22P082-R
NOx Removal Using Non-thermal Surface Plasma Discharge Powered by a
Modulated High Voltage Waveform
変調高電圧を用いた非熱平衡沿面放電プラズマによるNOx除去
Jerome Jolibois, Kazunori Takashima, and Akira Mizuno
ジェローム ジョリボア, 高島和則，水野彰
Dept. Environmental and Life Sciences, Toyohashi University Technology
1-1 Hibarigaoka, Tempaku-cho, Toyohashi 441-8580, Japan
豊橋技術科学大学 環境・生命工学系 〒441-8580 豊橋市天伯町雲雀ヶ丘1-1
This paper focus on the NOx removal with the help of a non-thermal surface plasma discharge powered by amodulated high voltage waveform. The underlying idea is the use of an unsteady actuation in order to reduce
the power consumption of the cleaning device. To achieve this, the effect of amplitude and burst modulation
on NOx remediation is analyzed. These experiments show an important decrease of the electric power inboth cases. In addition, NOx removal is enhanced with the BM mode for a duty cycle of 50%. While the AM
mode has no effect on the gas exhaust treatment.

1. Introduction
Non-thermal plasma as a possible solution toclean the gas exhaust of next vehicle have generated
significant interest. In labs experiments alreadydemonstrated that non-thermal plasma by wet way
can overcame some practical problems such as NOx
removal [1,2]. A large variety of plasma reactors
used for remediation of NOx is based on a volume
discharge. Another way to treat the gas exhaust
consists of using a surface discharge [3,4].
This paper presents an experimental study on
NOx removal using a non-thermal surface plasma
discharge powered by a modulated high voltage
waveform. The aim is to use an unsteady actuation inorder to reduce the power consumption of thecleaning device. To achieve this, the effect ofamplitude modulation (AM) and burst modulation(BM) of the high voltage waveform on the treatment
process is analyzed.
2. Experimental setup
Figure 1 displays a schematic side-view of the
non-thermal surface plasma reactor used in thisstudy. It is composed of two parts. The first partconsists of a test chamber with two openings thatallow the inlet and the exhaust of gas flow. This test
chamber made of PP plate has a rectangularcross-section of 100 mm × 30 mm for 150 mm-long.
The second part of the plasma reactor corresponds tothe surface discharge placed on the top side of thetest chamber. The whole forms the non-thermal
surface plasma reactors.
The wet condition is obtained by adding a sodium
sulfite solution inside the reactor (see Fig. 1). Thissolution is used as NOx gas absorbent.

Fig.1. Schematic side-view of the plasma reactor.

The discharge is composed by a surface DBD witha three-electrode configuration [5]. To initiate theplasma discharge, the AC HV must exceed the onset
voltage (with Von ≈ 5 kV peak). Here, a sinusoidal
waveform with a peak voltage ranging between 6 to13 kV and a frequency fAC of 1 kHz is used.
The sinusoidal waveform is modulated by amodulating sinusoidal wave, corresponding to theamplitude modulation (AM). This modulation
results in an AC sine waveform driving by themodulation frequency fAM ( set at 100 Hz) with 80%
modulation depth (see Fig. 2). When the sinusoidal
waveform is modulated by a Rectangular function
with a duty cycle of 50%, the AC sine waveform isalternatively switched on and off: the discharge isassured by the carrier signal while the modulation
frequency fBM (fixed at 100 Hz) drives its ignition.
All experiments are characterized by measuring
the power injected into the gas, and the evolution ofremoval rate of NO and NOx gases via FTIR
measurements. In addition, they are conducted at
low and stationary flow-rate (1 L/min), with 100
ppm of initial content of NO.

Fig.2. High voltage applied to the discharge with AM(left) and BM (right) modes.

3. Results
3.1 Amplitude modulation (AM)Figure 3 presents the removal efficiencies of NOand NOx as a function of the energy density with theconventional (steady) and modulated (unsteady)actuation. It appears clearly that the AM actuation
reduces the injected energy and also does not
improve the NOx treatment.

Fig.３. Removal efficiency versus energy density. (■:NO, □: NOx with sine and ●: NO, ○: NOx with BM).

3.2 Burst modulation (BM)The evolution of the NO and NOx removal
efficiencies as a function of the energy density isshown in Fig. 4. When the discharge operates withthe burst modulation mode, the injected energy into
the polluted gas is lower than the steady actuation,
resulting a decrease of the gas exhaust cleaning.
However, we can remark that at a given energy
density, stressing the discharge with the modulated
voltage (VBM) seems given higher values of removal
efficiency as compared with the sinusoidal ACvoltage. The gain reaches 10% on the NO treatment
while only 5% on NOx removal. It suggests that thenon-thermal surface plasma discharge generates
more radical species and / or allows a high contact
efﬁciency between the plasma discharge and the gas
to be treated.

Fig.4. Removal efficiency versus energy density. (■:NO, □: NOx with sine and ●: NO, ○: NOx with BM).

4. Conclusion
In this paper, we have investigated the NOxremoval by using a modulated waveform, especiallythe amplitude and burst modulations of the highvoltage waveform.
The main results are as follows:(1) The fact of using a modulated voltage has asignificant effect on the power consumed, i.e. a
decrease of it. In addition the evolution of theelectrical power consumption versus the applied
voltage always follows the behavioral law of Pons etal. [6].
(2) The AM mode has no effect on the NOx
remediation.
(3) On the contrary, the burst modulation allows toenhance the NO conversion with a duty cycle of 50%.
The maximum gain reaches up to 10%.
However, effects of the modulated high voltage on
the interaction (increase of radical species due to theuse of a pseudo-pulsed discharge, etc.) between theplasma and the polluted gas aren't yet totallydistinguished.
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