Corresponding Author: Sapto
Raharjo
E-mail: [email protected] �
INTRODUCTION
By the increasing of world population, energy needs
are also increasing. Currently, the world's energy is still dominated by
non-renewable energy obtained from fossil fuel energy. If there is no
exploration of other forms of energy, then it is certain that fossil energy
reserves will be depleted faster. Therefore, other energy explorations are needed
as the alternative to the fossil energy. One of the potential energies as a
solution to this problem is biomass energy (Kr�l�k et al., 2023). Biomass energy comes from organic materials, so it
is a renewable energy. One example of biomass energy is charcoal briquettes.
Charcoal briquettes can be made from organic materials. Because it can be made
from organic materials, biomass energy has other significant benefits apart
from being an alternative to fossil energy, which can reduce organic waste (Otieno et al., 2022).
Briquette is a resized charcoal powder, solidified by
pressure and blended with an adhesive agent to form a solid shape (Surup et al., 2020). A briquette's quality, which is reflected by its
density, moisture content, ash content, volatile matter, fixed carbon, and
calorific value, is greatly impacted by the manufacturing procedures (Saleh et al., 2017). The combustion characteristic of briquette depends
on the quality mentioned before. Good quality briquettes must have a short
ignition time, a low combustion rate to reach maximum temperature, a long
combustion time at maximum temperature, and the temperature slowly decreases
after reaching maximum temperature (Zuhri & Saifudin,
2018). Another way to improve briquette combustion
characteristics is by activating the briquette and setting the optimum
compaction pressure since the activation and compaction process can provide
enough pores to trap oxygen. In this research, briquettes are made from corncob
waste.
Based on the background above, this study aims to
investigate and analyze the proximate and combustion characteristics of
activated-charcoal briquettes. This study can improve the efficiency of corncob
charcoal utilization and reduce the environmental damage caused by the
inefficient combustion of corncob charcoal.
METHOD
This study was an experiment in research design.
Corncob trash was used to make charcoal briquettes. The sago, which was
utilized as the glue, was taken from the Ranomeeto region of Konawe Selatan
regency, and the corncob waste (Zea mays L.) was taken from the Tongkuno
area of Muna regency. First, corncob waste was dried in a furnace for 120
minutes at 110�C, and then it was carbonized in an electric furnace for 60
minutes at 499�C (L Lestari et al., 2019). An 80-mesh strainer sieved the charcoal powder to
obtain grain homogenization (Lina Lestari et al.,
2020). Subsequently, using an electric furnace, it was
activated at two different temperatures of 550�C and 650�C for 5, 10, 15, 20,
25, 30 and 35 minutes. Sago powder was used as the adhesive ingredient, and
activated charcoal powder was combined with it in a 9:1 mass ratio while being
agitated with hot water. The mixture was put into a cylindrical mold with a
diameter of 4 cm and a hole in the center with a diameter of 0.8 cm, and it was
then solidified under three different pressures: 70.33 kg/cm2, 94.22
kg/cm2, and 117.78 kg/cm2 (L Lestari et al., 2019). The resulting briquettes were then dried using oven
for 48 hours at temperature of 60�C (Lina Lestari et al.,
2017).
Combustion characteristics are represented by the
temperature change when it starts to burn until becoming ash. The combustion
time, combustion rate, and maximum briquette temperature was determined by
burning it in outdoor at temperature of 25�C and wind speed of 0.25 m/s. The burning temperature
was measured using an infrared thermometer (L Lestari et al.,
2019). The proximate characteristics, such as the moisture
content, ash content, volatile matter, and fixed carbon, was analyzed using the
ASTM standard method (Deshannavar et al.,
2018). The effect of the activation process on briquette�s
pores was characterized using Scanning Electron Microscope (SEM), and the
result was processed using Image-J free software (Abr�moff et al., 2004;
Kurniawan et al., 2011).
RESULTS AND DISCUSSION
Based on preliminary experiments, the lowest ash content was obtained in
briquettes produced from activated charcoal at 550�C and 650�C for 30 and 20
minutes, respectively. Therefore, briquette parameter measurements were carried
out under these conditions.
Moisture Content, Ash Content, Volatile Matter, and Fix Carbon of Charcoal and Activated
Charcoal
Table 1 shows the moisture content, ash content, volatile matter, and
fixed carbon. Activation treatment decreases the moisture content and volatile
matter. However, the ash content and fixed carbon are increased. If the
volatile matter is high, the burning could start at low temperatures,
indicating that the charcoal is easy to ignite and burn. However, it will cause
a fast and uncontrolled combustion process (Estiaty & Fatimah, 2018). Less than 7%
moisture content is expected to control the burning, so it is easy to ignite.
High ash content could be a challenge in the burning process. However, from the
research results (Table 1), the ash content is about 7%. Therefore the
activated corncob briquette still met the quality standard for briquette
fabrication (Irmawati, 2020). Likewise, as the
fixed carbon increase, it is expected to have a higher burning temperature.
Table 1. The Moisture Content, Ash Content,
Volatile
Matter, Fixed Carbon of Corncob Charcoal
|
Charcoal
|
Moisture content (%)
|
Ash content (%)
|
Volatile matter (%)
|
Fixed carbon (%)
|
|
Without activation
|
7.249
|
3.431
|
30.449
|
58.870
|
|
Activation
(550�C, 30 minutes)
|
1.777
|
7.389
|
28.323
|
62.511
|
|
Activation
(650�C, 20 minutes)
|
1.559
|
6.324
|
18.001
|
74.116
|
The Calorific Value of Activated Charcoal
The calorific
value of corncob charcoal without activation treatment is 6764.12 cal/gr. In
contrast, activation treatment at temperatures 550�C (30 minutes) and 650�C
(20 minutes) causes the calorific value changes to 6771.98 cal/gr and 7674.86
cal/gr for 550�C and 650�C respectively. The increasing calorific value confirms the
hypothesis that activated charcoal will produce an excellent burning
characteristic.
Effect of
Compacting Pressure on Briquette Fabrication
On the briquette
fabrication, the adhesive was mixed with the charcoal by a mass ratio of 9:1, then compacted with various compacting pressure,
specifically 70.33 kg/cm2, 94.22 kg/cm2, and 117.78
kg/cm2, and
then dried. The processes change their calorific value to 5929.49 cal/gr,
5698.26 cal/gr, and 5844.06 cal/gr, respectively (L Lestari et al., 2019). While the briquette from charcoal that activated at a
temperature of 550�C for 30 minutes,
its calorific value changed to 6467.71 cal/gr, 6532.23 cal/gr, and 6784.82
cal/gr; charcoal that is activated at a temperature of 650�C for 20 minutes, its calorific value
changes to 5932.60 cal/gr, 5894.02 cal/gr, and 5905.59 cal/gr (L Lestari et al., 2019). The decrease in the calorific value is caused by the uplift of
moisture content resulting from adding an adhesive. Likewise, briquette
fabrication changes the ash content, volatile matter,
and fixed carbon (L Lestari et al., 2019). However, the briquette still met the quality standard of the
briquette (Vachlepi & Suwardin, 2013).
Briquette
Burning Test
Briquette
burned in a room with a temperature of 25�C,
wind speed of 0.25 m/s, and a mass of 4 gr
for each sample. The change in
the combustion temperature of the briquette that compacted at
a pressure of 70.33 kg/cm2
is shown in Figure 1.
Figure 1. Change in Burning
Temperature of
Activated
�Charcoal
That Compacted at 70.33 kg/cm2
Figure
1 shows that the activation treatment causes the briquette burning to reach a
higher maximum temperature than the briquette without activation treatment.
Briquettes made from charcoal that activated at 550�C for 30 minutes could reach a maximum temperature of
528�C and stand for six to twenty minutes. Otherwise, the
briquette made from charcoal that activated at a temperature of 650�C for 20 minutes could reach a temperature of 497�C and remains constant for six to seventeen minutes. Briquette made from
charcoal without activation treatment reaches a maximum temperature of 461�C and quickly decreases to ash. Figures 2 and 3 show
the change in the temperature
of the briquette that compacted at a pressure of 94.22 kg/cm2
and 117.78 kg/cm2.
Figure 2. Change in Burning
Temperature of Activated
Charcoal That Compacted at 94.22 kg/cm2
Figure 3. Change in burning temperature of
�activated
charcoal that compacted at 117.78 kg/cm2
Figures 2
and 3 show a better burning characteristic of activated charcoal than the
charcoal without activation treatment. The
burning process of solid matter consists of several stages: heating, drying,
devolatilization, and charcoal burning. During the devolatilization process,
the volatile matter will escape in the form of CO, CO2, CH4,
and H2 gases (Abdulkareem et al., 2018). The
devolatilization process is
followed by the oxidation of briquette fuel, which
rate depends on oxygen concentration, size, and charcoal porosity. Figure 4 shows SEM results for
characterizing the charcoal and activated charcoal at 650�C for 20 minutes, with 2500
times magnification.
Figure 4. Pores Of Corncob Charcoals And Pores Of Activated Corncob Charcoals.
Figure 4. shows that the charcoal pores are still not overt, and its
average pore diameter is 39.488 �m. Otherwise, the pores of activated charcoal seem more overt, represented by
several black spots with an average pore diameter of 47.220 �m. These pores provide sufficient oxygen during the burning process, improving activated charcoal briquette
burning characteristics.
CONCLUSION
Briquette produced with an activation
treatment at a temperature and compacted pressure of 550�C
(30 minutes) and 70.33 kg/cm2, respectively, shows the preferable
burning characteristic. Activation of
charcoal will cause a reduction in water content and volatile matter so that
the fixed carbon and calorific value increase. This results in the combustion
characteristics of the briquettes being better than the briquettes made from
charcoal without activation. Activation also causes a higher maximum briquette
burning temperature and a longer burning duration.
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