US2504858A - Electrical precipitator - Google Patents

Description

April 18, 1950 w MaGKENZIE 2,504,858

ELECTRICAL PRECIPITATOR Filed Oct. 29, 1946 /NVENTO/? lg /wvezw W MACKENZIE IVE V Patented Apr. 18, 1950 g-Mass, assignor to Raytheon Manufacturing Company, Newton, Mass a corporation of Delaware Application October 29, 1946, Serial No. 706,380

-8 Claims.

This invention relates toelectrical precipitators for separating dust, smoke, and similar impurities from air or other gases. More particularly, the invention relates to electrical .pnecipitators of the type in which the air or other gas to be purified is first ionized and thereafter passed through a collecting device in which the impurities are collected.

in the copending application .of Hans Klemperer, Serial No. 678,155, filedJuneZO, 1946, there is disclosed a precipitator in which the ionizing device is energized from .an alternating current source without the necessity of providing rectifiers between the source and the ionizing electrodes.

The present invention concerns a construction in which the ionization is effected in a, smilar manner from the alternating .current source and in which advantage is taken of the rectifying property of the ionizingdevice to obtain a rectifled voltage for application to the collecting device.

Accordingly, it is among the objects of the present invention to provide, in a .precipitator of the type having separate ionizing and precipitating means, a construction which avoids the necessity of providing rectifiers for effecting either ionization or collection of the .dust particles.

The above and other objects and features of the invention willbemade fully apparent to those skilled in :the art from a consideration of the .following detailed description taken in conjunction with the accompanying ,drawing, wherein:

1 illustrates schematically .a circuit in accordance withtheinvention; and

Fig.2 is a time-voltage and time-current graph illustrating the operationof Fig. 1.

' In Fig. l of the drawing, reference number .13 indicates generally a three phase transformer having Aeconnected primary. windings 1.! and Y-connected secondary -.Wihdin-gs .12. The outer. terminals l3, l4, and !5 of theYeconnected sec.- ondary windings l2 are directly connected, respectively, to fine wire electrodes it, H, and I3, which fine wire electrodes extend transversely through a tubular member I!) of metal or other conductive material providing an air channel. The channel I9 constitutes an electrode coacting with each of the fine wire electrodes l6. ll, and I8. Some point 22 on the tubular member is is connected through a resistor 23 to the neutral point .2 5 ofthesecondary windings l2. The connection between the resistor 23 and the neutral point 24 may be grounded, as indicated at 25. A collecting device 26, comprising a plurality of alternately charged and ground plates 2'! and 28, is disposed in the path of vthe gas stream dise char ed from the.ionizinadevice, is. In .order to energize the collecting device 26. this device is connected across the resistor 23, the charged 2 plates 2'1 being connected at some point between the resistor 23 and the point 22 or directly to the tubular member l9 itself. The plates 28 which alternate with the plates 27 are jointly connected to ground or to the grounded end of resistor 23;

In operation, it will be understood that the velocity of the air passing through the channel I9 is so correlated to the spacing between the electrodes l6, l7, and I8 that all parts of the air passing through the tubular member 1% are treated by at least one of the electrodes l5, l1, and I8 in the manner disclosed in the copending application previously mentioned, and that no part of such air remains unionized. The positive peaks of potential on the electrodes 5, ll, and I8 are synchronized with the velocity of the air flow, to the end that separate portions of the air will be treated by an ionizing discharge between each electrode and the common electrode provided by tubular member I9 during the SEC:- cessive positive peaks of potential upon the fine wire electrodes. The positive peaks are applied in order It, It, ll, respectively. Although the alternating potential applied to the electrodes :16, ii, and it reverses in polarity, it will be understood ;that conduction is greater when the polarity is in one direction than when it is in the opposite direction. Thus, when the potential upon any given fine wire electrode has reached the value at which an ionizingdischarge can occurin the .posi: tive direction, the current fiow is far greater than when the polarity of the electrodes is reversed. Such a. discharge betweenan electrode of relatively large area and an electrode of relatively small area will be referred to as an asymmetric discharge.

The greater conduction in one direction than in the opposite direction permits the ionizing means to be utilized as a rectifier, to provide a substantially constant voltage for energizing the collecting device 26. Thus, due to the unidirecr tional nature of the conductionthrough the "ionizing device, the tubular member l9 may be main tained at a high potential relative ,to ground, which potential will depend upon the value of the resistor 23.,which should be high. Preferably, a potentialdifference of about 12 k. v. willexist between any oneof the fine wire electrodes I6. I l, and I8 and thecommcn electrode 153 duringv the positive peak of potential upon that electrode. The potential across the plates of collecting device will preferably be of the order of 6 ;k. v.

Referring now to Fig. 2, a sinusoidal curve A illustrates the volta e wave which is applied .by one of the secondary windings between its fine wire electrodeand-the tubular member it. -When the ,wire electrode isposi-tive with respect to the tubularrmember, current begins to flow through the resistor 23at a relatively low voltage value,

as is indicated by shaded area B. When the polarity is reversed during the succeeding halfcycle of curve A, a relatively higher voltage value must be reached before current begins to flow through resistor 23, and therefore current flows in the reverse direction for a relatively shorter period of time, as is indicated by shaded area C. Now, collector assembly 26 is connected across resistor 23, and is, as is well known, a capacitor, due to the interleaved plate construction of plates 21 and 28. fore has an average value which is'in one drection, as is indicated by the straight line D. The secondary voltage values and interelectrode spacings may be so adjusted that shaded area C is reduced substantially to the vanishing point. Fig. 2 illustrates only one of the three phases, but it will be readily seen that the other phases have the same effect in the collector assembly.

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

What is claimed is:

1. An electrical precipitator comprising a metallic member forming a channel for passing a gas stream and constituting a relatively fiat surface electrode, at least one electrode of relatively sharp surface curvature within said channel, a source of alternating potential for energizing said electrodes to effect an asymmetric ionizing discharge therebetween, a plurality of collector plates disposed in the gas stream on the gas discharge side of said ionizing electrodes, means for deriving a unidirectional potential from asymmetric discharge, and means for applying the potential so derived across said collector plates.

2. An electrical precipitator comprising a metallic member forming a channel for passing a gas stream and constituting a relatively fiat surface electrode, a plurality of electrodes of relatively sharp surface curvature within said channel, a source of alternating potential for energizing said electrodes to effect asymmetric ionizing discharges between said large surface electrode and each of said electrodes of small surface area, a plurality of collector plates disposed in the gas stream on the gas discharge side of said ionizing electrodes, means for deriving a unidirectional potential from said asymmetric discharges, and means for applying the potential so derived across said collector plates.

3. An electrical precipitator comprising a metallic member forming a. channel for passing a gas stream and constituting a large surface electrode, at least one fine wire electrode within said channel, a source of alternating potential for energizing said electrodes to effect an asymmetric ionizing discharge therebetween, a plurality of collector plates disposed in the gas stream on the gas discharge side of said ionizing electrodes, means between said surface electrode and said source for deriving a unidirectional potential from said asymmetric discharge, and means for applying the potential so derived across said collector plates.

4. An electrical precipitator comprising a plurality of electrodes between which an asymmetric ionizing discharge is adapted to occur and past which a gas stream may be caused to flow, an alternating current source for energizing said The charge on this capacitor thereelectrodes, a plurality of collector plates disposed in the gas stream on the gas discharge side of said ionizing electrodes, means for deriving a unidirectional potential from said asymmetric discharge, and means for applying the potential so derived directly across said collector plates.

5. An electrical precipitator comprising an electrode of relatively flat surface and an electrode of relatively sharp surface curvature between which an asymmetric ionizing discharge is adapted to occur and past which a gas stream may be caused to flow, an alternating current source for energizing said electrodes, a plurality of collector plates disposed in the gas stream on the gas discharge side of said ionizing electrodes, means for deriving a unidirectional potential from said asymmetric discharge, and means for applying the potential so derived directly across said collector plates,

6. An electrical precipitator comprising a fine wire electrode and a surface electrode between which an asymmetric ionizing discharge is adapted to occur and past which a gas stream may be caused to flow, an alternating current source for energizing said electrodes, a plurality of collector plates disposed in the gas stream on the gas discharge side of said ionizing electrodes, means for deriving a unidirectional potential from said asymmetric discharge, and means for applying the potential so derived directly across said collector plates.

7. An electrical precipitator comprising a plurality of fine wire electrodes, a surface electrode coacting with each of said fine wire electrodes to produce an asymmetric ionizing discharge, means including in part said surface electrode for passing a gas stream past said electrodes, an alternating current source for energizing said electrodes, a plurality of collector plates disposed in the gas stream on the gas discharge side of said ionizing electrodes, means for deriving a unidirectional potential from said asymmetric discharge, and means for applying the potential so derived directly across said collector plates.

8. An electrical precipitator comprising a fine wire electrode and a surface electrode between which an asymmetric ionizing discharge is adapted to occur and past which a gas stream may be caused to flow, an alternating current source for energizing said electrodes, a plurality of collector plates disposed in the gas stream on the gas discharge side of said ionizing electrodes, means between said surface electrode and said source for deriving a unidirectional potential from said asymmetric discharge, and means for applying the potential so derived directly across said collector plates.

KENNETH W. MACKENZIE.

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

UNITED STATES PATENTS Number Name Date 1,343,285 Schmidt June 15. 1920 1,389,126 Chubb Aug. 30, 1921 2,142,129 Hoss Jan. 3, 1939 2,295,152 Bennett Sept. 8, 1942 FOREIGN PATENTS Number Country Date 682,588 Germany c Oct. 18, 1939

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