A method for preparing aluminum titanate-anorthite heat storage ceramic by using titanium-iron slag

Abstract

The application discloses a method for preparing aluminum titanate-anorthite heat storage ceramics by using titaniferous slag, which comprises the following steps: calcining and removing impurities from raw materials including the titaniferous slag, MgO, TiO2 and SiO2, then carrying out ball milling and mixing, adding polyvinyl alcohol for granulation, aging, dry pressing and sintering in sequence, and obtaining the aluminum titanate-anorthite heat storage ceramics. The method has the advantages of simple technological process, high utilization rate of the titaniferous slag, high economic benefits, low cost, and the like. The obtained aluminum titanate-anorthite heat storage ceramics has the advantages of high heat storage capacity and good thermal shock resistance.

Description

TECHNICAL FIELD

[0001] The application relates to a method for preparing aluminum titanate-anorthite heat storage ceramics from titanium-iron slag, and belongs to the technical field of heat storage ceramics. TECHNICAL BACKGROUND

[0002] Titanium-iron slag, also known as aluminum-titanium slag, is a common by-product in the smelting process of ferroaluminum-titanium. Under normal circumstances, about 1.2-1.5 tons of titanium-iron slag is discharged for every ton of ferroaluminum-titanium produced. If the large amount of titanium-iron slag is not disposed of in a timely manner and is randomly piled up, land resources will be wasted. In addition, the toxic metal ions existing in the titanium-iron slag cause serious environmental pollution. Therefore, under the background of the continuous development of society, the effective utilization of titanium-iron slag becomes more and more important.

[0003] At present, many researchers begin to prepare heat storage ceramics from solid waste. For example, Chinese patent CN115466103A discloses a magnesium-aluminum spinel heat storage ceramic and a preparation method thereof. The method uses fused magnesia as a raw material to prepare a ceramic with magnesium-aluminum spinel as a main crystal phase and a heat storage density of 1397 KJ / kg (room temperature-1000 DEG C). Chinese patent CN117049863A discloses a magnesium olivine-based solar heat storage ceramic and a preparation method and application thereof. The invention discloses a heat storage ceramic with magnesium olivine as a main crystal phase. The above technologies all prepare heat storage materials with excellent performance, but the thermal expansion coefficients of magnesium-aluminum spinel and magnesium olivine are relatively large, which is not conducive to the thermal shock resistance of the heat storage ceramic.

[0004] The main components of titanium-iron slag are Al2O3, TiO2 and CaO, and the composition is similar to that of aluminum titanate. Aluminum titanate (Al2TiO5, AT) has excellent properties such as low thermal expansion and high temperature resistance, and is an ideal heat storage material. However, the high content of CaO in the titanium-iron slag is not conducive to the thermal shock resistance of the whole ceramic. Therefore, it is of great significance and prospect to find a heat storage ceramic with excellent thermal shock resistance prepared from titanium-iron slag as the main raw material. SUMMARY

[0005] In view of the deficiencies in the prior art in which titanium-iron slag is used to prepare aluminum titanate-anorthite heat storage ceramics, the purpose of the present application is to provide a simple process for preparing aluminum titanate-anorthite heat storage ceramics. The method utilizes the solid-phase reaction of SiO2 added with Al2O3 and CaO in the titanium-iron slag to convert into aluminum titanate-anorthite through a specific process, which not only realizes the recycling of titanium-iron slag resources, but also avoids the technical problem that the high content of CaO in the titanium-iron slag is not conducive to the thermal shock resistance of the ceramic. The heat storage ceramic prepared by the method has the advantages of low thermal expansion coefficient, high thermal density and good thermal shock resistance.

[0006] In order to achieve the above technical purposes, the application provides a method for preparing aluminum titanate-anorthite heat storage ceramic by using ferrotitanium slag, which comprises the following steps: calcining and removing impurities from raw materials including ferrotitanium slag, MgO, TiO2 and SiO2, then sequentially performing ball milling, adding polyvinyl alcohol for granulation, aging, dry pressing and sintering, and finally obtaining the aluminum titanate-anorthite heat storage ceramic.

[0007] The key of the application lies in that CaO and Al2O3 components and SiO2 contained in the ferrotitanium slag are used to generate anorthite CaAl2Si2O8 through high-temperature solid-phase reaction, thereby avoiding the problem that the high content of CaO in the ferrotitanium slag is not conducive to the thermal shock resistance of the ceramic as a whole, and the converted anorthite CaAl2Si2O8 has the characteristics of high temperature resistance and small thermal expansion. Meanwhile, Al2O3 and TiO2 contained in the ferrotitanium slag are easily converted into aluminum titanate material with low thermal expansion and high temperature resistance. In addition, the added MgO in the raw materials can not only reduce the sintering temperature and viscosity of the ceramic, promote the combination and melting of the ceramic particles, and be conducive to the sintering of the ceramic, but also can adjust the crystal phase composition and phase equilibrium of the ceramic, help to form the phase structure required by the aluminum titanate-anorthite ceramic, inhibit the grain growth of the aluminum titanate-anorthite ceramic at high temperature, and improve the density and mechanical properties of the ceramic, so that the aluminum titanate-anorthite heat storage ceramic with excellent thermal shock resistance and heat storage density is finally obtained. In the preparation process of the application, the chemical reaction shown in formula 1 mainly occurs:

[0008] Al2O3+TiO2→TiAlO4

[0009] 2CaO+Al2O3+5SiO2→CaAl2Si2O8+2SiO2

[0010] Formula 1

[0011] As a preferred scheme, the ferrotitanium slag is a metallurgical slag produced by smelting ferrotitanium slag alloy by aluminum thermal reduction method, and the content of Al2O3 in the ferrotitanium slag is greater than 65wt%. The high content of the ferrotitanium slag in the application is conducive to the subsequent reaction of CaO with Al2O3 and SiO2, and fully realizes the recycling of ferrotitanium slag solid waste; if the content of Al2O3 is too low, CaO cannot be completely converted into anorthite, thereby affecting the performance of the final product.

[0012] The content of CaO in the ferrotitanium slag used in the application is 10-15wt%, and the content of TiO2 is 15-18wt%.

[0013] As a preferred scheme, the calcination impurity removal conditions are: increasing the temperature to 800-1000℃ at a rate of 3-5℃ / min, calcining for 12-24h, and then decreasing the temperature to room temperature at a rate of 3-5℃ / min. The present application increases the calcination temperature to accelerate the chemical reaction rate, promote the oxidative decomposition and volatilization of impurities and moisture, and facilitate the removal of impurities and moisture. However, if the temperature is too high, it may cause excessive sintering, making it difficult for impurities to volatilize or causing the target product to be burned. The calcination time affects the completeness of the calcination reaction. A longer calcination time allows the reaction to proceed completely, thereby facilitating the removal of impurities and moisture. However, a too long calcination time may increase energy consumption and reduce product quality.

[0014] The inventors have found that it is necessary to remove moisture during the preparation of the aluminum titanate-anorthite ceramic from titanium slag. The removal of moisture can avoid sintering problems, promote the conversion of the anorthite phase, improve the thermal stability, and reduce the sintering temperature, thereby ensuring the performance and quality of the material.

[0015] As a preferred scheme, the raw materials consist of the following materials in parts by mass: titanium slag 60-75 parts; MgO 0.1-5 parts; TiO2 5-23 parts; SiO2 13-16 parts. The titanium slag in the raw materials is mainly to provide the raw materials Al2O3, SiO2, and TiO2 for synthesizing aluminum titanate and anorthite. However, the content of TiO2 is insufficient to form aluminum titanate, so a certain amount of TiO2 needs to be added additionally. By adding a certain amount of SiO2, the silicon-oxygen ratio in the raw materials can be adjusted, thereby facilitating the formation of anorthite. The higher the amounts of titanium slag and SiO2, the higher the flexural strength and porosity of the prepared heat storage ceramic, but the heat storage performance and shock resistance will decrease to a certain extent. However, if the amount of SiO2 is too small, the thermal shock resistance of the ceramic will also decrease significantly. The main role of adding MgO is to inhibit the grain growth of the aluminum titanate-anorthite ceramic at high temperatures, thereby improving the density and mechanical properties of the ceramic. If the amount of MgO is too low, the required sintering temperature will increase, which will decrease the density and mechanical properties of the ceramic. If the amount of MgO is too high, the stability of the ceramic material will decrease, and even undesirable phases will be formed. Therefore, only when the amounts of the components are within the ranges of the present application, can the ceramic with excellent thermal shock resistance and heat storage performance be prepared. Further preferably, the amounts of the components are as follows: titanium slag 60-65 parts; MgO 4-5 parts; TiO2 17-23 parts; SiO2 13-14 parts.

[0016] As a preferred scheme, the ball milling conditions are: a speed of 300-500r / min, a time of 12-24h, and a ball-to-material ratio of 1-2:1. The ball milling can mix the raw materials to make the sizes and shapes of the particles of the various raw materials more uniform, and also has an activating effect, thereby facilitating the subsequent processing and molding.

[0017] As a preferred scheme, the powder after ball milling needs to be dried, the drying temperature is 100-110 DEG C, and the time is 12-24h. The drying treatment is mainly to remove the moisture in the powder.

[0018] As a preferred scheme, the mass ratio of polyvinyl alcohol to raw material is (0.1-0.15):1; and the aging time is 12-24h. The added polyvinyl alcohol increases the adhesion between the powder particles and the morphological stability, and promotes the formation and growth of the particles.

[0019] As a preferred scheme, the dry pressing forming condition is that the pressure is 10-15MPa, and the pressure maintaining time is 1-2min. In the selected pressure range, the density of the ceramic material is ensured.

[0020] As a preferred scheme, the green body after dry pressing forming needs to be dried, the drying temperature is 100-110 DEG C, and the time is 12-24h.

[0021] As a preferred scheme, the sintering condition is that the temperature is increased to 300 DEG C at a rate of 2-3 DEG C / min, and the temperature is maintained for 0.5-1h; then the temperature is increased to 600 DEG C at a rate of 2-3 DEG C / min, and the temperature is maintained for 0.5-1h; then the temperature is increased to 900 DEG C at a rate of 2-3 DEG C / min, and the temperature is maintained for 0.5-1h; finally the temperature is increased to 1370-1375 DEG C at a rate of 2-3 DEG C / min, and the temperature is maintained for 2-3h.

[0022] Compared with the prior art, the application has the following beneficial effects:

[0023] 1) The application uses titanium slag as raw material, adjusts the silicon oxygen ratio by adding SiO2, and uses the Al2O3 contained in the titanium slag to perform calcination, ball milling, forming and sintering, etc., so that CaO in the titanium slag which affects the thermal shock resistance of the ceramic is converted into calcium feldspar CaAl2Si2O8, and the prepared aluminum titanate-calcium feldspar heat storage ceramic has a volume density of 3.04-3.11g / cm -3 , the heat storage density of unit volume is up to 1.54KJ / cm 3 (25-500 DEG C), the heat storage capacity is relatively strong, the thermal expansion coefficient is low, is 3.18-5.99 / DEG C (25-1000 DEG C), the critical temperature difference of water cooling is up to 650 DEG C, and the thermal shock resistance is good.

[0024] 2) The process flow of the application is simple, the utilization rate of the titanium slag is up to 60-75%, the economic benefit is high, the cost is low, and the application has important significance for the efficient comprehensive utilization of the titanium slag resource.

[0025] 3) The preparation method of the application obtains aluminum titanate-anorthite heat storage ceramic with excellent thermal shock resistance and heat storage density, and ensures the mechanical properties of the material, and the maximum bending strength is 137.78 MPa. DETAILED DESCRIPTION

[0026] The application will be further described below in conjunction with specific examples, but the protection scope of the application is not limited to the following specific examples. Obviously, the following described examples are only a part of examples, and all other examples obtained by those skilled in the art without creative labor still belong to the protection scope of the application.

[0027] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the application can be purchased from the market or can be prepared by existing methods.

[0028] In the examples and comparative examples of the application, the content of Al2O3 in the ilmenite slag is greater than 65wt%, the content of CaO is 13wt%, and the content of TiO2 is 17wt%.

[0029] Example 1

[0030] A method for preparing aluminum titanate-anorthite ceramic by using ilmenite slag, and the specific steps are as follows:

[0031] (1) Raw material calcination: the ilmenite slag produced by smelting ilmenite alloy by aluminum thermal reduction method, MgO, TiO2 and SiO2 are placed in a box furnace for calcination and impurity removal, the temperature is set to 1000℃, the calcination time is 12h, the heating rate is 3℃ / min, and the cooling rate is 5℃ / min.

[0032] (2) Ball milling and mixing: 60 parts of the impurity-removed ilmenite slag, 4 parts of MgO, 23 parts of TiO2 and 13 parts of SiO2 are mixed, and a planetary ball mill is used for ball milling for 12h, the ball milling speed is 300-500r / min, and the ball-to-material ratio is 2:1.

[0033] (3) Granulation and aging: the well-milled mixture is placed in an oven for drying, the temperature is 110℃, and the time is 24h; then polyvinyl alcohol is added to the dried mixture for granulation treatment, the mass ratio of polyvinyl alcohol to raw materials is 0.1:1, and the granulated mixture is aged at room temperature for 24h.

[0034] (4) Dry pressing: the aged powder is pressed into a shape by a press machine, the forming pressure is 12MPa, and the pressure holding time is 1min.

[0035] (5) Drying: the formed green body is dried in an oven at 110℃ for 24h.

[0036] (6) Sintering: Put the dried green body into a box furnace for sintering to obtain aluminum titanate-orthoclase heat storage ceramic. The sintering schedule is: the heating rate is 2 ℃ / min below 1000 ℃, the heating rate is 3 ℃ / min above 1000 ℃, and the holding time is 1 h at 300 ℃, 600 ℃ and 900 ℃ respectively, and the holding time is 2 h at the highest temperature 1370 ℃.

[0037] The aluminum titanate-orthoclase heat storage ceramic obtained in this example is tested for performance, the porosity is 4.54%, the bulk density reaches 3.11 g / cm 3 , the heat storage density is 1.54 KJ / cm 3 (25-500 ℃), and the bending strength reaches 75.92 MPa. The thermal expansion coefficient is 3.18 / ℃ (25-1000 ℃), the critical thermal shock temperature difference of water cooling is 650 ℃ measured according to the ASTM C1525-18 standard, and the thermal shock resistance is good.

[0038] Example 2

[0039] A method for preparing aluminum titanate-orthoclase ceramic from titanium slag, the specific steps are as follows:

[0040] (1) Raw material calcination: Put the titanium slag produced by smelting titanium-iron alloy by aluminothermic reduction, MgO, TiO2 and SiO2 into a box furnace for calcination and impurity removal, the temperature is set to 1000 ℃, the time is 12 h, and the heating rate is 3 ℃ / min and the cooling rate is 5 ℃ / min.

[0041] (2) Ball milling and mixing: Mix 65 parts of titanium slag after impurity removal, 4 parts of MgO, 17 parts of TiO2 and 14 parts of SiO2, ball mill for 12 h with a planetary ball mill, the ball milling speed is 300-500 r / min, and the ball-to-material ratio is 2:1 to obtain uniformly mixed powder.

[0042] (3) Granulation and aging: Put the ball-milled mixture into an oven for drying at a temperature of 110 ℃ for 24 h; then add polyvinyl alcohol to the dried mixture for granulation treatment, the mass ratio of polyvinyl alcohol to mixture is 0.1:1, and the granulated mixture is aged at room temperature for 24 h.

[0043] (4) Dry pressing: Use a press to press the aged powder into a shape, the forming pressure is 10 MPa, and the pressure holding time is 1 min.

[0044] (5) Drying: Put the formed green body into an oven at 110 ℃ for drying for 24 h.

[0045] (6) Sintering: Put the dried green body into a box furnace for sintering to obtain aluminum titanate-orthoclase heat storage ceramic. The sintering schedule is: the heating rate is 2 ℃ / min below 1000 ℃, the heating rate is 3 ℃ / min above 1000 ℃, and the holding time is 1 h at 300 ℃, 600 ℃ and 900 ℃ respectively, and the holding time is 2 h at the highest temperature 1370 ℃.

[0046] The aluminum titanate-orthoclase heat storage ceramic obtained in this example is tested for performance, the porosity is 4.69%, the bulk density reaches 3.11 g / cm 3 , the heat storage density is 1.49 KJ / cm 3 (25-500 ℃), and the bending strength reaches 92.01 MPa. The thermal expansion coefficient is 4.18 / ℃ (25-1000 ℃), the critical thermal shock temperature difference of water cooling is 500 ℃ measured according to the ASTM C1525-18 standard, and the thermal shock resistance is good.

[0047] Example 3

[0048] A method for preparing aluminum titanate-orthoclase ceramic from titanium slag, the specific steps are as follows:

[0049] (1) Raw material calcination: Put the titanium slag produced by smelting titanium-iron alloy by aluminothermic reduction, MgO, TiO2 and SiO2 into a box furnace for calcination, the temperature is set to 1000 ℃, the time is 12 h, the heating rate is 3 ℃ / min, and the cooling rate is 5 ℃ / min.

[0050] (2) Ball milling and mixing: Mix 75 parts of titanium slag after impurity removal, 4 parts of MgO, 5 parts of TiO2 and 16 parts of SiO2, ball mill for 12 h with a planetary ball mill, the ball milling speed is 300-500 r / min, and the ball-to-material ratio is 2:1 to obtain uniformly mixed powder.

[0051] (3) Granulation and aging: Put the ball-milled mixture into an oven for drying at a temperature of 110 ℃ for 24 h, then add polyvinyl alcohol to the dried mixture for granulation treatment, the mass ratio of polyvinyl alcohol to mixture is 0.1:1, and the granulated mixture is aged at room temperature for 24 h.

[0052] (4) Dry pressing: Use a press to press the aged powder into a shape, the forming pressure is 10 MPa, and the pressure holding time is 1 min.

[0053] (5) Drying: Dry the formed green body in an oven at 110 ℃ for 24 h.

[0054] (6) Sintering: Put the dried green body into a box furnace for sintering to obtain the aluminum titanate-anorthite heat storage ceramic. The sintering schedule is as follows: the heating rate is 2 ℃ / min below 1000 ℃, and the heating rate is 3 ℃ / min above 1000 ℃, and the temperature is kept at 300 ℃, 600 ℃ and 900 ℃ for 1 h respectively, and the temperature is kept at the highest temperature 1375 ℃ for 2 h.

[0055] The aluminum titanate-anorthite heat storage ceramic obtained in this example is tested for performance, and the porosity is 4.91%, the bulk density reaches 3.04 g / cm 3 , the heat storage density is 1.43 KJ / cm 3 (25-500 ℃), and the bending strength reaches 137.78 MPa. The thermal expansion coefficient is 5.99 / ℃ (25-1000 ℃), and the critical thermal shock temperature difference of water cooling is 300 ℃ according to the ASTM C1525-18 standard.

[0056] Comparative Example 1

[0057] The difference between this comparative example and Example 1 is only that SiO2 is not added, and the rest of the steps and conditions are consistent. The experimental results show that the thermal shock resistance of the prepared ceramic material is greatly reduced, and the critical thermal shock temperature difference of water cooling is only 100 ℃ according to the ASTM C1525-18 standard, and the thermal expansion coefficient is 7.01 / ℃ (25-1000 ℃).

[0058] Comparative Example 2

[0059] The difference between this comparative example and Example 1 is only that the raw materials are not calcined and impurities are removed, and the rest of the steps and conditions are consistent. The experimental results show that due to the high moisture and impurities in the raw materials without calcination and impurity removal, the prepared ceramic material has cracking phenomenon.

Claims

1. A method for preparing aluminum titanate-anorthite heat storage ceramics using ilmenite slag, characterized by comprising the following steps: The raw materials including titanium slag, MgO, TiO2 and SiO2 are calcined to remove impurities, then ball-milled, granulated by adding polyvinyl alcohol, stale, dry-pressed and sintered in sequence, so as to obtain the product. ​ The titanium slag is a metallurgical slag produced in smelting of ferrotitanium alloy by aluminum thermal reduction method, wherein the content of Al2O3 is greater than 65wt%, the content of CaO is 10-15wt%, and the content of TiO2 is 15-18wt%. The raw materials for mixing are composed of the following materials in parts by mass: titanium slag 60-75 parts, MgO 0.1-5 parts, TiO2 5-23 parts, and SiO2 13-16 parts.

2. The method for preparing aluminum titanate-anorthite heat storage ceramics from ilmenite slag according to claim 1, characterized in that: The calcination conditions are as follows: heating to 800-1000℃ at a rate of 3-5℃ / min, calcining for 12-24h, and then cooling to room temperature at a rate of 3-5℃ / min.

3. The method for preparing aluminum titanate-anorthite heat storage ceramics from ilmenite slag according to claim 2, characterized in that: The ball-milling conditions are as follows: speed of 300-500r / min, time of 12-24h, and ball-to-material ratio of 1-2:

1.

4. The method for preparing aluminum titanate-anorthite heat storage ceramics from ilmenite slag according to claim 1, characterized in that: The mass ratio of polyvinyl alcohol to raw materials is (0.1-0.15):

1. The stale time is 12-24h.

5. The method for preparing aluminum titanate-anorthite heat storage ceramics from ilmenite slag according to claim 4, characterized in that: The dry-pressing conditions are as follows: pressure of 10-15MPa, and pressure maintaining time of 1-2min.

6. The method for preparing aluminum titanate-anorthite heat storage ceramics from ilmenite slag according to claim 5, characterized in that: The sintering conditions are as follows: first heating to 300℃ at a rate of 2-3℃ / min, maintaining for 0.5-1h; then heating to 600℃ at a rate of 2-3℃ / min, maintaining for 0.5-1h; then heating to 900℃ at a rate of 2-3℃ / min, maintaining for 0.5-1h; finally heating to 1370-1375℃ at a rate of 2-3℃ / min, maintaining for 2-3h.