US2101168A - Electrical precipitation apparatus - Google Patents

Description

Dec. 7, 1937.

w DEUTSCH ELECTRICAL PRECIPITATION APPARATUS Filed Feb. 23, 1957 7 A I .5 E R f, 1 fi INVENTOR. WdDeuiscio, BYMM? M ATTR EYS.

Patented Dec. 7, 1937 PATENT OFFICE 2,101,168 ELECTRICAL PRECIPITATION APPARATUS Walther Dentsch, FrankIort-on-the-Main, Germany, assignor to International Precipitation Company, Los Angeles, Calif., a corporation oi California Application February 23, 1937, Serial No. 127,287 In Germany February 24, 1936 1 Claim.

This invention relates to the electrical treatment of fluids, in which a fluid to be treatedeithera gas or a liquid-is passed through an electrical field between opposirig electrode means. As examples of such treatments, there may be mentioned the electrical precipitation of suspended particles from gases, and the electrical de-emulsifying or separation of liquid emulsions. The present invention is concerned particularly with electrical fluid treating apparatus in which a unidirectional high potential field is maintained between the opposing electrode means.

In such apparatus, it is frequently desirable to pass the fluid successively through two electrical fields maintained between two separate sets or systems of oppositely charged electrode members, and in these cases it is sometimes advantageous to apply potentials of different magnitudes between the opposing electrodes of the respective sets or systems. For example, in the treatment of either gases or liquids, it may be desired to first subject the fluid to the action of an electrical field at relatively low potential and then to the action of a higher potential field. In other cases, different arrangements or spacings of the opposing electrodes, or different types of electrodes, may be employed in the successive fields, making it either necessary or preferable to utilize potentials of different magnitudes.

The principal object of the invention is to provide a simple and advantageous means of obtaining two unidirectional potentials of difierent magnitudes and applying these potentials to the respective electrode systems in an apparatus such as above described.

A further object is to provide for obtaining the two different unidirectional potentials from a common source of alternating electric current, and with the employment of a single mechanical rectifying apparatus of simple design and construction.

The rectifier employed according to this invention is a 'polyphase mechanical rectifier, which may be of the general type described in German as the respective electrodes of an electrode system) whereby, successive pairs of phases are successively connected in series to the terminals of the load. The operation is such that one terminal of the load is substantially continuously connected to a point of highest positive potential of the polyphase source and the other terminal is substantially continuously connected to a point of highest negative potential of said source, so that the effective unidirectional potential supplied to the load is approximately twice the efiective potential of the individual phases. According to the present invention, a separate unidirectional potential is also supplied to another load (in this case the respective electrodes of a separate electrode system) by connecting one terminal of. this other load to one of the rotating contact members of the rectifier, and connecting the other terminal of this load to the star-point or common connection of the several phase windings of the alternating current source, so that the rectified voltages of the individual phases are successively connected to this other load. Thus, the potential applied to the last mentioned load is approximately'half the potential applied to the first mentioned load. It will be understood that rectification may be obtained ina similar manner by connecting the loads to fixed contact means and connecting the several phases of the polyphase source to rotating contact means, but the arrangement first described is ordinarily preferred, since it minimizes the number of brush contacts required to maintain connection to the rotating contact means.

The following specific description will serve to illustrate the application of this invention to one particular type of apparatus for electrical precipitation of suspended material from gas, but it will be understood that the invention may be employed in a like or comparable manner in connection with any apparatus in which a fluid, either gas or liquid, is passed successively between two separate electrode systems, and in which it is desired to supply unidirectional potentials of difierent magnitudes to the opposing electrodes of the respective systems.

According to one method which has long been known for the electrical separation of suspended solid or liquid particles from gases, the gas is first passed through a unidirectional electrical field in which ionization is caused to occur, for the purpose of electrically charging the suspended particles, and is then passed through a separate unidirectional field in which substantially no ionization is produced, for the purpose of precipitating the charged particles. In apparatus of this type, 5

some difliculty has been encountered in obtaining suillcient ionization in the first or charging field to efiectively charge the suspended particles, without causing an objectionably large proportion of the suspended particles to be actually precipitated in this field instead of in the second or precipitating held in which, according to this method, the actual separation may be more advantageously carried out.

For the above reason, it is advantageous in some cases to pass the gas through the charging held at a velocity severaljimes as great as the velocity at which it is passed through the precipitating field. This may be accomplished adtactmembers 2|,22 andiispecedlzflapartin' position for efiective spark contact with mental;- ing contact is and conneded respectively totheextremitiesoithesevm'alphase vantageously by placing the electrodes relatively I, l1 and III. The inner ends of the several close together in the charging field, to provide a phases are co together at a common point gas passage space therebetween of relatively small 2!, commonly referred to as the star-point.

cross-sectional area, and placing the electrodes It will be understood that the rotating contact relatively farther apart in the precipitating field, assembly of the rectifier may be mounted in the to provide a gas passage space therebetween usual manner upon the shaft of a synchronous whose cross-sectional area is several times that motor for rotation in the proper direction, for exof the charging field. For example, the charging ample as shown by the arrow in Fig. 1, and that electrode system may comprise a. discharging suitable insulating means are provided for elecelectrode formed as a wire of sufliciently small trically insulating the segments 12 and I2 and diameter to provide eiiective corona discharge or conductor ll hum ts l3 and i3 and-conionization, disposed axially within a. substantially ductor l6. Owing to the fact that the device is cylindrical tube or pipe which constitutes the opshown as provided with two contact to posing nondischarging electrode or extended for each polarity of the rectified potential, the

surface, while the precipitating electrode system rotating is operated at one-half synmay comprise two concentric cylindrical electrode members, both of suiiiciently extended surface to substantially prevent corona discharge therefrom, and spaced from one another by a distance somewhat greater than the spacing of the two electrodes of the charging field, so as to provide the desired increase in cross-sectional area. of the gas passage space therebetween.

mth such an arrangement, it becomes desirchronous speed, as by means of a four-pole synchronous motor, soihat 180 rotation thereof corresponds to 360 electrical degrees. It will be understood, however, that only one rotating contact segment for each polarity may be provided, in which case thetwo ts would he located 180" apart in space, and the rotating assembly would be operated at synchronous speed.

The elezarical precipitator is shown as comable to apply a higher potential to the electrodes prising a. charging zone or field 25 and a precipiof the precipitating electrode system than to the tating zone or field 26. The electrode system in electrodes of the charging electrode system, and the charging field comprises a non the arrangement according to the present invenp pe e de Ti d a di charge electrode memtion may be employed advantageously for this er 2 such as a wire or thelikc, extending axialpurpose, Y t 51y within said pipe and insulated therei'rmn. The

The accompanying drawing illustrates the inelectrode system of the zone comvention as applied to an apparatus of this type prises a non-discharging cylindrical electrode and reigning thereto: 9 member 29 0f sufliciently extended surface, and

Fig. 1 is a diagrammatic representation of an preferably rounded at its ends 115 811m, P electrical precipitation apparatus of the type vent corona discharge therefrom, and a. pipe or above described and an associated electric circuit y fi fi electrode m r fl fl fl arrangement according to this invention; surrounding and insulated from the electrode 2!.

Fig. 2 is a diagram of the poiyphase potential E r es an 3! ar l rically grounded as supplied by the alternating current source; indicated at 3!. The other electrode 28 of the Fig. 3 is a diagram representing the positive p ifi at ng el de System is connected and negative potentials applied to the respective through the above mentioned conductor ll to the rotating contact members of the rectifier; and high lifinsion con ctnts l3 and 13', while Fig. 4 is a diagram of the rectified potentials the other electrode 28 of the charging electrode supplied to the respective electrode systems, it system is connected by conductor 32 to the above being understood that the relationships shown in mentioned -P t m ctmncction 01' Figs. 3 and 4 are somewhat idealized for purposes he hre s m I 11 and 331 0f the inc of illustration. current source.

Referring to Fig. l, the secondary phase wind- The be filmed Elli/BIS the zone ings of a high potential three-phase transformer at 33 and is conducted from this zone by a due or are shown at I, II and III. pipe connection 34 to the zone, Th

The rectifier comprises a rotating assembly incleaned gas is tom the open upper dicated tieally at ll provided with t end of the tubular electrode 3!, and suitable diametrically opposed contact segments iland 12' n h as a pp r re provided below and another pair of diametrically opposed contact the p c pi a ng me r meeiving and collectsegments 13 and 13' disposed circumferentially ns the midway between the contact segmmts l2 and l 2. Referring to the potentials of e everal The contact segments 12 and i2 are electrically phase windings I, II and HI (and consequently connected together as at I4 and are shown as the Potentials maintaineflfitheflmdmnm grounded at 15. This connection may be made 22 and 23) are-represented at E1, E1 and E3, reeither through the shaft of the rotating assembly spectiveb. This flame represents tely orbymeansofabrushorothersuitablecontact onefullcycleof cm'rentlnwhich'll electrical degrees are plot-ted horizontally, while the ordinates of the respective curves with respect to the zero axis --0 represent the difference in potential between the respective fixed'contacts '2l, 22 and 23 and the star-point 24.

In the operation of the rectifier, the efiective contacts between the fixed and rotating contact elements are made and broken at times corresponding substantially to the points of intersection of the respective curves in Fig. 2. For purposes of illustration, it may be assumed that the high tension electrodes 28 and 29 of the respective electrode systems are to be maintained at positive potentials with respect to the grounded electrodes 21 and 30, respectively. In this case, the rectifier is so operated that one or the other of the high tension rotating contact segments l3 or it is substantially at all times in contact with a fixed contact member which is at the greatest positive potential, while one of the grounded rotating contact segments I2 or I2 is substantially at all times in contact with a fixed contact member which is at the greatest negative potential, so that, at any instant, the combined potentials of the two phases corresponding to the two fixed contact members so contacted are impressed in series upon the respective electrodes 29 and 30 of the precipitating electrode system, while the potential of the individual phase corresponding to the fixed contact which is at that time contacted by one of the grounded rotating contact segments I2 and I2 is impressed upon the electrodes 21 and 28 of the charging electrode system, due to thepremanent connection of high tension electrode 28 to the star-point 24 of neutral or intermediate potential. l

Referring to Fig. 3, the positive potential supplied to the set of rotating contact segments l3 and I3 is represented by the curve E13, which corresponds in position to the positive peak portions of the several phase potential curves E1, E2 and E: of Fig. 2. Similarly; the negative potential supplied to the high tension set of rotating contact segments l2 and I2 is represented by the curve A E12, which corresponds to the negative peak portions of the several phase potential curves E1, E2 and E3. Thus, the vertical distance between these two curves, as indicated by the line 38, represents the unidirectional potential supplied to the precipitating electrodes 29 and 30, while the vertical distance between curve E12 and the zero axis 0-0, as indicated by the line 39, represents the.

unidirectional potential supplied to the charging electrodes 21 and 28.

The fluctuating unidirectional potentials of the respective electrode systems are more clearly shown in Fig. 4, in which curve'E represents the potential of the electrode 29 with respect to the grounded electrode 30 of the precipitating zone, while Ec represents the potential of the electrode 28 with respect to the grounded electrode 21 of the charging zone, the ground potential line being shown at 0'-0. It will be seen that the curve Ep has sixpeaks per cycle of the alternating current, while the curve E0 has three peaks per cycle of the alternating current, and that the eflective potential in the precipitating zone is approximately twice the effective potential in the charging zone.

It will be understood that the spacing between electrodes 27 and 28 in the charging zone is such as to provide the desired corona discharge from electrode 28, without producing disruptive discharge or arcing, while the spacing between electrodes 29 and 30 is such as to provide a high electrostatic field therebetween without disruptive discharge. Due to the difference in the potentials in these two fields, the electrode spacing in the precipitating field may be in the neighborhood of twice that in the charging field, thus obtaining the above mentioned advantage of a relatively high velocity in the charging field as compared with the precipitating field.

I claim:

An apparatus for electrical treatment of fluids comprising two separate electrode systems each comprising two opposing electrode members spaced from one another to accommodate flow of gas therebetween; a polyphase transformer with Y-connected secondary phasewindings having a common point connected to one end of each winding; means electrically connecting one electrode member of one of said electrode systems to said common point; and synchronously operated mechanical rectifying means associated with the other terminals of said windings, and with the other electrode member of said one system, and also with the two electrodes of the other electrode system, said rectifying means being operable to successively connect the several phases individually to said other electrode member of said one system and to successively connect difi'erent successive pairs of phases in series between the two electrode members of said other system.

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