• Clean Technology
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• v.25 no.3
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• pp.179-188
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• 2019

Upon the combustion of coal particles in a coal-fired power plant, fly ash (80%) and bottom ash (20%) are unavoidably produced. Most of the ashes are, however, just dumped onto a landfill site. When the landfill site that takes the fly ash and bottom ash is saturated, further operation of the coal-fired power plant might be discontinued unless a new alternative landfill site is prepared. In this study, wet flotation separation system (floating process) was employed in order to recover unburned carbon (UC), ceramic microsphere (CM) and cleaned ash (CA), all of which serving as useful components within fly ash. The average recovered fractions of UC, CM, and CA from fly ash were 92.10, 75.75, and 69.71, respectively, while the recovered fractions of UC were higher than those of CM and CA by 16% and 22%, respectively. The combustible component (CC) within the recovered UC possessed a weight percentage as high as 52.54wt%, whereas the burning heat of UC was estimated to be $4,232kcal\;kg^{-1}$. As more carbon-containing UC is recovered from fly ash, UC is expected to be used successfully as an industrial fuel. Owing to the effects of pH, more efficient chemical separations of CM and CA, rather than UC, were obtained. The average $SiO_2$ contents within the separated CM and CA had a value of 53.55wt% and 78.66wt%, respectively, which is indicative of their plausible future application as industrial materials in many fields.

• Journal of Energy Engineering
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• v.26 no.1
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• pp.1-8
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• 2017

This study was carried out to physicochemical properties and free CaO contents of coal ash in domestic circulating fludized bed combustion power plant using ethylene glycol method. Results of physicochemical properties, there are many differences in CaO contents for the region position in CFBC plant. The reason, It is considered to be reflected that regulation of exhaust concentration for oxides of sulfur and other operation characteristics of region position in CFBC plant. Free CaO contents are 1.96 ~ 10.78% of fly ash and 0.07~4.24 % of bottom ash, fly ash is higher than in the bottom ash. besides CaO contents of raw materials, particle distribution have a lot of influence Free CaO contents.

• Applied Chemistry for Engineering
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• v.23 no.3
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• pp.259-265
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• 2012

Differently from fly ash, the bottom ash produced from thermal power generation has been treated as an industrial waste matter, and almost reclaimed or was applied with the additive of the part concrete. Bottom ash has various problems to use with the aggregate. Bottom ash is lighter than typically the sand or the gravel and it's physical properties (compressive strength etc.) is somewhat low because of high absorptance. In order to manufacture the ash concrete, we used a bottom ash as a main material and a pure sulfur as a binder. In this study, fundamental research methods that vary the grain-size of bottom ash and the ratio of sulfur vs ash were investigated to improve the quality of ash concrete such as compressive strength. Bottom ash in this research which occurs from domestic 4 place power plants, was checked physical and chemical properties. The compressive strength seems the result which simultaneously undergoes an influence in content of the sulfur and Bottom ash grain-size. We got the result of the maximum 92 MPa. The compressive strength was high result for grain size below 1.2 mm and high sulfur content.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.125-128
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• 2005

Coal ash, which is generated as a byproduct at a coal thermal power plant, can be classified into fly ash and bottom ash. Most of fly ash is recycled as an admixture for concrete, while bottom ash is not recycled but dumped into an ash landfill disposal site. So, if a technology for recycling bottom ash efficiently, which is increasingly generated year by year, is not developed, environmental problems will take place as a matter course and further an enormous economical cost will be required for construction of additional ash landfill disposal sites. In this study an optimum mix proportion design and a quality control method for utilizing the reclamation coal ash as an aggregate for secondary concrete products such as an artificial reef was successfully developed.

• Korean Journal of Soil Science and Fertilizer
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• v.20 no.4
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• pp.309-314
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• 1987

This study was conducted to examine mineralogical aspects on anthractite and bituminous coal-fired power-plant ashes as a source of mineral fertilizer. Fly ashes contain dominant amounts of silica and alumina and considerable quantitites of potassium and boron. However, potassium and silica present in unavailable forms for plant growth. X-ray, DTA, and IR analysis of ash particles indicated the formation of new mineral, mullite with shape of which were spherical in the surface morphologies of SEM. Detailed SEM investigation showed the presence of imbedded blocky shape silicate material.

• Journal of Powder Materials
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• v.13 no.2 s.55
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• pp.102-107
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• 2006

Recycling industrial wastes such as fly ash from a coal burning heat power plant and shell from an oyster farming were investigated to prevent environment contamination as well as to enhance the value of recycling materials. In this study, the lightweight aggregates and the red bricks were fabricated from fly ashes with other inorganic materials and wastes. The starting materials of the lightweight aggregate were fly ash powder and water glass, and the compacts of these materials were heat treated at $1100^{\circ}C$. The fabricated lightweight aggregates had low bulk density, $0.9-1.2\;g/cm^3$, hence floated on the water and had the strength of 7.0-11.0 MPa and the modulus of 2900-3300 MPa which indicates it has enough strength as the aggregate. Another type of the light weight aggregate was prepared from fly ashes, shell powders and clays. The bulk density, porosity, and compressive strength of these aggregates were $1.19-1.34\;g/cm^3,\;18.3{\sim}56.1%$ and 5-12 MPa, respectively. The addition of a small amount of fly ash powder prevented hydration of the light weight aggregates. The red brick was also fabricated from the fly ash containing materials. It is suitable for the brick facing of a building as it has moderate strength and low water absorption rate.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.23 no.4
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• pp.201-206
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• 2013

The coal bottom ash and reject ash discharged from a coal-fired power plant are difficult to recycle so most of them are mainly landfill-disposed. In this study, the artificial aggregate were produced using reject ash, bottom ash and dredged soil emitted from the coal-fired power plant in Korea and the effect of experimental factors on the bloating behavior and the properties of the aggregates were analyzed. In particular, a lot of unburned carbon in the reject ash was removed by calcination and the activated carbon was added to batch powders then the dependence of those process upon bloating properties of artificial aggregate were investigated. For this purpose, the specific gravity and water absorption values of artificial aggregates were investigated in conjunction with microstructural observations. This study could contribute to increase the recycling rate of the reject ash.

• Resources Recycling
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• v.26 no.1
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• pp.11-15
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• 2017

The amount of the wood chip ash is expected to increase continuously as demand of wood chip-based heat and electricity increase. Thus, there is increased interest in wood chip ash utilization. In this study, as a program of utilization in wood chip ash, the physical and chemical properties of wood chip ashes generated from a combined heat and power plant were investigated. The chemical analysis showed that the main contents of wood chip ash are composed of silica, alumina and alkali. A possibility of reuse as secondary cementitious materials was investigated by the analysis of strength activity index, and compared with coal ash. The highest value for Strength activity index of wood chip fly ash was 78% at 90 days curing time. This result revealed that wood chip fly ash has the potential to be utilized as the admixture for cementitious material.

• Korean Chemical Engineering Research
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• v.51 no.4
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• pp.493-499
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• 2013

For the purpose of utilizing fly ash from gasification of low rank coal, we performed the series of experiments such as pyrolysis and char-$CO_2$ gasification on fly ash by using the thermogravimetric analyzer (TGA) at non-isothermal heating conditions (10, 20 and $30^{\circ}C/min$). Pyrolysis rate has been analyzed by Kissinger method as a first order, the reliability of the model was lower because of the low content of volatile matter contained in the fly ash. The experimental results for the fly ash char-$CO_2$ gasification were analyzed by the shrinking core model, homogeneous model and random pore model and then were compared with them for the coal char-$CO_2$ gasification. The fly ash char (LG coal) with low-carbon has been successfully simulated by the homogeneous model as an activation energy of 200.8 kJ/mol. In particular, the fly ash char of KPU coal with high-carbon has been successfully described by the random pore model with the activation energy of 198.3 kJ/mol and was similar to the behavior for the $CO_2$ gasification of the coal char. As a result, the activation energy for the $CO_2$ gasification of two fly ash chars don't show a large difference, but we can confirm that the models for their $CO_2$ gasification depend on the amount of fixed carbon.

• KEPCO Journal on Electric Power and Energy
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• v.8 no.2
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• pp.97-101
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• 2022

In this study we investigated the gas to solid heat transfer of bubbling fluidized bed bottom ash cooler installed at the Donghae power plant in South Korea. Several different analyses are done through 1-D calculations and 3-D CFD simulation to predict the bottom ash exit temperatures when it exits the ash cooler. Three different cases are set up to have consideration of unburnt carbon in the bottom ash. Sensible heat comparison and heat transfer calculation between the fluidization air and the bottom ash are conducted and 3-D CFD analysis is done on three cases. We have obtained the results that the bottom ash with unburnt carbon is exiting the ash cooler, exceeding the targeted temperature from both 1-D calculation and 3-D CFD simulation.