KR101118607B1 - Silicon carbide ceramic compositions added strontium carbonate for high temperature filtration filters and preparing method of high temperature filtration filters using the same - Google Patents

Abstract

PURPOSE: A strontium carbonate containing silicon carbide ceramic composition for manufacturing a high temperature dust collecting filter and a method for manufacturing the same are provided to improve the porosity and the intensity of the filter by including silicon carbide powder, mullite supplying materials, and strontium carbonate. CONSTITUTION: A strontium carbonate containing silicon carbide ceramic composition for manufacturing a high temperature dust collecting filter includes 3-5 parts by weight of mullite powder and 1-3 parts by weight of strontium carbonate based on 100 parts by weight of silicon carbide powder. A method for manufacturing a mullite combined porous silicon carbide high temperature dust collecting filter includes the following: 1-15 parts by weight of an organic binder as a molding agent and 5-20 parts by weight of a solvent based on 100 parts by weight of the silicon carbide ceramic composition; a molded dust filter is dried based on hot air; the dried filter is sintered under atmosphere at a temperature between 1400 and 1450 degrees Celsius for 0.5 to 1 hours. The organic binder is at least one of methylcellulose, ethylcellulose, carboxymehylcellulose, and polyvinyl alcohol.

Description

Silicon carbide ceramic compositions added strontium carbonate for high temperature filtration filters and preparing method of high temperature filtration filters using the same}

The present invention relates to a silicon carbide ceramic composition for producing a high temperature dust collecting filter and a method of manufacturing a high temperature dust collecting filter using the same, and more particularly, including a silicon carbide (SiC) powder, a mullite feedstock and a strontium carbonate. The present invention relates to a method for manufacturing a high temperature dust collecting filter using the ceramic composition for manufacturing a high temperature dust collecting filter made of silicon carbide.

Recently, with the rise of energy and environmental problems, studies on liquefaction and gasification of coal have been actively conducted as technologies for solving energy efficiency and environmental problems at the same time. In addition, after the liquefaction or gasification process of coal, in order to undergo the process of reburning the flammable coal gas in the turbine combustor, the research on the high-strength high temperature dust collecting filter material with high temperature and high pressure dust collection performance is actively being conducted. In particular, there is an increasing need for a ceramic high temperature dust collecting filter for a next-generation coal-composite for simultaneously treating fine particulate matter and pollutants contained in syngas under high temperature and high pressure conditions.

In general, in order to form a smooth flow of combustion exhaust gas in a high temperature dust collecting filter, the porosity of the filter is high and the air permeability is good, so that the pressure loss is low. There is a disadvantage in that cracks are generated or destroyed due to thermal fatigue. As such, since the air permeability and the strength characteristics of the filter have a mutually opposite relationship, there is a difficulty in improving the mechanical properties of the high temperature dust collecting filter while securing a constant air permeability.

Porous silicon carbide ceramics, on the other hand, have excellent properties such as corrosion resistance, abrasion resistance, thermal shock resistance, and high temperature stability, and are used as high temperature dust collecting filters, various refractory materials, dust filters for diesel vehicles, and semiconductor vacuum chuck materials. Pure sintered silicon carbide using high-purity fine powders may be used for these applications, but such products are too expensive to produce at temperatures above 2000 ^o C, and manufacturing equipment is too expensive to manufacture large products. There are disadvantages.

Therefore, a silicon carbide material prepared by adding a sintered binder to a silicon carbide raw material is used depending on the application. Such binders include clay, silicon oxynitride, alumina and silicon nitride. However, these binders have a large difference in coefficient of thermal expansion with silicon carbide, and thus have low thermal shock resistance. The non-oxide silicon oxynitride and silicon nitride binders are oxidized when used at high temperature, and thus SiO ₂ Since a phase is formed, oxidation resistance falls and it has a disadvantage that a crack generate | occur | produces.

Korean Patent Registration No. 10-0419779 provides a method for manufacturing a high strength silicon carbide ceramic filter for dust collection. In summary, 1.0 to 15.0 wt% of clay, 0.1 to 5.0 wt% based on 100 wt% of silicon carbide powder High strength silicon carbide ceramics for dust collection through mixing, aging and sintering of calcium carbonate, 1.0 to 5.0 wt% molding aid, 0.5 to 5.0 wt% dispersant, and 5.0 to 15.0 wt% water Provided is a method of making a filter. However, the silicon carbide filter manufactured by such a process has a disadvantage that the bending strength is not excellent as 30 MPa or less.

Meanwhile, Korean Patent No. 10-0891956 provides a method for preparing a paste composition for sintering silicon carbide and a porous silicon carbide filter to which a mullite-based hollow sphere is added. In summary, the starting material includes silicon carbide powder, organic binder, and mullite hollow spheres, which assist in the formation of the connection site between the silicon carbide particles during the sintering process and the porous structure of the sintered body. Characterized in that the action to give. The patent is also the production of silicon carbide filter, which is sintered at 1200 ~ 1600 ^o C by adding Y ₂ O ₃ , Al ₂ O ₃ , SiO ₂ , CaO, MgO as an additive to lower the melting temperature of the hollow spheres Provide a method. However, this method has a problem in that the mullite-based binder is present only at the bonding sites of the SiC particles, thereby deteriorating oxidation resistance, and excessive SiO ₂ formed by additional oxidation of SiC remains during sintering, resulting in phase transformation of SiO ₂ . It has the disadvantage that the strength is lowered during use due to cracking.

Accordingly, an object of the present invention is to provide a ceramic composition for producing a mullite-bonded silicon carbide high temperature dust filter comprising a silicon carbide powder, mullite powder and strontium carbonate.

In addition, by using the composition, the mullite-strontium monooxide eutectic phase, which is an oxide having excellent oxidation resistance, covers the silicon carbide particles, thereby preventing oxidation of the surface of the silicon carbide particles, thereby preventing the oxidation of the silicon carbide particles. Another object is to provide a method for producing the same.

In order to achieve the above object, according to the present invention, the ceramic composition for mullite-bonded silicon carbide high temperature dust filter manufacturing by mixing 3 to 5 parts by weight of mullite powder and 1 to 3 parts by weight of strontium carbonate with respect to 100 parts by weight of silicon carbide powder is Is provided.

According to the present invention to achieve the above another object,

i) mixing 1 to 15 parts by weight of an organic binder and 5 to 20 parts by weight of a solvent as a molding aid with respect to 100 parts by weight of the ceramic composition for preparing the dust collecting filter;

ii) drying the molded dust collecting filter with hot air; And

iii) A method for manufacturing a mullite-bonded porous silicon carbide high temperature dust filter comprising the step of sintering the dried filter by heat treatment for 0.5 to 1 hour in air at a temperature range of 1400 to 1450 ° C.

The organic binder may be at least one selected from the group consisting of methylcellulose, ethylcellulose, carboxymehylcellulose, and polyvinyl alcohol. In the case where the organic binder is added in an amount less than 1 part by weight, the bonding strength of the silicon carbide ceramic filter molded body becomes weak, and when the organic binder content exceeds 15 parts by weight, a large number of internal defects may be generated during heat treatment of the filter material. not.

The solvent may be any solvent as long as it can dissolve the organic binder, but water is most economically used. When the content of the solvent is added less than 5 parts by weight, the flexibility of the mixture is insufficient, which is not suitable for molding. When the solvent is added more than 20 parts by weight, the viscosity of the raw material mixture is too low, difficult to mold, long time to dry It is not desirable because it takes.

The molding step may be molded by pressing in a hydrostatic pressure molding method, a ramming molding method according to the shape of the desired filter, or an extrusion molding method for producing the composition into a tube shape.

The sintering step is preferably made by heat treatment for 0.5 to 1 hour in the air at a temperature range of 1400 ~ 1450 ℃. At this time, the heat treatment process is carried out in the temperature range of 1400 ~ 1450 ℃, sintering does not proceed because the eutectic liquid phase of mullite and strontium monooxide is not produced at a temperature of less than 1400 ℃, if the sintering exceeds 1450 ℃ There is no additional strength increase even if this proceeds, so it is not economically effective.

In addition, the heat treatment process is heat-treated for 0.5 to 1 hour in the temperature range of 1400 ~ 1450 ℃, when the heat treatment time is less than 0.5 hours is not enough time to coat the silicon carbide particles in the eutectic phase is low sintered density It is difficult to develop strength after sintering, and even if the heat treatment time exceeds 1 hour, there is no additional eutectic phase formation or an increase in strength, so that the heat treatment time at the sintering temperature is preferably limited to 0.5 to 1 hour.

The filter manufactured by the method of manufacturing a mullite-bonded silicon carbide filter for a high temperature dust collecting filter including the strontium carbonate of the present invention is a mixture of silicon carbide powder, mullite powder and strontium carbonate powder, whereby strontium carbonate is strontium mono during sintering in the air. Carbon dioxide is decomposed into oxide and carbon dioxide, and carbon dioxide is discharged into the gas phase, and strontium monooxide is melted and reacts with mullite to form a eutectic phase, thereby strongly binding these eutectic phase silicon carbide particles to enable the production of a high strength dust collecting filter support. There is this.

In addition, the mullite-bonded silicon carbide filter including the strontium carbonate prepared according to the present invention by coating the silicon carbide particles constituting the matrix by the formation of the mullite phase and strontium monooxide, which is an oxide having excellent oxidation resistance acting as a binder In addition, by preventing additional oxidation of silicon carbide, there is an excellent effect expected to improve the long-term durability when used.

In the present invention, when the mullite powder is added to the silicon carbide main raw material and a small amount of strontium carbonate is added thereto as a sintering aid, the strontium carbonate decomposes into strontium monooxide (SrO) and carbon dioxide (CO ₂ ) during sintering in air. Is melted to react with mullite to form a mullite-strontium oxide eutectic phase, and the formed eutectic phase is uniformly formed around the silicon carbide particles to act as a binder of the silicon carbide particles, thereby lowering the sintering temperature. It is characterized by the use of porosity that also plays a role in contributing to the increase in strength.

The mullite-bonded silicon carbide ceramic composition for a high temperature dust collecting filter including strontium of the present invention comprises 3 to 5 parts by weight of mullite powder and 1 to 3 parts by weight of strontium carbonate based on 100 parts by weight of silicon carbide powder.

At this time, the mullite powder is preferably added in a proportion of 3 to 5 parts by weight, because if too much mullite is added, the baking does not proceed smoothly. In addition, the strontium carbonate is preferably added in a ratio of 1 to 3 parts by weight. When the strontium carbonate content is less than 1 part by weight, the amount of strontium monooxide generated by the decomposition of strontium carbonate during the sintering process is too small, so that the eutectic liquid phase with mullite is not smoothly produced and sintering does not proceed. On the other hand, when the content of strontium carbonate exceeds 3 parts by weight, the amount of eutectic liquid with mullite is too large to swell at the sintering temperature, thereby forming a large amount of defects on the surface of the silicon carbide material.

In addition, when the content of strontium carbonate is less than 1 part by weight, the sintering does not proceed smoothly and the porosity is too high, resulting in a decrease in strength after sintering. When the content exceeds 3 parts by weight, the strength after sintering is maintained to some extent, but it is uneven. It is preferable to limit the amount to 1 to 3 parts by weight because there is a disadvantage in that it does not function as a porous dust collecting filter due to one pore distribution.

According to an example of the present invention regarding a method of manufacturing a dust filter of a silicon carbide material using a ceramic composition for preparing a mullite-bonded silicon carbide filter including the strontium carbonate, it may be prepared by a manufacturing method comprising the following steps. have.

i) 1 to 15 parts by weight of an organic binder as a molding aid to 100 parts by weight of a ceramic composition for dust collection filter comprising 3 to 5 parts by weight of mullite powder and 1 to 3 parts by weight of strontium carbonate, based on 100 parts by weight of silicon carbide powder; Molding by mixing 5 to 20 parts by weight of the solvent;

ii) drying the molded dust collecting filter with hot air; And

iii) The mullite-bonded porous silicon carbide dust collecting filter may be manufactured by sintering the dried filter in a temperature range of 1400 to 1450 ° C. for 0.5 to 1 hour in the air.

The organic binder may be at least one selected from the group consisting of methylcellulose, ethylcellulose, carboxymehylcellulose, and polyvinyl alcohol. When the organic binder is less than 1 part by weight, the bonding strength of the silicon carbide ceramic filter molded body becomes weak, and when the organic binder content exceeds 15 parts by weight, a large number of internal defects may be generated during heat treatment of the filter material. not.

The solvent may be any solvent as long as it can dissolve the organic binder, but water is most economically used. When the content of the solvent is added less than 5 parts by weight, the flexibility of the mixture is insufficient, which is not suitable for molding. When the solvent is added more than 20 parts by weight, the viscosity of the raw material mixture is too low, difficult to mold, long time to dry It is not desirable because it takes.

The molding step may be molded by pressing in a hydrostatic pressure molding method, a ramming molding method according to the shape of the desired filter, or an extrusion molding method for producing the composition into a tube shape.

The sintering step is preferably heat-treated for 0.5 to 1 hour in the air at a temperature section of 1400 ~ 1450 ℃. At this time, the heat treatment process is carried out in the temperature range of 1400 ~ 1450 ℃, sintering does not proceed because the eutectic liquid phase of mullite and strontium monooxide is not produced at a temperature of less than 1400 ℃, if the sintering exceeds 1450 ℃ There is no additional strength increase even if this proceeds, so it is not economically effective.

In addition, the heat treatment process is heat-treated for 0.5 to 1 hour in the temperature range of 1400 ~ 1450 ℃, when the heat treatment time is less than 0.5 hours is not enough time to coat the silicon carbide particles in the eutectic phase is low sintered density It is difficult to develop strength after sintering, and even if the heat treatment time exceeds 1 hour, there is no additional eutectic phase formation or an increase in strength, so that the heat treatment time at the sintering temperature is preferably limited to 0.5 to 1 hour.

The mullite-bonded silicon carbide high temperature dust collecting filter including the strontium carbonate exhibits a very good strength characteristic with room temperature bending strength of 35 MPa or more at a porosity of 30% or more.

Hereinafter, although an Example and a test example demonstrate this invention in detail, this invention is not limited by an Example.

[Example]

Example  1-4: Preparation of the dust collecting filter

As shown in Table 1 below, silicon carbide (SiC) powder having an average particle size of 85 μm, mullite (3Al ₂ O ₃ 2SiO ₂ ) powder having an average particle size, and strontium carbonate having an average particle size of 44 μm (SrCO ₃ ) The powder was mixed to prepare a mullite-bonded silicon carbide ceramic composition, and then fired to prepare a dust collecting filter.

5 parts by weight of mullite powder and 1 to 3 parts by weight of strontium carbonate powder are added to 100 parts by weight of silicon carbide in the ceramic composition, and 2 parts by weight of carboxymethyl cellulose (CMC) and 20 parts by weight of water are added as a vibrating mill. (vibratory pot mill) was mixed uniformly for 4 hours. The mixture was aged for 24 hours and then molded in an automatic ramming apparatus to produce shaped candles shaped candles. The molded body of the filter thus prepared was dried at room temperature for at least 24 hours and then completely dried at least 24 hours using a hot air dryer. The dried molded body was sintered for 0.5 to 1 hour in the temperature range of 1400 ~ 1450 ^° C to prepare a dust collecting filter of the present invention.

Comparative example  1: Preparation of the dust collecting filter

Calcium carbonate (CaCO ₃ ) was added to the same silicon carbide powder and mullite powder as in the above example, and the mixture, molding, and drying process were performed in the same manner as in the above example. A dust collecting filter was prepared by sintering at 1450 ^° C. for 1 hour in air.

Division (parts by weight)
SiC
Mullite
SrCO ₃
CaCO ₃ Firing conditions Temperature
( ^o C) Retention time
(h) Comparative example One 100 5 - One 1450 One
Example One 100 5 One - 1400 One 2 100 5 3 - 1400 One 3 100 5 One - 1450 One 4 100 5 3 - 1400 One

Test Example   1: Physical mechanical property test

In order to measure the porosity and bending strength of the filters prepared in Examples 1 to 4 and Comparative Example 1, a sintered filter was cut to a size of 5 mmW × 4 mmH × 40 mmL using a diamond wheel to prepare specimens for bending strength measurement. In the strength measurement, the tensile surface was ground with a resin-bonded diamond wheel. The porosity of the specimens was calculated by using the Archimedes method (ASTM C20) after boiling each specimen in distilled water for 3 hours and then measuring the suspended weight, the saturated weight and the dried weight. In addition, the bending strength of each specimen was measured using a universal testing machine, and the lower distance 30 mm jig and cross-head speed 0.5 mm / min. It was measured by three-point bending strength under the conditions. The sintered density, porosity and bending strength values of the dust collecting filter material thus measured are shown in Table 2 below.

division Sintered Density
(g / cm ³⁾ Porosity
(%) Bending strength
(MPa) Comparative example One 1.97 26.3 45 Example One 1.88 37.7 36 2 1.96 32.7 51 3 1.91 35.9 42 4 1.93 33.5 53

As shown in Table 2, the specimen to which the calcium carbonate was added in Comparative Example 1 prepared by applying the conventional technique showed a high sintered density and showed a bending strength of 45 MPa, but the porosity was 26.3%. These results indicate that the porosity is too low to be used as the dust collection filter, considering that both conditions of porosity of at least 30% and bending strength of 35 MPa or more must be satisfied for use as the dust collection filter. It can be seen that.

On the other hand, in Examples 1 to 4, the porosity was 30% or more, and the bending strength value was also 36 MPa or more, indicating that all of the requirements for use as the dust collecting filter were satisfied. In particular, a German filter currently commercially available as a dust collecting filter has a strength value of 40 MPa, but a composition obtained by adding 3 parts by weight of SrCO ₃ of the present invention and firing it at 1400 ° C., but 1 part by weight and 3 parts by weight of SrCO ₃ . Addition and firing at 1450 ° C. resulted in better bending strength characteristics than the prototype.

These results therefore indicate that the present invention provides a silicon carbide filter with significantly improved mechanical strength properties compared to the prior art.

Claims (4)

The ceramic composition for mullite-bonded silicon carbide high temperature dust filter manufacture which mixes 3-5 weight part of mullite powders and 1-3 weight part of strontium carbonate with respect to 100 weight part of silicon carbide powders.
i) mixing 1 to 15 parts by weight of an organic binder and 5 to 20 parts by weight of a solvent as a molding aid with respect to 100 parts by weight of the ceramic composition for preparing the dust collecting filter according to claim 1;
ii) drying the molded dust collecting filter with hot air; And
iii) A method of manufacturing a mullite-bonded porous silicon carbide high temperature dust filter comprising the step of sintering the dried filter in a temperature range of 1400 ~ 1450 ℃ for 0.5 to 1 hour in the air.
The method of claim 2,
The organic binder is at least one selected from the group consisting of methyl cellulose (MC), ethyl cellulose (ethylcellulose, EC), carboxymehylcellulose (CMC) and polyvinyl alcohol (PVA). A method for producing a mullite-bonded porous silicon carbide high temperature dust filter.
The method of claim 2,
The solvent is a method for producing a mullite-bonded porous silicon carbide high temperature dust filter, characterized in that the water.