Method for preparing mullite-based porous ceramic material from biochar and coal co-gasification fly ash

Abstract

The invention discloses a method for preparing a mullite-based porous ceramic material from biochar and coal co-gasification fly ash, and belongs to the technical field of porous ceramic materials. Aiming at the technical bottlenecks of single raw material, dependence of a pore-forming mode on an additional material, poor controllability of a pore channel structure, low resource utilization efficiency of industrial byproducts and the like in the preparation of the existing mullite-based porous ceramic, the invention provides the preparation method of the mullite-based porous ceramic. The preparation method comprises the following steps: by taking charcoal and coal co-gasification fly ash as a silicon source and an additional aluminum source as a mixed raw material, proportioning according to a specific mass ratio of aluminum oxide to silicon oxide, adding a binder and a pore-forming agent, and uniformly mixing to obtain a mixture; and adding a whisker accelerant, granulating, sieving, carrying out static-pressure blank forming, drying and sintering to obtain the mullite-based porous ceramic material. The preparation method has a new path for preparing the mullite-based porous ceramic with remarkable resource value and industrialization potential, and provides technical support for promoting high-value utilization of multi-source solid wastes and development of functional ceramics.

Description

Technical Field

[0001] The present invention belongs to the technical field of porous ceramic materials, and specifically relates to a method for preparing mullite-based porous ceramic materials using biochar and coal co-gasification fly ash as main raw materials. It belongs to the cross-technical category of industrial solid waste resource utilization and porous structure ceramic material preparation. Background Art

[0002] Mullite (3Al2O3·2SiO2) has broad application prospects in high-temperature applications, including refractories, thermal insulation structures, ceramic-based composites, and functional coatings, due to its excellent thermal stability, thermal shock resistance, corrosion resistance, and low thermal expansion coefficient. In recent years, with the advancement of structural-functional integrated material design, porous mullite ceramics have attracted increasing attention due to their combined strength and high porosity. Microstructural characteristics such as porosity, pore size distribution, and connectivity have a decisive influence on functional parameters such as thermal conductivity, acoustic properties, and catalytic efficiency.

[0003] Currently, porous mullite ceramics are typically made from high-purity alumina and a silicon source, with pores constructed through processes such as the addition of pore-forming agents, sacrificial templates, or foam replication. However, these methods suffer from high raw material costs, high energy consumption, and difficulty in precisely controlling the pore structure, hindering their large-scale application.

[0004] In contrast, the large amount of gasification fly ash produced during the co-gasification of biomass and coal is a typical industrial byproduct. Rich in SiO₂ and Al₂O₃, along with a certain amount of residual carbon and alkali metals (such as K and Na), it has significant potential as a ceramic raw material. Direct disposal would not only waste resources but also pose environmental risks. Therefore, developing processes for preparing functional ceramics using gasification fly ash as a primary material is a current research hotspot at the intersection of materials science and environmental engineering.

[0005] At present, a lot of research has been carried out on the preparation of mullite-based porous ceramics using industrial waste.

[0006] CN119912271A discloses a mullite porous ceramic and its preparation method. The raw material is solid waste fly ash, and andalusite is introduced as a silicon source regulator. Alumina or calcined bauxite is used as the aluminum source. The ingredients are formulated based on a near-mullite chemical composition. The structure of the mullite ceramic is regulated by combining the raw material particle size, the pressing molding process, and the staged sintering process. In this process, the near-net-size mullite porous ceramic is effectively prepared by particle accumulation and the volume expansion associated with mullite formation during sintering. The resulting mullite-based porous ceramic exhibits low sintering shrinkage, good gas flux, and structural strength.

[0007] CN116813367A discloses a porous ceramic and a method for preparing the same. This method utilizes controlled raw material sources, selecting high-alumina fly ash primarily composed of mullite and quartz phases as the primary raw material, rationally combining additional aluminum and silicon sources, and adding a small amount of a fluorine-free whisker accelerator and sintering aid to regulate the balance between whisker production and porosity. The resulting porous ceramic exhibits a high whisker content and high porosity. The mullite whiskers in the resulting porous ceramic have a diameter of 0.5 to 0.8 μm, an aspect ratio of 10 to 30, and grow in the c-axis

[001] direction. The mullite whisker content in the resulting ceramic is 55 to 65% by volume, and the ceramic has a porosity greater than 80%.

[0008] While existing technologies have attempted to recycle various industrial byproducts, there has been no systematic research on the use of biochar and coal co-gasification fly ash for the preparation of mullite porous ceramics. Furthermore, there is a lack of in-depth research and engineering implementation on the synergistic mechanism between residual carbon and alkali metal elements in fly ash. For example, the gasification behavior of residual carbon during sintering can be used to construct in-situ microporous structures, while the mobile K element in fly ash may impart certain catalytic activity or ionic conductivity to the material. However, there are currently few literature or technical solutions to systematically utilize these properties.

[0009] Therefore, it is urgent to propose a method for preparing mullite-based porous ceramics that can systematically utilize the multi-component characteristics of co-gasification fly ash and take into account both structural regulation and functional development, so as to achieve high-value and functional transformation of industrial by-products and expand their application boundaries in filtration, thermal isolation, energy catalysis and other fields. Summary of the Invention

[0010] In response to the technical bottlenecks in the preparation of existing mullite-based porous ceramics, such as single raw materials, pore-forming methods relying on external materials, poor controllability of pore structure, and low efficiency in resource utilization of industrial by-products, a new ceramic preparation method is proposed that integrates high-value utilization of industrial by-products, precise construction of multi-scale pores and empowerment of material functions.

[0011] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0012] A method for preparing a mullite-based porous ceramic material from fly ash from the co-gasification of biochar and coal comprises the following steps: using fly ash from the co-gasification of biochar and coal as a silicon source and an external aluminum source as a mixed raw material; preparing the materials according to a specific mass ratio of aluminum oxide to silicon oxide; adding a binder and a pore-forming agent; and adding a whisker promoter; granulating, screening, statically pressing into a blank, drying, and sintering to obtain the mullite-based porous ceramic material.

[0013] Furthermore, the residual carbon in the fly ash from the co-gasification of biochar and coal acts as a pore-forming agent, pyrolyzing to generate gas during the sintering process, thereby forming an in-situ pore structure within the ceramic matrix and enhancing the material's interconnected porosity. This pore-forming mechanism is a dual, synergistic one, where the externally added pore-forming agent primarily creates regular macropores, while the residual carbon in the fly ash, during sintering, pyrolyzes to generate gas, creating interconnected micropores. This allows for the integrated construction of a multi-scale pore structure across the material.

[0014] Furthermore, the granulation conditions are as follows: using an inclined intensive mixer or a disc granulator, granulation for 1 to 30 minutes, and mixing the binder and the mixed raw materials in a step-by-step manner or a one-time mixing manner; during the granulation process, by controlling the granulation particle size within the range of 0.2 to 5 mm, the distribution and structure of the macropores in the ceramic material are adjusted to construct regular macropores.

[0015] Furthermore, the sintering specifically includes a first stage of preheating and removal, a second stage of mullite crystal phase formation and growth, and a third stage of cooling, and the entire sintering process is carried out in air or an inert atmosphere;

[0016] The first stage of preheating and removal is a heating rate of 0.5-15°C / min, a temperature of 400-600°C, and a heat preservation time of 1-3 hours to fully remove the pore former, binder and volatile components;

[0017] The second stage of mullite crystal phase formation and growth is a heating rate of 0.5-15°C / min, a temperature of 900-1500°C, and a holding time of 1-6 hours to promote the formation and crystal growth of the mullite phase, and at the same time promote the whisker precipitation induced by the whisker promoter and the densification of the skeleton;

[0018] The third stage, cooling, is to lower the temperature to room temperature at a cooling rate of 5-20°C / min.

[0019] Furthermore, the biochar and coal co-gasification fly ash has the following component contents: 8.67 wt% alumina, 50.40 wt% silica, 4.76 wt% potassium oxide, and 25.37 wt% unburned carbon.

[0020] Furthermore, the external aluminum source is one of calcined bauxite powder, γ-Al2O3, and Al(OH)3, and its aluminum oxide content is ≥70wt%.

[0021] Furthermore, the mass ratio of aluminum oxide to silicon oxide is 1.3 to 2.3.

[0022] Furthermore, the binder is one or more of water, starch, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC); the binder accounts for 2-30 wt% of the mass fraction of the mixed raw materials.

[0023] Furthermore, the pore-forming agent is one of starch, hydrogen peroxide, polymethyl methacrylate (PMMA), and ammonium bicarbonate; the pore-forming agent accounts for 5-40 wt % of the mass fraction of the mixed raw materials.

[0024] Furthermore, the whisker promoter is one of B2O3, AlF3·3H2O, and MnO2; the mass fraction of the whisker promoter in the mixed raw materials is 0.2-10wt%.

[0025] Mullite-based porous ceramic materials,

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] The present invention introduces a pore control mechanism. On the one hand, by controlling the granulation time and equipment parameters and limiting the particle size to the range of 0.2~5 mm, it not only ensures the density of particle accumulation, but also forms regular large pores of uniform size in the ceramic body. On the other hand, during the sintering process, the residual carbon components in the fly ash undergo in-situ pyrolysis and gas evolution to form a through-hole microporous structure, effectively improving the connected porosity of the ceramic. Through this mechanism, a human-controllable through-hole multi-scale pore structure system is constructed. This structural control mechanism can significantly improve the gas permeability and specific surface area of ​​the material, providing structural support for its functional applications.

[0028] In terms of forming, a cold isostatic pressing process is used to achieve high-density billets, and then a three-stage sintering process is used to complete material densification and the construction of a multi-scale pore structure. At the same time, the alkali metal elements in the gasified fly ash can create a sintering liquid phase, reducing the sintering temperature while promoting the growth of mullite whiskers, which is economical and environmentally friendly. In addition, the present invention fully utilizes the active behavior of mobile alkali metals (such as K) in fly ash at high temperatures, not only reducing the sintering temperature, but also showing a synergistic effect in crystal phase induction, skeleton densification, and the formation of surface functional sites. This gives the material potential ion exchange capacity, weak catalytic activity, or thermoelectric response characteristics, expanding its application boundaries in high-temperature filtration, carrier catalysis, environmental functional ceramics, and other areas.

[0029] In summary, the present invention provides a new preparation path for mullite-based porous ceramics that combines structural regulation and functional development, has significant resource value and industrialization potential, and provides technical support for promoting the high-value utilization of multi-source solid waste and the development of functional ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0031] Figure 1 is an SEM image of the mullite-based porous ceramic in Example 1.

[0032] Figure 2 This is the XRD image of the mullite-based porous ceramic in Example 1. DETAILED DESCRIPTION

[0033] To gain a deeper understanding of the present invention, we will provide a comprehensive and detailed description thereof. However, the present invention has various implementations and is not limited to the specific examples listed herein. These examples are presented to enhance a comprehensive understanding of the present disclosure.

[0034] The biochar and coal co-gasification fly ash in the following examples was sourced from a fluidized bed gasifier in Shanxi Province, wherein the aluminum oxide content was 8.67 wt%, the silicon dioxide content was 50.40 wt%, the potassium oxide content was 4.76 wt%, and the unburned carbon content was 25.37 wt%. The calcined bauxite powder was sourced from Inner Mongolia Autonomous Region, and the aluminum oxide content was 78.45 wt%.

[0035] Example 1

[0036] A method for preparing a mullite-based porous ceramic material from fly ash from the co-gasification of biochar and coal comprises the following steps:

[0037] (1) The materials were prepared according to a mass ratio of alumina to silica of 1.7, and then 10 wt% of water, 10 wt% of starch, and 3 wt% of B2O3 were added to the fly ash from the co-gasification of biochar and coal and the calcined bauxite powder. The water acted as a binder, and the starch acted as both a binder and a pore-forming agent. The mixture was poured into an inclined high-power mixer for mixing and granulation. The granulation lasted for 5 minutes. After the granulation was completed, the mixture was sieved through a standard sieve of 20-40 mesh to obtain a granular raw material of 0.425-0.850 mm.

[0038] (2) placing the obtained granular raw material in a mold and forming it using a tablet press at a molding pressure of 20 MPa, and drying to obtain a ceramic green body;

[0039] (3) The ceramic green body is placed in an electric heating furnace for firing. First, the temperature is raised to 500 °C at a heating rate of 2 °C / min and kept at this temperature for 1 h. Then the temperature is raised to 1350 °C at a heating rate of 10 °C / min and kept at this temperature for 3 h to promote the formation of mullite phase and crystal growth, and at the same time promote the whisker precipitation and skeleton densification induced by the whisker promoter. Finally, the temperature is lowered to room temperature at a cooling rate of 15 °C / min. After cooling in the furnace, the mullite-based porous ceramic material is obtained.

[0040] In order to further verify the structure and performance of the prepared mullite-based porous ceramic material, a number of structural characterizations and performance tests were performed on the sample obtained in Example 1, as follows:

[0041] The sample was examined by scanning electron microscopy (SEM). Figure 1 Analysis shows that its cross-section exhibits a distinct multi-scale pore structure, comprising uniformly distributed regular macropores (approximately 1-2 mm in diameter) and through-hole micropores (approximately 0.5-10 μm in diameter). The macropores primarily originate from the decomposition of the added starch pore-forming agent, while the small pores are caused by the in-situ thermal decomposition of residual carbon components in the fly ash during the sintering process. The pore structure is well connected.

[0042] The specific surface area analysis was carried out using nitrogen adsorption method (BET), and the results showed that the specific surface area of ​​the material was 16.8 m 2 / g, the porosity is 48.3%, and the average pore diameter is 7.6 nm, which is consistent with the structural characteristics of typical porous ceramics.

[0043] The gas permeability test uses the constant flow pressure difference method (air medium, 25°C room temperature). At a pressure difference of 1.0 kPa, the gas flux can reach 1150 mL / min·cm 2 , indicating that the material has good gas permeability and is suitable for functional application scenarios such as high-temperature filtration and gas reaction medium transmission.

[0044] The XRD diffraction results are as follows Figure 2 As shown, the results show that the main crystal phases in the material are mullite (3Al2O3·2SiO2), potassium feldspar (K2O·Al2O3·6SiO2) and calcium feldspar (CaO·Al2O3·2SiO2), without obvious impurity phases, and the crystal structure is complete. Combined with the rod-like whisker morphology observed by SEM, it can be inferred that the B2O3 whisker induction effect is significant, which helps to enhance the structural stability of the ceramic matrix.

[0045] In summary, the prepared mullite-based porous ceramics not only have good structural controllability and molding density, but also exhibit high specific surface area and gas permeability, laying a structural foundation for subsequent applications in high-temperature gas filtration, catalytic reaction carriers, thermal insulation or electrical properties.

[0046] Example 2

[0047] A method for preparing a mullite-based porous ceramic material from fly ash from the co-gasification of biochar and coal comprises the following steps:

[0048] (1) The materials were prepared in a mass ratio of alumina to silica of 2:1, and then 10 wt% of polyvinyl alcohol (PVA), 10 wt% of polymethyl methacrylate (PMMA), and 5 wt% of MnO2 were added to the fly ash from the co-gasification of biochar and coal and γ-Al2O3 powder. PVA served as a binder and PMMA served as a pore-forming agent. The materials were poured into a disc granulator for mixing and granulation. The granulation lasted for 5 minutes. After granulation, the materials were sieved through a standard sieve of 20-40 mesh to obtain granular raw materials with a diameter of 0.425-0.850 mm.

[0049] (2) placing the obtained granular raw material in a mold and forming it using a tablet press at a molding pressure of 20 MPa, and drying to obtain a ceramic green body;

[0050] (3) The ceramic green body is placed in an electric heating furnace for firing. First, the temperature is raised to 500 °C at a heating rate of 2 °C / min and kept at this temperature for 1 h. Then the temperature is raised to 1420 °C at a heating rate of 10 °C / min and kept at this temperature for 3 h to promote the formation of mullite phase and crystal growth, and at the same time promote the whisker precipitation and skeleton densification induced by the whisker promoter. Finally, the temperature is lowered to room temperature at a cooling rate of 15 °C / min. After cooling in the furnace, the mullite-based porous ceramic material is obtained.

[0051] Gas permeability test results: The mullite-based porous ceramic obtained in Example 2 was tested for gas flux using the constant current pressure difference method (air medium, room temperature 25°C). At a pressure difference of 1.0 kPa, the gas flux of the test sample was 860 mL / min·cm 2 , slightly lower than 1150 mL / min·cm in Example 1 2 This difference may be related to the presence of a small amount of corundum phase in the material. Corundum has a higher density and crystal integrity, which may partially inhibit the formation of through-holes during the sintering process, thereby reducing the gas permeability.

[0052] Compared to Example 1, this example uses γ-Al2O3 powder and a 2:1 mass ratio of aluminum oxide to silicon oxide. This increases the aluminum-silicon ratio in the reaction system, but also increases the sintering temperature, resulting in excessive energy consumption and the formation of an impure corundum phase. Using polyvinyl alcohol (PVA) and polymethyl methacrylate (PMMA) instead of starch as the binder and pore-forming agent further complicates the process.

[0053] Example 3

[0054] A method for preparing a mullite-based porous ceramic material from fly ash from the co-gasification of biochar and coal comprises the following steps:

[0055] (1) The materials were prepared according to the mass ratio of alumina to silica of 1.5, and then 10 wt% of sodium carboxymethyl cellulose (CMC) accounting for the total mass of biochar and coal co-gasification fly ash and calcined bauxite powder; 10 wt% of hydrogen peroxide; and 2 wt% of AlF3·3H2O were added. Among them, CMC was used as a binder and hydrogen peroxide was used as a pore-forming agent. The mixture was poured into a disc granulator, mixed evenly, and granulated. The granulation time was 15 min, and the sieved particle size was 0.425~0.850 mm.

[0056] (2) The obtained granular raw material is placed in a mold, formed using a tablet press at a pressure of 25 MPa, and dried to obtain a ceramic green body;

[0057] (3) The ceramic green body was placed in an electric furnace for sintering at a heating rate of 5°C / min. The temperature was first raised to 550°C and kept for 1 hour, then further raised to 1300°C and kept for 2 hours, and finally cooled to room temperature at a rate of 10°C / min to obtain a mullite-based porous ceramic material.

[0058] The prepared ceramic material has a specific surface area of ​​24.6 m² / g, a porosity of 52.7%, an average pore diameter of 11.4 nm, and has a good micro-mesoporous structure and gas transmission capacity.

[0059] Example 4

[0060] A method for preparing a mullite-based porous ceramic material from fly ash from the co-gasification of biochar and coal comprises the following steps:

[0061] (1) The materials were prepared in a mass ratio of alumina to silica of 1.3, and 10 wt% of water and 10 wt% of ammonium bicarbonate were added as a binder and pore-forming agent, and 5 wt% of MnO2 was added as a whisker promoter. The mixture was mixed and granulated in an inclined strong mixer. The granulation time was controlled to be 10 min, and the obtained particle size range was controlled to be 0.2~0.6 mm.

[0062] (2) The granular raw materials are placed in a mold, pressed at a pressure of 20 MPa, and dried to obtain a ceramic green body;

[0063] (3) The green body was sintered in air atmosphere with the following procedure: heating to 500 °C (2 °C / min) and holding for 1 h, then heating to 1250 °C (8 °C / min) and holding for 4 h, and cooling to room temperature at a rate of 10 °C / min.

[0064] The prepared ceramic material has a specific surface area of ​​31.2 m² / g, a porosity of 65.4%, an average pore diameter of 42.8 nm, a uniform structure, and good gas flux.

[0065] Example 5

[0066] A method for preparing a mullite-based porous ceramic material from fly ash from the co-gasification of biochar and coal comprises the following steps:

[0067] (1) Alumina and silica were prepared in a mass ratio of 2.2, supplemented with 10 wt% polyvinyl alcohol (PVA), 15 wt% PMMA, and 0.5 wt% B2O3 as binders, pore formers, and whisker promoters. After mixing, the mixture was put into an inclined intensive mixer for granulation for 20 min, and the sieved particle size was controlled to be 0.85-1.2 mm.

[0068] (2) The obtained particles are formed in a tableting mold at a pressure of 30 MPa and dried into a ceramic green body;

[0069] (3) The sintering process is as follows: heating to 600℃ (3℃ / min) and keeping it for 2h, then heating to 1450℃ (12℃ / min) and keeping it for 3h, and finally cooling to room temperature at 15℃ / min.

[0070] The prepared ceramic material has a specific surface area of ​​13.4 m² / g, a porosity of 39.6%, an average pore diameter of 712 nm, and a pore structure containing a significant number of macropores, making it suitable for high-temperature particle filtration and carrier reactions.

[0071] Any matters not described in detail in this specification are prior art known to those skilled in the art. Although the above description of the present invention is based on specific embodiments to facilitate understanding of the present invention by those skilled in the art, it should be understood that the present invention is not limited to the scope of the specific embodiments. As long as various modifications are within the spirit and scope of the present invention as defined and determined by the appended claims, such modifications will be obvious to those skilled in the art, and all inventions and creations utilizing the concepts of the present invention are protected.

Claims

1. A method for preparing mullite-based porous ceramic materials from fly ash from the co-gasification of biochar and coal, characterized by: The biochar and coal co-gasification fly ash are used as a silicon source and an external aluminum source as a mixed raw material, the ingredients are prepared according to a specific mass ratio of aluminum oxide to silicon oxide, a binder and a pore-forming agent are added, a whisker promoter is added, and the material is granulated, sieved, statically pressed into a green body, dried, and sintered to obtain a mullite-based porous ceramic material.

2. The method for preparing mullite-based porous ceramic materials from fly ash co-gasified with biochar and coal according to claim 1, characterized in that: The granulation conditions are as follows: using an inclined intensive mixer or a disc granulator, granulating for 1 to 30 minutes, and mixing the binder and the mixed raw materials in a step-by-step mixing or a one-time mixing manner; during the granulation process, by controlling the granulation particle size within the range of 0.2 to 5 mm, the distribution and structure of the macropores in the ceramic material are adjusted to construct regular macropores.

3. The method for preparing mullite-based porous ceramic materials from fly ash co-gasified with biochar and coal according to claim 1, characterized in that: The sintering specifically includes a first stage of preheating and removal, a second stage of mullite crystal phase formation and growth, and a third stage of cooling. The entire sintering process is carried out in air or an inert atmosphere. The first stage of preheating and removal is a heating rate of 0.5-15°C / min, a temperature of 400-600°C, and a heat preservation time of 1-3 hours to fully remove the pore former, binder and volatile components; The second stage of mullite crystal phase formation and growth is a heating rate of 0.5-15°C / min, a temperature of 900-1500°C, and a holding time of 1-6 hours to promote the formation and crystal growth of the mullite phase, and at the same time promote the whisker precipitation induced by the whisker promoter and the densification of the skeleton; The third stage, cooling, is to lower the temperature to room temperature at a cooling rate of 5-20°C / min.

4. The method for preparing mullite-based porous ceramic materials from fly ash co-gasified with biochar and coal according to claim 1, characterized in that: The biochar and coal co-gasification fly ash has the following component contents: 8.67 wt % aluminum oxide, 50.40 wt % silicon dioxide, 4.76 wt % potassium oxide, and 25.37 wt % unburned carbon.

5. The method for preparing mullite-based porous ceramic materials from fly ash from the co-gasification of biochar and coal according to claim 1, characterized in that: The external aluminum source is one of calcined bauxite powder, γ-Al2O3, and Al(OH)3, and its aluminum oxide content is ≥70wt%.

6. The method for preparing mullite-based porous ceramic materials from fly ash co-gasified with biochar and coal according to claim 1, characterized in that: The mass ratio of aluminum oxide to silicon oxide is 1.3 to 2.

3.

7. The method for preparing mullite-based porous ceramic materials from fly ash from the co-gasification of biochar and coal according to claim 1, characterized in that: The binder is one or more of water, starch, polyvinyl alcohol (PVA), and sodium carboxymethyl cellulose (CMC); the binder accounts for 2-30 wt% of the mass fraction of the mixed raw materials.

8. The method for preparing mullite-based porous ceramic materials from fly ash from the co-gasification of biochar and coal according to claim 1, characterized in that: The pore-forming agent is one of starch, hydrogen peroxide, polymethyl methacrylate (PMMA), and ammonium bicarbonate; and the pore-forming agent accounts for 5-40 wt % of the mass fraction of the mixed raw materials.

9. The method for preparing mullite-based porous ceramic materials from fly ash co-gasified with biochar and coal according to claim 1, characterized in that: The whisker promoter is one of B2O3, AlF3·3H2O, and MnO2; the mass fraction of the whisker promoter in the mixed raw materials is 0.2-10wt%.

10. The mullite-based porous ceramic material obtained by the preparation method according to any one of claims 1 to 9, characterized in that: The material has a specific surface area of ​​10-50 m² / g, a porosity of 35-85%, and an average pore diameter of 5-1000 nm.

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