US2476248A

US2476248A - Electrical precipitator

Info

Publication number: US2476248A
Application number: US713221A
Authority: US
Inventors: Kenneth W Mackenzie
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1946-11-30
Filing date: 1946-11-30
Publication date: 1949-07-12
Anticipated expiration: 1966-07-12

Description

- 4 Shets-Shet 1 Filed Nov. 50, 1946 ELECTRICAL PREGIPITATOR Filed Nov. 30, 1946 I 4 Sheets-Sheet 2 4 kivx July 12, 1949. K. w. M KENZIE 2, 7

' ELECTRICAL PRECIPITATOR v Filed Nov. 30, 1946 4 Sheets-Sheet 3 July 12, 1949. K. w. MacKENZlE ELECTRICAL PRECIPITATOR 4 Sheets-Sheet 4 Filed NOV. 50, 1946 arwdflii Patented July 12, 1949 UNITED STATES PATENT QFFJ'GE,

Kenneth.- W. MacKenzie, Newton. Highlands, s

Mass, assignor to Raytheon Manufacturing Company,- Newton, Mass, a corporation.

Delaware Application'Novemher 30, 1946, Seriak.-No.1713.,,221;

7 Claims. 1,

This invention relatesv to electrical precipitators for electrically separating dust, smoke, and other impurities from air, andmore particularly to an electrical precipitator of the type in which the air to be purifiedis "first ionized in-an ionizing zone and thereafter passed through a co1lecting zone wherein-the dust particles are collected.

It is among the objects of the invention toprovide an electrical precipitator of the type described which is suitable for domestic purposes, such as for purifying the air supply for a home, large room or oflice.-

It is a further object of the present. invention to provide a self-contained unit which may be readily installed and'conveniently serviced.-

It is a further object of the invention to provide, in a unitof the type described, a construc tion in which the. dust collecting elements may be cleaned or Washed in-situ, so-that the necessity for removing the dust collecting elements for the purpose of cleaning is avoided.

Other objects and features of-the inventionwill be made fully apparent to those skilled'in theart from a consideration of .the-followingdctailecl description taken ineconjunction with the accompanying drawing in which:

Fig. 1 shows a front elevation of the precipitator unit with a 'portionof the casing removed to show internal construction;

Fig. 2 represents a section taken on the line 2-2 of Fig. 1;

Fig. 3 represents a section taken on the line 33 of Fig.2;

Fig. 4 shows a-planzview-of one of the walls: of the ionizer and col-lectorxplate assembly; and

Figs. 5, 6,-7, 8, and 9-.showv plan views'of the various collector plates .used in'the collector plate assembly.

Referringtothe drawingreference numeral I2 indicates a casingior "housing'all of the elements of the precipitatorincluding .a unitary ionizer and collector plate assembly, indicated generally at l3. The ionizer-and. collector plate assembly is supported'on intemal shoulders provided by the angle irons =14 andJ which: are welded to the.

internal wall. of'the 'casing l2. The casing 12 is provided withsa removable .front panel or. door I! which in this rinstanceqextends across the entire front face :of the :housing [2 from alevel below the angle irons l4 and 15 to the top of the v housing, andis-hingedat-IS as .shown in Fig. 3.

The ionizer and. collector plate assembly comprises a pair. o.eend.plates.-I'9 and 20 which are supported on-..the1led ges -;provided by the angle irons 1'4 and I 6 :andwhich end 'platesin tum support the entire ionizing and collector plate assembly as-.-a :unitary structure.

The ionizing-means comprises a plurality of fine wireielectrodes each of which lies between and extends parallel .With two: surface electrodes, which surface. electrodes are preferably formed integrally with certainof thecharge plates of the collector plates-assemblyin a manner to be described. Theflne'wirerelectrodes of the ionizingmeans are mounted :upon a framework supported by four insulators l2, two of whichv insulators are mounted at 'theupperend 0f..eachof the end plates l9 and 20. Thecharged plates of the collector :plate. assembly are supported from the -.end'"plates. l9 .anduzfitthrough insulators 23 inamannenwhich will hereinafter .be more ,fully described.-.

Theirameworln-for supporting-the fine wire electrodes .oi.the:iQniZing.;-means comprises a pair of :angleirons .24-.and. 2.5 secured adjacent .to their vangle -ironssifl, vll, andi28-i may .be added to give theframework additional I rigidity. A plurality of:pins*33.for supponting the fine wire electrodes 34-pro-ject downwardly from. each of the angle irons zs-randzl pf.-the.--frameworlr, which pins are I secured inv regularly spaced openingsrin the-angle irons..126-and i2 1,- each/pin being secured by means of two nuts 35,-; one-on-,.eaoh faceofthe horizontal side; or these. irons.-. The. nuts 35 coact with threaded .portions of the upper ends of the pins to rigidly secure the pins .in. proper adjusted position.. The lower-endoteach of the pins this provided-witha notched portion-.36. and-the-pi ls are suiiiciently resilient to .permitthefine wire electrodes .34 to. be held. under some tensionwhen looped..p ortions at .the. ends. of the wire are secured in .the. notches..36. The angle iron .28. as shown in Fig, 2. supportsna plurality.of hooks each: of which, .is spaced in. alignment with two of the. coacting -;p ins-.33. Eachofthe hooks ill engages .a fineewire electrode. 3% .at a point about rality of spaced parallel plates, alternate of said plates being charged to a potential of the opposite polarity to that of the fine wire electrodes 34, and the intervening plates being grounded. The support and arrangement of these plates will now be described. The end plates is and as, one of which Is is shown in Fig. 4, are provided with a plurality of relatively small openings 38. this instance six of the small openings 35 are provided in each of the end plates, and these are adapted to accommodate a similar number of rods 39 which extend from oneof the end plates to the other and are provided with threaded por-- tions at the outer ends thereof, which threaded portions project through the openings 38 in each of the plates and are secured thereto by means of paired nuts 39 which engage the inner an outer faces respectively of each of the end plates to provide a rigid structure and maintain said end plates in a proper spaced parallel relation. The end plates is and 2d are also provided a plurality of relatively large openings In this instance five of the openings 48 are provided and are so spaced and of sufilcient diameter to permit an insulating clearance between the outer ends of a corresponding number of rods which support the charge plates in a manner to be described. End plates l9 and 23 are also provided with small openings 41 at the upper ends thereof to facilitate the fastening of the insulators 2?. to the end plates. Small openings 42 are also provided to facilitate the securing of the insulators 23 to the end plates.

Next adjacent each of the end plates l9 and 28 is an electrode-carrying plate 44. The plates id constitute two of the charge plates. Each carries at its upper end a curved portion 45 formed integrally with the plate. The axis of curvature of the upper portion 45 lies in the same plane and parallel to the fine wire electrodes 34, portion 55 providing a curved surface electrode coacting with the outermost of the fine wire electrodes. The upper projecting curved portion 45 and each of the plates 44 are provided with a pair of openings 46 to permit the uppermost of the insulators 23 to pass through the plate with a small clearance therebetween. Each of the plates 44 is also provided with cut-out portions 41 and relatively large openings 48, which cut-out portions and openings permit the rods 39 and the spacing bushings thereon to pass adjacent to and through the plate with an insulating clearance therebetween. Each of the plates 44 is also provided with five relatively small openings 49 corresponding in position to that of the large openings 40 in the end plates IS) and 2B. The openings 49 accommodate the threaded ends of a plurality of rods for supporting the charge plates. These rods project through each of the plates M and are secured by nuts 5| engaging the outer faces of the plates 44 at the openings lfi. The opposite faces of the plates 44 are engaged at the openings 39 by spacing bushings on each of the rods 58 extending to the next succeeding of the charge plates, and maintaining said next succeedin charge plates in proper spaced and parallel relationship relative to the plates 43.

The plates next adjacent to the plates as constitute two of the ground plates 54 which are constructed as shown in Fig. 6. These plates are of slightly greater length than the plates 44 and are provided with a pattern of small openings 33 corresponding in number and position to the openings 38 in the end walls It and 20. These relatively small openings 38 are of sumcient diameter to permit the rods 39 to pass therethrough but without substantial clearance. These plates are thus directly supported from the end walls ill and 2:: by the rods 39 and are thus electrically connected to the end walls [9 and 25] and are hence maintained at ground potential. The plates 54 are maintained in proper spaced relation to the end walls on one side and to the next succeeding of the ground plates on the other side by means of spacing bushings on the rods 39 which engage each face of the plate B l at the openings 38. These spacing bushings pass through the openings 48 in the adjacent plates 4-3 and through the cut-out portions 41 with a sufficient clearance to provide an insulating space therebetween. The plates 54 are also provided with a pattern of relatively large openings andcorresponding in size and position to the openings 45! in the

end walls

19 and 2%. These openings are sufiiciently large and so placed that the supporting rods which carry the charge plates together with the spacing bushings thereon may pass freely therethrough with an insulating space therebetween.

The plates 56 next adjacent the plates 5:; constitute charge plates and are constructed as shown in Fig. 7. These plates are similar in construc-- tion to the plates 44 except that the electrode portion 45 is omitted. Otherwise the plates con" tain a pattern of five openings 49 corresponding in size and position to the openings 49 in the plate :4 and having the same purpose of supporting these plates from the rods 58. The plates 56 are also provided with the relatively large openings i8 and cut-out portions 47 to permit the passage therethrough of the supporting rods 39 together with the spacing bushings thereon.

The

plates

54 and 56 alternate throughout the length of the collector plate assembly except that two of the charge plates at a short distance from each end of the collector plate assembly are constructed as shown at 58 in Fig. 8. These plates are identical with the charge plates 56 except that they are provided with projecting tabs 59 at each corner thereof, which tabs are provided with small openings 60 to permit the plates 58 to be secured at each corner to the insulators 233. Thus instead of being supported by the rods 56 which pass through the small openings 49, these plates are supported by the insulators 23 and in turn provide a support for the rods 58 and the remainder of the charge plates supported by these rods. Thus there is no other support for the charge plates through which electrical losses could occur. Also those of the charge plates which lie in a plane midway between any two of the fine wire electrodes 34 are constructed as shown at 62 in Fig. 9. These plates are identical with the other of the charge plates 56 except that they are provided at their upper ends with a curved surface electrode 63 which projects upwardly between any two of the fine wire electrodes 34. As seen in Fig. 1 the center of curvature of the upper portion of these electrodes lies in a vertical plane including the fine wire electrodes. The electrode portions 63 are shaped to present a streamline to the flow of air through the precipitator, the air intake being indicated at 65 and the air flow being downwardly through the unit to be discharged from the lower end thereof at66.

In operation the fine Wire electrodes 34 may be charged to a high positive potential, for example 6 kv. from any suitable source for example byan electrical circuit such as disclosed in my copending application, Serial No. 692393," filed *5 August 24, I946. The "electrical connection-a the fine wire electrodes may be made to any point on the supporting framework which "is otherwise insulated by the insulators 22. "Thecharge "plates of the collector plate assembly and hence the

electrodes

45 and 63 are connected-to 'ftheopposl te terminal of the source and hence are chargedto a negative potential of 6 kv. The potential "between the fine wire electrodes 3! and "the relatively large surface electrodes provided by the portions '45 and 153 is thus 12kv. wliich is 'sufiicient to produce an "ionizing "dischargebetween the fine wire electrodes and the

surface electrodes

45 and 63. All of the air passing throughthe unit must thus pass through the ionizing *discharge prior to passing "through the collector plate assembly. The potential diflerence'between the charge plates and the ground plates is B kv.

which 'is insufficient 'to 'cause ionizing discharges between the plates but Sufficient to cause the charged dust and smoke particles to be collected thereon. In-orderto prevent'any ofthe air from passing between the "upper "end :of the electrodes 45 and'the adjacent end walls "I 9"or "f rom which said electrode must be'spaced'ledges li'dformed r by angle ironsw'e'ld'ed on the end walls I9 and 20 may be provided tode'fle'ct any air, that might otherwise flow along "the interior surface of the end walls, into the space between the electrodes t5 and the adjacent fine wireelectrodes 34. The electrical connection "for the charge plates and the curved surface electrodesmay berm'adeto'any one of these "charge plates or conveniently "to one of the projecting electrodes '0r63. Upon disconnecting the two electrical connections, "one to the fine wire electrodes '34 and the "other to the charge plates, "the entire ionizing andco'llector plate assenib'lymay be removed as *alm'it through the front door "for servicing and repair.

The substantially streamlined contour presented by eachofthe electrodes '63 *inthe'direction of gas flow and by the interior surface of the electrodes 45 avoids "the formation of eddy currents in the region behindthe electrodes and thus permits a more'un'iform distribution of the 'airto the spaces between the cbllectoriplates than is possible where purely cylindricabelectrodes:are used.

The streamlined contourpresentedby the surface electrodes 63 of the-Ionizing meanstalso has the effect of minimizing ithe 'deposition of :solid impurities from the air .upon 'ithe surfaces participating in theionizing dischar'ge. Where purely cylindrical surface electrodes are used in this position there isa tendency riforlsubstantial deposits of impurities to build up in a short time upon the surface electrodes, a'particularl y on the downstream sides thereof an'd' to a lesser extent on the areas adjacent the fine wire electrodes and on the upstream sides of the surface electrodes. Such deposits on the surface electrodes of the ionizing means are objectionable in that alterations in the nature and size of the surface electrodes alter the characteristics of the ionizing discharge. I have found that by streamlining the surface electrodes 63 in the manner shown, such depositions on all portions of the surface participating in the ionizing discharge are greatly reduced. This is believed to be due to the fact that in prior constructions the contour of the surface electrodes has introduced a substantial amount of turbulence into the air stream. This turbulence acting in conjunction with the electrical attraction between the ionized particles and the surface electrodes has tended to throw larce quantities of the impurities onto the electrode surface where it was'deposited. By the improved construction of thesurface electrode, the-force of electrical attraction alone tends to move the charged particles in the direction of the surface electrode. Since the particles are swept downwardly in a uniformly expanding air column, they do not come onto contact with "the streamlined surface until they reach a zone much farther down in the air stream. The particles are thus carried beyond those portions of the surface area participating in the ionizing discharge and the ionizing surfaces remain substantially unaltered over relatively long operating periods.

Inorder to avoid thenecesslty for removing the ionizing and collector plate assembly for the purpose of cleaning accumulations .of dust-andzsmoke from the precipitator plates, cleaning fluid may be supplied through the pipe -68 controlled 'by'a :solenold valve '69 to a plurality of nozzles 10 by way ofa plurality of branch lines H. lfhe branch lines 17'! may be supported in the upper portion-of "the housing 'l21ona pair of rods 12, which rods are in turn supported on .ledges 13 "formed by welding :angle irons on the interior "wall of the-casing .12. The nozzles :10 are sufficient in number to direct the cleaning fluid, which may :be .hot or soapy water, to all parts :of the ionizing and collector plate assembly. -The streamline formpf the sur- 'face'el'ectrodes 4.5 and 83-:also permits thecleaning-*fluid to reach all :surfaces of these electrodes and "be deflected through the collector plate assembly.

-During operation it may occasionally .happen that-dumps or zaggl'omerations'of dust, dirt, and smoke particles previously precipitated upon the collector plates will become dislodged and fallto the chamber below ithe :ic'ollector :plate assembly. These agglomerations of dust, "dirt, and ,smoke particlesare %not to be iconfused with the unpre- -cipitated impurities originally :present in the: unitreated air, but all ofappreciable size and capable of beingfiltered or -'otherwise separated from the airstream. Inordertotprevent such agglomerates from being: carriedoutwardly throughthe duct-16.6, Ilprovide ran-eliminator comprising a plurality iof angle *irons 7.! disposed across :the discharge K 66 so that theiair passing itherethroughsmust .movez-up- 'wardlyifor at least :a short distance. '.The agglomerated particles are 'of such weight-thatithey .will mt ordinarily be .drawn :upwardly against the forceiofgravityaby the air streamiandithus remain :-inithe-'lower= chamber'to be .washedoutcupon the :next was'hingnperation. X

While there "has been herein described ;a pre- 'ferred embodiment of the invention, other em- :bodiments within the scope zofjthe :appended claims -:will be apparentzto' those skilled 5' in: the :art .ifr om azconsiderati'on "of the form shovvnand "of the teachings hereof.

What is claimed is:

1. An electrical precipitator for separating impurities from air and other gases comprising a housing, a combined ionizer and collector Plate assembly removably mounted in said housing, said assembly comprising a frame, collector plates and ionizer elements mounted on said frame, and insulators separating said ionizer elements and at least part of said plates from said frame and from each other, means in said housing for supporting said frame therein, and means in said housing for supplying cleaning fluid to said combined ionizer and collector plate assembly to wash accumulations of precipitated matter therefrom.

, 2. An electrical precipitator for separating impurities from air and other gases comprising a housing, at least one fine wire electrode, and a plurality of collector plates comprising charge flow of said air or other gas, and means insulating said charge plates and said fine wire electrode from said housing and from each other.

3. An electrical precipita-tor for separating impurities from air and other gases comprising a housing, at least one fine wire electrode, and a plurality of collector plates mounted in said housing, at least one of said collector plates having a projecting portion integral therewith providing a surface electrode coacting with said fine wire electrode, said surface electrode presenting a Substantially streamlined contour to the flow of air through the precipitator, said contour being substantially cylindrical on the side toward incoming air or other gas and tapered in the direction of flow of said air or other gas, and means in said housing on the upstream side of said collector plates and ionizer electrodes for supplying cleaning fluid to said electrodes and plates to wash accumulations of precipitated matter therefrom.

4. An electrical precipitator for separating impurities from air and other gases comprising a frame, a plurality of spaced, parallel collector plates mounted on said frame, alternate of said plates being electrically insulated from the intervening plates and constituting charge plates, a fine wire electrode insulatedly mounted in said frame, said wire being insulated from said Plates, positioned in the gas stream ahead of said collector plates, at least one of said charge plates having a projecting portion extending beyond other of said plates in the direction of the incoming air, said projecting portion having a curved surface providing an electrode coacting with said fine wire electrode and presenting a substantially streamlined contour to the flow of air through said precipitator.

5. An electrical precipitator for separating impurities from air and other gases comprising a framework having a pair of opposite side walls, at least one fine wire electrode, and a plurality of spaced, parallel collector plates comprising charge plates and ground plates supported by said side walls and parallel thereto, the charge plate next adjacent at least one of said side walls at the end of said plurality. of collector plates having a projecting portion extending beyond other of said plates in the direction of the incomin air, said projecting portion having a curved surface providing an electrode coacting with said fine wire electrode and being spaced from said one Side wall, said wire electrode being located on the side of said charge plate opposite from said one side wall, and means positioned on the upstream side of said projecting portion for deflecting air away from the space between said charge plate and saidqone wall and into the space between said charge plate and said fine wire electrode. v

6. In a particle precipitator having an ionizer and a collector plate assembly adapted for the precipitation of ionized particles from a gas passing therethrough, a frame having side-walls parallel to the plates of said assembly, a plate of said assembly adjacent a side wall having a surface lying in the direction of gas flow and extending forward of said assembly toward the oncoming gas, said plate being convexed at the side away from said wall near its forward edge to present on said side a streamlined convex obstruction in the path of said flow, and a bafiie mounted on said wall confronting said forward edge on the upstream side thereof positioned to deflect flowing gas to said convexed side and away from the space between said wall and said plate.

7. An electrical precipitator for separating impurities from air and other gases comprising a frame, first and second spaced collector plates mounted in said frame, one of said plates being lnsulatedly mounted, a fine wire electrode insu latedly mounted in said frame, said wire being insulated from said plates, said insulated plate having a projecting portion extending beyond said collector plates in the direction of incoming air, said portion having a curved surface providing an electrode coacting with said fine wire elec trode.

KENNETH W. MACKENZIE.

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

' UNITED STATES PATENTS Number France Dec. 12, 1931