US1995790A - Apparatus for electrical precipitation - Google Patents

Description

March 26, 1935. I

E. ANDERSON APPARATUS FOR EELECTRICAL PRECIPITATION Filed July 26, 19:52

2 Sheets-Sheet 2 11v VENTO R fl ALD ANamsm A TTOR/VEKj Patented Mar. 26, 1935 UNITED STATES PATENT OFFICE APPARATUS FOR ELECTRICAL PRECIPITATION Evald Anderson, San Marlno, Callf., assignor to International Precipitation Comp ,LOSAIl geles, Calif., a corporation of California Application July 26, 1932, Serial No. 624,819

2 Claims.

agglomeration or alteration of the suspended particlessuch as to facilitate subsequent mechanical collection thereof. In the apparatus commonly employed for this purpose the gas is passed between two oppositely charged electrodes, between which a suiilcient potential difierence is maintained to cause a silent or corona discharge to occur from one of said electrode members, commonly called the discharge electrode. The gas in the region of the discharge electrode becomes highly ionized and causes suspended particles entering such zone of ionization to become electrically charged, the particles so charged being ordi-' narily then precipitated by electrical attraction upon the oppositely charged electrode, commonly called the collecting or passive electrode. Inescrease the efliciency of electrical precipitation apparatus by causing all of the suspended particles to pass positively through the zone of ionization and thus increase the rate of charging of such particles. This object is accomplished essentially by delivering the gas to the electric held in such manner that all of such gas containing suspended particles is caused to'pass in close proximity to the discharge electrode means and hence through a zone of intense ionization. in passing through such zone all of the suspended particles will be subjected to ionizing action and substantially all or a large percentage of them will become electrically charged and a high efiiciency of precipitation or agglomeration will thus be obtained.

The apparatus of the invention comprises discharge electrode means and other electrode means opposing said discharge electrode means, and suitable energizing means are provided for maintaining a high potential difference therebetween. Said discharge electrode means are so formed and disposed as to provide for delivering gas containing suspended particles in close proximity to the discharge electrode means and through the zone of intense ionization surrounding the same and into the electric field between said electrodes, whereby the charged suspended particles are precipitated upon the opposing electrodes or agglomerated, and n'ieans for permitting outflow of the cleaned gas from the space between the electrodes.

The discharge electrode means may be formed as hollow members connected to gas inlet means for delivering gas to the interior thereof, and said dischargeelectrode means may be provided with openings for outflow of gas therefrom and with outwardly projecting discharging elements formed to promote electric discharge. The opposing electrode means may be provided with extended collecting surfaces disposed opposite said discharging electrodes. Furthermore, according to the preferred embodiment of the invention, the discharge electrode means and the gas inlet means are electrically grounded, while the opposing electrode means is mounted on insulating supporting means so as to be electrically insulated from ground and from the discharge electrode means.

The accompanying drawings illustrate forms of electrical precipitation apparatus according to this invention, and referring thereto:

Fig. 1 is a diagrammatic vertical section of a form of discharging element for use in the present invention.

Fig. 2 is a front view of the discharging element, taken on line 2-2 in Fig. l.

Fig. 3 is a similar view of a modified form of discharging element.

Figs. 4 and 5 are sectional views, showing modfied forms of discharging elements.

Fig. 6 is a vertical section showing another modification of discharging element.

Fig. 7 is a section on line 7-7 in Fig. 6.

Fig. ii is a view similar to Fig. 7 showing another possible modification.

Fig. 9 is a vertical section of a complete apparatus in accordance with this invention, provided with discharge elements of the type shown in Figs. 1 and 2.

Fig. 10 is a horizontal section of this form of apparatus, the upper portion of this figure being taken on line 10-10 in Fig. 9, and the lower portion thereof being taken on line 10b10b in Fig. 9.

Fig. 11 is a side elevation of a modified form of discharge electrode means which may be substituted for that shown in Fig. 9, having discharging elements of the type shown in Fig. 3.

Fig. 12 is a partial horizontal section showing tion toward, and preferably substantially perpendicular to, the opposing electrode. The discharge electrode is formed with a discharging element having a sharply pointed edge 5 around or adjacent said opening, in order to promote electric discharge therefrom, it being well known that such discharge is promoted by using members having sharp curvature and limited area, such as points, sharp edges, wires and the like. The hol low member .2 may be of circular cross-section having an inwardly tapered end portion, and the opening 4 may be round, as shown in Fig. 2; or said hollow member may consist of fiat spaced plates and the opening 4 may consist of a longitudinal slot between the convergent ends of said plates as shown in Fig. 3. Electrical connections are indicated at 7 and 8 for supplying electrical energy at high potential difference to the respective electrode means.

Modified arrangements of the discharge electrode means are shown in Figs. 4 to 8 inclusive. In Figs. 4 and 5 the gas is delivered through a hollow member 12, formed of insulating material and'provided with an opening 13 directed toward the opposing electrode 1". Said hollow member may be of the same shape as the discharge electrode member 2 in either Fig. 2 or Fig. 3 above mentioned. Adjacent the opening 13 there is provided a discharging element which may comprise a rod or wire 14 having its end 15 disposed in front of the opening 13 as shown in Fig. 4, or a rod or wire 14 having its end 15 disposed inside the opening 13 as shown in Fig. 5. Electrical connections Land 8 are provided as before for maintaining the necessary potential diiference between the discharge and collecting electrode means.

In Figs. 6 and '7 the opposing electrode is again shown as a fiat plate 1, while the gas is delivered between two parallel walls or plates 17 formed of insulating material and having their ends converging to provide an elongated slot 18 directed toward said opposing electrode. The discharging element 19 may comprise a wire or rod of small diameter extending just in front of slot 18 and throughout the length thereof. A slight modification is shown in Fig. 8 in which the wire or small rod 19' extends Just within the opening 18.

The electrical precipitating process may be carried out in apparatus provided with discharging elements of any of the forms above described, by completing the electric circuit from a suitable source of high potential electrical energy, to maintain a high potential difference between the discharge and opposing electrodes, and delivering the gas to be treated and containing suspended liquid or solid particles through the gas delivering means shown in the respective figures. In' each case the gas so delivered passes through, around, or in direct proximity to the discharging element such as 5, 14, 14', 19 or 19', and hence directly through the zone of intense ionization surrounding said discharging element, so that all of the suspended particles contained therein are subjected to ionizing action and substantially all or a large portion thereof become electrically charged, whereby said particles upon entering the electric field between the discharge electrode and the opposing electrode are immediately precipitated upon the latter due to the force of electrical attraction therebetween. It will also be noted that the inertia of the susparticles acts in the same direction as the electric field, thus further enhancing the precipitating action and insuring substantially complete depomtion of the suspended particles on the opposing electrode, which thus serves as a collecting electrode. In the case of finely divided dust or solid particles, some or all of the material depomted on the collecting electrode directly of said discharge electrode members is opposite the point of entrance of the gas may be dislodged therefrom by the force of the gas stream impinging therein, but it has been found that even such momentary deposition of the charged particles causes agglomeration thereof to form larger bodies which readily fall into the collecting or receiving means usually provided beneath the collecting electrodes, instead of being carried out of the apparatus by the gas stream.

Such dislodgement of particles by the gas stream from the portions of the collecting electrode upon which such gas stream impinges may, in some cases, be actually advantageous in that it keeps such portions of the collecting electrode free from deposited material and thus prevents disturbances in the electric field which are frequently occasioned by the accumulation of precipitated material thereon.

The clean gas, having thus been freed from suspended particles, may be allowed to escape to the atmosphere or conducted away through any suitable means provided for that purpose.

A complete apparatus embodying my invention, having discharging elements of the type illustrated in Figs. 1 and 2, is shown in Figs. 9 and 10, it being understood that any of the other types of discharging elements above-described may be substituted therein. The casing or housing is shown as comprising side walls 25 and top wall 26 and may be provided with hopper means 27 at the bottom having means such as screw conveyors 28 for collection and removal of precipitated material falling into said hoppers. An inlet fiue 30 extends along one side of said casing and outlet flue 31 extends along the other side thereof. Each discharge electrode member is shown as comprising two parallel vertical plates 32 each provided with a plurality of outwardly opening pipes or nozzles 33. The space 34 within each closed at one end by plate 35 and is in free communication at the other end with inletflue30 asindicatedat36. Each of the nozzles 33 is provided with an opening 3'1 at its outer end and the edges of said nozzles around said openings constitute the discharging elements, said edges being formed, for example, in the same manner as shown in Fig. l, to promote electric discharge therefrom. The nozzles 33 are of such cross-section and number as to provide for the desired rate of introduction of gas to the precipitating field, but said nozzles should be spaced sufiiciently far apart so as to permit adequate corona discharge to be maintained from the sharp outer edges thereof. The space 34 is also closed at the top and bottom as indicated at 39 and 40 respectively, so that all of the gas delivered to said space must issue therefrom through the openings 37. A wall or plate 41 closes off the interior of the casing from the inlet flue 30 except for the openings 36, while an opening or short connecting flue 42 permits free exit of the gas from the interior of said casing to outlet flue 31.

The collecting electrodes comprise fiat plates 44 hung or supported mid-way between the respective discharge electrode members. Said collecting electrode plates are shown as supported by transverse bars 46 which are in turn supported by vertical bars or hangers 4'? from the main supporting bars 48 resting upon insulators 49. It will be noted as a distinguishing feature of the above construction that the collecting electrode means, instead of the discharge electrode means, are insulated from the housing and hence from ground. The discharge electrode means may be grounded aeamo as indicated at '51 while the collecting electrode means may be connected as by wire 52 to the high tension side of an electrical supply circuit. This is just the reverse of the usual arrangement of electrical precipitating apparatusinwhichthecollecting electrodes are grounded and the discharge electrodes are connected to the high tension side of the circuit. The arrangement shown in these figures, however, is particularly advantageous in connection with the introduction of the gas through or in direct proximity to the discharge electrode means, as it eliminates the necessity of insulating the discharge electrode means and the portions of the gas delivery means adjacent the same from the casing and from the gas inlet flue. It is also advantageous because the discharge electrode means, including the confining plates 32 and nozzle members 33, necessarily have considerable weight, while the collecting electrode plates it are relatively light, and the weight to be carried by the insulating supports 49 is therefore less than if the discharge electrode members were to be supported thereon.

By way of example, high tension connecting wire 52 is shown as connected to the high tension contact of a mechanical rectifying device 9, the diametrically opposite contact of said rectiher being grounded at 10. The intermediate contacts of rectifier 9 are connected by wires 11 to the high tension winding of step-up transformer 12, whose primary winding may be connected by Wires 13 to any suitable source of alternating current at commercial voltage. The ratio of transformer 12 may be such as to provide the necessary high voltage, say from 15,000 to 75,000 volts, in the secondary circuit thereof.

The operation of this apparatus is essentially the same as above described. The gas from inlet flue 30 enters the spaces 34 of the hollow discharge electrode members and issues through the nozzles 33 and openings 37, being thus caused to pass directly through the zone of intense ionization adjacent the edges of said nozzles, and the particles charged in passing through said zone of ionization are largely or wholly precipitated upon the collecting electrodes 44 whence they may be permitted to fall into hopper 27. Any suitable means may be provided for rapping or jarring the collecting electrodes either manually or automatically to loosen the precipitated material therefrom. As pointed out above, however, the jets of gas delivered through nozzles 33 may serve in a large measure to keep clean the collecting electrode surfaces opposite said nozzles. The clean gas passes through opening 42 and hence out through outlet flue 31.

As shown in Fig. 11, the discharge electrode means of the apparatus shown in Figs. 9 and 10 may be provided with elongated slots or openings 37 extending either horizontally or vertically between elongated nozzle means comprising inwardly tapering walls 33, instead of the round openings of nozzles 33, the outer edges of the tapering walls 33' serving in this case as discharge elements, in substantially the same manner as shown in Fig. 3.

Another modification of the apparatus of Figs. 9 and 10 is shown in Fig. 12, in which the collecting electrodes are formed as pervious members, such as screens 44 instead of plates. The discharge electrode means may be either of the form shown in Fig. 9 or that shown in Fig. 11. The respective air delivering openings 37 (or 37') and the discharging electrodes surrounding or adjacent said openings, which oppose the opposite sides of the respective collecting electrodes, may be disposed in line with one as shown, or they may be off set from one another so that the streams of gas delivered by said openings will not impinge directly against one another.

lin the foregoing description, it has been assurned that the suspended particles were largely precipitated upon the opposing or collecting electrode means. However, it is also possible to pass the gas through the apparatus at such velocity that little or no actual precipitation or collection takes place on the electrodes. In that case, the action of the electrical field on the charged particles consists principally of agglomerating or otherwise altering the same so as to facilitate subsequent collection thereof, which may be effected by any suitable mechanical separating means, such as settling chambers, centrifugal dust collectors, filters, spray washing apparatus or the like.

In the forms of apparatus shown, the openings or nozzles through which the gas is delivered into the ionization zone are directed substantially perpendicularly toward the opposing electrode members. While this relationship is generally to be preferred, it will be understood that, if desired, these openings or nozzles may be directed at any other angle toward said opposing electrode members.

I claim:

1. An apparatus for electrical precipitation of suspended particles from gases comprising a plurality of parallel hollow discharge electrode members, each of said members comprising two parallel plates providing a gas inflow space within said member and provided with openings for discharge of gas from said space and with electrical discharging elements of sharp curvature disposed outwardly of the planes of said plates, a plurality of collecting electrode members of extended surface disposed between and substantially parallel to said discharge electrode members to provide gas treating passages between the discharge and collecting-electrode members, a common gas inlet flue communicating with said gas inflow spaces within the discharge electrode members at one end of the respective discharge electrode members, a common gas outlet means communicating with said gas treating passages at the end opposite the gas inlet flue, said discharge electrode members and gas inlet flue being electrically grounded and said collecting electrode members being electrically insulated from the discharge electrode members, and high tension electrical supply means connected to said collecting electrode members.

2. An apparatus for electrical precipitation of suspended particles from gases comprising a hollow gas delivering member provided with an opening for discharge of gas therefrom, means for supplying gas containing suspended material to the interior of said hollow member, an electrical discharging element of sharp curvature disposed centrally of said opening and immediately forwardly thereof, collecting electrode means opposing and spaced from said electrical discharging element and extending in front of said gas discharge opening, and means for maintaining a high electrical potential between said electrical discharging element and said collecting electrode member.

EVALD ANDERSON.

Images