Plasma-catalytic reforming of rich ethanol-air mixtures
Influence of the ratio between the components of the ethanol-air mixture on the characteristics of the plasma components was investigated using optical emission spectroscopy. The vibrational population distribution of excited OH molecules during the hybrid plasma-catalytic reforming was shown to not...
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| Cite this: | Plasma-catalytic reforming of rich ethanol-air mixtures / I.I. Fedirchyk, O.A. Nedybaliuk, V.Ya. Chernyak, V.P. Demchina // Problems of atomic science and technology. — 2019. — № 1. — С. 164-167. — Бібліогр.: 4 назв. — англ. |
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Fedirchyk, I.I. Nedybaliuk, O.A. Chernyak, V.Ya. Demchina, V.P. 2023-11-29T09:16:45Z 2023-11-29T09:16:45Z 2019 Plasma-catalytic reforming of rich ethanol-air mixtures / I.I. Fedirchyk, O.A. Nedybaliuk, V.Ya. Chernyak, V.P. Demchina // Problems of atomic science and technology. — 2019. — № 1. — С. 164-167. — Бібліогр.: 4 назв. — англ. 1562-6016 PACS: 50., 52., 52.50.Dg, 52.80.Dg https://nasplib.isofts.kiev.ua/handle/123456789/194710 Influence of the ratio between the components of the ethanol-air mixture on the characteristics of the plasma components was investigated using optical emission spectroscopy. The vibrational population distribution of excited OH molecules during the hybrid plasma-catalytic reforming was shown to not correspond with the Boltzmann distribution. Вплив співвідношення між компонентами суміші етанол-повітря на характеристики компонент плазми було досліджено за допомогою оптичної емісійної спектроскопії. Показано, що під час реформування розподіл заселення коливних рівнів збуджених молекул OH не відповідає розподілу Больцмана. Влияние соотношения между компонентами этанол-воздушной смеси на характеристики компонент плазмы было исследовано с помощью оптической эмиссионной спектроскопии. Показано, что во время реформирования распределение заселения колебательных уровней возбуждённых молекул ОН не соответствует распределению Больцмана. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Low temperature plasma and plasma technologies Plasma-catalytic reforming of rich ethanol-air mixtures Плазмово-каталітичне реформування збагачених етанол-повітряних сумішей Плазменно-каталитическое реформирование обогащенных этанол-воздушных смесей Article published earlier |
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Plasma-catalytic reforming of rich ethanol-air mixtures |
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Plasma-catalytic reforming of rich ethanol-air mixtures Fedirchyk, I.I. Nedybaliuk, O.A. Chernyak, V.Ya. Demchina, V.P. Low temperature plasma and plasma technologies |
| title_short |
Plasma-catalytic reforming of rich ethanol-air mixtures |
| title_full |
Plasma-catalytic reforming of rich ethanol-air mixtures |
| title_fullStr |
Plasma-catalytic reforming of rich ethanol-air mixtures |
| title_full_unstemmed |
Plasma-catalytic reforming of rich ethanol-air mixtures |
| title_sort |
plasma-catalytic reforming of rich ethanol-air mixtures |
| author |
Fedirchyk, I.I. Nedybaliuk, O.A. Chernyak, V.Ya. Demchina, V.P. |
| author_facet |
Fedirchyk, I.I. Nedybaliuk, O.A. Chernyak, V.Ya. Demchina, V.P. |
| topic |
Low temperature plasma and plasma technologies |
| topic_facet |
Low temperature plasma and plasma technologies |
| publishDate |
2019 |
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English |
| container_title |
Вопросы атомной науки и техники |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Article |
| title_alt |
Плазмово-каталітичне реформування збагачених етанол-повітряних сумішей Плазменно-каталитическое реформирование обогащенных этанол-воздушных смесей |
| description |
Influence of the ratio between the components of the ethanol-air mixture on the characteristics of the plasma components was investigated using optical emission spectroscopy. The vibrational population distribution of excited OH molecules during the hybrid plasma-catalytic reforming was shown to not correspond with the Boltzmann distribution.
Вплив співвідношення між компонентами суміші етанол-повітря на характеристики компонент плазми було досліджено за допомогою оптичної емісійної спектроскопії. Показано, що під час реформування розподіл заселення коливних рівнів збуджених молекул OH не відповідає розподілу Больцмана.
Влияние соотношения между компонентами этанол-воздушной смеси на характеристики компонент плазмы было исследовано с помощью оптической эмиссионной спектроскопии. Показано, что во время реформирования распределение заселения колебательных уровней возбуждённых молекул ОН не соответствует распределению Больцмана.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/194710 |
| citation_txt |
Plasma-catalytic reforming of rich ethanol-air mixtures / I.I. Fedirchyk, O.A. Nedybaliuk, V.Ya. Chernyak, V.P. Demchina // Problems of atomic science and technology. — 2019. — № 1. — С. 164-167. — Бібліогр.: 4 назв. — англ. |
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2025-11-24T16:50:23Z |
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2025-11-24T16:50:23Z |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2019. №1(119)
164 PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2019, № 1. Series: Plasma Physics (25), p. 164-167.
PLASMA-CATALYTIC REFORMING OF RICH ETHANOL-AIR
MIXTURES
I.I. Fedirchyk
1
, O.A. Nedybaliuk
1
, V.Ya. Chernyak
1
, V.P. Demchina
2
1
Taras Shevchenko National University of Kyiv, Kyiv, Ukraine;
2
Gas Institute of NASU, Kyiv, Ukraine
E-mail: chernyak_v@ukr.net, igor.fedirchyk@univ.net.ua
Influence of the ratio between the components of the ethanol-air mixture on the characteristics of the plasma
components was investigated using optical emission spectroscopy. The vibrational population distribution of excited
OH molecules during the hybrid plasma-catalytic reforming was shown to not correspond with the Boltzmann
distribution.
PACS: 50., 52., 52.50.Dg, 52.80.Dg
INTRODUCTION
Interest in the conversion of renewable hydrocarbon
raw materials into the feedstock suitable as a crude oil
replacement for chemical industry increased with the
global shift towards sustainability at the start of the 21st
century. Despite important advantages, conversion of
renewable raw materials into value-added chemicals has
complications, which stem from the complexity and
variety of their composition. The most well-developed
are indirect approaches, which first convert renewable
raw materials into the syngas (a mixture of H2, CO, and
light hydrocarbons) mainly via the gasification process.
Produced syngas is then used in methanol or Fischer-
Tropsch synthesis to obtain the desired chemicals.
Unfortunately, this pathway of renewable raw materials
conversion requires high energy input and provides low
product yields.
Among the alternative processes that show great
potential in this area is plasma technology. Low-
temperature non-thermal plasma has the advantage of
being able to activate chemical processes by producing
electrons, excited atoms, and excited molecules, instead
of initiating the reactions via heating of the reactor. In
addition, plasma has already been successfully used to
produce syngas from renewable raw materials.
Considering this, several recent studies examined the
prospect of value-added chemicals synthesis from light
hydrocarbons using plasma [1] or plasma-like
conditions in rich flames [2].
This work focuses on the experimental investigation
of the system for the synthesis of value-added chemicals
and raw materials from renewable liquid hydrocarbon
using plasma-catalytic approach to the activation of
chemical reactions.
1. EXPERIMENTAL SETUP AND METHODS
Fig. 1 presents the scheme of the system for plasma
catalytic reforming of liquid hydrocarbons, which is
based on rotating gliding discharge. The reforming
system has two connected chambers: a discharge
chamber and a reaction chamber. During the
experiment, food-grade ethanol was used as a model
hydrocarbon and atmospheric air was used as a model
oxidant. The flow of air that was needed for the
reforming was divided between the discharge chamber
and the reaction chamber. Part of the air was introduced
into the system through the discharge chamber,
activated by a discharge and used as a source of active
species for reforming initiation. Plasma-activated air
was introduced into the reaction chamber as a torch
through the aperture in one of the electrodes. The rest of
the air was mixed with ethanol and introduced through
the top of the reaction chamber. Reagents were
introduced into chambers tangentially to their walls as
formed rotating flows. The plasma-catalytic reforming
of ethanol was conducted using cylindrical quartz
reaction chamber 100 mm in height and with 36 mm
internal diameter. The discharge was ignited between
the internal T-shaped stainless-steel anode electrode,
which diameter was 25 mm, and the external grounded
stainless-steel ring cathode with a 20 mm wide circular
aperture in its center.
Fig. 1. Scheme of the hybrid plasma-catalytic system
with rotating gliding discharge for the reforming of
liquid hydrocarbons into synthesis gas
ISSN 1562-6016. ВАНТ. 2019. №1(119) 165
The rotating gliding discharge was powered by
BP-100 power source (PS), which provided 7 kV
voltage at 33 k ballast resistance (Rb). Discharge
voltage and current were measured using a voltmeter
and an ammeter.
Optical emission spectroscopy (OES) of the plasma
torch radiation in the quartz reaction chamber was
conducted using a system consisting of an optical fiber,
Solar TII (S-150-2-3648 USB) spectral device and a PC.
Spectrometer operated in a wavelength range from 200
to 1000 nm. PC was used for controlling measurements
and processing data obtained from the spectrometer.
Spectra were measured at distance h from the discharge
chamber. OES was conducted at several distances h: 0,
2.5, 5, and 7.5 mm. Optical emission spectra were used
to determine the vibrational and rotational temperatures
of excited hydroxyl (OH) molecules in different zones
of the reforming reactor.
Reaction chamber wall temperature was measured
using two thermocouples, which were connected to the
top (T1) and bottom (T2) of the reaction chamber at
10 mm distance from the reaction chamber input and
reaction zone, respectively.
The flows of introduced ethanol were 324, 648, and
810 ml·h
-1
. The ratios between the introduced ethanol
and oxygen were 1:1, 2:1, and 5:2, which correspond to
rich mixtures with fuel-air equivalence ratios of 3, 6,
and 7.5 respectively. During the study, input air flow
was 10 l∙min
-1
, which at 2:1 ratio between introduced
ethanol and oxygen corresponded to the stoichiometry
of ethanol partial oxidation reaction.
The air flow introduced inside the discharge
chamber was equal 6 l∙min
-1
and the air flow that was
mixed with ethanol and introduced inside the reaction
chamber was 4 l∙min
-1
. Based on the bottom
thermocouple measurements, the temperature the
reaction chamber wall during reforming ranged from
200 to 300 °С. The photographs of the system during its
operation were done using a Nikon™ D7100 camera.
2. RESULTS AND THEIR DISCUSSION
The discharge current during the reforming was set
to 60 mA. Discharge voltage was oscillating between
600 and 800 V. Average discharge power during the
reforming was approximately 45 W.
Fig. 2 shows the photographs of the reforming
system in operation.
OES was conducted at T1 ≈ 150
o
C and T2 ≈ 250
o
C.
The 100
o
C difference between temperatures is due to
the low thermal conductivity of the reaction chamber
material – quartz.
Fig. 3 shows optical emission spectra of the rotating
gliding discharge plasma torch inside a quartz reaction
chamber with air as a working gas without ethanol and
during the hybrid plasma-catalytic reforming of
810 ml∙h
-1
ethanol flow.
Fig. 2. Photographs of the system operating (A)
only with discharge and (B) during ethanol reforming
Fig. 3. Normalized emission spectra from reaction chamber at h = 0 mm during operation at 10 l·min
−1
airflow
without ethanol flow (grey) and with 810 ml·h
−1
ethanol flow (black) (I = 60 mA, U = 0.7 kV)
166 ISSN 1562-6016. ВАНТ. 2019. №1(119)
Both displayed spectra (see Fig. 3) are normalized.
In case of air without ethanol, the emission spectra
contain bands of hydroxyl OH, nitrogen monoxide NO
and low-intensity bands of nitrogen N2. The
introduction of 96 % ethanol (810 ml∙h
-1
) led to the
significant decrease of the intensities of NO bands in the
emission spectra and a slight decrease in the intensities
of N2 bands. The intensity drop of NO bands could
appear as a response to the start of H2 production after
the introduction of ethanol, which reduces NO.
The spectra show that relative intensity of OH band
in 280…300 nm wavelength range in comparison to the
intensity of OH band in 300…320 nm wavelength range
decreased with the introduction of ethanol. This drop of
OH band intensity is caused either by the decrease of
NO bands intensity that can overlap with OH bands in
this wavelength range or by the decreased amount of
vibrationally excited OH molecules inside the reaction
chamber during the reforming of ethanol.
Obtained optical emission spectra were used to
determine the temperatures that characterize the
distributions of vibrational and rotational populations of
excited molecules that are present in plasma.
Temperatures were determined by importing the
experimental spectra into Specair software [3] and
compared with the spectra that were modeled for
specific vibrational and rotational temperatures of
studied plasma species. Hydroxyl bands were used to
obtain the desired temperatures due to their higher
intensity in comparison to other species that have their
bands visible on the obtained spectra.
During the fitting of spectra, shapes of the
experimentally obtained OH bands located between 280
and 300 nm, which correspond to OH(A-X)(1.0),
OH(A-X)(2.1), and OH(A-X)(3.2) transitions and
depend on the vibrational temperature of OH, did not fit
with the shapes of modeled OH spectra in this
wavelength range. The comparison is presented in
Fig. 4.
The lower intensity of OH(1.0) in comparison to
OH(2.1) in the experimental spectra is different from
the shape of modeled spectra. The difference can be
caused by the non-Boltzmann distribution of the
vibrational population of excited OH molecules during
the reforming.
Fig. 5,a shows the rotational temperatures of
hydroxyl molecules determined from the optical
emission spectra measured during the reforming of
324 ml∙h
-1
ethanol flow at different distances h from the
discharge chamber.
Fig. 4. Comparison between shape of experimental emission spectrum of hydroxyl (OH) and modeled spectra for
different vibrational temperatures of OH, experimental spectrum obtained for 10 l·min
−1
airflow and 324 ml·h
−1
ethanol flow (I = 60 mA, U = 0.7 kV)
a b
Fig. 5. Rotational (Tr) temperatures of hydroxyl (OH) during reforming determined from OES at different distances
h, 10 l·min
−1
airflow and 324 ml·h
−1
ethanol flow (I = 60 mA, U = 0.7 kV) (a); rotational (Tr) temperatures of
hydroxyl (OH) determined at h = 0 mm, 10 l·min
−1
airflow and different ethanol flows (I = 60 mA, U = 0.7 kV);
ethanol flow 0 corresponds to OH temperatures in RGD without reforming (b)
ISSN 1562-6016. ВАНТ. 2019. №1(119) 167
Temperatures were compared for four different
distances h: 0, 2.5, 5, and 7.5 mm. Obtained
temperatures show that for h ranging from 0 to 5 mm
during the plasma-catalytic reforming of ethanol
rotational temperatures of hydroxyl remained almost
unchanged: Tr(OH) = (3200±200) K. At h = 7.5 mm
rotational temperature of hydroxyl molecules dropped to
(2400±400) K. Higher temperature error margins at
h = 7.5 mm stem from lower signal-to-noise ratio in
spectra obtained at this distance.
Fig. 5,b shows the change of the rotational
temperatures of hydroxyl species at different ethanol
flows at distance h = 0 mm.
Ethanol flows that were used for the comparison
were 0, 324, 648, and 810 ml∙h
-1
. Supplied air flow was
10 l·min
-1
. 0 ml·h
-1
ethanol flow corresponded to the
operation of discharge without ethanol supply and
reforming.
At 0 ml·h
-1
, the vibrational temperature of hydroxyl
was (4000±200) K, which was higher than the rotational
temperature ((2800±200) K). These temperatures
indicate that rotating gliding discharge produced non-
equilibrium plasma. The addition of ethanol flow
(324 ml·h
-1
) and initiation of the reforming led to the
rise of the rotational temperature of OH to
(3200±200) K; however, as was previously mentioned,
the determination of vibrational temperature during the
reforming was impossible due to the shape difference
between the modeled and experimental spectra. With
the increase of the ethanol flow to 648 ml∙h
-1
rotational
temperature of excited OH molecules slightly increased
to (3400±200) K and at 810 ml·h
-1
ethanol flow
rotational temperature of OH was (3200±200) K.
Obtained data shows that the increase of the ethanol
flow at the same airflow has little effect on the
rotational temperature of OH molecules near the
reaction zone, which remains the same within the error
margin of the used temperature measurement method.
At the same time, the shape of experimental spectra
indicates the non-Boltzmann distribution of the
vibrational population of excited OH molecules during
the hybrid plasma-catalytic reforming of ethanol. The
shift from the Boltzmann distribution observed during
the discharge operation without reforming can be
caused by the active role of the energy of vibrationally
excited molecules in the reforming reactions. This
differentiates hybrid plasma-catalytic reforming from
the situation during the direct injection of ethanol into
the discharge chamber [4]. In that case, the vibrational
temperature of excited OH molecules remained
unchanged while their rotational temperature increased
with the increase of ethanol flow.
CONCLUSIONS
Research showed that during plasma-catalytic
reforming of rich ethanol-air mixtures the vibrational
population distribution of OH does not correspond to
Boltzmann distribution. The deviation from the
Boltzmann vibrational population distribution may
indicate the active role of the vibrationally excited OH
molecules in the reforming reactions. The influence of
the specific vibrational energy levels of OH on the
reforming process requires further investigation via
experiments and numerical simulation of reforming
kinetics.
Reforming leads to a slight increase of OH rotational
temperature when compared to the operation of rotating
gliding discharge. In the experimental setup, rotational
temperature remains stable alongside the axis of the
reaction chamber for h ranging from 0 to 7.5 mm. The
increase of fuel-air equivalence ratio has little impact on
the rotational temperature of excited OH molecules.
REFERENCES
1. R. Snoeckx et al. Plasma-based liquefaction of
methane: The road from hydrogen production to direct
methane liquefaction // Plasma Process. Polym. 2017,
v. 14, № 6, p. 1600115.
2. V. Arutyunov et al. Production of olefins by the
conjugated oxidation of light hydrocarbons // Chem.
Eng. J. 2017, v. 329, p. 231-237.
3. C.O. Laux et al. Optical diagnostics of atmospheric
pressure air plasmas // Plasma Sources Sci. Technol.
2003, v. 12, № 2, p. 125-138.
4. V.Y. Chernyak et al. Plasma catalysis of chemical
reactions // Probl. At. Sci. Technol. 2014, v. 94, № 6,
p. 124-129.
Article received 11.11.2018
ПЛАЗМЕННО-КАТАЛИТИЧЕСКОЕ РЕФОРМИРОВАНИЕ ОБОГАЩЕННЫХ
ЭТАНОЛ-ВОЗДУШНЫХ СМЕСЕЙ
И.И. Федирчик, О.А. Недыбалюк, В.Я. Черняк, В.П. Демчина
Влияние соотношения между компонентами этанол-воздушной смеси на характеристики компонент
плазмы было исследовано с помощью оптической эмиссионной спектроскопии. Показано, что во время
реформирования распределение заселения колебательных уровней возбуждённых молекул ОН не
соответствует распределению Больцмана.
ПЛАЗМОВО-КАТАЛІТИЧНЕ РЕФОРМУВАННЯ ЗБАГАЧЕНИХ
ЕТАНОЛ-ПОВІТРЯНИХ СУМІШЕЙ
І.І. Федірчик, О.А. Недибалюк, В.Я. Черняк, В.П. Демчина
Вплив співвідношення між компонентами суміші етанол-повітря на характеристики компонент плазми
було досліджено за допомогою оптичної емісійної спектроскопії. Показано, що під час реформування
розподіл заселення коливних рівнів збуджених молекул OH не відповідає розподілу Больцмана.
|