US2937711A - Electrode structure for electrostatic precipitator - Google Patents

Description

May 24, 1960 M. ROBERTS EI'AL 2,937,711

ELECTRODE STRUCTURE FOR ELECTROSTATIC PRECIPITATOR Filed July 8, 1957 2 Sheets-Sheet 1 INVENTORS LAWRENCE M. ROBERTS RALPH E. WILLISON ATTORNEY May 24, 1960 M. ROBERTS EI'AL 2,937,711

ELECTRODE STRUCTURE FOR ELECTROSTATIC PRECIPITATOR Filed July 8, 1957 2 Sheets-Sheet 2 INVENTORS LAWRENCE M. ROBERTS RALPH E. WlLLlSON BY A M W ATTORNEY ELECTRODE STRUCTURE FOR ELECTROSTATIC PRECIPITATOR Lawrence M. Roberts, Bound Brook, and Ralph E. Willison, North Branch, N.J., assignors to Research- Cottrell, Inc., Bridgewater Township, Somerset County, N.J., a corporation of New Jersey Filed July 8, 1957, Ser. No. 673,752

4 Claims. (Cl. 1837) The present invention relates to electrical precipitators and more particularly and specifically to new and improved electrode structures for electrical precipitators.

Heretofore, various methods and apparatus have been utilized in electrical precipitators for removing accumulated deposits from discharge electrodes. These prior methods and apparatus have principally incorporated means for inducing vibration or shock impact to the electrode supporting structures. It has been discovered that these prior methods and apparatus have provided reasonably efiicient electrode cleaning over limited operating periods, but they are ineffectual to remove encrusted, built-up layers of accumulated deposit from prior electrodes without requiring such a degree of vibration as to bring about fatigue failures in the electrodes which failures result from excessive vibration. I

It is a general object of the present invention to provide a new and improved electrode structure which results in a greatly improved cleaning operation of the electrode lending to the achievement of improved precipitator efiiciencies.

Another object of this invention is the provision of an electrode structure for electrical precipitators which provides for greatly increased activation of the electrode over prior structures for dislodging precipitated material therefrom.

' Still another object of this invention is the provision of an electrode structure having the advantages hereinbefore set forth which is adaptable to either wire or ribbon type electrodes wherein each electrode consists of a pair of identical components secured together under axial tension at the ends thereof with the intermediate portions of said components being unconnected.

A still further object of the present invention is the provision of an electrode structure including two components suspended under axial tension in parallel contiguity in such a manner as to permit the intermediate portions thereof to be moved intermittently into and out of contact with each other upon increase and decrease in the axial tension thereon, or upon vibration of the electrode support.

Still another object of the present invention is the provision of an electrode structure wherein the discharge electrode components are suspended under axial tension in parallel contiguity in such a manner as to permit the intermediate portions thereto to be vibrated by the electric fields established by the energization of the electrodes.

Still another object and advantage of this invention is the provision of an electrode structure as herein described which is of extremely simple and inexpensive construction and which is easily removed and installed in precipitator apparatus with a minimum of time and labor costs.

Still further objects and advantages of this invention will become readily evident to one skilled in the art upon reading the following description in the light of the accompanying drawings.

The nature of the present invention may be stated in atcnt O 2,937,711 Patented May 24, 1960 general terms as relating to .an electrode structure for electrical precipitation. apparatus wherein said electrode consists of a pair of elongated components disposed in parallel contiguity, and clamping means engaging the ends of said electrode components.

Referring now to the accompanying drawings in which like numerals designate similar parts throughout the several views: 7

Fig. 1 is a sectional elevation of a precipitator apparatus embodying the electrode structure constituting the present invention;

Fig. 2 is an enlarged side elevation of one of the electrode structures shown in Fig. 1; V

Fig. 3 is a front elevation disclosing a modified form of the electrode structure; and

Fig. 4 is a sectional view similar to Fig. 2 taken on line 4-4 of Fig. 3.

In reference to the drawings there is disclosed in Fig. 1a precipitator 10 including a shell 12 having an inclined hopper type bottom 14 for collecting anddischarging precipitated materials, a gas inlet 16 in one side wall of the shell in the lower regions thereof, and a gas outlet 18 in the side wall of the shell opposite to the gas inlet and opening outwardly from the upper regions of the shell.

Disposed within the precipitator shell 12 is a plurality of typical collecting electrodes 20 of the plate type which are supported from brackets on the inner walls of the shell in vertical arrangement and in parallel spaced relationship. interposed between each adjacent pair of plate, electrodes 23) is a row of discharge electrodes 22 which are arranged in spacedrelationship and which are suspended from a frame 24 which in turn is suspended from a typical insulator 26 mounted on the upper wall of the shell. A source of high potential electrical energy, shown diagrammatically at 21, supplies electrical energy to' the electrode system, through suitable conductors 23 and 23', the latter of which is grounded. The source 21 is of conventional design and includes a transformer25 and synchronous rectifying switch 27. It will be understood that the described source may be substituted by other satisfactory high potential electrical energy sources being capable of supplying full-wave, half-wave, or pulsating energization to the electrode system. Associated with 32 and are securely aifixed therebetween by means of nut and bolt connectors generally designated at 34 which interconnect the two clamping plate members. The upper ends of the clamping plate members 32, which angularly diverge from each other, are supported by a bolt 36 which extends through each of the plates and through the supporting frame 24. A nut 38 carried on the bolt 36 affixes the clamping plates to the frame.

The lower adjacent ends of the ribbon components 30 are secured in the same manner as the upper ends within a second pair of clamping plates 40, the lower diverging ends 42 of which are secured by nut and bolt means 44 to an eye hook 46 which, as best seen in Fig. 1', has its lower extremity in engagement with a tensioning weight 48 and a typical alignment or steadying frame 50in the lower region of the precipitator.

ing of a pair of like ribbon components 30 is suspended The upper ends of the two ribbon com- By the foregoing construction the electrode 22 consistoccurring centrally of the length of the electrode.

from the supporting frame 24 with the lower extremity thereof weighted to maintain the electrode in vertical alignment and to place the same under axial tension within the precipitator.

In operation, the components 30 constituting the electrode are caused to separate and set up mechanical vibrations and oscillations under the influence of the electric field established by the energization of the electrodes. The vibration and oscillation of the components 30 of the electrode loosens the precipitated materials from the electrode surface freeing the material to fall into the hopper or receptacle bottom of the precipitator shell.

It has been found that satisfactory results were obtained through the use of one-half by 0.036-inch dual ribbon components 30. Ribbon components 30 tend to remain parallel to the shell 12 and. do not develop rotational oscillations at high voltages.

In certain applications it has been found advantageous to combine the cleaning of the electrode effected by the vibrations and oscillations due to the electric field with mechanical vibrating means. The rapping members 28 are thus provided.

Operation of the rapping members 28 in the present construction would serve to intermittently vibrate the supporting frame 24 which vibration causes a displacement of the components 30 constituting the electrode laterally one from the other with their greatest spaced separation The separation of the components laterally one from the other occurs with the intermittent vibration of the frame thereby causing the component elements 30 of the electrode to slap or snap one against the other thus jarring and loosening precipitated materials from the electrode components freeing the material to fall into the hopper or receptacle bottom of the precipitator shell.

The flexing and impact action of the electrode components one with the other establishes a maximum of activity and cleaning operation of each of the electrodes with a minimum of stress establishment in the electrodes adjacent their points of attachment and support thereby maintaining fatigue failures at a minimum.

In Figs. 3 and 4 of the drawings there is disclosed a modified form of the electrode structure wherein the electrode 22 is composed of a pair of wire components 48 which are supported vertically in parallel contiguity with the adjacent paired ends of said components being secured within top and bottom ferrules 50 with each of the ferrule members being securely clamped between clamping barsv 32 such as heretofore described.

In this modified form the wire electrode components constituting each electrode are caused to be vibrated or oscillated by the electric field in a manner similar to that described in connection with Fig. 2 and also may be caused to be intermittently snapped one against the other by vibration of the frame 24 for achievement of the same eflicient cleaning of the electrodes as heretofore described and attributed to the primary embodiment.

It will be understood that both the wire components 48 of Figs. 3 and 4 and the ribbon-like components 30 of Fig. 2 which comprise the discharge electrodes under the influence of the electric field tend to spread apart and set up mechanical vibrations and oscillations. These vibrations and oscillations tend to occur strongly in the region of the corona starting voltage range, slight to moderate in the middle operating voltage range, and again strongly near the sparking voltage range.

It has been found that the separation between the components of the discharge electrode increases with wire or ribbon length and with operating voltage and decreases with tension.

Typical maximum wire separations caused by the associated electric fields at the center of sixteen foot lengths of dual wires at 0.080, 0.109, and 0.135 inch diameter with single fourteen pound weights range from A to /2 inch at 30 k.v.p., to one inchof 60 k.v.p. and A to 1 inch at k.v.p. When ribbon-like components 30 are employed to form the discharge electrodes, the results exhibited are similar to those of the wire components 48; however, vibration in the electric field is slightly less than with wires 48.

A theoretical expression for the maximum wire separation may be given by the following equation:

where: D is the wire separation at the center; L is the length of the wire; F is the force on the wires due to the electric field. (This force is uniform along the wire length and is directed toward the associated collecting plate); and T is the total tension on the wire due to the weight at the bottom.

The above formula is based on a catenary curve for the wires and neglects any effects due to wire stifiness. The force F due to the electric field is computed by merely considering the electrostatic field and an approximation can be made as follows:

where: E is the electrostatic field near the collecting plate surface, and A is the area of the collecting plate between the discharge electrodes.

For a typical case where the potential across the eleo' trode and the collecting plate was 60 k.v.p. half-wave (approximately 50 kv. average); E225 kv./cm.; and A=8l30 cm. whence F a 45,000 dynes or approximately 0.1 pound. The calculated wire separation was:

LF rr :07 inch L=16 feet F=0.l pound T=1 l pounds Relative vibration of the components comprising the discharge electrodes whether they be wires 48 or ribhon-like components 30 is somewhat more pronounced. when pulsating half-wave energization is employed com-. pared to the smoother full-wave voltage.

When the energizing potential is raised sufficiently, bursts of sparking will occur which cause the electrode components to slap together and vibrate vigorously. This slapping action will manifestly be supplemental to the vibrations and oscillations of the electrode components caused by the electrical fields. The effects of this slapping action are similar to that effected by the mechanical rapping described hereinabove.

Thus, from the foregoing descriptions, it is seen that a new and greatly improved electrode structure has been provided for use in an electrical precipitator wherein maximum cleaning of the electrodes is achieved either mechanically, electrically, or the combined effect of both, permitting the employment of electrostatic precipitators. on gas cleaning jobs where the material to be collected readily forms hard crusts or cakes on electrodes. It is also seen that a new and novel electrode structure has been provided accomplishing; newand improved results and satisfying all of. the objects and; advantages heretofore set forth.

This application is a continuation-in-part of our application Serial No. 612,691, filed September 28, 1956, now abandoned.

We claim:

1. In an electrical precipitator, a collector electrode, a discharge electrode structure consisting of a pair of elongate flexible components disposed in parallel relation with respect to one another, clamping means associated with each pair of adjacent ends of said electrode components for supporting said components under axial tension, rapping means associated with one of said clamping means for imparting vibratory movement thereto, and means associated with said discharge electrode for establishing an electric field to thereby augment vibratory movement of said components.

2. In an electric precipitator as described in claim 1 1 wherein said components consist of ribbon members.

3. In an electric precipitator as described in claim 1 wherein said components consist of wire members.

4. An electrode structure as defined in claim 1 wherein said clamping means each consists of a pair of clamping 15 plates including means for securing said plates in face to face opposition, and means associated with said paltea for attachment to a supporting member.

References Cited in the file of this patent UNITED STATES PATENTS 945,917 Cottrell Jan. 10, 1910 1,357,201 Nesbit Oct. 26, 1920 2,660,260 Brixius et al. Nov. 24, 1953 2,722,992 Roberts et a1. Nov. 8, 1955 FOREIGN PATENTS Great Britain Feb. 1, 1938

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