US2578558A - Electrical precipitator - Google Patents

Description

Dec. 1l, 1951 H. KLEMPERER ELECTRICAL `,PRECIPIlAToR 2 SHEETS-SHEET l Filed OCC. 16, 1946 A T B yr Clli R V mk w M w Dec. 1l, 1951 H. KLEMPERER ELECTRICAL PRECIPITATOR 2 SHEETS-SHEET 2 Filed oct. 1e, 194e /NvENTo/e AJA/'vs KLEMPERER BV QZ ATT RNEY Patented Dec. 11,v 1951 ELECTRICAL PRECIPITTR Hans Klemperer, Belmont, Mass., ass'i'gnor 'to :Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application October 16, 19.46, Serial No. 703,504

'2 Claims.

This invention relates to electrical precipita- -l`tors for separating dust, smoke, and similar impurities from air or other gases. More particularly, the invention relates to a precipitator of the type iny which an alternating potential is applied to the electrodes of the precipitator.

In my 'copendin'g application Serial No. 67S,- 1155, led June 20, 1946, now Patentilo. 2,542,035, dated February 20, 195i, there is disclosed a precipitator 'in which the ionizing device 'thereof is supplied with an alternating current without the necessity of providing rectiiiers between the source and the ionizing electrodes. The present lnventionconcerns a construction in which both the ionization of the air or other gases and the precipitation and collection of dust particles are leffected by `means of alternating potential without the necessity of providing rectiiiers for either the ionization-or collection rof the dust particles.

V'Io these ends the invention contemplates construction in which an alternating `potential is applied to a plurality of electrodes or the type adapted to eiect both ionization and collection, the number and length of said electrodes being correlated to the number of phases of the power junction with the accompanying drawing in.

which:

Fig. 1 is a diagrammatic view of anelectrical precipitator whichillustratesvthe principles ci the invention;

Fig.. '2 is a schematic illustration representing gas conditions in my device at the ends of lsuccessive time intervals;

Fig. 3 is a series of :voltage waveforms useful :in explaining the operation of the invention; and

Fig. 4 is a view `similar to Fig. l showingfan apparatus constructed in `accordance. with the invention.

Referring :to the drawing, and first to Fig. 1, reference numeral E6 indicates generally a threephase .transformer `having A-connected primary windings |'2 :and Y-connected secondary windings I 4..' The iouter terminals .15, t8 Avand 12e of the Y secondary windings f 'the transformer 'it are Ydirectly connected, respectively, to the ionizing electrodes Il, |9 and 2|. The neutral point 23 oi' the secondary windings is directly connected to a metallic casing 22 providing an air channel surrounding the `electrodes il, I9, and 2|. Preferably the connection between the center point 23 and the channel 22 is grounded. The wire electrodes I9 `and 2| are arranged in alignment, each extending longitudinally ofthe channel 22, and are so spaced with respect to the direction of air flow and the speed of the air passing through the channel 22 that portions fof kthe air to `be cleaned are acted upon successively by each of the electrodes I7, lil and 2| to the lend that Aduring the positive peaks of potential upon any one of 'the electrodes il, |9 and 2| 'the air passing the electrode at which a positivepeak occurs will be ionized and the dust particles precipitated upon walls yoi the channel 22 'forming a common grounded electrode. The length of each of the electrodes |"l', 'I9 and 2| is so correlated `to vthe velocity of the kair passing through the channel -22 that, during the positive peak upon 'a given wire electrode, the air in channel 22 will traverse a distance equal to the length of the electrode. It will be understood that the duration of the positive peak upon any given electrode does not correspond to the full halfwave of positive potential upon the electrode. The potential must reach a value of some 6 kv. before kan ionizing discharge can occur. Accord- 'ingly during the early portion of the positive half-wave upon a given electrode the potential is insuicient to .produce an ionizing discharge. Similarly, as the potential drops from the positive peak toward the end of the positive halfwave of potential upon the electrode, the potential is again insuflicient to effect an ionizing discharge. However, during this latter portion of the positive half-wave, the potential will, nevertheless, aid in the movement of the charged dust particles to the `collecting electrode.

Accordingly, during approximately of Vthe positive half-wave of potential lupon any given electrode, the potential will be suicient to Veiec't both ionization and collection of the dust particles.

The length vof each of the ionizing electrodes Il, I9 and 2| .is so correlated to the velocity of the air .through the channel 22 that the time interval oi approximately 120 of the positive half-wave -upon any electrode will allow the air originally at the upstream end of this electrode to just reach the opposite end of the electrode vat the end of fsuch .positive peak. Thus, if the length vupon the electrode II.

of the wires is such that when the positive peak of one phase is effective in zone A, the body of air traversing this zone will be ionized and the dust particles thereof collected during this positive peak.

The air in the zones B and C will be untreated. The condition of the air at the end of this first positive peak effective in the zone A is shown in column I of Fig. 2 in which the stippling indicates ionized air and dust particles in the process of collection. If the positive peak of the next successive phase is effective upon the electrode 2I, the untreated air in the zone B at the beginning of this positive peak will be ionized and the dust particles collected as it is displaced from the zone B into the zone C. The body of the treated air in the zone A at the beginning of the second positive peak will have moved into the zone B by the end of this second positive peak effective on the electrode 2|. The state of the air in the `various zones at the end of the second positive -meantime the ionized air originally in the zone A at the beginning of the second positive peak has been displaced into the zone B. The positive peak of the third phase is effective upon `the electrode I9. The untreated air in the zone A at the beginning of this third phase is displaced into the zone B during the positive peak of this phase, and is ionized and dust particles precipitated. The state of the air in the vari- -ous zones at the end of the third positive peak of potential is indicated in column III of Fig. 2. It will thus be seen that during the three successive phases of any three-phase cycle all prtions of the air passing through the channel 22 `are acted upon, particular portions thereof being acted upon by each of the electrodes in turn and all portions thereof being acted upon by at Vleast one of the electrodes. Thus no portion of the air passing through the channel 22 escapes treatment.

The cycle thereupon repeats itself, the first phase of the second cycle being again effective The state of the air in the various zones at the end of this first phase 'of the second cycle will be as indicated in column IV of Fig. 2. The second phase of the second cycle is again effective upon the electrode.

2l and the state of the air in the various zones at the end of this second positive peak of potential of the second cycle is shown in column V of Fig. 2. The third phase of the second cycle Ais again effective upon the electrode IQ, and the state of the air in the various zones at the end of the third positive peak of potential of the second cycle is indicated in column VI of Fig. 2.

It will be understood that a negative potential is also applied to each of the electrodes I1, I9 vand 2| during each cycle of the three phases of potential; however, this negative potential is less effective in the ionization of the air than the positive peaks of potential. The present invention insures that each portion of the air to be treated Will be subjected to the highly ionizing effect of a positive peak of potential upon one -of the electrodes and the less effective ionization of the negative peaks of potential is additive to the effective ionization and collection t@ which.

each portion of the air is subjected during one positive peak of potential of the three-phase cycle.

As shown in Fig. 3, the positive peaks of potential of a sine wave may rise considerably above the potential necessary to effect an ionizing discharge. In order to smooth out the positive peaks, resistors 25, 26 and 21 may be inserted in each of the conductors between the terminals I6, I8 and 20 and the electrodes I1, I9 and 2I, respectively. These peak current-limiting resistors thus provide wave forms of the type indicated by solid lines in Fig. 3, rather than the Wave form indicated by dotted lines which occurs where these resistors are omitted. Accordingly, during that portion of the positive half-wave on any given electrode in which the potential is rising to or falling below the value at which an ionizing discharge occurs, the resistor in the electrode circuit concerned has no material effect upon the Wave form. During the portion of the positive half- Wave in which the potential is above the value at which an ionizing discharge occurs, the resistor offers an impedance to the flow of current and thus prevents the voltage on the electrode from rising to the peak value that would otherwise occur. The portion of the positive half-wave during which the potential is rising to the value at which an ionizing discharge occurs covers about 30 of the total 180. During the following 120 the potential will be above the ionizing potential and during the final 30 the potential will again be below the ionizing potential.

Referring now to Fig. 4, the present invention is illustrated. In this figure, reference numeral 3B indicates a transformer having a primary Winding 3I connected across the terminals of an alternating current source. The secondary winding 32 of the transformer 3Il has one end connected through a resistance 33 to a fine wire electrode 34. The other terminal of the secondary winding 32 is connected through a resistor 35 to a ne wire electrode 36. The electrodes 34 and 36 are, as in the construction previously described, disposed longitudinally of a tubular member 31 providing an air channel, which channel is of metallic material and grounded, as indicated at 38. In this instance, the electrodes 34 and 36 are spaced by distances substantially equal to their length, providing a zone B therebetween in which no ionization occurs. The length of the electrodes 34 and 36 is so correlated to the velocity of air flow that, during the positive peaks of potential upon either of the electrodes, the air iiowing through the channel traverses the length of the electrode. Thus, when the potential is positive upon the electrode 34, the air in zone A is ionized and dust particles precipitated and a body of untreated air will be present in the zone B' between the electrodes 34 and 36. On the next half-wave of the single phase source the potential on the electrode 36 will be positive and the untreated air in the Zone B will be ionized and dust particles precipitated as it moves into and through the zone C. In the meantime the air previously treated in the zone A will move into the zone B' so that, at the'end of the positive half-wave of potential upon the electrode 36, the bodies of air treated in the zones A and C constitute a continuous stream oi' treated air with no intervening portionsof untreated air therebetween. The cycle thereupon repeats itself.

While there have been herein described a preferred embodiment of the invention, other embodiments within the scope of the appended claims will be apparent to those skilled in the art from a consideration of the forms shown and the teachings hereof.

What is claimed is:

1. An electrical precipitator comprising means deiining an elongated passage for a -gas stream, said passage comprising lrst, second and third sequentially disposed zones of substantially equal extent, an ionizing electrode in each of said rst and third zones only, said electrodes each being elongated and of substantially the same length as the zone it occupies, said electrodes being further disposed endwise in said tube with said second zone between their confronting ends, a source of alternating potential connected at one side to one of said electrodes and at the other sideto the other electrode, means to pass gas to be cleaned in a continuous stream through said passage and successively past each of said first, second and third zones at a prescribed velocity, said velocity being chosen to provide that during a rst half cycle cf the alternating potential the gas in said first zone is ionized and in the succeeding half cycle the gas that was in said second zone during the rst half cycle arrives in said third zone and is ionized.

2. An electrical precipitator comprising means dening an elongated passage for a gas stream, said means being ane1ectrically conductive tube surrounding the passage and being electrically grounded, said passage comprising rst, second and third sequentially disposed zones of substantially equal extent, an ionizing electrode in each of said rst and third zones only, said electrodes each'being elongated and of substantially the same length as the zone it occupies and insulated from said tube, said electrodes being disposed endwise in said tube with said second zone between their confronting ends, a source of alternating potential connected at one side to one of said electrodes and at the other side to the other electrode, means to pass gas to be cleaned in a Ycontinuous stream through said passage and successively past each of said nrst, second and third zones at a prescribed velocity, said velocity being chosen to provide that during a half cycle 0f the alternating potential the gas in said first zone is ionized and in the succeeding half cycle the gas that was in said second zone during the rst half cycle arrives in said third zone and is ionized.

HANS KLEMPERER.

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

UNITED STATES PATENTS Number Name Date 1,130,212 Steere Mar. 2, 1915 1,976,214 Brion et al Oct. 9, 1934 FOREIGN PATENTS Number Country Date 374.207 Germany Apr. 20, 1923 114,909 Switzerland Julv 4. 1925

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