Research of the Process of Briquette Preparation from Coal Powder
in a Screw Press
Akmaljon Xakimov
1a
, Rasuljon Tojiev
1b
, Ikromali Karimov
1
, Nasiba Vokhidova
2
,
Abdurasul Davronbekov
2
, Avazbek Xoshimov
2
, Muxammadbobir Xusanboyev
2
, Oybek Soliyev
2
and
O’tkirbek Hamdamov
2
Fergana Polytechnic Institute, Uzbekistan
Keywords: Briquette, Coal, Powder, Granulometric.
Abstract: The article analyzes the granulometric composition of unusable coal grains mined from the Angren coal mine.
For making briquettes from coal fines of selected size, percentage amounts of fine coal grains were determined
by intervals, and depending on these values, average diameters and relative contact surfaces were determined.
As a binder, alcohol cask, which is a distillery waste, was selected, and briquettes were prepared in a press,
and the limit of compressive strength was determined. The number of nozzle revolutions, the percentage of
coal fine fractions and the optimal values of binder moisture are recommended for obtaining quality
briquettes.
1 INTRODUCTION
The need for oil, gas, coal and other types of fuels is
increasing year by year as a result of the growth of the
population and the growth of the economy. Among
these fuels, coal has a special place. Coal fuels are
economical and widely used raw materials for various
industrial zones. Coal does not always meet the
required standards. An example of this is the crushing
of coal under the influence of external forces and the
loss of mechanical strength. Therefore, briquetting in
special devices with the help of binders is of great
importance to increase the flammability of the formed
coal particles.
Currently in the worldimprovement of coal powder
briquetting technology and justification of the
following scientific solutions for its implementation:
determination of physico-chemical properties of coal;
systematic study of the composition and properties of
coal fines from local industrial waste; increasing the
porosity of coal briquettes by adding combustible
substances and materials; improving environmental
safety in the use of coal briquettes; use of industrial
waste in the production of highly porous coal
a
https://orcid.org/0000-0003-0840-9305
b
https://orcid.org/0000-0001-5636-5840
briquettes; it is necessary to improve the pressing
structure to obtain high porosity coal briquettes.
All over the world, scientists are doing extensive
work in large industrial areas to keep atmospheric
ecology clean. In Uzbekistan, on the basis of
innovative projects for keeping the environment
clean, work is being carried out on the rational use of
local coal raw materials.
2 RESEARCH OBJECT
It is known that in the process of coal mining,
transportation, sorting and storage, a large amount of
small pieces of coal are formed, which require
briquetting in special devices using effective binders.
In recent years, a number of binders have been
proposed for briquetting small pieces of coal, most of
which are polluting the air with harmful and toxic
gases. For example, when burning coal briquetted
with petroleum bitumen and its derivatives, it does not
burn completely and at the same time pollutes the
environment. As a result of incomplete combustion of
coal, the amount of ash increases and accumulates in
770
Xakimov, A., Tojiev, R., Karimov, I., Vokhidova, N., Davronbekov, A., Xoshimov, A., Xusanboyev, M., Soliyev, O. and Hamdamov, O.
Research of the Process of Briquette Preparation from Coal Powder in a Screw Press.
DOI: 10.5220/0013425100004654
In Proceedings of the 4th International Conference on Humanities Education, Law, and Social Science (ICHELS 2024), pages 770-778
ISBN: 978-989-758-752-8
Copyright © 2025 by Paper published under CC license (CC BY-NC-ND 4.0)

the furnaces, while the coal lumps reduce the burning
rate. Regulating the porosity of the obtained coal
briquettes is one of the important tasks of increasing
their combustibility and environmental cleanliness of
the atmosphere.
We should consider the scientific basis of the
formation of the structure of coal briquettes with
binders and additives as one of the types of bonding of
dispersible solid materials using binders. The mixture
forms the basis of the formation of the interconnection
of individual contact particles in the structure, which
are self-regulating and self-regulating processes, and
determine the attachment process. As the initial stage
of the bonding process, adhesion is associated with the
formation of an adhesive film on the surface of a solid
body (substrate). Adhesion is characterized by the
viscous liquid state of the binder. Further processes
lead to an increase in the maximum strength of the
binder. As a result, separated solid particles coated
with a binder are attached in the form of briquettes
(Petrova, Latyshev, & Burenina, 2007).
In this process, the diffusion coefficient is the
difference between the adhesion energy of the binder
to the substrate and the adhesion of the binder. It
serves as a measure to evaluate the wettability of the
binder, which describes the relationship between the
structure of the binder and the orientation of its
molecules on the surface of the substrate. Substances
containing binding and multipolar groups have a high
scattering coefficient. With higher values, the binder
is sufficiently wetted. If its value is negative, it does
not spread to the solid body and wraps in the form of
a lens (Aleksandrova, Rasskazova, & Prokhorov,
2012; Semenov, Podolskaya, Buzaeva, & Klimov,
2009).
The granulometric structural value is determined
by the total contact surface of the grains, the number
and size of the voids in the structural frame of the
briquettes, the content of sharp-cornered grains, the
relief and impact of the hard surface. The principle of
choosing a mixture of coal particles of different sizes
is to create a structural composition that meets the
standard requirements (Podolskaya, Buzaeva, &
Klimov, 2011; Chiari, 1990) .
Small grains are more angular than large ones, and
the heat content of hydration is about 4 times higher
than that of the latter. The addition of large grains to
briquettes (more than 6 mm) negatively affects the
strength of coal briquettes, that is, new surfaces that
are not covered with binder appear. The porosity of the
structure significantly affects the packing density of
coal briquettes. No matter how carefully the solid
grains are packed into briquettes, there will always be
holes between them. The number and size of voids
affect the durability of briquettes. Briquettes made of
fine coal particles have small holes and are mostly
filled with binder. If there are few defects in the form
of voids, the strength of coal briquettes is high.
Briquettes consisting of large grains will have many
defects. The adhesive layer will not be enough to fill
the gaps in them. Therefore, these briquettes are
considered to have low strength. To increase the
strength, it is recommended to add dust-like coal
particles to the briquette mixture, which easily
penetrate into the voids. The unevenness and
unevenness of the material has a positive effect on the
mechanical fastening of the binder and increases the
strength of the briquettes. If the composition of the
sieve is homogeneous, the strength of the briquettes
decreases. A homogeneous mixture does not allow to
ensure compaction density. Grains accumulate in the
briquette with a significant number of voids [6; 7;]. To
increase the strength, it is recommended to add dust-
like coal particles to the briquette mixture, which
easily penetrate into the voids. The unevenness and
unevenness of the material has a positive effect on the
mechanical fastening of the binder and increases the
strength of the briquettes. If the composition of the
sieve is homogeneous, the strength of the briquettes
decreases. A homogeneous mixture does not allow to
ensure compaction density. Grains accumulate in the
briquette with a significant number of voids (Gos,
2021; Salikhanova, Abdurahimov, & Jumayeva,
2020). To increase the strength, it is recommended to
add dust-like coal particles to the briquette mixture,
which easily penetrate into the voids. The unevenness
and unevenness of the material has a positive effect on
the mechanical fastening of the binder and increases
the strength of the briquettes. If the composition of the
sieve is homogeneous, the strength of the briquettes
decreases. A homogeneous mixture does not allow to
ensure compaction density. Grains accumulate in the
briquette with a significant number of voids (Gos,
2021; Salikhanova, Abdurahimov, & Jumayeva,
2020);]. Grains accumulate in the briquette with a
significant number of voids (Gos, 2021; Salikhanova,
Abdurahimov, & Jumayeva, 2020). Grains
accumulate in the briquette with a significant number
of voids (Gos, 2021; Salikhanova, Abdurahimov, &
Jumayeva, 2020).
In nature, there are several types of coals, formed
underground at different times and conditions from
different types of plant and animal sources.
Therefore, coals mined in opposite continents and
regions of our planet have significant differences in
composition and physical and chemical properties.
Their composition and properties should be taken into
Research of the Process of Briquette Preparation from Coal Powder in a Screw Press
771

account in their transportation, sorting, storage, use,
etc.
Thus, the problem of rational use of these coals is
primarily related to the briquetting of small fractions,
which make up 50-60% of the total amount mined.
Efficient use of coal and rational methods of its
storage include, first of all, briquetting of small
particles, which solves the problem of converting low-
grade fuel with limited sales into complete lump fuel,
convenient for transportation, long-term storage and
burning.
3 MATERIALS AND METHODS
The granulometric composition of coal fines is the
main indicator for the preparation of briquettes and
the selection of its binders. In Angren coals, these
indicators are mainly determined in average (50-
60%) percentages, which makes it difficult to carry
out the process of briquetting without excessive
consumption of binders. Taking this into account, we
analyzed the granulometric composition of coal fines
selected from different areas of the Angren coal mine
(Table 1).
As can be seen from Table 1, depending on the
sampling location of the coal mine, the granulometric
composition of coal fines changes significantly,
which requires adjusting the consumption of binders
and additives. At the same time, it indicates that there
will be changes in the technological modes of
obtaining coal briquettes.
The study of the granulometric composition of
coal fines from the Angren mine by the method of
saturation analysis made it possible to determine that
the amount of coal dust (less than 0.2 mm) reaches an
average of 8%, and this indicator ranges from 3 to
14%, which indicates the need for briquetting.
As mentioned above, one of the important
components in the production of coal briquettes are
binders, which include: bentonite clay soil, starch,
liquid glass, gossypol tar, beer wort, etc.
There are more than 100 alcohol production plants
in Uzbekistan, where beer kegs are produced as
waste. Its composition is protein (7-8%), starch (up to
3%), ash (up to 2.5%), connective tissue (up to 10%),
and the rest is water.
When obtaining combustible briquettes, it is
necessary to pay attention to their granularity. The
mass fraction of coal powder in briquettes is 80-85%,
and the remaining 15-20% is the binder, i.e. alcohol
waste in the bar. Due to the presence of a combustible
layer in the briquettes, they are highly flammable.
This makes it convenient to use (Salikhanova,
Abdurahimov, & Jumayeva, 2020).
Table 1: Granulometric composition of Angren mine coal fines
Name of
samples %
The size of the granules, mm
3-5 2-3 1-2 0, 5-1 0.2-0.5 0, 1-0,
2
0-0, 1 total
1 33, 99 6, 51 18, 13 16, 2 13, 08 4, 12 7, 97 100
2 60, 61 3, 85 12, 47 8, 29 6, 76 2, 25 5, 77 100
3 60, 07 3, 88 10, 77 9, 83 8, 91 3, 11 3, 43 100
4 65, 0 4, 27 9, 58 8, 33 8, 38 2, 19 2, 25 100
5 71, 97 5, 06 7, 96 7, 13 4, 93 1, 42 1, 53 100
6 43, 0 6, 15 10, 52 16, 2 12, 91 4, 12 7, 1 100
7 62, 30 4, 22 13, 10 6, 29 5, 22 3, 10 5, 77 100
8 42, 6 3, 88 14, 37 9, 83 15, 65 7, 17 6, 5 100
9 63, 99 5, 26 10, 1 8, 12 7, 24 2, 03 3, 26 100
10 69, 0 7, 2 6, 88 7, 13 3, 15 2, 34 4, 3 100
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772

Coal powder grain size is determined in a linear
dimension as follows,
length -a
width-b
thickness-s
These three dimensions can generally be
characterized by its diameter.
That is
3
abs
d
⋅⋅
=
– arithmetic mean size,
3dabs=⋅⋅
- average geometric size,
or
22
das=+
(mm)
To determine the average characteristic size of
crushed pieces, the average size of the largest and
smallest pieces in several fractions of the material,
mm, is determined using a sorting machine.
max min
2
average
dd
d
+
=
(1)
To determine the average characteristic size of
coal powder, it is determined from the following
formula, mm.
11 2 2 3 3
..
.......
100
nn
av char
dm d m dm d m
d
++
=
( 2 )
where d
1
,d
2
,d
3
…..dn is the average size of classes
or fractions, m
1
, m
2
, m
3
….mn is the percentage of
given classes.
The density of coal powder intended for research
is equal to ρ=880 kg/m
3
. We determine the amount of
material allocated to the experiment in % for a 10 kg
sample and calculate the total surface area of the
particles in volume, m
3
0.011
n
XV==
(3)
The following formula is used to determine the
particle size of coal powder, m3
3
3
4
3
VR
π =⋅
(4)
using this formula, it is possible to derive the
number of particles of size Vn, pcs
3
n
B
n
V
=
(5)
We determine the surface area of a particle of coal
powder, m2
2
4SnR π =⋅⋅⋅
(6)
The obtained results are presented in Table 2
Table 2: Results obtained in determining the surface area of coal particles
N
o
Average
character
istic size
of coal
grains,
..av char
d
,
mm
Coal powder
particle size,
B
z
= m
3
Number
of
particles,
p
Particle
surface area,
S = m
2
B = total
surface
area of
particles
with a
volume of
0.011m
3
Coal powder
density,
kg/m
3
10 kg sample
volume, m
3
1 0.9 0.0000000004 22000000 0.0000025 69.94
ρ =880
X=V
n
=0,011
2 1.1 0.0000000007 15714285 0.0000038 59.7
3 1.4 0.0000000014 7857142 0.0000061 48.3
4 1.6 0.0000000021 5238095 0.0000080 41.9
5 1.8 0.0000000031 3548387 0.0000101 36.1
6 2.0 0.0000000042 2619047 0.0000125 32.9
7 2.3 0.0000000064 1718750 0.0000166 28.55
8 2.5 0.0000000082 1341463 0.0000190 26,32
9 2.7 0.0000000103 1067961 0.0000229 24.44
Research of the Process of Briquette Preparation from Coal Powder in a Screw Press
773

Figure 1: Scheme of the screw press.
Figure 2: Overview of the experimental device of the screw press.
When entering the press, the required size of the
coal powder mixture fraction is 0-5 mm. The moisture
content of the coal mixture should be between 5 and
20%. To increase the strength of briquettes, a fraction
of up to 5 mm is recommended, but the share of up to
5 mm should not exceed 10% of the total mass.
Briquettes must withstand a static load of 3 kg/sm
2
to
meet the condition of resistance to accidental
collisions.
When the briquette falls from a height of 1.5-2 m,
the breakage rate should not exceed 15%. [9; 10].
In the further course of experiments, research
work was carried out on the pilot device of the screw
press for briquetting of coal powder. The kinematic
scheme of the screw press is shown in Fig. 1, and its
general view is shown in Figure 2.
1-electric motor, 2-worm reducer, 3-product
receiving part, 4-pressing part, 5-mouthpiece,
6-hopper, 7,9-coupling, 8-screw, 10-screw shaft,
11-bearing, 12- pressing part, 13-product receiving
case.
4 RESULTS
In the preparation of briquettes from coal powder,
alcohol waste, which is considered as a waste of an
alcohol production enterprise, was selected. The
chemical composition of the alcohol bar is given in
Table 3.
Coal briquettes with varying values of coal fine
fractions and moisture content were prepared and
dried in an oven at a temperature of 120
0
C for 8 hours.
Coal briquette samples are shown in Fig. 3.
The limit of compressive strength of these
briquette samples was determined using a universal
device of brand WP 300 (Fig. 4).
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The compressive strength of these briquette
samples was determined using the WP 300 universal
device (Fig. 4). The results of the experiments are
presented in Tables 4, 5, and 6.
Table 3: Bardani chemical composition.
Indicators
Dry
matter
Protein in
tissues (protein)
protein fat Fiber
Biologically
effective
substances
Ash
Wheat bar
d
11.5 2.9 1.7 0.6 0.7 5.7 0.6
Mouthpiece diameter,
d
m
=35 mm
Mouthpiece diameter,
d
m
=30 mm
Mouthpiece diameter,
d
m
=25 mm
Figure 3: Samples of coal briquettes produced in a screw press
Figure 4: WP 300 universal device for determining the limit of compressive strength of coal briquettes
Table 4: Device productivity Q=200kg/hour, the number of revolutions of the screw is 1.5 revolutions/sec. Mouthpiece
diameter d
m
=25 mm – const
0-1mm 1-2 mm 2-5 mm Compressive strength limit, N/mm
2
Amount of fraction, % Humidity 10% Humidity 15% Humidity 20% Humidity 25%
1 20 40 40 96.5 147.5 212.4 325.1
2 40 30 30 192.2 292.6 425.7 652
3 60 20 20 205 314 638.6 977.2
4 80 10 10 288 440.1 851.3 1302
Mouthpiece diameter d
m
=30 mm – const
0-1mm 1-2 mm 2-5 mm Compressive strength limit, N/mm
2
Amount of fraction, % Humidity 10% Humidity 15% Humidity 20% Humidity 25%
1 20 40 40 68.3 104.6 152 232
2 40 30 30 136.6 209.3 304 465
3 60 20 20 205 314 456 698
4 80 10 10 273.3 418.6 608 930
Research of the Process of Briquette Preparation from Coal Powder in a Screw Press
775

Mouthpiece diameter d
m
=35 mm – const
0-1mm 1-2 mm 2-5 mm Compressive strength limit, N/mm
2
Amount of fraction, % Humidity 10% Humidity 15% Humidity 20% Humidity 25%
1 20 40 40 53.3 81.2 121 181.2
2 40 30 30 106.2 163.5 237 363.2
3 60 20 20 160.1 245.3 356 545.3
4 80 10 10 213.2 326.6 475 726.5
Table 5: The number of revolutions of the auger is 1 rot/sec. The diameter of the nozzle is d
m
=25 mm – const
0-1mm 1-2 mm 2-5 mm Compressive strength limit, N/mm
2
Amount of fraction, % Humidity 10% Humidity 15% Humidity 20% Humidity 25%
1 20 40 40 63.3 100.3 140.9 215.8
2 40 30 30 124.9 201.3 280.7 429.1
3 60 20 20 143.5 206.8 420.4 645.8
4 80 10 10 184.3 291.2 563.6 862.1
Mouthpiece diameter d
m
=30 mm – const
0-1mm 1-2 mm 2-5 mm Compressive strength limit, N/mm
2
Amount of fraction, % Humidity 10% Humidity 15% Humidity 20% Humidity 25%
1 20 40 40 45.12 69.1 100.23 153.12
2 40 30 30 90,21 136.87 200.1 306.94
3 60 20 20 136.9 207.66 300.96 460.05
4 80 10 10 181.09 276.01 401.25 613.12
Mouthpiece diameter d
m
=35 mm – const
0-1mm 1-2 mm 2-5 mm Compressive strength limit, N/mm
2
Amount of fraction, % Humidity 10%
Humidity
15%
Humidity 20% Humidity 25%
1 20 40 40 35,21 53.96 80.5 124.5
2 40 30 30 71.25 106.86 155.9 235.86
3 60 20 20 104.88 161.93 232.9 359.9
4 80 10 10 141.02 217.91 313.45 478.83
ICHELS 2024 - The International Conference on Humanities Education, Law, and Social Science
776

Table 6: The number of revolutions of the screw is 2 revolutions/sec. The diameter of the nozzle is d
m
=25 mm – const
0-1mm 1-2 mm 2-5 mm Compressive strength limit, N/mm
2
Amount of fraction, % Humidity 10% Humidity 15% Humidity 20% Humidity 25%
1 20 40 40 128.6 196.1 282.4 429.8
2 40 30 30 254.9 388.53 566.1 867.45
3 60 20 20 275.8 418.05 849.3 1301.1
4 80 10 10 385.1 587.2 1132.4 1729.8
Mouthpiece diameter d
m
=30 mm – const
0-1mm 1-2 mm 2-5 mm Compressive strength limit, N/mm
2
Amount of fraction, % Humidity 10% Humidity 15% Humidity 20% Humidity 25%
1 20 40 40 91.02 139.6 202.5 305.56
2 40 30 30 180.98 279.5 405.6 618.8
3 60 20 20 275.4 418.2 607.1 928.34
4 80 10 10 362.1 557.3 802.9 1234.9
Mouthpiece diameter d
m
=35 mm – const
0-1mm 1-2 mm 2-5 mm Compressive strength limit, N/mm
2
Amount of fraction, % Humidity 10% Humidity 15% Humidity 20% Humidity 25%
1 20 40 40 71.01 109.4 160.1 241.6
2 40 30 30 141.6 214.9 314.9 485.3
3 60 20 20 212.8 326.3 475.2 724.8
4 80 10 10 283.9 432.9 637.4 966.4
It can be seen from the given tables 4, 5, 6 that
when the number of revolutions of the screw is 2
revolutions/sec, the diameter of the nozzle is d
m
=25
mm – const, when the fractions are 0-1mm-80%, 1-
2mm-10%, 2-5mm-10% , according to 10%, 15%,
20%, 25% humidity, the compressive strength limit
was σ =385.1, σ = 587.2, σ =1132.4, σ =1729.8
N/mm
2
. It can be seen that the mixture with 15%
moisture content in order to obtain briquettes at the
required level, the number of revolutions of the auger
is 2 revolutions per second, the diameter of the nozzle
is d
m
=25 mm - const, are the optimal parameters for
obtaining high-quality briquettes.
5 CONCLUSION
As a result of the conducted scientific research, small
particles of unusable coal mined from the Angren
coal mine were sorted, and their granulometric
composition was analyzed. For making briquettes
from coal fines of selected size, percentage amounts
of fine coal grains were determined by intervals, and
depending on these values, average diameters and
relative contact surfaces were determined. As a
binder, alcohol cask, which is a distillery waste, was
selected, and briquettes were prepared in a press, and
the limit of compressive strength was determined.
The number of nozzle revolutions, the percentage of
coal fine fractions and the optimal values of binder
Research of the Process of Briquette Preparation from Coal Powder in a Screw Press
777

moisture were recommended for obtaining quality
briquettes.
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