A method for simultaneously preparing dense calcium hexaluminate and titanium-silicon alloy by aluminothermic reduction of ilmenite slag and dense calcium hexaluminate prepared by the method

Abstract

The application discloses a method for preparing dense calcium hexaluminate and titanium-silicon alloy by simultaneously performing aluminum thermal reduction on ilmenite slag, and the dense calcium hexaluminate prepared by the method. The application relates to the technical field of waste treatment and resource utilization. The method uses 70-74 wt% of ilmenite slag, 7-10 wt% of Al particles, 6-8 wt% of SiO2 micro powder and 10-15 wt% of lime as raw materials, and the raw materials are loaded into a container and subjected to high-temperature smelting. After the smelting is completed, the upper oxide slag and the lower metal melt are sequentially poured out and separated, the lower metal melt is cooled to obtain a titanium-silicon alloy byproduct, and the upper oxide slag is cooled to room temperature to obtain the dense calcium hexaluminate. In the application, TiO2 in the ilmenite slag is extracted and utilized, CaO and Al2O3 in the remaining tail slag are fully utilized, the dense calcium hexaluminate is prepared, and high-value utilization of the ilmenite slag is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste treatment and resource utilization, and particularly relates to a method for preparing dense calcium hexaluminate and titanium-silicon alloy by aluminothermic reduction of titanium-iron slag and the dense calcium hexaluminate prepared by the method. BACKGROUND

[0002] Calcium hexaluminate (CaAl 12 O 19 , abbreviated as CA6) is the compound with the highest Al2O3 content in the CaO-Al2O3 binary system, and has a theoretical density of 3.79 g·cm -3 . It has high melting point (1875℃), low thermal expansion coefficient (8.0×10 -6 ℃ -1 ) and is not easy to hydrate, and has many other excellent high-temperature properties. In addition, CA6 is chemically stable under high-temperature reducing atmosphere (Li S F, Chen D, Fu L P, et al. Gas corrosion behavior of calcium hexaluminate materials for hydrogen metallurgy[J]. Ceramics International, 2023, 49(10): 15787-15792.), and has broad application prospects in the fields of metallurgy and petrochemical industry. However, CA6 has a unique lamellar growth structure, and the lamellar CA6 grains overlap each other to produce many pores, making it difficult to sinter. Even after sintering at 1750℃, it is difficult to achieve complete densification. The commercially available dense CA6 raw material has a bulk density of only 3.0-3.1 g·cm -3 , and contains a certain amount of CA2 and Al2O3 (Liu X, Andreas Buhr, Gunter Bueche, R P Rather. Bonite, a new synthetic dense CA6 refractory raw material [C]. Proceedings of the Twentieth Refractories Application and Development Technology Seminar. 2017: 153-163.). The low density and high price limit its large-scale use.

[0003] Titanium-iron slag is a waste slag produced in the process of smelting titanium-iron alloy, and its main components are Al2O3, CaO and TiO2, and it also contains a small amount of MgO and SiO2. The amount of titanium-iron slag is huge, and its phase composition is complex, which increases the difficulty of practical application and causes serious environmental burden. At present, titanium-iron slag is mainly used as a cheap raw material to replace bauxite to prepare refractory materials, and a certain scale has been formed. However, the rich titanium resources cannot be utilized. SUMMARY

[0004] The present application aims at the above-mentioned deficiencies of the prior art, and provides a method for preparing dense calcium hexaluminate and titanium-silicon alloy by aluminothermic reduction of ilmenite slag and the dense calcium hexaluminate prepared by the method.

[0005] The method for preparing dense calcium hexaluminate and titanium-silicon alloy by aluminothermic reduction of ilmenite slag according to the present application uses 70-74 wt% of ilmenite slag, 7-10 wt% of Al particles, 6-8 wt% of SiO2 micro powder and 10-15 wt% of lime as raw materials, and the raw materials are loaded into a container and smelted at high temperature. After the smelting is completed, the upper oxide slag and the lower metal melt are poured out and separated in sequence, the lower metal melt is cooled to obtain a titanium-silicon alloy byproduct, and the upper oxide slag is cooled to room temperature to obtain dense calcium hexaluminate.

[0006] Further, the smelting temperature is 1800-2200°C, and the smelting time is 5-8 h.

[0007] Further, the ilmenite slag contains ≥70 wt% of Al2O3, ≥10 wt% of CaO, ≥10 wt% of TiO2, ≤2 wt% of MgO and ≤2 wt% of SiO2.

[0008] Further, the particle size of the ilmenite slag is not greater than 1 mm.

[0009] Further, the lime contains ≥90 wt% of CaO.

[0010] Further, the particle size of the lime is not greater than 3 mm.

[0011] Further, the Al particles contain ≥95 wt% of Al.

[0012] Further, the particle size of the Al particles is not greater than 2.5 mm.

[0013] Further, the SiO2 micro powder contains ≥95 wt% of SiO2.

[0014] A dense calcium hexaluminate prepared by the above-mentioned preparation method.

[0015] The ilmenite slag of this invention is a waste residue generated during the production of ilmenite alloys. Its main components are Al2O3, CaO, and TiO2, and it also contains a small amount of MgO and SiO2. As an industrial solid waste, its large-scale stockpiling will cause serious environmental problems. This invention uses ilmenite slag as the main raw material, adds Al and SiO2 micro powder, and uses a high-temperature aluminothermic reduction method (Formula (1)) to reduce TiO2 in the ilmenite slag to form a titanium-silicon alloy (Ti5Si3). At the same time, lime is added to adjust the composition of the tailings so that the composition of the slag is close to the theoretical ratio of calcium hexaaluminate (CA6). At high temperature, the alloy melt and the oxide slag separate due to the difference in density, and the slag and gold are separated. After cooling, titanium-silicon alloy and dense CA6 are obtained. The by-product titanium-silicon alloy has low density, high specific strength and specific stiffness, and has broad application prospects in the aerospace and metallurgical fields. It can significantly reduce the production cost of dense CA6. Meanwhile, during the cooling process of CaO-Al2O3 melt, CA6 gradually crystallizes (Equation (2)), and the crystals can fully develop to form dense coarse CA6 crystals; the oxide slag after titanium extraction also contains a small amount of TiO2, which can be solidified in CA6 grains during the cooling crystallization process. Titanium doping promotes the growth behavior of CA6 grains along the c-axis direction, promotes the thickening of CA6 lamellar grains, and achieves a higher level of densification.

[0016] 15TiO2+32Al+9SiO2=3Ti5Si3+16Al2O3 (1)

[0017] CaO + 6Al₂O₃ = CaAl 12 O 19 (CA6) (2)

[0018] This invention uses ilmenite slag as raw material and obtains CA6 tailings through high-temperature aluminothermic reduction. Figure 1 As shown in the diagram, TiO2 is solidified within the CA6 grains, promoting the growth of CA6 grains along the c-axis. This results in thicker CA6 lamellar grains, better grain development, and higher density. Figure 2 No other phase diffraction peaks were found in the XRD pattern, indicating higher purity. The calcium hexaaluminate refractory raw material prepared in this invention was tested and found to have a purity of 90–98% and a bulk density of 3.05–3.62 g·cm³. -3 Therefore, the calcium hexaaluminate refractory raw material prepared by this invention has the advantages of low cost, high bulk density, and high purity.

[0019] This invention extracts and utilizes TiO2 from titanium-iron slag, while fully utilizing CaO and Al2O3 in the remaining tailings to prepare dense calcium hexaaluminate, achieving high-value-added utilization of titanium-iron slag. This is of great significance for promoting the treatment and resource utilization of metallurgical solid waste in my country. Attached Figure Description

[0020] Figure 1SEM of CA6 prepared for Example 3;

[0021] Figure 2 XRD of CA6 prepared for Example 3;

[0022] Figure 3 XRD of titanium-silicon alloy prepared for Example 3;

[0023] Figure 4 SEM of titanium-silicon alloy prepared for Example 3;

[0024] Figure 5 SEM of CA6 prepared for Comparative Example 1;

[0025] Figure 6 XRD of CA6 prepared for Comparative Example 1. DETAILED DESCRIPTION

[0026] The following is a specific embodiment of the present application and further describes the technical solutions of the present application in conjunction with the accompanying drawings, but the present application is not limited to these embodiments.

[0027] To avoid repetition, the materials used in the present detailed description are described as follows, and will not be described again in the embodiments:

[0028] The Al2O3 content of the titanium-iron slag is ≥70wt%, the CaO content is ≥10wt%, the TiO2 content is ≥10wt%, the MgO content is ≤2wt%, and the SiO2 content is ≤2wt%, and the particle size distribution of the titanium-iron slag is 1-0mm.

[0029] The CaO content of the lime is ≥90wt%, and the particle size distribution of the lime is 3-0mm.

[0030] The Al content of the aluminum particles is ≥95wt%, and the particle size of the aluminum particles is 2.5-0mm.

[0031] The SiO2 content of the silicon micro-powder is ≥95wt%.

[0032] Example 1

[0033] A titanium-iron slag aluminothermic reduction method for preparing a dense calcium hexaluminate refractory raw material and a preparation method thereof. The preparation method described in the present embodiment is:

[0034] Take 70wt% of titanium slag, 7wt% of Al particles, 8wt% of SiO2 micro powder and 15wt% of lime as raw materials, put the above raw materials into graphite crucible, and then put into induction furnace; power heating to the bottom material melting, then keep warm for 5h, after smelting, the upper layer oxide slag and the lower layer metal melt are poured out respectively, separated, and then put into corundum crucible, the lower layer metal melt is cooled to obtain titanium silicon alloy byproduct, and the upper layer oxide slag is cooled to room temperature to obtain dense calcium hexaluminate refractory raw material.

[0035] The calcium hexaluminate refractory raw material of the embodiment is detected: the purity is 90%; the bulk density is 3.05g·cm -3 .

[0036] Example 2

[0037] A dense calcium hexaluminate refractory raw material prepared by titanium slag aluminothermic reduction and a preparation method thereof. The preparation method of the embodiment is:

[0038] Take 72wt% of titanium slag, 9wt% of Al particles, 7wt% of SiO2 micro powder and 12wt% of lime as raw materials, put the above raw materials into graphite crucible, and then put into induction furnace; power heating to the bottom material melting, then keep warm for 6h, after smelting, the upper layer oxide slag and the lower layer metal melt are poured out respectively, separated, and then put into corundum crucible, the lower layer metal melt is cooled to obtain titanium silicon alloy byproduct, and the upper layer oxide slag is cooled to room temperature to obtain dense calcium hexaluminate refractory raw material.

[0039] The calcium hexaluminate refractory raw material of the embodiment is detected: the purity is 94%; the bulk density is 3.20g·cm -3 .

[0040] Example 3

[0041] A dense calcium hexaluminate refractory raw material prepared by titanium slag aluminothermic reduction and a preparation method thereof. The preparation method of the embodiment is:

[0042] Take 74wt% of titanium slag, 10wt% of Al particles, 6wt% of SiO2 micro powder and 10wt% of lime as raw materials, put the above raw materials into graphite crucible, and then put into induction furnace; power heating to the bottom material melting, then keep warm for 8h, after smelting, the upper layer oxide slag and the lower layer metal melt are poured out respectively, separated, and then put into corundum crucible, the lower layer metal melt is cooled to obtain titanium silicon alloy byproduct, and the upper layer oxide slag is cooled to room temperature to obtain dense calcium hexaluminate refractory raw material.

[0043] The calcium hexaluminate refractory raw material of the embodiment is detected: the purity is 98%; the bulk density is 3.62g·cm -3 .

[0044] This invention uses ilmenite slag as raw material and obtains CA6 tailings through high-temperature aluminothermic reduction. Figure 1 As shown in the diagram, TiO2 is solidified within the CA6 grains, promoting the growth of CA6 grains along the c-axis. This results in thicker CA6 lamellar grains, better grain development, and higher density. Figure 2 No other phase diffraction peaks were found in the XRD pattern, indicating higher purity.

[0045] Table 1 shows the elemental analysis of the titanium-silicon alloy prepared in Example 3. Figure 3 The XRD pattern of the titanium-silicon alloy prepared in Example 3; Figure 4 A scanning electron microscope image of the titanium-silicon alloy prepared in Example 3;

[0046] Table 1 Figure 4 Elemental composition (at.%) at each point in the table.

[0047]

[0048] Comparative Example 1

[0049] CA6 (prepared from activated alumina and Secar71 cement) Figure 5 (As shown) They are mostly rod-shaped, irregular in shape, and granular, with only a small number being plate-shaped, and the grains are poorly developed and have low density; Figure 6 The XRD patterns show that unreacted α-Al2O3 phase and intermediate product CA2 were present in the samples after heat treatment at different temperatures, indicating low purity (Li Xinwei, Li Zhijian, Wu Feng, et al. Effects of calcium source type and calcination temperature on the synthesis of flake calcium hexaaluminate [J]. Refractory Materials. 2017, 51(2): 131-133.)

[0050] For any points not covered above, existing technologies shall apply.

[0051] Although specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them, without departing from the direction of the invention or exceeding the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for simultaneously preparing dense calcium hexaaluminate and titanium-silicon alloy by aluminothermic reduction of ferrotitanium slag, characterized in that: Using 70-74 wt% ilmenite slag, 7-10 wt% Al particles, 6-8 wt% SiO2 micro powder, and 10-15 wt% lime as raw materials, the raw materials are placed in a container and smelted at high temperature. After smelting, the upper oxide slag and the lower metal melt are poured out and separated in sequence. The lower metal melt is cooled to obtain a titanium-silicon alloy by-product, and the upper oxide slag is cooled to room temperature to obtain dense calcium hexaaluminate. The ilmenite slag has an Al2O3 content ≥ 70 wt%, a CaO content ≥ 10 wt%, a TiO2 content ≥ 10 wt%, a MgO content ≤ 2 wt%, and a SiO2 content ≤ 2 wt%.

2. The method for simultaneously preparing dense calcium hexaaluminate and titanium-silicon alloy by aluminothermic reduction of ferrotitanium slag as described in claim 1, characterized in that: The melting temperature is 1800-2200℃, and the melting time is 5-8 hours.

3. The method for simultaneously preparing dense calcium hexaaluminate and titanium-silicon alloy by aluminothermic reduction of ferrotitanium slag as described in claim 1, characterized in that: The particle size of the ilmenite slag is no greater than 1 mm.

4. The method for simultaneously preparing dense calcium hexaaluminate and titanium-silicon alloy by aluminothermic reduction of ferrotitanium slag as described in claim 1, characterized in that: The lime contains ≥ 90 wt% CaO.

5. The method for simultaneously preparing dense calcium hexaaluminate and titanium-silicon alloy by aluminothermic reduction of ferrotitanium slag as described in claim 1, characterized in that: The particle size of the lime is no greater than 3 mm.

6. The method for simultaneously preparing dense calcium hexaaluminate and titanium-silicon alloy by aluminothermic reduction of ferrotitanium slag as described in claim 1, characterized in that: The aluminum particles contain ≥95 wt% Al.

7. The method for simultaneously preparing dense calcium hexaaluminate and titanium-silicon alloy by aluminothermic reduction of ferrotitanium slag as described in claim 1, characterized in that: The aluminum particles have a particle size of no more than 2.5 mm.

8. The method for simultaneously preparing dense calcium hexaaluminate and titanium-silicon alloy by aluminothermic reduction of ferrotitanium slag as described in claim 1, characterized in that: The silicon micropowder has a SiO2 content of ≥95 wt%.

9. A dense calcium hexaaluminate prepared by the preparation method according to any one of claims 1-8.

Images