High-vanadium magnesium flux oxidized pellet and preparation method thereof

Abstract

The invention relates to the technical field of mineral processing, in particular to a high-vanadium magnesium flux oxidized pellet which comprises the following chemical components in percentage by mass: 63.64% of TFe; the mass percent of FeO is 0.4%; the mass percent of V2O5 is 0.34%; the mass percent of TiO2 is 0.90%; the mass percent of MgO is 1.50%. The pellet prepared by the method is a full-self-melting magnesium oxidized pellet, and the binary alkalinity and the quaternary alkalinity are both in the range of 1.0 + / -0.05. The prepared pellet is high in strength, low in powder rate and good in metallurgical performance (high in reduction degree and excellent in molten drop softening performance), is particularly suitable for a blast furnace with the furnace volume being 3500 m < 3 > or below, and can effectively improve the air permeability of the blast furnace and reduce the fuel ratio. The pellet prepared by the method is high in vanadium content, and the steel slag can be used as a high-quality raw material for extracting vanadium from the vanadium slag when the pellet is matched with the vanadium-containing sintered ore.

Description

Technical Field

[0001] This invention relates to the field of mineral processing technology, specifically to a high-vanadium magnesium flux oxide pellet and its preparation method, which is particularly suitable for providing high-quality furnace feed for metallurgical plants using pyrometallurgical ironmaking-vanadium slag extraction processes such as blast furnace ironmaking or direct reduction. Background Technology

[0002] Iron pellets are one of the important raw materials for modern blast furnace ironmaking. Traditional natural basicity pellets are generally acidic (binary basicity ≤ 0.4), requiring the addition of large amounts of calcium and magnesium mineral fluxes during blast furnace smelting, leading to increased slag volume and coke ratio. Magnesium flux pellets, by adding magnesium- and calcium-containing fluxes to the pellets, can improve the metallurgical properties of the pellets and reduce smelting costs. In particular, they can significantly increase the pellet ratio in the furnace charge structure, resulting in significant energy-saving and environmental benefits.

[0003] However, there is currently a severe shortage of low-silicon, high-iron iron concentrate raw materials suitable for preparing magnesium flux pellets in China. Magnesium flux pelletizing technology is also immature, resulting in problems such as insufficient production volume and unstable quality. Particularly for vanadium-containing iron concentrate, a critical technical challenge in this field is how to effectively control its magnesium, calcium, and titanium content while ensuring high vanadium content, in order to produce magnesium flux pellets with excellent physical and metallurgical properties. Summary of the Invention

[0004] The purpose of this invention is to provide a high-vanadium magnesium flux oxide pellet and its preparation method. This pellet not only has excellent physical strength and metallurgical properties, but also makes up for the shortage of magnesium flux pellets in China, providing a high-quality furnace charge for blast furnace ironmaking, thereby solving the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a high-vanadium magnesium flux oxide pellet, the chemical composition of which, by mass percentage, comprises: The mass percentage of TFe is 63.64%; The mass percentage of FeO is 0.4%; The mass percentage of V2O5 is 0.34%; The mass percentage of TiO2 is 0.90%; The mass percentage of MgO is 1.50%; The binary and quaternary basicities are between 1.0±0.05, exhibiting self-fluxing properties; their physical properties are: compressive strength ≥2500N / piece, strength index of +6.3mm drum ≥95.02%, abrasion resistance index of -0.5mm drum ≤4.48%, and particle size of 8~16mm ≥95.0%; their metallurgical properties are: reducing expansion index RSI ≤17.52%, and reduction index RI ≥80.8%.

[0006] Preferably, the softening start temperature of the pellet is 1045°C, the softening range is 105°C, the melting start temperature is 1309°C, the droplet range is 41°C, and the maximum pressure difference is 2.9 kPa.

[0007] A method for preparing high-vanadium magnesium flux oxide pellets includes the following steps: Ingredients: The main iron raw material is vanadium-containing iron concentrate, with magnesium and calcium additives added for conditioning to make the MgO content in the finished balls ≥1.5%, and bentonite is added as a binder.

[0008] Pelletizing: The process of forming green pellets from the mixture, including the following technical parameters: a) The suitable moisture content of the mixture is 5.86%~6.22%; b) The ideal moisture content for raw bulbs is 8.01%~8.39%; c) Ball-making time is approximately 10 minutes; d) Drop intensity of raw balls: 5.0~5.1 times / ball; e) Compressive strength of green pellets: 16~17N / pellet; f) Green pellet bursting temperature ≥350℃; Calcination: The green pellets were calcined using a belt calciner for a total time of 42.2 minutes. The process included the following steps: a) Forced air drying: temperature 220℃, time 2.2min, wind speed 2.0m / s; b) Exhaust drying: temperature 300℃, time 5.6min, wind speed 2.0m / s; c) Preheating stage: temperature 500℃~900℃, time 3min, wind speed 2.0m / s; d) Preheating stage 2: temperature 950℃, time 6min, wind speed 1.5m / s; e) Calcination: Temperature 1220℃~1240℃, time 11.2min, wind speed 1.3m / s; f) Heat equalization: Temperature 1210℃~900℃, time 2.2min, wind speed 1.4m / s; g) Forced air cooling: Use ambient temperature air for 12 minutes at a wind speed of 2.2 m / s. The exhaust gas temperature after cooling is 150℃. Throughout the entire roasting process, the total thickness of the material layer is 400mm, including: a 300mm thick raw ball material layer, a 100mm thick bottom layer, and an 80mm thick edge layer.

[0009] Preferably, the batching step adopts online quality detection and intelligent batching process, with online quality detection of six elements Fe, V, Ga, Mg, Si and Al and free water throughout the process, controlling the mixing ratio of four elements calcium, magnesium, silicon and aluminum, and online batching according to the binary basicity and quaternary basicity of 1.0±0.05.

[0010] Preferably, the iron agent is high-iron, medium-vanadium, or low-titanium iron concentrate; the magnesium source additive is one or more of magnesite powder and lightly calcined dolomite powder; the calcium source additive is one or more of quicklime and limestone powder; and the binder is high-quality domestic bentonite.

[0011] Compared with the prior art, the beneficial effects of the present invention are: (1) Superior product performance: The pellets prepared by this invention have high strength, low powder content, and good metallurgical properties (high reducibility and excellent softening and dripping properties), and are particularly suitable for 3500m 3 Blast furnaces with the following capacities can effectively improve blast furnace permeability and reduce fuel ratio; (2) Efficient utilization of resources: Vanadium-containing iron concentrate was successfully utilized, and the pellets prepared are not only high-quality iron raw materials, but also efficient vanadium slag vanadium extraction raw materials, realizing comprehensive value-added utilization of resources; (3) Filling market gaps: It provides a stable and high-quality magnesium flux pellet production technology, which helps to alleviate the domestic market demand pressure for such products; (4) Stable and controllable process: Through intelligent batching and precise thermal regime, the stability and reproducibility of product quality are guaranteed, which is suitable for large-scale industrial production; (5) The pellets prepared by the present invention are fully self-fluxing magnesium oxide pellets, and the binary basicity and quaternary basicity are both in the range of 1.0±0.05; (6) The pellets prepared by this invention have a high vanadium content, and when used in combination with vanadium-containing sinter, their steel slag can be used as a high-quality raw material for vanadium extraction from vanadium slag. Attached Figure Description

[0012] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0013] Figure 1 This is a process flow diagram of the belt roasting machine of the present invention; Figure 2 This is a microstructure diagram of the inner and outer layers of the pellets of the present invention. Detailed Implementation

[0014] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Please see Figures 1 to 2 The present invention provides a technical solution: This invention is achieved through the following technical solution: On the one hand, a high-vanadium-magnesium flux oxide pellet is provided, which possesses specific chemical composition, physical properties, and metallurgical properties. On the other hand, a method for preparing the above-mentioned pellet is provided, the core of which lies in: (1) Raw material innovation: Using vanadium-containing iron concentrate as the iron source, the concentration and stability of vanadium grade are guaranteed (V2O5 content reaches 0.34%). By precisely adding magnesium and calcium source additives, the TiO2 content is controlled to a very low level of less than 0.91%, while MgO reaches 1.50%, realizing the self-melting property of the pellets (binary basicity and quaternary basicity are between 1.0±0.05).

[0016] (2) Process innovation: A belt calciner was adopted and a unique thermal regime was optimized. This regime ensured the stability of the pellets during the internal structural transformation and crystallization process by precisely controlling the temperature, time and wind speed of each stage of drying, preheating, calcining, homogenization and cooling, and with a specific material layer thickness of 400mm, thereby obtaining excellent properties of high strength (compressive strength ≥2500N / pellet) and low reduction expansion (RSI≤17.52%).

[0017] Example: 1. Raw material preparation The main iron raw material is vanadium-containing iron concentrate from a local production area. Auxiliary materials: magnesite powder is used as the magnesium source additive, quicklime as the calcium source additive, and sodium-based bentonite as the binder. The chemical composition of each material is shown in Table 1.

[0018] Table 1. List of Chemical Composition of Raw and Auxiliary Materials

[0019] As shown in Table 1, this iron concentrate is a mixture of magnetite and hematite, with a high overall iron content. FeO contributes to heat storage in the feed layer during preheating and roasting. It has low levels of acidic oxides such as silicon and aluminum, as well as alkali metals such as sodium and potassium. The content of harmful elements such as manganese, lead, zinc, and titanium dioxide is also low. Overall, except for the relatively high content of harmful elements such as sulfur and phosphorus, its comprehensive quality is excellent. It can replace Brazilian iron concentrate, which has a high iron content and low impurities, in the preparation of flux-type oxide pellets. The auxiliary materials are widely available and reliable.

[0020] 2. Raw material processing The iron concentrate was pretreated using a high-pressure roller mill, and the auxiliary materials were supplied from the market as finished dry fine powder that met quality requirements. The particle size distribution and specific surface area of ​​each raw and auxiliary material after treatment are shown in Table 2.

[0021] Table 2. Results of Particle Size Composition Test of Raw and Auxiliary Materials

[0022] 2. Ingredients and Mixing The raw materials are analyzed online using intelligent methods to determine the levels of Fe, Ca, Mg, Si, and Al. Fe is used as the float, and the MgO content of the pellets is ≥1.5%, with a binary alkalinity (…). ) and quaternary alkalinity ( The values ​​fluctuated within the range of (1.0±0.05) to simulate quantitative mixing, achieving AI-powered intelligent batching. A high-powered mixer was used for homogenization, and the suitable moisture content of the mixture was controlled between 5.86% and 6.22%. A typical batch composition includes (by mass percentage): 95.16% iron concentrate, 1.52% quicklime, 2.41% magnesite powder, and 0.91% bentonite.

[0023] 2. Ball making In the disc pelletizer, unqualified small mature pellets are crushed and mixed with the mixed material, then sprayed with water to form pellets. The moisture content of the raw pellets is controlled at 8.2%, and the proportion of raw pellets with a particle size of 8-16mm reaches more than 95%.

[0024] 3. Roasting Green pellets are fed into a belt roaster with a bed thickness of 400 mm. The green pellets prepared from this single vanadium-iron concentrate have a low bursting temperature (≥350℃), and require a long drying and preheating period; therefore, the following thermal regime must be strictly adhered to: Blower air drying: temperature 220℃, time 2.2 min, wind speed 2.0 m / s; Exhaust drying: temperature 300℃, time 5.6 min, wind speed 2.0 m / s; Preheating stage: temperature 500℃~900℃, time 3min, wind speed 2.0m / s; Preheating stage 2: temperature 950℃, time 6min, wind speed 1.5m / s; Firing: Temperature 1220℃~1240℃, time 11.2min, wind speed 1.3m / s; Heat equalization: temperature 1210℃~900℃, time 2.2min, wind speed 1.4m / s; Forced air cooling: Use ambient temperature air for 12 minutes at a wind speed of 2.2 m / s. The exhaust gas temperature after cooling is 150℃. 4. Finished product inspection The cooled finished balls were tested, and the results are as follows: Chemical composition: TFe mass percentage is 63.5%, FeO mass percentage is 0.4%, V2O5 mass percentage is 0.34%, TiO2 mass percentage is 0.90%, MgO mass percentage is 1.50%, binary basicity is 0.96, quaternary basicity is 1.05.

[0025] Physical properties: average compressive strength of 2550N / piece, +6.3mm drum index of 95.02%, -0.5mm abrasion resistance index of 4.48%.

[0026] Metallurgical properties: Reduction expansion index (RSI) is 17.50%, reduction index (RI) is 81.0%, softening start temperature is 1045℃, and melting start temperature is 1309℃.

[0027] The results of this embodiment demonstrate that the method of the present invention has successfully prepared high vanadium-magnesium flux pellets with excellent properties.

[0028] This application Figure 2 Photo 1 on the left shows the microstructure of the inner layer of the ore pellet (500× reflectance). This application Figure 2 Photo 2 (left side): Microstructure of the outer layer of the ore pellet (500× reflectance). Note: 1. Fe2O3 particles (white, interconnected); 2. Fe3O4 particles (brownish-gray, strip-shaped or dot-shaped); 3. SiO2 particles (dark-colored, round); 4. Pores (black, irregular shape).

[0029] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high-vanadium magnesium flux oxide pellet, characterized in that, Its chemical composition, by mass percentage, includes: The mass percentage of TFe is 63.64%; The mass percentage of FeO is 0.4%; The mass percentage of V2O5 is 0.34%; The mass percentage of TiO2 is 0.90%; The mass percentage of MgO is 1.50%; The binary and quaternary basicities are between 1.0±0.05, exhibiting self-fluxing properties; their physical properties are: compressive strength ≥2500N / piece, strength index of +6.3mm drum ≥95.02%, abrasion resistance index of -0.5mm drum ≤4.48%, and particle size of 8~16mm ≥95.0%; their metallurgical properties are: reducing expansion index RSI ≤17.52%, and reduction index RI ≥80.8%.

2. The high-vanadium magnesium flux oxide pellets according to claim 1, characterized in that: The softening start temperature of the pellets is 1045℃, the softening range is 105℃, the melting start temperature is 1309℃, the droplet range is 41℃, and the maximum pressure difference is 2.9KPa.

3. A method for preparing high-vanadium magnesium flux pellets as described in claim 1 or 2, characterized in that, Includes the following steps: Ingredients: The main iron raw material is vanadium-containing iron concentrate, with magnesium and calcium additives added for conditioning to make the MgO content in the finished balls ≥1.5%, and bentonite is added as a binder. Pelletizing: The process of forming green pellets from the mixture, including the following technical parameters: a) The suitable moisture content of the mixture is 5.86%~6.22%; b) The ideal moisture content for raw bulbs is 8.01%~8.39%; c) Ball-making time is approximately 10 minutes; d) Drop intensity of raw balls: 5.0~5.1 times / ball; e) Compressive strength of green pellets: 16~17N / pellet; f) Green pellet bursting temperature ≥350℃; Calcination: The green pellets were calcined using a belt calciner for a total time of 42.2 minutes. The process included the following steps: a) Forced air drying: temperature 220℃, time 2.2min, wind speed 2.0m / s; b) Exhaust drying: temperature 300℃, time 5.6min, wind speed 2.0m / s; c) Preheating stage: temperature 500℃~900℃, time 3min, wind speed 2.0m / s; d) Preheating stage 2: temperature 950℃, time 6min, wind speed 1.5m / s; e) Calcination: Temperature 1220℃~1240℃, time 11.2min, wind speed 1.3m / s; f) Heat equalization: Temperature 1210℃~900℃, time 2.2min, wind speed 1.4m / s; g) Forced air cooling: Use ambient temperature air for 12 minutes at a wind speed of 2.2 m / s. The exhaust gas temperature after cooling is 150℃. Throughout the entire roasting process, the total thickness of the material layer is 400mm, including: a 300mm thick raw ball material layer, a 100mm thick bottom layer, and an 80mm thick edge layer.

4. The method for preparing high-vanadium magnesium flux oxide pellets according to claim 3, characterized in that: The batching process employs online quality detection and intelligent batching technology. The entire process involves online quality detection of six elements (Fe, V, Ga, Mg, Si, and Al) and free water, controlling the mixing ratio of four elements (calcium, magnesium, silicon, and aluminum), and online batching is carried out according to the binary and quaternary basicities being both within 1.0 ± 0.

05.

5. The method for preparing high-vanadium magnesium flux oxide pellets according to claim 3, characterized in that: The magnesium source additive is one or more of magnesite powder and lightly calcined dolomite powder, and the calcium source additive is one or more of quicklime and limestone powder.

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