US 2142129 A
Description (OCR text may contain errors)
Jan. 3, 1939. F. w. Hoss ET AL APPARATUS FOR ELECTRICAL PRECIPITATION Filed April 19, 1957 n 0000000. 00000000 ooeomvooo 0 n. I 0 0 O U O U PIIIIIIIII/Illlll/ I 71 I .15 I; I91 I71 I .Id I? lilrfffffll H I INYENTORS. m 4/4 ::7-M BY @ozza/ ATTORNEYS Patented Jan. 3, 1939 UNITED STATES APPARATUS FOR ELECTRICAL PBEOlPITATION Friedrich Wilhelm Hossand Walther Deutscli, Frankfort-on-the-Main, Germany, assignors to International Precipitation Company, Los Angeles', CaliL, a corporation oi. California Application April 19, 1937, Serial No. 137,865
Germany April 22, 1936 Claims. (01. 183-7) The present invention'relates generally to' improvements for effecting the electrical precipitation of suspended particles from a stream of gas,
and more especially to apparatus for this purpose "5 in which the particles are. first charged intone field and'then precipitated out in a second field. In precipitators of this latter type, the gas is first passed. through a discharging or ionizing field in which the particles become electrically charged, and then the gas is passed through a separate substantially non-discharging field in which precipitation of the particles takes place on one or more collecting electrodes. In electrical precipitators as usually constructed, the gas stream flows past the electrode surfaces in a direction generally parallel thereto, while the electrical field is maintained between the electrodes and so is more or less at right angles to the gas fiow. This arrangement is sat- .20 isfactory for ionizing purposes but in the area of precipitation the gas stream oiTers little or no assistance to the separation of particles from the gas, but rather interferes with the separation, for there is a tendency to pick up and carry 25 along in the gas stream material that has been previously deposited;
It is a general object of our invention to in-. crease the efficiency of a precipitatorof the kind described and especially to increase the efiectiveso ness of the precipitation field in bringing about complete separation of the suspended particles from the gas stream. It is also a main object of our invention to provide a precipitator of the two-field type in 35 which the gas stream and the precipitating field exert their forces in the same direction on the suspended particles and so reinforce each other in effecting precipitation oi. the particles.
A further object is to 40 of the two field type in which the precipitating field has a fiuid-pervious electrode through which gas passes to bring about intimate contact oi the entire gas. stream with the electrode and complete precipitation of the suspended particles. 45 These objects are attained according to our invention by passing the stream of gas,containing suspended particles previously charged'electrically, through a non-discharging precipitation field, and maintaining the precipitation field in I 50 such a direction that the force it exerts on the suspended particles generally coincides with the direction of stream flow and so aids the movement or the particles toward the collecting electrode.
u One form of apparatus embodying the prinprovide a precipitator ciples of the invention includes a discharge electrode, an intermediate fiuid-pervious electrode through which gas flows, and a collecting electrode, which may or may not be fluid-pervious.
.There is also provided means for establishing a 6 high potential ionizing field between the discharge and intermediate electrodes and-a sepa-' rate substantially non-discharging field between the intermediate and. collecting electrodes to;
effect precipitation of the charged particles. The' lii' polarity of the intermediate and collecting electrodes relative to each other is such that the precipitating field moves the charged particles in the general direction of the 'gas flow from the intermediate to the collecting electrode. 15
How these and other objects and advantages of our invention are attained will be better understood by reference to the following description .and the annexed drawing, in which:
Fig. 1 is a vertical section through a preferred form of precipitator, illustrated somewhat diagrammatically, with suitable electrical equipment also indicated diagrammatically;
Fig. 2 is a horizontal section on line 2-2 01' Fig.1; i
Fig- 3 is a fragmentary vertical section through a variational form of precipitator; and
Fig. 4 is a horizontal section upon line 4-4 in Fig. 3.
The form of precipitator illustrated in Figs. 1 and 2 comprises an external housing III which is preferably circular in cross-section and is provided with a trap door l2 at the bottom through which precipitated material can be periodically removed. The-housing i0, which serves asa 001- lecting electrode, is of sufiiciently extended surface and smallsurface curvature to substantially preclude corona 'discharge therefrom. Fluidpervious intermediate electrode i4 is placed within and concentrically of the housing and is sup.- 40 ported upon insulators l5 which electrically insulate the electrode from the housing. Electrode i4 is shown as made of perforated plate, butit may be made of wire screen or any other similar material that allows free passage of the gas through the electrode and is of sufilciently extended surface and low surface curvature to substantially preclude corona discharge therefrom. Intermediate'electrode i4 is closed at its upper end by plate It which also serves as a support for insulator l8 by'means of which discharge electrode 20 is mounted axially of the intermediate electrode. The discharge electrode is a wire or'small diameter rod and is provided at its lower end with tensioning means, such as weight II.
Gas is introduced into the precipitator through inlet pipe 24 which discharges upwardly from nozzle 25 into the lower end of intermediate electrode 14., The gas passes through the openings in the intermediate electrode and is discharged from the precipitator through the open upper end 26 of housing Ill. Although the lower end of electrode l4 may be closed by means of a nonconducting member, which will insulate the electrode from gas nozzle 25, this 'is not necessary with the construction illustrated. The gas, issuing from nozzle at a relatively high velocity, is
projected into the upper portion of the electrode, and by constricting the open lower end of the electrode around nozzle 25, substantially no gas escapes from the electrode at this point.
The electrical equipment may be varied as desired to suit operating requirements. As typical of a preferred arrangement, but without limitation thereto, we show means for supplying the precipitator with rectified high tension alternating current. After the alternating current is stepped up by transformer 30, it is passed through a full wave rectifier 3! so that unidirectional current is supplied to discharge electrode 20 by leads 32 and 33. A voltage divider 34 is included in the circuit so that current at a lower voltage may be supplied to intermediate electrode l4 by lead 35. It will be realized that there may be employed a separate source of electric power for each of the discharge and intermediate electrodes, instead of the single source shown.
Housing i0 is connected with the ground at 38 so that, with respect to it, electrodes i4 and 20 are both of the same polarity. The potential applied to discharge electrode 20 is sufficiently great' to produce the well known corona or silent discharge from it, but not sufiicient to bring about a disruptive or spark discharge. A lesser potential is applied to electrode [4 than that applied to the discharge electrode and, electrode I4 being without sharp corners or projections of small radius which would promote the formation of corona discharge, there is maintained'in the annular space between electrode l4 and housi'ng In a substantially non-discharging electri-- cal field. It is preferred, but not necessary, that discharge electrode 20 be charged negatively and consequently electrode I4 is also negative with respect to housing Ill but is positive with respect to the discharge electrode.
The gas issuing from nozzle 25 first reaches the discharge electrode and travels' parallel to it, bringing the suspended particles into the ionizing field where they become charged negatively, that is of the. same polarity as the charge of electrode 20. The fiow of gas is then radially outward through the openings in electrode l4 and the charged particles, being repelled by electrode 20, are moved by the electric field in the same directicn. The gas and suspended particles after passing through fiuid-pervious electrode l4, enter the precipitating field maintained in the annular' space around electrode l4. The charged particles are then in a strong field of such polarity that they are repelled by electrode II, the direction of the field moving them toward housing Ill which acts as a collecting eleotrode upon' which the particles are precipitated when'they come in contact therewith and lose their charge.
' Thedlrection of gas movement through the intermediate fiuid-pervious electrode is radially-outward in the same direction as the movement of which is grounded at 36.
that the gas movement and the field reinforce each other. Thus both the ionizing and precipitation fields are of a polarity to reinforce the gas stream in moving suspended particles. The cleaned gas is then deflected upwardly and dischargedfrom the open upper end of housing It. mFigs. 3 and 4 disclose a variational form of precipitator in which the discharge, intermediate and collecting electrodes are mounted in planes across 'flue 40, typically rectangular in crosssection. The discharge electrodes 20a are mounted in a rectangular frame 4| supported from the top of the flue on insulators 42. Fluidpervious intermediate electrode a is likewise mounted on a rectangular frame and supported from insulators 43. Insulators 42 and 43 electrically insulate the discharge and intermediate electrodes from each other and .from fiue' 40 Collecting electrode 45, herein shown as a fiuid-pervious member made of wire screen or the like, is supported directly from the flue walls and is electrically connected therewith. The electrical connections 33 and 35 are the same as described in Fig. 1 and respectively supply high tension unidirectional current to the discharge and intermediate electrodes.
The electrodes are so arranged that the gas stream moving toward the right, as indicated by the arrow in Fig. 3, will encounter successively electrodes 20a and Na, in which field the particles suspended in the gas become charged electrically with the same polarity as the discharge electrodes. The gas stream with its charged particles then moves through the fiuid-pervious intermediate electrode I40 and enters the nondicharging field maintained between electrodes "a and 45, in which the polarity of the electrodesis such that the suspended particles are moved in the direction .of stream flow toward the collecting electrode 45. It will be noted that the mode of operation and electrode arrangement are the same as described in connection with Fig. 1, except that in the present form both the intermediate and collecting electrodes are fluid-pervious.
Apparatus in which the ionizing field is spaced from the precipitating field by a substantial distance, asby replacing the intermediate electrode by twoindividual electrodes so that the ionizing field is maintained between one pair of electrodes and the precipitating field between a separate second pair, is described and claimed in our copending application Serial No. 137,864, filed April 19, 1937, which application also broadly claims the apparatus and the method of operation embodied in both applications. Since various changes in the shape, arrangement and application of the various parts of our invention may be made without departing from its true spirit and scope, the description and drawing are to be construed as illustrative of rather than restrictive upon the appended claims.
1. In an electrical precipitation apparatus through which flows a stream of gas containing suspended particles to be removed, the combina- 4 tion of a discharge electrode; an intermediate 75 particles induced by the precipitating iield. so and a separa e tially non-discharging The gas first passes ,through an ionizing ,field maintained between precipitating field between the, intermediate and collecting electrodes, the precipitating field being of such direction as to reinforce gas flow from the intermediate to the collecting electrode for' collection thereon of suspended particles.
2. In an electrical precipitation apparatus through which flows a stream of gas containing suspended particles to be removed, the combination oia discharge electrode; an intermediate fiuid-pervious electrode through which gas flows; a collecting electrode; said three electrodes being arranged successively in the path of gas flow; and means for establishing an ionizing field between the discharge and intermediateelectrodes, and a separate substantially non-discharging precipitating field between the intermediate and collecting electrodes, the polarity of the discharge and intermediate electrodes being the same, relative to the collecting electrode, with a potential lecting electrodes, the precipitating field being of such direction as to reiniorcegas fiow from the intermediate to the collecting electrode ior collection thereon of suspended particles.
' arcane I 4. In an electrical precipitation apparatus through which flows a stream of gas containing suspended particles to be removed, the combination of a discharge electrode; a hollow intermediate fiuid-pervious electrode through which gas flows, surrounding the discharge electrode; a hollow collecting electrode surrounding the intermediate electrode; said three electrodes being arranged successively in, the path of gas flow; and means for establishing an ionizing field between the discharge and intermediate electrodes, and a separate, substantially non-discharging precipitating field between the intermediate and collecting electrodes, the precipitating field beingof such direction 'as tolreinforce gas flow from the intermediate to the collecting electrode for collection thereon of suspended particles.
5.- In an electrical precipitation apparatus through which flows a streamof gas containing suspended particles to be removed, the combination of a discharge electrode; an intermediate fluid-pervious electrode through which gas flows; a collecting electrode said three electrodes being arranged successively in the path oi gas fiow; and means for establishing an ionizing field between the discharge and intermediate electrode, and a separate substantially non-discharging precipitating field between the intermediate and collecting electrodes, both the ionizing and the precipitation fields being of such polarity as to move particles in the same direction to reinforce gas flow through the intermediate pervious electrode.
FRIEDRICH WILHELM H088. WALT-HER DEUTSCH.