Support construction of filter element in dust collecting apparatus

Abstract: A support construction of a ceramic filter element (11) adapted for use in a dust collecting apparatus, wherein the ceramic filter element (11) is mounted within a tubular support housing (12) which is formed at its inner periphery with an inward flange (12c) enclosing an outer periphery of the filter element (11), the filter element having one end portion formed at its outer periphery with an outward flange (11c) which is coupled with the internal wall surface of the support housing (12) through encircling sealing members (13b) and engaged at one side thereof with the inward flange (12c) of the support housing (12), and wherein a pressure plate (14) in the form of a window frame is coupled within one end portion of the support housing (12) and pressed to the outward flange (11c) of the filter element such that the outward flange (11c) of the filter element (11) is clamped by the pressure plate (14) and the inward flange (12c) of the support housing (12).

Description: The present invention relates to a dust collecting apparatus adapted for use in various industrial plants such as a steel manufacturing plant, a cement plant, various kinds of chemical plants and the like for purifying high-temperature exhaust gases discharged therefrom, and more particularly to a support construction of a ceramic filter element in the dust collecting apparatus. Disclosed in JP-A-4-354506 is a dust collecting apparatus of this kind which includes an upright housing provided at its upper portion with an inlet duct and at its bottom portion with a discharge duct, and a ceramic filter assembly composed of a plurality of ceramic filter elements aligned in parallel and mounted within the upright support housing to form an inlet chamber in open communication with the inlet duct and a discharge chamber in open communication with the discharge duct. Each of the filter elements is made of porous ceramic material and has a thin walled cellular structure formed with a plurality of axially extending passages separated from each other by thin partition walls. A first group of axial passages are in the form of inlet passages closed at their one ends and opened at their other ends to introduce exhaust gases supplied from the inlet chamber to be purified, while a second group of axial passages are in the form of outlet passages opened at their one ends to discharge purified gases therefrom into the discharge chamber and closed at their other ends. In the dust collecting apparatus, exhaust gases to be purified are introduced into the first group of the axial inlet passages at an upstream side of the filter assembly so that the thin partition walls of the filter elements act to collect dust from the exhaust gases permeating therethrough from the first group of the axial inlet passages into the second group of the axial outlet passages thereby to purify the exhaust gases. In this dust collecting apparatus, each of the ceramic filter elements is enclosed by a sealing member and fixed in place within the upright housing through the sealing member to prevent leakage of exhaust gases passing therethrough. In such a support construction of the filter elements, however, the filling condition of the sealing member depends on the worker's skill. Accordingly, when the exhaust gases under high pressure are supplied into the inlet chamber of the dust collecting apparatus, the sealing members tend to be moved toward a downstream side of the filter assembly by a difference in pressure between the inlet and discharge chambers. This causes undesired influence to the sealed condition of the filter elements. During a reverse washing process of the filter elements, the sealing members tend to be moved toward the upstream side of the filter assembly by the pressure of washing gas supplied into the downstream side of the filter elements. EP-A-657202, published 14 June 1995, shows dust collecting apparatus comprising a honeycomb filter element as described above, having an outward flange, engaged through sealing means with an inward flange of a support frame. The filter elements are mounted in the support frame by metal fittings, provided with fixing bolts, pressing the filter outward flange against the support frame inward flange. EP-A-410200 shows filter apparatus having a porous sintered metal honeycomb filter body which is mounted in a support housing by means of a flange at one end of the honeycomb body which has a pair of bevelled surfaces which are trapped between crucial faces of ring members welded to the housing. It is, therefore, a primary object of the present invention to provide an improved support construction of the ceramic filter element in the dust collecting apparatus capable of overcoming the problems discussed above. According to the present invention, there is provided a dust collecting apparatus as set out in claim 1. For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings, in which: Fig. 1 is a sectional view of a ceramic filter element supported by a support construction in a dust collecting apparatus in accordance with the present invention; Fig. 2 is a perspective view of the ceramic filter element shown in Fig. 1; Fig. 3 is a partly broken perspective view of the support construction shown in Fig. 1; Fig. 4 is a front view of a ceramic filter assembly unit composed of a plurality of ceramic filter elements; Fig. 5 is a vertical sectional view of the ceramic filter assembly taken along line V-V in Fig. 4; and Fig. 6 is a vertical sectional view of the dust collecting apparatus. In Figs. 1 and 3 of the drawings, there is illustrated a ceramic filter element 11 supported by a support construction in a dust collecting apparatus in accordance with the present invention. As shown in Figs. 4 and 5, a plurality of the filter elements 11 are vertically piled up in columns and laterally arranged in rows. Thus, a ceramic filter assembly unit 10 is composed of the plurality of filter elements 11. Illustrated in Fig. 6 is a dust collecting apparatus which includes an upright cylindrical housing 21 provided therein with a plurality of circumferentially placed lateral support beams 22 arranged at vertically equally spaced plural stages to form a plurality of circumferentially spaced vertical gas induction passages r1 along an internal peripheral surface of the housing 21 and a vertical discharge passage r2 at the center of the housing 21. In the dust collecting apparatus, plural sets of the ceramic filter assembly units 10 are circumferentially arranged and vertically mounted on each of the support beams 22 in such a manner that the filter assembly units 10 are exposed at their outer ends to the gas induction passages r1 and at their inner ends to the discharge passage r2. The cylindrical upright housing 21 is provided with inlet ducts 21a at its upper side walls and a discharge duct 21b at its upper end. A pyramidal hopper 21c is integrally assembled with a bottom portion of housing 21 to permit dust to fall through into a container chamber (not shown). The ceramic filter elements 11 of the respective filter assembly units 10 each are supported by a tubular support housing 12 of square cross-section as shown in Fig. 5 and clamped by a pair of flanged side shell members 16 each formed in a L-letter shape in cross-section. As shown in Fig. 2, the filter elements 11 each are made of porous ceramic material and have a thin-walled cellular or honeycomb structure of square cross-section formed with a plurality of axially extending passages separated from each other by thin partition walls. A first group of the axial passages are in the form of inlet passages lla closed at their one ends in a checked pattern and opened at their other ends to introduce therein exhaust gases to be purified. A second group of the axial passages are in the form of outlet passages 11b opened at their one ends to discharge purified gases therefrom and closed at their other ends in a checked pattern. The ceramic filter element 11 mounted within the support housing 12 has one end portion integrally formed at its outer periphery with an outward flange 11c which is coupled with the internal wall surface of the support housing 12. As shown in Fig. 3, the support housing 12 is composed of a pair of vertical side wall members 12a laterally spaced in parallel to one another and a pair of horizontal wall members 12b vertically spaced in parallel to one another. As shown in Figs. 1 and 3, the support housing 12 is provided at its inner periphery with an inward flange 12c which is inwardly projected and coupled over the outer periphery of the filter element 11. The inward flange 12c of support housing 12 is engaged at one side thereof with the outward flange 11c of filter element 11 through a sheet-like sealing member 13a formed in a square frame. Disposed between the outward flange 11c of filter element 11 and the internal wall surface of the support housing 12 is a plurality of encircling sealing members 13b of circular cross-section. Additionally, a sheet-like encircling sealing member 13c is disposed between the inward flange 12c of support housing 12 and the corresponding outer surface of filter element 11. A pressure plate 14 in the form of a window frame is engaged with the outward flange 11c of filter element 11 through a sheet-like encircling sealing member 13d and is pressed towards the filter element 11 by fastening bolts 15 to clamp the outward flange 11c of filter element 11 against the inward flange 12c of support housing 12. As shown in Fig. 3, the pressure plate 14 has four corner portions 14a, a pair of vertical portions 14b and an upper horizontal portion 14c which are formed with front flat surfaces and a lower horizontal portion 14d formed with an downwardly inclined front surface. The outer dimension of pressure plate 14 is slightly smaller that the inner dimension of the support housing 12. The fastening bolts 15 are threaded into horizontal support brackets 12d which are secured to the vertical wall member 12a of support housing 12. Thus, the fastening bolts 15 are advanced to press the pressure plate 14 toward the outward flange 11c of filter element 11 or retracted to release the pressure plate 14 from the outward flange 11c of filter element 11. In the dust collecting apparatus as described above, exhaust gases under pressure to be purified are introduced into the ceramic filter assembly units 10 from the inlet ducts 21a through the gas induction passages r1 and purified by the filter elements in the ceramic filter assembly units 10. The purified gases are introduced into the discharge passage r2 and discharged outwardly therefrom through the discharge duct 21b. During such treatment of the exhaust gases, fine particles of dust contained in the exhaust gases are collected at the partition walls of the filter elements and accumulated on the surfaces of the partition walls. In a reverse washing process of the dust collecting apparatus, washing gas under high pressure is supplied into the discharge passage r2 through the discharge duct 21b. In this instance, the washing gas is introduced into the outlet passages of the filter elements in the respective filter assembly units 10 to flow into the inlet passages of the filter elements through the partition walls. This increases a difference in pressure between the outlet and inlet passages of the filter elements. Thus, the accumulated fine particles of dust are separated from the partition walls of the filter elements and fall into the container chamber (not shown) from the hopper 21c. In each support construction of the filter elements in the respective filter assembly units 10, the outward flange llc of the filter element 11 is clamped by the inward flange 12c of support frame 12 and the pressure plate 14 through the sheet-like encircling sealing members 13a and 13d, while the encircling sealing members 13b are placed between the outer periphery of the outward flange 11c and the internal wall surface of the support housing 12. Thus, the encircling sealing members 13b are retained in place without any movement even when subjected to the pressure of the exhaust gases or the washing gas. Since the filter element 11 is engaged with the support housing 12 only at its outward flange 11c, any longitudinal bending stress does not occur in the filter element 11 in spite of thermal deformation of the support housing 12. Thus, the filter element 11 is retained in a stable condition for a long period of time without causing any damage at its outward flange 11c. Although in the foregoing support construction, a portion of dust is accumulated on the pressure plate 14 during treatment of the exhaust gases, the inclined surface of the lower horizontal portion 14d of pressure plate 14 causes the accumulated dust to slide down thereby to prevent accumulation of the dust.

Claims: Dust collecting apparatus having a ceramic filter element (11) made of porous ceramic material and having a thin walled cellular structure having a plurality of axially extending passages separated from each other by thin partition walls, a first group of the axial passages being in the form of inlet passages closed at their one ends and open at their other ends to introduce therein exhaust gases to be purified, while a second group of the axial passages are in the form of outlet passages open at their one ends to discharge purified gases therefrom and closed at their other ends, wherein said ceramic filter element (11) is mounted within a tubular support housing (12) which is provided at its inner periphery with an inward flange (12c) enclosing the outer periphery of said filter element (11), said filter element having one end portion formed at its outer periphery with an outward flange (11c) which is coupled with the internal wall surface of said support housing (12) through an encircling, peripheral sealing means (13b) and is positioned on one side adjacent to the inward flange (12c) of said support housing (12), and wherein a pressure plate (14) in the form of a window frame is coupled within one end portion of said support housing (12) and pressed towards the outward flange (11c) of said filter element (11) such that the outward flange (11c) of said filter element is clamped by said pressure plate (14) and the inward flange (12c) of said support housing (12), said sealing means (13b) being retained in place at its axial ends by additional sealing members (13a, 13d) which press on the side faces of the flange (11c) of the filter element. Dust collecting apparatus according to Claim 1, wherein said sealing members (13a, 13d) are sheet-like encircling members (13a, 13d). Dust collecting apparatus according to Claim 1 or 2, wherein said pressure plate (14) is pressed towards the outward flange (11c) of said filter element by means of plurality of fastening bolts (15) which are threaded into plurality of support brackets (12d) secured to the one end portion of said support housing (12). Dust collecting apparatus according to any one of Claims 1 to 3, wherein said encircling, peripheral sealing means (13b) disposed between the outward flange (11c) of said filter element (11) and the internal wall surface of said support housing (12) comprises a plurality of encircling sealing members of circular cross-section.

Inventors: AKITSU YASUO, HORI YOSHIAKI, AKITSU, YASUO, HORI, YOSHIAKI
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 1995
Main classification: B01D46
IPC codes: B01D46