• Clean Technology
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• v.19 no.4
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• pp.469-475
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• 2013

In this research, the stabilization characteristics of upgraded coal using palm oil residues were investigated. The Eco coal, which is the Indonesian low-rank coal, was used as a raw material. The low-rank coal was mixed with palm fatty acid distillate (PFAD), and then dried in a nitrogen atmosphere at $107^{\circ}C$. The trend of spontaneous combustion of upgraded coal was studied by measuring of crossing-point temperature (CPT), low temperature oxidation and moisture readsorption. The results of the CPT measuring and low temperature oxidation showed that the propensity of spontaneous combustion of the upgraded coal was improved compared to the dried coal. The moisture readsorption characteristics of the upgraded coal was also improved. The upgraded coal was stabilized through the surface coating with PFAD, and stability of upgraded coal was proportional to the content of PFAD.

• Clean Technology
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• v.24 no.2
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• pp.119-126
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• 2018

This study introduced a treatment process that was developed to treat Indonesian low-rank coal with high-ash content, which has the same characteristics as residual coal from the biosolubilization process. The treatment process includes separation of ash, solid-liquid separation, pelletizing, and drying. To reduce the ash content, flotation was performed using 4-methyl-2-pentanol (MIBC) as frother, and kerosene, waste oil, and cashew nut shell liquid (CNSL) as collectors. The increasing amount of collector had an effect on combustible coal recovery and ash reduction. After flotation, a filter press, extruder, and an oven drier were used to make a dried coal pellet. Then another coal pellet was made using asphalt as a binder. The compressive strength and friability of the coal pellets were tested and compared.

• Clean Technology
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• v.19 no.4
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• pp.464-468
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• 2013

In this study, in order to increase solid content of coal water fuel (CWF), various experimental parameters (i.e., coal type, additive, particle size distribution, drying method) were evaluated. To investigate the drying method, specimen is compared to using flash dry, fluidized bed dry and oil deposit stabilized coal. Difference of the solid content between low rank coal and high rank coal in this case indicate that high rank coal exhibits more higher than 20% of the solid cotent. And specimen for dispersibility was prepared by using dispersing agent of 4 types. As a result, using the dispersing agent was shown 5% higher in sold content than the case of not using the dispersing agent. Efficiency of CWF was improved by using fine coal of 80% in the particle size distribution of coal. Result of CWF using drying methods of 3 types, oil deposit stabilized (ODS) coal dried and stabilized was effective 12% higher in sold content than raw coal.

• Clean Technology
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• v.20 no.3
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• pp.321-329
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• 2014

In this study, Indonesia low rank coal, which has moisture content of around 26%, is dried less than 5% by using a laboratory-scale (batch type) steam fluidized-bed dryer in order to produce the low-moisture, high rank coal. Normally, CCS (carbon capture and storage) process discharges $CO_2$ and steam mixture gas around $100-150^{\circ}C$ of temperature after regeneration reactor. The final purpose of this research is to dry low rank coal by using the outlet gas of CCS process. At this stage, steam is used as heat source for drying through the heat exchanger and $CO_2$ is used as fluidizing gas to the dryer. The experimental variables were the steam flow rate ranging from 0.3 to 1.1 kg/hr, steam temperature ranging from 100 to $130^{\circ}C$, and bed height ranging from 9 to 25 cm. The characteristics of the coal, before and after drying, were analyzed by a proximate analysis, the heating value analysis and particle size analysis. In summary, the drying rate of low rank coal was increased as steam flow rate and steam temperature increased and increased as bed height decreased.

• Korean Chemical Engineering Research
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• v.53 no.2
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• pp.231-235
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• 2015

The characteristics of binderless briquettes for dried low-rank coal was studied in this work. Two kinds of Indonesian coals were used to briquette after drying them in electric oven. The characteristics of briquettes have been examined by moisture contents, particle size, hydraulic force, and storing period. The optimum moisture contents of briquettes were observed at between 10 wt% and 15 wt%. The strength of coal briquette was stronger as particle size became smaller. The strength of coal briquette was proportional to the hydraulic force under 300 kN, whereas there was little difference among the briquettes made at more than 300 kN of hydraulic force. The strength of briquettes sharply decreased for a week after produced, and then showed the tendency of converging. The results from this work can be a useful guideline of manufacturing and managing upgraded coal briquettes.

• Clean Technology
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• v.19 no.1
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• pp.30-37
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• 2013

Low-rank coal with high water content (32.3 wt%) was dried by fry drying, and the fuel characteristics of the dried coal from which the oil was separated by using a high-speed centrifugal separator were analyzed. After fry drying for 6 min and 10 min, the water content decreased to 5.0 wt% and 4.2 wt% respectively. The higher calorific value (HCV) of the coal increased remarkably after fry drying, from 11,442.0 kJ/kg-wet. The oil content of the fry-dried coal was 15.0 wt% and it decreased with an increase in the reheating temperature: 9.7 wt% at $80^{\circ}C$ to 9.3 wt% at $100^{\circ}C$, and then to 8.5 wt% at $120^{\circ}C$. The recovered oil could then be reused. According to of thermogravimetric analysis (TGA), there was no difference in the weight loss patterns of the coal samples with different coal diameters at a reheating temperature of $120^{\circ}C$. This was because the amount of oil separated by the centrifugal separator was affected by the reheating temperature rather than the coal diameter. And derivative thermogravimetry (DTG) curves of raw coal before the fry-drying process, a peak is formed at $400^{\circ}C$ in which the volatile matter is gasified. In case of the fry-dried coal, the first peak is generated at $350^{\circ}C$, and the second peak is generated at $400^{\circ}C$. The first peak is caused by the oil that is replaced with the water contained in the coal during the fry-drying process. Further, the peaks of the coal samples in which the oil is separated at a reheating temperature of $80^{\circ}C$, $100^{\circ}C$, $120^{\circ}C$, respectively are smaller than that of the coal in which the oil is not separated, and this is caused by that the oil is separated by the centrifugal separator.

• Clean Technology
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• v.19 no.1
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• pp.38-43
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• 2013

Vapor adsorption of hydrocarbon has been studied for stabilization after drying low-rank coal. The surface characteristics and the propensity of spontaneous combustion were observed for stabilized coal which was maintained with hydrocarbons as stabilizer at several conditions of residence time and temperature. Surface area of micropores in coal mainly decreased after vapor adsorption. As residence time and temperature of adsorption process increased, the propensity of spontaneous combustion decreased. The type of hydrocarbons did not effect on the propensity of spontaneous combustion. As the analysis results of this work, the amount of hydrocarbon adsorbates required to stabilize dried coal was 0.5 wt% or less of coal, and the stabilizing effect was induced by adsorption of low-molecular-weight hydrocarbons.

• Applied Chemistry for Engineering
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• v.22 no.5
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• pp.532-539
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• 2011

The physical and chemical properties of the dried low rank coals (LRCs) before and after the surface treatment using ozone and ammonia were characterized in this study. The contents of moisture, volatiles, fixed carbon and ash consisting of dried LRCs before the surface treatment were about 2.0, 44.8, 44.9 and 8.9%, respectively. Also, it was composed of carbon of 62.66%, hydrogen of 4.33%, nitrogen of 0.94%, oxygen of 27.01% and sulfur of 0.09%. The dried LRCs was surface-treated with the various dry methods using gases such as ozone at room temperature, ammonia at $200^{\circ}C$ and then the dried LRCs before and after the surface treatment were characterized by the various analysis methods such as FT-IR, TGA, proximate and elemental analysis, caloric value, ignition test, adsorption of $H_2O$ and $NH_3-TPD$. As a result, the oxygen content increased and the calorific value, ignition temperature and the contents of carbon and hydrogen relatively decreased because the oxygen-contained functional groups were additionally generated by the surface oxidation with ozone which plays a role as an oxidant. Also, its $H_2O$ adsorption ability got higher because the hydrophilic oxygen-contained functional groups were additionally generated by the surface oxidation with ozone. On the other hand, it was confirmed that the dried LRCs after the surface treatment with $NH_3$ at $200^{\circ}C$ have the decreased oxygen content, but the increased calorific value, ignition temperature and contents of carbon and hydrogen because of the decomposition of oxygen-contained functional groups the on the surface. In addition, the $H_2O$ adsorption ability was lowered bucause the surface of the dried LRCs might be hydrophobicized by the loss of the hydrophilic oxygen-contained functional groups. It was concluded that the various physico-chemical properties of the dried LRCs can be changed by the surface treatment.