US2797429A - Zone cleaning of precipitator - Google Patents

Description

July 2, 1957 A. JENSEN ETAL ZONE CLEANING OF PRECIPITATOR 3 sheets-sheei i l Filed Nov. 14, 1952 INVENTOR. Ar Jensen lc a/ecy W ATTORNEY vJuly 2, 1957 A. JENSEN ETAL ZONE CLEANING OF PRECIPITATOR 3 Sheets-Sheet 2 Filed Nov. 14. 1952 INVENTOR. Arfhur- Jen July 2, 1957 JENSEN ET AL 2,797,429

ZONE CLEANING OF PRECIPITATOR Filed Nov. 14, 1952 3 Sheets-Sheet 3 INVENTOR. Arr/wr- Jens en ob 7 C V/c/(L'q/VD. y 905/ 6- wxm/e o/eo ATTORNEY United States Patent G1 ZONE CLEANING OF PRECIPITATOR Arthur Jensen, John C. Vickland, and Roy G. Winklepleck, Wellsville, N. Y., assignors, by mesne assignments, to Apra Precipitator Corporation, New York,

N. Y., a corporation of Delaware Application November 14, 1952, Serial No. 320,552

4 Claims. (Cl. -318) a series of tubes, usually metallic, which are provided with electrodes extending centrally therethrough for charging the particles of dust and the like with which the gas passing through the tubes is laden so that the charged particles move to and are collected upon the collecting surfaces afl'orded by the inner wall surfaces of tubes. To maintain the efficiency of the precipitator and avoid flashovers it is desirable to remove the deposited particles from the collecting surfaces. In accordance with the present invention this cleaning is carried out by means of a cleaning hood which moves relative to the collecting surfaces to direct a stream of purging gas through collecting tubes that are periodically isolated from the remainder of those in the precipitator so that deposited particles may beblown from the collecting surfaces and discharged into a collecting hopper moving in unison with the purging nozzle and registering with the particular group of collecting tubes that is isolated.

The present invention proposes to also direct high pressure jets of a cleaning fluid, such as steam or compressed air, periodically against the collecting surfaces of the tubes to remove therefrom particles which are relatively more adhesive and tenacious and are not removed by the low pressure stream of purging gas. When the blowing fluid utilized is high pressure air, at a pressure of say, approximately 100 pounds to the square inch and at a temperature of 150 F. the expense fior thus cleaning the collecting surface becomes a costly item which it is desirable to reduce. The present invention contemplates that the cleaning member for directing the jets of high pressure air against the collecting surface be arranged to clean a zone of the bank of collecting tubes including a lesser number of tubes than the entire bank, the cleaning occurring in each cycle with different zones being cleaned successively so that after a number of cycles of operation the entire bank of collecting tubes has been cleaned in repeated cleaning cycles.

The invention will best be understood upon consideration of the following detailed description of illustrative embodiments thereof when read in'eonjunction with the accompanying drawings in which:

Figure l is a sectional elevation of an electrostatic precipitator provided with cleaning apparatus embodying the present invention.

Figures 1A, 1B and 1C are sectional views on an enlarged scale of the nozzle pipes of the cleaning apparatus shown in Figure 1 illustrating different numbers of nozzles in radially spaced portions of the cleaning nozzle pipe assembly.

Figure 2 is a transverse sectional view on the line Patented July 2, 1957 ice 22 in Figure 1, showing part of the cleaning apparatus as viewed in plan.

Figures 3A to 31 are diagrammatic views illustrating the different relative positions of the fluid distributing valve of Figure 1.

Figure 4 is a partial sectional elevation similar to Figure 1 showing a modified fluid distributing valve; and

Figure 5 is an enlarged transverse sectional view of part of the valve.

In the form chosen for illustration herein the electrostatic precipitator comprises a stationary cylindrical casing 10 divided by radial partitions 12 into a number of wedge or sector shaped compartments 11. Each compartment contains a plurality of hexagonal tubes 14 whose inner Walls provide surfaces for the collecting of dust particles precipitated thereon by electrostatic action when charged by electrical currents applied to an electrode 16 that extends in an axial direction centrally through each of the tubes 14. The stream of laden gases enters the precipitator casing 10 at its lower end through 1211']. inlet duct and the clean gas leaves through the outlet duct 13 at the upper end of the precipitator.

'llo purge the collecting surfaces of deposited particles one or several of the sector shaped compartments 11 containing the collector tubes are periodically isolated from the remainder of the entire bank. A rotary air duct is provided in the form of a hood 20 supplied with cleaning air from the air duct 21 located centrally at the upper end of the precipitator. Opposite the upper end of the cylinder of the precipitator casing 10 there is provided a rotary end plate 23 (Figure 1) comprising the outer and inner annular members 25 and 27 whose spaced relation provides an annular port 28 for the flow of gas directly to and from the bank of collecting tubes. The outer annulus 25 is supported by webs or ribs 26 extending radially inward therefrom to the central tube 29 which rise from the inner annulus 27. The inner annulus 27 is rotatively supported on the end portion 30 of the standard 31 which extends centrally through the precipitator casing 10 along its axis and provides a support on which the 'end plate 23 may be rotated with respect to the bank of collecting tubes that is within the casing 10. Side plates 32 and 33 extending radially from the tube 29 to a flange 34 together with the sector shaped top plate 35 therebetween constitutes the hood 20 for directing a stream of cleaning air through the collecting tubes located in the compartment or compartments with which the cleaning hood 20 is in registration;

The jets of high pressure air are directed into the collecting tubes 14 at their upper ends by a series of cleaning members 51, 52, 53, 54 carried within the hood 20 and spaced radially so that the nozzles 59 of the cleaning members 51, 52, 53, 54 register withor direct the jects of the fluid into the collecting tubes confronting the latter. The various cleaning members 51, 52, 53, 54 confront tubes located in separate cleaning zones constituted by annular bands of collecting tubes made up of a number of collecting tubes in each of the contiguous compartments of the entire bank of tubes. The cleaning members 51, 52, 53, 54 are radially spaced so that each confronts individual radially spaced zones of collecting tubes 14, these zones in a cylindrical casing being in the form of annular bands extending around the casing including collecting tubes in each of the several compartments that make up the entire bank. The nozzled cleaning members 51 to 54 are supplied with the cleaning fluid through individual pipe connections 55, 56, 57, 58 which extend inwardly and upwardly to enter individual ports 60, 61, 62, 63 mounted at the upper end of the centrally located tube 64 that rotates in unison with the air hood 20. Mounted within the valve casing 65 is a cylindrical distributing valve 66 having a radially directed port 67 which may communicate during its rotation with one of the ports 60 to 63 at a time. The valve member 66 is in the form of a cylinder rotating between or against the end plates 68, 69 of the valve casing so that the periphery 69 of the cylindrical valve member rotates in contact with the radial partitions 70 that divide the interior of the valve easing into individual chambers that communicate with the respective pipes 55 to 58. Compressed air is supplied to the rotary valve 66 through the pipe 73 extending out to the rotary joint 75 to which compressed air line 76 is connected. A motor 80 connected through a speed reducer 81 and gears 82 and 83 is drivingly connected to the hollow hub 84 fixed at its lower end to the hollow center portion 64 of the rotary upper end plate 23. The arrangement is such that the entire end plate 23 carrying the air hood 20 rotates with respect to the end of the cylindrical casing 10 so that the cleaning hood 20 sweeps over the entire bank of the collecting tubes in each rotation. The rotary element 66 of the valve which is carried as a whole along with the tube 64 and hub 84, within which it is mounted, is separately driven through a connection of the pipe 73 at its upper end to the gear 86 driven by the driving gear 87 from the speed reducer 81. The speed of rotation of the distributing valve 66 is somewhat faster than that of the cleaning hood 20 with which it moves as a whole. The distributing valve 66 is driven at a rate faster than the hood 20 by a fraction corresponding to the number of cleaning members 51, 52, 53, 54. With four cleaning members 51 to 54 the distributing valve 66 makes 1% revolutions for each revolution of the hood 20 while partaking of the rotation of the latter. Thus, the driving ratio between valve and hood is to 4. This causes relative movement between the distributing valve 66 and the ports 61, 62, 63 and 64 so that during a complete revolution of the hood 20 the distributing valve 66 advances from communication with one port, such as 61, to communication with the next succeeding port 62. This is illustrated in Figures 3A to 31 wherein the relative location of the ports 61, etc., moving with the hood 20 relatively to the distributing valve 66 that moves at a faster rate is illustrated in the six steps represented by 3A to 3H, respectively Figure 31 represents the position of the distributing valve 66 when about to communicate with the port 62 at the beginning of a second cycle or second rotation of the cleaning hood 20. Thus, the nozzles 59 of the cleaning members discharge jets of cleaning fluid into the annular band of collector tubes opposite the latter as it sweeps in a full circle along with the hood 20; at this time the supply of fluid to the cleaning members 52, 53, 54 is cut off due to the sealing action of the parts 70 against the cylindrical surface 69 of the distributing valve 66. At the end of a complete rotation of the valve 66 the cleaning member 51 is no longer supplied with pressure air because the distributing port 66 has advanced to communicate with the port 62 as represented in Figure 31 so that during the following cycle the next outside annular band of collecting tubes 14 receives a cleaning blast from the nozzles of the cleaning member 52 while the cleaning members 51, 53 and 54 are not supplied with fluid. In the third and fourth rotations of the cleaning hood 20 the cleaning members 53 and 54 are supplied with jets of high pressure air and at the end of the fourth cycle the port of the distributing valve 66 again communicates with the port 61 to restore the supply of fluid to the cleaning member 51. The result. of this operation is that contiguous annular bands of collecting tubes'14 are cleaned in succession in a full cycle including a number of rotations of the cleaning hood 20. The supply of high pressure air to only one cleaning member at a time reduces air consumption to a minimum and thereby cuts the cost.

To facilitate the effective use of the compressed air the collecting members 51, 52, 53 and 54 have different numbers of nozzles (Figures lA1C) there being more in the cleaning member 51 at the periphery of the bank of cleaning tubes with decreases by steps towards the center from cleaning member 52 to member 53 to the innermost cleaning member 54. This is illustrated in Figure 2. This arrangement allows approximately the same time for cleaning of each collecting tube of the entire bank with a jet of high pressure fluid while at the same time avoiding the costly waste that would occur by simultaneously directing jets of high pressure fluid into all of the collecting tubes between the center and periphery of a section of tubes located in compartments with which the cleaning hood and nozzles are aligned.

In Figure 4 the valve casing is divided in a plurality of separated annular chambers 181, 182, 183, 184, 185 and 186 whose interior annular walls are ported at 91 to 98 in circumferentially spaced locations (Figure 5) to communicate with the center space in which the distributing valve member 187 is located so that the single port of the valve member may communicate with one chamber 181-186 at a time and be moved progressively from the port 93 for one cleaning member to that 94 of the next one as one of the cleaning members 101-106 functions in successive rotations of the cleaning hood.

Although not illustrated herein it is desirable that a rotary hopper be provided to rotate in unison and beneath the hood 20 so as to collect the material cleaned from the tubes 14 both by the purging stream and by the cleaning jets. Such a hopper is disclosed in the Karlsson Patent 2,582,133 issued January 8, 1952.

With the arrangements disclosed an economical use is made of the jets of high pressure cleaning air so that contiguous zones of the bank of collecting tubes of the particular compartments with which the cleaning hood registers so that the material loosened from the walls of the collecting tubes by the jet of high pressure air may be blown out of the tubes even at a time when the related cleaning member is not in operation. This occurs because of the cleaning hood in a single rotation directs a stream of purging air through the entire bank of collecting tubes in a single rotation while the cleaning member directs the high pressure jets of fluid in succession through tubes of contiguous zones of bands.

What we claim is:

1. Cleaning apparatus for a bank of tubular elements comprising; a plurality of mutually spaced groups of cleaning members opposite said tubular elements and so disposed in confronting relation to said elements that each member is positioned to traverse a separate group of tubular members; individual conduits for supplying pressure fluid to said cleaning members; a valve casing formed with a separate port for each conduit and the respective cleaning member; a movable distributor having a distributing port alignable with said casing ports in succession; means for supplying cleaning fluid to said distributor for discharge through its port; means for cyclically moving said cleaning members in unison relatively to said bank of tubular elements for traversing said entire bank in each movement; means for moving said valve casing simultaneously and in unison with said nozzle cleaning members; and means for moving said distributor rela tively to said valve casing at a rate of movement so diflering from that of said casing'as to progressively place said distributing port in communication with said casing ports in succession in successive traverses of said cleaning member with respect to said bank.

2. Cleaning apparatus for a bank of tubular elements grouped about a central axis comprising; a plurality of radially spaced groups of cleaning members confronting said tubular elements and so disposed in confronting relation to said elements that each member is positioned to traverse a separate annular group of tubular members; individual conduits for supplying pressure fluid to said cleaning members; a valve casing formed with a separate port for each conduit and the respective cleaning member; a movable distributor having a distributing port alignable with said casing ports in succession; means for supplying cleaning fluid to said distributor for discharge through its port; means for rotating said cleaning members in unison relatively to said bank of tubular elements for traversing said entire bank in each rotation; means for rotating said valve casing simultaneously and in unison with said nozzle cleaning members; and means for rotating said distributor relatively to said valve casing at a rate of movement so differing from that of said casing as to progressively place said distributing port in communication with said casing ports in succession in successive rotations of said cleaning members with respect to said bank.

3. Cleaning apparatus for a bank of tubular elements comprising; a plurality of spaced groups of nozzles confronting said tubular elements and so disposed that each group traverses a separate band or zone of tubular members; individual conduits for supplying pressure fluid to said groups of nozzles; a valve casing formed with a separate chamber for each conduit and the respective group of nozzles; a rotary distributor having a port alignable with said chambers in succession; means for moving said groups of nozzles relatively to said bank of tubular elements for traversing said entire bank in each movement; means for moving said valve casing in unison with said nozzle groups; and means for moving said distributor with respect to said valve casing at a rate to progressively place said port in communication with said chambers in succession in successive traverses of said nozzle groups with respect to said bank.

4. Cleaning apparatus for a bank of tubular elements disposed around a central axis comprising; a plurality of radially spaced groups of nozzles confronting said tubular elements and so disposed that each group traverses a separate annular band or zone of tubular members radially spaced with respect to said axis; individual conduits for supplying pressure fluid to said groups of nozzles; a valve casing formed with a separate chamber for each conduit and the respective group of nozzles; a rotary distributor having a port alignable with said chambers in succession; means for rotating said groups of nozzles relatively to said bank of tubular elements for traversing said entire bank in each rotation; means for moving said valve casing in unison with said nozzle groups; and means for moving said distributor with respect to said valve casing at a rate to progressively place said port in communication with said chambers in succession in successive traverses of said nozzle groups with respect to said bank.

References Cited in the file of this patent UNITED STATES PATENTS 1,317,346 Bayer Sept. 30, 1919 2,006,295 Chewning June 25, 1935 2,537,558 Tigges Jan. 9, 1951 2,582,133 Karlsson Jan. 8, 1952 2,609,061 Hahn Sept. 2, 1952

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