Method for preparing environment-friendly magnesium aluminate spinel raw material by utilizing industrial solid waste

Abstract

The invention discloses a method for preparing an environment-friendly magnesium aluminate spinel raw material by utilizing industrial solid wastes, and relates to the technical field of magnesium aluminate spinel raw material production. The method comprises the following steps: a, raw material synergistic purification treatment: crushing magnesium slag into coarse particles, and mixing the coarse particles with aluminum ash raw powder which is not subjected to desalting treatment according to a mass ratio of (1-3): 1 to obtain a mixture; the mixture is subjected to first heat treatment at the temperature of 450-650 DEG C in a non-oxidizing atmosphere, and heat preservation is conducted for 1-3 h; according to the method, two industrial solid wastes, namely the magnesium slag and the aluminum ash, are subjected to direct synergistic heat treatment in a non-oxidizing atmosphere, and chloride impurities in the aluminum ash are used for synchronously removing free calcium oxide on the surface of the magnesium slag and removing part of soluble salt of the aluminum ash in the volatilization and migration process, so that coupling purification of treating wastes with wastes is realized; the problem that various solid wastes need to be subjected to complex pretreatment in a traditional process is solved, the process is simplified, the impurity removal efficiency is improved, and meanwhile the risk of environmental pollution caused by solid waste stockpiling or landfill is reduced.

Description

Technical Field

[0001] This invention belongs to the field of magnesium aluminum spinel raw material production technology, and in particular relates to a method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste. Background Technology

[0002] Magnesium aluminum spinel, as a high-quality refractory raw material, traditionally relies on high-grade natural minerals such as magnesite and bauxite for its production. It faces pressure from resource consumption and rising costs. At the same time, industries such as metallurgy and aluminum processing generate a large amount of solid waste rich in magnesium and aluminum, such as aluminum ash, magnesium slag, and waste refractory materials.

[0003] If these solid wastes are stockpiled or landfilled, they not only occupy land, but their soluble salts, fluorides and other components can also cause water and soil pollution. Therefore, converting industrial solid waste into high-value-added magnesium aluminum spinel raw materials is in line with the circular economy concept of treating waste with waste and turning waste into treasure. It is one of the key paths to achieve sustainable development in the refractory materials industry. However, the complex composition, large fluctuations and high impurity content of solid waste bring huge challenges to its high-value and homogeneous utilization.

[0004] Currently, the preparation of magnesium aluminum spinel raw materials mainly relies on high-purity natural minerals or chemical raw materials. Not only do raw material costs account for more than 60%, but there is also a problem of high resource consumption. At the same time, the industrial sector generates a large amount of solid waste such as aluminum ash and magnesium slag. Conventional disposal methods can easily cause soil and water pollution. Moreover, the utilization rate of magnesium and aluminum elements in solid waste is less than 20%, making it difficult to achieve resource recycling and resulting in a large waste of resources, which is not conducive to use.

[0005] To address this issue, we provide a method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing environmentally friendly magnesium aluminum spinel raw materials from industrial solid waste. Through the integrated process design of synergistic purification and activation sintering, this invention solves the problems in the prior art where the solid waste is difficult to use directly to prepare high-performance refractory raw materials due to its complex composition and high impurity content, as well as the problems of the traditional step-by-step processing process being lengthy, inefficient, and having insufficient resource utilization.

[0007] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution.

[0008] This invention discloses a method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste, comprising the following steps: Step a: Co-purification treatment of raw materials: Crush magnesium slag into coarse particles and mix it with aluminum ash powder that has not undergone desalination treatment at a mass ratio of (1-3):1 to obtain a mixture; subject the mixture to a first heat treatment at 450-650℃ under a non-oxidizing atmosphere and hold for 1-3 hours. Utilize the volatilization and migration of chlorides in aluminum ash during the heat treatment process to simultaneously remove free calcium oxide on the surface of magnesium slag particles and remove some soluble salts from aluminum ash to obtain a co-purified material. Step b: Batching and activation grinding: The co-purified material and aluminum-rich industrial solid waste are mixed to make the molar ratio of magnesium to aluminum in the mixture reach 1:(2.0-2.1); then wet activation grinding is carried out, the grinding medium is a weakly alkaline solution with a pH value of 8-10, and the grinding is carried out until the particle size of the slurry D90≤15μm to obtain the activated slurry; Step c: Reaction molding and pre-firing: The activated slurry is pressed and filtered to form a green body, and the green body is subjected to a second heat treatment at 1100-1250℃ in an oxygen-containing atmosphere for 1-2 hours to complete the initial formation of the spinel main crystal phase and obtain a pre-fired body; Step d: Densification sintering and grain control: The pre-sintered body is subjected to a third heat treatment at 1600-1700℃ in a reducing atmosphere and held for 2-4 hours. After the holding stage, the cooling rate is controlled to quickly pass through the temperature range of 1300-1450℃ within the range of 10-30℃ / min, and finally high-purity magnesium aluminum spinel raw material is obtained.

[0009] By directly coupling the treatment of two types of solid waste under specific conditions, and using chloride impurities in aluminum ash as a purifying agent, the key impurities of both raw materials are simultaneously removed in one step, achieving waste-to-waste treatment. This not only greatly simplifies the complex pretreatment process of traditional step-by-step impurity removal and improves efficiency, but also achieves a better purification effect than individual treatment through the interaction between impurities. Wet co-grinding using a weakly alkaline medium not only achieves ultrafine grinding and highly uniform mixing of materials, but also continuously neutralizes and fixes acidic impurities that may remain from previous steps during the grinding process. Simultaneously, the alkaline environment is beneficial for protecting... The aluminum phase is active, and pressure filtration molding can obtain high-density green bodies, reducing subsequent sintering shrinkage. Medium-temperature pre-firing in an oxygen-containing atmosphere can fully oxidize and remove organic matter, carbon, and residual nitrides in the green body. At the same time, it drives solid-phase reactions between magnesium and aluminum oxides, initially forming a spinel main crystal phase network framework, giving the green body sufficient strength and preventing deformation during final high-temperature sintering. The reducing atmosphere can effectively suppress impurities such as iron oxide in the raw materials to be in a high valence state, avoid the formation of low-melting-point phases that are not conducive to high-temperature performance, promote sintering densification, and directly improve the strength, toughness, and thermal shock stability of the final product.

[0010] The present invention is further configured such that, before the first heat treatment, 0.5%-2% of calcium fluoride powder by mass of the mixture is uniformly added to the mixture in step a. The addition of calcium fluoride powder is used to react with silicon dioxide in aluminum ash and magnesium slag during the first heat treatment to generate an early liquid phase, which encapsulates and further separates impurities. The addition of calcium fluoride as a mineralizer can react with silicon dioxide in solid waste at a relatively low first heat treatment temperature to generate a small amount of low-temperature liquid phase. This liquid phase can effectively encapsulate and bind fine impurity particles, making them easier to separate or solidify in subsequent processes, thereby improving the removal and fixation effect of the main impurity silicon and further improving the purity of the raw materials.

[0011] The present invention is further configured such that the weakly alkaline solution in step b is a solution containing 0.1-0.5 mol / L sodium silicate. The silicate colloid produced by the hydrolysis of sodium silicate during the activation and grinding process can be adsorbed on the surface of solid particles, playing an electrostatic dispersion role, and participating in subsequent sintering, forming a high-melting-point magnesium aluminum silicate phase at the grain boundaries, thus strengthening the grain boundaries. Using sodium silicate solution as a grinding medium enables the hydrolyzed colloid to have excellent dispersion effect, preventing the agglomeration of ultrafine particles and ensuring uniform mixing. Secondly, the introduced silicon element can form high-melting-point silicate phases such as cordierite at the grain boundaries with excess magnesium, aluminum, etc. during subsequent high-temperature sintering, thereby strengthening the grain boundaries and significantly improving the high-temperature strength and creep resistance of the material.

[0012] The present invention is further configured such that, before entering the second heat treatment, the green body obtained after pressure filtration and molding in step c is first immersed in a 5-15% magnesium nitrate ethanol solution for 5-30 minutes, and then removed and dried; the magnesium nitrate decomposes into active magnesium oxide in the subsequent pre-calcination, which is used to supplement and precisely control the magnesium-aluminum ratio of the green body surface. By immersing in the magnesium nitrate ethanol solution, a highly active magnesium source can be uniformly introduced into the green body surface. The nano-sized magnesium oxide formed by its decomposition during pre-calcination can efficiently compensate for the loss, ensuring that the overall phase composition of the product and the surface layer are uniform and consistent, and avoiding performance degradation due to magnesium deficiency on the surface.

[0013] The present invention is further configured such that, in the third heat treatment process in step d, when the temperature reaches 1550℃, a gas containing a chlorine source is pulsedly introduced into the reducing atmosphere. The gas containing the chlorine source is dry chlorine, and the volume of a single pulse does not exceed 1% of the volume of the reaction vessel, and the total gas flow time does not exceed 10% of the holding time. The chlorine source is used to vaporize the residual alkali metal impurities at high temperature and carry them out of the system through the gas flow. Alkali metal oxides are harmful impurities that seriously reduce the high-temperature performance of refractory materials. During the high-temperature sintering stage, a trace amount of chlorine is pulsedly introduced, which can react with the residual alkali metal impurities such as sodium and potassium to generate volatile chlorides, which are then completely carried away from the sintered body by the gas flow, thus solving the problem that conventional solid-phase sintering is difficult to remove alkali metals.

[0014] The present invention is further configured such that, after the heat preservation stage in step d and before the rapid cooling is performed, the sintering temperature is briefly reduced by 50-100°C and held for 10-30 minutes, and then the rapid cooling procedure is performed. This brief cooling process is used to induce a small amount of secondary liquid phase to condense back to the grain boundaries, thereby achieving partial glass healing of the grain boundaries. During the brief cooling and heat preservation stage after the high-temperature sintering is completed, the viscosity of the small amount of liquid phase formed at high temperature increases during cooling. This process promotes the liquid phase to shrink back and fill the micropores and microcracks of the grain boundaries, eliminating internal micro-defects and improving the density, mechanical strength and impermeability of the material.

[0015] The present invention is further configured such that step d includes a heat treatment process, the heat treatment process including: After the raw material obtained in step d is crushed to a certain particle size, it is annealed in an oxidizing atmosphere at 1200-1350℃ for 2-6 hours. This annealing treatment is used to re-oxidize and stabilize the trace low-valence metal ions present in the raw material due to reducing sintering, and to eliminate residual stress. Oxidizing annealing treatment can re-oxidize the trace ferrous ions that may be generated during reducing atmosphere sintering, stabilize the lattice state, and prevent the product from undergoing volume changes due to oxidation during use. Secondly, it can effectively eliminate the internal stress generated by the previous rapid cooling, and improve the dimensional stability and thermal shock fatigue resistance of the product.

[0016] The present invention is further configured such that, in step b, wet activation grinding is carried out using a planetary ball mill, the ball mill is filled with a portion of zirconia grinding balls, the filling volume of which is 30-50% of the grinding jar volume, of which zirconia microspheres with a particle size of 3-5mm account for no less than 60%, the ball mill speed is 300-500 rpm, and grinding is carried out in a high-energy planetary ball mill with a specific ratio of zirconia microspheres. This not only efficiently grinds the material to the submicron level and achieves atomic-scale mixing, but also allows a trace amount of zirconia to be worn into the raw material during the grinding process. These unintentionally introduced zirconia can act as nucleation sites or a second phase, forming nanoscale dispersed particles after sintering, which has the unexpected beneficial effect of refining grains and strengthening and toughening.

[0017] The present invention is further configured such that the high-purity magnesium aluminum spinel raw material in step d has magnesium aluminum spinel as its main crystalline phase and contains dispersed zirconium-containing second-phase particles with a size of less than 200 nm inside the grains. The nanoparticles can effectively pin dislocations and grain boundaries, prevent the grains from growing too fast at high temperatures, and at the same time, through the second-phase strengthening, improve the high-temperature mechanical properties and creep resistance of the material.

[0018] The present invention further specifies that the high-purity magnesium aluminum spinel raw material has a flexural strength of not less than 30 MPa at a high temperature of 1600℃ and a soluble chloride ion content of less than 100 ppm, ensuring that the product, as a high-end refractory raw material, will not be prematurely damaged due to impurities during use and its service life will be extended.

[0019] The present invention has the following beneficial effects.

[0020] 1. This invention directly and synergistically heat-treats two types of industrial solid waste, magnesium slag and aluminum ash, in a non-oxidizing atmosphere. During the volatilization and migration of chloride impurities in the aluminum ash, free calcium oxide on the surface of magnesium slag is removed simultaneously, and some soluble salts in the aluminum ash itself are also removed. This achieves coupled purification of waste-to-waste, avoiding the problem of complex pretreatment of various solid wastes in traditional processes. It simplifies the process, improves the efficiency of impurity removal, and reduces the environmental pollution risk caused by solid waste stockpiling or landfilling. It provides a feasible path for the efficient resource utilization of industrial solid waste, helps to alleviate dependence on natural mineral resources, and promotes the transformation of the refractory materials industry towards a circular economy model.

[0021] 2. This invention achieves ultra-fine and uniform mixing of materials by using a weakly alkaline medium and introducing sodium silicate in wet grinding. Furthermore, the silicate colloid generated by hydrolysis acts as a dispersant, forming a high-melting-point silicate phase at the grain boundaries during subsequent sintering, thus strengthening the grain boundary structure. Combined with high-temperature sintering under a reducing atmosphere and pulsed chlorine impurity removal, the formation of low-melting-point phases is effectively suppressed and alkali metal impurities are removed. Finally, a controllable cooling process regulates the microstructure, resulting in magnesium aluminum spinel raw materials with fine grains, containing nanoscale second-phase particles, high high-temperature strength, and low impurity content, thereby improving the overall performance and service life of the product. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0023] Figure 1 This is a schematic diagram of a method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste; Figure 2 This is a schematic diagram of a synergistic purification process for a method of preparing environmentally friendly magnesium aluminum spinel raw materials from industrial solid waste. Figure 3 This is a schematic diagram of the activation grinding and grain boundary strengthening process in a method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste. Figure 4 This is a schematic diagram of the process for controlling the surface composition of the green body in a method for preparing environmentally friendly magnesium-aluminum spinel raw materials using industrial solid waste. Figure 5 This is a schematic diagram of a high-temperature deep purification process in a method for preparing environmentally friendly magnesium-aluminum spinel raw materials using industrial solid waste. Detailed Implementation

[0024] The technical solutions of the present invention will be described below with reference to the accompanying drawings. The described embodiments are only some embodiments of the present invention, and not all embodiments.

[0025] Example 1 like Figures 1-5 As shown, the present invention is a method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste. In this embodiment, the equipment of each process unit is preferably made of materials that are resistant to high temperature, corrosion and have good sealing properties (such as Inconel alloy, specific types of stainless steel or corundum) to ensure the stable operation of the process and the purity of the materials under high temperature and specific atmosphere.

[0026] The system mainly includes a raw material co-purification unit, a batching and fine grinding unit, a reaction molding and pre-firing unit, and a final densification sintering and control unit.

[0027] The raw material co-purification unit is the starting point for treating industrial solid waste. This unit includes a crusher, a mixer, and a first heat treatment furnace with a controlled atmosphere. Magnesium slag is crushed into coarse particles and then fully mixed with undesalinated aluminum ash powder in the mixer at a set mass ratio. The mixture is then sent to the first heat treatment furnace for heat treatment in a non-oxidizing atmosphere. The specific temperature window in the furnace is set to utilize the volatilization and migration characteristics of chloride impurities in aluminum ash to simultaneously act on the free calcium oxide on the surface of magnesium slag particles and the soluble salts in aluminum ash itself, thereby achieving the co-removal of key impurities from both types of solid waste in a waste-to-waste manner, resulting in purified material.

[0028] The batching and fine grinding unit is used to achieve high homogenization and micro-activation of materials. The core of this unit is a high-energy planetary ball mill and a matching slurry preparation system. After the co-purified material and additional aluminum-rich industrial solid waste are batched according to a precise stoichiometric ratio, they are added to the ball mill along with a weakly alkaline solution with a specific pH value. The ball mill is filled with zirconium oxide grinding balls of a specific gradation. The material is wet co-milled at high speed until the slurry particle size reaches an ultrafine level of D90≤15μm, and an activated slurry with highly uniform chemical composition and particle size is obtained.

[0029] The reaction molding and pre-firing unit aims to achieve the initial consolidation of materials and the formation of the spinel main crystalline phase. This unit includes a pressure filter molding device and a second heat treatment furnace with a controllable atmosphere. The activated slurry is pressure filtered to form a green body with a high density. The green body can optionally undergo supplementary treatments such as impregnation, and then it is sent to the pre-firing furnace for heat treatment in an oxygen-containing atmosphere and at a medium temperature of 1100-1250°C. This process oxidizes and removes organic matter and residual nitrides in the green body, and drives solid-state reactions between magnesium and aluminum oxides, initially constructing the crystal network framework of the spinel phase to obtain a pre-firing body with sufficient strength.

[0030] The final densification sintering and control unit is key to obtaining high-performance products. The main body of this unit is a high-temperature sintering furnace that can precisely control the heating program, cooling rate and atmosphere. The pre-sintered body is placed in the furnace and undergoes high-temperature sintering in a reducing atmosphere to achieve densification. During this process, fine control methods such as pulsed airflow can be introduced to remove trace impurities. After the holding period, a specific cooling program is executed to control the microstructure of the final product, thereby obtaining high-purity, high-density magnesium aluminum spinel raw materials with excellent high-temperature performance.

[0031] Example 2 Please see Figures 1-5 Based on Specific Embodiment 1, this embodiment is applicable to situations where high-impurity solid waste is being processed and high raw material purity is required.

[0032] To address the issue of high aluminum ash impurity content and prominent silicon content, magnesium slag and aluminum ash were mixed at a mass ratio of 1.5:1, and the amount of calcium fluoride added was increased to 1.8% of the mixture mass. The mixture was then subjected to a first heat treatment at 600℃ for 2.5 hours to fully generate an early liquid phase that encapsulates the silicon impurities. After purification, the magnesium-aluminum molar ratio was adjusted to 1:2.08. Wet milling was performed using a sodium silicate solution with a pH of 9, and the planetary ball mill speed was increased to 450 rpm to enhance dispersion and activation. During the pre-calcination stage, the mixture was held at 1250℃ for 2 hours to ensure complete decomposition of impurities. During the high-temperature sintering stage, a trace amount of chlorine gas was pulsed through at 1580℃ to enhance the removal of alkali metals. Finally, by controlling the cooling regime, a magnesium-aluminum spinel product with clean grain boundaries and solidified silicon impurities was obtained.

[0033] Example 3 Please see Figures 1-5 Based on the first specific embodiment, this embodiment is applicable to the preparation of refractory materials with stringent requirements for high-temperature flexural strength and creep performance.

[0034] To prepare magnesium-aluminum spinel raw materials with excellent high-temperature mechanical properties, a magnesium-rich ratio of 3:1 (magnesium slag to aluminum ash) was used in the synergistic purification stage, and 1.2% calcium fluoride was added to optimize the amount of early liquid phase. The magnesium-aluminum molar ratio was precisely controlled at 1:2.0 during the batching process. In the wet grinding stage, a high proportion of zirconia microspheres, accounting for 70% of the total volume of the grinding balls, and a 0.4 mol / L sodium silicate solution were used for long-term activation grinding to promote the adsorption of silica colloids and the introduction of zirconium micropowder. The green body was impregnated with a high concentration of magnesium nitrate solution to enhance the magnesium supplementation effect on the surface. After pre-firing, a long-term sintering at 1680℃ under a reducing atmosphere was used to promote densification and the formation of nano-zirconia-containing second phase. After sintering, an oxidation annealing process at 1300℃ for 4 hours was added to stabilize the crystal lattice and eliminate stress.

[0035] Example 4 Please see Figures 1-5Based on Specific Embodiment 1, this embodiment is applicable to application areas with special standards for the environmental friendliness of products.

[0036] For applications with extremely high environmental requirements and the need to minimize soluble chloride ion residues, a relatively low first heat treatment temperature of 480℃ and a longer holding time are used in the synergistic purification stage. This inhibits the rapid volatilization of chlorides while promoting their full reaction and fixation with free calcium oxide. In the wet grinding stage, a freshly prepared high-pH sodium silicate solution is used to enhance the adsorption and fixation of residual chloride ions. In the high-temperature sintering stage, in addition to pulsed chlorine gas to remove alkali metals at 1550℃, a small amount of humid air is introduced in the range above 1200℃ during the cooling process after sintering. This allows the residual trace amounts of chlorides to be converted into chlorine oxides or hydrochloric acid gas and escape. Finally, the sintered product undergoes a two-stage annealing treatment: first, oxidative annealing at 1350℃ for 2 hours, followed by low-temperature stabilization treatment at 800℃ to ensure that the soluble chloride ion content is reduced to an extremely low level.

[0037] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste, characterized in that: Includes the following steps: Step a: Co-purification treatment of raw materials: The magnesium slag is crushed into coarse particles and mixed with aluminum ash powder that has not undergone desalination treatment at a mass ratio of (1-3):1 to obtain a mixture; the mixture is subjected to a first heat treatment at 450-650℃ under a non-oxidizing atmosphere and held for 1-3 hours. By utilizing the volatilization and migration of chlorides in aluminum ash during the heat treatment process, the free calcium oxide on the surface of magnesium slag particles is removed and some soluble salts in aluminum ash are removed, resulting in a co-purified material. Step b: Batching and activation grinding: The synergistic purification material is mixed with aluminum-rich industrial solid waste to achieve a molar ratio of magnesium to aluminum of 1:(2.0-2.1); then wet activation grinding is performed with a weakly alkaline solution with a pH of 8-10, and the mixture is ground until the particle size D90 ≤ 15μm to obtain the activated slurry. Step c: Reaction molding and pre-firing: The activated slurry is pressed and filtered to form a green body, and the green body is subjected to a second heat treatment at 1100-1250℃ in an oxygen-containing atmosphere for 1-2 hours to complete the initial formation of the spinel main crystal phase and obtain a pre-fired body; Step d: Densification sintering and grain control: The pre-sintered body is subjected to a third heat treatment at 1600-1700℃ in a reducing atmosphere and held for 2-4 hours; After the heat preservation stage, the cooling rate is controlled to quickly pass through the temperature range of 1300-1450℃ within the range of 10-30℃ / min, and finally the high-purity magnesium aluminum spinel raw material is obtained.

2. The method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste according to claim 1, characterized in that: Before the first heat treatment, the mixture in step a is uniformly mixed with calcium fluoride powder accounting for 0.5%-2% of the mass of the mixture. The addition of the calcium fluoride powder is used to react with the silicon oxide in the aluminum ash and magnesium slag during the first heat treatment to generate an early liquid phase, which encapsulates and further separates impurities.

3. The method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste according to claim 1, characterized in that: In step b, the weakly alkaline solution is a solution containing 0.1-0.5 mol / L sodium silicate. The silicic acid colloid produced by the hydrolysis of sodium silicate during the activation and grinding process can be adsorbed on the surface of solid particles, playing an electrostatic dispersion role, and participating in subsequent sintering to form a high-melting-point magnesium aluminum silicate phase at the grain boundaries, thereby strengthening the grain boundaries.

4. The method for preparing environmentally friendly magnesium aluminum spinel raw material using industrial solid waste according to claim 1, characterized in that: The green body obtained after pressure filtration and molding in step c is first immersed in a 5-15% magnesium nitrate ethanol solution for 5-30 minutes before entering the second heat treatment, and then taken out and dried; the magnesium nitrate decomposes into active magnesium oxide in the subsequent pre-calcination, which is used to supplement and precisely control the magnesium-aluminum ratio on the surface of the green body.

5. The method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste according to claim 1, characterized in that: In the third heat treatment process in step d, when the temperature reaches 1550℃, a chlorine-containing gas source is pulsedly introduced into the reducing atmosphere. The chlorine-containing gas source is dry chlorine gas, and the volume of a single pulse does not exceed 1% of the volume of the reaction vessel, and the total gas flow time does not exceed 10% of the heat preservation time. The chlorine gas source is used to vaporize residual alkali metal impurities at high temperature and carry them out of the system through the gas flow.

6. The method for preparing environmentally friendly magnesium aluminum spinel raw material from industrial solid waste according to claim 1, characterized in that: After the heat preservation stage in step d is completed and before rapid cooling is performed, the sintering temperature is briefly reduced by 50-100°C and held for 10-30 minutes before the rapid cooling procedure is performed. This brief cooling process is used to induce a small amount of secondary liquid phase to condense back to the grain boundaries, thereby achieving partial glass healing of the grain boundaries.

7. The method for preparing environmentally friendly magnesium aluminum spinel raw materials using industrial solid waste according to claim 1, characterized in that: Step d includes a heat treatment process, which includes: After the raw material obtained in step d is crushed to a certain particle size, it is annealed in an oxidizing atmosphere at 1200-1350℃ for 2-6 hours. This annealing treatment is used to re-oxidize and stabilize the trace low-valence metal ions present in the raw material due to reducing sintering, and to eliminate residual stress.

8. The method for preparing environmentally friendly magnesium aluminum spinel raw material using industrial solid waste according to claim 1, characterized in that: In step b, wet activation grinding is carried out using a planetary ball mill. The ball mill is filled with some zirconia grinding balls, and the filling volume is 30-50% of the grinding tank volume. Among them, the proportion of zirconia small balls with a particle size of 3-5mm is not less than 60%, and the ball mill speed is 300-500 rpm.

9. The method for preparing environmentally friendly magnesium aluminum spinel raw material from industrial solid waste according to claim 1, characterized in that: The high-purity magnesium aluminum spinel raw material in step d has magnesium aluminum spinel as its main crystalline phase, and the grains contain dispersed zirconium-containing second-phase particles with a size of less than 200 nm.

10. A method for preparing environmentally friendly magnesium aluminum spinel raw material from industrial solid waste according to claim 9, characterized in that: The high-purity magnesium aluminum spinel raw material has a flexural strength of not less than 30 MPa at a high temperature of 1600℃, and its soluble chloride ion content is less than 100 ppm.

Images