US2114682A - Method and apparatus for electrical precipitation of dust - Google Patents

Description

ION OF DUST R E A M U G w P METHOD AND APPARATUS FOR ELECTRICAL PRECIPITAT 2 Sheets-Sheet 1 Filed June 28, 1955 INVENTOR April 19, 1938.. P. w. GUMAER METHOD AND APPARATUS FOR ELECTRICAL PRECIPITATION OF DUST Filed June 28, 1935 2 Sheets-Sheet 2 INVENTOR.

Patented Apr. 19, 1938 UNITED STATES METHOD AND APPARATUS Foa ELECTRI- CAL PRECIPITATION or nus-r Percy W. Gumaer, West Englewood, N. J.

Application June 28, 1935, Serial No. 28,814

16 Claims.

This invention relates to a method. and apparatus for electrical precipitation of dust, and particularly the ionization of dust particles by means of friction and turbulence.

An object of the invention is to provide such a method and apparatus which is easy and inexpensive to install and operate.

A further object is to provide such a method and apparatus in which the dust particles are ionized by friction with parts of the apparatus and with each other, and in which the ionized particles are then removed from the air or gas stream, at least in part, through the action of electricity generated by the friction of the dust particles.

A further object consists in providing certain improvements in the form, construction and arrangement of the parts, and in the steps of the process, whereby the above named and other objects may effectively be attained.

In the methods of dust precipitation heretofore known, it has been customary to utilize an apparatus which includes a wire centrally located within a hollow cylinder, the wire being charged with a high voltage direct current of sufficient potential to produce a corona which ionizes the dust particles within the cylinder. The charged particles are then attracted to oppositely charged terminals where they accumulate and leave the air relatively free from dust. A great disadvantage of this procedure resides in the fact that it is necessary to use a voltage gradient of 30,000 volts per cm. in order to produce the corona effect, the total voltage now generally used being from 50,000 to 100,000 volts; and it has been determined that more than ninety per cent. of the electrical energy is used to produce the corona while less than ten per cent. remains to perform the useful work of attracting the dust particles and depositing them out of the air or gas stream.

In the present invention it is proposed to conduct the air or gas stream through an insulated pipe at a high velocity which causes a turbulent motion resulting in impact and friction of the r dust particles against the insulated pipe and against each other, the impact and friction serving to ionize the dust particles and to give a corresponding charge to the insulated pipe. The charged particles are then conducted past the outside surface of the pipe at a relatively low velocity, whereupon the particles are attracted to the pipe or to an outer casing so as to be precipitated from the air or gas stream.

Various forms of apparatus suitable for carrying out this invention are shown in the accompanying drawings in which,

Fig. 1 represents, in vertical section, a simple form of apparatus in which the air or gas to be cleaned is supplied at' a point near the top of the apparatus, and the clean air or gas passes out of the apparatus also at the top.

Fig. 2 represents, in vertical section, an apparatus including the same elements as those of Fig. 1, but in inverted relationship.

Fig. 3 represents, in vertical section, an apparatus similar to that shown in Fig. 1, in which a group of small tubes are included within a portion of the large central tube.

Fig. 4 represents, in vertical section, a form of apparatus in which there are two groups of small tubes similar to those represented in Fig. 3.

Fig. 5 represents, in vertical section, a form of apparatus including the same elements as those of Fig. 1, with the addition of electrical connections for supplementing the operative charge on parts of the apparatus.

Fig. 6 represents, in vertical section, a form of apparatus in which the features of Figs. 3 and 5 are combined.

Fig. '7 represents, in vertical section, a form of apparatus in which the elements of Fig. 1 are supplemented by the addition of a charged screen beneath the central insulated pipe.

Fig. 8 represents, in vertical section, a form of apparatus in which the central insulated pipe is surrounded by a charged cylindrical screen located substantially midway between the central pipe and the outer casing.

Fig. 9 represents, in vertical section, a. form of apparatus in which a charged screen similar to that shown in Fig. '7 is used in conjunction with a charged plate.

Fig. 10 represents, in vertical section, a form of apparatus in which the elements of Fig. 1 are supplemented by the addition of an insulating sleeve surrounding the central pipe, together with a second metallic pipe surrounding the insulating sleeve.

Fig. 11 represents a horizontal section taken along the line XIXI of Fig. 3, showing the arrangement of the group of small tubes.

Fig. 12 represents, in vertical section, a form of apparatus in which the central pipe is curved in order to increase the turbulence of the air or gas passing therethrough.

Fig. 13 represents, in vertical longitudinal section, a form of apparatus including a plurality of pipes and discharge nozzles located within a single outer casing.

a typical form of the apparatus includes an outer casing I which may be of cylindrical form, having an enlarged container portion 2 formed at its lower end. A central pipe 3 is located within the cylindrical casing I, this pipe having an elbow at its upper end which is connected to a tubular insulating portion-4 at the point where the pipe passes through the wall of the outer casing I. At the bottom of the central pipe 3 is attached a diverging nozzle 5 of insulating material, and a tapered connection 6 is provided adjacent the insulating tube 4. In order to facilitate the removal of precipitated dust from the container 2, a door 1 may be provided in the bottom of said container. It is important that the cross sectional area of the central insulated pipe 3 should be considerably less than the annular cross sectional area of the space between said pipe and the cylindrical casing I, in order that the velocity of the air or gas may be relatively low when passing out through said space, as compared with its velocity when passing in through the pipe.

In the form of apparatus shown in Fig. 2 the central pipe 3, the insulating elements 4 and 5, and the tapered connection 6 are the same as the parts shown in Fig. 1, but are in an inverted position. These parts are used in connection with a cylindrical outer casing 8 having an enlarged portion 9 at its upper end, and a dust containing extension In at its lower end; a pipe H being provided at a point above the extension ID for conducting away the clean air or gas. A door l2 may be provided at the bottom of the extension H) to permit removal of the precipitated dust.

In the form of apparatus shown in Fig. 3, the parts are identical with those shown in Fig. l, but there is added a group of small tubes l3, located within the central pipe 3, these tubes serving to increase the friction of the air or gas to be cleaned, as it passes through said pipe. A plurality of groups of small tubes I3, l3 may be installed if desired, as shown in Fig. 4. The grouping of the tubes I3 is shown on an enlarged scale in Fig. 11.

It' has been found that extremely fine dust particles, which are the most dangerous to health, will be precipitated from the air .or gas, without the use of any electricity other than that which is generated by the friction of the dust in passing through apparatus such as that shown in Figs. 1, 2, 3 and 4, above described. However, if it is deemed important to effect a more complete removal of the particles, the electrical charge generated by friction may be supplemented by connecting parts of the apparatus to a high voltage direct current having the same polarity as the respective parts of the apparatus, and such connections are indicated in Fig. 5 wherein the central insulated tube 3 is regarded as having a positive charge which is supplemented by connection with the positive wire l4 from a source of direct current. The negative wire l5 from the same source may be connected to the outer casing l of the apparatus.

In Fig. 6 is shown a form of apparatus combining the features of Figs. 3 and 5, the central pipe being divided into an upper portion IS, an insulating portion I! and a lower portion l8. The charge on the upper portion I6 is supplemented by connection with a source of direct current through the positive. wire I9, while the negative wire 20 is connected to the outer casing, as ex.- plained in connection with Fig. 5. The lower 2,114,682 Referring to the drawings, it will be seen that,"

portion l8 of the central pipe contains a group of small tubes 2| of the sort described in connection with Fig. 3.

In the form of apparatus shown in Fig. 7 there is provided a screen 22 located directly beneath the lower end of the diverging nozzle 5, but spaced slightly from said nozzle. A dust collecting compartment 23 is located beneath the screen 22, and a door 24 may be provided in the bottom of the compartment 23. The screen 22 is shown as being connected to the positive wire 25 from 'a source of high voltage direct current, and the negative wire 26 is connected to the outer casing of the apparatus as before described.

In Fig. 8 is shown a form of the apparatus wherein a cylindrical screen 21 is located in the space between the central insulated pipe and the outer casing, the screen being connected to a source of high voltage direct current through the wire 28, and the casing being connected to the negative wire 29 from the same source. By grounding the positive wire 28 a series efiect will result wherein the screen 21 is negative with respect to the central pipe but positive with respect to the outer casing, so that ionized particles will be precipitated at all three points.

In Fig. 9 is shown a further modification of the form of apparatus shown in Fig. 7, there being a plate-or collar the diverging nozzle 3| in close proximity to a screen 32. Both the plate 30 and the screen 32 are insulated from the rest of the apparatus, the screen 32 being connected to the positive wire 33 from a source of direct current, and the plate 30 being connected to the negative wire 34 from the same source.

In Fig. 10 is shown a form of apparatus includ ing the same elements as those shown in Fig. 1, with the addition of a sleeve or tube of insulating material 35 closely surrounding the central pipe 36 and being in turn enclosed within a second metallic sleeve or tube 31. This alternation of materials results in a condenser effect so that the polarity of the sleeve or tube 31 is the opposite of the polarity of the central pipe 36, and of the outer cylindrical casing 38.

It will generally be found that the provision of a right angle bend close to the intake end of the central pipe, together with the high velocity of the air or gas as it passes through said pipe, causes suflicient turbulence in the air or gas stream to ionize the dust particles by impact and friction, as above described, but this efiect can be increased by forming the pipe with a greater curve as shown in Fig. 12. In the form there shown, the pipe 39 is bent through an angle of 270, and it could, if desired, be formed with several complete turns. Such a pipe could be used in any of the combinations disclosed in Figs.

.1 to 10 inclusive, as will readily be understood;

the form shown in Fig. 12 includes elements corresponding to those of Fig. 9, there being a plate 40 attached to the diverging insulating nozzle 4| adjacent ascreen 42, the plate 40 and screen 42 being connected by wires 43 and 44 to a source of direct current. I

If it is desired to increase the capacity of the apparatus, a multiple installation, such as that shown in Fig. 13, might be provided. In this form, a plurality of metallic pipes 45 are mounted in an insulating tube portion 48 which passes through the wall of a casing 41, each of the tubes 45 having at its discharge end a diverging insulating nozzle 48 bearing a metallic plate or collar 49. An insulated screen 50 extends across the casing 30 attached atthe lower end of directly beneath the plates 49, and below the screen suitable receptacles 5| may be provided for catching the precipitated dust. As in the forms of apparatus shown in Figs. 9 and 12, the screen 50 is connected to the positive wire 52 from a source of direct current and the plates 49 are connected to the negative wires 53 from the same source. The cleaned air or gas may be conducted out of the apparatus through a pipe 54 in the top of the casing.

The successful operation of the apparatus, in any of its various forms, depends largely upon the fact that the dust particles present in any given stream of air or gas will, when subjected to the friction incident to passage at high velocity through a metallic tube, become ionized with charges which are predominantly of the same polarity, at the same time giving the tube a corresponding charge of the opposite polarity. In the forms shown and described herein, it is assumed that the dust particles will become negatively charged during their passage through the metallic pipes, so that the particles will tend to be attracted toward any adjacent positively charged surface. In Figs. 1, 2,3, 4, and 10, the negatively charged particles are conducted, after their passage at high velocity through the central pipe, back along a path adjacent the pipe to which they have given a positive charge, the velocity of the air or gas stream at this point being greatly reduced. According to Figs. 1, 2, 3 and 4, the negatively charged particles will accumulate on the outside of the central pipe where they are neutralized and tend to form themselves into larger units which will drop off into the container at the bottom of the apparatus. Those particles which may emerge from the central pipe with a positive charge will be repelled from the pipe toward the casing, where they will give up their charge, accumulate, and also drop into the dust container. The operation of the apparatus shown in Fig. 10 is the same as that just described, except that the polarity of the inner and outer walls of the low velocity passage is reversed.

The principle of operation of all forms of the apparatus wherein supplementary energy is provided by connection of the apparatus to a source a of direct current, is exactly the same as in the forms where only the frictionally generated charge is relied upon. The supplementary energy serves particularly to strengthen the electrical field through which the particles pass, in order that a greater quantityof the dust particles may be drawn out of the air or gas stream. It will be noted that the particles are ionized solely by means of impact, collision and friction, due to the high velocity and turbulence of the gas stream, so that no electrical energy is required except for performing the useful work of moving the particles out of the air or gas stream, neutralizing the charge of the particles, and precipitating them for removal from the apparatus. The total voltage needed for this work will normally not exceed 5,000 to 10,000 volts. It will be understood that the air or gas may be driven or drawn through the apparatus by fan or pump means on either the intake or exhaust connections. The word friction is intended to include the impacts and collisions of the particles with each other and with the apparatus, as well as the actual rubbing with which friction is generally associated; the'ionization of the particles being a molecular phenomenon found to result from the turbulence of the gas stream.

It is evident that various changes may be resorted to inthe construction, form and arrangement of the several parts and in the steps of the method without departing from the spirit and scope of my invention, and hence I do not intend to be limited to the particular embodiment herein shown and described.

What I claim is:

1. An apparatus of the character described comprising, an outer casing, an electrically insulated pipe portion within said casing, the inside cross-sectional area of the pipe portion being substantially less than the cross-sectional area of the space between the pipe and the casing, and means for passing gases through said pipe portion with a highly turbulent motion and subsequently through said casing adjacent the pipe portion at a. low velocity.

2. An apparatus of the character described comprising, an outer casing, a bent electrically insulated pipe portion within said casing, the inside cross-sectional area of the pipe portion being substantially less than the cross-sectional area of the space between the pipe and the casing, and means for passing gases through said pipe portion with a highly turbulent motion and through said casing adjacent the pipe portion at a low velocity.

3. An apparatus of the character described comprising, an outer casing, an electrically insulated pipe portion within said casing, the inside cross-sectional area of the pipe portion being substantially less than the cross-sectional area of the space between the pipe and the casing, means located within the pipe portion for increasing the surface area of the interior of the pipe, and means for passing gases through said pipe portion with a highly turbulent motion and through said casing adjacent the pipe portion at a low velocity.

4. An apparatus of the character described comprising, an outer casing, an electrically insulated pipe portion within said casing, the inside cross-sectional area of the pipe portion being substantially less than the cross-sectional area of the space between the pipe and the casing, means for supplying an electric potential of one polarity to one portion of the apparatus and a potential of relatively opposite polarity to an adjacent portion of the apparatus, and means for passing gases through said pipe portion with a highly turbulent motion and between said charged portions at a low velocity.

5. An apparatus of the character described comprising, an outer casing, an electrically insulated pipe portion within said casing, the inside a cross-sectional area of the pipe portion being substantially less than the cross-sectional area of the space between the pipe and the casing, means for supplying an electric potential of one polarity to the pipe portion and a potential of relatively opposite polarity to the casing, and means for passing gases through said pipe portion with a highly turbulent motion and through the space between the pipe and the casing at a low velocity.

6. An apparatus comprising, an outer casing, an electrically insulated pipe portion passing through a wall of the casing and terminating at a point within the casing, means for passing gases through said pipe portion with a highly turbulent motion, means associated with the terminus of the pipe portion for gradually changing said turbulent motion to a low velocity motion, precipitating electrode means disposed in the path of said gases adjacent of the character'described said last named means, and means for supplying 76 a high voltage to said precipitating electrode means.

7. An apparatus of the character described comprising, an outer casing, an electrically insulated 'pipe portion passing through a wall of the casing and terminating at a point within the casing, an electrically insulated screen adjacent the termination of the pipe portion, means for supplying an electric potential of one polarity to the screen and a potential of relatively opposite polarity to the casing, and means for passing gases through said pipe portion with a highly turbulent motion and past said screen at a low velocity.

8. An apparatus of the character described comprising, an outer casing, an electrically insulated pipe portion passing through a wall of the casing and terminating at a point within the casing, an electrically insulated screen adjacent the termination of the pipe portion, an electrically insulated plate adjacent said screen, means for supplying an electric potential of one polarity to the screen and a potential of relatively opposite polarity to the plate, and means for passing gases through said pipe portion with a highly turbulent motion and through the space between the screen and the plate at a low velocity.

9. An apparatus of the character described comprising, an outer casing, a plurality of electrically insulated pipe portions within said casing, the inside cross-sectional area of the" pipe portions being substantially less than the crosssectional area of the space between the pipes and the casing, means for supplying an electric potential of one polarity to one of said pipe portions and an electric potential of opposite polarity to said casing, and means for passing gases through said pipe portions with a highly turbulent motion and through the space between the pipe and the casing at a low velocity.

10. An apparatus of the character described comprising, an outer casing, an electrically insulated pipe portion passing through a wall of the casing and terminating at a point within the casing, means for passing gases through said pipe' portion with a highly turbulent motion, means for increasing said turbulent motion Within the pipe portion, means associated with the terminus of the pipe portion for gradually changing said turbulent motion to a low velocity motion, precipitating electrode means disposed in the path of said gases adjacent said last named means, and means for supplying a high voltage to said precipitating electrode means.

11. The method of electrical precipitation of suspended material from gases which includes, passing the gas at a high velocity through a passage, ionizing the particles of material by turbulent motion within the passage, and passing the gas and ionized particles at a relatively low velocity through a precipitating field between oppositely charged electrode means.

12. The method of electrical precipitation of suspended material from gases, which includes, passing the gas at a high velocity through a passage, ionizing the particles of material by turbulent motion within the passage, and passing the gas and ionized particles at a relatively low velocity through an electric field the voltage for which is generated, at least in part, by the turbulent motion of the particles, whereby the particles are precipitated out of the gas.

13. The method of electrical precipitation of suspended material from gases which includes, passing the gas at a high velocity through a passage, ionizing the particles of material by turbulent motion within the passage, and passing the gas and ionized particles at a relatively low velocity through an electric field the voltage for which is generated in part by the turbulent motion of the particles and in part by an external source of high voltage, whereby the particles are precipitated out of the gas.

14. The method of electrical precipitation of suspended material from gases which includes, passing the gas at a high velocity through a passage, ionizing the particles of material by turbulent motion within the passage, and passing the gas and ionized particles at a relatively low velocity through an electric field the voltage for which is generated by anexternal source of high voltage and through an electric field the voltage of which is generated by the friction of the particles, whereby the particles are precipitated out of the gas.

15. The method of electrical precipitation of suspended material from gases which includes, passing the gas at a high velocity through a passage, ionizing the particles of material by turbulent motion within the passage, and passing the gas and ionized particles at a relatively low velocity through an electric field the voltage for which is generated, at least in part, by the friction of the particles, moving the ionized particles across the gas stream, neutralizing the charge of said particles, and removing the neutralized particles from the gas.

16. The method of electrical precipitation of suspended material from gases, which includes, passing the gas at a high velocity through a passage, ionizing the particles of material by turbulent motion within the passage, and passing the gas and ionized particles at a relatively low velocity through an electric field the voltage for which is generated, at least in part, by an external source of high voltage, whereby the particles are precipitated out of the gas.

PERCY W. GUMAER.

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