US2069692A - Electrical precipitation - Google Patents

Description

Feb. 2, 1937. A. WINTERMUTE 2,069,592

ELECTRICAL PREC IPITATION Filed April 9, 1935 e Sheets-Shet 1 Feb. 2, 1937. H. A. WINTERMUTE ELECTRICAL PRECIPITATION Filed April 9, 1935 I I J.

Feb. 2, 1937. H. A. WINTERMUTE 2,059,692 I ELECTRICAL PRECIPITATION Filed April 9; 1935 I s Sheets -Sheet s.

,F gqw. i7 da/ 8 a fih g Feb. 2, 1937. H. A. WINTERMUTE ELECTRICAL PREC IPITATION Filed April 9, 1935 6 Sheets-Sheet 4 Feb. 2, 1937. H. A. WINTERMUTE ELECTRICAL PRECIPITATION Filed A ril 9, 19:55 6 Shets-Sheet s H. A. WINTERMUTE 2,069,692 ELECTRICAL PRECIiPITATION Feb. 2, 1 937.

Fild April 9, 1935 6 Sheets- Sheet 6 Patented Feb. 2, 1937 I UNITED STATES J PATENT OFFICE amassenmc'rmcsr. rancrrrmrron Application April a; 1935, Serial No. 15.496

In Great Britain November 16, 1933 1 1401...... (on. 183-7) Y This invention relates to the electrical treatof the electrical precipitation of suspended parti-- cles from gases.

It has been found that by dividing the gas to be treated into a plurality of parallel streams, and passing each of said streamsthrough separate treater units wherein the parallel streams are subjected to impulses of the same polarity derived from alternate successive half cycles of 1 a common source of alternating current, a number of highly important advantages may be attained.

Among these advantages are the following:

1. The amount of energy required to treat a given amount of gas is reduced.

2. Better operating characteristics are obtained in each of the parallel streams when they are subjected to impulses from alternate half cycles than when each stream is subjected to impulses from every half cycle of the current.

3. Poor operation in one of the parallel treater units, such as arcing over, is not reflected to the other units as is the case when all of the units are electrically connected in parallel.

4. The fact that electrical disturbances inone unit cannot be electrically reflected to another makes possible higher voltage and higher current input per impulse, both of which help to increase the efliciency of operation.

gizing the precipitators is less when the method of the invention is used.'

The invention provides method and apparatus grounded or both may be insulated from ground. The opposing electrodes may be brought to the 55 same potential or to ground potential between 5. The electrical equipment required for ener The half cycles of the current source may be (11- electrodes of the preclpitator units may beimpulses, or they may lie-insulated from each other during the period between impulses. The electrical connections may be so arranged as to impress either the full available voltage or one half the available voltage across the electrodes at each impulse. Other possible variations will be obviousto those skilled in the art from the following detailed description of various embodiments of the invention. The invention will be more particularly described for the purpose of illustration with ref-. 'erence to the accompanying drawings in which:

Figs. 1-5 are schematic representations of electrical precipitation systems embodying the principles of the invention, wherein the full transw former voltage is impressed across the electrodes,

' the systems of Figs. 1, 3 and 4 utilizing mechanical energy directing devices, and the systems of I Figs. 2 and 5 utilizing thermionic energy directing devices; and 96 Figs. 6-10 are schematic representations of electrical precipitation systems, in .which half the full transformer voltage is impressed across the electrodes,the system, of Fig.6 utilizing thermionic energy directing devices, and the systems of Figs. 7-10 utilizing mechanical energy direct:

ing'devicas.

Figs. 3a, 4a., 9a and 9b are partial representations of the systems of Figs. 3, 4 and 9 respectively. showing modified forms of the systems of these o figures. I

In the figures A, B, C and D are precipitating chamber units comprising shells I, which are grounded at 2 and in most of the embodiments illustrated also constitute collecting electrodes and discharge electrodes 3, which are insulated by bushings from the collecting electrodes. The gasesto be treated are supplied to the treating units in parallel streams from common headers v "3. The electrical current supp y is shown as conductors 5 from a source of alternating current, connected to the primaries 6 of transformers T. The secondaries of the transformers are I denoted by i. v

Referring more particularly to Fig. 1, the transformer T steps up the low voltage alternating ourrent supply, for example, at 60 cycles per second and 440 volts (root mean square) to60,000 volts (R. M. S.). The discharge electrodes of precipitators A and B are connected permanently to 5'0 opposite terminals 8 and 9 of the secondary i, of the transformer. Collecting electrodes l of A and B are alternately connected to the opposite terminals a and 9 through a common conductor ill and the conductive shoes of a mechani cal rectifying switch S. Switch S, which is of the Lemp type and turnsin synchronism with the source of alternating current (i. e. at 1800 R. P. M. for 60 cycle current), is similar to those com- [monly in use except that there is no need for four stationary shoes and only three are provided,

designated by numerals I2, I3 and I 4. The conducting strips' I5 and I8 are mounted on insulating disc I1, which is mounted upon and rotated by shaft l8, and alternately connect first terminal 8 and then terminal 9 of the transformer to the collecting electrodes I and ground 2.

As shown in Fig. 1, strip I6 is connecting shoes I3 and I4 and grounding terminal 8 through conductor I8. When the switch is in this position,

winding I of the transformer and the electric field set up'between them will effectively remove suspended particles from gases passing through the field. When shaft I8 turns 90 mechanical degrees in the direction indicated by the arrow, the voltage relationship in the transformer will have changed 180 electrical degrees, and terminal 8 will be at the same voltage but of opposite po-' larity with relation to the potential at 8. At this time, conducting strip I5 will be connecting stationary shoes I2 and I3 and will be grounding terminal 8 so that there will'be no difierence of potential between the electrodes of treater B. The opposing electrodes of treater A will now be at the potential difierence of 8 and 9 and electrical precipitation will result therefrom'in that unit.

The arrangement shown in Fig. 2 gives results similar to those obtained with the arrangement in Fig. 1, but in Fig. 2 two thermionic rectifiers V1 and V: are used in place of the mechanical rectifier in Fig. 1. The anode of V1 is connected to terminal 8 by conductor 23 and the anode ofrectifier V: is connected to terminal 9 by conductor 24. The cathodes of both rectiflers are connected to the casings and the collecting electrodes of treater units A and B by conductor I0.

In there treaters the side walls I function as collecting electrodes. Another wall 2| divides the unit into two parallel passages and this functions as a collecting electrode. Suspended vertically in the passages formed by 'I and 2| are discharge electrodes 3 connected in parallel by conductors 28 and 23 or 24 to terminal 8 or! of the transformer, respectively The discharge electrodes 3 in A are permanently connected to 8, and those in'IB to 8. .The collecting electrodes and fiues are all conductively joined and are permanently connected to grounded conductor III.

.Variable resistances R, R, are for the purpose of ballasting the electric circuits of which they are a part, and as they are adjustable, one re-- sistance can be made to furnish greater impedance and voltage drop than the other, with the result that a lower voltage can beim pressed across the complementary electrodes of one unit should the gas passing in'that unit be more conductive than the gas passing in the-other unit.

In operation, when the voltage of terminal 8 is positive with respect to conductor l0 and he collecting electrodes connected thereto, current will easily pass through the rectifier V1 connected to 8 and the potentials of I, 2| and 3 in treater A will be substantially the same. No en:

ergy will be expended in A when this condition exists. The potential of terminal 9 is now negative with relation to 8 and to conductor I0, and as current cannot pass through rectifier V2 when the anode is negative, the full voltage diilerence between terminals 8 and 8 is across that rectifier and consequently the same voltage difference is present between collecting electrodes 'I,'2I and their complementary discharge electrodes 3 in unit B. In the next half cycle of the current supply, terminal 9 is positive and rectifier V2 bypasses the current from the transformer around'treater B. The complementary electrodes of treater A are now at full potential difference and the gas paths between them become part of the' electric circuit.

With. the hookups'of Figs. 1 and 2, connections are established every other half cycle, by means of the mechanical switch It) in Fig. 1 and by means of thermionic rectifiers 2| and 22 in Fig; 2, whereby the complementary electrodes of each unit are'brought to equal potential every other half cycle, andduring that half cycle, full transformer voltage is impressed across the complementary electrodes 'of the other unit. This set of conditions has been found to give good results in practice, but even better results may be secured in some installations by isolating the discharge electrodes of 'one unit during the half cycle that the discharge electrodes of the other unit are being charged. In other words, the potential of any discharge electrode is never allowed to drop to the potential of its complementary collecting electrode, .even during the periods when it is bypassed or isolated from the unit undergoing energization. In the embodiment shownin Fig. 5, this isolationof the discharge electrodes of alternate units during alternate half cycles is brought about by thermionic rectifiers Va and-V4. Otherwise the electrical connections are the same as those shown in Fig.2. As shown, rectifier V: permits current to flow readily from terminal 8 to discharge electrode 3 when 8 is negative with relation to 3, but when 8-is positive, rectifier Va acts as'a closed electrical valve and the charge on 3 can only get away by leaking'through the gas surrounding 3 to the collecting electrode. Spark gaps may be used in place of rectifiers V3 and V4- with satisfactory results, but the vacuum tube rectifiers, although much more expensive, seem to give smoother circuit conditions.

Figs. 3,and 4 show' circuits in which the results obtained in the circuit of Fig. 5 can be obtained with mechanical switch rectifiers. All the switches shown are turned with four pole synchronous motors and rotate mechanical degrees while the alternating current source changes through electrical degrees. The two switches ofany arrangement shown in these figures can, therefore, be rotated by the same motor if that is a convenient manner of operation. In Fig. 3,

the switchingjs accomplished. with two switches S1 and $2, each of which has two circumferentially positioned rotating conductors 3|, 3!, 33

- and 34. If terminal 8 is positive and terminal 9- is negative when the switches are in the position shown in Fig. 3, the collecting electrodes of both units will be positive, discharge electrode 3 of unit B will be negative, and discharge electrode 3 01 unit A will be isolated. Upon elecaocaeea trode 3 of unit A will be the residual charge from the previous half cycle. It will be again energized during the next half cycle when terminal 8 is negative and conductors 3l-3fl have been rotated through 90 mechanical degrees. The collecting electrodes are always positive.

a By adding to the system a shoe grounded as shown in Fig. 3a, this system also will operate to bring the opposing electrodes to ground potential in alternate half cycles.

It is sometimes advisable to divide an electrical precipitator into more than two units or sections and to energize each unit independently of the-others. Fig. 4 shows how this can be done by using the principles of the present invention. The four units A, B, C, D indicated are connected through three mechanical switches S1, S2, S3 to the high voltage winding of a trans former. Rectifier S1 causes the current in conductors 4i and 42 to be of a chosen polarity at all times. Bectifying switch S2, making one complete revolution for every two complete cycles of the supply current, connects 'unit A to one of the 'half cycles and unit B to another half cycle during that period. Switch S3 separately connects units C and D to the supply source during the other two half cycles during the two cycle Y period.

The addition to the system of shoes 43 and 45, connected to ground as shown in Fig. 4a, changes the system from one in which the discharge electrodes are isolated between charges to one in which the discharge electrodes are grounded between charges.

In the hookups shown in Figs. 6, '7 and 8, the collecting electrodes and the midpoint of the secondary winding of the transformer are permanently connected to ground. In these sys-' ms therefore the charge across the opposed electrodes of the treating unit is one half the full available voltage of the transformer.

In Fig. 6, thermionic rectifiers V1 and V2 permit the discharge electrode 3 of treater A to be charged when terminal 8 is negative and discharge electrode 3 of treater B to be charged when terminal 9 is negative, the dischargeelectrodesbeing isolated between charges.

In Fig. 7, the same effect is obtained with mechanical rotating switches.

In Fig. 8, rotating switches S1 and S2 alternately connect terminals 8 and 9 with the discharge electrodes 3 of the treater units in the order A, D, B, C, isolating the discharge electrode between charges.

In the hookup shown in Fig. 9, both the discharge electrodes 3 and the collecting electrodes 90 are insulated from the grounded treater shells l. The collecting electrodes 90 of treaters A and B are permanently connected to terminals 3 and 9, respectively, of the transformer secondary. Switch S1 alt nately connects the midpoint of the secondary discharge electrode 3 of treater unit A and to discharge electrode 3 of treater unit B.

By the addition of shoe H, connected to ground as shown in Fig. 9a, the discharge electrodes can be brought to ground potential between charges.

A similar result to that obtained by the hookup shown in Fig. 9, can be obtained by replacing switch S1 by two thermionic valves as shown in Fig. 91), having their filaments connected to the midpoint of the transformer and their plates connected. one to the discharge electrode of treater unitA and the other to the discharge electrode of treater unit 3.

In Fig. 10 is shown a hookup in which the midpoint of the secondary winding of the transformer and the collecting electrodes of the treater units are permanently connected to ground, while the discharge electrodes 3 of treater units A and B are alternately connected to terminals 8 and 9 of the secondary through synchronous switches S2 and S3, respectively. Between charges, the electrodes 3 of treater units A and B are connected to ground through synchronous switches S1, S2 and S1, S5, respectively.

It will be noted that in all of the embodiments of the invention shown or described, every successive half cycle is applied at the same polarity (in the same electrical direction) alternately to a plurality of parallel divided streams of the gas to be treated, so that each half cycle of current is effectively used to energize in the same direction one of a plurality of gas treating units carrying parallel streams of the gas under treat nected to a source of alternating current, means connecting one electrode of each of said pairs of complementary electrodes to a high voltage terminal of the transformer, means connecting the opposed electrodes of saidpairs in common to at least one point on the high voltage winding of said transformer, and energy directing devices adapted intermittently to disconnect an electrode of successive treater units from the high voltage winding of the transformer in synchronism with the alternations of current, whereby the current is intermittently impressed across the complementary electrodes of the treater units so as to produce in each of said units when energized an electric field of the same polarity.

2. Apparatus for treating gases comprising a said pairs of complementary electrodes to a high voltage terminal of the transformer, means connecting the opposed electrodes of said pairs in common to at least one point on the high voltage winding of said transformer, and thermionic rectifiers adapted intermittently to disconnect an electrode of successive treater units from the high voltage winding of the transformer in synchronism with the alternations of current, whereby the current is intermittently impressed across the complementary electrodes of the treater units so as to produce in each of said units when energized an electric field of the same polarity.

3. Apparatus for treating gases comprising a plurality of treater units each ofwhichcomprises at least -one pair of complementary electrodes, means for passing a gas to be treated through said treater units in parallel streams, a high voltage transformer having its low voltage winding connected to a source of alternating current, means connecting one electrode of each of said pairs of complementary electrodes to a high Has voltage terminal of the transformer; means connecting the opposed. electrodes of said pairs in common to the midpoint of the high voltage winding of the transformer, and energy directing de- 5 vices adapted intermittently to disconnect an electrode of successive treater units from the high voltage winding of the transformer in synchronism with the alternations of current, whereby the current is intermittently impressed across the complementary electrodes of the treater units so as to produce in each -of said units when energized an electric field of the same.polarlty.-

4. Apparatus for treating gases comprising a plurality of treater units each of which comprisesat least one pair of complementary electrodes, means for passing a gas to be treated tillers adapted intermittently to disconnect an electrode of successive treater units from the high voltage winding of the transformer in synchronism with the alternations of current, whereby the current is intermittently impressed across the complementary electrodes of the treater units so as to producein each of said units when energized an electric field of the same polarity.

5. Apparatus for treating gases comprising a plurality of tneaterunits each of which comprises at least one pair of complementary electrodes, means for passing a gas to be treated through said treater units in parallel streams, ahigh voltage transformer having its low voltage wind ing connected to a source of alternating current, means connecting pairs of complementary electrodes to a high voltage terminal of the transformer, means connect- \ing the opposed electrodes of said pairs in common to the midpoint of the high voltage winding of said transformer, and energy directing devices adapted-alternately to disconnect one and the other of said high voltage terminals. from electrodes of successive treater units in synchronism with the alternations of current, whereby the current is intermittently impressed across the complementary electrodes of the treater units so as to produce in each of said units when energized an electric field of the same polarity.

6.'Apparatus for treating gases comprising a plurality of treater units each of which comprises at least one pairof complementary electrodes, means for passing a gas to be treated through said treater units' in parallel streams, a high voltage transformer having its low voltage winding connectedto a source of alternating current, means connecting one electrode of each of said pairs of complementary electrodes to a high voltage terminal of the transformer, means connecting the opposed electrodes of said pairs in common to the midpoint of the high voltage winding of said transformer, and thermionic rectifiers adapted alternately to disconnect one and the other of said high voltage terminals from n'ism with the alternations of "current, whereby ,the current is intermittently impressed across the complementary electrodes of the-treater units so as to produce in each of said units when energized an electric field of the same polarity. I

one electrode of each of said electrodes of successive treater units in synchrowinding of said transformer," and energy directi ng devices adapted intermittently to disconnect an. electrode of successive treater units from the midpoint of the high voltage winding in synchronism with the alternations of current whereby the current is intermittentlfi impressed across the complementary electrodes of the treater units so as to produce in each of said units when energized an electric field of the same polarity.

8. Apparatus for treating gases comprising a plurality of treater units each of which comprises at least one pair of complementary electrodes, means for passing a gas to be treated through said treater units in parallel streams, a highvoltage transformer having its'low voltage winding connected to a source of alternating current, means connecting one electrode ofeach of said pairs of complementary electrodes to a high voltage terminal of the transformen'means connecting the opposed electrodes of said pairs in common to the midpoint of the high voltage winding of said transformer, and thermionic rectifiers adapted intermittently to disconnect an electrode of successive treater units from the midpoint ofthe; high voltage winding in syn'-. chronism with the alternations of current,

whereby the current is intermittently impressed I across the complementary electrodes of the treater units so as to produce in each of said units when energized an electric field of the same polarity.

.'9. Apparatus for treating gases comprising two treater units each of which comprises at leastone pair of complementary electrodes, means .for

passing a gas to be treated through said'treater units in parallel streams, a high voltage transformer having its low voltage winding connected to a source of alternating current, means connecting an electrode of. one treater unit to one terminal of the secondary winding of the transformer including a thermionic rectifier positioned a to pass current from the secondary to the electrode when said terminal is negative, means connecting a corresponding electrode of the other treater unit to the other terminal of the secondary including a thermionic rectifier positioned to pass current from the secondary to the electrode when the latter terminal is negative, and

means connecting the opposed electrodes of the treater units in'common'to the midpoint of the secondary winding of the transformer, whereby- 'a charge of constant direction is intermittently impressed across the electrodes -of said treater units in alternation. r

10. Apparatus for treating gases comprising two treater units each of which comprises at least one pair of complementary electrodes, means for passing a gas to be treated through said treater units in parallel streams, a high voltage transformer having its low voltagewinding connected to a source of alternating current, means connecting an electrode of one treater unit to one terminal of the secondary windingof the transformer, means connecting the corresponding electrode of the other treater unit to'the other tervminal o! the secondary, means connecting the from the transformer to the electrode; whereby a charge of constant direction is intermittently impressed across the electrodes of saidtreater units in alternation.

11. A method of precipitating suspended particles from gases which comprises dividing the gas to be treated into a plurality of parallel gas streams, passing each of said gas streams through a treater unit comprising. at least one pair of opposed electrode members, and impressing successive half cycles of a high potential alternating current in the same direction across opposed electrode members of each'oi said treater units in succession.

12. A method of precipitating suspended particles from gases which comprises dividing the gas to be treated into a plurality of parallel gas streams, passing each of said gas streams through a treater unit comprising at least one pair of opposed electrode members, impressing successive half cycles of a high potential alternating current in the same direction across opposed electrode'members of each of said treater units in succession, and bringing the opposed electrodes to the same potential during the interval between charges? 13. A method -of precipitatingsuspended particles from gases which comprises dividing the gas to be treated into a plurality of parallel gas streams, subjecting 'each of said parallel gas streams intermittently to the efiect of a half cycle of a high potential alternatingcurrent in the same direction, and bringing the opposed electrodes to the same potential during the interval between charges.

14. Apparatus for treating gases comprising a plurality of treater units each of which' comprises at least one pair of complementary electrodes, means for passing a gas to be treated through said treater units in parallel streams, a high voltage transformer having its low voltage winding connected to a source 01 alternating current, circuit elements connecting one electrode of each of said. pairsof complementary electrodes to a high voltage terminal 01 the transformer, and circuit elements connecting the opposed electrodes of said pairs to at least one point on the high voltage winding, said circuit elements including energy-directing devices adapted intermittently. to brealgi the conductive connection to one point on the high voltage winding of the transformer. in synchronism with the alternations of current, whereby the. current is intermittently impressed across the complementary electrodes of the treater units so as'to produce in each of said units when energized'an electric field oi the same polarity.

HARRY A.

Images