US2694464A - Electrical precipitator - Google Patents

Description

Nov. 16, 1954 H. A. WINTERMUTE ELECTRICAL PRECIPITATOR 3 Sheets-Sheet 1 Filed Feb. 9, 1951 /1NVENTOR mw mwm HARRY A. W INTERMUTE ATTORNEYS Nov. 16, 1954 H. A. WINTERMUTE 2,694,464

ELECTRICAL PRECIPITATOR Filed Feb. 9, 1951 3 Sheets-Sheet 2 g ea \ I I I A a Y L62 INVENTOR F 7 HARRY A.WINTERMUTE BY M-=- W ATTORNEYS Nov. 16, 1954 wlNTERMUTE 2,694,464

ELECTRICAL PRECIPITATOR Filed Feb. 9, 1951 3 Sheets-Sheet 3 INVENTOR HARRY A. WINTE RMUTE nited ELECTRICAL PRECIPITATOR Application February 9, 1951, Serial No. 210,212

4 Claims. (Cl. 183--7) This invention relates to electrical precipitation apparatus for the separation of suspended materials from gases.

More particularly the invention relates to discharge electrode structures for electrical precipitators of the Cottrell type, providing a strong, lightweight, flexible electrode particularly useful for precipitators employing plate type collecting electrodes.

An object of the invention is to provide a ribbon type discharge electrode which may be used without individual tension weights.

A further object is the provision of such an electrode that may be rapped or vibrated and that will have exceptional dust shedding properties.

Another object is to provide a discharge electrode which will not substantially affect the spacing distance between the corona discharge edges and the collecting electrode surfaces upon elongation due to temperature expansion.

A further object is the provision of a ribbon type discharge electrode which will substantially eliminate pith ball action of dust particles between the collecting and discharge electrodes.

Another object of the invention is the provision of a discharge electrode which, when it flexes will bend or wave in a direction parallel to the plane of the collecting electrodes, thereby reducing the possibility of arcing and back corona discharge.

These and other objects and advantages are provided by the discharge electrode of the invention comprising generally ribbon-shaped discharge electrodes provided with projecting elements on the lateral faces thereof and positioned with said lateral faces extending perpendicularly to the extended surfaces of the complementary collecting electrodes.

The invention will be more particularly described with reference to the illustrative embodiments of the invention shown in the accompanying drawings in which:

Fig. l is a fragmentary section of a horizonal flow electrical precipitator emplo ing discharge electrodes constructed in accordance with the principles of the invention;

Fig. 2 is a partial section on line 2-2 of Fig. l more clearly showing the electrode supporting frame;

Fig. 3 is a fragmentary section of a di charge electrode of the invention showing the dust build up on the electrode;

Fig. 4 is an enlarged fragmentary side view of one form o the dischar e electrodes constructed in accordance wi h the principles of he invention consisting of two ribbon-like sheets tack-welded together;

Fig. 5 is an enlarged sectional view of the electrode shown in Fig. 4;

Fig. 6 is an enlarged fragmentary side view of another form of the discharge electrodes constructed from a sin le sheet of conductive material with punched out V-shaned corona discharge points:

Fig. 7 is an enlarged sectional view of the electrode sho n in Fig. 6;

Fig. 8 is an enlarged fragmentary view of the electrode shown in Fig. 6 to more clearly show the shape of the V-shaped corona discharge points;

Fig. 9 is an enlarged fragmentary side view of still another form of the discharge electrodes constructed in accordance with the principles of the invention comprising a single strip of conductive material provided with tates Patent Hce pin type corona discharge points secured along the medial line thereof;

Fig. 10 is a diagrammatic view of the pith ball action on ordinary ribbon type discharge electrodes;

Fig. 11 is an enlarged fragmentary vertical section of one of the discharge electrodes and its corresponding plate electrodes shown in Fig. 1 of the drawings;

Fig. 12 is an enlarged section of the base of an electrode showing the web extension; and

Fig. 13 is an enlarged section of the discharge electrodes shown in Fig. 1 more clearly showing a method of maintaining a uniform spacing between the collecting surface and the edge of the discharge electrode facing it.

Referring to the drawings and in particular to Figs.

. l and 2, 10 is the shell or casing of a horizontal flow electrical precipitator having a gas inlet 12, gas outlet 14, and dust storage hoppers 16. Within the casing parallel plate type collecting electrodes 18 are shown supported by the side walls of the precipitator by beams 20 and spacing rods 22.

The discharge electrodes 24 of the invention which are to be more fully described hereinafter are vertically supported in parallel rows between the collecting electrodes 18. The discharge electrode frame is of cantilever construction to aid in transmitting vibratory action of the electrode rapping means 19 to both the tops and bottoms of the electrodes.

The cantilever frame generally comprises a main support beam 26 supported from the precipitator casing by means of insulating supports, not shown in the drawings,- and beams 28 and 30 parallel thereto. Beams 28 and 30 carry the upper and lower discharge electrode support members, 32 and 34, respectively, and are connected to the main support beam 26 by vertical members 36 and 38.

Between corresponding electrode support members 32 and 34 are provided turnbuckle connectors 40 and wires 41 for squaring up the discharge electrode framework. In order to prevent swinging of the cantilever supported discharge electrode assembly guide members 42, which are insulated from the precipitator casing may be loosely connected to the ends of support members 34 as shown in Figs. 1 and 2 of the drawings.

The ribbon discharge electrodes of the invention generally comprise a strip of sheet metal having substan tially greater width than thickness, and means projecting outwardly along the medial line of its faces to provide points of corona discharge therefrom. The electrode thus constructed is adapted to be positioned within the precipitator with its longitudinal edges directed toward the complementary collecting plates and with the proiections along the electrode faces directed parallel to the direction of was flow.

Figs. 4 and 5 of the illustrative embodiments of the in ention show a pref rred form of construction of the dischar e electrode. The electrode 24a is formed from two sheets 44, one ed e of each being bent at right angles to form proiections 46, and the two sheets being tackwelded ether al ng the bend lines as at 48. To increase the efiiciency of the precipit tor the ed es of ea h sheet forming the electrode are advantageously provided with serr tures to provide points of increased corona disch ge.

The po ition of the ele trode in the preci it t r is clearlv shown. in Fig. 11 where it will be seen that even though the discharge electrode is provided with the project on along its medial axis, the width of the electrode is considerably greater in the plane perpendicular to its complementary collecting electrodes, then in the direction of gas flow. With this form of construction any tendency of the electrode to oscillate or bend will be in the direction of the gas fiow and not towards the collectinn electr des thus substantially eliminating one of the principal factors causing arc-overs and loss of efliciency in electrical gas cleaning apparatus.

In electrical precipitators wherein the discharge electrodes extend beyond the top and bottom of its corresponding collecting electrodes as shown in illustrative embodiments of the invention, the edges of discharge electrodes are advantageously cut back at points 25 where they pass the bottom and top members of the collecting electrode plates, whereby a more uniform electrical potential is maintainable throughout the entire gas treating zone.

One of the disadvantages of employing ordinary sheet or ribbon type discharge electrodes is the pith ball action of dust particles between the collecting electrodes and the broad surfaces of the ribbon. Pith ball action is the result of the attraction and repulsion forces upon a particle in an electrostatic field created between two oppositely charged surfaces. This action is diagrammatically illustrated in Fig. of the drawings in which 52 are plate type collecting electrodes in a horizontal fiow precipitator such as shown in Fig. l of the drawings and 54 is a ribbon type discharge electrode without the provision of projections of the invention along its medial line. With this form of construction it has been found that during the precipitation of material from gas some particles, designated 56, will take the charge of the collecting electrode, then jump in an arc to the discharge electrode, pick up the charge of the discharge electrode and continue thus to oscillate between the two electrodes. Each time a particle oscillates between the electrodes it comes under the influence of the gas stream and is moved toward the gas discharge end of the precipitator. The rapidity of the to and fro motion depends upon such factors as size and electrical conductivity of the particle, the distance between the charged plates, the humidity of the carrier gas stream and the potential difference between the charged plates.

A particle when charged by a corona discharge emanating from a fine wire discharge electrode moves to the opposing collecting surface and does not return as the fine wire does not present a non-corona discharge surface to attract the particle. However, when a strip or ribbon is used as the discharge electrode, the action is quite different. Due to the pencil-like form of a corona discharge a particle can move from the discharge electrode and hit the collecting electrode outside of the field of discharge. The particle is then free to jump in an are around the corona field to the broad surface of the strip electrode. It has been found that pith ball action can be eliminated by the provision of edges, or points along the medial line of the ribbon electrode. These edges as hereinbefore described form points of corona discharge establishing an electrical Wind which prevents particles from returning to the broad surface of the discharge electrode.

The provision of points of corona discharge along the broad surfaces of the electrode of the invention aid in t the removal of material deposits from these surfaces. This is particularly important when the material suspended in the gas to be cleaned is of a cementatory nature. It has been found that material build-up or deposits on discharge electrodes of the ribbon type is substantially less at the points of corona discharge, thus preventing uniform self supporting deposits. At the edges of the electrode and at the edges of the projections along its broad surfaces Weak points of dust build-up are formed whereby when the electrode is rapped or vibrated the deposited material is readily jarred loose. A typical material deposit formation on a discharge electrode of the invention is shown in cross section in Fig. 3 wherein the weak points 58 of the deposited material 60 are clearly shown.

In Figs. 6 through 9 other modifications of the discharge electrode of the invention are shown. The electrode 24b shown in Figs. 6 through 8 is constructed from a single sheet of conductive material 61 with corona discharge points 62 formed therein by cutting and punching V-shaped members along the medial line of the sheet. Each punched out member 62 alternately projects toward one side then the other in staggered relationship.

The electrode 240 as shown in Fig. 9 comprises a single strip or sheet 64 provided with pointed pins or rods 66 welded along the medial line thereof. In the drawing, pins 66 are shown as alternately projecting toward one side of the electrode then toward the other; however, if desired each pin may be inserted in holes punched in sheet 64 and the pins provided with points at both ends.

On installations where the electrodes are to be rapped or vibrated to remove deposits of material collected thereon, it has been found that there is often severe bending of the electrode close to the points where the electrodes are attached to its supporting frame. With the electrode of the invention breakage at the point of attachment has been substantially eliminated by widening or flaring the edges of the electrode that are directed toward the complementary collecting electrodes.

It will be seen that flanges 68 shown on discharge electrodes 24 of Figs. 1 and 12 of the drawings provides an increased area of contact between the electrode and its supporting frame members 32 and 34, and increased rigidity to the electrode in the attaching area, without decreasing the distance between the electrode and its corresponding collecting plates.

From the foregoing description it will be seen that the present invention provides a novel ribbon type discharge electrode whereby the aims, objects and advantages of the invention are fully accomplished.

It will be evident that various modifications may be made in the construction of the electrode and the form of its use. For example, the discharge electrodes of the invention may be used in vertical gas flow as well as in horizontal flow precipitators particularly disclosed by way of example in the drawings and description.

I claim:

1. In an electrical precipitator including a plurality of extended surface collecting electrodes, ribbon-shaped discharge electrodes positioned adjacent the collecting electrodes with the extended surfaces of the ribbonshaped discharge electrodes extending substantially normal to the extended surfaces of the adjacent collecting electrodes, the width of said ribbon-shaped discharge electrodes being substantially greater in the plane perpendicular to its complementary collecting electrodes than in the direction of gas flow, a plurality of elements projecting from the extended surface of the ribbonshaped discharge electrodes substantially along the medial line thereof, said elements having sharp points directed normal to the extended surface of the discharge electrode to form points of electrical discharge whereby pith ball action of dust particles between the collecting and discharge electrodes is substantially eliminated, and said elements being spaced apart along the discharge electrode whereby the flexibility of the discharge electrodes in a direction perpendicular to the plane of extension thereof is not substantially reduced.

2. The invention defined in claim 1 wherein said elements projecting along the medial line of said discharge electrodes are punched out from the electrode with successive elements projecting in opposite directions.

3. The invention defined in claim 1 wherein said elements projecting along the medial line of said discharge electrodes comprises pins secured thereto with the points of successive pins projecting in opposite directions.

4. The invention defined in claim 1 wherein said ribbon-shaped discharge electrode comprises a pair of ribbon-shaped strips one edge of each of said strips being bent substantially normal to the major axis thereof, said bent strips being serrated to form said points of electrical discaharge along the medial line of said discharge electro es.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,917,522 Heinrich July 11, 1933 FOREIGN PATENTS Number Country Date 45,703 Netherlands May 15, 1939 461,370 France Dec. 27, 1913 487,444 Germany Dec. 12, 1929 709,433 France May 18, 1931 719,354 France Nov. 14, 1931

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