US2853156A - Cleaning device for precipitator - Google Patents

Description

Sept. 23, 1958 P. HODSON 2,853,156

CLEANING DEVICE FOR PRECIPITATOR Filed Feb. 8, 1956 2 Sheets-Sheet 1 INVENTOR. Peter 60500 Sept. 23, 1958 P. HODSON 2,853,156

CLEANING DEVICE FOR PRECIPITATOR Filed Feb. 8, 1956 2 Sheets-Sheet 2 1 J8 "HM 26 q 1 :}3 G 1 28 29 J6 H/, 38 34 [IE/I l 4 7 l 2% f IT 49 i6 INVENTOR.

pater 60500 BY Q AGENT United States Patent 6 CLEANING DEVICE FOR PRECIPITATOR Peter Hudson, Wellsville, N. Y., assiguor to The APRA Precipitator Corporation, New York, N. Y., a corporation of New York Application February 8, 1956, Serial No. 564,184 7 Claims. (Cl. 183-76) The present invention relates to gas cleaning apparatus and more particularly it relates to an arrangement for removing dust particles from the collecting surfaces of an electrostatic precipitator on which they have been deposited by a process of electrostatic precipitation.

In dust collecting apparatus of the electrostatic type herein disclosed, dust laden gases are directed through a strong electric field between discharge electrodes and grounded collector surfaces. As the dust particles carried by the gas stream become electrically charged they move, under the influence of the strong electric field, to the grounded collector surfaces upon which they are deposited.

In order that the dust collecting apparatus may be maintained at or near its peak operating efficiency, it is important that all electrodes and collecting surfaces be periodically subjected to a cleaning action to remove the deposited particles and thereby present a substantially clean surface to the incoming dust entrained fluid. Since the operating efiiciency of dust collecting apparatus is dependent to a great extent upon the efliciency by which the deposited particles are removed from the collecting surface of the precipitator, it becomes a principal object of this invention to provide an arrangement for efficiently removing the deposited particles from the collecting surfaces thereof.

' In modern steam boiler installations of relatively large size, which utilize gas cleaning apparatus of the general type herein disclosed, the dust collecting surface is fre quently so extensive that it is not feasible to attempt to simultaneously clean the entire surface with the usually employed blowing apparatus because the demand for blowing fluid would be excessively great thereby presenting an excessive demand on existing equipment.

It therefore becomes a further object of this invention to provide an arrangement which subjects only a portion of the entire dust collecting surface to a cleaning action at any particular time whereby a minimum amount of cleaning fluid will provide suflicient cleaning action. A still further object of this invention is to provide a cleaning arrangement for gas cleaning means which will not interfere with normal operating procedure of the apparatus as a whole.

The invention will be best understood upon consideration of the following detailed description of an illustrated embodiment thereof when read in conjunction with the accompanying drawings in which:

Figure l is a perspective view, partially in section, of an electrostatic precipitator and integral cleaning device therefor constructed according to this invention.

Figure 2 is an end sectional elevation of a slightly modified form of precipitator and integral cleaning arrangement.

v In the drawings numeral 10 designates an electrostatic precipitator having an inlet duct through which dust laden gases enter to pass upward through collecting compartments 16 and 17 to outlet duct 25. Compartments 16 and 17 lie between a series of transverse division plates 18 which extend through the housing on opposite sides of a longitudinal division plate 19. The Walls of compartments 17 and 16 are grounded to provide surface on which electrostatically charged dust particles are attracted. At the upper ends of division plates 18 angularly disposed extensions 22 of varying length are arranged to permit the end faces thereof to cooperatively comprise an arcuate surface 24 with a plurality of ports discharging into an outlet duct 25.

Centrally positioned on a pair of supports 27 within the arcuate periphery of end faces 24 are a pair of bearings 26 which support trunnions 28 at the axially remote ends of a hollow cylindrical housing 32. A duct 34 with a diverging end portion or hood 36 is interconnected with the cylindrical member 32 and adapted to rotate or swing therewith whereby an opening in the end of the hood is progressively moved into registry with the similar openings in the end face 24. When the duct 34 is in engagement with any of chambers 16 or 17, gaseous fluid from these chambers may be drawn through hood 36, duct 34, horizontal cylindrical member 32 to openings 38 and thence to outlet duct 42 by means of an induced draft fan (not illustrated) whose suction is in the outlet duct.

A division plate 46 extending longitudinally through hood 36, duct 34, and across cylinder 32 divides therotating hood assembly into similar sections which are adapted to be placed in registry with the banks of collecting sections on opposite sides of the housing division plate 19. A damper 44 is arranged to be selectively moved by actuator 45 to control flow of fluid from ports 38 and 38-A whereby fluid may be drawn through either end of the cylindrical duct 32, its corresponding portion of swinging duct 34 and the temporarily aligned compartment in either bank 16 or 17. By this expedient the quantity of purge fluid required to maintain a predetermined rate of flow through the collecting compartments is limited by the capacity of a single collecting compartment.

An actuating device 47 operatively attached to one of trunnions 28 provides means by which the cylinder 32 and its interconnected assembly may be rotated about its bearing supported axis. As the assembly is rotated the opening in the end of hood 36 leading to duct 34 is pro gressively moved across the series of arcuate faces 24 to receive purging fluid being drawn through compartments 16 or 17 and their corresponding extensions. Actuating devices 45 and 47 are only schematically illustrated and may readily be adapted to any available source of motive power.

In operation dust entrained gas entering connecting duct 15 is drawn upward through any of dust precipitation compartments 16 or 17 which are provided with the usual electrostatic dust collecting means not here illustrated. As the dust particles are removed from the gas stream they are deposited upon the surface of walls 18 or other collecting surface of the compartments while the cleaned gas continues to flow upward through the compartments to outlet duct 25.

When the cleaning mechanism is in operation a quantity of high velocity cleaning fluid is drawn through the hood 36 and the particular collecting compartment 16 or 17 that is in registry therewith by an induced draft fan having its suction in outlet duct 42. As the high velocity cleaning fluid impinges against the dust particles clinging to the collecting surface of each compartment the particles are first loosened and then entrained in the stream of cleaning fluid. In the manner disclosed, damper 44 may be actuated to permit fluid to flow through either end of cylindrical duct 32 and its interconnected ducts and compartments. By the proper coordination of actuators 45 and 47 the purging fluid may be directed through any predetermined series of compartments 16 or 17. For example, during a single sweep of actuator 47 the duct 34 and its integral .hood .36 is moved arcuately from one extreme to another whereby the complete bank of compartments 16 or 17 may be successively subjected to the flow of cleaning fluid.

The position of damper 44 determines which bank of collecting surfaces will be subjected to the flow of cleaning fluid. If the damper 44 is positioned vertically as illustrated in Figure 1, port 39A is interconnected through openings 38A and duct 46A to any of compartments 17 whereby the cleaning fluid may be drawn therethrough.

After purging the last compartment in the bank of aligned compartments 17, actuator 45' moves damper 44 to close port 39A while opening port 39 to outlet 42 whereby purging fluid may be drawn through port 39, openings 38, duct 46 and any of compartments 16 with which hood 36 is in registry. In operation actuator 45 is timed to move damper 44 only after actuator 46 has swung hood 36 to cover the last compartment in either bank 16 or '17, whereby the damper 44 may effectively alternate flow of purging fluid between parallel banks of compartments 16 and 17.

The coordination between actuators 45 and 46 may be effected manually or by automatic means not here illustrated, however, the basic operation of the device remains materially unchanged.

In Figure 2 an alternate form of cleaning device is illustrated wherein a swing damper 52 in hood 36 is hinged at 54 to provide means by which purge fluid may be directed through one bank of compartments while flow through its adjacent bank is curtailed. The damper 52 is positioned by an actuator 56 operatively attached thereto by an intermediate linkage system extending through hollow trunnion 29.

In both forms of the device disclosed sealing means 62 are provided along edges of the arcuate surface 24 to preclude excessive leakage of fluid from high to relatively low pressure areas.

The cycle of operation for both forms of the device illustrated is similar and originates with hood 36 lying in registry with a single one of compartments 16. When in such a position the electric power to the particular compartment being cleaned is discontinued or reduced to level below that required for ionization whereby particles which have been electrostatically attracted to its collecting surfaces may readily be removed therefrom and entrained in the high velocity cleaning fluid. After a predetermined period a timing mechanism (not illustrated) effects return of electric power to the compartment being cleaned while simultaneously discontinuing the power being supplied to an adjacent compartment of the same series. During the corresponding period actuator 46 moves duct 34 and its hood 36 to the same compartment whereby cleaning fluid may traverse the electrically inactive compartment. Similarly the swinging duct is moved to progressively register with each remaining compartment in the original series 16. After a period of communication with the last compartment of the 16 series, actuator 45 (Figure 1) or 56 (Figure 2) moves damper 44 (Figure 1) or 52 (Figure 2) to their opposite positions whereby the adjacent compartments 17 are placed in registry with the open passageway of hood 36. Simultaneously actuator 47 begins its return swing whereby each of compartments 17 will be progressively placed in alignment with the hood member.

The cycle of operation above described is dependent upon an intermittent actuation of the swinging duct assembly 323436, however altering the action of actuator 46 to provide a continuous sweep of hood 36 across the collecting compartments 16 or 17 would in no way alter the basic cleaning cycle. Similarly, further dividing the compartments to reduce their size while providing additional dampers to control the flow of fluid therethrough is believed to be entirely within the scope of this invention.

A further possible variation of the above disclosed arrangement would be to provide a swinging duct arrangement similar to assembly 32-3435 adjacent the inlet 15 so that when synchronized with the cleaning system adjacent the outlet end the combined arrangement would provide a closed circuit for the circulation of cleaning or purging fluid. By using such a closed circuit it would become quite practical to use a separate medium for the purging fluid since there would be no intermixing with the principal gas flow.

While the purging arrangements disclosed are particularly directed to use with an electrostatic precipitator, the same arrangement may readily be applied to a mechanical dust collector or even a heat exchanger, and it will be apparent that the invention herein disclosed is therefore susceptible to further modification without departingfrom the purview of the appended claims.

What I claim is:

1. Gas cleaning apparatus including a dust collecting section having a housing divided into a series of adjacent compartments by parallel division plates; an outlet section superposed on the collecting section and divided into a series of converging compartments whose end faces terminate in an arcuate surface; purging means for the removal of dust particles from the collecting section of said apparatus comprising a cylindrical duct mounted for rotation about its longitudinal axis, said longitudinal axis lying at the projected center of said arcuate surface; duct means interconnected with said cylindrical member and depending therefrom to permit the end face thereof to swing about the longitudinal axis of the cylindrical duct in an arcuate path adjacent the arcuate surface of said outlet section, and valve means adapted to control fluid flow thru the purging means and the compartments of the housing.

2. Gas cleaning apparatus as defined in claim 1 wherein the opening in the end of said swinging duct is arranged to sequentially coincide with the individual end openings of the compartments formed between parallel division plates.

3. Gas cleaning apparatus including a dust collecting section having a housing divided by parallel division plates into a series of adjacent compartments; an outlet section superposed on the collecting section and divided into a series of coincident compartments that converge to provide an arcuate sealing surface; a housing partition normal to the division plates subdividing the collecting section and its superposed outlet-section into a plurality of similar collecting assemblies; purging apparatus adapted to remove dust particles from the surface of the apparatus comprising a cylindrical duct positioned at the projected center of said arcuate surface and mounted for rotation about its longitudinal axis; other duct means normal to said cylindrical duct and depending therefrom; and a hood member comprising a diverging continuation of said other duct; said hood member having an end opening conforming to the laterally aligned compartments formed between parallel division plates.

4. Gas cleaning apparatus as defined in claim 3 having means dividing the purging apparatus into a plurality of separate passageways, said means dividing the purging apparatus positioned in alignment with the housing partition to provide a separate fl'ow passageway for the flow of fluid through each collecting assembly of the gas cleaning apparatus.

5. Gas cleaning apparatus as defined in claim 4 having outlet ports at spaced ends of the cylindrical duct, and valve means controlling fluid flow through the outlet ports and their interconnected passageways.

6. Gas cleaning apparatus including a dust collecting section having a housing divided by parallel division plates into a series of transverse compartments; an outlet section superposed on said collecting section and divided into a series of coincident compartments that converge to provide an arcuate sealing surface on the end edges thereof; a housing partition normal to the parallel division plates adapted to longitudinally sub-divide the transverse compartments; means adapted to remove dust deposits from the walls of said compartments comprising a first duct mounted at the projected center of said arcuate surface for rotation about its longitudinal axis; other duct means normal to said first duct depending therefrom and having a longitudinal partition extending therethrough in alignment with said housing partition to provide spaced passageways in said duct aligned with the compartments on opposite sides of the housing partition; and valve means arranged to alternately close one and open the other of said passageways whereby fluid may be directed through a single pre-selected passageway.

7. Gas cleaning apparatus including a dust collecting section having a housing divided by parallel division plates into a series of adjacent compartments; an outlet section superposed on the collecting section and divided into a series of coincident compartments that converge to provide an arcuate sealing surface on the end edges thereof;

a housing partition normal to the division plates subdividing the collecting section and its superposed outlet section into a plurality of similar assemblies; purging apparatus adapted to remove dust particles from the surface of said apparatus comprising a cylindrical duct member mounted for rotation about its longitudinal axis; other duct means normal to said cylindrical duct depending therefrom including a hood portion at its distal end lying adjacent said sealing surface; means dividing the hood into a plurality of separate passageways coincident with the compartments on opposite sides of said housing partition; and valve means in said hood limiting flow therethrough to a single pre-selected passageway.

References Cited in the file of this patent UNITED STATES PATENTS 1,957,560 Thompson May 8, 1934 FOREIGN PATENTS 16,392 Great Britain May 30, 1912 737,362 Great Britain Sept. 21, 1955

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