A method for homogeneous sintering of iron ore with ultra-high bed thickness

Abstract

This invention discloses a method for homogeneous sintering of iron ore with ultra-high bed thickness. The method involves blending iron ore according to particle size and the composition and proportion of liquid phase masterbatch. After mixing and granulation, the ore is distributed according to different particle size proportions, components, and fuel quantity. Sintering is performed within a range of 4.0–6.0 GJ / t-raw material, yielding sintered ore. The liquid phase masterbatch accounts for 30–70% of the mixture, and is mainly composed of the granulated -3mm mixture. The resulting liquid phase after reaction comprises the following main components by mass: CaO 15–30 parts, Al₂O₃ 1–4 parts, SiO₂ 3–6 parts, and MgO 0–4 parts. Based on the mineralization characteristics of sintered ore, this method stimulates the synergistic effect of particle size, heat and composition by strictly controlling the parameter settings of particle size, composition and heat distribution of the mixture. This not only ensures the uniformity of liquid phase composition in the sintering process, but also significantly improves fuel utilization, reduces the amount of solid fuel and carbon emissions, and improves the uniformity and stability of sintered ore.

Description

Technical Field

[0001] This invention relates to a mineral sintering method, specifically a homogeneous sintering method for iron ore with ultra-high material layer, belonging to the field of iron and steel metallurgy. Background Technology

[0002] High-bed sintering is an important development direction for sintering and even low-carbon ironmaking. Since the beginning of the new century, the average height of sintering bed in iron ore sintering has been increasing year by year, with some steel plants in China reaching 900mm or even 1000mm. As the sintering bed height increases, the energy consumption of the sintering process gradually decreases. Studies show that when the bed height is below 750mm, every 10mm increase in bed height increases the sintering yield by 0.5%–1%, the drum index by about 1%, and the solid fuel consumption by about 1kgce / t. However, when the bed height is increased from 750mm to 1000mm, simply increasing the sintering bed height will not only lead to a decrease in sintering production efficiency but also cause uneven quality of the sintered ore, resulting in reduced RDI (Reduced Dioxide) levels. +3.15mm The decline in solid fuel consumption was less pronounced. Specifically, the difference in drum strength across the sintering car section exceeded 25%, and the difference in porosity exceeded 12%. In some enterprises, the RDI+3.15mm decreased from around 70% to 40-50%. To improve RDI, the fuel ratio had to be increased, leading to an increase in fuel consumption instead of a decrease. A joint analysis of multiple sintering machines in China (CN202310269094.1) revealed that the uneven sintering quality and decreased solid fuel consumption in ultra-high bed sintering were due to the unreasonable distribution of particle size, composition, and fuel in the mixture, resulting in unreasonable sintering and thus uneven sinter structure and quality. To fully utilize the beneficial effects of ultra-high bed sintering technology in energy saving and carbon reduction, it is urgent to develop new methods for homogeneous sintering from the perspective of homogeneous mineralization. Summary of the Invention

[0003] To address the problems existing in the prior art, the present invention aims to provide a method for homogeneous sintering of iron ore with ultra-high bed thickness. Based on the characteristics of sinter formation, this method, by adjusting the parameters of particle size, composition, and heat distribution of the mixture, stimulates the synergistic effect of particle size-heat and composition-heat. This not only ensures uniform dispersion within the ore body during sintering but also significantly improves fuel utilization, achieving a homogeneous and low-carbon sintering effect.

[0004] To achieve the above technical objectives, this invention provides a method for homogeneous sintering of iron ore with ultra-high bed thickness. The method involves blending iron ore according to particle size and the composition and proportion of liquid phase masterbatch, followed by mixing and granulation. The ore is then distributed according to the different particle size proportions, components, and fuel quantity of the blend, and finally sintered to obtain sintered ore. The liquid phase masterbatch accounts for 30-70% of the blend, and is mainly a granulated -3mm blend. The liquid phase masterbatch comprises the following main components by mass: CaO 15-30 parts, Al2O3 1-4 parts, and SiO2 3-6 parts. The heat required for sintering, including fuel combustion and bed heat storage, is 4.0-6.0 GJ / t-raw material.

[0005] As a preferred embodiment, the liquid phase masterbatch further includes 0-4% MgO by mass.

[0006] The liquid phase masterbatch in this invention is a raw material in which iron ore and flux generate a liquid phase during the sintering process. The -3mm mixture is the main part of the liquid phase masterbatch. Therefore, by controlling the proportion of -3mm, the liquid phase generated during the sintering process can be effectively controlled, thereby controlling the strength and cohesiveness of the sintered ore.

[0007] In the technical solution provided by this invention, the raw materials of each component in the liquid phase masterbatch must be strictly implemented according to the above requirements. When the SiO2 content is too high, the basicity of the sintering liquid phase decreases, the amount of high-quality binder phases such as calcium ferrite decreases, and the amount of binder phases such as silicates increases, resulting in a decrease in the strength of the sinter. When the MgO content is too high, the high-melting-point spinel phase in the liquid phase increases, and the grain size of calcium ferrite shrinks, resulting in a decrease in the strength of the sinter. When the CaO content is too low, the basicity of the liquid phase is low, which is not conducive to the formation of composite calcium ferrite, resulting in a low strength of the sinter. When the Al2O3 content is too high, the amount of medium-aluminum spinel in the liquid phase increases, and the amount of liquid phase decreases, resulting in a decrease in sintering strength.

[0008] As a preferred embodiment, the sintering height of the ultra-high material layer is ≥800mm.

[0009] As a preferred embodiment, the mixing and homogenization process is carried out using a high-power mixer with a rotation speed of 600–1200 r / min and a time of 20–40 s.

[0010] As a preferred embodiment, the heat required for sintering the ore is 4.6–5.6 GJ / t-raw material.

[0011] As a preferred embodiment, the fuel-to-raw material ratio is 4.6–5.6 GJ / t-raw material per layer of heat. When the heat is high, the initial liquid phase will further react with the iron ore to generate more liquid phase. However, because the iron ore mainly contains Al₂O₃ and SiO₂, the CaO content in the final liquid phase is too low, resulting in a reduction in calcium ferrite content. When the heat of the material layer is too low, the amount of liquid phase generated is insufficient, making it difficult for the iron ore to be bound by the liquid phase, leading to low sintering strength.

[0012] As a preferred embodiment, the mass percentage content of the main components in the sinter is as follows: CaO 8-15%, MgO 0.1-3.0%, Al2O3 1-4%, SiO2 3-6%.

[0013] As a preferred embodiment, the mass ratio of the -3mm mixture is positively correlated with the heat required for sintering and ore formation.

[0014] As a preferred embodiment, the heat required for sintering is positively correlated with the saturated Fe2O3 capacity in the generated liquid phase. Fe2O3 capacity refers to the maximum amount of Fe2O3 that can dissolve in the equilibrium liquid phase at 1300℃, and it is influenced by the composition of the liquid phase masterbatch.

[0015] As a preferred embodiment, the saturated Fe2O3 capacity in the generated liquid phase is positively correlated with the CaO content in the -3mm mixture and negatively correlated with the Al2O3 content.

[0016] By leveraging the synergistic effects of particle size-heat and composition-heat in the mixture, the uniformity of the sinter in the longitudinal direction can be effectively ensured. Combined with the uniform distribution in the transverse direction, this achieves overall uniformity and low variability of the sinter.

[0017] The essence of uneven sinter quality lies in uneven mineralization, and its quality depends on the sintering mineralization behavior. Sinter is formed by the solid-phase consolidation of iron oxides, the liquid-phase condensation, and the mineralization at the liquid-solid interface, among which the liquid-phase and liquid-solid interface mineralization are key. The initial liquid phase assimilates unmelted iron ore to generate the final liquid phase, and the assimilation process is affected by the iron oxide capacity in the initial liquid phase. Therefore, the uniform distribution of the liquid phase is the basis for the homogeneous mineralization of sinter. The formation of the sintering liquid phase can be divided into two stages: the reaction of -3mm iron ore with flux to generate the initial liquid phase, which is mainly affected by the iron ore particle size and composition; on the other hand, the distribution and matching of heat is also one of the keys to liquid phase formation. By controlling the particle size-heat and composition-heat, suitable liquid phase formation conditions can be determined, which can not only ensure the uniform formation of the liquid phase, but also reduce fuel consumption and significantly improve fuel utilization.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0019] 1) The ultra-high material layer homogeneous low-carbon sintering method provided by the present invention, based on the mineralization characteristics of sintered ore, stimulates the synergistic effect of particle size-heat and composition-heat by strictly controlling the parameter settings of particle size, composition and heat distribution of the mixture. This not only ensures that the mixture is uniformly dispersed in the ore body during the sintering process, but also greatly improves the fuel utilization rate and achieves a homogeneous low-carbon sintering effect.

[0020] 2) The technical solution provided by this invention proposes an optimal heat matching range from the perspective of sintering liquid phase generation, so as to make full use of heat to generate a high-quality binder phase, improve fuel utilization efficiency, further reduce sintering fuel consumption, and reduce carbon emissions.

[0021] 3) In the technical solution provided by the present invention, the homogenization of the liquid phase composition ensures the homogenization of the structure, strength and metallurgical properties of the sinter in the direction of the material layer height and the width of the trolley, thereby improving the quality and stability of the sinter. Attached Figure Description

[0022] Figure 1 This is a schematic diagram illustrating the matching of particle size, composition, and heat of the material layer in a specific embodiment of the present invention;

[0023] in, Figure 1 (a) is a schematic diagram of the amount of liquid phase generated by the mixture under different material layer heats with different particle sizes; Figure 1 (b) is a schematic diagram of the ratio of -3mm mixture and heat of the material layer under the condition of equal liquid phase generation. Detailed Implementation

[0024] The following examples are intended to further illustrate the present invention, but not to limit it.

[0025] Comparative Example 1

[0026] Under laboratory conditions, based on the raw material composition and particle size distribution, the composition of the -3mm material was first configured as follows: CaO: 20%; MgO: 2.9%; Al2O3: 2%; SiO2: 5%. The designed sinter composition was: CaO: 11%; MgO: 1.6%; Al2O3: 1.9%; SiO2: 5.5%. The sintering raw materials were mixed and granulated in a cylindrical mixer and uniformly loaded into a sintering cup. The heat, fuel ratio, liquid phase masterbatch ratio, and particle size of the mixture for different layers are shown in Table 1. Sintering was carried out at 1100℃, with a sintering negative pressure of 10 kPa and a material layer height of 1000 mm. The sintered product was longitudinally sampled by layer, and the results are shown in Table 1. It can be seen that the difference in the strength of the sintered ore in the drum exceeds 17.7%.

[0027]

[0028] Example 1

[0029] Under the same raw material conditions as Comparative Example 1, all materials were mixed for 30 seconds using a high-intensity mixer before being fed into a cylindrical mixer for granulation. The proportion, chemical composition, and fixed carbon of the -3mm particles in different particle sizes were then analyzed. Based on heat storage calculations, the matching results between the particle size distribution of the mixture and the fuel were obtained. The material layer was simplified to 5 layers, and the specific distribution of the mixture and fuel is shown in Table 2. Sintering was then carried out at 1100℃ with a sintering negative pressure of 10 kPa and a material layer height of 1000 mm. The sintered product was sampled longitudinally by layer, and the results are shown in Table 3. The longitudinal range of the sinter drum strength was 7.4%.

[0030] Table 2 Particle size and fuel distribution of mixtures in different layers

[0031]

[0032] Example 2

[0033] Under industrial production conditions, a certain 265m 2 The sintering machine mixing silo is 4.2m wide, and the trolley is 3.5m wide. The distance between the material drop point and the side wall on the north side of the silo is 0.2m, and the distance between the material drop point and the side wall on the south side of the silo is 1.2m. Therefore, the material is piled higher on the north side of the mixing silo and lower on the south side, causing the coarse particles of the mixture to migrate from the north side to the south side. This results in a non-uniform lateral distribution of the mixture on the trolley. The results of the particle size, fuel, and CaO distribution of the mixture are shown in Table 3.

[0034] Due to the mismatch between the shuttle feeder belt's travel and the material feeding position, the average particle size on the north side of the mixing bin was approximately 1.6 mm smaller than that on the south side during production. This caused an unreasonable distribution of airflow and volume on both sides of the sintering machine, resulting in asynchronous sintering speeds on both sides of the sintering trolley and uneven sinter quality. By increasing the southward travel of the shuttle feeder belt by 1 m, the uniformity of the mixture in the bin was improved. The lateral particle size distribution before and after the adjustment is shown in Table 3. Ensuring that the feeding structure is identical on both sides of the sintering machine trolley achieved homogeneous sintering laterally, and the sinter return rate was stably reduced by 3%.

[0035] Table 3265m 2 Transverse average particle size distribution before and after sintering machine adjustment

[0036]

[0037] This invention also conducted experiments on the effect of particle size-heat on the amount of liquid phase generated during the sintering process for different particle sizes of the mixture, and the results are as follows: Figure 1As shown in (a), it can be seen from the figure that, under the same heat of the material layer, the smaller the particle size of the mixture, the higher the amount of liquid phase generated. There is a large difference between the particle sizes of 3 mm and 5 mm. It can be seen that the -3 mm mixture is the main source of liquid phase in sinter. Furthermore, experiments on the proportion of -3 mm mixture and the heat of the material layer under the same amount of liquid phase generated show that the proportion of -3 mm mixture is not necessarily better the higher it is. There is an optimal range for liquid phase growth, that is, the proportion of -3 mm mixture is 30% to 70%. Therefore, only under the premise of a suitable particle size-heat ratio can the uniform mineralization of sinter be achieved.

[0038] As can be seen from Comparative Example 1 and Example 1, under the same raw material composition, adjusting the particle size-heat ratio can directly change the uniformity of the sinter. In Comparative Example 1, the heat of the first, third, and fifth layers is not within the required range. The heat of the first and third layers is lower than the standard, while the heat of the fifth layer is higher than the standard. This leads to significant differences in the sintering strength of the resulting sinter. Furthermore, due to the uneven heat distribution, the RDI of each layer is affected. +3.15mm Both porosity and heat content exhibit different trends. If the heat is too low, sintering is insufficient, resulting in sinter with high porosity and low strength. If the heat is too high, the sinter is excessively liquefied, resulting in sinter with low porosity and high strength. Consequently, the longitudinal range of the sinter strength in the drum exceeds 17.7%. However, in Example 1, by strictly controlling the particle size-heat ratio, the heat of each layer is within the specified range, and the longitudinal range of the sinter strength in the drum is only 7.4%, which greatly improves the uniformity of the sinter.

Claims

1. A method for homogeneous sintering of iron ore with ultra-high bed thickness, characterized in that: Iron ore is blended according to particle size and liquid phase masterbatch composition and proportion. After mixing and granulation, the mixture is then distributed according to different particle size proportions, components, and fuel quantity, and then sintered to obtain sintered ore. The liquid phase masterbatch accounts for 30-70% of the mixture, and the liquid phase masterbatch is mainly the granulated -3mm mixture. The liquid phase masterbatch includes the following main components by mass: CaO 15-30 parts, Al2O3 1-4 parts, SiO2 3-6 parts. The heat required for sintering includes fuel combustion and material layer heat storage, which is 4.0-6.0 GJ / t-raw material. The saturated Fe2O3 capacity in the generated liquid phase is positively correlated with the CaO content in the -3mm mixture and negatively correlated with the Al2O3 content.

2. The method for homogeneous sintering of ultra-high bed iron ore according to claim 1, characterized in that: The height of the sintered material layer of the ultra-high material layer is ≥800mm.

3. The method for homogeneous sintering of ultra-high bed iron ore according to claim 1, characterized in that: The mixing and homogenization process is carried out using a high-power mixer with a rotation speed of 600~1200 r / min and a time of 20~40 s.

4. The method for homogeneous sintering of ultra-high layer iron ore according to claim 1, characterized in that: The heat required for sintering and ore formation is 4.6~5.6 GJ / t-raw material.

5. A method for homogeneous sintering of ultra-high bed iron ore according to claim 1, characterized in that: The main components of the sintered ore have the following mass percentage content: CaO 8~15%, MgO 0.1~3.0%, Al2O3 1~4%, SiO2 3~6%.

6. The method for homogeneous sintering of ultra-high bed iron ore according to claim 1, characterized in that: The mass ratio of -3mm in the mixture is positively correlated with the heat required for sintering and ore formation.

7. A method for homogeneous sintering of ultra-high bed iron ore according to claim 1 or 6, characterized in that: The heat required for sintering and ore formation is positively correlated with the saturated Fe2O3 capacity in the generated liquid phase.

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