NOx Removal Processes byMicroplasma Generation in
Multiple Electrode Configuration
M. Blajan, M. Kanamori, H. Mimura, K. Shimizu,
Innovation and Joint Research Center, Shizuoka University,
3-5-1 Jyouhoku, Hamamatsu, 432-8561, Japan
E-mail：blajanmarius@yahoo.com

Introduction(３) Design of Experiments

Nonthermal plasma was investigated in
the decade as a solution to theenvironmental problems generated by
the exhaust gases from factories,
automobiles and other sources. Highenergy electrons and active species
generated by non thermal plasma, could
transform pollutants from exhaust gasesin simpler compounds.
Microplasma is a nonthermal plasma atatmospheric pressure generated at verysmall discharge gaps and low discharge
voltages. NOx removal from simulated
exhaust gas is investigated by using
microplasma.

Experimental Setup(1)Microplasma Electrodes
The electrodes consist in perforated
metallic plates covered with a dielectriclayer.

SIDE VIEWFRONT VIEW

The methodology of design ofexperiments proposes a factorial
experimentation in which the factors•Discharge voltage A•Discharge voltage B
vary simultaneously.

Detail of microplasma electrodes
Two small size power supplies (LECIP,M-1H) to supply to the electrodes
alternative voltages with frequencies
around 25 kHz.
Discharge gas: NO 500 ppm, C2H4
3500 ppm, O2 5% and N2 balance.
Gas flow rate: 5 L/min.

Contour plot of the predicted responseof NOx removal concentration

Aperture of electrodes:•Middle pair1.5 mm holes•Intermediate pair 2 mm holes•Extremities 3 mm holes⇨honeycomb like structure
The treated gas was analyzed by aNOx and O2 gas analyzer (ShimadzuNOA-7000).

NOx Removal Processes(1) Electrical Characteristics
DISCHARGE
ZONES

Microplasma electrodes
electrodes configuration

inmultiple

6 electrodes with Ø 42 mm faced
together with a discharge gap of 0 µm ⇨5 discharge zones.

Very small discharge gaps andrelatively low discharge voltages (about1 kV)⇨A high intensity electric field (107-108V/m) assures the formation of
microplasma and a corresponding
discharge current.

Contour plot of the predicted responseof NO removal concentration

Contour plot of the predicted responseof generated NO2 concentration
Waveforms of the discharge voltagesand discharge current
Photo of the microplasma discharge(2) Experimental Setup

Three discharge zones are supplied withvoltage

from

one
discharge voltage A.

powersupply:

Two discharge zones are supplied fromthe second power supply: discharge
voltage B.

(2) NOx Removal
The highest values were obtained at
1.2 kV discharge voltage A and 1.2 kVdischarge voltage B:•NOx removal 51 ppm•NO removal 218 ppm•Generated NO2 171 ppm
NOxremoval
concentration,NO
removal concentration and generated
NO2 concentration for different values ofthe discharge voltages
Discharge
Voltage A(kV)

Discharge
Voltage B(kV)

NO Removal
Concentration(ppm)

NOx Removal
Concentration
(ppm)

NO2
Concentration
(ppm)

0.7
0.7
0.7
0.7
0.7
0.7
0.9
0.9
0.9
0.9
0.95
0.95
0.95
1.1
1.1
1.1
1.2
1.2

0.7
1.2
0.8
0.9
1
1.1
0.9
0.9
0.9
1.2
0.95
0.95
0.95
0.7
1.1
1.2
0.7
1.2

45
113
53
61
79
94
120
135
133
155
160
167
169
147
171
195
181
218

921
17
19
21
26
34
28
35
35
39
47
44
43
51
48
48
51

42
102
47
527381101111
110136
126
140
132
124
136
158
141
171

The dissociation energy for N2 is 9 eVand for O2 is 5-6 eV⇨ with the increase of discharge
voltage the NOx removal concentration
will be higher:e  N2  e  N(4S)  N(2D)NO  N(2D)  N2  O

Schematic
viewofmicroplasma
electrodes and the supply circuite  O2  e  O(3P)  O(1D)O O2 M  O3  M

NO  O3  NO2  O2

Using MODDE 5.0 software the data
were analyzed.
Larger microplasma area powered byhigh voltage power supply A:
predicted value of NOxremoval concentration: 1.2 kV fordischarge voltage A and 1 kV fordischarge voltage B.
⇨optimalpredicted value of NO
removal concentration: 1.2 kV fordischarge voltage A and 1.2 kV fordischarge voltage B.
⇨optimal⇨optimal predicted value of generated

NO2 concentration: 1.2 kV for discharge
voltage A and 0.95 kV to 1.2 kV fordischarge voltage B.

Conclusions
voltages wereNOx
removalconcentration,NO
removalconcentration and generated NO2
concentration increased.
•Astheincreased

dischargethe•Design of experiments software
analysis shows that with the increase ofboth discharge voltages higher valuesof the NOx and NO removal
concentrations and generated NO2
concentration are obtained.