ArticlePDF Available

Influence of oxygen concentration, feed gas flow rate and air humidity on the output of ozone produced by corona discharge: Frailty and Life Satisfaction in Elderly

Authors:
Le Cao Cuong
Le Cao Cuong
Nguyen Hoang Nghi at VNU University of Science
Nguyen Hoang Nghi
Tran Vinh Dieu
Tran Vinh Dieu
Tran Vinh Dieu
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Doan Thi Yen Oanh at Vietnam Academy of Science and Technology
Doan Thi Yen Oanh
Show all 5 authorsHide
Download full-text PDF
Read full-text
Download citation

Abstract and Figures

Ozone (trioxygen) shows a lack of stability and quickly breaks down to dioxygen, meaning that ozone in any way can not be stored. It is therefore necessary to produce ozone on site where it is used. This leads to the idea of having an ozone generator with high efficiency. Ozone generator is an electrical device to convert oxygen as feed gas into ozone. Besides electrical parameters, feed gas plays an important role for ozone output. Feed gas for an ozone generator may be ambient air, dry air or oxygen rich gas. The influence of air humidity, oxygen concentration, flow rates of feed gas and their effects on ozone output of the corona discharge ozone generator have been investigated. For small‐scale ozone production (i.e. one hundred grams per hour or less), using oxygen produced by pressure swing adsorption method (PSA) is considered to be a reasonable solution. The authors intend to connect the studies with the practical reality of using low‐powered ozone generators in tropical area with high humidity condition.
Figures - uploaded by Doan Thi Yen Oanh
Author content
All figure content in this area was uploaded by Doan Thi Yen Oanh
Content may be subject to copyright.
Content uploaded by Doan Thi Yen Oanh
Author content
All content in this area was uploaded by Doan Thi Yen Oanh on Mar 24, 2020
Content may be subject to copyright.
Cite this paper: Vietnam J. Chem., 2019, 57(5) 604-608 Article
DOI: vjch.201900095
604 Wiley Online Library © 2019 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Influence of oxygen concentration, feed gas flow rate and air humidity
on the output of ozone produced by corona discharge
Le Cao Cuong1, Nguyen Hoang Nghi1*, Tran Vinh Dieu1,
Doan Thi Yen Oanh2*, Dang Duc Vuong1
1Hanoi University of Science and Technology, 1 Dai Co Viet, Hai Ba Trung, Hanoi 100000, Viet Nam
2Publishing House for Science and Technology, Vietnam Academy of Science and Technology, 18 Hoang
Quoc Viet, Cau Giay, Hanoi 100000, Viet Nam
Received July 23, 2019; Accepted for publication July 26, 2019
Abstract
Ozone (trioxygen) shows a lack of stability and quickly breaks down to dioxygen, meaning that ozone in any way
can not be stored. It is therefore necessary to produce ozone on site where it is used. This leads to the idea of having an
ozone generator with high efficiency. Ozone generator is an electrical device to convert oxygen as feed gas into ozone.
Besides electrical parameters, feed gas plays an important role for ozone output. Feed gas for an ozone generator may
be ambient air, dry air or oxygen rich gas. The influence of air humidity, oxygen concentration, flow rates of feed gas
and their effects on ozone output of the corona discharge ozone generator have been investigated. For small-scale ozone
production (i.e. one hundred grams per hour or less), using oxygen produced by pressure swing adsorption method
(PSA) is considered to be a reasonable solution. The authors intend to connect the studies with the practical reality of
using low-powered ozone generators in tropical area with high humidity condition.
Keywords. Ozone, generator, ozone output, oxygen concentration, humidity, flow rate.
1. INTRODUCTION
Ozone as a powerful oxidant is widely used for
water and air disinfection because it can destruct
varied compounds especially organic ones such as
bacteria and fungi which comes in contact with
ozone molecules, or more accurately speaking, with
the extra oxygen radicals disassociated from
ozone.[1] Ozone is commonly known as chemically
not stable and spontaneously breaks down into
oxygen after a few hours. This is the reason why
ozone cannot be stored in high pressured cylinder,
hence ozone must be produced on site where it is
used. For this reason, ozone application is always
coupled with ozone generators. Quality of ozone
generators depends on electrical parameters such as
voltage, frequencies and, also, it strongly depends on
the quality of the feed gas (oxygen-rich gas). Feed
gas for ozone generators must be dry and oxygen
rich. Flow rate of feed gas also plays a significant
role. Three requirements for professional ozone
production include (i) high ozone output (ozone
production power), (ii) high ozone concentration and
(iii) low concentration of nitrogen oxides. The study
in this paper mainly focuses on the quality of feed
gas and its effect on ozone output and concentration.
The influence of air humidity, oxygen concentration
and flow rate on the ozone output and concentration
will be shown and discussed in details. It should be
noted that, ozone generators of low power (i.e. a few
grams per hour or less) usually use ambient air as
feed gas. Therefore, investigation of the influence of
ambient air humidity on work of low power
generator has practical meanings for use in the area
with high humidity such as North Vietnam. Besides,
oxygen generators based on PSA technique have
been designed and manufactured in BKIDT
Company (Hanoi). Oxygen as feed gas produced by
PSA is considered to be a suitable solution for small
and high efficiency ozone generators in comparison
with those by fractional distillation of liquefied air.
2. MATERIALS AND METHODS
The output P of ozone in the corona discharge
generator is investigated. The ozone output value is
shown in a mass over time value g/hr, i.e. the mass
of ozone produced by ozone generator in a given
period of time. This value can be calculated through
the flow rate R of feed gas (m3/hr) and ozone
concentration C (g/m3) by:
P = R x C
Vietnam Journal of Chemistry Nguyen Hoang Nghi et al.
© 2019 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.vjc.wiley-vch.de 605
It is commonly known that flow rate is measured
in LPM (liter per minute) and ozone concentration in
g/m3; in this case the output is calculated as:
P (g/hr)= [R x (LPM x 60) x 0.001] x C(g/m3)
The above conversion formula shows the
relation between ozone output (g/h), the flow rate
(L/min) of feed gas and ozone concentration (g/m3).
Feed gas plays a very important role in corona
discharge ozone production. There exist three types
of feed gases used for ozone generation. They are
ambient air, dry air and concentrated oxygen. The
dry air refers to air which has moisture removed so
the dew point is –60 oC or lower. (At –60 oC, mass
of water in 1 m3 of air is near zero (0.008 g/m3), at
+20 oC, it is 17.5 g/m3, i.e. 2,180 times greater).
Concentrated oxygen made by the fractional
distillation of liquefied and stored in pressured
cylinders (> 96 %) or in the form of liquid oxygen
issued in large-scale ozone production, for instance
P~100 kg ozone per hour. Oxygen produced by PSA
is used on site and for small-scale ozone production
(i.e. hundreds grams of ozone per hour).
For small output ozone generator (a few up to
~100 gr. per hour), ambient air and oxygen-rich gas
produced by PSA equipment are used. Our research
focuses on these feed gases for small generators.
Ambient air with high relative humidity up to 90 %
or higher is usually observed in the tropical area.
The experiments are performed in a room where the
air is controlled by a humidifier to change the
relative humidity from 25 % to 96 % at the
temperature of around 24 oC. Ozone output vs.
humidity is measured while air flow rates are kept
unchanged (5 L/min). The influence of oxygen
concentration on ozone output is investigated by
using the 98 % oxygen from high pressure cylinder
and its mix with air.
To realize the above mentioned tasks, the
following devices are used: an ozone corona
discharge generator and oxygen PSA generator
manufactured in BKIDT company (Hanoi), an ozone
and oxygen concentration meters (in gr/m3 and in
%), a gas rotor flow meter and a 98 % oxygen from
a pressure cylinder. Ozone production discharge is
the dielectric-barrier discharge (DBD) that is the
electrical discharge between two electrodes
separated by a quartz dielectric barrier. Thanks to a
dielectric barrier, discharge becomes silent
(inaudible) and soft. This kind of discharge is called
corona discharge that differs from the spark or arc
discharge. Corona (DBD) discharge is also called
volume discharge, i.e. it is pervasive to all space
between electrodes. When oxygen flows to the cell
filled with corona media, the bombardment between
radicals (high energy electrons) and oxygen
molecules takes place with high probability.
Oxygen generator PSA used in this work is
based on the ability of porous zeolite (adsorbent) to
selectively adsorb gas molecules. Nitrogen molecule
from air is kept in zeolite layers but oxygen crosses
it and goes to user.
The scheme for ozone measurement is shown in
figure 1. Inlet gas comes to the ozone generator
(ozone cell) from three sources: (i) high pressure
oxygen cylinder, (ii) oxygen from PSA generator
and (iii) humidified ambient air. The oxygen
concentration, humidity and feed gas flow rate are
measured and controlled. An ozone meter is used to
measure the ozone concentration.
Figure 1: Scheme for ozone measurement
(Ozone output vs oxygen concentration, feed gas flow rate and air humidity)
Vietnam Journal of Chemistry Influence of oxygen concentration, feed…
© 2019 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.vjc.wiley-vch.de 606
3. RESULTS AND DISCUSSION
3.1. Influence of oxygen concentration on the
ozone output
There are two values characterizing the quality of an
ozone generator: the ozone output (or ozone power
production) P (g/hour) and the ozone concentration
C (g/m3). Both are important for application. The
first refers to the power of the generator that needs
to know for different purposes of application. As
commonly known, the greater ozone concentration is
higher soluble in water.
Figure 2 shows the increase of ozone output
from near 3 g/hr to ~24 g/hr vs. oxygen
concentration increase from 21 % to 98 %. Ozone
output of a generator using oxygen is usually twice
more than using dry air (2X). In this work, this ratio
is near 8 (8X), (24 g/hr vs. 2.85 g/hr). Very high
productivity of oxygen compared with ambient air as
feed gas is reached because ambient air was not dry
(air humidity very high, > 80 %, at 24 oC),
consequently, output is low. The feed gas of 35 %
oxygen increases ozone output twice in comparison
with the humid ambient air (5.94 vs. 2.85 g/hr).
The high ozone productivity of oxygen (98 %)
feed gas was achieved because high oxygen
concentration increases the probability of
bombardment between oxygen molecules and
radicals (electrons and ions) created by corona
discharge. Ozone concentration vs. oxygen
concentration shows a similar result: the higher
oxygen concentration in feed gas is, the higher
ozone concentration (21 % oxygen produced ~9
g/m3 ozone, 98 % oxygen gives 80 g/m3 ozone).
Figure 2: Ozone output (g/hr) and ozone concentration (g/cubic meter) vs. oxygen concentration (%) of inlet
gas (ambient temperature 24 oC, flow rate 5 L/min, electric current of ozone generator ~AC 2.5 A, 220 V
The use of oxygen from pressure cylinder or
liquid oxygen usually takes place in industrial
application of ozone (for example where the ozone
output reaches hundreds of kilograms ozone per
hour). For small-scale ozone generator (50-200g per
hour), feed gas is oxygen produced by PSA oxygen
generator using zeolites as adsorbent. Oxygen
concentration produced by PSA equipment made in
BKIDT Company (Hanoi) is high enough (near 96-
98 %). Ozone output using this oxygen reaches 24
g/hr, which equals to that using oxygen produced by
fractional distillation of liquefied air in Hanoi.
Besides, concentrated oxygen does not cause
formation of nitrogen dioxides in ozone cell that
prevents formation of nitric acid as a factor
damaging metallic details of ozone generator.
3.2. Influence of feed gas humidity on ozone
output
There are a lot of studies on effect of humidity in
ozone production including numerical simulation.[2]
In this paper, the investigation of effects of moisture
in feed gas was carried out in a narrow range of
humidity from 25 to 96 % that is usually observed in
the ambient air in tropical area. The moisture causes
a reduction of ozone output in corona discharge
generator by some mechanisms. Radicals (high
energy electrons) in corona interact with the water
molecules and it results in the formation of radical
OH*. In turn, the OH* radicals react with ozone
molecules and destroys the last.
Naturally, in water vapor there always exists
anion hydroxide OH—. Ozone reacts with OH— to
Vietnam Journal of Chemistry Nguyen Hoang Nghi et al.
© 2019 Vietnam Academy of Science and Technology, Hanoi & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim www.vjc.wiley-vch.de 607
create radicals O2
∗−2 , HO2*—, OH* + O2*— as
follows:
O3 + (OH)— 𝐎𝟐
∗−𝟐 + HO2*—
or O3 + OH— → HO2— + O2
and next: 2 O3 + HO2— → OH* + O2*—+ O2
These reactions consume an amount of ozone so
it results in ozone output decrease.[3] According to
Salvermoser and Kogelschatz, high energy electrons
in corona discharge causes formation of radical OH*
in water vapor that sets up a catalytic reaction cycle
resulting in enhanced ozone destruction.
There is another way to explain the decrease in
ozone output by moisture in feed gas. Moisture stuck
in dielectric surface changes its conductivity that
decreases the power of corona discharge.
As mentioned above, moisture in ambient air
causes damage to the generator by forming nitrogen
oxides and nitric acid inside ozone cell.
It is not easy to get dry air (i.e. air with very low
dew point, -60 to -20 oC). It is believed that for small
ozone generators (a few grams per hour), inlet air
with humidity of lower than 50-60 % should be used
because relative humidity in the range of 20-50 %
does not significantly decrease ozone output (see
Fig. 3).
Relative humidity, % (at 24oC)
Figure 3: Ozone output (g/hr) vs. relative humidity of air as inlet gas (ambient temperature ~ 24 oC, flow rate
~ 5 L/min, electric current of ozone generator ~ AC 2.8 A, 220 V). Ozone output decreases 1.4 times while
humidity increases from 21 to 96 %
3.3. Influence of feed gas flow rates on ozone
output and ozone concentration
Concentration change: Flow rate of feed gas
controls the mass of oxygen molecules that interacts
with plasma in the ozone cell to produce ozone. Low
flow rate causes an increase of the contact time of
oxygen molecules with the radicals (high energy
electrons) in corona and on the other hand, yielded
ozone slowly is released from ozone cell. In total, it
results in keeping high ozone concentration in ozone
cell. The increase of flow rate leads to the decrease
of ozone concentration (88 g/m3 at 3 L/min down to
29 g/m3 at 20 L/min) (figure 4). From the application
point of the view, high ozone concentration
enhances the solubility of ozone in water. For
instance, ozone dissolved in water increases 5 times
(from 10 to 50 mg/L), while ozone concentration
increases from 25 to 125 g/m3. Therefore, for water
disinfection high ozone concentration is desired.
Output change: Flow rate also significantly
exerts influence on ozone output of an ozone
generator.[4] Low flow rate produces low ozone.
Low flow rate inhibits the oxygen volume going to
and taking part in reaction in ozone cell. Let us
imagine an ozone cell having a given, no-changing
volume of oxygen (flow rate is very small). The
reaction to produce ozone consumes an amount of
oxygen inside the cell. Consequently, an oxygen
lack in the cell leads to a limit of ozone yield.
Pumping feed gas into ozone cell (rising the flow
rate) increases the amount of oxygen in the cell,
which results in an enhancement of ozone output. In
addition increasing flow rates, ozone output will get
saturated, or even slightly decreases, when flow rate
gets to a certain high value. In the ozone cell, the
molecules being interacted by the electrons can be
considered as immobile, because its thermal and
flow velocity is negligible compared to the speed of
the electron passing through it (~10-15 s). Therefore,
this motion does not effect on the ozone output.
According to Bernoulli principle, the speed of the
fluid goes up and its pressure goes down (ozone cell
is made in form of a tubes of small radius like to the
venturi tube). As a result, density of the gas
(oxygen) inside the ozone cell becomes lower, so
Vietnam Journal of Chemistry Influence of oxygen concentration, feed…
608
probability of bombardment between oxygen
molecules and radicals in corona media becomes
smaller, leading to a decrease of ozone output. In
sum, ozone output, first, will increase with the
increase of flow rates, then, at a certain high flow
rate output becomes saturated or even slightly
decrease (figure 4).
From the application point of view, it is
necessary to have both high output and high ozone
concentration. High ozone concentration is
important particularly for water disinfection because
ozone solubility in water is higher using ozone of
higher concentration.
Figure 4: Ozone output (g/hr) and ozone concentration (g/cubic meter) vs flow rate of oxygen as feed gas.
Concentration of oxygen ~ 98 %, ambient temperature ~ 24 oC
4. CONCLUSIONS
1. Using oxygen feed gas increases ozone output up
to 8 times in comparison with using high humid
ambient air.
2. Using oxygen produced by Pressure Swing
Adsorption oxygen generator (PSA) designed and
made in BKIDT Company (Hanoi) yields the same
ozone output as using oxygen from pressure
cylinder.
3. The ambient air with humidity from 25 % up
to 50 % (at 24 oC) almost does not change ozone
output. But humidity higher (70-80 %) significantly
reduces ozone output.
4. Increasing the flow rate would first causes an
increase of output, and then at a certain high flow
rate, the output reaches saturation or even slightly
decreases. There is a need to choose optimal flow
rate for every sort of ozone generator.
Acknowledgments. The experiments have been
carried out at the Lab of BKIDT Company (Hanoi).
The authors were thankful to Miss L. D. Lam, L. T.
Lam, N. V. Thin and V. X. Huong for performing
some measurements.
REFERENCES
1. Nguyen Hoang Nghi, Le Cao Cuong, Tran Vinh Dieu
and Doan Thi Yen Oanh. Study of water disinfection
by analyzing the ozone decomposition process,
Vietnam J. Chem., 2018, 56(5), 590-594.
2. R. Peyrous. The Effect of Relative humidity on ozone
production by corona discharge in oxygen or air – A
numerical simulation - Part II: Air, Ozone Science
and Engineering, 2008, 12(1), 41-64.
3. Nguyen Hoang Nghi et al. Book: Water in nature and
the principles of water filtration and disfection,
Chapter 8, Publishing House for Science &
Technique, 2013 (in Vietnamese).
4. F. Tanaka, T. Iwaishi, T. Sakugawa, H. Akiyama.
Influence of gas flow rate and pressure in reactors on
ozone production using a compact pulsed power
generator, IEEE Pulsed Power Conference, 2011.
Corresponding authors: Nguyen Hoang Nghi
Hanoi University of Science and Technology
1, Dai Co Viet, Hai Ba Trung, Hanoi 100000, Viet Nam
E-mail: nghi.bachkhoa@gmail.com
Doan Thi Yen Oanh
Publishing House for Science and Technology
Vietnam Academy of Science and Technology,
18, Hoang Quoc Viet, Cau Giay, Hanoi 100000, Viet Nam
Email: doanyenoanh@vjs.ac.vn
... However, given the presence of impurities (e.g., humidity, dust) within the atmosphere, undried air gives rise to some problems, mainly because of nitric acid formation and dust precipitation, increasing the ozone generator maintenance cost and reducing the generation efficiency. The removal of moisture from the air results in higher efficiencies in transforming O 2 into O 3 within the discharge chamber ( Fig. 1a) (Cuong et al., 2019). In this context, filters and dryers to remove impurities like dust and moisture, respectively, provide a significant contribution in improving the ozone generator efficiency as well as diminishing the plausible damage to the apparatus. ...
... Apart from the ozone generation unit which is important for ozone generation, other factors are also important Fig. 1 a Schematic illustration of a corona discharged-based ozone generator; b the absorption of various wavelengths of UV by ozone and oxygen, reprinted with permission from (Claus, 2021); c the extent of the generated ozone for various temperatures of ozonizer chamber i.e., ○: 10 °C, □: 30 °C, Δ: 50 °C, and ◊: 70 °C, reprinted with permission from (Jodzis & Baran, 2022); d the impact of relative humidity of the inlet gas on generated ozone, reprinted with permission from (Cuong, et al., 2019); e the changes in generated ozone upon the application of various extent of oxygen within the inlet air, reprinted with permission from (Cuong, et al., 2019) in increasing the efficiency of the ozonation process. The humidity of the feed gas is one of them, having a drastic impact on ozone generation and stability. ...
... Apart from the ozone generation unit which is important for ozone generation, other factors are also important Fig. 1 a Schematic illustration of a corona discharged-based ozone generator; b the absorption of various wavelengths of UV by ozone and oxygen, reprinted with permission from (Claus, 2021); c the extent of the generated ozone for various temperatures of ozonizer chamber i.e., ○: 10 °C, □: 30 °C, Δ: 50 °C, and ◊: 70 °C, reprinted with permission from (Jodzis & Baran, 2022); d the impact of relative humidity of the inlet gas on generated ozone, reprinted with permission from (Cuong, et al., 2019); e the changes in generated ozone upon the application of various extent of oxygen within the inlet air, reprinted with permission from (Cuong, et al., 2019) in increasing the efficiency of the ozonation process. The humidity of the feed gas is one of them, having a drastic impact on ozone generation and stability. ...
Ozone-Based Oxidation Treatment to Enhance Food Drying Rate and Quality: Mechanisms, Current Knowledge, and Future Outlook
Article
Full-text available
  • Feb 2025
  • FOOD BIOPROCESS TECH
Agriculture is a significant part of the gross domestic product of almost all nations. Food production is a priority to sustain ever-increasing populations. Since food production is seasonal, long-term storage is imperative. Drying is a predominant processing technique for effective storage, used in the agri-food sector for moisture reduction, hence inactivating the numerous microorganisms (both spoilage and pathogenic) in food products and increasing shelf life. This technique, however, is known to cause significant changes in the natural quality of treated products. Ozone processing is a potential pretreatment technique that can drive the drying process affirmatively in terms of processing factors and overall keeping quality without leaving any trace residues. This review covers recent research and applications and focuses on the effectiveness, pros and cons, challenges, and limitations of ozone pretreatment on the drying of agricultural products. Alongside the numerous mathematical models demonstrating the behavior of pretreated products during the drying process, it is shown how ozonation can enhance drying, save energy, and shorten the drying time. It extends the shelf life and improves textural properties, antioxidant activity, phenolic content, nutritional, and color profile of dehydrated products. However, excessive ozone concentration and prolonged treatment time can have detrimental effects. Overall, it is an efficient hurdle technology for preserving products with better retention of natural properties. However, the challenges to scaling up ozonation need to be addressed to bring this technology to commercial implementation.
View
... However, given the presence of impurities (e.g., humidity, dust) within the atmosphere, undried air gives rise to some problems, mainly because of nitric acid formation and dust precipitation, increasing the ozone generator maintenance cost and reducing the generation efficiency. The removal of moisture from the air results in higher efficiencies in transforming O 2 into O 3 within the discharge chamber ( Fig. 1a) (Cuong et al., 2019). In this context, filters and dryers to remove impurities like dust and moisture, respectively, provide a significant contribution in improving the ozone generator efficiency as well as diminishing the plausible damage to the apparatus. ...
... Apart from the ozone generation unit which is important for ozone generation, other factors are also important Fig. 1 a Schematic illustration of a corona discharged-based ozone generator; b the absorption of various wavelengths of UV by ozone and oxygen, reprinted with permission from (Claus, 2021); c the extent of the generated ozone for various temperatures of ozonizer chamber i.e., ○: 10 °C, □: 30 °C, Δ: 50 °C, and ◊: 70 °C, reprinted with permission from (Jodzis & Baran, 2022); d the impact of relative humidity of the inlet gas on generated ozone, reprinted with permission from (Cuong, et al., 2019); e the changes in generated ozone upon the application of various extent of oxygen within the inlet air, reprinted with permission from (Cuong, et al., 2019) in increasing the efficiency of the ozonation process. The humidity of the feed gas is one of them, having a drastic impact on ozone generation and stability. ...
... Apart from the ozone generation unit which is important for ozone generation, other factors are also important Fig. 1 a Schematic illustration of a corona discharged-based ozone generator; b the absorption of various wavelengths of UV by ozone and oxygen, reprinted with permission from (Claus, 2021); c the extent of the generated ozone for various temperatures of ozonizer chamber i.e., ○: 10 °C, □: 30 °C, Δ: 50 °C, and ◊: 70 °C, reprinted with permission from (Jodzis & Baran, 2022); d the impact of relative humidity of the inlet gas on generated ozone, reprinted with permission from (Cuong, et al., 2019); e the changes in generated ozone upon the application of various extent of oxygen within the inlet air, reprinted with permission from (Cuong, et al., 2019) in increasing the efficiency of the ozonation process. The humidity of the feed gas is one of them, having a drastic impact on ozone generation and stability. ...
Ozone-Based Oxidation Treatment to Enhance Food Drying Rate and Quality: Mechanisms, Current Knowledge, and Future Outlook
Article
  • Jan 2025
  • FOOD BIOPROCESS TECH
Agriculture is a significant part of the gross domestic product of almost all nations. Food production is a priority to sustain ever-increasing populations. Since food production is seasonal, long-term storage is imperative. Drying is a predominant processing technique for effective storage, used in the agri-food sector for moisture reduction, hence inactivating the numerous microorganisms (both spoilage and pathogenic) in food products and increasing shelf life. This technique, however, is known to cause significant changes in the natural quality of treated products. Ozone processing is a potential pretreatment technique that can drive the drying process affirmatively in terms of processing factors and overall keeping quality without leaving any trace residues. This review covers recent research and applications and focuses on the effectiveness, pros and cons, challenges, and limitations of ozone pretreatment on the drying of agricultural products. Alongside the numerous mathematical models demonstrating the behavior of pretreated products during the drying process, it is shown how ozonation can enhance drying, save energy, and shorten the drying time. It extends the shelf life and improves textural properties, antioxidant activity, phenolic content, nutritional, and color profile of dehydrated products. However, excessive ozone concentration and prolonged treatment time can have detrimental effects. Overall, it is an efficient hurdle technology for preserving products with better retention of natural properties. However, the challenges to scaling up ozonation need to be addressed to bring this technology to commercial implementation.
View
... Subsequently, These radicals initiate further reactions that consume O atoms, leading to a decrease in ozone density [37]. Furthermore, ozone reacts with OH − to produce radicals such as O −2 2 , HO − 2 , OH and O − 2 [52]. Therefore, the density of O 3 in dry air is higher than in humid air. ...
Spatial Distributions of Chemical Species in a Pin-to-plate Dry Air Corona Discharge
Article
Full-text available
  • Feb 2025
  • PLASMA CHEM PLASMA P
The reactive oxygen and nitrogen species generated by plasma have demonstrated consequential effects on diverse commercial applications. Hence, studying the chemistry and spatial distribution of reactive species in plasma is imperative for understanding the influence of plasma in various applications. This study aims to systematically explore the plasma chemistry of a pin-to-plate negative direct current (DC) corona discharge in dry air, using simulations based on a two dimensional (2D) axisymmetric fluid model. The model encompasses a comprehensive set of chemical reactions involving 33 biomedically active species (ROS and RNS). This study entails a rigorous evaluation of the 2D spatial distribution of all chemical species, detailing their minimum and maximum values, at a needle voltage of −10 kV. To enhance visualization and enable comparisons, we integrate contour lines into the density distributions to indicate the average density of each species. N2(A3∑){\text{N}}_{2}\left({\text{A}}^{3}\sum\right) among nitrogen species, O3 and O2(a1Δ){\text{O}}_{2}\left({\text{a}}^{1}\Delta\right) among oxygen species, and N2O among NOx species exhibit the highest average density in the simulation domain. Furthermore, key reactions involved in the production and consumption of each species are thoroughly discussed. Additionally, the research examines the influence of needle voltage, ranging from −5 to −12.5 kV, on the peak and average densities of all species investigated. Lastly, to validate the simulation model, an experimental study of the pin-to-plate negative DC corona discharge is conducted, during which the voltage-current characteristics and optical emission spectrometry (OES) profiles are measured. The simulation results are in good agreement with the experimental data.
View
... At a flow rate of 5 LPM, 0.281 mmol of •OH was generated at 30 min with air as the gas feed. This is because the greater the gas flow rate entering the reactor, the more reactants or compounds that react to form •OH [20]. Increasing the gas flow rate into the reactor will increase the amount of O 2 reacting to form O 3 , and the O 3 produced will decompose into •OH. ...
Ozone Plasma Nanobubble (OPN) Reactor Combined with Coagulation-Flocculation Process: A Promising Technology for Leachate Treatment
Article
Full-text available
  • Oct 2024
According to World Bank data, approximately 2.01 billion tons of urban waste is produced annually, with approximately 33% of waste being improperly managed, leading to concentrated and toxic leachate. This poses a global challenge due to its varied characteristics influenced by climate, landfill age, and waste composition, resulting in groundwater and surface water pollution with severe impacts on human health, ecosystems, and biodiversity, necessitating stringent treatment measures. To address this, a study integrated coagulation-flocculation and advanced oxidation processes (AOPs) using a dielectric barrier discharge (DBD) ozone plasma nanobubble (OPN) reactor to degrade leachate. Gas flow rate, plasma voltage, and gas sources are variated. This research uses O 2 or air as a gas source that produces plasma. The leachate is fed into the DBD reactor, so the bubble will burst and produce further ROS. Optimal results were observed after 60 min, with oxygen gas feed reducing total suspended solids (TSS), chemical oxygen demand (COD), and biological oxygen demand (BOD) by 100, 93.93, and 74.12%, respectively, alongside a decrease in pH. This study indicates the promising potential of this technology for leachate treatment and demonstrates the potential for nitrate production using both types of gas feed.
View
... Ozone applications have been evaluated for a very long time, because it was quickly produced by different technologies (Da Silva et al., 2001;Metheniti et al., 2018;Rice, 2010;Rodríguez et al., 2008), among which pulse corona discharge outstands (Cuong et al., 2019;Zhu et al., 2020). Recently, electrochemical alternatives have been reported for producing ozone with higher efficiency (Da Silva et al., 2010;Hu et al., 2020;Rodríguez-Peña et al., 2021). ...
Electrochemical generation of chlorine dioxide for use in environmental remediation
Article
Full-text available
  • Aug 2023
  • PROCESS SAF ENVIRON
This work focuses on the production, in continuous mode, of chlorate and hydrogen peroxide, using tailored electrochemical cells specially designed to obtain high efficiencies in these electrochemical processes. Then, these chlorate and hydrogen peroxide electrochemically produced were mixed for the chemical formation of chlorine dioxide, susceptible to be used for environmental applications. In this work, not only the prototype’s conceptualization, design, and 3-D printing manufacturing are realized, but also the characterization of the cells in terms of fluid dynamics, mass transfer, and production of the target compounds is made. The chlorate pro- totype, with an electrode area of 78.5 cm2 , produced up to 1200 mg h− 1 of a chlorate solution with a purity of 50 %. The hydrogen peroxide prototype, with an electrode surface area of 10.9 cm2 , produced up to 9 mg h− 1 of hydrogen peroxide with a concentration of up to 70 mg L− 1 . The chlorine dioxide was produced continuously with these compounds (HClO3 and H2O2), operating at low H2O2/HClO3 ratios and with a highly acidic sup- porting media. The oxidant was effectively transferred to a gaseous stream through air stripping. It was then introduced to solutions containing iodine or methomyl to confirm its ability to oxidize substances and to assess its potential use for environmental applications. These findings indicate that using Gaseous Oxidants Mediated Electrochemical Technology (GOMET) with chlorine dioxide is a viable solution for environmental remediation, offering promising prospects for future research on this topic.
View
View
Boundary Layer Control with a Plasma Actuator Utilizing a Large GND Mesh Electrode and Two HV Electrode Configurations
Article
Full-text available
This article presents the results of experimental studies on the influence of the geometry of high-voltage plasma actuator electrodes on the change in flow in the boundary layer and their influence on the change in the lift coefficient. The plasma actuator used in the described experimental studies has a completely different structure. The experimental model of the plasma actuator uses a large mesh ground electrode and different geometries of the high-voltage electrodes, namely copper solid electrodes and mesh electrodes (the use of mesh electrodes, large GND and HV is a new solution). The plasma actuator was placed directly on the surface of the wing model with the SD 7003 profile. The wing model with the plasma actuator was placed in the wind tunnel. All experimental tests carried out were carried out for various configurations. The DBD plasma actuator was powered by a high-voltage power supply with a voltage range from Vp = 7.5–15 kV. The use of a high-voltage mesh electrode allowed for an increase in the lift coefficient (CL) for the angle of attack α = 5 degrees and the air flow velocity in the range from V = 5 m/s to 20 m/s, while the use of copper electrodes HV with the plasma actuator turned off and on, were very small (close to zero). The experimental studies were conducted for Reynolds numbers in the range of Re = 87,985–351,939.
View
View
View
The Influence of Flow Rate and Voltage in the DDBD Reactor in Producing Medical Ozone for Antihiperglikemia Major Authohemotherapy
Article
Full-text available
  • Nov 2023
The influence of flow rate and voltage in the Double Dielectic Barrier Discharge (DDBD) reactor in producing medical ozone has been carried out. The aim of this study was to obtain medical ozone as a standard dose for Major Autohemotherapy (MAH) in cases of hyperglycemia. DDBD is a double cylinder made of borosilicate glass with a thickness of 0.2 cm and electrodes made of aluminum mesh with a length of 6.2 cm, an inner diameter of 2 cm and an outer diameter of 4.2 cm. The input gas is oxygen (O 2) with flowrates of 0.2 L/minute-0.8 L/minute. At the flowrate limit used, this study found that the ozone concentration increased with increasing flowrate and operating voltage. The standard dose of MAH which is in accordance with the provisions of the Madrid Declaration for cases of diabetes mellitus/hyperglycemia, the specific dose is at the flow rate. of 0.4 L/min and a voltage of 3400 V, concentration of 293.64 µg/ml, capacity of 117.45 µg/second, with a dose obtained for the low dose of 18 µg and the high dose of 33 µg.
View
Study of water disinfection by analyzing the ozone decomposition process
Article
Full-text available
  • Oct 2018
Possessing high binding energy, molecular ozone (O3) is not stable and spontaneously breaks down into oxygen especially at high temperature. It is called thermal decomposition of ozone. On other hand, ozone with high redox potential (2.06 V) is considered to be a powerful oxidant. In water ozone reacts with both of inorganic and organic substances. Interaction of ozone with the matters consumes an amount of ozone dissolved in water. So by analysing the ozone decomposition curves, we can measure and calculate the reaction rate R, rate constant k, the half‐life time and reaction order of the ozone reaction with the matters. These parameters indicate the disinfection ability of ozone and its mechanism. Calculated value of half‐life time can be used to estimate the water quality and the water disinfection level.
View
The Effect of Relative Humidity on Ozone Production by Corona Discharge in Oxygen or Air – A Numerical Simulation – Part II : Air
Article
  • Jul 2008
The simulation of the temporal evolution of the various neutral gaseous species studied (O, O3, H, OH, HO2, H2O2, N, NO, NO2, NO3, N2O, N2O5, HNO2, and HNO3) use corona effects. The physical conditions of the discharge were used. The reactions take place in dry or humid air, after the dissociation of O2, N2, and H2O by an electronic pulse. When water vapor is present, there is a probability of production of H2O2, HNO2, and HNO3 in air. Temperature and humidity have cumulative effects. With multiple pulses, the O3 maximal concentration is obtained for a limited number of pulses.
View
Influence of gas flow rate and pressure in reactors on ozone production using a compact pulsed power generator
Article
  • Jun 2011
Ozone concentration and ozone yield are throughly studied as part of an ozone production system. In addition to these values, ozone production per hour is the most important parameter to determine processable volume of ozone. Our final goal is to improve ozone production per hour. Here the influence of gas flow rate and pressure in reactor on ozone production is investigated using a compact pulsed power generator.
View
Study of water disinfection by analyzing the ozone decomposition process
  • Jan 2018
  • 590-594
  • Le Cao Nguyen Hoang Nghi
  • Tran Vinh Cuong
  • Doan Thi Yen Dieu
  • Oanh
Nguyen Hoang Nghi, Le Cao Cuong, Tran Vinh Dieu and Doan Thi Yen Oanh. Study of water disinfection by analyzing the ozone decomposition process, Vietnam J. Chem., 2018, 56(5), 590-594.
Book: Water in nature and the principles of water filtration and disfection Chapter 8 Publishing House for Science & Technique
  • Nguyen Hoang Nghi