American Journal of Applied Science and Technology
50
https://theusajournals.com/index.php/ajast
VOLUME
Vol.05 Issue 05 2025
PAGE NO.
50-54
10.37547/ajast/Volume05Issue05-12
Investigation of Emissions Released During the
Combustion of Coal Briquettes Produced from Distillery
Stillage and Paraffin Waste
Akmaljon Khakimov
PhD in Technical Sciences, Associate Professor, Fergana Polytechnic Institute, Fergana, Republic of Uzbekistan
Received:
21 March 2025;
Accepted:
17 April 2025;
Published:
19 May 2025
Abstract:
This article presents the results of analytical research on the formation of smoke and exhaust gases during
the combustion of coal briquettes produced with the addition of binding agents. Separate briquettes were prepared
using distillery stillage and paraffin waste, and the emissions generated during combustion were analysed in
accordance with standard Maximum Allowable Concentration (MAC) requirements. During the experimental study,
the variable parameters were defined as follows: screw press with variable-pitch auger and nozzle diameter of
Dnozzle = 25 mm, pressing force Fpress= 2.4 kN, working chamber diameter Dchamber= 100 mm, and a moisture
and binder content of 15%. The distillery stillage had a 17% water content, while the paraffin waste had 15% water
content. These components were used as part of the briquetting mixture to evaluate their combustion behaviour
and associated emissions. The experimental findings include quantitative data on smoke density, ash content, and
concentrations of harmful gases such as carbon monoxide (CO) and sulfur dioxide (SO₂), all measured against
environmental safety standards.
Keywords:
Briquette, powder, MAC, distillery stillage, paraffin waste, carbon monoxide, sulfur dioxide, ash
content, smoke emissions.
Introduction:
The combustion of coal briquettes releases various
gases and solid residues that are subject to
environmental and sanitary regulations. These
standards are defined in terms of Maximum
Allowable Concentrations (MAC), which may vary
depending on the country and specific industry
legislation. In this context, Uzbekistan has established
a set of MAC values for pollutants typically emitted
during the combustion of coal-based briquettes
[1,2,3].
The primary gases released during the burning
process include:
1.
Carbon Monoxide (CO)
o
MAC (according to air quality standards in
Uzbekistan and Russia):
▪
For short-term exposure: 5 mg/m³
▪
For
average
concentrations
in
working
environments: up to 3 mg/m³
2. Carbon Dioxide (CO
₂
). Although CO
₂
is not directly
classified under MAC limits, its accumulation during
combustion requires sufficient ventilation.
o
Acceptable exposure in normal working
conditions: 9,000 mg/m³ (0.5%)
o
Short-term exposure: 27,000 mg/m³ (1.5%)
2.
3.
Nitrogen Oxides (NOₓ)
–
hazardous to human
health:
o
Nitric oxide (NO): 0.4 mg/m³
o
Nitrogen dioxide (NO
₂
): 0.085 mg/m³ (as per
Uzbekistan’s sanitary regulations)
3.
4. Sulfur Dioxide (SO
₂
)
o
MAC in Uzbekistan: 0.5 mg/m³
In addition to gaseous emissions, the
combustion of briquettes produces solid residues,
such as:
American Journal of Applied Science and Technology
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American Journal of Applied Science and Technology (ISSN: 2771-2745)
5.
Ash content. Ideally, the ash content in coal
briquettes should not exceed 10%, with technical
standards (e.g., GOST) allowing up to 15%. The
median particle size typically ranges from 0.1 to
10 μm
.
6.
Particulate Matter (PM). These are fine airborne
particles that pose health risks when inhaled:
o
PM
₁₀
MAC: 0.05 mg/m³
o
PM
₂
.
₅
MAC: 0.025 mg/m³
Research Object
Based on the aforementioned considerations, this
study investigates the environmental impact of
combusting briquettes produced from distillery
stillage and paraffin waste [1,3,4]. For the purpose of
the analysis, separate briquette samples were
prepared from each type of waste material, and their
performance was tested in accordance with
established
environmental
and
combustion
standards.
The following experimental parameters were applied:
•
Press type: Variable-pitch screw press
•
Nozzle diameter D
nozzle
= 25 mm
•
Compression force F
press
= 2.4 kN
•
Working chamber diameter D
chamber
= 100 mm
Figure 1 presents the general view of the variable-
pitch screw press apparatus, while Figure 2 illustrates
the briquette production process.
The moisture and binder content used for briquetting
was fixed at 15%, with the distillery stillage having a
17% water content, and paraffin waste containing
15% moisture in the selected mixture ratios.
Environmental parameters were also taken into
account during the experimental procedures. Since
the experiments were conducted during the months
of May and June, the ambient temperature for the
Fergana region of Uzbekistan was assumed to be
approximately 30°C, with average relative humidity
measured at 18.7%.
The research was carried out in two stages, involving
both laboratory preparation and combustion testing
phases [1,4,5].
Figure 1. Overview of the briquetting device.
American Journal of Applied Science and Technology
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American Journal of Applied Science and Technology (ISSN: 2771-2745)
Figure 2. Briquette production process.
Results of Theoretical and Experimental Studies
In the first stage of the research, the amount of
smoke and exhaust gases released during the
combustion of the briquettes was determined
experimentally. The volume of volatile substances
generated during combustion was measured in
accordance with GOST 6382-2001 (State Standard)
[1,4,7]. The procedure involved heating the sample to
90°C in an oxygen-free environment for a duration of
7 minutes.
The mass loss of the sample was recorded, and
corrections were made by subtracting the portion of
the mass loss associated with the initial moisture
content of the briquette. The final value represents
the loss due solely to the volatilisation of combustible
compounds.
The amount of volatile matter V
a
released during
briquette combustion was calculated using the
following equation [1,8]:
(1)
Here:
m
₁
–
mass of the steel tray used for burning
the briquette, kg;
m
₂
–
combined mass of the steel tray and the
ash produced after combustion, kg;
m
₃
–
combined mass of the steel tray and the
coal briquette before combustion, kg;
Wₐ –
mass fraction of moisture in the
analytical sample, %.
The formation of non-volatile residues (ash, salts, and
other types of solid substances) during the
combustion of the test briquette is determined using
the following formula, in grams [1,9]:
(2)
If the mass fraction of carbon dioxide from
carbonates formed during the combustion of fuel
briquettes is more than 2%, then the volume of
volatile substances is determined by the following
formula: the output from carbonates corrected for
carbon dioxide is determined by the formula CO
V2
,%,
gr [1.9];
(3)
Here,
(
SO
2
)
a
−
mass fraction of sulfur dioxide (SO
₂
)
derived from carbonates in the analytical sample
(volatile form);
−
mass fraction of non-volatile
sulfur dioxide remaining in the residue (non-volatile
2
3
2
1
100(
)
a
a
m
m
V
W
m
m
−
=
−
−
3
1
2
1
100(
)
(
)
a
m
m
NV
m
m
−
=
−
(
) (
)
(
)
2
2
2
100
a
a
a
a
a
CO
NV
NV
V
V
CO
CO
=
−
−
2
(
)
a
NV
CO
American Journal of Applied Science and Technology
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American Journal of Applied Science and Technology (ISSN: 2771-2745)
form).
As a result, the arithmetic mean of the two measured
values
—
within the range of permissible deviation
—
was
accepted
as
the
final
result.
The outcomes of the study are presented in Figures 3
and 4 [1,10].
Briquette obtained based on 1 bar of alcohol; 2-briquette obtained based on paraffin waste.
Figure 3. The amount of smoke released during briquette burning.
Briquette obtained based on 1 bar of alcohol; 2-briquette obtained based on paraffin waste.
Figure 4. The amount of exhaust gas released during briquette burning.
From the graphical dependencies presented in
Figures 2 and 3, it can be seen that as the ignition
delay time of the coal briquette increases, the
amount of smoke and exhaust gases released also
increases. For example, in the graph shown in Figure
3, when the ignition delay time was in the range of
90
–
100 seconds, the smoke emissions from the
briquette made from distillery stillage increased up to
83
–
86%. However, starting from 120 seconds, a sharp
decrease was observed.
Similarly, for briquettes made from paraffin waste,
smoke emissions increased up to 90
–
95% within the
ignition delay range of 90
–
100 seconds, followed by a
sharp decline starting from 125 seconds. This
behaviour is associated with the transition of the
briquette into the complete combustion phase.
In contrast, the graph in Figure 4 shows that the
volatile components (light volatile gases formed
during combustion) in the briquette exhibit a slight
increase at the beginning of combustion. This occurs
until the briquette reaches full combustion. During
the period of glowing, stable combustion (between
150
–
400 seconds), the curve remains relatively flat
for some time, and as the heat capacity of the
briquette decreases, the release of light volatile gases
also declines. This process continues until the
briquette is fully burned out.
The conducted studies show that in both cases, the
amount of exhaust and smoke gases released does
not exceed the MAC (Maximum Allowable
American Journal of Applied Science and Technology
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American Journal of Applied Science and Technology (ISSN: 2771-2745)
Concentration) standards. This fully satisfies the
environmental requirements imposed on such
briquettes.
The
difference
from
theoretical
calculations did not exceed 4.1%.
CONCLUSION
The conducted studies revealed that the addition of
binders to increase briquette strength has a minimal
effect on the amount of smoke and exhaust gases
released during combustion. Experimental results
showed that this effect also depends on the
proportion of the binders added. For example, when
the binder content exceeded 15%, the amount of
smoke increased in coal briquettes made from
paraffin waste, whereas a noticeable decrease in
smoke was observed in briquettes made from
distillery stillage. Conversely, the volume of light
volatile gases increased in inverse proportion.
The reprocessing of experimental results and
laboratory analyses confirmed that both types of
binders are suitable options for producing quality
briquettes. However, in order to comply with MAC
(Maximum Allowable Concentration) environmental
standards (see paragraph two), it was determined
that the use of a combination of these binder types is
more appropriate.
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A.
A.
(2020).
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