• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.7 s.94
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• pp.1823-1832
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• 1993

CWS(coal-water slurry) is used for application in power plants, boilers, industrial furnaces. A single coal-water slurry droplet ignition has been examined to reveal the basic nature of their evaporation, volatilization and heating processes. The interior droplet temperature distribution has been considered. The effect of coal thermal conductivity, droplet size, water fraction in the slurry, gas temperature and velocity and radiation on the ignition phenomena were also studied. Either increasing the velocity and gas temperature or decreasing the droplet size and water fraction in the slurry may reduce the time for evaporation and ignition delay time.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.11
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• pp.2159-2168
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• 1992

Coal-water slurry is considered to have the potential for displacing petroleum used in the existing oil-fired industrial and utility boilers. The combustion of coal-water slurry(CWS) is a complex process and little is known about the detailed mechanism. In this paper the combustion behavior of a single suspended droplet of CWS in hot gas stream was investigated. The effect of coal particle size, water content in droplet, initial droplet size, ambient temperature and oxygen fraction in ambient gas were studied. The results are as follows; (1) Increasing the oxygen fraction in ambient gas considerably reduced the char combustion time. (2) The variation of water content and coal particle size in droplet showed little effect on the combustion behavior. (3) In the relatively high temperature ambient gas, the water evaporation time became shorter and the combustion process was stable.

• 연구논문집
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• s.25
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• pp.31-45
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• 1995

• Transactions of the Korean Society of Mechanical Engineers
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• v.15 no.2
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• pp.618-629
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• 1991

The purpose of this experiment is to understand the distribution of coal particles inside CWM droplet which is believed to be a very important factor controlling the flame stability. CWM slurry is atomized by an air assisted twin fluid nozzle. An experimental rig is designed and fabricated. The mean size of coal particle distribution in CWM slurry, atomizing air pressure, coal particle loading in slurry and sampling position inside spray are main experimental variables. The atomized CWM droplets are sampled on the thin white layer of magnesium oxide by the emergency sampling shutter. The sampled coal particles on magnesium oxide layers are collected into test tubes and dispersed completely by Ultra-Sonicator. The size distribution of coal particles inside droplets are measured by Coulter Counter. The presence of coal particle inside the impressions of droplets on magnesium oxide layer are investigated by photo technique. There are quite many droplets which do not have any coal particles. Those are just water droplets, not CWM droplets. The population ratio of droplets without coal particles to toal number of droplets is strongly affected by the mean size of coal particle distribution in slurry and this ration becomes bigger number as the mean size of coal particles be larger. The size distribution of coal particles inside CWM droplets is not even and depends on the size of droplet. Experimental results show that the larger CWM droplets has droplets has bigger mean value of particle size distribution. This trend becomes more evident as the atomizing air pressure is raised and the mean size of coal particles in CWM slurry is bigger. That is, the distribution of coal particles inside CWM dropolets is very much affected by the atomizing air pressure and the mean size of pulverized coal particles in CWM slurry.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.2
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• pp.632-640
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• 1996

The ignition and combustion characteristics of CWS droplets were investigated in the postflame region generated by a flat burner. The effect of radiation by screen and heating eleements ws taken into account. Also the theoretical claculations considering the temporal temeprature variation have been performed and compared with experimental results. The ignition delays were reduced by the radiation of the screen or heating elements. Therfore the radiation was considered to play some role in predicting the ignition delay.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1211-1221
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• 1990

The purpose of this study is to get experimental data on the distribution of CWM (Coal- Water Mixture) droplets size and the presence of pulverized coal particles inside CWM droplets. Atomization of CWM is done by Twin-Fluid Atomizer. The operational parameters are atomizing air pressure, coal particle loading, mean size of pulverized coal particles and sampling positions across spray. Th data analysis is initiated by Impression Sampling Method(Magnesium Oxide Technique) and Photo-technique and counting works are followed. Experimental work induces following research results. The variation of particle loadings in slurry makes no appreciable effects on the mean size of CWM droplets. It is evident that atomizing air pressure has very strong effect on the atomization of slurry. The mean size of atomized fuel droplets is dramatically reduced with the increasing air pressure. The population ratio of droplets without coal particles to total number of droplets is decreased as atomizing air pressure or loading rises and the same trend is obtained as the mean size of coal particles becomes smaller but a certain tendency of coal particle presence inside droplets could not be found from the change of sampling positions.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.21 no.8
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• pp.1068-1076
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• 1997

Emission control of acid exhaust gases from coal-fired power plants and waste incinerators has become an increasing concern of both industries and regulators. Among those gaseous emissions, SO$_{2}$ has been eliminated by a Spray Drying Absorber (SDA) system, where the exhaust gas is mixed with atomized limestone-water slurry droplets and then the chemical reaction of SO$_{2}$ with alkaline components of the liquid feed forms sulfates. Liquid atomization is necessary because it maximizes the reaction efficiency by increasing the total surface area of the alkaline components. An experimental study was performed with a laboratory scale SDA to investigate whether the scrubbing efficiency for SO$_{2}$ reduction increased or not with the application of a DC electric field to the limestone-water slurry. For a selected experimental condition SO$_{2}$ concentrations exited from the reactor were measured with various applied voltages and liquid flow rates. The applied voltage varied from -10 to 10 kV by 1 kV, and the volume flow rate of slurry was set to 15, 25, 35 ml/min which were within the range of emission mode. Consequently, the SO$_{2}$ scrubbing efficiency increased with increasing the applied voltage but was independent of the polarity of the applied voltage. For the electrical and flow conditions considered a theoretical study of estimating average size and charge of the atomized droplets was carried out based on the measured current-voltage characteristics. The droplet charge to mass ratio increased and the droplet diameter decreased as the strength of the applied voltage increased.

• Korean Chemical Engineering Research
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• v.46 no.3
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• pp.561-566
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• 2008

Gasification plant using petroleum coke for refinery and power generation process is increased from considering petroleum coke as a valuable fuel. In this study, gasification of petroleum coke was performed to utilize petroleum coke and to develop essential technology using 1T/D coal gasification system. In case of petroleum coke gasification, because of lower reactivity, consumption of oxygen is higher than coal gasification. The calorific value of syngas from petroleum coke mixed with coal at a mass ratio of 1:1 shows about $6.7{\sim}7.2MJ/Nm^3$. Although carbon conversion could reach more than 92% according to oxygen amount, cold gas efficiency shows lower value than the case of coal. Therefore, it was shown that complemental study in burner design to atomize slurry droplet is required to elevate gasification performance of petroleum coke which has lower reactivity than coal.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1246-1252
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• 1993

Coal-Water slurry (CWS) is a new potential form of fuel for use in power plants and industrial furnaces. The evaporation and ignition characteristics of CWS have been studied in the post-flame region generated by a flat flame burner. Individual droplets with initial diameters of 1-3mm were supported around the thermocouples and raidly exposed to a hot gas stream. The gas temperature ranged between $950^{\circ}C$ and 1600.deg. C at atmospheric pressure. The effect of droplet size, gas temperature and radiative heat transfer by screen were studied experimentally. The ignition criterion was either a rapid temperature rise in time-temperatuire curves or onset of visible flame in experiment. Incresing the gas temperature or decreasing the droplet size reduced the time required for evaporation and ignition.