US2571079A - Electrostatic precipitator - Google Patents

Description

1951 R. w. WARBURTON 2,571,079

ELECTROSTATIC PRECIPITATOR Filed Dec. 1, 1948 3 Sheets-Sheet 3 IN V EN TOR.

Patented Oct. 9, 1951 UNITED STATES PATENT OFFICE Ray W.

Westinghouse Warburton, Medfield, Mass., assignor to Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application December 1, 1948, Serial No. 62,931

'7 Claims.

This invention relates to electrostatic precipitators for removing dust and other small foreign particles from gases, such as air.

A successful type of electrostatic precipitator for removing dust and other small foreign particles entrained in air is disclosed in the G. W. Penney Patent No. 2,181,717. Such a precipitator has an ionizing chamber in which the air to be cleaned is ionized, whereby the particles entrained therein are given electrostatic charges, and has a collector chamber containing spaced collector electrodes, alternate of which are grounded and the others of which are electrically charged. Usually the collector electrodes of such a precipitator are cleaned at intervals as by being washed down by water or with a flushing oil.

In some cases, it is undesirable or inconvenient to provide facilities for washing the collector electrodes, and in other cases, the users of the precipitators have expressed preference for dis- 'posable collector electrodes which can be removed and replaced after a period of use.

This invention provides a disposable collector cell of inexpensive construction and which can be easily removed, after a period of use, from a precipitator, and which can be easily replaced.

An object of the invention is to provide an inexpensive, disposable, collector cell for an electrostatic precipitator.

I The invention will now be described with reference to the drawing of which:

Figs. 1 and 2 are diagrammatic views of portions of collector cells embodying this invention, and illustrate its principle;

Fig. 3 is a side elevation, with a portion of a side wall removed, of an electrostatic precipitator embodying this invention;

Fig. 4 is a front elevation of the precipitator of Fig. 3; I

Fig. 5 is a front elevation of the collector cell of the precipitator;

of Fig. 5;

Fig. 8 is an enlarged, projected view illustrating the construction of the collector cell;

Fig. 9 is an enlarged, projected view of a portion of another form of collector cell;

Fig. 10 is a sectional view along the lines llll 0 of Fig. 9;

Fig. 11 is an enlarged, front elevation of a portion of another form of collector cell embodying this invention;

Fig. 12 is a side elevation of the cell portion shown by Fig. 11, and

Fig. 13 he plan viewlooking down on the cell portion shown by Figs. 11 and 12.

The principle of the invention will first be de scribed with reference to Figs. 1 and 2. The rectangular metal frame 20 is formed by wires which are interconnected and grounded. The filaments 21 are formed as a woven mesh screen within the frame 20 with their ends attached thereto. The filaments may be of relatively high resistance, electric conducting material, such as asbestos fibers-paper or cloth base filaments or threads which have been impregnated with a liquid containing electrically conductive particles, such as carbon or metallic salts, or filaments of semiconductive plastics, such as urea-resin plastics. The intersection of the filaments at 23 at the center of the screen is connected to a positive highvoltage terminal of a power supply source,

which may be a +12,000 volt terminal, the negative terminal of the source being connected to ground and to the frame 20. Asmall electric current will flow through the mesh in all directions between the central point 23 and the frame 20. Every point of the screen will be charged to a voltagedepending upon its location.

With reference now to Fig. 2, assuming that electric current flows from the point A to the point C along the filament sections 25, 25, 21, and 28, and assuming the electrical resistance of the sections 25, 26, 21, and 28 is equal, then the voltage drops across the sections will be equal, and the potential at the points B andD will be the same, and equal to one-half the potential difference between the points A and C. 5 The potentials along the filament section 25 between the points A and B will be higher than those along the filament section 26 between the points B and C, and the potentials along the filament section 21 between the points A and D will be higher than those along the filament section 28 between the points D and C. There is an electrostatic field between the filament sections 26 and 21, and an electrostatic field between the filament sections 25 and 28, the resultant of the electrostatic field being between the'points A and C. Sincethe spacing between adjacent, oppositely disposed filaments is small, the electrostatic field between them will be relatively large.

The current flow is not, of course, confined to one loop on the screen but will flow in every filament section between the central point 23 and the frame 20.

If- ;the electrified screen of Fig. 1 is placed transverse the direction of the flow of gas containing electrostatically charged dust particles, the particles will precipitate upon the fiiaments. By using filaments having a low electrical conductivity, voltage drops caused by current flow will establish charges along different points of the screen, and the electrostatic charges on the particles which deposit upon the screen, will leak off through the filaments to ground, .thus preventing a space charge effect being set up by the deposited particles.

Figs. 3 to 13 of the drawing illustrate practical embodiments of the invention in which collector cells having substantial depth in the direction of gas flow are provided.

Figs. 3 and 4 illustrate an electrostatic precipitator having a conventional metal casing with the conventional ionizer wire electrodes 3| and the conventional tubular ionizer electrodes 32 arranged across its gas inlet. The collector cell 33 is arranged within the casing 30 downstream with respect to gas flow of the ionizer electrodes, and its details are illustrated by Figs. 5 to 8 of the drawing.

The cell 33 has an enclosure 34 of electric insulating material with the hinged portions 35 in its upstream side, and which may be swung out of the way for permitting the insertion of, and the removal of, the screens 36 and their associated wires 31.

The screens 36 are formed from the spaced, horizontal, relatively large, metal wires 38 which are folded at equally spaced points so as to form vzig-zag outlines, and the straight, relatively large, vertical, metal wires 39 extend perpendicular to the wires 38 midpoint the apices of the folds. The meshed, closely spaced, filaments 40 which are similar to those described in the foregoing in connection with Figs. 1 and 2, are attached to the wires 38 and 39. grounded, and are seen to form a number of grounded frames similar, except for the folds in the wires 38, to the frame 20 illustrated by Fig. 1. .Each frame contains a filamentary screen section similar, except for its being folded, to the screen section of Fig. 1. Alternate screen sections are folded so as to have their central, vertical filaments form apices upstream, with respect to gas flow, of the wires 39, and the others of the screen sections are folded so as to have their central, vertical filaments form apices, downstream with respect to gas flow, of the wires 39. The wires of the vertically aligned set of Wires 3'! contact the centers of the alternate screen sections of each screen 35 at 4|, and the Wires of another set of vertically aligned wires 31 contact the centers of the other screen sections at 43. The wires 31 are connected to the +6,000 volt terminal of the direct current supply source for the precipitator, the negative terminal of which is grounded, so that each screen section of each screen 36 is seen to have a central point at a 6,000 volt potential, with a grounded frame around it. Thus the filaments of each screen section are electrically charged as described in the foregoing in connection with Figs. 1 and 2. The ionizer wires of the precipitator illustrated by Figs, 1 and 2 are adapted to be connected to the +12,000 volt terminal of the power supply, and the tubular ionizer wires are adapted to be grounded, so that dust particles in the gas passing between the ionizer electrodes are given positive electrostatic charges. The particles are then attracted to, and are deposited upon, the charged filaments of the screen 36.

When the collector cell 33 becomes loaded with The wires 38 and 39 are,

Lil

dust and other collected particles, it may be re moved and replaced, following which the used one can be discarded or its screens 36 removed and replaced. It may be possible to clean the screens so they can be used again.

Figs. 11 to 13 of the drawing illustrate a modification of the collector cell of Figs. 3 to 8 in which the horizontal wires 3'! are intersected by equally spaced vertical wires 44, forming square frames within which are placed the filaments 45, to form screen sections similar to that illustrated by Fig. 1. The upstream apices of the grounded wires 38 of the screens 36, contact the centers of the screens within the charged frames formed by the wires 31 and 44 which are upstream of the screens 36, at 46, and the downstream apices of the grounded wires 38 of the screens 36, contact the centers of the screens within the charged frames formed by the wires 31 and 44 which are downstream of the screens 36, at 41.

The screen sections between the wires 31 and 4d are seen to be similar to that illustrated by Fig. 1, except that the frame around each section, instead of being grounded, is at a +6,000 volt potential, and ground is applied to the center of the screen sections. This means that the current flows in the filaments in the opposite direction to the current flow in the filaments of the screen of Fig, l, but the voltage drops at corresponding points along the filaments are the same in each case, and the same electrostatic fields will be established.

An advantage of the embodiment of Figs. 11-13 of the drawing, over that of the embodiment of Figs. 3-8, is that since the spaces between the wires 3'! contain filamentary screens, more collecting surface is provided in the same space.

Figs. 9 and 10 illustrate another embodiment of the invention in which the filamentary screens are arranged in pairs of flat sheets and 5| having spaced, rounded projections 52 and 53 respectively, the projections on one sheet of each pair being staggered with respect to the projections on the other sheet of each pair, whereby the projections space the flat portions of the sheets apart. The filaments are not shown but are similar to those described in the foregoing. The spaced vertical wires 54 and the spaced horizontal wires 55 of the sheets 50 intersect at the centers of the projections 52, and form substantially rectangular frames around screen sections substantially similar to that illustrated by Fig. l of the drawing. The wires 54 and 55 are grounded so that the frames around the screen sections are grounded.

The spaced vertical wires 56 and the spaced horizontal wires 5! of the sheets 5| intersect at the centers of the projections 53, and form frames around screen sections which are substantially similar to that illustrated by Fig. 1. The wires 56 and 57 are connected to the +6,000 volt terminal of the power supply so that the frames they form around screen sections are charged to that voltage.

The'wires 56 and 51 in each projection 53 of each sheet 5| contact the center of a screen section in an adjacent sheet 50, within a grounded frame formed by the grounded wires 54 and 55, so that there is an electrostatic field established between the filaments as described in the foregoing in connection with Figs. 1 and 2.

Likewise, the wires 54 and 55 in each projection 52 of each sheet 50 contact the center of a screen section in an adjacent sheet 5|, within a charged frame formed by the wires 56 and 51, so

that there is an electrostatic field established between the filaments in each sheet 50.

The charged filaments in the sheets 50 and El would attract the electrostatically charged dust particles in an electrostatic precipitator in which they are used, as described in the foregoing in connection with Figs. 2 to 8 of the drawing.

While the filaments have been illustrated as having rectangular openings therebetween, the openings may be circular, or have other shapes, such as those in honey combs or egg crates. The sheets containing the filament may be of the woven thread type with holes punched therein. The cells could be circular or have other shapes than the rectangular ones illustrated. The filaments could be coated with an adhesive for aiding in holding the deposited particles.

While embodiments of the invention have been described for the purpose of illustration, it should be understood that the invention is not limited to the exact apparatus and arrangement of apparatus illustrated, as modifications thereof may be suggested by those skilled in the art without departure from the essence of the invention.

What is claimed is:

1. A collector cell for an electrostatic precipitator comprising a plurality of frames formed by mutually perpendicular, metal wires, screens of meshed filaments having relatively high, electrical resistances in said frames with their ends contacting same, said frames and screens being folded along substantially central lines so as to follow a zig-zag outline, a plurality of interconnected wires contacting said screens at substantially the centers thereof, and means for connecting said interconnecting wires and said mutually perpendicular wires to a source of electric current.

2. A collector cell for'an electrostatic precipitator comprising a plurality of frames formed by mutually perpendicular, metal wires, screens of meshed filaments having relatively high, electrical resistance in said frames with their ends contacting same, said frames and screens being folded along substantially central lines so as to follow a zig-zag outline, a plurality of substantially parallel wires contacting said screens at substantially the centers thereof, a plurality of other wires forming with said parallel wires other frames, other screens of meshed filaments having relatively high electrical resistances in said other frames, the apices of said first mentioned frames contacting said other screens at substantially the centers thereof, and means for connecting said mutually perpendicular wires to one side of a high voltage, electric current source, and for connecting said parallel wires to the other side of said source.

3. A collector cell for an electrostatic precipitator comprising a pair of electrode sheets, each. sheet including a plurality of intersecting wires forming frames, the sheets having bulges therein at the intersections of the wires, screens of meshed filaments having relatively high,'electrical resistances in said frames, the wire intersections in the bulges in each sheet contacting the other sheet at substantially the centers of the screens therein, and means for connecting the wires in one sheet to one side of a high voltage, electric current source, and for connecting the wires in the other sheet to the other side of the source.

4. A collector cell for an electrostatic precipitator comprising an outer supporting frame, a plurality of inner frames formed by mutually perpendicular wires having relatively low electrical resistance supported within said outer frame, screens of meshed filaments having relatively high electrical resistance in said inner frames with their ends contacting said inner frames, means for connecting said wires to one side of an electric source, and means for connecting said screens at substantially their centers to the other side of said source.

5. A collector cell for an electrostatic precipitator comprising an outer frame, a plurality of spaced apart frame members supported within said outer frame, each member comprising a plurality of inner frames formed by mutually perpendicular wires having relatively low electrical resistance, screens of meshed filaments having relatively high electrical resistance in said inner frames with their ends contacting said inner frames, said wires of one member being staggered with respect to said wires of another member so that the wires forming the frames of one member extend past the centers of the frames of another member, means for connecting said wires of said one member and the screens of said other member to one side of an electric source, and means for connecting said wires of said other member and said screens of said one member to the other side of said source.

6. A collector cell for an electrostatic precipitator comprising an outer frame, a pair of spaced apart frame members supported within said outer frame, each member comprising a plurality of inner frames formed by mutually perpendicular wires having relatively low electrical resistance, screens of meshed filaments having relatively high electrical resistance in said inner frames with their ends contacting said inner frames, said wires of one member being staggered with respect to said wires of the other member so that said wires of said one member extend past the centers of the screens of the other member, means for connecting an electric source, and means including a wire folded in a zig-zag path with its apices contacting the centers of said screens for connecting said screens to the other side of said source.

7. A collector cell as claimed in claim 6 in which other wires form with said folded wire other inner frames containing other screens of meshed filaments having relatively high electrical resistances, said other screens being folded in zig-zag planes with their apices contacting the first mentioned wires, said other wires having relatively low electrical resistances.

RAY W. WARBURTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,461,441 Davis July 10, 1923 2,278,538 Dublier Apr. '7, 1942 2,422,564 Page June 17, 1947 said wires to one side of

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