IEEE Transactions on Electrical Insulation Vol. EI-17 No.2, April 1982

PULSE CORONA DISCHARGE IN ELECTROSTATIC PRECIPITATORS

H. I. Milde

Ion Physics CompanyA Division of High Voltage Engineering Corporation

Burglington, Massachusetts

ABSTRACTIn electrostatic precipitators (ESPs) the electric

field is responsible for producing ions in thevicinity of the corona wires, charging particles,and transporting charged particles to the collectingplate. In standard Cottrell-type precipitators,these functions are performed by applying a dc vol-tage between corona electrodes and collecting plates.Because ion production requires a high electricfield strength near the cathode while particletransport is optimized in a uniform field, thisarrangement is always a compromise, and sometimes apoor one. Energizing precipitators with both a dcbase voltage and superimposed pulse voltage, on theother hand, provides for a separation of the functions;particle transport being performed by the dc basevoltage and ion production by the pulse voltage.

Besides offering improved control, pulsed energiza-tion provides for inherently better performance ofESPs, due in part to enhancement of particle chargeas a result of ion density concentration and also toa more uniform corona current distribution along thelength of the corona wire. This paper discussesthese aspects of pulse charging as well as its effecton back corona, a phenomenon which degrades performanceof ESPs for high resistivity dust conditions. Labor-atory and full scale field tests of pulse energizedESPs are also described and analyzed. These testsshow that the application of fast pulses to ESPsresults in considerable improvement of collectionefficiency.

1. INTRODUCTION

Electrostatic precipitation is one of the mostpractical methods of separating particulates fromexhaust gas streams. For large gas flows the conven-tional electrostatic precipitator consists of a multi-tude of ducts, each approximately 0.2 m (9") in width,2.5 m (7') long, and 10 m (30') high. [see Fig. 1].Each duct is bounded by collecting plates and in thecenter are several corona wires about 2.5 mm (.1") indiameter. A negative voltage on the order of 30 to50 kV is applied to the corona wires producing coronacurrents of 30 PA to 3 mA per m (10 PA to 1 mA perfoot) of wire length. Particulates entrained in thegas stream will be charged by the corona current andpulled towards the anode by the action of the electricfield. The particulates are collected, in the formof a dust layer, on the anode which is periodicallyrapped.

While ESPs operate, in most cases, very efficientlyand reliably, the collection of dust with a specificresistivity p >1011 Qcm poses very severe problems.In such cases the product of current density J and

resistivity p can reach values in excess of theelectrical breakdown strength of the dust layer. Theresulting breakdown produces, among other constituents,positive ions which will travel towards the negativelycharged particulates and thus partially offset thenegative charge on the particles. This phenomenon,called back corona, is especially prevalent in ESPsat coal burning power plants using coal with a sulfurcontent below 1%, since low sulfur coal usuallyproduces a high resistivity dust layer.

When back corona conditions exist, it is necessaryto lower the base voltage until the condition is undercontrol. This reduction in voltage results in a non-uniform or spotty corona emission along the wireelectrodes, insufficient current, and control diffi-culties.

Pulse energization offers a most attractive solutionto the back corona problems.

0018-9367/82/0400-01 79$00. 75 c3 1982 IEEE

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IEEE Transactions on Electrical Insulation Vol. EI-17 No.2, April 1982

)highpvopltyge

powersuppl1y

Di rectionof

gas flow

Fig. 1: Standard Two-EZectrode Precipitator

2. BACKGROUNDThe origins of pulse energization of ESPs reach back

as far as 1931, when R. Heinrich et al [1] applied fora U.S. patent in which the application of sharp elec-trical impulses to a precipitator is described.

In 1952 H. J. White [2] reported on the results ofthe first full scale field tests. During the testshigh voltage pulses of approximately 100 l's durationwere applied to a wire-plate type precipitator. Thepulses were applied by the action of a rotary sparkgap, a pulse transformer, and a blocking diode whichprevented the current from flowing back to the pulsegenerator.

In 1967, J. E. Luthi [3,4] described a three elec-trode arrangement whereby the charge carriers wereproduced by a pulse voltage between the third elec-trode and the anode. A more sophisticated three-electrode arrangement was recently discussed by Penneyand Gelfand [5], whereby the potential on the thirdelectrode was reduced at the same time that a pulsevoltage was applied to the corona wire. This methodrequires, however, handling of rather large displace-ment currents.

A unique pulse energization system nicknamed "BoxerCharger" was described by Masuda et al. [6,7]. Thesystem operates as a precharger to an ESP. In thelatest version the electrodes consist of double-helices energized by a pulse propagated along thedouble-helix. A separate charging field is providedby an alternating voltage applied to adjacent double-helical arrangements.

Full-scale commercial pulse energization systems forthe standard wire-plate arrangement have recently beendeveloped [8,9,10] and are beginning to find applica-tion.

3. BENEFITS OF PULSED ENERGIZATIONFor the following discussion only two-electrode

arrangements were considered and it was assumed thatnarrow pulses were superposed over a dc base voltageat a frequency of approximately 100 to 300 pulses persecond (pps), as indicated in Fig. 2.

3.1 Independent ControZ of VoZtage and Current

In standard precipitators, the applied dc field isresponsible for ion production, particle charging,and particle transport. Performing these three func-tions in a fixed geometry can lead to severe ineffi-ciencies, especially under back corona conditionswhere the current density must be limited. Pulseenergization offers here a unique advantage by allow-ing independent control of voltage and current. Thebase voltage is adjusted to a value just below coronaonset, while the corona current is controlled by thepulse repetition frequency and pulse amplitude to ashigh a value as is beneficial without encounteringsparking or back corona problems.

Voltage

Time

Fig. 2: VoZtage-time characteristics of pulseenergization system

3.2 Uniform Production of Corona Current

Since the electric field is far in excess of thecorona onset voltage during the pulse period, a verybright glow is produced over the entire length of thecorona wires during pulse application. This is instark contrast to the spotty corona observed for lowvoltage dc corona. This is shown in Fig. 3, wheretime-integrated photos of the corona appearance fordc and dc-plus-pulse conditions are presented.Uniform production of corona by pulse energizationallows each precipitator section to contribute equallytowards particle collection. In the case of spottycorona some portion of the precipitator might receive

too much current and exhibit back corona while otherportions have insufficient corona current.

Pulse energization also overcomes minor localizedwire contamination, since the electric field duringpulse application is high enough to produce coronaeven around a contaminated wire.

18Q

181Milde: Pulse corona discharqe in electrostatic precipitators

the basic assumption of an increased collection fieldwith an increase in wire diameter holds true also forthese conditions as for examnple shown in Fig. 3.9 ofReference [12].

3.4 Reduced Ervosion by the Use of Larzger Di=reterCorona WZires

Wire erosion leading to breakage is one of the mostpersistent and troublesome maintenance problems inESPs. Using larger diameter wires would reduce thisproblem in two ways, firstly by operating the precipi-tator in a pulse mode sparking frequency is greatlyreduced (approximately one spark per minute comparedto a typical 60 sparks/minute for dc operation), andsecondly, using heavier gauge wire more material mustbe eroded before wire breakage occurs.

_" _ T \,x, X ,/ / / _ !:'}~~~~~~~~~1

0 2'5 75 I

Fig. 4: Distiibuxtion of? electricaZ potfentiaZ insidea precipitator duc7t. Radiuls 0f wre = 1.38x10O3m;WiPe-to_-wir2e_spactrng - 1. 5xl2o- im; wiJre-tc-pZatespacinzg = 0~lm; corona voZtage = 60 kV.

3. 5 Redztued ChaiPging Time as a :Reou It of SpaceeCharge Buncehing

Particles entrained in the gas stream are chargedby negative ions emanating from the high field regionclose to the cathode. This process is briefly illus-trated in Fig. 6. Free electrons in the high fieldregion near the cathode are ziccelerated towards theanode and produce, by inelastic collisions with gasmolecules, positive ions, and free electrons. Tlleseelectrons, in turn, attach p-refe-rentially to elect-ro-negative molecules such as S02 and 02 to form negativeions. As those ions move across the cathode-anodegap, some will encounter particles aiid contribute tothe charging.

Fig. 3: CorRonar appearvance undep de: and de-pZws-puwZae conldi tionzs.A. dc cond ition. dc VoZtacge: 36 krV; average current>:

4.5 mAB. dc + puZse. de voZt>age: 27~kV; avr7sYage cuP2rentf:

6;.2 mA, pulDse vso7tage : 55 kV atv 150 pps-.

3.3 Increased Ch<arging and CoZZection Field by theUse of Corona Wi}ve8 of L,arger o)icetep

Because ve-rv higli elec-tric fields are producedaround corona wires during pulsing, it is possibleto utilize corona wires of larger diameter and stillobtain adequate corona current. This fact can beutilized to produce a highier and more uniform elec-t-ric field in the proximity of thie aniode [l1], whereit is most beneficial for particle transport. A con-ventionally energized precipitator requires a strongfield concentration a-round the coronia wire to provideadequate corona current without sparking. Such apotential distribution is presented in Fig. 4. Bychoosing larger diameter corona wires and closerspacing between them, miore uniform and higher(collecting) fields can be obtained for the sameapplied voltage as shown in Fig. S. Fnergization bysharp voltage spikes are, however, requiired for thesesomewhat unfavorable emission conditions.

The plots for Figs. 4 and 5 were calculated for zerocorona current and are therefore not accurate for allcases, but represenit a good first approximation,especially for poorly energized precipitators. Fornonizero current flows, the fi.eld is reduced at thecatlhode and increased towards the anode. Hlowever,

IEEE Transactions on Electrical Insulation Vol. EI-17 No.2, April 1982

14

12

10

wire: 0 2.5 5 7. 5 1

Fig. 5: Electric field between corona wire and ductwaZZ for an applied voZtage of 50 kV. 1) .276 cmwire diameter, 15 cm wire-to-wire distance. 2) .276cm wire diameter, 7.5 cm wire-to-wire distance.3) .47 cm wire dia., 7.5 wire-to-wire distance.4) .79 cm wire diameter, 3.8 cm wire-to-wiredistance. 5) IdeaZZy uniform.

Electron

WIRE 0>NEG |-- 8- 9-

Positive Molele NegativeIon Ion Particle

/ /-"Atiode

D ustPay

Fig. 6: IZlustration of particZe charging process

Since the electric field determines the maximumobtainable charge, a comparison of the electric fieldfor dc and pulsed energization shall be made. For dcenergization the electric current flows continuouslyfrom cathode to anode and the electric field, whichis primarily a function of geometry, applied voltageand average current, falls off quickly from a highvalue near the cathode and reaches a plateau which isthen maintained to the anode (Fig. 3.3 of Ref. [12]).The average particle charge will approach a valuecorresponding to the plateau-field.

For pulsed energization, the current flows in theform of distinctive ion clouds which move at anapproximate speed of 40 m/s to the anode. Each ioncloud will interact with an entrained particle forapproximately 1 to 3 ms, depending on the particlelocation within the duct (Fig. 8 of Ref. [13]). Onlyduring this interaction time will the particle becharged. Further charging must await the arrival ofthe next ion cloud which will occur at the appliedpulse repetition frequency.Associated with the ion cloud is a very high spacecharge concentration which causes the electric field

to peak towards the moving front of the ion cloud asshown in Fig. 7. In calculating the electrical fieldin Fig. 7, a cylindrical geometry and a constantcharge density between rl and r2 was assumed formathematical ease. Under these conditions the electri-cal field is determined by the following relations(The assumption of constant current density is notvery restrictive since it affects only the fieldwithin the ion cloud, but not at its end points r1and r2. See also Ref. [14] . )

x

r.,

.,,

*,1

Radial Distance in cm

Fig. 7: EZectric field within concentric cyZindricaZelectrodes for pulsed energization (approximately1 msec after puZse appZication, when the ion cloudhad propagated from the cathode to the region be-tween r1 and r2)-

The maximum or saturation charge that can be im-parted to a particle entrained in the gas stream isdetermined by the relation (which ignores diffusioncharging which is important for submicron-sizeparticles)

q = 12K

orE a2E5 c+2 (1)

where qs is the saturation charge [C], K the relativedielectric constant, co the dielectric constant ofvacuum 8.8x10-12 [F/m], a the particle radius [m],and E the electric field in the vicinity of particle[V/m].

182

3

2

Mlilde: Pulse corona discnarre in electrostotic precipitators

2 X C0 E = qr for ro < r < r

q ((r2 r2 )2 E = q/r + 2 for r, < r < r2

(r 2-r 2)r2 1

qw + q =27c0r

for r2 <r <R

(2)

2 V £o U _ - + _ r12 ln(R/rl) - r22 rn(R-r2)(r22-rl2)

ln(R/r0)

Plower Switch

C ouplingCapacitor

BlockingInductor

where E is the electric field V/m, qw the charge oncorona wire C/m, r0 the radius of corona wire 1.5x10-3m, r1 the inner boundary of ion cloud 5x10-2 i, r2 theouter boundary of ion cloud 9Xl0-2 m, R the anoderadius I.3xO-1m,U the applied base voltage 30 kV,qc the charge emitted per pulse 10-6 C/m and co di-electric constant of vacuum 8.8x0l-12 F/m.

This high field, which is substantially higher thanthe corresponding plateau field in dc energization forequal voltage, geometry, and average current providesthe means for increased particle charging. Eventhough the particle remains only for a fraction of theinteraction time in the very high field zone, it canbe shown that 90% particle charging corresponding tothe maximum field can be accomplished in approximately100 particle-ion cloud interactions, or in less than1 meter of travel.

The above discussion gives a reason why pulse ener-gization should provide enhanced charging for parti-cles moving somewhere in the mainstream of the duct.However, at every corona wire location approximately10% of all entrained particles will pass in thevicinity of the corona wires and be exposed to elec-tric fields several times larger than in the centerof the duct. In this case the particle will receivea substantially higher charge, which will be lessdependent on dc or pulsed energization. Since thecorona wires are approximately 20 cm apart from eachother, it is obvious that this charging process re-

quires many particle-corona wire interactions, anddust re-entrainment might not allow the average

particle to obtain a charge corresponding to the highfield around the corona wire. Nonetheless, particlecharging in the vicinity of the corona wires couldreduce or eliminate the charge difference between dcand pulsed energization. Detailed measurements ofparticle charge for dc and pulsed energization arestill needed to provide an answer to the possiblecharge enhancement by pulsed energization.

3.6 Increased ColZection Field Due to SpaceCharge Bunching

The electric field near the anode, which is primarilyresponsible for the transport of the particles is en-hanced over the pure dc case as can be seen in Fig. 7.The magnitude of the effect was analyzed in Ref. [13]for a specific case where a 20% increase in the aver-age collection field or particle migration velocitywas estimated.

a.) High Voltage Pulse Capacitor Circuit (Narrow Pulse)

BlockingInductor

CouplingCapacitor

SwitchPowerSupply L Precipitator TR

Pulse TransformerCapacitor

b.) Pulse Transformer Circuit

Fig. 8: Circuit diagrams of pulse generators

4. PULSING CIRCUITS

4.1 GeneraZ

Today two systems, schematically shown in Fig. 8 arecommercially available. The first one is based oncharging a capacitor or pulse forming network to thedesired pulse voltage and then discharging it througha low inductance path onto the precipitator, while thesecond system charges a capacitor to a relatively lowvoltage and then applies the pulse via an SCR switchand pulse transformer.

The main difference between the two systems is pulsewidth and pulse risetime. The first system, becauseof its low inductance, is capable of producing pulsesof 1 lisec duration, while the second system has alimited di/dt capability and produces pulses on theorder of 100 ps.

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IEEE Transactions on Electrical Insu'lation Vol. EI-17 flo.2, April 1982

Generation of fast rising, narrow pulses requires aswitch which exhibits low inductance, high currentcarrying capacity and high di/dt-capability. Also,the switch must be able to recover its electricalholdoff strength after pulsing and have low resistanceand low losses during conduction. The only switchingdevice capable of fulfilling all these requirements isa high voltage spark gap. At first glance spark gapsmight appear as a step back in history, but preliminarydesigns for a very futuristic energy scheme, fusion,incorporate spark gaps to fulfill the demanding switch-ing requirements of commercial reactors 115].

Z.Z - - jE6ATIVE TIP

d2 0SCM2.0

tPOSITIVE PLANE1.8 _\I-

1.4

iz

It'

,O5 .1 .5 5 S0_- PULSE WIDTH IN MICROSECONDS

Fig. 9: Breakdown voZtage as function of puZse widthfor atmospheric air. R. Strigel, "EZektrischeStoBfestigkeit", Springer VerZag, (1955) .

Vp . . breakdown voZtage for puZse voltage

V0 . breakdown voltage for static voZtage

Risetime of appZied voltage is 35 nanoseconds.

4.2 Short Versus Long Pulses

4.2.1 GeneraZ

To utilize pulses in precipitators short pulsesoffer some inherent advantages, partly because of thehigher breakdown strength of gases under short pulseconditions, as for example shown in Fig. 9 and partlybecause of unusual corona characteristics under shortpulse application [16,17]. Very early in our experi-mental effort we had also found that the emittedcharge per pulse was only slightly determined by pulsewidth and primarily by pulse amplitude [18]. Thisfinding, which was recently confirmed by ProfessorMasuda et al. [19], provided the basis for selectingpulses with a pulse width less than 1 ps.

In the following an attempt is made to identify dis-tinguishing features of precipitator behavior forshort versus long pulses.

4.2.2 VoZtage Decay

If short pulses are applied, it is possible to con-vert nearly all the capacitively stored energy intocorona energy. On the other hand for long pulses itis reported [10] that the voltage on the precipitatoris returned to the base value by special circuitrywhich recovers some of the stored energy in the pre-cipitator and returns it to the pulse capacitor.

It is here speculated that this difference is dueto the space charge effects of the positive ion cloud.At the end of a very narrow voltage pulse a positiveand negative space charge cloud remains in the vicin-ity of the cathode as calculated in Ref. [13] andshown in Fig. 10. This space charge enhances thefield in close proximity to the cathode and depressesit in the region of the negative ion cloud. As longas the positive ion cloud is present, strong coronaemission will take place from the cathode and willcontinue even during the decaying portion of theapplied voltage thus providing a means to return theprecipitator voltage to the base dc level.

Contrary, in the case of long pulses with slow rise-time, the positive ion cloud is constantly depleted sothat at peak voltage only negative space charge re-mains which depresses the cathode field and quenchesany further corona emission. Under these conditionsthe pulse voltage would remain on the precipitatoruntil removed by sparking or transfer of the storedenergy from the precipitator to storage capacitoroccurs. The distinction between short and long pulsesdepends on the removal time of positive ions. Forthe conditions shown in Fig. 10 the removal time is8.3 ps, using an ion mobility of 2x104 m2/Vs, anelectric field of 3 MV/m and an ion travel of 5xlO-3 m.Pulses on the order of 1 Ps would therefore be termedshort while pulses on the order of 100 ps would beconsidered long.

With the help of this picture one could then postu-late that for long pulses the maximum charge emittedby the corona wire is lIimited and can be calculatedfrom Eq. (2) by setting the field on the cathodeequal to the corona onset voltage. Settingqw/(27coro) = 20 kV/cm, r1 = r1 = 0.15 cm, r2 2 ca,R = 13 cm, U = 60 kV one arrives at the quenchingcharge qc of 1.lx10-6 C/m of corona wire. At 100 ppsthis would correspond to a current limit of 110 oA/m,which is in very close agreement with actual voltage-current measurements [20].

> 49.

3 .

~.4 16.

i4lon D nsity

Fied11

8 1() 12 14

Radial listance (mr)

Fig. 10: FieLd distortion due to space chargeimmediately after pulse termination.(From a paper by L. IV. Menegozzi and P. L. FeZdman.The 70hysics of P?uZse Energization of EZe'trostaticPrecipitators presented at Third Symposium on theTransfer and UtilZization of ParticuZate ControZTechnoZogy - EPA Sponsored, OrZando, 4arch 1981.)

184

J.

Milde: Pulse corona discharge in electrostatic precipitators1

4.2.3 Narrow Pulses More Suitable to Large DicaneterCorona Wires

In order to realize the benefit of a larger diametercorona wire (see Sections 3.3 and 3.4) it is necessaryto apply very high voltages to the corona wires inorder to overcome the less favorable emission geome-tries. Since the electrical breakdown strength ofgases is strongly influenced by the pulse width,narrow pulses have a distinct advantage in providingample corona current without excessive sparking.

The associated increase in collection efficiency ispresented in Fig. 11, which clearly shows the signifi-cant improvement in particulate collection for pulsedenergization. However, it also shows that for lowresistivity a conventionally energized precipitatoroperates at a higher collection efficiency than apulse-energized precipitator for very high resistivity.

100 -

90 -4.2.4 Effect of FieZd Bunching is Reduced by LongPulses

If the negative ions are produced over a long period,the ions produced first will have already traveled aconsiderable distance towards the anode before the endof the applied pulse, thus producing a more extendedion cloud. For example, in 50 ps the ions producedfirst would have already traveled a distance of approx-imately half a centimeter. This fact would reduce themaximum E-field within the cloud, as can be shown withthe aid of Eq. (2) and would therefore also reducethe benefits of field bunching.

N,80 -

a)

0)

P.0

0)

t5. EXPERIMENTAL RESULTS

Pulse energization experiments have been performedfor several years jointly by Research Cottrell and IonPhysics Company, a division of High Voltage Engineer-ing Corporation, both in the laboratory and on severalfield installations. The main emphasis of these testswas directed toward measurement of particle collectionefficiency by means of optical density measurementsand duct sampling.

I'l

70

60 -

50 -

40 -

30 -

20 -

> pulsed

I "I

N ,dc

\N-

10P1c1 i v12

Particulate Resistivity in

NI

N1-

iol3ohm cm

Collection efficiency of an electrostatic precipi-tator can be expressed by the modified Deutschequation [21]

ri = 1 - exp[- (WA/V) ]

Fig. 11: CoZZection efficiency as function ofFZy-Ash resistivity for puZsed and dc energization(from laboratory data).

(3)

where n is the collection efficiency, WK the modifiedmigration velocity ft/min, A the collection area inft2, V the gas flow in acfm, and m the exponent depen-dent on inlet particle size distribution (typicallybetween 0.5 and 1).

From numerous measurements it was found that theration (frequently referred to as enhancementfactor) of migration velocities for pulsed versus dcenergization varied between 1.2 and 2 depending onresistivity of the collected fly ash, as shown inTable 1.

TABLE 1

Enhancement as Function of Ash Resistivity

Resistivity - ohm cm 10 | 10 | 10

Enhancement H 1.2 1.5 2

An increase in migration velocity is of great eco-nomic significance, since according to Eq. (3) an in-crease in migration velocity is equivalent to a corres-ponding increase in collection area. Consequently,an increase of wK by a factor of two due to pulseenergization has the same performance impact as in-creasing dc energized precipitator's size by a factorof two.

6. CONCLUSIONSAfter many years of incubation, it appears that

pulsed energization will become a welcome addition toelectrostatic precipitators. In particular it willextend the range of efficient particle collection toparticulate matter of higher resistivity.

In March 1980 a large precipitator for a 425 MWutility station was equipped with six IPC pulsesystems each consisting of 4 pulser units. The systemhas been in constant use, 24 hours a day, over thelast Il2 years. The measured increase in particle mi-gration velocity was on the order of 50% which is inagreement with expectations for the type of coal used.

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IEEE Transactions on Electrical Insulation Vol. EI-17 No.2, April 1982

AC KNOWLEDGMENT

The author wishes to express his gratitude to theresearch staff of Research Cottrell and Ion Physicsfor fruitful discussions. In particular P. Feldman,L. Menegozzi, and S. Kumar from Research Cottrell andC. Schubert, N. Harris, J. Ottesen, R. Evans, andC. Salisbury from IPC.

REFERENCES

[1] R. Heinrich, W. Feldmann,Electrical Cleaning ofFluids, U.S. Patent 2,000,017, Applied April 4,1931, granted May 7, 1935.

[2] H. J. White, A Pulse Method for Supplying HighVoltage Power for Electrostatic Precipitation.Trans, AIEE, Nov. 1952, p. 326-329.

[3] J. E. Liuthi, Grundlagen zur elektrostatischenAbscheidung von hochohmigen Stauben, Diss. Nr.3924 ETH Zurich 1967, Prof. A. Guyer Referent.

[4] B. B6hlen, J. Luthi, A Guyer, Neues Verfahrenzur elektrostatischen Gasentstaubung, Chemie-Ing.-Techn. 39 (1967) Heft 15 910-913.

[5] G. W. Penney, P. C. Gelfand, The TrielectrodeElectrostatic Precipitator for Collecting HighResistivity Dust, JAPCA, Jan. 1978, Vol. 28,53-55.

[6] S. Masuda, D. Akutsu, Boxer Charger - A NovelCharging Device for High Resistivity Powders,Conf. record of IEEE/IAS Annual Mtg., 1978,16-22.

[7] S. Masuda, A. Mizuna, H. Nakatani, H. Kawahara,Application of Boxer Charger in Pulsed Electro-static Precipitators, Conf. record of IEEE/1ASAnnual Mtg. 1980, 904-911.

[8] H. I. Milde, P. L. Feldman, Pulse Energization ofElectrostatic Precipitators IEEE/IAS (1978)Annual Mtg., Conf. record, p. 66-70.

[9] P. L. Feldman, P. Aa, Operating Results from theFirst Commercial Pulse Energization System toEnhance Electrostatic Precipitator Performance,Conf. records, American Power Conference, Chicago,April 1981.

[10] P. Lausen, H. Henriksen, H. M. Petersen, EnergyConserving Pulse Energization of Precipitators,IEEE/IAS 1979 Annual Mtg., Conf. record, 163-171.

[11] H. I. Milde, Electrostatic Precipitation, U.S.Patent 4,183,736, Applied August 1972, grantedJanuary 1980.

[12] S. Oglesby, G. B. Nichols, Electrostatic Precipi-tation Pollution Engineering and Technology/8,M. Kekker, Inc., p. 62 (1978).

[13] L. N. Menegozzi, P. L. Feldman, The Physics ofPulse Energization of Electrostatic Precipitators,Presented at Third EPA Sponsored Symposium onTransfer and Utilization of Particulate Control

Technology - Orlando, March 1981.

[14] M. J. Joergense, J. T. Kristinusen, P. Lausen,Influence on Particle Charging of ElectricalParameters at dc and Pulsed Voltages, Presentedat Third EPA Sponsored Symposium on Transfer andUtilization of Particulate Control Technology,Orlando, March 1981.

[15] Proceedings of Workshop on Switching Requirementsand R&D for Fusion Reactors, March 24-26, 1976,EPRI Report #ER376-SR.

[16] J. B. Thomas, T. R. Williams, Pulsed Corona Dis-charges, 1962 Gas Discharge and the SupplyIndustry, London: Butterworth, p. 202-208.

[17] D. B. Miller, S. E. Collier, J. L. Maitten,J. M. Niziolek, P. J. Phillips, Measurements ofPulsed Corona in Coaxial Electrode Structures,IEEE/IAS 1978, Conf. Records, Annual Mtg. 128-135.

[18] H. I. Milde, Reduced Power Input for ImprovedElectrostatic Precipitation Systems, U.S. Patent4,133,649, Applied December 1973, grantedJanuary 9, 1979.

[19] S. Masuda, H. Nakatani, K. Yamada, M. Arikawa,A. Mizuno, Production of Monopolar Ions byTravelling Wave Corona Discharge, IEEE/IAS 1981Conf. Records, Annual Mtg. 1066-1073.

[20] H. H. Petersen, P. Lausen, Precipitator Energiza-tion Utilizing an Energy Consuming Pulse Genera-tor, Conf. Records of Second Symposium on theTransfer and Utilization of Particulate ControlTechnology, Vol. II, 352-369.

[21] P. L. Feldman, Effects of Particle Size Distri-butlon on the Performance of Electrostatic Pre-cipitators. Paper 75.02-3, Presented at the 68thAnnual Mtg. of APCA, Boston, June 1975.

This pa.per was presented at the Symposiun on Coronaand Non-spark Discharges, held at the Conference onEZectricaZ InsulZtion and DieZectric Phenomena,27 October 1981 in Whitehaven, PA.

Manuscript was received 12 December 1981.

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