Simulated experiment for elimination of air contaminated with odorous chemical agents by microwave plasma burner

Article abstract of DOI:10.1063/1.2800302

An experimental study on elimination of odorous chemical agent was carried out by making use of a microwave plasma burner, which consists of a microwave plasma torch and a reaction chamber with a fuel injector. Injection of hydrocarbon fuels into a high-temperature microwave torch plasma generates a plasma flame. The plasma flame can eliminate the odorous chemical agent diluted in air or purify the interior air of a large volume in isolated spaces. The specially designed reaction chamber eliminated H2 S and N H3 diluted in airflow rate of 5000 lpm (liters per minute), showing Β values of 46.52 and 39.69 Jl, respectively.

Full text of DOI:10.1063/1.2800302

Simulated experiment for elimination of air contaminated with odorous chemical agents
by microwave plasma burner
Yong Cheol Hong, Dong Hun Shin, and Han Sup Uhm
Citation: Applied Physics Letters 91, 161502 (2007); doi: 10.1063/1.2800302
View online: http://dx.doi.org/10.1063/1.2800302
View Table of Contents: http://scitation.aip.org/content/aip/journal/apl/91/16?ver=pdfcov
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APPLIED PHYSICS LETTERS 91, 161502 ͑2007͒
Simulated experiment for elimination of air contaminated with odorous
chemical agents by microwave plasma burner
a͒
Yong Cheol Hong
Odeur System Korea, 201 Shin Young Royal Palace, 249-6, Nonhyun Dong, Kangnam-gu, Seoul 135-832,
Korea
Dong Hun Shin
Nano-Mechanical Systems Research Center, Korea Institute of Machinery and Materials, 171 Jang-Dong,
Yuseong-gu, Daejeon 305-343, Korea
Han Sup Uhm
Department of Molecular Science and Technology, Ajou University, San 5, Wonchon-dong, Youngtong-gu,
Suwon 443-749, Korea
͑
Received 29 May 2007; accepted 27 September 2007; published online 16 October 2007͒
An experimental study on elimination of odorous chemical agent was carried out by making use of
a microwave plasma burner, which consists of a microwave plasma torch and a reaction chamber
with a fuel injector. Injection of hydrocarbon fuels into a high-temperature microwave torch plasma
generates a plasma flame. The plasma flame can eliminate the odorous chemical agent diluted in air
or purify the interior air of a large volume in isolated spaces. The specially designed reaction
chamber eliminated H S and NH diluted in airflow rate of 5000 lpm ͑liters per minute͒, showing
2
3
␤
values of 46.52 and 39.69 J/l, respectively. © 2007 American Institute of Physics.
͓
DOI: 10.1063/1.2800302͔
Volatile organic acids, alcohols, carbonyls, esters,
amines, sulfides, mercaptans, and nitrogen heterocycles are
mainly responsible for foul odors emitted from animal pro-
duction facilities, sewage waste installations, petroleum re-
hancing molecular dissociation, and producing free radicals
to enhance chemical reactions.
Here, we present an experimental study on elimination
of odorous chemical agent by making use of a microwave
plasma burner, which produces a plasma flame made of at-
mospheric microwave plasma and a fuel-burning flame. In
1
,2
fining factories, manure storage facilities, etc. Odor re-
moval has become an important and challenging issue in the
world because these noxious odors are harmful to human and
animal health, and have also resulted in numerous com-
plaints from neighbors of the facilities mentioned above.
There exist a large number of techniques for eliminating
odorous chemical agents. Classical techniques utilize pro-
cesses of dilution, incineration, adsorption, wet adsorption
1
4
the previous article, we reported the significant results of
simulated experiments for mass purification of air contami-
nated with biological and chemical warfare agents. It was
clearly revealed that the toluene decomposition by the high-
1
3
temperature plasma flame was far more efficient than that
1
5
8
by the pulse corona or by the microwave torch. In this
work, we chose H S and NH as odorous chemical agents
3
by gas scrubbing, as well as biological treatments. Even
2
3
because many odor-causing compounds are sulfur ͑S͒ and
nitrogen ͑N͒ containing. A detailed characterization of elimi-
nation of H S and NH are presented in terms of the input
though these processes are generally used, ecological con-
cerns have guided industry managers and scientists to seek
new solutions. In this context, many works using plasma
processes have been reported with increasing attention, in-
2
3
energy density of the microwave plasma burner.
4
The design and operation of the microwave plasma
burner are briefly summarized here for completeness, al-
though they have been reported in detail in the previous
volving d,6ielectric barrier discharge, p7ulsed corona
5
discharge,
radio frequency discharge,
microwave
8
9
1
discharge, and gliding arc. For example, Ma et al. inves-
1
3,14,16
articles.
As shown in Fig. 1͑a͒, the microwave plasma
tigated treatment of H S and NH by nonthermal plasma
2
3
burner consists of a microwave plasma torch and a reaction
chamber with a fuel injection port. The torch system mainly
consists of 2.45 GHz microwave parts, such as a 2.45 GHz
magnetron, a directional coupler, a three-stub tuner, and a
tapered waveguide, a quartz tube as a discharge tube not
shown in Fig. 1͑a͒, and feeders of a swirl gas that creates a
with a plate-to-wire reactor, showing removal efficiency of
ϳ50% at initial concentrations of 10 ppm and airflow rate of
3
10
6
m /min. Zhang et al. tested the ability of an ac-powered
ferroelectric packed-bed plasma reactor to decompose NH
3
11
and odors in animal houses. Helfritch used a wire-in-tube
corona reactor energized by short voltage spikes to decom-
pose small concentrations of H S contained in H . Ruan et
8
vortex flow in the discharge tube. The vortex flow stabilizes
2
2
the torch flame in the center of the tube and protects the
discharge tube from the heat of the torch. Microwave from a
magnetron propagates toward the discharge tube through the
waveguide, concentrating its power in the tube and generat-
ing a high-temperature torch plasma. As shown in Fig. 1͑a͒,
a fuel injection port and a reaction chamber were connected
in a series on the wide wall of the tapered waveguide. Gas-
eous or liquid hydrocarbon fuels from the injection port were
sprayed toward the microwave torch plasma, instantaneously
1
2
al. demonstrated the decomposition of simulated odors,
NH , C H SH, and N͑CH ͒ , in municipal waste water treat-
3
2
5
3 3
ment plants in a plate-to-wire pulse corona reactor. Eventu-
1
,10–13
ally, the previous articles
show that plasma chemical
processes are highly effective in promoting oxidation, en-
a͒Author to whom correspondence should be addressed. Electronic mail:
bullplasma@nate.com
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003-6951/2007/91͑16͒/161502/3/$23.00 91, 161502-1 © 2007 American Institute of Physics
29.21.35.191 On: Thu, 18 Dec 2014 14:19:50
0
1

161502-2
Hong, Shin, and Uhm
Appl. Phys. Lett. 91, 161502 ͑2007͒
ing the necessary residence time for the best elimination ef-
fects. These sequential processes then eliminate the odorous
chemical agents in the passing air.
Aqua ammonia ͑NH OH͒ was used to obtain NH gas in
4
3
the simulated experiment for eliminating NH and was main-
3
tained at 60 °C by a vaporization device in Fig. 1. On the
other hand, in the case of the simulated experiment of elimi-
nating H S, gas-phase H S was directly injected into the
2
2
blower fan and was mixed with air. The blower fan suck up
air contaminated with NH and H S gas, and transferred the
3
2
contaminants into the reaction chamber. Then, the total air-
flow rate was approximately 5000 lpm. 40 lpm of the com-
pressed air as a swirl gas was injected into the microwave
plasma torch. The injection rates of the kerosene were 1.15,
1
.46, and 1.87 kg/h. The 1.15 kg/h nozzle is the smallest
fuel nozzle ever found. The methane flow rates were 5, 10,
5, 20, and 30 lpm. The energy contained in kerosene and in
1
7
6
3
methane are 10 cal/kg and 9.52ϫ10 cal/m , respectively.
The injected fuel-flow rates can be translated into J/s. The
power of 1.15 kg/h kerosene energy corresponds to
1
1
3.3 kJ/s and that of 20 lpm methane energy is also
3.3 kJ/s. The detailed simulated experiments for eliminat-
ing NH and H S were carried out in terms of the input
3
2
energy density of the microwave plasma burner. For in-
stance, the kerosene injection rates of 1.15, 1.46, and
1
.87 kg/h with the 1.4 kJ/s plasma power correspond to the
FIG. 1. ͑Color online͒ ͑a͒ Experimental setup for eliminating NH and H S
3
2
input energy densities of 176.4, 219.4, and 276.3 J/l, respec-
tively, for the total air-flow rate of 5000 lpm.
In this work, the experimental results were presented by
making use of a simple first order decay model for eliminat-
as odor-causing chemical materials by making use of a microwave plasma
burner. ͑b͒ Schematic presentation showing the cross section of the reaction
chamber. The inset is the picture of the kerosene plasma flame.
8
,17
ing target chemicals. The destruction model
of the odor-
decomposing the hydrocarbon fuels from the microwave
plasma with high temperature, mixing the resultant gaseous
hydrogen and carbon compounds with air or oxygen gas
quickly and generating a large volume of the high-
temperature plasma flame, which enters the reaction chamber
where the contaminated air passes.
ous chemicals can be expressed as X/X =exp͑−E/␤͒, where
0
X represents the leftover concentration of the odorous chemi-
cals after the plasma flame treatment and X is the initial
0
concentration before the treatment, E denotes the input en-
ergy density ͑in units of J/L͒ deposited on the contaminated
air by the plasma flame during the treatment, and ␤ repre-
sents the energy density required for bringing down the con-
centration to 1/e of its initial concentration, i.e., the energy
density needed for 63% destruction. The leftover concentra-
tions of NH and H S were measured by employing detector
The reaction chamber provides the required residence
time for the best decontamination effects, thus creating a
unique environment for efficient chemical reactions with
high-energy electrons and other chemically active radicals in
the plasma torch and flame from fuel combustion. The inset
in Fig. 1͑a͒ shows the picture of the plasma flame produced
from the microwave plasma burner at 1.4 kJ/s plasma power
with no reflected power and 1.15 kg/h kerosene. In Fig. 1͑a͒,
the blower fan connected to the reaction chamber by four
stainless steel bellows sucks up air contaminated odorous
gases, and transfers the contaminants into the reaction cham-
ber. It can suck and blow airflow more than 5000 lpm ͑liters
per minute͒ at least. As shown in Fig. 1͑b͒, the reaction
chamber consists of inner and outer compartments, providing
a space between them. The contaminated air was injected
into the reaction chamber via four injection ports in tangen-
tial direction installed on the outer compartment, thereby ro-
tating in the space. In turn, the rotating airflows enter the
inner compartment with tangential slits, which are also in
tangential directions along the inner surface of the inner
compartment wall, mixing with the plasma flame made of
atmospheric microwave plasma and a fuel-burning flame.
The dimensions of the reaction chamber used in the experi-
ment were 22 cm diameter and 30 cm long. The plasma
flame and the contaminated air in the inner compartment
3
2
tubes from the GASTECH Company in Japan. The measure-
ment by detector tubes was done at the flame exit of the
reaction chamber without any delay or any interference.
Therefore, the detector tube may reliably measure the left-
over NH and H S, although the data may have a large error
3
2
bar. The data points in Fig. 2 indicate the average leftover
NH ͑open circle dots͒ and H S ͑open square dots͒ concen-
3
2
trations obtained from the repeated measurements in terms of
the input energy densities by means of the methane plasma
burner. The closed square dots are the leftover H S concen-
2
trations by means of the kerosene plasma burner. The initial
concentrations of NH and H S were X =159 and 120 ppm,
3
2
0
respectively. The curves in Fig. 2 represent the least squared
fits to the experimental data points for the microwave plasma
burner. Eventually, the ␤ values of the NH and H S elimi-
3
2
nations by the methane plasma burner are 39.69 and
56.45 J/l, respectively. On the other hand, the ␤ value of
H S elimination by the kerosene plasma burner is 46.52 J/l.
2
The ␤ values of NH3 and H S elimination by methane
2
plasma burner are considerably less than 62.74 J/l for tolu-
ene and 138.02 J/l soot elimination, which were reported in
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rotate in the same direction as indicated in Fig. 1͑b͒, provid-
Ref. 14. In the recent article for decomposition of H S and
2
129.21.35.191 On: Thu, 18 Dec 2014 14:19:50

161502-3
Hong, Shin, and Uhm
Appl. Phys. Lett. 91, 161502 ͑2007͒
−
1
teeth of a comb near 1600 and 3700 cm . However, after the
H S decomposition by the microwave plasma burner, SO
2
2
−
1
was detected as a main byproduct at 1360.9 cm , which is
from oxidation processes of sulfur compounds, such as com-
bustion and incineration. H O and CO are the main by-
2
2
products due to CH combustion but very small amount of
4
CO and NO are also shown. In the case of NH , the main
2
3
by-products are NO and H O. However, NO as a by-
2
2
2
product of NH oxidation is not significant due to NO re-
3
2
duction by injecting hydrocarbon fuels, such as kerosene and
methane. Also, NH is conventionally used as a catalyst in
3
the reduction process of NO and NO . In FTIR experiments,
2
NO and NO gases were hardly detected.
2
FIG. 2. Plots of leftover H S and NH concentrations in terms of the input
energy density E. The closed and open square dots represent the data points
2
3
In conclusion, we presented the detailed description of
the plasma flame device and the significant results for elimi-
nating NH and H S as odor-causing compounds. Prior to
of H S concentrations for kerosene and methane injections, respectively, and
2
the open circle dots are NH concentration data for methane injection. Each
3
2
3
2
0
data point indicates the average value of eight repeated measurements.
this, we had developed the microwave plasma burner to
significantly increase the volume and temperature of the mi-
2
1
5
crowave plasma torch and had investigated the properties
NH using a plate-to-wire pulse corona reactor, the ␤ values
3
1
3
of the plasma flames. Also, the microwave plasma burner
had been applied to abate SF and CF gases emitted from
of H S ͑X =148 ppm͒ and NH ͑X =58 ppm͒ decomposi-
2
0
3
0
tions were 65 and 60 J/l, respectively. Gliding arc
6
4
2
2
9
,18,19
semiconductor industries, revealing that it can significantly
reduce their emissions to atmosphere. From the previous se-
rial researches and the experimental results in this work, the
microwave plasma burner is a very effective means for
discharges
have been used as other example of H S
2
1
8
3
depollution. Czernichowski reported that 7 N m /h of air
contaminated with 0.7% H S was completely purified at the
2
3
energy consumption of 0.14 kW h/N m without any pre-
eliminating the odorous chemical materials, such as H S and
heating. The energy in bringing down the concentration of its
initial concentration to zero in Ref. 18 was estimated to be
2
NH , providing a unique opportunity of a simultaneous
3
elimination and burnout of odor-causing chemical agents di-
luted in air.
540 J/l. In Fig. 2, the energy is approximately 300 J/l. Even
though the initial concentrations are different for H S elimi-
2
nation, this work reveals that the kerosene microwave
plasma burner may be more effective than the pulse corona
1
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1
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CH microwave plasma burner decomposition of H S.
114504 ͑2006͒.
4
2
1
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