1

Efficient streamer plasma generationGuus Pemen, Hans Winands, Liu Zhen,Dorota Pawelek, Bert van HeeschEindhoven University of Technology, Department of Electrical Engineering, The

Netherlands

• Power sources for streamer plasma generation• Streamer observations• Quantification of radical yields• Discussion

2

10 ns

20 ns

30 ns

40 ns

10 ns

20 ns

30 ns

40 ns

10 ns

20 ns

30 ns

40 ns

10 ns

20 ns

30 ns

40 ns

Gas cleaning effect by:• Interaction through free radicals

• Using ions to charge particles to

enhance their collection

• Electrical discharge, fast HV-pulses

• “Shower of electrons (<12 eV)

• Inelastic collisions with gas molecules

>> Radicals such as O* or OH*

>> chemically highly active

>> easily attach/modify other molecules

3

10 ns

20 ns

30 ns

40 ns

fast CCDend-onview

4

Efficient streamer plasma generation• Creating a streamer plasma in an efficient

manner (use all energy from the mains)

• Creating a streamer plasma that is efficient (from radical production point of view)

5

ns-Pulsed power sources - iExample: TU/e resonant charging – sparkgap - TLT

Filter

3-phase 400 V50 Hz AC

continuous5 kW

1 kV30 s1 kHz

500 kW

30 kV30 s1 kHz

500 kW

100 kV100 ns1 kHz

100 MW

K. Yan et.al., IEEE Trans. Industry Appl., Vol. 38, No.3, May/June 2002, pp.866-872

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ns-Pulsed power sources - iiExample: TU/e 30 kW system for odor control

Corona reactor

DC-bias supply

TLT

Pulse generator

950.5 ppm10.1 ppmH2S

8711858987Total

100013Terpens

841066Furane

10022363Organic sulphur

1000200Chlorinatedcomponents

40570946Aldehydes

932733881Ketone

(cannot be determined)2630Esters

9444787Alcohol

9513271Aliphatic CH’s

100066Cyclic CH’s

9710395Aromatic CH’s

Removal Efficiency [%]Ouput [µg/m3]Input [µg/m3]

950.5 ppm10.1 ppmH2S

8711858987Total

100013Terpens

841066Furane

10022363Organic sulphur

1000200Chlorinatedcomponents

40570946Aldehydes

932733881Ketone

(cannot be determined)2630Esters

9444787Alcohol

9513271Aliphatic CH’s

100066Cyclic CH’s

9710395Aromatic CH’s

Removal Efficiency [%]Ouput [µg/m3]Input [µg/m3]

G.J.J. Winands et.al., IEEE Trans.on Plasma Science, Vol.34, No.5, October 2006, pp.2426-2433

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ns-Pulsed power sources - iiiExample: high temperature corona tar removal in syngas

Corona Reactor

Fan

Window for FTIR

Tar Injector

Corona Reactor

Fan

Window for FTIR

Tar Injector

Effect of temperature on naphthalene removal in synthetic fuel gas

0

20

40

60

80

100

0 200 400 600 800

Corona energy density (kJ/Nm3)

Rem

ain

ing

fra

ctio

n (

%) 200 degr.C, dry

200 degr.C, wet

biogas 400400 degr.C, dry

0

20

40

60

80

100

0 200 400 600 800

Corona energy density (kJ/Nm3)

Rem

ain

ing

fra

ctio

n (

%) 200 degr.C, dry

200 degr.C, wet

biogas 400400 degr.C, dry

S.A. Nair, et.al., Ind. Eng. Chem. Res. 2005, 44, 1734-1741

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AC/DC corona generation - iExample: 2 kW TU/e pilot

Mains

T1

T2T3

C0 CL

L1 L2

L3

D1

TR Corona reactor

-5 -4 -3 -2 -1 0 1 2 3 4 50

2

4

6

8

10

12

14

16

18

Time (ms)

Vo

ltag

e (

kV)

1.5 2.0 2.5 3.0

14

15

16

17

18

Time (ms)

Vol

tage

(kV

)

TU/e patents WO2005/031488 and WO2005/112212

courtesy of EnviTech, Belgium

dV/dt

1 – 3 kV/μs • Few HV components

• High energy efficiency (>90 %)

• Good radical yield (20 % less than for pulsed corona)

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AC/DC corona generation - iiExample: investigations on TU/e – Oranjewoud system

-5 -4 -3 -2 -1 0 1 2 3 4 50

2

4

6

8

10

12

14

16

18

Time (ms)

Vo

ltag

e (

kV)

1.5 2.0 2.5 3.0

14

15

16

17

18

Time (ms)

Vol

tage

(kV

)

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Efficient streamer plasma generation

• Power sources for streamer plasma generation• Streamer observations• Quantification of radical yields• Discussion

11

Overview of experimental set-up

Pulsed PowerModulator

Oscilloscope Computer

Deuterium lightsource

ICCDcamera

UV spectrometer

LensesAir flow in

V I

Trigger signal

Quartzwindow

Air flow out

HVCorona wire

Plate electrode

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Pulse parameters and reactor configurations

Parameter Range

Pulse width 30 - 250 ns

Rise-time (20-80%) 15 - 45 ns

Peak voltage 50 - 90 kV

DC Voltage 0 - 20 kV

Pulse repetition rate 10-1000 pps

Energy per pulse 0 – 2.5 J

Voltage polarity Positive-negative

Parameter Value

Plate heigth [m] 1.1

Plate width [cm] 22

Plate-plate distance [cm] 7.4 – 15.4

# wires 1 - 7

Wire diameter [mm] 0.2 - 15

Wire length [m] < 0.9

Reactor capacitance [pF] 80

Max. flow used [m3∙h-1] 30

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Time-resolved side-view ICCD pictures - i

t = 21 ns t = 26 nst = 16 ns

t = 31 ns t = 41 ns t = 52 ns

t = 62 ns t = 102 ns

a) b) c)

d) e) f)

g) h) 0 100Time [ns]

-40

-20

0

20

40

60

80

100

-50

Vol

tage

[kV

]

15050

a b c d e f g h

i)

G.J.J. Winands, et.al., J. Phys. D: Appl. Phys. 39 (2006) 3010–3017

Pulse width 110 ns, pulse voltage 74 kV, rise rate 2.7 kV/ns. Picture size is ~7x5 cm. White line: reactor wire. Dotted line: reactor wall.

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Time-resolved side-view ICCD pictures - i i

G.J.J. Winands, et.al., J. Phys. D: Appl. Phys. 39 (2006) 3010–3017

Pulse-width 110 ns, pulse voltage -72 kV, rise rate 2.7 kV∙ns-1. Picture size is ~5.5x4 cm. White line: reactor wire. Dotted line: reactor wall.

t = 29 ns t = 34 nst = 25 ns

t = 44 ns t = 49 ns t = 59 ns

a) b) c)

d) e) f)

g) h)

abc de f g h

-50 0 50 100 150

Time [ns]

Vol

tage

[kV

]

t = 105 nst = 87 ns

i)

-100

-80

-60

-40

-20

0

20

40

15

0

1

2

3

4

5

6

40 60 80

Str

ea

me

r h

ea

d p

osi

tion

[cm

]

77 kV (0kV DC)70 kV (0kV DC)70 kV (20kV DC)60 kV (0kV DC)60 kV (10kV DC)52 kV (0kV DC)

Time [ns]

a)

20 1000

0.1

0.2

0.3

Str

ea

me

r d

iam

ete

r [c

m]

b)

Time [ns]

40 60 8020 100

70 kV (20kV DC)

60 kV (10 kV DC)

77 kV (0kV DC)70 kV (0kV DC)

60 kV (0kV DC)

52 kV (0kV DC)

0

20

40

60

80

100

120

140

20 40 60 80 100 120

Time [ns]

Inte

nsi

ty [

cou

nts

/pix

el]

77 kV (0 kV DC)70 kV (0 kV DC)70 kV (20 kV DC)

60 kV (0 kV DC)

60 kV (10 kV DC)

52 kV (0 kV DC)

c)

140

• Streamer density

• Streamer velocity

• Streamer diameter

• Streamer intensity

• Secundary streamer length

• Branching, interconnecting, re-ignition

• Effect of repetition rate and preceding pulses

• Effect of DC-bias voltage

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Primary streamer velocityV

elo

city

[1

06 m

s-1

]

Rise rate [kV ns-1]

0

0.5

1.0

1.5

2.0

0 1 2 3

a)0

0.5

1.0

1.5

2.0

2.5

3.0

40 60 80 100

Voltage [kV]

37 mm57 mm77 mm

Ve

loci

ty [

10

6 m

s-1

]

b)

Results for pulse widths between 30 and 250 ns. a) Wire-plate distance fixed at 57 mm. Peak voltage: 60-70 kV. b) Voltage rise rate fixed at 1.8-2.2 kV∙ns-1.

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Efficient streamer plasma generation

• Power sources for streamer plasma generation• Streamer observations• Quantification of radical yields• Discussion

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Quantification of O-radical yields - i

[O3] per m3 plasma volume

UV absorbtion spectroscopy [O3, exhaust]

Gas flow + plasma volume

Kinetic model (65 reactions, 17 species, RH, T)

[O*] per m3 plasma volume

Plasma volume

total number of [O*]

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Quantification of O-radical yields - ii

It appears so !

Primary streamers better than secondary ?

40 60 80 100

Voltage [kV]

0

2

4

6

8

30 ns FWHM

50 ns FWHM

100 ns FWHM130 ns FWHM

O* p

rod

uct

ion

[m

ole

kW

h-1

]

O* radical yield as function of voltage and pulse width. The rise rate of the pulses was

fixed 2.2-2.7 kV/ns. DC bias: 0-20 kV.

• 7.0 mole/kWh corresponds to 5.3 eV/molecule.

• Theoretical cost to produce an O* radical is 3 eV.

• Thus more than half of the available energy is used to produce O* radicals

• Excellent yield.

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Quantification of O-radical yields - iii

• Primary better than secondary streamers

• Primary yield increases if velocity is increased (because local E-field increases and consequently so does the electron energy)

0

2

4

6

8Primary

Secondary

0 0.5 1.0 1.5 2.0 2.5

Velocity [106 m s-1]

O* pr

oduc

tion

[mol

e kW

h-1]

O* radical yield for primary and secondary cathode directed streamers as a function of the primary streamer velocity. The error bars

indicate the standard deviation.

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Quantification of O-radical yields - iv

• Negative polarity better for radical production

• However, matching is worse for negative polarity

0

2

4

6

8

10

12

0 0.5 1.0 1.5 2.0 2.5

Velocity [106 m s-1]

Primary CDSSecondary CDSPrimary ADSSecondary ADS

O* ra

dic

al y

ield

[m

ole

kW

h-1

]

O* radical yield of primary and secondary streamers as function of the primary

streamer velocity. Results for ADS and CDS.

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Reactor–modulator matching - i

-20

0

20

40

60

80

100

0 50 100 150 200

Time [ns]

Vo

ltag

e [

kV]

-200

800

Cu

rre

nt

[A]

Voltage

Current

600

400

200

0

1000

a)

0

0.25

0.50

0.75

1.00

0 50 100 150 200

Time [ns]

Volta

ge

Cu

rre

nt-1

[k

]

63 kV67 kV70 kV74 kV82 kV

b)

0

0.25

0.50

0.75

0 50 100 150

Time [ns]

1.00

200

Vo

ltag

e C

urr

en

t-1 [k

] 63 kV

67 kV70 kV74 kV82 kV

c)

Calculations of load impedance, with peak voltages as indicated. The pulse width was 110 ns for all shown

results. a) Typical voltage and current waveform. b) Load impedance as determined by dividing reactor voltage by

the total current. c) Load impedance when using the plasma current only. The crosses indicate the moment the primary streamers have crossed the reactor-gap.

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Reactor–modulator matching - ii

0

500

1000

1500ADS Vsg -28 kV

ADS Vsg -36 kV

ADS Vsg -45 kV

CDS

Imp

ed

an

ce [

]

0 20 40 60 80 100

Voltage [kV]

a)

0

0.2

0.4

0.6

0.8

1.0ADSCDS

0 20 40 60 80 100

Voltage [kV]E

ffic

ien

cy

ma

tch

ing

b)

Comparison between positive and negative voltage polarity streamers. Wire-plate distance was 3.7 cm. Pulse width was fixed at 100 ns. a) Impedance as function of the absolute value of the reactor peak voltage. For the negative

polarity the rise-rate was fixed to 1.7 2.0 kV/ns. For the positive polarity rise times of 1.6-3.0 kV/ns were used. Voltage was varied by varying DC level and charging voltage Vsg. b) Energy transfer efficiency for the same markers shown in

a).

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Quantification of O-radical yields - v

0 2 4 6 8

O-radical yield (mole/kWh)

Pulsed

AC/DC

AC ?

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Efficient streamer plasma generation

• Power sources for streamer plasma generation• Streamer observations• Quantification of radical yields• Discussion

26

Discussion - i

• Primary streamers more efficient for radical production. Due to larger local electric field ?

• Better radical production yield for fast primary streamers. Due to larger local electric field ?

• Why are negative corona’s so efficient ?

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Discussion - iiExample of streamer branching and streamer interconnecting

plat

e

wire

sup

port

wire

sup

port

b)a)

57 mm 37 mm

50 m

m

50 m

m

a) b)

Pulse width 100 ns, rise rate 1.5 kV/ns, peak voltage +45 kV (no DC bias).

Pulse width 100 ns, rise rate 2.3 kV/ns, peak voltage -79 kV (-15 kV DC bias).