A gradient ceramic fiber filter tube for dust removal and its preparation method

Abstract

The present invention relates to the field of dust removal, and particularly to a gradient ceramic fiber filter tube for dust removal and a preparation method thereof, which are used to solve the problems that existing porous ceramic fiber filters still have poor filtering effect, low filtering efficiency, and insufficient mechanical properties and high-temperature resistance; in this preparation method, the ceramic fiber filter tube is set as a three-layer composite structure, so that the support layer plays a good supporting role, the purification layer can carry out redox reactions on harmful gases in the flue gas, effectively purifying the flue gas, and the high-strength layer can withstand the high temperature and impact of the flue gas, thereby effectively protecting the entire ceramic fiber filter tube. Moreover, the pore diameters of the support layer, the purification layer, and the high-strength layer are set in a gradient manner, making the ceramic fiber filter tube have good thermal shock resistance, reducing its filtration resistance, and through the contact between the ceramic fiber and the particulate matter, the plastic deformation is greatly improved, enhancing the backwashing effect between layers.

Description

Technical Field

[0001] The present invention relates to the field of dust removal, and particularly to a gradient ceramic fiber filter tube for dust removal and a preparation method thereof. Background Art

[0002] The waste gas discharged from various industrial furnaces in industries such as metallurgy, machinery, and chemical engineering is not only at a high temperature but also contains a large amount of dust and harmful substances, which is one of the main factors causing environmental pollution. Under high-temperature conditions, due to large changes in the viscosity of the waste gas, a significant decrease in humidity, and a great reduction in the agglomeration phenomenon of fine particles, it is difficult to separate fine particles. At present, the technologies that have been maturely applied in this field include electrostatic dust removal and bag filter dust removal, etc. However, these technologies all have more or less some problems in the application process: for example, the bag filter cannot withstand the high temperature of the waste gas, and electrostatic dust removal has problems such as high initial investment, large floor area, and insulation. Therefore, the purification technology of soot under high-temperature conditions is a topic with high difficulty and urgent need for development in chemical engineering. The emergence of porous ceramic fibers provides a possibility for the research and development of this technology. However, the current porous ceramic fiber filters still have problems such as poor filtration effect, low filtration efficiency, insufficient mechanical properties and high-temperature resistance, which limit the application of porous ceramic fiber filters in the field of high-temperature flue gas purification. Summary of the Invention

[0003] In order to overcome the above technical problems, the purpose of the present invention is to provide a gradient ceramic fiber filter tube for dust removal and a preparation method thereof: by adding polyvinylpyrrolidone, sodium silicate, carboxymethyl cellulose, and deionized water into a mixer and stirring and mixing to obtain a matrix slurry, adding ceramic fibers, purification particles, and high-strength particles into the matrix slurry respectively and stirring and mixing to obtain a fiber slurry, a purification slurry, and a high-strength slurry respectively, injecting the fiber slurry into a suction filtration mold for vacuum suction filtration, drying and curing after forming to form a support layer, then injecting the purification slurry for vacuum suction filtration, drying and curing after forming to form a purification layer on the outer surface of the support layer, then injecting the high-strength slurry for vacuum suction filtration, drying and curing after forming to form a high-strength layer on the outer surface of the purification layer, then demolding and placing it in a tube furnace for calcination, and then cooling with the furnace to obtain the gradient ceramic fiber filter tube for dust removal, solving the problems that the existing porous ceramic fiber filters still have poor filtration effect, low filtration efficiency, insufficient mechanical properties and high-temperature resistance, which limit the application of porous ceramic fiber filters in the field of high-temperature flue gas purification.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A preparation method of a gradient ceramic fiber filter tube for dust removal, comprising the following steps:

[0006] Step 1: Weigh 0.5 - 1 part of polyvinylpyrrolidone, 25 - 30 parts of sodium silicate, 4 - 6 parts of carboxymethyl cellulose, and 80 - 90 parts of deionized water by weight, and set aside;

[0007] Step 2: Add polyvinylpyrrolidone, sodium silicate, carboxymethyl cellulose, and deionized water into a mixer, and stir and mix for 1 - 2 h under the conditions of a temperature of 25 - 30 °C and a stirring rate of 800 - 1000 r / min to obtain a matrix slurry;

[0008] Step 3: Add ceramic fibers, purification particles, and high-strength particles into the matrix slurry respectively, and stir and mix for 1 - 2 h under the conditions of a temperature of 25 - 30 °C and a stirring rate of 800 - 1000 r / min to obtain a fiber slurry, a purification slurry, and a high-strength slurry respectively;

[0009] Step 4: Inject the fiber slurry into a suction filtration mold for vacuum suction filtration, dry and cure after forming to form a support layer, then inject the purification slurry for vacuum suction filtration, dry and cure after forming to form a purification layer on the outer surface of the support layer, then inject the high-strength slurry for vacuum suction filtration, dry and cure after forming to form a high-strength layer on the outer surface of the purification layer, then demold and place it in a tubular furnace, calcine at a temperature of 1200 - 1250 °C for 3 - 3.5 h, and then cool with the furnace to obtain the gradient ceramic fiber filter tube for dust removal.

[0010] As a further scheme of the present invention: The ceramic fibers are a mixture of alumina ceramic fibers and wollastonite fibers in a mass ratio of 1 - 2:1. The fiber diameter of the alumina ceramic fibers is 10 - 20 μm, and the fiber length is 100 - 300 μm. The fiber diameter of the wollastonite fibers is 1 - 5 μm, and the fiber length is 30 - 50 μm.

[0011] As a further scheme of the present invention: The dosage ratio of the ceramic fibers to the matrix slurry is 10 - 15 g:100 g. The dosage ratio of the purification particles to the matrix slurry is 20 - 25 g:100 g. The dosage ratio of the high-strength particles to the matrix slurry is 30 - 40 g:100 g.

[0012] As a further scheme of the present invention: The purification particles are prepared by the following steps:

[0013] Step a1: Add glacial acetic acid into a three-necked flask equipped with a stirrer, a thermometer and a constant-pressure dropping funnel. While stirring at a temperature of 25 - 30 °C and a stirring rate of 300 - 400 r / min, dropwise add tetrabutyl titanate drop by drop, control the dropping rate to be 1 - 2 drops / s. After the dropping is completed, continue stirring and reacting for 30 - 50 min, then raise the temperature to 160 - 165 °C and continue stirring and reacting for 8 - 10 h. After the reaction is completed, cool the reaction product to room temperature, then wash it 3 - 5 times with deionized water and anhydrous ethanol in sequence, then centrifuge. Add the precipitate into a muffle furnace and calcine it at a temperature of 400 - 410 °C for 1 - 1.5 h, then heat it while raising the temperature at a heating rate of 2 - 3 °C / min for 2 - 3 h, then cool it to room temperature with the furnace, then let it stand for 5 - 6 h, then introduce hydrogen and calcine it at a temperature of 400 - 410 °C for 3 - 5 h to obtain defective TiO₂ nanotubes;

[0014] Step a2: Add ammonium metavanadate, ammonium tungstate and deionized water into a three-necked flask equipped with a stirrer and a thermometer, ultrasonically disperse it for 20 - 30 min under the condition of an ultrasonic power of 200 - 300 W, then add oxalic acid and continue ultrasonically dispersing for 1 - 1.5 h, then add manganese chloride and continue ultrasonically dispersing for 20 - 30 min, then add defective TiO₂ nanotubes, then stir and react at a temperature of 45 - 50 °C and a stirring rate of 300 - 400 r / min for 5 - 6 h. After the reaction is completed, cool the reaction product to room temperature, then rotary evaporate to remove the solvent, then place it in a vacuum drying oven and dry it at a temperature of 120 - 125 °C for 2 - 3 h, then place it in a tube furnace and calcine it at a temperature of 350 - 360 °C for 1 - 1.5 h, then raise the temperature to 450 - 460 °C and calcine it for 4 - 5 h, then cool it with the furnace to obtain purified particles.

[0015] As a further scheme of the present invention: The dosage ratio of the glacial acetic acid and tetrabutyl titanate in step a1 is 50 mL : 1 - 3 mL.

[0016] As a further scheme of the present invention: The dosage ratio of the ammonium metavanadate, ammonium tungstate, deionized water, oxalic acid, manganese chloride and defective TiO₂ nanotubes in step a2 is 1 - 3 g : 1 - 3 g : 100 - 120 mL : 3.6 - 5.2 g : 0.15 - 0.35 g : 15 - 20 g.

[0017] As a further scheme of the present invention: The high-strength particles are prepared by the following steps:

[0018] Step b1: Add silicon nitride powder, silicon carbide powder, yttrium oxide powder, and alumina powder into absolute ethanol, then perform ultrasonic treatment for 30 - 40 min under the condition of an ultrasonic power of 200 - 300 W, and then add it into a ball milling tank. Ball mill for 20 - 30 h under the conditions of a ball-to-material ratio of 4 - 5:1 and a rotation speed of 300 - 400 r / min to obtain ball-milled material;

[0019] Step b2: Place the ball-milled material in a vacuum drying oven and dry it for 3 - 5 h under the condition of a temperature of 120 - 125 °C, then cool it to room temperature, crush it and pass it through a 150 - 200 mesh sieve, and then add it into a graphite mold, introduce argon for protection, and then perform hot pressing sintering for 4 - 6 h under the condition of a temperature of 1800 - 1850 °C, and then cool it with the furnace to obtain high-strength particles.

[0020] As a further solution of the present invention: The dosage ratio of the silicon nitride powder, silicon carbide powder, yttrium oxide powder, alumina powder, and absolute ethanol in step b1 is 70 - 80 g:10 - 30 g:3.5 - 5.5 g:4 - 6 g:180 - 220 mL.

[0021] As a further solution of the present invention: A gradient ceramic fiber filter tube for dust removal, the gradient ceramic fiber filter tube for dust removal is prepared according to the preparation method of the gradient ceramic fiber filter tube for dust removal, and the gradient ceramic fiber filter tube for dust removal successively includes a support layer, a purification layer, and a high-strength layer from the inside to the outside.

[0022] As a further solution of the present invention: The thickness of the gradient ceramic fiber filter tube for dust removal is 2 - 2.5 cm, and the thickness ratio of the support layer, the purification layer, and the high-strength layer is 1:0.8 - 1.2:0.5 - 0.7.

[0023] As a further solution of the present invention: The pore diameter of the support layer is 100 - 120 μm, the pore diameter of the purification layer is 30 - 50 μm, and the pore diameter of the high-strength layer is 8 - 10 μm.

[0024] The beneficial effects of the present invention:

[0025] A gradient ceramic fiber filter tube for dust removal and its preparation method according to the present invention. Polyvinylpyrrolidone, sodium silicate, carboxymethyl cellulose and deionized water are added to a mixer and stirred and mixed to obtain a matrix slurry. Ceramic fibers, purification particles and high-strength particles are respectively added to the matrix slurry and stirred and mixed to obtain a fiber slurry, a purification slurry and a high-strength slurry. The fiber slurry is injected into a suction filtration mold for vacuum suction filtration, dried and cured after forming to form a support layer. Then the purification slurry is injected for vacuum suction filtration, dried and cured after forming to form a purification layer on the outer surface of the support layer. Then the high-strength slurry is injected for vacuum suction filtration, dried and cured after forming to form a high-strength layer on the outer surface of the purification layer. Then it is demolded and placed in a tube furnace for calcination, and then cooled with the furnace to obtain the gradient ceramic fiber filter tube for dust removal; in this preparation method, the ceramic fiber filter tube is set as a three-layer composite structure, so that the support layer provides support. The alumina ceramic fibers in the support have good mechanical properties. Then wollastonite fibers are added. Since wollastonite has a unique needle-like structure and is a good filling material, it has the characteristics of improving impact strength, enhancing fluidity and improving tensile strength, impact strength, linear tensile and mold shrinkage rate, further improving the mechanical properties of the support layer and playing a good supporting role. Then a purification layer is compounded on it. The purification layer is composed of defective TiO2 nanotubes loaded with vanadium-based catalysts, tungsten-based catalysts and manganese-based catalysts. Under the synergistic action of the defective TiO2 nanotubes, vanadium-based catalysts, tungsten-based catalysts and manganese-based catalysts, redox reactions can be carried out on harmful gases in the flue gas, effectively purifying the flue gas. Then a high-strength layer is compounded on it. The high-strength layer is composed of a composite of silicon nitride and silicon carbide. Both have good high-temperature resistance and mechanical properties, and their performance is further improved when combined, so that it can withstand the high temperature and impact of the flue gas, thus effectively protecting the entire ceramic fiber filter tube. Moreover, the pore diameters of the support layer, the purification layer and the high-strength layer are set in a gradient manner, increasing the number of cross-sectional layers and making the microporous gradient change gently, so that the thermal shock resistance of the ceramic fiber filter tube is better, reducing its filtration resistance, overcoming the problems of high pressure loss and low filtration efficiency of homogeneous porous ceramics, thereby reducing the dust removal difficulty and achieving the purpose of energy saving. And by contacting the ceramic fibers with the particulate matter, when the ceramic fibers or between the ceramic fibers and the grains are subjected to external forces, their plastic deformation can be greatly improved. Therefore, under the action of reverse external forces, the impurities in the middle are easily removed, thus improving the backwashing effect between layers; in summary, the gradient ceramic fiber filter tube for dust removal has good filtration effect and filtration efficiency, excellent high-temperature resistance and mechanical properties, and also has a good backwashing effect, does not need to be replaced frequently, has a long service life, and thus reduces the dust removal cost. Specific embodiments

[0026] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0027] Example 1:

[0028] This embodiment is a preparation method of purification particles, including the following steps:

[0029] Step a1: Add 50 mL of glacial acetic acid to a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. While stirring at a temperature of 25°C and a stirring rate of 300 r / min, gradually add 1 mL of tetrabutyl titanate drop by drop, control the dropping rate at 1 drop / s. After the dropping is completed, continue to stir and react for 30 min. Then, raise the temperature to 160°C and continue to stir and react for 8 h. After the reaction is completed, cool the reaction product to room temperature. Then, wash it three times with deionized water and anhydrous ethanol in sequence. Then, centrifuge it. Add the precipitate to a muffle furnace and calcine it at a temperature of 400°C for 1 h. Then, heat it while raising the temperature at a rate of 2°C / min for 2 h. Then, cool it to room temperature with the furnace. Then, let it stand for 5 h. Then, introduce hydrogen and calcine it at a temperature of 400°C for 3 h to obtain defective TiO2 nanotubes;

[0030] Step a2: Add 1 g of ammonium metavanadate, 1 g of ammonium tungstate, and 100 mL of deionized water to a three-necked flask equipped with a stirrer and a thermometer. Ultrasonically disperse it for 20 min under the condition of an ultrasonic power of 200 W. Then, add 3.6 g of oxalic acid and continue to ultrasonically disperse it for 1 h. Then, add 0.15 g of manganese chloride and continue to ultrasonically disperse it for 20 min. Then, add 15 g of defective TiO2 nanotubes. Then, stir and react at a temperature of 45°C and a stirring rate of 300 r / min for 5 h. After the reaction is completed, cool the reaction product to room temperature. Then, rotate and evaporate to remove the solvent. Then, place it in a vacuum drying oven and dry it at a temperature of 120°C for 2 h. Then, place it in a tube furnace and calcine it at a temperature of 350°C for 1 h. Then, raise the temperature to 450°C and calcine it for 4 h. Then, cool it with the furnace to obtain purification particles.

[0031] Example 2:

[0032] This embodiment is a preparation method of purification particles, including the following steps:

[0033] Step a1: Add 50 mL of glacial acetic acid into a three-necked flask equipped with a stirrer, a thermometer, and a constant-pressure dropping funnel. While stirring at a temperature of 30 °C and a stirring rate of 400 r / min, dropwise add 3 mL of tetrabutyl titanate drop by drop, controlling the dropping rate at 2 drops / s. After the addition is complete, continue stirring and reacting for 50 min. Then, raise the temperature to 165 °C and continue stirring and reacting for 10 h. After the reaction is completed, cool the reaction product to room temperature. Then, wash it 5 times with deionized water and anhydrous ethanol in sequence. After that, centrifuge it, add the precipitate into a muffle furnace, and calcine it at a temperature of 410 °C for 1.5 h. Then, heat it while raising the temperature at a rate of 3 °C / min for 3 h. Then, cool it to room temperature with the furnace. Then, let it stand for 6 h. Then, introduce hydrogen gas and calcine it at a temperature of 410 °C for 5 h to obtain defective TiO2 nanotubes;

[0034] Step a2: Add 3 g of ammonium metavanadate, 3 g of ammonium tungstate, and 120 mL of deionized water into a three-necked flask equipped with a stirrer and a thermometer. Ultrasonically disperse it for 30 min under the condition of an ultrasonic power of 300 W. Then, add 5.2 g of oxalic acid and continue ultrasonically dispersing for 1.5 h. Then, add 0.35 g of manganese chloride and continue ultrasonically dispersing for 30 min. Then, add 20 g of defective TiO2 nanotubes. Then, stir and react at a temperature of 50 °C and a stirring rate of 400 r / min for 6 h. After the reaction is completed, cool the reaction product to room temperature. Then, remove the solvent by rotary evaporation. Then, place it in a vacuum drying oven and dry it at a temperature of 125 °C for 3 h. Then, place it in a tube furnace and calcine it at a temperature of 360 °C for 1.5 h. Then, raise the temperature to 460 °C and calcine it for 5 h. Then, cool it with the furnace to obtain purified particles.

[0035] Example 3:

[0036] This example is a preparation method of high-strength particles, including the following steps:

[0037] Step b1: Add 70 g of silicon nitride powder, 10 g of silicon carbide powder, 3.5 g of yttrium oxide powder, and 4 g of alumina powder into 180 mL of anhydrous ethanol. Then, ultrasonically treat it for 30 min under the condition of an ultrasonic power of 200 W. Then, add it into a ball mill tank and ball mill it for 20 h under the conditions of a ball-to-material ratio of 4:1 and a rotation speed of 300 r / min to obtain a ball-milled material;

[0038] Step b2: Place the ball-milled material in a vacuum drying oven and dry it at a temperature of 120 °C for 3 h. Then, cool it to room temperature, crush it and pass it through a 150-mesh sieve. Then, add it into a graphite mold, introduce argon gas for protection. Then, hot press and sinter it at a temperature of 1800 °C for 4 h. Then, cool it with the furnace to obtain high-strength particles.

[0039] Example 4:

[0040] This embodiment is a method for preparing high-strength particles, comprising the following steps:

[0041] Step b1: Add 80 g of silicon nitride powder, 30 g of silicon carbide powder, 5.5 g of yttrium oxide powder, and 6 g of alumina powder into 220 mL of absolute ethanol. Then, ultrasonic treatment is carried out for 40 min under the condition of an ultrasonic power of 300 W. After that, it is added into a ball mill tank and ball milled for 30 h under the conditions of a ball-to-material ratio of 5:1 and a rotation speed of 400 r / min to obtain ball-milled material;

[0042] Step b2: Place the ball-milled material in a vacuum drying oven and dry it for 5 h under the condition of a temperature of 125 °C. Then, it is cooled to room temperature, pulverized and sieved through a 200-mesh sieve. After that, it is added into a graphite mold, argon is introduced for protection, and then hot press sintering is carried out for 6 h under the condition of a temperature of 1850 °C. Then, it is cooled in the furnace to obtain high-strength particles.

[0043] Example 5:

[0044] This embodiment is a method for preparing a gradient ceramic fiber filter tube for dust removal, comprising the following steps:

[0045] Step 1: Weigh 0.5 part of polyvinylpyrrolidone, 25 parts of sodium silicate, 4 parts of carboxymethyl cellulose, and 80 parts of deionized water by weight and set aside;

[0046] Step 2: Add polyvinylpyrrolidone, sodium silicate, carboxymethyl cellulose, and deionized water into a mixer and stir and mix for 1 h under the conditions of a temperature of 25 °C and a stirring rate of 800 r / min to obtain a matrix slurry;

[0047] Step 3: Add 10 g of alumina ceramic fibers with a fiber diameter of 10 μm and a fiber length of 100 μm, ceramic fibers formed by mixing wollastonite fibers with a fiber diameter of 1 μm and a fiber length of 30 μm in a mass ratio of 1:1, 20 g of purification particles from Example 1, and 30 g of high-strength particles from Example 3 into 100 g of the matrix slurry respectively, and stir and mix for 1 h under the conditions of a temperature of 25 °C and a stirring rate of 800 r / min to obtain fiber slurry, purification slurry, and high-strength slurry respectively;

[0048] Step 4: Inject the fiber slurry into a suction filtration mold for vacuum suction filtration. After forming, it is dried and cured to form a support layer. Then, the purified slurry is injected for vacuum suction filtration. After forming, it is dried and cured to form a purification layer on the outer surface of the support layer. Then, the high-strength slurry is injected for vacuum suction filtration. After forming, it is dried and cured to form a high-strength layer on the outer surface of the purification layer. Then, it is demolded and placed in a tubular furnace, calcined at 1200 °C for 3 h, and then cooled with the furnace to obtain a gradient ceramic fiber filter tube for dust removal with a thickness of 2 cm. The thickness ratio of the support layer, the purification layer, and the high-strength layer is 1:0.8:0.5. The pore size of the support layer is 120 μm, the pore size of the purification layer is 50 μm, and the pore size of the high-strength layer is 10 μm.

[0049] Example 6:

[0050] This example is a preparation method of a gradient ceramic fiber filter tube for dust removal, including the following steps:

[0051] Step 1: Weigh 1 part of polyvinylpyrrolidone, 30 parts of sodium silicate, 6 parts of carboxymethyl cellulose, and 90 parts of deionized water by weight, and set aside.

[0052] Step 2: Add polyvinylpyrrolidone, sodium silicate, carboxymethyl cellulose, and deionized water to a mixer, and stir and mix at 30 °C and a stirring rate of 1000 r / min for 2 h to obtain a matrix slurry.

[0053] Step 3: Add 15 g of alumina ceramic fibers with a fiber diameter of 20 μm and a fiber length of 300 μm, ceramic fibers formed by mixing wollastonite fibers with a fiber diameter of 5 μm and a fiber length of 50 μm in a mass ratio of 2:1, 25 g of purification particles from Example 2, and 40 g of high-strength particles from Example 4 into 100 g of the matrix slurry respectively, and stir and mix at 30 °C and a stirring rate of 1000 r / min for 2 h to obtain a fiber slurry, a purification slurry, and a high-strength slurry respectively.

[0054] Step 4: Inject the fiber slurry into a suction filtration mold for vacuum suction filtration. After forming, it is dried and cured to form a support layer. Then, the purified slurry is injected for vacuum suction filtration. After forming, it is dried and cured to form a purification layer on the outer surface of the support layer. Then, the high-strength slurry is injected for vacuum suction filtration. After forming, it is dried and cured to form a high-strength layer on the outer surface of the purification layer. Then, it is demolded and placed in a tubular furnace, calcined at 1250 °C for 3.5 h, and then cooled with the furnace to obtain a gradient ceramic fiber filter tube for dust removal with a thickness of 2.5 cm. The thickness ratio of the support layer, the purification layer, and the high-strength layer is 1:1.2:0.7. The pore size of the support layer is 100 μm, the pore size of the purification layer is 30 μm, and the pore size of the high-strength layer is 8 μm.

[0055] Example 7:

[0056] This example is a preparation method of a gradient ceramic fiber filter tube for dust removal, including the following steps:

[0057] Step 1: Weigh 1 part of polyvinylpyrrolidone, 30 parts of sodium silicate, 6 parts of carboxymethyl cellulose and 90 parts of deionized water by weight, and set aside;

[0058] Step 2: Add polyvinylpyrrolidone, sodium silicate, carboxymethyl cellulose and deionized water into a mixer, and stir and mix for 2 h under the conditions of a temperature of 30 °C and a stirring rate of 1000 r / min to obtain a matrix slurry;

[0059] Step 3: Add 15 g of alumina ceramic fibers with a fiber diameter of 20 μm and a fiber length of 300 μm, ceramic fibers formed by mixing wollastonite fibers with a fiber diameter of 5 μm and a fiber length of 50 μm in a mass ratio of 2:1, and 40 g of high-strength particles from Example 4 into 100 g of the matrix slurry respectively, and stir and mix for 2 h under the conditions of a temperature of 30 °C and a stirring rate of 1000 r / min to obtain a fiber slurry and a high-strength slurry respectively;

[0060] Step 4: Inject the fiber slurry into a suction filtration mold for vacuum suction filtration, dry and solidify after forming to form a support layer, then inject the high-strength slurry for vacuum suction filtration to form a high-strength layer on the outer surface of the support layer, then demold and place it in a tubular furnace, calcine at a temperature of 1250 °C for 3.5 h, and then cool with the furnace to obtain a gradient ceramic fiber filter tube for dust removal with a thickness of 2.5 cm, and the thickness ratio of the support layer to the high-strength layer is 1:0.7. The pore diameter of the support layer is 100 μm, and the pore diameter of the high-strength layer is 8 μm.

[0061] Example 8:

[0062] This example is a preparation method of a gradient ceramic fiber filter tube for dust removal, including the following steps:

[0063] Step 1: Weigh 1 part of polyvinylpyrrolidone, 30 parts of sodium silicate, 6 parts of carboxymethyl cellulose and 90 parts of deionized water by weight, and set aside;

[0064] Step 2: Add polyvinylpyrrolidone, sodium silicate, carboxymethyl cellulose and deionized water into a mixer, and stir and mix for 2 h under the conditions of a temperature of 30 °C and a stirring rate of 1000 r / min to obtain a matrix slurry;

[0065] Step 3: Add 15 g of alumina ceramic fibers with a fiber diameter of 20 μm and a fiber length of 300 μm, ceramic fibers formed by mixing wollastonite fibers with a fiber diameter of 5 μm and a fiber length of 50 μm in a mass ratio of 2:1, and 25 g of purification particles from Example 2 into 100 g of the matrix slurry respectively. Stir and mix for 2 h under the conditions of a temperature of 30 °C and a stirring rate of 1000 r / min to obtain a fiber slurry and a purification slurry respectively;

[0066] Step 4: Inject the fiber slurry into a suction filtration mold for vacuum suction filtration. After molding, dry and cure to form a support layer. Then inject the purification slurry for vacuum suction filtration. After molding, dry and cure to form a purification layer on the outer surface of the support layer. Then demold and place it in a tube furnace, calcine at a temperature of 1250 °C for 3.5 h, and then cool with the furnace to obtain a dust removal gradient ceramic fiber filter tube with a thickness of 2.5 cm. The thickness ratio of the support layer to the purification layer is 1:1.2. The pore diameter of the support layer is 100 μm, and the pore diameter of the purification layer is 30 μm.

[0067] Example 9:

[0068] This example is a preparation method of a dust removal gradient ceramic fiber filter tube, which includes the following steps:

[0069] Step 1: Weigh 1 part of polyvinylpyrrolidone, 30 parts of sodium silicate, 6 parts of carboxymethyl cellulose and 90 parts of deionized water by weight, and set aside;

[0070] Step 2: Add polyvinylpyrrolidone, sodium silicate, carboxymethyl cellulose and deionized water into a mixer, and stir and mix for 2 h under the conditions of a temperature of 30 °C and a stirring rate of 1000 r / min to obtain a matrix slurry;

[0071] Step 3: Add 15 g of alumina ceramic fibers with a fiber diameter of 20 μm and a fiber length of 300 μm, ceramic fibers formed by mixing wollastonite fibers with a fiber diameter of 5 μm and a fiber length of 50 μm in a mass ratio of 2:1 into 100 g of the matrix slurry, and stir and mix for 2 h under the conditions of a temperature of 30 °C and a stirring rate of 1000 r / min to obtain a fiber slurry;

[0072] Step 4: Inject the fiber slurry into a suction filtration mold for vacuum suction filtration. After molding, dry and cure, then demold and place it in a tube furnace, calcine at a temperature of 1250 °C for 3.5 h, and then cool with the furnace to obtain a dust removal gradient ceramic fiber filter tube with a thickness of 2.5 cm and a pore diameter of 100 μm.

[0073] The mechanical properties of the gradient ceramic fiber filter tubes for dust removal in Examples 5-9 were tested. Then, dust particles were filtered and removed using the gradient ceramic fiber filter tubes for dust removal in Examples 5-9 respectively. The filtration speed was 4 m / min, and the particle size distribution of the dust particles was D10 = 2.0 μm, D50 = 30.8 μm, and D90 = 79.9 μm. The detection results are as follows:

[0074]

[0075] Referring to the data in the above table, according to the comparison between Examples 5-9, it can be known that setting the gradient ceramic fiber filter tube for dust removal into a multi-layer structure and the pore size being set in a gradient can greatly improve its dust removal effect, and can also improve its mechanical properties, thereby making it not easily damaged and achieving the purpose of long-term and efficient dust removal.

[0076] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0077] The above content is only an example and explanation of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them. As long as they do not deviate from the invention or exceed the scope defined by this claim book, they should all belong to the protection scope of the present invention.

Claims

1. A preparation method of a gradient ceramic fiber filter tube for dust removal, characterized in that, It includes the following steps: Step 1: Weigh 0.5 - 1 part of polyvinylpyrrolidone, 25 - 30 parts of sodium silicate, 4 - 6 parts of carboxymethyl cellulose and 80 - 90 parts of deionized water by weight, and set aside; Step 2: Add polyvinylpyrrolidone, sodium silicate, carboxymethyl cellulose and deionized water into a mixer, and stir and mix for 1 - 2 h under the conditions of a temperature of 25 - 30 °C and a stirring rate of 800 - 1000 r / min to obtain a matrix slurry; Step 3: Add ceramic fibers, purification particles and high-strength particles into the matrix slurry respectively, and stir and mix for 1 - 2 h under the conditions of a temperature of 25 - 30 °C and a stirring rate of 800 - 1000 r / min to obtain a fiber slurry, a purification slurry and a high-strength slurry respectively; Step 4: Inject the fiber slurry into a suction filtration mold for vacuum suction filtration, dry and cure after forming to form a support layer, then inject the purification slurry for vacuum suction filtration, dry and cure after forming to form a purification layer on the outer surface of the support layer, then inject the high-strength slurry for vacuum suction filtration, dry and cure after forming to form a high-strength layer on the outer surface of the purification layer, then demold and place it in a tubular furnace, calcine at a temperature of 1200 - 1250 °C for 3 - 3.5 h, and then cool with the furnace to obtain the gradient ceramic fiber filter tube for dust removal; The purification particles are prepared by the following steps: Step a1: Add glacial acetic acid into a three-necked flask equipped with a stirrer, a thermometer and a constant-pressure dropping funnel, and dropwise add tetrabutyl titanate drop by drop while stirring under the conditions of a temperature of 25 - 30 °C and a stirring rate of 300 - 400 r / min, control the dropping rate at 1 - 2 drops / s, continue to stir and react for 30 - 50 min after dropping, then raise the temperature to 160 - 165 °C and continue to stir and react for 8 - 10 h. After the reaction is completed, cool the reaction product to room temperature, then wash it 3 - 5 times with deionized water and absolute ethanol in sequence, then centrifuge, add the precipitate into a muffle furnace, calcine at a temperature of 400 - 410 °C for 1 - 1.5 h, then heat while raising the temperature at a rate of 2 - 3 °C / min for 2 - 3 h, then cool with the furnace to room temperature, then let it stand for 5 - 6 h, then introduce hydrogen, and calcine at a temperature of 400 - 410 °C for 3 - 5 h to obtain defective TiO2 nanotubes; Step a2: Add ammonium metavanadate, ammonium tungstate, and deionized water into a three-necked flask equipped with a stirrer and a thermometer. Under the condition of an ultrasonic power of 200 - 300 W, ultrasonically disperse for 20 - 30 min, then add oxalic acid and continue to ultrasonically disperse for 1 - 1.5 h, then add manganese chloride and continue to ultrasonically disperse for 20 - 30 min, then add defective TiO2 nanotubes, and then stir and react at a temperature of 45 - 50 °C and a stirring rate of 300 - 400 r / min for 5 - 6 h. After the reaction is completed, cool the reaction product to room temperature, then rotate and evaporate to remove the solvent, then place it in a vacuum drying oven and dry at a temperature of 120 - 125 °C for 2 - 3 h, then place it in a tubular furnace and calcine at a temperature of 350 - 360 °C for 1 - 1.5 h, then raise the temperature to 450 - 460 °C and calcine for 4 - 5 h, and then cool with the furnace to obtain purified particles; The high-strength particles are prepared by the following steps: Step b1: Add silicon nitride powder, silicon carbide powder, yttrium oxide powder, and alumina powder into absolute ethanol, then under the condition of an ultrasonic power of 200 - 300 W, ultrasonically treat for 30 - 40 min, then add it into a ball milling tank and ball mill for 20 - 30 h under the condition of a ball-to-material ratio of 4 - 5:1 and a rotation speed of 300 - 400 r / min to obtain ball-milled material; Step b2: Place the ball-milled material in a vacuum drying oven and dry at a temperature of 120 - 125 °C for 3 - 5 h, then cool to room temperature, crush and pass through a 150 - 200 mesh sieve, then add it into a graphite mold, introduce argon for protection, and then hot press and sinter at a temperature of 1800 - 1850 °C for 4 - 6 h, and then cool with the furnace to obtain high-strength particles.

2. The preparation method of a gradient ceramic fiber filter tube for dust removal according to claim 1, characterized in that, The ceramic fiber is a mixture of alumina ceramic fiber and wollastonite fiber in a mass ratio of 1 - 2:

1. The fiber diameter of the alumina ceramic fiber is 10 - 20 μm, and the fiber length is 100 - 300 μm. The fiber diameter of the wollastonite fiber is 1 - 5 μm, and the fiber length is 30 - 50 μm.

3. The preparation method of a gradient ceramic fiber filter tube for dust removal according to claim 1, characterized in that, The dosage ratio of the ceramic fiber to the matrix slurry is 10 - 15 g:100 g, the dosage ratio of the purified particles to the matrix slurry is 20 - 25 g:100 g, and the dosage ratio of the high-strength particles to the matrix slurry is 30 - 40 g:100 g.

4. The preparation method of a gradient ceramic fiber filter tube for dust removal according to claim 1, characterized in that, The dosage ratio of the glacial acetic acid to tetrabutyl titanate in step a1 is 50 mL:1 - 3 mL; the dosage ratio of the ammonium metavanadate, ammonium tungstate, deionized water, oxalic acid, manganese chloride, and defective TiO2 nanotubes in step a2 is 1 - 3 g:1 - 3 g:100 - 120 mL:3.6 - 5.2 g:0.15 - 0.35 g:15 - 20 g.

5. The preparation method of a gradient ceramic fiber filter tube for dust removal according to claim 1, characterized in that, The dosage ratio of the silicon nitride powder, silicon carbide powder, yttrium oxide powder, alumina powder, and absolute ethanol in step b1 is 70 - 80 g:10 - 30 g:3.5 - 5.5 g:4 - 6 g:180 - 220 mL.

6. A gradient ceramic fiber filter tube for dust removal, characterized in that, The gradient ceramic fiber filter tube for dust removal is prepared by the preparation method of the gradient ceramic fiber filter tube for dust removal according to any one of claims 1-5. The gradient ceramic fiber filter tube for dust removal sequentially comprises a support layer, a purification layer and a high-strength layer from the inside to the outside.

7. The gradient ceramic fiber filter tube for dust removal according to claim 6, wherein, The thickness of the gradient ceramic fiber filter tube for dust removal is 2-2.5 cm, and the thickness ratio of the support layer, the purification layer and the high-strength layer is 1:0.8-1.2:0.5-0.

7.

8. The gradient ceramic fiber filter tube for dust removal according to claim 6, wherein, The pore diameter of the support layer is 100-120 μm, the pore diameter of the purification layer is 30-50 μm, and the pore diameter of the high-strength layer is 8-10 μm.

Images