US3819985A - Discharge electrodes for electrostatic precipitators and method of shipment and installation - Google Patents

Abstract

An electrostatic precipitator discharge electrode having an outer conductive sheath with a generally axially extending inner core therein and an insulator therebetween. To increase the electrode corona current emission the outer sheath has a plurality of conductive integral ribs terminating in apices extending generally radially outwardly of the sheath. The electrodes can be coiled and shipped to the job site where they are straightened and cut to the proper length for installation in a precipitator.

Description

Umted States Patent 1 91 1111 3,819,985 Dusevoir June 25, 1974 [5 DISCHARGE ELECTRODES FOR 3,385,966 5/1968 Rosenthal 250/325 ELECTROSTATIC PRECIPITATORS AND FOREIGN PATENTS OR APPLICATIONS METHOD OF SHIPMENT AND 299,476 10/1916 Germany 55/152 INSTALLATION 1,016,905 l/l966 Great Britain 55/152 [76] Inventor: Robert H. Dusevoir, 3014 Newburgh Rd,, Wa Mi h Primary Examiner-J. D. Miller 4 134 Assistant Examiner-Harry E. Moose, Jr. Filed: Dec. 1972 Attorney, Agent, or Firm-Barnes, KIsselle, RaIsch &

- Choate [2l] Appl. No.: 311,214

[57] ABSTRACT 521 US. Cl 317/3, 55/146, 55/151, An electrostatic precipitator discharge electrode 5 5 /1 52 ing an outer conductive sheath with a generally axially [51] Int. Cl. B030 3/41 extending inner core rei d an insulator therebe- [58] Field of Search 55/146, 150-152; tween- To increase the electrode co o a current emis- 313/351, 354; 174/126 R 131 A 133 R; sion the outer sheath has a plurality of conductive in- 3l7/3, 262 A; 250/324, 325, 326 tegral ribs terminating in apices extending generally radially outwardly of the sheath. The electrodes can [56] References Cit d be coiled and shipped to the job site where they are UNTED STATES PATENTS straightened cut to the proper length for installa- 1,333,790 3/1920 Bradley 55/152 m a preclpltator' 3,200,566 8/1965 Gustafsson et al 55/152 24 Claims, 9 Drawing Figures DISCHARGE ELECTRODES FOR ELECTROSTATIC PRECIPITATORS AND METHOD OF SHIPMENT AND INSTALLATION This invention relates to electrostatic dust precipitators and more particularly to discharge electrodes therefor and methods of shipment and installation of discharge electrodes.

A typical industrial electrostatic dust precipitator has a plurality of interleaved ground and high potential electrodes between which gases such as those produced by combustion with particulate contaminants therein are passed. A high voltage in the order of 40KV is supplied to the electrodes so that the particulate contaminants in the gases passing over the electrodes are deposited on the ground plates. One such precipitator is shown in US. Pat. No. 3,633,262, issued Jan. 11, 1972, in which the ground electrodes are flat generally vertically extending plates on the order of 6 feet wide and 27 feet high and the high potential or discharge electrodes are rows of long thin wires extending generally vertically between the ground plates. Typically, these long thin solid wire discharge electrodes have a diameter of approximately 0.100 of an inch and are 25 to 30 feet long. Usually, these solid wire electrodes are crated and shipped as long straight strands so that they are not permanently deformed or bent although some of these electrodes are sufiiciently resilient to. be shipped in large diameter coils without exceeding the elastic limit of the solid wire electrodes. In use, these long thin solid wire discharge electrodes tend to break and whip about thereby electrically shorting out and damaging the other electrodes of the precipitator. These solid wire electrodes break due to concentration of the electrical discharge at certain points thereon, arcing, material fatigue, erosion, corrosion, etc.

Objects of this invention are to provide a discharge electrode for an electrostatic precipitator which does not whip about and short out other electrodes when in use for an extended period of time, has a substantially longer service life and a greater corona emission than prior discharge electrodes, is of economical manufacture and assembly, and can be readily and economically shipped to the job site and installed in a precipitator.

These and other objects, features and advantages of this invention will be apparent from the following description, appended claims and accompanying drawing in which:

FIG. I is a fragmentary sectional view of an electrostatic dust precipitator with discharge electrodes embodying this invention.

FIG. 2 is a fragmentary sectional view on line 2-2 of FIG. 1 showing a dischargeelectrode suspended between two ground electrode plates.

FIG. 3 is a cross sectional view of the discharge electrode on line 3-3 of FIG. 2.

FIG. 4 is a fragmentary perspective view of a modifled form of the discharge electrode of FIG. 1 with helical ribs.

FIGS. 5 through 8 are cross sectional views of modified forms of discharge electrodes embodying this invention.

FIG. 9 is a fragmentary perspective view of the discharge electrode of FIG. 7 showing a hook for suspending the electrode in an electrostatic precipitator.

Referring to the drawing, FIGS. 1 and 2 illustrate an electrostatic dust precipitator 10 with a generally rectangular gas chamber 12 having spaced generally parallel side walls 14 (only one of which is shown) and a front wall 16 having an inlet opening 18 therein through which gases with particulate contaminants are forced in the direction of arrows 20 (FIG. 1). A plurality of ground potential electrodes in the form of generally rectangular plates 22 are mounted in chamber 12 by transversely extending lower tie bars 26, intermediate spacer bars 28, and upper tie bars 30. Upper tie bars 30 are carried on members 32 fixed to side walls 14. Tie bars 26 and 30 and spacer bars 28 are pivotally connected to ground electrode plates 22 as shown in the aforesaid US. Pat. No. 3,633,262 which is incorporated herein by reference and, hence, will not be explained in greater detail. A plurality of discharge electrodes 34 each with a milkbottle weight 36 fixed to its lower end are suspended between ground electrode plates 22 by a rack 38. Rack 38 has a generally rectangular outer frame 40 with a plurality of bars 42 fixed thereto and extending generally parallel with ground plates 22. Rack 38 is suspended above the ground electrodes by a carrier frame 44 which is electrically connected with a high potential source of current through an electrically conductive connector bar 46.

As shown in FIG. 3, each discharge electrode 34 embodying this invention has an outer sheath 48 of an electrically conductive material such as aluminum, copper or steel and an inner core 50 of a high tensile strength material such as a solid steel wire or rod. An insulator 52 of a dielectric material such as Teflon or nylon is interposed between outer sheath 48 and inner core 50 and retains core 50 generally axially within outer sheath 48 in fixed relation thereto. Insulator 52 can be cast within outer sheath 48 so that it adheres to both the outer sheath and inner core. Preferably, insulator 52 is preformed on inner core 50 and then pulled into outer sheath 48 in firm frictional engagement therewith to retain the insulator and core in the sheath. Preferably, insulator 52 extends the entire longitude of outersheath 48 and inner core 50 extends at least substantially the length of sheath 48 and can extend beyond the sheath (as shown in FIG. I) to provide a means for attaching weight 36 to the lower end thereof. To increase the corona current emission of electrode 34, six integral circumferentially spaced ribs 54 on the periphery of outer sheath 48 extend substantially the entire longitude thereof. Ribs 54 have a generally V- shaped cross section and terminate in longitudinally extending radially outwardly projecting apices 56 providing sharp projections on outer sheath 48 which are believed to increase the corona current emission of the electrode and produce a so-called daisy corona discharge pattern. Ribs 54 extend in a generally straight line throughout substantially the entire length of outer sheath 48.

FIG. 4 illustrates a discharge electrode 34' with ribs 54' coiled in a helix on outer sheath 48'. Electrode 34' is the same as electrode 34 except for helical ribs 54. Due to the coiling of ribs 54, they have a greater lineal length than the axial length of the portion of the outer sheath on which they are coiled. Helical ribs 48 are believed to increase the corona discharge of electrode 34 by increasing the effective area of the ribs.

FIGS. 5 through 8 show electrodes with modified forms of outer sheath cross sectional configurations believed to increase corona current emission and produce a daisy corona discharge pattern. Electrodes 58, 60 and 62 have the same inner core 50 andinsulator 52 as electrode 34. Electrodes 58, 60 and 62 have generally star-shaped outer sheaths 64, 66 and 68 with six, five and four points or apices 70, 72 and 74 respectively with generally concave outer surfaces between the points. The electrode 76 of FIG. 8 has an inner core 50 and a triangular shaped outer sheath 78 with a triangular shaped insulator 80 therebetween. Triangular shaped electrode 76 provides three equally spaced sharp points or apices 82 for increasing the corona current emission.

As shown in FIG. 9, a hook 84 can be provided on one end of the electrodes such as electrode 62 to facilitate suspending the electrode in electrostatic precipitators l0. Hook 84 can be provided on electrode 62 by turning down an end portion of outer sheath 62 to remove a portion of ribs 74, thereby providing an integral tubular end portion 86 which is provided with a return bend 88 to make the hook. If desired, another hook can be provided on the other end of the electrode for attaching a weight such as milkbottle weight 36 to the lower end of the electrode. I

Materials suitable for making the outer sheath, insulator and inner core of electrodes embodying this invention must perform satisfactorily in the particular operating environment of the precipitator in which the electrodes are used. The gases processed by most precipitators may be corrosive, have abrasive particulate contaminants therein, and are usually at elevated temperatures in the range of 250 to 800F. Under such conditions, it is desirable to make the outer sheath of corrosion and abrasive resistant materials which remain substantially rigid at'these elevated temperatures such as stainless steel, anodized aluminum and nickel steel. Like-wise, the particular insulator material must remain in solid form, retain its dielectric properties at these elevated temperatures and not be subject to attack and substantial deterioration by corrosive gases or abrasive particulate contaminants therein over a long period of use. Suitable insulator materials are believed to be Teflon plastic preferably with fiberglass fibers embedded-therein, polyvinyl fluoride plastic, pressed asbestos fibers, or other plastic or inorganic insulator materials. The inner core must be made of a suitable material such as high carbon steel wire to retain its tensile strength and should not become substantially corroded or abraded over a long period of use at these elevated temperatures.

To decrease the cost of crating, handling and shipping electrodes embodying this invention to the end user, the long electrodes can be plastically deformed into coils preferably three to 6 feet in diameter. The minimum diameter of such coils is dependent on the rupture strength or fracture point of the particular materials used in making the discharge electrodes. Coils 3 feet in diameter are highly satisfactory when the outer sheath is made of so-called half hard aluminum, the insulator of Teflon plastic and the inner core of high carbon steel wire. The coiled electrodes can be straightened at the job site for use in a precipitator with any of the several commercially available tube or wire straightener devices such as the rotary wire straightener sold by the Heppenstall Co., 4620 Hatfield St., Pittsburg, Pa. If desired, the coils can be of sufficient length to provide several electrodes which can be cut to the proper length after straightening at the job site and the hook bent or formed thereon for suspending the electrodes in a precipitator. This method of shipment and installation of the discharged electrodes greatly decreases the cost of providing straight and true discharge electrodes to the ultimate user of a precipitator since the expense for handling, crating and shipping of straight electrodes is often substantially greater than the cost of the electrodes themselves. Moreover, this method of shipment and installation of discharge electrodes substantially decreases the likelihood of damage to the electrodes during transit and storage prior to use. Furthermore, the cutting of the electrodes to the proper length at the job site from long coils eliminates the need for the manufacturer thereof to have a large inventory of discharge electrodes of various lengths.

In use, the outer sheaths of the electrodes embodying this invention tend to develop discontinuities or holes therein due to the concentration of the electrical discharge at certain points thereon, arcing, material fatigue, erosion, corrosion, etc. However, the high tensile strength of inner core 50 and the insulator 52 or prevents the outer sheath from dropping or falling away from the electrodes even if the outer sheath becomes completely severed around its entire periphery so that it is completely separated into two or more portions. Even when the outer sheath becomes completely separated, it usually continues to function effectively in producing a corona current emission throughout its entire length which contributes to the long useful life of this discharge electrode. If the insulator is continuous throughout the longitude of the electrode, it prevents an electrically conductive path from developing through the center core and thus precludes any electrical discharge or arcing involving the center core from occurring and, hence, prevents the center core from being severed. Therefore, even though the outer sheath of the electrode becomes severed in use, the entire electrode does not become severed and, hence, no portion of the electrode breaks away or begins to whip about and short out the other electrodes of the precipitator. Thus, electrodes embodying this invention have a long useful life compared to prior electrodes and do not, when their useful life terminates, short out and damage other electrodes of the precipitator. The outer sheath configurations of these electrodes can be readily extruded of an electrically conductive material such as aluminum and the insulator readily cast or inserted into the outer sheath to securely fix the outer sheath to a high strength inner core such as a commercially available solid steel wire resulting in an electrode assembly having a minimum number of component parts and which is of economical manufacture and assembly.

The outer sheath configuration having a plurality of longitudinally and radially outwardly extending portions terminating in sharp points or apices provides a discharge electrode having a higher corona current emission than conventional wire electrodes. For example, an electrode with an aluminum outer sheath having a cross section shown in FIG. 3 with six longitudinally extending integral outer ribs when positioned in an electrostatic precipitator having a spacing of 9 inches between the ground plates has a corona current of 16 micro amperes per linear foot compared to 1 micro ampere per linear foot of a conventional medium carbon steel solid wire electrode with a diameter of approximately 0.092 inches at a potential of 30KV on the electrodes of the precipitator and a corona current of 32 micro amperes per linear foot compared to 14 micro arnperes per linear foot of the conventional wire at a potential of 40KV. The electrode of this example had an aluminum sheath with an inside diameter of 0.18 inches, a steel wire inner core with a diameter of 0.020 inches and a Teflon insulator therebetween. The cross section of the integral ribs of this outer sheath were substantially equilateral triangles having a height of approximately 0.062 inches and the thickness of the wall of the sheath between the ribs was substantially 0.062 inches.

1 claim:

1. An electrostatic precipitator discharge electrode comprising an outer tubular sheath of an electrically conductive material providing a corona discharge emission when connected to a high potential electric source, an inner core extending generally axially through the outer sheath and having sufficient tensile strength to carry the weight of the electrode, and an insulator of a dielectric material interposed between said outer tubular sheath and said inner core retaining said outer tubular sheath and said inner core in generally fixed relation to each other such that the electrode, when in use, will not be completely severed if said outer sheath is completely severed, whereby the likelihood of the electrode in use becoming completely severed and shorting out other electrodes in a precipitator is substantially decreased.

2. The electrode of claim 1 wherein said insulator extends generally longitudinally substantially the entire length of the overlapped portion of said outer tubular sheath and said inner core.

3. The electrode of claim 2 wherein said inner core adjacent one end of said electrode is adapted to have a weight suspended therefrom.

4. The electrode of claim 2 wherein said outer tubular sheath has at least two homogeneously integral electrically conductive ribs thereon terminating in apices extending generally radially outwardly of said tubular sheath.

5. The electrode of claim 2 wherein said inner core comprises an electrically conductive metallic material electrically insulated by said insulator of a dielectric material.

6. The electrode of claim 1 wherein said insulator extends generally longitudinally substantially the entire length of the overlapped portion of said outer tubular sheath and said inner core and engages with said outer tubular sheath and said inner core substantially throughout said overlapped portion.

7. The electrode of claim 6 wherein said outer tubular sheath has at least two homogeneously integral electrically conductive ribs thereon terminating in apices extending generally radially outwardly of said tubular sheath.

8. The electrode of claim 7 wherein said inner core comprises an electrically conductive metallic material electrically insulated by said insulator of a dielectric material.

9. The electrode of claim 6 wherein said outer tubular sheath has not less than four nor more than six generally longitudinally extending ribs thereon with each of said ribs terminating in a generally radially outwardly projecting apex, and extending substantially the entire longitude of said outer tubular sheath.

10. The electrode of claim 9 wherein said electrically conductive material of said outer tubular sheath comprises aluminum or steel.

11. The electrode of claim 9 wherein said ribs are homogeneously integral with said outer tubular sheath.

12. The electrode of claim 11 wherein said inner core comprises a steel wire.

13. The electrode of claim 1 wherein said outer tubular sheath has at least two homogeneously integral electrically conductive ribs thereon terminating in apices extending generally radially outwardly of said tubular sheath.

14. The electrode of claim 13 wherein said ribs extend throughout substantially the entire longitude of said outer tubular sheath.

15. The electrode of claim 14 wherein said ribs extend in generally straight lines on said outer tubular sheath.

16. The electrode of claim 13 wherein said outer tubular sheath has a homogeneously integral hook adjacent at least one end thereof.

17. The electrode of claim 12 wherein said inner core extends beyond the other end of said outer tubular sheath for suspending a weight from one end of the electrode.

18. The electrode of claim 5 wherein said electrically conductive material of said outer tubular sheath comprises steel or aluminum.

19. The electrode of claim 13 wherein said inner core comprises an electrically conductive metallic material electrically insulated by said insulator of a dielectric material.

20. The electrode of claim 13 wherein said electrically conductive ribs are coiled on said outer tubular sheath and extend generally longitudinally thereon such that the effective linear length of said ribs exceeds the axial length of the portion of the tubular sheath on which said ribs are coiled.

21. The electrode of claim 20 wherein said electrically conductive material of said outer tubular sheath comprises aluminum or steel.

22. The electrode of claim 1 wherein said inner core extends beyond said outer tubular sheath adjacent one end thereof for suspending a weight from one end of the electrode.

23. The electrode of claim 1 wherein the discharge electrode is capable of being coiled such that said outer tubular sheath is plastically deformed with none of the components of the coiled portion of the discharge electrode being fractured.

24. The electrode of claim 19 wherein said discharge electrode is capable of being coiled to coil has a diameter not substantially greater than six feet.

H050 UNITED S'I'ATES PATENT OFFICE CERTIFICATE OF CORREC'I ION Patent No. 3,819,985 Dated June 25, 1974 Inventor(s) ROBERT H. DUSEVOIR It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 28 (Claim 17);: Delete "121'. and insert Column 6, line 32 (Claim 18) Delete "5" and insert Column 6, line 57 (Claim 24) Delete "19" and insert line 58 (Claim 24) After "to" delete "coil has".

Signed and sealed this 19th day of November 1974.

(SEAL) Attest:

MCCOY M. GIBSGN JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents Poms) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Petent No. 3,819,985 I Dated June 25, 1974 Inventor(s) ROBERT H. DUSEVOIR It: is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 6, line 28 (claix n 17y; ne ge gy, and insert Column 6, line 32 (Claim 18) Delete "5" and insert Column 6, line 57 (Claim 24) Delete "19" and insert line 58 (Claim 24) After "to" delete "coil has".

Signed and sealed this 19th day of November 1974.

(SEAL) Attest:

McCOY M. GIBSON JR. C MARSHALL DANN Attesting Officer Commissioner of Patents

Claims (24)

1. An electrostatic precipitator discharge electrode comprising an outer tubular sheath of an electrically conductive material providing a corona discharge emission when connected tO a high potential electric source, an inner core extending generally axially through the outer sheath and having sufficient tensile strength to carry the weight of the electrode, and an insulator of a dielectric material interposed between said outer tubular sheath and said inner core retaining said outer tubular sheath and said inner core in generally fixed relation to each other such that the electrode, when in use, will not be completely severed if said outer sheath is completely severed, whereby the likelihood of the electrode in use becoming completely severed and shorting out other electrodes in a precipitator is substantially decreased.

2. The electrode of claim 1 wherein said insulator extends generally longitudinally substantially the entire length of the overlapped portion of said outer tubular sheath and said inner core.

3. The electrode of claim 2 wherein said inner core adjacent one end of said electrode is adapted to have a weight suspended therefrom.

4. The electrode of claim 2 wherein said outer tubular sheath has at least two homogeneously integral electrically conductive ribs thereon terminating in apices extending generally radially outwardly of said tubular sheath.

5. The electrode of claim 2 wherein said inner core comprises an electrically conductive metallic material electrically insulated by said insulator of a dielectric material.

6. The electrode of claim 1 wherein said insulator extends generally longitudinally substantially the entire length of the overlapped portion of said outer tubular sheath and said inner core and engages with said outer tubular sheath and said inner core substantially throughout said overlapped portion.

7. The electrode of claim 6 wherein said outer tubular sheath has at least two homogeneously integral electrically conductive ribs thereon terminating in apices extending generally radially outwardly of said tubular sheath.

8. The electrode of claim 7 wherein said inner core comprises an electrically conductive metallic material electrically insulated by said insulator of a dielectric material.

9. The electrode of claim 6 wherein said outer tubular sheath has not less than four nor more than six generally longitudinally extending ribs thereon with each of said ribs terminating in a generally radially outwardly projecting apex, and extending substantially the entire longitude of said outer tubular sheath.

10. The electrode of claim 9 wherein said electrically conductive material of said outer tubular sheath comprises aluminum or steel.

11. The electrode of claim 9 wherein said ribs are homogeneously integral with said outer tubular sheath.

12. The electrode of claim 11 wherein said inner core comprises a steel wire.

13. The electrode of claim 1 wherein said outer tubular sheath has at least two homogeneously integral electrically conductive ribs thereon terminating in apices extending generally radially outwardly of said tubular sheath.

14. The electrode of claim 13 wherein said ribs extend throughout substantially the entire longitude of said outer tubular sheath.

15. The electrode of claim 14 wherein said ribs extend in generally straight lines on said outer tubular sheath.

16. The electrode of claim 13 wherein said outer tubular sheath has a homogeneously integral hook adjacent at least one end thereof.

17. The electrode of claim 12 wherein said inner core extends beyond the other end of said outer tubular sheath for suspending a weight from one end of the electrode.

18. The electrode of claim 5 wherein said electrically conductive material of said outer tubular sheath comprises steel or aluminum.

19. The electrode of claim 13 wherein said inner core comprises an electrically conductive metallic material electrically insulated by said insulator of a dielectric material.

20. The electrode of claim 13 wherein said electrically conductive ribs are coiled on said outer tubular sheath and extend generally longitudinally thereon such that the effective linear length of said ribs exceeds the axial length of the portion of the tubular sheath on which said ribs are coiled.

21. The electrode of claim 20 wherein said electrically conductive material of said outer tubular sheath comprises aluminum or steel.

22. The electrode of claim 1 wherein said inner core extends beyond said outer tubular sheath adjacent one end thereof for suspending a weight from one end of the electrode.

23. The electrode of claim 1 wherein the discharge electrode is capable of being coiled such that said outer tubular sheath is plastically deformed with none of the components of the coiled portion of the discharge electrode being fractured.

24. The electrode of claim 19 wherein said discharge electrode is capable of being coiled to coil has a diameter not substantially greater than six feet.

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