Preparation method of high-quality vanadium-titanium pellets from all-sea sand mine

Abstract

The application discloses a preparation method of high-quality vanadium-titanium pellets from sea sand ore. The method comprises the following steps: uniformly mixing sea sand ore and high-pressure roller grinding circulating edge material of the sea sand ore, pre-pressing and high-pressure roller grinding the obtained mixed material, returning the edge material obtained by the high-pressure roller grinding to participate in the mixing of the mixed material, uniformly mixing the medium material obtained by the high-pressure roller grinding and a binder, and then sequentially performing balling, low-temperature preheating and roasting to obtain the pellets. The method can promote the uniform action and transmission of the roller surface pressure among the particles by forming a uniform and dense material layer structure in the sea sand ore during the laminated crushing process, and is beneficial to the efficient activation of the sea sand ore during the high-pressure roller grinding process, can improve the green ball quality of the sea sand ore, strengthens the oxidation and consolidation of the pellets, can realize the low-temperature, low-cost and efficient preparation of the vanadium-titanium pellets from the sea sand ore, and is beneficial to the industrial production.

Description

Technical Field

[0001] This invention relates to a method for producing vanadium-titanium pellets, and more particularly to a method for preparing high-quality vanadium-titanium pellets from sea sand, belonging to the field of iron ore pellet preparation in iron and steel metallurgy. Background Technology

[0002] Marine sand-type vanadium-titanium magnetite (hereinafter referred to as marine sand) is a typical polymetallic symbiotic deposit of iron, vanadium, and titanium, widely distributed in New Zealand, Indonesia, the Philippines, and other regions. It boasts large reserves, is easy to mine, inexpensive, and has low transportation costs, making it an important source of titanium and vanadium resources with significant development value and application prospects. However, marine sand has a relatively coarse particle size, with an average particle size of approximately 150 μm. The particles are spherical or ellipsoidal, with smooth surfaces, poor hydrophilicity, and poor spherical formation. Furthermore, vanadium and titanium are isomorphously present in the main phase, titanate magnetite, resulting in poor chemical reactivity, making it a typical difficult-to-process iron ore resource.

[0003] Regardless of whether the blast furnace process or the non-blast furnace process is used to process sea sand ore, the ore must first be agglomerated before subsequent smelting. Sintering is primarily used in the blast furnace process for processing sea sand ore. Studies have shown that the proportion of sea sand ore in the iron ore sintering process should not exceed 10%, otherwise it will significantly affect sintering production indicators and sinter quality, making large-scale processing of sea sand ore difficult. In contrast, the pelletizing process for processing sea sand ore has lower energy consumption and fewer pollutant emissions. Furthermore, the vanadium-titanium pellets produced are not only a high-quality raw material for the blast furnace process but also an important raw material for the non-blast furnace process.

[0004] Currently, when preparing pellets from sea sand, it is typically mixed with ordinary iron concentrate or ordinary vanadium-titanium magnetite to improve pelletizing and roasting properties, with the mixing ratio generally not exceeding 30%. Some researchers have attempted to process sea sand into pellets using ball milling and wet grinding processes, but these methods suffer from long grinding processes and high energy consumption. Therefore, fully utilizing the abundant and inexpensive sea sand to produce high-quality vanadium-titanium pellets while simultaneously reducing energy consumption in pellet production would be of great significance for promoting the development of vanadium-titanium pellets, broadening the types of vanadium-titanium resources utilized, and reducing ore costs. Summary of the Invention

[0005] Because sea sand has a coarse particle size, is spherical or ellipsoidal in shape, and has a smooth surface, its pelletizing and roasting properties are poor. When sea sand is used alone to produce pellets, the quality indicators are poor. Pre-treatment of sea sand through processes such as ball milling and lubrication also has the problems of long process flow and high energy consumption.

[0006] The purpose of this invention is to provide a method for preparing high-quality vanadium-titanium pellets from marine sand ore. This method involves activating the marine sand ore using a high-pressure roller mill, and optimizing the particle stacking structure by introducing high-pressure roller mill circulating edge material and pre-compression techniques. This enhances the effect and transmission of roller surface pressure during the lamination and crushing process, thereby increasing the surface free energy of the marine sand ore particles and improving their hydrophilicity and pelletizing properties. Simultaneously, it achieves the dissociation of iron-bearing minerals and gangue in the marine sand ore, improving the reaction between particles and the mineralization conditions. Furthermore, it promotes the distortion, deformation, and dislocation of the titanomagnetite lattice, transforming it into an amorphous state, reducing the activation energy of the reaction, and increasing the chemical reactivity, thus achieving the goal of preparing high-quality vanadium-titanium pellets with low energy consumption and high efficiency.

[0007] To achieve the above-mentioned technical objectives, the present invention provides a method for preparing high-quality vanadium-titanium pellets from sea sand. The method involves vigorously mixing sea sand with the edge material from a high-pressure roller mill, and then subjecting the resulting mixture to pre-compression and high-pressure roller milling in sequence. The edge material obtained from the high-pressure roller milling is returned to participate in the batching of the mixture, and the medium material obtained from the high-pressure roller milling is vigorously mixed with a binder, and then subjected to pelletizing, low-temperature preheating, and roasting in sequence to obtain pellet ore.

[0008] The key to this invention lies in optimizing the particle packing structure of marine sand ore by combining "introducing high-pressure roller mill circulating edge material for strong mixing" with "pre-compression of the mixed material," thereby enhancing the effect of high-pressure roller milling, reducing roller mill energy consumption, improving the pelletizing conditions of marine sand ore, and increasing the reactivity of the pellets. This facilitates the low-energy, high-efficiency preparation of high-quality vanadium-titanium pellets. On one hand, introducing high-pressure roller mill circulating edge material utilizes fine particles to improve the particle size distribution of the mixed material, ensuring uniform particle size and moisture distribution. On the other hand, pre-compression treatment with rollers makes the particles inside the mixed material before high-pressure roller milling more compact. Based on this, high-pressure roller milling promotes the crushing force between marine sand ore particles, reduces shear stress, and prevents excessive plastic deformation of the pellet, thus optimizing the particle packing structure of marine sand ore. This results in a uniform and dense material layer formed during the high-pressure roller milling process, promoting the uniform action and transmission of roller surface pressure between particles, improving roller mill efficiency, and achieving efficient activation of marine sand ore. Activated marine sands have greater surface free energy, which improves their hydrophilicity and pelletizing properties. At the same time, the dissociation of mineral particles along different phase boundaries improves the oxidation reaction and mineralization consolidation conditions of iron-bearing minerals. Furthermore, under mechanical activation, iron-bearing minerals undergo lattice distortion, deformation, and dislocations, transforming into amorphous forms, which lowers the activation energy and enhances the chemical reactivity, thereby enabling the low-temperature and efficient preparation of high-quality vanadium-titanium pellets.

[0009] As a preferred embodiment, the content of the sea sand with a particle size of less than 150 μm is greater than 50 wt.%, and the specific surface area is not less than 200 cm². 2 / g. This invention can select conventional sea sand as raw material. However, this type of sea sand has a relatively coarse particle size, with spherical or ellipsoidal particles, a small specific surface area, a smooth surface, poor hydrophilicity, and poor spherical formation using conventional methods.

[0010] As a preferred embodiment, the mass percentage composition of the mixed material from sea sand to recycled edge material is 60%–80%: 20%–40%. By controlling the proportion of high-pressure recycled edge material, the mixed material can have a denser particle packing structure. By controlling the proportion of recycled edge material, the mass percentage of particles smaller than 74μm in the entire mixed material can be controlled to be 15%–25%, and the packing porosity can be lower than 45%. The denser particle packing structure of the mixed material is beneficial to the action and transmission of roller surface pressure during lamination and crushing, thereby improving the roller mill efficiency.

[0011] As a preferred embodiment, the moisture content of the blended material is controlled at 4.5 wt.% to 5.5 wt.% when it enters the high-pressure roller mill. Controlling the moisture content of the blended material at a low level can, on the one hand, improve the strong mixing effect; on the other hand, it helps to improve the efficiency of subsequent pre-compression and roller mill activation, and reduce the plastic deformation of the material cake and adhesion to the roller surface.

[0012] As a preferred embodiment, the pre-compression conditions are: a roller spacing of 3mm to 4mm and a roller speed of 27r / min to 30r / min. Controlling the edge width of the pre-compression rollers to be smaller than that of the high-pressure roller mill facilitates continuous and uniform feeding in the subsequent high-pressure roller mill and reduces edge effects.

[0013] As a preferred embodiment, the conditions for the high-pressure roller mill are: projected pressure of 2.7 MPa to 3.2 MPa, roller speed of 23 r / min to 26 r / min, edge material circulation ratio of 20 wt.% to 40 wt.%, and roller spacing of 1 mm to 2 mm. Because sea sand ore has a relatively coarse particle size and is spherical or ellipsoidal with a smooth surface, the material cake is prone to plastic deformation during the high-pressure roller milling process, thus affecting the milling efficiency. Therefore, sufficient roller milling pressure is required, and maintaining a small roller spacing can promote the interaction between particles during the lamination and crushing process.

[0014] This invention is based on optimizing the material layer accumulation structure of sea sand ore particles by means of "introducing high-pressure roller mill circulation edge material for strong mixing" and "pre-compressing the mixed material". It further combines the use of "high pressure, low water" high-pressure roller mill technology, which can promote the uniform action and transmission of roller surface pressure between particles, improve roller mill efficiency, and achieve efficient activation of sea sand ore.

[0015] As a preferred embodiment, the mass of the binder is 0.5% to 0.7% of the mass of the intermediate material. A suitable binder ratio can ensure that the marine sand ore pellets have sufficient strength and bursting temperature, but when the binder ratio is too high, the iron grade of the pellets decreases, the plasticity of the pellets increases, and the compressive strength decreases.

[0016] As a preferred embodiment, the binder comprises bentonite. The binder is a conventional binder used in pellet preparation, such as inorganic binders like bentonite, or other conventional binders may be used as alternatives.

[0017] As a preferred embodiment, the pelletizing process employs a disc pelletizer. During pelletizing, the moisture content of the green pellets is controlled at 7 wt.%–7.5 wt.%, the pelletizing time is 12–14 minutes, and the disc inclination angle is 47°–48°. Because marine sand minerals have relatively poor hydrophilicity, the pelletizing process requires maintaining appropriate moisture content, pelletizing time, and disc inclination angle to facilitate the compaction of the green pellets.

[0018] As a preferred embodiment, the preheating adopts a low-temperature slow oxidation method, with a preheating temperature of 800℃~860℃ and a preheating time of 10min~14min.

[0019] As a preferred embodiment, the calcination is carried out at a low temperature of 1100℃~1170℃ and for 10min~20min.

[0020] Under optimized pelletizing, preheating, and roasting process conditions, this invention can reduce energy consumption in the production process while ensuring the quality of the prepared pellets.

[0021] Compared with the prior art, the advantages of the technical solution of the present invention are as follows:

[0022] (1) The present invention involves a strong mixing of raw sea sand ore and circulating edge material of high pressure roller mill. On the one hand, this makes the moisture and particle size distribution of the mixed material uniform, which can reduce the impact of raw material performance fluctuations caused by the addition of circulating edge material of high pressure roller mill on high pressure roller mill. On the other hand, the introduction of fine particles in circulating edge material of high pressure roller mill can improve the problem of narrow particle size distribution range and large particle packing porosity of sea sand ore, so that a denser particle packing structure is formed during the lamination and crushing process, thereby improving the roller mill efficiency.

[0023] (2) The present invention adopts a strengthening process of pre-pressing with high pressure roller mill, which makes the internal particle structure of the mixed material before high pressure roller milling more compact. On the one hand, it is conducive to continuous and uniform feeding of high pressure roller mill, avoiding material accumulation, blockage, and suspension, and improving the uniformity of roller mill operation and product quality. On the other hand, the more compact material layer structure during roller milling can promote the action and transmission of roller surface pressure, which is conducive to the efficient and full activation of sea sand.

[0024] (3) The roller milling parameters used in this invention are set based on the characteristics of sea sand ore and the overall process flow. Because sea sand ore particles are relatively coarse, have smooth surfaces, and are mostly spherical, the material layer has strong plasticity. Using a "high pressure, low water" roller milling system helps to improve the pre-compression and roller milling activation effect of sea sand ore, while preventing roller surface adhesion; on the other hand, maintaining a low moisture content when pre-mixing the raw sea sand ore and edge material can enhance the strong mixing effect.

[0025] (4) This invention employs the processes of "edge material strengthening and homogenization" and "mixed material pre-pressing against rollers," combined with a "high-pressure, low-water" roller milling system, which facilitates the formation of a uniform and dense material layer structure during the lamination and crushing process of sea sand ore, thereby achieving efficient activation of sea sand ore. This increases the surface free energy and reactivity of sea sand ore, thereby improving its pelletizing and roasting properties.

[0026] (5) The pretreated and activated sea sand ore of the present invention has high activity. The low-temperature slow oxidation thermal process can prevent the outer layer of the pellets from becoming dense during the preheating process, ensuring uniform oxidation of the pellets. This allows the pellets to solidify completely at a low temperature during the roasting process, thereby achieving the low-temperature and efficient preparation of high-quality vanadium-titanium pellets from all sea sand ore. Attached Figure Description

[0027] Figure 1 This is a production flow diagram of high-quality vanadium-titanium pellets from all-sea sand ore in an embodiment of the present invention. Detailed Implementation

[0028] To further illustrate the present invention, the following description, in conjunction with preferred embodiments, will provide a more comprehensive and detailed account. However, the scope of protection of the present invention is not limited to the specific embodiments described below. Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of protection of the present invention.

[0029] Tables 1 and 2 show the chemical composition, particle size distribution, and specific surface area of ​​the sea sand and bentonite used, respectively.

[0030] Table 1 Chemical composition of raw materials / wt.%

[0031]

[0032] Table 2 Particle size distribution and specific surface area of ​​raw materials

[0033]

[0034] Comparative Example 1

[0035] The only difference compared to Example 1 is that after the high-pressure roller mill circulating edge material is added to the raw sea sand ore, it is not subjected to strong mixing, but is directly pre-pressed and high-pressure roller milled.

[0036] The resulting green pellets had a drop strength of 3.2 times / 0.5m, a compressive strength of 10.7N / pellet, and a bursting temperature of 570℃. Under the conditions of preheating at 850℃ for 14 min and calcining at 1150℃ for 10 min, the preheated pellet strength was 362N, and the calcined pellet strength was 2243N.

[0037] Compared to Example 1, after the high-pressure roller mill circulating material is added to the raw sea sand ore, it is directly pre-compressed and high-pressure roller milled. At this time, the moisture and particle size distribution in the cake during the lamination and crushing process are uneven, making it difficult to form a suitable particle accumulation structure, which affects the activation effect of the high-pressure roller mill, resulting in a decrease in the strength of green pellets and ore pellets. In addition, some areas with finer particle size in the cake are prone to over-crushing, which reduces the pellet bursting temperature.

[0038] Comparative Example 2

[0039] The only difference compared to Example 1 is that after the high-pressure roller mill circulating edge material is mixed with the raw sea sand ore for strong mixing, it is directly subjected to high-pressure roller milling without pre-compression.

[0040] The resulting green pellets had a drop strength of 3.0 drops / 0.5m, a compressive strength of 11.2N / pellet, and a bursting temperature of 600℃. Under the conditions of preheating at 850℃ for 14 min and calcining at 1150℃ for 10 min, the preheated pellets had a strength of 353N, and the calcined pellets had a strength of 2137N.

[0041] Compared to Example 1, when the raw sea sand ore is vigorously mixed with the circulating edge material from a high-pressure roller mill and then directly subjected to high-pressure roller milling, the activation effect of the sea sand ore during roller milling is poor because the roller pressure partially acts on the air expulsion between particles, and the loose cake structure is not conducive to the action and transmission of roller pressure. As a result, all indicators of the pellets are reduced.

[0042] Comparative Example 3

[0043] The only difference compared to Example 1 is:

[0044] 1) The moisture content of the mixed material is controlled at 6.5 wt.%.

[0045] 2) The projected pressure of the high-pressure roller mill is 4 MPa.

[0046] The resulting green pellets had a drop strength of 3.9 times / 0.5m, a compressive strength of 12.3N / pellet, and a bursting temperature of 510℃. Under the conditions of preheating at 850℃ for 14min and calcining at 1150℃ for 10min, the preheated pellet strength was 389N, and the calcined pellet strength was 2351N.

[0047] Compared to Example 1, higher roller mill pressure and feed moisture were used to activate sea sand ore. While higher roller mill pressure helps improve the crushing force between particles in the material layer, once the roller mill pressure increases to a certain level, further increases have limited effect on improving the activation effect, and the roller mill efficiency gradually decreases. Excessive feed moisture hinders the uniform distribution of moisture and particle size in the mixture, thus affecting the roller milling effect. Simultaneously, excessive feed moisture also enhances the plastic deformation of the material layer, increasing the shear stress between particles and reducing activation efficiency. Therefore, the quality of the prepared green pellets is reduced, the bursting temperature decreases, and the strength of preheated and roasted pellets decreases.

[0048] Comparative Example 4

[0049] The only difference compared to Example 1 is that the sea sand ore and the high-pressure roller mill circulating edge material are strongly mixed in a 5:5 ratio to obtain a homogeneous material.

[0050] The resulting green pellets had a drop strength of 4.5 times / 0.5m, a compressive strength of 13.8N / pellet, and a bursting temperature of 470℃. Under the conditions of preheating at 850℃ for 14 min and calcining at 1150℃ for 10 min, the preheated pellet strength was 396N, and the calcined pellet strength was 2367N.

[0051] Compared to Example 1, increasing the proportion of recycled edge material in the blended material and simultaneously increasing the recycling ratio of edge material from the high-pressure roller mill significantly increases the content of fine particles in the blended ore, making the pellet more compact during the lamination and crushing process, which is beneficial for the action and transmission of roller pressure. At the same time, it also makes the internal structure of the pellets more compact, thus significantly increasing the strength of the green pellets, but the bursting temperature decreases noticeably. Due to the compact packing structure of the particles inside the pellets, the outer layer of the preheated pellets is prone to consolidation, hindering the oxidation of the inner layer of the pellets, resulting in large concentric cracks in the roasted pellets, thereby affecting the quality of the pellet ore.

[0052] Example 1

[0053] Sea sand ore and high-pressure roller mill scrap were vigorously mixed at a ratio of 7:3 to obtain a homogenized material, with the moisture content controlled at 4.5 wt.%. The homogenized material was then subjected to pre-compression and high-pressure roller milling. The pre-compression rollers had a 4 mm gap and a rotation speed of 27 r / min. The high-pressure roller milling had a projected pressure of 3 MPa, a rotation speed of 23 r / min, a scrap recycling ratio of 30 wt.%, and a roller gap of 1 mm. The scrap obtained from the high-pressure roller milling was returned to the buffer silo to participate in the batching of the homogenized material. The resulting medium-weight material was mixed with 0.6 wt.% bentonite and then vigorously mixed to obtain pellet raw material. The pellet raw material was prepared into green pellets, with the pelleting moisture content controlled at 7.5 wt.%, a pelleting time of 12 min, and a disc inclination angle of 47°. The resulting green pellets had a drop strength of 4.9 drops / 0.5 m, a compressive strength of 15.3 N / pellet, and a bursting temperature of 610℃. Under the conditions of preheating at 850℃ for 14 min and calcining at 1150℃ for 10 min, the strength of the preheated ball is 487 N and the strength of the calcined ball is 2633 N.

[0054] Example 2

[0055] Sea sand ore and high-pressure roller mill scrap were vigorously mixed at a ratio of 6:4 to obtain a homogenized material, with the moisture content controlled at 4.5 wt.%. The homogenized material was then subjected to pre-compression and high-pressure roller milling. The pre-compression rollers had a 3 mm gap and a rotation speed of 30 r / min. The high-pressure roller milling had a projected pressure of 3.2 MPa, a rotation speed of 26 r / min, a scrap recycling ratio of 40 wt.%, and a roller gap of 1 mm. The scrap obtained from the high-pressure roller milling was returned to the buffer silo to participate in the batching of the aforementioned homogenized material. The resulting medium-weight material was mixed with 0.5 wt.% bentonite and then vigorously mixed to obtain pellet raw material. The pellet raw material was prepared into green pellets, with the pelleting moisture content controlled at 7.5 wt.%, a pelleting time of 12 min, and a disc inclination angle of 47°. The resulting green pellets had a drop strength of 5.7 times / 0.5 m, a compressive strength of 16.1 N / pellet, and a bursting temperature of 560℃. Under the conditions of preheating at 800℃ for 14 min and calcining at 1110℃ for 20 min, the strength of the preheated ball is 477 N and the strength of the calcined ball is 2788 N.

[0056] Example 3

[0057] Sea sand ore and high-pressure roller mill scrap were vigorously mixed at an 8:2 ratio to obtain a homogenized material, with the moisture content controlled at 5.5 wt.%. The homogenized material was then subjected to pre-compression and high-pressure roller milling. The pre-compression rollers had a 4 mm gap and a roller speed of 30 r / min. The high-pressure roller mill had a projected pressure of 2.7 MPa, a roller speed of 26 r / min, a scrap recycling ratio of 20 wt.%, and a roller gap of 2 mm. The scrap obtained from the high-pressure roller mill was returned to the buffer silo to participate in the batching of the homogenized material. The resulting medium-weight material was mixed with 0.7 wt.% bentonite and then vigorously mixed to obtain pellet raw material. The pellet raw material was prepared into green pellets, with the pelleting moisture content controlled at 7 wt.%, a pelleting time of 14 min, and a disc inclination angle of 48°. The resulting green pellets had a drop strength of 4.5 drops / 0.5 m, a compressive strength of 14.5 N / pellet, and a bursting temperature of 630℃. Under the conditions of preheating at 860℃ for 10 min and calcining at 1170℃ for 10 min, the strength of the preheated ball is 536 N and the strength of the calcined ball is 2745 N.

Claims

1. A method for preparing high-quality vanadium-titanium pellets from marine sand ore, characterized in that: The edge material of the high-pressure roller mill is strongly mixed with the edge material of the sea sand ore. The resulting mixture is then subjected to pre-compression and high-pressure roller milling in sequence. The edge material obtained from the high-pressure roller milling is returned to participate in the batching of the mixture. The medium material obtained from the high-pressure roller milling is strongly mixed with the binder and then subjected to pelletizing, low-temperature preheating and roasting in sequence to obtain pellets. The content of the sea sand with a particle size of less than 150 μm is greater than 50 wt.%, and the specific surface area is not less than 200 cm². 2 / g; The mass percentage composition of the mixed material from marine sand to recycled edge material is 60%~80% : 20%~40%; The moisture content of the mixed material is controlled to be 4.5 wt.%~5.5 wt.% when it enters the high-pressure roller mill. The pre-compression conditions are: roller spacing of 3 mm to 4 mm, and roller rotation speed of 27 r / min to 30 r / min; The conditions for the high-pressure roller mill are as follows: projected pressure of 2.7 MPa to 3.2 MPa, roller speed of 23 r / min to 26 r / min, edge material circulation ratio of 20 wt.% to 40 wt.%, and roller spacing of 1 mm to 2 mm.

2. The method for preparing high-quality vanadium-titanium pellets from all-sea sand ore according to claim 1, characterized in that: The binder accounts for 0.5% to 0.7% of the mass of the intermediate material; the binder includes bentonite.

3. The method for preparing high-quality vanadium-titanium pellets from all-sea sand ore according to claim 1, characterized in that: The pelletizing process uses a disc pelletizing machine. During the pelletizing process, the moisture content of the raw pellets is controlled at 7 wt.%~7.5 wt.%, the pelletizing time is 12 min~14 min, and the disc tilt angle is 47°~48°.

4. The method for preparing high-quality vanadium-titanium pellets from all-sea sand ore according to claim 1, characterized in that: The preheating adopts a low-temperature slow oxidation method, with a preheating temperature of 800 ℃~860 ℃ and a preheating time of 10 min~14 min.

5. The method for preparing high-quality vanadium-titanium pellets from all-sea sand ore according to claim 1, characterized in that: The roasting is carried out at a low temperature, with a roasting temperature of 1100 ℃ to 1170 ℃ and a roasting time of 10 min to 20 min.

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