97
Indonesian Journal of Science & Technology 8.
97-112 Indonesian Journal of Science & Technology Journal homepage: http://ejournal.
edu/index.
php/ijost/ Potential Alternative Energy of Hybrid Coal from Copyrolysis of Lignite with Palm Empty Fruit Bunch and the Kinetic Study Rinny Jelita.
Iryanti Fatyasari Nata.
Chairul Irawan.
Jefriadi.
Meda Nur Anisa.
Muhammad Jauhar Mahdi.
Meilana Dharma Putra* Department of Chemical Engineering.
Lambung Mangkurat University.
Indonesia Correspondence: E-mail: mdputra@ulm.
ABSTRACT
Lignite is classified as a low-rank coal due to its low content of calories.
Co-pyrolysis with biomass waste such as palm empty fruit bunches (EFB) here can be used to increase ligniteAos economic value.
The mixture of these two materials can produce an alternative energy source called hybrid coal (HC).
This study aims to determine the optimum temperature for co-pyrolysis of lignite and EFB as well as characterize liquid .
and solid product (HC).
Its kinetic study was evaluated as well.
A raw material of 200 grams with a composition of 22.
5% .
EFB to lignite was put into a reactor to react at a temperature range of 300-450oC for 1 To form hybrid coal briquettes (HCB), tapioca adhesive with a concentration of 6% .
was added to the solid product (HC).
The results showed that the tar yield increased with increasing temperature from 300 to 450oC.
Similarly, the calorific value of HC increased by 14.
50% as also occurred in other physical properties of HC.
Meanwhile, the kinetic study revealed that the model was well-fitted to the data, and confirmed the obtained results.
Thus, this research can support the development of affordable alternative energy to be implemented in large-scale production.
A 2022 Tim Pengembang Jurnal UPI
ARTICLE INFO
Article History:
Submitted/Received 31 Aug 2021
First Revised 28 Oct 2022
Accepted 13 Dec 2022
First Available Online 15 Dec 2022
Publication Date 01 April 2023
____________________
Keyword:
Alternative energy.
Co-pyrolysis.
Empty fruit bunch.
Hybrid coal.
Lignite.
Jelita et al.
Potential Alternative Energy of Hybrid Coal from Co-pyrolysis of A | 98
INTRODUCTION
Undeniably, coal still becomes one of the main sources to meet the current energy Most coals, however, are in low grades, leading them to be less prioritized.
Lignite is the lowest rank of coal for having less economic value due to the presence of volatile matter and moisture content with low fixed carbon content.
This further causes high carbon dioxide emissions leading to inefficient fuel.
To increase the added value, a simple and environmentally-friendly process is required.
Meanwhile, the significant increase in plantations and the palm oil industry has brought negative impacts on the production of an abundant amount of waste, including palm empty fruit bunches (EFB).
If not managed properly, this biomass waste might cause environmental problems.
In fact, the waste is rich in cellulose and other organic compounds in which the appropriate use of the waste can address the energy demand as well as the environmental problems.
To improve the lignite value can be combustion process without oxygen such as pyrolysis combined with additional biomass.
Hence, this co-processing of biomass with coal eliminates the disadvantages of both materials (Byambajav et al.
, 2.
Each coal and EFB possesses a complex structure and shows different thermal decomposition, thus resulting in a synergistic effect of the two raw materials (Chen et al.
, 2.
The co-pyrolysis process of using appropriate biomass can improve the bio-oil quality resulted as it is possible to obtain a reduction in moisture, oxygen, and acid content and an increase in carbon content (Gouws et al.
, 2.
Furthermore, the resulting solid product from the process can also be used as briquettes, which are the densification of the biomass mixture decomposing particles through specific variable pressure, temperature, and other Having a uniform shape and size, this densified product makes it simpler and more affordable to store and transport (Bajwa et al.
, 2.
Several studies related to the co-pyrolysis of biomass and coal have been carried out (Huang et al.
, 2019.
Ismail et al.
, 2020.
Saeed et al.
, 2020.
Wang et al.
, 2.
, for instance, the co-pyrolysis of lignite and rice husk and sawdust (Sasongko et al.
, 2.
and copyrolysis of lignite and Aspen wood (Byambajav et al.
, 2.
The co-pyrolysis of lignite and EFB was carried out by Siti et al.
find the effect of the blending ratio on the liquid product.
However, in literature, studies on lignite and EFB co-pyrolysis are found limited in number.
In turn, this study aims to discover the temperature effect of the copyrolysis process and characterize both liquid and solid products.
To analyze and support the results, kinetic studies became a critical part to be applied in large-scale production (Yeo et al.
, 2.
Furthermore, the kinetic parameters consider the process to operate under optimal conditions, thereby increasing This research is expected to describe a new solution of alternative energy based on lignite and EFB as efficient and affordable materials.
METHODS
Materials EFB .
mpty fruit bunche.
were obtained from PT.
Perkebunan Nusantara Xi Pelaihari.
Tanah Laut District.
South Kalimantan.
Indonesia.
,14%), cellulose .
,85%,) and lignin .
,41%).
Meanwhile, lignite was obtained from Asam-Asam.
Tanah Bumbu District.
South Kalimantan.
Indonesia.
Pre-Treatment of Raw Material The lignite was pulverized and sifted to 2050 mesh.
The EFB, meanwhile, was cut and washed to remove any dirt particles prior to being dried under the sunlight.
It was mashed with a particle size of 50-100 mesh DOI: https://doi.
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Co-Pyrolysis and Briquetting A total of 200 grams of a mixture with the composition of EFB/lignite 22.
5% was put into the reactor and heated at the temperatures of 300oC, 350oC, 400oC, and 450oC for 1 hour with 1.
5 L/minute of nitrogen gas flow rate.
The liquid .
and solid product (HC) resulting from co-pyrolysis were then weighed.
Furthermore, a tapioca adhesive of 6% was added to HC to form a cylindrical pellet with a diameter of 5 cm with a pressure of 750 psi.
Characterization The liquid compound identification was conducted by a Gas Chromatography Spectroscopy Mass (GC-MS) QP2010S SHIMADZU embedded with Column Rastek RXi-5MS, 30 meters in length.
ID 0.
25 mm.
Helium carrier gas.
EI ionization, and 70 Ev.
The quantification of calorific numbers, meanwhile, was performed using a bomb calorimeter (Gallenkamp Adiabatic Bomb Calorimeter CBA-.
and the proximate analysis was determined following ASTM D3172-07a.
SEM was performed for microscopic observation (Hitachi Se3400 N model.
Horiba EMAX) using backscattered electrons mode at 5.
0 and 10.
0 kV.
X-ray fluorescence (XRF) spectrometer analysis of materials was performed to analyze the chemical constituents or elements present in the sample using Perkin Elmer 1800 model instrument from 450 cmOe1 to 4400 cmOe1 by using a KBr tablet.
The X-ray diffraction pattern of the material was recorded by XRD (Bruker AXS).
These analyses were conducted using Cu K alpha radiation.
The functional groups were detected using FTIR (Nicolet Magna-IR550.
Madiso.
Further.
BET Micromeritics TriStar II 3020 and thermogravimetric analysis (TGA) was performed on approximately 10 mg of the sample heated at 800AC at a rate of 0.
5AC/s under 50 mL/min of nitrogen using a thermogravimetric analyzer.
Kinetic Study The kinetic study of EFB and lignite copyrolysis was evaluated using TGA data.
Commonly, the decomposition rate of a solid is given in the following Eq.
(Zhang et al.
dA = k (T ) f (A ) .
where is the mass conversion ratio with = .
o Oe m.
o Oe m.
, mo, mt, and mf demonstrate the initial, current, and terminal sample weight, respectively, t refers to time, f() is the reaction model and k(T) is the rate constant of ArrheniusAo law in Eq.
E E E
k (T ) = A exp E Oe
E RT E
where A is the pre-exponential factor.
E is the activation energy.
R is the ideal gas constant and T is the absolute temperature.
The combination of Eq.
with the assumption of the one-step process of converting raw material to product is described as follows Eq.
E E E
= A exp E Oe E .
Oe A ) E RT E where n is the reaction order.
First-order reactions are suitable for describing experimental data obtained by TGA (Saddawi et al.
, 2.
E E E
= A exp E Oe E .
Oe A ) E RT E Equation .
can be converted for a constant heating rate during pyrolysis, = dT/dt, hence leading to Eq.
E E E
= exp E Oe E dT 1OeA A E RT E Integration and linearization Eq.
resulted in Eq.
E AR E E
E Oe ln.
Oe A ) E
= ln E
EOe
E A E E RT
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Potential Alternative Energy of Hybrid Coal from Co-pyrolysis of A | 100 A plot of ln [Oeln .
Oe )/T.
1/T provided the values of A from the intercept and E from the slope.
RESULTS AND DISCUSSION
Temperature Effect on Tar and Char Yield In both the pyrolysis and co-pyrolysis processes, the mass of raw materials in the reactor was substantially reduced because decomposed into liquid products .
, gas, and solids .
Figure 1 presents the yield of tar and char (HC) based on temperature As shown in Figure 1, the increase in copyrolysis temperature increased tar yield, while the char decreased.
Here, temperature affects the co-pyrolysis process because a decomposition process will be more complete with an increasing temperature (Ma et al.
, 2.
The increase in tar yield at higher temperatures described an increase in decomposition reaction rate.
At lower temperatures, heat from pyrolysis can encourage the thermal decomposition of coal to form more liquid products (Chen et , 2.
At higher temperatures, the heat received by the particles became greater, thus leading to an increase in energy.
This caused the breakdown of more polymer chains into smaller molecules.
As a result, more products became tar and gas at higher The high content of lignin due to its stable structure can lead to higher biochar yields (Muigai et al.
, 2.
Lignocellulosic biomass is composed of a cell wall matrix.
During pyrolysis, volatile organic compounds left the matrix, but the lignin-rich cell walls were not easily degassed, they remained intact after heat treatment, in contrast to the charcoal and the cell wall that were no longer intact (Abdelsayed et al.
, 2.
Increasing the temperature in the co-pyrolysis of lignite and EFB can inhibit any secondary reactions .
uch as re-polymerization and cross-linking reaction.
and generates more free radicals (Huang et al.
, 2.
hence, the char yield Characterization of Tar The liquid product .
resulted from the co-pyrolysis of EFB and lignite was blackishbrown with a pungent odor.
It contains an organic phase and a higher water content.
identify the composition of the compound of the tar produced by co-pyrolysis of lignite and EFB, the mixture of compounds was passed through gas chromatography (GC) and then separated into individual Figure 2 presents the results of the GC-MS analysis of tar.
Figure 1.
Relation of .
solid yield to temperature.
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Chromatogram of Tar from Lignite and EFB Co-Pyrolysis DOI: https://doi.
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Potential Alternative Energy of Hybrid Coal from Co-pyrolysis of A | 102 As shown in Figure 2, in the coal tar chromatogram, approximately 21-36 peaks were observed indicating the number of compounds contained in the tar product.
The major components identified in the tar product are presented in Table 1.
Table 1 shows the compounds in tar consisting of phenol, acids, and ketones.
The pyrolysis process degraded the hemicellulose in EFB to alcohol and carboxylic acid at low temperatures .
-300CC).
This was confirmed by the presence of acetic acid in each variation and the declining value at a high temperature of 450oC.
The cellulose was decomposed into carbonyl and heterocyclic compound at medium temperature .
400CC), but furfural in this study was only observed at 300CC.
The lignin is degraded to monomeric phenolic compounds and light aromatic hydrocarbon at high temperatures .
500oC) (Huang et al.
, 2018.
Yogalakshmi et , 2.
Here, the presence of phenol was detected for all temperatures but no benzene was found.
Furthermore, phenol followed by acetic acid was found as the largest compound .
ritten in bol.
identified in tar.
The largest compound of phenol was observed due to the content of lignin contained in the plant and cell walls matrix to stabilize the structure (Muigai et al.
, 2.
The observation was also found in coal as it was made from plants and decomposed over millions of years (Abdelsayed et al.
, 2.
Characterization of Char (Hybrid Coa.
Solids produced from the co-pyrolysis of lignite and EFB are called hybrid coals (HC) in the form of black powder.
The physical properties of lignite.
EFB, and HC are shown in Table 2.
Hybrid coal, which is glued with a starch solution is then called hybrid coal briquettes (HCB) in the form of black pellets with a diameter of 5 cm.
As shown in Table 2, increasing the temperature of co-pyrolysis increased the calorific value of hybrid coal.
In the temperature range of 200-300CC, biomass underwent degassing and carbonization, thereby increasing the calorific value.
Furthermore, at 300-400CC, carbonization began to release carbon monoxide, carbon dioxide, and other short hydrocarbons (Sasongko et al.
, 2.
Table 1.
Tar compound identified by GC-MS.
Compounds Diphenylmaleic anhydride Glyceraldehyde Methanol
Hydroxyacetone Acetic acid
Acetone Furfural -Butyrolactone Phenol
o-Cresol
m-Cresol
3-Ethylphenol
Catechol
2,6-Dimethoxyphenol Chemical Formula
C16H10O3
C3H6O3
CH4O
C3H6O2
C2H4O2
C3H6O
C5H4O2
C4H6O2
C6H6O
C7H8O
C7H8O
C8H10O
C6H6O2
C8H10O3
Temperature (CC) Peak (%) DOI: https://doi.
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Physical properties of raw materials and hybrid coal.
Condition EFB before pyrolysis Lignite before pyrolysis EFB after pyrolysis at 400oC
Lignite after pyrolysis at 400oC
HC at 300 CC
HC at 350 CC
HC at 400 CC
HC at 450 CC
SNI 13-4931-2010
Calorific Value .
4,157.
4,785.
6,522.
6,475.
5,964.
6,400.
6,734.
6,828.
5,000-6,000
Furthermore, coal carbonization above 400CC increased the calorific value of hybrid coal more significantly.
Here, the calorific value of hybrid coal increased by 14.
5% at a temperature of 450CC compared to HC at 300CC.
This study also performed individual lignite pyrolysis at a temperature of 400oC as a comparison in which it produced a calorific value of 6,475.
11 cal/g - still lower than that of a mixture of lignite and EFB at the same It showed that the presence of EFB increased the calorific value of hybrid coal products and the value continued to increase with the increasing temperature.
The calorific value of this hybrid coal greatly affected the quality of the briquettes The calorific value of a briquette describes the value of the heat of combustion produced by briquettes (Ujjinappa & Sreepathi, 2.
Hybrid coal briquettes showed a lower calorific value than the value of HC (Figure 3.
but they still met the solid fuel quality requirements.
The increase in calorific value also led to an increase in the fixed carbon content in hybrid coal.
This increase then affected the calorific value of HC.
at the greater fixed carbon content, the calorific value increased.
Similar to the calorific value, it was also observed that the fixed carbon content decreased after becoming HCB (Figure 3.
Ash
14,17
Max 15
Proximate Analysis (%) Volatile Moisture Matter
Max 12
Max 22
Fixed Carbon
> 30
This was possibly caused by the presence of starch solution formed in the process, thereby increasing the water content.
Briquettes with a high water content decrease the calorific value because more energy will be absorbed in water evaporation (Saeed et al.
, 2.
The level of fixed carbon is inversely proportional to the number of volatile species in the material (Muigai et al.
, 2.
As shown in Table 2, materials with high volatility levels had lower solid carbon Since EFB had the highest volatile matter content, it was thus suggested to be a suitable feedstock for processes with thermochemical transformation such as The high volatile content also makes biomass a highly reactive fuel burning faster (Shariff et al.
, 2.
The volatile components of biomass pyrolysis contain abundant OH free radicals.
H free radicals, and other trace small molecules with free radicals, which migrate to the surface of coke and enter the matrix of coke (Muigai et al.
The decomposition reaction of charcoal matrix combined with the above-mentioned small free radicals derived from biomass volatiles produce a large number of fragment structures, thereby inhibiting the secondary cracking reactions (Chen et al.
, 2.
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Potential Alternative Energy of Hybrid Coal from Co-pyrolysis of A | 104 Figure 3.
Calorific value, .
fixed carbon content, .
volatile matter, .
moisture content, and .
ash content of HC and HCB at any temperatures.
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The higher the temperature and burn time processed, the more volatiles to be wasted, resulting in a low volatile sample during the test (Wang et al.
, 2.
, as seen in Table 2.
The high volatile matter content in the briquettes caused more smoke but was easier to combust (Ifa et al.
, 2.
Hence, low volatile matter content is preferable in use for producing less smoke (Kongprasert et , 2.
In HCB, the volatile matter content, compared to HC, increased by 89% (Figure 3.
Along with the volatile matter content, the moisture of hybrid coal decreased with the increasing pyrolysis temperature.
The decrease in water content was due to a higher co-pyrolysis temperature allowing more water to evaporate.
The water contained in HC affected the quality of the briquettes produced.
The moisture content of the briquettes should be as low as possible to produce a high calorific value and then easily ignited for combustion (Saeed et al.
As shown in Table 2, the water content in EFB was much smaller than lignite and followed the requirements for water content in pyrolysis raw materials, i.
10% (Muigai et al.
, 2.
The moisture content of HCB, as shown in Figure 3d, increased significantly to 190.
63% due to gluing with a starch solution.
The other physic property of HC was ash content that decreased with the increasing co-pyrolysis temperature.
It indicated that more complete combustion remained less The ash content indicated the presence of inorganic components in the raw material in the form of metal oxides.
High ash content in the fuel leads to corrosion, scaling, and lower heating value (Mohammed et al.
, thus the higher the ash content observed, the lower quality of the briquettes Low ash content in the biomass feedstock (EFB) as shown in Table 2 could reduce slagging and fouling in furnaces used in thermochemical conversion processes (Shariff et al.
, 2.
In general, the ash content decreases after becoming HCB (Figure 3.
Other analyses such as SEM.
XRF.
XRD.
FTIR, and BET were performed on hybrid coal at a temperature of 450oC.
The selection was made based on the best hybrid coal quality from the previous proximate In addition, the characterization was carried out on lignite.
EFB, a mixture of the two materials before pyrolysis .
5% by weight of EFB/lignit.
It helped to ease the discussion and the comparison of results with raw materials.
Figure 4 presents the results of SEM analysis for lignite and EFB and their mixtures before and after co-pyrolysis.
The lignite surface (Figure 4.
showed the presence of minerals through a distributed microstructure.
The bright part was due to the presence of potassium.
EFB
fiber (Figure 4.
had a rigid surface with a layer of lignin covering the fiber surface.
The mixture of the two materials (Figure 4.
showed the presence of lignite and EFB simultaneously but not bonded, while after pyrolysis the two materials appeared to bind to each other (Figure 4.
where the gaps in the EFB were filled with lignite.
The qualitative analysis of oil palm shells was also characterized using XRF (X-Ray Fluorescen.
The concentration of elements contained in lignite.
EFB, a mixture of both .
5% by weight of EFB/lignit.
, and HC is shown in Table 3.
Most of the constituent elements of lignite and EFB were the same as the largest component of Fe in lignite and K in EFB.
The main element in hybrid coal was Fe.
As shown in Table 3, the elemental sulfur contained in lignite was lost after undergoing the co-pyrolysis process.
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Potential Alternative Energy of Hybrid Coal from Co-pyrolysis of A | 106 Figure 4.
SEM images of .
EFB .
5% by weight of EFB/lignite .
HC.
Table 3.
Elements at material according to XRF data.
Element Lignite EFB Concentration (%) 25% EFB/Lignite Hybrid Coal DOI: https://doi.
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Cellulose crystals were identified at an angle of 2 between 20oAe30o because at that angle there were dominant The mixture of EFB with lignite still .
emicellulose and ligni.
and crystalline .
forms, while in lignite and hybrid coal there was no peak indicating a crystal structure of the three main components of biomass, it was only cellulose had crystalline domains, while both hemicellulose and lignin had amorphous structures following the literature (Karimi & Taherzadeh, 2016.
Tong et al.
, 2.
Wu et al.
found that biomass may promote the formation of disordered structures in co-dissociated char, but cellulose in biomass favors the generation of more ordered carbon structures (Wu et al.
The structure of lignite.
EFB, mixture of lignite and EFB, and hybrid coal were also studied through FTIR and their spectra as presented in Figure 6.
Here, the characteristics of the adsorption band changed in the hybrid coal product, where the peaks located at a wavelength of 34503600 cm-1 were assigned to the O-H stretch.
This indicated the loss of hydrogen and water bonds in lignite and EFB degradation of hemicellulose and cellulose (Martyn-Lara et , 2.
At a wavelength of 2800-2900 cm-1, there was an enhancement in the wave band in hybrid coal.
This was given a stretching vibration of C-H from the alkane section.
While, the stretching at a wavelength of 1560-1750 cm-1 was caused by the strain vibration of C = O in aldehyde groups and ester groups in cellulose and hemicellulose.
and aromatic structures in lignin (Duranay & Akku, 2.
The characteristic stretching at a wavelength between 830 Ae 890 cm-1, was associated with the strain vibration of the C = C portion of the alkene as contributed by the EFB.
BET analysis aims to determine the surface area, pore volume, and pore size in raw materials and hybrid coal products.
The results of the BET analysis are shown in Table 4 in which the surface area of lignite was found larger than the surface area of EFB.
In particular, when these two materials were mixed, the surface area was much However, after pyrolysis, there was an increase in the surface area of the High temperatures can remove water molecules, other impurities, and volatile organic compounds (Zhuang et al.
Furthermore, the surface area is affected by pore volume and pore size (Leng et al.
, 2.
The smaller pore size led to a greater number of pores, thus resulting in a larger surface area.
The larger pore volume also led to a larger surface area.
Figure 5.
X-Ray Diffraction (XRD) Lignite.
EFB, and Hybrid Coal (HC).
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Potential Alternative Energy of Hybrid Coal from Co-pyrolysis of A | 108 Figure 6.
FTIR spectra of lignite.
EFB, 22.
5% by weight of EFB/lignite, and hybrid coal.
Table 4.
BET results for the materials.
Sample Surface Area .
A/.
Average pore size (A) Pore volume .
Lignite EFB 5% EFB/Lignite Char Kinetic Study Analysis Kinetic calculations were performed according to the assumptions and procedures outlined in Method Section.
The data were obtained by various compositions of EFB and lignite.
Figure 7 and Table 5 present the linearization results and the summary of calculation results, respectively.
The linearized result in Figure 7 showed that the model of kinetic study well fitted to the data, thus the model was reliably used.
Table 5 presents the kinetic parameters obtained from the model.
From these parameters, it was observed that the produced hybrid coal with the highest EFB resulted in the lowest activation energy, indicating that the energy required for the decomposition reaction was also small, allowing the reaction to proceed faster.
Increasing the biomass content in the raw material might cause bonds to break easily, thus reducing the energy required for The apparent activation energy was significantly reduced as indicated by the result of the mixing effect, which increased the biomass fraction of the mixture (Gouws, et al.
, 2.
Since the thermogravimetric unit is a model of a pyrolysis reactor, it could be concluded from this kinetic study that using more biomass reduced the energy consumption during the pyrolysis reaction since the main step of reaction in pyrolysis was the decomposition reaction, thus biomass such as EFB plays a major role in the process of co-pyrolysis with coal.
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ln [Oeln .
Oe )/T.
vs 1/T for .
15% by weight of EFB/lignite, .
5% by weight of EFB/lignite and .
30% by weight of EFB/lignite.
Table 5.
Kinetic properties of hybrid coal at various compositions.
Hybrid Coal Temperature(CC) E .
J/mo.
A .
15% EFB/Lignite 496,088 3,29923x1085 5% EFB/Lignite 441,631 1,35077x1076 30% EFB/Lignite 439,203 1,15922x1075 DOI: https://doi.
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CONCLUSION
Co-pyrolysis of lignite and EFB was successfully conducted to produce hybrid coal (HC) and liquid product .
The temperature effect in the pyrolysis process led to some significant results.
The results showed that the tar yield increased with the increasing temperature.
Though the yield of HC decreased, the calorific value of HC increased by 14,5% from a temperature of between 300 and 450oC.
Other physical properties of HC were also improved.
The largest compounds identified in tar were phenol and acetic acid.
The optimum temperature for lignite and EFB copyrolysis was 450oC as the greatest tar and the best specifications to produce briquettes were obtained.
The resulting briquettes also met the quality requirements as alternative energy.
Through kinetic study, the addition of more biomass to coal at the co-pyrolysis process reduced activation energy to the decomposition reaction.
The application of co-pyrolysis could increase the value of coal and EFB and thus contribute to alternative energy sources.
The use of simple and environmentally friendly production of solid fuels to meet the energy demand.
ACKNOWLEDGMENT