DETERMINATION OF THE FEATURES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK IN A FLUIDIZED BED
Sunflower husk (SH) is a plant waste fuel. The carbon content in different samples of SH ranges from 40.5% to 54.5% in an operating state, with ash content ranging from 1.5% to 8.5%, moisture content ranging from 6.9% to 9.5%, chlorine content ranging from 0.05% to 0.3%, and lower heating value rang...
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| Date: | 2024 |
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| Language: | Ukrainian |
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Vidnovluvana energetika| _version_ | 1871103775639339008 |
|---|---|
| author | Haponych, L. Topal , O. Holenko , I. Kobzar , S. |
| author_facet | Haponych, L. Topal , O. Holenko , I. Kobzar , S. |
| author_institution_txt_mv | [
{
"author": " L. Haponych",
"institution": "Thermal Energy Technology Institute of the National Academy of Sciences of Ukraine, Leading Researcher, Kyiv, Ukraine"
},
{
"author": "O. Topal ",
"institution": "Thermal Energy Technology Institute of the National Academy of Sciences of Ukraine, Leading Researcher, Kyiv, Ukraine"
},
{
"author": "I. Holenko ",
"institution": "Thermal Energy Technology Institute of the National Academy of Sciences of Ukraine, Leading Researcher, Kyiv, Ukraine"
},
{
"author": "S. Kobzar ",
"institution": "Institute of Engineering Thermophysics of the National Academy of Sciences of Ukraine, Kyiv, Ukraine"
}
] |
| author_sort | Haponych, L. |
| baseUrl_str | https://ve.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2026-07-18T06:32:20Z |
| description | Sunflower husk (SH) is a plant waste fuel. The carbon content in different samples of SH ranges from 40.5% to 54.5% in an operating state, with ash content ranging from 1.5% to 8.5%, moisture content ranging from 6.9% to 9.5%, chlorine content ranging from 0.05% to 0.3%, and lower heating value ranging from 14.5 MJ/kg to 20.5 MJ/kg. These characteristics make it a suitable substitute for fossil fuels in power boilers.
Waste-to-energy (WTE) technologies are rapidly developing worldwide, offering the potential for generating renewable energy from waste, including agricultural and food industry waste such as SH. According to our estimates, Ukraine has an annual energy potential of approximately 3.4 million tons of SH or about two million tons of fuel equivalent. Approximately half of this volume is currently being burned in oil extraction plants' boilers; however, up to one million tons of SH end up in landfills annually, resulting in significant energy losses.
To develop new and improve existing WTE technologies that utilize SH as a fuel source, it's essential to understand the thermal processing characteristics of SH under conditions similar to those found in different zones within real power boilers - specifically the heating of fuel particles at rates up to 500 °C/s over a temperature range of 500–1000 °C. In this study, we aimed to investigate the thermal processing characteristics by subjecting SH particles within a laboratory fluidized bed reactor to high-speed heating within the aforementioned temperature range.
During rapid heating between 500–1000 °C temperatures range, SH particles undergo conversion into volatile compounds and solid carbon residue. Two distinct stages can be observed on the dynamic yield curves for volatiles. The release and burnout of volatiles occurs during the first stage while the second stage involves coke ash residue burnout. We obtained empirical temperature-dependents for total heat treatment time and carbon residue burnout time under fast heating conditions in the investigated temperature range.
The stage of carbon residue combustion is the most enduring and determines the overall duration of thermal treatment. This stage determines the degree of fuel transformation, especially in cases where low-reactivity carbon residue enters the low-temperature combustion chamber area of the boiler. The obtained regularities have practical significance in designing combustion chambers for thermal processing of sunflower husk. |
| doi_str_mv | 10.36296/1819-8058.2024.2(77).137-149 |
| first_indexed | 2025-07-17T11:39:32Z |
| format | Article |
| fulltext |
136
Відновлювана енергетика. №2/2024 | Біоенергетика
UDC 620.92 https://doi.org/10.36296/1819-8058.2024.2(77)137-149
DETERMINATION OF THE FEATURES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK
IN A FLUIDIZED BED
Received Apr. 24, 2024; accepted Jun. 21, 2024
Available online Jul. 01, 2024
Haponych L.1, Topal O.2, Holenko I.3, Kobzar S.4
Author for correspondence: Haponych Liudmyla,
e-mail: haponych@ukr.net
Sunflower husk (SH) is a plant waste fuel. The carbon content in
different samples of SH ranges from 40.5% to 54.5% in an operat-
ing state, with ash content ranging from 1.5% to 8.5%, moisture
content ranging from 6.9% to 9.5%, chlorine content ranging from
0.05% to 0.3%, and lower heating value ranging from 14.5 MJ/kg
to 20.5 MJ/kg. These characteristics make it a suitable substitute
for fossil fuels in power boilers.
Waste-to-energy (WTE) technologies are rapidly developing
worldwide, offering the potential for generating renewable energy from waste, including agricultural and food
industry waste such as SH. According to our estimates, Ukraine has an annual energy potential of approximately
3.4 million tons of SH or about two million tons of fuel equivalent. Approximately half of this volume is currently
being burned in oil extraction plants' boilers; however, up to one million tons of SH end up in landfills annually,
resulting in significant energy losses.
To develop new and improve existing WTE technologies that utilize SH as a fuel source, it's essential to under-
stand the thermal processing characteristics of SH under conditions similar to those found in different zones
within real power boilers - specifically the heating of fuel particles at rates up to 500 °C/s over a temperature
range of 500–1000 °C. In this study, we aimed to investigate the thermal processing characteristics by subject-
ing SH particles within a laboratory fluidized bed reactor to high-speed heating within the aforementioned tem-
perature range.
During rapid heating between 500–1000 °C temperatures range, SH particles undergo conversion into volatile
compounds and solid carbon residue. Two distinct stages can be observed on the dynamic yield curves for vol-
atiles. The release and burnout of volatiles occurs during the first stage while the second stage involves coke
ash residue burnout. We obtained empirical temperature-dependents for total heat treatment time and carbon
residue burnout time under fast heating conditions in the investigated temperature range.
The stage of carbon residue combustion is the most enduring and determines the overall duration of thermal
treatment. This stage determines the degree of fuel transformation, especially in cases where low-reactivity
carbon residue enters the low-temperature combustion chamber area of the boiler. The obtained regularities
have practical significance in designing combustion chambers for thermal processing of sunflower husk.
Keywords: biomass; sunflower husks; waste-to-energy; fluidized bed; heat treatment; pyrolysis; volatiles; car-
bon residue.
1 Ph. D.
https://orcid.org/0000-0003-4611-3193
2 Ph. D.
https://orcid.org/0000-0002-9458-9420
3 Ph. D.
https://orcid.org/0000-0003-3487-8025
4 Ph. D.
https://orcid.org/0000-0002-8615-4400
1,2,3 Thermal Energy Technology Institute of
the National Academy of Sciences of Ukraine,
Leading Researcher, Kyiv, Ukraine
4 Institute of Engineering Thermophysics of
the National Academy of Sciences of Ukraine,
Kyiv, Ukraine
137
Відновлювана енергетика. №2/2024 | Біоенергетика
ВИЗНАЧЕННЯ ОСОБЛИВОСТЕЙ ТЕРМІЧНОГО РОЗКЛАДАННЯ ЛУШПИННЯ СОНЯШНИКА В
КИПЛЯЧОМУ ШАРІ
Отримано 24 квіт. 2024 р.; рекомендовано до публікації 21 чер. 2024 р.
Доступно онлайн 01 лип. 2024 р.
Гапонич Л.1, Топал О.2, Голенко І.3, Кобзар С.4
Автор для кореспонденції: Гапонич Людмила,
e-mail: haponych@ukr.net
Лушпиння соняшника (ЛС) – це паливні відходи рослинного по-
ходження. Вміст вуглецю в перерахунку на робочий стан у різ-
них зразках ЛС коливається в межах 40,5–54,5 %, зольності –
1,5–8,5 %, вологості – 6,9–9,5 %, хлору – 0,05–0,3 %, а нижча те-
плота згоряння в межах 14,5–20,5 МДж/кг. З огляду на вказані
характеристики це паливо придатне для використання як за-
мінник викопного палива в енергетичних котлах.
Останніми роками у світі стрімко розвиваються технології
перетворення відходів на енергію (WTE), які мають потенціал для отримання відновлюваної енергії з
відходів, зокрема сільськогосподарських. За нашими оцінками, щорічний енергетичний потенціал ЛС в
Україні сягає 3,4 млн т, або близько 2 млн т умовного палива. Близько половини цього обсягу спалю-
ється в котлах олійноекстракційних заводів, але щорічно до 1 млн т лушпиння потрапляє на звалища,
що призводить до значних енергетичних втрат.
Розробка нових та вдосконалення існуючих технологій WTE, що використовують ЛС як паливо, має
базуватися на розумінні закономірностей його термічної переробки. Тому метою цієї роботи було
дослідження закономірностей термічної переробки ЛС у характерних для різних зон енергетичних ко-
тлів умовах – при нагріванні частинок палива зі швидкістю до 500 °С/с в інтервалі температур 500–
1000 °С. Така швидкість нагріву була реалізована в лабораторному реакторі киплячого шару.
При швидкісному нагріванні в діапазоні температур 500–1000 °C частинки ЛС перетворюються на
леткі і твердий вуглецевий залишок. Динамічні криві виходу газоподібних летких мають дві ділянки:
перша відповідає виходу і вигорянню летких, а друга – вигорянню вуглецевого залишку. Отримано ем-
піричні температурні залежності загального часу термообробки та часу вигоряння вуглецевого за-
лишку лушпиння соняшника при швидкому нагріванні в інтервалі температур 500–1000 оС.
Стадія вигоряння вуглецевого залишку є найтривалішою і визначає загальний час термообробки. Ця
стадія визначає ступінь перетворення палива, особливо у випадках, коли низькореакційний вуглеце-
вий залишок потрапляє в низькотемпературну область камери згоряння котла. Отримані закономі-
рності мають практичне значення при проєктуванні камер згоряння котлів термічної переробки лу-
шпиння соняшника.
Ключові слова: біомаса, лушпиння соняшника, перетворення відходів на енергію, киплячий шар, тер-
мічна обробка, піроліз, леткі речовини, вуглецевий залишок.
The list of used symbols and abbreviations
CR – carbon residue
CHPs – combined heat and power plants
FB – fluidized bed
LHV – lower heating values
OEP – oil extraction plant
SH – sunflower husk
TPPs – thermal power plants
WTE – Waste-to-energy
1 канд. техн. наук
https://orcid.org/0000-0003-4611-3193
2 канд. техн. наук
https://orcid.org/0000-0002-9458-9420
3 канд. техн. наук.
https://orcid.org/0000-0003-3487-8025
4 канд. техн. наук
https://orcid.org/0000-0002-8615-4400
1,2,3 Інститут теплоенергетичних технологій
національної академії наук України, м.
Київ, Україна
4 Інститут технічної теплофізики національ-
ної академії наук України, Київ, Україна
138
Відновлювана енергетика. №2/2024 | Біоенергетика
Introduction. Sunflower is one of the most widely grown
oilseeds in the world. According to the Food and Agriculture
Organization of the United Nations, global production
amounted to 55 million tons in the 2022/2023 season. In
Ukraine, sunflower production reached 15 million tons in
the same season [1].
The modern oil and fat complex of Ukraine includes 32
large oil extraction plants (OEPs) and almost a thousand
small enterprises and processes about 70% of sunflower
seeds. According to the Ukroliyaprom Association, sun-
flower seed processing reached 13.5 million tons in the
2022/2023 season, resulting in a production of 6 million
tons of sunflower oil. The production of sunflower oil gen-
erates approximately 15-25% husk waste [2].
Sunflower husk (SH) is a plant-based fuel waste with a car-
bon content ranging from 40%–55%, and a heating value
between 15–21 MJ/kg [3]. Various scientific studies have
shown that sunflower husk samples have low ash and sulfur
content [4]. Articles [5, 6] have determined that the chlo-
rine content in SH samples ranges from 0.05% to 0.3%.
These qualities make SH suitable for replacing organic fuel
in both industrial and municipal energy boilers due to their
high volatile yield as well as low sulfur and chlorine con-
tents. SH can be burned either uncompressed or com-
pacted into higher-quality biofuels such as pellets or bri-
quettes [7]. Additionally, SH is considered CO2 neutral fuel.
On April 22nd, 2016, Ukraine signed the Paris Agreement
on climate change for 2021–2030 under the United Nations
Framework Convention on Climate Change. According to
this agreement, majority of countries globally have made
commitments to reduce their anthropogenic greenhouse
gas emissions with the goal of limiting temperature in-
creases to a maximum of 1.5°C compared to pre-industrial
levels. The substitution of fossil fuels with renewable alter-
natives including biomass, is one of the main focuses in
many national decarbonization strategies [8].
The National Action Plan for Renewable Energy Develop-
ment until 2030 sets an indicative target of boosting the re-
newable energy share in final energy consumption three
times from 9% in 2020 to 27% in 2030, and up to 25% in the
electricity sector. In addition, the substitution of organic
fuels, such as coal and gas, with eco-friendly fuels becomes
more relevant. Waste-to-energy (WTE) technologies have
been rapidly developing worldwide and have the potential
to recover renewable energy from waste, including agricul-
tural and food industry waste. WTE technologies convert
waste matter into various forms of fuel that can be used to
supply energy. Waste from agriculture and the food indus-
try, including SH, also has significant renewable energy po-
tential.
According to our estimates, the energy potential of sun-
flower husks (SH) in Ukraine reaches 3.4 million tons or 2.0
million tons of fuel equivalent. In recent years, approxi-
mately 1.7 million tonnes of SH (about half of the annual
volume) have been utilized in energy boilers in Ukraine,
with 1.3 million tonnes in uncompressed form and 0.4
million tonnes in briquette form [2]. Additionally, 0.2 mil-
lion pellets are exported each year. However, up to one mil-
lion tons of sunflower husks end up in landfills annually, re-
sulting in energy losses.
Since 2000, almost all large oil extraction plants (OEPs) in
Ukraine have implemented SH combustion technology
[9]. Several thermal power plants (TPPs) and combined
heat and power plants (CHPs) are currently operational
[10]. The largest biomass TPP in Ukraine is the 15 MW
Ajax-Dnipro TPP (OEP Potoky, Dnipro), which was com-
missioned in the summer of 2020. The TPP is equipped
with two boilers that produce 35 tons of steam per hour
(Kotloenergoproekt project, Kharkiv) and a Siemens tur-
bine generator. The main fuel used is sunflower husks and
husk pellets. The boilers can also runon other types of bi-
omass such as wood chips and waste from sunflower cul-
tivation, transportation, and processing. Аccording to pro-
ducer data the environmental characteristics of the
boilers are as follows: NOx – 100 ppm; CO – 0 ppm; effi-
ciency – 90%; load control range – from 30 to 110%, al-
lowing the TPP to operate in a maneuvering mode.
In 2009, the Kropyvnytskyi OEP’s CHP plant with a capacity
of 12.3 MW (33 MW thermal) was equipped with three E-
16-3.9-360-D boilers (manufactured in Ukraine) capable of
burning sunflower husks with steam capacity of 16 tons per
hour. These boilers can also run on natural gas. The elec-
tricity and heat generated are used for the technological
needs of the OEP.
In 2020, AGL Energy's oil extraction plant located in Kharkiv
region commissioned a biofuel TPP with an electric capacity
of 7 MW. This TPP utilizes wood pellets as its primary fuel
source. It is equipped with two steam boiler units manufac-
tured by Kharkiv Boiler and Mechanical Plant, each having
a steam capacity of 16 tons per year, along with a steam
condensing turbine generator manufactured by TRIVENI
TURBINE LTD.
In 2012, two solid fuel boilers DKVr-10-23-370 with a steam
capacity of 20.0 tons per hour were reconstructed at the
CHP plant of Mykolaiv Oil and Gas Processing Plant (Agroin-
dustrial Company EVGROIL) to burn wood pellets. The plant
has an electric capacity of 5 MW and a thermal capacity of
10 MW [11]. In 2020, a RAFACO boiler designed to burn
sunflower husks was installed at the Zaporizhzhia TPP,
which has a capacity of 2.7 MW. ArcelorMittal Kryvyi Rih
also uses biofuel burners at furnaces 4-5, where sunflower
husks are utilized.
Furthermore, boilers at Ukrainian sugar factories have been
converted to burn biomass, including sunflower husks [10].
In 2019, coal boilers manufactured by Babcock-Wilcox in
the Khorostkiv branch of Radekhiv Sugar Plant were con-
verted to burn sunflower husk pellets. The Radekhiv Sugar
Plant's BKZ-75GMA boiler uses a grate manufactured by
FPM S.A. Mikulov from Poland with a dense layer of direct
run. The Haisyn Sugar Plant's BGM-35M boilers were recon-
structed for pellet combustion via the installation of flame-
layer furnaces equipped with mechanical feeders.
139
Відновлювана енергетика. №2/2024 | Біоенергетика
There are three types of boilers used in the oil and fat in-
dustry: 1) modern boilers manufactured by companies
such as Vyncke (Belgium), Rafako (Poland), Larget-Bad-
cock (France); 2) new boilers designed and manufactured
within Ukraine: 3) old boilers originally designed for fossil
fuels but reconstructed for husk combustion even after
exceeding their design life [10]. When designing new fur-
nace devices, significant attention is given to the combus-
tion process of the initial fuel particles. The combustion of
solid organic fuel particles can be divided into several
stages: 1) pyrolysis of the fuel particle, including heating,
drying, and release of volatiles; 2) combustion of volatiles
and coke residue (CR), including ignition [12]. These
stages have different rates, durations, and degrees of in-
fluence on combustion depending on the process condi-
tions [13]. The total combustion time for sunflower husks
(SH) can be represented as a sum of two time intervals
corresponding to: 1) release and combustion of volatiles,
and 2) combustion of CR [14, 15].
Pyrolysis of biomass is the direct thermal decomposition of
organic components with the production of CR and volatile
liquids (tars) and gaseous products [16]. This complex pro-
cess involves multiphase reactions, complex chemical path-
ways, highly unstable intermediate products as well as heat
and mass transfer effects. The volatile fraction includes
combustible components such as H2, CH4, CO2 along with
small amounts of C2H6, C2H4 higher hydrocarbons, and wa-
ter vapor [13]. The volatiles formed during thermal decom-
position significantly influence subsequent ignition pro-
cesses. Higher yields of volatiles in initial fuels result in
faster ignition rates for CR leading to more intense burning.
Heating rates during pyrolysis also affect the ratio between
volatiles’ yield (both gaseous and liquid) to coke residues.
Depending on heating rates slow or fast pyrolysis can be
distinguished.
The yield and combustion of volatiles, which precede the
combustion of CR, can hinder the diffusion of the oxidizer
to its surface [17]. This is because the intense saturation of
the boundary layer adjacent to the particle with volatiles
leads to the formation of a gas mixture of fuel and oxidizer
in it. The combustion of this mixture leads to a sharp de-
crease in the concentration of oxidizer on the surface of the
coke particle. As a result, the coke residue hardly partici-
pates in the ignition and combustion process at the initial
stage, leading to a phenomenon known as homogeneous-
heterogeneous ignition.
Biomass is a very complex fuel consisting of many compo-
nents. The three main organic components of biomass are
cellulose, hemicellulose, and lignin [18]. Cellulose is a car-
bohydrate polymer composed of glucose monomers – pol-
ysaccharides with a chemical formula С6Н10О5 [19]. Its
structure includes five carbon atoms forming a ring struc-
ture with attached H and OH groups, while oxygen occupies
another angle [20]. Due to its high degree of hydrogen
bonding, cellulose is resistant to chemical degradation [21].
It serves as the main structural component in most
terrestrial biomass [22]. Within the lignocellulosic complex,
cellulose retains its crystalline fibrous structure and acts as
its core. Many properties exhibited by cellulose depend on
its polymerization degree i.e., the number of glucose mole-
cules that make up one polymer molecule.
Hemicelluloses is a collective term used to describe a wide
range of heteropolysaccharides, such as xylan. The chemi-
cal formula of a hemicellulose molecule is (C5H8O4)n [12].
Hemicellulose is an amorphous organic polymer that de-
composes more rapidly than cellulose when exposed to
heat, and its thermal decomposition begins at lower tem-
peratures [22]. Hemicellulose is a mixture of various pol-
ymerized monosaccharides and can be relatively easily hy-
drolyzed into its constituent sugars.
Lignin, on the other hand, is a large hydrophobic (mostly
aromatic) polymer composed of phenolic monomeric units
linked together in a three-dimensional structure [23]. Its
chemical formula is [C9H10O3(OCH3)0.9–1.7]n [24]. Lignin is the
second most abundant organic material on Earth after cel-
lulose. It provides the framework, in which cellulose and
hemicellulose are embedded [25]. While most lignin is
found in the middle lamella where it serves as support for
plant cell walls, there may also be smaller amounts located
on the cell surface.
As a general rule, cellulose is the most abundant natural
polymer, accounting for 35%–55% of biomass [26]. Hemi-
cellulose is the second most abundant natural polymer, ac-
counting for 20%–40% of mass, followed by lignin, which
makes up 10%–30% of lignocellulosic biomass. The content
of each component varies for different types of biomasses,
as well as between different parts of the same type of bio-
mass. For example, sunflower seeds, husks and stalks are
characterized by different compositions of cellulose, hemi-
cellulose and lignin. As a result, they have different ele-
mental compositions and lower heating values (LHV).
The structural composition of sunflower husks also varies
between different cultivars [27]. SH generally contain ap-
proximately 30%–48% wt. cellulose, 34%–38% wt. hemicel-
lulose, and 17%-26% wt. lignin [28]. The elemental compo-
sition of the fuel and the amount of volatiles (which affects
LHV) can also vary depending on the structure.
Chemical analysis has shown that SH contains approxi-
mately 14%-18% bound carbon, 70%-76% volatiles, and
6%-10% moisture [29]. Table shows the elemental compo-
sition of the operating state and LHV from various samples
of SH: 1 - [4], 2 - [3], 3 - [6], 4 - [10], and 5 - [30]. Different
samples of SH have a content (on the operating state of
fuel) of carbon Cr = 40.5%–54.5%, sulphur Sr = 0.1%–0.2%,
chlorine Clr = 0.05%–0.3%, ash Ar =1.5%–8.5%, and mois-
ture Wr =7.0%–9.5%. The lower heating values range from
14.5 to 20.5 MJ/kg. The high lignin content in biomass is as-
sociated with LHV since lignin contains approximately 30%
higher heating value than cellulose and hemicellulose [29].
Sunflower husks have a high LHV due to their high lignin
content.
140
Відновлювана енергетика. №2/2024 | Біоенергетика
Table. Elemental composition and lower heating values of different samples of sunflower husks
Sunflower
husks samples
The elemental composition of the operating state, % LHV,
MJ/kg
Wr, % Ar, % Cr, % Or, % Nr, % Hr, % Sr*, %
1 6.9 3.5 54.3 26.3 1.5 7.4 0.1 20.7
2 7.7 4.0 47.4 35.0 5.8 0.1 18.0
3 9.3 8.5 40.7 35.6 0.7 5.0 0.2 14.8
4 9.5 3.5 44.1 38.2 4.6 0.1 20.5
5 9.2 1.4 45.1 38.5 0.4 5.3 0.1 17.4**
*sum of organic and sulphide sulphur or pyritic; **according to our calculations
The pyrolysis rate of biomass is considered to be the sum
of the rates of the main components: cellulose, hemicellu-
lose, and lignin [21]. Each component contributes to this
rate in proportion to its contribution to the composition of
the biomass [31]. Interactions between biomass compo-
nents have a negligible effect on pyrolysis results.
The mechanism of the chemical reaction of lignocellulose
pyrolysis is not fully understood and remains ambiguous
and controversial. Pyrolysis of lignocellulose is a complex
process involving multiphase reactions, intricate chemical
pathways, highly unstable intermediate products, and the
effects of heat and mass transfer. The pyrolysis of hemicel-
lulose and cellulose occurs in three stages. The first stage is
an intramolecular dehydration process that leads to the
formation of anhydrocelluloses. This process is weakly en-
dothermic and occurs at a temperature around 220°C. The
second stage involves the production of levoglucosan,
which is an endothermic process occurring at a tempera-
ture around 280°C. The third stage involves numerous re-
actions leading to the cleavage of С–С and С–О bonds as
well as radical reactions that form gases or volatile com-
pounds, mainly through the decomposition of anhydrocel-
luloses. The breaking of glycosidic bonds in cellulose R–О–
R, R-radical occurs at temperatures between 300°C and
500°C [22].
Since lignin is an aromatic polymer, kinetic models that are
valid for cellulose cannot be applied to it. Lignin is usually
considered the most stable of the biomass components.
However, lignin undergoes weak decomposition at very low
temperatures and is less stable than cellulose at the initial
stages of decomposition. This initial instability of lignin is
likely related to the breakage of side groups that form the
lignin polymer. Due to the structural similarity between lig-
nin and coal, some models developed for coal pyrolysis can
be applied to lignin pyrolysis. Obviously, direct extrapola-
tion of results obtained with coal, cellulose, and lignin to
the pyrolysis of specific biomass is possible only for qualita-
tive analysis and evaluative calculations.
Primary pyrolysis of biomass begins with dehydration at
temperatures below 200 °C, while secondary pyrolysis (de-
struction and synthesis), which includes the aromatization
process, begins at temperatures above 400 °C [32]. The
initial decomposition temperatures of biomass range from
220–240 °C with significant structural modifications occur-
ring between 350 °C and 400 °C [13]. These modifications
are characterized by a reduction in intensity in С–О and C=C
bonds formation as well as alkyl bond С–С formation in-
creases. As the temperature increases, there is a continu-
ous decrease in the intensity of the valence bonds -OH and
an increase in the production of aromatic compounds. The
maximum yield of these compounds is observed at temper-
atures above 600 °C and depends on the ratio of cellulose
to lignin in the fuel.
The temperature dependence of mass loss during pyrolysis
of different biomass samples is characterized by two
stages. The first stage involves the decomposition of hemi-
cellulose at temperatures between 250–300 °C and cellu-
lose at temperatures close to 350 °C [33]. The second stage
is associated with lignin decomposition, which occurs at
higher temperatures [34]. While the characteristic pyrolysis
temperatures are similar for different types of biomasses,
the amount of volatile yield at each stage depends on the
type of biomass, specifically on its ratio of cellulose, hemi-
cellulose, and lignin, as well as the elemental composition
of the biomass.
The regularities of fast high-temperature pyrolysis of bio-
mass and the simultaneous combustion of its coke residue
have not been sufficiently studied. Most biomass pyrolysis
studies focus on the results of thermogravimetric analysis
[23]. Thermogravimetric analysis is a method that records
the weight loss of a sample against temperature under con-
trolled heating rate and gas atmosphere. Differential ther-
mogravimetric analysis curves are derived from thermo-
gravimetric curves and are widely used to evaluate
pyrolysis kinetics in biomass [13]. These methods provide
data in the form of kinetic information at a low heating rate
(2–30 °C/min.). In the articles [31, 33], the fast pyrolysis of
biomass in a fluidized bed was studied, but the dynamic
characteristics of the process were not determined. The ar-
ticle [35] investigated the fast pyrolysis of isolated compo-
nents of biomass. It was found that the maximum volatile
hemicellulose yield occurs at layer temperatures above
500 °C, while lignin yield is maximized above 800 °C. H2O,
CO2, and CO make up the largest fractions of all three
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Відновлювана енергетика. №2/2024 | Біоенергетика
biomass components at all the temperatures studied. In
the study [36], it was found that for fast pyrolysis, the max-
imum volatile yield for hemicellulose occurs at a tempera-
ture of 550 °C, for cellulose at 700 °C, and for lignin at
900 °C and above.
The transfer of the results of existing studies on the pyroly-
sis of individual components of lignocellulose to real bio-
mass will inevitably result in some inaccuracies. However,
the established patterns allow us to interpret the results of
experimental studies on the thermal degradation of real bi-
omass. We have not found any studies on the fast pyrolysis
of sunflower husks.
Setting of tasks. According to the Recovery and Develop-
ment Plan of Ukraine (part of the United 24 initiative), re-
newable energy development plays a crucial role in shaping
the future structure of Ukraine's power system. The Energy
Strategy of Ukraine aims to increase the use of renewable
fuels, including agricultural and food industry waste. To
achieve this, it is necessary to improve existing waste-to-
energy (WTE) technologies and develop new ones for the
incineration of agricultural and food industry waste [37].
These efforts should be based on the thermal processing
characteristics of such fuels [38]. It is worth emphasizing
that the waste from oil extraction plants, such as sunflower
husks, holds particular interest due to its suitability as a
substitute for fossil fuels in power boilers. As mentioned
earlier, its annual energy potential in Ukraine amounts to
3.4 million tons.
The aim was to determine the dynamic regularities of ther-
mal decomposition for SH particles across a wide tempera-
ture range. The study focuses on investigating the thermal
processing patterns of SH under conditions representative
of different zones in energy boilers. In boiler units, fuel par-
ticles undergo high heating rates and process tempera-
tures. Therefore, it examines heating fuel particles at rates
up to 500 °C/s within a temperature range of 500-1000 °C.
To achieve these heating rates, experimental research was
conducted using a fluidized bed (FB) system.
The characteristics of the investigated fuel. Waste from
the production of the Pology Oil Extraction Plant in the Za-
porizhzhia region of Ukraine was chosen for the study. The
initial samples used in the study were intact halves of solid
sunflower seed shells with sizes ranging from 10-14 mm.
The average technical analysis results for sunflower husks
are as follows: ash content in dry state (Ad) is 2.4%, volatile
yield to dry ash-free state (Vdaf) is 76.8%, moisture per op-
erating state (Wr) is 10.2%. The lower heating value is meas-
ured at 20 MJ/kg. The husk material was not subjected to
any pre-treatment or particle size modification during ex-
periments.
The following standard methods were used to determine
the lower heating value and technical parameters of sun-
flower husk samples: ISO/CD 21645: Solid recovered
fuels — Methods for sampling; ISO/CD 21646: Solid re-
covered fuels — Sample preparation; ISO/DIS 21654:
Solid recovered fuels — Determination of calorific value;
ISO/DIS 21656: Solid recovered fuels — Determination of
ash content; CEN/TS 15414-1:2010: Solid recovered fuels
— Determination of moisture content using the oven dry
method — Part 1: Determination of total moisture by a
reference method.
Fluidized bed reactor. FB reactors are commonly used for
thermal processing of various materials, including sun-
flower husk. In this study, the dynamics of SH thermal pro-
cessing were investigated using a laboratory setup consist-
ing of a vertically positioned quartz reactor with a pseudo-
fluidized bed. The reactor had an internal diameter of 0.05
m and a height of 0.9 m. To achieve optimal heating condi-
tions, it is important to control the rate at which tempera-
ture changes occur in the reactor. Heating rates between
250 and 500 °C/s were implemented in this study.
Before conducting combustion experiments, preliminary
tests were conducted on a "cold" model to determine
the air flow rate required to create pseudo-fluidization
conditions for the husk particles. Pseudo-fluidization re-
fers to when particles behave like fluid in response to an
upward-flowing gas stream. The results showed that in-
creasing the air flow rate did not result in pseudo-fluidi-
zation of the husk particles until a certain threshold
value was reached. Instead, the particles formed a weak-
moving layer that acted as a filter. However, once this
critical flow rate (linear velocity) was exceeded, inten-
sive removal of particles from the reactor occurred.
Based on these observations, it was concluded that sun-
flower husk particles belong to group A materials [39],
which are unable to undergo pseudo-fluidization with-
out the presence of layer-forming material. Therefore,
pre-burned sand with particle sizes ranging from 0.05-
0.63 mm and heated to 950 °C was used as an inert ma-
terial for subsequent combustion experiments involving
SH particles.
The addition of pre-burned sand facilitated intense mix-
ing between SH and sand particles within the reaction
zone while ensuring uniform access of oxygen to fuel
particles during combustion's final stage. This approach
helped avoid concentration gradients along the husk
layer (when airflow rates were below entrainment veloc-
ity) and potential uncertainties caused by uncontrolled
entrainment from reaction zones (near swirling speed
boundaries).
In summary, studying combustion dynamics in FB reac-
tors requires careful consideration of particle character-
istics such as their ability for pseudo-fluidization and im-
plementing appropriate measures like using layer-
forming inert materials for achieving uniform mixing and
controlled reactions.
Experimental procedure. During the experiments, the air
flow rate was chosen based on the pseudo-fluidization con-
dition of sand particles with a size range of 0.05-0.63 mm.
Initially, 50 grams of inert material (sand) were loaded into
the reactor to create a boiling layer at an air flow rate (Gair)
ranging from (91–104)·10-6 m3/s, corresponding to air
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Відновлювана енергетика. №2/2024 | Біоенергетика
velocities (wair) of 0.15-0.18 m/s. The reactor was vertically
installed in an electric tube furnace with a power output of
2.5 kW. The temperature of the layer was measured using
a type K thermocouple (Chromel-Alumel), which was
placed within the layer for accurate temperature monitor-
ing.
After heating and stabilizing the layer temperature, a
known weight of sunflower husk was introduced into the
reactor through a gate system. Under these conditions,
rapid heating and subsequent reaction of the husk took
place at the predetermined layer temperature. The com-
bustion experiments were conducted at atmospheric pres-
sure within a range of layer temperatures from 500 to 1000
°C with intervals of 100 °C. The volatile products resulting
from thermal destruction of the husk were carried upwards
by airflow and passed through several stages including a
bubbler, condensate collector (to delay condensation), fine
filtration packing, and finally entered into a mass spectrom-
eter connected to specialized analog-to-digital converter
equipment controlled by a personal computer for data ac-
quisition and processing using specific techniques. tThis
way, valuable information about combustion characteris-
tics such as gas composition and evolution rates during sun-
flower husk combustion could be obtained.
Gas analysis methodology. The gas analysis methodology
described here utilizes a mass spectrometer with six chan-
nels to measure the concentration of specific gases in a gas
mixture at a pressure of 0.1 MPa. The output voltage of
each channel is linearly related to the concentration of the
corresponding gas. The measurement system is able to
continuously determine and store partial pressures (ex-
pressed as n, % vol.) of CO, CO2, CH4, H2, O2, and Ar. During
the measurements, data is continuously monitored and
recorded in dynamic curves that represent the component
composition (partial pressure) of these gases over time
[CO, CO2, CH4, H2, O2, Ar] = n(τ). The collected data can then
be further analyzed to determine the characteristic time for
the pyrolysis and combustion of volatiles, as well as the
time required for the combustion of residual coke. This
methodology provides valuable insights into the behavior
and pyrolysis/combustion properties of different gases in a
gas mixture.
Measurement instrument errors. The main parameters di-
rectly measured in the experiments were temperature,
pressure, gas flow rates, and volumetric fractions of gase-
ous components. For each of these parameters, the types
of measuring instruments and the allowable relative meas-
urement errors δi (according to the instrument specifica-
tions) are provided below.
Temperature: Thermocouple transducers type TXA(K),
measurement range 200-1300 °C, with a constant δt =
0.75% within the range of 500-1000 °C. Pressure: Sample
spring gauge type MO, measurement range for excess pres-
sure 0-2.5 MPa, with a constant δp = 0.5%. Gas flow rates:
Rotameters types RM A-0.1 GUZ (for tracer gas), RM-0.63
GUZ and RC-3 (for carrier gas), with a normalized δG = 2.5%
based on scale length. Volumetric fractions of gaseous
components: Magnetostatic mass spectrometer type MX-
1215, measurement ranges 0-20% (Ar and CH4) and 0-100%
(other components), with a δn = 2.5% for the upper value.
It is worth noting that for computer registration of temper-
atures and volumetric fractions of gaseous components, a
multi-channel ADC with a step size of 1/1024 was used per
channel's range. Taking into account the ADC's step size, it
can be considered that additional errors were practically
not introduced during direct measurement registration.
Dynamic errors. During the experiment, the pressure in the
reactor and the flow rate of the tracer gas remain constant,
while the temperatures vary by no more than 2 °C between
the two measurements. This allows us to consider the dy-
namic error of measuring these parameters negligible. As
for the volumetric fractions of gas components ni, it is
taken into account that according to the technical descrip-
tion of mass spectrometer MX-1215, its measurement time
constant is up to 0.5 s (including integration of gas compo-
sition in the inlet system). Therefore, ni values are meas-
ured with a step size of 0.005 s for each mass spectrometer
channel and averaged values are recorded every 0.5 s. The
recorded dynamic curve of output impulses represents a
histogram. The dynamic characteristics of the process were
considered reliably measured at timescales exceeding 5 s.
Other errors. Among the factors that contribute to addi-
tional difficult-to-account-for measurement errors, the fol-
lowing should be mentioned: variations in the ash content
and moisture content in low-mass samples, uneven gas car-
rier flow rate during manual adjustment of the output flow
valve, temperature gradient throughout the reaction zone
volume, possible uneven accessibility of gas carrier flow to
LS particles, etc. The errors caused by these factors are con-
sidered random [40], and the results are statistically pro-
cessed using the EXCEL software package with an approxi-
mation selected in each case to maximize correlation with
experimental data points.
Results and discussion. During pyrolysis, a portion of the
husk mass is converted into volatile matter, while the re-
maining portion (up to 20%–30% of the initial mass) forms
a solid coke residue, which is characterized by low reactivity
and high strength. Fig. 1 presents the dynamic curves of
partial pressures of gas products generated during the
combustion of a discrete sample of sunflower seed husks
weighing of m = 0.1 g at a temperature of T = 500 °C. In
comparative experiments, the mass of the sunflower husk
sample was kept constant for all temperatures studied. The
figure shows that the dynamic curves for CO2 and CO have
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Відновлювана енергетика. №2/2024 | Біоенергетика
two fundamentally different sections. The first section cor-
responds to the release and combustion of volatiles, while
the second section corresponds to the combustion of the
carbon residue. The first section has a pronounced maxi-
mum. The duration of the initial section (up to the
maximum) depends on the duration of the sequentially-
parallel stages of fuel particle heating and mixing in the flu-
idized bed. In the specified experiments, the initial section
before the maximum is 2–3 seconds, and its duration
slightly decreases with an increase in the bed temperature.
Fig. 1. The dynamics of gas component emissions during the combustion of SH samples at a temperature of T = 500 °C
and an air flow rate of Gair = 95.2 ml/s (wair = 0.16 m/s)
The second stage, which is the burning of carbon residue, is
longer compared to the release and burning of volatiles.
The point where the CO2 curve changes direction can be
chosen as a convention to distinguish between the end of
the pyrolysis stage and the beginning of the carbon residue
burning stage. It can be observed that the process of burn-
ing carbon residue is accompanied by a slow release of CO2
until it reaches a quasi-steady state level. This trend was
observed for all investigated temperatures and indicates a
reduced reaction rate of carbon coke from sunflower husks
with oxygen in the air, especially at the final stages of com-
bustion (conversion). The release and combustion of vola-
tiles counteract the diffusion of oxidizer to the surface of
fuel particles. This is explained by the intensive saturation
of boundary film adjacent to carbon residue particles with
volatiles, leading to the formation of vapor-gas mixture
consisting of combustible components and oxidizer. When
it burns out, the concentration of oxidizer on the surface of
the carbon residue sharply decreases, and as a result, the
residue is almost not involved in ignition and combustion
processes at the initial stage. Homogeneous-heterogene-
ous ignition is realized. The observed fact may indicate the
presence of significant mechanical unburned residue of
sunflower husk material due to a mismatch between the
time it spends in the combustion chamber and the time
necessary for the complete combustion of coke residue to
the required degree of conversion.
For layer temperatures up to 900 °C, the aforementioned
trends persist: the dynamic curves (for CO2 and CO) have
two distinct segments, one of which corresponds to the re-
lease and combustion of volatiles, while the other corre-
sponds to the combustion of carbon residue (Fig. 2).
Throughout the entire range of investigated temperatures,
the longest stage of combustion for sunflower husk parti-
cles is the combustion of carbon residue: 22–23 seconds at
500 °C; 14–15 seconds at 600 °C; 11–12 seconds at 700 °C;
10–11 seconds at 800 °C; 9–10 seconds at 900 °C; and 6-7
seconds at 1000°C. Increasing the layer temperature also
leads to a decrease in the total burning time of sunflower
husk particles, mainly due to a reduction in the burning
time of carbon residue. Therefore, this stage in combustion
chambers is recommended to be conducted at tempera-
tures above 800-900 °C.
An increase in temperature in the reaction zone is accom-
panied by an increase in the recorded peaks of methane
and hydrogen at the pyrolysis stage: at T = 500 °C for H2 up
to 0.8% vol. and for CH4 – up to 0.14% vol.; at T = 700 °C for
H2 up to 1.2% vol. and for CH4 up to 1.0% vol.; at T = 800 °C
for H2 and CH4 up to 2.0% vol.; at T = 900 °C for H2 and CH4
up to 2.5% vol. The observed increase in the yield of CH4
and H2 with increasing temperature during sunflower husk
pyrolysis qualitatively matches the results of previous stud-
ies on fast pyrolysis of olive kernels, as well as isolated bio-
mass components such as hemicellulose, cellulose, and lig-
nin [33, 35].
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Fig. 2. The dynamics of the release of gaseous components during the combustion of SH samples at a temperature of T =
900 °C and an air flow rate of Gair = 103.7 ml/s (wair = 0.18 m/s)
It should be noted that distinguishing between volatile
burning stages and carbon residue burnout becomes diffi-
cult when temperatures exceed 900°C based on dynamic
curve analysis (Fig. 3).
In addition to a comprehensive study on the pyrolysis-com-
bustion process conducted in these experiments, it is
necessary to separately investigate pyrolysis in an inert en-
vironment as well as carbon residue burnout in an oxidizer.
One disadvantage of this analysis is that coke preparation
conditions may influence its subsequent burnout; however,
a clear advantage is the ability to divide the process into
distinct stages.
Fig. 3. Dynamics of volatile gases emission during thermal processing of SH samples at a temperature of 1000 °C
The study enabled the determination of the main patterns
of pyrolysis and burnout of SH during rapid heating to a
temperature of 1000 °C. A notable characteristic of SH,
which influences its thermal decomposition, is its lignocel-
lulosic structure. During pyrolysis in a fluidized bed, the
maximum yield of volatile hemicellulose occurs at approxi-
mately 500 °C, cellulose at 700 °C, and lignin at 900°C.
The highest proportions of H2O, CO2, and CO are observed for
all three biomass components across all studied tempera-
tures. This can be attributed to the fact that hemicellulose and
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Відновлювана енергетика. №2/2024 | Біоенергетика
cellulose contain around 45%-50% wt. oxygen while lignin con-
tains about 25%-30% wt. Consequently, hydrocarbons pro-
duced during pyrolysis rapidly react with oxygen radicals gen-
erated within the process and undergo oxidation.
The initial stage of thermal processing of SH involves the
degradation of hemicellulose. At temperatures ranging
from 220-280 °C, intramolecular dehydration occurs, re-
sulting in the formation of anhydrocellulose [22]. During
this process, weakly bound impurity groups, primarily
consisting of CO, CO2, and H2O, are released. Significant
structural modifications occur between 350-400 °C as evi-
denced by a decrease in intensity and the breaking of C-O
and C=C bonds [13]. Additionally, alkyl bonds (C-C) are
formed during this stage. The production of CH4 begins at
400 °C and increases as the temperature rises [36]. The pro-
portions of CO, H2, and CH4 in the total volatile yield in-
crease with temperature while H2O gradually decreases
[35]. Fig. 4 illustrates an increase in the partial pressure of
H2 with rising temperature.
Fig. 4. Partial pressures of H2 for the temperature range 500–1000 oC
Within the temperature range of up to 500 °C, bonds be-
tween monomolecules are broken, and the material loses
plasticity and becomes brittle [22]. With an increase in tem-
perature, the intensity of valence bonds –OH decreases con-
tinuously, and there is an increase in the yield of aromatic
compounds. The maximum yield of these aromatic com-
pounds depends on the ratio of cellulose to lignin in the fuel
and is typically observed at temperatures above 600 °C [35].
In the temperature range of 450–600 °C, the ring structure
of lignocellulose molecules breaks along oxygen heteroa-
toms (O) and forms linear (aliphatic) radicals [36]. This leads
to numerous reactions involving the splitting of C–C and C–
O bonds as well as radical reactions that result in the for-
mation of gases or volatile compounds. These reactions pri-
marily occur due to the decomposition of anhydrocellulose
[22]. Light peripheral groups such as СН2, H, OH break off
from these molecules and are released in gaseous form.
With rapid heating, detachment of light functional groups
and degradation occur simultaneously. The yield of gaseous
products depends on the environment. In an oxidizing at-
mosphere (as in the conducted experiments), light H- and
CO- groups quickly combine or undergo oxidation, resulting
in an increased proportion of CO2 in the pyrolysis products.
As the pyrolysis temperature further increases, more bonds
break down into the initial substance, leading to an in-
crease in small radical fragments and ultimately increasing
the yield of gas phase products.
Based on experimental data, both total heat treatment
time (Fig. 5) and time required for complete combustion of
CR from sunflower husk were determined for temperatures
ranging from 500 to 1000 °C.
The results for the temperature range of 500-1000 °C were
summarized in the form of empirical equations. For the to-
tal heat treatment time (τ), the equation is = 415.0Т-
1.552.0, where T is the layer temperature in °C. The equa-
tion for the time required for complete combustion of car-
bon residue from sunflower husk = 572.0Т-1.641.5,
where τ represents the burnout time of husk particles in
seconds.
The proposed equations have an average error of less than
1.8%.
In the temperature range of 600-1000 °C, an empirical
equation for the total heat treatment time can be used: =
160.0Т-1.42.2, with an average error of 2%.
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For temperatures ranging from 700-1000 °C, there is a lin-
ear relationship between the total heat treatment time and
process temperature: = 28.0-0.019Т1.7, with an aver-
age error of 1.5%.
Fig. 5. Temperature dependence of the total heat treatment time of sunflower husk samples on temperature
Conclusions
1. Sunflower husks are plant-derived fuel waste. The carbon
content in different samples of lignocellulosic biomass ranges
from 40%-55% by dry weight, with a heat of combustion
ranging from 15-21 MJ/kg. The characteristics of high volatile
yield, low sulfur content, chlorine, ash, and moisture make it
suitable for replacing fossil fuels in industrial and municipal
energy boilers. According to our estimates, the annual energy
potential of SH in Ukraine is 3.4 million tonnes or 2.0 million
tonnes of equivalent fuel.
2. Thermal treatment of sunflower husks is a complex of
physicochemical processes that can be conditionally di-
vided into the following sequential-parallel stages: 1) pyrol-
ysis, which includes heating, drying, formation and release
of volatiles; 2) combustion of volatiles and solid carbon res-
idue. The volatile substances include H2, CH4, CO, CO2, Н2О
and a small amount of C2H6 and C2H4. These stages have
different speeds, durations and degrees of influence on
combustion depending on the technological conditions of
the process and the type of fuel.
3. Sunflower husk is a complex multicomponent fuel con-
taining approximately 30%-48% cellulose, 34%-38% hemi-
cellulose, and 17-26% lignin by mass. Depending on the
structure, the elemental composition of the fuel varies as
well as the quantitative and qualitative composition of vol-
atiles and, as a result, the heat of combustion. In addition,
different molecular structures of individual components
lead to different decomposition mechanisms during pyrol-
ysis. The major components of volatile sunflower husks at
temperatures ranging from 500-1000 °C are H2O, CO2, and
CO. This can be explained by the fact that cellulose and
hemicellulose contain approximately 45%-50% oxygen by
mass, while lignin contains about 25%-30% oxygen by mass.
The yield of gaseous products depends on the environ-
ment. In an oxidizing environment (as in the conducted ex-
periments), the light H and CO groups quickly combine or
oxidize, resulting in an increase in the proportion of CO2 in
the gaseous reaction products. As the temperature in-
creases, the number of bond breaks in the feedstock and
small radical fragments increases, leading to an increase in
gas phase yield.
4. Dynamic curves describing volatile yields exhibit two dis-
tinct stages: the first region corresponds to the release and
combustion of volatiles, while the second region corresponds
to the combustion of carbonaceous residue. Upon its combus-
tion, there is a sharp decrease in oxidizer concentration on the
surface of carbonaceous residue, which consequently has little
involvement in ignition and burning processes during the ini-
tial stage. Homogeneous-heterogeneous ignition is realized.
The combustion of CR is considered as the dominant process
in thermal decomposition of SH particles, which is also charac-
terized by longer duration and determines overall burning
time. Increasing the layer temperature leads to a decrease in
the total burning time of SH particles, mainly due to a reduc-
tion in the burning time of CR.
5. The stage of carbon residue combustion is the longest
and determines the overall duration of thermal treatment.
This stage determines the degree of fuel conversion, espe-
cially in cases where low-reactivity carbon residue enters
the low-temperature zone of the boiler combustion cham-
ber. Empirical temperature dependencies were obtained
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Відновлювана енергетика. №2/2024 | Біоенергетика
for the overall duration of thermal treatment and the dura-
tion of CR combustion during rapid heating in the temper-
ature range of 500-1000 °C. These regularities are practi-
cally significant in designing combustion chambers for
thermal processing boilers for SH.
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|
| id | veorgua-article-464 |
| institution | Vidnovluvana energetika |
| keywords_txt_mv | keywords |
| language | Ukrainian |
| last_indexed | 2026-07-19T01:13:34Z |
| publishDate | 2024 |
| publisher | Institute of Renewable Energy National Academy of Sciences of Ukraine |
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| resource_txt_mv | veorgua/63/536909bfe438b6dab1763dcb4abfe863.pdf |
| spelling | veorgua-article-4642026-07-18T06:32:20Z DETERMINATION OF THE FEATURES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK IN A FLUIDIZED BED ВИЗНАЧЕННЯ ОСОБЛИВОСТЕЙ ТЕРМІЧНОГО РОЗКЛАДАННЯ ЛУШПИННЯ СОНЯШНИКА В КИПЛЯЧОМУ ШАРІ Haponych, L. Topal , O. Holenko , I. Kobzar , S. biomass; sunflower husks; waste-to-energy; fluidized bed; heat treatment; pyrolysis; volatiles; carbon resi-due. біомаса, лушпиння соняшника, перетворення відходів на енергію, киплячий шар, термічна оброб-ка, піроліз, леткі речовини, вуглецевий залишок. Sunflower husk (SH) is a plant waste fuel. The carbon content in different samples of SH ranges from 40.5% to 54.5% in an operating state, with ash content ranging from 1.5% to 8.5%, moisture content ranging from 6.9% to 9.5%, chlorine content ranging from 0.05% to 0.3%, and lower heating value ranging from 14.5 MJ/kg to 20.5 MJ/kg. These characteristics make it a suitable substitute for fossil fuels in power boilers. Waste-to-energy (WTE) technologies are rapidly developing worldwide, offering the potential for generating renewable energy from waste, including agricultural and food industry waste such as SH. According to our estimates, Ukraine has an annual energy potential of approximately 3.4 million tons of SH or about two million tons of fuel equivalent. Approximately half of this volume is currently being burned in oil extraction plants' boilers; however, up to one million tons of SH end up in landfills annually, resulting in significant energy losses. To develop new and improve existing WTE technologies that utilize SH as a fuel source, it's essential to understand the thermal processing characteristics of SH under conditions similar to those found in different zones within real power boilers - specifically the heating of fuel particles at rates up to 500 °C/s over a temperature range of 500–1000 °C. In this study, we aimed to investigate the thermal processing characteristics by subjecting SH particles within a laboratory fluidized bed reactor to high-speed heating within the aforementioned temperature range. During rapid heating between 500–1000 °C temperatures range, SH particles undergo conversion into volatile compounds and solid carbon residue. Two distinct stages can be observed on the dynamic yield curves for volatiles. The release and burnout of volatiles occurs during the first stage while the second stage involves coke ash residue burnout. We obtained empirical temperature-dependents for total heat treatment time and carbon residue burnout time under fast heating conditions in the investigated temperature range. The stage of carbon residue combustion is the most enduring and determines the overall duration of thermal treatment. This stage determines the degree of fuel transformation, especially in cases where low-reactivity carbon residue enters the low-temperature combustion chamber area of the boiler. The obtained regularities have practical significance in designing combustion chambers for thermal processing of sunflower husk. Лушпиння соняшника (ЛС) – це паливні відходи рослинного походження. Вміст вуглецю в перерахунку на робочий стан у різних зразках ЛС коливається в межах 40,5–54,5 %, зольності – 1,5–8,5 %, вологості – 6,9–9,5 %, хлору – 0,05–0,3 %, а нижча теплота згоряння в межах 14,5–20,5 МДж/кг. З огляду на вказані характеристики це паливо придатне для використання як замінник викопного палива в енергетичних котлах. Останніми роками у світі стрімко розвиваються технології перетворення відходів на енергію (WTE), які мають потенціал для отримання відновлюваної енергії з відходів, зокрема сільськогосподарських. За нашими оцінками, щорічний енергетичний потенціал ЛС в Україні сягає 3,4 млн т, або близько 2 млн т умовного палива. Близько половини цього обсягу спалюється в котлах олійноекстракційних заводів, але щорічно до 1 млн т лушпиння потрапляє на звалища, що призводить до значних енергетичних втрат. Розробка нових та вдосконалення існуючих технологій WTE, що використовують ЛС як паливо, має базуватися на розумінні закономірностей його термічної переробки. Тому метою цієї роботи було дослідження закономірностей термічної переробки ЛС у характерних для різних зон енергетичних котлів умовах – при нагріванні частинок палива зі швидкістю до 500 °С/с в інтервалі температур 500–1000 °С. Така швидкість нагріву була реалізована в лабораторному реакторі киплячого шару. При швидкісному нагріванні в діапазоні температур 500–1000 °C частинки ЛС перетворюються на леткі і твердий вуглецевий залишок. Динамічні криві виходу газоподібних летких мають дві ділянки: перша відповідає виходу і вигорянню летких, а друга – вигорянню вуглецевого залишку. Отримано емпіричні температурні залежності загального часу термообробки та часу вигоряння вуглецевого залишку лушпиння соняшника при швидкому нагріванні в інтервалі температур 500–1000 оС. Стадія вигоряння вуглецевого залишку є найтривалішою і визначає загальний час термообробки. Ця стадія визначає ступінь перетворення палива, особливо у випадках, коли низькореакційний вуглецевий залишок потрапляє в низькотемпературну область камери згоряння котла. Отримані закономірності мають практичне значення при проєктуванні камер згоряння котлів термічної переробки лушпиння соняшника. Institute of Renewable Energy National Academy of Sciences of Ukraine 2024-07-01 Article Article application/pdf https://ve.org.ua/index.php/journal/article/view/464 10.36296/1819-8058.2024.2(77).137-149 Vidnovluvana energetika ; No. 2(77) (2024): Scientific and applied Journal renewable energy ; 137-149 Возобновляемая энергетика; ##issue.no## 2(77) (2024): Scientific and applied Journal renewable energy ; 137-149 Відновлювана енергетика; № 2(77) (2024): Науково-прикладний журнал Відновлювана енергетика; 137-149 2664-8172 1819-8058 10.36296/1819-8058.2024.2(77) uk https://ve.org.ua/index.php/journal/article/view/464/373 Copyright (c) 2024 L. Haponych, O. Topal , I. Holenko , S. Kobzar https://creativecommons.org/licenses/by-nc-nd/4.0 |
| spellingShingle | biomass sunflower husks waste-to-energy fluidized bed heat treatment pyrolysis volatiles carbon resi-due. Haponych, L. Topal , O. Holenko , I. Kobzar , S. DETERMINATION OF THE FEATURES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK IN A FLUIDIZED BED |
| title | DETERMINATION OF THE FEATURES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK IN A FLUIDIZED BED |
| title_alt | ВИЗНАЧЕННЯ ОСОБЛИВОСТЕЙ ТЕРМІЧНОГО РОЗКЛАДАННЯ ЛУШПИННЯ СОНЯШНИКА В КИПЛЯЧОМУ ШАРІ |
| title_full | DETERMINATION OF THE FEATURES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK IN A FLUIDIZED BED |
| title_fullStr | DETERMINATION OF THE FEATURES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK IN A FLUIDIZED BED |
| title_full_unstemmed | DETERMINATION OF THE FEATURES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK IN A FLUIDIZED BED |
| title_short | DETERMINATION OF THE FEATURES OF THERMAL DECOMPOSITION OF SUNFLOWER HUSK IN A FLUIDIZED BED |
| title_sort | determination of the features of thermal decomposition of sunflower husk in a fluidized bed |
| topic | biomass sunflower husks waste-to-energy fluidized bed heat treatment pyrolysis volatiles carbon resi-due. |
| topic_facet | biomass sunflower husks waste-to-energy fluidized bed heat treatment pyrolysis volatiles carbon resi-due. біомаса лушпиння соняшника перетворення відходів на енергію киплячий шар термічна оброб-ка піроліз леткі речовини вуглецевий залишок. |
| url | https://ve.org.ua/index.php/journal/article/view/464 |
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