US2181147A - Electrostatic precipitator - Google Patents

Description

N Q Q E. H."R- PEGG 2,131,147

T QsTATIc PRECIPITA'IOfi Filed March 26, 1936 IINVENTOR EdWd/d bf)? P2 ATTORNEY Patented Nov. 28, 1939 PATENT- OFFICE;

ELEG'I'ROSTATIC PREOIPITATOR Edward H. R. Pegs, Wilkinsburg, to Westinghouse Electric 8; Company, East Plttsbu of Pennsylvania.

Pa., assignor Manufacturing rgh, Pa., a corporation Application March 26, 1938, Serial No. 198,247

My invention relates to electrical precipitators for atmospheric dust, and particularly, although not necessarily, such 'precipitators asv may be used for the conditioning of air which is to be breathed.

The present invention is an improvement-over that which constitutes the subject matter of Gaylord W. Penneys application Serial No. 45,070, filed ,October 15, 1935, Patent No. 2,129,783, granted September 13, 1938, relating to a gaspurifying precipitator in which the gas is blown first through an ionizing chamber, and then through a separate precipitating chamber, a significant feature of the precipitator being that the ionizing wire is of such small diameter that practically utilizable ionization of suspended par-- ticles in the gas maybe obtained at a wire-charging voltage which is below the critical corona voltage, so that the wire-charging voltage may a be below this critical value, thereby limiting the 20 ionizing current input and also limiting the -ozone-generation when the precipltator is used for cleaning air.

Such a precipitator utilizes an ionizing wire of less than 32 mils thickness, which is a some-- what roughly critical value of the wire-diameter, somewhere near the knee of the curve expressing the relation between the critical corona voltage and the wire diameter. In ordinary practice, the

wire is much finer than this upper limit, and is frequently a tungsten wire 5 mils in diameter,

or even very much less in diameter. In order to ensure against breakage and to facilitate handling wire must be fairly rigid and strong, and if the wire is longer than about a foot, it should be supported at frequent intervals along its length, say

at every 8 inches, in order to protect it against vibration and breakage, .or, in remote cases, against excessive sagging. These supports in- 40 some half inch to three quarters of an inch' on either side of the support, defining regions at which the ionizing current isquite inadequate, so .that the air or gas which passes these regions is 45 not adequately ionized, thus reducing the efliciency of the precipitation. It is invention to avoid the foregoing difiiculties.

One object of my invention is to provide suitable means such as baflies or air-guides for ensuring 50 a negligibly small, or greatly-reduced, rate of gas-flow past the regions near the supportingpoints where there is inadequate ionization.

Another object of my invention is to provide an improved form of intermediate wire-steadying troduce dark spots along the wire, extending from,

an object of my.

means in the form of a flexible filamentary memher in tension, lying substantially parallel to the line 'of gas-fiow, and pulling upon the fine ionizing wire with enough force to prevent destructive vibration of the ionizing wire. Such a flexible filamentary member will be so small in physical dimensions that it will not produce the dark space of poor ionization which is characteristic of the'more massive rigid intermediate supports which have heretofore frequently been necessary.

With the foregoing objects in View, and others which will become apparent as the description proceeds, my invention consists in the systems, methods, apparatus and combinations hereinafter described and claimed, and illustrated in the accompanying drawing, wherein:

Figure 1 is a longitudinal vertical sectional view of an exemplary form of embodiment of my invention, the section plane being indicated at I-I in Fig.2;

Fig. 2 is a vertlcal cross-sectional vview, on the plane indicated byjthev line 11-11 in Fig. 1,

.. and

Fig. 3 is a top plan view, with parts broken away for clarity of illustration.

In the illustrated embodiment of my invention, which is only one of many forms which the invention can take, air to .be treated is drawn in through the top of the precipitator-cabinet i through a protective screening 2, and passes downwardly through an ionizing chamber 3 in the top of the cabinet, after'which the air continues downwardly and passes through a precipof the equipment, the end-supports for such a fine itatlng chamber 4, the bottom of which discharges into a blower 5 for drawing the air through the apparatus. The outlet of the blower may either discharge the treated air near the fioor or the treated air may be led away from the blower by any means and in any manner which may commend itself as desirable.

The ionizing chamber usually-comprises a plurality of ionizing units disposed transversely with respect to the direction of air-flow, each ionizing unit consisting of a centrally disposed fine wire 6 which is disposed in spaced relation to provide adequate insulation. It will thus be seen that the air in the spaces between the endsupports 8 and the end-walls i3 is not adequately ionized, and that this region of inadequate ionization also extends for some half inch to three quarters of an inch in from the end-supports 8. According to one phase of my invention, I provide suitable bailies or other air-directing means for keeping the air-stream from passing overthese regionsof poor ionization. In the particular embodiment of my invention shown in the drawing, these baflies take the form of end-shields l5 dis-- posed at the ends of the screening 2 at the top of the cabinet'l, so that the air enters'the top of the. cabinet at points sufficiently removed from the end-walls l3 to prevent, or substantially prevent, the air-stream from .playing over the points i where the end-supports 8 engage the wires 6.

Unless the wires 6 are very short, it will .usually be found desirable to steady these wires at one or more intermediate points between the endsupports 8. In accordance with my invention, I have preferred to accomplish this process through the. utilization of one or more flexible filamentary means 16, in tension, which may consist of phosphor-bronze or tungsten wire, of say, 10 mils diameter, not necessarily quite as small as the ionizing wire 6, but small enough so that it does not seriously hinder the flow of ionizing current at the point where the steadying wire l6 hooks over the ionizing wire 6. The'steadying wire or I filamentary member I6 is supported by a rigid stub I! connected to the skeleton framework 9 and extending a short distance toward the ionizing wire 6, so that the hooked wire l6 lies substantially parallel to the gas-flow. By being, in tension, the hooked wire-support l6 pulls the ionizing wire 6 just slightly out of a straight line, so that the ionizing wire is prevented from vibrations which wouldquickly cause its breakage.

The precipitating chamber 4 consists of a large number of spaced insulated plates 20 and ground-'- ed plates 2 I, spaced closely together, and disposed parallel to the direction of air-flow. The insu- 'lated precipitating plates 20 are supported by notched metallic supports 22 which are carried by insulators 23. The non-insulated precipitating plates 2| are supported and spaced by means of notched plates 24 carried by the cabinet I.

As explained in the aforesaid Penney application, theionizing wires 6 and the insulated precipitator-plates 20 are unidirectionally charged 1 with respect to the uninsulated or grounded parts.

Because of the greater spacing between each wire 6 and its associated tubular electrodes'l, as comparedwiththespacingbetweenthe alternate plates 20 and 2| of the. precipitator chamber, the ioniz-. ing voltage is frequently higher than the precipitating voltage. I have indicated that unidirectional voltages are applied to the ionizing wires 6 and the. precipitator-plates 20 by showing leads 25 and 26, respectively, marked on the drawing as being energized, respectively, by the positive terminal of the unidirectional ionizing source of voltage I+, and by the'p'ositive terminal of the unidirectional precipitating source of voltage P+, thenegative terminals being grounded on the frame of the cabinet I, as indicated at 30.

In operation, the air entering the top of the cabinet I, as shown by the, arrows, is first ionized in theionizing chamber 3 so as to charge the particles which are suspended in the incoming air. The air then passes through the precipitating chamber 4 where the charged suspended particles become attracted to the oppositely charged prespaces which'seem dark in the sunlight.

cipitating plates, after which the purified air is be taken outdoors and washed with a hose, after which it is again ready for use.

By my invention, it will be observed that the the 'air, in the 5 efficiency of precipitation is increased by the 10 measures which I have taken to combat the dimculties heretofore experienced as the result of dark regions along the ionizing wires 6,'where inadequate ionization is obtained. When I refer to the dark regions around the supporting-points of the ionizing wire, as obtained in previous structures utilizing massive wire-supports 8 without means for providing supplementary ionization at these points, I refer to regions which appear to be dark when viewed in a dark room. Normally,

there will be a slight discharge or corona-glow which is distinctly visible in a dark room, in the immediate vicinity of the ionizing wires 6, when the precipitator is operating correctly, but this phenomenon is distinctly different from the corona-discharge which is visible in sunlight and which requires a much higher ionizing voltage than I utilize on my wires 6. I term the lowest voltage which produces a corona-discharge of the sort which is visible in sunlight'the critical corona voltage of the wire. My present invention follows the practices explained in the aforesaid'Penney application, in utilizing an ionizing voltage which is'conside'rably lower than this critical coronavoltage, this practice being made possible by the utilization of a sufiiciently fine ionizing wire.

When I refer to dark spaces appearing around the ionizing wire, therefore, I refer to spaces which seem dark in a darkened room, and not to While I have described my invention in a pre-. ferred form of embodiment, and have suggested certain limits in accordance with my best understanding of the same atthe present time, I desire it to be distinctly understood that I am not altogether limited to these limits or understandings, or to the particular form of embodiment shown in the drawing. I desire, therefore, that the appended claims shallbe accorded the broadest construction consistent with their language and the prior art'.

I claim as' my invention: 1. A gas-purifying precipitator comprising an ionizing chamber, aseparate precipitating chamher, and means folrcausing a gas-flow successively through first said ionizing chamber, and then said'precipitating chamber; said ionizing chamber being provided with one or more ionizing units, each unit being disposed transverse to the ga's-flow'and comprising oppositely charged electrodes comprising'a single fine wire spaced between relatively large electrodes, and an intermediate steadying-means for said fine wire, said intermediate steadying-meanscomprising a flexible filamentary-member in tension, for pulling said fine wire only slightly out of a straight line, said steadying-means lying. substantially parallelto the direction 'of gas-flow; said precipitating chamber comprising oppositely charged, spaced precipitating electrodes substantially parallel to the direction of gas-flow; and means associated with both the ionizing chamber and the precipitating chamber for unidirectionally charging said oppositely charged electrodes; said fine wire or wires being of less than 32 mils diameter and beionizing chamber, a separate precipitating ch'am ing of such fineness that substantially utilizable ionization of suspended particles in the gas is obtained at a wire-charging voltage below the critical corona voltage, and the wire-charging voltage being below-said critical corona voltage.

2. A gas-purifying precipitator comprising an ber, and means for causing a gas-flow successive ly through first said ionizing chamber and then said precipitating chamber; said ionizing chamber being provided with one or more ionizing units, each unit being disposed transverse to the gas-flow and comprising oppositely charged electrodes comprising a, single fine wire spaced between relatively large electrodes, one or more relatively rigid supporting-means for saidfine wire, and gas-directing means disposed in sumciently close relation to the-supporting-points of the fine wire for ensuring a greatly reduced rate of gas- -flow past one or more of said supporting-points of said fine wire; said precipitating chamber com- 3. A gas-purifying precipitator comprising an ionizing chamber, a separate precipitating chamber, and means for causing a gas-flow successively'through first said ionizing chamber and then said precipitating chamber; said ionizing cham her being provided with one or more ionizing units, each unit being disposed transverse to the gas-flow and comprising oppositely charged electrodes comprising a wire spaced between relatively large electrodes," and an intermediate steadying-means for said wire, said intermediate steadying-means comprising a flexible filamentary member in tension, for pulling said wire only slightly out of a straight line, said steadyingmeans lying substantially parallel to the direction of gas-flow; said precipitating chamber comprising oppositely, charged, spaced precipitating electrodes substantially parallel. to the direction oi! gas-flow; and means associated with both the,

ionizing chamber and the precipitating chamber for unidirectionally charging said oppositely charged electrodes.

4. A gas-purifying precipitator comprising an ionizing chamber, a separate precipitating chamber, and means for causing a gas-flow successively through first said ionizing chamber .and then said precipitating chamber; said ionizing chamber being provided with one or more ionizing units, each unit being disposed transverse to the gas-flow and comprising oppositely charged electrodescomprising a wire spaced between relatively large electrodes, one or more relatively rigid supporting-means for said wire, and gasdirecting means disposed in sufliciently close relation to the supporting-points of the wire for ensuring a greatly reduced rate of gas-flow past one or more of saidsupporting-points of said wire; said precipitating chamber comprising oppositely charged, spaced precipitating electrodes substantially parallelto the direction ofgas-flow; .and means associated with both the ionizing chamber and the precipitating chamber for unidirectionally charging said oppositely charged electrodes.

. 5. The invention as defined in' claim 1, characterized by.the relatively large electrodes of the ionizing chamber having a limited effective extent in the direction lengthwise of said, filamentary steadying means so that said relatively large electrodes are, .for the most part, more 1 closely spaced from the fine wire than from said filamentary steadying means.

6. The invention as. defined in claim 3, characterized by the relatively large electrodes of the ionizing chamber having a limited eii'ective extent in the direction lengthwise ot said filamentary steadying-means so that said relatively large electrodes are, for the most part, more closely spaced from the fine wire than from said filamentary steadying means.

EDWARD H. R. PEGG.

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