AU2010265842C1

AU2010265842C1 - Slotted inductor

Info

Publication number: AU2010265842C1
Application number: AU2010265842A
Authority: AU
Inventors: John Walter Baker
Original assignee: Outotec Oyj
Current assignee: Metso Outotec Oyj
Priority date: 2009-06-23
Filing date: 2010-06-22
Publication date: 2014-04-10
Anticipated expiration: 2030-06-22
Also published as: AU2010265842A1; WO2010148438A1; EP2445609A4; EP2445609A1; AU2010265842B2; NZ597294A

Abstract

A fabric filter is disclosed including a clean air plenum and a dirty gas side separated by a cell plate which includes concentric rings of holes providing gas communication between the two sections. The holes have connected thereto respective filter media bags for collecting contamination held in suspension in the gas being filtered. In order to clean the filter bags there is provided a back flushing gas pulse generator which includes a main diaphragm valve in direct communication with a hollow rotatable shaft which leads to a gas pulse distributor having arms which sweep across the clean air plenum side of the cell plate. The arms of the high volume low pressure pulse jet manifold have apertures aligned with the respective holes of the cell plate so as to inject into the filter media bags a pulse of clean gas in a reversed direction so as to shake out any contaminants that have been collected in the bags. An inductor is fitted to some or all of the apertures on the manifold arm as required to enhance a flow of back-flush air into each hole in the cell plate. The inductor includes a central passage and a venturi passage to increase air flow.

Description

WO 2010/148438 PCT/AU2010/000780 1 Slotted Inductor Introduction 5 The present invention relates to a baghouse or fabric filter apparatus of the gas pulse type and more particularly to such apparatus which includes an improved nozzle for injecting an air pulse into filter bags to be backflushed. Background 10 Baghouse or fabric filter apparatus for dust collection is known in which a gas stream to be cleaned is directed through an elongate filter bag from its outside to its inside and the bag is periodically cleaned by injecting into it, against the gas stream, a gas pulse which serves to very briefly reverse the direction of gas flow through the filter bag and to thereby remove from the bag particulate matter that had been retained 15 on the filter medium from which the filter bag is constructed. In one known type of such filter low pressure cleaning air is used for cleaning the filter bags. The unique feature of this type of filter is that each pulse valve is able to clean a large number of filter bags. The number of bags flushed by each cleaning pulse valve can be up to 2000 and the length of the filter bags can be up to 8 metres. 20 The cleaning pulse valve is a diaphragm pulse valve and is integrated with a reservoir or tank making a pulse valve/tank assembly. The cleaning air pulse is generated by a rapid opening of the diaphragm valve, which allows the pressurized air in the tank to discharge rapidly into a centre extension pipe. This cleaning air pulse is then delivered to a number of rotating manifold arms that are fitted with nozzles. These 25 nozzles rotate over coaxial rows of filter bags that hang below the rotating manifold arms such that each pulse flushes a plurality of bags in each sector over which a manifold arm is present. US Patent No. 4,854,951 discloses a fabric filter apparatus of the gas pulse type having: 30 a) a housing body including a dirty gas side with an inlet thereto and a clean air plenum with an outlet therefrom; b) a cell plate cell plate mounted in the housing body separating the dirty gas side from the clean air plenum and having a plurality of concentric rings of holes in the cell plate which are circularly spaced thereon, each hole in a ring 35 having a filter bag depending therefrom; c) a gas pulse generator, for generating pulses of back-flushing gas from a single source and having an outlet therefrom; and WO 2010/148438 PCT/AU2010/000780 2 d) a high volume low pressure pulse jet manifold arm extending radially across and spaced above the concentric rings of holes in the cell plate within the clean air plenum and, having an inlet in fluid communication with the outlet of the back-flushing gas pulse generator and a plurality of radially 5 spaced orifices therefrom, each of the orifices being fitted with a nozzle and being spaced to rotationally traverse over and successively fluid communicate with some or all of the holes in a one of the radially spaced concentric rings. In this apparatus the back-flushing gas pulse generator includes a gas reservoir which is located over and connected to the inlet of the high volume low pressure pulse 10 jet manifold arm by a pulsing valve provided between the pulsing tank and the rotating manifold arm to periodically allow a pulse of gas to flow from the pulsing tank, into the manifold arm from which it is directed into filter bags over which the nozzles of the manifold arm are currently located. Typically pulse jet systems are built with a number of housing bodies located 15 adjacent to one another with a corresponding number of gas pulse generators operated in parallel such that one gas pulse generator services each housing body. A pulse tank (i.e. reservoir) of each gas pulse generator is connected to a common supply main from which it is refilled after discharging to clean a set of bags. Therefore gas will flow in reverse toward the supply main from other pulse tanks while one tank is 20 discharged or at a lower pressure when compared to the pressure in the supply main or the other pulse tanks. Successful bag cleaning relies among other things on optimizing the relationship between the total open area of these slotted nozzles and pulse tank volume. The cleaning effectiveness of an individual nozzle depends on the width of 25 that nozzle, the wider the better. There is obviously a limit on the total cumulative width of all the nozzles that can be accommodated by a given size tank and still have effective pulses. There is therefore benefit in improving the cleaning effectiveness of individual nozzles of a given width, so a greater number of nozzles can be used, which then allows additional nozzles to be fitted to the outer rows. This is of benefit 30 as the outer rows have greater bag numbers than the inner rows, so more nozzles are needed to achieve regular cleaning of any one filter bag. Summary In a broad form the present invention may be said to provide a gas filter 35 apparatus having a housing body including a dusty gas section with a main inlet thereto and a clean gas section with a main outlet therefrom; a cell plate mounted in the housing body separating the dusty gas section from the clean gas section and having a plurality holes, each having a filter media sleeve depending therefrom; a gas WO 2010/148438 PCT/AU2010/000780 3 pulse generator mounted on the body for generating pulses of back-flushing gas from a single source and having a generator outlet for discharging gas therefrom; and a rotary back-flushing gas pulse distributor within the clean gas section, including a manifold arm extending across the cell plate and spaced from the holes in the cell 5 plate, having a distributor inlet in fluid communication with the generator outlet and a plurality of spaced orifices, each respective orifice being aligned with one of the holes so as to provide gas communication therewith; the apparatus being characterised in that each of the spaced orifices comprises a nozzle having a first passage formed by a sleeve extending from the manifold arm towards the cell plate and converging as it 10 extends away from the arm, the first passage terminating within a second passage also formed by a sleeve converging as it extends towards a cell plate, the second sleeve being spaced from the first sleeve whereby gas is drawn into the second passage by gas flow through the first passage and the gas flow through the first passage, the gas drawn into the second passage combining with the gas flow through the first passage 15 to flow from an outlet of the second passage. In a preferred form of the invention at least one further passage is provided comprising a sleeve located on the manifold side of the second sleeve and converging into a space between the first sleeve and the second sleeve to form a further passage between the first sleeve and the further sleeve, whereby gas is drawn into the further 20 passage by gas flow through the first and second passages, the gas drawn into the further passage combining with the gas flow through the first passage and the gas flow drawn into the second passage to flow from an outlet of the second passage. The area of the outlet of the second passage is greater than an area of an outlet of the first passage. In at least one embodiment the area of the outlet of the second 25 passage is 2 to 4 times the area of an outlet of the first passage and preferably 2.8 to 3 times the area. The outlet of the second passage extends beyond the outlet of the first passage (i.e. away from the manifold) and in at least one embodiment the extension of the outlet of the first passage is 3 to 7 times the width of the outlet of the first passage and preferably 4.5 to 5.5 times the width of the outlet of the first passage. The second 30 converging sleeve preferably converges at a slower rate than the first converging sleeve such that the walls of second converging sleeve diverge from the walls the first converging sleeve in the direction away from the manifold. The further converging sleeve preferably converges at approximately the same rate as the first converging sleeve such that the walls of the further converging sleeve are substantially parallel 35 with the walls of the first converging sleeve in the direction away from the manifold. The holes in the cell plate will generally be formed in radially spaced, concentric rings with each hole in a ring having a filter media depending therefrom although other configurations are also possible.

WO 2010/148438 PCT/AU2010/000780 4 The manifolds generally extend radially across and spaced from the concentric rings of holes in the cell plate and include a plurality of radially spaced orifices, one respective orifice for each respective ring of holes, each respective orifice subscribing a circular path over the holes of the respective ring of holes. The orifices are 5 preferably aligned with the holes of a respective ring so as to provide successive flushing of the holes in the ring. Brief description of the drawings Hereinafter given by way of example only is a preferred embodiment of the 10 present invention described with reference to the accompanying drawings in which: Fig. 1 is a perspective top view of a filter installation having four individual sets of pulse jet filters; Fig. 2 is a vertical sectional view through an upper part of apparatus according to the present invention; and 15 Fig. 3 is a side view of the gas pulse generator of the apparatus of Fig. 2 on an enlarged scale. Fig. 4 is a schematic diagram of a slotted nozzle item 25 from figure 2, for a rotating manifold arm. 20 Detailed description Fig. 1 provides an overview of the bag house or fabric filter apparatus 100 for dust collection to which the present invention applies. The installation illustrated in Fig. 1 has 4 pulse jet filters 101, 102, 103, 104 constructed in a single structure. Each Pulse jet filter includes an air pulse generator 18 supplied from a common blower 105 25 via a common supply line 106 and individual branch supply lines 51. Inlet ducting 107 under the baghouse 100 provides dirty air to inlets 108 in the bottom of the apparatus. The individual filter apparatus 10, as is best seen in Fig. 2 comprises: (a) a housing 11 which includes a dirty gas side 12 having an inlet 108 (see 30 Fig. 1) and a clean air plenum 13 with an outlet 109 (see Fig. 2); (b) a cell plate 14 mounted in the housing 11 and separating the dirty gas side 12 from the clean air plenum 13 and having a plurality of concentric rings of holes 15 circularly spaced on the cell plate 14; each hole 15 has a filter bag 16 depending therefrom. Each of the bags 16 is supported against collapse by a wire cage 17; 35 (c) an air pulse generator 18 mounted on the housing 11 for generating pulses of back-flushing gas; and WO 2010/148438 PCT/AU2010/000780 5 (d) a high volume low pressure pulse jet manifold arms 23, 24 extending radially across and spaced above the concentric rings of holes 15 in the cell plate 14 within the clean air plenum 13 of the housing 11. The housing 11, cell plate 14, and filter bags 15 may be of entirely 5 conventional construction and will not be further described herein. The high volume low pressure pulse jet manifold 19 includes a vertical extension tube 21 which is in fluid communication with an outlet tube or blow pipe 22 of the gas pulse generator 18. At its lower end tube 21 is connected to a number of radially extending gas manifold arms 23 and 24. Each manifold arm 23 and 24 extends across 10 and above the cell plate 14 and carries a plurality of downwardly directed nozzles 25. The nozzles 25 of manifold arm 23 are positioned so that they respectively rotate over one of the even numbered rings of holes 15 while the nozzles 25 of the manifold arm 24 are positioned so that they respectively rotate over the odd numbered rings of holes 15. The number of arms can also vary. 15 The nozzles 25 of the manifold arms 23, 24 are so positioned that they distribute cleaning air pulses to clean all filter bags evenly. Clearly the manifold arms 23, 24 can be produced in alternative manners as a matter of design preference. For example, the nozzle 25 of each manifold 23 and 24 can be arranged as a plurality of equally radially spaced pairs, each nozzle 25 of a respective pair aligning upon 20 rotation with its respective ring of holes 15. Referring to Fig. 4, each nozzle 25 incorporates a simple primary nozzle 125 and a slotted inductor 140 to improve the effectiveness of the cleaning air pulse in the filter bag. The primary nozzle 125 comprises a first converging sleeve and the slotted inductor 140 comprises two additional (i.e. second and third) converging sleeves 141, 25 142. A lower or second converging sleeve 141 encompasses the primary nozzle adjacent the outlet port 143 of the primary nozzle 125 and extends below the outlet port 143 by a distance 145 to form a secondary outlet port 144. The third converging sleeve 142 encompasses of the primary nozzle 125 toward the manifold relative to the second converging sleeve 141 and converges towards the space between the second 30 converging sleeve 141 and the primary nozzle 125 to form a first pair of slots between the third converging sleeve 142 and the second converging sleeve 141 and a second pair of slots between the third converging sleeve and the sides of the primary nozzle 125. Air is drawn through the first pair of slots 151 between the third converging sleeve 142 and the second converging sleeve 141 as well as through the second pair of 35 slots 152 between the third converging sleeve and the sides of the primary nozzle 125 a result of a low pressure area created by the flow of the air 150 through the port 143 of the primary nozzle 125 and the secondary port 145 formed by the second converging sleeve.

WO 2010/148438 PCT/AU2010/000780 6 The resultant flow 153 through the secondary port 145 comprises the combination of air flows 150, 151 & 152. This increased flow through each nozzle 25 and into a respective bag to be back flushed results in a higher flow of flushing air into the respective bag for a given flow through the primary nozzle 125. This in turn 5 can allow more nozzles to operate from a single pulse tank, as each primary nozzle 125 can be narrower. The area of the secondary port 144 is greater than the area of the port 143 of primary nozzle 125 and in the illustrated embodiment the area of the secondary nozzle is approximately 2.8 times the area of the port 143 in the primary nozzle 125. The 10 secondary port 145 extends beyond the port 143 (i.e. away from the manifold) and in the illustrated embodiment the extension of the secondary port is approximately 5 times the width of the port 143 of the primary nozzle 125. The second converging sleeve 141, in the illustrated embodiment, converges at a slower rate than the primary nozzle 125 such that the walls of the sleeve 141 diverge from the walls of the primary 15 nozzle 125 in the direction away from the manifold 23, 24. The third converging sleeve 142, in the illustrated embodiment, converges at approximately the same rate as the primary nozzle 125 such that the walls of the sleeve 142 are substantially parallel with the walls of the primary nozzle 125 in the direction away from the manifold 23, 24. This arrangement provides an increase in pulse pressure in the bag 20 of from 5 to 20% depending on the configuration. The tube 21 and manifolds 23 and 24 are supported by an upper bearing 26 connected to the housing 11 and by a support 27 and a lower bearing 28. A seal 36 is provided around the tube 21 where it penetrates the housing 11. Referring to Fig. 3 the air pulse generator 18 is illustrated in greater detail. 25 Associated with the upper bearing 26 is a drive assembly comprising a motor 43 and a gearbox 42 which cause the high volume low pressure pulse jet manifold 19 to rotate The air pulse generator 18 includes a body 40 which is mounted directly above housing 11. The body 40 constitutes an air pulse tank or reservoir which receives air from the blower 105 through the common supply line 106 (see Fig. 1) and the branch 30 supply line 51, isolation valve 52, a compression connector 53 and inlet stub 44. The housing 40 includes a substantially cylindrical side wall 54 and a curved top wall 55 and bottom wall 49. A main diaphragm valve assembly 56 is bolted onto brackets 45 extending from the top wall 55 and sits in concentric alignment with the blow pipe 22. The diaphragm valve 56 includes a normally closed two way unloading valve 35 57 which cooperates with a valve seat 60 formed on the upper end of the blow pipe 22. The valve 57 comprises a main valve diaphragm 58 made of a neoprene impregnated woven nylon fabric sheet which has two small diametrically spaced orifices in it (not shown). A circular seal plate 59 and a backing plate 61 are WO 2010/148438 PCT/AU2010/000780 7 connected to the diaphragm 58 concentrically therewith. The seal plate 59 serves to make sealing engagement with the valve seat 60 at the upper end of the blow pipe 22. A coned cover 62 having a flat centre (top) section 63 incorporates an O.D. flange 64 which is bolted to the bracket 45. A bumper 65 is bonded to the underside 5 of the flat section 63 of cover 62 in concentric relation therewith. A main diaphragm spring upper retainer cup 66 mounts a main valve exhaust port 67 in concentric and inverted relationship atop the cover section 63. A main valve compression spring 70 seats in the upper retainer cup 66 and bears against the backing plate 61 to urge the seal plate 59 against the valve seat 60. 10 A reverse logic, normally closed, two-way pilot diaphragm valve 68 is mounted on the top side of cover 62. The pilot diaphragm valve 68 comprises a cylindrical body 69 which encompasses the spring retainer cup 66 and main valve exhaust port (not shown) and has a plurality of exhaust ports (not shown) in the wall thereof. 15 A solenoid operated or pneumatically-operated trigger valve 74 sits on top of the pilot diaphragm valve 68 and when operated, dumps the pilot diaphragm valve to generate a pulse of gas by unloading the main valve thereby allowing the gas pulse to flow through the blow pipe 22 into the high volume low pressure pulse jet manifold 19. The valves 56, 68 and 74 are housed within a silencer 81 to reduce operating 20 noise. It will be recognised by persons skilled in the art that numerous variations and modifications may be made to the invention as described above without departing from the spirit or scope of the invention as broadly described.

Claims

1. A gas filter apparatus having a housing body including: a dusty gas section with a main inlet thereto and a clean gas section with a 5 main outlet therefrom; a cell plate mounted in the housing body separating the dusty gas section from the clean gas section and having a plurality holes, each having a filter media sleeve depending therefrom; a pulse generator mounted on the body for generating pulses of back-flushing 10 gas from a single source and having a generator outlet for discharging gas therefrom; and a rotary back-flushing gas pulse distributor within the clean gas section, including a manifold arm extending across the cell plate and spaced from the holes in the cell plate, having a distributor inlet in fluid communication with the generator 15 outlet and a plurality of spaced orifices, each respective orifice being aligned with one of the holes so as to provide gas communication therewith; the apparatus being characterised in that each of the spaced orifices comprises a nozzle having a first passage formed by a first converging sleeve which extends from the manifold arm towards the cell plate and converges as it extends away from 20 the arm, the first passage terminating within a second passage formed by a second converging sleeve which converges as it extends towards a cell plate, the second converging sleeve being spaced from the first converging sleeve whereby gas is drawn into the second passage by gas flow through the first passage, the gas drawn into the second passage combining with the gas flow through the first passage to flow 25 from an outlet of the second passage.

2. The gas filter apparatus of claim 1 wherein at least one further passage is provided comprising a further converging sleeve located on the manifold side of the second sleeve and converging into a space between the first converging sleeve and the second converging sleeve to form a further passage between the first converging 30 sleeve and the further converging sleeve.

3. The gas filter apparatus as claimed in claim 2 wherein gas is drawn into the further passage by gas flow through the first and second passages, the gas drawn into the further passage combining with the gas flow through the first passage and the gas flow drawn into the second passage to flow from an outlet of the second passage. 35

4. The gas filter apparatus as claimed in claim 1 wherein the area of the outlet of the second passage is greater than an area of an outlet of the first passage. 9

5. The gas filter apparatus as claimed in any one of claims I to 4 wherein the area of the outlet of the second passage is 2 to 4 times the area of an outlet of the first passage.

6. The gas filter apparatus as claimed in claim 5 wherein the area of the outlet of 5 the second passage is 2.8 to 3 times the area of an outlet of the first passage.

7. The gas filter apparatus as claimed in any one of claims 4 to 6 wherein the outlet of the second passage extends beyond the outlet of the first passage.

8. The gas filter apparatus as claimed in any one of claims 4 to 7 wherein an extension of the outlet of the first passage is 3 to 7 times a width of the outlet of the 10 first passage.

9. The gas filter apparatus as claimed in claim 8 wherein the extension of the outlet of the first passage is 4.5 to 5.5 times the width of the outlet of the first passage.

10. The gas filter apparatus as claimed in any one of claims 1 to 9 wherein the further converging sleeve converges at generally the same rate as the first converging 15 sleeve such that the walls of the further converging sleeve are substantially parallel with the walls of the first converging sleeve.

11. The gas filter apparatus as claimed in any one of claims I to 10 wherein the second converging sleeve converges at a slower rate than the first converging sleeve such that the walls of second converging sleeve diverge from the walls the first 20 converging sleeve in the direction away from the manifold.

12. The gas filter apparatus as claimed in any one of claims 1 to 11 wherein the holes in the cell plate are formed generally in radially spaced, concentric rings with each hole in a ring having a filter media depending therefrom.

13. The gas filter apparatus as claimed in any one of claims I to 12 wherein the 25 manifold extends generally radially across and spaced from the concentric rings of holes in the cell plate and include a plurality of radially spaced orifices, one respective orifice for each respective ring of holes, each respective orifice subscribing a circular path over the holes of the respective ring of holes.

14. The gas filter apparatus as claimed in claim 12 or 13 wherein the orifices are 30 aligned with the holes of a respective ring so as to provide successive flushing of the holes in the ring.