US2295152A - Fluid movement with precipitation - Google Patents

Description

Sept. 8, 1942. w. H. BENNETT FLUID MOVEMENT WITH PRECIPITATION 2 Sheets-Sheet l Filed Aug. 31, 1940 INVENTOR.

P 8, 1942- w. H. BENNETT 2,295,152-

FLUID MOVEMENT WITH PRECIPITATION Filed Aug. 31, 1940 2 Sheets-Sheet 2 INVENTOR. I j

lawn/a156 @wMQ/W,

' UCMM K Patented Sept. 8, 1942 UNITED STATES PATENT orrics I nummovilmslv 'r m ranolrrrs'rrolv I Willard EBennett, sewn-nous Application August :1, 1940, Serial N 355,054

(on. lac-'1) 16 Claims.

My invention relates broadly to precipitation of solid particles suspended in a gaseous medium. such as dust'in air, and more particularly to an electrode assembly for use in electric precipitation v in combination in anelectrically related system an electrode arrangement ior producing movement in a fluid medium and electrodes :ior precipitating solid particles from the medium prior to the action of the draft electrodes.

A further object of my invention is to provide an electrode arrangement for precipitation of charged particles from gaseous susp mion, with the electrodes energized by a rectified voltage derived irom an alternating current source through an electric discharge type of rectifier operative in conjunction with the precipitation electrode arrangement in the gaseous medium.

Still another object oi my invention is to provide an electric precipitation circuit including filter means tor the rectified voltage applied to the precipitation electrodes and a blocking condenser ior localizing the bias voltage applied to the control means in the rectifier arran ement.

Another object of my invention is to provide an arrangement of electrodes for an electricprecipitator in which a group of charging electrodes and a group at precipitation electrodes may be arranged in any selected or alternate order with respect to a set at driving electrodes.

A still further object of my inventionis to provide an assembly 01! precipitator electrodes and electric discharge electrodes in which polarizing potentials ior energizing the precipitator electrodes are derived directly (mm the operation oi the electric discharge electrodes which operate to produce fluid movement.

Other and further objects oi my invention reside in the electrode and circuit arrangement hereinafter described in more detail with reference to the accompanying drawings, in which:

Figure 1 is a diagrammatic plan view of the electrode arrangement employed in the system or my invention, with the circuit arrangement schematically illustrated in connection therewith;

. employ a type 01 electric to point out that the assembly, with parts broken away and shown in section.

In the precipitation system of my invention, I discharge which I have termed "diiiuse discharge. ,Diiiuse discharge is characterized by the absence of the disruptive sparking, arcing and streamering conditions usually present in point to plane asymmetric electric discharge equipment. The manner in which the difluse discharge" is obtained is described in detail in my copending application, Serial No. 338,379, flied June 1,- 1940, for Method and apparatus for conversion of energy, and this invention employs this type of discharge in connection with an electrical precipitation system for charging particles in gaseous suspension.

For the purposeloi this invention it will sufllce is obtained by controlling density in the medium acent, the emittingelec trode so that this um current density does not exceed the amount which the electrode can sustain and convey either transiently or under ,diiiuse discharge steady conditions. More particularly the desired is accomplished by predetermining (1) the spacing between the emitting and collecting electrodes, (2) conductivity 0! the emitting electrode, ('8) diameter oi thetips'oi the emitting electrodes and (4) spacial distance between adjacent emitting electrodes. The speciiications or one particular construction which has been iound to operate satisfactorily without arcing. sparking or streamering are given in the a following description.

The electrical precipitation systemoi my invention is operable directly from .a source 0! high I potential alternating current and one of the principal functions involved is a conversion at alternating current to direct current tor energizin the charging and precipitates plate electrodes;

this iunction is eflected by the operation oi electrio discharge 'means which at the same time serve'to roduce movement oi the gaseous medtum by a conversion od'electrical to mechanical energy in accordance with the principles set forth in my copending application. Serial No. 838,379, supra. In general and, as will be more fully hereinaiter set iorth, the electric dischar takes place in an electron attaching gas wherein the electrons readily attach to molecules at the gas and dorm ions which are. of course, much larger than the electrons and provide the numerous collisions required to obtain the necessary movement oithe gas. It hasbeen found that the 'load'i'actor ot a I and Fig. 2 is a perspective view oi the electrode so precipitates comprising charging electrodes and socalled "diffuse discharge the'maximum current ciently met by a rectifier of a diff-us discharge type wherein a measure of the alternating current energy applied is converted into movement of the gaseous medium and a further portion is I rectified and maintained at high potential for application to the charging and precipitatcr plate electrodes.

Referring to the drawings in more detail, reference character i designates a frame structure for housing the various electrodes and providing a duct for the passage of. air and gases to be cleared of suspended particles, the inlet and the outlet being indicated by arrows on the drawings. At the inlet there is first a bank of charging electrodes, indicated generally at 2 and constituted as emitters provided with wires 3 terminating in discharge points. Next are two groups of precipitator plate electrodes 4 and 5, disposed in par allel and alternating in position. The plates 4 of one group are interconnected through bus 6 and have the leading edges thereof disposed in advance of the leading edges of plates for coaction as target elements for the difiuse discharge from emitter wires 3. The alternate plates 5 are interconnected through bus 1. Electrodes 2, 4 and 5 comprise in particular the means for removing suspended particles from the gaseous medium and are required to be energized in fixed polarity at high potential. The means for providing such potentials and at the same time producing movement 01' the gaseous medium through the apparatus includes a first bank of discharge electrodes, indicated generally at 8 and constituted as emitters provided with wires 9 terminating in discharge points, a coacting bank of control electrodes at l0 and coacting target electrodes indicated generally at I I, and also a second bank of discharge electrodes, indicated generally at I2 and constituted as emitters provided with -wires I3 terminating in discharge points, a. coacting bank or control electrodes at l4 and coacting target electrodes indicated generally at l5.

A source of alternating current of high potential is provided at the transformer 16. A circuit extends from terminal I! of the secondary of transformer IE to discharge electrodes l2, which produce a diffuse discharge received at target electrodes l5, and continues through a ballast resistance I8 and condenser is back to terminal of the secondary of transformer IS; a blocking condenser 2| is included in the lead to terminal 20 to permit condenser I9, and another condenser 22 in the system, to acquire independent charges ror maintaining substantially constant bias potential difierences across their terminals.

Another circuit extends from terminal 28 to the discharge electrodes 8 and continues through the condenser 22 back to the source at terminal l1.

As a result, the disccharge. from the electrodes 8 is inherently asymmetric and is predominantly negativein the absence of efl'ective control of the discharge. Assuming that the. discharge from the electrodes 8 is negative with respect to the target electrodes I l it follows that the condenser 22 acquires a charge in the polarity indicatedin Figure 1 and this difierence of potential across the condenser 22 is employed as a bias voltage to control the discharge from the discharge electrodes 12. In detail, the negative side of the condenser 22 is connected to. the controlelectrodes l4 andthe positive side is connected to the discharge electrodes i2. Inasmuch as the control electrodes H are of negative potential with respect to the discharge electrodes l2, the

' sets of precipitator plate electrodes may be efilnegative phase of the electric discharge from the electrodes I2 is suppressed and, accordingly, the

discharge from the electrodes l2 to the target electrodes l5 becomes predominately of positive polarity. The condenser I9 is connected in circuit with the target electrodes l5 and, as a result, acquires an electrostatic charge in the polarity also indicated in Figure 1.

The control electrodes I0 associated with the discharge electrodes 8 are connected to the positive terminal or the condenser I9 and suppress the positive phase of the discharge from the electrodes 8. As a result, this discharge is maintained predominately negative. It may be pointefd out at this'time that while a small amount of discharge from the discharge electrodes 8 to control electrodes I0 may take place, nevertheless,

this discharge is negligible as compared to the discharge from the electrodes 8 to the electrodes ll because the latter are much more advantageously positioned with respect to the normal electron path from the tips of the electrodes 8. This is also true of the bank of electrodes l2 to l5, inclusive.

The electric discharges from both emitting electrodes 8 and I2 are produced in an electron attaching gas which is characterized in that electrons attach themselves to molecules of the-gas and form ions. These molecules are many times greater in size than the electrons and produce a sufllciently large number of collisions to insure a substantial movement of the gas. In other words, electric energy is directly converted to kinetic energy in the gas by the above apparatus and this is evidenced by the fact that gas velocities of feet per minute have been obtained in practice.

The difference in potenfial obtained across the condensers l8 and 22 as. a result of the cooperative action of the electric discharge means 8 to l5, inclusive, superimposes a direct current bias potential on the alternating current. This superimposed direct current energizes the electrodes 2 to 5, inclusive, in such. a manner that the charging electrodes 2 are predominately positive and the precipitator plate electrodes 4 and 5 are respectively predominately negative and positive. The plates 4 project beyondthe' plates 5 in a direction toward the charging electrodes 2 andcoact with the latter in producing a discharge from the tips of the electrodes to the adjacent edges of the plates 4 which electrostatically charges the particles in suspension in the gaseous medium. In detail, one circuit extends from the positive terminal of condenser l 9 through resistor I8 to emitters 2, which produce a diifuse discharge opposite the precipitator plates 4 and 5, and continues from plates 4 back to the negative terminal of condenser l8 through bus 6. Plates 4 are thus charged at negative potential, and in order to complete the circuit, plates 5 are connected through bus I to positive terminal of condenser IS. A voltage of upwards of 6000 volts has been observed at the terminals of condenser I9, and a field intensity of approximately 16,000 volts per inch' is provided between the precipitator plates 4 and 5.

The electrodes employed in the apparatus of my invention may be of various types, shapes and sizes. By way of example, the electrodes shown are of composite construction comprising essentially a core of pressed paper, cardboard, wood or plastic material on the surface of which is disposed a layer of semi-conductive material such as a paper incorporating carbon black and having a predetermined resistivity, or an ink or paint .001" diameter and are of tungsten They are A" apart and long. The core or the emitters is A cardboard coated with styrene, tos'eal it against moisture, and is covered with semiconducting paper with a resistance of from 50-150 megohms. Adjacent the charging bank are the two' sets'oi collecting plates 4 and 5. Theplates of set 4 are x 9%" x and the plates of set 5 are 7" x 11%" x Va". Both havea center paper core V8" thick covered with a semi-conducting paper with a resistance or from 200-400 megohms.

Next to the charging plates is the combination fan and air rectifier which comprisesthe row of emitters 8, the row of control electrodes l0, and the row of targets II, the second row of emitters I2, the second row of control electrodes l4, and

the second row of targets l5. Each row or emitters has a number of emitter columns therein and each row of control electrodes and targets has columns one more in number than the number of emitter columnsa Each electrode has a Va",-

cardboard core coated with styrene to seal it against moisture. The emitters are 9 /2" long, 1 wide, and ,4," thick. and are covered with a paper having a resistance or from 50-150 megohms. The control electrodes and targets are 1%" wide, thick, and 11 long. The control electrodes are covered with a paper having a resistance or from 200-400 megohms and the targets are covered with a paper having a resistance of from 30-75 megohms. The purpose of the resistances specifiedis to produce as quiet a discharge as possible by. providing the emitters with as much resistance as possible without aifecting the operation thereof. The lateral spacing of the control electrodes, emitters, and targets is '78", that is, from .one emitter to the next emitter is "/3", and from one control electrode or target to the. next control electrode or target, is The control electrodes are spaced on each side of the emitters in a manner such that the leading edge of a control electrode is A" ahead of the leading edge or the wirein the coacting emitter, and the trailing edge or the target ish 1%" directly in iront oi the corresponding control electrode, for most efiective operation.

01 the three condensers in the system, the two' of them between the control electrodes and the adjacent emitters have a capacity of .02 mid, which is not particularly critical. The third condenser is a high-voltage blocking condenser having a capacity or .01 mgtd. Iv

In the'operation or the precipitation system of my invention, diffuse electric discharge is initiated in the emitter banks l2 and 5, that from bank 12 being maintained positive while that from bank 8 becomes predominantly negative by virtue of the control bias from condenser I5 applied to control electrodes It; at the same time, the resulting potential difl'erence across condenser 22 serves to bias control electrodes l4 and increase the positive discharge rrom emitters l2. When stabilized conditions of operation are reached in this portion or the system, condenser is has acquired a sufllcient charge for operation tentials which are predominantly of opposite polarity. By virtue of the difiuse discharges thus established, the air or whatever gaseous medium is supplied is placed in motion and passes through the apparatus at the proper velocity-to permit the I particles in suspension, now charged by the action of emitters 2, to be precipitated to the charged plates 4 or 5.

Suitable means may be provided'for removal of the precipitated material from plates 4 and 5 as by scraping with mechanical means or flushing by fluid means, gas or liquid, when the apparatus is out of service, or means may be employed for the continuousremoval of precipitated material during the operation of the apparatus. Such means form no part of my present invention. 1

It will be observed that the combined fan and air rectifier portion of the system of my invention includes a biasing component in electrodes 8-'ll and a rectifier component in electrodes |2.l5, through which condenser I9 is charged, in the circuit arrangement disclosed. That is,

, besides contributing to the production or movement in the gaseous medium, the electrodes 5-ll serve to produce a difference of potential across condenser 22 which is employed to bias the discharge from emitters l2 in the rectifier component i.2-i5. At the same time, the entire functions of air movement and rectification may be more distinctly attributed to different groups.

of electrodes, each group. being especially de-. vised for the intended function. The essential cooperative relationship, however, will be maintained whereby the rectifier component is biased .from .a diffuse discharge means other than itself,

and connected with the precipitation means for supplying direct potentials thereto. For example, a rectifier devised with consideration prior the charging and precipitator plate electrodes,.

whereupon difluse discharge is produced Irom emitters 2 and plates 4 and 5 assume high pomm said am electrodes.

marily for current carrying properties may be placed in cooperation with a fan-devised with consideration primarily for air movement, in the manner set forth, and both the rectifier'and the fan then combined with electric precipitation means, in accordance with my invention.

' Thus, while I have described my invention in a preferred embodiment, I -desi re it understood that modfications may be made in the system and apparatus of my invention, and that no limitations upon my invention are intended except as are contained within the scope of the appended claims.

What I claim as new and desire to secure by; H

Letters Patent of the United States is as iollows:

1. An electrical system operative in a gaseous medium for precipitation of solids from said rnedium comprising a source of alternating current, charging electrodes connected to said source, plate electrodes for precipitating solids in proximity to said charging electrodes, fan electrodes for movement of' the medium through said device-,' the fan electrodes being connected to said alternatingsource, the charging electrodes and plate electrodes being connected to the fan electrodes in a manner to receive rectified current 2. An electrical system operative in a common gaseous medium in a unitary sphere of action for'the precipitation of solids from gaseous suspension in said medium comprising a source of alternating current, electric discharge and target electrodes connected across said source and operative for charging the particles in suspension; electrical precipitation electrodes coopermeans disposed in proximity to the electrodes constituting said rectifier and connected with said source of alternating current, said means being operative to provide a rectified bias potential for said control electrode,and a connection from the control electrode to the last said means.

4. An electrical precipitation system comprising charging electrodes, precipitator plate electrodes, electric discharge means including a 'rectifier component and a biasing component cooperative to convert alternating electric energy into direct-electric energy and kinetic energy in the medium of the discharge and means for energizing said charging electrodes and said precipitator plate electrodes by the direct electric energy from the rectifier component of the last saidmeans, said biasing component being connected with said rectifier component for increasing the direct electric energy output of said rectifier component.

5. An electrical precipitation system comprising charging electrodes, precipitator plate electrodes, electric discharge means including a rectifier component and a biasing component cooperative to convert alternating electric energy into direct electric energy and kinetic energy in the medium of the discharge, means for energizing said charging electrodes and said precipitator plate electrodes by the direct electric encipitator plate electrodes.

erative to convert 'a portion of the alternating electric energy supplied thereto into kinetic energy in the medium or the discharge.

'7. An electrical precipitation system comprising'charging electrodes,- precipitator plate electrodes, electric discharge means 'for converting alternating electric energy into kinetic energy for moving the medium to be clarified through said charging and precipitator plate electrodes, 9. capacitance in circuit with said diffuse electric discharge means operative to maintain a substantially constant difference of potential thereacross and means for energizing said charging and pre- 8. An electrical precipitation system comprising, in combination, charging electrodes, precipitator plate electrodes, and electric discharge means; said means being energized by alternating electric energy and operative to convert such energy partially into direct electric energy by rectification, and partially into kinetic energy by transformation; the direct electric energy being applied to said charging and precipitator plate electrodes for operation thereof, and said kinetic energy being expended in the movement or the gases to be clarified between said charging electrodes and said precipitator plate electrodes.

9. An electrical precipitation system comprising, in combination, charging electrodes, precipiergy from said rectifier component, said biasing component being connected with said rectifier component for increasing the direct electric energy output of said rectifier component, and a biasing connection from said rectifier component to said biasing component for stabilizing the operation of said electric discharge means.

6. An electrical precipitation system comprising charging electrodes, precipitator plate electrodes, electric discharge means including a first group of emitter, control and target electrodes and a second group of emitter, control and target electrodes, means for energizing said discharge means byalternating electric energy including a capacitance in circuit with the emitter and target electrodes of each group, a biasing connection of one polarity from the capacitance in circuit with the emitterand target electrodes of one group to the control electrodes of the other group, a second biasing connection in opposite polarity from the other capacitance to the tator plate electrodes and difi'use electric discharge means; said means including a rectifier component and a biasing component energized by alternating electric energy and cooperative to convert such energy partially into direct electric energy by rectification in said rectifier component, and partially into kinetic energy by transformation in both said components; the

, direct electric energy being applied to said charging and precipitator plate electrodes for operation thereof, and said; kinetic energy being expended in the movement of the gases to be clarified between said charging electrodes and said precipitator plate electrodes.

10. An electrical precipitation system comprising, in combination, charging electrodeaPrecipi- I tator plat electrodes, and electric discharge means; said means including a rectifier component and a biasing component energized by alternating electric energy and cooperative to convert such energy partially into direct electric energy by rectification, and partially into kinetic energy by transtormation; said biasing component being connected with said rectifier component for increasing the direct electric energy output 01' said rectifier component, and said rectifier,

component being connected with said biasins .component for stabilizing the operation of said difi'use electric discharge means; the direct elec tric energy from said rectifier component being applied to said charging and precipitator plate electrodes for operation thereof, and said kinetic energy beingexpended in the movement of the gasesto be clarified between said charging electrodes and said precipitator plate electrodes.

11. Electric discharge equipment for precipitating particles from a gaseous medium having a predetermined direction of movement, comprising a 30 7 0 of alternating current, means for electrostatlcally charging the particles in suspension in the gaseous medium including emitting electrodes connected in a circuit with the source of alternating current and extending in the general direction of movement of the gaseous medium, electric discharge means also connected in a circuit with the source 01 alternating current and operable to impart movement to thegaseous medium past the emitting electrodes, said electrio discharge means including electric discharge electrodes and collecting electrodes coacting with the discharge electrodes to produce an electric discharge in the direction of movement of the gaseous medium, precipitator plate electrodes electrodes connected in a circuit with the source of alternating current and extending in the general direction of movement of the gaseous medium, electric discharge means also connected in a circuit with the source of alternating current and operable to impart movement to the gaseous medium past the emitting electrodes, said electric electricallyconneoting opposite sides of the capacitance to the emitting electrodes and preoipitator plate electrodes.

14. Electric discharge equipment for preoipi tating particles from'a gaseous medium having a predetermined direction of movement, comprising a source of alternating current, means for electrostaticallycharging the particles in suspension in the gaseous medium including emitting, electrodes connected in a circuit with the source of alternating current and extending in the general direction of movement of the gaseous medium, electric discharge means also connected in a circuit with the source of alternating current and operable to. impart movement to the gaseous medium past the emitting electrodes,v

said electric discharge means including electric discharge electrodes and collecting electrodes coactingwith the discharge electrodes to produce an electric discharge in the direction of movement of the gaseous medium, means for controlling the electric discharge between the discharge electrodes and collecting electrodes to produce an electric discharge predominately of one polarity therebetween, precipitator plate electrodes supported between the emitting electrodes and the electric discharge means in a discharge means including electric discharge electrodes and collecting electrodes ooacting with the discharge electrodes to produce an electric discharge in the-direction of movement of the gaseous medium; means for controlling the electric discharge between the discharge electrodes and collecting electrodes to produce an electric discharge predominately of one polarity therebetween, precipitator plate electrodes supported between the emitting electrodes andthe electric discharge means in a manner to require the gaseous medium to pass therebetween, means electrically connecting the emitting electrodes to said collecting electrodes for energizing the emitting electrodes with the same potential as the controlled electric discharge between the discharge electrodes and collecting electrodes, and means for energizing the plate electrodes with a different potential.

13. Electric discharge equipment for precipitating particles from a gaseous medium having a predetermined direction of movement, comprising a source of alternating current, means for electrostatically charging the particles in suspension in the gaseous medium including emitting electrodes connected in a circuit with the source of alternating current and extending in the general direction of movement of thegaseous medium, electric discharge means also connected in a circuit with the source of alternating current and operable to impart movement to the gaseous medium past the emitting electrodes, said electrio discharge means including electric discharge electrodes and collecting electrodes coacting with the discharge electrodes to produce an electric discharge in the direction of movement of the gaseous medium, means for controlling the electric discharge between the discharge electrodes and collecting electrodes to-produoe an electric discharge predominately of one polarity therebetween, preoipitator plate electrodes supported between the emitting electrodes and the electric discharge means in a manner to require the gaseous medium to pass therebetween, a capacitance electrically connected to the electric dismanner to require the gaseous medium to pass therebetween, a capacitance electrically connected to the electric discharge means and having a difference of potential across the-same, means electrically connecting one side of the capacitance to alternate precipitator plate electrodes,

and means electrically connecting the opposite side of the capacitance to the remaining precipitator plate electrodes.

15. Electric discharge equipment for precipitating particles from a gaseous medium having a predetermined direction of movement, comprising asource of alternating current, electric discharge means connected to the source of alternating current and operable to electrostatically-charge ,the particles in suspension in the gaseous medium, said means including emitting electrodes and collecting plate electrodes coacting with the emitting electrodes to produce an electric discharge in the direction of flow of the gaseous medium, precipitating plate electrodes alternating with the collecting plate electrodes and cooperating with the latter to precipitate particles from the gaseous medium, additional charge means and having a diflerence of potential across the same, and means respectively electric discharge means also connected in a circuit with the source of alternating current and operable to impart movement to the gaseous medium past the emitting electrodes and between the'plate electrodes, said additional electric discharge means including electric discharge electrodes and collecting electrodes coacting with the discharge electrodes to produce an electric discharge in the direction of flow of the gaseous medium, a capacitance electrically connected to the second electric discharge means and having a difference of potential across the same, means electrically connecting one side of the capacitance-to the emitting electrodes and precipitator plate electrodes, and means electrically connecting the opposite side of the capacitance to the collecting plate electrodes.

16. Electric discharge equipment for precipitating particles from a gaseous medium having a predetermined direction of movement, com-- pension in the gaseous medium including emitting electrodesconnected in a circuit with the source of alternating current'and extending in the general direction of movement of the gaseous medium, electric discharge means also connected in a circuit with the source of alternating current and operable to impart movement to the gaseous medium past the emitting electrodes,

said electric discharge means including electric discharge electrodes and collecting electrodes coacting with the discharge electrodes to produce an electric discharge in the direction of move-.

ment of the gaseous medium, a second electrical discharge means also connected to the source of alternating current and including discharge electrodes and collecting electrodes coacting with the latter discharge electrodes to produce an electrical discharge in the direction of flow of the gaseous medium, means including the second electric discharge device for applying a direct current bias to the first electric discharge means to produce an electric discharge predominately of one polarity in the first named electric discharge means, means electrically connecting the emitting electrodesto the first named electric discharge means to energize the emitting electrodes with a direct current of the same polarity as the discharge of the first named electric discharge means, precipitator plate electrodes supported adjacent the emitting electrodes in a manner to v require the gaseous medium charged by the emit

Images