A method for preparing sintered ore with excellent low-temperature reduction and pulverization performance

Abstract

The present invention discloses a method for preparing sintered ore with excellent low-temperature reduction and pulverization performance, which mainly solves the technical problem that the sintered ore produced by the prior art has poor low-temperature reduction and pulverization performance. The technical solution adopted by the present invention is a method for preparing sintered ore with excellent low-temperature reduction and pulverization performance, comprising: 1) pre-grinding of olivine ore, controlling the particle size of the ground olivine ore powder to be ≤50μm; 2) ore blending, calculating the ore blending mass ratio of iron ore powder, flux and solid fuel according to the technical quality indicators of the sintered ore; 3) mixing and granulation, transferring the primary mixed material to the secondary mixing drum for mixing and granulation, and obtaining the secondary mixed material after granulation; 4) exhaust sintering of the secondary mixed material, and obtaining sintered ore after sintering; 5) cooling and screening the sintered ore to obtain the finished sintered ore for blast furnace ironmaking with a particle size of >5mm. The RDI of the sintered ore produced by the method of the present invention is +3.15mm ≥65%.

Description

Technical Field

[0001] The present invention relates to a method for preparing sintered ore as a raw material for blast furnace ironmaking, and in particular to a method for preparing sintered ore with excellent low-temperature reduction and pulverization performance, belonging to the technical field of steel metallurgy sintering. Background Art

[0002] Sintered ore is an important raw material for blast furnaces, and its excellent metallurgical properties are crucial for blast furnace smelting. Excellent sintered ore metallurgical properties not only facilitate smooth blast furnace operation but also reduce blast furnace fuel consumption.

[0003] Low temperature reduction pulverization performance is one of the main indicators of ore metallurgical performance, and is also one of the important indicators to measure the quality of its metallurgical performance. The low temperature reduction pulverization index is RDI. +3.15mm Characterization, RDI +3.15mm A higher value indicates greater resistance to low-temperature reduction pulverization. Excellent low-temperature reduction pulverization performance of sintered ore significantly impacts blast furnace production and the permeability of the charge column within the blast furnace. The primary cause of low-temperature reduction pulverization is the formation of large amounts of hematite, particularly skeletal rhombohedral hematite, during the ore reduction process. During reduction, this transforms from trigonal hematite to isometric magnetite, causing the lattice volume to expand by approximately 30%, resulting in pulverization of the iron ore. Because this phenomenon occurs at temperatures around 500°C, it is referred to as the low-temperature reduction pulverization index. Low-temperature reduction pulverization deteriorates the permeability of the blast furnace charge, hindering contact between the reducing gas and the iron ore, and slowing the reduction process. Therefore, suppressing the low-temperature reduction pulverization index of iron ore is a crucial technical task.

[0004] Numerous studies have shown that the SiO2, MgO and FeO contents in sintered ore are important factors affecting the low-temperature reduction pulverization index of sintered ore.

[0005] Currently, most technologies for suppressing the low-temperature reduction pulverization of sintered ore use methods such as spraying calcium chloride or other inhibitors to prevent this phenomenon in the low-temperature range. This is an effective method, but the residual chloride ions in the sintered ore can corrode blast furnace dust removal equipment. Furthermore, after spraying calcium chloride, chlorides are introduced into the blast furnace during smelting, causing corrosion to the hot blast furnace. When discharged, the chlorine can cause serious environmental pollution to the atmosphere.

[0006] Generally speaking, blast furnaces require the sintered ore low-temperature reduction pulverization rate performance index RDI +3.15mm ≥60%, RDI of sintered ore produced by existing process +3.15mm <60%.

[0007] The existing technology lacks effective measures to improve the low-temperature reduction pulverization performance of sintered ore. Summary of the Invention

[0008] The purpose of the present invention is to provide a method for preparing sintered ore with excellent low-temperature reduction pulverization performance, which mainly solves the technical problem that the sintered ore produced by the prior art has poor low-temperature reduction pulverization performance. The RDI of the sintered ore produced by the method of the present invention is +3.15mm ≥65%, the sintered ore has good sintered ore quality and metallurgical properties, overcoming the problem of easy pulverization and crushing in the low temperature section of the blast furnace, resulting in poor low-temperature reduction pulverization performance of the sintered ore.

[0009] The technical idea of the present invention is to use olivine ore in the sintering ore raw material to give full play to the high content of MgO and SiO2 in the olivine ore, and at the same time add a certain amount of iron oxide scale to the sintered ore, thereby effectively improving the low-temperature reduction and pulverization performance of the sintered ore, solving the problem of inhibiting the low-temperature reduction and pulverization of the sintered ore during the sintering reduction process; and solving the problem of poor low-temperature reduction and pulverization performance of iron ore sintered ore.

[0010] The technical solution adopted by the present invention is a method for preparing sintered ore with excellent low-temperature reduction and pulverization performance, comprising the following steps:

[0011] 1) Pre-grinding of olivine ore, grinding the olivine ore to control the particle size of the ground olivine ore powder to ≤50μm;

[0012] 2) Ore blending: Calculate the mass proportions of iron ore powder, flux, and solid fuel based on the technical quality indicators of the sintered ore. The mass percentages of the components of the sintered ore blending raw materials are as follows: iron ore powder 60% to 75%, olivine powder 0.5% to 1.5%, iron oxide scale 3% to 8%, solid fuel 3.8% to 4.3%, and the total amount of quicklime, dolomite, and limestone 8% to 15%. The sum of the mass percentages of the components is 100%. The binary basicity R2 of the sintered ore is controlled to be 1.70 to 2.10, and the weight percentage of MgO in the sintered ore is controlled to be 0.8 to 1.6%.

[0013] 3) Mixing and granulating: using a primary mixer to mix the iron ore powder, olivine ore powder, iron oxide scale, solid fuel, quicklime, dolomite and limestone, adding water during the mixing process, and mixing to form a primary mixture, wherein the weight percentage of water in the primary mixture is 6.5-7.0%; transferring the primary mixture to a secondary mixing drum for mixing and granulation, and obtaining a secondary mixture after granulation;

[0014] 4) The secondary mixed material is subjected to ventilation sintering, and the secondary mixed material is transferred to a sintering trolley for ventilation sintering. The ventilation negative pressure during the sintering process is controlled to be 12-19 kPa, and the ignition temperature is 1150-1250° C. After the sintering is completed, a sintered ore is obtained;

[0015] 5) Sintered ore cooling and screening: cooling the sintered ore; when the sintered ore temperature is less than 200°C, the sintered ore is screened to obtain finished sintered ore for blast furnace ironmaking with a particle size greater than 5mm.

[0016] The low temperature reduction pulverization performance of the finished sintered ore produced by the present invention is tested. The particle size of the sintered ore sample is 10.0-12.5 mm. The RDI of the sintered ore is +3.15mm ≥65%; iron grade ≥58.5%, drum strength ≥83.54%, finished product rate ≥70%.

[0017] Compared with the existing process, the finished sintered ore RDI produced by the present invention is +3.15mm The iron grade increases by 0.12%, the drum strength increases by 0.5%, and the finished product rate increases by 0.5%. The finished sintered ore produced by the present invention reduces the consumption of sintering solid fuel by more than 0.2 kg / t.

[0018] The chemical components of the iron oxide scale used in the present invention are FeO 51% to 62% and Fe2O3 38% to 40% by weight.

[0019] The solid fuel is any one of coke powder, anthracite powder or a mixture of coke powder and anthracite powder; the mass percentage of C in the solid fuel is 77-85%; and the solid fuel with a particle size of ≤3mm accounts for more than 85% of the total mass proportion of the solid fuel.

[0020] The binary basicity R2 of the sintered ore is w(CaO) / w(SiO2) in the sintered ore.

[0021] The reasons for the process parameters adopted in the method of the present invention are as follows:

[0022] 1. Olivine particle size range setting

[0023] Olivine is a common mineral with an island structure. Its chemical composition by weight is: MgO 47-49%, SiO₂ 40-43%, and Fe₂O 35-10%. The MgO in olivine prevents the C₂S phase transition, making the sinter less susceptible to low-temperature reduction pulverization due to volume expansion and cracking. The SiO₂ in olivine is a beneficial component of the binder phase in the sinter. Increasing the SiO₂ content in the sinter prevents the formation of excessive hematite with a skeletal structure, which can cause hematite crystal expansion and improve the sinter's low-temperature reduction pulverization performance.

[0024] To better utilize the effects of olivine and facilitate its mineralization, olivine must be roller-milled to less than 50 μm. After olivine refinement, its mineralization efficiency will be improved. At the same time, the MgO in olivine reacts with Fe2O3, favoring the formation of minerals such as hemicalcium ferrite and magnesium ferrite, improving the structure of the sintered ore and increasing its strength. More importantly, 1) the MgO in olivine prevents the C2S phase transition, making the sintered ore less susceptible to low-temperature reduction pulverization due to volume expansion and rupture; 2) the SiO2 in olivine is a beneficial component of the binder phase in the sintered ore. Fine grinding increases the mineralization efficiency and prevents the presence of excessive hematite with a skeletal structure in the sintered ore, which causes hematite crystal expansion, thereby improving the low-temperature reduction pulverization performance of the sintered ore. Taking all these factors into consideration, the present invention limits the olivine particle size to less than 50 μm.

[0025] 2. Setting the mass percentage of iron oxide scale in sintering raw materials

[0026] During the hot rolling process of continuous casting slabs into hot-rolled steel plates, a large amount of hot mill scale is produced, a byproduct of steel production. The chemical composition of hot mill scale by weight is 51% to 62% FeO and 38% to 40% Fe2O3. Adding a certain amount of hot mill scale to the sintering ore mix not only saves energy by utilizing the heat generated during the oxidation process, but also improves the low-temperature reduction and pulverization of the sintered ore.

[0027] Add 3-8% iron oxide scale. The chemical composition of iron oxide scale is as follows: FeO 52%, Fe2O3 39% by weight. Adding 3-8% iron oxide scale to the sintering process not only saves a certain amount of heat by utilizing the heat generated by the iron oxide scale during the oxidation process, but also has a positive effect on improving the low-temperature reduction and pulverization of the sintered ore. Taking all factors into consideration, the present invention limits the iron oxide scale ratio to 3-8%.

[0028] 3. Setting the weight percentage of MgO in sintered ore

[0029] The weight percentage of MgO in sintered ore is 0.8-1.6%. Keeping the MgO content at a low level will reduce the Mg 2+ Penetration into the Fe3O4 lattice is beneficial to the transformation of Fe3O4 to Fe2O3 to form calcium ferrite, which is beneficial to the development of the calcium ferrite system, improves the quality of sintered ore, and compensates for the adverse effects of reduced silica and alkalinity.

[0030] The present invention utilizes olivine and iron oxide scale, a by-product of steel mills, to prepare sintered ore, thereby obtaining a sintered ore product with relatively ideal low-temperature reduction and pulverization performance, thereby solving the problem of poor low-temperature reduction and pulverization performance of iron ore sintered ore. It not only improves the low-temperature reduction and pulverization performance of the sintered ore, but also increases the iron grade and drum strength of the sintered ore, reduces solid fuel consumption, and is a green and environmentally friendly technology.

[0031] Compared with the existing technology, the present invention has the following positive effects: 1. The method of the present invention can effectively improve the low-temperature reduction pulverization performance by adding olivine, and improve the low-temperature reduction pulverization performance of sintered ore; and effectively improve the low-temperature reduction pulverization performance by adding iron oxide scale. The FeO in the iron oxide scale can prevent the volume expansion of the sintered ore during the reduction process, effectively improving the low-temperature reduction pulverization performance; the RDI of the sintered ore +3.15mm ≥65%, RDI of finished sintered ore +3.15mm Increased by 5%. 2. The method of the present invention saves sintering solid fuel consumption. Since the iron oxide scale contains a high FeO content, an exothermic oxidation reaction occurs during the sintering process, which provides a large amount of heat for sintering, thereby reducing the sintering solid fuel consumption by more than 0.2kg / t. 3. The method of the present invention improves the iron grade. Since the iron content of the iron oxide scale is relatively high, as high as more than 50%, the iron grade of the sintered ore can be improved, and the iron grade is increased by more than 0.12%. 4. The method of the present invention improves the quality of the sintered ore. Due to the addition of olivine, the silica content is increased, and silica increases the amount of the sintered ore liquid phase that plays a bonding role during the sintering process, thereby improving the quality of the sintered ore, improving the yield and drum strength of the sintered ore, and greatly reducing the production cost; the iron grade improvement value of the finished sintered ore is ≥0.12%, and the drum strength improvement value is ≥0.5%. DETAILED DESCRIPTION

[0032] The present invention will be further illustrated below with reference to specific embodiments.

[0033] The solid fuel used in Examples 1 and 2 is any one of coke powder, anthracite powder or a mixture of coke powder and anthracite powder; the mass percentage of C in the solid fuel is 77-85%; and the solid fuel with a particle size of ≤3 mm accounts for more than 85% of the total mass proportion of the solid fuel.

[0034] Example 1, a method for preparing sintered ore with excellent low-temperature reduction pulverization performance, comprising the following steps:

[0035] 1) Pre-grinding of olivine ore, grinding the olivine ore to control the particle size of the ground olivine ore powder to ≤50μm;

[0036] 2) Ore blending: The mass ratios of iron ore fines, flux, and solid fuel are calculated based on the technical quality indicators of the sintered ore. The mass percentages of the components of the sintered ore blending raw materials are as follows: iron ore fines 74%, olivine fines 0.8%, iron oxide scale 5%, solid fuel 4.0%, and the total of quicklime, dolomite, and limestone 14.2%. The binary basicity R2 of the sintered ore is controlled to be 1.85, and the weight percentage of MgO in the sintered ore is controlled to be 1.6%.

[0037] 3) Mixing and granulating: using a primary mixer to mix the iron ore powder, olivine ore powder, iron oxide scale, solid fuel, quicklime, dolomite and limestone, adding water during the mixing process to form a primary mixture after mixing, wherein the weight percentage of water in the primary mixture is 6.8%; transferring the primary mixture to a secondary mixing drum for mixing and granulation, and obtaining a secondary mixture after granulation;

[0038] 4) The secondary mixed material is subjected to ventilation sintering, and the secondary mixed material is transferred to a sintering trolley for ventilation sintering. The thickness of the sintering material layer is 750 mm. The ventilation negative pressure during the sintering process is controlled to be 16.5 kPa, and the ignition temperature is 1150-1250° C. After the sintering is completed, a sintered ore is obtained;

[0039] 5) Sintered ore cooling and screening: cooling the sintered ore; when the sintered ore temperature is less than 200°C, the sintered ore is screened to obtain finished sintered ore for blast furnace ironmaking with a particle size greater than 5mm.

[0040] The low-temperature reduction pulverization performance of the finished sintered ore of Example 1 was tested. The particle size of the tested sample sintered ore was 10.0-12.5 mm. The quality indicators of the sintered ore are shown in Table 1.

[0041] Example 2, a method for preparing sintered ore with excellent low-temperature reduction pulverization performance, comprising the following steps:

[0042] 1) Pre-grinding of olivine ore, grinding the olivine ore to control the particle size of the ground olivine ore powder to ≤50μm;

[0043] 2) Ore blending: The mass ratios of iron ore fines, flux, and solid fuel are calculated based on the technical quality indicators of the sintered ore. The mass percentages of the components of the sintered ore blending raw materials are as follows: iron ore fines 73.1%, olivine fines 0.5%, iron oxide scale 3.2%, solid fuel 4.2%, and the total of quicklime, dolomite, and limestone 14.5%. The binary basicity R2 of the sintered ore is controlled to be 1.9, and the weight percentage of MgO in the sintered ore is controlled to be 1.4%.

[0044] 3) Mixing and granulating: using a primary mixer to mix the iron ore powder, olivine ore powder, iron oxide scale, solid fuel, quicklime, dolomite and limestone, adding water during the mixing process to form a primary mixture after mixing, wherein the weight percentage of water in the primary mixture is 6.8%; transferring the primary mixture to a secondary mixing drum for mixing and granulation, and obtaining a secondary mixture after granulation;

[0045] 4) The secondary mixed material is subjected to ventilation sintering, and the secondary mixed material is transferred to a sintering trolley for ventilation sintering. The thickness of the sintering material layer is 760 mm. The ventilation negative pressure during the sintering process is controlled to be 16.5 kPa, and the ignition temperature is 1150-1250° C. After the sintering is completed, a sintered ore is obtained;

[0046] 5) Sintered ore cooling and screening: cooling the sintered ore; when the sintered ore temperature is less than 200°C, the sintered ore is screened to obtain finished sintered ore for blast furnace ironmaking with a particle size greater than 5mm.

[0047] The low-temperature reduction pulverization performance of the finished sintered ore of Example 2 was tested. The particle size of the tested sample sintered ore was 10.0-12.5 mm. The quality indicators of the sintered ore are shown in Table 1.

[0048] The existing process uses the same solid fuel as in the example. The weight percentages of the sintering raw material components are: iron ore powder 70%, solid fuel 4.5%, and the combined weight of quicklime, dolomite, and limestone 25.5%. The binary basicity is 1.90, and the MgO content is 1.70%. Conventional mixing and granulation are performed, with the target moisture content of the second mix maintained at 6.85%. Finally, exhaust sintering is performed, maintaining a negative pressure of 16 kPa and an ignition temperature of 1150-1200°C. Sintered ore is obtained after sintering. The quality indicators of the sintered ore are shown in Table 1.

[0049] Table 1 Sintered ore quality indicators of the embodiments of the present invention

[0050]

[0051] As shown in Table 1, compared with the existing process: Example 1 Sintered ore low temperature reduction pulverization index RDI +3.15mm From 58.5% to 69.50%, the iron grade of sintered ore increased from 58.2% to 58.5%, the drum strength increased from 82.23% to 83.54%, and the yield rate increased from 68.58% to 70.06%; Example 2 Sintered ore low temperature reduction powder index RDI +3.15mm The iron content of the sintered ore increased from 58.5% to 67.5%, the iron grade of the sintered ore increased from 58.2% to 58.6%, the drum strength increased from 82.23% to 84.14%, and the yield rate increased from 68.58% to 71.16%. The technical effects of Examples 1 and 2 are significant.

[0052] In addition to the above embodiments, the present invention may also have other implementations. Any technical solution formed by equivalent replacement or equivalent transformation falls within the protection scope of the present invention.

Claims

1. A method for preparing sintered ore with excellent low-temperature reduction and pulverization performance, characterized in that: The method comprises the following steps: 1) Pre-grinding of olivine ore, grinding the olivine ore to control the particle size of the ground olivine ore powder to ≤50μm; 2) Ore blending: Calculate the mass proportions of iron ore powder, flux, and solid fuel based on the technical quality indicators of the sintered ore. The mass percentages of the components of the sintered ore blending raw materials are as follows: iron ore powder 60% to 75%, olivine powder 0.5% to 1.5%, iron oxide scale 3% to 8%, solid fuel 3.8% to 4.3%, and the total amount of quicklime, dolomite, and limestone 8% to 15%. The sum of the mass percentages of the components is 100%. The binary basicity R2 of the sintered ore is controlled to be 1.70 to 2.10, and the weight percentage of MgO in the sintered ore is controlled to be 0.8 to 1.6%. 3) Mixing and granulating: using a primary mixer to mix the iron ore powder, olivine ore powder, iron oxide scale, solid fuel, quicklime, dolomite and limestone, adding water during the mixing process, and mixing to form a primary mixture, wherein the weight percentage of water in the primary mixture is 6.5-7.0%; transferring the primary mixture to a secondary mixing drum for mixing and granulation, and obtaining a secondary mixture after granulation; 4) The secondary mixed material is subjected to ventilation sintering, and the secondary mixed material is transferred to a sintering trolley for ventilation sintering. The ventilation negative pressure during the sintering process is controlled to be 12-19 kPa, and the ignition temperature is 1150-1250° C. After the sintering is completed, a sintered ore is obtained; 5) Sintered ore cooling and screening: cooling the sintered ore; when the sintered ore temperature is less than 200°C, the sintered ore is screened to obtain finished sintered ore for blast furnace ironmaking with a particle size greater than 5mm.

2. The method for preparing sintered ore with excellent low-temperature reduction pulverization performance according to claim 1, characterized in that: RDI of finished sinter +3.15mm ≥65%.

3. The method for preparing sintered ore with excellent low-temperature reduction pulverization performance according to claim 1, characterized in that: The chemical components of the iron oxide scale are as follows: FeO 51% to 62% and Fe2O3 38% to 40% by weight.

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