this furnace, in °C. T 平均 This is the average temperature of molten iron from all furnaces in this shift, in °C. (Si+P) represents the sum of the Si and P content in this batch of molten iron, expressed in wt% (%). (Si+P) 平均 This represents the average sum of Si and P content in the molten steel from all heats in this shift, expressed in wt%; T 经验 This represents the historical average temperature of molten iron for this year, in °C. This is the correction factor for the temperature of the molten iron in this furnace. t 预熔 The pre-melting time of limestone is expressed in minutes (min). It is the predicted time from when the mixture is injected into the molten iron until the start of blowing operations, expressed in tons (t). 预熔经验 This represents the historical average of limestone pre-melting time for this year, in minutes. This is a correction factor for the limestone pre-melting time; t 分解 This represents the theoretical calculation time for the decomposition of limestone into CaO and CO2, expressed in minutes (t). 分解经验 This represents the historical average of the time taken for limestone to decompose into CaO and CO2 in the current year, expressed in minutes. This is a correction factor for the theoretical calculation time of limestone decomposing into CaO and CO2.

[0011] Furthermore, in the iron-rich red mud, the content of Fe2O3 is 30wt%-60wt%, the content of SiO2 is 3wt%-20wt%, the content of Al2O3 is 10wt%-20wt%, the content of CaO is 2wt%-10wt%, the content of Na2O is 2wt%-10wt%, and the content of TiO2 is 0.1wt%-10wt%.

[0012] Furthermore, the LT dry dust contains 46wt%-47wt% TFe, 15wt%-20wt% CaO, 1.2wt%-1.5wt% SiO2, 0wt%-1wt% Al2O3, 1wt%-6.5wt% MgO, and 0.06wt%-0.37wt% S. Other components include, but are not limited to, P, MnO, TiO2, Na2O, and K2O. The LT dry dust is produced using an evaporative cooler + electrostatic precipitator + gas cooler system. This type of dust exhibits excellent slag-forming effects, with a cooling capacity approximately 0.85 times that of ore. It effectively reduces the consumption of slag-forming materials and high-priced cold materials, improves converter endpoint control, and allows for the maximum recovery of iron elements through the return of LT dry dust to the furnace.

[0013] Furthermore, the limestone has a particle size of 5-15mm and is dry and free of impurities. Small-particle limestone can decompose into CaO and CO2 at a relatively fast rate in molten iron. CaO can increase the basicity of converter slag and reduce the consumption of lime in slag-forming materials, and can also provide a calcium source for the formation of composite calcium ferrite. CO2 can improve the fluidity of pre-melted slag in the ladle and prevent clumping and caking.

[0014] Furthermore, in step two, the stirring head is lowered to 300-500mm below the molten iron surface for the first stirring. The stirring head rotates at 30-50 rpm, and the first stirring lasts for 3-5 minutes. A KR stirring head is preferred. During the first stirring, the iron-rich red mud, LT dry dust, and fine-grained limestone are thoroughly mixed with the iron slag in the ladle. Controlling the stirring head speed at 30-50 rpm avoids dust overflow caused by vigorous stirring, reducing material loss and waste.

[0015] Furthermore, in step three, the stirring head is lowered to 200-300mm below the molten iron surface for a second stirring. The stirring head rotates at 40-60 rpm, and the second stirring lasts for 1-2 minutes. During the second stirring, the iron-rich red mud, LT dry dust, and fine-grained limestone can be further mixed with the iron slag in the ladle to ensure uniform mixing.

[0016] Furthermore, the feeding device includes a high-pressure nitrogen source, which is connected to the airflow inlet of the mixing storage tank, the airflow inlet of the molten iron ladle, and the desulfurizing agent tank. The inlet of the mixing storage tank is connected to the rich iron red mud silo, the LT dry dust collector ash silo, and the small-particle limestone silo. The outlet of the mixing storage tank and the outlet of the desulfurizing agent tank are connected to the molten iron ladle. A mixing chamber can be installed between the inlet of the mixing storage tank and the rich iron red mud silo, the LT dry dust collector ash silo, and the small-particle limestone silo. A stirring device is installed in the mixing chamber. The rich iron red mud, LT dry dust collector ash, and small-particle limestone can first enter the mixing chamber and be mixed evenly before entering the mixing storage tank for storage as a mixture. The high-pressure nitrogen source can be used as a transport carrier to transport the mixture or desulfurizing agent to the molten iron ladle, or it can directly enter the molten iron ladle to blow nitrogen.

[0017] The beneficial effects of this invention are as follows: This invention provides a method for feeding iron-rich red mud into the pretreatment process of molten iron. It fully utilizes the waiting time between the end of desulfurization and the addition to the converter during the pretreatment process. Limestone, industrial solid waste iron-rich red mud, and LT dry dust are mixed evenly and then injected into the molten iron using nitrogen gas as a carrier. The existing stirring head used in the pretreatment process is then used to perform a first and second stirring of the molten iron, promoting the uniform dispersion of limestone, iron-rich red mud, and LT dry dust in the molten iron. Under the heat provided by the molten iron, limestone, iron-rich red mud, and LT dry dust can form a low-melting-point composite calcium ferrite phase. This provides favorable conditions for the recovery of iron resources and valuable minerals from the red mud and LT dry dust, as well as for slag formation and rapid dephosphorization in the early stages of smelting. Simultaneously, the composite calcium ferrite covering the slag layer on the ladle also provides insulation, reducing heat loss and temperature drop in the molten iron during the pretreatment process. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the connection relationship of the feeding device in Example 1.

[0020] In the diagram, 1-rich iron-rich red mud silo, 2-LT dry dust removal ash silo, 3-small-particle limestone silo, 4-first feed pipe, 5-second feed pipe, 6-third feed pipe, 7-mixing silo, 8-fourth feed pipe, 9-mixing storage tank, 10-first pneumatic conveying pipe, 11-second pneumatic conveying pipe, 12-desulfurizing agent tank, 13-high-pressure nitrogen source, 14-third pneumatic conveying pipe, 15-first mixing conveying pipe, 16-second mixing conveying pipe, 17-switching valve, 18-feeding chute, 19-molten iron ladle. Detailed Implementation

[0021] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0022] Example 1 A feeding device, such as Figure 1As shown, the system includes a rich iron red mud silo 1, an LT dry dust removal ash silo 2, and a small-particle limestone silo 3. The outlets of the rich iron red mud silo 1, the LT dry dust removal ash silo 2, and the small-particle limestone silo 3 are connected to the inlet of a mixing silo 7 via a first feed pipe 4, a second feed pipe 5, and a third feed pipe 6, respectively. The mixing silo 7 is equipped with a mechanical stirring paddle. The outlet of the mixing silo 7 is connected to the inlet of a mixing storage tank 9 via a fourth feed pipe 8. The outlet of the mixing storage tank 9 is connected to the inlet of a switching valve 17 via a first mixing conveying pipe 15. The outlet of the switching valve 17 is connected to a ladle 19 via a discharge chute 18. The mixing storage tank 9 is equipped with an airflow inlet. The airflow inlet of the mixing storage tank 9 is connected to the high-pressure nitrogen source 13 through the first airflow conveying pipe 10. The high-pressure nitrogen source 13 is connected to the airflow inlet of the desulfurizing agent tank 12 through the second airflow conveying pipe 11. The outlet of the desulfurizing agent tank 12 is connected to the inlet of the switching valve 17 through the second mixing conveying pipe 16. The high-pressure nitrogen source 13 is also connected to the inlet of the switching valve 17 through the third airflow conveying pipe 14.

[0023] The discharge ports of the iron-rich red mud silo 1, the LT dry dust removal ash silo 2, the small-particle limestone silo 3, the mixing silo 7, the mixing storage tank 9, and the desulfurizing agent tank 12 are each equipped with a discharge gate valve. A first nitrogen shut-off valve, a second nitrogen shut-off valve, and a third nitrogen shut-off valve are respectively installed at the connections between the high-pressure nitrogen source 13 and the first airflow conveying pipe 10, the second airflow conveying pipe 11, and the third airflow conveying pipe 14.

[0024] Example 2 A method for feeding iron-rich red mud into the molten iron pretreatment process using the feeding device described in Example 1 includes the following steps: Step 1: Open the discharge valves of the rich iron red mud silo, the LT dry dust collector ash silo, and the small-particle limestone silo. Discharge the rich iron red mud from the rich iron red mud silo, the LT dry dust collector ash from the LT dry dust collector silo, and the small-particle limestone from the small-particle limestone silo into the mixing chamber at a mass ratio of 4.25:2.15:1. Then, use the mechanical agitator in the mixing chamber to mix the materials evenly. The resulting mixture is stored in a mixing storage tank for later use. The rich iron red mud contains 30wt%-60wt% Fe2O3, 3wt%-20wt% SiO2, 10wt%-20wt% Al2O3, 2wt%-10wt% CaO, 2wt%-10wt% Na2O, and 0.1wt%-10wt% TiO2. In the LT dry dust collector ash, the content of TFe is 46wt%-47wt%, CaO is 15wt%-20wt%, SiO2 is 1.2wt%-1.5wt%, Al2O3 is 0wt%-1wt%, MgO is 6.5wt%, and S is 0.06wt%-0.37wt%. Other components include, but are not limited to, P, MnO, TiO2, Na2O, and K2O. The limestone is dry, free of impurities, and has a particle size of 5-15mm.

[0025] The historical average annual amount of the mixed feedstock added per ton of steel, G0, is 8.6 kg / t, and the historical average annual temperature of the molten iron, T, is... 经验 =1536℃, the historical average of limestone pre-melting time for this year (t) 预熔经验 =8 min, the historical average time (t) of limestone decomposition into CaO and CO2 for this year's furnace runs. 分解经验 =12min. The molten iron temperature of this furnace is T=1362℃, and the average temperature of the molten iron in all furnaces during this shift is T. 平均 =1356℃; t 预熔 t 分解 The times were 8.3 min and 12.6 min respectively; the sum of Si and P elements in the molten iron of this batch (Si+P) = 0.62 wt%; the sum of Si and P elements in the molten steel of each batch in this shift (Si+P) 平均 =0.56wt%, substitute the above parameters into the following formula to calculate the amount of steel added per ton of the mixture, G:

[0026]

[0027] ≈9.238 kg / t; The amount of molten iron processed in this embodiment is 140t, therefore the total amount of mixed materials added in this furnace is G. 总 The weight is G × 140 = 1293.32 kg. 总 =G 泥 +G 灰 +G 石 G 泥 The amount of iron-rich red mud added, G 灰 G represents the amount of dust added during the LT dry dust removal process. 石 This refers to the amount of fine-grained limestone added. (G) 泥 :G 灰 :G 石 The formula G = 4.25 : 2.15 : 1 can be used to calculate G. 泥 =742.79kg, G 灰 =375.76kg, G 石 =174.77kg.

[0028] The total CaO content and total SiO2 content in the mixture can be calculated using the following formulas: [CaO(G) 泥 ) + CaO (G 灰 ) + CaO (G 石 )] / G 总 =23wt% [SiO2(G 泥 ) + SiO2 (G 灰 ) + SiO2 (G 石 )] / G 总 =2.25wt%; CaO (G) 泥 ), CaO (G 灰 ), CaO (G 石 The following are the masses of CaO introduced into the mixture from iron-rich red mud, LT dry dust removal ash, and fine-grained limestone, respectively, in kg; SiO2 (G 泥 ), SiO2 (G 灰 ), SiO2 (G 石 The figures () represent the mass of iron-rich red mud, LT dry dust, and SiO2 introduced from small-particle limestone in the mixture, respectively, in kg.

[0029] Step 2: Open the discharge gate valve and the second nitrogen shut-off valve of the desulfurizing agent silo, and control the switching valve to open the passage between the desulfurizing agent tank and the molten iron ladle. Use the high-pressure nitrogen gas flow to spray the desulfurizing agent in the desulfurizing agent tank into the molten iron in the molten iron ladle, stir and desulfurize, and then remove the slag.

[0030] Step 3: After the slag removal is completed, close the discharge gate valve of the desulfurizing agent silo and the second nitrogen shut-off valve. At the same time, open the discharge gate valve of the mixing storage tank and the first nitrogen shut-off valve, and control the switching valve to open the passage between the mixing storage tank and the molten iron ladle. Use high-pressure nitrogen gas flow to spray the mixture in the mixing storage tank into the molten iron. Then, slowly lower the KR stirring head to 350mm below the molten iron surface for the first stirring. The rotation speed of the KR stirring head is 40 rpm, and the duration of the first stirring is 3.5 minutes. After the first stirring is completed, raise the KR stirring head to the waiting position and wait for 2 minutes.

[0031] Step 4: Slowly lower the KR stirring head to 250mm below the molten iron surface to stir the molten iron a second time. The KR stirring head rotates at 50 rpm and the second stirring lasts for 2 minutes. After the second stirring is completed, raise the stirring head to the waiting position to obtain molten iron containing pre-melted slag.

[0032] Step 5: Move the ladle car to the waiting position, awaiting the overhead crane to transport it to the converter. Add scrap steel and molten iron containing pre-melted slag into the converter, then begin blowing. During blowing, first lower the oxygen lance to a position 1000mm from the molten pool surface, controlling the oxygen flow rate at 10000m³. 3 / h, time is 3min, then switch to normal blowing and corresponding operations.

[0033] The oxygen lance position was adjusted according to the slag formation. The blowing process was stable, without any abnormalities such as "splashing" or "drying out." The steel was tapped and alloyed normally after the blowing process. Compared with the historical average, the amount of active lime added per ton of steel was reduced by 0.23 kg, the blowing time was shortened by 15 seconds, the phosphorus content at the end of the blowing process was reduced by 0.002%, and the weight of the molten steel increased by 210 kg.

[0034] Example 3 A method for feeding iron-rich red mud into the molten iron pretreatment process using the feeding device described in Example 1 includes the following steps: Step 1: Open the discharge valves of the rich iron red mud silo, the LT dry dust collector ash silo, and the small-particle limestone silo. Discharge the rich iron red mud from the rich iron red mud silo, the LT dry dust collector ash from the LT dry dust collector silo, and the small-particle limestone from the small-particle limestone silo into the mixing silo at a mass ratio of 4.5:2.25:1. Then, use the mechanical agitator in the mixing silo to mix the materials evenly. The resulting mixture is stored in a mixing storage tank for later use. The rich iron red mud contains 30wt%-60wt% Fe2O3, 3wt%-20wt% SiO2, 10wt%-20wt% Al2O3, 2wt%-10wt% CaO, 2wt%-10wt% Na2O, and 0.1wt%-10wt% TiO2. In the LT dry dust collector ash, the content of TFe is 46wt%-47wt%, CaO is 15wt%-20wt%, SiO2 is 1.2wt%-1.5wt%, Al2O3 is 0wt%-1wt%, MgO is 6.5wt%, and S is 0.06wt%-0.37wt%. Other components include, but are not limited to, P, MnO, TiO2, Na2O, and K2O. The limestone is dry, free of impurities, and has a particle size of 5-15mm.

[0035] The historical average annual amount of the mixed feedstock added per ton of steel, G0, is 8.6 kg / t; the historical average annual temperature of the molten iron, T, is... 经验 =1536℃, the historical average of limestone pre-melting time for this year (t) 预熔经验 =8 min, the historical average time (t) of limestone decomposition into CaO and CO2 for this year's furnace runs. 分解经验 =12min. The molten iron temperature of this furnace is T=1356℃, and the average temperature of the molten iron in all furnaces during this shift is T. 平均 =1365℃; t 预熔 t 分解 The times were 8.1 min and 12.3 min respectively; the sum of Si and P elements in the molten iron of this batch (Si+P) = 0.58 wt%; the sum of Si and P elements in the molten steel of each batch in this shift (Si+P) 平均 =0.55wt%, substitute the above parameters into the following formula to calculate the amount of steel added per ton of the mixture, G:

[0036]

[0037] ≈8.254 kg / t; The amount of molten iron processed in this embodiment is 142t, therefore the total amount of mixed materials added in this furnace is G. 总 G × 142 = 1172.068 kg, G 总 =G 泥 +G 灰 +G 石 G 泥 The amount of iron-rich red mud added, G 灰 G represents the amount of dust added during the LT dry dust removal process. 石 This refers to the amount of fine-grained limestone added. (G) 泥 :G 灰 :G 石 G can be calculated from the ratio 4.5:2.25:1. 泥 :G 灰 :G 石 =4.5 : 2.25 : 1 = 680.56 : 340.28 : 151.23, which is G 泥 =680.56kg, G 灰 =340.28kg, G 石 =151.23kg.

[0038] The total CaO content and total SiO2 content in the mixture can be calculated using the following formulas: [CaO(G) 泥 ) + CaO (G 灰 ) + CaO (G 石 )] / G 总 =21wt%; [SiO2(G 泥 ) + SiO2 (G 灰 ) + SiO2 (G 石 )] / G 总 =2.35wt%; CaO (G) 泥 ), CaO (G 灰 ), CaO (G 石 The following are the masses of CaO introduced into the mixture from iron-rich red mud, LT dry dust removal ash, and fine-grained limestone, respectively, in kg; SiO2 (G 泥 ), SiO2 (G 灰 ), SiO2 (G 石 The figures () represent the mass of iron-rich red mud, LT dry dust, and SiO2 introduced from small-particle limestone in the mixture, respectively, in kg.

[0039] Step 2: Open the discharge gate valve and the second nitrogen shut-off valve of the desulfurizing agent silo, and control the switching valve to open the passage between the desulfurizing agent tank and the molten iron ladle. Use the high-pressure nitrogen gas flow to spray the desulfurizing agent in the desulfurizing agent tank into the molten iron in the molten iron ladle, stir and desulfurize, and then remove the slag.

[0040] Step 3: After the slag removal is completed, close the discharge gate valve of the desulfurizing agent silo and the second nitrogen shut-off valve. At the same time, open the discharge gate valve of the mixing storage tank and the first nitrogen shut-off valve, and control the switching valve to open the passage between the mixing storage tank and the molten iron ladle. Use high-pressure nitrogen gas flow to spray the mixture in the mixing storage tank into the molten iron. Then, slowly lower the KR stirring head to 350mm below the molten iron surface for the first stirring. The rotation speed of the KR stirring head is 45 rpm, and the duration of the first stirring is 3.2 minutes. After the first stirring is completed, raise the KR stirring head to the waiting position and wait for 2 minutes.

[0041] Step 4: Slowly lower the KR stirring head to 280mm below the molten iron surface to stir the molten iron a second time. The KR stirring head rotates at 40 rpm and the second stirring lasts for 2 minutes. After the second stirring is completed, raise the stirring head to the waiting position to obtain molten iron containing pre-melted slag.

[0042] Step 5: Move the ladle car to the waiting position, awaiting the overhead crane to transport it to the converter. Add scrap steel and molten iron containing pre-melted slag into the converter, then begin blowing. During blowing, first lower the oxygen lance to a position 1000mm from the molten pool surface, controlling the oxygen flow rate at 10000m³. 3 / h, time is 2.5min, then switch to normal blowing and corresponding operations.

[0043] The oxygen lance position was adjusted according to the slag formation. The blowing process was stable, without any abnormalities such as "splashing" or "drying out." The steel was tapped and alloyed normally after the blowing process. Compared with the historical average, the amount of active lime added per ton of steel was reduced by 0.18 kg, the blowing time was shortened by 12 seconds, the phosphorus content at the end of the blowing process was reduced by 0.002%, and the weight of the molten steel increased by 170 kg.

[0044] Comparative Example 1 A method for feeding iron-rich red mud into the molten iron pretreatment process using the feeding device described in Example 1 includes the following steps: Step 1: Open the discharge valves of the rich iron red mud silo, the LT dry dust collector ash silo, and the small-particle limestone silo. Discharge the rich iron red mud from the rich iron red mud silo, the LT dry dust collector ash from the LT dry dust collector silo, and the small-particle limestone from the small-particle limestone silo into the mixing chamber at a mass ratio of 3.5:2.0:1. Then, use the mechanical agitator in the mixing chamber to mix the materials evenly. The resulting mixture is stored in a mixing storage tank for later use. The rich iron red mud contains 30wt%-60wt% Fe2O3, 3wt%-20wt% SiO2, 10wt%-20wt% Al2O3, 2wt%-10wt% CaO, 2wt%-10wt% Na2O, and 0.1wt%-10wt% TiO2. In the LT dry dust collector ash, the content of TFe is 46wt%-47wt%, CaO is 15wt%-20wt%, SiO2 is 1.2wt%-1.5wt%, Al2O3 is 0wt%-1wt%, MgO is 6.5wt%, and S is 0.06wt%-0.37wt%. Other components include, but are not limited to, P, MnO, TiO2, Na2O, and K2O. The limestone is dry, free of impurities, and has a particle size of 5-15mm.

[0045] The historical average annual amount of the mixed feedstock added per ton of steel, G0, is 8.6 kg / t, and the historical average annual temperature of the molten iron, T, is... 经验 =1536℃, the historical average of limestone pre-melting time for this year (t) 预熔经验 =8 min, the historical average time (t) of limestone decomposition into CaO and CO2 for this year's furnace runs. 分解经验 =12min. The molten iron temperature of this furnace is T=1376℃, and the average temperature of the molten iron in all furnaces during this shift is T. 平均 =1365℃; The sum of Si and P elements in this heat of molten iron (Si+P) = 0.58wt%; The sum of Si and P elements in the molten steel of all heats in this shift (Si+P) 平均 =0.55wt%, the iron temperature T of this heat and the average iron temperature T of all heats in this shift. 平均 The sum of Si and P elements in the molten iron of this batch (Si+P) and the sum of Si and P elements in the molten steel of all batches in this shift (Si+P). 平均 Substitute the following formula to calculate the amount of steel added per ton of the mixture, G:

[0046]

[0047] ≈8.50kg / t; The amount of molten iron processed in this embodiment is 142t, therefore the total amount of mixed materials added in this furnace is G. 总 G × 142 = 1207 kg, G 总 =G 泥 +G 灰 +G 石 G 泥 The amount of iron-rich red mud added, G 灰 G represents the amount of dust added during the LT dry dust removal process. 石 This refers to the amount of fine-grained limestone added. (G) 泥 :G 灰 :G 石 G can be calculated from the ratio 3.5:2.0:1. 泥 :G 灰 :G 石 =3.5 : 2.0 : 1 = 649.92 : 371.38 : 185.69, which is G 泥 =649.92kg, G 灰 =371.38kg, G 石 =185.69kg.

[0048] The total CaO content and total SiO2 content in the mixture can be calculated using the following formulas: [CaO(G) 泥 ) + CaO (G 灰 ) + CaO (G 石 )] / G 总 =21wt%; [SiO2(G 泥 ) + SiO2 (G 灰 ) + SiO2 (G 石 )] / G 总 =2.35wt%; CaO (G) 泥 ), CaO (G 灰 ), CaO (G 石 The following are the masses of CaO introduced into the mixture from iron-rich red mud, LT dry dust removal ash, and fine-grained limestone, respectively, in kg; SiO2 (G 泥 ), SiO2 (G 灰 ), SiO2 (G 石 The figures () represent the mass of iron-rich red mud, LT dry dust, and SiO2 introduced from small-particle limestone in the mixture, respectively, in kg.

[0049] Step 2: Open the discharge gate valve and the second nitrogen shut-off valve of the desulfurizing agent silo, and control the switching valve to open the passage between the desulfurizing agent tank and the molten iron ladle. Use the high-pressure nitrogen gas flow to spray the desulfurizing agent in the desulfurizing agent tank into the molten iron in the molten iron ladle, stir and desulfurize, and then remove the slag.

[0050] Step 3: After the slag removal is completed, close the discharge gate valve of the desulfurizing agent silo and the second nitrogen shut-off valve. At the same time, close the discharge gate valve and the first nitrogen shut-off valve of the mixing storage tank, and control the switching valve to open the passage between the mixing storage tank and the molten iron ladle. Use high-pressure nitrogen gas flow to spray the mixture in the mixing storage tank into the molten iron. Then, slowly lower the KR stirring head to 350mm below the molten iron surface for the first stirring. The rotation speed of the KR stirring head is 45 rpm, and the duration of the first stirring is 3.2 minutes. After the first stirring is completed, raise the KR stirring head to the waiting position and wait for 2 minutes.

[0051] Step 4: Slowly lower the KR stirring head to 280mm below the molten iron surface to stir the molten iron a second time. The KR stirring head rotates at 40 rpm and the second stirring lasts for 2 minutes. After the second stirring is completed, raise the stirring head to the waiting position to obtain molten iron containing pre-melted slag.

[0052] Step 5: Move the ladle car to the waiting position, awaiting the overhead crane to transport it to the converter. Add scrap steel and molten iron containing pre-melted slag into the converter, then begin blowing. During blowing, first lower the oxygen lance to a position 1000mm from the molten pool surface, controlling the oxygen flow rate at 10000m³. 3 / h, time is 2.5min, then switch to normal blowing and corresponding operations.

[0053] The oxygen lance position was adjusted according to the slag formation. The blowing process was stable, without any abnormalities such as "splashing" or "drying out." The steel was tapped and alloyed normally after the blowing process. Compared with the historical average, the amount of active lime added per ton of steel was reduced by 0.01 kg, the blowing time was shortened by 1 second, the phosphorus content at the blowing endpoint was reduced by 0.001%, and the weight of the molten steel increased by 30 kg.

[0054] Although the present invention has been described in detail with reference to the accompanying drawings and preferred embodiments, the present invention is not limited thereto. Various equivalent modifications or substitutions can be made to the embodiments of the present invention by those skilled in the art without departing from the spirit and essence of the invention, and such modifications or substitutions should all be within the scope of the present invention. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should also be covered within the protection scope of the present invention.

Claims

1. A method for adding iron-rich red mud during the pretreatment process of molten iron, characterized in that, Includes the following steps: Step 1: Use a feeding device to mix the iron-rich red mud, LT dry dust, and limestone evenly to obtain a mixture. Step 2: Use nitrogen gas flow to spray the mixture into the molten iron, lower the stirring head to stir the molten iron for the first time, and after the first stirring is completed, raise the stirring head to the waiting position; Step 3: Lower the stirring head to stir the molten iron a second time. After the second stirring is completed, raise the stirring head to the waiting position. Step 4: Transport the molten iron to the converter, add scrap steel, and then blow it. In the mixture, the mass ratio of iron-rich red mud, LT dry dust, and limestone is 4-5:2-2.5:1; In the mixture, the total content of CaO is 15wt%-25wt%; the total content of SiO2 is 2wt%-2.5wt%. In step two, the amount of the mixture added per ton of steel is calculated according to the following formula: ， G represents the amount of steel added per ton of the mixture, expressed in kg / t. G0 represents the historical average of the amount of mixed materials added per ton of steel in this year, expressed in kg / t. T represents the temperature of the molten iron in this furnace, in °C. T 平均 This is the average temperature of molten iron from all furnaces in this shift, in °C. (Si+P) represents the sum of the Si and P content in this batch of molten iron, expressed in wt% (%). (Si+P) 平均 This represents the average sum of Si and P content in the molten steel from all heats in this shift, expressed in wt%; T 经验 This represents the historical average temperature of molten iron for this year, in °C. t 预熔 The pre-melting time of limestone is expressed in minutes (t). 预熔经验 This represents the historical average of limestone pre-melting time for this year, in minutes. t 分解 This represents the theoretical calculation time for the decomposition of limestone into CaO and CO2, expressed in minutes (t). 分解经验 This is the historical average of the time it takes for limestone to decompose into CaO and CO2 in the current year, in minutes. In step two, the stirring head is lowered to 300-500mm below the surface of the molten iron to stir the molten iron for the first time. The stirring head rotates at 30-50 rpm and the first stirring lasts for 3-5 minutes. In step three, the stirring head is lowered to 200-300mm below the surface of the molten iron to stir the molten iron a second time. The stirring head rotates at 40-60 rpm, and the second stirring lasts for 1-2 minutes.

2. The feeding method as described in claim 1, characterized in that, The iron-rich red mud contains 30wt%-60wt% Fe2O3, 3wt%-20wt% SiO2, 10wt%-20wt% Al2O3, 2wt%-10wt% CaO, 2wt%-10wt% Na2O, and 0.1wt%-10wt% TiO2.

3. The feeding method as described in claim 1, characterized in that, In the LT dry dust collector, the contents of TFe are 46wt%-47wt%, CaO is 15wt%-20wt%, SiO2 is 1.2wt%-1.5wt%, Al2O3 is 0wt%-1wt%, MgO is 1wt%-6.5wt%, and S is 0.06wt%-0.37wt%.

4. The feeding method as described in claim 1, characterized in that, The limestone has a particle size of 5-15mm.

5. The feeding method according to any one of claims 1-4, characterized in that, The feeding device includes a high-pressure nitrogen source, which is connected to the airflow inlet of the mixing storage tank, the airflow inlet of the molten iron ladle and the desulfurizing agent tank. The feed inlet of the mixing storage tank is connected to the iron-rich red mud silo, the LT dry dust removal ash silo and the small-particle limestone silo. The discharge outlet of the mixing storage tank and the discharge outlet of the desulfurizing agent tank are connected to the molten iron ladle.

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