IL91255A - Filter for separation of particulate matter from hot gaseous or liquid media - Google Patents

Description

7Π3 ΛΗ Τλ ΊΪ> πη πττηη "»Ϊ·»Ϊ7*7Π mm mian7 ΊΙΌΪΙ FILTER FOR SEPARATION OF PARTICULATE MATTER FROM HOT GASEOUS OR LIQUID MEDIA HERDING .1 The invention relates to a filter for separating solid particles from hot and/or aggressive gaseous or liquid media, in particular dust particles from hot flue gases in the temperature range between 120 to 800 "C, comprising a ervious carrier material of fixed configuration nd provided with relatively large pores, i.e. a carrier body, the carrier material being su tably heat-resistant and/or made of components of non-cor oding materials such as glass, ceramics, metals or compounds thereof, and in which filter he carrier material is producible by intimate partial bonding of its heat resistant particles, the carrier material moreover having a structure adapted to the purpose and given volume requirements, respectively three-dimensional configuration.

It is generally known to use filters for separating particles from gaseous or liquid media and, depending on the field of use to provide these in the form of textile, carbon fibre filters, felt filters, pa er filters, plastics filters, metal or ceramics filters. Whereas the textile, felt, paper and plastics filters can be employed in a relatively low temperature range up to about 150eC, the metal anad ceramics filters extend into the higher temperature range, such as to about 800°C so that the latter filters are suitalbe to be also employed in the flue gas region of thermal plant. This is particuarly desirable, since wit the increasing reduction requirements of environmentally polluting emissions, the filtration of hot gases at temperatures above 250° is constantly gaining in importance, because on the one hand the high sensible heat of the cleaned gases can then be utilised without further measures, whilst on the other hand suc flue gases cause less environmental pollution.

The employment of the aforesaid materials for the filters brought to light, however, that glass, ceramics and carbon fibres, because of their brittleness, can break easily, whilst in the case of metal wires, respectively metal fabrics, the clearances between the wires are too large for attaining an adequate filter effect in the case of fine dusts. Moreover, even the use of such heat-resis ant materials as sinter materials, porous, ceramic materials of fine pore size and the like is relatively ineffective, because the initially good separation effect declines continuously, because the very fine dust enters into the pores of such materials and cannot be released therefrom not even by special cleaning procedures, leading eventually to the blockage of such filters.

In the case of filters for use in the so-called high temperature range, those have become established, the filter t elements of which are often made of clay or ceramics and which for the sake of simplicity are designed as cylindrical tubes in the form of filter candles. Such filter candles open on one side are installed between mounting brackets in the casing for the filter and are there so fixed that the medium to be filtered enters through the wall of the filter candle into its interior from where it leaves through an aperture at one end of the filter candle. This aperture of the filter candle enters into a sp ce for the filtered medium from where the medium exits by way of an ou let nipple of the filter. The filter candles fitted to the brackets are in rigid contact with the former and cannot cope with the stresses caused by the flow of the medium and particularly the stresses during the flushing of such candles by flows in the opposite direction so that fractures, particularly at the necks of the filter candles cannot be avoided (cf. DE PS 30 17 851).

In order particularly to avoid such damage to the filter candles, this kind of filter candle is fitted pivotally to its brackets. This pivotal fixing of the respective filter candles is rendered possible in that on the one hand the brackets separating the clean space from the filter space takes the form of a perforated plate, the perforations being so designed that their open cross section towards the clean space is larger than towards the filter space. In turn the filter candle is provided at its end facing the clean space witli a flange-shaped beading by means of which this filter candle is supported on the inwardly drawn beading of the aperture in this bracket. In order to improve the fit of the filter candle on this beading, the latter may also take the form of a spherical cap-shaped annular shoulder and from there onwardly the cross section of this aperture increases in size towards the filter space in order to provide adequate room for pivoting of the filter element. The end of the filter element, i.e. the filter candle, remote from this collar comprises a bore into which engages a pin fitted to the bracket. This pin may be inserted in the bore with or with out play and in the absence of play, he bolt is supported against the filter candle by way of a resilient sleeve. The cap-shaped annular shoulder on the neck of the filter element and the resilient support of the pin at the opposite end on the one hand permit the support of the pin at the opposite end and on the other hand the pivotal suspension of the filter candle on the brackets so that it is better protected against damage as compared with fixed filter candles. However, in this filter it is considered a disadvantage that the respective filter candle is clamped too loosely between the brackets, resulting on the one hand in sealing problems and thus in contamination of the filtered medium, whilst on the other hand, due to the suspension of the filter candles from the cup-shaped annular shoulders the removal of the filter candles is rendered more difficult (cf. DE-PS 35 15 365).

Accordingly there exists a need for a filter of the type specified in the introduction, suitable for the filtering of hot and/or aggressive media such as flue gases and where in spite of high thermal loads, e.g. 600°C and possibly more, the filter retains its conf igurational stability and filter effect and is neither inclined to crack nor to suffer mechanical loss of material components and wherein moreover this filter can be fitted tightly to the brackets and can be fitted thereto and removed without great effort, remaining moreover in such close contact with such brackets that even mechanical stresses thereto, in particular during flushing will not result in damage thereof.

According to the invention, a filter is provided as set out in the opening paragraph, wherein the structure of the carrier material comprising relatively large pores, is covered on one of its outlining surfaces at least on the outer surface with a finely particulate, similarly heat-resistant filler material permitting the formation of finer pores, this filler material being applied to the carrier material as a thin coating, and this filler material is composed of parts of components of a dispersed mixture of which one part is volatisable from the mixture during a baking procedure, whereas another part is capable of forming a deposit in the larger pores of the carrier material and this mixture is made up by means of a bonding agent and a suspension liquid and in this aggregate state is adapted to be applied to the carrier material where it is adapted to enter into a bond partly with itself and partly with the carrier material and wherein these finely particulate components of the filler material as well as the bonding agent each are composed of a substance having a linear thermal expansion coefficient approximately equal to that of the carrier material, the material of the filler material being of such particle dimensions that the pore size of this filler material is kept below 10 um and this filler material is deposited into the larger pores in the peripheral region of the carrier material and there at least partly fills, in particular those relatively large pores of the carrier material .

Not only has it been found that such filters can be made to comply with the aforesaid need, but in addition the advantage has been observed, that the various structures of the filter, i.e. its carrier material and filler material have the same or approximately the same thermal expansion properties and that in spite of special bonding conditions these are neither inclined to cause damage to their structures, nor to cause pore size increases, in particular of the filler materials. This particular concept of the filter permits an excellent filter effect, even in the event of strongly fluctuating temperatures of the media to be filtered, so that such filters can be very well suited, particularly for hot gases in the temperature region from 250 ° upwards up to 600 to 800°C. Due to the fact that all materials if suitably selected nd thereby also all structures of the filter can follow temperature fluctuations without damage, it is hardly possible for cracks or defoliations, in particuar in the coating to arise so that in this filter as well a surface filtration takes place which provides the advantage of a fnr-reachingly blockage-free filter effect. Due to this surface filtration, increasing pressure losses can also be avoided, so that the filter can be operated with uniformly low energy expend ture .

The various structural parts of the filter may also, depending on the requirements for the filter, be varied so that for example, the carrier material may be given a greater or lesser pore width. In analogy to this pore width the pore widths of the filler material may also be rendered greater or lesser, e.g. in such a manner that either coarsely or finely particulate filler material is applied onto the carrier material or the carrier material is coated with a greater or lesser number of layers thereof. The filler material may in this con ext also be composed, e.g. of heat-resistant glass beads, ceramic granules or powders, fibres and the like which after having been applied to the carrier material cover it in the form of a ilm. Λ further advantageous embodiment of the invention comprises the feature that the filter is designed as a filter candle of stable configuration and that the filter element takes the form of a filter candle of fixed configuration and that this filter candle is clamped with sp ingloading between the mounting brackets and is hermetically sealed along those brackets against the interior of the filter casing, that for holding each filter candle on such mounting brackets each filter candle at that end which faces the clean space comprises an in jector- shaped tube flange and on its end which faces the discharge chute comprises a round pin, both of which, tube flange and round pin, comprise a circumferential beading between which and the filter element on the one hand and between which and the mounting bracket on the other hand, in each case a seal is provided and that in addition to those calibrated guide and mounting means for the filter candle between the beading of its round pin and the mounting bracket, a spring is provided which presses the filter element against all its sealing means and /or individual seals as such.

In a further embodiment of the invention the injector-shaped tube flange, as from its annular beading, comprises a sleeve projecting into the filter element and a collar projecting from this beading in the opposite direction, and this collar extends through the aperture of the mounting brackets into the clean space.

Similarly, an advantageous embodiment resides in the feature that the round pin comprises annular grooves at least along its section extending between its annular beading and its collar-like projection nd that this section of each projection projects into bores of the mounting bracket.

Further advantageous embodiments of the invention can be derived from the remaining subsidiary claims, for which within the scope of this application independent protection is also claimed.

In the drawings some possible embodiments of the invention are illustrated diagrammatically. There is shown in: Fig. 1, a side elevation of a filter element in the form of a cylindrical tube, Fig. 2, a section through the filter element in the plane II-II in Fig. 1.

Fig. 3, a side elevation onto a filter element in the form of a lammelae stack, Fig. 4, a section through the filter element in the plane IV-IV in Fig. 3, Fig. 5, a larger scale plan view onto a portion of the sect ional i sed filter element according to Fig. 1 or 3 with a plurality of beads forming the coating thereof, e.g. of uniform diameter, Fig. 6, a similar plan view on a larger scale, as in Fig. 1, however, with beads of e.g. different diameters, Fig. 7, a section through the filter element in the region of its coating with a series of beads heaped there against and powder particles embedded in the carrier material in accordance with sectional region III, Fig. 8, a longitudinal central section through a filter casing, including a filter element composed of a plurality of filter candles, Fig. 9, a cross section through the filter casing, including two filter elements in parallel arrangement in the plane II-II in Fig. 1, Fig. 10, a larger scale elevation onto a filter element in the form of a filter candle and the supporting means holding the filter candle there, in section, Fig. 11, a longitudinal centre section on a larger scale through the top of the filter candle, including the tube flange which supports it against its bracket and Fig. 12, a longitudinal central section on a larger scale through the base of the filter candle, including a round pin which supports it against its bracket.

The filter element 1 according to Figs. 1 to 7, is illustrated and described here by way of an example of two possible configurations. Λ simple such configuration may be a tubular filter element 1 as illustrated in Figs. 1 and 2. This filter element 1 is of such design that it forms a cylindrical carrier body 2 which at its one end comprises a f 1 ange- shaped top 3 and at its other end a base 4. Whereas the flange- shaped top 3 has therein the aperture cross section 5 of the filter element 1, i.e. the carrier body which simultaneously corresponds to the aperture cross section 6 approximately of the cylindrical carrier body 2, the bottom 4 of the carrier body serves as a closure thereof and is there optionally provided with a foot 7 in order to permit the carrier body to be fixed in a carrier structure 8 of a filter casing 13. The carrier body 2 itself, manufactured of a heat-resistant material, e.g. ceramics, comprises a large pore structure, i.e. large pores 9 onto which a fine pore structure in the form of a coating 11 comprising fine pores 10 has been applied. This coating 11 forms the filtering surface of the filter element 1, on which the particles to be separated from the medium to be filtered becomes separated.

The filter element 1 according to the further possible configuration of Fig. 4 is based on a so-called Lamella filter as illustrated in DE-OS 34 13 213 and differs from the latter essentially in that its carrier body 2, respectively its carrier material is manufactured of a heat-resistant material, e.g. the a foredescr ibed ceramically based material and the coating 11 of which is formed by a plurality of preferably spherical and/or powder- shaped bodies 12 similarly of heat-resistant material connected to the material of the carrier body 2 and/or to one another.

The different parts of the filter element 1, i.e. the carrier material 2 and its coating 11 comprise the different pore widths, the pores 9 of the carrier material being larger than the pores 10 of the coating, so that a filtration of the medium on the surface of the filter element 1 can take place.

In this context the carrier material 2 may be composed of ceramics in the form of an aluminium oxide (AI2O3), a zinc oxide (Zn02) or silicon oxide (Si02), the manufacture thereof proceeding such that the respectively selected material is processed in a conventional manner into a moulded body, e.g. being extruded into tubes and subsequently baked, from which thereafter the open-pored, i.e. large pore carrier body, i.e. the carrier material 2 is formed. However, if the material of the carrier material 2 is cast into moulds which may often be more advantageous, the f lange- shaped top 3 and the bottom 4 which closes the tube may be cast at the same time.

The fin nore coating 11 is then applied onto the outer peripheral surface of this coarse-pored carrier material 2, either in the form of an emulsion by spraying or painting, such that this emulsion predominantly becomes embedded in the openings, respectively holes of the carrier material and there covers the larger pores 9 by a large number of smaller apertures, respectively pores 10. The small pores 10 of the coating 11 are formed by virtue of the material of the coating, e.g. in the form of larger and smaller bodies 12, e.g. beads, becoming partially interconnected, e.g. in point or line fashion and the non-bonded surfaces retain the openings in he form of pores 10. These pores 10, respectively apertures, can be dimensioned substantially in optional sizes, so that the coating 11, respectively the covering, forms a finely porous layer in the nature of a film which still permits passage of the medium, comprising a fine dimension of its pores 10. Λ further possibility for applying the coating 11 resides in that, from the finely particulate powder for the coating a sludge is formed of similar consistency to that used in enamelling. The carrier body, i.e. the carrier material 2 may be dipped into this sludge. This coating is then baked jointly with the carrier material whereby a finely and open pored covering, similar to a glazing is formed. As in the case of the carrier material 2, here as well the required open small pores 10 are formed by the evaporation of the suspension liquor.

For the manufacture of the filter element 1 from such heat-resistant materials, a first expedient requires using for the carrier material 2 and its coating 11 components of the same basic materials, the bonding agent used during the heating of these materials (e.g. during the baking process) providing a melting together of these materials on their surfaces in a sinter-like fashion, whereby a homogeneous firm bond is formed.

This is the case and was established by various experiments in the event of carrier materials 2 and coating material 11 of aluminium oxide (ΛΙ2Ο3) and a ceramic adhesive of similar cons is tency · Similar stable structures are formed if chemically non-identical but similar substances coact and these mix ith one another in the liquid state (eutecticum, e.g. of M2O and SiC>2 or Zn02 and SiC^ Λ chemical compounding of carrier material 2 and coating 11 is also possible provided it is stable at the temperature of employment and provides approximately the same or better chemical resistance against structural changes as does the carrier or coating material 2,11. The partial bonding between the carrier and coating material 2,11 is brought about by a bonding agent 14 which, depending on the nature of bonding during the baking procedure may be provided in a form similar to an applied glazing or as an adhesive composition.

The thickness 15 of the coating, i.e. the coating layer 11 can readily be adapted to the particular requirements of purity of the medium, in that onto the carrier material 2, more or less coating material is applied. By this expedient the filter effect of this coating 11 can be increased corr spondingly .

The bonding of the coating 11, i.e. its filler material, to the carrier material 2 is preferably a homogeneous, intimate bonding which as a rule can no longer be released. This is important in that the coating 11 cannot be washed off the carrier material 2 which otherwise might easily happen in the case of filtering liquids.

The filter elemen 1 acco ding to the invention, in accordance with the embodiment of Figs. 8 to 12 hardly differs from the filter elements according to Figs. 1 - 7 and similarly serves for the separation of particles from gaseous or liquid media. For the sake of easier unde standing, this filter element 1 is made in the form of a tube or filter candle and is provided essentially in a filter casing 13 jointly with at least one further filter element provided in this casing. The casing 13 itself comprises a clean space 16 for the filtered medium and a discharge chute 17 for the particles, in addition to inlet and outlet nipples 37 and 38 for the medium. The filter element 1 which according to the example here illustrated takes the form of a tubular filter candle, is preferably similar made of a ceramic material which e.g. comprises a carrier body 2 comprising larger pores 9 and a surface coating, e.g. coating layer 11 with fine pores 10. The mounting of this filter element 1, i.e. the respective i 1255 candle in the filtering space of the filter casing 13 may be done vertically or horizontally, for which purpose each filter candle at its respective end, i.e. the candle top 18 and the candle base 19 comprises special fixing means by way of which it is fixed to brackets 20, 21 in the filter space. The fixing parts at the top of the candle 18 are formed essentially by an injector-shaped tube flange 22 and at least one seal 23, 24 of which the tube flange next to an annular beading 25 comprises a collar 26 projecting into the clean space 16 and a sleeve projecting into the filter element 1. The annular beading 25 which approximately forms the waist line of the tube flange 22 has a larger diameter than the jacket of the filter element 1. Accordingly, the tube flange 22 has adequately large contact areas against which the ends of the filter element, i.e. the filter candle can find support on one side against the bracket 21 for such candle and on the other side against the bracket 20 on the clean gas side end.

In order to render the sealing more effective in this context, it is advisable to provide seals 23, 24 on both sides of the annular beading 25, i.e. coaxial thereto, of which the one takes the form of an annular seal 32 and the other se.al 24 may besides the annular surface also comprise a bag-like expanded portion. The bag-like expanded portion would in such case concentrically enclose the sleeve 27 projecting into the filter element 1 and would provide there not only sealing but also a radial resilient support. It stands to reason that it is also possible instead of such bag-like seal to provide in that position an annular seal 32 and to support the filter candle only by way of this seal in relation to the bracket 20.

At the other end of the filter element 1 a round pin 29 is primarily supported on the beading 28, this pin - similar to the tube flange 22 - similarly comprising a collar 30 and a projection 31 directed in opposition thereto. The round pin 29 by virtue of the collar 30 is inserted up to the beading 28 in the free end of the filter element 1, this collar providing optionally no^or little radial play between itself and the inner periphery of the filter element. The actual sealing of this end of the filter element 1 at the candle base 19 takes place, as also in the case of the candle top 18, by way of an annular seal 32 against which the end of the filter element bears in sealing contact. The projection 31 of the round pin 29 itself is inserted into a bore 33 of the bracket 21 and so far engages into this, that the filter element 1 is secured not only against radial movement, but also against axial movement in the bore. In order to seal the respective filter element hermetically against the filter ring space of the filter casing 13, a spiral spring 34 is placed around the projection 31 between the beading 28 of the round pin 29 and the bracket 21 and finds support against the beading 28 on the one hand and against the bracket 21 on the other hand. This spiral spring 34 presses the filter element 1, i.e. the filter candle, also against the seals 23, 24 at the top 18 of the candle as well as the beading 28 against the annular seal 32, such that these seals enter there into full contact.

The round pin 29 itself may be solid walled along its collar 30 and projection 31 or may comprise annular grooves 35 as illustrated in the drawing of Fig. 10. It is also possible instead of the round pin 29 to employ an equivalent guide member, such as for example a pine tree shaped spring or a spider. Similarly, instead of the spiral spring 34 a cup spring package ca be used which provides the axial pretens ioning of the filter element 1.

The brackets 20, 21 themselves, which may e.g. be formed as U-shaped struts are supported at their ends on cantilevers 36 of the filter casing 13 and may be supported there rigidly or resiliently.

The medium to be filtered which enters through the feed nipple 37 into the filter ring space of the filtring casing 13, flows around the original filter elements 1 and passes through them into the clean space 16, whereas the particles entrained therein become deposited on the walls of the filter element. The medium thus entering into the clean space 16 leaves this by way of the outlet nipple 38 in order to enter the atmosphere or be passed on to a further process. The particles deposited on the filter candles are cast off by counter directional blowing of the filter candles from inside to the outside known per se and enter into the discharge chute 17 from where they are discharged continuously or discontinuously. The counter blow means may be a jet cleaning means known per se, the nozzles of which blow their cleaning medium, e.g. compressed air into the apertures of the in jector- shaped tube flanges 22.

The assembly and dismantling of the filter elements 1, e.g. the filter candles, is particularly facilitated in the case of this candle- shaped embodiment in that after inserting the projection 31 of the round pin 29 into the bore 33 of the bracket 22 and pressing it against the force of the spiral spring 34, the collar 30 of the tube flange 22 at the top 18 of the candle is first pressed under the hole of the bracket 20 at that end and after slow release of the pressure applied to this collar, snaps into that aperture there to fix the filter candle. The dismantling of the filter candle, respectively of the filter element 1 proceeds in the reverse sequence when it is to be removed from its brackets 20, 21.

The composition of the filler material, i.e. of the coating 11 which is applied onto the carrier body 2, is composed according to an advantageous selection of materials of the following components.

These components wh ch are dispersed as a mixture, are applied onto the carrier body 2, e.g. by means of a brush, and this filler material jointly with the carrier body is exposed for about 1 hour to a temperature of about 500°C whereby the filler material is baked into the material, respectively the pores 9 of the carrier body 2.

The components of the filler material, respectively the coating layer 11, can have the following composition: 1 part by volume sodium waterglass 14 parts by volume water 4 parts by volume kaolin 2 parts by volume feldspar 2 parts by volume starch (starch flour) 0,2 parts by volume sodium. diphosphate The filler material produced in this manner and applied on the carrier body 2 becomes deposited in the region of the outer surfaces of the pores 9 of the carrier body 2 and fills these to such an extent that on the surface thereof a film-like coating is formed. The water is then evaporated off by thermal action and the starch is similarly eliminated at that temperature from the mixture by combust ion .

As mentioned further above, the filter elements 1 are produced of ceramic heat-resistant material. This obviously does not exclude the employment of other filter elements 1, for example of plastics, if such filter is to operate in a different temperature range. Similarly, it is possible to employ other configurations of filter elements 1.

The filter element 1 has in this case been illustrated and explained for the filtration of hot gases. It stands to reason that this filter element 1, by suitable selection of materials, can also be employed for the filtration of hot liquids or liquids which are not hot. This filter element 1 is also of particular interest for aggressive media in gaseous or liquid form, since it is hardly attacked by aggressive substances.

The heat- res i s tatit filter element 1 was illustrated and described here by way of the examples of tubes and the so-called lammelae filters as illustrated in Figs. 1 - 4. It stands to reason that this filter element may also have different configurations. It is advantageous here to select that configuration which provides the greatest possible filter area. Such a configuration can also be a combination, such as for example an oval, triangular and other configuration. The configuration will usually depend on the volume to be filtered, the conf igurational stability of the filter element, i.e. the filter candle and the medium which is to be filtered. The latter also determines the pore width which for the purpose of optimising the pressure losses is adapted to the medium.

The function of the filter has been here illustrated and described wi h reference to jet cleaning, by way of the example of the separation of particles from gaseous media. The separation of particles from liquids takes place in similar manner, however, in such a case the cleaning must proceed differently, i.e. by countercur rent flow of a clean liquid. If, however, the liquid permits the injection of air, it is also possible to employ compressed air for the cleaning .

The claims which follow are to be considered an integral part of the present disclosure. Reference numbers (directed to the drawings) shown in the claims serve to facilitate the correlation of integers of the claims with illustrated features of the preferred e mbod i m en t ( s ) , but are not intended to restrict in any way the language of the claims, to what is shown in the drawings, unless the contrary is clearly apparent from the context.

Claims (25)

1. K 35480/8-St Patent Claims 1, A hot fluid filter element (l) , in particular for separating solid particles from hot flue gases in the temperature range between 120 and 800°c, consisting of: (a) a refractory, permeably porous supporting body (2) of inherent stability and made of bonded together particles (12) of ceramics and/or glass; (b) and a refractory, permeably porous coating (11) on the surface of the filter element (1) to be acted upon by the hot fluid, said coating (11) containing particles of ceramics and/or glass as well as an inorganic binder (14) and being produced by baking an applied coating mass; (c) said coating (11) having a smaller pore size than the supporting body (2) and the coefficients of linear thermal expansion of the supporting body (2) , the ooating partiolee and of the binder (14) being substantially the same; o h a r a c t o r i 2 © d in (d) that the porous coating (11) consists of the coating particles bonded to each other and to the supporting body (2) by means of said binder (14), the porosity of the coating (11) being the result of the evaporation of a suspending liquid and of a burning-out component of the coating mass during baking thereof; (e) that the pores (9) of the supporting body (2) at the coating surface thereof are filled, to at 25 91255/3 least part of their depth, by the coating particles bonded together by the binder (14) ; (f) and in that the pore size of the coating (11) is smaller than 10 μτη.

2. A filter element (1) according to claim 1, characterized in that the particles (12) of the supporting body (2) consist of aluminium oxide and/or zinc oxide and/or silicon oxide.

3. A filter element (1) according to claim 1 or 2, characterized in that the particles of the coating (11) consist of aluminium oxide and/or zinc oxide and/or silicon oxide.

4. A filter element (l) according to any one of claims 1 to 3, characterized in that the binder (14) is soda water glass.

5. A filter element (1) according to any one of claims 1 to 4, characterized in that the suspending liquid is water.

6. A filter element (l) according to any one fo claims 1 to 5, characterized in that the coating mass has the following composition: 14 parts by volume water 4 parts by volume Kaolin 2 parts by volume feldspar 2 parts by volume starch flour 1 part by volume soda water glass 0.2 parts by volume sodium diphosphate, 91255/3

7. A filter element (1) according to any one of claims l to 6, characterized in that the coating (ll) consists of two layers, the outer layer being of finer porosity than the inner layer.

8. A hot fluid filter device, in particular for separating solid particles from hot flue gases in the temperature range between 120 and 800°C, comprising: (a) a housing (13) subdivided by a first support (20) into a filtering space and a clean space (16); (b) and a plurality of tubular filter elements (1) resiliently mounted in the filtering space between the first support (20) and a second support (21) , c h a r a c t e r i z e d in (c) that the filter elements (1) are designed as indicated in any one of claims 1 to 7.

9. A filter device according to claim 6, characterized in (a) that the filter elements (1) are each fixed to the first support (20) by means of an injector-shaped tubular bush (22) , (b) the tubular bush (22) having a collar (25), and a seal (23) being provided between the collar (25) and the first support (20) as well as a seal (24) being provided between the collar (25) and the filter element (l) ; (c) that the filter elements (l) are each fixed to the second support (21) .by means of a round bolt (29), (d) the round bolt (29) having a collar (28) and a seal (32) being provided between the collar (28) and tho filter element (1); (e) and in that a spring (34) for resiliently clamping the filter clement (1) between the first support (20) and the second support (21) and for pressing 91255/3 the same against the seals (23 , 24, 32) is disposed between the collar (28) of the round bolt (29) and the second support (21).

10. A filter device according to claim 9, characterized in that the tubular bush (22) comprises a portion (27) projecting beyond the collar (25) and protruding into the filter element (1) as well as a portion (26) projecting in the opposite direction beyond the collar (25) and reaching into the clean space (16) through an opening in the first support (20).

11. A filter device according to claim 9 or 10, characterized in that the round bold (29) has a portion (30) projecting beyond the collar (28) and protruding into the filter element (1), as well as a portion (31) projecting in the opposite direction beyond the collar (28) and protruding into a bore (33) in the second support (21) .

12. A filter device according to claim 11, characterized in that the oppositely projecting portion (31) of the round bolt (29) has annular grooves (35) .

13. A filter device according to any one of claims 8 to 12, characterized in that the first support (20) and/or the second support (21)- is formed as a U-shaped, brace.

14. A filter device according to any one of claims 8 to 13, characterized in that several supports (20, 21) are provided in juxtaposed manner for one filter element row each. 91255/3

15. A filter device according to any one of claims 8 to 14, characterized in that both the first support (20) and the second support (21) extend substantially from one wall to an opposite wall of the filter housing (13) .

16. A filter device according to any one of cloime Θ to 15, characterized in that clamping of the filter elements (1) between the first and second supports (20, 21) is effected in floating fashion.

17. A filter device according to any one of claims 9 to 16, characterized in that the filter element (l) is slidable in axial direction against the action of the spring (34) , to such an extent that the projecting portion (26) of the tubular bush (22) comes free from the opening of the first support (20) .

18. A method of making a hot fluid filter element (l) , in particular for separating solid particles from hot flue gases in the temperature range between 120 and 800°C, comprising the following steps: (a) producing a refractory, per eably porous supporting body (2) of inherent stability and made of bonded together particles (12) of ceramics and/or glass; (b) applying a coating ■ mass , containing particles of ceramics and/or glass as well as an inorganic binder (14), to the supporting body (2) on the surface of the filter element (l) to be acted upon by the hot fluid; (o) and baking the applied coating mass, thereby forming a refractory, permeably porous coating 91255/3 (11) of the supporting body (2) of smaller pore aire than the supporting body (2), with the coefficients of linear thermal expansion of the supporting body (2) , the coating particles and of the binder (14) being substantially the same; c h a r a c t e r * 2 e d in (d) that the applied coating mass contains the coating particles, the binder (14) , a suspending liquid and a component adapted to be burnt out; (e) that, by baking of the coating mass, the suspending liquid as well as the burnable component are caused to evaporate and the porous coating (11) is formed of the coating particles bonded to each other and to the supporting body (2) by means of the binder (14), the pores (9) of the supporting body (2) at the coating surface thereof being filled, to at least part of their depth, by the coating particles bonded together by the binder (14), and the pore size of the coating (11) being smaller than 10 μπι.

19. A method according to claim 18, characterized in that aluminium oxide and/or zinc oxide and/or silicon oxide is used for the particles (12) of the supporting body (2) .

20. A method according to claim 18 or 19, characterized in that aluminium oxide and/or zinc oxide and/or silicon oxide is used for the particles of the coating (11).

21. A method according to any one of claims 18 to 20, characterized in that the binder (14) used is soda water glass.

22. A method according to any one of claims 18 to 21, 91255/3 characterized in that the suspending liquid used is water.

23. A method according to any one of claims 18 to 22, characterized in that a coating mass with the following composition is used: 14 parts by volume water 4 parts by volume kaolin 2 parts by volume feldspar 2 parts by volume starch flour 1 part by volume tsoda water glass 0,2 parts by volume sodium diphosphate.

24. A method according to any one of claims 18 to 23, characterized in that the coating (11) is applied in two layers, the outer layer being of finer porosity than the inner layer.

25. A method according to any one of claims 18 to 24, characterized in that the coating mass is applied by spraying on, spread-coating or immersion of the supporting body (2) .