• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.21-24
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• 2014

In the entrained-flow coal gasifier, coal ash turns into a molten slag most of which deposits onto the wall to form liquid and solid layers. Critical viscosity refers to the viscosity at the interface of the two layers. The slag layers play an important role in protecting the wall from physical/chemical attack from the hot syngas and in continuously discharging the ash to the slag tap at the bottom of the gasifier. For coal with high ash melting point and slag viscosity, CaO-based flux is added to coal to lower the viscosity. This study evaulates the effect of critical viscosity temperature and ash/flux ratio on the slag behavior using numerical modelling in a commercial gasifier. The changes in the slag layer thickness, heat transfer rate, surface temperature and velocity profiles were analyzed to understand the underlying mechanism of slag flow and heat transfer.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.20 no.3
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• pp.147-152
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• 2010

In this study, the artificial coarse aggregate was manufactured by using coal ash and low grade clay. The characteristics of a coal ash-clay system were investigated using XRD, XRF, TG-DTA, SEM and Dilatometer with various coal ash contents. The chemical compositions are the fly ash, bottom ash and clay, $Al_2O_3$ are 28.5 wt%, 32.4 wt% and 18.1 wt%, and $SiO_2$ are 33.0 wt%, 53.7 wt% and 68.4 wt% in weight ratio, respectively. The shrinkage of specimens started at around $850^{\circ}C$ and changed little up to $1100^{\circ}C$, but increased markedly at above $1100^{\circ}C$. The shrinkage rate is strongly related to the decarbonization amount of coal ash. At the sintering temperature $1150^{\circ}C$, it was found that quartz, mullite, anorthite and albite phase exist in all specimens. It was found that bottom-clay system specimen sintered at $1150^{\circ}C$ had a good compressive strength of 87.5 kg/$cm^2$, and the compressive strength of bottom-clay specimen was higher than that of fly-clay system specimen. The reusability of coal ash as a raw material in the process of shotcrete resources such as artifical coarse aggregate is highly expected.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.38 no.12
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• pp.963-969
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• 2014

Four coal sources that had different ash contents were evaluated in a drop tube furnace (DTF). Combustion experiments were conducted by using several sources with different particle sizes and excess air ratios under air-staging conditions to determine the optimized combustion conditions of high-ash coal, with an emphasis on the combustion efficiency and NOx emissions. The results show that the higher ash content results in a large amount of carbon remaining unburned, and that this effect is dominant when the largest particle size is used. Furthermore, the ash content of coal does affect the Char-NOx concentration, which decreases with the particle size. The results of this study suggest that an air-staged system can be useful to reduce the NOx emissions of high-ash coal and that control of the air stoichiometric ratio of the primary combustion zone (SR1) is effective for reducing NOx emissions, especially by considering unburned carbon contents.

• Journal of the Korean GEO-environmental Society
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• v.6 no.1
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• pp.15-21
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• 2005

In this study, the utilization of coal-ash and phosphogypsum was considered as the evapotranspiration final landfill cover(ET cover) material. Cover material considered was the mixture of the weathered granite soil, coal-ash and phosphogypsum and so we sequentially performed the leaching test, column test and field model test to investigate the environmental effects of mixtures of coal-ash and phosphogypsum. In the leaching test, all materials had lower heavy metal concentration than the regulated threshold values. The column test and the review of related regulations were carried out to determine the optimum mixing ratio(OMR) and OMR was soil(4):coal-ash(1): phosphogypsum(1) on the volume base, which was applied to field model test. Field model tests were continued from February to June, 2004 in the soil box that was constructed with cement block. It was verified that coal-ash and phospogypsum mixed with soil was safe environmentally and the mixture of both wastes could improve the water retention capacity of cover materials.

• 한국연소학회:학술대회논문집
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• 2013.06a
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• pp.87-90
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• 2013

In pulverized coal fired boilers, slagging and fouling may cause significant effect on the operational life of boiler. As increasing a consumption of low rank coal, slagging and fouling are main issues in pulverized coal combustion. This study predicts ash deposition propensity in a 0.7 MW pilot-scale furnace. Slagging model is employed as a User-Defined Function (UDF) of FLUENT and validated against measurement and prediction. The results show good agreement compared with experiment. There is need to development of a pulverized coal combustion and slagging analysis at low coal.

• Resources Recycling
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• v.11 no.1
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• pp.32-36
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• 2002

This study was conducted to compost the mixture of Pig manure, gypsum and fly ash. Initial moisture contents of sample A (Pig manure : saw dust = 6 : 4) and C (Pig manure : saw dust : gypsum : coal fly ash= 6 : 2 : 1 : 1) in the reactor were 64 and 50%. Also temperature and pH of samples in the reactor was nearly the same. Total Organic Carbon (TOC) concentration of sample A and C were about 5500, 2900 mg/kg respectively. This sample was needed a lot of time to mature as viewing cation exchange capacity (CEC) after experiment was over. However added with gypsum and coal fly ash in Process of Pig manure composting Process was suggested that gypsum and coal fly ash have a roles of additive agent.

• Journal of the Korean Society of Tobacco Science
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• v.19 no.2
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• pp.92-101
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• 1997

This study was conducted to investigate the effect of fly ash on the yield and quality and to determine the optimum application amount of fly ash for tobacco(Nicotiana tabacum L). Two kinds of fly ash, anthracite and bituminous coal, were treated with different levels of 0, 20, 40, 60 MT/ha. Dry weights of tobacco at middle and topping growth stage were increased with application of fly ash, showing the highest dry weight at 40 MT/ha in both kinds of fly ash. It was showed that the bituminous coal had a little more effective for yield than that of anthracite. Comparing with the control, yields of tobacco applied with fly ash were significantly increased about 17.7% and 17.1% by the application of bituminous coal and anthracite, respectively. Quality of flue-cured leaves was better by application of fly ash than that of the control. The quality index was given the highest at 40 MT/ha for bituminous coal increasing by 24.6% and at 60 MT/ha fur anthracite increasing by 13.4% compared with the control. The economical efficiency considered of the yield and quality of tobacco was the highest at 40 MT/ha of bituminous. Soil pH, contents of available P2O5, organic matter, exchangeable Ca2+ and Mg2+ of soil during the growing season were increased by application of fly ash, showing more effectiveness in bituminous than that in anthracite. By the application of fly ash, the nutrients availability and the acidity of soil were reformed and they caused significantly the increase of growths yield, and quality of tobacco. By the application of lime reforming soil acidity, growth response, yields and quality of tobacco were not increased compared to the control, although the effect of reforming soil pH was remarkable.

• Resources Recycling
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• v.26 no.2
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• pp.80-88
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• 2017

Globally, there has been a lot of research related to recycling coal ash from power plant stations. This research is happening because there is a considerable shortage of sites for reclamation of increased coal ash every year. In addition, a variety of environmental pollutants have appeared because of mining activity. Abandoned coal mine, pits, and mine tailing piles caused pollutants to come to the surface resulting in serious damage for humans and the environment. Therefore in this study, we investigated whether or not coal ashes have the ability to prevent several environmental problems by mining in Korea and a manageable form recycling coal ashes. In overseas countries, there is a sufficient field of applicable cases where coal ash is used for neutralizing AMD (Acid Mine Drainage), covering of the waste materials, grouting, and soil amendments. However in Korea, since the coal ash is classified as a 'waste', there is an insufficient field applicable cases so far. Therefore it is necessary to establish a specific standard and management system for the utilization of coal ash based on the relevant precedent cases applied abroad in order to prevent environmental pollution caused by mining activity in Korea.

• 플라이애쉬
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• s.1
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• pp.4-4
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• 2004

• 플라이애쉬
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• s.1
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• pp.1-2
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• 2004