US2609061A - Rotary electrical precipitator - Google Patents

Description

Sept, 2, 1952 A, z, H H 2,609,061

ROTARY ELECTRICAL PRECIPITATOR Filed Nov. 28, 1947 5 Sheets-Sheet l Sept. 2, 1952 A. z. HAHN ROTARY ELECTRICAL PRECIPITATOR 3 Sheets-Sheet 2 Filed Nov. 28, 1947 INVENTOR. FR E 0 ZHA H N BY M M/[r M,

Sept. 2, 1952 A. z. HAHN ROTARY ELECTRICAL PRECIPITATOR 3 Sheets-Sheet 5 Filed Nov. 28, 1947 2 LINE IN V EN TOR.

ALFRED- Z HAH N Patented Sept. 2, 1952 UNITED STATES PATENT Alfred :Z. Hahn, Bound Brook, N. 11., assignor to Research Corporation, New York, N. Y., acorv I .poration of New York Application November 28, 1947, Serial No. 788,40

i 1 Claim. (01. 183-4) This invention relates to electrical precipitators and more particularly to arotary electrical precipitator including a device for .washing the electrodes thereof.

An object of the invention is to provide a rotary electrical precipitator that is continuously operable for the purpose of cleaning air or other gas and in which" the electrodes may be washed without interrupting operation of the precipitator.

Another object is to provide a'rotary cylindrical electrical precipitator having a fixed ibafiie or bafiies providing a zone in the precipitator from which the stream of gas to be cleaned is excluded and in which the washing of the electrodes is carried out. Means may be provided for deenergizing the electrodes of that part of the precipitator located within the washing zone.

Another object is to-provide a'precipitator of this type wherein the cylindrical precipitating zone is partitioned into sector shaped sections, each section being subdivided by extended surface sheet members into individual precipitation cells extending longitudinally ofthe cylinder. The sheet members are so constructed and arranged that washing liquid will drain by gravity down the surfaces of the sheet members from superior to subjacent cells and 'will' leave the precipitator sections at the bottom.

Still another objectis "to provide in a precipitator of the rotary type automatic control means for intermittently rotating the precipitator to bring adjacent precipitator sections into the washing zone and to actuate the electrode washing sprays.

Yet another object is to provide a two-stage rotary precipitator havingmeans providingrotary cylindrical zones in one of which zones the particles suspended'in the "stream of gas to be cleaned are charged and in the other of which the charged particles are precipitated. Awashing zone is provided from which the gas stream is excluded. v 3

Typically, the electrical precipitator of the invention includes a complementary electrode assembly defining a cylindrical gas treating zone, means for energizing said electrodes, means directing a stream of gas to be treated longitudinally through said assembly, means mounting said assembly for rotation aboutits axis, means for rotating said assembly,relatively fixed baflie means adjacent to one end of said cylindrical zone defining with that part of said assembly adjacent thereto a section "in said cylindrical zone from which thegas stream is substantially excluded, and means for directing washing liquid into said section. A ispray device may be positioned between the ,baiile and the electrode assembly ,for directing washing liquid into said section longitudinally thereof.

Preferably, the cylindrical gas-treating zone of the precipitator is divided by radial partitionsint'o six sector shaped sections. The charging or precipitating cells within the sections may be of hexagonal crossesection for eflicient utilization of available space; or they may have a crosssection substantially in. the shape. of a rhombus in which the acute angle of the rhom-bus equals the central angle of the sector, 1. e.

The foregoing and other aim s,:objects and advantages of the invention will bedeveloped with greater particularity in the following detailed description taken in connection with the accompanying drawings wherein: 1

Fig. 1 is a verticallongitudinal sectional view of one form of precipitator embodying the invention;

1 Fig. 2 is a sectional-view taken along the line Z.2 of Fig. l;

Fig. 3 is a sectional viewtaken along the line 3-3 of Fig. 1.,looking in the direction of the arrows;

-Fig. 4' is an enlargedsectional view of a slip ring'embodied inwtheprecipitator of Figs. 1-3;

Figs. 5 and 6 are enlarged end views of individual sectoral sections of the precipitating zones;

and 1 1' Fig. '7 is anelectrical circuit diagram showing automatic devices used :to control the operation of the precipitator.

Referring to the drawings, particularlyto Figs. 1 and 2 thereof, the precipitator shown has a casing or housing It. The standards ll support the shaft 1 2 for'rotation in bearings l3. Mounted on the shaft for rotation therewith are two cylindrical electrode assemblies l4 and IS. The precipitator' is of the two-stage type in which particle charging is effected in the first or charging stage l4 and precipitation of the charged particles is carried out in the second or precipitating stage I5. Although someprecipitation may occur in the charging stage 14, the bulk of the vprecipitable suspended matter is deposited-in the collecting stage [5. 1

As best seen in Fig. 2, the casing is provided with transverse plates 16 having circular openings and located at the inlet and outlet ends of the apparatus to direct theflow of gas through the cylindrical precipitator zones and to prevent flow of gas therearound. The direction of gas fiow is from right to left as seen in Fig. 1, as indicated by the arrows in that figure.

Each of the stages I4 and I5 is divided by radially extending plates i! into sector shaped sections H3. The plates I! extend the full length in the axial direction of each cylindrical zone and the plates in each section are in alignment longitudinally of the cylinders.

Referring to Fig. 5, showing an end of one of the precipitation sectors in enlarged detail, the sector is divided by the extended surface sheet members I9 into a structure having a plurality of hexagonal precipitation cells 20 extending in honeycomb relation for the fulllength of the cylindrical zone. member I9 is rectilinear in the horizontal direction and warped in the vertical direction to As seen in Fig. 5 'each sheet provide the cellular structure shown. Each cell l is connected to the cell which is directly below it by a narrow channel 2 formed by appropriate spacing ofthe sheet members, and each vertical column'of cells has an outlet slot 22 at the bottom. It will thus be seen that the entire cellular structure will drain through the channels 2! and outlets 22 when the precipitation sector is oriented as shown in Fig. 5. 7

An" alternative extended surface electrode structure is shown inFig. 6; In this modification, the extended surface sheet members l9 are sinuously warped in the vertical direction to provide the cells Here, the cells are interconnected by the channels 2 I and each vertical column of cells has a bottom outlet slot 22' that may be wide or narrow depending upon what part of the cell is cut at the periphery of the sector. High tension electrodes 23' extend centrally of the cells and are similar to the high tension electrodes 23 presently to be described. It will be noted that each of the cells 20' has, in cross section, the'general appearance of a rhombus curved at the corners. The upper and lower angles of the rhombus are equal to the angle subtended by the partition plates ll which permits very eificient utilization of the sector shaped space. Drainage from the cells 20' occurs readily when the section [8 is oriented as shown in Fig. 6.

Referring again to Fig. 5, the sheet members Iii-provide the extended surface electrodes of the precipitator. The complementary electrodes are provided by rod members 23. extending centrally of the cells 20 for substantially the full length thereof. These rods are supported in cantilever fashion from the frames 24, as shown in Fig. 3. Frames 24 have cross members25 attached thereto as by welding. Cross members 25 support the rods 23 by extensions 26 which are welded to the cross members and. are bent and extended at right angles to provide the rod electrodes 23. The rods 23 extend back into the precipitator stage [4.

The high tension electrode frames 24 are mounted on insulators 21 that are carried by the cylindrical precipitator assemblies. Although only one high tension electrode assembly is completely shown in Fig.3, it will be understood that high tension or rod electrode assemblies are provided one for each of the six precipitator sectors [8 in each of the stages l4 and 15.

It may be mentioned that the rod electrodes 23 for the charging stage are provided with fine wire tips for the purpose of creating corona discharge, while those in the precipitating section have no fine wire tips and cooperate with the extended surface electrodes to set up static electric fields only. For further details'of the electrode structure, reference may be had to the copending application of Harry A. Wintermute, Serial No. 576,734, filed February 8, 1945, for Electrical Precipitator, now U. S. Patent No. 2,443,780, issued June 22, 1948.

The high tension electrode assemblies are made of metal and are conductive. High tension current is supplied to these assemblies through a stationary slip ring and sliding contact arrangement now to be described. Longitudinally aligned high tension electrode assemblies of the charging and precipitation stages are electrically interconnected by bridge members 28. Each bridge member has a contact finger 29 that slides around the stationary slip ring 30. The slip ring is supported on insulators 3| carried by struts 32 aflixed to the casing l0.

As shown in enlarged detail in Fig. 4, the slip ring has a removable segment 33 at the bottom. This segment extends over an arc of about 60 and is positionedto be engaged by one of the fingers 29 when the latter is inbottom position and when the segment is continuous with the rest of the ring. The ring segment 33 is supported on one arm of a bell-crank 34 pivoted on a pin 35 carried by a bracket 36. A solenoid 31 has a core 38 connected by a link 39 to the other arm of the bell-crank. It will be seen that when the solenoid 31 is energized, the core 38 will be drawn into the coil and this movement, as transmitted through the link 39 and bell-crank, will swing the segment 33 into a position to fill the gap in the ring 30. When the solenoid is deenergized, the segment 33 will drop out of continuity with the ring 30 under the influence of gravity. A spring may be provided if desired, to swing the segment out of contact position.- The bell-crank 34 and bracket preferably are formed of insulating material to prevent grounding of the slip ring and removable segment. High tension current i conducted to the slip ring through an electric cable (not shown) and the precipitator may be grounded to connect the cylindrical precipitator stages l4 and i5 to ground.

As-illustrated in;Figs. 1 and 2, a sump 40 is provided in the bottom of the casing [0 over which the sectors l8 {may be-brought in turn. The width of the sump is such that it will receive all of the drainage from sector-shaped sections l8 centered thereover andthe sump extends longitudinally for the full length of the casing. At each end of the sump, a substantially triangular plate 4| extends upwardly from the sump to the bearings 13 to provide baffles substantially coextensive with the ends of the sector-shaped sections l8. These battles, in cooperation with the sectors I8 included therebetween, substantially exclude flow of gases through a pair of opposed sectors aligned therebetweenand provide a section in which the electrodes are washed.

Spray devices 42, including the header pipes 43, branch pipes 44 and nozzles 45, direct sprays of water, oil or other flushing liquid into the cells 20 of precipitation sections l8 positioned between the baliies 4! to wash the electrodes forthe purpose of removing accumulated precipitated matter. By virtue of theconstruction hereinbefore described, washing liquid quickly drains from the cell 20 into thesump 40. v

Liquid is drawn from the lmp through a pipe 46 by a centrifugal pump 47 and circulated to the spray device42 through pipes 48 and 49. The pump is driven by an electric'motor 50.

The precipitator control system and a typical operation cycle will now be "described with reference to the diagramof Fig. -7. "The main driving motor 5|, which is mechanically coupled (by means not shown) to theshaft l2 for rotating the latter, is connectedto line currentin series with the solenoid 31 and is controlled by a switch 52. .When switch 52 is closed the motor. 5|. rotates the cylindrical precipitator assembly and the slip ring segment 33 is rockedinto continuity with the slipring 30. v

The motor 56, which drives the liquid pump 41, is connected to the line through a switch 53. When the switch 53 is open, as shown, the pump does not operate, and when the switch is closed the pum 'operates to effect washing.

The movable contacts of switches 52 and 53 are mounted on opposite ends of a continuous core piece 54 of the solenoid 55. When the latter is energized, the core piece moves upwardly to close switch 52 and open switch 53 and when the solenoid is deenergized, the core piece drops to close switch 53 and open switch 52.

The solenoid 55 is controlled by either the mercury switch 55 or the timer-controlled holding switch 51 that are connected in parallel with each other in the solenoid circuit. When either of the switches 56 or 51 is closed, the solenoid 55 is energized, but both switches must be open to deenergize the solenoid.

A timer motor 58, connected to the line, turns a cam 59 that closes the switch 51 for a brief period at predetermined intervals. Switch 51 stays closed only long enough for the motor 5| to rotate the cylindrical precipitator through an arc of or then the cam 59 moves to open the switch 51.

Referring now to Fig. 2, the mercury switch 56 has a conventional mercury switch element 60 mounted on an arm 6| that is pivoted on a pin '52 and urged to swing in a counterclockwise direction by a spring 63 tensioned between the arm 61 and a pin 64 on the baffle plate I6. Mounted around the periphery of the precipitator electrode assembly l5 are six pins B5 corresponding to the six sectors [8. The pins 65 are positioned to engage the switch arm 6| as the precipitator assembly rotates and to swing the switch arm in a clockwise direction to open the switch.

In the position shown in Fig. 2 the mercury switch is open and, assuming that the timer switch 51 is also open, the solenoid 55 is deenergized, the drive motor 5| is inoperative and the fluid pump 41 is operating to wash the electrodes in the lowermost zones [8. During this phase, the removable segment 33 is out of contact with the slip ring and the high tension electrodes of the lowermost zones are deenergized, thus eliminating likelihood of creating short circuits in the washing zone.

Upon the elapse of a predetermined time interval, the timer rotates the cam 59 to close the switch 51, whereupon solenoid is energized to open switch 53 and stop the pump motor and to close the switch 52 thus starting the drive motor 51 and swinging the removable segment 33 into the opening in the slip ring 30 to energize the high tension electrode assemblies in the lower sectors.

The cylindrical precipitator is rotated in a counterclockwise direction as seen in Fig. 2. As soon as the pin that holds the mercury switch 56 open has cleared the end of the switch arm 6 l the spring 63 rocks the switch to closed position. Timer cam 59 is so designed that it opens the holding switch 51 very shortly after the mercury switch assumes control of the solenoid 55.

The precipitator continues to rotate until the next pin 65 engages themercury switch arm 6| and moves the switch to open position, whereuponthe' drive motor stops and the slip ring segment 33 drops to inoperative position. At the same time, the washing pump starts and washing of the sectors in lowermost position continues until the timer closes the holding switch 51 to start a new cycle.

. It will thus be seen that the operation of the precipitator is entirely automatic. Gas bearing suspended matter to be removed therefrom is passed continuously through the precipitator. It flows through the cylindrical percipitator assemblies in allsector's except the sector defined between the two triangular baffles 41. Rotation of the precipitator assemblies is accomplished in a stepwise manner to bring pairs of aligned sectors ill of the stages l4 and I5 into the washing zones in consecutive'order. During periods of rotation, the high tension electrodes of all sectors 18 are energized so that no loss of eificiency occurs. During washing periods, the sectors in the washing section are deenergized to avoid short circuits.

Variations may be made in the control cycle without departing from the invention. For example, the timer motor 58 may have a second cam that controls a second switch in the pump motor circuit to stop the pump motor a short time before rotation of the precipitator begins in order to allow a period of time for the flushed sectors to drain prior to the beginning of rotation.

Although, for purposes of illustration a two stage precipitator has been shown and described, it will be apparent that the principles of the invention can be applied with equal advantage to a single stage precipitator in which charging and precipitation are carried out in a single cylindrical zone. In such case, a single baffle may be used to define the washing section. It will also be understood that other types of electrodes than those illustrated may be used in the sector-shaped zones. Also, the washing liquid may be introduced into the washing section from points other than those shown; for instance, the shaft 12 may be provided with internal conduits for conducting washing liquid to the several sectors I8 and suitable valve means may be provided for performing the washing operation only in the bottom section and only during the intervals of rest between periods of stepwise rotation of the cylindrical assembly.

From the foregoing description it will be seen that the present invention provides an electrical precipitator that is highly efiicient, that operates continuously without having to be shut down for cleaning, and that includes devices for automatically washing or flushing the electrodes in a step-by-step sequence.

I claim:

An electrical precipitator comprising an assembly providing a cylindrical gas treating zone, radially extending partitions dividing said assembly into a plurality of treating sections, a plurality of complementary extended surface and high tension electrodes in each of said treating sections, said extended surface electrodes in each section comprising a plurality of sheet members positioned in parallel spaced relation, said members being rectilinear in the direction of the axis of the cylindrical assembly and warped in the direction at right angles thereto to define a plurality of parallel conduits extending in the direction of the said axis, said sheet members providing means guiding the flow of liquid in the direction in which the sheet members are warped from each of said conduits to an adjacent conduit, means for energizing said electrodes, means directing a stream of gas to be treated longitudinally through saidtreating zone, means mounting said assembly for rotation about its axis, means for rotating said assembly, relatively fixed baflie means adjacent to an. end of said cylindrical assembly for inhibiting gas flow through a treating section in alignment therewith, and means operable to introduce washing liquid into a section in alignment with said baflie means.

' ALFRED Z. HAHN.

file of this patent:

UNITED STATES PATENTS Number 1,412,248 1,905,993 2,255,677 2,333,551 2,443,780 2,537,558 2,582,133

Number Name Date Laughlin 1 Apr. 11, 1922 Buff Apr. 25, 1933 Penney Sept. 9, 1941 Pegg Nov. 2, 1943 Wintermute June 22, 1948 Tigges Jan. 9, 1951 Kailsson Jan. 8, 1952 FOREIGN PATENTS Country Date France Aug. 17, 1931

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