A method for recovering iron and titanium from vanadium extraction slag via hydrogen-based reduction-electric furnace smelting.

Abstract

This invention belongs to the field of metallurgical engineering technology, specifically disclosing a method for recovering iron and titanium from vanadium extraction slag using hydrogen-based reduction and electric furnace smelting. The method includes: preparing green pellets with a particle size of 10-14 mm by fine grinding, acid leaching, concentration, filtration, and high-pressure roller milling of sodium-treated vanadium-titanium magnetite concentrate slag; subjecting the green pellets to oxidative roasting and direct reduction in a hydrogen-based vertical furnace to obtain reduced pellets containing elemental iron and titanium oxide; and directly loading the reduced pellets into an electric furnace without cooling for smelting to obtain molten iron and high-titanium slag. This invention successfully solves the problem of pellet reduction and pulverization of sodium-treated vanadium-titanium magnetite concentrate slag pellets. Simultaneously, by utilizing hydrogen-rich gas as a reducing agent to pre-reduce the vanadium extraction slag pellets and combining this with electric furnace smelting, it effectively achieves efficient separation and recovery of iron and titanium from the vanadium extraction slag, eliminates the environmental pollution problems caused by vanadium extraction slag stockpiling, and realizes efficient recovery and utilization of iron, vanadium, and titanium in vanadium-titanium magnetite, greatly improving the resource utilization rate of vanadium-titanium magnetite.

Description

Technical Field

[0001] This invention relates to the field of metallurgical engineering technology, specifically to a method for recovering iron and titanium from vanadium extraction slag via hydrogen-based reduction-electric furnace smelting. Background Technology

[0002] Sodium vanadium extraction is one of the most efficient methods for directly extracting vanadium resources from vanadium-titanium magnetite. The process is simple, and the vanadium recovery rate is much higher than other methods. However, the vanadium extraction slag contains a large amount of alkali metals and aluminosilicate impurities, which seriously affects the subsequent recovery of iron and titanium resources. Currently, there are few industrial production lines in China that perform sodium vanadium extraction from vanadium-titanium magnetite concentrate, mainly because the sodium vanadium extraction slag is difficult to utilize, and the iron and titanium in it are difficult to effectively separate and recover. The vanadium extraction slag contains abundant titanium and iron resources. The mineral composition of the vanadium extraction slag is mainly ilmenite and magnetite, with a typical TiO2 grade of 5-15% and a TFe grade of 30-65%.

[0003] Currently, the main methods for recovering titanium and iron from vanadium extraction slag are the blast furnace method or the pre-reduction-smelting method. This involves using the vanadium extraction slag as a raw material for ironmaking, separating iron and titanium in a blast furnace, or pelletizing the vanadium extraction slag, pre-reducing it, and then smelting it in an electric furnace to achieve titanium and iron separation. Because vanadium extraction slag contains a large amount of alkali metals, the pre-reduction process causes severe pellet pulverization, significantly worsening the permeability of the material during subsequent smelting and increasing smelting energy consumption. Furthermore, the titanium in the titanium-containing slag after smelting exists mainly in the form of pyroxene and perovskite, making economical recovery difficult. The severe reduction expansion and pulverization of vanadium extraction slag pellets also prevent its use in blast furnace ironmaking, resulting in a titanium resource recovery rate of generally less than 60% in China. In contrast, vanadium extraction slag abroad is mainly dumped, causing not only serious resource waste but also secondary environmental pollution.

[0004] To address the aforementioned issues, Chinese patent (patent application number: CN201310035277.3) discloses a method for separating and recovering valuable substances from vanadium extraction slag using superconducting high gradient magnetic separation technology. This method involves recovering valuable elements from sodium-treated vanadium extraction slag using a superconducting high gradient magnetic field, with the recovered material containing up to 56% Fe2O3. This method primarily targets the magnetic separation of vanadium extraction slag for iron extraction but does not address the recovery of titanium resources from the vanadium extraction slag.

[0005] Chinese patent (patent application number: CN202310123415.7) discloses a method for separating iron, vanadium, titanium, and chromium in high-chromium vanadium-titanium magnetite. The method involves reducing and melting vanadium-titanium magnetite into vanadium-containing molten iron, and then chlorinating and roasting the molten slag to recover titanium. The vanadium recovery rate is 43%–79%, the titanium recovery rate is 55%–82%, and the iron recovery rate is 72%–93%. This method is for vanadium-titanium magnetite, where vanadium recovery is mainly achieved from the molten iron, and the titanium slag has a low titanium grade, requiring further chlorination roasting for titanium recovery.

[0006] Meanwhile, Bi Xiurong, Liu Gang, et al. (Metallurgical Equipment, 2014(01):20-23) published an experimental study on the basic performance of sodium removal and iron extraction from vanadium slag, proposing two methods for treating vanadium slag through chlorination roasting-reduction-magnetic separation. After magnetic separation, the TFe content in the molten iron product was 36.18%, the Na content was 1.95%, and the Fe recovery rate was 90.82%. This method did not involve the removal of impurities from the vanadium slag, the pelletizing phenomenon was serious during reduction, and it also did not involve the recovery of titanium resources.

[0007] Wu Enhui, Zhu Rong, et al. (Iron and Steel Vanadium Titanium, 2015, 36(05):40-46) published a paper on the molten reduction of carbon-containing pellets from vanadium extraction tailings in an electric arc furnace to extract iron, proposing a method for extracting titanium slag by molten reduction in an electric arc furnace, obtaining molten iron with an iron recovery rate of over 90%. This method does not involve the pre-reduction of vanadium extraction slag pellets, but rather the simultaneous reduction and molten separation of carbon-containing pellets from vanadium extraction tailings in the electric furnace. The molten titanium-containing slag is difficult to recover due to its low titanium content, and the electric furnace slag is not utilized.

[0008] Although sodium vanadium extraction is one of the most efficient methods for recovering vanadium from vanadium-titanium magnetite, none of the aforementioned methods have solved the problem of excessively high alkali metal or aluminosilicate impurities in the vanadium extraction slag. This leads to severe pulverization during the vanadium extraction slag pellet reduction process, poor titanium-iron separation, high product impurity content, and the near-complete ineffective recovery of titanium resources. Therefore, to achieve effective recovery of titanium and iron resources from vanadium extraction slag, there is an urgent need to develop an economical and environmentally friendly method for titanium-iron separation. Summary of the Invention

[0009] In view of the above-mentioned shortcomings, this invention provides a method for recovering iron and titanium from vanadium extraction slag via hydrogen-based reduction and electric furnace smelting. This invention solves the problems of severe pulverization of vanadium extraction slag pellets due to high impurities such as alkali metals and aluminosilicates, and poor separation of titanium and iron in vanadium extraction slag, which prevents the effective recovery and utilization of titanium. Furthermore, this invention solves the problem of effective heat supply in hydrogen-based vertical shaft furnaces (hydrogen-based reduction is usually an endothermic reaction, requiring a large amount of heat, and the vertical shaft furnace often suffers from insufficient heat, resulting in low output).

[0010] To achieve the above objectives, the present invention provides a method for recovering iron and titanium from vanadium extraction slag via hydrogen-based reduction-electric furnace smelting, comprising the following steps:

[0011] S1. Vanadium-titanium magnetite concentrate is subjected to sodium vanadium extraction to obtain sodium vanadium extraction slag; the sodium vanadium extraction slag is finely ground to make its particle size of -0.074mm account for 72-82% and its specific surface area of ​​1000-1350m². 2 / g;

[0012] S2. The finely ground vanadium-containing sodium leaching slag from S1 is subjected to acid leaching to obtain acid-leached slag. The acid-leached slag is then filtered, dewatered, and then subjected to high-pressure roller milling to achieve a particle size of -0.074 mm accounting for 83-92% and a specific surface area of ​​1750-2150 m². 2 / g;

[0013] S3. After mixing the material from the high-pressure roller mill in S2 with an organic composite binder, pelletize it to obtain green pellets with a particle size of 10-14 mm; oxidize and calcine the green pellets to obtain vanadium extraction slag oxidized pellets with a compressive strength greater than 2550 N / P.

[0014] S4. The hot vanadium-extraction slag oxide pellets after S3 oxidation roasting are directly reduced in a hydrogen-based vertical shaft furnace to obtain reduced pellets containing elemental iron and titanium oxide. The hot vanadium-extraction slag oxide pellets are added from the top of the hydrogen-based vertical shaft furnace, and hydrogen-based gas in the furnace is introduced through a gas supply pipe surrounding the furnace cylinder at the bottom. A heating device is provided on the lower side wall of the furnace cylinder. The temperature of the hydrogen-based gas entering the furnace cylinder is 900–1050°C.

[0015] S5. The reduced pellets from S4 are directly loaded into the electric furnace without cooling, and then melted in the electric furnace to obtain molten iron and high-titanium slag.

[0016] According to one aspect of the present invention, in step S1, the TFe content in the sodium vanadium extraction slag is 48% to 63%, the TiO2 content in the sodium vanadium extraction slag is 7% to 16%, the alkali metal content in the sodium vanadium extraction slag is 1.5% to 5.5%, and the aluminosilicate content is greater than 7.2%.

[0017] According to one aspect of the present invention, in step S2, the acid used for acid leaching is composed of sulfuric acid and hydrofluoric acid, wherein the mass ratio of sulfuric acid to hydrofluoric acid is 0 to 2.5, and the amount of acid used for acid leaching is 0.1 to 4.0 g / L.

[0018] According to one aspect of the present invention, in step S2, the acid leaching temperature is 55-80°C and the time is 14-120 min; the alkali metal content in the acid leaching residue is less than 0.27%, and the aluminosilicate content is less than 3.1%.

[0019] According to one aspect of the present invention, in step S2, the acid leaching residue needs to be precipitated and concentrated in a sedimentation tank before filtration. The concentrated acid leaching residue is then filtered and dewatered by a filter press or a disc vacuum filter. After dewatering, the material is subjected to a high-pressure roller mill.

[0020] According to one aspect of the present invention, in step S3, the organic composite adhesive is composed of sodium humate, starch and polyacrylamide; the mass ratio of sodium humate, starch and polyacrylamide is 1-3:3-1:0.05-0.2; and the amount of the organic composite adhesive is 0.05-0.7 wt%.

[0021] According to one aspect of the present invention, in step S3, the oxidative roasting includes four stages, namely, a drying stage, a preheating stage, a roasting stage, and a homogenization stage; the temperature of the drying stage is 220-370°C, and the time is 3-7 min; the temperature of the preheating stage is 750-1000°C, and the time is 13-19 min; the temperature of the roasting stage is 1270-1320°C, and the time is 8-40 min; the temperature of the homogenization stage is 900-1000°C, and the time is 5 min; after oxidative roasting, the temperature is cooled for 3-5 min until the temperature of the vanadium extraction slag oxidized pellets is 700-900°C.

[0022] According to one aspect of the present invention, in step S3, the compressive strength of the vanadium extraction slag oxide pellets is 2520-3000 N / P.

[0023] According to one aspect of the present invention, in step S4, the hydrogen-based gas in the hydrogen-based vertical furnace is H2 or a mixture of H2 and CO; the temperature of the reduction zone in the upper part of the hydrogen-based vertical furnace is 850-1020°C, the gas pressure is 0.15-0.3 MPa, and the reduction time is 45-120 min.

[0024] According to one aspect of the present invention, in step S5, the temperature at which the reduced pellets are loaded into the electric furnace is 500-700°C, the melting temperature of the electric furnace is 1500-1700°C, and the melting time is 15-75 min; a reducing agent is also added to the electric furnace, the reducing agent being semi-coke or biomass char; the amount of the reducing agent is 2-10 wt%.

[0025] The principle of this invention:

[0026] This invention first utilizes the acid solubility of alkali metals, aluminosilicates, and calcium and magnesium oxides to remove impurities such as alkali metals, aluminosilicates, and calcium and magnesium oxides through acid leaching. This avoids the severe pulverization problem caused by alkali metals during subsequent direct reduction of pellets, improves the titanium and iron content in the vanadium extraction slag, and weakens the adverse effects of aluminosilicate slag on the subsequent reduction process. Hot vanadium extraction slag oxidized pellets are charged into a vertical shaft furnace and heated by hydrogen-containing reducing gas (heating device), compensating for insufficient heat in the furnace. Hydrogen-based direct reduction utilizes the stronger reducing power of hydrogen and the difference in reducing properties between iron oxides and titanium oxides, promoting the preferential reduction of more iron oxides to metallic iron, creating conditions for efficient separation of titanium oxides and metallic iron. During electric furnace smelting, the differences in viscosity, melting point, and density of metallic iron and titanium oxides at high temperatures are utilized to achieve efficient separation of molten iron and high-titanium slag, producing two products: reduced iron powder (molten iron) and high-titanium slag. Simultaneously, titanium and iron resources are recovered, completely solving the problem of titanium recycling. Simultaneously, the hot heat of the reduced pellets is charged into the electric furnace, which is beneficial for making full use of the waste heat of the reduced pellets and reducing the power consumption of the electric furnace smelting.

[0027] The beneficial effects of this invention are:

[0028] (1) This invention removes impurities (mainly alkali metals, aluminosilicates and calcium and magnesium oxides) from finely ground sodium vanadium slag by acid leaching, thereby reducing the content of impurities such as sodium, silicon, aluminum, calcium and magnesium in sodium vanadium slag. This not only completely solves the problem of reduction and pulverization caused by excessive alkali metals in vanadium slag, but also improves the grade of iron and titanium in vanadium slag, which helps to achieve efficient reduction of vanadium slag pellets and separation of iron and titanium.

[0029] (2) Compared with direct coal-based reduction, the present invention directly reduces the hot vanadium slag oxide pellets after oxidation roasting by hydrogen-based vertical furnace, which can achieve a significant reduction in carbon dioxide emissions during the reduction process.

[0030] (3) The present invention improves the temperature of the reducing gas entering the furnace by hot charging the vanadium slag oxide pellets into the vertical furnace and heating the reducing gas with a reducing gas heating device, which significantly improves the problem of insufficient heat supply for direct reduction in hydrogen-based vertical furnaces, significantly accelerates the reduction reaction rate, and improves the metallization rate of the reduced pellet products.

[0031] (4) The present invention directly heats the vanadium slag reduced pellets into the electric furnace for smelting, which helps to realize the utilization of the waste heat of the reduced pellets, increase the initial temperature of the smelting raw materials, and reduce the energy consumption of the electric furnace smelting.

[0032] (5) The present invention uses metallized reduction pellets to be smelted in an electric furnace, which reduces the resistance of the furnace charge and helps to reduce the energy consumption of electric furnace smelting.

[0033] (6) In the electric furnace smelting of the present invention, semi-coke or biomass carbon is used as a reducing agent for smelting. In particular, biomass carbon is carbon neutral, which can significantly reduce CO2 emissions and reduce production costs.

[0034] (7) Compared with the traditional long process of blast furnace, the present invention is more economical, simpler, has a higher recovery rate of iron and titanium resources, and less carbon dioxide emissions; it successfully produces two products, molten iron and high titanium slag, from vanadium slag, with an iron recovery rate of more than 90% throughout the process, a TiO2 content of more than 76% in the high titanium slag, and a titanium recovery rate of more than 95%; it successfully solves the problem of titanium recovery in vanadium-titanium magnetite. Attached Figure Description

[0035] Figure 1 This is a process flow diagram of a method for recovering iron and titanium from vanadium extraction slag using hydrogen-based reduction and electric furnace smelting, as described in this invention. Detailed Implementation

[0036] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0037] 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 particular embodiments only and are not intended to limit the scope of the invention.

[0038] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0039] To address the issue of effectively recovering titanium and iron resources from vanadium extraction slag, the inventors of this application provide a method for recovering iron and titanium from vanadium extraction slag via hydrogen-based reduction and electric furnace smelting, the process flow diagram of which is shown below. Figure 1 As shown, it includes the following steps:

[0040] S1. Vanadium-titanium magnetite concentrate is subjected to sodium vanadium extraction to obtain sodium vanadium extraction slag; the sodium vanadium extraction slag is finely ground to make its particle size of -0.074mm account for 72-82% and its specific surface area of ​​1000-1350m². 2 / g;

[0041] S2. The finely ground vanadium-containing sodium leaching slag from S1 is subjected to acid leaching to obtain acid-leached slag. The acid-leached slag is then filtered, dewatered, and then subjected to high-pressure roller milling to achieve a particle size of -0.074 mm accounting for 83-92% and a specific surface area of ​​1750-2150 m². 2 / g;

[0042] In step S2 of the present invention, acid leaching utilizes the characteristics that Na2O, sodium salts (sodium silicate, sodium aluminate), aluminosilicates and calcium salts are easily soluble in acid. Acid leaching reduces the Na2O content in the sodium vanadium extraction slag, avoids excessive Na2O content which would cause pellet reduction and pulverization, and is beneficial to improving the titanium and iron content in the sodium vanadium extraction slag.

[0043] In step S2 of the present invention, the purpose of high-pressure roller milling is to increase the specific surface area of ​​the material, which is beneficial to enhancing the sphericity and oxidation performance of the material.

[0044] S3. After mixing the material from the high-pressure roller mill in S2 with an organic composite binder, pelletize it to obtain green pellets with a particle size of 10-14 mm; oxidize and calcine the green pellets to obtain vanadium extraction slag oxidized pellets with a compressive strength greater than 2550 N / P.

[0045] In step S3 of the present invention, the oxidative roasting can be carried out on a chain grate machine-rotary kiln-ring cooler or a belt roaster.

[0046] S4. The hot vanadium-extraction slag oxide pellets after S3 oxidation roasting are directly reduced in a hydrogen-based vertical shaft furnace to obtain reduced pellets containing elemental iron and titanium oxide. The hot vanadium-extraction slag oxide pellets are added from the top of the hydrogen-based vertical shaft furnace, and hydrogen-based gas in the furnace is introduced through a gas supply pipe surrounding the furnace cylinder at the bottom. A heating device is provided on the lower side wall of the furnace cylinder. The temperature of the hydrogen-based gas entering the furnace cylinder is 900–1050°C.

[0047] In step S4 of the present invention, the hydrogen-based gas is heated to the required temperature by a heating device, so that the high-temperature hydrogen-based gas comes into contact with the hot vanadium extraction slag oxide pellets, thereby reducing them.

[0048] For example, the heating device is a heat exchange tube, an electromagnetic induction coil, or a combined heating device of heat exchange tube and electromagnetic induction.

[0049] In step S4 of the present invention, the hot vanadium slag oxidized pellets after oxidative roasting do not need to be cooled. On the one hand, this can increase the output of the oxidized pellet roasting machine. On the other hand, when the pellets are hot-charged into the furnace during the subsequent gas-based vertical furnace reduction, the reduction reaction can be accelerated, thereby increasing the output of the vertical furnace reduced pellets.

[0050] In step S4 of the present invention, the hydrogen-based vertical shaft furnace directly utilizes the difference in reduction potential between iron oxide and titanium oxide to preferentially reduce iron oxide to metallic iron, while titanium remains a metallic oxide, thus initially achieving the dissociation of titanium and iron. At the same time, the resistivity of the pellets is reduced, which helps to reduce the energy consumption of the subsequent electric furnace.

[0051] S5. The reduced pellets from S4 are directly loaded into the electric furnace without cooling, and then melted in the electric furnace to obtain molten iron and high-titanium slag.

[0052] In step S5 of this invention, the reduced pellets are directly charged into the electric furnace without cooling. This hot charging of the reduced pellets into the electric furnace not only effectively utilizes the waste heat of the reduced pellets and increases the initial temperature of the smelting raw materials, which is beneficial to reducing the energy consumption of the electric furnace smelting, but also effectively prevents carbon deposition and pulverization during the cooling process of the reduced pellets, reducing the pellet powder rate. Furthermore, by utilizing the differences in viscosity, melting point, and density between metallic iron and titanium oxide at high temperatures, the metallic iron and titanium oxide are fully dissociated, ultimately obtaining two products: molten iron and high-titanium slag. This achieves the separation and recovery of titanium and iron in vanadium extraction slag.

[0053] As an optional implementation, in step S1, the TFe content in the sodium vanadium extraction slag is 48% to 63%, the TiO2 content in the sodium vanadium extraction slag is 7% to 16%, the alkali metal content in the sodium vanadium extraction slag is 1.5% to 5.5%, and the aluminosilicate content is greater than 7.2%.

[0054] In this invention, the alkali metal in the sodium vanadium extraction slag is Na2O+K2O; the aluminosilicate in the sodium vanadium extraction slag is SiO2+Al2O3.

[0055] As an optional implementation, in step S2, the acid used for pickling is composed of sulfuric acid and hydrofluoric acid, the mass ratio of sulfuric acid to hydrofluoric acid is 0 to 2.5, and the amount of acid used for pickling is 0.1 to 4.0 g / L.

[0056] As an optional implementation, in step S2, the acid leaching temperature is 55-80°C and the time is 14-120 min; the alkali metal content in the acid leaching residue is less than 0.27%, and the aluminosilicate content is less than 3.1%.

[0057] As an optional implementation, in step S2, the acid leaching residue needs to be precipitated and concentrated in a sedimentation tank before filtration. The concentrated acid leaching residue is then filtered and dewatered by a filter press or a disc vacuum filter. After dewatering, the material is subjected to a high-pressure roller mill.

[0058] As an optional implementation, in step S3, the organic composite adhesive is composed of sodium humate, starch and polyacrylamide; the mass ratio of sodium humate, starch and polyacrylamide is 1-3:3-1:0.05-0.2; and the amount of the organic composite adhesive is 0.05-0.7 wt%.

[0059] In this invention, to avoid introducing new aluminosilicate impurities, the pelletizing binder is an organic composite binder.

[0060] As an optional implementation, step S3 includes four stages of oxidative roasting: a drying stage, a preheating stage, a roasting stage, and a homogenization stage. The drying stage has a temperature of 220–370°C and a time of 3–7 min. The preheating stage has a temperature of 750–1000°C and a time of 13–19 min. The roasting stage has a temperature of 1270–1320°C and a time of 8–40 min. The homogenization stage has a temperature of 900–1000°C and a time of 5 min. After oxidative roasting, the temperature is cooled for 3–5 min until the temperature of the vanadium extraction slag oxidized pellets is 700–900°C.

[0061] As an optional implementation, in step S3, the compressive strength of the vanadium extraction slag oxide pellets is 2520-3000 N / P.

[0062] As an optional implementation, in step S4, the hydrogen-based gas in the hydrogen-based vertical furnace is H2 or a mixture of H2 and CO; the temperature of the reduction zone in the upper part of the hydrogen-based vertical furnace is 850-1020°C, the gas pressure is 0.15-0.3 MPa, and the reduction time is 45-120 min.

[0063] As an optional implementation, in step S5, the temperature at which the reduced pellets are loaded into the electric furnace is 500-700°C, the melting temperature of the electric furnace is 1500-1700°C, and the melting time is 15-75 min; a reducing agent, which is semi-coke or biomass carbon, is also added to the electric furnace; the amount of the reducing agent is 2-10 wt%.

[0064] The specific implementation methods of this application have been described above. In order to objectively explain the technical effects produced by this application, the following embodiments will be described.

[0065] Example 1

[0066] A method for recovering iron and titanium from vanadium extraction slag via hydrogen-based reduction-electric furnace smelting:

[0067] In this embodiment, a vanadium-titanium magnetite concentrate sodium vanadium extraction slag is used, which has an iron content of 48.2%, a TiO2 content of 15.74%, a SiO2 content of 6.5%, an Al2O3 content of 4.2%, a Na2O content of 5.5%, and 47% of the original ore particles smaller than 0.074 mm. Figure 1 The process shown describes the treatment of vanadium-titanium magnetite concentrate sodium vanadium extraction slag, including the following steps:

[0068] S1. The vanadium-titanium magnetite concentrate sodium-treated vanadium-refining slag is ball-milled to achieve a particle size of -0.074mm (72.3%) and a specific surface area of ​​1008m². 2 / g;

[0069] S2. The finely ground vanadium extraction slag was subjected to acid leaching to remove impurities. The acid dosage was 0.1 g / L (mass ratio, sulfuric acid: hydrofluoric acid = 0:2), and leaching was carried out at 55℃ for 120 min. After acid leaching, the total amount of vanadium extraction slag (SiO2 + Al2O3) was 3.1%, and the alkali metal content (Na2O + K2O) was 0.27%. The acid-leached slag was concentrated in a sedimentation tank, filtered through a filter press, and dewatered. The material was then subjected to high-pressure roller milling to achieve a particle size of -0.074 mm (83.9%) and a specific surface area of ​​1756 μm. 2 / g.

[0070] S3. The pelletizing binder is an organic composite binder (sodium humate: starch: PAM = 3:1:0.1), with a dosage of 0.05%. The calcination equipment is a chain grate rotary kiln. The calcination process is as follows: First, drying is carried out at a temperature of 220℃ for 7 minutes with a drying wind speed of 1.2 m / s. Second, preheating is carried out at a temperature of 750℃ for 19 minutes. Third, oxidation calcination is carried out at a temperature of 1270℃ for 40 minutes, followed by a homogenization time of 5 minutes at a homogenization temperature of 1000℃. Finally, cooling takes 3 minutes. The wind speed in the preheating, calcination, homogenization, and cooling sections is 2.4 m / s. The compressive strength of the oxidized pellets after calcination is 2520 N / P, and the exit temperature of the oxidized pellets is 900℃.

[0071] S4. The hot oxidized pellets are charged into a hydrogen-based vertical shaft furnace for reduction. The reducing agent introduced into the furnace is 100% H2. The reducing gas is first heated to 900℃ through a heat exchange tube and electromagnetic induction combined heater before being introduced into the furnace. The temperature in the reduction zone of the furnace is 800℃, the reduction time is 90 minutes, the gas pressure inside the furnace is 0.15 MPa, and the metallization rate of the reduced pellets after reduction is 92.3%. The temperature at which the reduced pellets exit the furnace is 700℃.

[0072] S5. The hot-reduced pellets are directly loaded into the electric furnace at a temperature of 700℃. The melting temperature in the electric furnace is 1500℃, the melting time is 75min, and the amount of semi-coke added as the reducing agent is 2.1wt%. Two products, molten iron and high-titanium slag, are obtained, realizing the efficient separation and recycling of iron and titanium.

[0073] Using the above methods, the TiO2 content in the high-titanium slag throughout the entire process was 77.11%, and the titanium recovery rate was 95.1%; the iron grade in the molten iron product was 97.21%, and the total iron recovery rate was 94.14%.

[0074] Example 2

[0075] A method for recovering iron and titanium from vanadium extraction slag via hydrogen-based reduction-electric furnace smelting:

[0076] In this embodiment, a vanadium-titanium magnetite concentrate sodium vanadium extraction slag is used, which has an iron content of 63.16%, a TiO2 content of 7.1%, a SiO2 content of 5.36%, an Al2O3 content of 1.75%, a Na2O content of 1.2%, and a raw ore particle size of less than 0.074 mm accounting for 64.7%. The treatment of the vanadium-titanium magnetite concentrate sodium vanadium extraction slag includes the following steps:

[0077] S1. The vanadium-titanium magnetite concentrate sodium-treated vanadium extraction slag is wet-ball-milled to achieve a particle size of -0.074mm (82.2%) and a specific surface area of ​​1357m². 2 / g;

[0078] S2. The finely ground vanadium extraction slag is subjected to acid leaching to remove impurities. The acid dosage is 4.0 g / L (mass ratio, sulfuric acid: hydrofluoric acid = 2:1), and leaching is carried out at 80℃ for 15 min. After acid leaching, the total amount of vanadium extraction slag (SiO2 + Al2O3) is 2.34%, and the alkali metal content (Na2O + K2O) is 0.18%. The acid-leached slag is concentrated in a sedimentation tank, filtered through a filter press, and dehydrated. The material is then subjected to high-pressure roller milling to achieve a particle size of -0.074 mm (91.7%) and a specific surface area of ​​2140 μm. 2 / g.

[0079] S3. The pelletizing binder is an organic composite binder (sodium humate: starch: PAM = 1:3:0.2), with a dosage of 0.7%. The calcination equipment is a belt calciner. The calcination process is as follows: First, drying is carried out at a temperature of 370℃ for 4 minutes with a drying wind speed of 1.2 m / s. Second, preheating is carried out at a temperature of 1000℃ for 13 minutes. Finally, calcination is completed at a temperature of 1320℃ for 8 minutes, followed by a soaking time of 5 minutes at a soaking temperature of 1000℃ and a cooling time of 5 minutes. The wind speed in both the preheating and calcination sections is 2.4 m / s. The compressive strength of the oxidized pellets after calcination is 3011 N / P, and the exit temperature of the oxidized pellets is 900℃.

[0080] S4. The hot oxidized pellets are charged into a hydrogen-based vertical shaft furnace for reduction. The reducing agent introduced into the furnace is a mixture of 80% H2 and 20% CO. The reducing gas is first heated to 1050℃ through a heat exchange tube and electromagnetic induction heater before being introduced into the furnace. The temperature in the reduction zone of the furnace is 1020℃, the reduction time is 45 minutes, the gas pressure inside the furnace is 0.3 MPa, and the metallization rate of the reduced pellets after reduction is 80.3%. The temperature at which the reduced pellets exit the furnace is 500℃.

[0081] S5. The reduced pellets are directly charged into the electric furnace at a temperature of 500℃. The melting temperature in the electric furnace is 1700℃, the melting time is 15min, and the amount of biomass carbon added as the reducing agent is 9.8wt%, resulting in two products: molten iron and high-titanium slag.

[0082] Using the above methods, the TiO2 content in the high-titanium slag throughout the entire process was 76.21%, and the titanium recovery rate was 95.44%; the iron grade in the reduced iron powder product was 97.13%, and the total iron recovery rate was 95.84%.

[0083] Example 3

[0084] A method for recovering iron and titanium from vanadium extraction slag via hydrogen-based reduction-electric furnace smelting:

[0085] In this embodiment, a vanadium-titanium magnetite concentrate sodium vanadium extraction slag is used, which has an iron content of 55.1%, a TiO2 content of 12.34%, a SiO2 content of 7.1%, an Al2O3 content of 3.56%, a Na2O content of 4.5%, and a raw ore particle size of less than 0.074 mm accounting for 63.8%. The treatment of the vanadium-titanium magnetite concentrate sodium vanadium extraction slag includes the following steps:

[0086] S1. The vanadium-titanium magnetite concentrate sodium-treated vanadium extraction slag is wet-ball-milled to achieve a particle size of -0.074mm (75.2%) and a specific surface area of ​​1104m². 2 / g;

[0087] S2. The finely ground vanadium extraction slag is subjected to acid leaching to remove impurities. The acid dosage is 1.5 g / L (mass ratio, sulfuric acid: hydrofluoric acid = 2:1), and leaching is carried out at 75℃ for 100 min. After acid leaching, the total amount of vanadium extraction slag (SiO2 + Al2O3) is 2.68%, and the alkali metal content (Na2O + K2O) is 0.21%. The acid-leached slag is concentrated in a sedimentation tank, filtered through a filter press, and dewatered. The material is then subjected to high-pressure roller milling to achieve a particle size of -0.074 mm (89.7%) and a specific surface area of ​​1950 μm. 2 / g.

[0088] S3. The pelletizing binder is an organic composite binder (sodium humate: starch: PAM = 2:2:0.1), with a dosage of 0.3%. The calcination equipment is a belt calciner. The calcination process is as follows: First, drying is carried out at a temperature of 300℃ for 6 minutes with a drying wind speed of 1.2 m / s. Second, preheating is carried out at a temperature of 900℃ for 15 minutes. Finally, calcination is completed at a temperature of 1280℃ for 25 minutes, with a homogenization time of 4 minutes and a homogenization temperature of 1000℃. The cooling time is 5 minutes. The wind speed in both the preheating and calcination sections is 2.4 m / s. The compressive strength of the oxidized pellets after calcination is 2520 N / P, and the exit temperature of the oxidized pellets is 800℃.

[0089] S4. The hot oxidized pellets are directly reduced in a hydrogen-rich vertical shaft furnace. The reducing agent input into the furnace is a mixture of 70% H2 and 30% CO. The reducing gas is first heated to 950°C through a heat exchange tube and an electromagnetic induction heater before being input into the furnace. The temperature in the reduction zone of the furnace is 900°C, the reduction time is 90 minutes, the gas pressure inside the furnace is 0.25 MPa, and the metallization rate of the reduced pellets after reduction is 87.3%. The temperature of the reduced pellets exiting the furnace is 600°C.

[0090] S5. The reduced pellets are directly charged into the electric furnace at a temperature of 600℃. The melting temperature in the electric furnace is 1600℃, the melting time is 45min, and the amount of biomass carbon added as the reducing agent is 7.0wt%. Two products are obtained: molten iron and high-titanium slag.

[0091] Using the above methods, the TiO2 content in the high-titanium slag throughout the entire process is 77.1%, and the titanium recovery rate is 95.4%; the iron grade in the reduced iron powder (molten iron) product is 96.2%, and the total iron recovery rate is 94.23%.

[0092] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for recovering iron and titanium from vanadium extraction slag via hydrogen-based reduction-electric furnace smelting, characterized in that, Includes the following steps: S1. Vanadium-titanium magnetite concentrate is subjected to sodium vanadium extraction to obtain sodium vanadium extraction slag; the sodium vanadium extraction slag is finely ground to make its particle size of -0.074mm account for 72~82% and its specific surface area of ​​1000~1350m². 2 / g; wherein, the TFe content in the sodium vanadium extraction slag is 48%~63%, the TiO2 content in the sodium vanadium extraction slag is 7%~16%, the alkali metal content in the sodium vanadium extraction slag is 1.5%~5.5%, and the aluminosilicate content is greater than 7.2%; S2. The finely ground vanadium-containing sodium leaching slag from S1 is subjected to acid leaching to obtain acid-leached slag. The acid-leached slag is then filtered, dewatered, and then subjected to high-pressure roller milling to achieve a particle size of -0.074mm accounting for 83~92% and a specific surface area of ​​1750~2150m². 2 / g; S3. After mixing the material from the high-pressure roller mill in S2 with an organic composite binder, pelletize the mixture to obtain green pellets with a particle size of 10-14 mm. Then, oxidize and calcine the green pellets to obtain vanadium extraction slag oxidized pellets with a compressive strength of 2520-3000 N / P. The organic composite binder is composed of sodium humate, starch, and polyacrylamide; the mass ratio of sodium humate, starch, and polyacrylamide is 1-3:3-1:0.05-0.2; the amount of organic composite binder is 0.05-0.7 wt%. The oxidative calcination includes four stages: drying, preheating, calcination, and homogenization. The drying stage is performed at 220-370℃ for 3-7 minutes; the preheating stage is performed at 750-1000℃ for 13-19 minutes. The roasting stage temperature is 1270~1320℃, and the time is 8~40min; the homogenization stage temperature is 900-1000℃, and the time is 5min; the oxidative roasting followed by cooling for 3-5min until the temperature of the vanadium extraction slag oxidized pellets is 700~900℃. S4. The hot vanadium-extraction slag oxide pellets after S3 oxidation roasting are directly reduced in a hydrogen-based vertical shaft furnace to obtain reduced pellets containing elemental iron and titanium oxide. The hot vanadium-extraction slag oxide pellets are added from the top of the hydrogen-based vertical shaft furnace, and hydrogen-based gas in the furnace is introduced through a gas supply pipe surrounding the furnace cylinder at the bottom. A heating device is provided on the lower side wall of the furnace cylinder. The temperature of the hydrogen-based gas entering the furnace cylinder is 900~1050℃. S5. The reduced pellets from S4 are directly charged into an electric furnace without cooling, and then melted in the electric furnace to obtain molten iron and high-titanium slag. The temperature at which the reduced pellets are charged into the electric furnace is 500~700℃, the melting temperature of the electric furnace is 1500~1700℃, and the melting time is 15~75min. A reducing agent, which is semi-coke or biochar, is also added to the electric furnace. The amount of the reducing agent is 2~10wt%.

2. The method for recovering iron and titanium from vanadium slag by hydrogen-based reduction-electric furnace smelting according to claim 1, characterized in that, In step S2, the acid used for pickling is composed of sulfuric acid and hydrofluoric acid, the mass ratio of sulfuric acid to hydrofluoric acid is 2~2.5, and the amount of acid used for pickling is 0.1~4.0 g / L.

3. The method for recovering iron and titanium from vanadium extraction slag using hydrogen-based reduction-electric furnace smelting according to claim 1, characterized in that, In step S2, the acid leaching temperature is 55~80℃ and the time is 14~120min; the alkali metal content in the acid leaching residue is less than 0.27% and the aluminosilicate content is less than 3.1%.

4. The method for recovering iron and titanium from vanadium extraction slag using hydrogen-based reduction-electric furnace smelting according to claim 1, characterized in that, In step S2, the acid leaching residue needs to be precipitated and concentrated in a sedimentation tank before filtration. The concentrated acid leaching residue is then filtered and dewatered by a filter press or a disc vacuum filter. After dewatering, the material is subjected to a high-pressure roller mill.

5. The method for recovering iron and titanium from vanadium extraction slag via hydrogen-based reduction-electric furnace smelting according to claim 1, characterized in that, In step S4, the hydrogen-based gas in the hydrogen-based vertical furnace is H2 or a mixture of H2 and CO; the temperature of the reduction zone in the upper part of the hydrogen-based vertical furnace is 850~1020℃, the gas pressure is 0.15~0.3MPa, and the reduction time is 45~120min.

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