阅读说明：本技术 一种铝灰渣高温自发泡制备低收缩多孔陶瓷的方法 (Method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash ) 是由 张笑妍 张深根 李雯昊 于 2021-09-26 设计创作，主要内容包括：本发明涉及固废资源综合利用技术领域,公开了一种铝灰渣高温自发泡制备低收缩多孔陶瓷的方法,本发明以提铝后的二次铝灰渣为主要原料,铝灰渣无需除盐除氮处理,将二次铝灰渣进行喷雾造粒、干压成型、高温烧结最终得到低收缩多孔陶瓷材料。该发明方法工艺过程简便易行,免去复杂的除盐除氮过程,充分利用二次铝灰渣成分特点实现高温自发泡过程进而获得多孔结构,能够实现二次铝灰渣无害化处置及固废资源化利用,制得多孔陶瓷材料具有低收缩、强度高、隔热性能优异等特点,可应用于保温隔热材料等领域。(The invention relates to the technical field of comprehensive utilization of solid waste resources, and discloses a method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash. The method has the advantages that the technological process is simple and easy to implement, the complex desalting and denitrogenating process is omitted, the high-temperature self-foaming process is realized by fully utilizing the characteristics of the secondary aluminum ash components, the porous structure is further obtained, the harmless treatment and the solid waste resource utilization of the secondary aluminum ash can be realized, and the prepared porous ceramic material has the characteristics of low shrinkage, high strength, excellent heat-insulating property and the like, and can be applied to the fields of heat-insulating materials and the like.)

1. A method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash is characterized by comprising the following steps: carrying out spray granulation, dry pressing molding and high-temperature sintering on secondary aluminum ash obtained after aluminum is extracted from the aluminum ash to obtain low-shrinkage porous ceramic;

the secondary aluminum ash slag is characterized in that nitrides and carbides in the secondary aluminum ash slag provide gas sources in the high-temperature sintering process to play the role of a high-temperature foaming agent, the volume expansion generated in the high-temperature oxidation and high-temperature foaming processes of simple substance aluminum and simple substance silicon in the secondary aluminum ash slag is offset with the volume shrinkage generated in sintering densification, and oxides in the secondary aluminum ash slag can be used as sintering aids of porous ceramics.

2. The method for preparing the low-shrinkage porous ceramic by self-foaming the aluminum ash at the high temperature according to claim 1, wherein the porosity of the low-shrinkage porous ceramic is 20-80%, the shrinkage rate is-10%, and the bending strength is 1-120 MPa.

3. The method for preparing the low-shrinkage porous ceramic by the high-temperature self-foaming of the aluminum ash according to claim 1, wherein the method specifically comprises the following steps:

(1) performing ball milling, drying and sieving treatment on secondary aluminum ash obtained after aluminum extraction to obtain secondary aluminum ash powder;

(2) adding a binder into the secondary aluminum ash powder, uniformly mixing, performing spray granulation, and performing dry pressing to obtain a biscuit;

(3) and (3) sintering the biscuit obtained in the step (2) at a high temperature to obtain the low-shrinkage porous ceramic.

4. The method for preparing the low-shrinkage porous ceramic through the high-temperature self-foaming of the aluminum ash as claimed in claim 3, wherein in the step (1), the ball milling time is 0.5 h-48 h, and the ball milling process is dry milling or wet milling with alcohol as an auxiliary agent.

5. The method for preparing the low-shrinkage porous ceramic through the high-temperature self-foaming of the aluminum ash according to claim 3, wherein in the step (1), the drying treatment time is 10 min-72 h, and the temperature is 35-100 ℃; the mesh number of the screening is 100 meshes and 500 meshes.

6. The method for preparing the low-shrinkage porous ceramic by self-foaming the aluminum ash at high temperature according to claim 3, wherein in the step (2), the binder comprises one or more of polyethylene glycol, polyvinyl alcohol, sodium carboxymethylcellulose and polyvinylpyrrolidone,

and preparing a binder to obtain a binder solution with the concentration of 0.01-10.00 wt%, and then adding the binder solution into the secondary aluminum ash powder, wherein the addition amount of the binder solution is 0.01-8.00 wt% of the total mass of the secondary aluminum ash powder.

7. The method for preparing the low-shrinkage porous ceramic by the high-temperature self-foaming of the aluminum ash as claimed in claim 3, wherein in the step (2), the pressure of the dry pressing is 2-50MPa, and the pressure maintaining time is 1 min-30 min.

8. The method for preparing low shrinkage porous ceramic by high temperature self-foaming of aluminum ash as claimed in claim 3, wherein in the step (3), the high temperature sintering temperature is 1200-1750 ℃, the heating rate is 0.1-20 ℃/min, and the holding time is 10min-24 h.

Technical Field

The invention belongs to the technical field of green treatment and resource utilization of solid wastes, and particularly relates to a method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash, wherein the prepared low-shrinkage porous ceramic can be used as a heat insulation material in the fields of hot blast furnace bricks, protective pipes and the like.

Background

The aluminum ash is obtained by electrolyzing molten salt and casting in the production process of metal aluminum or aluminum alloyProcessing and recycling the generated solid waste. In the national records of dangerous wastes published in 2021, aluminum ash slag generated in the processing of recycled aluminum and aluminum materials and secondary aluminum ash generated in the aluminum recovery process are listed as dangerous solid wastes (HW 48). The aluminum ash can be divided into primary aluminum ash and secondary aluminum ash according to the source, wherein the primary aluminum ash generated in the aluminum electrolysis process contains 15-75% of metallic aluminum, and has recovery value; and the primary aluminum ash is treated again to obtain secondary aluminum ash, wherein the content of metallic aluminum is only 5-10%, and the component is Al₂O₃、AlN、MgAl₂O₄Oxides and salts are the main. In 2019, the annual output of the aluminum ash in China reaches 319 ten thousand tons, the treatment of the aluminum ash mainly comprises stockpiling, filling and resource utilization, particularly more than 95 percent of secondary aluminum ash is subjected to filling or stockpiling treatment, and the aluminum ash contains F^-、Cl^-And toxic metal ions such As Cd, Cr, Pb, Ba, As and the like, the traditional stacking or landfill mode not only causes resource waste, but also causes land resource occupation, underground water pollution and environmental hazard, and in addition, AlN in the secondary aluminous ash slag is easy to generate a hydrolysis reaction to generate toxic or combustible gas (NH)₃、CH₄、PH₃、H₂Etc.) cause atmospheric pollution and seriously threaten life and health. Therefore, the resource utilization of the aluminum ash is not only beneficial to improving the environment, but also provides an effective way for the development of resources.

At present, the resource utilization approach of secondary aluminous ash mainly comprises the following steps: metallic aluminium or Al₂O₃The method comprises the following steps of extraction, synthesis of cryolite and magnesium aluminate spinel, preparation of alumina-based ceramic, magnesium titanate-based ceramic, mullite ceramic and beta-SiAlON ceramic, and preparation of foam glass ceramics, refractory bricks, concrete and the like by cooperating with other solid wastes. Porous ceramics are often used for light heat-insulating materials due to their high porosity, high specific strength and low thermal conductivity coefficient caused by the porous structure, such as the linings of traditional kilns and high-temperature electric furnaces are generally porous ceramics. Common porous ceramic preparation methods include an organic foam impregnation process, a direct foaming method, a pore-forming agent adding method, a freeze drying technology, a 3D printing technology and the like. Wherein the high temperature foaming process is carried out byThe high-temperature foaming agent is mixed in the raw materials, and the porous ceramic is prepared by utilizing the gas generated by the reaction of the high-temperature foaming agent at high temperature, so that the method has the characteristics of simple and easy process, wide application and suitability for industrial production. The sintering stage in the ceramic preparation process is a key link influencing the integrity, final size and performance of a ceramic part, and the problem of ceramic sintering shrinkage is solved by adopting a reaction sintering method, a phase transition method, adding a low-sintering active component and the like. Claussen firstly proposes that the single-phase or complex-phase low-shrinkage ceramic containing aluminum oxide is prepared by utilizing 28% volume expansion generated in the phase conversion process of metal aluminum particles to aluminum oxide particles, and the volume expansion is offset with the densification in the particle sintering process, and the addition amount of aluminum powder in raw material powder is 30-65% by volume fraction, and the additional addition of aluminum powder improves the raw material cost.

Chinese patent CN108689695A discloses an application method of aluminum ash in high-alumina ceramic, wherein the aluminum ash is not treated by rinsing, calcining and other methods, is added into a high-alumina ceramic formula as a composite pore-forming agent, and is subjected to batching, dry ball milling, dry compression molding and firing to obtain a porous high-alumina ceramic product with excellent thermal shock resistance. However, the main raw material in the invention is alumina powder 85-99.8 wt.%, the addition amount of aluminum ash is only 0.2-15 wt.%, and the pore-forming principle is that the components of metal aluminum, nitride, carbide and the like in the aluminum ash form pores at high temperature. The technology mainly solves the problem of pore forming of the high-alumina ceramic, and simultaneously has the problem of low utilization rate of aluminum ash in order to avoid introducing excessive impurities.

Chinese patent CN109970456A discloses a method for recycling and reusing aluminum ash, which comprises the steps of firstly carrying out pretreatment processes of separating iron impurities and metallic aluminum and washing with water to remove aluminum nitride and salts from the aluminum ash, further mixing the aluminum ash with kaolin, bentonite and talc, carrying out wet milling on the mixture to obtain slurry, further adding a stabilizer and a surfactant, and carrying out slurry coating, drying, binder removal and firing to obtain foamed ceramic. However, in the invention, the components of metallic aluminum and aluminum nitride of the aluminum ash are removed, the pore-forming and molding modes are realized by an organic foam impregnation process, the aluminum ash accounts for 70-80% of the total mass of the raw materials, and the desalting and nitrogen removing processes increase the production period, energy consumption and cost.

Chinese patent CN108996930A discloses a method for preparing a foamed geopolymer gelled material from aluminum ash, which comprises the steps of pretreating the aluminum ash to remove salt flux impurities, mixing the aluminum ash with blast furnace mineral powder and fly ash, introducing a foam stabilizer and an alkaline activator, foaming, forming and curing to obtain the foamed geopolymer gelled material. However, the utilization rate of the aluminum ash is only 50-60 wt.%, and the aluminum metal component in the aluminum ash is used as a foaming agent, and the forming mode is mainly realized by alkali excitation to obtain a gelled substance for forming and maintaining.

Disclosure of Invention

Aiming at the technical problems, the invention provides a method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash, which takes the aluminum ash as a main raw material by utilizing the component characteristics of the aluminum ash and prepares the low-shrinkage porous ceramic through dry pressing molding and dry sintering.

The invention is realized by the following technical scheme:

a method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash, which comprises the following steps: carrying out spray granulation, dry pressing molding and high-temperature sintering on secondary aluminum ash obtained after aluminum is extracted from the aluminum ash to obtain low-shrinkage porous ceramic;

the components such as nitride, carbide and the like in the secondary aluminum ash provide a gas source in the high-temperature sintering process to play the role of a high-temperature foaming agent, the simple substance aluminum and the simple substance silicon in the secondary aluminum ash can be oxidized at high temperature to generate volume expansion, and the volume expansion generated in the high-temperature self-foaming process can be offset with the volume contraction generated by sintering densification, and the oxide in the secondary aluminum ash can be used as a sintering aid of the porous ceramic, so that the low-contraction porous ceramic is finally obtained.

Furthermore, the low-shrinkage porous ceramic has the characteristics of low sintering shrinkage, light weight and high strength, and has the porosity of 20-80%, the shrinkage rate of-10% and the bending strength of 1-120 MPa.

Further, the method specifically comprises:

(1) performing ball milling, drying and sieving treatment on secondary aluminum ash obtained after aluminum extraction to obtain secondary aluminum ash powder;

(2) adding a binder into the secondary aluminum ash powder, uniformly mixing, performing spray granulation, and performing dry pressing to obtain a biscuit;

(3) and (3) sintering the biscuit obtained in the step (2) at a high temperature to obtain the low-shrinkage porous ceramic.

Further, in the step (1), the ball milling time is 0.5 h-48 h, and the ball milling process is dry milling or wet milling by using alcohol as an auxiliary agent.

Further, in the step (1), the drying treatment time is 10 min-72 h, and the temperature is 35-100 ℃; the mesh number of the screening is 100 meshes and 500 meshes.

Further, in the step (2), the binder comprises one or more of polyethylene glycol, polyvinyl alcohol, sodium carboxymethyl cellulose and polyvinylpyrrolidone solution;

and preparing a binder to obtain a binder solution with the concentration of 0.01-10.00 wt%, and then adding the binder solution into the secondary aluminum ash powder, wherein the addition amount of the binder solution is 0.01-8.00 wt% of the total mass of the secondary aluminum ash powder.

Further, in the step (2), the pressure of the dry pressing is 2-50MPa, and the pressure maintaining time is 1-30 min.

Further, in the step (3), the high-temperature sintering temperature is 1200-.

The invention has the beneficial technical effects that:

the method takes the secondary aluminum ash after aluminum extraction as a main raw material, does not need the process of desalting and denitrogenating, obtains a biscuit through ball milling, drying, sieving, granulating and dry pressing molding, and further prepares the porous ceramic through high-temperature sintering. The characteristics of the components of the secondary aluminum ash slag of the raw material are fully utilized, wherein the nitride and the carbide can react in the high-temperature sintering process to provide a gas source to play the role of a high-temperature foaming agent, and the components of simple substance aluminum, simple substance silicon and the like in the matrix constructed by the high-temperature foaming process and the aluminum ash slag can be oxidized at high temperature to generate volume expansion and can be offset with the volume contraction generated by sintering densification. Easy hydrolysis in aluminous ash to generate NH₃The AlN component causing pollution and harm can be converted into Al at high temperature₂O₃And generates N₂To act as a high temperature blowing agent; sodium salt, fluoride salt flux, heavy metal and the like which are easy to pollute soil and water can be converted into crystalline phase at high temperature to be stably solidified; CaO, MgO, SiO₂The oxide component can be used as a sintering aid of the porous ceramic. The whole process avoids the use of water, obtains high-valued low-shrinkage porous ceramic materials, and effectively solves the problems of pollution and harm of aluminum ash.

The porous ceramic prepared by the invention has the characteristics of low shrinkage, light weight, high strength and heat insulation, can be used as a light heat-insulating material, has low cost in the production process, is simple and feasible, can realize the treatment and recovery of wastes, and is beneficial to environmental protection.

Drawings

FIG. 1 is a macroscopic photograph of a low shrinkage porous ceramic obtained by preparing secondary aluminum ash in example 1 of the present invention.

FIG. 2 is a microscopic morphology of the low shrinkage porous ceramic prepared from the secondary aluminum ash in example 1.

FIG. 3 is an XRD spectrum of a low shrinkage porous ceramic prepared from secondary aluminum dross in example 1.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

On the contrary, the invention is intended to cover alternatives, modifications, equivalents and alternatives which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of the present invention, certain specific details are set forth in order to provide a better understanding of the present invention. It will be apparent to one skilled in the art that the present invention may be practiced without these specific details.

Example 1

A method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash, which comprises the following steps: and (3) carrying out dry grinding on the aluminum ash slag for 24 hours by adopting a planetary ball mill, and transferring the ball-ground aluminum ash slag to an oven. The oven temperature was set at 60 deg.C, and the product was dried for 24h and sieved through a 115 mesh screen. Uniformly spraying 10.00 wt.% polyvinyl pyrrolidone solution on the sieved aluminum ash powder for spray granulation, wherein the addition amount of the solution accounts for 1.00 wt.% of the total mass of the powder. And (3) dry-pressing the uniformly mixed powder under 10MPa by using a dry pressing forming machine, keeping the pressure for 1min, and then demoulding. And (3) preserving the heat of the demolded green body at 1500 ℃ for 2h for sintering, and setting the heating rate to be 2 ℃/min to prepare the porous ceramic, wherein the porosity is 40%, the shrinkage rate is 2%, and the bending strength is 78 MPa.

As shown in fig. 1-3, it is a macro-photograph, a micro-morphology and an XRD pattern of the low shrinkage porous ceramic obtained by the second preparation of the aluminous ash in the embodiment of the present invention. The result shows that the sample obtained by the method has no defects of deformation, cracking and the like, the pore structure is uniformly distributed, and the pore diameter is about 30.2 mu m; the main crystal phase of the sample is alpha-Al₂O₃And MgAl₂O₄And a small amount of albite and anorthite.

Example 2

A method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash, which comprises the following steps: wet grinding the aluminum ash with alcohol for 15h by adopting a planetary ball mill, and transferring the ball-milled aluminum ash to an oven. The oven temperature was set at 75 deg.C, dried at this temperature for 30h, and sieved through a mesh screen with 240 mesh openings. And uniformly spraying polyethylene glycol with the concentration of 1.00 wt.% on the sieved aluminum ash powder, wherein the addition amount of the solution accounts for 1.25 wt.% of the total mass of the powder. And (3) dry-pressing the uniformly mixed powder under 8MPa by using a dry pressing forming machine, keeping the pressure for 10min, and then demoulding. And (3) preserving the heat of the demolded green body at 1350 ℃ for 0.5h, sintering, and setting the heating rate to be 8 ℃/min to obtain the porous ceramic, wherein the porosity is 78%, the shrinkage rate is-9%, and the bending strength is 1.8 MPa.

Example 3

A method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash, which comprises the following steps: wet grinding the aluminum ash slag by adopting alcohol for 0.5h by adopting a planetary ball mill, and transferring the ball-milled aluminum ash slag to an oven. The temperature of the oven is set to 35 ℃, and the mixture is dried for 72 hours at the temperature and then sieved by a sieve with the aperture of 240 meshes. And uniformly spraying 5.00 wt.% polyvinyl alcohol solution on the sieved aluminum ash powder for spray granulation, wherein the addition amount of the solution accounts for 2.00 wt.% of the total mass of the powder. And (3) dry-pressing the uniformly mixed powder under 20MPa by using a dry pressing forming machine, keeping the pressure for 20min, and then demoulding. And (3) preserving the heat of the demolded green body at 1200 ℃ for 24h for sintering, and setting the heating rate to be 20 ℃/min to prepare the porous ceramic, wherein the porosity is 70%, the shrinkage rate is-10%, and the bending strength is 5 MPa.

Example 4

A method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash, which comprises the following steps: and (3) carrying out dry grinding on the aluminum ash slag for 48 hours by adopting a planetary ball mill, and transferring the ball-ground aluminum ash slag to an oven. The temperature of the oven is set to 100 ℃, the drying is carried out for 10min at the temperature, and the dried product is sieved by a sieve with 100 meshes of apertures. And uniformly spraying a polyvinyl alcohol solution with the concentration of 2.00 wt.% on the sieved aluminum ash powder for spray granulation, wherein the addition amount of the solution accounts for 1.50 wt.% of the total mass of the powder. And (3) dry-pressing the uniformly mixed powder under 50MPa by using a dry pressing forming machine, keeping the pressure for 5min, and then demoulding. And (3) preserving the temperature of the demoulded green body at 1750 ℃ for 10min, sintering, and setting the heating rate to be 5 ℃/min to prepare the porous ceramic, wherein the porosity is 25%, the shrinkage rate is 10%, and the bending strength is 112 MPa.

Example 5

A method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash, which comprises the following steps: wet grinding the aluminum ash with alcohol for 5h by adopting a planetary ball mill, and transferring the ball-milled aluminum ash to an oven. The oven temperature was set at 55 deg.C, dried at this temperature for 6h, and sieved through a 500 mesh screen. And uniformly spraying polyvinyl alcohol solution with the concentration of 0.01 wt.% on the sieved aluminum ash powder for spray granulation, wherein the addition amount of the solution accounts for 0.01 wt.% of the total mass of the powder. And (3) carrying out dry pressing on the uniformly mixed powder under 2MPa by using a dry pressing forming machine, keeping the pressure for 30min, and then demoulding. And (3) preserving the temperature of the demolded green body at 1300 ℃ for 5h for sintering, and setting the heating rate to be 0.1 ℃/min to prepare the porous ceramic, wherein the porosity is 50%, the shrinkage rate is-7%, and the bending strength is 28 MPa.

Example 6

A method for preparing low-shrinkage porous ceramic by high-temperature self-foaming of aluminum ash, which comprises the following steps: and (3) carrying out dry grinding on the aluminum ash slag for 10 hours by adopting a planetary ball mill, and transferring the ball-ground aluminum ash slag to an oven. The temperature of the oven is set to 80 ℃, the drying is carried out for 30min at the temperature, and the dried product is sieved by a sieve with the aperture of 300 meshes. And uniformly spraying sodium carboxymethylcellulose solution with the concentration of 0.50 wt.% on the sieved aluminum ash powder for spray granulation, wherein the addition amount of the solution accounts for 0.08 wt.% of the total mass of the powder. And (3) dry-pressing the uniformly mixed powder under 15MPa by using a dry pressing forming machine, keeping the pressure for 3min, and then demoulding. And (3) preserving the temperature of the demolded green body at 1550 ℃ for 3h, sintering at a high temperature, and setting the heating rate to be 10 ℃/min to obtain the porous ceramic, wherein the porosity is 44%, the shrinkage rate is-0.5%, and the bending strength is 58 MPa.

The invention takes the secondary aluminum ash slag after aluminum extraction as a main raw material, and the low-shrinkage porous ceramic material is obtained by carrying out spray granulation, dry pressing and molding and high-temperature sintering on the secondary aluminum ash slag. The method has the advantages that the technological process is simple and easy to implement, the complex desalting and denitrogenating process is omitted, the high-temperature self-foaming process is realized by fully utilizing the characteristics of the secondary aluminum ash components, the porous structure is further obtained, the harmless treatment and the solid waste resource utilization of the secondary aluminum ash can be realized, and the prepared porous ceramic material has the characteristics of low shrinkage, high strength, excellent heat-insulating property and the like, and can be applied to the fields of heat-insulating materials and the like.