CN110872188A - Ceramic particle, filter element and preparation method of filter element - Google Patents
Ceramic particle, filter element and preparation method of filter element Download PDFInfo
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- CN110872188A CN110872188A CN201810605353.2A CN201810605353A CN110872188A CN 110872188 A CN110872188 A CN 110872188A CN 201810605353 A CN201810605353 A CN 201810605353A CN 110872188 A CN110872188 A CN 110872188A
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- B01D39/14—Other self-supporting filtering material ; Other filtering material
- B01D39/20—Other self-supporting filtering material ; Other filtering material of inorganic material, e.g. asbestos paper, metallic filtering material of non-woven wires
- B01D39/2068—Other inorganic materials, e.g. ceramics
- B01D39/2072—Other inorganic materials, e.g. ceramics the material being particulate or granular
- B01D39/2075—Other inorganic materials, e.g. ceramics the material being particulate or granular sintered or bonded by inorganic agents
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- B01D46/0001—Making filtering elements
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- C04B35/18—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on silicates other than clay rich in aluminium oxide
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Abstract
The invention discloses a ceramic particle, a filter element and a preparation method of the filter element, wherein the ceramic particle is prepared by the following steps: mixing kaolin, talc, bauxite and spodumene, and preparing spherical particles by dry method powder preparation, roll forming and sintering. The spherical particles have uniform particle size, smooth surface and high compressive strength, and the prepared filter element has uniform aperture and low filtration resistance and can improve the filtration performance.
Description
Technical Field
The invention relates to the field of ceramic filter materials in inorganic non-metallic materials, in particular to ceramic particles, a filter element and a preparation method of the filter element.
Background
The ceramic filter material has the advantages of high temperature resistance, good thermal stability and the like, and can be widely used as a hot gas purification material, a catalyst carrier and the like. Especially, the cordierite high-temperature ceramic filter material has the advantages of light weight, small thermal expansion coefficient and the like, and is an excellent hot gas purification material;
the traditional cordierite ceramic filter material is mainly prepared by two process methods, wherein one process method is characterized in that clay and talc are used as main raw materials, a part of cordierite clinker is added, and the cordierite ceramic filter element with smaller pore diameter is prepared by extrusion process molding and high-temperature firing;
the other preparation process is to use high temperature synthesized cordierite aggregate as raw material, to be crushed into particles with certain size as aggregate, to be sintered with high temperature binder to prepare porous ceramic material. The ceramic filter element prepared by the process has the advantages that the cordierite aggregate synthesized at high temperature has irregular shape and poor surface smoothness, and the aggregate is crushed to a large degree during compression molding, so that the uniformity of particle size is poor, the uniformity of pore diameter of the filter element is poor, the porosity is low and the air permeability resistance is large; even though cordierite is crushed into nearly spherical particles, the uniformity of particle size is still poor although the particle size is improved, and the particle surface is not smooth enough under the influence of crushing, so that the filtering resistance is increased, and the cordierite cannot be well applied to high-temperature gas purification;
in the two preparation methods, due to the reasons of poor shape of the aggregate particles forming the micropores, poor particle size distribution, poor compressive strength of the aggregate particles and the like, the pore diameter is small or very uneven, so that the air permeability resistance is large during filtration;
in addition, the general cordierite body formula in the existing porous ceramic preparation mainly comprises a magnesium-aluminum-silicon system, the main crystal phase of the crystal phase structure in the synthesized product is cordierite, and the synthesized product contains a small amount of cristobalite and spinel phases, particularly the existence of the cristobalite phase, so that the thermal expansion coefficient of the product is increased, the thermal stability is reduced, and the cordierite body cannot be well adapted to the purification of high-temperature gas.
Disclosure of Invention
In order to solve the above technical problems, an object of the present invention is to provide a ceramic particle, a filter element and a method for manufacturing the filter element, wherein the spherical particle has uniform particle size, smooth surface and high compressive strength, and the prepared filter element has wide and narrow pore size distribution and low thermal expansion coefficient, and can reduce filtration resistance and improve filtration performance.
According to one aspect of the present invention, there is provided a ceramic particle prepared by: mixing kaolin, talc, bauxite and spodumene, and preparing spherical particles by powder preparation, rolling molding and sintering, wherein the powder preparation is preferably ball milling dry method powder preparation.
Further, the components and the proportion are as follows: by mass, 40-50 parts of kaolin, 35-45 parts of talc, 15-25 parts of bauxite and 3-10 parts of spodumene.
Furthermore, the particle size range of the spherical particles is 100-1000 microns, and the water absorption is 2-5%.
According to another aspect of the invention, the preparation method of the filter element is provided, the spherical particles, the pore-increasing agent, the high-temperature binding agent and the ceramic adhesive are mixed and then are granulated, formed and fired, and the granulation is formed by mixing a plurality of spherical particles, the high-temperature binding agent and the pore-increasing agent to prepare the molding powder material of the approximately spherical regular particles; the molding is preferably isostatic molding.
Further, the components and the proportion are as follows: 80-90 parts of spherical particles, 10-20 parts of high-temperature bonding agent and 5-8 parts of ceramic adhesive by mass; the addition amount of the pore-increasing agent is 5-10% of the sum of the mass of the spherical particles and the mass of the high-temperature bonding agent.
Further, the mixing comprises the following steps:
adding spherical particles and a pore-increasing agent, wherein the rotating speed of a stirring shaft of a mixing barrel is 40-60rpm, and stirring for 3-8 min;
secondly, adding 30-40% of the total amount of the ceramic adhesive, and stirring for 8-12 min;
thirdly, adding a high-temperature bonding agent, a lubricant and the balance of a ceramic adhesive;
and fourthly, increasing the rotating speed of a stirring shaft of the mixing barrel to 80-90rpm, and stirring for 25-30min to obtain a mixture.
Further, the high-temperature binder comprises kaolin, feldspar, spodumene and borax, wherein the borax accounts for 2-5% by mass.
Furthermore, a sintering mode of naked sintering is adopted during sintering, a blank body of the filter element is flatly placed on the high-temperature powder during sintering, the laying thickness of the high-temperature powder is 5-10mm, and a long tubular or candle-shaped finished product is obtained by sintering, wherein the finished product is the filter element prepared by the method.
Further, the pore-increasing agent is walnut shell powder or petroleum coke particles.
According to another aspect of the invention, a filter element is provided that is made by the above process.
Compared with the prior art, the invention has the following beneficial effects:
1. the main crystalline phase of the spherical particles is ceramic particles of cordierite, the adding amount of spodumene is 3-10 wt%, and the firing temperature of the ceramic particles is reduced by adding the spodumene. In order to obtain ceramic particles with ideal compressive strength and cordierite as a main crystal phase in the prior art, the firing temperature is higher than 1390 ℃, and the firing temperature of the invention is only 1360-1380 ℃.
The factors influencing the water absorption of the spherical particles are mainly the raw material formula, the sintering range of the cordierite ceramic is very narrow, the cordierite ceramic is difficult to be completely sintered, the common cordierite is in a porous structure after being sintered and has a plurality of internal pores, the water absorption is up to more than 20%, and the compressive strength of the porous structure is relatively low. The spodumene is added to enable the high-temperature ceramic binder to form a liquid phase at a lower temperature, so that the compactness of the sintered spherical particles is improved, the internal pores are reduced, the water absorption of the spherical particles is reduced, the compressive strength and the surface smoothness are improved, and the crushing rate of the spherical particles during static pressure forming can be effectively reduced.
Experiments prove that when the addition amount of spodumene is less than or equal to 3 wt%, the influence on the firing performance of the spherical particles is small, the firing temperature is high, the firing temperature needs to be higher than 1390 ℃, the water absorption rate of the fired spherical particles is not less than 18%, and the crushing breakage rate of the spherical particles is high; when the spodumene content exceeds 10 wt%, the spherical shapeThe particles will have more glass phase during firing and will blister easily, resulting in a decrease in the compressive strength of the particles, with spodumene being most preferably added in an amount of 5-8 wt%. For example, the spherical particles can be added with 5 wt% of spodumene to reduce the firing temperature of the spheres from 1390 deg.C to 1380 deg.C, and the thermal expansion coefficient at 900 deg.C is 2.89 x 10-6Reduced to 2.34 x 10-6Obviously improves the thermal stability at high temperature.
2. The spherical particles are prepared by a rolling ball process, the size of the spherical particles is controlled by the rolling ball time, the rolling ball time is 1-2h, and the particle size range of the spherical particles is controlled between 100-1000 microns.
The pore structure of the ceramic filter element is mainly formed by freely stacking spherical particles, the pore diameter of the pores is in direct proportion to the particle diameter of the spherical particles, the filter elements with different pore diameters can be obtained by selecting the spherical particles with proper particle diameters, experiments prove that the spherical particles with the particle diameter of less than 100 micrometers are used as aggregate, the pore diameter of the finally prepared product is less than 30 micrometers, the filtering resistance reaches more than 2000Pa at the wind speed of 1m/min, and the requirement of low-resistance gas filtration cannot be met. On the contrary, the particles larger than 1000 microns are difficult to form on one hand, and on the other hand, the product has large pore diameter (larger than 150 microns) and poor filtering effect, and the bending strength of the filtering element is less than 5MPa, so that the strength requirement cannot be met. Therefore, in order to obtain a ceramic filter element with low resistance and high bending strength, the particle size of the spherical particles should be selected within the range of 100-1000 microns.
The spherical particles have good compression resistance and smooth surfaces, and the filter element formed after free accumulation has smooth pore passages and uniform pore size distribution.
3. The preparation method of the filter element is sequentially prepared by powder granulation, isostatic pressing and high-temperature sintering. The spodumene and the borax are added, so that the high-temperature binding agent can be promoted to form a liquid phase at a lower temperature, the contact area between the high-temperature binding agent and the aggregate is increased, on one hand, the aggregate is fully infiltrated, a plurality of spherical particles are firmly bonded together, and the bending strength of the filter element is improved; on the other hand, a small amount of cristobalite phase can be promoted to be converted into acicular mullite phase, and the acicular mullite is coated on the cordierite substrate, so that the crack diffusion resistance is increased, the thermal expansion coefficient of the filter element is effectively reduced, and the thermal stability is improved.
4. According to the invention, firstly, the aggregate and the pore-increasing agent are added to be uniformly mixed, a layer of ceramic adhesive is uniformly adhered to the surfaces of the aggregate and the pore-increasing agent by adding a small amount of ceramic adhesive, and then the high-temperature bonding agent is added, so that the high-temperature bonding agent is easily adhered to the ceramic adhesive on the surfaces of the aggregate and the pore-increasing agent in the material mixing process, and the phenomena of layering and uneven material mixing of the high-temperature bonding agent, the aggregate and the pore-increasing agent caused by the particle fineness and specific gravity difference can be avoided.
The second addition of the ceramic adhesive is to make the surface of the mixed powder adhere a layer of adhesive, so as to increase the powder adhesion performance and facilitate isostatic pressing. Finally, a lubricant (such as graphite) is added to the mixed powder so that the lubricant can be attached to the surface of the mixed powder to increase the fluidity of the powder.
The mixing is uniform, a layer of ceramic adhesive is uniformly adhered to the surfaces of the aggregate and the pore-increasing agent, and the ceramic adhesive is continuously added subsequently, so that the adhesion and strength among spherical particles can be increased, and the mechanical strength of a formed blank is increased.
5. The forming pressure is controlled to be 50-70MPa during isostatic pressing, and if the forming pressure is too high (greater than 70MPa), on one hand, the compactness of a formed blank is improved, the porosity of a filter element is reduced, and the air permeability resistance is increased; on the other hand, during compression molding, the breaking rate of spherical particles is easily increased, so that the pore surface is not smooth, the pore diameter is not uniform, and the filtration resistance is also increased; if the forming pressure is too low (less than 40MPa), the formed product has poor compactness, low bonding strength among spherical particles, low mechanical strength of a formed blank body and difficult demoulding.
6. The vibration amplitude of the vibration feeding is controlled to be 20-30 Hz. The vibration aims to ensure that the molding powder can completely fill the inner cavity of the molding die in the molding process. Too large amplitude causes powder layering, resulting in poor structural uniformity of the molded blank. The amplitude is too small, and due to poor flowability of the nearly spherical regular particles, bridging is easily caused in the die cavity, and the nearly spherical regular particles are difficult to completely fill in the die cavity, so that the structural uniformity of the blank is poor.
Drawings
FIG. 1 is a schematic diagram of the packing structure of spherical particles;
FIG. 2 is a schematic view showing the internal structure of a filter element according to example 6;
FIG. 3 is a schematic view of the internal structure of a prior art filter element;
FIG. 4 is a schematic view of a long tubular filter element;
FIG. 5 is a schematic view of a candle-type filter element.
In the figure: 1-spherical particles; 2-a high temperature binder; 3-pore space.
Detailed Description
In order to better understand the technical scheme of the invention, the invention is further explained by combining the drawings and the specific embodiments in the specification.
Example 1:
a ceramic particle prepared by the method of: mixing kaolin, talc, bauxite and spodumene according to the following mixture ratio: 40 parts of kaolin, 35 parts of talc, 15 parts of bauxite and 3 parts of spodumene by mass. Ball-milling dry powder preparation, rolling molding and firing are carried out to obtain the spherical particles with cordierite as the main crystal phase. Ball milling time is 10hr, rolling time is 1hr, and sieving is carried out to prepare spherical particles with the particle size range of 200-250 microns.
The particles, after sintering at 1280 ℃, had a water absorption of 2.5% and a coefficient of thermal expansion of 2.35 x 10-6V. C. The ceramic filter element prepared by adopting the spherical particles as the aggregate has the advantages of uniform pore size distribution, smooth pore channel, low filtration resistance, small thermal expansion coefficient and the like, and compared with the ceramic filter element in the prior art, the ceramic filter element has the advantages that the filtration resistance can be reduced by about 40 percent under the same average pore size, and is particularly suitable for high-temperature gas purification.
Example 2:
a ceramic particle prepared by the steps of: mixing kaolin, talc, bauxite and spodumene according to the following mixture ratio: 50 parts of kaolin, 45 parts of talc, 25 parts of bauxite and 8 parts of spodumene by mass. Ball-milling dry powder preparation, rolling molding and firing are carried out to obtain the spherical particles with cordierite as the main crystal phase. The ball milling time is 10hr, the ball rolling time is 1.5hr, and the particle size range of the spherical particles prepared by screening is 300-500 microns.
The particles after sintering at 1370 deg.C have a water absorption of 4% and a coefficient of thermal expansion of 2.4 x 10-6V. C. The ceramic filtering element prepared by using the spherical particles as the aggregate has the advantages of uniform pore size distribution, low filtering resistance, small thermal expansion coefficient and the like, and is particularly suitable for high-temperature gas purification. Compared with the ceramic filter element in the prior art, the filter resistance can be reduced by about 40 percent under the same average pore diameter.
Example 3:
weighing 45kg of kaolin, 40kg of calcined talc, 20kg of high-alumina bauxite and 6kg of spodumene, putting the materials into a ball mill for ball milling for 10 hours, and sieving the materials through a 200-mesh sieve after ball milling to obtain powder for later use.
The powder is put into a ball rolling machine and rolled to be spherical by adopting a ball rolling process, the ball rolling time is 2 hours, then the powder is put into a drying chamber or a drum dryer for drying and screening, and finally the powder is put into a high-temperature kiln for sintering, the sintering temperature is 1380 ℃, and the heat preservation time is 3 hours, so that the spherical ceramic particles with the main crystal phase of cordierite phase are prepared, and the particle size is 800-plus-material-1000 microns. The spherical particles obtained in this example had a water absorption of 3.4% and a ball crush of less than 8% at 50 KN.
The spodumene can form a liquid phase at a lower temperature, the compactness of spherical particles can be improved during sintering, the internal pores of cordierite are reduced, the water absorption of the spherical particles is reduced, the compressive strength and the surface smoothness of the sintered spherical particles are improved, the particles are uniform and have good sphericity, the crushing rate of the spherical particles is lower during static pressure forming, and the yield is ensured.
Experiments prove that when the addition amount of spodumene is less than or equal to 3 wt%, the influence on the sintering performance of the spherical particles is small, meanwhile, the water absorption rate of the sintered spherical particles is greater than or equal to 18%, and the crushing breakage rate of the balls is high; when the content of spodumene is over 10 wt%, more glass phase appears in the spherical particles in the sintering process and the spherical particles are easy to foam, so that the compressive strength of the particles is reduced, experiments prove that the most preferable adding amount of the spodumene is 5-8 wt%, in the embodiment, the adding amount of the spodumene is 5.7 wt%, the sintering temperature of the spheres can be reduced from 1390 ℃ to 1380 ℃ and reducedSintering temperature; the thermal expansion coefficient at room temperature of 900 ℃ is increased from the original 2.89 x 10-6Reduced to 2.34 x 10-6And the thermal stability at high temperature is greatly improved.
Table 1 shows the effect of spodumene addition on spherical particle performance.
Example 4:
a preparation method of a filter element comprises the steps of mixing the spherical particles, a pore-increasing agent, a high-temperature binding agent and a ceramic adhesive, granulating, forming and sintering to obtain the filter element, and sintering to obtain the long tubular or candle-shaped filter element, wherein the bending strength of the filter element is more than 8 MPa.
The filter element comprises the following components in percentage by weight: by mass, 80 parts of spherical particles, 10 parts of high-temperature bonding agent and 8 parts of ceramic adhesive; the addition amount of the pore-increasing agent is 5 percent of the sum of the mass of the spherical particles and the mass of the high-temperature bonding agent. The ceramic adhesive is used as a forming auxiliary agent, an external mode is adopted, and the hole-increasing agent is not added and is walnut shell powder; the high-temperature binder comprises kaolin, feldspar, spodumene and borax, wherein the borax accounts for 2% by mass.
The specific operation is as follows:
the material mixing method comprises the following steps:
firstly, adding spherical particles and a pore-increasing agent, wherein the rotating speed of a stirring shaft of a mixing barrel is 40-60rpm, and stirring for 3-8 min;
secondly, adding ceramic adhesive with total amount of about 1/3, and stirring for 8-12 min;
thirdly, adding a high-temperature bonding agent, the residual 2/3 ceramic bonding agent and a lubricant;
fourthly, increasing the rotating speed of a stirring shaft of the mixing barrel to 80-90rpm, and stirring for 25-30min to obtain a mixture;
after the mixing is finished, the mixture is placed into a heating roller for drying for 5-10min, and is screened for standby application, and preferably, the heating temperature of a mixing barrel is 55-60 ℃.
The feeding sequence is selected during material mixing:
firstly, adding the aggregate and the pore-increasing agent to uniformly mix the aggregate and the pore-increasing agent, adding a small amount of ceramic adhesive to uniformly adhere a layer of ceramic adhesive on the surfaces of the aggregate and the pore-increasing agent,
and then adding a high-temperature binding agent, wherein in the mixing process, the high-temperature binding agent is easily adhered to the ceramic adhesive on the surfaces of the aggregate and the pore-increasing agent, so that the phenomena of layering and uneven mixing of the high-temperature binding agent, the aggregate and the pore-increasing agent caused by the difference of particle fineness and specific gravity are avoided, the pore size distribution of the pores of the filter element is uniform, and the filtering resistance is reduced.
The ceramic adhesive is added for the second time, so that the viscosity of the mixture is further increased after the high-temperature binding agent is uniformly adhered to the surfaces of the aggregate and the pore-forming agent, and the forming is convenient. Finally, a lubricant (such as graphite) is added to the mixed powder so that the lubricant can be attached to the surface of the mixed powder to increase the fluidity of the powder.
The mixing is uniform, a layer of ceramic adhesive is uniformly adhered to the surfaces of the aggregate and the pore-increasing agent, and the ceramic adhesive is continuously added subsequently, so that the adhesion and strength among spherical particles can be increased, and the bending strength of the filter element is increased.
If the aggregate, the pore-increasing agent, the high-temperature bonding agent and the ceramic adhesive are added together, the high-temperature bonding agent is easy to agglomerate under the action of the adhesive and cannot be uniformly adhered to the surfaces of the aggregate and the pore-increasing agent in the mixing process, so that the high-temperature bonding agent and the aggregate are not uniformly mixed, the particle size is not uniform after granulation, the pore diameter is not uniform after the filter element is formed, and the filter resistance is increased.
Example 5:
a preparation method of a filter element comprises the steps of mixing the spherical particles, the pore-increasing agent, the high-temperature binding agent and the ceramic adhesive, granulating, isostatic pressing, sintering in a naked sintering mode during sintering to obtain the filter element, and sintering to obtain the long tubular or candle-shaped filter element, wherein the bending strength of the filter element is more than 10 MPa.
The filter element comprises the following components in percentage by weight: by mass, 85 parts of spherical particles, 15 parts of high-temperature bonding agent and 7 parts of ceramic bonding agent are added; the addition amount of the pore-increasing agent is 8 percent of the sum of the mass of the spherical particles and the mass of the high-temperature bonding agent. The pore-increasing agent is walnut shell powder; the high-temperature binder comprises kaolin, feldspar, spodumene and borax, wherein the borax accounts for 2.5% by mass; the ceramic binder is a resin binder.
During sintering, a sintering mode of naked sintering is adopted, namely, the blank body is flatly placed on the high-temperature ceramic backing plate paved with 5-10mm of high-temperature powder. The bare firing not only avoids the technical problems of complex hanging firing process and firing fracture, but also solves the problems of long burying firing process and firing period, and in addition, can improve the kiln loading efficiency and shorten the firing period. The method adopts a burying burning process, the burning period needs 7 days, the method only needs 4 days, and the kiln loading density can be improved by more than 40 percent.
The thermal expansion coefficient of the filter element is mainly determined by the components of the filter element after being fired, spodumene and borax are added into the high-temperature bonding agent, so that the temperature of the high-temperature bonding agent which is changed into a liquid phase is reduced, the firing temperature of the filter element can be reduced by 20-30 ℃, a cristobalite phase is promoted to be converted into an acicular mullite phase in the firing process, the existence of the quartz phase is reduced, the acicular mullite is coated on a cordierite substrate, the crack diffusion resistance is increased, the thermal expansion coefficient of the filter element can be reduced, the thermal stability of a cordierite product is effectively improved, in the embodiment, the borax accounts for 2% of the total mass of the high-temperature bonding agent by mass, the firing temperature of the ball can be reduced from 1390 ℃ to 1380 ℃ and from 2.89 to 10 by mass at 900 ℃, and the thermal expansion coefficient is-6Reduced to 2.34 x 10-6And the thermal stability at high temperature is greatly improved.
The purpose of the pore-increasing agent is to increase the porosity of the element. After the pore-increasing agent and the aggregates are uniformly mixed, the pore-increasing agent is burned out and pores are left among the aggregates in the firing process. The bigger the particle size of the pore-increasing agent is, the bigger the pores formed by the loss of ignition is, and vice versa, the smaller the pores are. The pore former particle size is controlled to be 50-500 microns in order not to cause the pore former to cause large changes to the pore size of the filter element.
Example 6:
the method is characterized in that 200-250 micron cordierite spherical particles are prepared as aggregates by the process method of the embodiment 1, 40Kg of spherical aggregates, 5Kg of the ceramic bond, 5 parts of additional ceramic adhesive and 2.5Kg of walnut shell powder pore-increasing agent with the particle size of 150-200 micron are weighed, liquid phenolic resin is used as organic adhesive, and the materials are mixed, granulated, formed under the pressure of 50-70MPa and the like, and finally sintered at the high temperature of 1270 ℃.
And (3) granulation: the spherical particles are mixed with high-temperature binder and pore-increasing agent to prepare the approximately spherical regular particles with larger particle size.
Adding the approximately spherical regular particles into a rubber mold, molding by adopting an isostatic pressing process, adopting a vibration feeding mode when feeding materials into the rubber mold, controlling the molding pressure to be 50-70MPa, and if the molding pressure is too high (more than 70MPa), on one hand, improving the compactness of a molded blank body, reducing the porosity of a filter element, and increasing the air permeability resistance, and on the other hand, easily increasing the breaking rate of the spherical particles during compression molding, causing unsmooth pore surfaces and uneven pore diameters, and also increasing the filtration resistance; if the molding pressure is too low (less than 40MPa), the compactness of a molded product is poor, the bonding strength among spherical particles is low, and the demolding is difficult; the forming pressure is controlled to be 50-70MPa, and the bonding strength among spherical particles can be increased and the bending strength of the filter element can be increased by combining the bonding effect of the ceramic adhesive.
The amplitude of the shaking charge was controlled at 20-30 Hz. The vibration aims to ensure that the molding powder can completely fill the inner cavity of the molding die in the molding process. Too large amplitude causes powder layering, resulting in poor structural uniformity of the molded blank. The amplitude is too small, and due to poor flowability of the nearly spherical regular particles, bridging is easily caused in the die cavity, and the nearly spherical regular particles are difficult to completely fill in the die cavity, so that the structural uniformity of the blank is poor.
The sintering mode of naked sintering is adopted, during sintering, 5-10mm of high-temperature powder is paved, a blank body of the filter element is flatly placed on the high-temperature powder, and a long tubular or candle-shaped finished product is obtained by sintering, wherein the finished product is the filter element prepared by the method in the embodiment.
The filter element prepared in this example had a porosity of 48%, a bending strength of 12MPa, a maximum pore size of 68 μm and an average pore size of 62 μm. Pore size difference between maximum pore size and average pore sizeSmall, even pore size distribution and smooth pore canal, and effectively reduces the filtration resistance of the filter element. Tests show that the gas filtration resistance is less than 150Pa and the thermal expansion coefficient is less than 2.5 x 10 at the wind speed of 1m/min-6/° c, maximum use temperature 800 ℃. Compared with the ceramic filter element in the prior art, the filter resistance can be reduced by about 40 percent under the same average pore diameter. See table 2 for details.
TABLE 2
Example 7:
the 300-micron cordierite spherical particles prepared by the process method in the example 2 are taken as aggregates, 42.5Kg of spherical particles are taken as the aggregates, 7.5Kg of high-temperature bonding agent, 6 parts of additional ceramic bonding agent and 2.7Kg of walnut shell powder pore-increasing agent with the particle size of 300-micron and 400-micron are weighed, liquid phenolic resin is taken as the ceramic bonding agent, and the materials are mixed, granulated, molded under the pressure of 60MPa and the like, and finally sintered at the high temperature of 1260 ℃.
The high-temperature ceramic filter element prepared by the process has the maximum pore size of 110 microns, the average pore size of 104 microns and uniform pore size distribution.
The filter element prepared by the embodiment has the porosity of more than 45 percent, the bending strength of 10.8MPa, the gas filtration resistance of 80Pa at the wind speed of 1m/min and the thermal expansion coefficient of less than 2.5 x 10 at 900 DEG C-6The catalyst has excellent thermal stability at 850 deg.c, and may be used in purifying various high temperature gas, membrane material and catalyst carrier.
The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by a person skilled in the art that the scope of the invention as referred to in the present application is not limited to the embodiments with a specific combination of the above-mentioned features, but also covers other embodiments with any combination of the above-mentioned features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.
Claims (10)
1. A ceramic particle, characterized by being prepared by the steps of:
mixing kaolin, talc, bauxite and spodumene, and preparing spherical particles by pulverizing, rolling and molding and sintering.
2. The ceramic particle as claimed in claim 1, wherein the composition ratio is: by mass, 40-50 parts of kaolin, 35-45 parts of talc, 15-25 parts of bauxite and 3-10 parts of spodumene.
3. The ceramic particle as claimed in claim 1, wherein the spherical particle has a particle size in the range of 100-1000 μm and a water absorption of 2-5%.
4. A method for preparing a filter element, which is characterized in that the filter element is prepared by mixing the spherical particles, the pore-increasing agent, the high-temperature binding agent and the ceramic adhesive according to the claims 1 to 3, granulating, molding and firing.
5. The method of manufacturing a filter element according to claim 4, wherein the composition ratio is: 80-90 parts of spherical particles, 10-20 parts of high-temperature bonding agent and 5-8 parts of ceramic adhesive by mass; the addition amount of the pore-increasing agent is 5-10% of the sum of the mass of the spherical particles and the mass of the high-temperature bonding agent.
6. A method of making a filter element as recited in claim 4 wherein said mixing comprises the steps of:
adding spherical particles and a pore-increasing agent, wherein the rotating speed of a stirring shaft of a mixing barrel is 40-60rpm, and stirring for 3-8 min;
secondly, adding 30-40% of the total amount of the ceramic adhesive, and stirring for 8-12 min;
thirdly, adding a high-temperature bonding agent, a lubricant and the balance of a ceramic adhesive;
and fourthly, increasing the rotating speed of a stirring shaft of the mixing barrel to 80-90rpm, and stirring for 25-30min to obtain a mixture.
7. The method of claim 4, wherein the high temperature binder comprises kaolin, feldspar, spodumene, and borax in a ratio of 2-5% by mass.
8. The method of claim 4, wherein the firing is conducted by a sintering method of bare firing, wherein the green body of the filter element is laid on the high temperature powder during the sintering, the laying thickness of the high temperature powder is 5-10mm, and the green body is fired to obtain a long tubular or candle-shaped finished product.
9. The method of claim 4 or 5, wherein the pore-increasing agent is walnut shell powder or petroleum coke particles.
10. A filter element, characterized by being prepared according to any one of claims 4 to 9.
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