WO2000048708A1

WO2000048708A1 - Device for cleaning a filter

Info

Publication number: WO2000048708A1
Application number: PCT/CH2000/000073
Authority: WO
Inventors: Frank Zimmerling
Original assignee: Jetclean Gmbh
Priority date: 1999-02-18
Filing date: 2000-02-09
Publication date: 2000-08-24
Also published as: AU2275600A; EP1029576A1; EP1152813A1

Abstract

The device comprises a collector (1) for feeding cleaning gas to a plurality of axially parallel cleaning nozzles (2) fastened to the collector (1), each cleaning nozzle (2) being assigned one pilot valve (10) each. The valve (10) controls the supply of cleaning gas from the collector (1) to the nozzle opening (19). The valve housing (25) of the valve (10) bears against a first wall (24) of the collector (1). The valve housing (25) has lateral bores (28) to a valve chamber (29). The output of the valve (10) is formed by a tube (40), which passes through the collector (1) and a bore (21) of a flange (15, 16) of the nozzle (2). The nozzle (2) is fastened to the collector (1) by means of a nut (45) screwed onto the tube (40). Cross-bores (43) of the tube (40) open out into an annular channel (18), which opens out into an annular-gap nozzle (19). With the device described, a simple structural design and cost-effective production are made possible.

Description

Device for cleaning a filter

DE-C-197 001 983 discloses a cleaning device according to the precharacterizing clause of Claim 1. An annular-gap nozzle comprises a flange composed of an upper ring and a lower ring, which together form an annular channel and the annular gap. The rings are screwed together by a plurality of screws distributed over the circumference. Built into the flange is a pilot valve, which in one configuration is designed as an annular diaphragm valve. In another configuration, it is designed as a seat valve with an actuating stem, which is actuated by a diaphragm. A common collector for a series of these annular-gap nozzles is welded to these nozzles. The control lines to the pilot valves are externally laid.

DE-U-298 12 702 discloses a further cleaning device of this type. In this device, the control valve is arranged on the collector and its output is connected to the annular channel of the annular-gap nozzle via a curved tube running through the collector.

Further such cleaning devices are described in NL-C-1-006 312, US-A-3 394 532, AU-A-526 396 and US-A-5 110 331. The present invention is based on the object of developing a device of the type mentioned at the beginning in such a way that it is of a simpler structural design and can be produced more cost- effectively. This object is achieved by the combination of features of the claims.

Exemplary embodiments of the invention are explained below with reference to the drawings, in which:

Figure 1 shows an axial section through a first embodiment,

Figure 2 shows a side view,

Figures 3 and 4 show a second embodiment, Figures 5 and 6 show a filter with the built-in device,

Figure 7 shows a third embodiment, and

Figure 8 shows a longitudinal section through a beater.

The cleaning device according to Figures 1 and 2 comprises a collector 1, to which cleaning gas is fed, for example compressed air at a feeding pressure of approximately 6 bar, as well as a series of annular- gap nozzles 2. The nozzle axis 3 is vertical and coaxial with respect to a filter bag 4, which is spread by a supporting cage 5 and suspended at the top at an opening in a filter plate 6, which subdivides the filter into an untreated-gas space 7 and a clean-gas space 8. Welded onto the upper end of the supporting cage 5 is a Venturi tube 9. Each nozzle 2 is assigned a separate valve 10.

The nozzle 2 has a flange, comprising two coaxial rings 15, 16. The rings 15, 16 are centred with each other by a shoulder 17 and are pressed together, welded or soldered at the periphery to form a unit. They enclose an annular space 18, which opens out into an annular gap 19 of approximately 0.3 to 0.4 mm in width. Starting from the annular gap 19, the ring 15 is rounded off toroidally. The central opening in the ring 15 opens out into a welded-on tube 20. The rings 15, 16 have at one point of their periphery an axially parallel through-bore 21.

The valve 10 has a valve housing 25, which is formed as a turned part and bears with a flange 26 against the lower wall 24 of the collector 1, with an O-ring 27 interposed. A plurality of radial bores 28 connect the inner space of the collector 1 to a valve chamber 29, which is bounded at the top by a planar valve seat 30 and at the bottom by a diaphragm 31, which is thickened in the centre. The periphery of the diaphragm 31 is braced against the housing 25 by means of a tubular stub of a closure screw 32. The control chamber 33 arranged between the diaphragm 31 and the closure screw 32 is connected via bores 34 to a control line 35, for example a flexiole tube. Fastened to the valve housing 25 is a coaxial tuoe 40, which is inserted through a bore 41 m a cover disc 42 and the bores 21. The cover disc & 2 bears _*'ith a flange 39 against the upper wall 46 of the collector 1. The tube 40 has in the region of the annular channel 18 a plurality of cross-bores 43 and at the top an external thread 44, onto which a cap nut 45 is screwed. The disc 42 is sealed off with respect to the upper wall 46 of the collector 1 and with respect to the ring 15, and the nut 45 is sealed off with respect to the ring 16, by further O-rings 47.

As Figure 2 reveals, all the control lines 35 are laid inside the collector 1. The latter is closed off at one end face by a cover 51. Fastened to this cover 51 is a multiple socket 52 of a multiple coupling 53. The lines 35 are connected to the individual connections of the socket 52. The connector 54 of the coupling 53 is connected to a pneumatic multiple cable 55.

The cleaning device described operates as follows: during operation, the untreated gas to be filtered is fed to the untreated-gas space 7 by a blower and passes via the filter bags 4 to the clean- gas space 8, the dust contained in the untreated gas being deposited on the filter bags 4. The control pressure is provided in all the control chambers 33 of the valves 10, so that the valves 10 are closed. Each valve is then periodically vented by brief venting of the control chamber 33 via the control line 35, by means of solenoid valves not represented, so that the relevant valve 10 opens briefly for aoout 0.12 sec. The cleaning gas leaves the annular nozzle 19 at high speed. Owing to the Coanda effect, the thin film of air flows along the toroidal edge of the disc 15 at high speed. This stream of cleaning gas entrains from the clean-gas space 8 a secondary flow 58 through the tube 20, which additionally induces a tertiary flow 59 above the Venturi nozzle 9. The pressure surge in the bag ^Δ caused as a result has the effect that the parts of the latter made to bulge inwards between the longitudinal bars of the supporting cage 5 during filter operation are thrown outwards and conseguently the adhering dust is shaken off, which J.S assisted by the short return gas flow.

Depending on the degree of contamination of the untreated gas, the cleaning intervals are approximately 1 to 10 mm. The valves 10 of the entire filter, that is of all its collectors 1 arranged parallel to one another, are activated one after the otner, in order that the pressure surge upstream of the αntreated-gas space 7 is minimized. In the case cf very large filters with many bags 4, two or three valves 10 may also be simultaneously opened at one time. In the case of the most heavily contaminated filter bags 4 m the region of the untreated-gas inlet into the space 7, the cleaning intervals may be made shorter. Reliable operation of the filter is monitored by measuring the pressure difference over the filter plate 6.

The device described is particularly simple in its structural design and production. Only very little welding work is reguired on the collector 1. The valves 10 and discs 42 are simple turneα parts. The assembly of the valves 10 and nozzles 2 with a single nut 45 also makes correspondingly easy disassembly possible. As a result, the collectors 1 can be made longer, without excessively making handling more difficult. This is because, for assembling and disassembling the device m the filter, the nozzles 2 can be removed in order to reduce the weight of the collector. This is not possible in the case of the device mentioned at the beginning. With the latter, it was necessary m practice to restrict the length of the collectors for reasons of weight. Because the control lines 35 are laid inside the collector 1, they are protected and inexpensive flexible tubes can be used, whereas with the device described at the beginning it was necessary to use stainless steel tubes. The collector 1 with the nozzles 2 is easy to clean.

Compared with cyclones, a much higher degree of purity of the clean gas is achieved. In addition, the filtered dust can be reclaimed and reused, in particular if CIP (Clean-In-Place) bags are used as filter bags.

The filter reguires less drive power for the feeding blower than a cyclone. The investment m a filter of the type described can therefore be paid off m a relatively short time.

In the case of the device according to Figures Ξ, 4, ^~ and 8, analogous parts are provided with the same reference numerals, so that a detailed description of these parts is not necessary. In the case of the device according to Figures 3 and 4, the wall 24 against which the valve housing 25 bears is at the top. The nut 65 bears directly on the disc 42 and is formed in one piece with the coaxial nozzle 66. Thus, apart from the cleaning gas from the nozzle 66, only the secondary flow 58 flows into the Laval nozzle 9. This embodiment is suitable in particular for relatively short or narrow filter bags 4, as well as for compressed air of relatively low pressure, for example of 1.5 to 3 bar, from screw compressors or rotary piston compressors.

Figures 5 and 6 show the device according to the invention built into a filter housing 71 in an application with 16 filter bags 4. The cover 51 is welded onto an extension tube 72, which is screwed to the housing wall 73. The pneumatic multiple cables 55 connect the four couplings 53 to a control device 74, whicn contains the solenoid valves. One of the lines of the multiple cable 55 serves for supplying pressure to the inside of the relevant collector 1. Since one of the nozzles 2 is actuated only approximately every 20 seconds in the case of one and the same collector 1, the supply of compressed air through a relatively narrow flexible tube is sufficient. Figure 7 shows an embodiment similar to the embodiment according to Figures 1, 2, 5 and 6. It mainly differs from it in that the bores 28 are arranged axially parallel, which is more cost-effective in production, and in that the control chamber 33 is connected to the inner space of the collector 1 via a non-return valve 79. A separate feed line for the collector 1 is therefore not necessary. This variant additionally has the advantage that the control lines 35 are flushed through with compressed air after every actuation of one of the valves 10. This has the effect of cooling the lines 35, which has advantageous effects on their service life and the reguirements for their temperature resistance. Represented in Figure 8 is a beater 8^, which is fastened to a wall 73 of the filter housing 71, in particular to a funnel-shaped constriction in the lower region of the filter housing 71. The beater 84 serves for shaking loose filtered-out particles adhering to the wall 73. The beater 84 has a cylindrical compressed-air storage space 86, built onto which there is a pilot valve 10 very similar to the valve 10 according to Figure 7. The control line 35 is connected to the control chamber 33 by means of a connection 87 on the closure screw 32. The storage space 86 is formed by a tube 88, onto which covers 89, 90 are welded on both sides. The tube 40 is welded onto the cover 89, and the valve housing 25 is screwed onto the tube 40. The tube 40 opens out into a further tube 91, the axis of which is inclined with respect to the horizontal. Guided in the tube 91 is an impact body in the form of a plastic ball 92 with a metal core, preferably a Vulkollan ball with a steel core. The tube 91 is directed at an impact plate 93, which is pressed against the wall 73 by means of a spring 94.

The opening pressure of the non-return valve 79 is adjustable. For this purpose, its valve element 95 is pressed against its seat by means of a spring 96. The preloading force of the spring 96 can be set by a nut 97.

The mode of operation of the beater 84 represented is as follows: m the position of rest, a control pressure, for example of 6 bar, is provided at the control line 35. A pressure reduced by the nonreturn valve 79, for example of 4 bar, prevails in the storage space 86. For initiating an impact, the pressure in the control line 35 is lowered briefly, for example for 0.2 sec, by means of a 3-way solenoid valve, not represented, so that the diaphragm 31 is lifted off the valve seat 30 and the compressed air escapes from the storage space 86 via the bores 28, the valve chamber 29 and the tune 40 into the tuoe 91 and accelerates the ball 92 against the impact plate 93, from which it rebounds after impact. The force of impact can be set by adjusting the opening pressure of the valve 79. Because the ball 92 rebounds immediately after striking the impact plate 93, the wall 73 can subsequently oscillate freely. This is not the case with previously known beaters and makes the beater more efficient. For the beater 84, largely the same parts can be used for the valve 10 as for the valve 10 according to Figure 7, which makes production in higher numbers, that is at lower prices, possible. For the covers 89, 90, the cutouts which are obtained when cutting the central bores m the rings 15, 16 of the annular-gap nozzle 2 according to Figures 1 or 7 can be used for example. Only a single line to the beater 84, namely the control line 35, is required. A separate feed line to the storage space 86 is not necessary.

Claims

Patent claims

1. Device for cleaning filter elements (4, 73), comprising a valve (10) with a valve chamber (29), a valve seat (30), which can be closed by a valve element (31), there being arranged on the side of the valve element (31) away from the valve chamber (29) a control chamber (33) which can be subjected to compressed gas via a control line (35), a compressed-gas chamber (1, 86) , which communicates with the valve chamber (29) , and a non-return valve (79), which allows a flow from the control chamber (33) to the compressed-gas chamber (1, 86) and blocks it in the opposite direction.

2. Device according to Claim 1, the opening pressure of the non-return valve (79) being adjustable.

3. Device according to Claim 1 or 2, the compressed-gas chamber being a collector (1) for feeding cleaning gas to a plurality of axially parallel cleaning nozzles (2, 66) fastened to the collector (1), each cleaning nozzle (2, 66) being assigned one pilot valve (10) each, which valve controls the supply of cleaning gas from the collector (1) to the nozzle opening, each valve (10) being arranged in or on the collector and the cleaning nozzles (2, 66) being screwed to the collector (1) .

4. Device according to Claim 3, the valve housing (25) of the valve (10) bearing against a first wall (24) of the collector (1), the valve housing (25) having bores (28) to the valve chamber (29) and the output of the valve (10) being formed by a tube (40), which passes through the collector (1) and is fastened to the collector by means of a nut (44, 65) screwed onto the tube (40) .

5. Device according to Claim 4, the nozzle being designed as an annular-gap nozzle (2) and having a flange (15, 16) with an annular channel (18), which communicates with the annular gap (19), the flange (15, 16) having a through-bore (21) , through which the tube (40) is inserted, the flange (15, 16) being screwed onto the second wall (46) of the collector (1) by means of the nut (44), which is preferably designed as a cap nut, and the tube (40) having at least one cross-bore (43), opening out into the annular channel (18).

6. Device according to Claim 4, the nozzle (66) being formed coaxially on the nut (65).

7. Device according to one of Claims 4 to 6, an annular disc (42) being fitted into the second wall (46) of the collector (1), lying opposite the first wall (24), the said disc having a central bore (41) through which the tube (40) is inserted, and the annular disc (42) and the valve housing (25) each having a flange (26, 39) , which bears against the relevant wall (24, 46) from outside in a sealing manner.

8. Device according to one of Claims 3 to 7, all the control lines (35) to the pilot valves (10) being laid inside the collector (1) .

9. Device according to Claim 1 or 2, the output of the valve (10) opening out into a tube (91), which contains an impact body (92) which, on actuation of the valve (10), is accelerated by the compressed gas against an impact plate (93), which bears against a wall (73) of a filter housing (71) .

10. Device according to Claim 9, the impact body (92) being a plastic ball with a metal core.