GB1598714A - Discharge electrode - Google Patents

Description

PATENT SPECIFICATION ('

( 21) Application No 23724,'80 ( 22) Filed 11 April 1978 ( 19) ( 62) Divided Out of No 1 598 713 > ( 31) Convention Application No 788 171 ( 32) Filed 18 April 1977 in ( 33) United States of America (US)

C ( 44) Complete Specification published 23 Sept 1981

Lf N ( 51) INT CL: B 03 C 3/41 ( 52) Index at acceptance B 2 J 101 202 206 K ( 54) DISCHARGE ELECTRODE ( 71) We, Jo Y MANUFACTURING COMPANY, a corporation organised and existing under the laws of the State of Pennsylvania, United States of America, located at Oliver Building, 535 Smithfield Street, Pittsburgh,

State of Pennsylvania, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: -

This invention relates to a discharge electrode means such as used in an electrostatic precipitator.

In the art of gas cleansing by electrostatic precipitation it is well known to provide laterally spaced apart and oppositely charged discharge and collector electrode means within an electrostatic precipitator for the purpose of arresting particulate matter from a stream of gas passed therethrough.

Among conventional discharge electrode means are the so-called pole or mast type electrodes which typically have been characterized by their elongate, formed structure including variously formed protrusions thereon to promote efficient corona discharge, for example as shown in U S Patents 3,985,524: 3,200,566, 3,616,608; 3,158,453; 3,158,454 and 3,257,779 among many others.

Although known mast or pole type discharge electrodes have generally served the intended purposes they have nevertheless often been subject to serious deficiencies For example, conventional electrode structures and particularly those formed in relatively thin sheet metal often have 'been subject to considerable lateral deflection as a result of periodic rapping or by their tendency to act as airfoils thus causing a pressure differential in the gas flowing at high velocity over the electrode Excessive electrode deflection may result in arcing between adjacent discharge and collector electrodes thereby degrading dust collecting efficiency or causing localized burning of the electrodes In the prior art, the requisite structural rigidity in such electrodes has been provided by such means as the use of heavier gauge sheet metal than would otherwise be required or 1 598714 by affixing additional structural members to the electrode This approach seriously complicates electrode fabrication, results in unduly heavy and cumbersome electrodes and is unnecessarily wasteful of materials 55 Additionally, many prior mast or pole type discharge electrodes have included integrally formed stiffener means adjacent the electrode edges from which corona discharge emanates Thus the design consideration for 60 desirable corona discharge and for required structural rigidity have often been in conflict and the difficulty of optimizing the electrode design has been correspondingly increased 65 Furthermore, the formed protrusions on prior electrodes constitute, in effect, point sources of corona emission whereby the resulting distribution of corona emission over the length of the electrode is quite 70 non-uniform.

According to this invention there is provided an electrode assembly for use in an electrostatic precipitator, said electrode assembly being operable to propagate corona 75 discharge upon application of a suitable voltage differential thereto, said electrode assembly comprising: at least a pair of collector electrodes disposed in laterally spaced generally parallel relationship; and at least 80 one elongated discharge electrode disposed laterally intermediate said collector electrodes, said discharge electrode including an elongated body member having corona discharge means extending longitudinally there 85 of in a manner such that the corona discharge from said discharge electrode defines a pair of spaced apart longitudinally extending lines of corona emission, which lines extend substantially in a common plane 90 generally parallel to said collector electrodes; said discharge electrode including an intermediate body portion extending intermediate said corona discharge means and generally parallel to said common plane and said in 95 termediate body portion including formed non-discharging stiffener means protruding outwardly thereof toward said collector electrodes whereby said electrode means provides, upon application thereto of a suitable 100 Figure 8 is an elevation taken on line VIII-VIII of Figure 7; Figure 9 is a transverse cross-section taken on line IX-IX of Figure 7; and Figure 10 is an elevation similar to Figure 70 7 showing a variation of the embodiment of Figure 7.

There is generally indicated at 10 in Figure 1 an electrostatic precipitator including a discharge electrode means in accord 75 ance with the present invention For purposes of illustration the precipitator 10 is shown in simplified schematic form and of course it is to be understood from the outset that such simplification is not intended to 80 unduly limit the scope of the invention described.

Precipitator 10 comprises a closed housing 12 which encloses a space 14 and includes gas inlet and outlet means 24, 26, 85 respectively, whereby a flow of gas may be directed through space 14 as indicated by arrows 28 for cleansing Within space 14 there is carried at least one discharge electrode bank 21 assembled from a plurality of dis 90 charge electrodes 20 Electrodes 20 are carried in generally vertically extending, parallel orientation by respective pairs of upper and lower electrode support members 15, 30 such that the electrodes 20 extend 95 transversely across the gas flow path with the plane of each electrode 20 generally aligned with the direction of gas flow Members 15, 30, supportingly and electrically conductively engage respective upper and lower end por 100 tions of the electrodes 20 The upper support members 15 are suitably secured to a rigid support frame 16 Frame 16 in turn is carried by and electrically insulated from housing 12 as by an elongated upwardly 105 extending frame hanger member 17 which is supportingly engaged by a well known compression insulator 18 such that frame 16 and the electrode bank 21 carried thereby are suspended within the flow path of gas 110 passed through space 14 Adjacent the lower ends of respective electrodes 20, the lower support members 30 are suitably secured to a base frame 22 which is electrically insulated from housing 12 as by the surround 115 ing air space.

As is well known, there may be provided a plurality of generally parallel, laterally spaced electrode banks 21 within space 14 with conventional grounded collector elec 120 trode plates 23 also carried within space 14 intermediate respective pairs of adjacent discharge electrode banks 21 and parallel there to whereby the discharge electrodes 20 may be electrically energized by any suitable 125 means (not shown) to set up corona discharge therefrom in the space between each discharge electrode 20 and the respective adjacent collectors 23 Accordingly, in practice the gas stream passed through space 14 130 voltage differential, corona discharge in a pattern of substantial symmetry about said common plane and substantial uniformity along said lines of corona emission.

Preferably said body member is a unitary member having said stiffener means and said corona discharge means formed integrally therewith.

Conveniently said corona discharge means extend at or adjacent the longitudinal edges of said body member.

Advantageously said corona discharge means includes longitudinally extending pluralities of elongated tabs and intervening is notches formed adjacent said longitudinal edges.

In the preferred embodiment said corona discharge means are substantially coplanar with said common plane.

Preferably alternate ones of said tabs are outstruck in opposite directions from said common plane.

Advantageously the longitudinal extent of at least some of said tabs is at least as great as the longitudinal extent of one of said intervening notches adjacent thereto.

Preferably said at least some of said tabs is a majority of said tabs.

Conveniently said formed stiffener means is of a generally serpentine cross-sectional form, or of a generally circular crosssectional form.

The invention also relates to an electrostatic precipitator provided with such an assembly.

In order that the invention may be more readily understood, and so that further features thereof may be appreciated the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a schematic cross-section of an electrostatic precipitator including an discharge electrode assembly in accordance with the present invention; Figure 2 is an enlarged fragmentary portion of Figure 1 showing an upper end portion of a discharge electrode forming part of an assembly in accordance with the invention.

Figure 3 is a transverse section of the electrode of Figure 2 taken on line III-III of Figure 2; Figure 4 is a transverse section similar to Figure 3 showing a variation of the embodiment of Figure 3; Figure 5 is a transverse section similar to Figures 3 and 4 showing yet another variation of the embodiment of Figure 3; Figure 6 is a partial side elevation taken on line VI-VI of Figure 5; Figure 7 is a partial side elevation of another electrode forming part of an assembly which is a preferred embodiment of the invention; 1,598,714 1,598,714 is cleansed by electrical precipitation of entrained particulate contaminants and deposition thereof on the collector electrode plates 23 in the well known manner Conventional rapping techniques are employed to dislodge the accumulated contaminants from collector electrodes 23 for disposal.

Inasmuch as electrostatic precipitators such as described hereinabove and the operation thereof are well known to those versed in the art, further detailed description thereof is considered unnecessary for an understanding of the present invention.

In one preferred embodiment of the invention as shown in Figs 2 and 3, each electrode 20 includes an elongated, generally planar and a unitary electrode body 36 formed as by roll forming or similar processes and comprising: a central axially extending elongated stiffener or support portion 38 formed intermediate the transversely opposed longitudinal edges 58 of the body 36 and corona discharge portions shown as elongated tabs 40 formed adjacent respective edges 58 to define respective lines of corona emission extending therealong Supporting web portions 42 extend intermediate respective tabs 40 and stiffener portion 38 The electrode portions 38, 40 and 42 ordinarily may be coextensive throughout substantially the entire length of body 36.

Stiffener portion 38 is so formed as to define a longitudinally extending opening 50 substantially coextensive therewith The opening 50, shown as having a circular cross section, is adapted to have secured therewithin the cooperably formed support members 15 and 30 adjacent respective opposed end portions of body 36 (only the upper end portion is shown in Fig 2) as by weldments whereby members 15 and 30 are electrically conductively affixed to body 36 As shown in Figs 2 and 3, body 36 is comprised of two identical and generally planar elongated, formed plates 44, each being formed for example from No 16 gauge steel to have a thickness of approximately 0 04 to 0 08 inches Each plate 44 includes a longitudinally extending semi-circular outward bend 48 intermediate the longitudinal edges thereof which forms one half of the stiffener portion 38, and a plurality of the longitudinally spaced tabs 40 spaced transversely to one side of bend 48 adjacent one longitudinal edge of each plate 44 In each plate 44, a longitudinal web portion 42 a extends transversely intermediate the bend 48 and tabs 40, and a second elongated web portion 42 b extends transversely outward from bend 48 generally coplanar with and in the opposite direction from web 42 a In assembly, two plates 44 are positioned adjacent one another so as to extend in generally parallel coplanar relation with the inner or concave sides of the bends 48 coaxially aligned and facing each other, and with the tabs 40 of each plate 44 being spaced laterally in opposite directions as shown in Fig.

3 The two plates 44 are affixed rigidly together in the position described as by a 70 plurality of resistance weldments 52 spaced longitudinally at intervals to rigidly secure together adjacent web portions 42 a and 42 b such that the juxtaposed outward bends 48 form the stiffener portion 38 and opening 75 Of course, any suitable alternative fastening means may be employed in lieu of weldments 52, for example other types of welding, threaded fasteners or rivets.

Longitudinally adjacent ones of tabs 40 80 are shown as being formed by intervening slots 39 and as shown may be bent or outstruck alternately in opposite directions from the plane of web portion 42 at an angle of approximately 45 degrees, for example such 85 that alternate tabs 40 provide corona emission to the collector plates 23 on opposite sides of the discharge electrode 20 Of course, the particular angle, shape and size of tabs 40 may be varied to achieve the 90 most desirable and efficient pattern of corona emission therefrom For example, in another preferred embodiment of this invention which is described in detail hereinbelow tabs 40 may be substantially coplanar with 95 web 42 such that corona will propagate from each tab to the collector plates 23 on both sides of the discharge electrode In any case, one desirable property in the described discharge electrode is that the pattern of 100 corona discharge to collectors on opposite sides of the discharge electrode is generally symmetrical about the plane of the discharge electrode By this it is meant that approximately equal corona discharge propagates 105 from one edge of the electrode 20 to each of the adjacent collector electrodes 23.

Fig 4 illustrates a variation of the embodiment of Figs 2 and 3 wherein electrode body 36 is comprised of a generally planar 110 elongated formed plate 441 having a formed semi-circular outward bend 481 which extends longitudinally of plate 441 and is located centrally intermediate opposed longitudinal edges 58 thereof Corona discharge 115 means such as outstruck tabs 40 are formed adjacent the edges 58 of plate 44 ' and identical coplanar web portions 421 extend intermediate the bend 481 and respective tabs In this embodiment an elongated stif 120 fener portion 381, including an elongated cylindrical opening 501 adapted to receive support members 15 and 30, is formed by bend 48 ' in cooperation with an elongated, formed means shown as a member 54 having 125 an elongated semi-circular outward bend 62 formed intermediate transversely extending coplanar web portions 64 thereof The members 441 and 54 are positioned with the respective inner or concave sides of bends 130 1,598,714 481 and 62 facing each other and coaxially aligned to form the stiffener portion 381 and opening 501 in the manner indicated hereinabove for the first described embodiment, and the respective web portions 64 and 421 are affixed rigidly together in any suitable manner as hereinabove described to form the substantially unitary body 36 ' Elongated means 54 may be comprised of a plurality of distinct members affixed at longitudinally spaced intervals along the member 441 if desired.

Another variation on the embodiment of Figs 2 and 3 is shown in Figs 5 and 6 wherein electrode body 361 " comprises a single, elongated, generally planar formed member 4411 having an elongated stiffener portion 38 " 1 and identical, coplanar web portions 421 " extending transversely in opposite directions therefrom Tabs 40 are formed adjacent respective opposed outer edges 58 of member 4411 In this embodiment, a cylindrical opening 50 " 1 to receive support members 15 and 30 is formed by a plurality of longitudinally adjacent segments 66 of stiffener portion 381 " being outwardly formed alternately in opposite directions.

In each of the hereinabove and hereinbelow described variations, the stiffener portions 38-381 " are suitably formed and dimensioned to provide the structural rigidity considered sufficient to render the electrode body 36-361 " substantially self supporting in that only the end support members 15 and 30 are needed to support the electrode and that portion of the electrode body extending longitudinally intermediate the respective electrode body ends has no support means other than its own formed structure.

The openings 50-50 "' as described may be substantially coextensive with stiffeners 38-38 " 1 whereby if desired the support members 15 and 30 may be longitudinally opposed end portions of a single elongated member disposed within the opening 50 and extending throughout the length of body 36 to provide added structural rigidity therefor.

If members 15 and 30 engage only the opposed end portions of the body 36, the stiffener portion 38 intermediate the end portions engaging members 15 and 30 need not necessarily be formed to include the opening 50, for example as in the hereinbelow described embodiment.

In Figs 7, 8 and 9, there is shown another preferred embodiment of the invention wherein the electrode body 361 "' includes a formed plate member 70 having a generally serpentine or S-curved longitudinally extending stiffener portion 72 formed laterally intermediate the longitudinal edges 74 thereof.

Generally coplanar side portions 76 of plate are spaced laterally to either side of stiffener portion 72 and each has formed therein corona discharge means such as a plurality of longitudinally spaced tabs 78 and intervening notches 80 The corona discharge tabs 78 may be coplanar with each other and with side portions 76 as shown or may be alternately outstruck as described herein 70 above The dimensions and spacing of notches 80 may be varied to alter the current-voltage characteristics and hence the corona discharge characteristics of the electrode For example, it may be desirable that 75 the electrode 20 have a current-voltage characteristic approximating that of a pair of laterally spaced, parallel-wire discharge electrodes One suitable configuration is shown in Fig 10 wherein the longitudinal extent 80 of tabs 78 is approximately equal to the longitudinal extent of notches 80 A similar configuration results from the tabs in the embodiment of Fig 3 being of substantially equal longitudinal extent and being out 85 struck in opposite directions It should be noted, however, that in general the longer the notches 80 are in relation to the length of the tabs 78, the more the corona propagation from the electrode will deviate from 90 longitudinal uniformity As notches 80 are lengthened and tabs 78 correspondingly shortened, the corona propagation pattern will approach that of plural, longitudinally spaced discharge points In a variation of 95 the Fig 10 configuration (not shown) the alternate notches 80 and tabs 78 formed in the opposite edges 74 of plate 70 may be longitudinally offset or staggered in such a manner that each tab 78 in one edge 74 is 100 transversely aligned with a notch 80 formed in the opposite edge 74 In an alternate embodiment the corona discharge means may be comprised of a continuous edge portion of the discharge electrode having no cutouts 105 or notches therein.

If corona emission from the discharge electrodes must be curtailed, as for example to promote the uniform current flow or corona discharge to the collectors near the 110 upper and lower ends of the body 36 whereat edges 74 are disposed laterally adjacent corresponding edge portions of collector plates 23, electrically conductive shroud means 82 may be employed as shown to 115 "soften" the contour of the electrode thereat by eliminating exposed edge portions and curtailing corona discharge from the covered edge portions As shown, shrouds 82 may be formed as elongated, generally tubular 120 members each having a longitudinally extending through slot 84 which receives the edge 74 of plate 70 whereby the edges of slot 84 grip plate 70 to secure the shroud 82 thereto 125 The formed plate member 70 extends intermediate frames 16, 22 and is secured thereto by respective upper and lower support members 151, 301 As shown, support member 151 comprises a formed body hav 130 1,598,714 ing a transversely extending upper body portion 86 by which the support 151 is releasably secured to a cooperably formed lower portion 88 of frame 16 as by threaded fasteners 90, and a pair of inwardly and downwardly converging side portions 92 the lower ends of which receive the respective upper ends of electrode side portions 76 therebetween for securing thereof as by threaded fasteners 94 In similar fashion an upwardly extending end portion 96 of generally H-shaped, elongated, lower alignment support 301 is secured by threaded fasteners 98 to the lower ends of respective electrode side portions 76, and the lower ends of support 301 is secured by threaded fasteners 100 to frame 22.

As will be appreciated the description hereinabove, relates to an improved discharge electrode assembly of the pole or mast type for electrostatic precipitators which is uncomplicated in fabrication and assembly, highly durable and sufficiently rigid by virtue of integrally formed stiffener portions therein to resist excessive lateral deflections without being wasteful of materials in fabrication.

Although only certain preferred embodiments of the invention have been described herein it is to be understood that the invention may be practiced in numerous alternative embodiments with various modifications thereto without departing from the scope thereof as defined by the appended claims For example: openings may be formed in web portions 42 to provide a lighter weight electrode assembly; the support members 15 and 30 may comprise tubular members or solid bars of any suitable cross section with the cross section of respective openings 50 being cooperably formed; the tabs 40 may be formed and positioned according to any of numerous suitable designs, for example a sawtooth configuration; the electrodes may be assembled from plural elongated electrode portions connected end to end; an electrode may combine elements of the several described embodiments in a single structure; and the like.

Reference is made to copending Application No 14086/78 (Serial No 1598713) from which the present application is described and which relates to an elongated corona discharge electrode for use in an electrostatic precipitator comprising: an elongated electrode body having an axial extent and a lateral extent transverse of said axial extent wherein said lateral extent is defined transversely intermediate a pair of laterally spaced apart longitudinally edge portions formed integrally with said body which are axially coextensive with said body; said lateral extent including an intermediate portion located intermediate a pair of laterally spaced apart side portions of said body with each of said pair of side portions including one of said edge portions and extending laterally inwardly therefrom; said electrode including axially extending formed stiffener means located entirely within said intermediate portion of said lateral extent of said body and axially extending corona discharge means located entirely within at least one of said pair of said portions.

Claims (14)

WHAT WE CLAIM IS:-

1 An electrode assembly for use in an electrostatic precipitator, said electrode assembly being operable to propagate corona 80 discharge upon application of a suitable voltage differential thereto, said electrode assembly comprising: at least a pair of collector electrodes disposed in laterally spaced generally parallel relationship; and at least 85 one elongated discharge eectrode disposed laterally intermediate said collector electrodes, said discharge electrode including an elongated electrode body member having corona discharge means ex 90 tending longitudinally thereof in a manner such that the corona discharge from said discharge electrode defines a pair of spaced apart longitudinally extending lines of corona emission, which lines 95 extend substantially in a common plane generally parallel to said collector electrodes; said discharge electrode including an intermediate body portion extending intermediate said corona discharge means and generally 100 parallel to said common plane and said intermediate body portion including formed non-discharging stiffener means protruding outwardly thereof toward said collector electrodes whereby said electrode means pro 105 vides, upon application thereto of a suitable voltage differential, corona discharge in a pattern of substantial symmetry about said common plane and substantial uniformity along said lines of corona emission 110

2 An electrode assembly as claimed in claim 1 wherein said body member is a unitary member having said stiffener means and said corona discharge means formed integrally therewith 115

3 An electrode assembly as claimed in claim 1 or 2 wherein said corona discharge means extend at or adjacent the longitudinal edges of said body member.

4 An electrode assembly as claimed in 120 claim 3 wherein said corona discharge means includes longitudinally extending pluralities of elongated tabs and intervening notches formed adjacent said longitudinal edges.

An electrode assembly as claimed in 125 claim 4 wherein said corona discharge means are substantially coplanar with said common plane.

6 An electrode assembly as claimed in claim 4 or 5 wherein alternate ones of said 130 1,598,714 tabs are outstruck in opposite directions from said common plane.

7 An electrode assembly as claimed in claim 4, 5 or 6 wherein the longitudinal extent of at least some of said tabs is at least as great as the longitudinal extent of one of said intervening notches adjacent thereto.

8 An electrode assembly as claimed in claim 7 wherein said at least some of said tabs is a majority of said tabs.

9 An electrode assembly as claimed in any one of the preceding claims wherein said formed stiffener means is of a generally serpentine cross sectional form.

10 An electrode assembly as claimed in any one of claims 1 to 8 wherein said formed stiffener means is of a generally circular cross sectional form.

11 An electrode assembly substantially as hereinbefore described with reference to and as shown in Figures 1 to 3, of the accompanying drawings.

12 An electrode assembly substantially as hereinbefore described with reference to and as shown in Figures 5 and 6 of the accompanying drawings.

13 An electrode assembly substantially as hereinbefore described with reference to and as shown in Figures 7 to 9 of the accompanying drawings.

14 An electrode assembly substantially as hereinbefore described with reference to and as shown in Figure 10 of the accompanying drawings.

An electrostatic precipitator having an electrode assembly according to any one of the preceding claims.

FORRESTER, KETLEY & CO Chartered Patent Agents, Forrester House, 52 Bounds Green Road, London, Nll 2 EY, also at Rutland House, 148 Edmund Street, Birmingham B 3 2 LD, and Scottish Provident Building, 29 St Vincent Place, Glasgow GI 2 DT.

Agents for the Applicants.

Printed for Her Majesty's Stationery Office by Burgess & Son (Abingdon), Ltd -1981 Published at The Patent Office, 25 Southampton Buildings, London, WC 2 A l AY from which copies may be obtained.