US1888022A - Apparatus for electrical precipitation - Google Patents

Description

Nov. 15, 1932. A. WINTERMUTE ET AL 1,388,022

APPARATUS FOR ELECTRICAL PRECIPITATION Original Filed Nov. 28. 1927 4 Sheets-Sheet 1 Zlwvwntoto:

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APPARATUS FOR ELECTRICAL PRECIPITATION Original Filed Nov. 28. 1927 4 Sheets-$heet 2 I Nov. 15, 1932. H. A. WINTERMUTE ET AL 1,388,022

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APPARATUS FOR ELECTRICAL PRECIPITATION inal File d Nov. 28, 1927 4 Sheets-Sheet 4 [gr] I Hal/(r7 (57 mm, W

Patented Nov. 15, 1932 I UNITED STATES PATENT OFFICE A HARRY A. WINTERMUTE, OF PLAINFIELD, AND CARL W. J. HEDBERG, OF MIDDLESEX,

NEW JERSEY, ASSIGNQRS TO RESEARCH CORPORATION, OF NEW YORK, N. Y., A CO3- PORATION OF NEW YORK APPARATUS FOR ELECTRICAL PRECIPITATION Original application filed November 28,

t 1929. Serial This invention relates to the art of electrically precipitating suspended particles from gases, and while applicable to a number of dust cleaning problems, is primarily adapted for the removal of ash and other suspended matter from the gaseous products of combustion from boilers fired with powdered fuel. This problem involves the separation of large quantities of refuse material from great volumes of gas which vary w dely in amount due to fluctuations in power loads. As much as possible is collected in a dry state to facilitate handling and removal. Furthermore it is desirable to maintain gas temperatures in order to provide sufficient stack draft and thereby reduce fan operating costs. This type of gas, moreover, may contain a certaln .percentage of sulfurous gases, so that the use of water in cleaning these gases must be controlled to minimize corrosion of metal parts of the apparatus.

" In the use 0f electrical precipitators for steam plants of the kind described it has been found that there is a certain critical velocity above which effective precipitation falls off very rapidly, due largely to the presence in the combustion gases of grit and unconsumed coal which are not retained at the collecting electrode, as commonly used, but travel along its surface. This content of grit and combustible matter, as well as the volume of the gas, increases at peak loads, and the electrical precipitators must he designed to take care of the maximum or peak load conditions.

In order to take care of these-conditions, we subject the gases first to the action of electrical precipitation conditions in the absence of flushin liquid, and then subject the gases from w iich themore finely divided particles have been removed, to further electrical precipitating conditions, including the use of liquid flushed collecting electrodes to thereby recover whatever suspended matter has escaped collection at the surface of the dry collecting electrodes. We contemplate the use of water as a flushing liquid, although it will be obvious that other flushing liquids may be used.

1927, Serial No. 236,835. Divided and this application filed Kay L water (see Burns Patent No. 1,250,088, De

cember 11, 1917), but under these conditions a sludge of water and precipitated material is formed which is troublesome to handle. We have found that this sludge is. caused principally' by the mixture of water and the very fine suspended particles of the gas, whereas, in a mixture of water and coarser particles, no sludge is formed, the precipitated matter sett-ling to the bottom of the container. Accordmg to our invention the bulk of the fine material is eliminated in a dry precipitator and the disadvantages of wet precipitators are,

obviated. d

Due to the necessary use of pipes for conducting the flushing liquids to the wet collecting electrodes, the usual system of suspension of the discharge electrodes is' not well adapted to the above-described, structure and as part of this invention we have devised a of flushed collecting novel supporting system for these electrodes.

Although this system is particularly well adapted for use with a wet precipitator, it Wlll be understood that it is not limited to use with a wet unit, but may be advantageously applied to any form of dry or wet unit. In this type of suspension, cleaning of the discharge electrodes is facilitated.

The invention will be understood from the accompanying drawings in which:

Fig; 1 is a. diagrammatic elevation of an electrical precipitation system having both dry and wet sections;

Figs. 2 to 6 are illustrations of various forms of collecting electrode units; and

Figs. 2a to 60 show corresponding horizontal cross-sections;

Fig. 7 shows modified forms of electrode units Fig. 8 is a section on plane 88 of Fig. 7 Figs. 9" and 10 are elevation and crosssection of a modification;

" tion may be the well-known type of electrical precipitator comprising a series of discharge electrodes 2, mounted in a frame 3, supported on insulators 5, and located between collecting plate electrodes 4:.

It will be noted, however, that the suspension for the discharge electrodes 2 is not of the conventional type but involves structural features which are particularly advantageous. The wires 2 are attached to rigid bell-crank members 21, said members being pivoted to the frame 3 at points 22. One end of the last electrode 2 is connected directly to the frame 3, as shown at 23, while one end of the first electrode is connected to a bell-crank supportinga weight 24. By this construction it will be seen that wire electrodes 2 are held taut by the weight 24. In this section the bulk of the finely divided suspended material is precipitated from the hot gases and drops down into a hopper. K

The hot gases then pass into the wet section, which has discharge electrodes mounted on the frame 6 and located between collecting electrodes 7, which may be of any suitable type such as flat or corrugated plates, but are here shown as made up of units 12, to be later described. These collecting electrodes are flushed with water, or other suitable liquid, by means of a pump-8 which delivers the liquid from the bottom of the section to a header 9, to which are connected the hollow units of the collecting electrode, the liquid passing upward through these hollow units, overflowing at the top, and then flowing down over the outside of the unit's.

The discharge electrodes of this wet section are suspended similarly to those of the dry section, this method of suspension being peculiarly advantageous in a wet section. As seen in Fig. 1, it is necessary forthe main feed pipes 9, at the bottom, to be much larger than the vertical pipes 12 which form the collecting electrodes. If the water level is below these main feed pipes, it means that the discharge electrode wires'must pass these pipes much closer than the normal gap between the discharge electrodes and s the streams of water, which would, of course, result in heavy discharges at these points. By the construction as shown, the water level eaaoaa is above the main feed pipe 9, and lever arms v 21 project toward the water level but properly spaced therefrom to avoid excessive arcing. An even tension is thus placed on all the discharge wires.

Another advantage particularly useful with a. wet section is that corona discharge will take place from the sharp points at the bottom of the lever arms to the surface of the water, thus giving an effective precipitation along the water level. Sneakage of the gas alon the surface of the water is thus eliminated and a high gas velocity may be maintained here also.

Another'advantage of the lever-arm suspension of discharge wires, whether applied to wet or dry sect-ions, is that the wires are prevented from swaying. When each dis- L charge electrode 1s weighted 1t is necessary streams which trap the deposited particles constitute but a minor portion of the total collecting surface. As shown in Figs. 2 and 2a, the units 12 may take the form of hollow pipes which, as shown in Fig. 1, have the wash liquid forced upwardly through the units to overflow at their openupper ends, thus wetting the entire surface of the pipe. In Fig. 3, the pipe is provided with a cap iorFbetter water distribution over the pipe.

11 1 side with their tops inclined so that the water will flow down the narrow channel or groove between the pipes, as indicated. Fig. 5 shows a special shape of pipe giving the same result as in Fig. 4. Fig. 6 is like Fig. 4 except that the pipes are elliptical in cross-section. These units may be made of any suitable material, such as metal, concrete or earthenware; and they may be arranged either side by side, as shown in Fig. 1, or spaced apart as shown in Fig. 7.

The structure shown in Figs. 7 and 8 includes alternately arranged rod units 12 of substantially circular cross-section, and units 12a of sub-circular section with shallow grooves. This arrangement is advantageous when a relatively large part, but less than the entire collecting electrode surface, is to be wetted to entrap the particles which tend to move along the collecting electrode with the moving gas stream. The arrangement shown in Figs. 9 and 10 includes rod units 12 which have their upper ends cutback, as indicated 4, two pipes are arranged side by are, so constructed or arranged that the water at 12?), to ermit water from the upper headfeed pipes, as shown in the Burns patent.

er-1l to ow down the narrow channels beabove referred to. tween adjacent rods. In operation the stream of gases carrying With-the exception of the form of unit ash, unconsumed coal particles and the like,

shown in Fig. 2, these collectin electrode flows through the dry section which is made svstems provide means by which t e Water is of sufficient length to collect and prec pitate lbcalized in streams which wet but a minor the bulk of the suspended materlal in dry portion of the total coll cting electrode surcondltlon. The partially cleaned gas stlll at face, whereby the temperature of the gas is high temperature and velocity then passes not materially lower d, 1101- i it h idity through the wet section which need be only increased to such an extent that condensed sllffiment gtht-O collect and preclpltate water i deposited i th tl t fl the coarser materlal wh ch has passed the Th rit, h, or g l t d t i l dry section. Thls material 1s washed down will be driven by the electrical discharge h collectlng S,b11t because of f {h digch'aro'e l t d to d its physical character does not form a sludge, against the collecting electrode, and will be but readlly Settles. out f Water 111 wash d d w b th stream f water i t the collect ng tank, from which it may be the receptacle at-the bottom, where it readremoved y y shltahh} meansily settles, thus permitting the water to be The gas is not hy copled 1n P i l t i mg through the wet section since only the Fig. 11 shows in longitudinal elevation the s portwns of t gas stream are brought wet section of an electrical precipitator in lhto Contact 71th the relahve-ly narrow which the collecting electrodes are formed Streams of .w i P h when the of units Such as are shown in Fig 4 or streams of water are localized in reentrant and Fig. 12 shows in sectional elevation a chanhels in the confictipg electrolgsurfhcel similar arrangement showing the form of nor Is there any oblectlohal h h' collecting electrode unit shown in Fig. 2. Wet and y p lpltator sectons may Instead of delivering the Water m below. be connected to a common high tension sysupwardly through the collecting electrode tem or each f be provlded 71th 1455 Own units, water may be poured from above over shhrce of l l ns gy- T System P the Outer Surface of the units as shown in v1des addltlonal flexibility as 1t maybe found Figs 13 and 14, in which Water is delivered advantageous to operate such wet sectons from pump 8 to a cross feederpipe 10, from which extend pipes 11 over each collecting are much abme the averageonly at peak load periods when the gas volelectrode, these pipes 11 having openings in their bottom portions into which project the upper ends of the units 12, these upper ends being of less diameter than the holes in the pipes, so that a stream of water flows down over the outs de of the pipe. These ends may By the combination described of dry and wet-electrical precipitating sections in series 'ortandem relation, the suspended material in the gases is efiiciently precipitated, while the draft conditions are not impaired. The finer particles, which would forma sludge be either circular or shaped as shown at 12a if l f with Water are recovered in d (Fig 8) 125 (Fig In this latter condition, and the coarser ash and the like instance the units 12 may be located in close are Washed down with Water from which P ty as wn in Fig. 9, d th fl they settle without difficulty. This arrangeof water is localized in the channel or groove between adjacent units, as is also the case localization of the stream has the advantage that itis not subjected to the draft of the rapidly flowing stream of gases. The discharge electrodes 2 are preferably arranged o posite these localized streams as shown in ig. 11a.

In these figures, the discharge electrodes are shown as suspended similarly to those of Fig. 1, except that a weight 24 is used at each end instead of fixing one end electrode directly to the frame.

lVhile we have described special forms of in the forms shown'in 4, 5 and 6. This ment moreover insures effective precipitation from a gas stream moving at high velocity.

This application is a division of our application Serial No. 236,335, filed Nov. 28, 1927, now Patent No. 1,7 66,422. Claims to the described method of employing both wet and dry precipitator units are presented in that patent, and the described discharge electrode structures are claimed in a continuation in part application, now Patent No. 1,7 98,964.

We claim:

1. An electrical precipitator comprising in combination with discharge electrodes, a collecting electrode system comprising a plurality of vertically disposed units of cylindraceous form whose exterior surfaces constitute collecting electrodes designed to produce unillecting surfaces opposed to said discharge formlty of water flow, it is obvious that these electrodes, and means for establishing a flow collect-mg electrodes may consist of flat or of liquid over the exterior surface of said corrugated plateswith the waterstreams units.

2. An electrical precipitator as defined in supplied at their tops by means of horizontal claim 1 in which the units are curved in crosssection and arranged in proximity thereby forming said vertical channels between adjacent units and discharge electrodes arranged opposite said' channels.

3. An electrical precipitator-as defined in claim 1 in which the units are formed as pipes having open upper ends and means are provided for forcing the liquid upwardly therethrough.

4. An electrical precipitator as defined in claim 1 in which means are provided for recirculating the liquid.

5. An electrical precipitator comprising discharge and collecting electrodes, the collecting electrodes being formed with curved surfaces defining vertical channels therein, the discharge electrodes being located opposite said channels, and means for causing streams of liquid to flow down said channels.

6. An electrical precipitator comprising discharge electrodes and a collecting electrode formed of hollow units circular in cross-section, arranged in close proximity to form vertical channels between adjacent units, the

' open upper ends being inclined inwardly, and

means for causing liquid to flow upwardly through said units.

7. An electrical precipitator comprising vertical collecting electrodes, means for flushing liquid over the surfaces thereof, means for retaining a pool of the flushing liquid beneath said collecting electrodes, the lower ends of said electrodes passing beneath the surface of said liquid, discharge electrodes, and supporting means therefor including levers connected to said discharge electrodes, a portion of said levers said pool of flushing liquid.

8. The structure as set forth in claim? wherein the discharge electrodes and said levers constitute in effect a continuous wire, and means for tensioning said discharge electrodes and levers.

9. An": electrical precipitator comprising a collecting electrode formed of a plurality of spaced vertically extending cylindraceous units whose exterior surfaces constitute colwhose exterior surfaces constitute collecting 1 surfaces opposed to said discharge'electrodes, and means for establishing a flow of liquid over the exterior surfaces of said units.

18. The invention as set forth in claim 12,

wherein said collecting electrode units have reentrant portions providing vertical channels down which the liquid flows in vertical streams.

14. An electrical precipitator comprising the combination with vertically arranged collecting electrodes having opposed vertically undulatory surfaces defining a gas passage, and discharge electrodes in said passage, of means for establishing spaced streams of liquid flowing down the faces of each of said electrodes.

In testimony whereof, we alfix our signatures.

HARRY A. WINTERNFUTE. CARL W. J. HEDBERG- projecting toward lecting electrode surfaces, means for flowing liquid over said exterior surfaces, and discharge electrode means disposed adjacent to said units and opposing said collecting electrode surfaces.

10. An electrical precipitatorcomprising a collecting electrode formed of a plurality of spaced vertically extending pipes Whose exterior surfaces constitute collecting electrode surfaces, means for flowing liquid over said exterior surfaces, and discharge electrode means disposed outside said pipes and opposing said collecting electrode surfaces.

11. An electrical precipitator as set forth in claim 13, said pipes having openings at their upper ends and being provided with means for supplying liquid upwardly through

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