High-aluminum slag low-magnesium-aluminum ratio blast furnace ironmaking method

Abstract

The application discloses a kind of high-aluminum slag low magnesium-aluminum ratio blast furnace iron-making methods, it includes the following steps: (1) ore proportioning stage: blast furnace ore proportioning structure is optimized, the sintered ore burden includes fuel, magnesium flux and iron-containing raw material;Regulate the ratio of iron-containing raw material to make the content of Al2O3 in the sintered ore prepared for 2.0~2.4%;The magnesium flux is raw dolomite powder, regulate the total amount of magnesium flux to make the content of MgO in the sintered ore prepared for 1.6~2.0%;(2) blast furnace smelting stage does not add magnesium-containing material into furnace;And optimize the charging system, the proportion of primary coke in coke is 20%~30%;When carrying out ore, coke is added in the position close to the center in blast furnace when burdening.The application breaks through the traditional technical path of adding a large amount of serpentine and dolomite in blast furnace, while increasing the proportion of high-aluminum iron ore of medium-high grade, realizes flux reduction, process simplification, stable furnace condition and cost reduction.

Description

Technical Field

[0001] This invention relates to iron and steel smelting processes, and more particularly to a blast furnace ironmaking method with high-alumina slag and low magnesium-aluminum ratio. Background Technology

[0002] In recent years, with the increasing scarcity of low-alumina, high-grade iron ore, a large amount of medium- to high-grade high-alumina iron ore (Al2O3 content > 2.0%) has been put into use, resulting in a significant increase in the Al2O3 content in blast furnace slag (often reaching 16%–18%). High-alumina slag can cause problems such as increased viscosity, a wider softening range, and a decrease in desulfurization capacity, which seriously restricts the smooth operation and economic efficiency of blast furnaces.

[0003] In their publicly available research, Shen Fengman's team, in their article "Theoretical Basis for Suitable Magnesium-Aluminum Ratio in Blast Furnace Slag" published in *Ironmaking*, pointed out that a higher magnesium-aluminum ratio is not necessarily better in blast furnace smelting. When the alumina content in the slag is in the high range of 16% to 18%, the suitable magnesium-aluminum ratio needs to be controlled within a narrow range of 0.45 to 0.55. If excessive amounts of magnesium flux are added to forcibly increase the ratio, it will not only significantly increase the amount of smelting slag and worsen the permeability of the charge column and the stability of the blast furnace thermal regime, but also lead to increased fuel consumption and iron production costs. There is significant room for improvement in production economics and blast furnace smoothness. The article also clearly provides a countermeasure for smelting high-Al2O3 iron ore—a certain amount of MgO needs to be added to the blast furnace during the smelting of high-Al2O3 iron ore.

[0004] The article "Study on the Addition Methods and Effectiveness of MgO Based on Appropriate Magnesium-Aluminum Ratio" published in Volume 38, Issue 2 of "Ironmaking" further proposed the following methods for adding MgO: one is to add finely ground magnesium-containing flux through sintering process; the second is to prepare high-quality MgO-containing pellets by activating and roasting magnesite; and the third is to supplement MgO by using a tuyer coal powder co-injection method.

[0005] However, the above-mentioned solutions have obvious limitations in engineering applications: relying solely on adding magnesite to pellets will reduce the options for raw material procurement and easily increase production costs for steel companies without supporting pellet production lines; the co-addition of magnesium-containing materials to pulverized coal during the blast furnace smelting stage not only increases the complexity of the process and easily generates dust pollution during operation, but also reduces the calorific value of pulverized coal and may even cause process failures such as pulverized coal lance blockage. In addition, the large-scale use of conventional magnesium fluxes, represented by serpentine and dolomite, will also increase the slag ratio as a whole, exacerbate the retention of slag and iron in the pores of coke, damage the permeability and liquid permeability of the charge column, induce furnace condition fluctuations, furnace wall adhesion and other problems, and simultaneously increase fuel consumption and the overall cost of molten iron preparation.

[0006] Therefore, under the premise of increasing the proportion of high-grade, high-alumina iron ore used in sinter, how to reasonably control the magnesium-aluminum ratio, and achieve flux reduction, process simplification, furnace condition stabilization and cost reduction while increasing the proportion of medium- and high-grade, high-alumina iron ore used, has become a technical problem that the industry urgently needs to solve. Summary of the Invention

[0007] The purpose of this invention is to provide a blast furnace ironmaking method with high-alumina slag and low magnesium-aluminum ratio.

[0008] The technical solution to achieve the objective of this invention is: a blast furnace ironmaking method with high-alumina slag and low magnesium-aluminum ratio, comprising the following steps: (1) Ore blending stage: The blast furnace ore blending structure is optimized, and the composition and weight percentage of each raw material in the blast furnace ore blending structure are as follows: 75-85% sintered ore 0-15% of the pellets Lump ore 0-20%, The sintering ore batch includes fuel, magnesium flux, and iron-containing raw materials; the iron-containing raw materials include high-alumina iron ore, and the proportion of iron-containing raw materials is adjusted by mass percentage to ensure that the Al2O3 content in the prepared sinter is 2.0-2.4%; the magnesium flux is raw dolomite powder, and the total amount of magnesium flux is adjusted by mass percentage to ensure that the MgO content in the prepared sinter is 1.6-2.0%; the pellets and the lump ore are conventional lump ore and pellets used in metallurgical sintering batching. (2) Blast furnace smelting stage: 2.1) No magnesium-containing materials should be added to the furnace; 2.2) Optimize the charging system, including optimizing the composition of the coke fed into the furnace, wherein the dry quenching coke accounts for more than 70% of the weight of the coke, and the proportion of primary coke in the coke is 20%-30%; at the same time, when charging the ore and coke, add coke near the center of the blast furnace. 2.3) Increase the binary basicity R2 of the slag to the range of 1.20 to 1.25, and control the molten iron temperature in the range of 1480 to 1520 ℃.

[0009] Furthermore, the high-alumina iron ore is any one or more of the following: Jingbuba powder, Brazilian coarse powder, SP10 powder, Caterpillar powder, Jinbao powder, Wiluna powder, super-fine powder, Kuli powder, and PMI powder.

[0010] This invention addresses numerous shortcomings in existing methods for controlling the magnesium-aluminum ratio in high-alumina iron ore smelting. It achieves this by adding an appropriate amount of magnesium flux to the sinter during the ore blending stage, eliminating the need for additional magnesium during blast furnace smelting, optimizing the charging system and coke structure, and precisely controlling the binary basicity of the slag and the temperature of the molten iron through an integrated control approach. This multi-stage technological synergy breaks through the traditional reliance on large-scale additions of serpentine and dolomite to the blast furnace. While increasing the proportion of medium-to-high grade high-alumina iron ore used, it also reduces flux usage, simplifies the process, stabilizes furnace conditions, and lowers costs. Specifically: 1. This invention uses raw dolomite powder containing magnesium oxide as a magnesium flux and adds it directly during the sintering and ore blending stage. This allows MgO to be uniformly pre-distributed in the sinter and participate in the mineral phase reconstruction, so that the material fed into the furnace has a reasonable magnesium content. No additional magnesium-containing materials are added during the blast furnace smelting process. This avoids the process failures and cost increases caused by magnesium addition at the blast furnace end from the source, and solves the problem of limited raw material selection for enterprises without pellet production lines. 2. This invention optimizes the charging system and controls the proportion of dry quenching coke to ≥70% and the proportion of primary coke to 20%-30%. Utilizing the high strength, low reactivity, and uniform particle size of dry quenching coke, it significantly improves the permeability and liquid permeability of the blast furnace column. This effectively offsets the risk of fluidity degradation caused by high-alumina slag, inhibits slag and iron retention in coke pores, and avoids furnace condition fluctuations and furnace wall adhesion. With improved raw material quality, especially coke quality, the temperature difference between the soft water and the blast furnace cooling wall decreases to approximately 1.5℃, resulting in smooth furnace operation. This creates a strong and stable central airflow and uniform peripheral airflow, ensuring smooth blast furnace operation and reducing fuel consumption. Central coke addition compensates for the weakened central airflow and insufficient hearth heat caused by slow blast, effectively overcoming the problem of deteriorated permeability due to increased slag viscosity under low magnesium-aluminum ratio conditions. Therefore, the charging system and pre-sintering magnesium addition work synergistically: on the one hand, forward flux movement reduces slag volume increase; on the other hand, high-quality coke strengthens the support of the blast furnace column, enabling stable smooth operation of the blast furnace without additional flux replenishment. 3. This invention controls the binary basicity R2 of the slag at 1.20–1.25 and the molten iron temperature at 1480–1520℃. Without blindly increasing the magnesium-aluminum ratio, it achieves optimal slag viscosity, fluidity, and desulfurization capacity simultaneously through the coupling of basicity optimization, temperature control, and pre-mixing of magnesium. This significantly increases the sulfur distribution coefficient, ensuring that the sulfur content of the molten iron is stably controlled within a reasonable range of 0.015%–0.030%, and the molten iron temperature is controlled within the range of 1480–1520℃ to maintain slag fluidity and avoid the decrease in heat exchange efficiency caused by increased viscosity. This avoids the problems of increased slag ratio and fuel consumption due to an excessively high magnesium-aluminum ratio, as well as the problems of slag stickiness and blast furnace instability caused by an excessively low magnesium-aluminum ratio. Detailed Implementation

[0011] The preferred embodiments of the present invention will be described in detail below. Example 1

[0012] A blast furnace ironmaking method with high-alumina slag and low magnesium-aluminum ratio includes the following steps: (1) Ore blending stage: The blast furnace ore blending structure is optimized, and the composition and weight percentage of each raw material in the blast furnace ore blending structure are as follows: 77% sintered ore 0% of the balls Lump ore 23%, The sintering ore batch includes fuel, magnesia flux, and iron-containing raw materials; the iron-containing raw materials include high-alumina iron ore, and the proportion of iron-containing raw materials is adjusted by mass percentage to ensure that the Al2O3 content in the prepared sintering ore is 2.37%; the magnesia flux is raw dolomite powder, and the total amount of magnesia flux is adjusted by mass percentage to ensure that the MgO content in the prepared sintering ore is 1.89%; The sintering ore batching table is shown in Table 1: Table 1

[0013] (2) Blast furnace smelting stage: 2.1) No magnesium-containing materials should be added to the furnace; 2.2) Optimize the charging system, including optimizing the composition of the coke fed into the furnace. The coke is classified into water-quenched coke and dry-quenched coke according to the moisture / equilibrium moisture index in T / CCIAA 33-2024. The dry-quenched coke accounts for 80% of the coke weight (20% of the first-grade coke conforms to GB / T 1996-2017). At the same time, when charging the ore and coke, coke is added near the center of the blast furnace. 2.3) Increase the binary basicity of the slag R2 to 1.26, control the molten iron temperature at 1485-1515℃ (average temperature 1501℃), and the magnesium-aluminum ratio of the slag is 0.48; the formula for calculating the binary basicity of the slag is R2=w(CaO) / w(SiO2).

[0014] This process adjustment, through optimization of raw material structure and slag control scheme, achieved simultaneous cost reductions in both sintering and blast furnace stages, resulting in significant economic benefits: After the adjustment in the sintering process, the amount of iron-containing raw materials used increased from 918 kg / t to 924.5 kg / t, the comprehensive unit price decreased from 825.88 yuan / t to 758.42 yuan / t, and the comprehensive cost of iron-containing raw materials decreased from 758.16 yuan / ton to 701.16 yuan / ton, a cost reduction of 57 yuan per ton of sinter. In the blast furnace process, the cost of molten iron raw materials decreased from 1531.58 yuan / ton to 1423.69 yuan / ton, a cost reduction of 107.89 yuan per ton of molten iron; the fuel ratio decreased from 515.4 kg / tFe to 508.48 kg / tFe, resulting in a significant decrease in fuel consumption; and the amount of serpentine flux used in the furnace decreased from 15.19 kg / tFe to 0. Example 2

[0015] A blast furnace ironmaking method with high-alumina slag and low magnesium-aluminum ratio includes the following steps: (1) Ore blending stage: The blast furnace ore blending structure is optimized, and the composition and weight percentage of each raw material in the blast furnace ore blending structure are as follows: 83% sintered ore 3% of the ball Block ore 14%, The sintering ore batch includes fuel, magnesia flux, and iron-containing raw materials; the iron-containing raw materials include high-alumina iron ore, and the proportion of iron-containing raw materials is adjusted by mass percentage to ensure that the Al2O3 content in the prepared sintering ore is 2.4%; the magnesia flux is raw dolomite powder, and the total amount of magnesia flux is adjusted by mass percentage to ensure that the MgO content in the prepared sintering ore is 1.9%; The sintering ore batching table is shown in Table 2: Table 2

[0016] (2) Blast furnace smelting stage: 2.1) No magnesium-containing materials should be added to the furnace; 2.2) Optimize the charging system, including optimizing the composition of the coke fed into the furnace. The coke includes water-quenched coke and dry-quenched coke, with dry-quenched coke accounting for 90% of the weight of the coke (of which Grade I coke accounts for 25%) and water-quenched coke accounting for 10%. At the same time, when charging the ore and coke, coke is added near the center of the blast furnace. 2.3) Increase the binary basicity R2 of the slag to 1.24, control the molten iron temperature in the range of 1488~1517 (average temperature 1502)℃, and the magnesium-aluminum ratio of the slag is 0.495.

[0017] This process adjustment, through optimization of raw material structure and slag control scheme, achieved a simultaneous reduction in costs for both sintering and blast furnace stages, resulting in a significant improvement in economic benefits: After the adjustment of the sintering process, the unit consumption of iron-containing raw materials is 922 kg / t, with a comprehensive unit price of 747.35 yuan / ton, and the comprehensive cost of iron-containing raw materials is 689.05 yuan / ton of sintered ore; the unit consumption of magnesia flux (raw dolomite powder) is 7.8 kg / ton of sintered ore, with a unit cost of 7.01 yuan; the total cost per ton of sintered ore is 851.83 yuan, a reduction of 76 yuan compared to before the adjustment. After the blast furnace process was adjusted, the unit consumption of raw materials for molten iron (sintered ore, Yangzhou pellets, and Newman lumps) was 1.66 tons / ton of molten iron, and the comprehensive cost was 1451.89 yuan / ton of molten iron. The cost of raw materials per ton of molten iron was reduced by 79.69 yuan compared with before the adjustment. The fuel ratio decreased from 515.4 kg / tFe to 511.96 kg / tFe, and fuel consumption decreased significantly. The use of serpentine and silica in the flux was eliminated, further reducing flux consumption and auxiliary material costs, while improving the stability of the furnace conditions. Example 3

[0018] A blast furnace ironmaking method with high-alumina slag and low magnesium-aluminum ratio includes the following steps: (1) Ore blending stage: The blast furnace ore blending structure is optimized, and the composition and weight percentage of each raw material in the blast furnace ore blending structure are as follows: 86% sintered ore 3% of the ball Block ore 11%, The sintering raw materials include fuel, magnesia flux, and iron-containing raw materials; the iron-containing raw materials include high-alumina iron ore, and the proportion of iron-containing raw materials is adjusted by mass percentage to ensure that the Al2O3 content in the prepared sintering is 2.39%; the magnesia flux is raw dolomite powder, and the total amount of magnesia flux is adjusted by mass percentage to ensure that the MgO content in the prepared sintering is 1.92%. The sintering ore batching table is shown in Table 3: Table 3

[0019] (2) Blast furnace smelting stage: 2.1) No magnesium-containing materials should be added to the furnace; 2.2) Optimize the charging system, including optimizing the composition of the coke fed into the furnace. The coke includes water-quenched coke and dry-quenched coke, with dry-quenched coke accounting for 70% of the weight of the coke (30% of the first-grade coke). At the same time, when charging the ore and coke, the coke is added to the center of the blast furnace near the center. 2.3) Increase the binary basicity R2 of the slag to 1.26, control the molten iron temperature within the range of 1485~1515 ℃ (average temperature 1500℃), and the magnesium-aluminum ratio of the slag is 0.51.

[0020] This process adjustment, through optimization of raw material structure and slag control scheme, achieved simultaneous cost reductions in both sintering and blast furnace stages, resulting in a significant improvement in economic benefits. After the adjustment in the sintering process, the iron-containing raw material consumption was 924.5 kg / t, with a comprehensive unit price of 770.92 yuan / t and a comprehensive cost of 712.71 yuan / ton; the flux raw dolomite powder unit consumption was 7.7 kg / t, with a unit cost of 7.98 yuan / ton. The total cost per ton of sintered ore was 868.23 yuan, a decrease of 43.77 yuan / ton compared to before the adjustment. In the blast furnace process, the raw material cost of molten iron was 1426.75 yuan / ton, a decrease compared to before the adjustment; the fuel ratio decreased from 514.27 kg / tFe to 509.41 kg / tFe, with a fuel cost of 764.03 yuan / ton, indicating a significant reduction in fuel consumption; the flux serpentine consumption was reduced from 14.52 kg / tFe to 0, and the use of silica was eliminated, further reducing flux consumption and auxiliary material costs, while also improving furnace stability. The economic benefits have been significantly improved, and the costs of both sintering and blast furnace have decreased simultaneously.

[0021] As can be seen from the comprehensive examples 1-3, the present invention achieves efficient utilization of medium and high grade ore, reduced flux, and reduced fuel consumption through process optimization, resulting in a significant decrease in the comprehensive cost per ton of molten iron and a simultaneous improvement in production economy and blast furnace smoothness.

[0022] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent process transformations made using the content of the present invention specification, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A blast furnace ironmaking method with high-alumina slag and low magnesium-aluminum ratio, characterized in that: It includes the following steps: (1) Ore blending stage: The blast furnace ore blending structure is optimized, and the composition and weight percentage of each raw material in the blast furnace ore blending structure are as follows: 75-85% sintered ore 0-15% of the pellets Lump ore 0-20%, The sintered ore batching includes fuel, magnesia flux, and iron-containing raw materials; the iron-containing raw materials include high-alumina iron ore, and the proportion of iron-containing raw materials is adjusted by mass percentage to ensure that the Al2O3 content in the prepared sintered ore is 2.0-2.4%; the magnesia flux is raw dolomite powder, and the total amount of magnesia flux is adjusted by mass percentage to ensure that the MgO content in the prepared sintered ore is 1.6-2.0%. (2) Blast furnace smelting stage: 2.1) No magnesium-containing materials should be added to the furnace; 2.2) Optimize the charging system, including optimizing the composition of the coke fed into the furnace, wherein the dry quenched coke accounts for more than 70% of the weight of the coke, and the proportion of primary coke is 20% to 30%; at the same time, when charging the ore and coke, add coke near the center of the blast furnace. 2.3) Increase the binary basicity R2 of the slag to the range of 1.20 to 1.25, and control the molten iron temperature in the range of 1480 to 1520 ℃.

2. The blast furnace ironmaking method with high-alumina slag and low magnesium-aluminum ratio as described in claim 1, characterized in that: The high-alumina iron ore is any one or more of the following: Jingbuba powder, Brazilian coarse powder, SP10 powder, Caterpillar powder, Jinbao powder, Wiluna powder, super-fine powder, Kuli powder, and PMI powder.

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