US2039094A - Electrical precipitation apparatus - Google Patents

Description

will W36. M. A. I ISSMAN ELECTRICAL PRECIPITATION APPARATUS Filed Aug. 2, 1932 3` Sheets-Sheet 1 /Zb l v Y 1 n 1 l W192i, 'L1-0:" L" t: '2: "TCL-: Ar-:J /ap a w a 2jr? a a l INVENTOR; I i JY Mmfe/ALIss/l/af, j 7/ l l( www 'fw/ Apnfl 8, 1936. l M. A. LISSMAN ELECTRICAL PRECIPITATION APPARATUS Filed Aug. 2, 1932 s sheets-sheet 2 IN V ENI OR.

M. A. LxssMAN Tf1 ELECTRICAL PRECIPITATION APPARATUS Filed Aug. 2, 1952 3 sheets-sheet s /V VE Nff m AMM, ,gym l Patented pr. 28, 1936` PATENT OFFICE 2,039,094 ELECTRICAL PRECIPITATION APPARATUS Marcel A. Lissman, Temple City,

Precipitation Company, Los

to International assigner' 7 Claims.

This invention relates to apparatus for the electrical precipitation of suspended particles from gases, and the principal object of the invention is to provide an advantageous construction oi such an apparatus, which has a high emciency oi' operation, so as to eiect a high degree of precipitatiop of suspended. particles from a relatively large volume of gas in` an apparatus of minimum size and with a minimum consumption of electrical energy, and which is' also so designed as to eliminate electrical disturbances and irregularitlesin operation such as occur in electrical precipitators now in use. l

n particular object of the invention is to provide for more eiifective ionization by means of a separate ionizing electric field, resulting in a more I rapid rate of electrical charging of the suspended particles, while the particles are simultaneously subjected to another electric held, which may be termed .a precipitating held, adapted to cause precipitation of the charged particles upon suitable receiving electrodes.

Theordinary type of electrical precipitation apparatus comprises opposing discharge and receiving electrodes, the receiving electrodes ordinarily consisting of plates, screens, pipes or other members of relatively extended surface and the discharge electrodes ordinarily consisting oi wires,

or rods oi small diameter, suitably spaced from one another and extending parallel to the surfaces oi the receiving electrodes, said discharge and receiving electrode means being insulated from one another and connected to the opposing terminals ci a suitable source of electric current,

preferably unidirectional, at sumcient voltage to maintain ionizing discharge from the discharge electrodes, and means being also provided for passing gas containing suspended particles through the 'spaces between the discharge and receiving electrodes and for removing and collecting the material precipitated. In such apparatus the electric potential between the discharge and receiving electrodes is utilized both for maintaining ionizing or corona discharge from the discharge electrode membersand for maintaining the' electrostatic force between said discharge electrode members and the receiving electrodes for cheating migration of charged particles toward the receiving electrodes. Practical considerations make it necessary to space the discharge electrode members a considerable distance from the receiving electrodes, this space being ordinarily from about 3 to 6 inches, so that a relatively high electric potential is required in order that the potential gradient at the discharge electrode shall be suiiicint to bring about a suitable degree of ionization for charging of the suspended particles. Furthermore, it is found that emcient ionization can be realized only when this electric potential is fairly close to the arcing po- 5 tential between the discharge and collecting electrodes, so that in operation arcing sometimes oc- -curs due to accumulation of suspended particles on the electrodes or to occurrence of high voltage surges produced in the electric circuit. Formation of an arc between the electrodes not only represents a waste of electrical energy but also lowers the potential difference between the electrodes to such an extent that ionization is no longer eected or is reduced to a minimum., This reduction in 15 potential dierence ordinarily results eventually in a breaking-oi the arc and a restoration of the normal potential diderence, but the precipitator is substantially ineective during the periodv oi maintenance of the arc. In many cases, particu- 20 larly in the collection of certain types or suspended material or in the treatment of certain types of gases, this arcing is of such frequent occurrence as to seriously reduce the eiiiciency oi the apparatus.

Furthermore, it has been round that in an apparatus of the type above described the discharge electrode members must be spaced not less than a certain distance from one another in order to avoid an interfering action therebetween resulting in a suppression of electrical discharge therefrom. lt may be said that in ordinary practice it has been found that maximum electrical discharge and ionization from each individual discharge electrode member can be obtained only when the spacing between adjacent discharge electrode members is not less than and preferably somewhat greater than the shortest distance between the discharge electrode members and the receiving electrodes. It is evident that this rela- 40 tionship imposes a limitation upon the closeness of spacing of the discharge electrode members and hence upon the number of discharge electrode members which may be provided in an apparatus of a given size, using a practical spacing of discharge electrodes from receiving electrodes. Thus, a limitation is placed upon the amount of ionization and consequent charging of the particles which can be eected in an apparatus of a certain sine.V

It is the purpose of the present invention to provide apparatus of relatively simple construction in which the above-mentioned disadvantages of ordinary electrical precipitation apparatus are largely overcome, so that arcing or disruptive discharge between the electrodes is avoided and a maximum amount of ionization is provided in an apparatus of a given size and with a minimum consumption of electrical energy.

Electrical' precipitation apparatus now in common use'consists of two general types. In the plate typev precipitator the receiving electrodes may consist of plates of metal, concrete or other suitable material or of plate-like members such as screens or rod curtains, such plates or platelike members being disposed in parallel planes, ordinarily vertical, defining ducts or passages through which the gas is passed either horizontally or vertically, `while the discharge electrode members ordinarily consist of wires or rods of small diameter disposed in suitably spaced relation to one another in planes extending parallel to the receiving electrodes and midway therebetween. In the pipe type precipitator the receiving electrodes consist of pipes or tubes through which the gas is passed longitudinally, said pipes generally extending vertically and usually being cylindrical in shape although sometimes of square, rectangular or other suitable shape, while the discharge electrode members consist of wires or rods of small diameter extending longitudinally and substantially axially within the respective pipes.

The present invention is applicable to best advantage to electrical precipitators of the plate type. In applying the invention to an apparatus of this type, the receiving electrodes are as-before formed as plates or plate-like members of extended surface disposed in substantially parallel and preferably vertical planes. However, instead of providing only a single set Aof discharge electrode members between each pair of adjacent receiving electrodes, I provide two sets of oppositely charged ionization eld electrode members spaced from one another, both sets being pref--` erably disposed in or adjacent a common plane extending parallel to and midway between adjacent receiving electrode plates, and the electrode.

members of one set being preferably alternately disposed with respect to the electrode members of the other set.

'I'he two sets of ionization field electrodes are so supported as to be insulated from one another v and also from the receiving electrodes, and separate electric potentials are applied between the respective sets of ionization field electrodes, and between one or both sets of ionization eld electrodes and the receiving electrodes. For this purpose the two sets of ionization field electrodes are connected to opposite terminals of a source of either alternating or unidirectional electric current at sufllcient voltage to maintain an ionizing or corona discharge from one or both of these sets of electrodes, in what may be termed an ionization field, while the receiving electrodes and one of the sets of ionization ileld electrodes are connected to opposite terminals of a second source of electric current', preferably unidirectional current, at sufficient Voltage to maintain an effective precipitating eld therebetween.

According to a preferred embodiment of the invention, one of the sets of ionization eld electrodes comprises a plurality of bare metallic elements of relatively small diameter such as wires or small rods whose diameter is sufficiently small to provide ionization or coronal discharge therefrom under the electrical potential applied between said elements and the elements, of the other set, while the other set of ionization eld electrodes, arranged alternately'with respect to tion. Either the large diameter or small diamev Ater electrode `members may be`connected to one terminal of the electric current source used for maintaining the precipitating field between said members and the receiving electrodes. It is evident' that with separate ionization and precipitation elds as above described, the oppositely charged ionization field electrodes may be spaced quite closely together in their respectiveplanes, without regard to the relation of this spacing to the distance between the plane of the ionization field electrodes and the surface of the adjacent receiving electrodes. It is possible, therefore, to space the ionization field electrodes at a relatively great distance from the receiving electrodes and to maintain a sufficient potential difference therebetween to produce substantially complete migration of charged particles across this space and onto the receiving electrodes, while at the same time spacing the ionization field electrode members relatively close together, and preferably at a closer spacing than the distance between the ionization field electrodes and the receiving electrodes, so as to provide a large number of ionization field electrodes and a consequent high production of ions in an apparatus of a given size. The invention therefore provides for utilization of electrical energy and also of the available space in the most eiiicient manner, both in the ionization of the gas and the consequent charging of the suspended particles and also'in the electrical attraction or migration of the charged particles toward and upon the receiving electrodes.

The invention also comprises novel and advantageous means for supporting the two sets of ionization field electrodes in such manner as to insulate ,the same from one another and from the receiving electrodes.

The accompanying drawings illustrate apparatusembodying' my invention and referring thereto:

Fig. 1 is a longitudinal section of a. plate type diagram showing a preferred the separate electric fields modification of the ionization electrode members.

Fig. 6 4is a horizontal section of a modified form of plate type precipitator, on line 6-6 in Fig. 7.

Fig. 7 is a longitudinal section of the precipitator shown in Fig. 6, taken on line 1-1 therein, with the nearest receiving electrode partly broken away. y The apparatus shown in Figs. l to 4 inclusive comprises a housing l provided with means such as inlet flue 2 and outlet flue 3 for effecting passage of gas thsough said housing, it being underpositionedin anys'uitable manner as 2,039,094 stood that the actual ow of gas at the desired may be formed as plates-or plate-likefmembers disposed'in parallel vertical planes.-4 By way of example. said receiving electrode members are shown as metal plates extending parallel to the direction of gas at A in Fig. i?, said plates being supported and by means of bars 8.". Gas passage ducts l are thus provided between the receiving. electrodes. Transverse partitions -9 are shown as extending across the housing l Vbelow the receiving electrode plates so as to obstruct ow of gas below said plates and cause the gas ow to be co'nned substantially to the spaces or ducts I0.

The two sets of ionizationeld electrodes are indicated at lla and Hb respectively, there being a plurality of-4 electrode members of each set disposed vertically in spaced relation in a vertical plane extending midway between each pair of adjacent receiving electrodes, and the electrode members lia and lib being alternately disposed in each such plane. Theelectrode members ila are shown as being of relatively smalldiameter so as to. providecorona discharge therefrom, said members consisting, for example, of wires or small diameter rods. Said members may be supported at their upper ends by means of bar i2a which extend transversely over the tops of the y receiving electrode plates and are carried by main @through openings |411-l in the erably supportingly connected supporting bars i3d which extend through openings ida in the end walls of the upper housing portion 0 and rest on insulating supports ita in inclosed insulator compartments ita. Said electrode members lid are also preferably spaced at their lower ends as by means of rods ila which .may be connected by rods iiia so as to form aV lower spacing frame, and are preferably kept in tension by means of weights ita. Said lower spacing frame may be supported by certain of the electrode which may for this purpose be made of larger diameter and greater strength than the other oi said members. I

The other electrode members lib are shown as rods or pipes of considerably larger diameter than the members iid so asto substantially prevent or inhibit corona discharge therefrom at the electrical potential employed, and are supported at their upper ends by means of bars or rods ith which extend longitudinally with respect to the planes in which said electrode members are disposed, and which are carried by main supporting bars 03h. Said supporting bars ith extend sidewalls of the upper` housing portion 0 and rest on insulating supports ib in inclosed insulator compartments |611. Said electrode members at their lower ends to longitudinal bars or rods l'lb which are in turn connected by rods or bars lab so as to provide a lower spacing and positioning frame therefor. It willbe. understood that the supporting members I2b and l3b :for the e1ectrod members IIb are at all points spaced sufficiently from the supporting members I2a and I3 for the other ow as indicated bythe arrowsV members such as indicated at tia lib, are also prefthat the distance between successive electrodes adapted to produce ionization, namely, in the present case the electrode members lla", is less than the distance between said electrode members and the receiving electrode members l.

` As shown in Fig. 4 the ionization ield electrode4 members lla and IIb respectively, are connected by means of electrical conductors 2| a and 2lb to the opposing terminals of-a transformer 22, or other suitable source of alternating current at suilicient voltage to maintain a corona 'or ionizing discharge from -the electrode members tic of smaller diameter. The electrode members lib of relatively large diameter and the receiving electrode members 'i are means of electrical conductors 2d and 25 respectively, to the output terminals oi a current rectifying device such as mechanical rectiiier 2li whose .operation is well understood, the input terminals be connected between the transformer it and the two sets of ionization held electrodes so as to utilize unidirectional current instead of alternating current in the ionization field circuit.

In View of the relatively close spacing between the ionization deld electrodes as compared to the spacing of said ionization field electrodes from transformer it may'be adapted to maintain a potential difference between 30,000 and 100,000 volts between the ionization field electrodes and the receiving electrodes.

In the operation of this form of the invention eld between electrode members .lla and lib causes ionization to occur adjacent the electrode and' Ila to pre- A shown. as connected byv maintain an electric field of the members lia, while the electric eld between the electrode members Hb (or lla) and the receiving electrodes 'i causes the ions thus produced to be 'terial collects in the hopper or bin 5 from which it may be removed by any suitable means.

It may be pointed out that if a unidirectional potential of relativey large magnitude is employed in the precipitating field and an alternating potential of relatively small magnitudein the ionization field, both/the electrode members lla and Hb will be at high potential with respect to the receiving electrodes, so that the precipitation field, which also serves to drive the ions out into the gas stream, will exist between both sets of ionization field electrodes and the receiving electrodes, and not only fromthe particular ionization field electrodes Ild which are directly connected in the precipitating field circuit. Furthermore, the potential difference between the electrode members Ha and the receiving electrodes will be greater during haf of each cycle and less during the next half of each cycle than the potential difference between the electrodes lib and said receiving electrodes, so that the precipitating field will at certain times be principally between the electrode members I la and the receiving electrodes and at other times principally between the eectrode members Hb and the 'receiving electrodes. i

As shown in Fig. 5, instead of employing electrode members of differentdiameters in the iwo sets of ionization field electrodes, I may employ ionization electrode members lic and ild of like diameter, both ofsuch sets of electrode members consisting, for example, of wires or rods of small diameter. Said 'electrode members may be mounted substantially as above described and in a similar relation with respect to the receiving eectrodes 1 and the respective electrode members may be similarly connected, so as to connect transformer 22 in the ionization field circuit and reclifying device and transformer 29 in tlie precipitation field cr.l uit, in the same manner as before.

The operation of this form of the invention is substantially the same as in the form of the invention first described with the exception that ionization occurs adjacent both sets oi' ionization field electrodes llc and Hd The form of apparatus shown in Figs. 6 and 7 is similar to that shown in Figs. 1 to 3 inclusive. with the exception that the ionization field electrode means are shown as comprising two sets of electrode members llc and iid, both consisting of wires or rods of small-diameter, in the manner shown in Fig.. 5, and with the further exception that somewhat dierent means are provided for supporting the respective sets -of ionization field electrode members. 'I'he electrode members llc are suspended, as before, from transversely extending rods or bars Ila which are in turn carried by longitudinal supporting bars lia resting on insulating supports lia. The other set of electrode members Hd are4 shown as suspended from longitudinally extending supporting bars or rods i2bwhich are in turn carried by transverse supporting bars lib'. These last-mentioned supporting bars Hb', instead of being provided with separate insulating supports, are shown as resting on insulating supports lib carried by the longitudinal supporting bars I3a. It will be seen, therefore, that the longitudinal supporting bars I3a serve not only to directly support the electrode members llc and the supporting mambers I2a therefor, but also to support the electrode members Ild and their supporting members I2b and I3b', which latter supporting members are insulated therefrom by the aforesaid insulators |5b.

'Ihe respective sets of ionization field electrode members may, as before, be provided at their lower ends with spacing members lla and l8a., and 11b and` lsb, and certain of the electrode membersof each set, such as indicated at llc and Hd', may be made of sufficiently vgreat d- -ameter to support the respective spacing members from the upper supporting means. Both sets of electrode members Hc and Hd may be provided at their lower ends with tensioning weights iSc and ISd respectively.

The operation of this form of apparatus is substantially the same as that shown in Figs. 1 to 3 inclusive, with the exception that ionization occurs adiacent both sets of ionization electrode members, as described before in connection with Fig. 5.

I claimz- 1. An electrical precipitator comprising a plurality of plate-like collecting electrodes disposed in parallel vertical planes, ionization electrode means disposed in vertical planes between the respective collecting electrodes, the ionization electrode means in each of said planes comprising two sets of electrode members spaced from one another and disposed in alternate relation, a plurality of supporting members extending longitudinally in the respective planes of the ionization electrode members and supporting all of the electrode members of one of said sets, additional supporting members extending transversely with respect to said planes, spaced from said first-named supporting members, and serving to support all of the electrode members of said other set, means supporting said first-named and second-named supporting members and insulating the same from one another, means connected to the respective sets of ionization electrode members for maintaining an electric. field therebetween, and means connected to said collecting electrodes and to one of the sets of ionization electrode members for maintaining a separate electric field therebetween.

2. An electrical precipitator as set forth in claim 1, said first-named and second-named supporting members being each provided with separate means for supporting the same and for insulating the same from one another and from the collecting electrodes.

3. An apparatus as set forth in claim 1, in which the means for supporting and insulating said supporting members comprises Ameans mounted on insulating supports and serving to directly support the supporting members for onel of the sets of ionization electrode members, and

additional supporting means mounted thereonand insulated therefrom and serving to support the supporting members for the other set of ionization electrode members.

4. In an electrical precipitator, the combination of a collecting electrode having an extended surface, a linear ionization field electrode consisting of a baremetallic element of suiliciently aoaaoea small diameter to provide corona discharge therefrom, another ionization field electrode consisting of a bare metallic element of sumciently large diameter to substantially prevent electrical discharge therefrom, spaced from and parallel to said first-named ionization field electrode, both of said ionization iield electrodes extending parallel to the surfaceof said collecting electrode and spaced therefrom, electric power supply means `connected to said ionization field electrodes for maintaining therebetween an electric field oi' sumcient intensity to cause corona discharge from said electrode of small diameter, and electric power supply means connected to one of said ionization eld electrodes and to said collecting electrode for separately maintaining an electric precipitating field between said ionization field electrodes and said collecting electrode.

5. ln an electrical precpitator, the combination of a plate "or plate-like collecting electrode, a series of parallel linear ionization eld electrodes disposed in a plane substantially parallel to the collecting electrode, alternate yones of said ionization eld electrodes consisting of bare metallic elements of suciently large diameter to substantially prevent electrical discharge therefrom, and the other ionization eld electrodes consisting of bare metallic elements of suficiently small diameter to provide corona discharge therefrom, electric power supply means connected to said collecting electrode and to one of the sets of alternate ionization eld electrodes for maintaining a unidirectional high potential electric precipitating field between said ionization iield electrodes and the collecting electrode, and separate electric power supply meansl connected to said ionization iield electrodes for separately maintaining an electric' field of relatively small potential between the two sets of alternate ionization eld electrodes sucient to cause corona discharge from said electrodes of small diameter.

6. lln an electrical precipitator, the combination of a collecting electrode having an extended surface, a linear ionization eld electrode consisting of a bare metallic element of sumciently small diameter to provide corona discharge therefrom, another ionization field electrode consisting of an element of sumcient large diameter to substantially prevent electrical discharge therefrom, spaced from and Aparallel to said nrst-named ionization iield electrode, both of said ionization iield electrodes extending parallel to the surface of said collecting electrode and spaced therefrom, electric power supply means connected to said ionization field electrodes for maintaining therebetween an electric iield of sullcient intensity to cause corona discharge from said electrode of small diameter, and electric power supply means connected to one of said ionization field electrodes and to said collecting electrode for separately maintaining an electric precipitating eid between said ionization neld electrodes and said collecting electrode.

7. ln an electrical precipitator, the combination of a plate or plate-like collecting electrode, a series of parallel linear ionization eld electrodes disposed in a plane substantially parallel to the collecting electrode, alternate ones of said ionization iield electrodes consisting of elements of sumciently large diameter to substantially prevent electrical discharge therefrom, and the other ionization eld electrodes consisting ofbare metallic elements of sulli'ciently small diameter to provide corona discharge therefrom, electric power supply means connected to said collecting electrode and to one of the sets of alternate ionization eld electrodes for maintaining a undirectional high potential electric precipitating field between said ionization field electrodes and the collecting electrode, and separate electric power supply means connected to said ionization eld electrodes `ior separately maintaining an electric field of relatively small potential between the two sets of alternate ionization field electrodes sulncient to cause corona discharge from said electrodes of small diameter.

MARCEL A. HSS.

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