Method for improving vanadium extraction rate of vanadium-titanium iron concentrate in acid leaching

Abstract

The present application belongs to the field of metallurgy, and particularly relates to a method for improving the vanadium leaching rate of vanadium-titanium iron concentrate acid leaching. The vanadium-titanium iron concentrate and hematite powder are pretreated by high-pressure roller grinding, mixed with slaked lime and calcium sulfate, and then pretreated by wet grinding and balling. The vanadium-titanium iron concentrate alkaline pellets are prepared by preheating and roasting. The pellets are subjected to dilute acid leaching to obtain a vanadium-containing mother liquor for vanadium recovery. The addition amount of hematite powder is 4.5-11% of the mass of the vanadium-titanium iron concentrate, the addition amount of slaked lime is 1-5% of the mass of the vanadium-titanium iron concentrate, and the addition amount of calcium sulfate is 0.5-3.0% of the mass of the vanadium-titanium iron concentrate. The present application avoids the use of bentonite in the pellet preparation process, and simultaneously strengthens the oxidation of vanadium oxides in the calcification roasting process, optimizes the pellet porosity, and thus significantly improves the vanadium leaching rate of the vanadium-titanium iron concentrate roasted pellets. The present application is simple and controllable, has a high vanadium leaching rate and a low other impurity leaching rate, and is convenient for industrial application.

Description

Technical Field

[0001] The invention belongs to the technical field of metallurgy, and in particular relates to a method for improving the leaching rate of vanadium from vanadium-titanium iron ore concentrate by acid leaching. Background Art

[0002] Currently, there are two main methods for extracting vanadium from vanadium-titanium iron concentrate. The first involves oxidizing the vanadium-titanium iron concentrate into pellets, which are then processed through ironmaking and converter vanadium blowing to produce vanadium slag, from which vanadium is extracted. This mainstream process consists of oxidizing the vanadium-titanium iron concentrate, reducing it in a blast furnace, producing vanadium slag in a converter, then roasting the vanadium slag with sodium, then leaching it, and finally vanadium precipitation with ammonium salts. Based on this process, a further process has been developed: oxidizing the vanadium-titanium iron concentrate, reducing it in a blast furnace, producing vanadium slag with hot metal, then roasting the vanadium slag with calcium, then acid leaching, and finally vanadium precipitation with hydrolysis. The main problem with this process is that significant vanadium is lost during the blast furnace reduction and converter vanadium blowing process of the oxidized vanadium-titanium iron concentrate. According to statistics, approximately 40% of the vanadium is lost during the blast furnace reduction and converter vanadium blowing process. Currently, the overall vanadium recovery rate from vanadium-titanium magnetite ore in the Panzhihua region is less than 50%.

[0003] To this end, a direct vanadium extraction process from vanadium-titanium iron concentrate has been developed, namely, sodium roasting of vanadium-titanium iron concentrate followed by water leaching and vanadium precipitation with ammonium salts. A certain amount of sodium salt is added to the vanadium-titanium iron concentrate, and after sodium roasting, the vanadium is converted into water-soluble sodium vanadate. After vanadium extraction through water leaching, the vanadium recovery rate can reach 80%. However, the main problem is that to increase the vanadium conversion rate during the sodium roasting process, sodium salt needs to be added in excess, which produces toxic gases during the roasting process. Furthermore, a large amount of sodium salt remains in the iron concentrate after water leaching, making the recovery of iron and titanium resources difficult. To address the problem of removing sodium from the iron concentrate after sodium roasting of vanadium-titanium iron concentrate, a calcium roasting process for vanadium-titanium iron concentrate, followed by acid leaching for vanadium extraction and ammonium salt precipitation, has been developed. Calcium salts are used instead of sodium salts to reduce waste gas production during the roasting process and facilitate the subsequent recovery of iron and titanium resources. However, the main problem of this process is that the reactivity of calcium salts is weaker than that of sodium salts, resulting in a low vanadium conversion rate in the calcification roasting process. At the same time, the calcium sulfate formed during the acid leaching process hinders the leaching kinetics of vanadium, resulting in a lower vanadium leaching rate in the calcification roasting-acid leaching process than in the sodium roasting-water leaching process.

[0004] Patent application CN 118497484 A discloses "a comprehensive extraction and separation method of vanadium, titanium and iron in vanadium-titanium magnetite", which obtains vanadium-containing leaching solution and leaching residue by calcification roasting-acid leaching. The vanadium-containing leaching solution is adjusted to obtain iron hydroxide precipitate and ammonium metavanadate product. The application uses calcium oxide or calcium carbonate as a calcifying agent, and directly roasts the mixed powder. Under the conditions of hot acid stirring leaching, the vanadium leaching rate of vanadium-titanium iron concentrate can reach 92.35%. Although powder roasting can strengthen the solid-phase reaction between vanadium-titanium iron concentrate and calcifying agent, and improve the oxidation and conversion rate of vanadium, the powder roasting process in the rotary kiln is prone to produce ring formation. At the same time, the acid leaching process uses hot acid, stirring and high liquid-solid ratio to strengthen leaching, but high liquid-solid ratio leads to too low vanadium concentration in the leaching solution, which requires the leaching mother liquor to be enriched before vanadium precipitation treatment, resulting in high cost of vanadium extraction from vanadium-titanium iron concentrate.

[0005] Patent application CN 107090551 A discloses "a method for directly extracting vanadium from vanadium-titanium magnetite", which uses vanadium-titanium magnetite, carbon-based additives and calciumizing agent for calcification roasting, and obtains vanadium-containing leaching solution after ammoniation. The application uses the method of adding carbon-based additives to destroy the spinel structure of vanadium-titanium iron concentrate, and the decomposition of carbon-based additives in the oxidation atmosphere can increase the permeability of the material and has anti-bonding effect. Although the addition of carbon-based additives can improve the permeability of vanadium-titanium iron concentrate pellets and improve the conversion rate of vanadium, the formation of CO2 will reduce the oxygen partial pressure inside the pellets, thereby destroying the oxidation atmosphere, reducing the oxidation rate of vanadium in vanadium-titanium iron concentrate, and affecting the subsequent vanadium extraction rate.

[0006] Patent CN201210137458.2 discloses "a method for recovering vanadium from vanadium-titanium magnetite", which mixes vanadium-titanium magnetite, calcium additive and binder to form pellets, then dries and oxidizes the pellets to obtain roasted clinker, and obtains vanadium-containing leaching solution and vanadium extraction pellets after carbonation leaching. The oxidation roasting process uses strong oxidizing atmosphere such as oxygen, oxygen-enriched air and ozone to strengthen the oxidation of vanadium in vanadium-titanium iron concentrate, in order to improve the subsequent vanadium leaching rate. Although this method can strengthen the oxidation atmosphere of vanadium-titanium iron concentrate pellets, it is still difficult for the oxidizing gas to reach the inside of the pellets, resulting in low vanadium oxidation rate and low vanadium leaching rate.

[0007] In summary, the current ways to strengthen the calcification roasting of vanadium-titanium iron concentrate and vanadium oxidation are mainly: 1) using powder roasting; 2) increasing the porosity of the pellets to strengthen the internal oxidation atmosphere; 3) using strong oxidizing atmosphere during calcification roasting to promote vanadium oxidation and conversion. However, the above methods are difficult to achieve the full oxidation of vanadium oxide in vanadium-titanium iron concentrate economically and efficiently, and to improve the vanadium leaching rate of the calcification roasting-acid leaching vanadium extraction process. To solve the above problems, the present application proposes a method for improving the acid leaching vanadium extraction leaching rate of vanadium-titanium iron concentrate. SUMMARY

[0008] The application provides a method for improving the vanadium leaching rate of vanadium-titanium iron concentrate acid leaching, which avoids the use of bentonite in the pellet preparation process, strengthens the oxidation of vanadium oxide in the calcification roasting process, optimizes the porosity of the pellets, and significantly improves the vanadium leaching rate of vanadium-titanium iron concentrate roasted pellets. To achieve the above-mentioned purpose, the patent includes the following steps:

[0009] A method for improving the vanadium leaching rate of vanadium-titanium iron concentrate acid leaching, which includes: pretreating vanadium-titanium iron concentrate and hematite powder by high-pressure roller milling, mixing with slaked lime and calcium sulfate, and then pretreating by wet grinding, preparing vanadium-titanium iron concentrate alkaline pellets after preheating and roasting, and obtaining vanadium-containing mother liquor by dilute acid leaching of the pellets to recover vanadium.

[0010] The method includes the following steps:

[0011] (1) After pretreating vanadium-titanium iron concentrate and hematite powder by high-pressure roller milling, mix them with slaked lime and calcium sulfate in a certain proportion, and then pretreat them by wet grinding; the addition amount of hematite powder is 4.5-11% of the mass of vanadium-titanium iron concentrate,

[0012] The addition amount of slaked lime is 1-5% of the mass of vanadium-titanium iron concentrate, and the addition amount of calcium sulfate is 0.5-3.0% of the mass of vanadium-titanium iron concentrate;

[0013] (2) Ball the mixed material, dry, preheat and roast the qualified green balls to obtain vanadium-titanium magnetite alkaline pellets;

[0014] (3) Perform acid leaching to recover vanadium from the vanadium leaching mother liquor.

[0015] Preferably, in step (1), the vanadium-titanium magnetite concentrate contains 50-60% TFe, 8-15% TiO2 and 0.5-1.50% V2O5 by mass percentage; the hematite contains 60-65% TFe.

[0016] Preferably, the particle size of the vanadium-titanium iron concentrate and hematite powder in step (1) is not less than 80wt% of -200 mesh.

[0017] Preferably, the addition amount of hematite powder is 5-10% of the mass of vanadium-titanium iron concentrate, the addition amount of slaked lime is 2-5% of the mass of vanadium-titanium iron concentrate, and the addition amount of calcium sulfate is 1.5-3.0% of the mass of vanadium-titanium iron concentrate.

[0018] Preferably, the calcifying agent in step (1) is dry slaked lime, which is produced by a dry digestion process from CaO, wherein CaO≥70%, particle size +100 mm≤5%, and bulk specific gravity≤0.5 g / ml; the calcium sulfate contains CaO≥30%, and particle size-200 mesh≥90%.

[0019] As preferred, the pelletizing in step (2) is pelletizing the mixture in a disc pelletizer with 0.5-1.0% water added, and the green pellets are screened by a 16 mm and 9 mm roller screen to obtain qualified green pellets of 9-16 mm.

[0020] As preferred, the drying in step (2) is drying at a temperature of 200-400℃ for 5-10 min.

[0021] As preferred, the first-stage preheating in step (2) is preheating at a temperature of 700-900℃ for 5-10 min.

[0022] As preferred, the preheating in step (2) is preheating at a temperature of 900-1100℃ for 8-15 min, and the Fe 2+ ≤0.5%;

[0023] As preferred, the roasting in step (2) is roasting at a temperature of 1100-1250℃ for 10-15 min, and the Fe 2+ ≤0.3%, and the average compressive strength of the roasted pellets is 1500-2500 N / pellet.

[0024] As preferred, the acid leaching in step (3) is acid leaching in a dilute acid solution, and the acid in the dilute acid solution is a mixture of one or more of sulfuric acid, nitric acid or hydrochloric acid solution, [H + ] concentration is 0.1-4 mol, and the dilute acid solution contains V, Fe, Al and other ions, and the V concentration is 3-6 g / l. The vanadium leaching mode is heap leaching, column leaching or soaking, and the vanadium is leached by multi-stage leaching, preferably 4-stage leaching plus 1-stage washing, the leaching temperature is normal temperature, the liquid-solid ratio is 0.3-5.0, and the leaching time is 5-30 days.

[0025] The mechanism mainly involved in the present application is as follows:

[0026] Vanadium element in vanadium-titanium iron concentrate mainly exists in the spinel structure of titanomagnetite. In order to realize the full oxidation of iron and vanadium oxides in vanadium-titanium iron concentrate, the spinel structure of titanomagnetite must be destroyed first. The oxidation of iron and vanadium oxides depends on the oxidation temperature and oxygen concentration of the preheating roasting process. Higher oxidation temperature and oxygen concentration are beneficial to the full oxidation of iron and vanadium oxides. In the roasting and solidification process of vanadium-titanium iron concentrate pellets at 1150-1250 DEG C, although the oxidation temperature is high, the crystal bond connection of titanomagnetite microcrystals in the pellets is fully developed, which leads to the decrease of pellet porosity and the low oxygen concentration in the pellets, which is not conducive to the full oxidation of iron and vanadium oxides. Therefore, the present application adds two-stage preheating oxidation before the roasting and solidification of the pellets. The preheated pellets have high porosity, and oxygen is easy to diffuse into the pellets. In the first preheating stage at 700-900 DEG C, the spinel structure of titanomagnetite is destroyed, which makes vanadium oxide fully exposed and partially oxidized. In the second preheating stage at 900-1100 DEG C, higher oxidation temperature and sufficient oxidation atmosphere are beneficial to the rapid oxidation of V2O3 and FeO in vanadium-titanium iron concentrate, and this oxidation process is beneficial to shorten the subsequent roasting and solidification time. After the two-stage preheating and full oxidation of vanadium-titanium iron concentrate pellets, the Fe 2+ content in the pellets is significantly reduced, and the V 5+ content is significantly increased, which is beneficial to the subsequent acid leaching process to improve the vanadium leaching rate and reduce the iron leaching rate. Most importantly, the present application also adds an appropriate amount of hematite powder. The appropriate amount of hematite powder can further strengthen the oxidation and conversion of vanadium under the action of the above preheating oxidation mechanism, and thus is more conducive to the leaching of vanadium. The present application uses an appropriate amount of slaked lime and calcium sulfate as additives in combination with an appropriate amount of hematite powder to obtain qualified pellets without bentonite, and the vanadium leaching rate is significantly improved.

[0027] The difference from the prior art is:

[0028] The present application optimizes the thermal system of the calcification roasting process of vanadium-titanium iron concentrate, promotes the full oxidation of iron and vanadium oxides, significantly improves the vanadium leaching rate and reduces the iron leaching rate under the conditions of low liquid-solid ratio and room temperature heap leaching, and can effectively solve the problems of high energy consumption in vanadium extraction, low vanadium mother liquor concentration and comprehensive utilization of iron-containing resources after acid leaching.

[0029] 2) The existing vanadium-titanium iron concentrate calcification roasting pellets are prepared by using the traditional iron ore pellet thermal system, the preheating stage temperature is low, and the time is short, only for preparing the preheated pellets with qualified strength, and the oxidation behavior of iron and vanadium oxides in the preheating process of vanadium-titanium iron concentrate pellets is not considered. The vanadium-titanium iron concentrate belongs to a typical complex ore, compared with ordinary iron ore, its oxidation is more difficult, and the traditional iron ore pellet preheating system is difficult to realize the full oxidation of iron and vanadium oxides in the vanadium-titanium iron concentrate pellets. Therefore, the two-stage preheating method is used in the preheated pellet preparation process, the spinel structure of titanomagnetite is destroyed in the 700-900 DEG C first preheating stage, the vanadium oxide is fully exposed and partially oxidized, the preheating temperature is increased and the preheating time is prolonged in the 900-1100 DEG C second preheating stage, so that the iron and vanadium oxides are fully oxidized, the Fe 2+ content in the preheated pellets is significantly reduced, and the V 5+ proportion is obviously increased. In the sulfuric acid leaching process, the V 5+ leaching rate is obviously higher than that of V 4+ and V 3+ ; and the Fe 3+ leaching rate is obviously lower than that of Fe 2+ , therefore, the thermal system proposed by the present application is beneficial to improve the vanadium leaching rate, reduce the iron leaching rate and shorten the leaching time in the acid leaching process of vanadium-titanium iron concentrate calcification roasting pellets. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 It is the real object diagram of vanadium-titanium iron concentrate in example 5.

[0031] Figure 2 It is the real object diagram of the pellet particles after vanadium leaching in example 5. DETAILED DESCRIPTION

[0032] The present application will be further described below with specific examples, the illustrative examples of the present application and the description are used to explain the present application, but not as a limitation of the present application.

[0033] The vanadium-titanium iron concentrate used in the example and the comparative example of the present application has typical physical properties as shown in Table 1, the typical particle size composition of the vanadium-titanium iron concentrate is as shown in Table 2, and the typical chemical composition of the vanadium-titanium iron concentrate is as shown in Table 3.

[0034]

[0035]

[0036]

[0037] The slaked lime used in the embodiment of the present invention is dry slaked lime, which is slaked lime produced from CaO using a dry digestion process, wherein CaO ≥ 70%, particle size + 100 mm ≤ 5%, and bulk density ≤ 0.5 g / ml; CaO ≥ 30% in calcium sulfate, and particle size - 200 mesh ≥ 90%.

[0038] Example series 1 (including comparative cases)

[0039] The vanadium-titanium iron concentrate and 10% hematite powder were pre-treated by high-pressure roller mill, and then mixed with 1.5% slaked lime and 1% calcium sulfate and milled for 3 minutes. The pellets were pelletized in a disc pelletizer. The diameter of the balls was 12±2 mm and the moisture content of the green balls was 7.89%. After drying at 400°C for 15 minutes, they were roasted according to the conditions in Table 1-1. The Fe content in the pellets prepared by the roasting system of the present invention was 0.04477 W / m. 2+ The content is 0.26%; while the Fe content in the pellets prepared by conventional roasting system is 2+ The content is 3.48%. The two-stage preheating step significantly increases the oxidation degree of iron and vanadium oxides in the pellets. Simultaneously, the roasting temperature of the present invention is reduced to 1170°C, and the porosity of the roasted pellets produced is 21.49%, significantly higher than the 14.45% porosity of roasted pellets produced using a conventional roasting system. The developed pore distribution and higher porosity of the calcified roasted pellets improve the vanadium leaching kinetics during the acid leaching process, increasing the vanadium leaching rate and shortening the leaching time. Vanadium extraction experiments using three calcified roasted pellets under the same acid leaching conditions yielded vanadium leaching rates of 62.69% (Conventional-1), 53.21% (Conventional-2), and 85.78% (Conventional-2). Acid leaching results from calcified roasted pellets of vanadium-titanium iron ore concentrate indicate that optimizing the thermal system improves the oxidation degree of iron and vanadium oxides and the porosity of the calcified roasted pellets, thereby significantly improving the vanadium leaching rate during the acid leaching process.

[0040]

[0041] Example 2

[0042] The vanadium-titanium iron concentrate and 5% hematite powder were pre-treated by high-pressure roller mill, and then mixed with 1.0% slaked lime and 3% calcium sulfate and milled for 3 minutes. The balls were pelletized in a disc pelletizer with a diameter of 12±2 mm and a water content of 7.35%. After drying at 400°C for 15 minutes, they were preheated and roasted using a chain grate-rotary kiln process according to the conditions of the present invention in Table 1-1. The Fe content in the pellets was 0.0447 W / m. 2+ 500g of pellets were placed in 8 1000ml graduated cylinders and leached at room temperature to extract vanadium. The liquid-to-solid ratio was 2 and the acid concentration of the leaching solution was [H +1.2M, 1.6M, 2.0M, 2.5M, 3.0M, and the acid concentration of the leaching solution was 1.2M, 1.6M, 2.0M, 2.5M, 3.0M, respectively, and the acid was added according to the acid consumption of the leaching solution every day. After 27 days of leaching and 1 day of washing, the vanadium leaching rates were 75.79%, 77.50%, 80.89%, 82.62%, and 86.31%, respectively.

[0043] Example 3

[0044] The vanadium-titanium iron concentrate was pretreated by high-pressure roller grinding with 5% hematite powder, then mixed with 5% slaked lime and 0.5% calcium sulfate for 3 minutes of damp grinding, and then balling in a disc balling machine, with the diameter of the ball being 12±2 mm and the water content being 7.99%. After drying at 400°C for 15 minutes, the balling was subjected to roasting treatment according to the conditions of the present application in Table 1-1. The Fe content in the balling was 0.38%. 500g of the balling was placed in four 1000ml measuring cylinders for vanadium leaching by immersion at room temperature, with the liquid-solid ratio being 2, and the acid concentration of the leaching solution being 1.2M, 1.5M, 1.8M, 2.0M, 2.5M, 3.0M, respectively, and the acid was added according to the acid consumption of the leaching solution every day. After 27 days of leaching and 1 day of washing, the vanadium leaching rates were 77.19%, 78.64%, 79.31%, 79.56%, 83.22%, and 85.45%, respectively. 2+ + The acid concentration of the leaching solution was 1.2M, 1.6M, 2.0M, 2.5M, 3.0M, respectively, and the acid was added according to the acid consumption of the leaching solution every day. After 27 days of leaching and 1 day of washing, the vanadium leaching rates were 75.79%, 77.50%, 80.89%, 82.62%, and 86.31%, respectively.

[0045] Example 4

[0046] The vanadium-titanium iron concentrate was pretreated by high-pressure roller grinding with 10% hematite powder, then mixed with 2.0% dry slaked lime and 1.5% calcium sulfate for 3 minutes of damp grinding, and then balling in a disc balling machine, with the diameter of the ball being 12±2 mm and the water content being 7.96%. After drying at 400°C for 15 minutes, the balling was subjected to roasting treatment according to the conditions of the present application in Table 1-1. The Fe content in the balling was 0.33%. 500g of the balling was placed in four 1000ml measuring cylinders for vanadium leaching by immersion at room temperature, with the liquid-solid ratio being 2, and the acid concentration of the leaching solution being 1.2M, 1.6M, 2.0M, 2.5M, 3.0M, respectively, and the acid was added according to the acid consumption of the leaching solution every day. After 27 days of leaching and 1 day of washing, the vanadium leaching rates were 76.05%, 80.53%, 80.64%, 83.23%, and 86.88%, respectively. 2+ + The acid concentration of the leaching solution was 1.2M, 1.6M, 2.0M, 2.5M, 3.0M, respectively, and the acid was added according to the acid consumption of the leaching solution every day. After 27 days of leaching and 1 day of washing, the vanadium leaching rates were 75.79%, 77.50%, 80.89%, 82.62%, and 86.31%, respectively.

[0047] Example 5

[0048] ​​Vanadium titanium iron concentrate was pretreated by high pressure roller grinding with 5% hematite powder, then mixed with 3.0% dry lime and 2% calcium sulfate for 3 minutes of wet grinding, and then balling in a disc balling machine, with a ball diameter of 12±2 mm and a water content of 8.00%. After drying at 400°C for 15 minutes, the pellets were roasted in a laboratory muffle furnace according to the following conditions: preheating at 900°C for 10 minutes, preheating at 1050°C for 20 minutes, and roasting at 1150°C for 15 minutes. The Fe 2+ content in the pellets was 0.39%.

[0049] 500g of the pellets were placed in a 1000ml measuring cylinder and immersed in vanadium at room temperature, with a liquid-solid ratio of 2 and an acid concentration [H + ] of the leaching solution of 3.0M, with replenishment according to the acid consumption of the leaching solution every day. After 27 days of immersion and 1 day of washing, the vanadium and iron leaching rates were 87.27% and 1.77%, respectively.

[0050] Comparative Example 1

[0051] The other systems were consistent with Example 4, except that no hematite powder was added, 500g of the pellets were placed in a 1000ml measuring cylinder and immersed in vanadium at room temperature, with a liquid-solid ratio of 2 and an acid concentration [H + ] of the leaching solution of 3.0M, with replenishment according to the acid consumption of the leaching solution every day. After 27 days of immersion and 1 day of washing, the vanadium and iron leaching rates were 78.38%.

[0052] Comparative Example 2

[0053] The other systems were consistent with Example 4, except that no lime was added, 500g of the pellets were placed in a 1000ml measuring cylinder and immersed in vanadium at room temperature, with a liquid-solid ratio of 2 and an acid concentration [H + ] of the leaching solution of 3.0M, with replenishment according to the acid consumption of the leaching solution every day. After 27 days of immersion and 1 day of washing, the vanadium and iron leaching rates were 72.38%.

[0054] Comparative Example 3

[0055] The other systems were consistent with Example 4, except that no calcium sulfate was added, 500g of the pellets were placed in a 1000ml measuring cylinder and immersed in vanadium at room temperature, with a liquid-solid ratio of 2 and an acid concentration [H + ] of the leaching solution of 3.0M, with replenishment according to the acid consumption of the leaching solution every day. After 27 days of immersion and 1 day of washing, the vanadium and iron leaching rates were 75.38%.

Claims

1. A method for improving the vanadium leaching rate of vanadium-titanium iron concentrate by acid leaching, characterized by: Vanadium-titanium iron concentrate and hematite powder are pre-treated by high-pressure roller mill, mixed with slaked lime and calcium sulfate, and then pre-treated by damp grinding to form pellets. After preheating and roasting, alkaline pellets of the vanadium-titanium iron concentrate are prepared. The pellets are leached with dilute acid to obtain a vanadium-containing mother liquor for recovering vanadium. The amount of hematite powder added is 4.5-11% of the mass of the vanadium-titanium iron concentrate, the amount of slaked lime added is 1-5% of the mass of the vanadium-titanium iron concentrate, and the amount of calcium sulfate added is 0.5-3.0% of the mass of the vanadium-titanium iron concentrate. The specific steps include: (1) The vanadium-titanium iron concentrate and hematite powder are pre-treated by high-pressure roller mill, and then fully mixed with slaked lime and calcium sulfate in a certain proportion and then subjected to damp grinding pre-treatment; (2) The mixed materials are pelletized, and the qualified green balls are dried, preheated, and roasted to obtain vanadium-titanium magnetite alkaline pellets; the preheating temperature of the first stage preheating in step (2) is 700-900°C, and the preheating time is 5-10 min; the preheating temperature of the second stage preheating is 900-1100°C, and the preheating time is 8-15 min, Fe 2+ ≤0.5%; the calcination temperature in step (2) is 1100~1250℃, the calcination time is 10~15 min, Fe 2+ ≤0.3%, the average compressive strength of the calcined pellets is 1500~2500N / piece; (3) The roasted pellets are subjected to acid leaching to extract vanadium, and vanadium can be recovered from the vanadium extraction mother liquor; In step (1), in terms of mass percentage, the vanadium-titanium magnetite concentrate contains 50-60% TFe, 8-15% TiO2, and 0.5-1.50% V2O5; the hematite contains 60-65% TFe; The particle size of the vanadium-titanium iron concentrate and hematite powder in step (1) is not less than 80% of -200 mesh.

2. The method for improving the vanadium leaching rate of vanadium-titanium iron concentrate by acid leaching according to claim 1, characterized in that: The amount of hematite powder added is 5-10% of the mass of the vanadium-titanium iron concentrate.

3. The method for improving the vanadium leaching rate of vanadium-titanium iron ore concentrate according to claim 1, characterized in that: The amount of slaked lime added is 2-5% of the mass of the vanadium-titanium iron concentrate, and the amount of calcium sulfate added is 1.5-3.0% of the mass of the vanadium-titanium iron concentrate.

4. The method for improving the vanadium leaching rate of vanadium-titanium iron concentrate by acid leaching according to claim 1, characterized in that: The pelletizing process in step (2) is to add 0.5-1.0% water to the mixed material in a disc pelletizing process, and the green balls are screened out with 16 mm and 9 mm roller screening machines to obtain qualified green balls of 9-16 mm.

5. The method for improving the vanadium leaching rate of vanadium-titanium iron ore concentrate according to claim 1, characterized in that: The drying in step (2) is carried out at a temperature of 200-400° C. and a drying time of 5-10 min.

6. The method for improving the vanadium leaching rate of vanadium-titanium iron concentrate by acid leaching according to claim 1, characterized in that: In the acid leaching of step (3), the acid in the dilute acid solution is a mixture of one or more of sulfuric acid, nitric acid or hydrochloric acid solution, [H + ] concentration is 0.1 to 4 mol / L, the dilute acid solution contains V, Fe, Al ions, and the V concentration is 3~6g / l.

7. The method for improving the vanadium leaching rate of vanadium-titanium iron ore concentrate according to claim 1, characterized in that: During acid leaching, four levels of leaching plus one level of washing are used, the leaching temperature is room temperature, the liquid-solid ratio is 0.3~5.0, and the leaching time is 5 to 30 days.

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