US2336625A - Dust collector - Google Patents

Description

Dec. 14,1943. J. MILTON 2,336,625

DUST COLLECTOR Filed Dec. 2, 1940 2 Sheets-Sheet 1 I INVENTOR 1 g rm 13 I Patented Dec. 14, 1943 UNITED STATES apart TENT OFFICE 4 1 Claim.

This invention relates to a method and apparatus for electrostatically precipitating particles from a fluid gas stream, and mixing the precipitated particles with a continuously flowing liquid.

lhe main object of the invention resides in the substitution of electrostatic precipitation, such as that disclosed in the United States Patent of W. A. Schmidt, No. 1,343,285, for the mechanical principle of separation disclosed in my earlier United States Patent No. 2,186,033, and in the utilization of electrostatic and centrifugal forces in combining and mixing the separated particles with the liquid.

Another object of this invention is to provide a method and apparatus for suspending particles in a gas stream while the gas is confined in a chamber or conducted through a duct, and then passing the gaseous body containing the particles through apparatus containing oppositely charged electrodes, so that the particles, in migrating through the electrostatic field between the said electrodes, will receive an electrostatic charge and thereafter electrostatically precipitate upon the surface of a liquid film maintained continuously flowing over the collecting surface of an appropriately charged collecting electrode.

A further object of the invention resides in the construction and arrangement of the apparatus so that the charged collecting electrode is continuously rotated to maintain the liquid continuously flowing over the collecting surface thereof by centrifugal force and in a film, or thin layer of substantially uniform thickness.

Another object of the invention is to provide apparatus that will function as a self-cleaning, continuously-operating gas-cleaner for removing minute particles from a gas stream as well as relatively large particles.

The advantages of these and other objects will be manifested as the following description is read in connection with the accompanying drawe ings in which:

Figure 1 is a side-elevational view of an apparatus employing my invention, which view is shown in a section taken along lines l! of Fi re 2;

Fig. 2 is a partial plan-view partially shown in section along lines 2-2 of Fig. 1;

Fig. 3 is a side elevational view of another apparatus embodying a modification of that shown in Figs. 1 and 2, which apparatus is also shown partially in section in a plane P ss through the vertical axis of the machine; and

Fig. 4 is a schematic diagram showing the electrical circuits of a high-voltage rectifier, and

theelectrical connections to the various electrodes forming a part of the apparatus shown in Figs. 1 and 2, it being understood that the electrical connections 2!, 4i) and M are similarly connected to corresponding electrodes of Fig. 3.

Referring now to Figs. 1 and 2, it will be observed that one embodiment of my invention employs a stationary assembly consisting of a. metal dome ii, metal cylinders 7, metal disc 9, insulating ring 9A, metal ring [5A, and metal ring 16.

It will be observed that the aforesaid embodiment also employs a rotating assembly consisting of a metal collector-plate l0 and pulley IUB, which rotating assembly is journaled upon a stationary column l2 by means of suitable ball bearings H---! l.

It is important to observe that the stationary column 5 2 is tubular, and that the interior thereof provides a duct or conduit I3 communicating with the interior I333 of a small dome [3D fixedly secured to the upper end of column l2.

The small dome I3D is provided with a floor member overlying the central portion of the rotating collector-plate Ill, which floor member has a plurality of small nozzles l4 through which liquid entering the conduit i3 is discharged upon the collecting surface IOA of the rotating collector-plate i ii, as indicated bythe arrows 13A.

It is important to observethat the central portion of the stationary disc 9 is apertured so that the small dome I3D extends slightly above the surface of the disc 9.

The centrally located aperture 98 in disc 9 is somewhat larger than the horizontal dimensions of the small dome I3D, so that the disc 9 may be adjusted relative to the rotating collector-plate lil by means of adjusting screws 13 threaded in the insulating ring 9A, and to provide the required electrical separation between the stationary'assembly including disc 9 and the rotating collector-plate Ill, since the disc 9 and the collector'plate I0 form oppositely charged electrodes for electrostatically precipitating charged particles onto the surface of the liquid flowing over the collectin surface [0A of the collector plate It.

Therefore, with further reference to Fig. 1, it will be observed that the stationary assembly has an enclosed metal-chamber or dome 6 into which a particle-laden gas-stream is conducted via con-' duit 5, as indicated by arrows 5A.

The metal-chamber or dome 6 is provided with a metal floor-member 8 having a plurality of metal-cylinders l-'1 depending therefrom, which cylinders are secured to the metal disc 9.

As illustrated in Fig. 1, each metal-cylinder forms a duct or conduit providing a communication between the interior of the enclosed dome 6, and a chamber l5 between the disc 9 and rotating collector-plate Ill.

The metal-disc 9 is fixedly secured to the insulating ring 9A, which ring is slidably mounted in the metal ring IGA, so that the metal-disc 9 may be adjustably raised and lowered relative to the rotating collector-plate I0 and retained in its adjusted relation by means of the screws 1B threaded in the insulating ring 9A.

As mentioned hereinbefore, liquid is conducted through the conduit I3 into the interior of the small dome 13D and then discharged upon the surface IOA of the collector plate I0 via a plurality of nozzles or ducts M, as indicated by the arrows I3A.

The collector-plate I0 is rotatably mounted upon the stationary column l2 by means of ball bearings Hl I, and is rotated at relatively high speeds by means of a suitable belt drive between a prime mover and the V-pulley [0B secured to the collector plate l0.

Therefore, it will be evident that the liquid delivered onto the surface [0A of the collector plate l0, via nozzles 14, will move outwardly over the surface of the plate by centrifugal force and in a film or layer of substantiall uniform thickness.

With further reference to Fig. 1, it will be observed that the rings ISA and I613 are constructed and arranged to collect the liquid discharged by centrifugal force from the surface of the collector plate 10. In this respect, it is to be observed that the ring IBB is provided with an aperture I! through which the collected liquid is discharged, and it is to be understood that a discharge conduit may be connected thereto without departing from the spirit of the invention.

Similarly, it is to be understood that the shape and location of the collecting channel I 6, relative to the collector plate I0, may be changed to accommodate various requirements without departing from the spirit of the invention.

As further illustrated in Fig. 1, a tubular highvoltage insulator 20 is mounted in the top of the dome 6, through which a conductor 2! extends and electrically connects a spider 22 constructed preferably from wire, which spider supports and electrically connects an ionizing conductor or wire 23 centrally of each of the cylinders I.

It is Well known that a particle may be removed from an air stream electrostatically, if the particle is given an electrostatic charge and then placed in an electrostatic field between two electrodes having a voltage gradient high enough to attract the charged particle out of the air stream and onto the surface of one of the electrodes.

In the present invention separate ionizing and collecting chambers are provided.

Each of the cylinders I form an ionizing chamber, and each metal cylinder 1, and its respective wire 23, constitute the oppositely charged electrodes of each ionizing chamber.

Similarly, the space between the metal disc 9 and the metal collector-plate l0 forms the collecting chamber, and the metal disc 9 and metal collector-plate l0 constitute the oppositely charged electrodes of the collecting chamber.

Accordingly, it is important to observe that each metal cylinder I, metal dom 6 and the metal disc 9 are electrically connected and insulated from the stationary rings ISA and IE3 by means of the insulating rin 9A, and electrically insulated from the ionizing wires 23 by means of insulator 20. It is also important to observe that the stationary assembly including disc 5 and cylinders 1 is electrically separated from the rotating collector-plate II! by means of the mechanical clearance existing between the disc 9 and small dome I3D.

It is well known in the art of electrical precipitation that high-Voltage direct-current of opposite polarity must be connected to the electrodes of the ionizing and collecting chambers, and it has been observed that approximately 12,000 volts between ionizing electrodes and approximately 5000 volts between collecting electrode provides satisfactory operation. However, it is to be understood that the magnitude of these voltages will vary in accordance with the electrical spacing and construction of the various electrodes and that they are suggested only to indicate the approximate magnitude of the voltages required.

While several different types of highvoltage machines have been satisfactorily employed to provide the required high voltage in various commercial precipitators, a conventional electronictype rectifier is illustrated in Fig. 4 to supply the required high voltage for the operation of the present invention.

With reference to Fig. 4 it will be evident that the half-wave rectifying tubes V and VI, capacitors C and Cl, and the transformer T, are electrically connected in a modified voltage-doubling rectifying circuit well known to those skilled in the art.

The filament of the rectifying tube V is supplied current by a small secondar F of the transformer T.

Similarly, the filament of the rectifying tube VI is supplied current by a small secondary Fl of the transformer T.

The high-voltage secondary of the transformer is tapped, thereby providing two secondary sections S and SI respectively.

With further reference to Fig, 4, it will be observed that the rectifying tubes V and Vi are connected so that they alternately pass current to the respective capacitors C and Cl. Accordingly, current from the secondary S is passed by the rectifying tube V to charge the capacitor C, wh le the tube Vi is non-conducting.

Similarly, current from the secondary Si is passed by the rectifying tube VI to charge the capacitor C! while the tube V is non-conducting.

In this respect it is to be understood that the capacitors C and Cl each have sufficient capacity to maintain their E. M. F. charge during the non-conducting period of their respective rectifying tubes. and that the output voltage of the secondary S is sufiicient to charge the capacitor C to approximately 5000 volts, While the output voltage of the secondary SI is suflicient to charge the capacitor CI to approximately 7000 volts.

As illustrated in Fig. 4, each capacitor is provided with a megohm discharge-resistor for d scharging the high voltage charge on each respective capacitor when the primary P of the transformer is electrically disconnected from the supply line, and it is to be understood that the value of each discharge resistor is sufficiently high to prevent discharge of the corresponding capacitor in normal operation.

As indicated in Fig. 4, the wire 40 is electrically connected to ground and to the stationary assembly consisting of dome 6, cylinders I, and disc 9. The two capacitors C and Cl are electrically connected in series and the wire 2| electrically connects the ionizing wires 23 via the supporting spider 22, thereby placing 12,000 volts between the cylinders l of the stationary assembly and the ionizing wires 23.

Wire 45 connects the rotating collector-plate #0. thereby placing the 5000 volt charge of the capacitor C between the disc 9 of the stationary assembly and the collector-plate It.

Accordingly, it will be apparent that all particles migrating through the electrostatic field between the ionizing wire 23 and the respective cylinder '1 will receive an electrical charge and subsequently be precipitated from the fluid airstream and onto the collector plate it, when the charged particles enter the electrostatic field between the disc 0 and the collector plate Hi.

As stated hereinbefore. wires it! and i! place a potential of 5000 volts between the stationary assembly consisting of dome 6, cylinders '1, disc :2 etc, and the rotating collector-plate Hi. Therefore, since the wire 50 is also electrically connected to round, it is apparent that the stationary column !2 must be electrically insulated from ground as well as from the stationary assembly 5, 1, 9, etc.

The elements required to electrically insulate the stationary column i2 from ground have not been shown in the drawings, inasmuch as it is believed such expedients are well known to those skilled in the art.

Obviously, the arrangement of the insulating elements may vary without departing from the spirit of this invention, however, one arrangement in accordance with principles well known to hose skilled in the art, consists of mounting the column 52, and the liquid container etc. for conducting liquid to the duct !3 upon a stationary base or foundation, which base is electrically insulated from ground by means of conventional high-tension insulators.

It is also well known that the column !2 may be mounted upon the aforesaid stationary base, and that a conduit of insulating material such as glass or rubber, etc, may operatively connect a liquid supply line and the duct 83.

Likewise, since it is not essential for an operator to contact the conductor 25 or the rotating collector plate Iii, while the parts are electrically connected for operation, a guard or cage of wire mesh may be employed to surround the machine in accordance with the conventional practice followed in the protection of high-voltage distribution transformers, etc.

Obviously, conventional belting between the pulley MB and the prime mover is of insulating material, and will therefore serve to electrically insulate the prime mover from the collector plate.

In Fig. 3, a modified arrangement of the ionizing and collecting electrodes is shown.

In Fig. 3, the stationary assembly comprises a cylindrical dome D having metallic walls 25, an inverted metal truncated-cone 3d, a metal conical-deflector 33, metal supports 32, an insulating plate 253, a metal-ring 38A and a metal-ring 38B.

The latter mentioned stationary assembly corresponds to that described in Fig. l which includes dome 6, cylinders 7 and disc 9.

It will also be observed that Fig. 3 employs a rotating assembly consisting of a metal col- "lector-plate or rotor 3i, and a pulley MA, which rotating assembly is journaled upon a stationary column ME by means of suitable ball bearings 3lA--31A.

The latter mentioned rotating assembly corresponds to that described for Fig. 1 which includes collector plate It and pulley loB.

It is important to observe that the stationary column 378 is tubular, and that the interior thereof provides a duct or conduit through which liquid is conveyed and discharged upon the collecting surface of the collector plate 3! via nozzles 3- 1. It will also be observed that the upper end of the column 3'53 is secured to and electrically insulated from the conical deflector 33 by means of an insulator 33A.

A frusto-conical disc 35 is secured to the inner surface of the collector plate 31 to form a channel or pocket for collecting any liquid that may descend from the processing area of the collector plate 3!, and it will be observed that the collector plate 3! is apertured at 35 to provide a drain for the liquid collected in the pocket above the disc 35.

The stationary assembly ha an enclosed cylindrical-dome or chamber D into which a particleladen gas-stream is conducted via conduit 25.

The cylindrical dom D has metal side walls 25 and an insulating disc 273 secured thereto and enclosing the upper end thereof.

The lower end of the cylindrical dome D is open, thus the particle-laden gas-stream received therein is discharged upon the conical deflector 33 and deflected outwardly onto the urface of the collector plate 3!.

The conical deflector 33 is preferably constructed of metal and electrically connected to the metal wall 25 by means of metallic supports secured to the apertured metallic lower-end 28A of the dome D.

As illustrated in Fig. 3, an inverted truncated cone Si] is also secured to and electrically connected to the wall 26 of dome D.

An insulating plate 26B is also secured to the wall 26 of dome D, which plate has metallic rings 38A and 31313 secured thereto.

As mentioned hereinbefore, liquid i conducted through the interior of the stationary column 3EB and discharged upon the interior surface of the collector plate 3! via a plurality of nozzles or ducts 3:3.

The collector plate 38 is rotatably mounted upon the stationary column 3713 by means of ball bearings slA3?A, and is rotated at relatively high speeds by means of a suitable belt drive between a prime mover and the v pulley em secured to the collector plate 3 I.

Therefore, it will be evident that the liquid delivered onto the surface of the collector late 5i, via nozzles 3 will move upwardly and outwardly over the surface of the plate by centrifugal force and in a film or layer of substantially uniform thickness.

It will be observed that the rings 30A and 30B are constructed and arranged to collect the liquid discharged by centrifugal force from the collector plate 3 i. In this respect it is to be observed that the ring MBA is provided with an aperture 23cc through which the collected liquid is discharged, and it is to be understood that a discharge conduit may be connected thereto without departing from the spirit of the invention.

Similarly, it is to be understood that the shape and location of the collecting channel in the rings 30A and 3133 may be changed to accommodate various requirements without departing from the spirit of the invention.

As further illustrated in Fig. 3, a tubular high voltage insulator 21A is mounted in the insulating disc 21B of dome D, through which a conductor 21 extends and electrically connects a spider 28 preferably constructed from wire, which spider supports and electrically connects a plurality of ionizing conductors or wires 29.

Thus, in the modification shown in Fig. 3, separate ionizing and collecting chambers are provided in accordance with the teachings of Fig. 1.

In this respect it will be apparent that the metallic walls of the cylinder 26 and the wires 29 constitute the oppositely charged electrodes of the ionizing chamber.

Similarly, the space between the surface of the inverted truncated-cone and the collector plate 3|, also the space between the metallic end 26A, supports 32, deflector 33 and the collector plate 3| constitutes the collecting chamber, and it will be apparent that the electrically-connected metallic- members 26, 25A, 30, 32 and 33 form one electrode while the collector plate 3| forms the other electrode, of the oppositely charged electrodes of the collecting chamber.

Accordingly, it is to be understood that the high-voltage rectifier shown in Fig. 4 may be electrically connected to the apparatus shown in Fig. 3 by connecting wire 2ll of Fig. 4 to wire 21 of Fig. 3; connecting wire 40 of Fig. 3 to ground and to the metallic parts of the stationary assembly comprising members 26, 26A, 30, 32 and 33; and connecting wire 4! of Fig, 4 to collector plate ill of Fig. 3.

Thus, as described for Fig. 1, it will be apparent that all particles migrating through the electrostatic field between the ionizing wires 29 and the wall 28 of Fig. 3 will receive an electrical charge and subsequentl be precipitated from the air-stream and onto the: collector plate 3|, when the charged particles enter the electrostatic field between the members 26, 26A, 30, 32, 33 and the collector plate 3!.

As stated hereinbeiore, wires 30 and 4| place a potential of 5000 volts between the stationary assembly 25, etc., and the rotating collector-plate 3|. Therefore, since wire 40 is also electrically connected to ground, it is apparent that the stationary column 31B must be electrically insulated from ground.

The elements required to electrically insulate the stationary column 313 from ground have not been shown in the Fig. 3, as it is believed such expedients are well known to those skilled in the art. Therefore, it is apparent that column 313 may be insulated from ground with conventional high-tension insulators similar to that outlined for Fig. 1.

In either Fig. 1 or Fig. 3, it is to be understood that the liquid flowing over the surface of each respective collector-plate ill or 31 can be varied from a mere wetting to a layer of liquid flowing thereover, or the liquid can be impounded near the discharge edge of each respective collector plate and subsequently discharged by increasing the velocity of the rotating collector-plate.

It will be evident that the construction and shape of the collector plate can be varied; the rate of feed of the liquid can be varied; the velocity of the rotating collector-plate can be varied; or the distance between the electrodes of the collecting chamber varied by means of adjusting screws as illustrated in Fig. 1, to obtain the latter mentioned conditions of operation.

Accordingly, it will be apparent that these and other modifications can be made in accordance with the teachings of this disclosure and which will come within the scope of the appended claim.

Having thus described the invention, I claim:

Apparatus for separating suspended particles from a gas stream and mixing the same with a liquid, comprising, a pair of electrically spaced members; means electrically connecting the said members to opposite electrical polarities for maintaining an electrostatic field therebetween; means operatively associated with one of the said members and adapted to rotate the same; means operatively associated with the said members and adapted to deliver liquid into the electrostatic field therebetween and onto the surface of the said one member substantially adjacent the axis of rotation thereof; another pair of electrically spaced members comprising a charging electrode adapted to facilitate discharge and an opposing electrode adapted to minimize discharge; means electrically connecting the said charging electrode to a polarity opposite to that of the said rotating member, and means electrically connecting the said opposing electrode to a polarity opposite to that of the charging electrode; means operatively associated with the said another members and adapted to deliver a gas stream containing suspended particles into the electrostatic field between the charging electrode and the said opposing electrode so that the particles in migrating therebetween will receive a charge similar to that of the charging electrode; other means operatively associated with the said another members, and adapted to deliver the charged particles into the electrostatic field between the first mentioned members, for electrostatically precipitating the charged particles into the liquid flowing over the said one member; and means operatively associated with the said first mentioned members for collecting the mixture of the particles and the liquid.

JOHN L. MILTON.

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