US2631684A - Collecting electrode construction for electrical precipitators - Google Patents

Description

March 17, 1953 w. M. SCHMIDT 2,631,684

COLLECTING ELECTRODE CONSTRUCTION FOR ELECTRICAL PRECIPITATORS Filed Nov. 1,v 1949 3 Sheets-Sheet 1 WALTER M ALUQLM SCHMIDT INVENTOR.

F'IIG. Il

ATTORNEYS March 17, 1953 w. M. SCHMIDT 2,631,684

COLLECTING ELECTRODE CONSTRUCTION FOR ELECTRICAL PRECIPITATORS Filed Nov. 1, 1949 5 Sheets-Sheet 2 A -30 WALTER MALCOLM SCHMI 34 INVEN I LLLL BY l2 l5 l3 F -G g lO ATTORNEYS March 17, 1953 w. M. SCHMIDT 2,631,684

' COLLECTING ELECTRODE CONSTRUCTION FOR ELECTRICAL PRECIPITATORS Filed Nov. 1, 1949 .5 Sheets-Sheet 5 HQ 6 FIIG. 8

WALTER MALCOLM SCHMIDT, INVENTOR.

ATTORNEYS which the liquid flows from the pond.

Patented Mar. 17, 1953 UNITED STATES PATENT OFFICE COLLECTING ELECTRODE CONSTRUCTION FOR ELECTRICAL PRECIPITATORS Walter Malcolm Schmidt, Los Angeles, Calif., as-

Signor to Western Precipitation Corporation,

6 Claims. 1

The present invention relates generally to the art of electrical precipitation and apparatus for use in the separation of suspended materials from gases; and it relates more particularly to collecting electrodes in which a thin film of liquid, for example water, is passed over the surface of the collecting electrode upon which the material is collected or precipitated. H

The invention in its broad aspects is concerned with liquid-flushed collecting electrodes which provide an extended surface upon which the suspended material is precipitated. Usually and typically these collecting electrodes take the form of vertical pipes or tubes of which the inner surface is the vertically extending collecting surface. The gas is passed vertically through the collecting electrode pipes, and an opposing electrode, maintained ata relatively high potential, extends centrally within each pipe. The spacing between the two electrodes is maintained as uniform as possible.

It has been common practice to place a number of collecting electrodes of this character within a housing or shell which supports a horizontally extending header plate upon which the collecting electrodes are supported. Water or other suitable liquid is supplied to the upper ends of the collecting electrodes and a thin film is formed inside the electrodes that flows down their inside surfaces.

Ordinarily, both the upper and the lower ends of the tubular electrodes are provided with terminal sections of larger diameter than the central collecting portion in order that-the liquid film may be formed and broken at locations at which the electric field is reduced in strength. This enlargement of the tubular elements prevents arcing over between the electrodes and favors maintaining continuity of the liquid film.

- Anearly precipitator of this general type is shown in Crowder et al. Patent No. 1,968,334

issued July 31, 1934. Inthis patent the header plate has a liquid-tight connection with the housing and with the several tubes so that a pond of liquid may be formed on the header plate to supply liquid to the upper ends of a plurality of collecting electrode tubes. The upper terminal sections of the collecting electrode tubes are fiared outwardly and their top edges form weirs over It is particularly to be noted that in this construction it is necessary not only to level each combined electrode and weir with respect to the pond surface but that all weirs must be placed as closely .as possible at exactly the same elevation in order to equalize flow of liquid in each electrode. Where the terminal sections are formed integrally with the main collecting portion of the electrodes, the movement of the weir to level it with respect to the pond moves the remainder of the electrode, and vice versa.

As a matter of practice, it has been found extremely difiicult and time-consuming, and therefore expensive, to obtain equal flow of liquid in all electrodes of a group supplied from a common pond. The tubes must be individually leveled and raised or lowered, and in many cases the weirs must be hand finished in place in order to obtain satisfactory operation. Some concept of the enormous amount of work involved in installing a precipitator of this type may be had when it is understood that the number of pipes to be leveled may run up as high as one to two hundred.

Even if the tubes can be satisfactorily leveled at the time of installation, this condition may not continue to exist. Precipitator installations are large and heavy and a certain amount of settlement in the foundations often occurs. Also, they usually operate at relatively high temperatures, and relative expansion and contraction of the parts takes place as a result of the operating temperatures. These conditions frequently combine to destroy the delicate adjustment of the tubes and it is found that some tubes are receiving little or no liquid and others considerably more than their share.

Viets Patent 2,397,302 issued March 26, 1946, and Schmidt et al. 2,412,912 issued December 17, 1946, disclose construction in which a separate weir ring is provided surrounding the flared upper end of each collecting electrode, the weir rings being individually adjustable and movable with respect to their electrodes. Various types of bafile means have also been provided to form a quiescent zone in which the liquid film is formed. While these devices have resulted in considerable improvement in the operation of liquid film precipitators, they both have the objections noted above due to the necessity of accurately leveling a plurality of weirs in a common pond, and also have the further objection of being relatively expensive because of the machine work necessary to fit the weir rings to the electrode pipes. These fits between the pipes and their weir rings must be relatively tight in order to prevent leakage and to leave no interruption in the surfaces which might break the continuity of the liquid film. On the other hand, if the tolerances are too close, then the range of move- 3 ment of the weir ring relative to the electrode is correspondingly limited.

Other types of construction are shown in White Patent 2,192,249 issued March 5, 1940. In this patent various types of film establishing means are shown. Both overflow and spray types are used, but primarily reliance for forming the liquid film in each case is placed upon an annular orifice of such dimension that a film of liquid may be maintained by capillary action between the sides of the orifice. For this purpose, the upper terminal section or" the tube is flared outwardly and formed integrally with the main portion. Within the flar d portion is a member which forms one side of the orifice and which also shields the orifice from the gas stream to permit establishment of the film in a quiet zone. The shield or spray ring, or other film forming member is rigidly mounted upon the upper flared end of the tube, or is formed integrally therewith. In this type of construction, little reliance is placed upon individual leveling or elevational movement of the weir or tubes. A difficulty found with that construction has been the fact that under some conditions the annular orifice forming the film becomes clogged and as a result the water film is not formed uniformly around the entire surface of the tube, but has breaks in it which may extend for the full length of the tube.

Hence, it becomes a general object of my invention to provide an electrode construction for a liquid film precipitator in which weir members can be leveled and elevated with a minimum of time and effort, and a minimum of adjustment of the weir members is required in order to maintain a continuous film of liquid in each electrode.

It is also an object of my invention to provide a collecting electrode construction in which the film is initially formed evenly and continuously around the collecting surface, and the flushed surface itself is free from interruptions or discontinuities which cause any break in the continuity of the liquid film.

An additional object is to provide means for supplying liquid to each electrode at a substantially constant rate, independently of accumulations of foreign matter in the liquid supply.

These and other objects of my invention have been accomplished by providing, at the top end of an electrode, a member that forms a liquid weir, the downstream surface of this weir-forming member being in substantial alignment with the collecting surface of the electrode. The weir member has wall means around the full periphery of the weir to form a reservoir space adapted to hold a body of liquid that overflows that weir. The liquid, ordinarily water, is supplied-separately to each individual reservoir space and weir. In this way the elevation of each weir is entirely independent of the elevation of each'other weir, as each weir is supplied from its own pond separately from all others.

Between the electrode and the weir member there is a liquid-tight joint yet one allowing limited relative movement of the members. Fastening means are provided for holding the weir member in place, this means preferably comprisin a plurality of screws or bolts by which the weir member may be leveled upon the upper end of the electrode without effecting any movement of the electrode itself or of other weir members. g r 7 Among others, I show and describe herein a accuses preferred form of sealing means to produce a liquid-tight joint between the electrode and weir member, consisting of a deformable gasket. This same gasket is shown and claimed broadly in the copending application of Lance Hardy on Construction of Water-Flushed Electrode for -lectrical Precipitator, Serial No. 124,820 filed November 1, 1949, and having common ownership with this application.

How the above objects and advantages of my invention, as Well as others not specifically referred to herein, are attained will be more readily understood by reference to the following description and the annexed drawings, in which:

Fig. l is a fragmentary view taken inside a precipitatcr housing showing in elevation several tubular collecting electrodes constructed according to my invention, portions of the apparatus being broken away for better illustration;

Fig. 2 is an enlarged fragmentary plan view showing a single collecting electrode of Fig. 1 in plan with portions of adjoining electrodes;

Fig. 3 is a further enlarged fragmentary vertical section through the upper end of the collecting electrode structure, as on line -3-3 of Fig. 2;

Fig. 4 is an enlarged section and elevation "of the flexible nozzle supplying liquid to each weir;

Fig. 5 is a partial plan view of a modified form of my invention;

Fig. 6 is a fragmentary'vertical section online 6-43 of Fig. 5;

Fig. i is a partial plan view or another embodiment of my invention; and

Fig. 3 is a fragmentary'vertical'section on line 88 of Fig. '7.

A plurality of tubular collecting electrodes in are shown as extending vertically through and supported by header plate l2, it being understood that these electrodes are ordinarily mounted within an enclosing precipitator housing or shell provided with gas inlet and gas outlet means (not shown) at opposite sides of the header plate. Header plate [2 is supported upon the housing by any suitable means "and subdivi'des the housing in such a manner that the portion or" the housing "interior below header plate 22 forms in effectan inlet chamber which distributes the gas to the bottom ends oi? tubular electrodes iii. The gas rises within'the electrodes into the space above header plate 1'2 and leaves the housingthrough the gas outlet means. Details of the housing and its gas inlet and outlet means are not illustrated in detail because they may takemany various forms and are well known in the art; but reference may be made to the above-mentioned Patent No. 1,968,334 for disclosure of one type of housing.

Each collecting electrode ill comprises a pipe or tube of suitable length and diameter, the diameter being substantially uniform. 'The axes of all'pipes arevertical, or substantially so. The

upper end of the tube'extends abovehe'aderplate l2, as shown in greater detail in Fig.3, and is provided with a surrounding flange it by which the electrode is suspended. Each of the several electrode-receiving openings 53 in header I2 is of slightly larger diameter than the electrode, and resilient gasket (5 is'interposed between electrode fiange i l and the upper surface of the header plate to provide a fiuid-tightseal between the electrode and the header plate. The weight of the tube resting upon the gasket forces it into intimate contact with 7 both the I header plate and the electrode; and it is preferable to incline flange l4 downwardly in order to confine the gasket and improve this contact.

The inside surface of each tubular electrode I is the collecting surface of the electrode and it can be seen from the drawings that this inner surface is of extended area. It is a comparatively smooth, continuous surface in order that the liquid film formed thereover, as will be further described, may be maintained as a continuous film.

It is to be understood that my invention is not necessarily limited to a tubular electrode; but I show and describe it in conjunction with such structure as liquid-flushed electrodes are most usually tubular. If the collecting surface is flat, as provided by a plate, or otherwise shaped,

then it will be self-evident from the following description to persons skilled in the art how my invention can be altered in its details to conform to collecting surfaces of other than cylindrical configuration.

On the upper end of each electrode I 0 is a weir member I8. The weir member has an inner wall I9 which is flared outwardly at its upper end and at its lower end is substantially the diameter of electrode Ill so that the collecting surface of the electrode and the inner surface of the weir member over which the liquid film flows are in substantially vertical alignment, as illustrated particularly in Fig. 3. The top edge 20 of the inner wall I9 is suitably finished, as by grinding, so that it lies in a single plane. This edge 20 forms a weir over which liquid flows to form the film flowing down the collecting surface of electrode ID. The film-covered inner surface of wall I9 is referred to herein as the downstream surface of the weir member.

Liquid for this purpose is contained in an annular reservoir space 2| formed entirely around the outside of weir 20 by outer wall means 22, which is preferably an integral part of weir member I8. Since weir 2D is annular in shape, wall 22 is also annular, except for the formation in the wall of bay 24 which provides a space for the introduction into reservoir 2! of fluid inlet pipe 26. The end of pipe 26 carries a nozzle 2! that directs .the entering stream of water tangentially at the bottom of the reservoir space to minimize turbulence. A common supply pipe 28 (see Fig. 1) extends horizontally above a row of electrodes and is connected to a number of individual inlet pipes 26, each of the latter supplying liquid to only a single electrode reservoir. The rate of liquid supply is controlled by the size of pipes 26 and the pressure in manifold 28.

It has been found by experience that the body of liquid in reservoir 2| should be free from turbulence or motion at its surface where the liquid overflows weir 20. For this reason nozzle 21 opens to the reservoir space at the bottom thereof and the reservoir preferably tapers upwardly to form a constricted top opening between the weir and the surrounding wall 22.

Nozzle 21 is preferably made of an elastic material, as for example rubber. In a preferred form shown in Fig. 4, it tapers from each end to a constricted central portion 21a like a Venturi tube. One advantage of this construction is that the nozzle is flexible and so can be easily inserted in the reservoir space and conform to it. But the principal advantage is that by increasing the rate of liquid flow to the nozzle, pressure can be built up in the initial'section.

21b behind the constricted opening 21a and thereby the nozzle can be expanded slightly. This breaks loose any accumulated sediment and flushes the nozzle so that it is self-cleaning and can be made to deliver liquid at a substantially constant rate at all times. The taper at the exit side of the central constriction 21a is optional and is preferred in order to provide a chamber in which the liquid velocity is reduced after leaving opening 21a and before actual discharge from the nozzle into the pond of liquid around'the weir. This serves to reduce turbulence in the pond. Without this terminal portion, the exit velocity from the constricted midsection may create objectionable turbulence in the reservoir pond and increase the rate of flow over the weir above the minimum required to keep the film unbroken around it.

Resilient gasket 3| is interposed between weir member I8 and the upper end of electrode ID in order to form a liquid-tight joint between these two members. The gasket is deformable, and preferably resilient, so that the weir member can be moved relative to the electrode in order to permit leveling weir 20 to bring the plane of the weir into a truly horizontal position without moving the electrode below. In order to adequately confine gasket 3I and force it to project into the electrode when it is deformed, it is desirable to providethe weir memberwith a gasket-receiving recess 32 formed between the lower portion of wall member I9 and an external flange or wall 25.

Adjustment of the position of the weir is accomplished by the fastening means which holds the weir member in place on the electrode. This fastening means comprises plate 34 surrounding the electrode and bearing against the under edge of electrode flange I4. The central opening in plate 3 4 is sufficiently large to receive gasket I5 between the plate and the electrode wall so that the plate forms a means for confining the gasket against outward movement as a result of the weight imposed upon it by flange I4. Plate 34 has fastened to it a plurality of upwardly extending bolts 35 each provided with a nut 35 and a lock nut 3'1 at its upper end. Each bolt 35 passes upwardly through a suitable opening in a lug 38 on the rim of weir member I8.

When the electrodes are placed in position, they are aligned vertically by any suitable mean engaging them at or near their lower ends. As an example of such means, there is shown in Fig. 1 an openrectangular grid consisting of bars 45 extending at right angles to each other and passing between successive electrodes I9. At the intersections of bars 4!], are mounted short, vertically extending plates 42 which have threaded bores to receive adjusting screws 43. Screws 43 are provided with lock nuts 44 to hold them in adjusted position. By means of this arrangement, which is shown in greater detail in Viets Patent No. 2,397,302, the lower end of each collecting electrode can be moved into and held in the desired position to make the electrode vertical. There is suflicient flexibility in the supporting connection between header plate I2 and flange l4 to permit movement of the electrode for this purpose.

After the collecting electrodes are in place, the discharge electrodes 45 are installed. These may be wires of relatively small diameter or twisted rods with peripheral portions of relatively small radius to facilitate corona discharge therefrom when the discharge electrode is maintained at a 7 sufficiently high potential relative to the collect? ing electrode. Discharge electrodes 45 are posiv tioned axially of the collecting electrodes and are supported from their upper ends by suitable frame members 46 and 4] attached to cross beam 48 which is suitably supported, by means not shown, to insulate it from the hQus-ing. At their l w r ends, electrodes 45 are engaged by spacers 50 attached to frame member 5| in order to hold the discharge electrodes in proper alignment with respect to the collecting electrodes. If desired, a weight v52 may be attached to the lower end of each discharge electrode to tension the electrode.

Since it is desired that the l uid film be broken, as well a esta l sh d. at a poin here the electric field is of reduced strength, the lpw r end of each collecting electrode may be provided with a removable ring 55. The ring is preferably recessed on its inner surface an amount equal to the thickness of the Wall of tube It in order to receive the lower end of tube L0, as shown in the right-hand side of Fig. 1, and the bottom portion of the ring is then fiaredcutwardly at 56 so that the inside diameter of the lower end 56 is of substantially greater diameter than the diameter of the major portion ,of the electrode. By virtue of the recess in the ring, the inner surface of the ri g forms a flush joint wi h t e n r c l ecting surface of the electrode pipe and there is thus provided a substantially smooth, continuous surface over which the liquid film flows. The liquid then drops off ring 55 at the lower end, which is the point of greatest diameter. Each ring has a plurality of set screws 51 by which it is fastened to electrode tube 10.

After a collecting electrode 10 has been placed in position, gasket 3| is placed on its upper end and then the weir member is placed in position with the upper ends of bolts .35 extending above the weir member to receive nuts 35, The gasket is shaped so that a small portion of it initially projects beyond the inner surface of members [0 and 9. as at 31a in la As uts 36 a e t ten d, the first action is to bring plates 34 snugly against l n e 14. If any o t 6 :is urther tighte ed on a bo t. e ir m r a d ol ec n e ect ode e drawn to ether a the i e where the nut is being ht n dh s move ent o he weir member relative to the electrode compresses gas, t i a d a mal P91 9 o it isordiea ilyer outwardly th u the a ow ap et een the inner surface of the weir member and the col ecting surface of the electrode proper. This addition to the portion which originally projects beyond the collecting surface of electrode I1 21 8..-

cause of the shape of the unstressed gasket. Any

one or more of nuts 35 may be tightened to i111.- prove the liquid-tight character of the seal pro-.- v d d y a k 1 a d to in Weir 0 nto a truly horizontal position. This adjusting move-- ment of weir 20 takes place without any move..- msnt f ect de o hat the erti al pos tioning of the tube is not altered by adjustingthe weir. in a horizontal position, liquid in reservoir 2! overflows the weir at a uniform rate at all points and a continuous liquid film of vsubstandtially rm th ess s es l shed and m intained. around the entire circumference of wall I9. This film then flows smoothly over the inner downstream surface of the wall member J9 Each i s ed ind p nde l o eve o he weir- Since each weir has its separate and individual liquid s pp y f o it o eser oi 21. p per op ati n 1 1 e is ind pend nt of he e evation o the weir ai e t others The quail 8 t y o l q d flow n er it is rmined no b the elevation of the weir with respect to the surface of a common pond supplying several weirs,

as former y, but only by the rate of liquid flow through nozzle 21.

When the weir member has been brought into a level position, some portion of gasket 3!, as indicated by the dotted lines at 3w, projects outwardly beyond the collecting surface and the inner surface of wall [9. This projecting portion from the gasket is removed in any suitable way, as for example by a portable power driven grinding wheel. When finished off in this manner, the final shape of the gasket is as shown in solid lines in Fig. 3 and the exposed inner surface of the gasket is a smooth cylindrical surface which is flush with the downstream surface of the weir l9 and the collecting surface of electrode member it immediately above and below it respectively. The co-pending case of Lance Hardy referred to above contains claims to a collecting electrode assembly of which this preferred form of sealing means is an element and also claims to the described method of finishing this sealing member.

There is shown in Figs. 5 and 6 a modified form of my invention which in many respects is similar to the form previously described. In this embodimerit, the tubular electrode it is supported upon header plate 12 by a plurality of lugs 6c welded to the outside surface of the electrode. Each opening 13 in the header plate has a plurality of recesses or bays 13a of a slightly reater length than lugs to so that the electrode may be raised upwardly through opening 53 when each lug 5i] is in registration with a recess i311. Then by rotating the tube a fraction of a turn about its longitudinal axis, lugs fill are brought to rest upon the top surface of header plate [2.

The gap between the electrode and header plate I2 is sealed by annular gasket 6! which is made of rubber or other similarly resilient material. The gasket rests upon header plate I2 and in turn weir member 18a rests upon the top surface of the gasket so that the gasket provides a fluid tight seal.

Weir member la is similar in general to the weir member is described above. It is provided with an inner wall is having a top edge 20 which provides a weir over which liquid flows downwardly into the electrode iii to form the liquid film on the collecting surface of the electrode. Surrounding weir 25 is an annular wall 22 forming the reservoir space 25 within which a pond of liquid is maintained to supply liquid to weir 26. Liquid is introduced to the pond through supply pipe 25 and a nozzle 52 arranged as previously described. Nozzle 62 is a simplified form of nozzle. It is the same as nozzle 2'5 except that the terminal section of outwardly increasing diameter is omitted. It is made of rubber or other flexible material so that it can be expanded by an increase in internal pressure and any @Ccumulation of sediment or the like can be broken loose and washed out.

Weir member its differs from the form of Fig. 3 by the omission of dependent flange 25 and the continuation of inner wall [9 downwardly to form a flange lilo which fits snugly within the upper end its of the tubular electrode.

The outer surface of flange Ida and the inner surface of the electrode section [0a are machined to fit snugly within each other in order to provide a substantially fluid-tight connection between the two members at this point. At the same time, a limited amo n f movemen i pe ted etween these two parts in order to level the weir member independently of the electrode. In this form of the invention, the elements we and Ella weir member is leveled to bring weir 2% into a truly horizontal plane. This is accomplished by tightening one or more nuts 36 on adjusting bolts 35 which in this form of the invention are attached directly to header plate i2 rather than to a separate plate, as in Fig. 3. By tightening or backing on selected ones of nuts 35, the weir member can be brought into a level position without necessitating any movement of electrode it. At the same time, the weir member is brought down into snug engagement with the top surface of gasket 6i.

Figs. 7 and 8 illustrate another embodiment of my invention utilizing a different type of weir member but employing certain features for construction and support of the tubular electrode disclosed above. In this form, the upper end section 10a of the electrode is finished on its inside and is provided on the outside with a sur-- rounding, inclined flange It by which the electrode is supported. Gasket i5 is interposed between flange l4 and header plate 12 to provide a fluid-tight seal of opening [3 in the header plate through which the electrode passes. Gasket i5 is confined between flange i l, the wall of electrode section Mia, and the header plate with the weight of the electrode resting upon it.

In this embodiment of my invention, weir member l8b is formed of sheet metal by a spinning operation, or the like. The weir over which the liquid flows to form the liquid film is provided at 20a by an upwardly convex section of the metal sheet which continues on at one side to form the downwardly and inwardly converging wall H! which provides the down stream surface of the weir.

Around and outside weir 20a, the sheet metal is formed with a U-shaped bend which provides the reservoir space 2|a and the outer wall 22a thereof, wall 22a rising higher than weir 20a. Water is supplied to the reservoir space by line 26 and nozzle 62, though a nozzle 21 may be used if desired. Wall 22a has no bay as at 2% in Fig. 5.

The inner wall section [9 of the weir member continues on downwardly into a substantially cylindrical section l9?) adapted to fit snugly within end section Illa of the electrode. If desired, the inner surface of electrode section Illa may be slightly tapered downwardly by a few thousandths of an inch per inch in order to improve the tightness of the fit between the weir member and the electrode surface and at the same time to allow the weir member to tilt slightly with respect to the electrode. Being of relatively thin sheet metal, the weir member can deform slightly as it is jammed down into the end of the electrode in order to conform thereto, and to give a, fluid-tight character to the seal between it and the electrode. No sealing means other than overlapping sections llla and lab of the electrode and weir member respectively is provided to obtain a liquid-tight joint.

In this form of the invention, no screws or bolts are provided for leveling the weir member. This can be done by laying a board or other protective member across weir 20c and tapping it I10 lightly with a hammer until the weir is brought into level position. The fit between the weir and electrode is such as to permit a limited amount of this movement independent of the electrode for leveling the weir. a

In view of the foregoing, it will be understood that various changes in the design and arrangement of the parts of my improved electrode construction may be made by persons skilled in the art without departing from the spirit and scope of my invention. Consequently, it is to be understood that the foregoing description is considered as illustrative of, rather than restrictive upon, the appended claims.

I claim:

1. A collecting electrode construction for a liquid-flushed electrical precipitator, comprising: a tubular electrode member providing a vertically extending collecting surface of cylindrical shape; an annular weir member extending upwardly above the electrode member and having an inner wall of which the top edge provides an annular Weir of larger diameter than the electrode collecting surface, the inner wall having an interior surface extending downwardly from the weir to a diameter substantially equal to that of the electrode collecting surface; impervious wall means formed integrally as a part of the weir member and extending above and around but spaced from the periphery of the weir to form an isolated space adapted to hold a body of liquid having access only to said one weir to overflow the weir; leveling means engaging the weir member for leveling the weir independently of the electrode member; and a resilient gasket member interposed between the upper end of the electrode member and the lower end of the weir member with its exposed interior surface filling the gap between the Wetted interior surfaces of the inner wall and the electrode member in continuation of said surfaces.

2. A collecting electrode construction for a liquid-flushed electrical precipitator, comprising: a cylindrical electrode member providing a ertically extending interior collecting surface generally of cylindrical shape; and a detachable annular weir member supported above the upper end of the electrode member and concentric therewith, said weir member having an inner wall of which the top edge provides an annular weir of larger diameter than-the electrode collecting surface and the interior surface extends downwardly and inwardly from the weir to a diameter substantially equal to that of the collecting surface at the upper end of the electrode, and an impervious outer wall formed as an integral part of the Weir member and extending around and spaced outwardly from the periphery of the weir to form a reservoir space adapted to hold a body of liquid having access to said weir to overflow the weir to establish a liquid film on the interior surface of the inner wall, said reservoir space being cut off by said outer wall means from communication with the space outside the outer wall means at all points below the level of the weir.

3. A collecting electrode construction as in claim 2 that also comprises sealing means that form a liquid-tight joint between the electrode member and the weir member while permitting limited tilting movement of the weir member relative to the electrode member and that directs the liquid film downwardly to the collecting surface of the electrode member.

4. A collecting electrode construction for a liquid-flushed electrical precipitator, comprising: an electrode member providing a vertically extending collecting surface of extended area; a weir member having an inner wall providing a liquid weir above the electrode member for forming a liquid film that flows down over said collecting surface; impervious outer wall means formed as an integral part of the weir member and extending around the periphery of the weir downwardly from a level above the weir to form a reservoir space adapted to hold a body of liquid for overflowing only said weir, said space being out 01f by said outer wall means from communication with the space outside the outer wall means at all points below the level of the weir; and elastic deformable member engaging both the electrode member and the weir member to provide a liquid-tight seal between the two members while permitting limited relative movement of the weir member.

5. A collecting electrode constructionilas in claim 4 that also comprises means for introducing liquid into said reservoir space, including a tangentially directed, elastic nozzle located adjacent the bottom of said space and expandible' upon an increase in fluid pressure to increase the size of the fluid passage through the nozzle and. flush out accumulated particles of foreign matter.

6. A collecting electrode construction for a liquid-flushed electrical precipitator, comprising: an electrode member providing a vertically ex- 12 tending collecting surface of extended area; a weir member having an inner wall providing a liquid weir above the electrode member for forming a liquid film that flows down over said collecting surface; impervious outer wall means formed as an integral part of the weir member and extending around the periphery of the weir downwardly from a level above the weir to form a space adapted to hold a body of liquid for over- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,329,817 Wolcott Feb. 3, 1920 1,339,480 Schmidt May 11, 1920 1,442,052 Dane Jan. 16, 1923 2,269,664 Hallerberg Jan. 13, 1942 2,412,912 Schmidt et a1. Dec. 17, 1946

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