• Journal of Hydrogen and New Energy
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• v.27 no.6
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• pp.693-701
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• 2016

Steam gasification of low rank coals is possible at relatively low temperature and low pressure, and thus shows higher efficiency compared to high rank coals. In this study, the gasification reactivity of four different Indonesian low rank coals (Samhwa, Eco, Roto, Kideco-L) was evaluated in $T=700-800^{\circ}C$. The low rank coals containing $53.8{\pm}3.4$ wt% volatile matter in proximate analysis and $71.6{\pm}1.2$ wt% carbon in ultimate analysis showed comparable gasification reactivity. In addition, $K_2CO_3$ catalyst rapidly accelerated the reaction rate at $700^{\circ}C$, and all of the coals were converted over 90% within 1 hour. The XRD analysis showed no significant difference in carbonization between the coals, and the FT-IR spectrum showed similar functional groups except for differences due to moisture and minerals. TGA results in pyrolysis ($N_2$) and $CO_2$ gasification atmosphere showed very similar behavior up to $800^{\circ}C$ regardless of the coal species, which is consistent with the steam gasification results. This confirms that the indirect evaluation of the reactivity can be made by the above instrumental analyses.

• Journal of Hydrogen and New Energy
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• v.26 no.6
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• pp.567-580
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• 2015

In order to select an optimum gasifier for specific low rank coal, evaluation elements were studied by analyzing characteristics of low rank coal compared with those of high rank coal and the effects of each gasifier type in accordance with the characteristics. And syngas composition calculation model was made on the basis of thermochemical equilibrium to quantify some of the evaluation elements. And then the suitable gasifier was selected for a kind of Indonesian low rank coal through this syngas composition calculation model and the evaluation elements of selecting gasifier.

• Applied Chemistry for Engineering
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• v.22 no.3
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• pp.312-318
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• 2011

We have investigated the kinetics and catalytic activity of $CO_2$-lignite gasification with various metal precursors as catalysts. $K_2CO_3$, $Mn(NO_3)_2$, and $Ce(NO_3)_3$ were used and impregnated on a coal using an evaporator. The gasification experiments were carried out with the low rank coal loaded with 5 wt% catalyst at the temperature range from $700{\sim}900^{\circ}C$ and atmospheric pressure with the $N_2-CO_2$ reactant gas mixture. The catalytic effect on the gasification rate of the low rank coal with $CO_2$ was determined by the thermogravimetric analyzer. It was observed that the low rank coal reached the complete carbon conversion regardless of the kinds of catalysts at $900^{\circ}C$ from the results of TGA. The catalytic activity was ranked as 5 wt% $K_2CO_3$ > 5 wt% $Mn(NO_3)_2$ > 5 wt% $Ce(NO_3)_3$ > Non-catalyst at $900^{\circ}C$. The gasification rate increased with increasing the temperature. The activation energy of the catalytic gasification with 5 wt% $K_2CO_3$ was 119.0 kJ/mol, which was the lowest among all catalysts.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.33 no.12
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• pp.1000-1006
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• 2009

Integrated Coal Gasification Combined Cycle (IGCC) power plants have been developed to reduce carbon dioxide emissions and to increase the efficiency of electricity generation. A devolatilization process of entrained coal gasification is predicted by CPD model which could describe the devolatilization behavior of rapidly heated coal based on the chemical structure of the coal. This paper is intended to compare the mass release behavior of char, tar and gas(CO, $CO_2,\;H_2O,\;CH_4$) for three different coals. The influence of coal structure on gas evolution is examined over the pressure range of 10${\sim}$30atm.

• Journal of Hydrogen and New Energy
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• v.23 no.6
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• pp.647-653
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• 2012

We have investigated the kinetics and activity of waste catalysts for steam-lignite gasification. Waste catalysts I, II, III and reference $K_2CO_3$ were used and physical mixed with a coal. The gasification experiments were carried out with the low rank coal loaded with 1 wt% and 5 wt% catalyst at the temperature range from 700 to $900^{\circ}C$ using thermobalance reactor. It was observed that the carbon conversion reached almost 100% regardless of the kinds of catalysts at $900^{\circ}C$. The shortest time to reach the designated conversion was obtained for 1 wt% waste catalyst II and 5 wt% $K_2CO_3$ at $900^{\circ}C$. The gasification reaction rate constant increased with increasing the temperature. Highest rate constant was obtained with $K_2CO_3$ at $900^{\circ}C$. The lowest activation energy was 69.42 kJ/mol for 5 wt% waste catalyst II. The waste catalyst had an influence on the reduction of activation energy.

• Journal of Hydrogen and New Energy
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• v.24 no.4
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• pp.340-346
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• 2013

Study on clean and efficient utilization technology for low rank coal with high moisture content is actively ongoing due to limited reserves of petroleum and of high grade coal and serious climate change caused by fossil fuel usage. In the present study, supercritical water gasification of low rank coal was performed. With increasing reaction temperature, content of combustible gases such as $H_2$ and $CH_4$ in the syngas increased while the $CO_2$ content decreased. As the reaction pressure increased from 210 to 300 bar, the $CO_2$ content in the syngas increased while the hydrocarbon gas content decreased. The $H_2$ and $CH_4$ content in the syngas increased slightly with pressure. With the addition of Pd, Pt, and Ru catalysts, it was possible to improve the production of $H_2$. Moreover, the increase of active metal content in the catalyst increased the $H_2$ productivity. The Ru catalyst shows the best performance for increasing the $H_2$ content in the syngas, while decreasing the $CO_2$ content.

• Journal of the Mineralogical Society of Korea
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• v.23 no.3
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• pp.199-209
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• 2010

Coal gasification technology in the sector of domestic clean coal technologies is being into the limelight since recent dramatic rise of international oil price. In this study, we used a low rank coal from Inner Mongolia, China as a starting material for gasification. Various properties including optical, mineralogical, X-ray spectroscopic, X-ray diffraction, and drying property were measured and tested in order to estimate the suitability of the coal to gasification. The coal was identified as a brown coal of lignite group from the measurement of vitrinite reflectance. The coal has very low slagging and fouling potentials, and the ignition temperature is about $250^{\circ}C$. The major impurities consist of quartz, siderite, and clay minerals. Additionally, the coal had moisture content above 28%. Tests for finding effective drying method showed that the microwave drying is more effective than thermal drying.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1086-1092
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• 2012

In this study, kinetic studies and analysis of the produced syngas were conducted for low rank coal gasification under $CO_2$ atmosphere. 6 coals were analyzed to measure amount of sulfur and ash by proximate and ultimate analyses. And then they were analyzed to select suitable sample by using Thermogravimetric analyzer (TGA). Selected coal sample Samhwa was mixed with catalysts. Mixed samples with catalysts were used to get activation energy under $CO_2$ atmosphere by using Kissinger's method and shrinking core model (SCM). Also, analysis of produced syngas was performed by Gas Chromatography (GC). In this experiment, activation of the $K_2CO_3$ was the best performance, and result of the analysis of the syngas showed similar trend with result of the activation energy.

• Korean Chemical Engineering Research
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• v.48 no.1
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• pp.80-87
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• 2010

Lignite of low rank coal and petroleum coke of high sulfur content can be high potential energy sources for coal gasification process because of their plentiful supply. The kinetic study of steam gasification has been performed in an atmospheric thermobalance with wood chip, lignite, bituminous, anthracite, pet-coke. The effects of gasification temperature($600{\sim}850^{\circ}C$) and partial pressure of steam(30~90 kPa) on the gasification rate have been investigated. The modified volumetric reaction model was applied to the experimental data to describe the behavior of carbon conversion and to evaluate the needed kinetic parameters. Lignite and wood chip with high volatile content showed high average gasification rates comparing to other fuel and thus they might be proper fuel for gasification processes. The activation energies for wood chip, lignite, bituminous, anthracite, and pet-coke through Arrhenius plot were found to be 260.3, 167.9, 134.6, 82.2, 168.9 kJ/mol, respectively. The expression of apparent reaction rates for steam gasification of various chars have been proposed as basic information for the design of coal gasification processes.

• Clean Technology
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• v.20 no.1
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• pp.64-71
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• 2014

We have investigated the effects of various additives on Eco coal gasification under $CO_2$ atmosphere. The temperature ranges from $750{\sim}900^{\circ}C$ and the gasification experimental was carried out with Eco coal adding 7 wt% $K_2CO_3$, $Na_2CO_3$, $CaCO_3$, Dolomite, and non-additive under $N_2$ and $CO_2$ gas mixture. At $850^{\circ}C$, we observed that the reaction rate increased when the concentration of $CO_2$ increased. However, we also observed that the increment of reaction rate was small at more than 70% of the concentration of $CO_2$. The additives activity was ranked as 7 wt% $Na_2CO_3$ > 7 wt% $K_2CO_3$ > non-additive > 7 wt% Dolomite > 7 wt% $CaCO_3$ at $850^{\circ}C$. At the temperatures of $750^{\circ}C$, $800^{\circ}C$, $850^{\circ}C$, and $900^{\circ}C$, when the temperature increased, the gasification rate increased. The gasification was suitably described by the volumetric reaction model. Using volumetric reaction model, the activation energy of Eco coal including 7 wt% $Na_2CO_3$ gasification was 83 kJ/mol, which was the lowest value among all the alkaline additives.