Method for preparing ferrotitanium alloy and aluminum-calcium slag by smelting reduction of ferrotitanium slag

Abstract

The present application relates to the technical field of metallurgy, and particularly relates to a method for preparing titanium-iron alloy and aluminum-calcium slag by smelting reduction of titanium-iron slag, and specifically to mixing titanium-iron slag particles with modified CaF2, modified ferrous oxide composite microspheres, modified iron powder and ferrosilicon powder in proportion, carrying out smelting reduction after low-temperature pretreatment, and obtaining Ti-Fe alloy and aluminum-calcium slag respectively after static stratification. Under the synergistic effect of the triple mechanism of modified CaF2, modified iron powder and modified ferrous oxide composite microspheres, the Ti yield is greatly improved compared with the traditional carbon thermal reduction process, and the TiC content in the product is significantly reduced. Under the synergistic effect of multiple mechanisms, the liquid iron droplet sedimentation rate is significantly improved, and the slag-gold separation rate is not less than 90%. The present application realizes the full-value conversion of the solid waste metal phase and slag phase of titanium-iron slag while efficiently recycling Ti to prepare Ti-Fe alloy.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically a method for preparing titanium-iron alloy and aluminum-calcium slag by melting and reducing titanium-iron slag. Background Technology

[0002] Titanium-iron slag is the main solid waste generated during the aluminothermic process of producing titanium-iron alloys. Its main chemical components are Al2O3, TiO2, CaO, MgO, and SiO2. The carbothermic reduction process is a potential route that could significantly enhance the value of industrial waste slag generated from titanium-iron alloy smelting. The resulting titanium-containing metallic materials can be used as additives in certain special steels, while the remaining low-impurity alumino-calcium compound slag can be used as a precursor material for calcium aluminate cement in refractory materials and as a binder for refractory castables.

[0003] However, during the carbothermic reduction of TiO2 in ilmenite slag, solid carbon directly contacts TiO2 at high temperatures to form titanium carbide (TiC). TiC is thermodynamically extremely stable and dispersed as solid particles in the slag phase, with a density between that of metallic iron and alumina-calcium slag. It cannot be effectively separated by simple gravity stratification. Therefore, the yield of metallic titanium in the traditional carbothermic reduction method is typically below 30%, and the product contains a large amount of TiC, making subsequent purification extremely difficult. Summary of the Invention

[0004] (1) Technical problems to be solved

[0005] The purpose of this invention is to provide a method for preparing titanium-iron alloys and aluminum-calcium slag by melting and reducing titanium-iron slag. This method aims to solve the problem that when TiO2 in titanium-iron slag is reduced by carbotherm, the yield of metallic titanium is extremely low and the products are difficult to separate because solid carbon is in direct contact with TiO2 and the reaction kinetics prefer to generate a stable TiC phase.

[0006] (2) Technical solution

[0007] To achieve the above objectives, on the one hand, the present invention provides a method for preparing titanium-iron alloy and aluminum-calcium slag by melting and reducing titanium-iron slag, comprising the following steps: mixing modified CaF2 with titanium-iron slag particles evenly and stirring evenly, then adding modified ferrous oxide composite microspheres and stirring and mixing, and finally adding modified iron powder and ferrosilicon powder and continuing to stir and mix to obtain a mixture, which is then melt-reduced after low-temperature pretreatment, and after standing and separating into layers, Ti-Fe alloy and aluminum-calcium slag are obtained respectively;

[0008] The modified iron powder is iron powder coated with coal tar pitch;

[0009] The modified CaF2 is CaO-Fe2O3 composite oxide / porous carbon bilayer coated CaF2 microspheres;

[0010] The modified ferrous oxide composite microspheres are K2TiF6 supported ferrous oxide composite microspheres.

[0011] Furthermore, based on 100 parts by mass of titanium-iron slag particles, the amount of modified iron powder added is 28-32 parts by mass, the amount of modified CaF2 added is 12-16 parts by mass, the amount of modified ferrous oxide composite microspheres added is 8-12 parts by mass, and the amount of ferrosilicon powder added is 3-5 parts by mass.

[0012] Furthermore, the preparation method of the modified iron powder includes the following steps:

[0013] S11. The reduced iron powder is placed in a tube furnace, pure hydrogen is introduced, and it is reduced at 480°C. After cooling to room temperature, it is transferred and sealed for storage under argon protection to obtain pretreated iron powder.

[0014] S12. Crush the coal tar pitch, add it to toluene, place it in a water bath and stir continuously to dissolve it, filter it to obtain a pitch toluene solution;

[0015] S13. The pretreated iron powder is loaded into a fluidized bed, and argon gas is introduced to make the iron powder fluidized. The temperature of the fluidized bed is raised to 185°C. The asphalt toluene solution is continuously atomized and sprayed into the fluidized bed using a peristaltic pump. After the spraying is completed, the temperature of the fluidized bed is raised to 480°C, kept at the temperature under argon protection, and cooled to room temperature to obtain modified iron powder.

[0016] Furthermore, the preparation method of the modified CaF2 includes the following steps:

[0017] S21. Add CaF2 powder to 5% dilute nitric acid, stir and soak, filter, wash with deionized water until neutral, dry, and ball mill the dried CaF2 for 6 hours to obtain pretreated CaF2 powder.

[0018] S22. Phenolic resin and CTAB were dissolved in a mixed solvent of anhydrous ethanol and deionized water, stirred in a water bath, and pretreated CaF2 powder was added. The mixture was ultrasonically dispersed and rotary evaporated. The resulting product was placed in a tube furnace and heated to 500℃ at 2℃ / min under argon protection. The temperature was maintained for 2 hours and then naturally cooled to room temperature to obtain CaF2@porous carbon.

[0019] S23. Dissolve Ca(NO3)2·4H2O and Fe(NO3)3·9H2O in deionized water and stir until completely dissolved. Add citric acid and continue stirring. Slowly add ammonia to adjust the pH and slowly add ethylene glycol. Heat and stir to obtain Fe-Ca sol.

[0020] S24. Impregnate CaF2@porous carbon into Fe-Ca sol, disperse by ultrasonication, evaporate by rotary evaporation, and then place in a vacuum drying oven for drying. Place the obtained product in a tube furnace, heat to 300℃ at 1℃ / min, hold for 1h, then heat to 750℃ at 2℃ / min, hold for 3h, cool to room temperature with the furnace, and pass through a 200-mesh sieve to obtain modified CaF2.

[0021] Furthermore, the preparation method of the modified ferrous oxide composite microspheres includes the following steps:

[0022] S31. Disperse FeO microspheres ultrasonically in anhydrous ethanol to obtain FeO ethanol suspension; add KH-550 to acetic acid / water mixture for hydrolysis, then slowly add the hydrolysate dropwise to FeO ethanol suspension, stir the reaction, filter, wash with anhydrous ethanol, and dry to obtain surface-aminated FeO microspheres.

[0023] S32. K2TiF6 fine powder was ultrasonically dispersed in anhydrous ethanol to obtain K2TiF6 ethanol suspension; surface-aminated FeO microspheres were redispersed in anhydrous ethanol, and K2TiF6 ethanol suspension was slowly added under argon protection. After mixing, the mixture was continuously stirred and reacted. After the reaction was completed, the mixture was filtered under argon protection, washed with anhydrous ethanol, and vacuum dried to obtain modified ferrous oxide composite microspheres.

[0024] Furthermore, the low-temperature pretreatment conditions are: argon protection, heating rate of 5℃ / min, pretreatment temperature of 850~950℃, and holding time of 50~70min.

[0025] Furthermore, the melting reduction is carried out in a medium-frequency induction furnace or an electric arc furnace under argon protection, at a temperature of 1500–1580°C, a holding time of 40–70 min, and a slight positive pressure of 0.03–0.08 MPa maintained inside the furnace.

[0026] Furthermore, the static stratification conditions are as follows: the phase is kept at 1400-1450℃ for 15-20 minutes, and gravity natural stratification is achieved by utilizing the density difference between the Ti-Fe alloy phase and the aluminous-calcium slag phase.

[0027] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0028] 1. This invention, through the synergistic effect of multiple mechanisms of modified CaF2, modified iron powder, and modified ferrous oxide composite microspheres, blocks the direct contact between solid carbon and TiO2, cuts off the TiC formation pathway, and thus significantly improves the Ti yield compared with the traditional carbothermal reduction process, and significantly reduces the TiC content in the product.

[0029] 2. Under the synergistic effect of multiple mechanisms of modified CaF2, ferrosilicon powder and modified ferrous oxide composite microspheres, the viscosity of the slag phase is significantly reduced, the slag-metal interface renewal is accelerated, the settling rate of liquid iron droplets is significantly improved, and the slag-metal separation rate is not less than 90%.

[0030] 3. This invention achieves efficient Ti recovery and Ti-Fe alloy preparation, while the by-product alumina-calcium slag possesses the compositional characteristics of calcium aluminate cement precursors. When added at 8 wt% to a corundum-based refractory castable system, the resulting compressive strength, flexural strength, and apparent porosity all meet the engineering application requirements of refractory castable binders, realizing a full-volume, high-value conversion of the metallic and slag phases in titanium-iron slag solid waste. Attached Figure Description

[0031] Figure 1 This is a process flow diagram of the preparation of titanium-iron alloy and aluminum-calcium slag by melting and reducing titanium-iron slag according to the present invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Example 1: This example discloses a method for preparing ferro-titanium alloy and alumina-calcium slag by melting and reducing ferro-titanium slag, including the following steps:

[0034] S1. Ingredient mixing: Mix 14kg of modified CaF2 with 100kg of ferrotitanium slag for 15min, add 10kg of modified ferrous oxide composite microspheres and mix for 5min, add 30kg of modified iron powder and 4kg of ferrosilicon powder and mix for 10min to obtain the mixture;

[0035] S2. Low-temperature pretreatment: The mixture is placed in a tube furnace and heated to 900°C at a heating rate of 5°C / min under argon protection, and held at that temperature for 1 hour to obtain the pretreated mixture;

[0036] S3. Melt reduction: The pretreated mixture is transferred into a medium-frequency induction furnace and rapidly heated to 1550℃ under argon protection, held for 50 minutes, and the pressure inside the furnace is slightly positive (0.05MPa).

[0037] S4. Static stratification and step-by-step discharge: After heating is stopped, the material is kept at 1420℃ for 18 minutes. Gravity stratification is achieved by utilizing the density difference between the Ti-Fe alloy melt and the aluminous-calcium slag phase. The upper layer of aluminous-calcium slag is first poured out, and then the bottom Ti-Fe alloy is collected.

[0038] It should be noted that, as Figure 1 The diagram shows the process flow for preparing titanium-iron alloy and alumina-calcium slag by melting and reducing titanium-iron slag according to the present invention. First, titanium-iron slag particles are mixed with modified CaF2, modified ferrous oxide composite microspheres, modified iron powder, and ferrosilicon powder. The entire process is carried out in a dry environment. After mixing, the mixture is immediately transferred to a tube furnace for low-temperature pretreatment to generate CaTiO3 and consume free carbon sources, blocking direct contact between solid carbon and TiO2. Then, the pretreated mixture is transferred to a medium-frequency induction furnace, where the iron powder melts to form a liquid iron melt. The liquid iron melt rapidly settles and aggregates in the low-viscosity slag phase, forming a continuous iron melt phase, with Ti continuously migrating from the slag phase into the iron melt. Finally, the density difference between the Ti-Fe alloy melt and the alumina-calcium slag phase is utilized to achieve natural gravity stratification.

[0039] The method for preparing the modified iron powder includes the following steps:

[0040] S11. Place 900g of reduced iron powder in a tube furnace, introduce pure hydrogen (flow rate 300 mL / min), and reduce it at 480℃ for 2 hours to completely reduce the FeO / Fe2O3 oxide film on the surface of the iron powder to metallic iron. After cooling to room temperature, transfer and seal it for later use under argon protection to obtain pretreated iron powder.

[0041] S12. Crush 100g of coal tar pitch into small pieces, add it to 400mL of toluene, place it in a 60℃ water bath and stir continuously for 2 hours to dissolve it, filter to remove insoluble residue, and obtain pitch toluene solution.

[0042] S13. The pretreated iron powder is loaded into a fluidized bed, and argon gas is introduced to make the iron powder fluidized (gas velocity 0.08~0.12m / s). The temperature of the fluidized bed is raised to 185℃, and the asphalt toluene solution is continuously atomized and sprayed into the fluidized bed at a rate of 8~10mL / min using a peristaltic pump. After the spraying is completed, the temperature of the fluidized bed is raised to 480℃ and kept at this temperature for 2 hours under argon protection to further crosslink and solidify the asphalt coating layer, forming a dense and continuous shell. The mixture is then cooled to room temperature under argon protection to obtain modified iron powder.

[0043] The preparation method of the modified CaF2 includes the following steps:

[0044] S21. Add 45g of CaF2 powder to 5% dilute nitric acid (liquid-solid ratio 4:1), stir and soak in a fume hood at room temperature for 30min, filter, wash with deionized water until neutral, dry, and ball mill the dried CaF2 for 6h to obtain pretreated CaF2 powder.

[0045] S22. Dissolve 25g of phenolic resin and 0.5g of CTAB in a mixed solvent of 150mL of anhydrous ethanol and 50mL of deionized water. Stir in a water bath at 40℃ until completely dissolved. Add pretreated CaF2 powder and ultrasonically disperse for 30min. Rotary evaporate in a water bath at 60℃ and a vacuum of -0.08MPa. Place the product in a tube furnace and heat it to 500℃ at 2℃ / min under argon protection. Hold the temperature for 2h and allow it to cool naturally to room temperature to obtain CaF2@porous carbon.

[0046] S23. Dissolve 97.3g Ca(NO3)2·4H2O and 18.6g Fe(NO3)3·9H2O in 150mL of deionized water, stir at 60℃ until completely dissolved, add 30g citric acid, continue stirring for 30min, slowly add ammonia water to adjust the pH to 6.5~7.0, slowly add 150mL ethylene glycol, heat to 80℃ and stir for 1h to obtain Fe-Ca sol;

[0047] S24. CaF2@porous carbon was immersed in Fe-Ca sol and ultrasonically dispersed for 15 min. It was then rotary evaporated at 70℃ and normal pressure, and then placed in a vacuum drying oven and dried at 80℃ for 12 h. The product was placed in a tube furnace and heated to 300℃ at 1℃ / min and held for 1 h. Then it was heated to 750℃ at 2℃ / min and held for 3 h. The product was cooled to room temperature with the furnace and passed through a 200-mesh sieve to obtain modified CaF2.

[0048] The preparation method of the modified ferrous oxide composite microspheres includes the following steps:

[0049] S31. 800g of FeO microspheres were ultrasonically dispersed in 1000mL of anhydrous ethanol to obtain FeO ethanol suspension; 16g of KH-550 was added to 50mL of acetic acid / water (volume ratio 95:5) mixture for hydrolysis for 10 minutes, and then the hydrolysate was slowly added dropwise to the FeO ethanol suspension. The reaction was carried out at 60℃ under argon protection and stirring at 300rpm for 2 hours. The mixture was filtered, washed with anhydrous ethanol, and dried at 60℃ for 2 hours to obtain surface-aminated FeO microspheres.

[0050] S32. 200g of K2TiF6 fine powder was ultrasonically dispersed in 500mL of anhydrous ethanol to obtain a K2TiF6 ethanol suspension; the surface-aminated FeO microspheres were redispersed in 450mL of anhydrous ethanol, and the K2TiF6 ethanol suspension was slowly added under argon protection. After mixing, the mixture was stirred continuously at 60℃ and 300rpm for 4 hours. After the reaction was completed, the mixture was filtered under argon protection, washed with anhydrous ethanol, and vacuum dried at 60℃ for 3 hours to obtain modified ferrous oxide composite microspheres.

[0051] Example 2: This example is based on Example 1, but differs from Example 1 in that it uses 100 parts by mass of titanium-iron slag particles as a base, with 32 parts by mass of modified iron powder, 16 parts by mass of modified CaF2, 12 parts by mass of modified ferrous oxide composite microspheres, and 5 parts by mass of ferrosilicon powder.

[0052] The other components and preparation methods are the same as in Example 1.

[0053] Example 3: This example is based on Example 1, but differs from Example 1 in that it uses 100 parts by mass of titanium-iron slag particles as a base, with 28 parts by mass of modified iron powder, 12 parts by mass of modified CaF2, 8 parts by mass of modified ferrous oxide composite microspheres, and 3 parts by mass of ferrosilicon powder.

[0054] The other components and preparation methods are the same as in Example 1.

[0055] Comparative Example 1: This comparative example is based on Example 1, but differs from Example 1 in that the modified iron powder is replaced with an equal mass of ordinary iron powder that is not coated with asphalt.

[0056] The other components and preparation methods are the same as in Example 1.

[0057] Comparative Example 2: This comparative example is based on Example 1, but differs from Example 1 in that the modified CaF2 described in this comparative example has no porous carbon layer.

[0058] The preparation method of the modified CaF2 includes the following steps:

[0059] S21. Add 45g of CaF2 powder to 5% dilute nitric acid (liquid-solid ratio 4:1), stir and soak in a fume hood at room temperature for 30min, filter, wash with deionized water until neutral, dry, and ball mill the dried CaF2 for 6h to obtain pretreated CaF2 powder.

[0060] S22. Dissolve 97.3g Ca(NO3)2·4H2O and 18.6g Fe(NO3)3·9H2O in 150mL of deionized water, stir at 60℃ until completely dissolved, add 30g citric acid, continue stirring for 30min, slowly add ammonia water to adjust the pH to 6.5~7.0, slowly add 150mL ethylene glycol, heat to 80℃ and stir for 1h to obtain Fe-Ca sol;

[0061] S23. The pretreated CaF2 powder was immersed in Fe-Ca sol and ultrasonically dispersed for 15 min. It was then rotary evaporated at 70℃ and normal pressure, and then placed in a vacuum drying oven and dried at 80℃ for 12 h. The product was placed in a tube furnace and heated to 300℃ at 1℃ / min and held for 1 h. Then it was heated to 750℃ at 2℃ / min and held for 3 h. The product was cooled to room temperature with the furnace and passed through a 200-mesh sieve to obtain modified CaF2.

[0062] The other components and preparation methods are the same as in Example 1.

[0063] Comparative Example 3: This comparative example is based on Example 1, but differs from Example 1 in that it modifies CaF2 without CaO-Fe2O3 composite oxide.

[0064] The preparation method of the modified CaF2 includes the following steps:

[0065] S21. Add 45g of CaF2 powder to 5% dilute nitric acid (liquid-solid ratio 4:1), stir and soak in a fume hood at room temperature for 30min, filter, wash with deionized water until neutral, dry, and ball mill the dried CaF2 for 6h to obtain pretreated CaF2 powder.

[0066] S22. Dissolve 25g of phenolic resin and 0.5g of CTAB in a mixed solvent of 150mL of anhydrous ethanol and 50mL of deionized water. Stir in a water bath at 40℃ until completely dissolved. Add pretreated CaF2 powder and ultrasonically disperse for 30min. Rotary evaporate in a water bath at 60℃ and a vacuum of -0.08MPa. Place the product in a tube furnace and heat it to 500℃ at 2℃ / min under argon protection. Hold the temperature for 2h and allow it to cool naturally to room temperature to obtain modified CaF2.

[0067] The other components and preparation methods are the same as in Example 1.

[0068] Comparative Example 4: This comparative example is based on Example 1, but differs from Example 1 in that the modified CaF2 is replaced with an equal mass of pure CaO powder.

[0069] The other components and preparation methods are the same as in Example 1.

[0070] Comparative Example 5: This comparative example is based on Example 1, but differs from Example 1 in that the modified ferrous oxide composite microspheres in this comparative example are not subjected to KH-550 amination treatment.

[0071] The other components and preparation methods are the same as in Example 1.

[0072] It should be noted that, because the aminated surface is positively charged, and TiF6... 2-Negatively charged, K2TiF6 is uniformly loaded on the surface of FeO microspheres as a tightly adsorbed layer due to electrostatic adsorption between the two.

[0073] Comparative Example 6: This comparative example is based on Example 1, but differs from Example 1 in that the modified ferrous oxide composite microspheres are not loaded with K2TiF6, that is, the modified ferrous oxide composite microspheres are replaced with ordinary ferrous oxide microspheres of equal mass.

[0074] The other components and preparation methods are the same as in Example 1.

[0075] Comparative Example 7: This comparative example is based on Example 1, but differs from Example 1 in that it does not have the S2 low-temperature pretreatment step. Instead, the mixture obtained in S1 is directly melt-reduced, then allowed to stand and separate into layers before being discharged in stages.

[0076] The other components and preparation methods are the same as in Example 1.

[0077] Comparative Example 8: This comparative example uses a traditional carbothermal reduction process, replacing the modified iron powder with an equal mass of metallurgical-grade graphite powder (fixed carbon ≥99%, particle size ≤0.074mm). Simultaneously, the modified ferrous oxide composite microspheres and modified CaF2 are removed, retaining only an equal mass of CaF2 powder as a flux. The amount of ferrosilicon powder used is the same as in Example 1. The mixture is not subjected to low-temperature pretreatment and is directly melt-reduced at 1550℃ for 50 min. The static separation conditions are the same as in Example 1.

[0078] Experimental verification:

[0079] Experiment 1: Titanium-iron alloys and aluminum-calcium slag were prepared by melting and reducing titanium-iron slag from Examples 1-3 and Comparative Examples 1-8, and the following indicators were uniformly measured:

[0080] (1) Ti yield: The Ti concentration of the prepared titanium-iron alloy was determined by ICP-OES, and the Ti yield was calculated as (total Ti in the alloy / total Ti in the raw material) × 100%;

[0081] (2) Slag-to-metal separation rate: Based on the total amount of metallic iron in the raw material and the metallic iron obtained from reduction, the slag-to-metal separation rate = actual collected Ti-Fe alloy mass / (total iron in the raw material + amount of iron obtained from reduction + amount of Ti migrating into the alloy) × 100%;

[0082] (3) TiC content in the product: quantitative analysis using a carbon-sulfur analyzer combined with XRD;

[0083] Repeat each batch 3 times.

[0084] Table 1: Results of Ti yield, slag-gold separation rate, and TiC content in the product:

[0085]

[0086] Table 1 shows the results of Ti yield, slag-gold separation rate, and TiC content in the product. As can be seen from the table, the Ti yield, slag-gold separation rate, and TiC content of the example product are all significantly better than those of the comparative example. Comparative Example 7 (without low-temperature pretreatment) has a low Ti yield and a high TiC content, indicating that the low-temperature pretreatment stage plays a crucial role in the overall process performance.

[0087] Experiment 2:

[0088] (1) Take 50g of each of the Ti-Fe alloys prepared in Examples 1 to 3, and test them using the following methods:

[0089] ICP-OES determination of Ti, Si, Al, and K contents;

[0090] Carbon and sulfur analyzer to determine C and S content;

[0091] (2) Cast the alloy into a standard sample and determine the Vickers hardness (HV, load 5N, holding pressure for 10s, take the average of 5 points).

[0092] (3) Simulation verification of its use as a steelmaking additive:

[0093] Ti-Fe alloy was added to low-carbon steel melt at a Ti content of 0.15 wt% (simulated in an induction furnace at 1600℃), and samples were taken after holding for 5 min to analyze the Ti yield in the steel.

[0094] Table 2: Verification results of Ti-Fe alloy composition and properties:

[0095]

[0096] The results of the Ti-Fe alloy composition and performance verification are shown in Table 2. As can be seen from the table, the Ti-Fe alloys prepared in Examples 1 to 3 have a Ti content of 19.8% to 25.1 wt%, a C content of ≤0.15 wt%, a S content of ≤0.03 wt%, and a K residue of ≤0.06 wt%. This indicates that most of the K element introduced by K2TiF6 enters the slag phase during the melting reduction and static stratification process, and its impact on the alloy purity is controllable. The Vickers hardness is 300 to 400 HV, which meets the requirements for the use of ferrotitanium alloy as a steelmaking additive. In the simulated steelmaking verification, the Ti yield is ≥83%, indicating that the prepared Ti-Fe alloy has good Ti transfer efficiency in steel and can effectively replace commercial ferrotitanium for deoxidation and microalloying of special steels.

[0097] Experiment 3:

[0098] (1) Chemical composition analysis of alumina-calcium slag:

[0099] Take 30g of each of the aluminum-calcium slag produced in Examples 1-3, and determine the content of Al2O3, CaO, SiO2, TiO2 (residual), and F by XRF. - The residual fluorine content was determined using a carbon-sulfur analyzer.

[0100] (2) Validation as a binder for refractory castables

[0101] Calcined alumina slag was added at a ratio of 8 wt% to a corundum refractory castable system (base material: white corundum aggregate, fine powder: α-Al2O3 micro powder), water was added, and the mixture was stirred and vibrated to form a mold. The mixture was then dried at 110℃ for 24 h and calcined at 1100℃ before testing.

[0102] room temperature compressive strength;

[0103] Flexural strength at room temperature;

[0104] Apparent porosity.

[0105] Table 3: Validation results of the composition and application performance of alumina-calcium slag:

[0106]

[0107] The results of the composition and application performance verification of alumina-calcium slag are shown in Table 3. As can be seen from the table, the alumina-calcium slag produced in Examples 1-3 showed relatively complete Ti extraction during the molten reduction process, and the residual fluorine content was controlled at a low level. When the alumina-calcium slag was added to the corundum refractory castable system at a ratio of 8 wt%, the compressive strength at room temperature after drying at 110℃ and firing at 1100℃ was ≥55 MPa, the flexural strength was ≥8.0 MPa, and the apparent porosity was ≤18%. All properties meet the engineering application requirements of refractory castable binders, verifying the feasibility of alumina-calcium slag as a precursor for calcium aluminate cement. This invention efficiently recovers Ti to prepare Ti-Fe alloys, while the by-product alumina-calcium slag possesses the compositional characteristics of a calcium aluminate cement precursor.

[0108] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made by those skilled in the art within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing ferro-titanium alloy and alumina-calcium slag by melting and reducing ferro-titanium slag, characterized in that, Includes the following steps: Modified CaF2 and ferrotitanium slag particles were mixed evenly and stirred evenly. Then, modified ferrous oxide composite microspheres were added and stirred and mixed. Finally, modified iron powder and ferrosilicon powder were added and stirred and mixed to obtain a mixture. After low-temperature pretreatment, the mixture was melt-reduced and allowed to stand and separate into layers to obtain Ti-Fe alloy and alumina-calcium slag respectively. The modified iron powder is iron powder coated with coal tar pitch; The modified CaF2 is CaO-Fe2O3 composite oxide / porous carbon bilayer coated CaF2 microspheres; The modified ferrous oxide composite microspheres are K2TiF6 supported ferrous oxide composite microspheres; The preparation method of the modified CaF2 includes the following steps: S21. Add CaF2 powder to 5% dilute nitric acid, stir and soak, filter, wash with deionized water until neutral, dry, and ball mill the dried CaF2 for 6 hours to obtain pretreated CaF2 powder. S22. Phenolic resin and CTAB were dissolved in a mixed solvent of anhydrous ethanol and deionized water, stirred in a water bath, and pretreated CaF2 powder was added. The mixture was ultrasonically dispersed and rotary evaporated. The resulting product was placed in a tube furnace and heated to 500℃ at 2℃ / min under argon protection. The temperature was maintained for 2 hours and then naturally cooled to room temperature to obtain CaF2@porous carbon. S23. Dissolve Ca(NO3)2·4H2O and Fe(NO3)3·9H2O in deionized water and stir until completely dissolved. Add citric acid and continue stirring. Slowly add ammonia to adjust the pH and slowly add ethylene glycol. Heat and stir to obtain Fe-Ca sol. S24. CaF2@porous carbon was immersed in Fe-Ca sol, ultrasonically dispersed, rotary evaporated, and then placed in a vacuum drying oven for drying. The resulting product was placed in a tube furnace, heated to 300℃ at 1℃ / min, held for 1h, then heated to 750℃ at 2℃ / min, held for 3h, cooled to room temperature with the furnace, and passed through a 200-mesh sieve to obtain modified CaF2. The low-temperature pretreatment conditions are: argon protection, heating rate of 5℃ / min, pretreatment temperature of 850~950℃, and holding time of 50~70min.

2. The method for preparing ferro-titanium alloy and alumina-calcium slag by melting and reducing ferro-titanium slag according to claim 1, characterized in that, Based on 100 parts by weight of titanium-iron slag particles, the amount of modified iron powder added is 28-32 parts by weight, the amount of modified CaF2 added is 12-16 parts by weight, the amount of modified ferrous oxide composite microspheres added is 8-12 parts by weight, and the amount of ferrosilicon powder added is 3-5 parts by weight.

3. The method for preparing ferro-titanium alloy and alumina-calcium slag by melting and reducing ferro-titanium slag according to claim 1, characterized in that, The method for preparing the modified iron powder includes the following steps: S11. The reduced iron powder is placed in a tube furnace, pure hydrogen is introduced, and it is reduced at 480°C. After cooling to room temperature, it is transferred and sealed for storage under argon protection to obtain pretreated iron powder. S12. Crush the coal tar pitch, add it to toluene, place it in a water bath and stir continuously to dissolve it, filter it to obtain a pitch toluene solution; S13. The pretreated iron powder is loaded into a fluidized bed, and argon gas is introduced to make the iron powder fluidized. The temperature of the fluidized bed is raised to 185°C. The asphalt toluene solution is continuously atomized and sprayed into the fluidized bed using a peristaltic pump. After the spraying is completed, the temperature of the fluidized bed is raised to 480°C, kept at the temperature under argon protection, and cooled to room temperature to obtain modified iron powder.

4. The method for preparing ferro-titanium alloy and alumina-calcium slag by melting and reducing ferro-titanium slag according to claim 1, characterized in that, The preparation method of the modified ferrous oxide composite microspheres includes the following steps: S31. Disperse FeO microspheres ultrasonically in anhydrous ethanol to obtain FeO ethanol suspension; add KH-550 to acetic acid / water mixture for hydrolysis, then slowly add the hydrolysate dropwise to FeO ethanol suspension, stir the reaction, filter, wash with anhydrous ethanol, and dry to obtain surface-aminated FeO microspheres. S32. K2TiF6 fine powder was ultrasonically dispersed in anhydrous ethanol to obtain K2TiF6 ethanol suspension; surface-aminated FeO microspheres were redispersed in anhydrous ethanol, and K2TiF6 ethanol suspension was slowly added under argon protection. After mixing, the mixture was continuously stirred and reacted. After the reaction was completed, the mixture was filtered under argon protection, washed with anhydrous ethanol, and vacuum dried to obtain modified ferrous oxide composite microspheres.

5. The method for preparing ferro-titanium alloy and alumina-calcium slag by melting and reducing ferro-titanium slag according to claim 1, characterized in that, The melting reduction is carried out in a medium-frequency induction furnace or an electric arc furnace under argon protection, at a temperature of 1500–1580℃, a holding time of 40–70 min, and a slight positive pressure of 0.03–0.08 MPa maintained inside the furnace.

6. The method for preparing ferro-titanium alloy and alumina-calcium slag by melting and reducing ferro-titanium slag according to claim 1, characterized in that, The static stratification conditions are as follows: the phase is kept at 1400-1450℃ for 15-20 minutes, and gravity natural stratification is achieved by utilizing the density difference between the Ti-Fe alloy phase and the aluminous-calcium slag phase.

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