A method for collaboratively treating iron-rich red mud, converter dust and refined slag in a steelmaking process

Abstract

The present invention relates to the technical field of comprehensive utilization of iron and steel smelting resources, and discloses a method for collaboratively processing iron-rich red mud, converter dust ash, and refining slag in the steelmaking process, comprising: step 1: using a normally used red-hot ladle to preheat and bake a mixture of iron-rich red mud and converter dust ash, evaporating water and drying; step 2: pouring the refining slag into the ladle for mixing, so that the refining slag, iron-rich red mud, and converter dust ash are fully mixed, and then using the waste heat of the refining slag to pre-melt during the waiting time of the ladle during production intervals to obtain pre-melted liquid slag; step 3: pouring the pre-melted liquid slag into a ladle containing molten iron, and further pre-melting during the waiting time for steelmaking to obtain pre-melted slag; step 4: adding scrap steel into the converter, and adding the pre-melted slag together with the molten iron into the converter for blowing. This method reduces the energy consumption of melting slag and the amount of slag-forming agent used, thereby reducing the consumption cost of the steelmaking process.

Description

Technical Field

[0001] The present invention relates to the technical field of comprehensive utilization of steel smelting resources, and in particular to a method for collaboratively processing iron-rich red mud, converter dust removal ash and refined slag in a steelmaking process. Background Art

[0002] Red mud is an industrial solid waste produced during the extraction of alumina by the aluminum industry. It is named for its high iron oxide content and its resemblance to reddish soil. In recent years, with the continuous development of my country's aluminum industry, red mud production has increased significantly. Currently, red mud is primarily treated by stockpiling, but it is also used in the preparation of building materials, adsorption materials, and calcium-silicon agricultural fertilizers. Because red mud is insoluble in water and highly alkaline, its application in construction, environmental protection, and agriculture requires complex pretreatment. This process is lengthy, energy-intensive, and costly, making large-scale industrial red mud disposal difficult. The overall utilization rate of red mud is less than 5%.

[0003] Converter dust generally refers to the fine dust obtained after dry dust removal from the flue gas generated during the converter blowing process. Converter dust contains approximately 60% iron and a large amount of alkaline oxides such as CaO, with the iron primarily present in the form of Fe₃O₄ and Fe₂O₃. Converter dust is characterized by high iron content, fine particle size, and large specific surface area. Current methods for processing and utilizing converter dust include producing iron-based pigments, synthesizing non-normalized iron, preparing new ferrite magnetic materials, producing sintered ore, and producing pellets. However, due to limited technological advancements, these methods have difficulty producing high-performance materials.

[0004] Steel slag is a by-product of the steelmaking process. After being treated in the LF refining furnace, the refined slag has the characteristics of high basicity, low oxidizing properties, and low melting point. Due to its special composition, the refined slag is particularly easy to pulverize, affecting the purity of steel and causing dust pollution. As a result, steel manufacturers have to minimize and control the amount of slag during the steelmaking process, and are unable to recycle the steel slag well. Summary of the Invention

[0005] In response to the technical problem that the comprehensive utilization rate of red mud, converter dust and refining slag is not high, the present invention provides a method for collaboratively treating iron-rich red mud, converter dust and refining slag in the steelmaking process, which fully utilizes the waste heat in the steelmaking process to treat iron-rich red mud, converter dust and refining slag, saves a lot of energy consumption, improves the efficiency of converter slagging, and reduces the use of additives.

[0006] In a first aspect, the present invention provides a method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process, comprising:

[0007] Step 1: Use a normally used red-hot ladle to preheat and bake the mixture of iron-rich red mud and converter dust ash to evaporate the water and dry it. A red-hot ladle refers to an empty ladle used for normal circulation when receiving molten steel during converter tapping, after replacing the ladle slide, nozzle, and filling with drainage sand. The ladle consists of a steel shell and an inner lining, which includes a working layer, an insulation layer, and a permanent layer. The presence of the insulation layer allows the ladle to maintain a high temperature for a long time after tapping, generating a large amount of waste heat. Adding iron-rich red mud and converter dust ash into the ladle can effectively utilize the waste heat to dehydrate and dry the iron-rich red mud and converter dust ash, reducing energy consumption.

[0008] The iron-rich red mud and converter dust ash are packed in bags, and preferably in ton bags, half-ton bags or 20kg hand bags. The ball making and ball pressing processes are omitted to ensure convenient transportation, avoid leakage and dust during transportation, and also reduce the cost of recycling.

[0009] Step 2: Pour the refined slag into the above-mentioned ladle for mixing, so that the refined slag and the iron-rich red mud and the converter dust are fully mixed, and then use the waste heat of the refined slag to pre-melt during the time when the ladle is waiting for steelmaking in the production interval to obtain a preliminary pre-melted liquid slag. The refined slag is the steel slag in the ladle after the continuous casting machine is finished pouring, and is preferably the refined slag treated by the LF refining furnace. This is because the refined slag treated by the LF refining furnace has the characteristics of high basicity, low oxidation, and low melting point. At the same time, due to its special composition, it is also particularly easy to pulverize. Pouring the refined slag into the ladle for mixing, on the one hand, can use the waste heat of the refined slag to increase the temperature of the ladle and provide more heat for preliminary pre-melting; on the other hand, it can reduce the melting point of the liquid slag, increase the slag formation speed during converter blowing, reduce the amount of slag-making materials such as lime and fluorite, reduce the power consumption of the molten slag, realize the recovery of excess steel after pouring, improve the metal yield, and reduce the discharge of industrial waste.

[0010] Step 3: Pour the pre-melted slag into a ladle containing molten iron and further pre-melt it during the steelmaking process to produce pre-melted slag. The pre-melted slag floats on top of the molten iron. While pre-melting further, it utilizes its own waste heat, the ladle's ambient temperature, and the heat within the molten iron to insulate the molten iron within the ladle, minimizing heat loss and thus reducing molten iron usage and steelmaking costs. The resulting pre-melted slag consists of a low-melting-point composite calcium ferrite (SFCA) pre-melted slag and a magnesium-containing composite calcium ferrite (SFCAM).

[0011] Step 4: Scrap is added to the converter, and pre-melted slag is added along with the molten iron for blowing. The addition of scrap helps maintain the thermal balance within the converter. The amount of scrap added depends on the converter's thermal balance and specific process conditions. Because scrap contains few impurities, it works together with the pre-melted slag to effectively reduce slagging and prevent splashing. The pre-melted slag containing SFCA and SFCAM quickly forms a well-melted pre-slag after the converter begins blowing, lowering the pre-melted slag's melting point.

[0012] Furthermore, iron-rich red mud includes the following components by mass fraction: Fe2O3 40%-60%, SiO2 5%-15%, Al2O3 10%-20%, CaO 5%-10%, Na2O 2%-10%, TiO2 2%-10%, and 0%-5% of other components. Fe2O3, CaO, Al2O3, SiO2, etc. contained in iron-rich red mud are all important components in the formation of composite calcium ferrite (SFCA).

[0013] Furthermore, converter dust ash includes the following components by mass: TFe 50%-63%, FeO 30%-50%, CaO 4%-15%, SiO2 0.9%-2.7%, Al2O3 0.4%-0.8%, and MgO 2%-5%. Converter dust ash contains few harmful impurities and contains basic oxides such as CaO and MgO, which can participate in the formation of composite calcium ferrite (SFCA) and magnesium-containing composite calcium ferrite (SFCAM), promoting slagging and dephosphorization.

[0014] Furthermore, the refined slag is the hot steel slag obtained after casting from a continuous casting machine and comprises the following components by mass: SiO2 8%-20%, Al2O3 15%-25%, CaO 40%-60%, MgO 4%-10%, and FeO 0.4%-0.8%. The SiO2, Al2O3, CaO, and MgO contained in the refined slag synergize with iron-rich red mud and converter dust to form composite calcium ferrite (SFCA) and magnesium-rich composite calcium ferrite (SFCAM), further promoting slagging and dephosphorization.

[0015] Furthermore, the mass ratio of iron-rich red mud, converter dust removal ash and refined slag is 1:0.4-0.7:5-8. The formation of the complex calcium ferrite (SFCA) is believed to be the result of the following reactions: 1. Formation of CaO·Fe2O3 (preferably at a reaction temperature of 1050-1150°C); 2. Reaction of Al2O3 with CaO to form calcium aluminate (preferably at a reaction temperature of 1100-1150°C); 3. Melting of calcium aluminate in CaO·Fe2O3 at 1100-1150°C to form monocalcium aluminoferrite; 4. Melting of monocalcium aluminoferrite at 1200-1250°C and reaction with Fe2O3 to form hemicalcium aluminoferrite; 5. Subsequent reaction of hemicalcium aluminoferrite with SiO2 to form SFCA (preferably at a reaction temperature of 1200-1250°C). When the pre-melted slag contains magnesium, a magnesium-containing complex calcium ferrite, known as SFCAM, is formed. The low-melting-point phases of SFCA and SFCAM are well-known as effective slagging and dephosphorization agents. Furthermore, the Al2O3 contained in the pre-melted slag itself also significantly promotes slagging.

[0016] Furthermore, before pouring the refined slag into the ladle in step 2, the ladle bottom argon blowing is turned on, the argon flow rate is controlled at 30-50L / min, and the argon pressure is controlled at 0.5-0.6MPa; after all the refined slag is poured into the ladle, the bottom argon blowing flow rate is increased to 50-70L / min, and stirring is carried out for 1-5 minutes. After the refined slag and the iron-rich red mud and the converter dust are fully mixed, the ladle bottom argon blowing is turned off. Bottom argon blowing can promote the uniform mixing of the refined slag, iron-rich red mud, and converter dust. Opening the ladle bottom argon blowing before pouring the refined slag into the ladle can prevent the slag in the ladle from cooling and solidifying and blocking the argon outlet.

[0017] Furthermore, in step 2, the temperature of the refined slag, iron-rich red mud, and converter dust after being fully mixed is 1200-1300° C., which is more suitable for the formation of composite calcium ferrite SFCA.

[0018] Furthermore, the molten iron in step three is molten iron that has undergone preliminary desulfurization pretreatment and slag skimming treatment.

[0019] Furthermore, after blowing begins in step 4, a slagging agent is added to the converter. The main component of the slagging agent is lime, preferably activated lime. Activated lime has a large specific surface area and is easily soluble, allowing for more complete contact with impurities and improved slagging. Under the action of SFCA and SFCAM, the activated lime dissolves faster, promoting the oxidation reaction and improving slagging efficiency. The addition of the slagging agent also maintains the basicity in the converter, providing favorable conditions for slag dephosphorization in the early stages of blowing, significantly improving the dephosphorization rate.

[0020] The beneficial effects of the present invention are:

[0021] The technical solution provided by the present invention utilizes the heat of the ladle, refined slag and molten iron to convert iron-rich red mud, converter dust removal ash and refined slag into pre-melted slag, thereby reducing the energy consumption of melting the slag and the use of slag-making agents, and reducing the consumption cost of auxiliary materials in the steelmaking process; the pre-melted slag is added to the converter along with the molten iron, thereby improving the recovery rate of the iron element in the pre-melted slag, and at the same time making full use of the slagging effect of other valuable elements, further improving the metal recovery rate of the converter. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention are clearly and completely described below. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention.

[0023] The iron-rich red mud used in the embodiments of the present invention comprises the following components by mass fraction: Fe₂O₃ 40%-60%, SiO₂ 5%-15%, Al₂O₃ 10%-20%, CaO 5%-10%, Na₂O 2%-10%, TiO₂ 2%-10%, and other components 0%-5%. The converter dust comprises the following components by mass fraction: TFe 50%-63%, FeO 30%-50%, CaO 4%-15%, SiO₂ 0.9%-2.7%, Al₂O₃ 0.4%-0.8%, and MgO 2%-5%. The refined slag comprises the following components by mass fraction: SiO₂ 8%-20%, Al₂O₃ 15%-25%, CaO 40%-60%, MgO 4%-10%, and FeO 0.4%-0.8%.

[0024] Example 1

[0025] A method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process, comprising:

[0026] Step 1: Add 1000kg (ton bag) of iron-rich red mud and 500kg (half ton bag) of converter dust ash into a red-hot ladle in normal use for preheating and baking to evaporate the moisture until dry.

[0027] Step 2: Open the bottom of the ladle to blow argon, control the argon flow rate at 30L / min, and the argon pressure at 0.5MPa. In an argon atmosphere, pour 7000kg of refined slag into the above-mentioned ladle for mixing. After all the refined slag is poured into the ladle, increase the bottom blowing argon flow rate to 50L / min and stir for 1 minute to fully mix the refined slag, iron-rich red mud, and converter dust ash. The temperature after mixing is 1260°C. At this time, turn off the bottom blowing argon of the ladle, and use the residual heat of the refined slag to pre-melt during the time when the ladle is waiting for steelmaking during the production interval to obtain a preliminarily pre-melted liquid slag. Among them, the mass ratio of iron-rich red mud, converter dust ash and refined slag is 1:0.5:7, and the refined slag is the hot steel slag obtained after the continuous casting machine is completed.

[0028] Step 3: Pour the pre-melted slag into a ladle containing molten iron, allowing it to float on top of the molten iron. During the waiting period for steelmaking, the slag is further pre-melted to obtain pre-melted slag. The molten iron is the molten iron that has undergone preliminary desulfurization and slag removal.

[0029] Step 4: After cleaning the slag from the previous heat in the converter, scrap steel was added, and pre-melted slag was added along with the molten iron for blowing. After blowing began, lime was added to the converter. Slagging was excellent in the early stages of blowing, and the blowing process was smooth, with no splashing or dry-out. The final blowing temperature and carbon content were perfectly matched, reaching 1635°C, 0.07% carbon, and 0.009% phosphorus. Lime consumption was reduced by 0.1 kg / t steel, and blowing time was shortened by 7 seconds.

[0030] Example 2

[0031] A method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process, comprising:

[0032] Step 1: Add 1000kg (ton bag) of iron-rich red mud and 600kg (half-ton bag) of converter dust into a red-hot ladle for preheating and baking to evaporate the water until dry. The red-hot ladle is the ladle after the previous pouring cycle has completed.

[0033] Step 2: Open the bottom of the ladle to blow argon, control the argon flow rate at 50L / min, and the argon pressure at 0.5MPa. In an argon atmosphere, pour 8000kg of refined slag into the above-mentioned ladle for mixing. After all the refined slag is poured into the ladle, increase the bottom blowing argon flow rate to 60L / min and stir for 2 minutes to fully mix the refined slag, iron-rich red mud, and converter dust ash. The temperature after mixing is 1290°C. At this time, turn off the bottom blowing argon of the ladle, and use the residual heat of the refined slag to pre-melt during the time when the ladle is waiting for steelmaking during the production interval to obtain a preliminarily pre-melted liquid slag. Among them, the mass ratio of iron-rich red mud, converter dust ash and refined slag is 1:0.6:8, and the refined slag is the hot steel slag obtained after the continuous casting machine is completed.

[0034] Step 3: Pour the pre-melted slag into a ladle containing molten iron, allowing it to float on top of the molten iron. During the waiting period for steelmaking, the slag is further pre-melted to obtain pre-melted slag. The molten iron is the molten iron that has undergone preliminary desulfurization and slag removal.

[0035] Step 4: After cleaning the slag from the previous heat in the converter, scrap steel was added, and pre-melted slag was added along with the molten iron for blowing. After blowing began, a slagging agent, lime, was added to the converter. Slagging was excellent in the early stages of blowing, and the blowing process was smooth, with no splashing or dry-out. The final blowing temperature and carbon content were perfectly matched, reaching 1625°C, 0.07% carbon, and 0.095% phosphorus. Lime consumption was reduced by 0.2 kg / t steel, and blowing time was shortened by 10 seconds.

[0036] Example 3

[0037] A method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process, comprising:

[0038] Step 1: Add 1000kg (ton bag) of iron-rich red mud and 400kg (half ton bag) of converter dust ash into a red-hot ladle in normal use for preheating and baking to evaporate the moisture until dry.

[0039] Step 2: Open the bottom of the ladle to blow argon, control the argon flow rate at 40L / min, and the argon pressure at 0.5MPa. In an argon atmosphere, pour 6000kg of refined slag into the above-mentioned ladle for mixing. After all the refined slag is poured into the ladle, increase the bottom blowing argon flow rate to 70L / min and stir for 2.5 minutes to fully mix the refined slag, iron-rich red mud, and converter dust ash. The temperature after mixing is 1220°C. At this time, turn off the bottom blowing argon of the ladle, and use the residual heat of the refined slag to pre-melt during the time when the ladle is waiting for steelmaking during the production interval to obtain a preliminarily pre-melted liquid slag. Among them, the mass ratio of iron-rich red mud, converter dust ash and refined slag is 1:0.4:6, and the refined slag is the hot steel slag obtained after the continuous casting machine is completed.

[0040] Step 2: Pour 6000 kg of refined slag into the above-mentioned ladle for mixing, so that the refined slag, iron-rich red mud and converter dust are fully mixed, and then use the waste heat of the refined slag to pre-melt it while waiting for steelmaking to obtain preliminarily pre-melted liquid slag.

[0041] Step 3: Pour the pre-melted slag into a ladle containing molten iron, allowing it to float on top of the molten iron. During the waiting period for steelmaking, the slag is further pre-melted to obtain pre-melted slag. The molten iron is the molten iron that has undergone preliminary desulfurization and slag removal.

[0042] Step 4: Scrap steel was added to the converter, and pre-melted slag was added along with the molten iron for blowing. After blowing began, lime was added to the converter. Slagging was excellent in the early stages of blowing, and the blowing process was smooth, with no splashing or dry-out. The final blowing temperature and carbon content were perfectly matched, reaching 1636°C, 0.075% carbon, and 0.09% phosphorus. Lime consumption was reduced by 0.25 kg / t steel, and blowing time was shortened by 12 seconds.

[0043] As can be seen from Examples 1-3, the coordinated treatment of iron-rich red mud, converter dust removal ash, and refined slag in the steelmaking process helps to smoothly carry out the blowing process, and there is no splashing during the blowing process, which avoids heat loss caused by splashing and further saves energy; the use of iron-rich red mud and converter dust removal ash increases the FeO content, the drying-out phenomenon occurs during the blowing process, and the slag has good fluidity; the blowing endpoint temperature and carbon content are hit at one time, which reduces the smelting cost; the use of the technical solution disclosed in the present application can also help dephosphorization, reduce lime consumption, and shorten the blowing time.

[0044] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and substance of the present invention, persons of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any changes or substitutions that can be readily conceived by persons skilled in the art within the technical scope disclosed in the present invention shall be within the scope of protection of the present invention.

Claims

1. A method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process, characterized in that: include: Step 1: Use a red-hot ladle in normal use to preheat and bake the mixture of iron-rich red mud and converter dust to evaporate the water until it is dry; Step 2: Pour the refined slag into the ladle for mixing, so that the refined slag, iron-rich red mud and converter dust are fully mixed, and then use the waste heat of the refined slag to pre-melt during the waiting time of the ladle during production intervals to obtain preliminarily pre-melted liquid slag; Step 3: Pour the pre-melted slag into a ladle containing molten iron, and further pre-melt it during the waiting time for steelmaking to obtain pre-melted slag; Step 4: Add scrap steel into the converter, and add pre-melted slag along with molten iron into the converter for blowing; Refined slag is the hot steel slag obtained after pouring in the continuous casting machine, and includes the following components by mass fraction: SiO2 8%-20%, Al2O3 15%-25%, CaO 40%-60%, MgO 4%-10%, FeO 0.4%-0.8%; The mass ratio of iron-rich red mud, converter dust removal ash and refined slag is 1:0.4-0.7:5-8.

2. The method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process according to claim 1, wherein: The iron-rich red mud includes the following components in mass fraction: Fe2O3 40%-60%, SiO2 5%-15%, Al2O3 10%-20%, CaO 5%-10%, Na2O 2%-10%, TiO2 2%-10%, and other components 0%-5%.

3. The method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process according to claim 1, wherein: Converter dust ash includes the following components by mass fraction: TFe 50%-63%, FeO 30%-50%, CaO4%-15%, SiO2 0.9%-2.7%, Al2O3 0.4%-0.8%, and MgO 2%-5%.

4. The method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process according to claim 1, wherein: Before pouring the refined slag into the ladle in step 2, open the bottom blowing argon of the ladle, control the argon flow rate at 30-50 L / min, and control the argon pressure at 0.5-0.6 MPa; after all the refined slag is poured into the ladle, increase the bottom blowing argon flow rate to 50-70 L / min, and stir for 1-5 minutes. After the refined slag, iron-rich red mud, and converter dust are fully mixed, close the bottom blowing argon of the ladle.

5. The method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process according to claim 1, wherein: In step 2, the temperature of the refined slag, iron-rich red mud and converter dust after being fully mixed is 1200-1300°C.

6. The method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process according to claim 1, wherein: The molten iron in step three is the molten iron that has undergone preliminary desulfurization pretreatment and slag skimming treatment.

7. The method for collaboratively treating iron-rich red mud, converter dust, and refined slag in a steelmaking process according to claim 1, wherein: After blowing begins in step 4, a slagging agent is added to the converter, the main component of which is lime.