US2362716A - Discharge electrode structure for electrical precipitation apparatus - Google Patents

Description

Nov. 14, 1944. F. w. PHILLIPS 2,362,716

DISCHARGE ELECTRODE STRUCTURE FOR ELECTRICAL PRECIPITATION APPARATUS Filed Nov. 21, 1942 2 Sheets-Sheet 1 0 g 7 .1. 20 17 15 v v 22 L/.. ,.\n.,..m i w 25 ATTORNEY:

Nov. 14, 1944. F. w. PHILLIPS DISCHARGE ELECTRODE STRUCTURE FOR ELECTRICAL PRECIPITATICN APPARATUS 2 Sheets-Sheet 2 Filed NOV, 21, 1942 iksosQ/cz MPH/Lugs,

INVENTQR.

' ATTORNEY.

Patented Nov. 14, 1944 DISCHARGE ELECTRODE STRUCTURE FOR ELECTRICAL PRECIPITATION APPARATUS Frederick W. Phillips, Toronto, Ontario, Canada, assignor to Western Precipitation Corporation, Los Angeles, Calif., a corporation of California Application November 21, 1942, Serial No. 466,467

11' Claims.

This invention relates generally to apparatus for electrical precipitation of suspended particles from gases, and more particularly to discharge electrode structures for such electrical precipitation apparatus.

It is common practice in electrical precipitation apparatus to employ a discharge electrode structure including one or more discharge electrodes in the form of linearly-extended elements of relatively small diameter, or having formations of relatively small radius of curvature, wellknown examples including wires, small diameter rods, twisted ribbons and twisted square bars. This discharge electrode structure, which in operation is maintained at a high uni-directional potential, is so constructed and mounted that the discharge electrode elements extend in parallel spaced relation with respect to an opposing grounded electrode structure which is of nondischarging character, such as an extendedsurface plate, relatively large diameter pipes, or the like, and the particle-laden gas is passed between the opposing electrodes, as is well understood in the art.

In the following description and appended claims, the term discharge electrode will be understood to designate an electrode that facilitates corona discharge therefrom, because it has a configuration that establishes a sufiiciently high potential gradient at or near its surface to create corona discharge before there is a disruptive discharge or sparkover. For this purpose, the discharge electrode usually takes the form ofa member of small surface area, such as a small diameter wire or a rod provided with sharp edges or points, whereby there may be created in the immediate vicinity thereof a sufficiently high electric field intensity to cause ionization and corona discharge. The term non-discharging electrode will be understood to designate an electrode that minimizes or prevents corona discharge therefrom because it has a configuration that establishes a sufiiciently low field concentration at or near the surface to suppress corona discharge at elevated potentials lower than the voltage required for disruptive discharge or sparkover. For this purpose, a non-discharging electrode is usually one of extended surface area, substantially free from sharp corners or other parts of sharp surface curvature at all portions whichare located within the electric field, so as substantially to avoid ionization or corona discharge at that electrode.

The discharge electrode structure for precipitators of the class mentioned usually embodies 5 'tential supporting means for the element.

supporting means which supports each linearlythe positions as to be restrained against longitudinal movement and in good electrical contact with the supporting means, and the elements beingmerely confined by the supporting means against transverse movement at the other position or positions and being left free for longitudinal movement to accommodate 'longitudinalexpansion and contraction relative to the supporting means. The support provided at the last-mentioned position orv positions is not such as affords a good electrical connection between the element and the supporting means. H

When the precipitator is handling certain types of gases, as, for example, dry converter gases, there issome considerable unavoidable sparking and arcing between thehigh potential discharge electrode structure and the grounded non-dischargingelectrode structure. This sparking or arcing may occur between any point on any of the linearly extending discharge electrode elements and a point on the opposing grounded electrode structure. Consequently, any tendency thereof to causeburning away of the discharge electrode elements is not apt to cause serious trouble because such sparks or arcs do not usually occur repeatedly at any one point on a discharge electrode element. However, when such a spark or an arc jumps the gap between the grounded non-discharging electrode structure and a point on a discharge electrode element, the potential of such point on the discharge electrode element is very greatly lowered, and a heavy current fiows momentarily between such point and the high posuch point happens to be near the position of support for the element at which the element is longitudinally restrained, at which position a good electrical connection between the element andthe supporting means has been provided, the heavy current fiow spoken of passes through said electrical connection to the supporting means without event. But if the-point of-sparkover or arc happens to benear a position of supportfor the element at which'only transverse restraint has been provided, andat which good electrical connection is diflicult to provide, arcing will occur between the electrode element and the supporting means at such position, due to the relatively high potential difierence thus created momentarily between these parts that'; are normally at substantially the same potential. Such arcing between ience, shut-down time for replacement, and

expense.

The primary object of the present invention is,

accordingly, the provision of a discharge e1ec'- trode structure adapted to be maintained at high potential with respect to an opposing grounded electrode structure, and embodying linearly-extended electrode elementssupported at two or more points by supporting means forming parts of said discharge electrode structure and normally maintained at substantially the same potential as the electrode elements, in which simple and .effective provision is made ,to safeguard against burning ofi the extended electrode ele-- ments at their pointsof supporton the supporting means as a result of arcing therebetween in the manner described.

Broadly stated, the present invention accomplishes- .this object by the provision of a hightension discharge electrode structure including a supporting means and linearly-extended dis.- charge electrode elements mounted thereon, in which the linearly-extended. discharge electrode elements are each provided with a support at one point on said supportingmeans which is'of such character as to provide a. good electrical connection between the elementand the supporting means, and with a positioning member of insulating material mounted on the supporting means which loosely engages the electrode element at a position spaced longitudinally from the first-mentioned point of. support and limits transverse movement of the element but leaves, it free of longitudinal restraint. Such insulation positioning members prevent arcing at all positions of support for the extended discharge electrode elements at which they are provided, causing all current flows between the electrode element and the supporting means totake place at the points of support at which the electrical con.- nections are provided, and hence eliminate burnofi of the electrode elements at those positions.

The invention will be more fully understood by now referring to the following detaileddescription of several illustrative embodiments thereof, reference for this purpose being directed to the accompanying drawings, in which:

Fig. 1 is an elevation of a high-tension discharge electrode structure embodying the invention; Fig. 2 is an enlarged detail taken from Fig. 1, with parts broken away, showing in detail the nature of the upper supporting means for the discharging electrode elements; Fig, 3 is a vertical medial section showing in detail the nature of the intermediate and lower positioning means for the discharge electrode elements of the structure of Fig. 1; Fig. 4 is a plan view of the positioning means shown in Fig. 3; Fig. 5 is a view similarto Fig. 3, but showing a modification; Fig. 6 is another view similar to Fig. 3, but showing a further modification; Fig, 7 is a somewhat diagrammatic sectiona1 view of a multiple'gas tube type of precipitator in which the improvements of the present invention have been incorporated; Fig. 7a is a detail showing an insulator of Fig. 7 in enlarged longitudinal section Fig; 8 is a fragmentary elevation of a modified form of high-tension discharge electrode structure embodying the improvements of the present invention; Fig. 9 is a fragmentary elevation of another type of discharging electrode structure embodying the invention; Fig. 10 is a detail section taken on line I 0 l0 of Fig. 9; and Fig. 11 is a detail section taken on line I |l I of Fig, 10.

, lshows the high-tension, discharge electrode structure of a typical electrical precipitator. The remainder of the precipitator may be of any conventional or appropriate type; for a description of a complete precipitator of a type utilizing a discharging electrode structure of the type of Fig. 1, see Patent No. 1,846,169, granted February 23, 1932, to C. H. Weiskopf in which an entire discharge electrode structure of generally similar construction is shown as maintained at high potential with respect to an opposing grounded electrode structure. Referring now more particularly to Fig, 1, the discharge electrode structure, generally designated by numeral I 5, in-

cludes a suitable supporting means or framework embodying horizontally-spaced vertical frame bars It, and horizontal, vertically-spaced upper. intermediate and lower cross-members. ll, t8: and I 9, respectively, inter-connecting vertical bars [6. These cross-members H, [8, and H2, which are preferably and illustratively in the form of pipes, m y e provided with any suitable form of m0unt ings on the vertical frame bars is. For instance, intermediate and lower pipes 18; and I9, may be received in sockets, [8a mounted on bars [6, and upper pipe I! may be supported'at each end by a pin Ila extending upwardly from the upper flange of a horizontal channel member l'lb mounted on the adjacent frame, bar I6, the pin Ila entering a hole l'lc in the lower side. oi the pipe and supporting the pipe by engaging its, up: per side from below, as clearly il-lustra-tedin Fig; 2.

Horizontal pipes I1, I18 and .19 are provided with horizontally-spaced sets, of vert ically-. aligned openings adapted for reception of the vertical, horizontally-spaced discharging electrode elements 20. These dischar ing electrode elements 20 may take various forms.-such as Wires, fine rods, twisted square bars,,twisted ribbons, orother forms of linearly-extended elements of relatively small diameter or affording formations of relatively small radius of curvae ture. For the purpose of the present disclosure, I show the elements .20 in the form of twisted square bars, as illustrated in. Fig. 3. These bars are received in vertically-aligned apertures 2| formed in the upper and lower sides of upper supporting pipe I11, the apertures 2i being preferably of such size asv to freely receive .the electrode element but to. confine it comparatively closely against transverse displacement. The upper endportion of eachelectrode element 20- is preferaby formed with a suitable head which engages the top side of pipe l1, and by which the element is suspended. In the form. illustrated in Figs. 1 and 2, this head is formed by the-simple expedient of doubling back the upper end portion 22 of the bar, so that the end. 23 engages the top side of. pipe I! in the manner clearly. illustrated in Fig. 2, This engagement between thehead formed on the upper end of bar 20 and at the top side of '15 members l8 .and I9, are in electrical contact with bernl'l :and vertical frame members H and are normally maintained at substantially the same potential. l a

The openings 25 formed in supporting pipes l8 and I9 for passage of electrode bars 20 are of substantially increased diameter as compared with the openings 2! in the upper pipe I1, and receive insulation positioning members for the bars 20, preferably and here shown as insulator bushings or sleeves 26, of glass, ceramic, or anysuitable insulation material, and preferably formed at their upper ends with shoulder means engageable with the supporting pipe to resist longitudinal displacement.

In the specific form illustrated in Fig. 3, this shoulder means is provided by flaring the upper end portion of the bushing outwardly, as indicated at 28. If the bushing is composed of glass, this may easily be accomplished by heating the upper end portion of the bushing and flaring it while it is hot. The flared portion 28 then serves as the shoulder, and supports the bushing as indicated in Fig. 3. The internal bore 29 of the bushing is, of such diameter as will freely or loosely receive the twisted bar 20, or other linearly-extended electrode element, so as to confine the bar against transverse displacement, without restraining it longitudinally. Preferably, the bore in the bushing is of at least slightly larger diameter than the maximum thickness dimension of the electrode element, so as to avoid any possibility of frictional bind between said element and the bushing. The bushing extends well above and below the pipe is to prevent sp-arkover between the electrode element and the pipe.

Fig. 5 shows a modified insulator bushing 26a, formed at the top with an enlarged head 30 presenting a downwardly-facing annular shoulder 3| which is engageable with the top of pipe l8. As a further modification, the bore 29a of the bushing of, Fig. 5'is shown to diverge in a downward direction from a point preferably a short distance below its upper end, as illustrated. This downwardly diverging bore permits foreign objects that might become-lodged between the electrode bar 20 and the bushing towork free and fall from'the bushing somewhat more readily than would otherwise be the case. However, this form of bushing may, if desired, be made with a cylindrical bore. In either case, bushings of this form may bemade by a moulding or other forming operation, using either ceramic or vitreous insulating materials.

Fig. 6 shows an insulator bushing 26b formed at the top with an enlarged head affording a downwardly-facing annular shoulder 35, the bushing in this instance being received within discharging electrode elements 20 and the. opposed non-discharging electrode (not illustrated) all currentflow between the elements 20 and the high-tension supporting structure I5 is confined to the pointsof'engagement between the heads of the elements and the supporting pipe 11, at which the elements 20 have good electrical connections with the framework IS. The bushings thus serve as longitudinal guides for the extended electrode elements 20, confining them against transverse displacement while permitting longitudinal movement owing to longitudinal expan sion orcontraction, and at the same time prevent destructive arc-over between the said electrode elements and the supporting members l8 and is through whichthey are extended.

Figs. 7 and 7a show, the application of the invention to a multiple-tube type of precipitator employing one or more linearly-extended dischargeelectl'ode elements in the form of .flexible wires. In Fig. 7, which is largely diagrammatic, numeral 4|] designates generally a fragmentarilyindicated gas supply header, understood to be supplied With gas by way of any suitable inlet means, not shown; numeral 4| designates a plurality of vertical gas tubes leading upwardly and receiving gas from header 4!! and constituting collecting electrodes; and numeral 42 designates a fragmentarily indicated gas discharge header into which the gas rising in tubes 4! is discharged. Mounted within header 42, on insulators indicated at 43, is a horizontal support 44.

for the high-tension discharge electrode elements which extend downwardly co-axially through collecting electrode tubes 4|. These high-tension discharge electrode elements, as here shown, in-

clude a pair of relatively heavy hanger elements 1 supportsaid pipe within header to through nuts and supported by a metal sleeve 36, which is in turn received by the openings 25 of the pipe. As shown, the upper.end of the sleeve has an outwardly-extending annular flange 37 engaging and supporting (bushing shoulder 35, and the underside of said flange provides a shoulder supported by the pipe. This sleeve 36, the lower end of which terminates substantially short of the lower end of the bushing, so as to prevent sparking between the electrode bar and the sleeve, afiords added support and protection for the bushing.

The described insulator bushings placed between the discharging electrode elements 20 and the supporting pipes l8 and I9 prevent arc-over between said elements and supporting pipes, and, i??? er e epe ke 9 r in w en t 19 screwed on their lower ends. Flexible electrode wires t6, hung from pipe 44 in any suitable manner, extend downwardly from the lower ends of tubes 4| through insulator bushings 52 mounted in pipe 38 (Fig. 7a), the insulator bushings 52 being, for example, of the same type as the bushing 26 of Fig. 3, though they may be somewhatsmaller in diameter. Electrode wires 46 are held taut by means of weights 53 at their lower ends. As will be evident, the insulator bushings 52 confine electrode wires 46 against transversedisplacement without interfering with relative longitudinal movement between thewires and the bushings, while at the same time the bushings serve to prevent arc-over between the wires and the pipe 48.

Fig. 8 shows a modified form of high-tension discharge electrode structure, which is in general respects of the same type as that shown in Fig. 1, with the exception that the linearly-extended discharge electrode elements are secured at their and understood to comprise one or morevertical frame'bars 6|", andinter -connecting.upper, interj-' mediate. and lowerv supporting. members 62;. 53 and 64*, respectively, preferably and here' indi-- cated. in the form of pipes; The: linearly-ex:-

tended discharge electrode elements. 6-5;.which. are in this instance of sufi'icient-stiffness to be supported from their lower ends; may again be.

typically in the formof twisted square bars, like the bars 20 of Figs. 1 and'3. of: the bars have heads 66 which engage the under side of pipe. 64, and nuts 6"! threaded onto the bars near the heads 66: are'set againstthe. top side of the pipe64 to secure the bars against. pass; through and are guided by insulator bushings 68 set into pipes 62 and 63, the bushings.G8I'and-" longitudinal displacement. The bars the-manner of their mounting beingillustratively'the'same as is shown in Fig. 3.

Figs. 9 through 11 show another application ofthe invention, the linearly-extended discharge electrode elements in this instance being horizontally disposed. The high-tension supporting frame 'lfl includes a vertical central frame member- H of channel section, having flanges I2 and outside vertical frame members 13, typically in the form of pipes, which are joined with member H by means of connecting members 14% The linearly-extended electrode elements 15 -are again illustratively in the form of twisted square bars,

and will be understood topass horizontally through suitable openings in the flanges 12 of member H and in the vertical supporting pipes 13-; the ends of the bars having heads 16 engageable with the flanges 12', and nuts I1 screw threaded on the bars and set up against said flanges cooperating withheads lfi' to support the bars'against longitudinal displacement; as well as providing the necessary electrical connection between the bars and the central frame member H. The outer end portions of bars 15 pass -freely through insulator bushings 18 supported in relatively large openings 80' in vertical members 13; In the particular example shown in the drawings, the bushings 18' have flared end portions 83 at each end, and the openings 80" are pref erably of such diameter as will just'receive theseflared end'portions as the bushings are inserted. The bushings being-inserted, their smaller diameter central portions 84, which are of lengths substantially equal to the diameter of the pipes 13, rest at the-bottoms of openings 80, and the flared end portions of the bushings then serve to restrain the bushings against longitudinal displacement withrespect to the pipes'l3;

In summary, in all of the disclosed forms'of the invention, each linearly-extended discharge electrode element is provided with a support on" the discharge electrode supporting frame which confines it against longitudinal displace"- ment and which also provides a good electrical connection between the element and the frame,

and with at least one insulation support'or guide on' said frame which confines it against trans verse displacement without restricting its free longitudinal movement. This insulationsupport or guide prevents currentfiow between the'electrode element andithe'fram'eexcept' at the point of'support where'the' element is longitudinally restrained; atwhich point a'sufiiciently good e'lec trica-l connection-is provided'to prevent destructive arcing; and *thus'elimina-tes the burning off of the electrode elements at 'their'longitudinallyunrestrainedpoints of support;

It"wi-ll--be' understood' thatthedrawings anddescription are merely illustrative of and not The lower ends assay-12c:

restrictive on: the invention; and that" various. changes: in: design;. structure: and: arrangement may-be made: without departing from the spirit and scope of the invention or of the appended claims.

1; In: at discharge electrode structure for an electrical precipitator, the combination compris ing: memberelectrode an positioning member formed of insulating material; and electrically connected conductive frame members including a member supporting said electrode member' at one-position" and electrically connected thereto and a member supporting said positioning mem'- her in loose engagement with said electrode member at a position" longitudinally removed from said one position'in such amanner as to'limit" transverse movement of said electrode member and permit "longitudinal movement thereof relative to said positioning member.

.connected thereto anda member supporting said positioningmember in engagement with said electrode member at a position longitudinally removedlfrom said one position, said positioning member electrically insulating said electrode memberfrom said last named supporting-mem-- her.

4.- In a discharge electrode structure". for an electrical precipitator, the combination: set: forth inc1aim-3, said positioning member being formed as a sleeve surrounding said electrode member;

5.-In a discharge electrodevstructure' for an electrical precipitator, the combination as setforth'inclaim 3, said positioning'member being formed as a sleeve: surrounding said electrode member and projecting longitudinally at both" ends beyond said last named supportingmeans.

6'- In adischarge. electrode structure-for an" electrical precipitator; the combination as set-1 forthv in claim 3; said last-named supporting means comprising a a supporting member extendv ing. transverselywith respect to said electrode member. and? having an opening through which saidaelectrode: member extends, and said positioning 'member being formed as'a sleeve extend.-

ingthrough said opening; surrounding-saidelec r 1 trode member; and provided withshoulder'means engaging aid last-mentioned supporting member to resist'longitudinal movement'of saidsleeve.

'7. In a disc-harge electrode structure for air electrical precipitator, the combination" compris;

ing: a vertically-extending discharge electrode" member; a positioning member formed'of insulating material loosely engaging said electrode member in'such manner as to' limit transverse" movement thereof 'and'permit longitudinal movement thereof relative to said positioning mem a linearly-extendeddischarge electrode ber; and electrically connected conductive frame members including a member supporting said' electrode member at one position and electrically connected thereto and a horizontally-extending supporting member supporting said positioning member in engagement with said lectrode member at a position vertically removed from said one position, said last-named supporting member having an opening through Which said electrode member extends, and said positioning member being formed as a sleeve extending through'said opening, surrounding said electrode member, and provided with houlder means engaging said supporting member to support said sleeve thereon.

8. A discharge electrode structure for an electrical precipitator comprising a supporting frame formed of electrically conducting material and including at least two electrically connected frame members extending substantially parallel to and spaced from each other; a linearly-extended discharge electrode member engaging and supported by and in electrical contact with one of aid frame members; and a positioning member formed of insulating material mounted on and supported by the other frame member, and loosely engaging said electrode member in such manner as to limit transverse movement thereof and permit longitudinalmovement thereof relative to said positioning member, and electrically insulating said. electrode member from aid other frame member.

9. A discharge electrode structure for an electrical precipitator as set forth in claim 8, wherein the positioning member is formed as a sleeve surrounding the electrode member.

10. In a discharge electrode structure for an electrical precipitator, the combination comprising: a linearly-extended discharge electrode member; a positioning member formed of insulating material loosely engaging said electrode member in such manner as to limit transverse movement thereof and permit longitudinal movement thereof relative to said positioning member; and electrically connected conductive frame members including a member supporting said electrode member at one position against both longitudinal and transverse displacements and electrically connected thereto and a member supporting said positioning member in engagement with said electrode member at a position longitudinally removed from said one position, said positioning member electrically insulating said electrode member from the last-named supporting member.

11. A discharge electrode tructure for an electrical precipitator as set forth in claim 10, wherein the positioning member is formed as a sleeve surrounding the electrode member.

FREDERICK W. PHILLIPS.

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