Composite porous ceramic as well as preparation method and application thereof

Abstract

The invention provides a composite porous ceramic which comprises spherical particles and neck connectors, and the spherical particles form a network structure through the neck connectors. Holes of the network structure are sphere-like holes, and a zigzag communicated pore channel structure is formed through the sphere-like holes; wherein the content of alumina in the neck connection is higher than the content of alumina in the spherical particles. The composite porous ceramic prepared by the invention has relatively high bending strength and corrosion resistance.

Description

Technical Field

[0001] This invention relates to the field of coal-based solid waste resource utilization, specifically to a composite porous ceramic and its preparation method and application. Background Technology

[0002] Fly ash, a coal-based solid waste generated during coal-fired power generation, has always been a research hotspot in environmental and materials science. Porous ceramics, as a high-value product for the comprehensive utilization of fly ash, have broad application prospects. However, the research and application of fly ash porous ceramics still face many challenges. First, the utilization rate of fly ash is low, and the amount added during the preparation of porous ceramics is usually limited, making large-scale application difficult. Second, existing preparation processes are relatively complex, resulting in high production costs and failing to meet the efficiency requirements of industrial production. Furthermore, the mechanical properties of fly ash porous ceramics are insufficient, especially their flexural strength and resistance to acid and alkali corrosion, which limits their application potential.

[0003] Although some studies have reported the use of fly ash as a raw material to prepare ceramic membranes, problems exist, including low fly ash utilization, complex processes, and poor strength and acid / alkali corrosion resistance of the resulting fly ash ceramic membranes. Furthermore, current technologies primarily use alumina as a raw material for preparing hollow thin-walled ceramic flat sheet membranes, making it difficult to use fly ash. This is mainly due to the difficulty in resolving the issues of low strength and poor acid / alkali corrosion resistance in porous ceramics prepared using fly ash. Therefore, there is an urgent need to develop a high-strength, acid- and alkali-resistant porous ceramic to address the various problems existing in current technologies. Summary of the Invention

[0004] The purpose of this invention is to address the problems of low strength and poor acid and alkali corrosion resistance in porous ceramics prepared using fly ash as raw material in the prior art. By controlling the formulation, morphology and particle size of the raw materials for preparing porous ceramics, a composite porous ceramic with a special structure is obtained, which has high flexural strength and good corrosion resistance.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] The first aspect of the present invention provides a composite porous ceramic, the composite porous ceramic comprising spherical particles and neck connections, the spherical particles forming a network structure through the neck connections; the pores of the network structure are quasi-spherical pores, forming a tortuous and interconnected channel structure through the quasi-spherical pores; wherein, the alumina content in the neck connections is higher than the alumina content in the spherical particles.

[0007] The composite porous ceramic of this invention has a unique morphology, comprising spherical particles and neck connections, wherein the spherical particles form a network structure through the neck connections. In this structure, the alumina content in the neck connections is higher than that in the spherical particles, allowing the material to overcome the shortcomings of ordinary fly ash ceramics, such as low flexural strength and poor alkali corrosion resistance. The resulting composite porous ceramic exhibits higher flexural strength and corrosion resistance. The pores in the network structure are quasi-spherical, forming a tortuous, interconnected pore structure. This pore structure differs from the slit pores formed by the sintering of ordinary angular alumina powder, and can significantly improve the throughput and contact area of ​​liquids and gases in applications such as water treatment, flue gas filtration, and catalyst carriers.

[0008] In a preferred embodiment, the alumina content in the neck connector is ≥73%, and the alumina content in the spherical particles is 40-65%. All contents are by mass, and the alumina content is relative to the mass of the neck connector or the spherical particles.

[0009] In a preferred embodiment, the phase of the composite porous ceramic is aluminum-rich mullite.

[0010] In some embodiments, the composite porous ceramic is made of a composite powder composition, a binder, and water, wherein, by weight, the composite powder composition comprises 89-97 parts, the binder comprises 3-11 parts, and the water comprises 20-45 parts.

[0011] In some preferred embodiments, the composite powder composition comprises, by weight 100%, 70-84% fly ash powder, 13-25% alumina powder, 0.5-1% potassium oxide powder, 0.5-1% sodium oxide powder, 0.5-1.5% magnesium oxide powder, 0.5-1% calcium oxide powder, and 1-5% kaolin.

[0012] In some preferred embodiments, the fly ash powder contains, by weight 100%, 38-60% alumina, 35-50% silicon dioxide, 0.2-4% iron oxide, 0.2-3.5% calcium oxide, and 0.1-4.5% titanium dioxide.

[0013] In some preferred embodiments, spherical powder accounts for 70-90% of the total mass of the fly ash powder, and the particle size D50 of the fly ash powder is 10-30 μm.

[0014] In some preferred embodiments, alumina accounts for more than 85% of the total mass of the alumina powder, such as 99.99%, and angular powder accounts for 80-100% of the total mass of the alumina powder. The particle size D50 of the alumina powder is 3-8 μm.

[0015] In some embodiments, the binder is selected from at least one of methylcellulose, carboxymethylcellulose, hydroxypropyl methylcellulose, polyanionic cellulose, glycerol, propylene glycol, raw tung oil, polyethylene glycol, castor oil, soybean oil, oleic acid, and polyvinyl alcohol.

[0016] When the binder contains two or more components, the cellulose content is greater than or equal to 50%. The cellulose includes the aforementioned methylcellulose, carboxymethylcellulose, hydroxypropyl methylcellulose, and polyanionic cellulose.

[0017] A second aspect of the present invention provides a method for preparing composite porous ceramics, the method comprising:

[0018] 1) Mix fly ash powder, alumina powder, potassium oxide powder, sodium oxide powder, magnesium oxide powder, calcium oxide powder and kaolin evenly to form a composite powder composition;

[0019] 2) Mix the binder and the composite powder composition evenly to form a mixture;

[0020] 3) Add water to the mixture, mix evenly to form a preform, and then shape it into a blank; the shaping can be achieved using common methods, such as dry pressing, extrusion molding, etc.

[0021] 4) The green body is dried and sintered to obtain composite porous ceramic, wherein the sintering temperature is 1100-1350℃.

[0022] The third aspect of the present invention provides the application of the above-mentioned composite porous ceramic or the composite porous ceramic prepared by the above-mentioned preparation method in construction, sound absorption, water treatment and flue gas filtration, and catalyst support.

[0023] The composite porous ceramic of this invention has a special morphology, comprising spherical particles, neck connections, and a network structure formed by the spherical particles and neck connections. The spherical particles are primarily fly ash, while the neck connections are composed of smaller fly ash particles and other composite powders. During preparation, the powders and binder are mixed and shaped, then sintered. During sintering, angular powders preferentially melt, and smaller particles preferentially melt. Combined with the formulation and particle size conditions of this invention, the material that preferentially melts alumina forms the neck connections, resulting in a high alumina content in the neck connections. This structure has a higher alumina content in the neck connections than in the spherical particles, allowing the material to overcome the shortcomings of ordinary fly ash ceramics, such as low flexural strength and poor alkali corrosion resistance. The resulting composite porous ceramic exhibits high flexural strength (40-100 MPa) and corrosion resistance (acid corrosion mass loss rate ≤0.3%, alkali corrosion mass loss rate ≤0.5%).

[0024] Furthermore, in this invention, the pores in the network structure are spherical pores, forming a tortuous and interconnected channel structure. This channel structure differs from the slit pores formed by the sintering of ordinary angular alumina powder. In applications such as water treatment, flue gas filtration, and catalyst carriers, it can significantly improve the throughput and contact area of ​​liquids and gases. Attached Figure Description

[0025] Figure 1 The image shows the surface microstructure of the porous fly ash sintered body prepared in Example 1 using SEM. Detailed Implementation

[0026] The present invention will be further illustrated below with specific embodiments. These embodiments are merely illustrative and do not imply that the scope of the invention is limited thereto.

[0027] Unless otherwise specified, the materials used in the following embodiments are all conventional materials in the art and can be obtained commercially. The methods used in the following embodiments are all conventional methods in the art, and those skilled in the art can readily confirm the operation process and obtain the corresponding results based on the content of the embodiments.

[0028] In this invention, the bulk density and porosity parameters of the composite porous ceramic are respectively measured by GB / T1966-1996 Test Method for Bulk Density and Apparent Porosity of Porous Ceramics; the flexural strength parameter of the composite porous ceramic is measured by GB / T 1965-1996 Test Method for Bending Strength of Porous Ceramics.

[0029] In this invention, acid corrosion mass loss rate is used to represent acid resistance and alkali corrosion mass loss rate is used to represent alkali resistance. The acid resistance and alkali resistance are measured by GB / T 1970-1996 Test Method for Acid and Alkali Corrosion Resistance of Porous Ceramics.

[0030] In this invention, unless otherwise specified, spherical powder refers to solid particles with a sphericity of 0.7 or higher; non-spherical powder refers to solid particles with a sphericity of less than 0.7.

[0031] In this invention, the spherical morphology and content parameters of the powder are determined by scanning electron microscopy. Specifically, five SEM images (magnification of 1000x) are selected for each fly ash sample, and each image covers an area of ​​300×300μm. The content of spherical powder with a sphericity greater than 0.7 within this area is measured and denoted as m1, m2, m3, m4, and m5, respectively. The content of spherical powder refers to the percentage of particles with a sphericity greater than 0.7 within the measured area out of the total number of particles. Therefore, the spherical powder content in fly ash = (m1 + m2 + m3 + m4 + m5) / 5. Sphericity is measured using a microscope, and sphericity = (4 × π × projected area) / (projected perimeter × projected perimeter).

[0032] Angular powder in powder refers to non-spherical powder.

[0033] The particle size parameters of the fly ash were determined using a Malvern MS2000 laser particle size analyzer. The powder mass content was determined by XRF. The morphology of porous ceramics was detected by SEM, the crystalline phase content by XRD, and the alumina content in the neck joints and spherical particles was determined by EDS.

[0034] Example 1

[0035] Methods for preparing porous ceramics include:

[0036] 1) Mix 70g of fly ash powder, 25g of alumina powder, 0.5g of potassium oxide powder, 1g of sodium oxide powder, 1g of magnesium oxide powder, 0.5g of calcium oxide powder and 2g of kaolin evenly to form a composite powder composition.

[0037] In the fly ash powder, based on the total weight of the fly ash powder as 100%, the alumina content is 60%, the silicon oxide content is 35%, the iron oxide content is 1%, the calcium oxide content is 0.2%, the titanium oxide content is 0.1%, and the remainder is impurities; spherical powder accounts for 90% of the total mass of fly ash powder, and the particle size D50 of fly ash powder is 10μm; in the alumina powder, alumina accounts for 100% of the total mass of alumina powder, angular powder accounts for 80% of the total mass of alumina powder, and the particle size D50 of alumina powder is 3μm.

[0038] 2) Mix the binder and the composite powder composition evenly to form a mixture;

[0039] The binder is methylcellulose.

[0040] 3) Add water to the mixture, mix evenly to form a preform, and then further shape it into a blank.

[0041] In the above steps, the ratio of the composite powder composition, binder, and water is: 90 parts composite powder, 4 parts binder, and 20 parts water.

[0042] 4) The porous ceramic material blank is dried and sintered to obtain composite porous ceramic, wherein the sintering temperature is 1100℃.

[0043] like Figure 1 As shown, SEM analysis revealed that the prepared composite porous ceramic comprises spherical particles and neck connections. The spherical particles form a network structure through the neck connections. The alumina content in the spherical particles is 64.2%, and the alumina content in the neck connections is 83.2%. The resulting composite porous ceramic exhibits a flexural strength of 100 MPa, an acid corrosion mass loss rate of 0.1%, and an alkali corrosion mass loss rate of 0.1%.

[0044] Examples 2-6 and Comparative Examples 1-4

[0045] The preparation steps for the composite porous ceramics are the same as in Example 1. Specific parameters of the raw materials, step parameters, and performance tests are detailed in Table 1.

[0046] Table 1. Properties of the porous ceramics prepared in Examples 1-6 and Comparative Examples 1-4

[0047]

[0048]

[0049]

[0050] In the comparative examples, the alumina content of the fly ash powder in Comparative Example 1 was too low, preventing the formation of a neck connection structure during sintering. This resulted in a significant reduction in the mechanical strength and acid / alkali corrosion resistance of the resulting composite porous ceramic. In Comparative Example 2, the alumina content in the composite powder composition was also too low, preventing the formation of a neck connection structure and significantly reducing both the mechanical strength and acid / alkali corrosion resistance of the resulting composite porous ceramic. In Comparative Example 3, the content of angular powder in the alumina powder was too low, failing to form a neck connection structure, resulting in a significant reduction in both the mechanical strength and acid / alkali corrosion resistance of the resulting composite porous ceramic. In Comparative Example 4, the content of spherical powder in the fly ash powder was too low, and the fly ash powder particle size D50 was low, resulting in a significant reduction in both the mechanical strength and acid / alkali corrosion resistance of the resulting composite porous ceramic.

[0051] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A composite porous ceramic, characterized in that, The composite porous ceramic comprises spherical particles and neck connections, wherein the spherical particles form a network structure through the neck connections; the pores of the network structure are quasi-spherical pores, forming a tortuous and interconnected channel structure through the quasi-spherical pores; The alumina content in the neck connector is higher than that in the spherical particles.

2. The composite porous ceramic according to claim 1, wherein, The alumina content in the neck connector is ≥73%, and the alumina content in the spherical particles is 40-65%.

3. The composite porous ceramic according to claim 1 or 2, wherein, The composite porous ceramic is made of a composite powder composition, a binder and water, wherein, by weight, the composite powder composition is 89-97 parts, the binder is 3-11 parts and the water is 20-45 parts.

4. The composite porous ceramic according to claim 3, wherein, Based on the total weight of the composite powder composition as 100%, the composite powder composition comprises: 70-84% fly ash powder, 13-25% alumina powder, 0.5-1% potassium oxide powder, 0.5-1% sodium oxide powder, 0.5-1.5% magnesium oxide powder, 0.5-1% calcium oxide powder, and 1-5% kaolin.

5. The composite porous ceramic according to claim 4, wherein, In the fly ash powder, based on the total weight of the fly ash powder as 100%, the alumina content is 38-60%, the silicon oxide content is 35-50%, the iron oxide content is 0.2-4%, the calcium oxide content is 0.2-3.5%, and the titanium oxide content is 0.1-4.5%.

6. The composite porous ceramic according to claim 5, wherein, Spherical powder accounts for 70-90% of the total mass of the fly ash powder, and the particle size D50 of the fly ash powder is 10-30 μm.

7. The composite porous ceramic according to claim 4, wherein, In the alumina powder, alumina accounts for more than 85% of the total mass of the alumina powder, angular powder accounts for 80-100% of the total mass of the alumina powder, and the particle size D50 of the alumina powder is 3-8μm.

8. The porous ceramic according to claim 3, wherein, The binder is selected from at least one of methylcellulose, carboxymethylcellulose, hydroxypropyl methylcellulose, polyvinyl alcohol, polyanionic cellulose, glycerol, propylene glycol, raw tung oil, polyethylene glycol, castor oil, soybean oil, and oleic acid; preferably, when the binder contains two or more components, the cellulose content is greater than or equal to 50%.

9. The method for preparing the composite porous ceramic according to any one of claims 1 to 8, characterized in that, The preparation method includes: 1) Mix fly ash powder, alumina powder, potassium oxide powder, sodium oxide powder, magnesium oxide powder, calcium oxide powder and kaolin evenly to form a composite powder composition; 2) Mix the binder and the composite powder composition evenly to form a mixture; 3) Add water to the mixture, mix evenly to form a pre-formed blank, and then shape it into a blank; 4) The green body is dried and sintered to obtain composite porous ceramic, wherein the sintering temperature is 1100-1350℃.

10. The application of the composite porous ceramic according to any one of claims 1-8 or the composite porous ceramic prepared by the preparation method according to claim 9 in construction, sound absorption, water treatment and flue gas filtration, and catalyst support.

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