US2381455A - Electrical precipitation apparatus - Google Patents

Description

ug- 7, 5- c. w. JACOB 2,331,455

ELECTRICAL PR'EOIPITATION APPARATUS Filed Oct. 31, 1942 INVENTOR.

' Cale WJcaZ v ATTO EY atented Aug. 7, 1945 UNITED STATES PATENT OFFICE 2,381,455 ELECTRICAL PRECIPITATION APPARATUS Carlyle W. Jacob, Lynn, Mass.

Application October 31, 1942, Serial No. 464,012 6 Claims. (oi. 183-7) This invention relates to precipitation apparatus, and has particular reference to improvements in methods of and means for the charging and precipitating of matter such as dust, smoke, bacteria, acid mist, chemical fumes, etc., suspended in air or gas whereby such matter may be removed by electrical means.

Heretofore electrical precipitators have employed electrodes through which the gas having solid or liquid matter suspended therein is passed and between which a high electrical potential is maintained for the purpose of producing ionization by collision in the gas. The suspended matter coming in contact with the ions thus produced becomes electrostatically charged and is attracted to one of the electrodes upon which it is deposited. One of the deterrents to a more general use of such precipitators is the relatively high electrical potential necessary to produce ionization- Having produced ionization, relatively low electrode potentials are required to effect percipi- ,tation of the charged matter.

In devices of this character it has been necessary to impress upon the ionizing electrodes voltages of the order of 10,000 volts so as to effect successful operation. Ionization thus is produced by a corona discharge between the electrodes. Volttages of this order of magnitude not only are unavailable in many locations where it may be desired to install such apparatus, but also are dangerous particularly to relatively unskilled operating personnel. Furthermore, in apparatus to. be used in the presence of inflammable gases or where the matter to be precipitated is combustible, such as is the case of many types of smoke, corona discharge devices are unsuitable because of the fire hazards. Moreover, some ozone inevitably is produced by the operation of corona discharge devices. Since ozone is toxic, precipitation apparatus which produces it is unsuited for the purification of air for breathing purposes. Additionally, apparatus of this character may not be used to cleanse gases in certain chemical processes for the reason that ozone is a catalyst and therefore is apt to produce undesired gas reactions to the detriment of the process.

Hence, it' is an object of the instant invention to provide means for producing ionization of a gas from which it is desired to electrically precipitate matter suspended therein without the employment of high electrode potentials.

A further object of the invention is to provide apparatus equipped with a radioactive ionizing agent for the electrical precipitation of matter suspended in a gas.

' bodying the invention and which is suitable for fixed installations, such as in laboratories, buildings and the like;

Fig. 2 shows one manner of constructing a capsule containing the radioactive substance which constitutes the ionizing agent;

Fig. 3 depicts a smoke or gas mask having a canister embodying the invention; I

Fig. 4 is a partial vertical sectional view to an enlarged scale of the gas mask canister of Fig. 3; and

Fig. 5 is a detail view to an enlarged scale of the collector plates of the gas mask canister.

Having reference first to the form of the invention depicted in Fig. 1, there is disclosed a. duct ll through the upper portion of which gas having matter in suspension entersin the direction indicated by the arrows. A plurality (of which two are shown) of projections l2 are formed on the inside of the duct and each supports on its under side a capsule I3 containing a radioactive sub stance such as certain well-known salts of radium, mesothorium, or the like. By placing the capsules of radioactive material in somewhat the manner shown, they do not come into direct contact with the incoming gas and the accumulation of deleterious films thereon is thereby minimized.

These radioactive substances emit rays which, in passing through the gas, produce ions which, in turn, impinge upon the solid or liquid matter suspended in the gas and deposit their ionic charges upon the matter. The ionization of the gas and the charging of the suspended matter occurs in a chamber l4 located between the capsules I3 and a plurality of collecting plates 15 passes between the plates, the charged matter is attracted to and deposited upon the plates.

The efficiency of such a precipitator may be increased by arranging several such units in cascade. The added units may be identical to that described, or they may employ additional facilities. For example, in the second unitillustrated, the gas is passed in proximity to a second plurality of capsules l1 containing-radioactive substances whereby suspended matter, which escaped being charged in the first precipitator stage, is given an electrostatic charge and passes into the section of the apparatus containing a second set of collecting plates I8. This precipitator stage may have filtering material 19 such as fine spun glass inserted between the collecting plates for the purpose of collecting some of the suspended matter including that which, at this point, is still uncharged.

For the purpose of maintaining the emitting surfaces of the'capsules free of deleterious films,

it may be desirable to equip the precipitator with cleaning facilities such as a nozzle 20 entering the duct I l at a point below the capsule and positioned so that an intermittent or steady Jet of clean air or cleaning liquid may be directed across the surface of the capsule.

Since some of the radioactive substances suitable for use in a precipitator according to this invention emit small quantities of gases which are injurious to human tissue, it is necessary to form the capsules containing these substances in a manner to prevent the escape of the gases and at the same time to permit the emission of the ion producing rays. Fig. 2 illustrates one manner of forming a capsule meeting these requirements. The main body'of the capsule is formed by a glass plate 2|. The radioactive substance 22 is placed between this plate and a thin glass foil 23. The foil is then pressed against the plate under considerable pressure and heat applied until a unitary structure is formed by fusion. The radioac- .tive substance will then be embedded in a glass capsule to a depth sufficient to prevent the escape of poisonous gases and yet near enough to the surface to allow the emission of the ion producing rays. In such a capsule there is no likelihood that dangerous gas pressures will be built up for the reason that the gas atoms decompose into solid. atoms before any appreciable pressure can develop.

The present invention is susceptible of embodiment in portable precipitators such as a gas or smoke mask, one type of which is illustrated in Fig. 3. A face mask 24 suitable for support upon the head of the wearer is provided with a canister 25 in which is mounted apparatus in accordance with the instant invention for removing by electrical precipitation suspended matter from the air to be breathed by the mask wearer. The canister is provided with an opening 26 in the bottom thereof for the admission of the contaminated air. The purified air is conducted through a neck 21 into the mask 24. The air exhaled by the mask wearer is exhausted through a vent 28. The mask may be equipped with an exhalation valve of conventional design (not shown), thereby making it unnecessary for the wearer to breathe out against the resistance of the canister by reducing the back pressure against expiration.

In Fig. 4 the essential details of the canister construction are shown without unnecessarily complicating the drawing with the mounting details for the apparatus which form no part of the present invention. The canister embodies a two stage precipitator, each incorporating the principles of the invention. The contaminated air en ters the canister by way of the opening 26 and passes into an ionizing chamber in which there is located a plurality of capsules 29, each containing a radioactive substance, and two screens or gridlike meshes 30 and 3| between which is maintained a low electrical potential of the order of 5 volts derived from a source of direct current potential such as a small battery 32. In its upward passage through the canister, the'air having in suspension the charged matter is drawn through a set of collector plates 33 between which there is maintained an electrical potential of suftlcient magnitude to cause preciptation of the charged matter.

v The second precipitator stage, as shown, is substantially a duplication of the first and comprises an ionizing chamber having a plurality of radioactive substance containing capsules 34 and a pair of screens 35 and 36 electrically connected to a small battery 31, and a set of collector plates 38 connected to a battery 39.

A convenient structure for the sets of collector plates 33 and 38 is illustrated in Fig. 5. Two strips of foil 40, preferably formed of a lightweight metal, such as aluminum or magnesium, are interspersed with two strips of insulating material 4| whichshould have characteristics necessary to permit the passage of air between the foil strips without appreciable resistance. Some fabrics such as certain types of marquisette laces have been found suitable for such use. Also small grained sand provided with a thin coating of a moisture repellant and adhesive substance such as ceresin wax has been used advantageously for this purpose. Any fabric which may be used for the strips 4| should also be treated with a water repellent material so that it will retain its insulating properties under all weather conditions. If desired, one of the strips of foil 40 may be coated with a thin film of an insulating material such as ceresin wax. By this means there may be effected an increase in the insulati'dn between the collector electrodes.

The alternate strips of foils 40 and separators ll are wound spirally upon a core, which for convenience may be the battery 39. Since the requirements of such a battery are such that no current capacity is needed, it may be made small enough to meet the space limitations for use in the canister of a gas mask and yet furnish an electrical potential of the order of several hundred volts. The necessary electrical connections may be made from the battery terminals to the strips of metal foils l0.

In operation, each stage of the gas mask canister precipitator is essentially the same as the previously described operation of the apparatus of Fig. 1. Considering only the second or upper precipitator stage, equal quantities of anions (negative ions) and cations (positive ions) are produced by the rays emitted by the capsules 34.

The ionizing rays emitted from capsules of the character described have the property of traveling for considerable distances to effect gas ionization. The space between the screens such. as 35 and 36 is well within the effective ionizing range of the rays emitted by these capsules. As a consequence, there is efiected the production of substantially equal quantities of anions and cations in the space between the screens 35 and 36. Normally, these ions move with and substantially at the rate of movement of the air in which they are suspended. However, through the action of the screens 35 and 36 between which an electrostatic fleld exists, the rate of movement of the ions of one polarity, say the anions, is retarded, while the rate of movement of the ions of the opposite polarity, the cations in the assumed case, is accelerated with the result that, in the region between the screens, there is a predominance of anions. This may be seen by considering a specific case, merely by way of example. When usin in capsules 34, a substance such as radium which is capable of emitting ionizing rays having substantial penetrating properties, in other words the abiltiy of effecting ionization at a distance from their source, ionization of the air occurs in the space between the screens 35 and 36. Assume that the field between the screens is such that anions are attracted toward the screen 35 and cations are attracted toward the screen 36, both at the rate in still air of centimeters per second. But support that the air is traveling thro gh and between the screens at the rate of 5 centimeters per second in the direction from screen 35 to screen 36. The movement of the ions thus is the result of two forces; viz, the attraction by the screens and the movement of the air. In the case of the cations both forces act in concert so that the cations are moved toward the screen 36 at the accelerated rate of centimeters per second. The cations, therefore, are quickly removed from the ionizing space between the screens and are collected by the screen 36. The anions, on the other hand, are acted upon by the two forces in opposition. Since the forces are of substantially equal magnitude, they effectively cancel one another with the result that the anions are rendered substantially motionless. or at least are materially retarded, in the space be-- tween the screens. Consequently, with the cations being removed from this space substantially as fast as they are produced, there is effected a concentration of anions for the charging of the particles of matter suspended in the air. Such a condition increases the efflciency of each precipitator stage for the reason that there is a lessening of the probability that a particle of suspended matter will be struck by an equal number of anions and cations and thereby rendered neutral and not in condition for electrical precipitation.

Another feature of thedisclosed structure for the collector plates which increases the efficiency of the device resides in the production of a somewhat inhomogeneous electrostatic field between the plates by the fibers of the separator fabric or by the sand grains. The distorted field thus produced in the vicinity of the. elements of the separator material tends to force uncharged suspended matter 7 to the separator elements for deposition thereon. Other expedients for the production of inhomogeneous fields, such as the perforation of the collector plates to form sharp edges, will be suggested to those skilled in the art, and such expedients are contemplated to be within the scope of the instant invention.

Obviously, it is also within the scope of the invention to incorporate in an electrical precipitator, either stationary or portable, any combination of the features disclosed in the two illustrative embodiments. If desired, chemicals for the removal of poisonous gases in a well-known manner, may be used in precipitators embodying the present invention.

The two embodiments of the invention disclosed herein are deemed sufficient to enable those skilled in the art to practice the invention. the scope of which is set forth in the appended claims.

What is claimed is:

1. Electrical recipitation apparatus comprising, an ionizing agent having radioactive properties, means for subjecting a gas having matter suspended therein to the influence of the ionizing rays emitted by said agent whereby said matter accumulates an electrostatic charge derived from the ions thus produced, and means including spaced field-producing collector electrodes to effect the deposition of said charged matter.

2. Electrical precipitation apparatus comprising, an ionizing chamber, a precipitating chamber, and means for effecting the passage successively through said ionizing chamber and said precipitating chamber of a gas having matter suspended therein, said ionizing chamber including radioactive material for ionizing said gas whereby the ions thus produced impart by impingement ionic charges to said matter, and said precipitating chamber including a plurality of spaced electrodes creating electrostatic fields to control the movement of said charged matter, said electrodes serving as depositories for said charged matter.

3. Electrical precipitation apparatus comprising in series, radioactive means for producing ionization of a gas having matter suspended therein, means including an electrically charged grid structure for producing in the vicinity thereof an electrostatic field wherein electrostatic charges predominantly of one polarity are imparted to said matter, and means including a plurality of electrically charged collector electrodes to separate said charged matter from the gas.

4. Electrical precipitation apparatus comprising in series, radioactive means for ionizing gas having matter suspended therein, a pair of spaced grids electrically charged to opposite polarities, said grid acting to retard the rates of movement of ions of one polarity while accelerating the rates of movement of ions of the opposite polarity to charge the. inter-grid space with a preponderance of said retarded ions whereby said matter is electrostatically charged to the polarity of said retarded ions, and electrically charged means having a surface for the collection of said charged matter.

5. In a gas mask canister, an inlet for air contaminated by having matter in suspension, an outlet for purified air, radioactive material located adjacent said inlet to ionize the incoming contaminated air whereby said matter is electrostatically charged, and spaced field-producing electrodes located adjacent said outlet to collect by deposition said charged matter.

6. In a gas mask .canister, an inlet for air contaminated by having matter in suspension, an outlet for purified air, radioactive material located adjacent said inlet to ionize the incoming contaminated air, an electrically charged grid structure serving to producean electrostatic field between said radioactive material and said outlet wherein said matter becomes electrostatically charged predominantly to one polarity, and an electrode charged to'the opposite polarity and located adjacent said outlet for. the deposition thereon of said charged matter. 7

CARLYLE W. JACOB.

I pER'nFIcAm OF conmacnon. v Patent No. 2,381,155- ne 7. 91+;-

CARLILE w. new. I

It is hereby certified thpt' orror appears in the printoo apociiioation of the above numborod potent requiring correction as follows: Pogo 1-, first column, line 21-22 for "percipitation" road --procipitltion--; page .5, first column, line 13, for abiltiy road --abi1ity--; line 20-, for supporfif' read --supposo--; antthat the said Letters. Pateni: ghould be read with this "5&- faction thoroin tha't'the same may'confonn to the record of the case in the Patent 'ornce.

Signed and sealed tfxis 16th day of October, AJD. 1915.

Leslie Frazer (Seal) I First .Masistantz-Comnissicme: of Ijatents.

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