1-s2.0-s1385894713007869-main.pdf
TRANSCRIPT
8/10/2019 1-s2.0-S1385894713007869-main.pdf
http://slidepdf.com/reader/full/1-s20-s1385894713007869-mainpdf 1/7
Electron beam treatment of gas stream containing high concentration
of NO x: An in situ FTIR study
P. Lakshmipathiraj a,b, Jingqiu Chen a, M. Doi c, N. Takasu c, S. Kato a, A. Yamasaki a,⇑, T. Kojima a,⇑
a Department of Materials and Life Sciences, SeiKei University, Kichijoji, Musashino, Tokyo 180-8633, Japanb Photocatalysis International Research Center, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japanc JFE Engineering Corporation, Research Centre, 2-1 Suehiro, Tsurumi-ku, Yokohama 230-8611, Japan
h i g h l i g h t s
The NO reduction is predominant in the absence of O 2 under EB processing.
The O2 presence in the gas stream increases the NO2 formation during EB operation.
The moisture content in the stimulated gas found to inhibit the NO2 formation.
The Na2SO3 scrubbing of the gas during EB operation increases the NO x removal.
The NO and NO x concentration is reduced to the extent of 95% using reactor type II.
a r t i c l e i n f o
Article history:
Received 31 January 2013
Received in revised form 7 June 2013
Accepted 10 June 2013
Available online 19 June 2013
Keywords:
Electron beam
NO
NO x
Reduction
Pollution control
a b s t r a c t
The NO x removal from gas stream by electron beam (EB) technique under flow through condition was
investigated using two different reactors. Initially reactor type I was fabricated to investigate the NO x
removal performance, based on its performance, the reactor type II was designed for further investigation
onNO x removal efficiency. The influence of the applied current, O2, water vapour and gas flow rate on the
removal of NO and NO x was studied. The FTIR spectrum of the NO gas samples acquired after EB irradi-
ation indicated the formation of NO2 and N2O. It was observed that the NO x concentration could be
reduced to 95% from the initial NO concentration of 1000 ppm using reactor type II. The possible removal
mechanism of NO x under EB irradiation is discussed. It is inferred that the EB irradiation accelerate the
reduction of NO to N2 and O2 in the absence of O2. Addition of O2 and water vapour in the NO/N2 gas
stream was found to influence the oxidation and reduction reaction, respectively under EB irradiation.
The Na2SO3 scrubbing of the gas increased the NO x removal performance during EB processing. The
N2O was observed to form mainly by the reduction of NO 2 during EB irradiation.
2013 Elsevier B.V. All rights reserved.
1. Introduction
Nitrogen oxides (NO x), are considered as one of the primary pol-
lutants in the atmosphere. Their emissions into atmosphere not
only cause the formation of acid rain and ozone depletion, but alsoadverse effect to human health [1]. The term NO x used to denote
both nitrogen monoxide (NO) and nitrogen dioxide (NO2). In the
recent decades, abatement of NO x from the combustion processes
has become one of national priorities and greatest challenges in
environmental protection. Though the efforts have been made to
control the NO x emission from the combustion process, post com-
bustion NO x control techniques are mandatory to meet the strin-
gent emission standards.
The most widely studied NO x control technique is selective cat-
alytic reduction (SCR) with ammonia in the presence of oxygen, in
which the NO x could be reduced to 85% [2–5]. The SCR reaction ispromoted by the catalyst which enables the reaction to proceed at
low temperature. Nevertheless, the catalyst life time, catalyst poi-
soning and corrosion are common problems encountered in the
SCR technique [2]. The other conventional NO x control method is
selective noncatalytic reduction (SNCR) performed with ammonia
or cyanuric acid [5,6,2]. The high temperature window (982–
1149 C) is necessary to operate the SNCR process, which limits
its application for the treatment of the diesel engine exhaust at
atmospheric pressure conditions. Similarly, the methods include
catalytic decomposition [7], adsorption [8,9], ion-exchanged zeo-
lites [10,11], etc., have suffered with their limitations and
disadvantages.
1385-8947/$ - see front matter 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.cej.2013.06.019
⇑ Corresponding authors. Tel.: +81422 37 3750; fax: +81422 37 3871 (T.Kojima),
tel./fax: +81 422 37 3887 (A. Yamasaki).
E-mail addresses: [email protected] (A. Yamasaki), [email protected],
[email protected] (T. Kojima).
Chemical Engineering Journal 229 (2013) 344–350
Contents lists available at SciVerse ScienceDirect
Chemical Engineering Journal
j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c e j
8/10/2019 1-s2.0-S1385894713007869-main.pdf
http://slidepdf.com/reader/full/1-s20-s1385894713007869-mainpdf 2/7
In the recent decades, nonthermal plasma methods such as
pulsed corona discharge [12–16], microwave discharge [13,17],
dielectric barrier discharge [13,15,16,18–20], and electron beam
(EB) irradiation [21,22], shown to be efficient compared to conven-
tional treatment techniques employed in the reduction of NO x and
undesired species from gas stream at atmospheric pressure condi-
tions. The nonthermal plasma or the nonequilibrium plasma is
generated by the reaction of high energy electrons produced dur-
ing EB or discharge processing with background gas molecules at
ambient temperature. The plasma consists of the active compo-
nents viz., free radicals, ions and secondary electrons which are
playing vital role in the abatement of the gaseous pollutant. The
advantage of the nonthermal plasma method is that the kinetic en-
ergy of the electrons mainly utilized for vibrational excitation or
dissociation of the gas molecule rather heating up the gas molecule
[21].
It is shown that the EB processing is remarkably high energy
efficient than the electrical discharge processing. The specific en-
ergy consumption for the dissociation of N2 molecule in the pulsed
corona processing is 480 eV while, it is only 80 eV in the EB pro-
cessing [23]. It is reported that the EB accelerator could reduce
the NO x to the extent of 82% from exhaust gas by combustion of
high sulphur fuel oil, containing the NO x concentration of 150–
170 ppmv [22]. In another study, it is shown that pulsed EB treat-
ment on exhaust gas from the combustion of polish light oil could
achieve 30% reduction of NO x from its initial concentration of
532 ppm [24]. The laboratory and the pilot scale test of EB flue
gas treatment demonstrated that the process can be prominently
applied for the simultaneous removal of three pollutant such as
NO x, SO x and volatile organic compounds (VOC) [25].
The present research work is aimed to develop the efficient EB
technique for the abatement of NO x, emitted from the diesel engine
in ships. Two different reactors named reactor type I and reactor
type II was investigated for the removal of the NO x at the labora-
tory scale. Initially reactor type I was fabricated to investigate
the NO x removal performance, based on its performance, the reac-
tor type II was designed for further investigation on NO x removalefficiency. The behaviour of the NO gas in the presence of O2 and
water vapour was studied at different experimental conditions un-
der EB irradiation. The NO and NO x removal efficiency and its pos-
sible mechanisms were discussed.
2. Materials and methods
2.1. EB reactor and experimental set up
The EB accelerator equipped with carbon nanotube (CNT) anode
and Ti windowcathode was used for the NO x removal experiments.
A DC rectifier with a maximumof 60 kVand0.05 mA was usedas a
radiation source for irradiating the pollutant gases. The distancebetween anode and cathode was fixed at 23 mm. The EB, acceler-
ated from the CNT anode at high vacuum pressure (105 Torr) pro-
jected perpendicular to the process vessel of the gas flow duct
through Ti window having the diameter of 1.3 cm and thickness
of 0.5 mm. The schematic diagram of the EB reactor experimental
setup and the gas flow configuration of the reactor type I and reac-
tor type II are illustrated in Fig. 1. The NO in N2 standard gas, con-
centration of 1000 ppm obtained from Sumitomo Seika Chemical
Co., Ltd. was used as a source pollutant gas. The O 2 gas with the
purity of 99.8% from Taiyo Nippon Sanso Co., was utilized to mix
with NO in order to stimulate the conditions of the diesel engine
exhaust. The mass flow controller was used to control the gas flow
into the EB reactor as given in Fig. 1. The O2 was used as a carrier
gas for the water vapour to study the influence of the water vapouron the removal of NO and NO x. The O2 gas from the mass flow
controller was purged through the airtight glass container half
filled with Milli-Q water placed in a thermoregulated water bath.
Thus, the resultant outlet O2 gas carried the water vapour was
facilitated to mix with the NO gas stream as depicted in Fig. 1.
The generation of the water vapour could be controlled to desire
amount by adjusting the temperature of the thermoregulated
water bath. All the EB experiments were conducted at ambient
room temperature of 25 C. The stimulated gas after EB irradiation
was routed to flow into the moisture trap kept at 2 ± 1 C to re-
move all its moisture prior to the FTIR analysis.
Initially, the reactor type I was designed to examine the NO x re-
moval performance. The volume of the process vessel for the EB
treatment was 2.3 cm3. The electron beam was directed to apply
perpendicular to the gas flow in the process vessel through Ti win-
dow cathode. The gas flow configuration of the reactor type I is gi-
ven in Fig. 1. Based on the NO x removal performance of reactor
type I, the reactor type II was designed and fabricated. The reactor
type II (Fig. 1) was accomplished in such a way that to circulate the
Na2SO3 reductant solution into the process vessel of the gas flow
duct to scrub the reactant gas during EB processing. The reductant
solution was circulated through the silicon tube with constant flow
rate using the peristaltic pressure pump from the external Na2SO3
reservoir tank. The volume of the process vessel was 3.2 cm3.
2.2. Analysis
The concentration of NO and other by-products in the gas
stream obtained after EB irradiation were analyzed using JASCO
FT/IR-4200 analyzer. The FTIR instrument is equipped with a glass
cell to analyze components of the resultant gas from the EB pro-
cessing. Forty scans were collected on the gas samples at a resolu-
tion of 4 cm1. The N2 gas with a purity of 99.8% obtained from
Toei Kagaku Co., Ltd., was used for background correction. The con-
centration of NO, NO2 and N2O was calibrated using commercial
NO in N2, NO2 in N2 and N2O in N2 standard gas, respectively.
The absorbance band assigned at 1903, 1625 and 2235 cm1 in
the FTIR spectra (Fig. 2) of NO, NO2 and N2O standard gas, respec-
tively was used to prepare the calibration curves.
3. Results and discussion
3.1. NO x removal performance of reactor type I
Primarily, the feasibility of the EB technique using CNT anode
for the treatment of the gas stream containing the high concentra-
tion of NO x was investigated using reactor type I. The systematic
preliminary investigations on behaviour of NO in N2 gas and the
stimulated NO in N2 gas with O2 and water vapour under EB irra-
diation were carried out to understand the removal mechanism of
NO x. The NO in N2 gas stream was stimulated with O2 and watervapour as it reflects in the real diesel combustion exhausts.
3.1.1. Effect of EB irradiation
The behaviour of the NO gas under EB irradiation was studied in
a flow-through configuration using reactor type I (Fig. 1). The effect
of the electron beam on dry nitrogen gas stream containing the
high initial NO concentration of 1000 ppm was examined at two
different dose of 186 and 400 J/L. The gas flow rate was fixed at
6.0 L/h. The reduction in the concentration of NO, NO x and the for-
mation of NO2 and N2O with respect to time is given in Fig. 3a. It
was observed that the removal efficiency of NO is attained to
40% at the applied dose of 186 J/L and further, the removal is en-
hanced to 50% while increasing the EB dose to 400 J/L. In a non-
equilibrium technique, the electron mean energy is considerablyhigher and efficiently utilized on selective decomposition of the
P. Lakshmipathiraj et al. / Chemical Engineering Journal 229 (2013) 344–350 345
8/10/2019 1-s2.0-S1385894713007869-main.pdf
http://slidepdf.com/reader/full/1-s20-s1385894713007869-mainpdf 3/7
pollutant molecule through the production of the ions and radicals
from the background gas molecules [26]. The electron beam treat-
ment induce both oxidation and reduction reaction with pollutant
gas molecule. The breakdown mechanism of NO in the nitrogenatmosphere under EB irradiation is initiated by producing the
atomic nitrogen through the electron impact dissociation of the
nitrogen gas molecule [23]. The N atom is generated as follows.
N2 þ e ! 2Nþ e
ð1Þ
The N atom is the most important reducing species in the ab-
sence of additives thus, promote mainly the reduction of NO to
N2 and O2 in the EB and discharge processing [23]. It was observed
from the Fig. 3a that around 370 ppm of NO is unaccounted after
EB processing. This is around 74% of total NO removal of
500 ppm. The unaccounted NO attributed to convert as N2 by the
N atom reduction on NO molecule. It is expressed as
Nþ NO ! N2 þO ð2Þ
Electron beam
Gas inlet
NO,N2,O2,H2O Gas outlet
Reactor type I
Na2SO3
Circulation
Gas inlet
NO,N2,O2,H2O
Gas outlet
Reactor type II
Electron beam
Mass flow controller
Water gas at 20 oC
Cathode: Ti foil
FTIR analyser
Anode: CNT
Na2SO3 solution (3% w/v)
Flow rate: 1 cc/min
Moisture trap
NO standard gas, (1000 ppm)
N2 as Base gas
N2 gas (99.99%)
O2 gas (99.99%)
EB reactor
Gas exit
Reactor type
Fig. 1. Schematic diagram of EB reactor set up and the reactor type I and reactor type II used for NO x removal performance.
Fig. 2. FTIR spectra of NO, NO2
and N2
O standard gases.
346 P. Lakshmipathiraj et al. / Chemical Engineering Journal 229 (2013) 344–350
8/10/2019 1-s2.0-S1385894713007869-main.pdf
http://slidepdf.com/reader/full/1-s20-s1385894713007869-mainpdf 4/7
The formation of the NO2 and N2O was identified in the FTIR
spectra of the gas stream (Fig. 3b). The NO2 concentration was ob-
served to increase from 40 to 60 ppm for the EB dose increased
from 186 to 400 J/L, respectively. It indicated that the EB would
also accelerate the oxidation of NO by the reaction with O atom.
The generation of the NO2 is represented in the following equation.
NOþOþN2 ! NO2 þ N2 ð3Þ
It was observed that the N2O is formed only after the NO2 gen-
eration (Fig. 3a). Also, it was noticed that the N2O concentration is
increased than the NO2 concentration while increasing the dose
from 186 to 400 J/L. It indicated that the generation of N2O is as-
cribed to occur from NO2 concentration. The NO2 would undergo
reduction reaction with N atom to form N2O as EB processing
accelerates the reduction reaction. The vibration bands assigned
at 2234 and 1299 cm1 in the FTIR spectra confirmed the N2O for-
mation (Fig. 3b). Thus, the N2O concentration was found to in-
crease from 40 to 70 ppm for the dose increased from 186 to
400 J/L, respectively. The formation of N2O is represented in the
following equation.
Nþ NO2 ! N2Oþ O ð4Þ
Though the 500 ppm of NO was reduced within a residential
time of 1.38 s of electron beam processing, the NO x removal was
achieved only to the extent of 44% at the applied dose of 400 J/L
using reactor type I. Conversely, the FTIR spectra of the gas after
EB processing revealed the formation of the by-products such asNO2 and N2O during course of EB irradiation of the NO gas (Fig. 3b).
3.1.2. Effect of O 2
To study the effect of O2 as in the real diesel combustion ex-
haust on NO removal during EB processing, the gas flow was stim-
ulated by mixing dry O2 in the N2 gas stream. The stimulated gas
that contains the composition of 1000 ppm of NO in 90.9% N2
and 9.1% O2 with the flow rate of 6.6 L/h was subjected to investi-
gate the removal performance of NO under EB irradiation using
reactor type I. The influence of the O2
was investigated under dif-
ferent EB dose varied from 169 to 583 J/L. The experimental condi-
tions and results are depicted in Fig. 4. It was observed that the
mixing of O2 in the NO gas stream increases the generation of
NO2 even before the EB process. The increase in the NO2 concentra-
tion was proportional to decrease in NO concentration (Fig. 4a).
The oxidation reaction of NO by O2 can be represented as follows.
2NOþ O2 ! 2NO2 ð5Þ
It was also noticed that the presence of O2 increases the oxida-
tion of NO to NO2 during EB irradiation. The NO2 generation was
increased from 295 to 389 ppm for the EB dose increased from
169 to 583 J/L, respectively (Fig. 4b).
The NO removal efficiency was increased to 49%, 65% and 67% at
the applied dose of 169, 363 and 583 J/L, respectively in the pres-ence of O2. Nevertheless, The NO x removal was achieved only to
the extent of 30% at the higher applied dose of 583 J/L (Fig. 4c). This
could be attributed to oxidation of NO by EB irradiation. Similarly,
the N2O concentration was found to form around 35 ppm at the
higher applied dose 583 J/L (Fig. 4d), which is lower compared to
EB experiment conducted in the absence of O2 gas (Fig. 3a). It
was observed that the 250 ppm of NO found to be unaccounted,
which could be attributed to convert as N2 as expressed in Eq.
(2). The NO reduction efficiency was lowered 12% compared to
the EB experiment conducted in the absence of O2 (Fig. 3a).
To understand the removal mechanism of the NO and NO x un-
der EB irradiation, it is necessary to find the species involved in
the oxidation and reduction reaction. For the better understanding,
the behaviour of the dry gases such as N2, O2 and the mixture of
90.9% N2 and 9.1% O2 investigated separately under EB irradiation
with a dose of 583 J/L. The flow rate was fixed at 6.6 L/h. The FTIR
spectra of the resultant gas obtained from the EB processing are gi-
ven inthe Fig. 5. The FTIR spectra recorded for N2 gas acquired after
EB processing (Fig. 5b) did not exhibit any significant difference
compared to the spectra of the N2 and O2 mixture gas obtained
in the absence of EB irradiation (Fig. 5a). The bands assigned at
2145 and 1052 cm1 in the FTIR spectra (Fig. 5c) recorded for the
Fig. 3. (a) Effect of EB dose on NO gas, and (b) FTIR spectra of the NO gas during EB
processing.
Fig. 4. Influence of O2 on (a) removal of NO during EB processing, (b) formation of
NO2 during EB processing, (c) removal of NO x during EB processing and (d)formation of N2O during EB processing.
P. Lakshmipathiraj et al. / Chemical Engineering Journal 229 (2013) 344–350 347
8/10/2019 1-s2.0-S1385894713007869-main.pdf
http://slidepdf.com/reader/full/1-s20-s1385894713007869-mainpdf 5/7
O2 gas after EB irradiation are the characteristic bands of O3. The O3
generation is consisting of the two steps that formation of singletoxygen from dissociation of O2 by the collision with high energy
electrons and its attachment to O2 molecule forming ozone [14].
The generation of the O3 during EB processing is given as follows.
O2 þ e ! Oþ Oþ e
ð6Þ
O2 þO ! O3 ð7Þ
It was observed that the O3 production is found to increase
while increasing the EB dose (results not given). Nevertheless,
the vibration bands of O3 could not be assigned in the FTIR spectra
of the NO and O2 gas mixture acquired after EB processing (FTIR
spectra not given). It indicated that the generated O3 might have
consumed completely in the oxidation of NO to NO2 as given in
the Eq. (8), resulted in increasing the NO2 concentration from295 to 389 ppm for the EB dose increasing from 169 to 583 J/L,
respectively (Fig. 4b).
NOþ O3 ! NO2 þ O2 ð8Þ
The spectra of mixture gas (N2 and O2) after the EB processing
shown in Fig. 5d. The bands at 2234 and 1052 cm1 could be attrib-
uted to vibration bands of N2O and O3, respectively. The N2O con-
centration was found to reach 28 ppm. The excitation and
dissociation of N2 leads to a number of additional reaction paths
involving nitrogen atom and excited molecular state N2 (N2(A)).
The generation of O3 and N2O can be expressed as follows.
Nþ O2 ! NOþ O ð9Þ
eþ N2O ! N2ðA Þ þO ð10Þ
N2ðA Þ þ O ! N2O ð11Þ
O2 þO ! O3 ð7Þ
The presence of O2 in the NO gas stream increases the removal
efficiency of NO by oxidation, which in turn inhibits the removal
efficiency of NO x. Hence, it is necessary to take remediation mea-
sures to inhibit the generation of the NO2 and to increase NO x re-
moval performance.
3.1.3. Effect of water vapour on the removal of NO x
To increase the NO x removal performance and stimulate the real
gas condition of the diesel engine exhaust, the gas mixture con-taining 1000 ppm of NO in 90.9% N2 and 9.1% O2 was stimulated
to the moisture content of 5%. The dry O2 gas was used as a carrier
gas for the water vapour generated from the water at 20 C (Fig. 1).
The stimulated gas mixture was subjected to the EB processing at a
dose of 169 J/L with the flow rate of 6.6 L/h. The reduction in the
concentration of NO and NO x is given in Fig. 6. It was observed that
the removal of NO and NO x is found to be 65% and 38%, respec-
tively. The NO2 generation was found to form 250 ppm. This is
50 ppm less compared to NO2
generation in the experiment con-
ducted with the dry mixture gas (Fig. 4b). The N2O generation is
reached to the extent of 10 ppm.
The EB processing is a promising technique to produce more
numbers of excited nitrogen atoms, N(2D) and N(2P) for the reduc-
tion of NO. Nevertheless, it is reported that the electronically ex-
cited metastable N atoms (N(2D)) react rapidly with O2 to
produce NO, and counter act the NO reduction process by the
ground state N radicals [27]. The presence of H2O found to inhibit
the reactivity of the N(2D) towards NO2 generation. It is reported
that the rate constant for the interaction of the N(2D) with H2O
(2.5 1010 cm3 molecule1 s1) is very high compared to rate
constant for the interaction of the N(2D) with O2 (6 1012 cm3 -
molecule1 s1) [28]. The reaction of H2O with N(2D) can be shown
as follows.
Nð2DÞ þH2O ! NH þ
OH ð12Þ
The NH undergo reduction reaction with NO and produce N2.
NH þNO ! N2 þ
OH ð13Þ
However, it is speculate that the presence of excess amount of
O2 and generation of the OH could have the possibilities to gener-
ate more NO and NO2 and it can be represented as follows
NH þO2 ! NOþ
OH ð14Þ
NOþ
OH ! HNO2 ð15Þ
2HNO2 ! NOþNO2 þH2O ð16Þ
It is shown that the compact EB processing on the gas stream
containing 1000 ppm of NO, 10% of O2 and 5% H2O at 100 C gov-
erns the NO removal mechanism via EB generated NH reduction.
The rate constant for the reaction of NH with NO (8 1011 cm3 -
molecule1 s1) is higher than that of the rate constant for the
reaction of O2 with NO (1.4 1014 cm3 molecule1 s1). The rate
constant for the reaction of NO with OH is 8.7 1014 cm3 mole-
cule1 s1, which is very slower compared to the reaction of NH
with NO [27,29]. However, if there is an excess amount of O2 pre-
sented in the NO/N2 gas mixture, the reaction likely to precede the
Fig. 5. FTIR spectra of the different gases during the EB processing(a) mixture of N2
(90.9%) and O2 (9.1%) gas (absence of EB processing), (b) N2 gas (Dose: 583 J/L), (c)
O2 gas (Dose: 583 J/L), (d) mixture of N2 (90.9%) and O2 (9.1%) gas (Dose: 583 J/L).
Fig. 6. Influence of H2O on removal of NO x.
348 P. Lakshmipathiraj et al. / Chemical Engineering Journal 229 (2013) 344–350
8/10/2019 1-s2.0-S1385894713007869-main.pdf
http://slidepdf.com/reader/full/1-s20-s1385894713007869-mainpdf 6/7
oxidation route and enhance the NO2 generation. In addition to
that the temperature and pressure conditions of the diesel engineexhaust would also influence the NO x removal mechanism. The NO
and NO x reduction was increased to 15% and 20% compared to the
earlier experiment with the dry gas mixture of NO in N 2 and O2
(Fig. 4). The higher NO x removal could attribute to less production
of the NO2 due to the influence of water.
The removal efficiency of NO x in the presence of O2 is observed
to be only 20% at the EB dose of 169 J/L. The poor performance of
NO x removal in the presence of O2 attributed to NO2 generation.
The influence of water vapour in the NO/N2 and O2 gas mixture
is not only increased the NO x removal to the extent of 40% but also,
decrease the NO2 generation. The preliminary experimental results
obtained using reactor I, exhibited that the NO2 generation should
minimize and the residential time of the gas in the EB reactor
should increase to improve the overall NO x
removal efficiency of
the EB processing. Accordingly, the reactor type II (Fig. 1) was de-
signed and fabricated to increase the overall NO x removal perfor-
mance. The performance of the reactor type II on NO x removal
efficiency is discussed in coming section.
3.2. NO x removal performance of the reactor type II
The gas mixture containing 1000 ppm of NO in 90.9% N2, 9.1%
O2 and 5% water vapour subjected to EB processing using reactor
II (Fig. 1). The selective reductant such as Na2SO3 (3% W/V) was
employed to scrub the NO2 formed during the EB processing. The
effect of the EB dose at 363 and 811 J/L on NO and NO x removal
was investigated with the gas flow rate of 6.6 L/h. The Na2SO3 solu-
tion flow to reactor was fixed at 1 cc/min. The reduction in the con-
centration of NO and NO x and the experimental conditions are
depicted in Fig. 7. It was observed that the NO and NO x removal
could be achieved to 87.5% and 85%, respectively, with the reten-
tiontime of1.7 s. The high NO x removal could be attributed to con-
version of NO2 to NO
2 by the Na2SO3 reduction. The overall
reaction of NO2 with SO23 can be expressed as follows [30,31].
2NO2 þ SO23 þH2O ! 2NO
2 þ 2H
þ þ SO24
ð17Þ
Though the Na2SO3 scrubbing was effective in the reduction of
generated NO2, the NO2 concentration was found to reach 95 ppm.
However, the NO2 concentration was dropped to 20 ppm while
applying the EB dose. Conversely, the N2O was observed to form
the extent of 120 ppm during the EB processing. Also it could be
seen that the N2O generation is proportional to the decline in the
NO2 concentration during EB processing. It is in good agreement
with our earlier experiments (Fig. 3a) that N2O generation is
mainly by NO2 reduction as given in the Eq. (4).Further, the experiment was conducted with similar gas com-
position with the flow rate of 4.95 L/h. The EB dose at 484 and
1082 J/L on the removal of NO and NO x was examined and the re-
sults are given in Fig. 8. The removal trend of NO and NO x was ob-
served as similar that of previous experiment. The NO and NO x
removal could achieved to the extent of 97% and 95%, respectively.
This could be attributed to the longer retention time of the reactant
gas mixture. The N2O concentration was found to increase
130 ppm.
4. Conclusion
The Study clearly demonstrated the feasibility of the EB tech-
nique for the treatment of gas stream containing very high concen-tration of NO x at atmospheric pressure conditions and provides the
scope for future investigation on treatment of real diesel engine ex-
haust in ships. The EB irradiation on dry mixture gas of N2 and O2
revealed the formation of the products such as O 3 and N2O. How-
ever, the O3 generation could not be identified in the NO and O2
gas mixture acquired after EB processing. It indicated that the gen-
erated O3 might have consumed completely in the oxidation of NO
to NO2 resulted in increasing the NO2 concentration. Conversely, it
was observed that the presence of water vapours in small amount
could inhibit the formation of NO2 under EB irradiation. The scrub-
bing of Na2SO3 during the EB processing was effective in the reduc-
tion of generated NO2 concentration thus increased the NO x
removal performance of the reactor. The NO2 was found to be
source for the formation of N2O under EB irradiation. Further, nec-essary measures to be investigated to minimize the generation of
N2O during EB processing.
References
[1] A. Chaloulakou, I. Mavroidis, I. Gavriil, Compliance with the annual NO2 air
quality standard in Athens. Required NO x levels an expected health
implications, Atoms. Environ. 42 (2008) 454–465.
[2] K. Skalska, J.S. Miller, S. Ledakowicz, Trends in NO x abatement: a review, Sci.
Total Environ. 408 (2010) 3976–3989.
[3] F. Luck, J. Roiron, Selective catalytic reduction of NO x emitted by nitric acid
plants, Catal. Today 4 (1989) 205–218.
[4] T.C. Bruggemann, F.J. Keil, Theoretical investigation of the mechanism of the
selective catalytic reduction of nitric oxide with ammonia on H-form zeolites,
J. Phys. Chem. C 112 (2008) 17378–17387.
[5] M.A. Gomez-Garcia, V. Pitchon, A. Kiennemann, Pollution by nitrogen oxides:
an approach to NO x abatement by using sorbing catalytic materials, Environ.Int. 31 (2005) 445–467.
Fig. 7. Effect of Na2SO3 on removal of NO x during EB processing (gas flow rate:
6.6 L/h).
Fig. 8. Effect of Na2SO3 on removal of NO x during EB processing (gas flow rate:4.95 L/h).
P. Lakshmipathiraj et al. / Chemical Engineering Journal 229 (2013) 344–350 349
8/10/2019 1-s2.0-S1385894713007869-main.pdf
http://slidepdf.com/reader/full/1-s20-s1385894713007869-mainpdf 7/7
[6] L.J. Muzio, G.C. Quartucy, Implementing NO x control: research to application,
Prog. Energy Combust. 23 (1997) 233–266.
[7] L.Z. Gao, H.T. Chua, S. Kawi, The direct decomposition of NO over the la2CuO4
nanofiber catalyst, J. Solid State Chem. 181 (2008) 2804–2807.
[8] X. Chang, G. Lu, Y. Guo, Y. Wang, Y. Guo, A high effective adsorbent of NO x:
preparation, characterization and performance of Ca-beta Zeolites, Micropore
Mesopore Mater. 165 (2013) 113–120.
[9] Z. Zheng, P. Lu, C. Li, L. Mai, Z. Li, Y. Zhang, Removal of NO by carbonaceous
materials at room temperature: a review, Catal. Sci. Technol. 2 (2012) 2188–2199.
[10] L. Olsson, H. Sjovall, R.J. Blint, Detailed kinetic modeling of NO x adsorption and
NO oxidation over Cu–ZSM-5, Appl. Catal. B 87 (2009) 200–210.[11] A. Heyden, N. Hansen, A.T. Bell, F.J.J. Keil, Nitrous oxide decomposition over
Fe–ZSM-5 in the presence of nitric oxide: a comprehensive DFT study, Phys.
Chem. B 110 (2006) 17096–17114.
[12] W. Wang, Z. Zhao, F. Liu, S. Wang, Study of NO/NO x removal from flue gas
contained fly ash and water vapour by pulsed corona discharge, J. Electrostat.
63 (2005) 155–164.
[13] R. McAdams, Prospects for non-thermal atmospheric plasmas for pollution
abatement, J. Phys. D: Appl. Phys. 34 (2001) 2810–2821.
[14] G. Sathiamoorthy, S. Kalyana, W.C. Finney, R.J. Clark, B.R. Locke, Chemical
reaction kinetics and reactor modelling of NO x removal in a pulsed streamer
corona discharge reactor, Ind. Eng. Chem. Res. 38 (1999) 1844–1855.
[15] B.M. Penetrante, M.C. Hsiao, B.T. Merritt, G.E. Vogtlin, P.H. Wallman, Pulsed
coronaand dielectric-barrier dischargeprocessing of NO in N2, Appl. Phys. Lett.
68 (1996) 3719–3721.
[16] A.M. Vandenbroucke, R. Morent, N. De Geyter, C. Leys, Non-thermal plasmas for
non-catalytic and catalytic VOC abatement, J. Hazard. Mater. 195 (2011) 30–54.
[17] H. Potts, J. Hugill, Studies of high-pressure, partially ionized plasma generated
by 2.45 GHz microwaves, Plasma Sources Sci. Technol. 9 (2000) 18–24.
[18] Y.S. Mok, V. Ravi, H.-C. Kang, B.S. Rajanikanth, Abatement of nitrogen oxides in
a Catalytic reactor enhanced by nonthermal plasma discharge, IEEE Trans.
Plasma Sci. 31 (2003) 157–165.
[19] C.W. Park, J.H. Byeon, K.Y. Yoon, J.H. Park, J. Hwang, Simultaneous removal of
odors, airborne particles, andbioaerosols in a municipalcomposting facility by
dielectric barrier discharge, Sep. Purif. Technol. 77 (2011) 87–93.
[20] Ch. Subrahmanyam, A. Renken, L. Kiwi-Minsker, Catalytic non-thermal plasma
reactor for abatement of toluene, Chem. Eng. J. 160 (2010) 677–682.
[21] B.M. Penetrante, M.C. Hsiao, J.N. Bardsley, B.T. Merritt, G.E. Vogtlin, A. Kuthi,
C.P. Burkhart, J.R. Bayless, Identification of mechanisms for decomposition of
air pollutants by non-thermal plasma processing, Plasma Sources Sci. Technol.
6 (1997) 251–259.
[22] A.A. Basfar, O.I. Fageeha, N. Kunnummal, S. Al-Ghamdi, A.G. Chmielewski, J.
Licki, A. Pawelec, B. Tyminski, Z. Zimek, Electron beam flue gas treatment
(EBFGT) technology for simultaneous removal of SO2 and NO x from
combustion of liquid fuels, Fuel 87 (2008) 1446–1452.
[23] B.M. Penetrante, M.C. Hsiao, B.T. Merritt, G.E. Vogtlin, P.H. Wallman, Electron-impact dissociation of molecular nitrogen in atmosphere-pressure nonthermal
reactor, Appl. Phys. Lett. 67 (1995) 3096–3098.
[24] A.G. Chmielewski, Y. Sun, J. Licki, A. Pawelec, S. Witman, Z. Zimek, Electron
beam treatment of high NO x concentration off-gases, Radiat. Phys. Chem. 81
(2012) 1036–1039.
[25] A.G. Chmielewski, Industrial application of electron beam flue gas treatment –
from laboratory to practice, Radiat. Phys. Chem. 76 (2007) 1480–1484.
[26] M. Magureanu, V.I. Parvulescu, Plasma-assisted NO x abatement processes: a
new promising technology for lean condition, Past Present De NO x Catal. 171
(2007) 361–396.
[27] B.M. Penetrante, M.C. Hsiao, B.T. Merritt, P.H. Wallman, G.E. Vogtlin, NO x
reduction by compact electron beam processing, in: Proceedings of the 1995
Diesel Engine Emissions Reduction Workshop, USDOE Office of Transportation
Technologies, 1995, pp. IV-75–IV-85.
[28] K. Schofield, Critically evaluated rate constants for gaseous reactions of
several electronically excited species, J. Phys. Chem. Ref. Data 8 (1979) 723–
798.
[29] R. Atkinson, D.L. Baulch, R.A. Cox Jr., R.F. Hampson, J.A. Kerr, J. Tore, Evaluated
and photochemical data for atmospheric chemistry: supplement IV, J. Phys.
Chem. Ref. Data 21 (1992) 1125–1568.
[30] D. Littlejohn, Y. Wang, S.-G. Chang, Oxidation of aqueous sulphite ion by
nitrogen dioxide, Environ. Sci. Technol. 27 (1993) 2162–2167.
[31] L. Chen, J.-W. Lin, C.-L. Yang, Absorption of NO2 in a packedtower with Na2SO3
aqueous solution, Environ. Prog. 21 (2002) 225–230.
350 P. Lakshmipathiraj et al. / Chemical Engineering Journal 229 (2013) 344–350