US1943070A - Electrical precipitation apparatus - Google Patents

Description

Jan. 9,'1934. G. GRAVE ELECTRICAL PRECIPITATION APPARATUS 2 Sheets-Sheet l Filed NOV 23 1931 f/g. e

INVENTOR.'

W ATTORNE Jan.. 9, 1934. G. GRAVE 1,943,070

ELECTRICAL FRECIPITATI/ON APPARATUS File Nov. 25,/ 1931 SheetS-She'ret 2 INI/ENTQR:

Patented Jan. 9, 1934 1,943,070 ELECTRICAL PRECIPITATION APPARATUS Georg Grave, Frankort-on-the-Main, Germany, assigner to International Precipitation Company, Los Angeles, Calif., a corporation of California Application November 4 Claims.

This invention relates to apparatus for electrical precipitation of suspended particles from gases, and particularly to an-,improvement in electrical precipitators employing collecting electrodes pro- 5 vided with pockets or internal spaces for the collection of the precipitated material.

The principal object of the invention is to provide automatic maintenance of an auxiliary electric eld within said pockets or spaces, by maintaining those parts which cooperate with the collecting electrode to form said pockets or spaces Y at a denite electric potential intermediate the potential of the discharge and collecting electrodes, and to accomplish this without requiring the use of an auxiliary electric supply circuit.

According to this invention, the above result is eiected by interposing semi-conducting material between the collecting electrode, which is preferably grounded and is connected to one terminal of a high voltage electric supply circuit, and the parts which cooperate with said collecting electrode to form the material receiving'pockets or spaces. The discharge electrode means, which are spaced in the ordinary manner from the collecting electrode means and the pocket defining means, are connected to the other terminal of' said electric supply circuit. It will be understood that the parts which cooperate with the collecting electrode todene the material receiving pockets or spaces are ordinarily disposed between the discharge electrode means and the collecting electrode. A main precipitating electric field is thus maintained between the discharge electrode means and the collecting electrode considered as a whole, such main electric eld, however, terminating at the low tension side principally at the surfaces of those parts which are disposed somewhat outwardly from the collecting electrode proper and which cooperate therewith to denne the material receiving pockets or spaces. Due to the intervening layers of semi-conducting material between such parts and the collecting electrode proper, however, an auxiliary electric field is also automatically established across said 5 pockets or spaces, Without requiring connection of said parts to a separate source of electric power, and this auxiliary eld tends to prevent deposition of precipitated' material on said pocket defining parts and insures that the electrically charged particles precipitated by the main electric field are caused to pass on into the receiving pockets or spaces and upon or into close proximity to the collecting electrode proper, where they are protected against dislodgment by the gas stream.

The potential of the auxiliary electric field and in Germany December 23,

(Cl. 18S-J7) 23, 1931, Serial N0.

thus established depends upon the nature and dimensions of the semi-conducting material interposed in the above-mentioned position. The greater the resistance ofthis semi-conducting material, the higher will be the potential difference between the collecting electrode proper and the pocket defining means, for a given total potential between the discharge and collecting electrodes.

A further advantage of this interposed semiconducting material'is that it prevents or damps out disruptive discharges or arcs which may tend to form between the discharge electrodes and the surfaces of the pocket dening means, by interposing sufficient resistance to-prevent any continued maintenance of such disruptive discharging or arcs.

The accompanying drawings illustrate embodiments of this invention, and referring thereto:

Fig. 1 is a horizontal section of one form of discharge and collecting electrode means according to said invention, with the electric power supply circuit "shown diagrammatically.

. Fig. 2 is a vertical section transverse to the direction of gas flow on line 2-2 in Fig. 1.v

Fig. 3 is a longitudinal vertical section on line 3--3 in Fig. 1.

Fig. 4 is a horizontal" section showing a modied construction of the collecting electrodes. v

Fig. 5 is a longitudinal section on line 5-5 in Fig. 4.

Fig. 6 Fig. 4.

In Figs. 1 tol 3 inclusive, the collecting electrodes comprise vertically disposed plates 1 and screens or grids 2 of suitable mesh, spaced somewhat from said plates and separated therefrom by strips 3 of suitable semi-conducting material such as, for example, cement or a mixture of cement and asbestos. The semi-conducting 95 strips 3 may be supported upon the plates 1, for example in the manner indicated at 4, and the screens or grids 2 may be supported upon said strips, for example, by being embedded in the is a transverse section on line 6-6 in surface layers of said strips or being secured f thereto in any suitable manner. derstood that, when both sides of a collecting electrode are to be utilized for precipitation, the screens or'grids above mentioned, together'with the intervening strips of semi-conducting material are provided at both sides of the electrode plate l, as in the case of the central collecting electrode shown at A in Figs. 1 and 2, while when only one side of the collecting electrode is to be utilized for precipitation, s'aid screen and semi- 110 It will be unwires or rods 5 disposed in planes parallel to andintermediate each pair of adjacent collecting electrodes, said discharge electrode members being spaced somewhat from the lfurthest projecting portions of the collecting electrodes, that is, from the screens or grids 2.

Any suitable electric supply means may be used to maintain the desired potential between the discharge and collecting electrodes, but I have shown an electric circuit comprising transformer 6 and mechanical rectifier 7, one of the output terminals of said rectier being connected by conductor 8 to the collecting electrode plates 1 and being preferably grounded as indicated at 9 and the other of said output terminals being connected by conductor 11 to the discharge electrode means 5, for example through the frame means 12 on which the discharge electrodes are mounted.

It will be understood that the discharge and collecting electrode means above described may be mounted within a suitable housing or chamber provided with inlet and outlet means for passage of gas therethroughV longitudinally of the collecting electrodes.L The direction of gas ow is 'preferably horizontal as indicated by the arrow at G in Fig. 1, although it will be understood that the gas may, if desired, be caused to pass vertically. It will also be understood that the discharge electrode means 5 and the frame means 12 therefor are insulated from the collecting electrodes and from ground in any suitable manner.

It will be seen that the screens or grids 2 cooperate with the plates 1 to define pockets or spaces therebetween, as indicated at 15, for receiving precipitated material, the material so received being protected against dislodgment by the gas stream passing in the ducts or passages 16 between said screens or grids and the discharge `electrode members 5.

In the operation of the above described apparatus, a suitable electric potential' is maintained between the discharge and collecting electrodes, for example, by operation of the above-described electric supply means. The electric discharge from members 5 serves to charge suspended particles contained in the gas passed through ducts Y or passages 16 and the particles so charged are driven by the electric field toward and through the screens or grids 2 and into the pockets or spaces 15. The auxiliary field maintained as above described, from the screens or grids 2 to the respective plates 1, serves to drive such particles inwardly toward said plates and to hold such particles within the pockets or spaces 15 so that substantially all material once precipitated by the electric field through the pocket deflning screens 2 is prevented from being subsequently picked up and carried away by the passing gas stream. It will be observed that when the gas flow is horizontaland the semi-conducting strips 3 are disposed vertically as shown, said strips also act as bailles so as to substantially prevent or minimize longitudinal gas flow behind the screens 2 and maintain a quiescent condition within the pockets or spaces 15.

` While I have shown particularly the provision of electric power supply means adapted to maintain a unidirectional electric field between the electrodes, and while it is believed that the best results are generally to be obtained by use of the invention in this manner, it will be understood that the invention is also applicable to electrical gas cleaning installations in which an alternating electric field is used.

The form of construction shown in Figs. 4 to 6 inclusive, differs from that above described principally in 4that the pocket defining means constitute metal strips or bales 2 which are bent or offset in a direction transverse to the thickness thereof, so as to provide portions 2a which lie relatively close to the collecting electrode plates 1 and portions 2b which are relatively remote from said plates. The portions 2a are secured in any suitable manner to strips 3 of suitable semiconducting material such as above-mentioned, which are in turn mounted upon plates 1', said semi-conducting material being disposed at all points between the strips 2 and plates 1'. The portions 2b of said strips are thus disposed opposite the portions of the collecting electrode plates 1v between adjacent strips 3 and serve to define material receiving pockets or spaces 15' between said strip portions 2b and saidportions of the plates. y

The construction may be otherwise substantially the same as above described and the operation is also substantially vthe same. The discharge electrodes, indicated at 5', and the collecting electrode plates 1 are connected as before to a suitable electric supply means, and the suspended particles are precipitated by the main electric field into the spaces 15' or upon the outer surfaces of the strips 2. Material precipitated upon said strips is carried along by the gas stream and into the next succeeding pocket 15. The semi-conducting material 3 serves to maintain said strips at a certain potential intermediate that of the discharge and collecting electrodes, respectively, thus creating an auxiliary electric field across the pockets 15' which acts as before to hold the precipitated material within said pockets. In this form of apparatus the strips 2' preferably extend substantially vertically, and

the direction of gas flow is preferably substan.

tially horizontal, as indicated by the arrow at G.

I claim:

1. An electrical precipitation apparatus comprising a discharge electrode, a collecting electrode, and means disposed between said electrodes and electrically connected with said collecting electrode by means-of semi-conducting material and cooperating with said collecting electrode to define collecting spaces for precipitated material. t

2. An apparatus for electrical precipitation comprising a discharge electrode, a collecting electrode spaced from said discharge electrode and provided with. means disposed between 4said discharge and collecting electrodes so disposed as to dene a collecting space for precipitated material adjacent said collecting electrode, said means providing openings for passage of material into said space, semi-conducting material connecting said collecting electrode and said collect-I ing space defining means, and a source of electrical energy connected to said discharge and collecting electrode to maintain an electric potential therebetween.

3. In an electrical precipitator, a collecting electrode structure comprising an electrode member having an extended surface, semi-conducting members connected to said electrode l member and disposed at one side thereof, and means connected to said semi-conducting members and electrically connected thereby with said '3 electrode member at oney side thereof and cooperating therewithto denne collecting spaces lfor precipitated material, and semi-conducting members electrically and mechanically connecting said means to said electrode member.

GEORG GRAVE.

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