• Advances in Energy Research
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• v.4 no.3
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• pp.203-211
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• 2016

A good understanding of the chemical composition and structural characteristics of a carbonaceous material is essential in conversion processes. Understanding how the composition and structural changes influence the burning behaviour of coal is important when assessing a coal's potential for utilization. To explore the potentials of a typical Nigerian coal, both conventional and advanced analytical techniques such as proximate analysis, ultimate analysis, calorific value, surface area analyser, SEM, FTIR, XRD and SAXS were employed. The results obtained from these characterizations agree favourable well with a typical South African coal that is of enormous contribution to the gross domestic product (GDP) of the nation economy.

• Geomechanics and Engineering
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• v.24 no.3
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• pp.205-213
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• 2021

Water infusion has long been taken as an effective way to eliminate coal burst risk as coal properties can be loosen and soften by water infusion. However, not all industrial trials of water infusion for coal burst prevention have been necessarily effective in all situations as the effectiveness of this method can be affected by water infusion time, coal properties and the parameters of water injection. Hence, some fundamental issues including the effects of water infusion time on burst propensity and energy evolution need to be further discussed. In this paper, four groups of coal specimens with 0 day, 5 days, 10 days, and 15 days water saturation time are tested under uniaxial compression load with the application of AE monitoring. To comprehensively compare the burst behavior of coal specimens under different water saturation time, stress-strain curves, AE counts, fragmentation characteristics and burst propensity of these groups are analyzed. It was found by this research that sufficient water saturation can mitigate the burst behavior of coal samples while insufficient water infusion might cannot reach the burst mitigation aims.

• Geomechanics and Engineering
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• v.32 no.2
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• pp.233-244
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• 2023

With the increasing amount of resources required by the society development, mining operations go deeper, which raises the requirements of studying the effects of temperature on the physical and mechanical properties of coal and adjacent rock. For now, these effects are yet to be fully revealed. In this paper, a mechanical-electromagnetic radiation (EMR) test system was established to understand the mechanical deterioration characteristics of coal by the effect of thermal treatment and its deformation and fracture characteristics under thermo-mechanical coupling conditions. The mechanical properties of high-temperature-treated coal were analyzed and recorded, based on which, reasons of coal mechanical deterioration as well as the damage parameters were obtained. Changes of the EMR time series under unconstrained conditions were further analyzed before characteristics of EMR signals under different damage conditions were obtained. The evolution process of thermal damage and deformation of coal was then analyzed through the frequency spectrum of EMR. In the end, based on the time-frequency variation characteristics of EMR, a method of determining combustion zones within the underground gasification area and combustion zones' stability level was proposed.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.841-844
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• 2008

Non-refining fly ash and bottom ash, the byproducts generated from the coal-fired power stations, have usually been disposed of in onshore ash disposal sites. With an increase of power consumption due to industrial development, the generation of coal ash has been growing tremendously. Current insufficiency of disposal sites and environmental concerns over newly-built disposal sites have also led a growing need to utilize the coal ash. Accordingly, this paper compares and analyzes the fundamental properties of the coal ash collected from each disposal sites in order to increase the usability of the coal ash generated from coal-fired power stations. The results of the study indicate that coal ash shall be separately applied by the properties for each intended use as the ash greatly differs in its properties depending on the site of disposal. In particular, it is shown that the overall evaluation on the ash shall be necessary as the quality might be varied by the change of absorptance when applied as an aggregate for concrete. From the examination on the salt content, it has been observed that the ash can be applied as an aggregate for concrete only after more than 3 times of washing process.

• Journal of the Korea Institute of Building Construction
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• v.17 no.2
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• pp.183-189
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• 2017

The aim of the research is to provide rheological properties of cement paste with various qualities of coal ash including fly ash, raw ash, and reject ash. Generally, fly ash is the well known supplementrary cementitious materials for concrete and is used to improve various properties. Although fly ash is obtained as a byproduct of fire powder plant, still reject ash is wasted from raw ash. In this research, thus, to provide a fundamental information on using not only fly ash but also raw ash or reject ash for cementitious materials, a rheological properties of cement paste was studied with three different coal ash. This research was conducted from particle conditions of three different coal ashes to rheological properties in cement paste phase. According to the expeirment, reject ash was consisted with large and coagulated particles although fly ash was consisted with a small and spherical shaped particles. based on the particle conditions of various coal ashes, rheological behaviors were tested, and it was shown as the coal ashes improved the fluidity of cement paste. Specifically, depending on the particle distributions of cement paste, it is considered that the viscosity of paste can be controlled.

• Journal of the Korean Society of Safety
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• v.14 no.3
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• pp.84-92
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• 1999

The effects of air velocity and excess air on combustion characteristics were studied in a fluidized bed combustor. The domestic low-grade anthracite coal with heating value of 2010 kcal/kg and the imported bituminous coal from Australia with heating value of 6520 kcal/kg were used as coal samples. The combustion characteristics of mixed fuels in a fluidized bed combustor could be interpreted by pressure fluctuation properties, ash distribution and gas emission. The properties of the pressure fluctuations, such as the standard deviation, cross-correlation function, dominant frequency and the power spectral density function, were obtained from the statistical analysis. From this study, the combustion region increased with increasing air velocity but decreased with excess air due to combustion characteristics of anthracite and bituminous coal.

• Geotechnical Engineering
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• v.11 no.2
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• pp.37-50
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• 1995

Recently, the treatment of coal ashes produced from thermal electric power plants have been raised as a serious problem in according to the increasing of electric power demand in Korea. This paper deals with a re -use method of coal ash as a fill material. Two domestic coal ashes are mixed with cement and lime to improve the mechanical properties of coal ash. The mechanical properties such as compressive strength, compressive deformation, permeability and frost heaving property are investigated in according to the change of admixture rate, curing temperature and curing time. In this study, it is found coal ash (fly ash+bottom ash) and fly ash with 2%~3% cement can be used as a fill material, respectively. It is also found the frost heaving properties of coal ash is effectively improved by the mixture of 6%~9% cement.

• Architectural research
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• v.4 no.1
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• pp.39-44
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• 2002

Recently, the coal-ash production has been increased by increase of consumption of electric power. So it is important to secure a reclaimed land from pollution and develop practical application of coal ash. This is an experimental study to compare and analyze the properties of concrete using high volume of coal ash (including fly ash and bottom ash) as a part of fine aggregate. For this purpose, the mix proportions of concrete according to replacement ratio of coal ash (10, 20, 35, 50%) were selected. And then air content, slump, setting time, bleeding content, chloride content, compressive strength and carbonation test were performed. According to test results, it was found that the bleeding content of concrete using the coal ash decreased according to increase of replacement ratio. And the chloride content of concrete using the bottom ash as a part of fine aggregate increased as the replacement ratio of bottom ash increased, but it is satisfied with the total chloride content of concrete recommended by KCI - $0.3kg/m^3$ below. Also, the compressive strength of concrete using the bottom ash was similar to that of plain concrete(BA 0) after 28days of curing and the carbonation depth of concrete increased as the replacement ratio increased. However, the carbonation depth of concrete using the fly ash decreased as the replacement ratio of fly ash increased.

• Advances in concrete construction
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• v.6 no.4
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• pp.407-422
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• 2018

The study evaluates properties of brick having coal ash and explores the possibility of utilization of coal bottom ash and coal fly ash as an alternative raw material in the production of coal ash bricks. Lower cement content was used in the investigations to attain appropriate strength and prohibit high carbon content that is cause of environmental pollution. The samples use up to 7% of cement whereas sand was replaced with bottom ash. Bricks were tested for compressive strength, modulus of rupture, ultrasonic pulse velocity (UPV), water absorption and durability. The results showed mix proportions of bottom ash, fly ash and cement as 1:1:0.15 i.e., M-15 achieved optimum values. The coal ash bricks were well bonded with mortar and could be feasible alternative to conventional bricks thus can contribute towards sustainable development.

• Transactions of the Korean hydrogen and new energy society
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• v.21 no.5
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• pp.442-451
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• 2010

This paper describes the calculation method to obtain the product composition of coal pyrolysis at high pressure and high temperature. The products of coal pyrolysis should be determined for the coal gasifier simulation, and this is the first step of the coal gasifier simulation. The pyrolysis product distribution greatly affects the coal gasifier efficiency such as carbon conversion, cold gas efficiency and the syngas composition at the outlet of the gasifier. The present calculation method is based on the coal ultimate/proximate analysis and several correlations among gasifier pressure, coal properties and pyrolysis products. The calculated products for 5 coals have been compared with those from the commercial pyrolysis model.