A blast furnace smelting method with high lump ore utilization ratio

Abstract

The present invention belongs to the field of blast furnace smelting technology, and specifically discloses a blast furnace smelting method with a high lump ore usage ratio, comprising the following steps: step 1, selecting a suitable lump ore type through a comprehensive charge metallurgical performance experiment; step 2, effectively screening the lump ore to ensure that the lump ore entering the furnace contains no more than 4% powder; step 3, ore blending according to a slag basicity of 1.1-1.2, an Al2O3 content of less than 20%, and a magnesium-aluminum ratio of 0.6-0.65; step 4, distributing the prepared charge according to a certain distribution process, and then putting it into the furnace for smelting. The present invention replaces pellets and part of the sintered ore with suitable natural lump ore, overcomes the adverse effects of the high lump ore ratio by optimizing the ore blending, distribution process, and smelting process parameters, and achieves the purpose of reducing costs and carbon emissions.

Description

Technical Field

[0001] The invention belongs to the technical field of blast furnace smelting, and in particular relates to a blast furnace smelting method with a high lump ore utilization ratio. Background Art

[0002] Blast furnace ironmaking is the largest energy consumer in the steelmaking process. In recent years, the steel industry has been moving toward using finer materials to reduce pollutant emissions and lower ironmaking costs. A rational charge structure is a key tool for effectively improving the technical and economic performance of blast furnaces. Natural lump ore offers significant price advantages over pellets in optimizing charge structure, and it also reduces the floor space and process equipment required for pellet production, thereby achieving energy savings and low-carbon production. Increasing the utilization of natural lump ore can significantly reduce the production cost per ton of iron.

[0003] It is generally believed that using lump ore instead of pellet ore to feed the furnace has the following adverse effects on blast furnace smelting:

[0004] (1) The permeability of the blast furnace deteriorates. The softening and melting temperatures of lump ore are lower than those of pellet ore and sintered ore, and the soft melting temperature range is wide. When the proportion of lump ore increases, the soft melting zone of the blast furnace becomes wider and moves upward. The volume of the wet area with poor permeability increases, and the lump ore has a relatively large powder content, which further deteriorates the permeability of the blast furnace.

[0005] (2) The fuel ratio will increase. From the perspective of the soft melting performance of the charge, sintered ore is the best, followed by pellets, and lump ore is the worst. When lump ore is used instead of pellets, the softening and melting starting temperatures of the charge are reduced, and the soft melting temperature range is increased, which means that the position of the soft melting zone in the blast furnace moves upward and the thickness increases. The indirect reduction zone in the furnace is correspondingly reduced, and the gas utilization rate is reduced, resulting in an increase in the fuel ratio.

[0006] (3) The gangue content in lump ore is low, but the Al2O3 content is high. As the proportion of lump ore entering the furnace increases, the Al2O3 content in the slag will increase, and the fluidity of the slag will deteriorate. When the alkalinity is high and the physical heat of the molten iron is low, it is difficult to discharge the slag in time, affecting the stability of the blast furnace condition.

[0007] Currently, blast furnaces can achieve a lump ore ratio of 20-24% while maintaining stable operation and maintaining consistent fuel consumption. However, few steel mills dare to raise the lump ore ratio to 35%. For example, one steel mill increased the lump ore ratio from 10% to 21.5% and discovered that this increased raw ore ratio resulted in fluctuating furnace conditions and poorer air permeability. Further increases would have been detrimental to normal blast furnace production. Summary of the Invention

[0008] The present invention aims to overcome the impact of a high proportion of lump ore on blast furnace production. By comprehensively considering the metallurgical properties of the charge, suitable lump ore is selected, and the lump ore screening effect is ensured. Furthermore, by optimizing the ore blending, charging, and distribution systems, the smelting process parameters are adjusted while gradually increasing the amount of lump ore used, thereby achieving stable blast furnace operation and stable production and consumption indicators. By using relatively low-cost lump ore instead of pellets and sintered ore, the cost of molten iron can be reduced. Replacing pellets and sintered ore with natural lump ore also reduces carbon emissions from the ironmaking process.

[0009] The present invention adopts the following technical solutions:

[0010] A blast furnace smelting method with a high lump ore utilization ratio, characterized by comprising the following steps:

[0011] Step 1. Sintered ore, lump ore and pellets are mixed in proportion to obtain a comprehensive charge. Through the comprehensive charge metallurgical performance experiment, lump ore that meets the following high-temperature metallurgical performance conditions is selected: when the mass ratio of lump ore to comprehensive charge is 2:10-3.5:10, the softening start temperature is above 1100°C and the softening end temperature is below 1250°C, that is, the softening range is within 150°C. At the same time, the melting start temperature is above 1270°C and the melting end temperature is below 1450°C, that is, the melting range is within 180°C.

[0012] Furthermore, the mass ratio of lump ore to comprehensive charge is 2:10-3.5:10, the mass ratio of sintered ore to comprehensive charge is 6.5:10-7:10, and the mass ratio of pelletized ore to comprehensive charge is 0:10-1:10.

[0013] Step 2: By effectively screening the lump ore, the powder content of the raw ore (particle size <5mm) is controlled to be no more than 8% before the lump ore enters the warehouse, and the powder content of the clean lump entering the furnace through screening under the blast furnace trough is no more than 4%.

[0014] Furthermore, the lump ore is effectively screened: the lump ore enters the raw material yard and first passes through an 8mm sieve. People are arranged on site to track and take samples. Unqualified lump ore continues to be screened for the second time. When the lump ore is wet on rainy days, the sintered return ore is poured into the lump ore for stirring and then screened. This is called mixing and returning screening.

[0015] Step 3: Blend ore according to the slag basicity of 1.1-1.2, Al2O3 content <20%, and magnesium-aluminum ratio of 0.6-0.65, wherein the mass ratio of lump ore to each batch of charge is 2:10-3.5:10, the mass ratio of sintered ore to each batch of charge is 6.5:10-7:10, and the mass ratio of pellet ore to each batch of charge is 0-1:10.

[0016] Furthermore, the requirements for sintered ore are: binary basicity between 1.95-2.05, Al2O3≤2.40%, and MgO≥2.8%.

[0017] Step 4: The prepared charge is distributed in a circular manner from outside to inside through the furnace top distribution chute in the order of coke, sintered ore, lump ore, coke dices, pellets, and sintered ore, and is put into the furnace for smelting under certain smelting process conditions.

[0018] Furthermore, the fabric process is C4 38.5 2 36 2 33 2 30 2 27 ↓O2 36.5 3 34 3 31.5 2 29 ↓ or C4 38 2 35.5 2 32.5 2 29.5 2 26.5 ↓O2 35.5 3 33.5 3 31 2 28.5 ↓

[0019] Furthermore, coke is placed on the bottom layer, with sintered ore, lump ore, and diced coke placed on top of the coke. From the outside in, they are sintered ore, lump ore, diced coke, and sintered ore. Placing the lump ore in the center of the ore belt does not affect the airflow at the center or the edges, while the addition of diced coke improves air permeability. By narrowing the angle of the coke and charge distribution and reducing the ore belt, stable airflow is maintained at both the center and the edges.

[0020] Furthermore, the mass ratio of lump ore to diced coke is 1:11-1:20.

[0021] Furthermore, the stable air volume of the smelting process is 1700m 3 / min, coal injection rate is 12.0t / h-13.0t / h, oxygen enrichment rate is 6000m 3 / hm 3 / h, the hot air temperature is 1180℃, the pressure difference is controlled at 114-116kPa, and the air permeability index is guaranteed to be 15-15.5.

[0022] Furthermore, the physical temperature of the molten iron is not lower than 1480°C, and the iron mouth qualification rate is guaranteed to be above 90%.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] First of all, the innovation of the present invention is to use the metallurgical properties of comprehensive furnace charges instead of the metallurgical properties of traditional single-variety furnace charges to judge whether the furnace charges used are within the appropriate soft melting range. The use of comprehensive furnace charge metallurgical properties is closer to actual production and more directly reflects whether the furnace charge structure used has good air permeability.

[0025] Secondly, it is very important to control the screening quality of lump ore. Through the above-mentioned lump ore screening method, the powder content of lump ore entering the furnace can be effectively reduced, and the impact of factors such as small lump ore particle size and heavy powder content on blast furnace permeability can be reduced.

[0026] Secondly, the batching structure was optimized. As the proportion of lump ore increased, the chemical composition of the slag changed significantly, especially the aluminum content in the slag. The increase in aluminum in the slag has a certain inhibitory effect on the fluidity of the slag. Properly increasing the MgO content in the high-aluminum slag can improve the fluidity of the slag. Therefore, controlling the magnesium-aluminum ratio (MgO / Al2O3) between 0.6-0.65 has a good effect.

[0027] Finally, as the proportion of lump ore usage gradually increased to 35%, corresponding adjustments were also made to the blast furnace operation, including reducing the angle of the outer circle of the ore and increasing the angle of the inner circle in the distribution matrix to make the ore belt smaller, which is conducive to the development of two streams of coal gas. In terms of operating parameters, the air volume and oxygen were appropriately reduced to reduce the smelting intensity, and the coal injection amount was reduced to improve the permeability of the material column. Through these methods, the blast furnace finally achieved stable production at a lump ore ratio of 35%, and the output and consumption indicators were stable. DETAILED DESCRIPTION

[0028] The present invention will be further described below with reference to specific embodiments.

[0029] In the implementation of a domestic ironmaking plant No. 3 510m 3 The blast furnace is used for production, with each batch of coke weighing 3.5 tons, each batch of ore weighing 17 tons (including sintered ore weighing 11.05-11.9 tons, lump ore weighing 3.4-5.95 tons, and pellets weighing 0-1.7 tons), and diced coke weighing 0.3 tons.

[0030] First, a comprehensive charge metallurgical performance experiment was conducted, and PB blocks were selected as the test objects. The test results are shown in Table 1 as follows:

[0031] Table 1 Metallurgical properties of PB blocks with different proportions

[0032]

[0033]

[0034] The lump ore was effectively screened, and the screening results are shown in Table 2:

[0035] Table 2 PB block screening data

[0036] Raw ore powder content% Powder content in furnace % Lump ore 5.56 3.87

[0037] The ingredients are batched according to the requirements, and the slag basicity and magnesium-aluminum ratio are well controlled. The slag composition is shown in Table 3:

[0038] Table 3 Slag composition during high-proportion lump ore production

[0039] Lump ore ratio Slag Slag basicity Aluminum in slag Magnesium-aluminum ratio 17％ 346 1.20 15.52 0.62 21％ 339 1.19 16.62 0.60 23％ 328 1.18 16.36 0.60 25％ 325 1.18 17.24 0.60 26％ 321 1.20 17.81 0.60 27％ 330 1.20 17.61 0.63 28％ 326 1.20 18.00 0.60 29％ 320 1.20 18.33 0.60 30％ 322 1.16 18.29 0.60 31％ 318 1.17 17.90 0.61 32％ 317 1.19 17.79 0.63 33％ 317 1.19 18.16 0.65 34％ 316 1.19 17.83 0.65 35％ 315 1.15 17.89 0.65 36％ 314 1.16 18.17 0.65 38％ 312 1.11 18.28 0.65

[0040] During the period of increasing the lump ore ratio, the parameters such as distribution matrix, air volume, oxygen enrichment, coal injection, etc. were adjusted, as shown in Table 4:

[0041] Table 4 Parameter adjustment during the period of increasing lump ore ratio

[0042]

[0043] The output, fuel consumption, cost and carbon emission data after the lump ore ratio is increased are shown in Table 5:

[0044] Table 5 Output, fuel consumption, cost and carbon emissions during the period of increasing the proportion of lump ore in blast furnace

[0045]

[0046] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solutions and concepts of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A blast furnace smelting method with a high lump ore usage ratio, characterized in that: The steps include: Step 1: Sintered ore and lump ore are mixed in proportion to obtain a comprehensive charge, and lump ore that meets the following high-temperature metallurgical performance conditions is selected through a comprehensive charge metallurgical performance test: when the mass ratio of lump ore to comprehensive charge is 3.5:10, the softening start temperature is above 1100°C and the softening end temperature is below 1250°C, that is, the softening range is within 150°C; at the same time, the melting start temperature is above 1270°C and the melting end temperature is below 1450°C, that is, the melting range is within 180°C; Step 2: By effectively screening the lump ore, the powder content of the raw ore with a particle size of less than 5mm is controlled to be no more than 8% before the lump ore enters the warehouse, and the powder content of the clean lump entering the blast furnace through screening under the trough is no more than 4%; Step 3: ore blending is carried out according to the slag basicity of 1.1-1.2, Al2O3 content <20%, and magnesium-aluminum ratio of 0.65, wherein the mass ratio of lump ore in each batch of charge to each batch of ore charge is 3.5:10, and the mass ratio of sintered ore to each batch of ore charge is 6.5:10; Step 4: The prepared charge is distributed in the order of coke, sintered ore, lump ore, coke dicing and sintered ore through the top distribution chute from outside to inside and then put into the furnace for smelting; the distribution process is C4 38 2 35.5 2 32.5 2 29.5 2 26.5 ↓O2 35.5 3 33.5 3 31 2 28.5 ↓; The stable air volume of the smelting process is 1700m 3 / min, coal injection rate is 12.0t / h-13.0t / h, oxygen enrichment rate is 6000m 3 / h, the hot air temperature is 1179℃-1180℃, the pressure difference is controlled at 114-116kPa, and the physical temperature of molten iron is not lower than 1480℃.

2. The blast furnace smelting method with a high lump ore usage ratio according to claim 1, characterized in that: The requirements for the sintered ore described in step 3 are: binary basicity between 1.95-2.05, Al2O3≤2.40%, and MgO≥2.8%.

3. The blast furnace smelting method with a high lump ore usage ratio according to claim 1, characterized in that: The coke described in step 4 is spread on the bottom layer, and the sintered ore, lump ore, and coke pieces are spread on the coke. From the outside to the inside, they are sintered ore, lump ore, coke pieces, and sintered ore respectively.

4. The blast furnace smelting method with a high lump ore usage ratio according to claim 3, characterized in that: The mass ratio of the coke cubes to the lump ore is 1:11-1:20.

Images