Transcript Document 7810132

Efficient streamer plasma generation
Guus Pemen, Hans Winands, Liu Zhen,
Dorota Pawelek, Bert van Heesch
Eindhoven University of Technology, Department of Electrical Engineering, The Netherlands
•
•
•
•
Power sources for streamer plasma generation
Streamer observations
Quantification of radical yields
Discussion
1
10 ns
20 ns
• 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
Gas cleaning effect by:
30 ns
• Interaction through free radicals
• Using ions to charge particles to
enhance their collection
40 ns
2
10 ns
20 ns
30 ns
fast CCD
end-on
view
40 ns
3
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)
4
ns-Pulsed power sources - i
Example: TU/e resonant charging – sparkgap - TLT
Fi
lt
er
3-phase 400 V
50 Hz AC
continuous
5 kW
1 kV
30 s
1 kHz
500 kW
30 kV
30 s
1 kHz
500 kW
K. Yan et.al., IEEE Trans. Industry Appl., Vol. 38, No.3, May/June 2002, pp.866-872
100 kV
100 ns
1 kHz
100 MW
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ns-Pulsed power sources - ii
Example: TU/e 30 kW system for odor control
Input [µg/m3]
Ouput [µg/m3]
Removal Efficiency [%]
Aromatic CH’s
395
10
97
Cyclic CH’s
66
0
100
Aliphatic CH’s
271
13
95
Alcohol
787
44
94
Esters
0
263
(cannot be determined)
Ketone
3881
273
93
Aldehydes
946
570
40
Chlorinated
components
200
0
100
Organic sulphur
2363
2
100
Furane
66
10
84
Terpens
13
0
100
Total
8987
1185
87
10.1 ppm
0.5 ppm
95
Corona reactor
DC-bias supply
TLT
Pulse generator
H2S
G.J.J. Winands et.al., IEEE Trans.on Plasma Science, Vol.34, No.5, October 2006, pp.2426-2433
6
ns-Pulsed power sources - iii
Example: high temperature corona tar removal in syngas
Effect of temperature on naphthalene
removal in synthetic fuel gas
Remaining fraction (%)
100
Corona Reactor
Window for FTIR
Tar Injector
200 degr.C, dry
80
200 degr.C, wet
400
degr.C,
biogas
400 dry
60
40
Fan
20
0
0
200
400
600
800
Corona energy density (kJ/Nm3)
S.A. Nair, et.al., Ind. Eng. Chem. Res. 2005, 44, 1734-1741
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AC/DC corona generation - i
Example: 2 kW TU/e pilot
T1
L1
D1
L2
L3
Mains
TR
C0
Corona
reactor
CL
T3
T2
18
16
dV/dt
12
10
• Few HV components
18
8
17
Voltage (kV)
Voltage (kV)
1 – 3 kV/μs
courtesy of EnviTech, Belgium
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6
• High energy efficiency (>90 %)
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15
4
14
2
1.5
2.0
2.5
3.0
Time (ms)
0
-5
-4
-3
-2
-1
0
1
2
3
4
5
• Good radical yield (20 % less
than for pulsed corona)
Time (ms)
TU/e patents WO2005/031488 and WO2005/112212
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AC/DC corona generation - ii
Example: investigations on TU/e – Oranjewoud system
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16
12
10
18
8
17
Voltage (kV)
Voltage (kV)
14
6
16
15
4
14
2
1.5
2.0
2.5
3.0
Time (ms)
0
-5
-4
-3
-2
-1
0
1
2
3
4
Time (ms)
9
5
Efficient streamer plasma generation
•
•
•
•
Power sources for streamer plasma generation
Streamer observations
Quantification of radical yields
Discussion
10
Overview of experimental set-up
Deuterium light
source
Air flow in
Plate electrode
Pulsed Power
Modulator
HV
Corona wire
ICCD
camera
Lenses
Air flow
out
Quartz
window
Trigger signal
V
I
UV spectrometer
Oscilloscope
Computer
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Pulse parameters and reactor configurations
Parameter
Range
Parameter
Value
Pulse width
30 - 250 ns
Plate heigth [m]
1.1
Rise-time (20-80%)
15 - 45 ns
Plate width [cm]
22
Peak voltage
50 - 90 kV
Plate-plate distance [cm]
7.4 – 15.4
DC Voltage
0 - 20 kV
# wires
1-7
Pulse repetition rate
10-1000 pps
Wire diameter [mm]
0.2 - 15
Energy per pulse
0 – 2.5 J
Wire length [m]
< 0.9
Voltage polarity
Positivenegative
Reactor capacitance [pF]
80
Max. flow used [m3∙h-1]
30
12
Time-resolved side-view ICCD pictures
-i
t = 16 ns
b)
a)
t = 26 ns
t = 21 ns
c)
t = 41 ns
t = 31 ns
t = 52 ns
e)
d)
t = 62 ns
f)
t = 102 ns
abc d e
100
f
g
h
80
Voltage [kV]
60
40
20
0
-20
g)
h)
i)
-40
-50
0
50
Time [ns]
100
150
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.
G.J.J. Winands, et.al., J. Phys. D: Appl. Phys. 39 (2006) 3010–3017
13
Time-resolved side-view ICCD pictures
- ii
t = 25 ns
t = 34 ns
t = 29 ns
b)
a)
t = 44 ns
c)
t = 49 ns
t = 59 ns
e)
d)
t = 87 ns
f)
abc d e f
40
t = 105 ns
g
h
20
Voltage [kV]
0
-20
-40
-60
-80
-100
g)
h)
i)
-50
0
50
100
150
Time [ns]
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.
G.J.J. Winands, et.al., J. Phys. D: Appl. Phys. 39 (2006) 3010–3017
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0.3
77 kV (0kV DC)
70 kV (0kV DC)
70 kV (20kV DC)
60 kV (0kV DC)
60 kV (10kV DC)
52 kV (0kV DC)
5
4
3
Streamer diameter [cm]
Streamer head position [cm]
6
2
77 kV
70 kV
70 kV
60 kV
60 kV
52 kV
0.2
0.1
1
a)
b)
0
0
20
40
100
80
60
140
120
100
80
20
40
60
80
100
Time [ns]
Time [ns]
Intensity [counts/pixel]
(0kV DC)
(0kV DC)
(20kV DC)
(0kV DC)
(10 kV DC)
(0kV DC)
77 kV (0 kV DC)
70 kV (0 kV DC)
70 kV (20 kV DC)
60 kV (10 kV DC)
60 kV (0 kV DC)
52 kV (0 kV DC)
• Streamer density
• Streamer velocity
• Streamer diameter
• Streamer intensity
60
• Secundary streamer length
40
• Branching, interconnecting, re-ignition
20
• Effect of repetition rate and preceding pulses
• Effect of DC-bias voltage
c)
0
20
40
60
80
Time [ns]
100
120
140
15
Primary streamer velocity
3.0
2.0
37 mm
57 mm
77 mm
1.5
Velocity [106 m s-1]
Velocity [106 m s-1]
2.5
1.0
2.0
1.5
1.0
0.5
0.5
a)
0
b)
0
0
1
2
Rise rate [kV
ns-1]
3
40
60
80
100
Voltage [kV]
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.
16
Efficient streamer plasma generation
•
•
•
•
Power sources for streamer plasma generation
Streamer observations
Quantification of radical yields
Discussion
17
Quantification of O-radical yields - i
UV absorbtion
spectroscopy [O3, exhaust]
Gas flow +
plasma volume
[O3] per m3
plasma volume
Kinetic model (65 reactions,
17 species, RH, T)
[O*] per m3
plasma volume
Plasma
volume
total number
of [O*]
18
Quantification of O-radical yields - ii
O* production [mole kWh-1]
8
Primary streamers better
than secondary ?
6
It appears so !
4
2
0
40
30 ns FWHM
50 ns FWHM
100 ns FWHM
130 ns FWHM
• 7.0 mole/kWh corresponds
to 5.3 eV/molecule.
Voltage [kV]
• Theoretical cost to produce
an O* radical is 3 eV.
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.
• Thus more than half of the
available energy is used to
produce O* radicals
60
80
100
• Excellent yield.
19
Quantification of O-radical yields - iii
8
• Primary better than
secondary streamers
Primary
O* production [mole kWh-1]
Secondary
6
• Primary yield increases if
velocity is increased
(because local E-field
increases and consequently
so does the electron energy)
4
2
0
0
0.5
1.0
1.5
2.0
2.5
Velocity [106 m s-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
O* radical yield [mole kWh-1]
12
Primary CDS
Secondary CDS
Primary ADS
Secondary ADS
10
• Negative polarity better
for radical production
8
6
• However, matching is
worse for negative
polarity
4
2
0
0
0.5
1.0
1.5
6
Velocity [10 m s-1]
2.0
2.5
O* radical yield of primary and secondary
streamers as function of the primary
streamer velocity. Results for ADS and CDS.
21
Reactor–modulator matching - i
1000
100
Voltage
800
60
600
40
400
20
200
Current [A]
Voltage [kV]
Current
Voltage Current-1 [k]
80
1.00
0.75
63 kV
67 kV
70 kV
74 kV
82 kV
0.50
0.25
0
0
a)
-200
-20
0
50
100
150
200
Time [ns]
c)
0
0
50
100
150
200
Time [ns]
Voltage Current-1 [k]
1.00
63 kV
67 kV
70 kV
74 kV
82 kV
0.75
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.
0.50
0.25
b)
0
0
50
100
Time [ns]
150
200
22
Reactor–modulator matching - ii
1500
1.0
ADS
CDS
ADS Vsg -28 kV
0.8
ADS Vsg -45 kV
CDS
1000
Efficiency matching
Impedance []
ADS Vsg -36 kV
500
0.6
0.4
0.2
a)
b)
0
0
20
40
60
Voltage [kV]
80
100
0
0
20
40
60
80
100
Voltage [kV]
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
Pulsed
AC/DC
?
AC
0
2
4
6
8
O-radical yield (mole/kWh)
24
Efficient streamer plasma generation
•
•
•
•
Power sources for streamer plasma generation
Streamer observations
Quantification of radical yields
Discussion
25
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 ?
26
Discussion - ii
a)a)
wire support
50 mm
wire support
plate
50 mm
Example of streamer branching and streamer interconnecting
b)
b)
57 mm
Pulse width 100 ns, rise rate 1.5 kV/ns,
peak voltage +45 kV (no DC bias).
37 mm
Pulse width 100 ns, rise rate 2.3 kV/ns,
peak voltage -79 kV (-15 kV DC bias).
27