A method for preparing cordierite ceramics from secondary aluminum dross

Abstract

The application provides a method for preparing a cordierite ceramic from secondary aluminum dross, the method comprising: mixing the secondary aluminum dross with a mineralizer and calcining to obtain a mineralized material; mixing the mineralized material with an acid solution and acidolysis to obtain an acidolysis residue; mixing the acidolysis residue with a silicon source and / or a magnesium source and ball milling to obtain a mixed material; dry-pressing the mixed material into a shape and sintering to obtain the cordierite ceramic. The method provided by the application realizes directional separation and deep removal of impurity components in the secondary aluminum dross by mineralization calcination-acidolysis regulation and coordination, and realizes step-by-step utilization of the impurity elements F and Cl, and can co-produce calcium fluoride and chlorinated salt fluxing agents. The secondary aluminum dross is used to prepare a cordierite ceramic, and the obtained ceramic material has high main phase content, high bulk density, low apparent porosity and low thermal expansion coefficient, and has good economic, social and environmental benefits.

Description

Technical Field

[0001] This invention belongs to the field of solid waste resource utilization technology, and relates to a method for the resource utilization of secondary aluminum ash, and more particularly to a method for preparing cordierite ceramics from secondary aluminum ash. Background Technology

[0002] Aluminum ash is the slag, skimmed dross, or furnace slag produced on the surface of the melt during the transfer of molten aluminum from electrolytic aluminum, alloying of molten aluminum, and aluminum refining and casting processes. The newly generated solid slag has a high aluminum content (15-75%) and is commonly referred to as aluminum ash slag. Aluminum ash slag treatment technology is mature. After extracting more than 80% of the metallic aluminum through heat treatment or cold treatment, the resulting fine ash with smaller particle size is called secondary aluminum ash, and its annual emissions are conservatively estimated to be over 4 million tons.

[0003] Secondary aluminum ash has a complex composition, mainly containing metallic aluminum (3-8%), aluminum oxide (60-80%), aluminum nitride (1-10%), chlorides (1-10%), and various fluorides (1-5%). It may also contain SiO2, Fe2O3, and NaAl depending on its source. 11 O 17 It contains other impurities such as metals Cu, Zn, Mn, and Cr. Currently, its main applications include the preparation of alumina, steelmaking deoxidizers, cement, and various refractory materials. However, most of these applications cannot be industrialized due to poor product quality, long processes, and low resource utilization rates.

[0004] Cordierite (2MgO·2Al2O3·5SiO2) is a silicate ceramic material with excellent physical properties. It is widely and maturely used in applications such as saggers, refractory materials for electric heaters, arc-resistant ceramics, chemical industrial equipment, and catalyst carriers for automotive exhaust purification systems. However, cordierite has a narrow firing temperature range, and the chemical composition of the raw materials and impurity ions can severely affect its firing and performance.

[0005] CN10858526A discloses a cordierite thermal insulation refractory ball and its preparation method. The method uses cordierite as the main material and aluminum ash, talc, sawdust, etc., as auxiliary materials. The cordierite thermal insulation refractory ball is prepared through a process of stirring, pelletizing, and calcination. However, this method only uses aluminum ash as the aluminum source, and the resulting refractory ball suffers from problems such as low bulk density and low flexural strength.

[0006] CN113860861A discloses a method for preparing cordierite mullite from aluminum ash. The method involves first calcining and cooling secondary aluminum ash at 1000-1200℃, then washing it with water to remove aluminum nitride, chlorides, and a small amount of water-soluble fluorides. Further, the secondary aluminum ash is shaped, dried, and calcined to prepare cordierite mullite material. While this method removes most of the toxic components such as F, Cl, and N from the secondary aluminum ash through calcination and washing, the secondary aluminum ash still contains a large amount of NaAl. 11 O 17 The method is difficult to remove heavy metal impurities such as Na3AlF6, K3AlF6, Cu, Zn, and Cr. In addition, the material prepared by this method has a low cordierite phase content and a high glass phase content, which seriously affects the performance of the product.

[0007] CN111960851A discloses a method for preparing cordierite ceramic filter plates based on aluminum ash raw materials. Aluminum ash, talc, and quartz sand are used as main materials, and a binder and impurity remover are added. The cordierite phase ceramic filter plates are then prepared by oxygen-enriched calcination. This method removes sodium and potassium salts from the aluminum ash at high temperatures above 1000℃ using the impurity remover, but a large number of impurities remain. Furthermore, it requires that the secondary aluminum ash contain SiO2 ≤ 0.5%, CaO ≤ 0.5%, MgO ≤ 0.5%, and Fe2O3 ≤ 0.5%, which is difficult for most secondary aluminum ash to meet.

[0008] It is evident that the numerous toxic components such as N, Cl, and F, as well as impurity elements such as Cu, Zn, Mn, Na, K, and Fe in secondary aluminum ash are the main factors limiting the preparation of high-end ceramic materials from secondary aluminum ash. How to effectively and deeply separate the toxic components and impurity elements in secondary aluminum ash is the key to improving its resource utilization, and it is an urgent problem that needs to be solved by those skilled in the art. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing cordierite ceramics from secondary aluminum ash, which deeply removes toxic elements and impurities from secondary aluminum ash, breaks through the technical bottleneck of the difficulty in preparing high-value functional materials from secondary aluminum ash, realizes the high-value resource utilization of secondary aluminum ash, and has good economic, social and environmental benefits.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] This invention provides a method for preparing cordierite ceramics using secondary aluminum ash, the method comprising the following steps:

[0012] (1) Mix secondary aluminum ash with mineralizing agent and calcine to obtain mineralized material;

[0013] (2) The mineralized material obtained in step (1) is mixed with acid solution for acid hydrolysis to obtain acid hydrolysis residue and mixed solution;

[0014] (3) According to the stoichiometric ratio of cordierite, the acid hydrolysis residue obtained in step (2) is mixed with a silicon source and / or a magnesium source and ball-milled to obtain a mixture;

[0015] (4) The mixture obtained in step (3) is dry-pressed into shape to obtain a green blank;

[0016] (5) The green body obtained in step (4) is sintered to obtain cordierite ceramic.

[0017] The method provided by this invention firstly transforms aluminum-containing components such as aluminum particles, aluminum nitride, γ-alumina, and aluminum alloy particles in secondary aluminum ash into α-Al2O3, which has poor chemical reactivity, through the mineralization-induced transformation effect of a mineralizing agent. At the same time, heavy metal elements in alloys such as Al-Fe, Al-Mn, Al-Cu, and Al-Zn in the secondary aluminum ash are transformed into their corresponding oxides, and the volatilization of the formed fluoride and chloride salts is inhibited. Then, impurities such as F, Cl, Na, K, and heavy metals in the secondary aluminum ash are removed through acid hydrolysis. The impurities such as F and Cl enter the acid hydrolysis solution, which can be further used to prepare fluoride and chloride salts, while minimizing the loss of aluminum components. Through the synergistic coupling effect of mineralization roasting and acid hydrolysis, the impurities are removed in stages and separated in a directional manner. The main components of the acid hydrolysis residue are alpha-alumina, magnesium aluminum spinel, and silicon dioxide. Then, by adding silicon and / or magnesium sources, ball milling, pressing, and sintering, high-quality cordierite ceramics are obtained, realizing the high-value resource utilization of secondary aluminum ash.

[0018] Preferably, the mineralizing agent in step (1) includes any one or a combination of at least two of cryolite, sodium fluoride, aluminum fluoride, magnesium fluoride, or ammonium chloride. Typical but non-limiting combinations include a combination of cryolite and sodium fluoride, a combination of cryolite and magnesium fluoride, a combination of sodium fluoride and ammonium chloride, a combination of magnesium fluoride and ammonium chloride, a combination of aluminum fluoride and ammonium chloride, or a combination of cryolite, magnesium fluoride, and ammonium chloride.

[0019] Preferably, the amount of mineralizer added in step (1) is 1-10 wt% of the total mass of secondary aluminum ash and mineralizer, for example, it can be 1 wt%, 2 wt%, 4 wt%, 5 wt%, 6 wt%, 8 wt% or 10 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] Preferably, the roasting temperature in step (1) is 500-900℃, for example, it can be 500℃, 600℃, 700℃, 800℃ or 900℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] The preferred calcination temperature of this invention is <1000℃. Through the induced transformation of mineralization, the aluminum-containing components in the secondary aluminum ash are directionally transformed into stable α-Al2O3, and the heavy metal elements in alloys such as Al-Fe, Al-Mn, Al-Cu, and Al-Zn are transformed into their corresponding oxides.

[0022] Preferably, the roasting time in step (1) is 30-300 min, for example, it can be 30 min, 50 min, 100 min, 150 min, 200 min, 250 min or 300 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] By using the preferred mineralizer, mineralizer addition amount, and calcination temperature and time of this invention, aluminum nitride can be efficiently removed, and aluminum-containing phases such as aluminum nitride and aluminum metal can be directionally transformed into stable α-Al2O3. At the same time, the fluoride salts and chloride salts in the secondary aluminum ash are almost non-volatile.

[0024] Preferably, the acid solution in step (2) includes a hydrochloric acid solution.

[0025] Preferably, the concentration of the acid solution in step (2) is 30-200 g / L, for example, it can be 30 g / L, 50 g / L, 80 g / L, 100 g / L, 120 g / L, 150 g / L, 180 g / L or 200 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the liquid-solid ratio of the acid solution to the mineralized material in step (2) is 3-20 mL / g, for example, it can be 3 mL / g, 5 mL / g, 8 mL / g, 10 mL / g, 12 mL / g, 15 mL / g, 18 mL / g or 20 mL / g, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the acid hydrolysis temperature in step (2) is 30-90℃, for example, it can be 30℃, 40℃, 50℃, 60℃, 70℃, 80℃ or 90℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the acid hydrolysis time in step (2) is 30-300 min, for example, it can be 30 min, 50 min, 100 min, 150 min, 200 min, 250 min or 300 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] The preferred acidolysis conditions of this invention can effectively achieve the stepwise separation and utilization of toxic elements such as F and Cl, and can also effectively achieve the deep removal of elements such as Na, K, Cu, Zn, Mn, Fe, and Si.

[0030] Preferably, the silicon source in step (3) includes any one or at least two combinations of talc, kaolin, silica, microsilica, or quartz. Typical but non-limiting combinations include combinations of talc and kaolin, kaolin and silica, microsilica and quartz, talc, kaolin and silica, silica, microsilica and quartz, or talc, kaolin, silica, microsilica and quartz.

[0031] Preferably, the magnesium source in step (3) includes any one or at least two combinations of talc, magnesium oxide, magnesite, or magnesium hydroxide. Typical but non-limiting combinations include combinations of talc and magnesium oxide, magnesite and magnesium hydroxide, talc, magnesium oxide and magnesite, magnesium oxide, magnesite and magnesium hydroxide, or talc, magnesium oxide, magnesite and magnesium hydroxide.

[0032] Preferably, the D50 particle size of the mixture in step (3) is 38-150μm, for example, it can be 38μm, 50μm, 80μm, 100μm, 120μm or 150μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the pressure of the dry pressing in step (4) is 20-200 MPa, for example, it can be 20 MPa, 50 MPa, 80 MPa, 100 MPa, 120 MPa, 150 MPa, 180 MPa or 200 MPa, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0034] Preferably, the sintering temperature in step (5) is 1100-1500℃, for example, it can be 1100℃, 1150℃, 1200℃, 1250℃, 1300℃, 1350℃, 1400℃, 1450℃ or 1500℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] Preferably, the sintering time in step (5) is 60-600 min, for example, it can be 60 min, 100 min, 150 min, 200 min, 250 min, 300 min, 350 min, 400 min, 450 min, 500 min, 550 min or 600 min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the method further includes: after solid-liquid separation of the mixture obtained in step (2), precipitation to remove fluoride to obtain calcium fluoride, and then evaporation and crystallization to obtain chloride salt.

[0037] As a preferred embodiment of the method provided by the present invention, the method includes the following steps:

[0038] (1) Mix secondary aluminum ash with mineralizer and calcine at 500-900℃ for 30-300min, wherein the amount of mineralizer added is 1-10wt% of the total mass of secondary aluminum ash and mineralizer, to obtain mineralized material.

[0039] (2) The mineralized material obtained in step (1) is mixed with a hydrochloric acid solution with a concentration of 30-200 g / L and acidified at 30-90℃ for 30-300 min. The liquid-solid ratio of the mineralized material to the hydrochloric acid solution is 3-20 mL / g. The resulting acidified residue and mixed liquid are obtained. After solid-liquid separation, the mixed liquid is first precipitated to remove fluoride to obtain calcium fluoride, and then evaporated and crystallized to obtain chloride.

[0040] (3) The acid hydrolysis residue obtained in step (2) is mixed with silicon source and / or magnesium source according to the stoichiometric ratio of cordierite and ball-milled to obtain a mixture with a D50 particle size of 38-150μm.

[0041] (4) The mixture obtained in step (3) is dry-pressed under a pressure of 20-200 MPa to obtain a green blank;

[0042] (5) The green body obtained in step (4) is solid-state sintered at 1100-1500℃ for 60-600 min to obtain cordierite ceramic.

[0043] Compared with the prior art, the present invention has the following beneficial effects:

[0044] The method provided by this invention transforms impurity components such as F and Cl in secondary aluminum ash into fluoride and chloride salts that enter the solution through the synergistic effect of mineralization roasting and acid hydrolysis, thereby achieving directional separation and deep removal of impurity components in secondary aluminum ash. It can also realize the cascade utilization of impurity elements F and Cl, and can co-produce calcium fluoride and chloride salt flux. The secondary aluminum ash can be used to prepare cordierite ceramics, and the resulting ceramic materials have high main phase content, high bulk density, low apparent porosity and low coefficient of thermal expansion, which have good economic, social and environmental benefits. Attached Figure Description

[0045] Figure 1 This is a process flow diagram of the method provided in Example 1.

[0046] Figure 2 The image shows the XRD pattern of the cordierite ceramic provided in Example 1. Detailed Implementation

[0047] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0048] To clearly illustrate the technical solution of the present invention, the composition of the secondary aluminum ash used in the specific embodiments is shown in Table 1.

[0049] Table 1

[0050]

[0051] Example 1

[0052] This embodiment provides a method such as Figure 1 The method for preparing cordierite ceramics using secondary aluminum ash, as shown, includes the following steps:

[0053] (1) Mix the secondary aluminum ash and cryolite evenly, wherein the cryolite accounts for 5wt% of the total mass of the secondary aluminum ash and cryolite, and after mineralizing and roasting at 800℃ for 90min, the mineralized material is obtained.

[0054] (2) The mineralized material obtained in step (1) was acidified in a 50 g / L hydrochloric acid solution. The liquid-solid ratio of the hydrochloric acid solution to the mineralized material was 6 mL / g. The acidification temperature was 80℃ and the acidification time was 180 min. Acidification residue and mixed salt solution were obtained. Calcium chloride was added to the mixed salt solution obtained by filtration and precipitation. After stirring and precipitation for a period of time, the precipitated calcium fluoride was filtered and recovered. The purity of calcium fluoride was 98.7%. Then, the chloride in the filtrate was recovered by evaporation and crystallization.

[0055] (3) Take the acid hydrolysis residue obtained in step (2) and mix it with kaolin and talc in the stoichiometric ratio of cordierite and then ball mill it. The mass ratio of acid hydrolysis residue, kaolin and talc is 14:56:39. After ball milling, a mixture with a D50 particle size of 68μm is obtained.

[0056] (4) The mixture obtained in step (3) is dry-pressed under a pressure of 150 MPa to obtain a green blank;

[0057] (5) The green body obtained in step (4) is solid-state sintered at 1350℃ for 200 min to obtain cordierite ceramic.

[0058] Figure 2 The image shows the XRD pattern of the cordierite ceramic obtained in this embodiment. The pattern indicates that the obtained cordierite ceramic is cordierite with very high crystal phase purity.

[0059] In the cordierite ceramic obtained in this embodiment, the cordierite phase content is 91%, and the bulk density is 2.08 g / cm³. 3The apparent porosity is 13.9%, and the coefficient of thermal expansion is 1.9 × 10⁻⁶. -6 / ℃.

[0060] Example 2

[0061] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash, the method comprising the following steps:

[0062] (1) The secondary aluminum ash is uniformly mixed with sodium fluoride and aluminum fluoride, wherein sodium fluoride and aluminum fluoride account for 6wt% of the total mass of the secondary aluminum ash, sodium fluoride and aluminum fluoride. After mineralization roasting at 760℃ for 140min, the mineralized material is obtained.

[0063] (2) The mineralized material obtained in step (1) is subjected to acid hydrolysis in a 100 g / L hydrochloric acid solution. The liquid-solid ratio of the hydrochloric acid solution to the mineralized material is 15 mL / g. The acid hydrolysis temperature is 70 °C and the acid hydrolysis time is 120 min. The acid hydrolysis residue and mixed salt solution are obtained. The mixed salt solution is first subjected to precipitation to remove fluoride and recover calcium fluoride. The purity of calcium fluoride is 97.6%. Then, the chloride salt in the filtrate is recovered by evaporation and crystallization.

[0064] (3) Take the acid hydrolysis residue obtained in step (2) and mix it with silica powder and talc according to the stoichiometric ratio of cordierite and then ball mill it. The mass ratio of acid hydrolysis residue, silica powder and talc is 39:29:33. After ball milling, a mixture with a D50 particle size of 50μm is obtained.

[0065] (4) The mixture obtained in step (3) is dry-pressed under a pressure of 90 MPa to obtain a green blank;

[0066] (5) The green body obtained in step (4) is solid-state sintered at 1290℃ for 240 min to obtain cordierite ceramic.

[0067] In the cordierite ceramic obtained in this embodiment, the cordierite phase content is 93%, and the bulk density is 1.97 g / cm³. 3 The apparent porosity is 16.2%, and the coefficient of thermal expansion is 2.2 × 10⁻⁶. -6 / ℃.

[0068] Example 3

[0069] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash, the method comprising the following steps:

[0070] (1) The secondary aluminum ash is uniformly mixed with sodium fluoride and aluminum fluoride, wherein sodium fluoride and aluminum fluoride account for 6wt% of the total mass of the secondary aluminum ash, sodium fluoride and aluminum fluoride. After mineralization roasting at 850℃ for 90min, mineralized material is obtained.

[0071] (2) The mineralized material obtained in step (1) is subjected to acid hydrolysis in a 170 g / L hydrochloric acid solution. The liquid-solid ratio of the hydrochloric acid solution to the mineralized material is 10 mL / g. The acid hydrolysis temperature is 90 °C and the acid hydrolysis time is 90 min. The acid hydrolysis residue and mixed salt solution are obtained. The mixed salt solution is first subjected to precipitation to remove fluoride and recover calcium fluoride. The purity of calcium fluoride is 98.9%. Then, the chloride salt in the filtrate is recovered by evaporation and crystallization.

[0072] (3) Take the acid lysis residue obtained in step (2) and mix it with silica powder and magnesite according to the stoichiometric ratio of cordierite and then ball mill it. The mass ratio of acid lysis residue, silica powder and magnesite is 39:50:22. After ball milling, a mixture with a D50 particle size of 100μm is obtained.

[0073] (4) The mixture obtained in step (3) is dry-pressed under a pressure of 200 MPa to obtain a green blank;

[0074] (5) The green body obtained in step (4) is solid-state sintered at 1420℃ for 280 min to obtain cordierite ceramic.

[0075] In the cordierite ceramic obtained in this embodiment, the cordierite phase content is 92%, and the bulk density is 2.13 g / cm³. 3 The apparent porosity is 12.4%, and the coefficient of thermal expansion is 2.1 × 10⁻⁶. -6 / ℃.

[0076] Example 4

[0077] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash, the method comprising the following steps:

[0078] (1) The secondary aluminum ash is uniformly mixed with sodium fluoride, aluminum fluoride and ammonium chloride, wherein sodium fluoride, aluminum fluoride and ammonium chloride account for 4wt% of the total mass of the secondary aluminum ash, sodium fluoride, aluminum fluoride and ammonium chloride. After mineralization roasting at 700℃ for 240min, mineralized material is obtained.

[0079] (2) The mineralized material obtained in step (1) is subjected to acid hydrolysis in a 90 g / L hydrochloric acid solution. The liquid-solid ratio of the hydrochloric acid solution to the mineralized material is 5 mL / g. The acid hydrolysis temperature is 50℃ and the acid hydrolysis time is 280 min. The acid hydrolysis residue and mixed salt solution are obtained. The mixed salt solution is first subjected to precipitation to remove fluoride and recover calcium fluoride. The purity of calcium fluoride is 97.4%. Then, the chloride salt in the filtrate is recovered by evaporation and crystallization.

[0080] (3) Take the acid lysis residue obtained in step (2) and mix it with silica powder, quartz and magnesite according to the stoichiometric ratio of cordierite and then ball mill it. The mass ratio of acid lysis residue, silica powder, quartz and magnesite is 39:24:26:22. After ball milling, a mixture with a D50 particle size of 80μm is obtained.

[0081] (4) The mixture obtained in step (3) is dry-pressed under a pressure of 60 MPa to obtain a green blank;

[0082] (5) The green body obtained in step (4) is solid-state sintered at 1460℃ for 100 min to obtain cordierite ceramic.

[0083] In the cordierite ceramic obtained in this embodiment, the cordierite phase content is 88%, and the bulk density is 2.05 g / cm³. 3 The apparent porosity is 14.2%, and the coefficient of thermal expansion is 2.4 × 10⁻⁶. -6 / ℃.

[0084] Example 5

[0085] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash, the method comprising the following steps:

[0086] (1) Mix the secondary aluminum ash and cryolite evenly, wherein the cryolite accounts for 1 wt% of the total mass of the secondary aluminum ash and cryolite, and after mineralizing and roasting at 900℃ for 30 min, the mineralized material is obtained.

[0087] (2) The mineralized material obtained in step (1) is subjected to acid hydrolysis in a 30 g / L hydrochloric acid solution. The liquid-solid ratio of the hydrochloric acid solution to the mineralized material is 20 mL / g. The acid hydrolysis temperature is 30 °C and the acid hydrolysis time is 300 min. The acid hydrolysis residue and mixed salt solution are obtained. The mixed salt solution is first subjected to precipitation to remove fluoride and recover calcium fluoride. The purity of calcium fluoride is 98.4%. Then, the chloride salt in the filtrate is recovered by evaporation and crystallization.

[0088] (3) Take the acid hydrolysis residue obtained in step (2) and mix it with kaolin and talc in the stoichiometric ratio of cordierite and then ball mill it. The mass ratio of acid hydrolysis residue, kaolin and talc is 14:56:39. After ball milling, a mixture with an average particle size of 38μm is obtained.

[0089] (4) The mixture obtained in step (3) is dry-pressed under a pressure of 200 MPa to obtain a green blank;

[0090] (5) The green body obtained in step (4) is solid-state sintered at 1100℃ for 600 min to obtain cordierite ceramic.

[0091] In the cordierite ceramic obtained in this embodiment, the cordierite phase content is 82%, and the bulk density is 1.75 g / cm³. 3 The apparent porosity is 18.6%, and the coefficient of thermal expansion is 3.4 × 10⁻⁶. -6 / ℃.

[0092] Example 6

[0093] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash, the method comprising the following steps:

[0094] (1) Mix the secondary aluminum ash and cryolite evenly, wherein the cryolite accounts for 10wt% of the total mass of the secondary aluminum ash and cryolite. After mineralizing and roasting at 500℃ for 300min, the mineralized material is obtained.

[0095] (2) The mineralized material obtained in step (1) is subjected to acid hydrolysis in a 200 g / L hydrochloric acid solution. The liquid-solid ratio of the hydrochloric acid solution to the mineralized material is 3 mL / g. The acid hydrolysis temperature is 90℃ and the acid hydrolysis time is 30 min. The acid hydrolysis residue and mixed salt solution are obtained. The mixed salt solution is first subjected to precipitation to remove fluoride and recover calcium fluoride. The purity of calcium fluoride is 99.5%. Then, the chloride salt in the filtrate is recovered by evaporation and crystallization.

[0096] (3) Take the acid hydrolysis residue obtained in step (2) and mix it with kaolin and talc in the stoichiometric ratio of cordierite and then ball mill it. The mass ratio of acid hydrolysis residue, kaolin and talc is 14:56:39. After ball milling, a mixture with an average particle size of 150μm is obtained.

[0097] (4) The mixture obtained in step (3) is dry-pressed under a pressure of 20 MPa to obtain a green blank;

[0098] (5) The green body obtained in step (4) is solid-state sintered at 1500℃ for 60 min to obtain cordierite ceramic.

[0099] In the cordierite ceramic obtained in this embodiment, the cordierite phase content is 87%, and the bulk density is 2.24 g / cm³. 3 The apparent porosity is 12.6%, and the coefficient of thermal expansion is 1.8 × 10⁻⁶. -6 / ℃.

[0100] Example 7

[0101] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash. Compared with Embodiment 1, the cryolite in step (1) is replaced with an equal amount of calcium fluoride, while the rest is the same as in Embodiment 1.

[0102] In the cordierite ceramic obtained in this embodiment, the cordierite phase content is 3%, and the bulk density is 3.05 g / cm³. 3 The apparent porosity is 10.2%, and the coefficient of thermal expansion is 3×10⁻⁶. -6 / ℃.

[0103] Example 8

[0104] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash. Compared with Example 1, the calcination temperature of step (1) is controlled at 400°C, while the rest is the same as in Example 1.

[0105] Example 9

[0106] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash. Compared with Embodiment 1, the firing temperature of step (1) is controlled at 1100℃, while the rest is the same as in Embodiment 1.

[0107] Example 10

[0108] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash. Compared with Example 1, the concentration of hydrochloric acid in step (2) is controlled at 25 g / L, while the rest is the same as in Example 1.

[0109] The cordierite ceramic obtained in this embodiment contains 53% cordierite phase and a large amount of mullite phase, with a bulk density of 1.21 g / cm³. 3 The apparent porosity is 28.2%, and the coefficient of thermal expansion is 3.2 × 10⁻⁶. -6 / ℃.

[0110] Example 11

[0111] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash. Compared with Example 1, the concentration of hydrochloric acid in step (2) is controlled at 210 g / L, while the rest is the same as in Example 1.

[0112] Example 12

[0113] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash. Compared with Embodiment 1, the sintering temperature of step (5) is controlled at 1050℃, while the rest is the same as in Embodiment 1.

[0114] Example 13

[0115] This embodiment provides a method for preparing cordierite ceramics using secondary aluminum ash. Compared with Embodiment 1, the sintering temperature of step (5) is controlled at 1550℃, while the rest is the same as in Embodiment 1.

[0116] In the cordierite ceramic obtained in this embodiment, the cordierite phase content is 3%, and the bulk density is 2.21 g / cm³. 3 The apparent porosity is 10.2%, and the coefficient of thermal expansion is 3.1 × 10⁻⁶. -6 / ℃.

[0117] Comparative Example 1

[0118] This comparative example provides a method for preparing cordierite ceramics using secondary aluminum ash. Compared with Example 1, step (2) acid hydrolysis is not performed, and the rest is the same as in Example 1.

[0119] Comparative Example 2

[0120] This comparative example provides a method for preparing cordierite ceramics using secondary aluminum ash. Compared with Example 1, step (1) does not involve the addition of a mineralizing agent, and step (2) does not involve acid hydrolysis. The rest of the process is the same as in Example 1.

[0121] Table 2

[0122]

[0123] As shown in Table 2, the method provided by this invention uses secondary aluminum ash to prepare cordierite ceramics, enabling high-value resource utilization of the secondary aluminum ash and achieving graded separation and recycling of the F and Cl impurities. The cordierite ceramics obtained using the preferred process parameters of this invention have advantages such as high phase content, high bulk density, low apparent porosity, and low coefficient of thermal expansion.

[0124] Compared to Example 1, in Example 7, calcium fluoride failed to mineralize, and the aluminum-containing phase failed to transform into stable α-Al₂O₃. This resulted in significant alumina loss during subsequent acidolysis. Furthermore, the introduction of Ca ions hindered the formation of the cordierite phase, ultimately leading to a substantial reduction in the cordierite content and a significant decrease in bulk density of the resulting ceramic. In Example 8, the calcination temperature was too low, resulting in incomplete removal of the aluminum-containing components and their failure to transform into stable α-phase alumina. These components entered the acid solution in large quantities during subsequent acidolysis, leading to incomplete impurity removal and ultimately a reduction in cordierite content. In Example 9, the calcination... Excessive temperature causes the formation of a glassy phase in the sample, and some impurities become solidified and difficult to remove, ultimately resulting in a decrease in the amount of cordierite formed and an increase in the coefficient of thermal expansion. In Example 10, the acid concentration was too low, causing insufficient reaction of sodium salt, potassium salt, calcium fluoride, and iron impurities, which affected the formation of the cordierite phase after entering the product. In Example 11, excessively high hydrochloric acid concentration caused a large loss of aluminum, resulting in compositional deviation and a significant decrease in cordierite content. In Examples 12 and 13, the sintering temperature directly affects the composition and properties of the ceramic. If the sintering temperature is too low, no cordierite phase is formed, while if the sintering temperature is too high, a large amount of glassy phase is formed.

[0125] In summary, the method provided by this invention achieves the directional separation and deep removal of impurity components in secondary aluminum ash through the synergistic effect of mineralization roasting-acid hydrolysis regulation, and enables the cascade utilization of impurity elements F and Cl. The secondary aluminum ash is then used to prepare cordierite ceramics, and the resulting ceramic materials have high main phase content, high bulk density, low apparent porosity, and low coefficient of thermal expansion, resulting in good economic, social, and environmental benefits.

[0126] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing cordierite ceramics using secondary aluminum ash, characterized in that, The method includes the following steps: (1) The secondary aluminum ash is mixed with a mineralizing agent and calcined at a temperature of 500-900℃ to obtain a mineralized material; wherein the mineralizing agent includes any one or a combination of at least two of cryolite, sodium fluoride, aluminum fluoride, magnesium fluoride or ammonium chloride. (2) The mineralized material obtained in step (1) is mixed with an acid solution for acid hydrolysis. The acid solution includes a hydrochloric acid solution with a concentration of 30-200 g / L, to obtain acid hydrolysis residue and a mixed solution. (3) According to the stoichiometric ratio of cordierite, the acid hydrolysis residue obtained in step (2) is mixed with a silicon source and / or a magnesium source and ball-milled to obtain a mixture; (4) The mixture obtained in step (3) is dry-pressed to form a blank; (5) The green body obtained in step (4) is sintered to obtain cordierite ceramic.

2. The method according to claim 1, characterized in that, The amount of mineralizer added in step (1) is 1-10 wt% of the total mass of secondary aluminum ash and mineralizer.

3. The method according to claim 1, characterized in that, The roasting time in step (1) is 30-300 min.

4. The method according to claim 1, characterized in that, The liquid-to-solid ratio of the acid solution to the mineralized material in step (2) is 3-20 mL / g.

5. The method according to claim 1, characterized in that, The acid hydrolysis temperature in step (2) is 30-90℃.

6. The method according to claim 1, characterized in that, The acid hydrolysis time in step (2) is 30-300 min.

7. The method according to claim 1, characterized in that, The silicon source in step (3) includes any one or a combination of at least two of talc, kaolin, silica, microsilica or quartz.

8. The method according to claim 1, characterized in that, The magnesium source in step (3) includes any one or a combination of at least two of talc, magnesium oxide, magnesite, or magnesium hydroxide.

9. The method according to claim 1, characterized in that, The D50 particle size of the mixture in step (3) is 38-150 μm.

10. The method according to claim 1, characterized in that, The pressure of the dry pressing in step (4) is 20-200 MPa.

11. The method according to claim 1, characterized in that, The sintering temperature in step (5) is 1100-1500℃.

12. The method according to claim 1, characterized in that, The sintering time in step (5) is 60-600 min.

13. The method according to claim 1, characterized in that, The method further includes: after separating the solid and liquid mixture obtained in step (2), first precipitating to remove fluoride to obtain calcium fluoride, and then evaporating and crystallizing to obtain chloride salt.

14. The method according to claim 1, characterized in that, The method includes the following steps: (1) Mix secondary aluminum ash with mineralizer and calcine at 500-900℃ for 30-300min, wherein the amount of mineralizer added is 1-10wt% of the total mass of secondary aluminum ash and mineralizer to obtain mineralized material; (2) The mineralized material obtained in step (1) is mixed with a hydrochloric acid solution with a concentration of 30-200 g / L and acidified at 30-90℃ for 30-300 min. The liquid-solid ratio of the mineralized material to the hydrochloric acid solution is 3-20 mL / g. The acidified residue and the mixed liquid are obtained. After solid-liquid separation, the mixed liquid is first precipitated to remove fluoride to obtain calcium fluoride, and then evaporated and crystallized to obtain chloride. (3) The acid hydrolysis residue obtained in step (2) is mixed with silicon source and / or magnesium source according to the stoichiometric ratio of cordierite and ball-milled to obtain a mixture with D50 particle size of 38-150μm; (4) The mixture obtained in step (3) is dry-pressed under a pressure of 20-200 MPa to obtain a green blank; (5) The green body obtained in step (4) is solid-state sintered at 1100-1500℃ for 60-600 min to obtain cordierite ceramic.

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