US2817413A - Electrostatic precipitators - Google Patents

Description

Dec. 24, 1957 J. E. MCDONALD ETAL 2,317,413

ELECTROSTATIC PRECIPITATORS Filed Nov. 3, 1955 III 1 POWER PACK eg- M United States Patent ELECTROSTATIC PRECIPITATORS John E. McDonald, Newton, and William Roos, Sharon, Mass., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 3, 1955, Serial No. 544,627

Claims. (Cl. 183-7) This invention relates to electrostatic precipitators for removing small foreign particles such as dust from gases such as air.

A feature of this invention is that it uses metal collector plates interspersed with dielectric plates, the metal plates being grounded and serving as the non-discharging ionizer electrodes, the dielectric plates being charged by the ionization current flowing from ionizer wires to the metal lates. p In one embodiment of this invention, the dielectric plates are coatings on corresponding sides of the metal plates.

In another embodiment of this invention, the dielectric plates are separate plates and are spaced from the metal lates. D By making the charge plates of dielectric material, the usual insulators are not required, and they are cheaper than metal plates.

Objects of this invention are to simplify and to reduce the cost of electrostatic precipitators.

This invention will now be described with reference to the annexed drawings, of which:

Fig. 1 is an end section of an electrostatic precipitator embodying this invention; the section being taken along the line 1-1 of Fig. 2;

Fig. 2 is a side section of the precipitator of Fig. 1;

Fig. 3 is a front or air inlet view of the precipitator of Figs. 1 and 2, and

Fig. 4 is an end section of another precipitator embodying this invention.

Referring first to Figs. 1-3, a metal casing has a plurality of parallel, spaced-apart plates 11 secured at their ends as being forced fitted to the inner surfaces of the top and bottom sides of the casing. Each plate has on one side, the right side facing Fig. 1, a sheet 12 of dielectric material such as polyester, polyethylene or vinyl. The sheets may be cemented to the plates. The casing has an air inlet 13 and the upstream ends of the sheets 12 extend upstream of the upstream ends of the plates 11 so that they are much closer to the inlet 13 than the upstream edges of the plates are.

Between the upstream ends of the sheets 12 and the air inlet 13, insulators 14 attached to the inner surface of the top and bottom sides of the casing support ionizer wires 15. The wires 15 are connected to the positive terminal of a conventional high voltage, direct cur-rent power pack 16, the negative terminal of which is grounded and connected to the casing 10, the plates 11 being grounded through their contact with the grounded casing.

In operation, ionization current flows between the ionizer wires and the upstream edges of the plates 11, and charges the sheets 12 electrostatically positive. Experiments have shown that the charges tend to concentrate 2,817,413 Patented Dec. 24, 1Q57 at the front or upstream edges of the sheets so that for distributing the charges more uniformly over the surfaces of the sheets, fine conductive lines 18 are formed as by printed circuit technique on the sides of the sheets opposite the sides attached to the plates 11. The sheets 12 form charged collector electrodes, electrostatic fields between them and the grounded plates 11 which are spaced therefrom, causing the dust particles charged by the ionization field to be attracted to the oppositely charged surfaces.

Since the sheets 12 are dielectrics, it does not matter if their ends contact the grounded casing walls. Obviously, they do not have to be supported by the usual separate insulators, thus reducing the cost of the precipitator. Another cost reduction results from using the upstream edges of the metal plates 11 as the non-discharging ionizer electrodes, eliminating the need for the usual ionizer electrodes on opposite sides of the ionizer wires.

The embodiment of the invention shown by Fig. 4 is similar to that of Figs. l-3 except that instead of the charged collector electrodes being formed from sheets on the metal plates, they are separate plates 20 of dielectric material such as mentioned in the foregoing or other conventional dielectrics.

In Fig. 4, both sides of the plates 20 are charged electrostatically by the ionization fields extending from the wires of the ionizer to the upstream edges of the metal plates, the upstream edges of the plates 20 extending nearer the ionizer wires than the upstream edges of the metal plates do. Electrostatic collector fields extend from both sides of each plate 20 to plates 11 on both sides thereof, or in the case of end plates 20, from both sides of such end plates to an adjacent plate 11 on one side thereof, and to an adjacent vertical side wall of the casing on the other side thereof. The sides of the plates 20 would have conductive lines thereon similar to the lines 18 of Fig. 2 for distributing the electrostatic charges on the plates 20.

What we claim as our invention, is:

1. An electrostatic precipitator comprising a collector cell having a plurality of parallel, spaced-apart, collector plate surfaces, some of said surfaces being conductive, others of said surfaces having a plurality of spaced-apart conductive lines thereon from their entering portions to their air leaving portions said others of said surfaces being dielectrics except for said lines, the air entering edges of said dielectric surfaces extending outwardly beyond the air entering edges of said conductive surfaces.

2. An electrostatic precipitator as claimed in claim 1 in which each conductive surface is one side of a metal plate, and each dielectric surface is the outer surface of alsheet in contact with the other side of one of the metal p ates.

3. An electrostatic precipitator comprising a casing having an air inlet and an air outlet, a collector cell in said casing having -a plurality of parallel, spaced-apart collector plate surfaces, some of said surfaces being conductive, others of said surfaces having spaced-apart conductive lines thereon from their air entering portions to their air leaving portions, and said others of said surfaces being dielectrics except for said lines, an ionizer wire supported in said casing between said cell and said inlet, the air entering edges of said other surfaces extending closer to said wire than the upstream edges of said conductive surfaces, the edges of said conductive surfaces nearest said wire forming the sole non-discharging electrode means for said wire.

4. An electrostatic precipitator as claimed in claim 3 in .which each conductive surface is .one side of a metal plate, and each dielectric surface is the 'outer surface of a sheet in contact with the other side of one of the metal plates.

5. An electrostatic precipitator as claimed in claim 3 in which the conductive surfaces are the opposite sides of metal plates, and the dielectric surfaces are the opposite from .said metal plates.

References Cited in the file of this patent UNITED STATES PATENTS Abbey June 13, 1944 Cooperman Nov. 1, 1955 True Ian. 3, 1956 FOREIGN PATENTS France June 1, 1931

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