AU630610B2 - Filter for the separation of solid particles from hot, gaseous or liquid media - Google Patents

Description

i COMMONWEALTH OF AUSTRALIA Patent Act 1952 6 COMPLETE SPEC I F I CATION

(ORIGINAL)

Class Int. Class Application Number Lodged Complete Specification Lodged Accepted Published Priority: 4 June 1988, to be advised Related Art a i /i

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i;: a. a '4 4p Name of Applicant HERDING GmbH Address of Applicant August-Borsig-Str. 3, D-8450 Amberg Federal Republic of Germany Actual Inventor Herr Walter Herding Address for Service F.B. RICE CO., Patent Attorneys, 28A Montague Street, BALMAIN. 2041.

Complete Specification for the invention entitled: "Filter for the separation of solid particles from hot, gaseous or liquid media" The following statement is a full description of this invention including the best method of performing it known to Us:i;li 2 This invention concerns a filter element for the separation of solid particles from hot, gaseous or liquid media, in particular dust particles from hot flue gases in the temperature range between 120 and 800 0

C.

It is commonly known, to use filters for the separation of particles from gaseous or liquid media and that these, depending on the application, are constructed as fabric, carbon fibre, felt, paper, plastic, metallic or ceramic filters.

While fabric, felt, paper and plastic filters are suitable for a low temperature range up to about 150°C, metallic and ceramic can cover the higher temperature range up to 800 0 C, so that the latter are suitable for use in the flue gas of thermal plants. This is particularly desirable, since, with the increasing need to reduce environmentally harmful emissions, the filtration of hot gases with temperatures above 2500C is steadily becoming more important. This is because, on the one hand, the high enthalpy of the clean gas can be used 20 without any further measures, and on the other hand, the e:: filtered flue gases constitute less of a problem for the environment.

The use of the above-mentioned materials as filters ee has shown that glass, ceramics and carbon fibre are S: 25 susceptible to breakage due to brittleness, and with metal wires or metal mesh, respectively, the gaps between the "i wires are too large to achieve adequate filter action for fine dusts. Also, the use of such heat resistant materials, such as sinter materials, or porous or S 30 fine-pored ceramic materials and similar is not useful, since the initially good separation action continuously deteriorates as fine dust enters the pores. This deposited dust which is difficult if not impossible to remove, even with special cleaning measures, and which finally leads to clogging of the filter.

z OWr -3- Among those filters which have been used in the so-called high temperature region, are those with filter cartridges, which frequently consist of clay or ceramic and which, for simplicity, are constructed as cylindrical tubes in the form of filter cartridges.

These filter cartridges, which are open at either end, are installed between holders within a housing for the filter and fixed in such a way that the medium to be filtered penetrates the casing of the filter cartridge and enters its internal space and leaves this internal space through an opening at the other end of the filter cartridge. This opening of the filter cartridge opens into a space for the filtered medium, whereby this medium then leaves through a discharge connector. The filter cartridges are rigidly connected to the holders so that they cannot move in relation to the loadings imposed on them (ie due to the flow of the medium and particularly the loadings through the cleaning process of these filter cartridges by way of counterflow), whereby breakages, in particular near the neck of the filter cartridge, cannot be avoided (see DE-PS 30 17 851).

:In order to avoid such damage to the filter cartridges, it is known that filter cartridges of this kind are mounted such that they can oscillate. This I e 25 oscillating mounting of the respective filter cartridges is made possible in such a way that the mounting, which :separates the clean room from the filter room, is arranged as an orifice plate, whereby the holes are formed such that those near the clean room are of larger diameter than 30 those near the filter room. On the other hand, the filter cartridge is provided with a flange-shaped shoulder at the end nearest to the clean room, with which this filter cartridge supports itself on the inwardly drawn bead of the hole in the mounting. In order to better support the filter cartridge on this bead, the bead can be formed as 4a spherical ring shoulder, and it is the wider cross section of this hole from this ring shoulder onward, increasing towards the filter room, which provides the necessary space for the oscillating motion. That end of the filter cartridge which is opposite the neck is provided with a hole into which a bolt engages, which is then fastened to the mounting.

This bolt may be inserted into the hole with play or without play, whereby in the case of the play-free arrangement of the bolt, the bolt is supported on an elastic bush against the filter cartridge. On the one hand, the spherical ring shoulder at the neck of the filter cartridge and the elastic support of the bolt at the other end facilitate the support of the bolt on the other end, and on the other hand, the oscillating suspension of the filter cartridges in the mounting provides better protection against damage compared with the rigidly fixed filter cartridges. However, it is considered a disadvantage of these type of filters that 1 20 the amount of the respective filter cartridge between the supports is too unstable, which on the one hand leads to Ii •sealing problems and thereby to contamination of the filtered medium and on the other hand, the removal thereof S: is made more difficult, due to the spherical ring S 25 shoulders for the attachment of the filter cartridges (see DE-PS 35 15 365).

Accordingly, there is a need to develop a filter of U i the abovementioned type, which is suitable for the S.filtering of hot media, such as flue gas and similar, 30 whereby, despite high temperature loading such as, for example, 600 0 C and possibly more, the filter retains its inherent stability and filter action and does not have a tendency to form cracks or cause spalling of filler material and, furthermore, that this filter sits absolutely tight on the mounting and that it can be

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1 5 mounted and dismounted without the difficulties of previous arrangements. Furthermore, it is desirable that it can be attached to this mounting in such a way that it is not subject to damage even under mechanical loading, such as would occur during the cleaning of the filter cartridge.

In one broad form the invention provides a filter element for the separation of solid particles from hot, gaseous or liquid media, especially dust particles from hot flue gases in the temperature range between 250 and 800 C, including a permeable, inherently stable, heat resistant carrier material forming a support member and having larger-sized pores, said material containing constituents of non-corroding materials selected from the group consisting of glass, ceramic, metal compounds, said carrier material being producible through intimate partial bonding of its heat-resistant particles and having a structure correlated with the intended utilization and 2 specific capacity of the filter element, wherein the larger pored carrier material has at least an outer surface of a mantle region thereof covered with a heat-resistant ceramic fine-grained filler material for the formation of a thin covering layer having finer pores, said filler material being applied onto the carrier material in a dispersed mixture with an adhesive agent, a I volatilisable component, and a suspension liquid whereby the mixture is introduced into the larger pores of the carrier material, and whereby the volatilisable component is volatilized and the filler material is partly bonded with itself and partly with the carrier material after a firing process; the fine-grained constituents of the filler material and the adhesive agent each being constituted from material having a linear coefficient of thermal expansion which is generally equal to that of

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-6the carrier material, the filler material having a grain size such that the pore size of said filler material is less than 10m, and said filler material is introduced into the larger pores about the mantle region of the carrier material and there at least partly fills the larger pores of the carrier material.

Such a filter element generally satisfies the above stated need. Further, since the support material and the filler material exhibit very similar thermal expansion characteristics, this avoids damage to their structure or a widening of the pores, in particular of those of the filler material.

This particular concept of the filter element ensures excellent filter action, even with strongly fluctuating temperatures of the media to be filtered, so that these filter elements are particularly suitable for hot gases in 0 0 the temperature range from 250°C up to 600-800°C.

Since all materials and therefore all structures of the filter element are able to follow temperature fluctuations without being damaged, any cracking or spalling, in particular in the cover layer, generally does not occur, thereby ensuring that surface filtration takes place with •ego this filter element, and which also ensures the advantage of a largely clog-free filter action. This surface filter 25 action also avoids increasing pressure drop, so that the filter can be operated with generally constant, minimal energy requirements.

The structure of the filter element can be varied according to the demands on the filter element, so that, 30 for example, a greater or smaller pore width may be given to the support material 2. Furthermore, the pore width of the filler material 11 may also be formed larger or smaller, for example, in such a way that either coarse- or fine-grained filler matt&ial is deposited on the supporting material or that the supporting material is O FF 0 oa~c 7 coated with more or less layers of the same. The filler material may, for example consist of heat-resistant glass spheres, ceramic grains or powders, fibres, etc., which, after coating of the support material, cover the support material in the form of a film.

Another advantageous form of construction of the invention is characterized in a filter apparatus comprising at least one of the filter elements as claimed in claim 1, wherein said filter element is generally tubular, the apparatus further comprising a filter housing having said at least one filter element arranged therein and including inlet and discharge connectors for the medium to be filtered and having been filtered, said housing including a discharge chute for particles separated from said medium, said medium being flowable through the mantle surface of said filter element(s) inwardly from the exterior thereof, and at intervals in a reverse direction of flow is blown or streamed through for the cleaning of the outer surface of the mantle region by a cleaning flow, said filter housing including a cleaning chamber for the collecting and discharging of the filtered Imedium in the region of the discharge connector, and at least one cleaning arrangement for the cleaning of the S: filter element, between said cleaning arrangement and the 25 bottom of the discharge chute there being located mountings for the at least one filter element extending therebetween, the mounting facing towards the cleaning chamber having an opening between the filter element and S. the cleaning chamber, and the mounting facing towards the 30 base having at least one support for the filter element, said filter element being constructed as an inherently S. stable filter cartridge, the filter cartridge being spring-oaded and clamped between the mountings and sealed at said mountings relative to the interior space of the filter housing; at the end thereof facing towards the nC- iprs w 7a cleaning chamber, has an injector-shaped tubular flange and at the end facing towards the base of the discharge chute has a cylindrical bolt for the retaining of each said filter cartridge on said mountings each said cartridge, said cylindrical bolt and said tubular flange each including a belt-shaped shoulder, seal means between the shoulder and the filter element and between the shoulder and the mounting, and wherein the calibering guide and mountings for the filter cartridge includes spring means between the shoulder and the cylindrical bolt and the mountings for imparting a spring-biasing action against said seal means.

Further advantageous developments of the invention I ee V. e *e 1 8 can be seen in the remaining subclaims, for which independent protection is claimed within the framework of this application.

Some exemplary embodiments of the invention are now described with reference to the drawings in which: Fig.l is a side elevation of a filter element shaped as a cylindrical tube, Fig.2 is a section through the filter element in the plane II-II in fig. 1, Fig.3 is a side elevation of a filter element formed as a multiple disc pack, Fig.4 is a section through the filter element in the plane IV-IV in fig. 3, Fig.5 is an enlarged plan view onto a section of the cut i 15 filter element according to fig. 1 or 3 with several spheres, which form the cover layer, for example, of equal diameter, Fig.6 is a similar, enlarged plan view as in however, with spheres of varying diameters, [i 20 Fig.7 is a section through the filter element in the region of its covering layer with a row of spheres *accumulated on to it and the powder particles embedded in the support material, according to section III, Fig.8 is a longitudinal section through a filter housing with one filter element, which consists of several filter cartridges, Fig.9 is a cross section through the filter housing with two filter elements arranged in parallel, in the 30 plane II-II of fig. 1, is an enlarged view of a filter element constructed as a filter cartridge and a section of the support components, which are holding it there, Fig.ll is an enlarged longitudinal central section through the head of the filter cartridge with the pipe flange, 9 which supports it against its holder, and Fig.12 is an enlarged longitudinal central section through the foot of the filter cartridge with the spigot, which supports it against its holder.

The filter element 1 according to figs. 1 to 7 is illustrated and described by way of two possible configurations. One configuration can be a tubular filter element 1, as it is shown in figs. 1 and 2. This filter element 1 is formed in such a way, that it forms a cylindrical support body 2 at one end of which is a flange-shaped head 3 and at the other end of which a bottom 4. The flange-shaped head 3 has in cross section, an opening or recess 5 which corresponds to (ie is aligned with) the opening 6 of the cylindrical support body 2.

The bottom 4 of the support body 2 is formed as a closure. The bottom 4 is provided with a foot 7 in order to be able to fix the support body 2 in a support frame 8 of the filter housing 13. The support body 2 itself, which consists of a heat-resistant material such as ceramics, has a large-pored structure (ie refer large pores 9) onto which a fine-pored structure in the form of a covering layer 11, which consists of fine pores 10, is applied. This covering layer 11 forms the filtering surface of the filter element 1, onto which the particles to be separated from the medium to be filtered are deposited during the filtering process.

The filter element 1 according to a further possible configuration as per fig. 4 is constructed as a so-called lamellar filter, as described in DE-OS 34 13 213, and distinguishes itself essentially through the fact that its support body 2, or its support material, respectively, o S" consists of a heat-resistant material such as, for example of the ceramic origin described earlier, and where its covering layer 11 is formed from a multitude of preferably spherical and/or powdery bodies 12, which form a bond with U 0 YT' I i i- i 10 the support body 2 and/or with each other, and which are also constituted of heat-resistant material(s).

The various parts of the filter element 1, that is, the support material 2 and its covering layer 11, have varying pore widths, whereby the pores 9 of the support material must be larger than the pores 10 of the covering layer, so that a filtration of the medium can take place at the outer surface of filter element i.

The support material 2 may consist of ceramics in the form of an aluminium oxide (A1 2 0 3 a zinc oxide (Zn0 2 or silicon oxide (Si0 2 whereby its manufacture may occur in such a way that the respective chosen material is processed into a moulding material in the conventional manner, that is, extruded in the form of pipes and then fired, which results in wide-pored supporting bodies consisting of the supporting material 2. Alternatively, a mass of the support material 2 is filled into a mould, whereby the flange-shaped head 3 and the bottom 4 (ie which closes the end of the filter 20 element) can be formed at the same time.

A ine-pored overing layer 11 is then applied to the •outer surface of this coarse-pored support material 2 in the form of an emulsion (comprising a filler material, an S"adhesive agent, a volatilisable component and a suspension liquid), either by way of spraying or brushing, whereby this emulsion settles primarily in the larger openings and :1 :~holes (ie the exposed interstices 9 of the support material 2 and thereby covers the larger pores 9 with a multitude of smaller openings or pores The smaller pores 10 in the covering layer 11 are produced when the material of the covering layer 11 combines partially with each other (that is, at the points or lines of contact therebetween). The material may be, for example, in the form of larger or smaller bodies 12, such as spheres which contact each other and bond at 1 11 certain points on their surfaces, and whereby the parts of surfaces which have not been bonded, define the openings or pores 10. To a large extent, the size of these pores can be dimensioned arbitrarily, so that the covering layer 11 or the coating, respectively, form a fine-pored layer (ie in the manner of a film), which still allows the transmission of the medium to be filtered, and which has small dimensioned pores 10 for filtering solid particles from the medium. That is, the size of the particles of the filler material of the covering layer 11 are preselected, and wherein a preselected amount by volume of the volatilisable component forms part of the emulsion and is burnt away volatilised) during a firing process of the filter element 1 so as to leave spaces between the particles of the filler material.

Another method for applying the covering layer 11 onto the support material is to prepare a coating sludge from the fine-grained powder which has a similar consistency to that used in an enamelling process. The supporting body, that is, che support material 2 may be dipped into this coating sludge. This covering layer is then fired, together with the support material, which results in a fine- and open-pored outer surface, similar to a glazing. In a similar manner, as occurs with the support material 2, the required open small pores 10 in *the covering layer 11 result from the evaporation of the suspension liquid.

t In the manufacture of the filter element 1 from these heat-resistant materials, a starting point is to use components of the same base material for the support material 2 and its covering layer 11, and to use an adhesive agent which causes melting and bonding of these materials on the surface (for example, during the firing process), in a similar manner to a sintering process, which results in a homogeneous, firm bond between the

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/4 ok) I lla support material 2 and the the covering layer 11.

This has been established by the present inventor with numerous experiments with support material 2 and covering material 11 out of aluminium oxide (A1 2 0 3 using a ceramic adhesive of the same consistency.

Similar stable forms result, if materials which are chemically not identical, but nevertheless related, interact with each other, and which mix with each other 9

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wi- 12 during the liquid phase (at the eutectic point, for example, of A1 2 0 3 and SiO 2 or Zn0 2 and Si0 2 Also, a chemical bond between the support material 2 and the covering layer 11 is possible, as long as it is stable at the temperature of the proposed filtering application and that it shows the same or better chemical resistance against structural changes as the support and covering materials 2, 11. The partial bonding between the support material 2 and the covering material 11 is facilitated through an adhesive agent 14, which may be applied, depending on the type of bonding during the firing operation, as a form of glazing or as an adhesive bond.

The thickness 15 of the covering layer 11 is predetermined to suit the required degree of purity of the filtered medium. That is, of the covering material 11 which is applied to the support material 2 allows the filter action of the covering layer 11 to be increased or decreased as desired.

The bonding of the coating layer 11, that is, its filler material, with the support material 2 is preferably a homogeneous, intimate bond, which normally cannot be dissolved. This is of importance insofar as the coating layer 11 cannot be washed off the support material 2, which could otherwise occur with filtration of liquid fluids.

The filter element 1 according to the invention, as shown in the form of construction according to figs. 8-12, is generally the same as the filter element according to figs. 1-7 and is also used for the separation of particles from gaseous or liquid media. For better understanding, this filter element 1 is constructed as a tube and arranged in a filter housing 13 together with at least one other filter element. Housing 13 itself has a clean room 16 for the filtered medium and a discharge shaft 17 for the particles, as well as an inlet and outlet connector 37 1* 1.

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i 13 and 38 for the medium. The filter element 1, which is, according to the illustrative example, constructed as a tubular filter cartridge, is preferably manufactured from a ceramic material, which, consists of a support material 2 with large pores 9 and a surface coating, that is, a coating layer 11 with fine pores 10. The mounting of this filter element 1, that is, the respective filter cartridge in the filter room of the filter housing 13 may occur horizontally or vertically, whereby each filter cartridge has at its respective ends special fastening components including a cartridge head 18 and cartridge foot 19 with which the cartridge is fixed to holders 20, 21 in the filtering room. The fastening components at the cartridge head 18 are in the form of an injector-shaped pipe flange 22 and at least one seal 23, 24, whereby the pipe flange has, apart from the annular shoulder 25, a collar, which penetrates into the clean room and a sleeve 27, which projects into the filter element 1. The annular shoulder which approximately forms the equator of the pipe flange 22, has larger diameter than the casing of the filter element 1. This is the reason for the sufficiently large support surfaces of the pipe flange 22, with which the ends of the filter element, that is, the filter cartridge, on the one hand, support themselves on the holder 21 and on the other hand, support themselves on the holder 20 at the end near the clean gas.

In order to make the sealing effective, it is recommended to provide seals 23, 24 on either side of the .annular shoulder, that is, coaxially to it, of which one is an annular seal 32 and the other seal 24 could, next to the annular surface, have a shroud-like enlargement. This S• shroud-like enlargement could in this case concentrically envelope the sleeve 27, which penetrates into the filter element 1 and thereby effects a sealing function, as well as providing a radial, elastic support. Of course, it is 13a (conceivable to provide, instead of these shroud-like seals, an annular seal 32 at this point and support the filter cartridge and holder 20 only through this seal.

The other end of the filter element 1 is primarily *1 *I:

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l" f .l o 'A e oI o* o* r 1 3 Fi I 14 supported on the shoulder 28 of a spigot 29, whereby this spigot shows similar to the pipe flange 22-also a collar and an extension 31 into the opposite direction to it.

With this collar 30, the spigot 29 is inserted into the free end of the filter element 1 up to the shoulder 28, whereby this collar must show no play or only a small amount of radial play between itself and the inner surface of the filter element. The actual sealing of this end of the filter element 1 at the foot of the cartridge 19 occurs, as with the cartridge head 18, through an annular seal 32, against which the end of the filter element makes sealing contact. The extension 31 of the spigot 29 penetrates into the hole 33 of the holder 21 and extends deep enough into it, so that the filter element 1 is guided in the borehole not only against radial movements, but also remains guided in the borehole during axial movements. In order to hermetically seal the respective filter element 1 against the filtering room of the filter u o: housing 13, a coil spring 34 is inserted between the 20 shoulder 28 of the spigot 29 and the holder 21 around the extension 31, which, on the one hand, supports itself on 4 the shoulder and, on the other hand, against the holder 21.

This helical spring 34 pushes this filter element i, that is, the filter cartridge against the seals 23, 24 at 25 the cartridge head 18, as well as the shoulder against the annular seal 32, so that these seals make full contact.

The spigot 29 itself may be solid at its collar and extension 31, or it may show circular grooves 35, as illustrated in the drawing of fig. 10. Instead of the 2 30 spigot 29, an equivalent guidance part, such as a conical spring or a spider may be used. But also, instead of a helical spring 34, a disc spring or a disc spring stack, respectively, may be used, which ensures the axial preloading of the filter element i.

The holder 20, 21 itself may be constructed in the

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15 form of U-shaped struts, which with their ends support themselves on brackets 36 of the filter housing 13, and at that point may be supported rigidly or elastically.

The medium to be filtered, which enters the filtering room of the filter housing 13 through the inlet connector 37, flows around the individual filter elements 1 and enters the clean room 16 through them, while its entrained particles deposit themselves on the casings of the filter elements. The medium, which in this manner enters the clean room 16, leaves it through the outlet connector 38, ewin order to enter free atomsphere, or to be fed into a further process. The particles deposited on the filter oo.. elements are dislodged through the known method of reverse see.

blowing, from the inside towards the outside, and enter 15 the discharge shaft 17, from where they are removed either continuously or intermittently. The reverse blowing device may be a known jet cleaner, the nozzles of which are inserted into the injector-shaped pipe flanges 22, in gee.

order to blow in the cleaning medium, such as compressed S 20 air.

The mounting and disassembly of the filter element 1 or the filter cartridges, respectively, is made particularly easy with this form of cartridge-type construction, whereby, following the insertion of the 25 extension 31 of the spigot 29 into the borehole 33 of the holder 21 and pushing it against the force of the helical spring 34, the collar 30 of the pipe flange 22 at the head of the cartridge 18 is pushed first under the borehole of the holder 20 at this end, and, after releasing the pressure slowly, this collar will engage in this hole and fix the filter cartridge in that position. Disassembly of the filter cartridge or the filter element 1, respectively, occurs in reverse sequence, if it is required to remove them from their holders 20, 21.

According to an advantageous material selection, the 16 composition of the filler material, that is, the coating layer 11, which is applied to the support body 2, consists of the following components.

These components, which are dispersed as a mixture, are applied to the support body 2 by means of, for example, a brush, and this filler material is exposed to a temperature of 500 0 C for about an hour, together with the support body, whereby the filler material is burnt into the material or the pores of the support body 2, 10 respectively.

•coo The components of the filler material or the coating oe layer, respectively, could be composed as follows: 1 part by volume of sodium silicate 14 parts by volume of water 4 parts by volume of kaolin 2 parts by volume of feldspar 2 parts by volume of starch (cornflour) 0.2 parts by volume of sodium diphosphate S 2The filler material, which is produced in this manner and which is applied to the support body 2, deposits itself in the region of the casing surface of the pores 9 of the support body and fills them until a film-like layer appears on its surface. Hereby, the water is evaporated Sunder the influence of the temperature, and at this temperature, the starch is also eliminated from the mixture by burning.

As already mentioned above, the filter elements 1 are manufactured from ceramic, heat-resistant material. This does, of course, not exclude the application of other filter elements i, for example, of plastic, if the filter element is supposed to work in a different temperature range. It is also possible, to use other configurations of filter elements 1.

Here, the filter element 1 has been illustrated and explained by means of filtration of hot gases. Of course, L 1 ~1 11~ T 17 this filter element 1 is also suitable for the filtration of hot liquids or for gases and liquids, which are not hot. This filter element 1 is of particular interest for aggressive media in the gaseous or liquid region, since it is hardly attacked by aggressive materials.

The heat-resistant filter element 1 has been illustrated and explained by means of pipes and the socalled lamellar filter, as shown in fig. 1-4. Of o course, this filter element 1 can also show other 10 configurations. Of advantage is a configuration, which ooeo shows the largest possible filter area.

o Such a configuration could also be a combination of shapes, such as elliptical, triangular etc. The S•configuration is mainly dependent on the volume to be filtered, the durability of the filter element, that is, the filter cartridge, and the medium to be filtered. The latter also determines the pore width, which for the purpose of optimization of the pressure drops, is matched 2 to the medium.

The function of the filter is here illustrated and described, relative to the jet-cleaning process, on an example of the deposition of particles from gaseous ee e media. The separation of particles from liquids occurs in Sa similar manner, but in this case, the cleaning process is different, that is, through reverse flow of pure liquids. If the liquid permits the use of air, compressed air may be used for the cleaning process.

Claims (21)

1. A filter element for the separation of solid particles from hot, gaseous or liquid media, especially dust particles from hot flue gases in the temperature range between 250 and 8000 C, comprising: a permeable, inherently stable, heat resistant carrier material forming a support member and having larger-sized pores, said material containing constituents of non-corroding materials selected from the group consisting of glass, ceramics and metal compounds, said carrier material being producible through intimate partial bonding of its heat-resistant particles and having a structure correlated with the intended utilization and specific capacity of the filter element; wherein the larger pored carrier material has at least an outer surface of a mantle region thereof covered with a heat-resistant ceramic fine-grained filler material for the formation of a thin covering layer having finer pores, said filler material being applied onto the carrier 20 material in a dispersed mixture with an adhesive agent, a volatilisable component and a suspension liquid, wherein the mixture is introduced into the larger pores of the carrier material, and whereby the volatilisable component is volatilized and the filler material is partly bonded with itself and partly with the carrier material after a firing process; the fine-grained constituents of the filler material and the adhesive agent each being constituted from material having a linear coefficient of thermal expansion which is generally equal to that of the carrier material; the material of the filler material being dimensioned so as to have a grain size such that the pore size of said filler material is less than 10pm; and wherein said filler material is introduced into the 19 larger pores about the mantle region of the carrier material and there at least partly fills the larger pores of the carrier material.

2. A filter element as claimed to claim 1, wherein the filler material forms a homogenous, insoluble bond with the carrier material upon the application of heat.

3. A filter element as claimed in claim 1, wherein the filler material is baked into the carrier material at an elevated temperature.

4. A filter element as claimed in claim 1, wherein the filler material is applied in at least one layer onto said carrier material.

A filter element as claimed in claim 1, wherein the filler material applied in two layers onto the carrier material, a first said layer being constituted from relatively coarse constituents which, in addition to causing a reduction in size of the larger pores of the carrier material also serves as a supporting matrix for a second said layer, said second layer being constituted from fine grain constituents and possessing small pores facilitating a surface filtration

6. A filter element as claim in claim 1, wherein the filler material is sprayed onto the carrier material, and said materials are jointly subjected to an adhesive or 25 baking process.

7. A filter element as claimed in claim 1, wherein the filler material is supplied as an emulsion in a bath, said carrier material being coated through immersion into the emulsion, and said materials being subsequently subjected to a baking process.

8. A filter element as claimed in claim 1, wherein the carrier material and the filler material are constituted of ceramic, and said materials are permanently baked to each other through the effects of heat but which remain open pored. I o. 20

9. A filter element as claimed in claim 1, wherein the carrier material and the filler material form a eutectic mixture, and upon cooling are permanently bonded to each other.

10. A filter element as claimed in claim 1, wherein fine-grained filler material is suspended in powder form with a liquid, after addition of said adhesive agent is applied onto the carrier material, and said filler material is bonded by the adhesive agent with the carrier material.

11. A filter as claimed in claim 10, wherein the liquid for the suspending of the filler material is a material which Jf volatilized under the effects of heat, such as water, and after application onto the carrier material causes said filler material to remain in the carrier material with the formation therein of fine pores.

12. A filter apparatus comprising at least one of the filter elements as claimed in any one of claims 1-11, wherein said filter element is generally tubular, the 20 apparatus further comprising a filter housing having said S" filter element arranged therein and including inlet and i discharge connectors for the medium to be filtered and having been filtered respectively; said housing including a discharge chute for particles separated from said 25 medium, said medium being flowable through the mantle surface of said filter inwardly from the exterior thereof, and at intervals in a reverse direction of flow is blown or streamed therethrough for the cleaning of the outer isurface of the mantle region by a cleaning flow, said Y 30 filter housing including a cleaning chamber for the collecting and discharging of the filtered medium in the region of the discharge connector, and at least one cleaning arrangement for the cleaning of the filter element, between said arrangement and the bottom of the discharge chute there being located mountings for the at 21 V least one filter element extending therebetween, one of the mountings which faces towards the cleaning chamber having an opening between the filter element and the cleaning chamber, and the other one of the mountings which faces towards the base having at least one support for the filter element, said filter element being constructed as an inherently stable filter cartridge, the filter cartridge being spring-loaded and clamped between the mountings and sealed at said mountings relative to the interior space of the filter housing; each said cartridge, at the end thereof facing towards the cleaning chamber, having an injector-shaped tubular flange and at the end facing towards the base of the discharge chute having a cylindrical bolt for the retaining of each said filter cartridge on said mountings, said cylindrical bolt and said tubular flange each including a belt-shaped shoulder, seal means between the shoulder and the filter element and between the shoulder and the mounting, and wherein the mountings for the filter cartridge includes spring means between the shoulder and the cylindrical bolt and the mountings for imparting a spring-biasing action against said seal means.

13. The filter apparatus as claimed in claim 12, wherein said injector-shaped tubular flange extending from the annular shoulder thereof includes a skirt received within the filter element and a collar oppositely directed from the shoulder, said collar extending through the opening of the mounting into the cleaning chamber.

14. The filter apparatus as claimed in claim 12, wherein said circular bolt includes annular grooves on least at a section between the annular shoulder and an outwardly projecting extension, said extension engaging into bores in the mountings.

The filter apparatus as claimed in claim 12, wherein the clamping of said filter elements between said ipil 22 mountings is pendulant.

16. The filter apparatus as claimed in claim 12, wherein each said mounting approximately from inner wall to another inner wall of the filter housing, and a plurality of filter elements are spring-loaded and clamped between two respective mountings.

17. The filter apparatus as claim.d in claim 12, wherein each said filter element is clamped between said mountings so as to be displaceable in at least an axial direction.

18. The filter element as claimed in claim 1, wherein said filler material is composed of a disperged mixture of a plurality of constituents consisting of 1 part by volume of sodium silicate, 14 parts by volume of water, 4 parts by volume of kaolin, 2 parts by volume of feldspar, 2 parts by volume of starch (starch flour) and 0.2 part by volume of sodium diphosphate.

19. The filter element as claimed in claim 18, wherein subsequent to the application of the filler material on the carrier material, said materials are jointly subjected 20 to a baking process whereby during the baking process the volumetric parts of water are vaporized and the volumetric parts of starch are combusted.

20. A filter element as hereinbefore described with reference to the accompanying drawings. I 25

21. A filter apparatus as hereinbefore described with reference to the accompanying drawings. DATED this 19th day of August 1992 HERDING GmbH Patent Attorneys for the Applicant: F.B. RICE CO. v 0