Method for detecting high-temperature ore-forming characteristics of sintered iron ore core particles

Abstract

The application discloses a kind of sintered iron ore core particle high-temperature ore-forming characteristics detection method, belong to iron ore sintering technical field.The method is after CaO digestion and mixed with Fe2O3 Form calcium-iron mixed sample, while natural iron ore particles are processed into straight cylinder to obtain iron ore core particle sample and measure its cross-sectional area S1;Iron ore core particle sample is vertically placed in calcium-iron mixed sample inside directly below and is pressed into shape to obtain briquette sample;Sintering is carried out to briquette sample, the obtained sintered briquette is polished with sandpaper until the residual iron ore core particle is exposed and its cross section S2 is measured;According to S1 and S2, the core particle liquid phase transformation fraction (LPTF) is calculated to measure the high-temperature ore-forming performance of iron ore core particle;The method can evaluate the quality and performance of iron ore by detecting the dissolution degree of iron ore core particle in liquid phase during sintering ore-forming process, and can quantify the dissolution characteristics of iron ore core particle, more directly and accurately reflect the dissolution assimilation degree of iron ore core particle in sintering liquid phase.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for detecting high-temperature ore-forming characteristics of sintered iron ore core particles, belonging to the technical field of iron ore sintering. BACKGROUND

[0002] In the steel industry, the sintering process of iron ore agglomeration accounts for more than 70% of the furnace charge of blast furnaces, and its quality directly determines whether the blast furnace smelting is smooth. The essence of sintering agglomeration is a "high-temperature physical and chemical interaction" process: in a sintering temperature field of 1200℃-1350℃, iron ore powder, flux (quicklime, dolomite) and fuel (coke powder) undergo a series of reactions. The iron ore powder in the fine powder and the flux lime first react to form low-melting-point compounds, which further melt to form an initial liquid phase. The remaining un-melted iron ore particles act as core particles, which are wrapped and aggregated by the liquid phase and gradually dissolved and assimilated. Finally, the liquid phase crystallizes and precipitates during the cooling process to form a binding phase, which binds the incompletely dissolved iron ore particles, thereby forming sinter with certain strength and metallurgical properties.

[0003] In this process, the degree of dissolution and assimilation of core particles in the initial liquid phase directly affects the organizational structure and ore-forming properties of sinter. If the core particles are difficult to dissolve, it will result in too many unreacted mineral particles remaining in the sinter, affecting the uniform distribution of the liquid phase and the amount of key mineral phases such as calcium ferrite (SFCA), and reducing the strength and metallurgical properties of the sinter. On the contrary, if the core particles are excessively dissolved, it may cause excessive liquid phase, leading to over-burning of the sinter, increased brittleness of the ore block, and other problems. Therefore, the degree of dissolution and assimilation of core particles in the sintering liquid phase is an important indicator for evaluating the application of iron ore in sintering production.

[0004] Currently, the evaluation of high-temperature ore-forming characteristics of iron ore raw materials in the sintering process is mainly based on observing the changes in the appearance of pressed iron ore samples under specific temperature conditions to draw conclusions. For example, the document ("Iron ore powder sintering liquid phase flow characteristics", Wu Shengli, et al., Journal of University of Science and Technology Beijing, 2005(03):291-293) discloses evaluating the liquid phase flow characteristics of iron ore by calculating the ratio of the area of the sintered iron ore sample to the initial sample area. Chinese patent (CN101666762B) discloses using the shrinkage ratio of the triangular pyramid side area to represent the liquid phase generation amount of iron ore. These detection methods are mostly indirect reflections of the soft melting ore-forming properties of iron ore, and cannot accurately reveal the dissolution and assimilation characteristics of a single iron ore in the sintering liquid phase, especially cannot directly reflect the dynamic changes of iron ore core particles in the sintering process.

[0005] Therefore, there is an urgent need to develop a detection method that can directly characterize the high-temperature ore-forming properties of iron ore core particles in the sintering liquid phase, in order to quantify the dissolution characteristics of core particles and provide a scientific basis for evaluating the suitability of iron ore in sintering ore blending. SUMMARY

[0006] In view of the problems in the prior art, the purpose of the present application aims to provide a detection method for high-temperature ore-forming characteristics of sintered iron ore core particles, which can evaluate the quality and performance of iron ore by detecting the dissolution degree index of iron ore core particles in the liquid phase during sintering ore-forming process, can quantify the dissolution characteristics of iron ore core particles, more directly and accurately reflect the dissolution and assimilation degree of iron ore core particles in the sintering liquid phase, not only can make up for the shortcomings of the prior art, but also can provide data support for raw material selection, sintering process optimization and stable operation of blast furnace.

[0007] In order to achieve the above technical purpose, the present application provides a detection method for high-temperature ore-forming characteristics of sintered iron ore core particles, which comprises the following steps:

[0008] Step 1:

[0009] After CaO digestion, mix with Fe2O3 uniformly to obtain a calcium-iron mixed material sample; at the same time, after calcining the natural iron ore particles to remove crystallization water, a straight cylinder is formed by mechanical processing to obtain an iron ore core particle sample, and the initial cross-sectional area of the iron ore core particle sample is measured and recorded as S1;

[0010] Step 2:

[0011] The iron ore core particle sample is vertically placed below the calcium-iron mixed material sample, and is pressed to form a briquette sample;

[0012] Step 3:

[0013] The briquette sample is sintered under air atmosphere, so that the calcium-iron mixed material sample forms a liquid phase to dissolve and assimilate the iron ore core particle sample, and a sintered briquette is obtained;

[0014] Step 4:

[0015] The sintered briquette is polished with sandpaper until the residual iron ore core particles are exposed, and the cross section of the residual iron ore particles is measured as S2;

[0016] Step 5:

[0017] According to S1 and S2, the core particle liquid phase transformation fraction LPTF is calculated, and LPTF is used as an index for measuring the high-temperature ore-forming performance of the iron ore core particles;

[0018] The core particle liquid phase transformation fraction is calculated according to the following formula:

[0019] .

[0020] The iron ore core particle is processed into a straight cylinder body, the cross-sectional area change of the iron ore core particle before and after dissolution and assimilation in a sintering process of mineral formation can be directly and accurately measured by using existing testing means, and the core particle liquid phase conversion fraction is calculated, a quantifiable high-temperature mineral formation performance index is formed, the accuracy is high, the high-temperature mineral formation behavior of the iron ore in a sintering liquid phase can be directly reflected, and the defects that too much experience or indirect inference is relied on in the previous evaluation are avoided.

[0021] As a preferred scheme, the mass ratio of CaO to Fe2O3 is fixed as 2:8. Under the preferred ratio, the temperature at which CaO and Fe2O3 generate a liquid phase is the eutectic temperature, effectively ensuring the smooth progress of the test.

[0022] As a preferred scheme, the particle size of the natural iron ore particle is +5 mm. The iron ore particle with the preferred particle size is convenient for preparing the iron ore core particle sample, and if the natural iron ore particle with too small particle size is used, it is difficult to prepare a straight cylinder body meeting the detection conditions in the processing process. +5 mm means that the oversize is taken after screening through a 5 mm screen.

[0023] As a preferred scheme, the straight cylinder body is a straight prism or a cylinder, and the cross section of the straight prism or the cylinder is a polygon or a circle, which is more conducive to area measurement.

[0024] As a preferred scheme, the calcination condition is that the temperature is 700 DEG C~800 DEG C, and the time is 4~6 min. Under the preferred calcination condition, the crystal water of the natural iron ore particle can be completely removed, and the measurement deviation caused by the crystal water release in the sintering process can be reduced.

[0025] As a preferred scheme, the size of the briquette sample is φ15 mm x (8~12) mm.

[0026] As a preferred scheme, the sintering condition is that the temperature is increased to 1300 DEG C~1350 DEG C at a temperature increasing rate of 400 DEG C / min, and the holding time is 1~2 min.

[0027] As a preferred scheme, the cross-sectional area of the residual iron ore particle is measured by using the measurement function of the ImageJ software. In the preferred measurement mode, high-precision measurement is effectively realized by image calibration.

[0028] The application provides a detection method for high-temperature mineral formation characteristics of sintered iron ore core particles.

[0029] 1) Material preparation: preparing a calcium-iron mixed material sample (for forming a liquid phase) and an iron ore core particle sample to be measured;

[0030] Preparation method of calcium-iron mixed sample: the mass ratio of CaO and Fe2O3 is fixed at 2:8 (under thermodynamic conditions, the mixed ratio is the eutectic temperature of liquid phase, and the CaO content is 20%), CaO pure reagent is first added to water and fully digested, then uniformly mixed with Fe2O3 pure reagent to prepare the calcium-iron mixed sample;

[0031] Preparation method of iron ore core particle sample: the natural iron ore particles with a particle size of +5mm are pre-burned to remove crystallization water (at a temperature of 750°C, the burning time is 5min), then the iron ore core particles are mechanically ground into straight cylinders (the side edges of the straight cylinders are perpendicular to the bottom surface, preferably the straight cylinders are straight prismatic cylinders or cylindrical bodies, the cross section of the straight prismatic cylinder can be a triangle, a quadrilateral, a pentagon or other polygons, which is convenient for measuring the cross-sectional area) using sandpaper, and the cross-sectional area is measured and recorded;

[0032] 2) Pressing briquettes: the iron ore particle sample is placed just below the calcium-iron mixed sample (which is beneficial to the complete coating of the iron ore particle sample by the calcium-iron mixed sample), and under a pressure of 300kg / cm 2 , a φ15mm × (8~12)mm overall briquette sample is formed;

[0033] 3) Micro-sintering: the overall briquette sample with the iron ore core particle is placed in a φ18mm × 20mm corundum crucible, and then placed on a corundum boat and sent into a tube furnace for heating and sintering, the sintering is carried out in an air atmosphere, the heating rate is 400°C / min, the highest sintering temperature is 1300°C~1350°C (through the measurement of the highest temperature in the iron ore sintering, the temperature for low-silicon high-alkalinity sintering is 1300°C, and the temperature for high-silicon low-alkalinity sintering is 1350°C), the sintering holding time is 1~2min (the highest sintering holding time is 1min under low carbon content, the highest sintering holding time is 1.5min under medium carbon content, and the highest sintering holding time is 2min under high carbon content), so that the liquid phase formed by the calcium-iron mixed sample dissolves and assimilates the iron ore core particle;

[0034] 4) Measurement step: the sintered briquette obtained after roasting is ground with sandpaper until the iron ore particles appear, the cross-sectional area of the dissolved iron ore particles is measured on an image processing software (the measurement function of ImageJ recognizes), and the corresponding core particle liquid phase transformation fraction (LPTF) is calculated, which is used as an index for measuring the high-temperature ore-forming performance of the iron ore core particle;

[0035] The calculation formula of the core particle liquid phase transformation fraction (LPTF) is:

[0036] ;

[0037] Wherein S1, S2 are cross-sectional areas of iron ore particles before and after sintering dissolution, respectively.

[0038] Compared with the prior art, the technical scheme of the present application has the following beneficial technical effects:

[0039] (1) Good scientificity: the method of the present application can directly reflect the high-temperature ore-forming behavior of iron ore in the sintering liquid phase, and compared with the conventional judgment of the liquid phase generation capacity according to the change in the external appearance form, it can more accurately reveal the behavior and action mechanism of the iron ore core particles in the sintering ore-forming process.

[0040] (2) Good feasibility and high accuracy: by measuring the change in the cross-sectional area of the iron ore core particles before and after assimilation dissolution, and calculating the liquid phase conversion fraction of the core particles, a quantifiable high-temperature ore-forming performance index is formed, avoiding the defects of excessive reliance on experience or indirect inference in the previous evaluation.

[0041] (3) Easy to implement: the operation of the method of the present application is relatively simple, the required sample amount is small, the experimental conditions are controllable, and higher repeatability and reliability can be obtained.

[0042] Therefore, the present method accurately and scientifically evaluates the high-temperature ore-forming characteristics of the iron ore core particles in the sintering liquid phase, and can provide a scientific basis for sintering ore blending optimization, and reasonably help the ironmaking sintering process to select iron ore varieties and blending, thereby improving the quality of sintered ore. BRIEF DESCRIPTION OF DRAWINGS

[0043] Figure 1 A schematic diagram of a sample briquette prepared by embedding a calcium-iron mixed sample and an iron ore core particle sample, wherein: 1 is a calcium-iron mixed sample; 2 is an iron ore core particle sample.

[0044] Figure 2 A flowchart for testing the high-temperature ore-forming characteristics of the iron ore core particles in the sintering liquid phase.

[0045] Figure 3 A schematic diagram of a straight cylinder made of an equiform mechanical grinding of an iron ore particle, for example, if the original particle shape is close to a triangle, it is ground into a triangular prism; if the original particle shape is close to a rectangle, it is ground into a quadrangular prism; if the original particle shape is close to a hexagon, it is ground into a hexagonal prism; if the original particle shape is close to a trapezoid, it is ground into a trapezoidal prism.

[0046] Figure 4 A schematic diagram of the change in the particle shape before and after sintering and dissolution of the briquette sample, wherein: a is a schematic diagram of the bottom surface of the pressed briquette, showing the morphological characteristics of the iron ore particles; b is the cross-sectional morphology of the briquette sample after sintering and grinding, which can identify the morphological characteristics between the undissolved particles and the molten liquid phase. DETAILED DESCRIPTION

[0047] For the convenience of understanding the content of the present application, the content of the present application is further described in detail below in combination with the accompanying drawings and specific examples, but the method of the present application is not limited by the specific examples.

[0048] Detection of the briquetted sample: The briquetted sample for detecting the high-temperature ore-forming characteristics is composed of two parts, i.e., a calcium-iron mixed sample and an iron ore core particle sample, as shown in Fig. 1, wherein the calcium-iron mixed sample is the source of liquid phase generation, and the iron ore core particle sample is the object to be assimilated by the liquid phase. Figure 1

[0049] Operation process: The test flow of the high-temperature ore-forming characteristics is shown in Fig. 2. Figure 2 .

[0050] Detection method:

[0051] (1) Preparation of the calcium-iron mixed sample: 2.0 g of CaO pure reagent is first dissolved in 20 ml of water, and then uniformly mixed with 8.0 g of Fe2O3 pure reagent to prepare the calcium-iron mixed sample.

[0052] (2) Preparation of the iron ore core particle sample: natural iron ore particles with a particle size of +5 mm are calcined at a temperature of 750℃ for 5 min to remove crystal water, and then mechanically ground into straight prisms using sandpaper as shown in Fig. 3, and the cross-sectional area S1 is measured and recorded. Figure 3

[0053] (3) Pressing of the briquetted sample: the iron ore particle sample is placed inside the calcium-iron mixed sample as shown in Fig. 4a, and a φ15mm×12mm overall briquetted sample is formed under a pressure of 300kg / cm 2 . Figure 4

[0054] (4) Micro-sintering: the overall briquetted sample with the iron ore core particle is placed in a φ18mm×20mm corundum crucible, and then placed on a corundum boat to be sent into a tube furnace for heating and sintering, and calcined in an air atmosphere, with a heating rate of 400℃ / min, a sintering maximum temperature of 1350℃, and a sintering holding time of 1 min, 1.5 min and 2 min respectively, to measure the dissolution and assimilation characteristics of the iron ore core particle under different holding times.

[0055] (5) Measurement of the cross-sectional area after dissolution: the sample obtained after sintering is ground using sandpaper as shown in Fig. 4b, and the area S2 of the cross-section of the particle after dissolution is measured using the measurement function of ImageJ, and the dissolution area difference and the core particle liquid phase conversion fraction are calculated. Figure 4

[0056] The calculation formula of the core particle liquid phase conversion fraction is as follows: . ​​​​

[0057] Application Examples:

[0058] A kind of domestic widely used Australian brown iron ore FMG mixed powder and South African hematite South Africa 63 powder were selected, and the chemical composition and particle size composition were shown in Table 1. The particles with particle size of +5 mm of the FMG mixed powder and South Africa 63 powder were prepared into straight prismatic samples (cross section is quadrilateral) for determining the high temperature ore-forming characteristics of the ore. The following four groups of examples were used to detect the high temperature ore-forming characteristics of the iron ore by changing the highest temperature holding time and the type of ore powder. The specific detection results were shown in Table 2.

[0059] (1) The hematite pure reagent was mixed with 20% calcium oxide pure reagent, and the prepared FMG mixed powder iron ore core particles were embedded. The briquetting sample was formed under the pressure of 300 kg / cm 2 , and sintered at 1350℃ for 1 min. The liquid phase conversion fraction of the iron ore core particle before and after sintering and dissolution was 31.84%.

[0060] (2) The hematite pure reagent was mixed with 20% calcium oxide pure reagent, and the prepared FMG mixed powder iron ore core particles were embedded. The briquetting sample was formed under the pressure of 300 kg / cm 2 , and sintered at 1350℃ for 1.5 min. The liquid phase conversion fraction of the iron ore core particle before and after sintering and dissolution was 48.29%.

[0061] (3) The hematite pure reagent was mixed with 20% calcium oxide pure reagent, and the prepared FMG mixed powder iron ore core particles were embedded. The briquetting sample was formed under the pressure of 300 kg / cm 2 , and sintered at 1350℃ for 2 min. The liquid phase conversion fraction of the iron ore core particle before and after sintering and dissolution was 57.12%.

[0062] (4) The hematite pure reagent was mixed with 20% calcium oxide pure reagent, and the prepared South Africa 63 powder iron ore core particles were embedded. The briquetting sample was formed under the pressure of 300 kg / cm 2 , and sintered at 1350℃ for 2 min. The liquid phase conversion fraction of the iron ore core particle before and after sintering and dissolution was 1.09%.

[0063] From (1), (2) and (3), it can be seen that the liquid phase conversion fraction of the particle dissolution area increased to 57.12% when the highest temperature holding time increased from 1 min to 2 min, which indicated that the increase of the highest temperature holding time in the sintering process would continuously promote the dissolution and assimilation degree of the particles.

[0064] Compared with (3) and (4), the liquid phase conversion fraction of the dissolved area of the South Africa 63 powder particles is reduced to 1.09% compared with the dissolution assimilation characteristics of the limonite FMG mixed powder, indicating that the dissolution assimilation degree of the hematite is lower under the same dissolution conditions.

[0065]

[0066] .

Claims

1. A method of detecting high temperature ore-forming characteristics of sintered iron ore core particles, characterized by: The method comprises the following steps: Step 1: CaO is digested and mixed with Fe2O3 to obtain a calcium-iron mixed sample; meanwhile, natural iron ore particles are calcined to remove crystal water, and then straight columns are formed by mechanical processing to obtain an iron ore core particle sample; the initial cross-sectional area of the iron ore core particle sample is measured and recorded as S1; the mass ratio of CaO to Fe2O3 is fixed at 2:8; the calcination conditions are as follows: the temperature is 700-800 DEG C, and the time is 4-6 min; Step 2: The iron ore core particle sample is vertically placed below the calcium-iron mixed sample, and then compression molding is performed to obtain a briquette sample; Step 3: The briquette sample is sintered in an air atmosphere, so that the calcium-iron mixed sample forms a liquid phase to dissolve and assimilate the iron ore core particle sample, thereby obtaining a sintered briquette; during the sintering process, the briquette sample is placed in a corundum crucible with a diameter of 18 mm and a height of 20 mm; the size of the briquette sample is 15 mm in diameter and (8-12) mm in height; Step 4: The sintered briquette is polished with sandpaper until the residual iron ore core particle is exposed, and the cross section of the residual iron ore particle is measured and recorded as S2; Step 5: The core particle liquid phase transformation fraction LPTF is calculated according to S1 and S2, and the LPTF is used as an index for measuring the high-temperature ore-forming performance of the iron ore core particle; The liquid phase conversion fraction of the core particles is calculated according to the following formula: .

2. The method for detecting high temperature ore-forming characteristics of sintered iron ore core particles according to claim 1, characterized in that: The particle size of the natural iron ore particles is +5 mm.

3. The method of claim 1, wherein the sintered iron ore core particle has a high-temperature ore-forming property. The sintering conditions are as follows: the temperature is increased to 1300-1350 DEG C at a rate of 400 DEG C / min, and the holding time is 1-2 min.

4. The method of claim 1, wherein the sintered iron ore core particle has a high-temperature ore-forming property. The cross-sectional area of the residual iron ore particle is measured by the measurement function of ImageJ software.

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