FI106702B - Ceramic filter for a dust-laden gas and method for the manufacture thereof - Google Patents

Description

. 1 106702

Ceramic filter for a gas containing dust and a process for its production

Divided by application 901 698 5

The present invention relates to a ceramic filter useful for removing dust from a gas, particularly high temperature gas containing dust, and to a method of making a filter.

Ceramic materials usually have excellent fire and corrosion resistance and are well suited as a material for filters used to filter high temperature or corrosive gases. On the other hand, there is a growing need for ceramic filters that can be used in demanding environmental conditions.

Their applications include not only controlling pollution or improving product quality, but also energy saving or, for example, developing carbon energy. Therefore, it has been desirable to develop a high performance dust-containing ceramic filter 20 which plays a key role in implementing these technological developments.

For filter devices for removing high temperature gas containing dust, two typical examples have been published, one using the tubular filters disclosed in U.S. Pat. Nos. 4,584,003 and 4,753,457, and the other the so-called candle type. uses tubular filters with one end closed and disclosed in JP 9 843/1985, which is reviewed.

30 If such a filter device has filters. .. during use, dust accumulates on the surface, pressure drop increases, t · and gas handling capacity decreases. To remove the accumulated dust and renew the filters, pressurized gas is blown into the filtering device, which performs the opposite purification operation by passing gas through the filters t 106702 in the opposite direction to the conventional filtration operation, whereupon the accumulated dust is peeled off

5 The device is designed so that dust collected in the hopper is withdrawn from the filter device when required using, for example, a valve at the bottom of the device. With reverse cleaning, the pressure loss of the filters is restored to a low level. This reverse cleaning operation is repeated repeatedly at appropriate intervals, whereby the operation of the filter device can be continued and the pressure loss of the filters is always low.

If the pressure drop of the filters used in the filter device is small, the small filter device 15 can handle a large amount of dust containing gas. Therefore, various proposals have been made to reduce the pressure loss of the filters.

One such method is the use of a filter material having a high porosity and an average pore diameter and the introduction of a powder, called a filtering layer, which is collected in these filters and which during operation forms a filtering layer so that dust accumulates in that filtering layer and is removed together with this filtering agent, non-irritating JP Patent Publication No. 64 315/1986 discloses a method in which this filtering agent layer is initially affixed to a filter surface.

Further, JP-A-31 517/1988 30 discloses a ceramic filter with a low pressure drop, although the walls of the filter are thick and do not substantially clog even when the dust-containing gas is removed from the particulate dust without the filter bed material and the filter material some changes have been made.

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For example, unexamined JP-A-133 810/1983 further discloses a method of using a thin, honeycombed filter wall in an attempt to remove dust consisting essentially of carbon in the exhaust gas of a diesel engine.

In the event that the filter device is placed. the filtering agent not only wastes the filtering agent but also increases the amount of dust to be removed as the filtering agent is contained in the collected dust; part of the dust 10 is likely to pass through the filter or the dust will adhere to the filter wall, thereby increasing the pressure drop and not returning to a low level even when a reverse cleaning is performed. If a cellular filter is used, the wall of the filter is so thin that it tends to distort upon repeatedly receiving the pressure exerted by the gas pressure during the reverse purge. Also, the technology of a large filter device has not yet been developed.

The method of varying the pore size distribution of the filter material may possibly provide a filter that is good enough for some dust-containing gases or a filter device that is not used for a long time if the filter is made in combination with a shamot with a suitable particle diameter distribution. However, it has been found that when this is used for a long time attached to the filter device, increasing the residual pressure drop is still a problem.

Such problems can be largely overcome by the method of applying a filterable layer to the surface of the filter, but the problem remains that

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the filtering layer is likely to peel off, or if the filtering layer does not peel, the residual pressure drop tends to increase periodically.

When the filter is operated at high temperature, 356702 rapid heating or cooling is often unavoidable. Therefore, a material with a low thermal expansion coefficient and good resistance to thermal shocks is required.

Of the various types of ceramic materials, Cordie rite ceramics have an extremely low coefficient of thermal expansion of 5 and are very resistant to heat shocks. Utilizing these features, a cordierite filter has been developed for use at high temperatures for a specific purpose.

For example, JP-A-133 810/1983 10 discloses a cordierite ceramic filter and a method of making it; this publication discloses a noble filter having a pore size suitable for removing fine dust from diesel engine exhaust gas, and a method for producing a cordierite carbon ceramic filter having a relatively large pore size. It is further proposed to add an alkaline component such as a lithium oxide component to form relatively large pores.

In addition, one of the inventors of the present invention has previously provided a tubular cordierite filter with a non-susceptible pore size distribution to remove dust from a high temperature gas containing dust. The smaller the pressure drop in the filter, the better, because then a high capacity filter device for treating dust containing gas can be obtained. For this purpose, the higher the porosity, the better. However, there is a problem that durability is substantially reduced when porosity is increased. Therefore, a compromise point is usually found and a filter is made based on such a compromise.

* · For alumina and silicon carbide, which have actually been used as ceramic filters, applications have been created as abrasives or polishes. Therefore, it is relatively easy to fabricate a filter with a low pressure drop and a durability level that is practical - 5 106702 by carefully selecting a technical preparation with a suitable particle size as a shamot.

Such a filter usually uses a honeycomb made of glass or clay. The problem with the glass cell 5 is that its high temperature resistance is very poor; resistance at 800 ° C is not more than 1/3 of that at room temperature. The problem with clay cells, on the other hand, is that even its room temperature resistance cannot be improved. On the other hand, the porosity of commercially available synthetic cordierite hamsters is high in most cases. Thus, if such commercially available shamots are used in the manufacture of ceramic filters, the resulting porosity and pressure loss are high, and there has been a problem that if porosity is added to reduce the pressure loss, it is very difficult to maintain durability at a practical level. When used with high temperature and corrosive air over a long period of time, it is essential that the durability of ceramic filters be adjusted over a wide temperature range - from room temperature to high temperature, to provide high reliability of the filter device and to provide excellent heat resistance. delicately, their pressure loss is low and their corrosion resistance, in particular * 25 acid corrosion resistance, is furthermore excellent in the case that dust is removed from a gas containing corrosive gases such as NOX or SOX.

The object of the present invention is to solve the conventional method of cordierite ceramic filters. 30 problems and provide cordierite filters for dust-containing gases with low pressure drop and practical durability and excellent corrosion resistance.

The present invention is made to solve the above-mentioned problems, and provides a dust-containing gas-based filter having a filter base having an average pore size of 10-100 µπι and a pore size ratio of 75% by volume and 25% by volume of accumulated pore distribution. at least 1.3, and a filter-5 filter layer having an average pore size of 0.2 to 10 μτη is applied to at least the filtering side of the filter base so that the filtering layer fills the pores open on the surface of the filter base. 75% by volume and 25% by volume are numerical values based on 10 assuming an apparent porosity of the filter base of 100% by volume.

In the accompanying drawings:

Fig. 1 is a graph showing the results of measurements of the accumulated pore distribution of a ceramic filter base and of a mercury porosity meter obtained from cubic specimens cut from a ceramic filter base of 1 cm3. In this figure, the ordinate represents the accumulated pore volume of the specimens, and the abs cat represents the pore size. In the figure, curves a, b, c and d represent the pore distributions of the samples taken from the filter bases of Examples 1, 2, 3 and 4, respectively. The curves e, f and g depict the pore distributions of the test samples obtained from the filter bases of Comparative Examples 1, 2 and 3, respectively.

The present invention will now be explained in more detail with reference to the preferred embodiments.

In a preferred embodiment of the ceramic filter of the present invention, the porosity of the filter base is 35-50%.

In another preferred embodiment of the ceramic filter of the present invention, the filter base is * made of cordierite or silicon carbide.

In another preferred embodiment of the ceramic filter of the present invention, the filtering layer is made of diatomaceous earth or rice husks.

35 106702

In another preferred embodiment of the ceramic filter of the present invention, the filter base is tubular and the filter layer is fixed to the inner surface of the tube.

In the process of the present invention for producing a dust-containing gas ceramic filter, the powder is rubbed onto at least a filter-side filtering surface having an average pore size of 10-100 µπι and a pore size ratio of 75 to 10% by volume. the powder used has an average particle diameter less than the average pore size of the filter base, the method also comprising attaching the powder with an inorganic binder.

In a preferred embodiment of the method of manufacturing the ceramic filter of the present invention, a first powder is first rubbed onto the surface of the filter base, then a second powder finer than the first powder is rubbed and both are adhered to the surface.

In another preferred embodiment of the method of making the ceramic filter of the present invention, the first powder has an average particle diameter of 20 to 70% of the average pore size of the filter base and 2 to 15% of the average pore size of the filter base.

In another preferred embodiment of the method of making the ceramic filter of the present invention, the inorganic binder is a solution consisting of silica. The solution is sprayed onto the surface on which the powder is rubbed, then heated and dried for attachment. Preferably, this silica-containing solution is 1-5% by weight of an aqueous solution of silica sol.

t 35 8 106702

The thickness and shape of the filter base of the ceramic filter of the present invention may be selected for a particular purpose. However, since large porous material is used to minimize pressure loss, durability 5 is usually poor. In order to provide the durability required to handle this dust-containing gas ceramic filter, and to provide sufficient strength to the filter base supporting the filter itself, and at the same time to withstand the gas pressure of the counter-cleaning, the thickness must usually be at least 5 mm.

The ceramic filter of the present invention has an average pore size of 10-100 µm. If the average pore size is less than 10 µm, the pressure loss of the filter base tends to be large, and the filter base 15 is not good enough in use. On the other hand, if the average pore size exceeds 100 µm, when a filter layer consisting of a powder having an average particle diameter of not more than 10 µm is formed on the surface of the filter base, the powder tends to go deep inside the filter base, whereby the pressure loss increases it is likely to enter the filter base from the rear end of the filter base by counter-cleaning, thereby causing an irreversible increase in pressure drop.

The present invention measures the accumulated pore distribution of a filter base by means of a mercury porosity meter for cube shaped samples obtained from a filter base of 1 cm3.

The ceramic filter of the present invention has a pore size ratio of 75 to 25% by volume of the accumulated pore distribution according to the test specimens above, at least 1.3, with pores of various sizes open on the surface of the filter base, and go inside these pores.

i 106702 This structure is good for attaching the filter layer firmly to the filter base; at the same time, the pressure drop is small because of the large pores on the inside of the filter bed, which are only communicated externally through the small pores 5 and although there is little dust leakage into the clean gas space, such leakage does not immediately cause irreversible increase in pressure loss. a filter layer.

If this pore size ratio is less than 1.3, no such beneficial effects will be obtained.

In order to ensure such beneficial effects, the pore size ratio should be at least 1.4.

Given the ease of preparation of the filter base, this pore size ratio is typically no more than 2, and the maximum for a man-lumen is 1.8.

The filtration layer has an average pore size in the range of 0.2 to 10 μτη. If the average pore size is less than 0.2 μτη, the pressure loss tends to become large, and when such a layer is used when attached to a filter-20 device, the filter device's processing capability is reduced, which is undesirable. On the other hand, for example, if the average pore size is greater than 10 μτη, some of the dust in the dust-containing gas tends to pass through the filtration bed, thereby causing dust to accumulate in the filtration bed * 25 or filter bed, thereby increasing undesirable pressure loss.

The apparent porosity of the filter base should preferably be at least 35% to ensure a favorable level of pressure drop.

However, if the apparent porosity is greater than 50%, the resistance of the marshy 30 sole will tend to be poor. Therefore, the apparent porosity should be no more than 50%.

Preferably, alumina, cordierite, mullite or silicon carbide are used as filter-bottom ceramics. It is preferable to use cordierite or silicon carbide for thermal and corrosion resistance.

106702

The silicon carbide filter has low resistance to, for example, oxidation by steam, but its heat resistance is much better than that of a cordierite filter.

The powder material forming the filtering layer 5 can be made of, for example, diatomaceous earth, rice husk ash, calcined perlite, calcium silicate, permutite, Bayer alumina, zirconium, cordierite, silicon carbide, quartz sand and mullite. Of these materials, it is preferable to use 10 diatomaceous earth or rice husks ash because of their excellent gas permeability and the ability to form a filtration layer with a relatively uniform pore size suitable for a dust containing gas filter.

Silica-15 is the major constituent of diatomaceous earth and rice husks, and is useful because it has good corrosion resistance and is particularly resistant to gas containing acidic material.

The shape of the filter base is advantageous to be tubular because during the back cleaning operations, the gas pressure will exert repeated pressure on the filter base and the pressure drop can be reduced when the back cleaning gas pressure is higher. In the form of a tube, the load is not easily concentrated, thereby avoiding the concentration of the load, which is likely to cause the filter base I-25 to break. This is used so that the pressure of the scrubbing gas is externally applied. Namely, it is better that the filtering layer of the filter is attached to the inner wall of the tube.

As a filter of this type, it is possible to construct a very reliable filter device because the filter-induced tensile stress, which is usually poorly resisted by ceramics, is small even when gas pressure is applied to the filter base.

The filter-data layer of the ceramic filter of the present invention preferably has a thickness that is small, so that the pressure loss is small. For example, the thickness should preferably be at a level where part of the shamot on the surface of the filter base faces the filter surface.

In the process of making the ceramic filter of the present invention, the powder to be formed as a filter layer is rubbed into the open pores on the surface of the filter base, e.g. Accordingly, the average particle diameter of the powder is preferably smaller than the average pore size of the filter base.

10 In order to scrub the powder forming the filter layer into the inner wall of the tubular filter base, a rod having a felt wrapped around one end can be inserted into the tube and the powder can be rubbed into the inner wall of the tube.

With such a filtration layer forming method, it is possible to form a thin filtration layer on the surface of the filter base, whereby the pressure loss becomes relatively small.

When it is desired to form a filter layer having a small average pore size on the surface of the filter base, it is preferable to scrub the surface first with a coarser first powder and then with a second powder having the required particle size.

In this way, a fine filtration layer of fine particle size is obtained, whereby the pressure loss, especially the residual pressure loss, can advantageously be reduced by using the layer as a filter.

The average particle diameter of the first powder should preferably be no more than 70% of the average pore size of the filter base, whereby the powder will readily rub on the surface of the filter base. In order to obtain a low-pressure filter, the first powder should not be fine * * and should be at least 20% of the average pore size of the filter base.

The average particle diameter of the second powder should preferably be 2-15% of the average pore size of the filter base.

* 106702

If a powder having an average particle diameter of less than 2% of the average pore size of the filter base is used, the pressure drop is so great that the filter is no longer practically usable as a 5 gas filter. On the other hand, if the powder is coarser than 15%, the rubbing step need not be divided into two separate operations.

Since the filter is also expected to be used at high temperatures, it is preferable to use an inorganic binder which is refractory and preferably corrosion resistant to attach the filter layer. A silica-based solution is preferable in that it can achieve a firm attachment with low solidity, as well as fire and corrosion resistance, without the substance being used so much that the pores opening on the surface become clogged. The aqueous silica sol solution is thus an inorganic binder suitable for adhering the filtering layer of the ceramic filter of the present invention.

The concentration of the aqueous silica sol solution is at least 1% by weight and at most 5% by weight, because if the concentration is too low, the anchor strength becomes low. At a concentration greater than 5% by weight, the solution tends to have a high viscosity, <25, which makes it difficult to spray in fine, small droplets and tends to block the pores opening on the surface and to reduce gas permeability, which is undesirable.

In the case where the filtration layer is formed by the first and second powders, the aqueous silica sol solution may be sprayed after both powders have been rubbed onto the surface. However, the aqueous silica sol solution may be sprayed twice, that is once after rubbing the first powder and once after rubbing the second powder.

35 106702

Moreover, it is also possible to use the third and fourth powders. However, no significant effects can be expected, but the processability is more difficult.

When the silica sol solution is used as an inorganic binder, the solidification can be controlled by heating and drying to provide the necessary and sufficient bonding strength.

Another ceramic filter of the present invention comprises at least 50% by weight of cordierite hammer-10 having an apparent porosity of up to 10% and a particle diameter of at least 74 µm, and a honeycomb comprising said silica (SiO 2) and alumina (Al 2 O 3) the amount of lithium oxide (Li 2 O) is 0.05 to 1.0% by weight of the total weight of the filter.

In a preferred embodiment of said second ceramic filter of the present invention, the honeycomb addition contains magnesium oxide (MgO).

In another preferred embodiment of said second ceramic filter of the present invention, the cordierite shamot 20 is a glass crystallized cordierite shamot with an average cordierite composition (2MgO -2A1203 * 5SiO2).

In another preferred embodiment of said second ceramic filter of the present invention, 25 cordierite shamots are obtained by impregnating a cordierite shamot with an alumina sol, a silica sol, a titanium oxide sol, a zirconium oxide sol, or a mixture of at least two such sols;

Said second ceramic of the present invention

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in another preferred embodiment of the filter, the filter material has a porosity of at least 35% and a bending strength at 800 ° C of at least 75 kg / cm 2.

In a second preferred embodiment of said second ceramic 35 filter of the present invention, raising the pitch 106702 contains TiO 2 and / or ZrO 2 0.5 to 12% by weight of the total weight of the filter.

In another preferred embodiment of said second ceramic filter of the present invention, the filter has the form of a straight tube.

The second ceramic filter of the present invention comprises a filter base comprising at least 50% by weight of a cordierite diatomaceous earth with an apparent porosity of not more than 10% and a particle diameter of 74-590 μιη, and 10 cells consisting of silica (SiO 2) and alumina {Al 2 O 3} (Li20) 0.2 - 0.6% by weight of the total weight of the filter, said filter base having an average pore size of 10-100 μιη and a pore size ratio of at least 1.3 at positions of 75 and 25% by volume of the accumulated pore distribution; the filter also comprises a filtering layer having an average pore size of 0.2 to 10 µm and attached to at least the filtering side of the filter base so that the filtering layer fills the pores open on the surface of the filter base.

In a preferred embodiment of another such ceramic filter of the present invention, the cordier-sufficient hammer is a glass crystallized cordierite hammer having an average cordierite composition (2MgO. 2A1203.5SiO2).

In another preferred embodiment of another such ceramic filter of the present invention, the filtering layer is made of diatomaceous earth or rice husks.

In another preferred embodiment of another such ceramic filter of the present invention, the filter base has a tubular shape and the filter layer is · · w attached to the surface of the inner wall of the tube.

Another method of making such a ceramic filter according to the present invention comprises mixing a powdered cellular material which is obtained by mixing clay and lithium oxide-containing flour / 106702 flakes with at least 50% by weight of cordierite ham with an apparent porosity of at least 10% and and adding an organic binder to the mixture, followed by molding and sintering.

In a preferred embodiment of such another method of making a ceramic filter of the present invention, a cordierite hammer having an apparent porosity of up to 10% is obtained by mixing the following materials: MgO, Al 2 O 3 and SiO 2 to form an average cordierite composition (2MgO and cooling it to obtain a glass which is then crystallized by heat treatment.

In a preferred embodiment of such another method of manufacturing a ceramic filter of the present invention, β-spodumen powder is added to the cellular powder material so that the lithium oxide content of the filter material is between 0.05% and 1.0% by weight.

In a preferred embodiment of another such method of manufacturing a ceramic filter of the present invention, a cordierite powder having a particle diameter of 'up to 74 µχη is added to the powder material to form a honeycomb.

In a preferred embodiment of another such ceramic filter manufacturing method of the present invention, powder made from ZrO2 and / or TiO2 is added to the powder material in an amount of 0.5 to 12% by weight of the filter material.

In a preferred embodiment of another such method of making a ceramic filter of the present invention, the starting material is admixed with a pore-forming agent to form a coke powder which forms upon burning the pores. . * 106702

In a preferred embodiment of another such method of manufacturing a ceramic filter of the present invention, the forming of the filter is accomplished by means of an isostatic press using a metal core mold 5 and an outer cylindrical rubber mold to form a straight tube.

In a preferred embodiment of another such method of manufacturing a ceramic filter of the present invention, sintering is carried out at a temperature of from 1,310 to 1,380 ° C.

In a method of manufacturing another such ceramic filter of the present invention, the apparent porosity of the cordierite hammer is adjusted to a maximum of 10%. This effectively reduces the pressure loss of the filter.

15 If the apparent porosity exceeds 10%, the pressure drop tends to be large.

By further adjusting the apparent porosity of the cordierite hammer to a maximum of 10%, the durability of the cordierite hammer becomes good. The filter itself thus becomes durable.

A cordierite hammer with a particle diameter of 74 µm or more (a particle diameter that does not pass through a 200 mesh filter) is mixed at a maximum of 50% by weight. Shamot, of a particle size of. 25 µm, is useful for forming pores with a size of at least 10 µτη and suitable for a gas filter. Part of the cordierite hammer may be up to 2 mm in diameter. When such shamotte is blended with at least 50% by weight, it is possible to obtain at least 30 required pores to form a filter. acceptable gas permeability.

If the shamot with a particle diameter of 74 μιη or less is less than 50% by weight, the shrinkage during sintering is significant, resulting in disadvantages, such as deformation of the filter and low porosity and high pressure drop. , 106702

It is still preferable to combine the cordierite hammer in an amount of at least 70% by weight with low sintering shrinkage, high apparent porosity and low pressure loss.

The remainder is usually mixed here in the form of a fine powder and forms in the filter a honeycomb for the corerite chamfer after sintering. The fire resistance of this cell is preferably slightly lower than that of corierite hammer and the coefficient of thermal expansion of 10 is close to that of cordierite hammerite. Thus, its composition should preferably be such that it partially forms glass during sintering. The powder material is combined with clay to form a honeycomb, since it is composed primarily of alumina and silica, and effectively improves ductility and sinterability.

When the honeycomb contains lithium oxide in addition to alumina and silica, the honeycomb meets the above requirements and, in combination with a low-porosity cordierite chamfer, produces a filter which is not only durable enough at room temperature but also at a higher temperature of about 800 ° C.

The concentration of lithium oxide (Li 2 O) in the filter material is 0.05 to 1% by weight (equivalent to combining 1 to 20% by weight of S-spodume * 25). With a content of less than 0.05%, it is difficult to obtain a sintered body that is sufficiently durable. On the other hand, if the concentration exceeds 1% by weight, the refractory properties of the ceramic cordierite filter are reduced, which is undesirable. Taking into account both the fire resistance and the strength of the filter thus obtained, it is good to have a lithium oxide content within the range of 0.2 to 0.6% by weight.

The reason why a lithium oxide (Li20) containing cell provides a filter that maintains its resistance even at high temperatures is not fully understood because the phase ratio between cordierite and β-spodumen, 18 106702 (Li20-A1203 * 4SiO2), is complex (Yoichi). , Fine Ceramics p. 310, 1976, Gihodo). However, it can be explained as follows.

In said second ceramic filter of the present invention, the filter cell containing the lithium oxide (Li 2 O), the main constituents of which are alumina (Al 2 O 3) and silica (SiO 2), is sufficiently vitrified during sintering to form a strong bond to the shamotte.

10 This glass contains most of the lithium oxide and has a low melting point compared to shamot.

The crystallization of the glass occurs later by subsequent cooling.

The crystals formed have a low coefficient of thermal expansion of 15 and the coefficient of thermal expansion of the entire honeycomb is close to that of a cordierite. Thus, a ceramic cordierite filter with a good resistance to room temperature and a low residual elongation due to the difference in thermal expansion of the shamot is shown, even when cooled to a temperature of 50 ° C. '

The β-spodumen is added to the powder material during the formation of the honeycomb, since it is advisable to avoid localization of lithium oxide, and the β-spodumen effectively reduces the thermal expansion coefficient of the entire honeycomb, even while remaining in the filter material. Cordierite powder is compounded because it brings the cell expansion coefficient close to the shamot thermal expansion coefficient.

Cordierite powder having a particle diameter of less than 74 µτη acts primarily to form a honeycomb of said second ceramic filter of the present invention. This is the reason for the restriction "finer than 74 μχα".

Because of the relatively high proportion of the crystalline component resulting from the honeycomb, the durability remains without significant softening at temperatures up to about 1000 ° C. / 106702

Natural ores containing lithium oxide, such as, for example, petalite and eucrypt, can also be used as cellular powder material.

In the process for manufacturing said second ceramic filter 5 of the present invention, it is advantageous to use a glass crystallized cordierite hammer, since it is possible to obtain a dense shamot, for example a shamot having an apparent porosity of not more than 4%, although the preparation of such a shamot may require In addition, the lamp expansion coefficient is about one-half lower than that of a conventional cordierite hammer obtained by sintering. The coefficient of thermal expansion of the filter material is thus low, so that it is possible to obtain a gas cordierite filter which has excellent heat resistance to change. Shamotti is very dense and therefore is a filter material with excellent corrosion resistance. Thus, it is possible to make a gas cordierite filter which is particularly suitable for use at very high temperatures.

20 Magnesium oxide clinker, Bayer alumina and quartz sand can be used as starting materials for a crystallized cordierite chamfer. Preferably, the preparation is carried out by rapidly cooling the melt once to form a glass which is then subjected to a heat treatment for crystallization, as disclosed, for example, in JP JP 20 269/1982.

As a synthetic cordierite hammer, a sintered preparation made of talc, clay and aluminum hydroxide as a starting material can be well used. In order to obtain coarser cordierite particles with an apparent porosity of up to 10%, there is sufficient Sint orbital material in the preparation of conventional synthetic cordierite, and it is efficient to use a starting material combined with zirconium powder to improve sintering. , 106702

The commercially available synthetic cordierite porosity is usually greater than 10% and cannot be used as a shamote for the cordierite filter of the present invention.

Under these conditions, it can be re-sintered to improve compactness. However, as a result of several studies, it has been found that the apparent porosity of shamot, which is not very high in porosity, can be changed to a level of up to 10% by impregnating a cordoid-10 into a complete colloidal solution such as alumina, silica sol or titanium oxide. When the porosity can be brought to a level of up to 10%, the material can be used without difficulty as a shamot of the cordie-sufficiency filter of the present invention, and the filter thus manufactured has low pressure loss and good resistance.

In order to sufficiently impregnate the colloidal solution, it is advisable to use reduced pressure. In addition, it is good that the shamot is dried and the impregnation is repeated to obtain additional density.

Once shelled or dried, the colloidal solution impregnated shamot can be used as a shamot for the purposes of the present invention.

The second ceramic filter of the present invention requires that the apparent porosity of the shamot after sintering is not more than 10%.

However, it is likely that if the raw material mixture is formed as a tubular filter and then impregnated with such a colloidal solution, the pores expected to act as gas passageways in the filter will become blocked. 30 decreases and the pressure drop in the filter increases, which is not desirable.

The reason that the pressure loss can be reduced by adjusting the apparent porosity of the cordierite hammer to 10% or less is believed to be: 35 First, provided that the gas flow through the ceramic filter can be approximated by - 21 106702 equation (Kozeny-Carman equation) fluid flow through the compacted powder bed, the following equation can be described as the pressure drop ΔΡ through the filter provided that the gas passage through the filter is 5 laminar flow (Fine particle measurement, Clyde Orr Jr. et al., Chapter 7, Macmillan, 1959).

Sv2 = (gcL / 2 ^ uLe) (ΔΡ / L) [7 (1-) 2] 10 Here Sv is the area per unit volume of the solid body, gc is the gravity constant, L is the thickness of the filter, μ is the viscosity of the gas, u is the apparent velocity of the gas, Le is the length of the capillary meander in the filter, porosity, and the ratio: uc = 15 (u /) <Le / L).

Namely, the pressure drop in the gas passing through the filter can be approximated to be proportional to the square of the total area of the particles per unit volume of the filter. In order to reduce the pressure loss of the filter, the total particle surface area per unit volume of the filter is minimized so that the pressure loss can be reduced.

Further, if the apparent porosity of the sintered body is not more than 10%, the gas permeability is so low that it can be substantially neglected (Porous material, compiled by Ren-ichi Kondo, published by Gihodo, 1973). Therefore, pores with a porosity of up to 10% in the sha-mot are not permeable to the gas and do not cause pressure loss.

30 The pressure drop is determined primarily by the surface areas of the structure between the shamot particles and the shamot particles, so that it is believed that a filter with a low pressure drop can be produced.

In order to minimize the pressure drop while improving gas permeability, it is effective to combine a pore-forming agent which is capable of forming pores when burned during sintering. As such a pore-forming agent, it is advantageous to use coke powder, in particular instant coke powder, since it contains a relatively small amount of impurities such as iron, which avoids discoloration, is easy to obtain and has a good hardness without adversely affecting plasticity.

The organic binder is incorporated into the starting material mainly to provide strength to the crude body, thereby facilitating the shaping of the filter and avoiding crushing of the crude body during processing. However, the combination of the organic binder also increases the porosity.

The filter molding process may be an isostatic molding process, a semi-moist ah-15 backing, or an extrusion process. Of these methods, the isostatic molding process has been most commonly used as a molding process which is well suited for the manufacture of a dense Sint body. There does not appear to have been any case where the isostatic molding process has been used as a method for making porous filters. However, it is also a good molding method in the manufacture of such a filter as the drying step can be omitted, a large tube filter can be easily formed, and the production capacity is also good.

* 25 The tubular ceramic filter produced by the isostatic molding process has a relatively smooth inner surface, since a mild metal core mold is usually used for molding, and when used as a filter base, the filtering layer is good to rub thin on the inner surface.

• Sintering is often carried out in tunnel furnaces. However, a shuttle oven or electric oven may also be used. The sintering is preferably carried out at a temperature of 1310 to 1380 ° C.

35 If the sintering temperature is lower than 1310 ° C, sintering is deficient and t 23 106702 tends to become poor. If, on the other hand, the sintering temperature exceeds 1380 ° C, disadvantages occur, for example, the filter deforms during sintering due to the weight of the filter itself, and due to excessive sintering, porosity becomes low, which is undesirable.

The apparent porosity is defined as at least 35%, as this will provide the filter with a more useful gas permeability. A bending strength of at least 75 kg / cm 2 at 800 ° C is a good value that has not been achieved with 10 conventional ceramic cordierite filters having an apparent porosity of at least 35%.

When a cordierite filter having good high temperature resistance was obtained in this way was in fact used at high temperature, and when its flexural strength was then examined at room temperature, it was observed that the strength was impaired.

The reason for this is not yet fully known. However, as the strength deteriorated, the presence of crystals of β-spodumen in the honeycomb was observed by X-ray powder diffraction.

20 It is generally believed that the loss of strength is due to a change in the structure of the honeycomb. By adding the ZrO 2 and / or TiO 2 components to this cell, it is intended to promote crystallization of the glass in the cell by adding such a component so that the glass in the cell crystallizes completely after cooling and reaches a steady state.

By adding such an ingredient, the presence of β-spodumen crystals in the filter cell after sintering can be confirmed by X-ray powder diffraction. As a result, this strength does not tend to deteriorate during use, as. has been found in the case where no such ingredient is added, although the initial strength has to be slightly abandoned as compared to the case where no such ingredient is added. This results in a ceramic cordierite-35 filter with high durability, repeated use and good reliability.

* 24 106702 The total amount of ZrO 2 and / or TiO 2 added herein is usually 0.5 to 12% by weight, preferably 1 to 10% by weight of the filter material. If the total amount is less than 0.5% by weight, a suitable effect for stabilizing the resistance is not achieved. On the other hand, if the total amount exceeds 12% by weight, the coefficient of thermal expansion of the filter becomes high, which tends to decrease the heat-variation resistance, which is undesirable.

The present invention will now be explained in more detail with reference to Examples. However, it is to be understood that the present invention is not limited in any way to these examples.

Example 1 Magnesium oxide, alumina and quartz sand were mixed to give a starting material having the composition of cordierite: 2MgO.2A1203.5SiO2. This starting material was electrically melted using carbon electrodes and the melt was poured into water and cooled to give a glass having a cordierite composition.

The glass was dried and crushed to obtain glass particles having a particle diameter of 1 to 10 mm, and the particles were wheeled, heated in a tunnel oven, and kept at 1380 ° C for 10 hours to crystallize into cordierite.

The product was crushed and further screened to give particles between 28 and 200 mesh (74-590 μτη), and the particles were used as a filter bed shamot.

When it is desired to adjust the accumulated pore distribution, the 30 shamots are further sorted into particles of particulate. _ the diameter range is different. The screened particles of different particle diameters are suitably mixed to provide a useful shamot.

70% by weight of this shamot was blended with 6 to 35% by weight of cordierite powder of the same material having a particle size of 200 mesh (maximum 106702 74 μπι), 10% of cordierite powder of the same material having a particle size of 325 mesh, spodumen powder with a particle size of 5 325 mesh (maximum 44 μπι) and 6% by weight of clay powder. 100 parts by weight of the mixture were admixed with 30 parts by weight of a pizza coke powder having a particle size of 50-100 μπι and 7 parts by weight of a 40% by weight aqueous solution of phenolic resin binder.

This mixture was dried at 110 ° C and crushed to give a granular material having a particle diameter of up to 3 mm.

This granular material was filled into a mold formed from a steel core mold and an outer cylindrical rubber mold and molded with an isostatic press at 1000 kg / cm 2 to give a tube having an outer diameter of about 170 mm, an inside diameter of about 140 mm and a length of about 850 mm. This tubular, molded body 20 was sintered in a shuttle oven at 1340 ° C for 5 hours to provide a tubular ceramic cordie filter base. This sintering state affects the pore distribution, and as the sintering progresses, the average pore size increases and the apparent porosity decreases. The filter base 25 is characterized in that both ends are cut off to provide a tubular base 800 mm in length.

The apparent porosity of this filter base was 42%.

For the cube-shaped samples cut from the filter base, the accumulated pore distribution was measured with mercury pores. with a gauge to give the results shown in Fig. 1a.

Namely, this filter base had an average pore size (at 50% by volume) of 60 μπι, a porosity of 35 at 76% by volume of D757 at 5% by volume, and 43 μπι at 25% by volume of D25. The ratio R> 106702 ^ 7s / ^ 25 * was thus 1.77 in this filter base.

Diatomaceous earth powder having an average particle size of 3.6 μτη was sprinkled on the surface of this 400 mm long 5-tube filter base, and the diatomaceous earth powder was rubbed on the inner surface with a felt.

The aqueous silica sol solution having a SiO 2 content of 2.3% by weight was uniformly sprayed onto the surface of the powdered silica and dried in a dryer at 150 ° C to solidify.

The pressure drop was measured at a flow rate of 5 cm / sec for this tube filter and was found to be 320 mmWG.

This filter was mounted on a filtration test apparatus, and air containing 7.3 g / m3 of blast furnace ash in the form of dust having an average particle diameter of 10 μτη and a temperature of 150 ° C was introduced into the filter and a filtration test was performed.

With the exception of the energy level of the reverse cleaning, the gas (which was air in this case) filtration rate in the test was set to about 7.6 cm / sec. During the filtration period, dust in the gas accumulated in the inner wall of the tubular filter, thereby gradually increasing the pressure drop.

Therefore, compressed air was blown from the nozzle into the filtration test apparatus at a pressure of about 6 kg / cm 2 once every 7.5 minutes for 0.4 seconds, thereby performing a reverse filter cleaning.

30 Filter pressure drop after reverse cleaning:. . gradually increased in the initial stages of operation, and after about 150 hours, the pressure drop before and after the counter-cleaning became constant, and the residual pressure drop was 1600 mmWG immediately before the counter-cleaning and 35 1300 mmWG immediately after the counter-cleaning.

t 106702

The experiment was then resumed. The test was conducted for a total of about 300 hours, but no increase in residual pressure loss was observed.

The filter manufacturing conditions, filter characteristics, test conditions, and test results for Examples 1-4 are shown in Table 1.

Example 2

The tubular filter base was prepared under the same conditions as in Example 1. The accumulated pore-10 distribution of this filter is shown in b in Figure 1. In this filter base, D7s was 65 µm, D25 was 36 µm and R was 1.80.

Diatomaceous earth powder having an average particle diameter of 20 μτη was sprinkled on the surface of this 400 mm long tubular filter bed, rubbed with 15 felts.

At this point, the pressure drop was measured by admitting air at a flow rate of 5cm / sec and was found to be 125mmWG.

In addition, siliceous powder having an average particle diameter of 3.6 μτη was similarly rubbed on the surface.

At this point, the pressure drop was measured by admitting air at a flow rate of 5 cm / sec and found to be 250 mmWG.

On this surface rubbed with diatomaceous earth powder: an aqueous solution of silica sol was sprayed in the same manner as in Example 1 and heated and dried.

The pressure drop at this stage was measured by venting air at a flow rate of 5 cm / sec and was found to be 30,300 mmWG. This ceramic filter was installed in the same

the data test apparatus used in Example 1 and the filtration test was carried out under the same conditions whereby a residual pressure drop of about 55 later before and after the back cleaning became constant, i.e., 1100 to 35 mmWG immediately before the back cleaning and 950 mmWG

immediately after reverse cleaning. t 106702 The test was then continued. The entire test was run for about 500 hours, after which no increase in residual pressure loss was observed.

Example 3 A tubular filter base was prepared under the same conditions as in Example 1. The accumulated pore distribution of this filter base is shown in c in Figure 1, with a D75 of 80 μτη, a D25 of 48 μπι and a D75 / D25 ratio of R 1.67.

The inner surface of this 400 mm long tube filter base 10 was sprinkled with alumina powder having an average particle diameter of 6 μπι and rubbed with a felt. The aqueous silica sol solution was sprayed onto it in the same manner as in Example 1 and heated and dried for attachment.

At this stage, the pressure drop was measured by venting air at a flow rate of 5 cm / sec and was found to be 350 mmWG.

This ceramic filter was mounted on the same filtration test apparatus used in Example 1, and the filtration test performed under the same conditions.

As a result, the pressure drop stabilized at the end of 170 hours. The test was then continued for about 130 hours, with no change in residual pressure drop.

The residual pressure drop after stabilization of this filter was 2200 mmWG immediately before the reverse cleaning and 1800 mmWG immediately after the reverse cleaning.

Example 4

A filter base was prepared in the same manner as in Example 1 except that shamot, honeycomb and pores were prepared. the raw material composition of the forming agent was changed as shown in Table 1.

The accumulated pore distribution of this filter base is shown in d in Figure 1. It has an apparent porosity of 41%, a mean 35 pore size of 38 μπι, a D75 of 3 8 μτη, a D25 of 27 μτη, and a D75 / D25 ratio of R 1.41. , 29 106702 A filter layer of diatomaceous earth powder having a mean particle diameter of 3.6 μπι was applied to a 400 mm long tube filter bottom, and the pressure drop was investigated at 5 cm / s at a flow rate of 290 mmW.

This filter was mounted on the same filtering apparatus and the test was performed in the same manner. As a result, the pressure drop stabilized at the end of about 100 hours, and the 10 residual pressure drop after stabilization was 1500 mmWG immediately before the counter-cleaning and 1250 mmWG immediately after the counter-cleaning.

The experiment was then continued for about 200 hours, with no change in residual pressure.

15 Comparative Example 1

A filter base was prepared under the conditions noted in Comparative Example 1 of Table 2. Other conditions are the same as in Example 1. The accumulated pore distribution of this filter base is shown in Figure 1. It has an apparent porosity · of 40%, average pore size of 37 μπι, D75 of 45 μπι , D2S was 30 μπι, D75 / D25 had a R ratio of 1.5, and a pressure drop of 96 mmWG when air was passed at a flow rate of 5 cm / sec.

This 400 mm cut filter base was mounted on the above filter test apparatus as such, i.e. without a filter bed, and the filtration test was performed in the same manner.

As a result, the residual pressure loss stabilized at the end of about 100 hours and was 1600 mmWG immediately prior to counter-cleaning and 1400 mmWG. v _ immediately after reverse cleaning.

However, the residual pressure drop showed a slight increase thereafter. The experiment was continued for about 200 hours, after which an increase of about 90 mmWG was observed.

35 t 106702

Table 2 shows, for comparative examples 1, 2 and 3, the filter manufacturing conditions, properties, test conditions, and test results.

Comparative Example 2 A filter base was prepared under the conditions shown in Comparative Table 2, Example 2.

The distribution of the accumulated pore s of this filter base is shown in Fig. 1. Its apparent porosity was 40%, the average pore size was 32 μτη, D75 was 35 μτη, D25 was 29 μπι and 10 D75 / D25 ratio R was 1.21.

A filtration layer was applied to a 400 mm long tube filter base in the same manner as in Example 1 and the pressure drop was examined by venting air at a flow rate of 5 cm / sec and found to be 290 mmWG.

This filter was mounted on the above-mentioned filtration test apparatus and the filtration test was performed in the same manner.

Approximately 100 hours later, the pressure drop stabilized and the residual pressure drop was 1700 mmWG immediately before the counter-cleaning and 1400 mmWG immediately after the counter-cleaning.

However, the residual pressure loss showed a slight increase. At the end of about 200 hours, an increase in residual pressure of 80 mmWG was observed.

Comparative Example 3

A filtration test was performed on a commercially available silicon carbide filter.

This filter uses a silicon carbide hammer with a particle size between 300 and 850 μιη: η, and the honeycomb 30 is considered to be predominantly composed of; _, savanna.

The size was about 60 Φ / 30 Φ x 1000 mm and the filter was tubular with the other end closed. It had an apparent porosity of 40% and a lower bending strength of 35 at a level of about 120 kg / cm 2.

106702

The pore distribution of the filter base, which was studied in the same manner as above, is shown in g in Figure 1.

As a result, it had an average pore size of 110 μτη, a D75 of 124 μτη, a D25 of 98 μτη and a D75 / D25 ratio of Rs of 5 1.26.

A filter layer containing an alumina-silica-type fiber was attached to the outer side surface of this tube filter. The pressure drop was investigated by venting air to this filter at a flow rate of 5 cm / sec, and was found to be 300 mmWG.

This filter was cut into a 400 mm tube and fitted in the above-mentioned filtration test apparatus. The filtration test was carried out in the same manner as above, except that the filtration apparatus was modified so that the gas containing the dust was supplied to the outside of the tube, in the same manner as in the above test.

As a result, about 200 hours later, the pressure drop appeared to be constant. The residual pressure drop at this time was 700 mmWG immediately before the counter-cleaning 20 and 600 mmWG immediately after the counter-cleaning.

After this, however, a gradual increase was observed. At the end of about 100 additional hours and about 250 hours thereafter, a periodic increase in residual pressure drop of 150 mmWGm and 350 mmWGm was observed.

- 25 The reason for this periodic increase in residual pressure loss has not been clearly established. However, such a phenomenon is likely to occur when the filtering layer is peeled off.

Examples of a second ceramic filter of the present invention will now be presented.

: - Seven types of material were prepared as cordurite hammer, namely a, b, c, d, e, f. And g.

a. Magnesium, alumina and quartz sand were mixed to form a cordierite composition of 35 2MgO * 2Al 2 O 3 -5SiO 2. The mixture was electrically thawed using 32670702 carbon electrodes, and the melt was poured into water and cooled to give a glass having a cordierite composition. The glass was removed and crushed to give glass particles having a particle diameter of 1 to 10 mm.

The particles were placed in a tunnel oven and heat treated at about 1380 ° C for 10 hours to crystallize.

The product was crushed and screened to give particles having a size of 74-590 μπι.

10 This shamot had an average particle diameter of 270 μιη and an apparent porosity of 3%.

b. A fine powder of talc, clay, aluminum hydroxide and zirconium was formed to form a cordierite composition based on a chemical composition of 15 2 MgO-2Al 2 O 3 * 5 SiO 2 and comprising 3% by weight of ZrO 2. To 100 parts by weight of the mixed raw material was added 2 parts by weight of methylcellulose and a suitable amount of water, and the mixture was kneaded and extruded into a rod having an outside diameter of about 30 mm.

The rod was dried and then wheeled, taken to a tunnel oven, and held for 10 hours at 1360 ° C at maximum temperature to obtain synthetic cordierite.

This product was crushed and sorted by screening, φ * 25, to give particles having a particle size of 74-590 μιη: η.

This shamot had an average particle diameter of 265 μπι and an apparent porosity of 7%.

c. Fine talc, clay and aluminum hydroxide powders were mixed to form a cordierite composite; _ us 2MgO * 2Al203 * 5Si02. To 100 parts by weight of the mixed raw material was added 2 parts by weight of methyl cellulose and a suitable amount of water, kneaded and extruded into a rod having an external diameter of about 30 mm.

35 t 33 106702

The rod was dried and cushioned, placed in a tunnel oven and kept at a maximum temperature of 1360 ° C for 10 hours to obtain synthetic cordierite.

The product was crushed and sorted by sieving to give a shamot having a particle size of 74-590 μτα.

This shamot had an average particle diameter of 250 μπι and an apparent porosity of 12%.

A technically prepared synthetic cordierite hammer was crushed and screened to give a shamot having a particle size of 74-590 μτα.

Shamot had a mean particle diameter of 23 0 μτη and an apparent porosity of 30%.

e. The cordierite hammer obtained in (c) was impregnated with alumina sol and dried under reduced pressure. The same operation was repeated again.

After heating this shamot at 1000 ° C, the apparent porosity was 8%.

f and g. The cordierite hammer obtained in (c) was repeatedly impregnated with silica sol and titanium dioxide sol, respectively, followed by drying.

After heating these shamots at 1000 ° C, the apparent porosities were 7% and 8% respectively, β-spodumen powder was prepared as follows. Pyrophyllite and lithium carbonate powder were mixed in a ratio of 25 wt.% To 85 wt.% And 15 wt.% Respectively, further blended and crushed in a wet system. The filter cake thus obtained was dried and then sintered in an electric oven at 1150 ° C to give β-spodumene. This powder-30 was fine and screened with a 325 mesh screen. Using. with seven different cordierite filters a-g, gas tubular cordierite filters were prepared under the conditions indicated in Tables 3 and 4.

The examples in Table 3 and comparative examples 35 are directed to investigate the effects of porosity of shamot and the mixing ratio of shamot t 34 106702, mainly with respect to filtration properties.

In these examples, a honeycomb blend of 10% by weight, 10-25% by weight of fine cordierite powder of the same shamotic material, and 5% by weight of fine β-spodumen powder was used in the honeycomb. To 100 parts by weight of this mixture were added 25 parts by weight of a coke powder having a particle diameter of 20-100 μτη as a pore forming agent and 7 parts by weight of a 40% by weight aqueous phenolic resin solution as an organic binder. The mixture was stirred, dried at 110 ° C and then crushed to give a granular material having a particle diameter of up to 3 mm.

This material was filled in a mold consisting of a steel columnar core mold and an outer cylindrical rubber mold and molded with an isostatic press at 1000 kg / cm2 to obtain a tube having an outer diameter of about 170 mm, an inside diameter of about 140 mm and a length of about 850 mm.

This tubular molded body was sintered in an electric furnace at 1320 ° C for a maximum of 5 hours to give a tubular ceramic filter.

When sintering was carried out in a tunnel oven, a filter was obtained which had a sintered state substantially similar to that of sintering at about 1350 ° C.

The properties investigated for the corresponding pipe filters are shown in Table 3.

In the other Examples and Comparative Examples, tube filters were prepared under the same conditions, c as above, except that the conditions and properties shown in Table 3 are also shown in Table 3.

Apparent porosity here is the value measured by the water immersion method and the average pore size from the 35 1 cm3 cubic test specimens t 106702 is the mercury porosity value.

The bending strength was further measured by a three-point bending test in a 70 mm area of influence on a test piece measuring 14 x 20 x 100 mm.

The acid corrosion resistance was examined by immersing the test specimen in an aqueous, room temperature solution of IN H 2 SO 4 for 72 hours, after which the change in flexural strength was examined.

The filtration property was further defined by installing a 400 mm long tube filter in a filtration test apparatus equipped with a counter-cleaning system, ferric oxide dust having an average particle diameter of about 50 μτη to a concentration of 40 g / Nm 3 at 300 ° C, a gas containing dust would be dosed, and both filtration experiments were performed for 100 hours at a gas filtration rate of 5 cm / sec.

The ferric oxide powder was used because this powder is colorful and can be easily observed when it penetrates the ceramic filter.

The particle size distribution of the ferric oxide powder was as follows: less than 1 μπι was 1% by weight, 7-10% by weight for 1-10 μτη, 011 35% by weight for 10-40 µm, 46-25% by weight for 40-100 μτη and 100-800 μπι the size of the particles was 11% by weight.

Table 4 shows the results of the study of the effects of the change in the composition of the honeycomb on the properties and filtering properties of the filter material. Conditions for the preparation of the filter 30 which are not shown in the table; ^ _, were the same as above.

The bentonite contains an alkali component and when sintered, it easily glazes and forms a glass honeycomb to provide a filter with good room temperature resistance.

106702

Table 4 shows the amount of ZrO 2 and / or TiO 2 in parts by weight relative to 100 parts by weight of the total weight of the shamot and honeycomb component.

To test for deterioration in durability or non-degradability during use, a specimen of a bending strength cut from a ceramic filter was held in an electric oven at 900 ° C for 24 hours, and then the bending strength at room temperature was measured.

As a result, it was found that ceramic filters with zirconia and / or titanium oxide added to the cell exhibit a slight decrease in initial durability, but no decrease in durability after heat treatment.

Comparative example of Table 2! also shows examples of filtering results of another ceramic filter of the present invention.

The dust used in this experiment was not ferric oxide powder. In this experiment, using ash from a blowhole furnace as a dust, a slight increase in the residual pressure drop was observed when the filter was used for an extended period of time. Growth at this level is not a critical issue in normal use.

In the gas ceramic filter of the present invention, the filter layer is adhered to the surface of the filter base having a special pore distribution, whereby the filter layer does not peel off easily. It can be prepared by a relatively simple method. It is effective when used as a gas filter because the filtering layer does not peel off, and when used and renewed repeatedly with counter-cleaning, no residual pressure drop • t <shows an increase after stabilization.

Additionally, when the ceramic filter of the present invention is properly constructed by combining a suitable shamot, cell, filter bed, and inorganic binder, it is possible to obtain a filter that can be continuously used for long term filtration of a dusty high temperature gas which is naturally corrosive.

Another ceramic filter of the present invention and a process for its preparation have disclosed a ceramic filter which is particularly suitable for high temperature gas filtration, has excellent heat exchange resistance and corrosion resistance, and has low pressure drop and good resistance even at 800 ° C. temperature as well as the process for its preparation.

Said second ceramic filter of the present invention employs a low sham porosity of up to 10%, and in particular a corerite porosity of very low porosity and crystallized from glass; this is combined with a honeycomb containing lithium oxide to provide a gas filter which has a low pressure drop, has a good resistance even to high porosity, maintains a high temperature resistance and has an excellent corrosion resistance, in particular acid corrosion resistance.

Because of the low pressure loss of the filter, the processing power of the dust-containing gas can be increased even with the same filter device. Because the filter has sufficient durability, the risk of filter breakage during installation and maintenance of the filter device is significantly reduced, and the reliability of the device is greatly improved.

It has further been found that a problem with the silicon carbide filter, which is now considered to be the filter of the future, is that it is susceptible to oxidation by the action of vapor in the combustion gas, whereby the pores are likely to become clogged, or pressure drop tends to be large. Whereas, the other ceramic filter of the present invention has excellent durability in acidic, corrosive gas air containing steam, 35 NOx and SOx, such as in coal fuel gas, and thus # 38 1 0 6 7 0 2 is useful for filtering the combustion gas coming from a fluidized bed combustion boiler or a pressurized fluidized bed combustion boiler burning coal for power generation, or for filtering synthetic gas produced by a coal gasification furnace.

Another ceramic filter of the present invention has tended to degrade durability when used at high temperature. However, it has been improved to be a dependable filter which has no tendency to degrade durability by adding TiO 2 and ZrO to the cell, such that the unstable Ia-phase of the cell is crystallized by sintering.

The other ceramic filter of the present invention is widely used to remove dust from various high-temperature gases containing dust, which is removed from the high temperature industry, and allows for the recovery and efficient use of heat energy that was previously difficult to recover and discarded, because that si-20 contained dust. In addition, filtered high-temperature gases are easier to remove NOx and SOx and the dust is recovered in a dried state, which facilitates efficient use of dust.

By installing the gas ceramic filter of the present invention in a filtration device, it is possible to obtain a filtration device which is relatively small in size but has a high performance and wide scope. For example, the scope of the filtration device extends to include the filtration of gas coming from the gasification process of coal and the pressure filtration of the combustion gas from a pressurized fluidized bed boiler which produces power and burns coal. The present invention thus opens the way to efficient utilization of coal energy without pollution 35 and thus its value in industrial use is significant.

/ "106702 39

Table 1 Example 1 5 Preparation conditions for the filter base

Shamotti: Substance Cordieritis

Particle diameter μτη 74 - 590 Amount by weight 70 70 Cell by weight Cordierite: max. 74 μπι 6, maximum 44 μτη 10 β-spodumene: max. 44 μπι 6, self 10

Pore forming agent 15, parts by weight Coke powder 30

Molding from Isost. press 1000 kg / cm2

Sintering 1340 ° C x 5 h, shuttle oven

The filter has a measuring ratio of mm · 170 Φ / 140 Φ x 800

Properties of the filter base

Porosity% 42

Mean I 25 pore size μιη 60 D75 / D25 = R 76/43 = 1.77

filtration layer

Material: 3.6 μιη Butter

Binding agent Silica sol 2.3% by weight 30 Properties of the filter

Pressure drop mmWG 320 (air 5 cm / sec) 4 35 106702

Table 1 (continued)

Example 1 5 Filter test conditions Dust gas 150 ° C air + blast furnace ash Dust content g / m3 7.3

Gas filtration rate 7.6

Compressed air, 10 gas about 6 kg / cm2

Reverse cleaning time sec 0.4

Reverse Cleanup Interval min 7.5 15 Filter Test Steady-state after about 150 hours, then no change observed Change in residual pressure drop 20 Pressure drop after stabilization Immediately before 1600 reverse cleanup Immediately 1300 • 25 clean. after 4 41 106702

Table 1 (continued)

Example 2 5 Preparation conditions of the filter base an_

Shamotti: Substance Cordieritis

Particle diameter μπι 74 - 590 Amount by weight 70 70 Cell by weight Cordierite: max. 74 μτα 6, maximum 44 μιη 10 β-spodumene: max. 44 μπι 6, self 10

Pore forming agent 15, parts by weight Coke powder 30

Molding from Isost. press 1000 kg / cm2

Sintering 1340 ° C x 5 h, shuttle oven

The filter has a measurement ratio of 170 Φ / 140 Φ x 800

Properties of the filter base

Porosity% 44

Mean * 25 pore size μιη 5 0 D75 / D25 = R 65 / 36.5 = 1.78

filtration layer

Material Diameter of 20 μπι, 3.6 μπι

Binding agent Silica sol 2.3% by weight 30 Properties of the filter

Pressure drop mmWG 300 (air 5 cm / sec) t 35

Table 1 (continued) 42 106702

Example 2 5 Test conditions for the filter Dust gas 150 ° C air + blast furnace ash Dust content g / m3 7.3

Gas filtration rate 7.6

Compressed air, 10 gas about 6 kg / cm2

Reverse cleaning time sec 0.4

Reverse Cleaning Interval min 7.5 15 Filter Test Steady-state after about 55 hours, no change observed after this Change in residual pressure drop 20 Pressure drop after stabilization Immediately before 1100 reverse cleaning Immediately reciprocal 950 l 25 Clean. after t 43 106702

Table 1 (continued)

Example 3 5 Preparation conditions of the filter base an_

Shamotti: Substance Cordieritis

Particle diameter μτη 74 - 590 Amount by weight 70 70 Cell by weight Cordierite: max. 74 μπι 6, maximum 44 μιη 10 β-spodumene: max. 44 μτη 6, self 10

Pore forming agent 15, parts by weight Coke powder 30

Molding from Isost. press 1000 kg / cm2

Sintering 1340 ° C x 5 h, shuttle oven

The filter has a measurement ratio of 170 Φ / 140 Φ x 800

Properties of the filter base

Porosity% 42

Mean · 25 pore size μτη 65 D75 / D2s = R 80/48 = 1.67

filtration layer

Material Aluminum oxide 6 μτη

Binding agent Silica sol 2.3% by weight 30 Properties of the filter

Pressure drop mmWG 350 (air 5 cm / sec) 35 44 106702

Table 1 (continued)

Example 3 5 Test conditions for the filter Dust gas 150 ° C air + blast furnace ash Dust content g / m3 7.3

Gas filtration rate 7.6

Compressed air, 10 gas about 6 kg / cm2

Reverse cleaning time sec 0.4

Reverse purge Interval min 7.5 15 Filter test Steady-state after about 70 hours, no change observed after this Change in residual pressure drop 20 Pressure drop after stabilization Immediately before 2200 reverse purge Immediately recalculate 1800 · 25 purge. after t 106702

Table 1 (continued)

Example 4 5 Preparation conditions of the filter base an_

Shamotti: Substance Cordieritis

Particle diameter μπι 74 - 590 Amount by weight 75 10 Cell% by weight Cordierite: maximum 74 μπι 10, β-spodumene: max. 44 μπι 5, self 10

Pore forming agent 15, parts by weight Coke powder 30

Molding from Isost. press 1000 kg / cm2

Sintering 1320 ° C x 5 h, electric oven

The filter has a measurement ratio of 170 Φ / 140 Φ x 800

Properties of the filter base

Porosity% 41

Mean 2 5 pore size μπι 3 2 D75 / D25 = R 38/27 = 1.41

filtration layer

Material 3.6 μπι Butter

Binding agent Silica sol 2.3 wt% 30 Own filter. characteristics

Pressure drop mmWG 290 (air 5 cm / sec) f 35 46 106702

Table 1 (continued)

Example 4 5 Test conditions for the filter Dust gas 150 ° C air + blast furnace ash Dust content g / m3 7.3

Gas filtration rate 7.6

Compressed air, 10 gas about 6 kg / cm2

Reverse cleaning time sec 0.4

Reverse purge Interval min 7.5 15 Filter test Steady-state after about 100 hours, then no change observed Change in residual pressure drop 20 Pressure drop after stabilization Immediately before 1200 reverse purge Immediately 1250 ♦ * '25 purge. after »* · 47

Comparative Example 1 106702

Table 2 5 Conditions for the preparation of the filter base

Shamotti: Substance Cordieritis

Particle diameter μτη 74 - 590 Content by weight 60 10 Cell% by weight Cordierite: maximum 74 μτη 25, β-spodumene: max. 44 μτη 5, self 10

Pore forming agent 15, parts by weight Coke powder 30

Molding from Isost. press 1000 kg / cm2

Sintering '1320 ° C x 5 h, electric oven

The filter has a measurement ratio of 170 Φ / 140 Φ x 800

Properties of the filter base

Porosity% 40

Mean • 25 pore size μτη 37 D75 / D25 = R 45/30 = 1.5

filtration layer

Material None

Binder 30 Filter% by weight. characteristics

Pressure drop mmWG 96 (air 5 cm / sec) / 35 106702

Table 2 (continued)

Comparative Example 1 5 Test conditions for the filter Dust gas 150 ° C air + blast furnace ash Dust content g / m3 7.3

Gas filtration rate 7.6

Compressed air, 10 gas about 6 kg / cm2

Reverse cleaning time sec 0.4

Reverse Cleanup Interval min 7.5 15 Filter Test Residual pressure drop results became substantially constant after about 100 hours of residual pressure drop. Later, however, a change after 200 hours of experimentation showed an increase of 20 to 90 mmWG.

• <

Comparative Example 2

Table 2 49 106702 5 Preparation conditions for the filter base

Shamotti: Substance Cordieritis

Particle diameter μπι 74 - 590 Content by weight 60 10 Cell by weight Cordierite: maximum 74 μιη 10, β-spodumene: max. 44 μπι 5, self 10

Pore forming agent 15, parts by weight Coke powder 25

Molding from Isost. press 1000 kg / cm2

Sintering 1320 ° C x 5 h, electric oven

The filter has a measurement ratio of 170 Φ / 140 Φ x 800

Properties of the filter base

Porosity% 39

Average * ·· 2 5 pore size μπι 32 D7S / D25 = R 35/29 = 1.21

filtration layer

Material: 3.6 μιη Butter

Binding agent Silica sol 2.3% by weight 30 Proprietary filter. characteristics

Pressure drop mmWG 290 (air 5 cm / sec) i 35

Table 2 (continued) 106702

Comparative Example 2 5 Test conditions for the filter Dust gas 150 ° C air + blast furnace ash Dust content g / m3 7.3

Gas filtration rate 7.6

Reverse purge- Compressed air, 10 gas about 6 kg / cm2

Reverse cleaning time sec 0.4

Reverse Cleanup Interval min 7.5 15 Filter Test Residual pressure drop results became substantially constant after about 100 hours of residual pressure drop. Later, however, a change after 200 hours of experimentation showed an increase of 20 to 80 mmWG.

• · /

Table 2

Comparative Example 3 * 1 106702 5 Preparation conditions for filter base an_

Shamotti: Substance of SiC

Particle diameter μτη Approx. 300 - 850 μτη Volume% 10 Column weight% Clayey

Pore forming agent, parts by weight Molding Sintering 15

Dimensions of the filter mm 60 Φ / 30 Φ x 1000

Characteristics of filter base 20 Porosity% 40

Mean pore size μιη 110 D75 / D25 = R 124/98 = 1.26

Filter Layer • · • 25 Material Contains alumina

The binder is silica fiber

Filter Properties

Pressure drop mmWG 300. 30 (without 5 cm / sec) - · «« i 52 106702

Table 2 (continued)

Comparative example 3 * 1 5 Filter test conditions Dust gas 150 ° C air + blast furnace ash Dust content g / m3 7.3

Gas filtration rate 7.6

Reverse purge- Compressed air, 10 gas about 6 kg / cm2

Reverse cleaning time sec 0.4

Reverse Cleanup Interval min 7.5 15 Filter Test Residual pressure drop results became substantially constant after about 200 hours of residual pressure drop. After its change, however, a gradual increase was observed and occasionally a gradual increase.

No stabilization.

* 1: Product on the market • · .. '*

Table 3 106702

Cordierite Chamotte (by weight) 5 a. Crystallized cordierite 11 b. Synthetic cordierite 1x c. Synthetic cordierite 11 d. Cordierite commercially available11e. Cordierite impregnated with alumina sol 10f. Cordierite impregnated with silica sol g. Cordierite impregnated with titanium oxide sol

Columnist (% by weight) 15 Fine cordierite powder 12

Clay

Fine powder of β-spodumen13

Pore-forming agent (coke powder 20-100 µm) 20 parts by weight

Filter Properties

Physical properties: 25 Apparent porosity (%)

Average pore size (/ xm)

Bending strength (kg / cm2)

Pressure drop (mmWG, air at 5 cm / sec) 30 Filtering features:

Loss of pressure after 100 hours after counter-cleaning (mmWG, air at 5 cm / sec) Increase of residual pressure loss after 100 hours 35. Acid corrosion resistance: 'Decrease in flexural strength after 72 hours immersion in 1N H 2 SO 4 at 40 ° C: 200-28 mesh. 74-590 / xm) particles.

* 2: Passes through a 200 mesh screen, the same material as the sha-mot.

* 3: Passes through a 325 mesh sieve: 45 ______ • <_ - - --- ------ 111 i (

Table 4 54 106702

Shamot,% by weight a. Crystallized cordierite11 5 b. Synthetic cordierite11 c. Synthetic cordierite11

Yield,% by weight 10 Cordierite powder made from the same substance as the other shamots used in the test (maximum 74 μτη) 12 Clay β-spodumene (maximum 44 μια) 13 15 Bentonite

Additives (parts by weight)

Zirconium Oxide Powder (ZrO2) 20 Titanium Oxide Powder (TiO2)

Pore forming agent (coke powder 20-100 μτη) 25 parts by weight

Originality 30 Apparent porosity (%)

Final strength at room temperature (kg / cm2)

Ultimate strength at 800 ° C / kg (kg / cm 2)

Average pore size (μτη)

Pressure loss (mmWG, air at 5 cm / sec) 35 __ • · * Bending strength after 24 hours heating at 900 ° C (kg / cm 2) 40 '

filtering Feature

Loss of pressure after 100 hours after back cleaning (mmWG, air at 5 cm / sec) 45 _ • Increase in residual pressure loss after 100 hours 1: Screened to give 200-28 mesh (74-590 μτη) 50 particles * 2: Passes 200 mesh * 3: Passes through a 325 mesh screen * 4: Small cracks were observed after sintering ·; 15: Significant distortion during sintering 1

Claims (11)

55 106702 Dust-containing gas ceramic filter, characterized in that it comprises at least 50% by weight of a cordierite filament with an apparent porosity of not more than 10% and a particle diameter of 74 μτη and a cellular body consisting of silica (SiO2) and alumina (Al2O3). ) and containing 0.05 to 1.0% by weight of lithium oxide (Li2O) by weight of the entire filter 10. Ceramic filter according to claim 1, characterized in that the honeycomb comprises magnesium oxide (MgO). Ceramic filter according to claim 1 or 2, characterized in that the cordierite hammer is a glass crystallized cordierite hammer having an average cordierite composition (2MgO * 2Al203 -5SiO2). Ceramic filter according to claim 1 or 2, characterized in that the cordierite hammer is obtained by impregnating the cordierite hammer with an alumina sol, a silica sol, a titanium oxide sol, a zirconia sol, or a mixture of at least two such sols, and after sintering it has a shamot. • · * 25 Ceramic filter according to one of claims 1 to 4, characterized in that the filter material has an apparent porosity of at least 35% and a bending strength of at least 75 kg / cm 2 at 800 ° C. The one of claims 1-5. Ceramic filter according to claim 30, characterized in that: · the honeycomb contains 0.5 to 12% by weight TiO 2 and / or ZrO 2 by weight of the entire filter. Ceramic filter according to one of Claims 1 to 5, characterized in that it has an average pore size of 10-100 µτη and a ratio of pore size of 106702 at positions of 75 and 25% by volume of the accumulated pore distribution, at least 1.3. 8. A process for producing a ceramic filter for a gas containing dust, characterized in that at least 50 wt. - 10 h and a particle size of less than 74 μιη, with a lithium oxide content of 0,05 to 1,0% by weight, relative to the total weight of the filter; an organic binder is added to the mixture, which is then molded using an isostatic press using a metal columnar die and an outer cylindrical rubber mold and sintered at 1310-1380 ° C. A method for making a ceramic filter according to claim 8, characterized in that the cordierite slurry having an apparent porosity of 2. up to 10% is produced by mixing magnesium oxide, alumina and quartz sand to produce an average cordierite composition (2MgO-2A1203.5SiO2), by melting and cooling it to obtain the glass is then crystallized by heat treatment. '25 Process for producing a ceramic filter according to claim 8 or 9, characterized in that β-spodumen powder is added to the powder material to form a honeycomb such that the filter has a lithium oxide content of 0.2 to 0.6% by weight. A process for making a ceramic filter according to claim 8, 9 or 10, characterized in that the starting material is admixed as a pore-forming agent with a coke powder which forms upon burning the pores. "/ 57 1 0 6 7 0 2