• Transactions of the Korean hydrogen and new energy society
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• v.23 no.5
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• pp.503-512
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• 2012

There is a new power generation system such as direct coal fuel cell (DCFC) with a solid oxide electrolyte operated at relatively high temperature. In the system, it is of great importance to feed coal continuously into anodic electrode surface for its better contact, otherwise it would reduce electrochemical conversion of coal. For that purpose, it is required to improve the electrochemical conversion efficiency by using either rigorous mixing condition such as fluidized bed condition or just by recirculating coal particle itself successively into the reaction zone of the system. In this preliminary study, we followed the second approach to investigate how significantly particle recycle would affect the coal conversion efficiency. As a first phase, coal conversion was analyzed and evaluated from the thermochemical reaction of carbon with air under particle recirculating condition. The coal conversion efficiency was obtained from raw data measured by two different techniques. Effects of temperature and fuel properties on the coal conversion are specifically examined from the thermochemical reaction.

• Journal of Energy Engineering
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• v.26 no.3
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• pp.78-89
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• 2017

Spontaneous combustion propensity of various coals of carbonization grade as a pulverized fuel of coal fired power plant has been tested from an initial temperature of $25^{\circ}C$ to $600^{\circ}C$ by heated in an oven with air to analyze an self oxidation starting temperature. This tests produce a CPT(Cross Point Temperature), IT(Ignition temperature) and CPS(Cross Point Slope) by calculated as the slope of time taken a rapid exothermic oxidation reaction at CPT base. CPS show a carbonization rank dependence, whereby wood pellet has the highest propensity to spontaneous combustion of $20.995^{\circ}C/min$. A subbituminous KIDECO coal shows an CPS values of $15.370^{\circ}C/min$ whereas it of pet coke of the highest carbonization rank has $20.950^{\circ}C/min$. The nature of this trend is most likely a concentration of volatile matter and oxygen functional groups of coal surface that governs the available component for oxidation as well as surface area of fuel char, and constant pressure molar heat.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.6
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• pp.629-634
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• 2010

Natural gas is a promising alternative fuel that can be used to satisfy the strict engine emission regulations in many countries. To develop natural-gas engines, low emission, efficient fuel consumption, and increased power ratings have to be realized. In this study, a cylindrical constant-volume combustion chamber (CVCC) was used to investigate natural-gas combustion characteristics for different prechamber design parameters and equivalence ratios. In particular, the maximum combustion pressure and mass fraction of the burned gas were evaluated by considering orifice diameter, volume ratio of prechamber and equivalence ratio. Using this result and by analyzing the changes in combustion characteristics with variations in design parameters, the optimum prechamber parameters were determined.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.492-497
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• 2008

The solubility of carbon dioxide in ionic liquids and amine solvents has been investigated in gas-liquid absorption equilibrium reactor. Absorption capacity and kinetics of $CO_2$ with $CO_2$ pressure and absorption time in 9 different ionic liquids and 2 kinds of amine solvents were evaluated. In order to understand the effect of ionic type, we changed the cation or anion of ionic liquids. $CO_2$ absorption capacity and absorption rate of amine solvents were higher than those of ionic liquids. $CO_2$ absorption capacity of [emim][$Tf_2N$], $0.14molCO_2/mol\;IL$ at 1 bar, was the highest among the ionic liquids. $CO_2$ absorption capacity of ionic liquid steeply decreased with increasing temperature. Anion of ionic liquid dominates interaction with $CO_2$ and cation plays secondary role.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.6
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• pp.471-478
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• 2009

The specific some types of compressors are appropriate for a use in hydrogen gas station. Metal diaphragm type of hydrogen compressor is one of them, which can satisfy the critical requirements of maintaining gas purity and producing high pressure over 850 bar. The objective of this study is to investigate an characteristics of compression through two-way Fluid-Structure-Interaction (FSI) analysis as bulk modulus and initial volume of oil independently varies. Deflection of diaphragm, oil density, gas and oil pressure were analyzed during a certain period of compression process. According to the analysis results, bulk modulus and initial volume remarkably affected deflection of diaphragm, oil density, gas and oil pressure. The highest gas pressure were attained with the highest bulk modulus of $7e^9\;N/m^2$ and the lowest initial oil volume of 80 cc.

• Korean Chemical Engineering Research
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• v.46 no.5
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• pp.983-987
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• 2008

Computational simulation has been performed to design optimally the filtration system for IGCC pilot plant. It was analyzed how the different inflow pattern influences the flow field and the particle behavior in a filter vessel. The particle loading onto the filter surface lowers significantly and decreases dramatically with particle size when the dusty gas flows into the filter vessel with a shroud tube through a tangential inlet setup tangentially on the vessel outer wall. However, the particle loading is considerably high when the dusty gas enters the filter vessel through a normal inlet setup vertically on the vessel top wall, and the decrease of the particle loading with particle size is not steeper compared with the tangential inflow pattern.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.10
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• pp.997-1003
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• 2011

In order to investigate devolatilization characteristics for ashless coal with relatively low ash content and high heating value, an experiment was performed in different bed configurations of TGA and DTF(Drop Tube Furnace) at atmospheric pressure condition. The heating rate was $10^{\circ}C$/min up to $950^{\circ}C$ in TGA, while the temperatures of DTF varied from 500 to $1300^{\circ}C$ in step of $200^{\circ}C$. A weight loss and particle temperature were obtained to determine devolatilization kinetics. The kinetic parameters including an activation energy and pre-exponential factor for ashless coal were obtained using Coats-Redfern method in TGA and single step method in DTF. Furthermore, the devolatilization kinetics of the ashless coal were compared with the results of different kinds of conventional coal such as sub-bituminous and bituminous. The results show that the activation energy of devolatilazation for ashless coal is lower than those of others in fixed and entrained conditions.

• Clean Technology
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• v.28 no.2
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• pp.117-122
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• 2022

This study developed and tested an ultra-low NO_x burner in an 80 kW combustion furnace. The experiment was conducted in an 80 kW single burner combustion furnace with changing the swirl numbers, total equivalence ratios, and primary/secondary oxidizer ratios. In this study, liquefied natural gas (LNG) was used as an auxiliary fuel to significantly reduce NO_x production. In a thermal power plant, the amount of NO_x generated during coal combustion is about 300 ppm. However, using the burner tested in this study, it was possible to reduce the amount of NO_x generated via LNG co-firing to 40 ppm. If the input amount of the primary oxidizer is enough for the gas to be completely combusted and the gas and coal are added simultaneously, the combusted gas forms a high-temperature region at the burner outlet and volatilizes the coal. As a result, the N contained in the devolatilized coal is discharged. Therefore, when the coal is subsequently burned, the amount of NO_x produced decreases because there is almost no N remaining in the coal. If a thermal power plant burner is developed based on the results of this study, it is expected that the NO_x generation will be significantly lower in the early stage of combustion.

• Clean Technology
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• v.19 no.3
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• pp.306-312
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• 2013

We investigated the effects of the concentration of carbon dioxide on the char-$CO_2$ gasification reaction under isothermal conditions of $850^{\circ}C$ using the Drayton coal. Potassium carbonate was used to improve the low-temperature gasification reactivity. The enhancement of carbon dioxide concentration increased the gasification rate of char, while gasification rate reached a saturated value at the concentration of 70%. The best $CO_2$ concentration for gasification is determined to be 70%. We compared the shrinking core model (SCM), volumetric reaction model (VRM) and modified volumetric reaction model (MVRM) of the gas-solid reaction models. The correlation coefficient values, by linear regression, of SCM are higher than that of VRM at low concentration. While the correlation coefficients values of VRM are higher than that of SCM at high concentration. The correlation coefficient values of MVRM are the highest than other models at all concentration.

• Korean Chemical Engineering Research
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• v.50 no.2
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• pp.358-364
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• 2012

The kinetics of the Fischer-Tropsch synthesis and water gas shift reactions over a precipitated iron catalyst were studied in a 5 channel fixed-bed reactor. Experimental conditions were changed as follows: synthesis gas $H_2$/CO feed ratios of 0.5~2, reactants flow rate of 60~80 ml/min, and reaction temperature of $255{\sim}275^{\circ}C$ at a constant pressure of 1.5 MPa. The reaction rate of Fischer-Tropsch synthesis was calculated from Eley-Rideal mechanism in which the rate-determining step was the formation of the monomer species (methylene) by hydrogenation of associatively adsorbed CO. Whereas water gas shift reaction rate was determined by the formation of a formate intermediate species as the rate-determining step. As a result, the reaction rates of Fischer-Tropsch synthesis for the hydrocarbon formation and water gas shift for the $CO_2$ production were in good agreement with the experimental values, respectively. Therefore, the reaction rates ($r_{FT}$, $r_{WGS}$, $-r_{CO}$) derived from the reaction mechanisms showed good agreement both with experimental values and with some kinetic models from literature.