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論文
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松江, 孝博 ; 新井, 雅隆 ; 廣安, 博之
概要:
application/pdf<br />Journal Article<br />Combustion characteristics of a single CWM (Coal-Water-Mixture) droplet placed on a hot surface in a test furnace were investigated. The collapsing load of an ash grain which is formed by the
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combustion of the CWM droplet was also measured to clarify the relationship between the burning temperature and burn-out state of the droplet. Two stage combustion which is usually observed in pulverized coal combustion was observed in the burning sequence of the CWM droplet on the hot surface. The first stage of combustion was due to the burning of flammable gas from the volatile matter in the coal. The second stage was the char combustion of the coal. As the temperature on the hot surface increased, the collapsing load of the ash grain decreased. It reached a minimum load and then increased with an increase of the temperature of the hot surface. It was considered that the combination of the unburned coal at low temperatures and melted ash at high temperatures resulted in the hard grain of ash which had a high collapsing load.
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論文
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松江, 孝博 ; 新井, 雅隆 ; 廣安, 博之
概要:
application/pdf<br />Journal Article<br />A single CWM droplet was suspended in a hot air stream by a fine R-type thermocouple. The surface temperature of this evaporating and burning droplet was measured by a radiation thermometer. The
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emissivity of the CWM droplet surface was kept at around 0.98 until the char combustion of the droplet proceeded to its middle stage. In the later stage of the char combustion, the emissivity decreased gradually to 0.82. Several degrees of temperature difference between the center and the surface of the droplet remained at the dry-up time, even when the diameter of the droplet was reduced to 2mm. The surface temperature at the start of char combustion was 700K when the droplet was exposed in surroundings of less than 900K. However, the surface temperature at the start increased from 700K in surroundings where it's temperature exceeded 900K. When the surroundings were 650K, the surface temperature at the char combustion start was 700K and higher than the surroundings, and the center temperature of the droplet was higher than that of the surface, which suggested that slow exothermic reactions in the droplet were already initiated before the char combustion started.
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論文
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松江, 孝博 ; 新井, 雅隆 ; 廣安, 博之
概要:
application/pdf<br />Journal Article<br />The evaporation and combustion characteristics of a small CWM droplet were analyzed on a hot surface in a test furnace. The minimum temperatures for decomposing combustion caused by the
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volatile matter of the coal and char combustion rise with a decrease of the initial diameter of the droplet. Droplets with diameters below about 1.3mm show different combustion characteristics from the larger droplets. From the photographic observation of the final state of the burned CWM droplet, the cracked shell and popcorn states were noted on the agglomerated surface of the ash. These symptoms appeared more clearly when the initial diameter of the droplet was larger than 1.3mm. The contraction ratio of the diameter in the dried-up state decreases correspondingly with the decrease in the initial diameter of the droplet.
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論文 |
論文
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松江, 孝博 ; 新井, 雅隆 ; 廣安, 博之
概要:
application/pdf<br />Journal Article<br />The evaporation and combustion characteristics of a single coal-water slurry droplet were studied in an elevated temperature environment and in a hot air stream by measuring the
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temperature of a burning droplet and observing its behavior. When the droplet was suspended in an elevated temperature environment, the decomposing combustion, that is, the combustion of an inflammable gas included in the coal, started after the dry-up. The surface reaction, that is, the combustion at the coal surface, followed after that. Thereby, the surface reaction was slightly influenced by the decomposing combustion. When the droplet was suspended in a hot air stream, the decomposing combustion started during the surface reaction process and a blue wake flame was induced. In this case, the spread of the surface reaction region was prevented by a flame of the decomposing combustion.
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