US2563297A

US2563297A - Electrical precipitator, including an electrode washing device

Info

Publication number: US2563297A
Application number: US787840A
Authority: US
Inventors: Wilson John Herbert
Original assignee: Research Corp
Current assignee: Research Corp
Priority date: 1947-11-24
Filing date: 1947-11-24
Publication date: 1951-08-07
Anticipated expiration: 1968-08-07

Description

Aug. 7, 1951 J. H. WILSON 2,563,297

ELECTRICAL PRECIPITATOR INCLUDING AN ELECTRODE WASHING DEVICE Filed Nov. 24, 1947 2 Sheets-Sheet 1 M Q Q Q l I] I I Q I! I R I, I I

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Aug. 7, 1951 H WILSON 2,563,297 ELECTRICA PRECIPITATOR INCLUDING AN ELECTRODE WASHING DEVICE Filed Nov. 24, 1947 2 Sheets-Sheet 2 IINVENTOR. Jul-IN HERE: ERTWILEIDN,

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i atented Aug. 7, l95l ELECTRICALPRECIPITATOR, INCLUDING AN ELECTRODE WASHING DEVICE John Herbert'Wilson, Middlesex, N. J., assignor to Research 'CorporatiomNew York, N. Y., a corporation-of New York Application November 24, 1947, Serial No. 787,840

UNITED STATES PATENT OFFICE 9 Claims. 1

This invention relates to electrical precipitators and more particularly to an electrical precipitator including a device for washing or wetting the electrodes thereof. 7

An object of the invention is to provide a washing device for the electrodes of electrical precipitators wherein wide distribution of washing liquid is obtained with a minimum number of nozzles.

Another object is to provide a washing device of the type described having relatively fixed nozzles that distribute jets of washing liquid over electrode areas several times greater than the cross sectional area of the jets.

Still another object is to provide in an electrical precipitator, including complementary hi tension and extended surface electrodes, an extended surface electrode washing device positioned entirely outside the regions of strong electric field, whereby to avoid distortion of the field with attendant decrease in precipitator efficiency and danger of short circuiting.

A further object is to provide an electrode Washing device of this character that is .relatively simple to construct and install, that is easy to operate and maintain, and that is rugged .and has a long service life, thus contributing to economy in manufacture and operation.

The foregoing and other objects of the invention are realized in an electricalprecipitation apparatus having complementary high tension and extended surface electrodes and equipped with an extended surface electrode washing device including a nozzle positioned to directs jet of washing liquid against the extended surface electrode, conduit means supplying washing liquid to the nozzle, and means for causing surges in the pressure of the washing liquid supplied to the nozzle.

The invention is of general utility in thefield of washing electrodes of electrical precipitators, but is especially useful in combination with a precipitator of the type disclosed in the copending applications of Harry A. Wintermute, Serial No. 576,734, filed February 8, 1945, for Electrical Precipita'tor (now Patent 2,443,780 dated June 22, 1948), and Serial No. 698,978,.iiledSep tember 24, 1946, for Electrical Precipitators (now Patent 2,555,216, dated May 29, 1951). Reference aims and advantages will be in artJappgre t and in part pointed out in the renewing detailed description of several embodiments thereof, as

shown in the accompanying drawings, wherein:

Fig. 1 is a perspective view of the electrode assembly of an electrical precipitator showing washing liquid conduits and nozzles in assembled position;

Fig. 2is a side view similar to Fig.1 showing the washing liquid conduits and nozzles in alternative positions;

Fig.3 is a diagrammatic end view ofan electricalprecipitator embodying the invention and showing the washing liquid circuit:

Figs. 4 through '6 are enlarged detail views of one form of device for causing surges in the flow of washing liquid to the nozzles;

Fig. 7 is an enlarged sectional view of another form of pressure varying device; and

Fig. 8 is an enlarged view, with parts broken away, of still another form of pressure varying device.

- Referring now to the drawings, particularly to Fig. 1 thereof, the electrode assembly shown is of the two-stage type having a charging section Il} l0 and a collecting section I l ll. Gas flows through the apparatus from right to'left as seen in Fig. l. A housing or casing, as indicated at 63 in Fig. 3, is provided to direct the gas stream in the desired path. The char ing sections [0 and [0 are in parallel as are alsothe 'collecting sections H and II.

Each precipitator section has an extendedsurface electrode assembly including a pluralityiof j'acent conduit. The sheet members maybe conductive, for example, metal sheets or metal surfaced sheet material or they "may be non-conductive, when used with conductive liquid films,

and they may be perforate or imperforate. They maybe shaped to provide conduits of any desired cross-section such as square, as shown,

"round or hexagonal.

As best seen in Fig. 3, the extended sheet members 12 are bent as indicated at it to provide liquid receiving troughs H5 at the top of thesisseinbly. The'trou hs 15 have substantially equal cross-sectional areas .so that each trough will receive substantially an equal quantityof liquid "descending thereinto in relatively uniform hori- 2,563,297 jj e 3 zontal distribution from above. Thus, each vertical column of aligned conduits [3 will receive about the same amount of liquid from its communicating trough.

Liquid received in the troughs flows downwardly over the surfaces of the extended surface sheet members I2 through successive subjacent conduits and wets and/or washes the surfaces. Referring to Fig. 1, it will be seen that liquid issuing from the bottom of section 10 falls into the troughs of the lower section ill and continues in the manner described, to flow down over the extended surfaces of the lower section. Liquid falls from the bottom of section I0 into a sump. It will be understood that the collecting sections H and H are constructed similarly to the precipitating sections I0 and ID with regard tov the extended surface electrodes, and that the fiow of liquid therethrough takes place in a similar manner.

Each of the sections l0, III, II and H is provided with high tension electrodes I6, as best seen in Figs. 2\and 3. The electrodes are in the form of rods supported on a frame ll carried by insulators I8. The rods extend centrally inwardly of the conduits I3 for substantially the entire length thereof. The rods in the charging sections may have fine wire tips to produce corona discharge; those in the collecting sections have no fine wire tips and assist in the establishment of non-discharge fields.

Suitable conduits or cables (not shown) conduct high tension current to the high tension electrodes, as will be understood, and the extended surface electrodes may be grounded or held at some fixed potential.

As regards the opertaion of the precipitator from the electrical point of View, such operation will be apparent to those skilled in the art. In brief, however, gas bearing suspended particulate matter is passed successively through the charging and collecting sections. With the maintenance of a suitable potential difference between the high tension electrodes and the complementary extended surface electrodes, corona discharge occurs in the charging section l0l0 which charges the suspended particles oppositely to the charge of the extended surface electrodes. In the charging section, some precipitation of the charged particles on the extended surface members [2 occurs, although gas velocities are usually established such that the bulk of the charged suspended particles are transported to the collecting section lI--l I. In the quiescent field of the collecting section, most of the residual charged particulate matter is attracted to and precipitated upon the walls of the extended surface members of that section. Cleaned gas issues from the collecting section. a

The extended surface electrodes must be maintained in a clean condition if efliciency is to be preserved. For cleaning or washing the electrodes, distribution of liquid over the surfaces of the extended surface electrodes is accomplished by a device now to be described in detail. In Fig. l, the pipe I9 is disposed transversely of the fiow of gas through the apparatus and centrally above the upper sections [0 and II. The pipe has a cap 20 closing one end thereof. Along the horizontal median plane of the pipe, a series of spaced orifices 2| are provided in both sides of the pipe walls. These orifices provide nozzles for projecting jets of liquid horizontally and outwardly over the sections In and II. The openings 2| are spaced along pipe l9 corresponding to the flushing requirements of troughs 15. One orifice may be sufiicient for each trough, as shown in In such case the liquid reaching a top Fig. 3. slot l5 as it fiows down either or both sides ofa trough, divides as it passes through the slotand fiows down the surface of each sheet l2 whichbounds the tier of conduits immediately below.- Where strong fiushing is desired the slots [5' are preferably made one-eighth inch or more in width and two orifices 2i, spaced apart, are provided for each trough to assure the formation of two substantial films of liquid, each flowing separately down the surface of a sheet l2.

The arrangement of Fig. 2 is similar to that of Fig. 1, differing primarily in the placement of the nozzle pipes. Instead of being centrally located, the nozzle pipes are positioned over the gas inlet and outlet sides of the precipitator and the nozzles are pointed inwardly. The nozzle pipes Na and l9b.supply washing liquid to the upper sections II and I0, respectively while the lower nozzle pipes I and [9d perform a similar function with respect to the lower sections H and Ill, respectively. In Fig. 2, the nozzles 2| are tubes as distinguished from simple orifices cut through the side walls of the pipe. The nozzles of each pipe may be arranged to direct their jets into alternate liquid receiving troughs so that the jets from opposite sides do not interfere with each other. 'Or the jets may be positioned to direct a jet into each trough from each side, in which case, the nozzle-pipes 13a and I9!) may be operated out of phase to avoid jet interference.

In Fig. 3, the liquid circuit is shown to best advantage. Liquid is introduced to the precipitator through the nozzle pipes |9l9'. After flowing down through the precipitator sections, the liquid falls into a sump 22 formed in the bottom of the precipitator housing and thence drains through pipe 23 into a settling tank 24 wherein the sludge is allowed to separate. Thickened sludge may be removed as necessary from the tank 24 through a valve controlled pipe 25. Clarified liquid fiows through pipe 26 to the rotary centrifugal pump 21 driven by the motor 23 and is circulated through the pipe 29 and the surge controller 30 through pipes 3|, 32 and 33 to the nozzle pipes 19 and I9. Valves 34 and 35, in

lines

32 and 33, are provided for eliminating or reducing flow of liquid to either of the nozzle pipes.

The surge controller, indicated generally by the reference numeral 30, may take a variety of forms, three of which will be described hereinafter by way of illustration. The purpose of the surge controller is to deliver liquid to the nozzle pipes in a pulsating or surging fiow so that liquid jets will be projected some distance from the nozzles during periods of high pressures and at lesser distances therefrom during periods of lower pressures. With oscillating or pulsating delivery of liquid to the nozzles, the jets will oscillate back and forth along the troughs l5, as indicated in Figs. 1 and 2 to distribute liquid more or less uniformly therealong and to insure wetting of the entire longitudinal area of the troughs and the electrode structures thereunder.

One form of surge controller 30 is illustrated in Figs. 4 through 6. This device is actuated by the fiow of liquid through it. The controller has a casing 36, rectangular in cross-section, through which liquid flows in the direction of the arrow from the inlet pipe 29 to the outlet pipe 3|. An S shaped vane 31, is integrally united to a shaft 38, carried in bearingsv in the walls of the cas electrode along a line extending substantially parallel to the top edge of the dependentextended surface portion of said electrode as the pressure of washing liquid in the nozzle is varied between predetermined limits, means including a conduit supplying washing liquid to said nozzle, and means for cyclically varying the pressure of the liquid in the nozzle between said predetermined limits.

3. Apparatus as defined in claim 2 wherein the dependent extended surface portions of said electrodes are warped in the vertical direction to define a plurality of horizontal fines. j V

r 4. Apparatus as defined in claim 2 wherein said washing liquid supplying means comprises a source of liquid under substantially constant pressure.

5. Apparatus as defined in claim 2 wherein said washing liquid supplying means comprises a centrifugal pump.

6. Apparatus as defined in claim 2 wherein said washing liquid supplying means comprises a centrifugal pump and said pressure varying means comprises means positioned in said conduit between said pump and said nozzle means and actuated by movement of liquid therethrough.

7. Apparatus as defined in claim 2 wherein said washing liquid supplying means comprises a centrifugal pump and said pressure varying means comprises an independently operated valve positioned in said conduit means between said pump and said nozzle means.

8. In an electrical precipitator including substantially vertically disposed spaced parallel extended surface electrodes rectilinear in the horizontal direction and complementary high tension electrodes, each of said extended surface electrodes having an upper portion inclined to the vertical to provide a sloping surface extending along substantially the entire top edge of the extended surface electrode and a dependent extended surface portion continuous with said inclined upper portion, stationary nozzle means positioned to play a jet of washing liquid back and forth on the inclined upper portion of said electrode along a line extending substantially parallel to the top edge of the dependent extended surface portion of said electrode as the pressure of washing liquid in the nozzle is varied between predetermined limits, means including a conduit supplying washing liquid to said nozzle, and means in said conduit means actuated by movement of liquid therethrough for cyclically varying the pressure of the liquid in the nozzle between said predetermined limits.

9. In an electrical precipitator including substantially vertically disposed spaced parallel extended surface electrodes rectilinear in the horizontal direction and complementary high tension electrodes, each of said extended surface electrodes having an upper portion inclined to the vertical to provide a sloping surface extending along substantially the entire top edge of the extended surface electrode and a dependent extended surface portion continuous with said inclined upper portion, stationary nozzle means positioned to play a jet of washing liquid back and forth on the inclined upper portion of said electrode along a line extending substantially parallel to the top edge of the dependent extended surface portion of said electrode as the pressure of washing liquid in the nozzle is varied between predetermined limits, means including a conduit supplying washing liquid to said nozzle, and means including an independently operated valve in said conduit means for cyclically varying the pressure of the liquid in the nozzle between said predetermined limits.

JOHN HERBERT WILSON.

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

UNITED STATES PATENTS