Vanadium-titanium pellet and method for improving compression strength of vanadium-titanium pellet

Abstract

This invention discloses a vanadium-titanium pellet ore and a method for improving the compressive strength of vanadium-titanium pellet ore. The method includes the following steps: mixing a predetermined mass percentage of upgraded vanadium-titanium concentrate, sintering dust from high-temperature roasting, and a binder to obtain a mixture; then drying the mixture; rolling the dried mixture; and then adding the rolled mixture into a pelletizing machine to prepare vanadium-titanium green pellets; and drying, preheating, roasting, homogenizing, and cooling the vanadium-titanium green pellets to obtain vanadium-titanium pellet ore. The method provided by this invention optimizes the iron-containing material structure of the roasted pellet ore, which is beneficial for promoting the oxidation of magnetite in the vanadium-titanium concentrate to Fe2O3, improving the grain composition and distribution of the upgraded vanadium-titanium concentrate pellets during the preheating and roasting process, promoting the optimization of the grain structure in the pellets, and promoting the interconnection between Fe2O3 grains in the ultrafine vanadium-titanium concentrate pellets, thereby greatly improving the compressive strength of the pellet ore.

Description

Technical Field

[0001] This invention relates to the field of iron and steel metallurgy, and more particularly to a vanadium-titanium pellet and a method for improving the compressive strength of the vanadium-titanium pellet. Background Technology

[0002] Blast furnace smelting, which mainly uses high-titanium vanadium-titanium magnetite, results in a low iron content due to the inherent iron-titanium symbiosis of vanadium-titanium magnetite. This leads to a blast furnace feed grade of only about 50%, and a fuel ratio of 570 kg per ton of pig iron, which increases the cost of pig iron by 100 yuan / ton. At the same time, the long-term low-grade smelting in the blast furnace also increases the energy consumption of the ironmaking process and the pressure to reduce emissions in the smelting process. Therefore, it is necessary to improve the TFe grade of vanadium-titanium magnetite concentrate to improve the blast furnace feed grade.

[0003] Currently, the main method to improve the grade of vanadium-titanium magnetite concentrate is to obtain it through ultrafine grinding followed by magnetic separation of gangue. This results in an extremely fine particle size of the upgraded vanadium-titanium concentrate. Screening analysis of the upgraded vanadium-titanium concentrate reveals that over 95% of the particles are smaller than 200 mesh, and approximately 80% are smaller than 320 mesh. Simultaneously, low-melting-point phases such as silicates are also separated out, leading to problems such as low liquid phase generation and significantly reduced sinter quality during subsequent sintering. To address this, a belt roasting and pelletizing process for upgraded vanadium-titanium concentrate is proposed, where the upgraded vanadium-titanium concentrate is roasted into pellets and then added to the blast furnace.

[0004] However, during the production process using the aforementioned belt roasting pelletizing process, it was found that when the daily output of upgraded vanadium-titanium concentrate pellets reached 9100 tons, the compressive strength of the finished pellets only remained at around 1900 N. This compressive strength only meets the standard requirements for smelting in small and medium-sized blast furnaces. Furthermore, the finished pellets exhibited a serious problem of a "double-layer" phenomenon. Analysis of the pellets revealed that the main reason for this "double-layer" phenomenon was the extremely fine particle size of the upgraded vanadium-titanium concentrate used in pellet preparation (e.g., particles smaller than 200 mesh). The percentage reaches over 85%, resulting in a dense internal structure of the pellets. During preheating, a dense oxide layer forms on the outer layer of the pellets, making it difficult for oxygen to diffuse into the interior. Consequently, the internal magnetite (mainly Fe3O4) cannot be fully oxidized (oxidized to Fe2O3). During roasting, the internal magnetite recrystallizes, while the outer layer of magnetite, under an oxygen atmosphere, oxidizes to Fe2O3 and also undergoes crystal form changes and recrystallization. This results in uneven shrinkage between the inner and outer layers, leading to concentric cracks in the finished pellets and reducing their compressive strength.

[0005] Therefore, existing technologies still need improvement. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a vanadium-titanium pellet ore and a method for improving the compressive strength of vanadium-titanium pellet ore. This method can solve the technical problem of low compressive strength of finished pellet ore when roasting upgraded vanadium-titanium concentrate into pellet ore using existing technologies.

[0007] On one hand, embodiments of the present invention disclose a method for improving the compressive strength of vanadium-titanium pellets, comprising the following steps:

[0008] S1. A predetermined mass percentage of upgraded vanadium-titanium concentrate, high-temperature roasted sintered dust, and binder are mixed to obtain a mixture, which is then dried.

[0009] S2. The dried mixture is roller-milled, and then the roller-milled mixture is added into a pelletizing machine to prepare vanadium-titanium green pellets.

[0010] S3. The vanadium-titanium green pellets are dried, preheated, roasted, homogenized and cooled to obtain vanadium-titanium ore pellets.

[0011] According to one embodiment of the present invention, in the mixture: the mass percentage of the upgraded vanadium-titanium concentrate is 92% to 98%, the mass percentage of the sintering dust after high-temperature roasting is 1% to 5%, and the mass percentage of the binder is 1.0% to 3.0%.

[0012] According to one embodiment of the present invention, the main components of the upgraded vanadium-titanium concentrate, by mass percentage, are: TFe≥57%, SiO2≤3.0%, TiO2≥9.0%, V2O5≥0.50%; the mass percentage of particles smaller than 200 mesh in the upgraded vanadium-titanium concentrate is ≥85%; the main components of the sintering dust after high-temperature roasting, by mass percentage, are: TFe≥40%, SiO2≥5%, CaO≥15%, C:1.00%~5.00%; the mass percentage of particles smaller than 200 mesh in the sintering dust after high-temperature roasting ranges from 30% to 80%.

[0013] According to one embodiment of the present invention, the binder is bentonite, and the main components of the bentonite, by mass percentage, are: CaO: 2.00%–5.00%, SiO2: 40.00%–60.00%, Al2O3: 12.00%–18%, MgO: 2.00%–5.00%; the mass percentage of particles with a particle size smaller than 200 mesh in the bentonite ranges from 97.00% to 99.00%.

[0014] According to one embodiment of the present invention, in step S1, the mixture is placed in a mixer for mixing for 8 min to 12 min, and after drying, the moisture content of the dried mixture is controlled to be 7% to 9%.

[0015] According to one embodiment of the present invention, in step S2, the dried mixture is placed in a roller mill for roller milling, the roller milling pressure is set to 58-61 Bar, and the specific surface area of ​​the mixture after roller milling is controlled to be >2200 cm². 2 / g.

[0016] According to one embodiment of the present invention, in step S2, the mixture after roller milling is transported to a rotating pelletizing machine, and droplets of water are sprayed onto the mixture to form a mother ball core of 1 mm to 3 mm. Atomized water and the mixture are continuously added to allow the mother ball to grow into a green ball within 10 to 20 minutes. Finally, the green ball is screened by a double-layer roller screen to obtain vanadium-titanium green pellets with a particle size of 8 to 16 mm. The moisture content of the vanadium-titanium green pellets is controlled to be 8% to 10% by mass, the drop strength of the vanadium-titanium green pellets is controlled to be >5 times / 0.5 m, and the compressive strength of the vanadium-titanium green pellets is controlled to be >10 N / piece.

[0017] According to one embodiment of the present invention, the pelletizing machine is a disc pelletizing machine, wherein the disc diameter is 7000 mm, the disc sidewall height is 750 mm, the rotation speed is 6-8 r / min, and the tilt angle is 45°-55°.

[0018] According to one embodiment of the present invention, in step S3, the drying, preheating, calcining, homogenizing, and cooling processes include: drying the vanadium-titanium green pellets by forced draft and forced draft, wherein the forced draft drying temperature is 200℃~400℃ and the forced draft drying time is 5min~7min, and the forced draft drying temperature is 350℃~450℃ and the forced draft drying time is 5min~7min; preheating and calcining the dried vanadium-titanium green pellets, wherein the preheating temperature is 800℃~1000℃ and the preheating time is 7min~10min, the calcining temperature is 1150℃~1300℃ and the calcining time is 10min~15min; and homogenizing and cooling the calcined vanadium-titanium green pellets, wherein the homogenizing temperature is 1000℃~1100℃ and the homogenizing time is 7min~10min, and the cooling temperature is 150℃~400℃ and the cooling time is 10min~15min.

[0019] On the other hand, embodiments of the present invention also disclose a vanadium-titanium pellet, which is prepared by the method for improving the compressive strength of vanadium-titanium pellets as described in any of the above embodiments.

[0020] By adopting the above technical solution, the present invention has at least the following beneficial effects:

[0021] The method for improving the compressive strength of vanadium-titanium ore pellets provided by this invention optimizes the iron-containing material structure of the roasted pellets by adding sintering dust from the high-temperature roasting process of the upgraded vanadium-titanium concentrate to the pellets during the roasting process. This promotes the oxidation of magnetite to Fe2O3 in the vanadium-titanium concentrate, improves the grain composition and distribution of the upgraded vanadium-titanium concentrate pellets during the preheating roasting process, optimizes the grain structure in the pellets, and promotes the interconnection between Fe2O3 grains in the ultrafine vanadium-titanium concentrate pellets, thereby greatly improving the compressive strength of the pellets.

[0022] Furthermore, by adding high-temperature roasted sintering dust to ultrafine vanadium-titanium concentrate, the high C content and high mass ratio of CaO to SiO2 in the sintering dust can be effectively utilized. During roasting, C undergoes a combustion reaction, generating CO2 gas that volatilizes, which is beneficial for forming pore channels between the grains of ultrafine vanadium-titanium concentrate pellets. Moreover, the high mass ratio of CaO and SiO2 can increase the low-melting-point phase inside the pellets. When the low-melting-point phase cools, it can promote the formation of pore channels inside the pellets. Both of these factors can promote the smoother entry of oxygen into the pellets during roasting, avoiding uneven shrinkage between the inner and outer layers caused by the difficulty of oxygen diffusion into the pellets. This also prevents concentric cracks from forming in the pellets and avoids the impact of concentric cracks on the compressive strength of the pellets.

[0023] Furthermore, the method for improving the compressive strength of vanadium-titanium pellets provided by this invention effectively utilizes the sintering dust generated during the sintering process of upgraded vanadium-titanium concentrate into sintered ore. This solves the problem of decreased sintered ore quality caused by recycling the sintering dust back into the sintering production process, thereby optimizing the vanadium-titanium sintered ore material structure and improving the quality of vanadium-titanium sintered ore. Simultaneously, it avoids the problem of harsh on-site working environment caused by dust generation from sintering dust during the batching process. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic flowchart of a method for improving the compressive strength of vanadium-titanium pellets according to an embodiment of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to specific examples and the accompanying drawings.

[0027] It should be noted that all uses of "first" and "second" in the embodiments of the present invention are for the purpose of distinguishing two entities or parameters with the same name but different names. It is clear that "first" and "second" are only for the convenience of expression and should not be construed as limiting the embodiments of the present invention. Subsequent embodiments will not explain this in detail.

[0028] According to a first aspect of the invention, such as Figure 1 As shown, an embodiment of the present invention discloses a method for improving the compressive strength of vanadium-titanium pellets, comprising the following steps:

[0029] S1. Mix the upgraded vanadium-titanium concentrate, the sintering dust removed after high-temperature roasting, and bentonite according to a predetermined mass percentage to obtain a mixture, and then dry the mixture.

[0030] S2. The dried mixture is roller-milled, and then the roller-milled mixture is added into a pelletizing machine to prepare vanadium-titanium green pellets.

[0031] S3. The vanadium-titanium green pellets are dried, preheated, roasted, homogenized and cooled to obtain vanadium-titanium ore pellets.

[0032] The high temperature range of the "sintering dust after high-temperature calcination" disclosed in the embodiments of the present invention is 1150℃~1350℃.

[0033] The method for improving the compressive strength of vanadium-titanium ore pellets provided in this invention optimizes the iron-containing material structure of the roasted pellets by adding sintering dust from the high-temperature roasting process of the upgraded vanadium-titanium concentrate to the pelletizing process. This promotes the oxidation of magnetite to Fe2O3 in the vanadium-titanium concentrate, improves the grain composition and distribution of the upgraded vanadium-titanium concentrate pellets during the preheating roasting process, optimizes the grain structure in the pellets, and facilitates the interconnection between Fe2O3 grains in the ultrafine-grained vanadium-titanium concentrate pellets, thereby significantly improving the compressive strength of the pellets. Simultaneously, it effectively utilizes the high C content and high CaO / SiO2 mass ratio of the sintering dust from the high-temperature roasting process to prevent concentric cracks from forming in the pellets, thus preventing the impact of concentric cracks on the compressive strength of the pellets.

[0034] In some embodiments, the mass percentage of upgraded vanadium-titanium concentrate in the mixture is 92% to 98%, the mass percentage of sintering dust after high-temperature roasting is 1% to 5%, and the mass percentage of binder is 1.0% to 3.0%.

[0035] In other embodiments, the mass percentage of upgraded vanadium-titanium concentrate in the mixture is 93.5%–95.5%, the mass percentage of sintered dust after high-temperature roasting is 3%–4%, and the mass percentage of binder is 1.5%–2.5%.

[0036] In this embodiment of the invention, the binder has strong bonding ability, which can improve the bonding between material particles and play a role in interparticle molecular transfer. Furthermore, by influencing the mechanical strength of the green pellets through its bonding properties, the mechanical strength of the green pellets is increased, thereby producing high-quality ore pellets.

[0037] In some embodiments, the main components of the upgraded vanadium-titanium concentrate, by mass percentage, are: TFe≥57%, SiO2≤3.0%, TiO2≥9.0%, V2O5≥0.50%; the mass percentage of particles smaller than 200 mesh in the upgraded vanadium-titanium concentrate is ≥85%; the main components of the sintering dust after high-temperature roasting, by mass percentage, are: TFe≥40%, SiO2≥5%, CaO≥15%, C:1.00%~5.00%; the mass percentage of particles smaller than 200 mesh in the sintering dust after high-temperature roasting ranges from 30% to 80%.

[0038] In other embodiments, the carbon content in the sintering dust after high-temperature roasting is preferably 2% to 3%. An increase in carbon content can easily lead to a greater reduction atmosphere in the local area of ​​the pellets, affecting the oxidation and consolidation of magnetite during the roasting process, thereby reducing the compressive strength of the pellets.

[0039] In other embodiments, the mass percentage of particles smaller than 200 mesh in the sintering dust after high-temperature roasting ranges from 50% to 60%. If the particle size of the sintering dust after high-temperature roasting is too small, it is not conducive to improving the grain composition in ultrafine vanadium-titanium concentrate pellets; conversely, if the particle size of the sintering dust after high-temperature roasting is too large, it can easily lead to cracks during the roasting and crystallization process.

[0040] In some embodiments, the binder is bentonite, the main components of which, by mass percentage, are: CaO: 2.00%–5.00%, SiO2: 40.00%–60.00%, Al2O3: 12.00%–18%, MgO: 2.00%–5.00%; the mass percentage of particles smaller than 200 mesh in the bentonite ranges from 97.00% to 99.00%. Bentonite, as a binder in pellet production, has the characteristics of good pelletizing properties and abundant resources. It is understood that in other embodiments of the present invention, the type of binder can be selected according to requirements, and the present invention does not limit it.

[0041] In some embodiments, in step S1, the mixture is placed in a mixer for mixing for 8 to 12 minutes, and after drying, the moisture content of the dried mixture is controlled to be 7% to 9% by mass. In other embodiments, in step S1, the mixture is placed in a mixer for mixing for 10 minutes, and after drying, the moisture content of the dried mixture is controlled to be 7.5% to 8.5% by mass. Moisture content has a significant impact on pelletizing. When pelletizing with a mixture that is insufficient in moisture, the green pellets are difficult to grow. If a mixture with excessive moisture is used for pelletizing, although the initial pelletizing speed is faster, it is easy to cause problems such as the mother pellets sticking together and deforming, resulting in uneven particle size distribution of the green pellets. In addition, excessively wet materials and excessively wet mother pellets are easy to stick to the pelletizing machine, causing operational difficulties. At best, it can damage the normal running track of the mother pellets; at worst, it can cause the mother pellets to lose their rolling ability, or even cause accidents such as shaft breakage due to overloading of the pelletizing machine. Therefore, controlling the moisture content is particularly important.

[0042] In some embodiments, in step S2, the dried mixture is placed in a roller mill for roller milling, the roller milling pressure is set to 58-61 Bar (1 Bar = 101 kPa), and the specific surface area of ​​the roller-milled mixture is controlled to be >2200 cm². 2 / g. In this embodiment, roller milling the mixture can improve the mixing effect between materials and increase the surface area of ​​the materials, thereby improving the pelletizing activity.

[0043] In some embodiments, in step S2, the mixture after roller milling is transported to a rotating pelletizing machine, and droplets of water are sprayed onto the mixture to form mother pellet cores of 1mm to 3mm. Atomized water and the mixture are continuously added, causing the mother pellets to grow into green pellets within 10 to 20 minutes. Finally, the green pellets are sieved using a double-layer roller screen to obtain vanadium-titanium green pellets with a particle size of 8 to 16mm. The moisture content of the vanadium-titanium green pellets is controlled to be 8% to 10% by mass, the drop strength of the vanadium-titanium green pellets is controlled to be >5 drops / 0.5m, and the compressive strength of the vanadium-titanium green pellets is controlled to be >10N / pellet. In other embodiments, in step S2, it is preferable that the mother pellets grow into green pellets within 10 to 15 minutes.

[0044] In the above embodiments, since moisture has a significant impact on the formation of green pellets, it is difficult for green pellets to grow when the raw material has insufficient moisture. Green pellets with a moisture content of 8-10% by mass are easier to form and grow, and the formation of green pellets with a particle size of less than 8 mm can be reduced, while also helping to improve the strength of the green pellets. After screening the green pellets, vanadium-titanium green pellets of suitable particle size are obtained, ensuring that the vanadium-titanium green pellet particles are closely packed together and the average diameter of the capillaries is small, thereby enhancing the molecular bonding force. The strength of the green pellets also increases as the porosity of the pellets decreases, thus ultimately obtaining high-quality pellets.

[0045] In the above embodiments, the drop strength of the green pellets was tested using the following method:

[0046] A green ball pattern is dropped freely from a height of 0.5m onto a 10mm thick steel plate. If the ball breaks after the nth drop, the drop strength of the ball is (n-1) drops / 0.5m. Ten green balls are measured each time, and the average value is taken as the drop strength of the green ball group (in drops / 0.5m).

[0047] In the above embodiments, the drop strength of the green pellets was tested using the following method:

[0048] Place the green pellets in a rigid tray, which is pre-laid flat on an electronic balance. Slowly apply a vertical downward pressure to the top of the green pellets until they break. The pressure value displayed on the balance at this point is the compressive strength of the green pellets. Measure 10 green pellets each time and take the average value as the compressive strength of the green pellets (unit: N / pellet).

[0049] In some embodiments, the pelletizing machine is a disc pelletizing machine, wherein the disc diameter is 7000 mm, the disc sidewall height is 750 mm, the rotational speed is 6-8 r / min, and the tilt angle is 45°-55°. It is understood that in other embodiments of the present invention, the parameters of the disc pelletizing machine can be adjusted as needed, and the present invention does not limit this adjustment.

[0050] In some embodiments, vanadium-titanium green pellets are fed onto a belt roasting trolley via a shuttle conveyor belt for drying, preheating, roasting, homogenization, and cooling. Pre-prepared finished vanadium-titanium pellets are laid as a base material and edge material at the bottom and sides near the baffles of the belt roasting trolley. The base material thickness is 50mm–90mm, and the edge material thickness is 40mm–50mm. In this embodiment, the heating equipment is positioned above the belt roasting trolley during preheating and roasting of the vanadium-titanium green pellets. Heat is transferred from the top of the belt roasting trolley into the trolley. The base material and edge material serve to protect the belt roasting trolley.

[0051] In some embodiments, step S3 includes the following processes: drying, preheating, calcining, homogenizing, and cooling: drying the vanadium-titanium green pellets by forced draft and forced draft, wherein the forced draft drying temperature is 200℃~400℃ and the forced draft drying time is 5min~7min, and the forced draft drying temperature is 350℃~450℃ and the forced draft drying time is 5min~7min; preheating and calcining the dried vanadium-titanium green pellets, wherein the preheating temperature is 800℃~1000℃ and the preheating time is 7min~10min, the calcining temperature is 1150℃~1300℃ and the calcining time is 10min~15min; and homogenizing and cooling the calcined vanadium-titanium green pellets, wherein the homogenizing temperature is 1000℃~1100℃ and the homogenizing time is 7min~10min, and the cooling temperature is 150℃~400℃ and the cooling time is 10min~15min.

[0052] In other embodiments, in step S3: the forced-air drying temperature is preferably 250℃~300℃, the exhaust drying temperature is 380℃~400℃; the preheating temperature is 900℃~950℃, the preheating time is 9min, the calcination temperature is 1220℃~1270℃, and the calcination time is 12min.

[0053] In an embodiment of the present invention, the calcination process is carried out in an oxidizing atmosphere.

[0054] According to a second aspect of the present invention, one embodiment of the present invention discloses a vanadium-titanium pellet, which is prepared by a method for improving the compressive strength of vanadium-titanium pellets as described in any of the above embodiments.

[0055] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0056] The particle size distribution of the upgraded vanadium-titanium concentrate, the sintering dust after high-temperature roasting, and the bentonite in the embodiments and comparative examples of this invention is shown in Table 1 below:

[0057] Table 1. Particle size distribution (wt%) of upgraded vanadium-titanium concentrate, sintering dust after high-temperature roasting, and bentonite.

[0058]

[0059] The chemical compositions of the upgraded vanadium-titanium concentrate, the sintering dust after high-temperature roasting, and the bentonite in the embodiments and comparative examples of this invention, by mass percentage, are as follows:

[0060] Upgraded vanadium-titanium concentrate: TFe: 57.00%–58.00%, FeO > 28%, CaO < 1.0%, SiO2: 2.00%–3.00%, Al2O3: 3.00%–4.00%, MgO: 2.00%–3.50%, TiO2: 9.00%–11.00%, v2O5: 0.50%–1.00%;

[0061] Sintered dust after high-temperature roasting: TFe: 40.00%–45.00%, CaO: 15.00%–18.00%, SiO2: 5.00%–9.00%, Al2O3: 3.00%–4.00%, MgO: 2.00%–3.00%, TiO2: 3.00%–5.00%, C: 1.00%–5.00%;

[0062] Bentonite: CaO: 2.00%–5.00%, SiO2: 40.00%–60.00%, Al2O3: 12.00%–18%, MgO: 2.00%–5.00%.

[0063] Comparative Example

[0064] The specific implementation method for the comparison ratio is as follows:

[0065] (1) Weigh out 98% of the upgraded vanadium-titanium concentrate and 2% of the bentonite by mass percentage. Put the weighed upgraded vanadium-titanium concentrate and bentonite into a high-power mixer for mixing for 10 minutes.

[0066] (2) Drying: The reinforced and well-mixed mixture is placed in a cylindrical dryer for drying, and the moisture content of the mixture after drying is controlled to be 8%.

[0067] (3) Roller milling: The dried mixture is placed in a high-pressure roller mill for roller milling. The roller milling pressure is set to 60 Bar, and the specific surface area of ​​the mixture after roller milling is controlled to be greater than 2200 cm². 2 / g;

[0068] (4) Preparation of mother balls: The mixture after roller milling is conveyed to the rotating baller through a belt, and droplets of water are sprayed onto the material to form a mother ball core of 1mm to 3mm.

[0069] (5) Mother ball growth: The mixture after roller milling continues to be conveyed to the pelletizing machine via belt, and atomized water is continuously added to make the dry material evenly coated on the outer layer of the mother ball core material. The pelletizing time is maintained at 12 minutes to ensure that the green balls are compact. The rolled green balls are screened by double-layer roller screen to obtain vanadium-titanium green balls with a particle size of 8-16mm. The moisture content of the vanadium-titanium green balls is controlled at 8.3%. The drop strength of the vanadium-titanium green balls is tested at 7.2 times / 0.5m, and the compressive strength of the vanadium-titanium green balls is tested at 10.12N / ball.

[0070] (6) Fabrication: The qualified raw pellets are fabricated onto the belt roasting trolley via a shuttle fabrication belt. Before this step, the bottom and sides of the trolley, which are adjacent to the baffles, have been covered with pre-prepared finished vanadium-titanium pellets as the base material and the edge material. The thickness of the base material is 75 mm, and the thickness of the edge material is preferably 45 mm.

[0071] (7) Drying: The raw pellets are dried by blowing and exhaust, wherein the blowing temperature is 280℃ and the blowing time is 6min, and the exhaust temperature is 390℃ and the exhaust time is 6min.

[0072] (8) Preheating and roasting: The dried raw pellets are preheated and roasted, with a preheating temperature of 930℃ and a preheating time of 9min, and a roasting temperature of 1245℃ and a roasting time of 12min.

[0073] (9) Heating and cooling: The roasted raw balls are heated and cooled. The heating temperature is 1050℃, the heating time is 8min, the cooling temperature is 300℃, and the cooling time is 12min.

[0074] (10) After cooling, vanadium-titanium pellets are obtained, and the compressive strength and mass percentage of the main components of the vanadium-titanium pellets are tested.

[0075] The vanadium-titanium pellets obtained in the above comparative example have a compressive strength of 1881 N / pellet; a TFe content of 55.11%, a SiO2 content of 3.46%, a CaO content of 0.44%, a TiO2 content of 9.86%, and a V2O5 content of 0.70%, wherein the mass ratio of CaO / SiO2 is 0.13.

[0076] Example 1

[0077] The specific implementation method of Example 1 is as follows:

[0078] (1) Weigh out 96.5% of the upgraded vanadium-titanium concentrate, 1.5% of the sintering dust after high-temperature roasting and 2% of the bentonite by mass percentage. Put the weighed upgraded vanadium-titanium concentrate and bentonite into a high-power mixer for mixing for 10 minutes.

[0079] (2) Drying: The reinforced and well-mixed mixture is placed in a cylindrical dryer for drying, and the moisture content of the mixture after drying is controlled to be 8%.

[0080] (3) Roller milling: The dried mixture is placed in a high-pressure roller mill for roller milling. The roller milling pressure is set to 60 Bar, and the specific surface area of ​​the mixture after roller milling is controlled to be greater than 2200 cm². 2 / g;

[0081] (4) Preparation of mother balls: The mixture after roller milling is conveyed to the rotating baller through a belt, and droplets of water are sprayed onto the material to form a mother ball core of 1mm to 3mm.

[0082] (5) Mother ball growth: The mixture after roller milling continues to be conveyed to the pelletizing machine via belt, and atomized water is continuously added to make the dry material evenly coated on the outer layer of the mother ball core material. The pelletizing time is maintained at 12 minutes to ensure that the green balls are compact. The rolled green balls are screened by double-layer roller screen to obtain vanadium-titanium green balls with a particle size of 8-16mm. The moisture content of the vanadium-titanium green balls is controlled at 8.0%. The drop strength of the vanadium-titanium green balls is tested at 5.5 times / 0.5m, and the compressive strength of the vanadium-titanium green balls is tested at 10.35N / ball.

[0083] (6) Fabrication: The qualified raw pellets are fabricated onto the belt roasting trolley via a shuttle fabrication belt. Before this step, the bottom and sides of the trolley, which are adjacent to the baffles, have been covered with pre-prepared finished vanadium-titanium pellets as the base material and the edge material. The thickness of the base material is 75 mm, and the thickness of the edge material is preferably 45 mm.

[0084] (7) Drying: The raw pellets are dried by blowing and exhaust, wherein the blowing temperature is 280℃ and the blowing time is 6min, and the exhaust temperature is 390℃ and the exhaust time is 6min.

[0085] (8) Preheating and roasting: The dried raw pellets are preheated and roasted, with a preheating temperature of 930℃ and a preheating time of 9min, and a roasting temperature of 1245℃ and a roasting time of 12min.

[0086] (9) Heating and cooling: The roasted raw balls are heated and cooled. The heating temperature is 1050℃, the heating time is 8min, the cooling temperature is 300℃, and the cooling time is 12min.

[0087] (10) After cooling, vanadium-titanium pellets are obtained, and the compressive strength and mass percentage of the main components of the vanadium-titanium pellets are tested.

[0088] The vanadium-titanium pellets obtained in Example 1 above have a compressive strength of 2202 N / pellet; a TFe content of 54.85%, a SiO2 content of 3.70%, a CaO content of 0.56%, a TiO2 content of 9.80%, and a V2O5 content of 0.69%, wherein the mass ratio of CaO / SiO2 is 0.15.

[0089] Example 2

[0090] The specific implementation method of Example 2 is as follows:

[0091] (1) Weigh out 95.0% of the upgraded vanadium-titanium concentrate, 3.0% of the sintering dust after high-temperature roasting and 2% of the bentonite by mass percentage. Put the weighed upgraded vanadium-titanium concentrate and bentonite into a high-power mixer for mixing for 10 minutes.

[0092] (2) Drying: The reinforced and well-mixed mixture is placed in a cylindrical dryer for drying, and the moisture content of the mixture after drying is controlled to be 8%.

[0093] (3) Roller milling: The dried mixture is placed in a high-pressure roller mill for roller milling. The roller milling pressure is set to 60 Bar, and the specific surface area of ​​the mixture after roller milling is controlled to be greater than 2200 cm². 2 / g;

[0094] (4) Preparation of mother balls: The mixture after roller milling is conveyed to the rotating baller through a belt, and droplets of water are sprayed onto the material to form a mother ball core of 1mm to 3mm.

[0095] (5) Mother ball growth: The mixture after roller milling continues to be conveyed to the pelletizing machine via belt, and atomized water is continuously added to make the dry material evenly coated on the outer layer of the mother ball core material. The pelletizing time is maintained at 12 minutes to ensure that the green balls are compact. The rolled green balls are screened by double-layer roller screen to obtain vanadium-titanium green balls with a particle size of 8-16mm. The moisture content of the vanadium-titanium green balls is controlled at 8.1%. The drop strength of the vanadium-titanium green balls is tested at 5.3 times / 0.5m, and the compressive strength of the vanadium-titanium green balls is tested at 10.77N / ball.

[0096] (6) Fabrication: The qualified raw pellets are fabricated onto the belt roasting trolley via a shuttle fabrication belt. Before this step, the bottom and sides of the trolley, which are adjacent to the baffles, have been covered with pre-prepared finished vanadium-titanium pellets as the base material and the edge material. The thickness of the base material is 75 mm, and the thickness of the edge material is preferably 45 mm.

[0097] (7) Drying: The raw pellets are dried by blowing and exhaust, wherein the blowing temperature is 280℃ and the blowing time is 6min, and the exhaust temperature is 390℃ and the exhaust time is 6min.

[0098] (8) Preheating and roasting: The dried raw pellets are preheated and roasted, with a preheating temperature of 930℃ and a preheating time of 9min, and a roasting temperature of 1245℃ and a roasting time of 12min.

[0099] (9) Heating and cooling: The roasted raw balls are heated and cooled. The heating temperature is 1050℃, the heating time is 8min, the cooling temperature is 300℃, and the cooling time is 12min.

[0100] (10) After cooling, vanadium-titanium pellets are obtained, and the compressive strength and mass percentage of the main components of the vanadium-titanium pellets are tested.

[0101] The vanadium-titanium pellets obtained in Example 2 above have a compressive strength of 2321 N / pellet; TFe content is 54.98%, SiO2 content is 3.74%, CaO content is 0.73%, TiO2 content is 9.60%, and V2O5 content is 0.69%, wherein the mass ratio of CaO / SiO2 is 0.20.

[0102] The test results of the vanadium-titanium pellets obtained in the comparative examples and Examples 1 and 2 of the present invention show that the compressive strength of the vanadium-titanium pellets obtained in Examples 1 and 2, which were prepared by adding high-temperature roasted sintering dust (low TFe content) to the upgraded vanadium-titanium concentrate (high TFe content), is greater than that of the vanadium-titanium pellets obtained in the comparative examples. Furthermore, as the proportion of high-temperature roasted sintering dust gradually increases, the compressive strength of the vanadium-titanium pellets significantly improves, increasing from 1881 N / pellet in the comparative examples to 2321 N / pellet. This achieves the preparation of high-quality vanadium-titanium pellets, meeting the requirement of producing vanadium-titanium pellets with superior properties for use in blast furnaces.

[0103] By comparing the mass ratios of CaO and SiO2 in the vanadium-titanium pellets obtained in the comparative example, Example 1, and Example 2, it can be seen that the mass ratios of CaO and SiO2 in the vanadium-titanium pellets obtained in Examples 1 and 2 of this invention are greater than those in the comparative example. This indicates that in Examples 1 and 2 of this invention, adding sintering dust from high-temperature roasting to the upgraded vanadium-titanium concentrate helps increase the low-melting-point phases (such as silicate phases) inside the vanadium-titanium pellets, thereby increasing the pore channels inside the pellets and facilitating the entry of oxygen into the pellets through these pore channels.

[0104] Furthermore, by comparing the TFe content in the vanadium-titanium pellets obtained in the comparative example, Example 1, and Example 2, it can be seen that the TFe content in the vanadium-titanium pellets obtained in Example 1 and Example 2 by adding high-temperature roasted sintering dust (low TFe content) to the upgraded vanadium-titanium concentrate (high TFe content) is comparable to the TFe content in the vanadium-titanium pellets obtained in the comparative example without adding high-temperature roasted sintering dust. That is, in the embodiments of the present invention, changing the pellet material structure by adding high-temperature roasted sintering dust does not reduce the TFe grade of the pellets. This shows that the vanadium-titanium pellets obtained by the method of the present invention can greatly increase the compressive strength of the vanadium-titanium pellets while ensuring the TFe grade.

[0105] In summary, the method for improving the compressive strength of vanadium-titanium ore pellets disclosed in this invention optimizes the iron-containing material structure of the roasted pellets by adding sintering dust from the high-temperature roasting process of the upgraded vanadium-titanium concentrate to the pelletizing process. This promotes the oxidation of magnetite in the vanadium-titanium concentrate to Fe2O3, improves the grain composition and distribution of the upgraded vanadium-titanium concentrate pellets during the preheating roasting process, optimizes the grain structure in the pellets, and facilitates the interconnection between Fe2O3 grains in the ultrafine vanadium-titanium concentrate pellets, thereby significantly improving the compressive strength of the pellets.

[0106] Furthermore, by adding high-temperature roasted sintering dust to ultrafine vanadium-titanium concentrate, the high C content and high mass ratio of CaO to SiO2 in the sintering dust can be effectively utilized. During roasting, C undergoes a combustion reaction, generating CO2 gas that volatilizes, which is beneficial for forming pore channels between the grains of ultrafine vanadium-titanium concentrate pellets. The high mass ratio of CaO and SiO2 can increase the low-melting-point phase inside the pellets. When the low-melting-point phase cools, it can promote the formation of pore channels inside the pellets. Both of these factors can promote the smoother entry of oxygen into the pellets during roasting, avoiding uneven shrinkage between the inner and outer layers caused by the difficulty of oxygen diffusion into the pellets. This also prevents concentric cracks in the pellets and avoids the impact of concentric cracks on the compressive strength of the pellets.

[0107] Furthermore, the method for improving the compressive strength of vanadium-titanium pellets provided by this invention effectively utilizes the sintering dust generated during the sintering process of upgraded vanadium-titanium concentrate into sintered ore. This solves the problem of decreased sintered ore quality caused by recycling the sintering dust back into the sintering production process, thereby optimizing the vanadium-titanium sintered ore material structure and improving the quality of vanadium-titanium sintered ore. Simultaneously, it avoids the problem of harsh on-site working environment caused by dust generation from sintering dust during the batching process.

[0108] It should be noted that the components or steps in the above embodiments can be interchanged, substituted, added, or deleted. Therefore, the combinations formed by these reasonable permutations and transformations should also fall within the protection scope of this invention, and the protection scope of this invention should not be limited to the above embodiments.

[0109] The above are exemplary embodiments disclosed in this invention. The order of the disclosed embodiments is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. However, it should be noted that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the disclosed embodiments of this invention (including the claims) is limited to these examples. Various changes and modifications can be made without departing from the scope defined by the claims. The functions, steps, and / or actions of the methods according to the disclosed embodiments described herein do not need to be performed in any particular order. Furthermore, although the elements disclosed in the embodiments of this invention may be described or claimed individually, they may be understood as multiple unless explicitly limited to a singular.

[0110] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of the invention (including the claims) is limited to these examples. Within the framework of the invention, technical features of the above embodiments or different embodiments can be combined, and many other variations of the different aspects of the invention as described above exist, which are not provided in the details for the sake of brevity. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the invention should be included within the protection scope of the invention.

Claims

1. A method for improving the compressive strength of vanadium-titanium pellets, characterized in that, Includes the following steps: S1. A predetermined mass percentage of upgraded vanadium-titanium concentrate, high-temperature roasted sintered dust, and binder are mixed to obtain a mixture, which is then dried. S2. The dried mixture is roller-milled, and then the roller-milled mixture is added into a pelletizing machine to prepare vanadium-titanium green pellets. S3. The vanadium-titanium green pellets are dried, preheated, roasted, homogenized and cooled to obtain vanadium-titanium pellet ore; The main components of the upgraded vanadium-titanium concentrate, by mass percentage, are: TFe≥57%, SiO2≤3.0%, TiO2≥9.0%, V2O5≥0.50%; the mass percentage of particles smaller than 200 mesh in the upgraded vanadium-titanium concentrate is ≥85%; the main components of the sintering dust after high-temperature roasting, by mass percentage, are: TFe≥40%, SiO2≥5%, CaO≥15%, C: 1.00%~5.00%; the mass percentage of particles smaller than 200 mesh in the sintering dust after high-temperature roasting ranges from 30% to 80%. In the mixture: the upgraded vanadium-titanium concentrate accounts for 92% to 98% by mass, the sintering dust from high-temperature roasting accounts for 1% to 5% by mass, and the binder accounts for 1.0% to 3.0% by mass. In step S2, the dried mixture is placed in a roller mill for milling, with the milling pressure set to 58-61 Bar, and the specific surface area of ​​the milled mixture is controlled to be >2200 cm². 2 / g.

2. The method for improving the compressive strength of vanadium-titanium pellet according to claim 1, characterized in that, The binder is bentonite, and the main components of the bentonite, by mass percentage, are: CaO: 2.00%–5.00%, SiO2: 40.00%–60.00%, Al2O3: 12.00%–18%, MgO: 2.00%–5.00%; the mass percentage of particles smaller than 200 mesh in the bentonite ranges from 97.00% to 99.00%.

3. The method for improving the compressive strength of vanadium-titanium pellets according to claim 1, characterized in that, In step S1, the mixture is placed in a mixer for mixing for 8 to 12 minutes. After drying, the moisture content of the dried mixture is controlled to be 7% to 9%.

4. The method for improving the compressive strength of vanadium-titanium pellets according to claim 1, characterized in that, In step S2, the mixture after roller milling is transported to a rotating pelletizing machine, and droplets of water are sprayed onto the mixture to form a mother pellet core of 1mm to 3mm. Atomized water and the mixture are continuously added, allowing the mother pellet to grow into a green pellet within 10 to 20 minutes. Finally, the green pellet is screened by a double-layer roller screen to obtain vanadium-titanium green pellets with a particle size of 8 to 16mm. The moisture content of the vanadium-titanium green pellets is controlled to be 8% to 10% by mass, the drop strength of the vanadium-titanium green pellets is controlled to be >5 times / 0.5m, and the compressive strength of the vanadium-titanium green pellets is controlled to be >10N / pellet.

5. The method for improving the compressive strength of vanadium-titanium pellet according to claim 1 or 4, characterized in that, The pelletizing machine is a disc pelletizing machine, with a disc diameter of 7000mm, a disc sidewall height of 750mm, a rotation speed of 6-8r / min, and an inclination angle of 45º-55º.

6. The method for improving the compressive strength of vanadium-titanium pellets according to claim 1, characterized in that, In step S3, the drying, preheating, calcining, homogenizing, and cooling processes include: drying the vanadium-titanium green pellets by forced draft and forced draft, wherein the forced draft drying temperature is 200℃~400℃ and the forced draft drying time is 5min~7min, and the forced draft drying temperature is 350℃~450℃ and the forced draft drying time is 5min~7min; preheating and calcining the dried vanadium-titanium green pellets, wherein the preheating temperature is 800℃~1000℃ and the preheating time is 7min~10min, the calcining temperature is 1150℃~1300℃ and the calcining time is 10min~15min; and homogenizing and cooling the calcined vanadium-titanium green pellets, wherein the homogenizing temperature is 1000℃~1100℃ and the homogenizing time is 7min~10min, and the cooling temperature is 150℃~400℃ and the cooling time is 10min~15min.

7. A vanadium titano-magnetite pellet, characterized in that, The vanadium-titanium pellets are prepared by the method described in any one of claims 1-6 for improving the compressive strength of vanadium-titanium pellets.

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