US2579445A - Electrostatic precipitator - Google Patents

Description

Dec. 18, 1951 R. w. WARBURTON ,5

ELECTROSTATIC PRECIPITATOR Filed Jan. 28, 1949 4 Sheei s-Sheet 1 Hal T" I 4- INVENTOR.

iay 14 k/arburfaq BY Dec. l8, '1951 R. w. WARBURTON 2,579,445

ELECTROSTATIC PRECIPITATOR Fiied Jan. 28, 1949 4 Sheets-Sheet 2 laKv INVENTOR.

P61) M ll arburfan Dec. 18, 1951 R. w. WARBURTON 2,579,445

v ELECTROSTATIC PRECIPITATOR Filed Jan. 28, 1949 4 Sheets-Sheet :s

* ZIL/ ments.

Patented Dec. 18, 1951 f UNITED STATES r NT QFFICE ELECTROSTATIC PRECIPITATOR Ray W. Warburton, Medfield, Mass, assignor to -Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application J anuary 28, 1949, Serial No. 73,277

electrostatic charges to be added to the dust entrained in the gas, following which the gas is passed between collector 'electrodesvupon which the charged dust deposits.

After the collector electrodes of sucha precipitator have become loaded with dust, it becomes necessary that they be cleaned. The usual cleaning method involves washin the surfaces of the electrodes with water or other light flushing liquids.

In some cases, it is undesirable or inconvenient to provide and operate electrode washing facilities, and in other cases, the users of precipitators have expressed preferences for collector electrodes which can be removed and replaced after a period of use. i This invention provides, a precipitator using a collector cell of such low cost that it is economical to remove and dispose of after it has been loaded with dust.

. A feature of the invention resides in providing a. collector cell containing inter-meshed filaments of relatively high resistance, electrically conductive material through which high voltage current is flowed forprovidin voltage drops therethrough, which establish electrical charges on the filaments whereby electrostatic fields are established between adjacent filaments. The dust particles deposit upon the charged fila- The filaments also provide mechanical collection which is effective, although at reduced efiiciency, in case of failure of any of the electrical components. I

Another-feature of the invention resides in providing a collector cell containing intermeshed filaments of'relatively high resistance, electrically conductive material within metal frames, and in placing metal spikes in the center of the frames. The spikes-and the frames are connected to the opposite terminals of a high voltage, direct current source, which causes current to flow between the spikes and the frames throughv the filaments, the current providing voltage drops through'the filaments, which, in turn, establish electrostatic fields between'adjacent filaments, v .1 Another feature, of. the invention resides in 2 providing the inlet of an electrostatic precipitator as a metal sheet with spaced openings therein, and in locating the previously described metal spikes in the centers of the openings,

whereby they, and the edges of the sheet around the openings, form ionizer electrodes for ionizing the gas entering the precipitator.

-A feature of one embodiment of the invention residesv in supporting the spikes which extend into the inter-meshed filaments from tubular ionizer electrodes of the type disclosed in the said Penney patent.

A feature of still another embodiment of the invention resides in using a frame which supports ionizer wire electrodes to support the spikes which extend into the inter-meshed filaments.

A feature of still another embodiment of the invention resides in usin spikes which penetrate inter-meshed filaments from one'side of the collector cell, and which are connected to one ter-' minal of a high voltage, direct current source, and in using other spikes around said spikes and penetrating the filaments from the other side of the collector cell and connected to the opposite terminal of the high voltage source, the last-mentioned spikes providing frame conducting points around the first-mentioned spikes.

An object of the invention is to reduce the cost of electrostatic precipitators for the removal of small foreign particles from gases.

Another object of the invention is to reduce the cost of the ionizer electrodesof an electrostatic precipitator.

Another object of the invention is to reduce the cost ofthe collector electrodes of an electrostatic precipitator.

Another object of the invention is to provide an inexpensive, disposable collector cell for an electrostatic precipitator.

inlet of the cell;

, Fig. 5 is a front elevation, partially in section,

of another form of electrostatic precipitator emform of electrostatic precipitator embodying this invention;

Fig. 11 is a sectional view of the collector cell of Fig. 10 with the upstream and downstream spikes removed;

Fig. 12 is a sectional view of the frame to which the downstreamcharging spikes of Fig. 10 are attached, and

Fig. 13 is a fragmentary view, in section, of the cell of Fig. 10, and of the upstream and downstream spikes therein.

Referring first to Figs. 1, 2, 3, and 4 of the drawing, the electrostatic .precipitator illustrated, has a metal inlet plate ill with the circular openings ll therein for the entrance of gas to be cleaned. The tubular ionizer electrodes 12 having semi-spherical ends adjacent the openings I l,

are supported by the insulators is from the side walls is of the precipitator casing, and are interconnected by the supporting grid formed by the tubular, metal rods 15.

The casing, and through it the plate 10, are grounded and connected to a high voltage terminal which may, for example, be a +12,000 volt terminal of a suitable, direct current, supply source, which is not illustrated, the electrodes 12 being connected to the negative terminal of the source. The gas entering the openings H is ionized by the electrostatic field between the semi-spherical ends of the electrodes l2 and the sharp inner edges 16 of "the plate l around the openings I l.

The collector cell l8 has a casing ill of fibre board or other suitable insulating material, with the rectangular inlet openings '20, and contains the intermeshed, fibrous filaments or threads 2!. Its construction is similar to that of the conventional glass wool or hair felt, mechanical filters, except that its filaments are high resistance, electrical conductors, such as asbestos fibers, urea plastic filaments, or'glass wool coated with a semi-conductive material such as "Vaseline. Another difierence is that the metal screens 22 are placed in the cells at equally spaced positions within the mesh formed by the filaments 2|, with intersecting wires which form square metal frames within the cell. The ends of the wires 22 extend through the side walls of the casing I9 of the cell, and contact the grounded casing of the precipitator, and are charged thereby to the +12,000 volt potential to which the grounded casing is charged.

The electrodes l2 have the metal prods, pins. or spikes 2'! of reduced diameter formed on their downstream ends and which extend into the cell l8 at the centers of the metal frames when the cell is in its, operating position-within the precipitator as illustrated by Figs. 1,3. The term spike. as used in the following description and in the claims, is :used generally to describe 8. 3!

4 such cell penetrating, and electrically conductive, member.

The gas outlet of the precipitator has the hinged extensions 28 which clamp the collector cell IS in its operating position in the precipitator casing against the structural angles 29, and

electrodes 3B and 3!.

which may be swung out of the way for permitting the collector cell to be withdrawn from the outlet of the casing and replaced when it has become loaded with collected foreign matter.

In operation, the gas passing through the circular-openings H in the inlet plate and between the outer ends of the electrodes I2 and the sharp edges of the metal around the openings H is ionized, so thatthe particles entrained therein aregiven positiveelectrostatic charges as described in said Penney patent. The 12,000 volts difference in potential between the spikes 21 and the metal frames therearound formed by the screen 22, causes current to flow between the spikes'and the frames through the high-resistance filaments 2| which contact each other and the spikes and the frames. Voltage drops occur across the filaments, and potentials appearon all por-tionsof the filaments, the potentials at difierent points depending upon their positions between the spikes and the frames, those nearest the frames having the highest potentials.

The difference in potential between adjacent, closely spaced, filaments causes electrostatic fields therebetween, and the charged dust particles passing through the cell are attracted to the charged filamentsand deposit thereon.

' The collector cell also has some mechanical filter collector action which aids in the dust collection, and which enables the cell to collect some dust in caseany of the electrical equipment fails for any reason.

Another advantage of havingelectrically conductive filaments within the collector cell, is that the charges caused by the deposited particles leak. off through them-to ground, thus preventing any space charge effect.

The embodiment of the invention illustrated by Figs. 5 and 6 is similar to that described in connection with Figs. l-4, except that the ionizer electrodes are of those of the type described in the said Penney patent, the only difie'rence being that the grounded tubular ionizer electrodes and the end ionizer electrodes 3|, have the metal spikes 21 attached to their inner endsso that the spikes are grounded as are the ionizer The ionizer wire electrodes 34 are attachedtc the arms 35, which are supported by the metal tubes 36 and the insulators 37 from the end ionizer electrodes 3|.

Another diiference in the embodiment of the invention illustrated by Figs. 5 and 6 from that illustrated by Figs. -1-4, is that the collector cell 40 has a casing 4| of electrical insulatingmaterial, such as rubber or a non-conducting synthetic plastic such as Bakelite, extending therearoundand which insulates the interior of the cell from theside Walls of the precipitator casing when the cellis in its operating position. Another difference is that instead of using the screens 22 around the spikes, an egg crate type of construction is used with the metal walls .42 extending parallel the spikes 32 and forming rectangular metal. frames extending the depth of the cell. The'walls 42 are connected to the +12,000 terminal of the high voltage source, the negative terminal of which, in this case, is grounded. There is thus a 12,000 volt difference i P e ial between the walls .42 and the spikes acreage;

3-2 located centrally therebetween, resulting. in current new in the filaments in the mesh between the spikes and the walls, and in electrical charges appearing on the filaments as described in the foregoing in connection with Figs. 1-4- of the drawing.

The embodiment of the invention illustrated by Figs. '7 and 8 ofthe drawing, is similar to that described in the foregoing in connection with Figs. 5 and 6, with the exception that the spikes-2 instead. of being grounded and connected to the negative terminal of the power supply, with the walls 42 connected to its +12,000 volt-terminal, the spikes 21 instead, are attached to the rod '59 which support the arms 5| to which the ionizer wires 5.2 are attached, the wires and the spikes being attached to the +12,000 volt terminal while the tubular ionizer electrodes and: the conductive W311S-42 are grounded and connected to the negative terminal of the power supply. The rods-:59, are supported by the insulators 5-3 from the side walls of the precipitator casing.

Fig. 9 illustrates. a modification. of the construction. shown. by Figs. '7 and 8, in which the spacing between the walls A2 is less so that there are more conductive frames and therefore more spikes. 21:. The potential difference between the spikes 21 and the walls 42, the conductivity of thefilaments and the spacing of the walls 42 are related so that for the same effect, a change in onewould require a change in another. For example, ifthe potential difference between the fra'mes and the spikes is increased, then for the same effect either the filament conductivity can be less or the sizes of the frames can be increased. Fig. 9 thus illustrates a construction in which, for the. same, applied potential difference, filaments having less conductivity can be used for the sameeifect, or for the same filament conductivity, l

the. applied potential difierence can be less.

The embodiment of the invention illustrated by Figs. 10-13 of the drawing is similar to that describedin the foregoing except that instead of I having the frames around the upstream spikes formed by intersecting wires as in Figs. 1-4 or by intersccting walls as in Figs. 7, 8, and 9, the downstream spikes 55 are positioned in the cor-v ners of. the frame areas. The spikes 55 are attached to the grid formed by the rods 55, which similar in construction to the ionizer wire supporting grid of Figs. 1 and 2, except that instead of being fixedly supported, it is removable from the downstream end of the casing. Thus, in removing a loaded cell, the grid formed by the rods 56 first would, be removed from the precipitator, following which, the collector cell I8 would be re moved and a new one inserted. As a new one is inserted, thev spikes 27 penetrate the centers frame areas. Then the grid vformed by the rods 55 is placed into the downstream end of the precipitator and pushed forward untilthe spikes 55 penetrate the cell, forming frame area corners. The spikes 2'! may be connected to the negative terminal of the power supply source while the spikes 56 may be, connected to the +12,000 volt terminal of the supply. The 12,000 volt difference in potential between the center spikes and the spikes in the corners of the frame areas, would cause current flow through the filaments resulting in voltage drops therethrough, andas described in the foregoing, in the estab lishment of charges on the filaments which will cause them to attract the dust which isv electrostatically charged in its passa e. between theione 6i izerelectrodes [2 and -16... The casing of the cell may be conductive or non conductive depending upon which form is least expensive.

More spikes 5'5 than. those illustrated by Fig. 13 could, of course, be used, such additional spikes being spaced between the corner spikes so as to provide additional frame conductors.

The collector cells described in the foregoing can be made at such a low cost that it is economfoal to remove and discard them after they have become loaded. with dust, the loaded ones being replaced with new ones. It is apparent, however, that in some cases, it may be economical to clean the cells as by dipping them in a cleaning fluid and using them again. The collector cells have the additional advantage that they are light in weight and are easily removed from, and replaced in, the precipitator.

While the invention has been described as used for cleaning air, it may be used for clean ing other gases, and can be used for cleaning liquids, in which case the ionizer electrodes need not be used.

While embodiments of the invention have been described for the purpose of illustration, it should be understood that the invention is not limited to the exact apparatus and arrangement of apparatus illustrated, as modifications thereof may be suggested. by' those skilled in the art, without departure from the essence of the invention.

What is claimed'is:

.1. In an electrostatic precipitator, a collector cell containing intermeshed electrically conduc-v tive filaments having relatively high electrical resistances, means for applying an electrical charge of" one polarity to said filaments at a plurality ofpoints around a plurality of groups thereof, and means including electrically conductive spikes having relatively low electrical resistances penetrating'said; groups for applying an. electrical charge of the opposite polarity to said filaments.

2. In an electrostatic, precipitator, a collector cell; containing intermeshed electrically conductive filaments having relatively high electrical resistances, with a plurality of electrically con ducti-ve frames having relatively low electrical resistances extending. around a plurality of groups of said filaments, means for applying an electrical charge of one polarity to'said frames, and means including electrically conductive spikes having relatively low electrical resistances penetrating said groups within said frames for applying an electrical charge of the opposite polarity to said filaments.

3.. A collector cell for an electrostatic precipitator comprising intermeshed electrically coneluctive filaments. having; relatively high electrical resistances, means for applying an electrical charge of one, polarity to said filaments at a plurality of points around same, and means including an electrically conductive spike having a relatively low electrical resistance penetrating said filaments at the center of the area bounded bysaid points for applying an electrical charge of the opposite polarity to said filaments at said center.

4. A collector chamber for an electrostatic precipitator comprising a collector cell containing intermeshed electrically conductive filaments having relatively high electrical resistances; an electrically conductive spike having a I relatively low electrical resistance, penetrating said filamentameans for anpbl ns an electrical charge of one polarity to said spike, and means for applying an electrical charge of the opposite polarity to said filaments around said spike.

. 5. The invention claimed in claim 4 in which the last mentioned means includes an electrically conductive frame extending around the spike.

6. The invention claimed in claim 4 in which the last mentioned means includes other spikes penetrating said filaments around the first mentioned spike.

7. A collector chamber for an electrostatic precipitator comprising a casing, a plurality of electrically conductive spikes having relatively low electrical resistances supported from the casing, a collector cell containing electrically conductive intermeshed filaments. having relatively high electrical resistances penetrated by said spikes, means for applying an electrical charge of one polarity to said spikes, and means for applying an electrical charge of the opposite polarity to said filaments around said spikes.

8. A collector chamber for an electrostatic precipitator comprising a casing, a plurality of spikes supported'irom the casing, a collector cell containing intermeshed filaments penetrated at one side by said spikes, other spikes penetrating said cell from the opposite side, means for applying an electrical charge of one polarity to the first mentioned spikes, and means for applying an'electrical charge of the opposite polarity to said other spikes.

9. The invention claimed in claim 8 in which the filaments are electrical conductors having relatively high resistances, and the spikes are electrical conductors having relatively low electrical resistances.

10. An electrostatic precipitator comprising'a casing, a plurality of non-discharging ionizer electrodes supported in said casing, means forming discharging ionizer electrodes between said electrodes, spikes supported from said non-discharging electrodes and extending downstream with respect to gas flow through said precipitator, thereof, a collector cell having intermeshed filaments penetrated at its upstream side by said spikes, means for applying an electrical charge of one polarity to said non-discharging electrodes and to said spikes, and means for applying an electrical charge of the opposite polarity to said dischargin electrodes and to said filaments around said spikes.

11. The invention claimed in claim 10 in which the filaments are electrical conductors having relatively high resistances, and the spikes are electrical conductors having relatively low electrical resistances.

12. The invention claimed in claim 10 in which the last mentioned means includes spikes penetrating said filaments at thedownstream side of said cell.

13. The invention claimed in claim 12 in which the filaments are electrical conductors having relatively high resistances, and the spikes are electrical conductors having relatively low 3160-1 trical resistances.

14. An electrostatic precipitator comprising a. casing, non-discharging ionizer electrodes supported in said casing, ionizer wires between said electrodes, a support for said wires, spikes attached to said support and extending downstream thereof with respect to gas flow through said precipitator, a collector cell having intermeshed filaments penetrated at its upstream side by said spikes, means for applying an electrical charge of one polarity to said wires and spikes,

and for applying an electrical charge of the op posite polarity to said filaments around said spikes.

15. An electrostatic precipitator as claimed in claim 14 in which the filaments are electrical conductors having relatively high resistances, and

the spikes are electrical conductors having relatively low electrical resistances.

16. A collector chamber for an electrostatic precipitator comprising a plurality of spikes, a collector cell containing intermeshed filaments penetrated at one side by said spikes, and removable therefrom, other spikes penetrating said cell at the opposite side and removable therefrom, means for applying an electrical charge of one polarity to said first mentioned spikes, and for applying an electrical charge of the opposite polarity to said other spikes.

17. The invention claimed in claim 16 in which the filaments are electrical conductors having relatively high resistances, and the spikes are electrical conductors having relatively low electrical resistances.

18. An electrostatic precipitator comprising a casing having a gas inlet, an electrically con-'- ductive plate extending across said inlet, said plate having a plurality of circular openings therein, a plurality of non-discharging, ionizer electrodes aligned axially with said openings, electrically conductive spikes supported from said elecrtodes and extending downstream thereof, a collector cell having intermeshed filaments penetrated at its upstream side by said spikes, means for applying an electrical charge to said non-dis charging electrodes and to said spikes, and means for applying electrical charges to said plate and to said filaments around said spikes.

19. A collector cell for an electrostatic precipitator, said cell having a gas inlet and outlet and having a boundary wall defining a gas passage between said inlet and outlet, comprising a mass of electrically conductive intermeshed filaments having relatively high electrical resistances, and having interstices therebetween in the direction of gas flow between said inlet and outlet and completely filling said passage; spaced apart, interconnected, electricaLfilament charging conductors, and having relatively low electrical resistances, extending in the direction of gas flow through said passage in contact with said filaments, and an electrical filament charging conductor having a relatively low electrical resistance, penetrating said mass between said first mentioned conductors and insulated therefrom and extending in the direction of gas flow through said passage, and means for applying a direct current electrical charge having one polarity to said first mentioned conductors, and for applying a direct current electrical charge having the opposite polarity to the one conductor.

20. An electrostatic precipitator comprising a casing, an electrically conductive spike fixedly attached to said casing, and a removable collector cell slidably positioned in said casin and penetrated by said spike, said cell containing electrically conductive intermeshed filaments, and containing filament charging means in contact with said filaments around said spikes.

21. An electrostatic precipitator comprising a casing, a plurality of equally spaced electrically conductive spikes fixedly attached to said casing, and a removable collector cell slidably positioned in said casing and penetrated by said spikes, said cell containing intermeshed electrically conductive filaments, and containing filament charging means in contact with said filaments around said Number spikes. 1,598,097 RAY W. WARBURTON. 2,167,395 2,199,632 1 REFERENCES CITED 5 2,297,601 The following references are of record in the 2,408,158 file of this patent: 2,443,780

UNITED STATES PATENTS Number Name Date 10 Number 913,941 Blake Mar, 2, 1909 96,717

Name Date Mathis Aug. 31, 1926 Thomas July 25, 1939 Keyes May 7, 1940 Williams Sept. 29, 1942 Belsher Sept. 24, 1946 Wintermute June 22, 1948 FOREIGN PATENTS Country Date Sweden July 6, 1939

Images