US2658582A - Liquid washed electrical precipitator - Google Patents

Description

Nov. 10, 1953 FiledSept. 19, 1952 H. A. WINTERMUTE LIQUID WASHED ELECTRICAL PRECIPITATOR 2 Sheets-Sheet l INVENTOR HARRY A. WINTERMUTE ATTORNEY 1953 H. A. WINTERMUTE 2, 58,5

LIQUID WASHED ELECTRICAL PRECIPITATOR Filed Sept. 19, 1952 2 Sheets-Sheet 2 INVENTOR HARRY A. WINTE RMUTE fiw 7. 4M

ATTQRNEY Patented Nov. 10, 1953 LIQUID WASHED ELECTRICAL PRECIPITATOR Harry A. Wintermute, Plainfield, N. J assignor to Research CorporatiomNew York, N. Y., a corporation of New York Application September 19, 1952, Serial No. 310,420

2Claims. 1

This invention relates to liquid-washed electrical precipitators and, in particular, to an improved apparatus and method of intermittently flushing spacedelectrodes of electrical precipitators.

It is a common practice to flush electrodes of electrical precipitators with liquids such as oil or water. In general, the prior art electrode flushing devices provide either a fine mist or spray of flushing liquid, or an even fiow'of liquid which continuously passes'over the electrode surfaces.

Neither of these systems has proven to be entirely satisfactory as the spray devices gave a random coverage over the-entire upper surface'of the precipitator in order toget flushing liquid to all parts of the electrodes, and the even flow method generally required expensive installations for storing pools or ponds of the liquid abovethe upper ends of the electrodes.

Both of these systems require substantially more flushing liquid than is theoretically'necessary to efiectively clean the electrodes. it has been found that an intermittent heavy flush of substantially large amounts of liquid whichsupplies a heavy film of liquid on the electrodes provides more efiective removal of precipitate than a continuous thin film.

It is, therefore, an objectof the present invention to provide a method and apparatus for intermittently flushing spaced electrodes with sheets or streams or" flushing liquid that is simple and highly effective and economical to install and operate.

A further object is to provide such an intermittent flushing system wherein only a small percentage of gas and air bubbles are entrained in the flushing liquid.

Another object is to provide an improved electrode washing method that insures even distribution of the washing liquid to spaced electrodes of the precipitator.

These and other objects and advantages of the invention are provided by the method of intermittently flushing spaced electrodes which generally comprises directing a stream of flushing liquid downwardly against a liquid actuated oscillatory deflector positioned above the spaced electrodes whereby the flushing liquid is alternately directed by the deflector to alternate electrodes.

The invention will be more fully disclosed with reference to the illustrative embodiments there of shown in the accompanying drawings in which:

Fig. 1 is a fragmentary vertical sectional view through an electrical precipitator including -a washing system in accordance with the method of the invention;

Fig. 2 is an enlarged detail view or a liquid deflector embodied in the system of the invention;

Fig. 3 is a detail view of one of the liquid distributing units shown in :Fig. 1;

Fig. 4 isa right-hand view of the distributing unit of Fig. 3;

Fig. 5 is a bottom view showing one or the spray nozzles employed in the unit of Figs. 3 and 4;

Fig. 6 is a fragmentary vertical sectional View or another form of electrical precipitator embodying the principles of the invention; and

Fig. 7 is a fragmentary top view of the system shown in Fig. 6.

Referring'to the drawings, particularly to Fig. 1, the electrical precipitator shown in fragmentary section has a casing it including extended surface collecting electrodes ii formed of vertically extending metallic wire screen panels and complementary discharge electrodes H2 in the form of rods positioned between the extended surface electrodes, the rods having short discharge wires !3. The spaced collecing electrodes provide passages i l through which gas to be cleaned is caused to flow in a vertical direction, as indicated by the arrows, the passages preferably being square in horizontal cross-section and each passage having a discharge electrode i2.

Over the top opening of each gas passage i i there may be provided a pyramidal cap it made of metallic wire screen, the-bottoms or" the caps being joined to the tops of the extended surface electrodes ll The caps,.being of mesh construction, do not substantially impede the flow of gas through the apparatus.

Any conventional electrode charging means may be used for energizingthe precipitator. As is customary, the extended surface electrodes may begrounded and the discharge electrodes may be supplied with direct current of high patential of the order of 50,000 lv., whereby a corona discharge occurs 'at the discharge wires it and a strong electric field'is produced between the discharge and extended surface electrodes. As gas containing suspended particulate matter flows between the electrodes, the particles therein are charged and the charged particles migrate to the collecting electrodes ii. When the charged particles come in contact with the collecting electrode, the particles are discharged and retained on the collecting electrodes, as is well understood in the art.

In the course of operation, the'deposit of precipitated material on the collecting electodes increases to such an extent that the efficiency of collection is impaired. If efiiciency is to be maintained, it is necessary to remove the collected material from the electrodes. For this purpose there is provided an electrode washing device 9 including a washing liquid conduit 16 projecting through the wall of the casing I and extending horizontally over the top of the electrode assembly. Nozzles H are spaced along the bottom of the conduit and positioned to direct washing liquid downwardly towards the electrode assembly. The nozzles ll are of the non-diffusing type and deliver more or less solid streams of flushing liquid, Immediately below each nozzle ll there is mounted on a horizontal axle it, supported by a bracket I9, carried by the conduit IS, a liquid actuated deflector 20. The deflector has an inverted V-shaped cross-section; it is generally wedge-shaped in the portion 2| above the axle and has downwardly and outwardly flaring skirt portions 22 below the axle. The deflector is mounted for free oscillation on the axle and has its center of gravity below the axle, thus being balanced to assume a rest position with the top edge 23 of the deflector uppermost.

The deflector preferably is made by bending a rectangular sheet of steel to the configuration shown in Figs. 1 and 3. .A tube 2 1 is then welded in the angle of the deflector to provide a pivot bearing as seen in Fig. 2. The axle l8 fits loosely inside the bearing tube and is secured in the bracket l9 by nuts screwed on the threaded ends of the axle that project through the bracket. Washers 2% are placed on the axle between the ends of the bearing tube 24 and the bracket to prevent the edges of the deflector from catching against the bracket.

As illustrated in Fig. 1 of the drawings each washing device 9 is positioned over a group of electrodes. The particular number of electrodes which a given washing device will flush efiectively depends in part upon the spacing between electrodes, the height of the washing device above the upper edges of the electrodes, the angle of the deflector and the discharge velocity and volume of the washing units.

In operation, flushing liquid is caused to issue from the nozzles ll. The liquid impinges on the upper edge 23 of the deflector, as shown at A in Fig. 1, and, because of slight unbalance of forces produced by the stream of liquid on the opposed faces of the deflector, the deflector is turned to assume one of the limiting positions shown at B or C. In either of these positions, the force of the liquid is exerted largely upon the skirt portion 22 of the upper face of the deflector which eifects a turning movement of the deflector to carry it through its rest position, as shown at A in Fig. 1, to its opposite limiting position. The deflector oscillates between its limiting positions as long as the liquid impinges upon it. Such oscillating action creates a uniform film or sheet of wash liquid having a relatively wide angle of distribution. Thus each of the electrodes with-- in the field of distribution is intermittently subjected to sheets of flushing liquid. These intermittent sheets of flushing liquid flow down the electrodes washing them free from precipitated material. It has been found that the employment of the intermittent sheets of flushing liquid is more effective than continuous flows of liquid in dislodging precipitated material and far more eifective than an equivalent volume of liquid in the form of fine mist or spray.

Although the nozzles I! may have orifices formed to deliver to the deflectors a usual liquid stream that has a cylindrical or conical crosssection, it is preferred to employ a nozzle having an orifice 27, as seen in Fig. 5, that is elongated in a direction parallel to the top edge 23 of the deflector. Such an orifice delivers to the deflector a stream of liquid that has a greater dimension in the direction parallel to the long axis of the orifice than in the direction at right-angles thereto. This is illustrated in Figs. 3 and 4 wherein it is seen that the liquid stream issuing from the nozzle is wider in Fig. 4 than in Fig. 3. As shown in Fig. 4, the liquid stream tends to fan out across the surface of the deflector whereby good lateral dispersion of the liquid is ob tained.

If desired, a spray eliminator 28 may be located in the stream of gas on the downstream side of the flushing devices. The eliminator removes substantially all entrained liquid from the gases flowing to the precipitator outlet 29.

The deflector creates a minimum of fine mist, thereby substantially minimizing carrythrough of entrained flushing liquid by the gas being treated and gas absorption in the flushing liquid which may interfere with efficient washing where the liquid is recirculated The flushing system of the invention has general application in the washing of the electrodes of electrical prccipitators and is not restricted to use in the particular electrical precipitator above described by way of illustration but may advantageously be used on other forms of precipitating devices. For example, in Figs. 6 and '7 of the drawings, there is shown a two-stage electrical precipitator characterized by two parallel gas treating sections, each comprising a plurality of parallel conduits for the passage of gas therebet'ween and liquid flushing means for intermittently flushing the adjacent sections.

In Figs. 6 and 7, 40 is the shell of the electrical precipitator having a charging section 42 and a precipitating section 44. In the charging section there are a plurality of sheet type collecting electrodes it which are rectilinear in one direction and warped in another direction and positioned in parallel spaced relation to define a plurality of parallel gas passages therebetween. Spaced from the collecting electrodes are the charging electrodes 43.

In the precipitating section of the precipitator, there are a plurality of collecting electrodes 46' similar in shape and position to the collecting electrodes 46 of the charging section. The high voltage discharge electrodes 50 of the precipitating section are spaced from the extended surface electrodes 46.

The high voltage electrodes 48 and 553 are electricaily connected to a common bus bar assembly 52 which extends between the charging and precipitating sections. The bus bar assembly is insulatably supported from the collecting electrodes 46 and ill y insulators 56.

In order to provide flushing liquid to remove precipitated and collected material from the collecting electrodes, the high tension electrodes, the high tension bus bar assembly and the supporting insulators a liquid flushing system 9 is provided above the spaced sections of the precipitator. The liquid flushing system 9 is of the type described hereinbefore with reference to Figs. 1 through 5. This flushing system includes a washing liquid supply conduit l6 which extends horizontally over the top of the bus bar as- 'smbly between adjacent sections of the precipitator. Nozzles ll are spaced along the bottom of the conduit. The nozzles H are preferably of the non-diffusing type and deliver substantially solid streams of flushing liquid to the liquid actuated deflectors 20. Each deflector is mounted on a horizontal axle l8 which is supported from the conduit l6 by a bracket l9. Thus the deflector is mounted for free oscillation on the axle and has its center of gravity below the axle so that it may assume a rest position with the top edge of the deflector uppermost.

The operation of the device shown in Figs. 6 and 7 is substantially identical with the operation as described with reference to Figs. 1 through 5, whereby the oscillatory action of the deflector 20 creates a uniform stream or sheet of wash liquid which intermittently washes the electrodes in the charging section, the precipitating section and the bus bar assembly positioned therebetween. The intermittent sheets of flushing liquid flow down the electrodes and bus bar assembly washing them free from precipitated material.

The method and the apparatus of the invention for flushing electrodes intermittently with streams of flushing liquids is not limited to the particular types of precipitators illustrated herein by way of example, but the invention may be advantageously employed to flush electrodes in precipitators having vertical or horizontal gas flow where intermittent sheets of flushing liquids are desired which are substantially free of entrained gas bubbles.

This application is a continuation-in-part of my copending application Serial No. 131,821, filed December 9, 1949 (now abandoned) which is a division of my application Serial No. 698,978, filed September 24, 1946, now U. S. Patent No. 2,555,216, issued May 29, 1951.

I claim:

1. In an electrical precipitator including adjacent banks of vertically extending extended surface collecting electrodes and discharge electrodes complementary thereto, means directing a stream of gas to be cleaned between said elec-' trodes and means for energizing said electrodes; electrode wash means comprising a liquid supply conduit positioned above and between said adjacent banks of extended surface electrodes, a plurality of spaced downwardly directed nozzle means communicating with the liquid supply conduit and liquid-actuated oscillatory deflector means associated with each of the nozzle means for directing substantially the entire stream of wash liquid intermittently to the adjacent banks of the extended surface electrodes.

2. In an electrical precipitator including adjacent banks of vertically extending extended surface collecting electrodes and, discharge electrodes complementary thereto, means directing a stream of gas to be cleaned between said electrodes and means for energizing said electrodes; electrode wash means comprising a liquid supply conduit positioned above and between said adjacent banks of extended surface electrodes, a plurality of spaced downwardly directed nozzle means communicating with the liquid supply conduit and liquid-actuated oscillatory deflector means associated with each of the nozzle means for directing substantially the entire stream of wash liquid intermittently to the adjacent banks of the extended surface electrodes said deflector means including an inverted substantially V-shaped member, and means pivotally mounting said substantially V-shaped member with its top edge in the spray path of its corresponding nozzle means.

HARRY A. WIN'I'ERMUTE.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 564,906 Van Camp July 28, 1896 932,618 Kunz Aug. 31, 1906 1,329,844 Meston Feb. 3, 1929 2,255,677 Penney Sept. 9, 1941 2,273,194 Hedberg et a1 Feb. 17, 1942

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