Note: Descriptions are shown in the official language in which they were submitted.
~136068
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This is a division of Canad.ian Application 300,045
filed rSarch 30, 1978.
In the art of gas cleansing by e~ectrostatic
precipitation it is well known to provide'laterally spaced
apar~ and oppos~teIy charged discharge and'collector
electrode means within an electrostatic precipitator for,
the purpose of arresting particulate matter from a stxeam
of gas passed therethrough.' Among conventlonal discharge
electrode means are the so-called pole or mast type
electrodes which typica~ly have been chaxacteriæed by their
.: .
- elongated, fonmed structure inc~uding variously oxmed
protrusions thereon to promote efficient corona discharge,
for ~Kample as shown in U.S. patents 3,985,524, ~,200,56~'
3,616,608, 3,~58,453, 3,158,454 and 3,25?,779 among many
others.
Al~hough known mas~ or pole type dLs~ha~ge
electrodes have'generally ser~ed ~he intended purpo~e~ ~hey
have neverthe~ess often been subiect to serîous deficien-
cies. For example, conventional electrode structures and
particularly those formed in re~atively thin sheet metal
of~en have been subject to considerable lateral defleetion
as a result of periodic rapping or by their tendency to
act as airfoils thus causing a pressure differentlal in the
'gas flowing at high velocity over the electrode. Excessiv~
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 requisi~e structural
rigidity in such electrodes has been provided by such means
as the use of heavier gauge sheet metal than would other-
wise be required or by af~ixing additional structural
members to the electrode.' This approach seriously
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complicates electrode fabrication, results in unduly
heavy and cumbersome electrodes and is unnecessarily
wasteful of materials. 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 con-
siderations for 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.
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 non-
uniform.
These and other deficiencies of prior mast type
discharge electrodes are alleviated by the present invention
according to which there is provided an elongated, formed
discharge electrode having support or stiffener means formed
integral therewith intermediate the corona emitting electrode
edge portions. The electrode of this invention additionally
offers improved corona propagating means and enhanced
durability and simplicity of fabrication.
In accordance with the present invention, therefore,
there is provided a discharge electrode adapted for use in an
electrostatic precipitator for propagation of corona discharge.
The discharge electrode includes an elongated electrode
assembly having an elongated support means which is
substantially longitudinally coextensive with at least a
major portion of the longitudinal extent of the electrode
assembly and is located laterally intermediate a pair of
laterally spaced apart longitudinal side portions of the
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assembly and wherein at least one of the side portions
is of a form to permit corona discharge therefrom. The
electrode assembly comprises a pair of elongated formed
body elements each substantially coe~tensive with the
electrode assembly. Each of the body elements includes a pair
of laterally spaced apart edge portions longitudinally
~` coextensive therewith and an elongated formed intermediate
portion substantially coextensive therewith and spaced
laterally from at least one of the pair of edge portions.
The pair of body elements are disposed with respect to
each other and fixedly secured together to form the electrode
assembly in a manner that the at least one edge portion
of the body element forms the laterally outermost extent
of a respective one of the side portions and the respective
formed intermediate portions of the body elements cooperate
to form the elongated support means. At least one of the
body elements includes formed corona discharge means
extending longitudinally adjacent at least one edge portion
thereof and spaced laterally from the elongated support means.
These and other objects and advantages of the
invention are more fully specified in the following
description with reference to the accompanying figures,
in which:
Fig. 1 is a schematic cross section of an
electrostatic precipitator including discharge electrode
means of the present invention;
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1~36068
Fig. 2 is an enlarged fragmentary portion of
Fig. 1 showing an upper end portion of a discharge electrode
according to one preferred embodiment of the invention;
Fig. 3 is a transverse section of the electrode
of Fig. 2 taken on line III-III of Fig. 2;
Fig. 4 is a transverse section similar to
Fig. 3 showing a variation of the embodiment of Fig. 3;
Fig. 5 is a transverse section similar to Figs. 3
and 4 showing yet another variation of the embodiment of
Fig. 3;
Fig. 6 is a partial side elevation taken on
line VI-VI of Fig. 5;
Fig. 7 is a partial side elevation of another
preferred embodiment of the invention;
Fig. 8 is an elevation taken on line 8-8 of
Fig. 7;
Fig. 9 is a transverse cross section taken on
line 9-9 of Fig. 7; and
Fig. 10 is an elevation similar to Fig. 7 showing
a variation of the embodiment of Fig. 7;
~here is generally indicated at 10 in Fig. 1 an
electrostatic precipitator including discharge electrode
means. Certain aspects of the discharge electrode means
as disclosed herein are disclosed and claimed in copending
Canadian Application Serial Number 300,045, filed March
30, 1978. 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 unduly limit the scope of the invention
3~ described.
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.
Precipitator 10 comprises a closed housing 12
which encloses a space 14 and includes gas inlet and
outlet means 24, 26, respectively, whereby a flow of
gas ma~ be directed through space 14 as indicated by
arrows 28 for cleansing. Within space 14 there is
carried at least one discharge elec~rode bank 21 assembled
from a plurality of discharge electrodes 20. Electrodes
20 are carried in generally verticalLy extending, parallel
orien~cation by respective pairs o~ upper ~nd ~ower ele~
~rode support members 15, 30 such tha~ ~he electrodes ~0
. extend transversely across t~e gas flow path with ~he
plane of each electrode 20 ~enerally aligned wi~h ~he
direc~ion o~ gas flow. Members 15, 30 supportingly and
electrically conduc~ively engage respective upper and
lower end portions o the electrodes 20. Th~ upper suppo~t
mem~ers 15 are suitably secured to a rigid support frame
16. Frame 16 in turn is carried by and electrically
insulated from housing ~2 as by an elongated upwardly
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 passed through
space 14. Adjacent the lower ends of respective electrodes
20, the lower support memebrs 30 are suitably secured to
a base frame 22 which is electrically insulated from hous-
ing 12 as by the surrounding 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 electrode plates 23 also carried within
1136~)68
.
space 14 intermediate respective pairs of adj acent
discharge electrode banks 21 and parallel theret'o whereby
the'discharge electrodes 20 may be electrically energized'
by a~y suitable means (not shown) to set up corona
discharge therefrom in the'space between each discharge
electrode 20 and the respective adjacent coLlecto~s 23,
Accordingly, in practice'the'gas stream passed through
~pace 14 is cleansed by electrical precipitation of
. entrained particulate contaminan~s and deposition ~hereof
on the collector electrode plates 23 in ~he we~l known
manner. Con~en~ional sapping ~echniques are employed
to dislodge the accumulatad contaminants from collec~or
electrodes 23 ~or disposal. ~nasmuch as electros~atic
precipitators-such as descr~bed hereinabove'and ~he
' ' . .operation ~hereo are well known ~o ~hose versed in the
art, ~urther'detailed description thereo~ i~ considered
unnecessary for an understanding o the present invenion.
According to one preferred embodiment o the
~ ~nvention as shown in Figs. 2 and 3, each electrode 20
~ncludes a~ elongated, generally planar and substantially
' unitary electrode body 36 formed as by roll forming or
similar processes and comprising:. a central axially
,
. e~tending elongated stifener or support portion 38 ~ormed
intermediate the transversely opposed longitudinal edges
58 of the body 36 and corona discharge portions shown as
' elongated tabs 40 ormed adjacent respective adges 58 ~o
' ' deine respective lines o corona e~ission extending
therealong, Supporting web portions 42 extend inter-
mediate respective-tabs 40 and stiffener portion 38. The
electrode portions 38, 40 and.42 ordinarily may be
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coextensive throughout substantially the entire'length
of body 36.
StiL~fener portion 38 is so formed ~s ~o define
a longitudinally extending opening 50 substantially co-
extensive therewith. The'opening 50, shown as having
a circular cross sec~ion, is adapted ~o have'secured
therewithin the cooperably formed support members~l5 and
30 adjacent respective opposed end portions of body 36
(only the upper end portion is shown in Fig. 2) as by weld-
ments 60 whereby members 15 and 30 are eIectrically con-
duc~ivèly affixed to bod~ 36. As sho~n 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 g~uge s~eel to have a thickness of
approxima~ely 0.04 to 0.08 inches ~ach plate 44 includes
a longitudinally extending semi-circular outward bend 48
intermediate the longi~udinal edges thereof which forms
one half of the stiffener portion 38, and a plurality
of'the longitudinally spaced tabs 40 transversely to
one side of bend 48 adjacent one longitudinal edge of
each plate 44. In each plate 44, a longitudinal web
portion 42a extends transversely intermediate the bend
48 and tabs 40, and a second elongated web portion 42b
extends transversely outward from bend 48 generally
coplanar with and in the opposite direction from web 42a.
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
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directions as shown in Fig. 3. The two plates 44 are
affixed rigidly together in the'position des'cribed as by
a plurality of resis~ance weIdments 52 spaced longitudinally
at intervals to rigidly secure'together adjacent web
poxtions 42a and'42b such'that the iuxtaposed outward bends
48 form the stiffener.portion 38 and opening 50. 0
course, any suitable alternative fastening means may be
employed in lieu weldments 52, for example ot~er types
of welding, threaded fasteners or rivets.
Longitudinally ad~acent ones of tabs 40 are
shown as being formed by intervening s~ots 39 and as
shown may be bent or outstruck alternately in opposite
directions rom the plane o~ web portion 42 at an angle
. of approx~mately 45 degrees, for example such that alter-
nate 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 o tabs
40 may be varied to achieve the most desirable and
efficient pattern of corona emission therefrom. For
example, in another preferred embodiment of ~his
invention which is described in detail heréinbelow tabs
40 may be substantially coplanar with 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 discharge electrode
of this invention is that the pattern of corona discharge
to collectors on opposite sides of the discharge electrode
be generally symmetrical about the plane of the discharge
electrode. By this it is meant that approximately equal
corona discharge propagates from one edge of the electrode
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20 to each of the ad;acent collector electrodes 23.
Fig. 4 illustrates a variation of the
embodiment of Figs. 2 and 3 wherein eIectrode body 36
is comprised of a generally planar elongated formed plate
44' having a formed semi-circular outward bend 48' which
extends longitudinally of plate'44' and is located
centrally intermediate opposed longitudinal edges 58
thereof. Corona discharge means such as outstruck tabs
40 are formed adjacen~ the edges 58 of plate'44' and
identi~al coplana~ web port~ons 42' extend inter-
mediate the bend 48' and respective tabs 40. A~cor~ng
to this embodiment an elongated s~iffener por~ion 3~',
including an elongated cylindrical opening S0' adapted
to receive suppor~ members lS and 30, is formed by bend 48
in cooperation with an elongated, formed means shown as
a member 54 having an elongated semi-circular outward
bend 62 formed intermediate transversely extending coplanar
web portions 64 thereof. The members 44' and 54 are
positioned with the respective inner or concave sides o~
bends 48' and 62 facing each other and coaxially aligned
to form the stiffener portion 38' and opening S0' in
the manner indicated hereinabove for the first described
~mbodiment, and the respective web portions 64 and 42'
are affixed rigidly together in any suitable manner as
~ereinabove described to form the substantially unitary
body 36'. Elongated means 54 may be comprised of a
plurality of distinc~ members affixed at longitudinally
spaced intervals along the member 44' if desired.
Another variation on the embodiment of Figs. 2
and 3 is shown in Figs. 5 and 6 wherein electrode body 36'''
1136~368
comprises a single, elongated, generally planar forned
member 44''having an elongated stiffener portion 38''
and identical9 coplanar web por~ions 42'' extending
transversely in opposite directions therefrom. Tabs
40 are formed adjacent respective opposed outer edges
58 of member 4411. According to this embodiment, a
cylindrical opening 50' ' to receive support members 15
and 30 is formed by a plurality of longitudinal~y adjacent
segments 66 of stifener portion 38'' being outwardly formed
alternately in opposite directions.
In each of ~he hereinabo~e and hereillbelow
described varia~io~s, the stiffener portions 38-381'
are suitably formed and dimensioned to provide the
struct~ral rigidity considered suff1cient to render ~he
electrode body 36-36'' substantially se~-supporting
in that` only the end support members 15 and 30 are
needed to support ~he electrode and that portion of the
electrode body extending longit~dinally intermediate the
respective electrode body ends has no support means other
than its own formed structure. The openings 50-50'' as
- described may be 6ubstantially coextensive with stiffeners
38-38'' whereby if desired the support members 15 and 3Q
may be longitudinally opposed end portions of a single
elongated member disposed within the opening 50 and extend-
ingthrouhgout thelength of body 36 to provide added struc-
tural 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
openin~ 50, for example as in the hereinbelow described
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embodiment.
In Figs. 7, 8 and 9, there is shown another
preferred embodiment of the invention wherein the electrode
body 36''' 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 70 are spaced laterally to eithe~
side of st~ffener portion 72 and Pach has formed thexein
corona discharge means such as a plura~ity of longitudinally
spaced tabs 78 and inter~ening notches 8Q. The coron~
discharge tabs 78 may be coplanar with each other and with
side portions 76 as shown or may be alternately outstruck
as described hereinbelow. The dimensions and spacing
of notches 80 may be varied to alter the current-voltage
characteristics and hence the corona discharge charac~eris-
tics of the electrode. For example, it may be desirable
that the electrode 20 ha~e a current-voltage characteristic
approximating ~hat of a pair of laterally spaced, parallel-
wire discharge electrodes. One suitable configuration is
shown in Fig. lO wherein the longitudinal extent of tabs 78
is approximately equal ~o the longitudinal extent ofnotches
80. A similar configuration results from the tabs in the
embodiment of Fig. 3 being of substantially equal longitud-
inal extent and being outstruck 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 corona propagation from the electrode will deviate
from longitudinal uniformity. As notches 80 are lengthened
and tabs 78 correspondingly shortened, the corona
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propagation pattern will approach that of plural,
longitudinally spaced discharge points. In a variation
of the Fig. 10 con~iguration (not shown) ~he alterna.te
- notches 80 and tabs 78 formed in the opposite edges
7~ of plate 70 may be longitudlnaily offset or staggered
ln such a manner that each tab 78 in one edge 74 is
transversely aligned with a notch 80 formed in the opposite
- edge 74. In an alternate embodiment the ~orona discharge
means may be comprised of a continuous edge portion o~ the
discharge elect~ode having no cutouts or notches therein.
corona emi.ssion from the disch~r~e elect-~odes
must be cur~ailed, as for example.to promote the uniform
current flow or corona discharge to the collectors near the
upper and lower ends of the body 36 whereat edgeg 74 are
disposed laterally adjacent corresponding edge portions
of collector plates 23, electrically conductive shroud
means 82 may be employed as shown to 'isoften" the contour
of the elctrode thereat by eliminating exposed edge por-
tions and curtailing corona discharge from the covered edge
portions. As shown, shrouds 82 may b~ formed as elongated,
generally tubular members each having a longitudinally `
exten~ing through slot 84 which receives the edge 74 of
plate 70 whereby the edges of slit 84 grip plate 7Q
to secure the shroud 82 thereto.
The formed plate member 70 extends intermediate
frames 16, 22 and is secured thereto by respective upper
and lower support members 15', 30'. As shown, member lS'
comprises a formed body having a transversely extending
upper body portion 86 by which t~e support 15' is releas-
ably secured to a cooperably formed lower portion 88 of
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frame 16 as by threaded fasteners 90, and a pair of
inwardly and downwardly converging side portions 92 ~he
lower ends of which receive ~he respec~ive upper ends of
e~.ectrode side portions 76 therebetween for securing
thereof as by threaded fasteners 94. In similar ~ashion
an upwardly extending end portion 96 of generally H-shaped,
elongated, lower alignment support.-30' is secured by
. threaded fasteners 98 to the lower ends of respective
electrode side portions 7~, and t~e lower end of suppor~
30' is secured by ~hreaded fasteners 100 ~o frame-22.
- According to the description hereinabove,
there is provided by the instant invention an improved
discharge electrode of the pole or mast type for
electrostatic precipitators which is uncomplicated in
fabrication and assembly, hlghly durable and su~ficiently
rigid by virtue of integrally formed stiffener portions
therein to resist excess lateral deflections without being
wasteful of materials in fabrication.
Although only certain preferred embodments of
the invention have been described herein it is to be under-
stood that the invention may be practiced in numerous
alternative embodiments with various modifications thereto
without departing from the broad spirit and scope thereof.
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 respecti~e openings 50 being cooperably formed; the
tabs 40 may be formed and positioned according to any
of numerous suitable desi~ns, for example, a sawtooth
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configuratiorl; the electrodes may be assembled from plural
elongated clectrode portions connected end to end; an
electrodc may co~)ine elements of the several described
embodiments in a single structure. These and other
embodiments and modifications have been envisioned and
anticipated by the inventor, this invention should be
interpreted as broadly as permitted by the scope of the claims
appended hereto.
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