US3483671A - Electrostatic dust precipitator - Google Patents

Description

Dec. 16, 1969 .1, WIEM-ER 3,

ELECTROSTAT IC DUST PRECIPITATOR Filed Dec. 1, 1967 2 Sheets-Sheet l In s/Qnwr:

Jean Wz'emer ATTORN 3,483,671 ELECTROSTATIC DUST PRECIPITATOR Jean Wiemer, Oherhochstadt, Taunus, Germany, assignor to Metallgesellschaft Aktiengesellschaft Filed Dec. 1, 1967, Ser. No. 687,221 Claims priority, application Germany, Dec. 3, 1966, M 71,877 Int. Cl. B03c 3/00 US. Cl. 55-136 2 Claims ABSTRACT OF THE DISCLOSURE The spark or discharging electrode hung in the tubular or pipe-type collecting or precipitating electrode in a vertical electrostatic dust precipitator is made, in the direction of gas flow through the precipitator, strongly dis charging in the first third of its length, moderately discharging in the second third, and non-discharging in the last third. This causes both coarse and fine dust particles to be precipitated from the gas at a greater efiiciency at a lower cost.

In all electrostatic dust collectors working with platetype of pipe-type collecting electrodes and with vertical gas passages, it is the practice to apply uniform discharge electrodes over the entire length of the electric field and to feed the discharge electrodes from one single high tension power line. Such discharge electrodes with a uniform discharge characteristic over the entire length of the electric field are appropriate for the treatment of gases which contain coarser solid or liquid particles. In gases with a larger amount of fine solid or liquid particles with a grain size below one micron, space charges frequently occur at the inlet to the electric field. These spaces charges suppress a certain current flow which is necessary for an effective dust collection, while at the end of the electric field these space charges have vanished and a current fiows corresponding to the normal gas property. Despite the differing electric characteristics of the gases to be cleaned or the varying electric conditions, respectively, it is desirable that a uniform discharge characteristic and thus a uniform collecting efiiciency be attained over the entire length of the electrodes.

To avoid the above-described disadvantages, this invention is composed of a vertical electrostatic dust collector with pipe-type collecting electrodes, and discharge electrodes having discharge points and discharge lugs, and with discharge wires of different discharge characteristies with star-shaped cross-section and round cross-section, in which in each individual pipe-type collecting electrode, in the gas flow direction, approximately the lower third of the discharge electrode is strongly discharging, approximately the middle third is moderately discharging and the upper third is non-discharging.

In a modified form of this invention, the discharge electrodes are formed of round rods which have discharge points in approximately the first third of their length, and in the second third have discharge lugs or shorter spikes.

In another modified form of this invention, the discharge electrodes are made of rods or wires of starshaped cross-section having discharge points in the lower third and with the edges of the electrode being screened in the last third by a pipe sleeve.

Comparative tests revealed that with the same current the w-value of the discharge electrode of this invention is about to higher than that of the discharge electrodes according to the present state of technology which are usually used in electrostatic dust collectors having pipe-type collecting electrodes. Thus, by using the electrodes with different discharge characteristics according nited States Patent 0 to this invention, a considerable reduction is possible in the collector size and the high tension power line and thereby results a decrease of the investment costs.

The means by which the objects of the invention are obtained are described more fully with reference to the accompanying drawings, in which:

FIGURE 1 is a vertical cross-sectional view through the electrostatic dust collector;

FIGURE 2 is a front view of the spark or discharge electrode usable for that shown in FIGURE 1;

FIGURE 2a is a cross-sectional view taken on the line 2a-2a, FIGURE 1;

FIGURE 2b is a similar view on the line 2b2b;

FIGURE 2c is a similar view on the line 2c-2c;

FIGURE 3 is a view of the electrode in FIGURE 1; and

FIGURES 3a, 3b, and 3c, respectively, are views taken on the lines 3a3a, 3b3b, and 3c3c in FIGURE 3.

The gases to be cleaned enter the raw gas chamber 2 of the electrostatic dust collector having pipe-type collecting electrodes through gas inlet connection 1. Below the raw gas chamber 2 is the dust hopper 3 with the dust outlet opening 4. The gases to be cleaned then pass upwardly through the pipe-type collecting electrodes 5 into the clean gas chamber 6 and leave the apparatus through the gas outlet duct 7. A hood 8 covers an insulator 9 from which is suspended a rod 10 holding a frame 11. The discharge electrodes 12 are hung from frame 11. The discharge electrodes are kept taut by means of weights 13 fastened to the lower end of the electrodes. The discharge electrodes 12 in FIGURE 1 have one of the shapes shown in FIGURES 2, 3, and 4, as for example FIGURE 4.

The discharge electrode in FIGURE 2 consists of a round rod 12' having in the lower part discharge points 14, and in the middle part discharge lugs of shorter spikes 15. The discharge electrode of FIGURE 3 consists of a rod of wire 12" of star-shaped cross-section on the lower part of which is slid a pipe 17 having discharge points 14. The middle part remains as the original wire with star-shaped cross-section, while the rod edges in the upper part are screened by a pipe 18 thus resembling a round rod.

Having now described the means by which the objects of the invention are obtained,

I claim:

1. An electrostatic dust precipitator comprising: a separating chamber in a dust collector, a raw gas inlet at the bottom of said chamber and a clean gas outlet at the top of said chamber, a dust hopper in said dust collector and beneath said chamber and operatively associated with said chamber to receive dust therefrom, a vertical pipe collecting electrode operatively mounted in said chamber in such a manner that gas entering said inlet must pass upwardly through the space encompassed by said collecting electrode before exiting said dust collector through said outlet, the improvement comprising a discharge electrode extending axially of said collecting electrode, said discharge electrode comprising three approximately equal thirds and, in the direction of gas flow through the collecting electrode, relatively long strongly discharging discharge points (14) mounted on the first and lower third of the length of the discharge electrode, moderately discharging relatively shorter points mounted on the second and middle third of the discharge electrode, and with the last an upper third of the discharge electrode being a nondischarging rod.

2. In a precipitator as in claim 1, said discharge electrode comprising a rod having a star-shaped cross-section (12"), said discharge points (14) being mounted on References Cited UNITED STATES PATENTS Schmidt et a1. 55150 X I Br adley 55-2 DENNIS E. TALBERT, JR., Assistant Examiner Anderson 55138 X v Mestor 55 152 V C Wiemer -s5 10 5s 147, 148, 151, 152

FOREIGN PATENTS J J 68K858 "671964" Canada? FRANK w. "LUTTER, Primar Examiner

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