US2019485A - Method and apparatus for electrical precipitation - Google Patents

Description

Nov. 5, 1935.

- w. DEUTSCH METHOD AND APPARATUS FOR ELECTRICAL PRECIEITATION Filed J1me 12, 1934 INVENTOYR." I

BYM I i v WATO EYS.

Patented Nov. 5, 1935 PATENT OFFICE METHOD AND APPARATUS FOR ELECTRI- CAL PRECIPITATION Walther Deutsch, Franki'ort-on-the-Main, Gerassignor to International Precipitation Company, Los Angeles, Calif., a corporation of California Application In '5 Claims.

This invention relates to electrical precipitation of suspended particles from gases, and particularly to an advantageous method and means for regulating the corona discharge utilized for electrically charging the suspended particles.

In the electrical precipitation of suspended particles from gases, the gas to be cleaned is ordinarily passed through an electric field between opposing discharge and collecting electrodes, and a sufficiently high potential is maintained between said electrodes to cause corona discharge from the discharge electrodes, whereby the suspended particles are electrically charged, and the particles thus charged are then precipitated upon the collecting electrodes by the action of the electric field. According to the present invention, means are provided for regulating the corona discharge from the discharge electrodes, without requiring regulation of the main electric potential maintained between the discharge electrodes and the collecting electrodes. This object is accomplished by providing an auxiliary or regulating electrode, adjacent the discharge electrode means and preferably at the opposite side thereof from the collecting electrode means, so that, by regulating the potential between the auxiliary or regulating electrode and the discharge electrode means, the corona discharge may be controlled, in a manner somewhat similar to the action of a grid or screen electrode in a thermionic tube. In this manner, it is possible to readily control thecorona discharge in accordance with variations in the electrical conductivity or other properties of the gas being treated, or in accordance with variations in the nature or amount of suspended material.

Experience in the operation of electrical precipitators has shown that changes in the composition or nature of the gas being treated, the velocity of the gas, or the nature or concentration of suspended material, frequently cause large changes in the amount of corona discharge produced by a given electrical potential between the discharge and collecting electrodes, and the present invention provides a means of overcoming this disadvantage, and-maintaining the desired amount of discharge at all times, to much greater advantage than by regulation of the main electrical potential between the discharge and collecting electrodes.

The accompanying drawing illustrates apparatus embodying this invention, and referring thereto:-

Fig.1 is a transverse sectional view through an electrical precipitator of a type employing a tubu- June 12, 1934, Serial No. 730,301 Germany June 23, 1933 lar collecting electrode, with the electrical circuits shown diagrammatically.

Fig. 2 is a partial sectional view of a precipitator provided with collecting electrode means of the plate type, the electrical circuits being again 5 shown diagrammatically.

In Fig. 1, the electrical precipitator is shown as comprising a tubular collecting electrode I, grounded as at la, a plurality of discharge electrode members 2, such as wires or small diameter 10 rods, disposed in a circular arrangement concentrically aboutthe axis of the collecting electrode, and a regulating electrode 3 formed as a rod or tube disposed concentrically within the discharge electrode members and at the opposite side 5 thereof from the collecting electrode. The main voltage source S is connected at one side to the discharge electrode members 2 and is grounded at the other side as indicated at ,4, while a regulating voltage source S is connected at one side 20 to the regulating electrode 3 and grounded at the other side as indicated at 4. Both 01 said voltage sources S and S are preferably of a type adapted to supply unidirectional current at high voltage. For example, each of said voltage 25 sources may comprise a transiormer having the desired output voltage, and suitable rectifying means such as a mechanical or thermionic rectifier associated therewith. The main voltage source S is adapted to maintain a sufliciently 30 high voltage between the discharge electrodes 2 and the collecting electrode means I, to produce corona discharge from the discharge electrodes, for example, a voltage of 50,000 volts, whilethe regulating voltage source S is adapted to main- 35 tain a voltage somewhat less than that of the main voltage source, so that the regulating electrode 3 is maintained at a voltage somewhat lower than the discharge electrodes. For example, said regulating voltage source may be adapt- 4 ed to supply a Volta-goof approximately 40,000 volts or more-and may provided with any suitable means such as a variable resistance or a series of taps connected at difierent voltages, whereby the voltage delivered thereby may be controlled as desired.

The amount of corona discharge from the discharge electrodes 2 will be dependent not only upon the main voltage between said electrodes and the collecting electrode, but also upon the voltage between the discharge electroc and the regulating electrode 3, so that by varying this last-mentioned voltage (through regulation of the voltage applied to electrode 3), the corona dis- 55 charge may be regulated without requiring adjustment or regulation of the main voltage.

In Fig. 2, the electrical precipitator is shown a comprising a collecting electrode 6 formed as afiat plate of extending surface, a plurality of discharge electrode members 8, such as wires or small rods, disposed in a plane parallel to the collecting electrode, and a regulating electrode 1 formed as a plate, also extending parallel to the plane of the discharge electrode members and spaced therefrom at the opposite side'from the collecting electrode.

The pole members 9 and I0 represent the opposite poles of a suitable source of high voltage unidirectional current (not shown), and said poles may be bridged by a high ohmic resistance ll. One of the poles, such as 9, is connected by conductor I4 to the discharge electrodes 8, while the other pole, such as I0, is connected by conductor [5 to the collecting electrode 6, and is preferably also grounded, as at I6. An adjustable contact I2 is adapted to be moved to any one of a plurality of different positions of contact along the resistance I l, and is connected by conductor l3' to the regulating electrode 1. By adjustment of the contact member l2, the voltage between discharge electrode members 8 and regulating electrode 1 may be adjusted to any desired value less than the main voltage between the discharge electrodes 8 and the collecting electrode 6, thus adjusting the corona discharge from the discharge electrodes without requiring adjustment of the main voltage.

In the operation of either of the forms of apparatus above described, the gas to be treated, containing suspended particles of solid or liquid material, is passed through the main electrical field maintained between the discharge electrodes and the collecting electrode means. The voltage between said electrodes produces corona discharge at the discharge electrodes, causing the suspended particles to become electrically charged, and the particles thus charged are precipitated upon the collecting electrode, in the usual manner of such apparatus.

As pointed out above, regulation of the corona discharge in the manner above described, without changing the main voltage employed for precipitation, may be advantageously employed in order to maintain the proper amount of corona discharge regardless of variations in the nature of the gas. the gas velocity, or the nature or concentration of the suspended material. If desired, suitable means may be provided for automatically adjusting the regulating voltage in accordance with variations in current flow in the main circuit connected to the discharge and collecting electrodes, so that if any change in operating conditions causes the current in this circuit to increase (or decrease) beyond the desired value, due to increased (or decreased) corona discharge, the voltage between the discharge electrodes and the regulating electrode may be correspondingly changed, to cause the desired reduction (or increase) in corona discharge.

I claim:

1. A method for electrical precipitation of suspended particles from gases comprising passing gas containing suspended particles through an electrical field between opposing discharge and collecting electrode means, maintaining an electrical potential between said opposing electrode means sufficient to cause production of corona discharge from the discharge electrode means and precipitation of suspended particles on the collecting electrode means, maintaining a potential between said discharge electrode means and an auxiliary electrode means disposed adjacent said discharge electrode means and varying said last-named potential to regulate said production of corona discharge.

2. An apparatu for electrical precipitation of suspended particles from gas comprising collecting electrode means, discharge electrode means, means for passing gas containing suspended material between said discharge and collecting electrode means, means for maintaining a high electric potential between said discharge and collecting electrode means, a regulating electrode means disposed adjacent said discharge electrode means, means for maintaining an electrical potential between said discharge electrode means and said regulating electrode means, and means for varying said last-named potential.

3. An apparatusas set forth in claim 2, said regulating electrode means being disposed at the opposite side of said discharge electrode means from said collecting electrode means.

4. An apparatus for electrical precipitation of suspended particles from gas comprising collecting electrode means, discharge electrode means, means for passing gas containing suspended material between said discharge and collecting electrode means, means for maintaining a high electric potential between said discharge and collecting electrode means, a regulating electrode means of extended surface disposed adjacent said discharge electrode means, means for maintaining an electrical potential between said discharge electrode means and said regulating electrode means, and means for varying said last-named potential.

5. An apparatus as set forth in claim 4, said regulating electrode means being disposed at the opposite side.oi said discharge electrode means from said collecting electrode means.

. WALTER DEUTSCH.

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