• Journal of Magnetics
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• v.18 no.3
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• pp.365-369
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• 2013

Coal ash is known to contain a noticeable amount of valuable elements, including transition metals and lanthanides. Therefore it is quite actual problem to extract them for metallurgy and other applications. This paper presents the results of high gradient magnetic and mechanical separation, microscopy, element analyses and optical spectroscopy of brown coal ash taken from the combustion camera and chimney-stalk of Angren thermal power station. The separated magnetic fraction was 3.4 wt.%, where the content of Fe in ferrospheres increased to 58 wt.%. The highest contents of Fe and rare earth elements were found in the fine fractions of $50-100{\mu}m$. Optical absorption spectroscopy of water solutions of the magnetic fractions revealed $Fe^{2+}$ and $Fe^{3+}$ ions in the ratio of ~1:1. The separated coal ash could be used for cleaning of technological liquid waste by means of the high gradient magnetic field.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.5
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• pp.73-80
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• 2006

The mono-layer cover system is composed of soils only as a filling material and various plants are planted on the surface to control the water balance in the cover system. In this paper, the mono-layer cover system was considered as an alternative landfill final cover system and developed a model that could utilize industrial by-product (especially, coal ash & phosphogypsum) as additive filling materials. The mixture of granite soil, coal ash, and phosphogypsum was placed as a cover material in a box constructed with cement. Laboratory tests were carried out to investigate the environmental effect on the utilization of coal ash & phosphogypsum and to determine the mxing ratio of each materials. In the leaching test, all materials showed lower heavy metal concentration than the threshold values of regulation. The optimum mixing ratio of materials which was applied to field model test was determined to soil (4) : coal ash (1) : phosphogypsum (1) on the volume base. Field model tests were continued from February to July, 2004 in the soil box that was constructed with cement block. It was verified that coal ash and phospogypsum mixed with soil was to be safe environmentally and the water balance of mono-layer cover system was reasonable.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.3 no.2
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• pp.185-201
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• 1993

The objectives of this study are to identify the physical, chemical and microstructural properties of coal fly ash and to increase the industrial use of coal fly ash. Experimental results show that 3 major constituents of coal fly ash are $SiO_2$, $Al_2O_3$ and coal fly ash includes the crystalline of Quartz and Mullite. Coal fly ash are classified into 7 groups based on the type of microstructure. Cenosphere is divided into floater and dry separated cenosphere which are consist mainly of $SiO_2$ and $Al_2O_3$. Cenosphere segregations are formed by adsorption and neck growth of the smaller sized cenosphere particles on the condition of the high temperature and air pressure.

• Journal of Environmental Impact Assessment
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• v.26 no.6
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• pp.563-573
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• 2017

Coal ash is generated from coal-fired thermal power plants every year. The remaining quantity of coal ash ends up in the landfills except for the recycled portion, and the existing ash pond capacity is limited almost. Currently, the difficulties are faced in building a new ash treatment plant because of the concerns about the environmental impacts of landfills at individual plant facilities. In terms of minimizing the environmental impact, the recycling and effective uses of coal ash are recognized as urgent issues to be challenged. Accordingly, this study examines the obstacles in expanding the recycling of the coal ash in South Korea and proposes solutions based on the case study analysis. The analysis results are as follows: 1) specific recycling guidelines and standards are required to be established in accordance with the contact medium (soil, ground water, surface water and sea water) and the chemical. 2) by providing the recognition environmentally safe in recycling the coal ash, transparency in establishing the planning stages and active communication with the community through promotion and research are essentially needed. 3) practical support system is required to encourage the power plant companies to use the coal ash as beneficial use.

• Asian Journal of Atmospheric Environment
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• v.6 no.1
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• pp.67-72
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• 2012

The chemical characterization of water-soluble organic carbon in ash emitted from a coal combustion boiler has not been reported yet. A total of 5 ash samples were collected from the outlet of an electrostatic precipitator in a commercial 500 MW coal-fired power plant, with their chemical characteristics investigated. XAD7HP resin was used to quantify the hydrophilic and hydrophobic water-soluble organic carbons (WSOC), which are the fractions of WSOC that penetrate and remain on the resin column, respectively. Calibration results indicate that the hydrophilic fraction includes aliphatic dicarboxylic acids and carbonyls (<4 carbons), amines and saccharides, while the hydrophobic fraction includes aliphatic dicarboxylic acids (>4-5 carbons), phenols, aromatic acids, cyclic acid and humic acid. The average mass of the WSOC in the ash samples was found to depend on the bituminous coal type being burned, and ranged from 163 to 259 ${\mu}g$ C/g of ash, which corresponds to 59-96 mg C of WSOC/kg of coal combusted. The WSOC mass accounted for 0.02-0.03 wt% of the used ash sample mass. Based on the flow rate of flue gas produced from the combustion of the blended coals in the 500 MW coal combustion boiler, it was estimated that the WSOC particles were emitted to the atmosphere at flow rates of 4.6-7.2 g C/hr. The results also indicated that the hydrophilic WSOC fraction in the coal burned accounted for 64-82% of the total WSOC, which was 2-4 times greater than the mass of the hydrophobic WSOC fraction.

• Tunnel and Underground Space
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• v.22 no.6
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• pp.449-461
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• 2012

Coal ash generated from thermal power plants is planned to use for mine filling in order to prevent subsidence of the ground. In according, the basic physical properties and flow characteristics were grasped using coal ash from generated Yeongdong thermal power plant, and hydraulic filling experiments were performed a total of eight times by manufacturing the model of 1 inclined shaft in Hanbo coal mine. The specific gravity of coal ash is 2.34, and the result of particle size analysis belongs to silty sand (SM). Coal ash of weight ratio of 60% was used in the filling experiments of the model, since liquefaction have shown in coal ash less than weight ratio of 70% from the result of slump and flow test. The outlet should be located at the bottom of the inclined and vertical shaft, this was favorable way in improving the filling efficiency from the experiment results regardless of groundwater exists.

• Journal of Environmental Impact Assessment
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• v.22 no.2
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• pp.135-145
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• 2013

The recycling of coal bottom ash generated from coal power plants in Korea has been limited due to heterogenous characteristics of the materials. The most common management option for the ash is disposal in landfills (i.e. ash pond) near ocean. The presence of large coarse and fine materials in the ash has prompted the desire to beneficially use it in an application such as fill materials. Prior to reuse application as fill materials, the potential risks to the environment must be assessed with regard to the impacts. In this study, a total of nine test cells with bottom ash samples collected from pretreated bottom ash piles and coal ash pond in a coal-fired power plant were constructed and operated under the field conditions to evaluate the leachability over a period of 210 days. Leachate samples from the test cells were analyzed for a number of chemical parameters (e.g., pH, salinity, electrical conductance, anions, and metals). The concentrations of chemicals detected in the leachate were compared to appropriate standards (drinking water standard) with dilution attenuation factor, if possible, to assess potential leaching risks to the surrounding area. Based on the leachate analysis, most of the samples showed slightly high pH values for the coal ash contained test cells, and contained several ions such as sodium, potassium, calcium, magnesium, chloride, sulfate, and nitrate in relatively large quantities. Three elements (aluminum, boron, and barium) were commonly detected above their respective detection limits in a number of leachate samples, especially in the early leaching period of time. The results of the test cell study indicate that the pollutants in the leachate from the coal ash test cells were not of a major concern in terms of leaching risk to surface water and groundwater under field conditions as fill materials. However, care must be taken in extending these results to actual applications because the results presented in this study are based on the limited field test settings and time frame. Structural characteristics and analysis for coal bottom ash may be warranted to apply the materials to actual field conditions.

• Journal of the Korean GEO-environmental Society
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• v.14 no.4
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• pp.53-58
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• 2013

The design for horizontal drain layer on soft ground starts from the decision that the material could be used or not, by verifying material condition in permeability of horizontal drain material according to the weight percent of the dry soil retained on #200 sieve. In the next step of the design, we estimate the thickness of horizontal drain layer to confirm trafficability of heavy machinery in construction work. Successively, the long-term functionality for good drainage of horizontal drain layer is checked and if needed, some means are considered. In this study, the system to recycle mixed coal ash in ash pond successfully as a horizontal drain material on soft ground is presented through the process and the result of its practical construction work. Namely, the pact is confirmed that mixed coal ash in ash pond should be sorted out by sieve screen to a certain extent and the remainders of this mixed coal ash on sieve openings be recycled, because the amount of finer particles than $75{\mu}m$ contained in mixed coal ash in ash pond is quite massive and irregular depending on the coal power plant or the location in same ash pond. In order to sort at large scale in situ, the dimension of a sieve squre hole and the sort-out method, etc. should be decided before the sort-out process. And, it is described that we need to manufacture classifier to sort out mixed coal ash in ash pond, too.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.19-24
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• 2003

Recently, the by-product of coal ash has been increased by increase of consumption of electric power. So in view of environmental aspect, it is important to secure a reclaimed land and treatment utility for coal ash. This is an experimental study to compare and analyze the properties of high volume coal-ash concrete using the bottom ash. For this purpose, the mix proportions of concrete according to the replacement ratio of bottom ash(l0, 20, 35, 50%). And then air content, slump, compressive strength, durability test were performed. According to test results, it was found that the compressive strength of bottom ash concrete was similar to that of plain concrete(BA0). And the carbonation depth of bottom ash concrete increased as the replacement ratio of bottom ash.

• Clean Technology
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• v.20 no.3
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• pp.298-305
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• 2014

Ash included in coal can cause environmental pollution and it can decrease efficiency of mass and heat transfer by getting scorched and stick in the facilities operated at high temperature. To solve this problem, a feasibility study on pulverized coal fired power plant and integrated gasification combined cycle (IGCC) using the AFC (Ash-Free Coal) as well as the development to remove the ash from the coal was conducted. In this research, optimization of operating condition was proposed by using sensitivity analysis of ASPEN $Plus^{(R)}$ to apply the coal containing under the 200 ppm ash for integrated gasification combined cycle. Particularly, the coal gasification process was classified as three parts : pyrolysis process, volatile matter combustion process and char gasification process. The dimension and operating condition of 1.5 ton/day class non-slagging gasifier are reflected in the coal gasification process model.