Method for improving softening property of sinter under high hematite proportioning condition

Abstract

This invention discloses a method for improving the softening performance of sintered ore under high limonite ratio conditions, belonging to the field of iron and steel metallurgical technology. The method involves blending limonite with silicon-containing iron ore (silicon content ≤ 4.5%) to form iron ore raw materials, then mixing, granulating, and sintering them with fuel, flux, and return ore to obtain sintered ore. This method promotes the directional formation of high-quality binder phases such as composite calcium ferrite and reduces the formation of low-melting-point silicate phases by introducing iron ore with lower silicon content and adjusting alkalinity. Simultaneously, by improving the proportion of fine-grained fuel, optimizing fuel reactivity and combustion rate, and improving the granulation coating structure, the heat supply is matched with the liquid phase formation rate of the high limonite system. This stabilizes the thermal state of the sintering process, optimizes the pore structure of the sintered ore, improves the softening performance of the sintered ore, optimizes the permeability of the softening zone, reduces the pressure difference during the softening process, and enhances the adaptability of the blast furnace.

Description

Technical Field

[0001] This invention relates to a method for improving the softening performance of sinter under high limonite ratio conditions, and particularly to an iron ore raw material system with a high proportion of limonite. By adjusting the binary basicity CaO / SiO2 and controlling the particle size structure of the fuel, the method achieves synergistic optimization of the thermal state and liquid phase generation path during the sintering process, promotes the formation of high-quality binder phase in the sinter, and inhibits the large-scale generation of low-melting-point silicate phase, thereby improving the softening performance of the sinter. This invention belongs to the field of iron and steel metallurgical technology. Background Technology

[0002] Sinter is one of the main iron-containing burdens in blast furnace ironmaking, and its high-temperature metallurgical properties directly affect the location of the softening zone, permeability, and furnace stability. Among these, the softening-melting-dripping behavior of sinter (hereinafter referred to as softening performance) is a key indicator for evaluating its high-temperature adaptability. Poor softening performance can lead to excessively rapid softening and shrinkage of the burden column in the high-temperature zone, premature liquid phase formation, and pore blockage. This manifests as a widening of the softening zone, increased pressure differential, and unstable dripping behavior, resulting in problems such as deterioration of the blast furnace gas flow distribution, fluctuations in upper suspended burden or lower slag and iron discharge, and reduced blast furnace smooth operation and fuel utilization efficiency. Therefore, given the fluctuating raw material structure and increasing demand for low-carbon, high-efficiency smelting, developing ore blending and process control methods that can stably improve the softening performance of sinter under specific raw material conditions is of significant engineering importance.

[0003] In recent years, influenced by resource regional changes and cost constraints, the proportion of limonite used in sintering raw materials has been continuously increasing. Limonite is typically characterized by high water content, large loss on ignition, loose structure, strong reactivity, and large fluctuations in gangue composition. While a certain proportion is beneficial for improving the assimilation performance of the mixture, excessively high proportions can lead to the following problems: Firstly, the dehydration, decomposition, and structural evolution of limonite during sintering can alter granulation and bed permeability, resulting in unstable combustion front advancement and reduced uniformity of the sinter structure. Secondly, due to the rapid liquid phase formation rate of limonite, in sinter systems dominated by limonite, it is easier to generate a low-melting-point silicate liquid phase dominated by FeO, which can lead to deterioration of the permeability of the softening zone, expansion of the softening zone, and upward shift of the softening zone position. Especially when the SiO2 content in the raw material system is high, it is easier to generate complex silicate phases with low melting point, high viscosity, and difficulty in reduction, further exacerbating the deterioration of softening performance.

[0004] Existing technologies often address these issues by increasing basicity, adjusting flux, fuel usage, and negative pressure, or introducing mineral powders that more readily form calcium ferrate binder phases. However, simply relying on increasing basicity or adjusting operating conditions often fails to control the liquid phase type under the engineering constraints of high-proportion limonite usage, and is sensitive to raw material fluctuations, leading to unstable improvements in softening performance. Furthermore, some methods focus more on improving sintering performance and production efficiency, while remaining insufficient in understanding the suppression mechanism of low-melting-point phases during the softening reduction stage. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a ore blending method for improving the softening performance of sintered ore under high-proportion limonite blending conditions. This method, constrained by a high limonite content, introduces silicon-containing iron ore for co-blending, enabling controllable adjustment of the SiO2 content in the iron ore raw material system. Simultaneously, it incorporates the control of fuel particle size structure into key control steps. By optimizing the coarse-fine fuel mix and the proportion of fine powder, the combustion zone advancement and heat distribution in the material bed become more uniform and stable. This, in turn, is synergistically optimized with the basicity window of the mixture, the granulation process, and the sintering regime. Thus, during the sintering stage, it promotes the directional formation of a high-quality binder phase, primarily composed of composite calcium ferrite, while inhibiting the formation and enrichment of low-melting-point silicate liquid phases such as calcium silicate. During the blast furnace softening-reduction stage, it further weakens the FeO-SiO2 bonding tendency, reducing the conditions for the formation of low-melting-point, difficult-to-reducible phases, ultimately improving the permeability of the softening zone and narrowing the softening interval. The method has a clear process flow, well-defined parameter windows, and strong adaptability. It can achieve a stable improvement in the softening performance of sintered ore in the high limonite system without relying on complex equipment modifications, and has good engineering application value.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a method for improving the softening properties of sintered ore under conditions of high limonite ratio, which includes the following steps:

[0007] S1: Blend limonite with silicon-containing iron ore to form iron ore raw materials;

[0008] S2: Iron ore raw materials, fuel, flux and return ore are mixed to form a mixture;

[0009] S3: Mix the mixture with water and granulate it. Sinter the resulting pellets to obtain sintered ore.

[0010] in,

[0011] The iron ore raw material contains more than 65% limonite by mass;

[0012] The silicon content of the silicon-containing iron ore is below 4.5%, and the amount of silicon-containing iron ore and flux is used to control the binary basicity R=CaO / SiO2 of the mixture to be between 1.8 and 2.2.

[0013] The fuel has an average particle size of 1.6 to 2.2 mm, and the total mass percentage of the -0.5 mm particle size is 10% to 60%.

[0014] The key technical solution of this invention lies in: by introducing silicon-containing iron ore, the SiO2 level and its reactive / free silica components in the mixture can be controlled and adjusted. This is combined with fuel particle size structure control and the granulation-sintering process, ensuring that the thermal state, liquid phase generation behavior, and mineral phase evolution path during sintering are within a controllable range, thereby achieving targeted optimization of the sintered ore structure and high-temperature metallurgical properties. More specifically: under conditions of high limonite content, the endothermic dehydration and loose mineral structure of limonite easily lead to fluctuations in granulation and bed permeability, resulting in uneven distribution of local temperature field and oxygen potential. This, in turn, induces problems such as premature formation of silicate liquid phase, local overmelting, and pore blockage. This invention, by introducing an appropriate proportion of low-silicon iron ore, while maintaining a fixed limonite proportion, reduces the overall SiO2 level of the system and weakens the material basis for its rapid coupling with FeO at high temperatures. Furthermore, it makes the gangue composition and basicity adjustment more operable, avoiding uncontrolled liquid phase type and distribution due to fluctuations in a single ore source. Simultaneously, the fuel is graded and its coarse-fine ratio is controlled, limiting the proportion of fine fuel powder and optimizing the proportion of medium and coarse particles. This makes the spatial distribution of fuel in the mixture more uniform, and the effective ignition and continuous combustion more stable. This improves the uniformity of heat release rhythm and combustion zone advancement within the material layer, and matches the rapid liquid phase formation characteristic of the high-proportion limonite system. This reduces the structural fluctuations caused by local underheating or overheating. Furthermore, by controlling the amount of flux added and the basicity range, CaO preferentially participates in the formation of calcium ferrite binder phases during high-temperature reactions, promoting the shift of the liquid phase formation path in the sintering process from a low-melting-point silicate liquid phase to a formation path dominated by composite calcium ferrite.

[0015] As a preferred embodiment, the main components of the iron ore raw material and the percentage content of each main component are as follows: TFe: 56~60%, SiO2: 4.3~5.5%, CaO: 0.1~0.5%, Al2O3: 1.8~2.2%, MgO: 0.8~1.2%, FeO: 0.5~2.0%.

[0016] As a preferred embodiment, the silicon-containing iron ore comprises low-silicon iron ore and medium-silicon iron ore.

[0017] As a preferred embodiment, the main components and percentage content of the low-silicon iron ore are as follows: TFe: 55~66%, SiO2: 1.5~3.0%, CaO: 0.1~1.5%, Al2O3: 1.0~1.5%, MgO: 0.1~1.5%, FeO: 0.5~2.0%. The LOI of the low-silicon iron ore is -1.0~3.5%. Controlling the SiO2 content of the low-silicon iron ore within the range of 1.5~3.0% is beneficial for effectively reducing the silica level of the raw material system under the constraint of a high proportion of limonite, and reducing the tendency of reactive SiO2 to form a low-melting-point silicate liquid phase with FeO at high temperatures; at the same time, controlling its TFe content at 55~66% can balance the ore grade and the availability of blending, avoiding an increase in flux demand and gangue load due to excessively low grade.

[0018] As a preferred embodiment, the main components and percentage content of the medium-silicon iron ore are as follows: TFe: 55~66%, SiO2: 3.5~4.5%, CaO: 0.1~1.5%, Al2O3: 1.0~1.5%, MgO: 0.1~1.5%, FeO: 0.5~2.0%. The LOI of the medium-silicon iron ore is -1.0~3.5%. As a silicon-regulating end, the medium-silicon iron ore, with its SiO2 content controlled at 3.5~4.5%, can provide adjustable silicon input while ensuring ore source adaptability. This allows for precise control of the SiO2 level in the raw material system by adjusting the ratio of low-silicon iron ore to medium-silicon iron ore, even when the proportion of limonite is as high as 65%. This ensures that the alkalinity of the mixture can be stably controlled within a predetermined window under different limonite fluctuation conditions.

[0019] As a preferred embodiment, the ratio of low-silicon iron ore to medium-silicon iron ore in the silicified iron ore is adjusted to control the SiO2 mass content of the medium-silicon iron ore raw material to be 4.3-5.5%. More preferably, the ratio of low-silicon iron ore to medium-silicon iron ore in the silicified iron ore is adjusted to control the SiO2 mass content of the medium-silicon iron ore raw material to be 4.5-5.2%.

[0020] As a preferred embodiment, the fuel includes at least one of coke powder, pulverized coal, and coal shale. As a sintering heat source, the selection and dosage of the fuel directly affect the combustion front temperature, oxygen potential distribution, and the degree of FeO formation, thereby influencing the liquid phase formation sequence and the type of binder phase. This invention preferably uses a combination of coke powder, pulverized coal, or coal shale, which balances combustion stability and cost adaptability.

[0021] As a preferred embodiment, the total mass proportion of -0.5mm particles in the fuel is 30% to 40%. This invention optimizes the particle size structure of the fuel, particularly by ensuring a suitable proportion of fine-particle fuel. Fine-particle fuel has a large specific surface area, strong reactivity, rapid ignition, and high combustion rate, providing more timely and uniform heat input during ignition and early sintering stages. This matches the rapid liquid phase generation requirement of a high-proportion limonite system. Furthermore, fine-particle fuel adheres more easily to the surface of iron ore particles during mixing and granulation, promoting uniform fuel distribution and stable quasi-particle structure, thereby improving the permeability of the material layer and enhancing the thermal consistency during sintering.

[0022] As a preferred embodiment, the flux includes at least one of quicklime, limestone, and dolomite. The preferred flux is one commonly used in the industry. The flux is used to regulate the alkalinity of the mixture. Quicklime has high reactivity and facilitates the rapid formation of a calcium ferrate binder phase; limestone helps alleviate localized overheating and improves temperature field uniformity; dolomite can introduce MgO while providing CaO to adjust the slag viscosity and the liquid phase fluidity during the softening stage. Appropriate fluxes can be selected or several fluxes can be used in combination as needed.

[0023] As a preferred embodiment, the binary basicity R=CaO / SiO2 of the mixture is more preferably controlled between 1.80 and 1.95. The binary basicity is adjusted by varying the amount of flux (quicklime, limestone, or dolomite, etc.) added.

[0024] As a preferred embodiment, the mass percentage composition of the mixture is: 64-76% iron ore raw material, 4-6% fuel, 10-15% flux, and 10-19% return ore.

[0025] As a preferred embodiment, the amount of water added accounts for 7-10% of the total weight of the mixture, more preferably 8.0-9.5%. This is because, under the high limonite ratio conditions of this invention, limonite typically possesses characteristics such as high porosity, large specific surface area, and strong surface hydrophilicity, exhibiting strong water absorption, high water holding capacity, and sensitivity to moisture distribution. If the amount of water added is too low, the limonite will preferentially adsorb and "lock in" water, resulting in insufficient free water in the system that can be used to form liquid bridges and promote fine powder coating, leading to uneven wetting of the mixture and difficulty in granulation.

[0026] As a preferred embodiment, the particle size of the spherical material meets the requirement that the mass proportion of particles in the 3-8mm range is ≥70%. When the proportion of particles in the 3-8mm range reaches the preferred level, the distribution of pores in the material layer after distribution is more uniform, the air permeability is more stable, which is conducive to the uniform transfer of heat and oxygen along the material layer direction, reduces the dispersion of the structure caused by local overheating or underheating, and thus makes the timing and spatial distribution of liquid phase generation more controllable.

[0027] As a preferred embodiment, the pellets are placed on a sintering machine, with the material layer height controlled within the range of 800~1000mm, ignited at a temperature of 1100~1250℃ for 1~3 minutes, followed by sintering under negative pressure with exhaust ventilation. The preferred sintering negative pressure is 10~16kPa. The above sintering parameters are used to stabilize the thermal state of the material layer and the combustion front advancement process under high proportion of limonite.

[0028] As a preferred embodiment, the iron ore raw material, by weight percentage, comprises more than 65% limonite, 15-35% low-silicon iron ore, and 0-20% medium-silicon iron ore, to meet the following requirements regarding the main components and percentage content of each main component of the iron ore raw material: TFe: 56-60%, SiO2: 4.3-5.5%, CaO: 0.1-0.5%, Al2O3: 1.8-2.2%, MgO: 0.8-1.2%, FeO: 0.5-2.0%.

[0029] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0030] (1) In this invention, under a high proportion of limonite, low-silicon iron ore and medium-silicon iron ore are used for synergistic blending to reduce and stabilize the SiO2 level of the raw material system. By adding flux, the basicity of the mixture is controlled within a reasonable range, making the liquid phase in the sintering stage more selective. More specifically, this makes the liquid phase of the sinter more inclined to generate high-quality binder phases such as composite calcium ferrite. Unlike the traditional high-silicon system, which easily generates silicate / calcium silicate liquid phases, this invention promotes the formation, growth and continuous distribution of composite calcium ferrite, enhances the high-temperature structural stability and pore connectivity of the sinter, and reduces the local enrichment of low-melting-point silicate liquid phases, reducing the risk of pore blockage caused by overmelting, thus weakening the structural basis for premature softening of the softening zone from the source.

[0031] (2) This invention couples fuel particle size structure optimization with the granulation-combustion process, providing more controllable heat and reaction environment support for liquid phase generation and mineral phase evolution during the sintering stage. More specifically: fine-particle fuel has a large specific surface area, strong reactivity, fast ignition, and high combustion rate, which can provide timely heating and stabilize the flame front advancement in the early stage of sintering, matching the faster liquid phase generation rate of the high-proportion limonite system and reducing the dispersion of the structure caused by local underheating / overheating; at the same time, fine-particle fuel is more likely to adhere to the surface of iron ore particles and form a more uniform fuel coating distribution during mixed granulation, promoting the stability of the quasi-particle structure and the uniformity of the material layer permeability, further ensuring the stable generation and spatial continuity of the composite calcium ferrite binder phase from the process side.

[0032] (3) This invention improves the proportion of composite calcium ferrite binder phase in sinter and makes it occupy the main binder structure by using low-silicon ore blending, alkalinity control and fuel particle size structure optimization. As a typical binder phase in sinter, composite calcium ferrite has a significantly different reduction path from silicate / FeO-rich slag phase after entering the blast furnace. Specifically, the reduction process of composite calcium ferrite usually does not generate a large amount of free FeO intermediate products, thus significantly reducing the possibility of local FeO enrichment in the softening reduction stage. For the FeO-dominated reduction stage, the content of free FeO and SiO2 is greatly reduced to further inhibit the formation of low-melting-point and difficult-to-reducible phases. Moreover, due to the excellent reducibility of composite calcium ferrite, it is more conducive to forming a "metal skeleton" structure with a certain strength in the indirect reduction zone, thereby playing a certain supporting role in the softening process of sinter, causing the softening zone to move as a whole to the high-temperature zone, and improving the softening performance of sinter produced by the high-limonite system.

[0033] (4) Based on the dual mechanisms of "directional generation of liquid phase in the sintering stage - microstructure optimization" and "low-melting-point phase suppression in the blast furnace softening and reduction stage - metal skeleton support", the sinter produced by this invention exhibits an increased softening initiation temperature, a narrowed softening range, a reduced maximum pressure difference in the feed column, improved permeability of the softening zone, and more stable dripping behavior. This reduces the risk of disturbance to the blast furnace gas flow distribution and furnace condition stability by the softening zone, and improves the smooth operation and adaptability of the blast furnace. At the same time, this invention imposes windowed constraints on key parameters such as ore blending ratio, basicity window, fuel particle size structure, water addition and pellet particle size, and sintering regime, making the granulation structure and sintering thermal state more stable and the finished product microstructure more uniform. This can significantly reduce the dispersion of softening performance caused by raw material fluctuations under high limonite conditions, and has the advantages of strong process feasibility, good adaptability, and ease of industrial promotion.

[0034] In summary, this invention achieves directional optimization of the liquid phase generation path during sintering by synergistically controlling the chemical composition of the blended ore, the flux system, and the basicity window, and by coupling the particle size structure of carbon-containing fuel with the granulation-sintering process. This promotes the formation of a high-quality binder phase and reduces the formation and enrichment of low-melting-point silicate phases. Consequently, it improves the softening performance of sintered ore, optimizes the permeability of the softening zone, reduces the pressure difference during the softening process, and enhances the adaptability of the blast furnace to smooth operation. Detailed Implementation

[0035] To facilitate understanding of the present invention, the present invention will be described more comprehensively and in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0036] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The patent terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the invention.

[0037] Unless otherwise specified, the various reagents and raw materials used in this invention are commercially available products or products that can be prepared by known methods.

[0038] The relevant standards for performance testing of sinter in the following examples are: Iron ore - Determination of high temperature load reduction softening drip performance GB / T 34211-2017; Determination of sinter and pellet strength in a drum G / B 8209-1987.

[0039] Example 1

[0040] Limonite, low-silicon iron ore, and medium-silicon iron ore are blended according to the following mass percentages of the iron ore raw material system: 65% limonite, 15% low-silicon iron ore, and 20% medium-silicon iron ore. The mixture is then stirred to form the iron ore raw material system. The main chemical components of limonite, by weight percentage, are: TFe: 56.78%, SiO2: 5.95%, CaO: 0.10%, Al2O3: 2.75%, MgO: 0.09%, FeO: 0.28%; the main chemical components of low-silicon iron ore, by weight percentage, are: TFe: 62.0%, SiO2: 1.7%, CaO: 0.6%, Al2O3: 1.2%, MgO: 0.8%, FeO: 1.2%; and the chemical components of medium-silicon iron ore, by weight percentage, are: TFe: 61.0%, SiO2: 3.5%, CaO: 0.5%, Al2O3: 1.2%, MgO: 0.7%, FeO: 1.1%. The mixture is prepared by weight percentage as follows: 65% iron ore, 5% fuel, 12% flux, and 18% recycled ore. The flux is composed of quicklime and dolomite in a 1:1 mass ratio. The fuel particle size distribution is 40% by weight of -0.5 mm particles, with an average particle size of 1.8 mm. The mixture is thoroughly mixed to form a composite material. The basicity of the composite material is controlled to R=1.85 by adding flux. Water is added to the composite material at 8% of the total raw material weight. Granulation is then performed to obtain pellets, with a particle size of 3-8 mm accounting for ≥70%. The pellets are then distributed on a sintering machine at a layer height of 1000 mm, an ignition temperature of 1150℃, an ignition time of 2 min, and a sintering negative pressure of 14 kPa. After sintering, the pellets are crushed and screened to obtain sintered ore.

[0041] The performance indicators of the sintered ore are as follows: sintering yield 78%, drum strength 69%, softening start temperature 1140 ℃, softening end temperature 1255 ℃, melting start temperature 1279 ℃, dripping temperature 1466 ℃, softening range temperature 115 ℃, dripping range temperature 187 ℃, and dripping range temperature 326 ℃.

[0042] Example 2

[0043] Limonite, low-silicon iron ore, and medium-silicon iron ore are blended according to the following mass percentages of the iron ore raw material system: 65% limonite, 25% low-silicon iron ore, and 10% medium-silicon iron ore. The mixture is then stirred to form the iron ore raw material system. The main chemical components of limonite, by weight percentage, are: TFe: 57.21%, SiO2: 5.87%, CaO: 0.33%, Al2O3: 2.49%, MgO: 0.12%, FeO: 0.30%; the chemical components of low-silicon iron ore, by weight percentage, are: TFe: 63.7%, SiO2: 1.6%, CaO: 0.7%, Al2O3: 1.3%, MgO: 0.6%, FeO: 0.7%; and the chemical components of medium-silicon iron ore, by weight percentage, are: TFe: 60.5%, SiO2: 3.4%, CaO: 1.1%, Al2O3: 1.4%, MgO: 0.8%, FeO: 1.2%. The mixture is prepared by weight percentage as follows: 63% iron ore, 5% fuel, 13% flux, and 19% recycled ore. The flux is composed of quicklime and dolomite in a 1:1 mass ratio. The fuel particle size distribution is 30% by weight of -0.5mm particles, with an average particle size of 1.9mm. The mixture is thoroughly mixed to form a composite material. The basicity of the composite material is controlled to R=1.85 by adding flux. Water is added to the composite material, accounting for 8.5% of the total raw material weight. Granulation is then performed to obtain pellets, with a particle size of 3-8mm accounting for ≥70%. The pellets are then distributed on a sintering machine with a layer height of 1000mm, an ignition temperature of 1150℃, an ignition negative pressure of 5.5 kPa, an ignition time of 1.5 min, and a sintering negative pressure of 13 kPa. After sintering, the sintered ore is obtained by crushing and screening.

[0044] The performance indicators of the sintered ore are as follows: sintering yield 79%, drum strength 69%, softening start temperature 1129℃, softening end temperature 1239℃, melting start temperature 1277℃, dripping temperature 1450℃, softening range temperature 110℃, dripping range temperature 175℃, and dripping range temperature 321℃.

[0045] Example 3

[0046] Limonite and low-silicon iron ore were blended according to the following weight percentages of the iron ore raw material system: 65% limonite and 35% low-silicon iron ore, and then mixed to form the iron ore raw material system. The main chemical components of limonite, by weight percentage, are: TFe: 56.82%, SiO2: 5.90%, CaO: 0.12%, Al2O3: 2.77%, MgO: 0.11%, FeO: 0.31%; the main chemical components of low-silicon iron ore, by weight percentage, are: TFe: 65.4%, SiO2: 1.5%, CaO: 1.1%, Al2O3: 1.4%, MgO: 0.7%, FeO: 1.0%. The mixture is prepared by weight percentage as follows: 65% iron ore, 5% fuel, 10% flux, and 19% recycled ore. The flux is composed of quicklime and dolomite in a 1:1 mass ratio. 50% of the fuel particles are of -0.5 mm size, with an average particle size of 1.6 mm. The mixture is thoroughly mixed to form a composite material. The basicity of the composite material is controlled to R=1.90 by adding flux. Water is added to the composite material at 9% of the total raw material weight. Granulation is then performed to obtain pellets, with ≥70% of the pellets having a diameter of 3-8 mm. The pellets are then distributed on a sintering machine at a layer height of 1000 mm, an ignition temperature of 1150℃, an ignition negative pressure of 5 kPa, an ignition time of 2 min, and a sintering negative pressure of 12 kPa. After sintering, the sintered ore is obtained by crushing and screening.

[0047] The performance indicators of the sintered ore are as follows: sintering yield 80%, drum strength 71%, softening start temperature 1151℃, softening end temperature 1250℃, melting start temperature 1279℃, dripping temperature 1456℃, softening range temperature 99℃, dripping range temperature 180℃, and dripping range temperature 305℃.

[0048] Comparative Example 1

[0049] The only difference compared to Example 1 is that the weight percentage of -0.5mm particles in the fuel particle size structure is 80%, and the average fuel particle size is 0.9mm.

[0050] The performance indicators of the sintered ore are as follows: sintering yield 69%, drum strength 62%, softening start temperature 1116℃, softening end temperature 1231℃, melting start temperature 1270℃, dripping temperature 1469℃, softening range temperature 115℃, dripping range temperature 199℃, and dripping range temperature 353℃.

[0051] Comparative Example 2

[0052] The only difference compared to Example 2 is that: 80% limonite, 0% low-silicon iron ore, and 20% medium-silicon iron ore.

[0053] The performance indicators of the sintered ore are as follows: sintering yield 74%, drum strength 67%, softening start temperature 1121 ℃, softening end temperature 1232 ℃, melting start temperature 1273 ℃, dripping temperature 1475 ℃, softening range temperature 108 ℃, dripping range temperature 202 ℃, and dripping range temperature 354 ℃.

[0054] Comparative Example 3

[0055] The only difference compared to Example 3 is that: 100% limonite, 0% low-silicon iron ore, and 0% medium-silicon iron ore.

[0056] The performance indicators of the sintered ore are as follows: sintering yield 72%, drum strength 65%, softening start temperature 1091 ℃, softening end temperature 1230 ℃, melting start temperature 1269 ℃, dripping temperature 1487 ℃, softening range temperature 139 ℃, dripping range temperature 218 ℃, and dripping range temperature 396 ℃.

Claims

1. A method for improving the softening properties of sintered ore under high limonite ratio conditions, characterized in that: Includes the following steps: S1: Blend limonite with silicon-containing iron ore to form iron ore raw materials; S2: Iron ore raw materials, fuel, flux and return ore are mixed to form a mixture; S3: Mix the mixture with water and granulate it. Sinter the resulting pellets to obtain sintered ore. in, The iron ore raw material contains more than 65% limonite by mass; The silicon content of the silicon-containing iron ore is below 4.5%, and the amount of silicon-containing iron ore and flux is used to control the binary basicity R=CaO / SiO2 of the mixture to be between 1.8 and 2.

2. The fuel has an average particle size of 1.6 to 2.2 mm, and the total mass percentage of the -0.5 mm particle size is 10% to 60%.

2. The method for improving the softening properties of sinter under high limonite ratio conditions according to claim 1, characterized in that: The main components of the iron ore raw material and the percentage content of each main component are as follows: TFe: 56~60%, SiO2: 4.3~5.5%, CaO: 0.1~0.5%, Al2O3: 1.8~2.2%, MgO: 0.8~1.2%, FeO: 0.5~2.0%.

3. The method for improving the softening properties of sinter under high limonite ratio conditions according to claim 1, characterized in that: The silicon-containing iron ore includes low-silicon iron ore and medium-silicon iron ore; The main components of the low-silicon iron ore and the percentage content of each main component are as follows: TFe: 55~66%, SiO2: 1.5~3.0%, CaO: 0.1~1.5%, Al2O3: 1.0~1.5%, MgO: 0.1~1.5%, FeO: 0.5~2.0%; The main components of the iron siliceous ore and the percentage content of each main component are as follows: TFe: 55~66%, SiO2: 3.5~4.5%, CaO: 0.1~1.5%, Al2O3: 1.0~1.5%, MgO: 0.1~1.5%, FeO: 0.5~2.0%.

4. The method for improving the softening properties of sintered ore under high limonite ratio conditions according to claim 3, characterized in that: The ratio of low-silicon iron ore to medium-silicon iron ore in the silicon-containing iron ore is adjusted to control the SiO2 mass content of the medium-silicon iron ore raw material to be 4.3~5.5%.

5. The method for improving the softening properties of sinter under high limonite ratio conditions according to claim 1, characterized in that: The fuel includes at least one of coke powder, coal powder, and coal shale.

6. A method for improving the softening properties of sinter under high limonite ratio conditions as described in claim 1 or 5, characterized in that: The total mass percentage of the fuel containing -0.5mm particles is 30% to 40%.

7. The method for improving the softening properties of sinter under high limonite ratio conditions according to claim 1, characterized in that: The flux includes at least one of quicklime, limestone, and dolomite.

8. A method for improving the softening properties of sinter under high limonite ratio conditions according to claim 1 or 7, characterized in that: The mass percentage composition of the mixture is: 60-76% iron ore, 4-6% fuel, 10-15% flux, and 10-19% recycled ore.

9. A method for improving the softening properties of sinter under high limonite ratio conditions according to claim 1, characterized in that: The particle size of the pellets must be 3-8 mm, and the mass percentage of such pellets must be ≥70%.

10. A method for improving the softening properties of sintered ore under high limonite ratio conditions according to claim 1, characterized in that: The ball material is placed on the sintering machine, with the material layer height controlled within the range of 800~1000mm, and ignited at a temperature of 1100~1250℃ for 1~3 minutes, followed by sintering under negative pressure with exhaust air.