• Journal of the Mineralogical Society of Korea
• /
• v.28 no.2
• /
• pp.147-163
• /
• 2015

Chemical and mineralogical properties of coal ash samples from the nine thermal power plants of Korea were investigated to acquire basic data for estimating the potential of rare metal recovery. Chemical compositions of coal ash were consistent with those of average shale and foreign coal ashes. However, there were small differences between the metal contents of domestic anthracitic and imported bituminous coal ashes. Unburned coal particles were much abundant in the ash of domestic anthracitic coal. Chalcophile elements were relatively enriched in the fly ash compared to bottom ash. Silicate glass was the major component of coal ash with minor minerals such as quartz, illite (muscovite), mullite, magnetite, lime, and anhydrite. Al and Si were the major components of the glass with varying contents of Ca, Fe, K, and Mg. Glass occurred in a form of porous sphere and irregular pumace-like grain often fused with iron oxide spheres or other glass grains. Iron oxide spheres were fine intergrowth of fast-grown iron oxide crystals in the matrix of silicate glass. Chemical, microstructural, and mineralogical properties would guide successful rare metal recovery from coal ash.

• Applied Chemistry for Engineering
• /
• v.9 no.3
• /
• pp.364-371
• /
• 1998

A theoretical model of particle agglomeration was developed to investigate the adhesive force between contiguous coal particles in CWM agglomerate. While heating bituminous coal to about $400^{\circ}C$ or above, the transient occurrence of plastic behavior of coal particles can be observed. The adhesive force in the process of agglomeration of coal particles was found to be proportional to the duration of plasticity of the particles. In the research, how the heating rate and the particle size distribution of CWM fuel influenced the formation of the agglomerate in CWM fuel at the heat-up stage was investigated by the model of particle agglomeration. Simulation program used to this experiment was RKG method and was programmed by Fortran. It was represented that by the model of particle agglomeration, the adhesive force in the process of the particle agglomeration in CWM fuel was inversely proportional to the heating rate but proportional to particle size.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.12 no.1
• /
• pp.177-186
• /
• 1992

In this study, the proper mixing ratio of fly ash to bottom ash is evaluated and bearing capacity of this mixed ash is examined for use of highway embankment and subgrade materials in large quantities. Independently of the mixing ratio of fly ash to bottom ash or the method of compaction test, maximum dry density ${\gamma}_{dmax}$ and CBR value of anthracite mixed coal ash is greater than that of bituminous mixed coal ash. The mixed ashes to contain more fly ash than that of which the ratio of fly ash to bottom ash is 8 : 2, are slaked readily when the water contents of compaction are greater than optimum moisture content O.M.C. The proper mixing ratios of fly ash to bottom ash are about 5 : 5 to 6 : 4. Coal ashes mixed with these ratios exhibit proper physical and geotechnical properties for use of highway embankment and subgrade materials, and enable coal ashes to be used in large quantities.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.8 no.2
• /
• pp.59-66
• /
• 1988

At the present time, annually about 2 million tons of coal ashes are generated from thermal power plants in Korea, however, they are dumped into ash ponds mixed with sea water very expensively. In this thesis, engineering characteristics of bituminous and anthracite ashes are studied to utilize them as construction materials. The coal ash is non-plactic material and its grain size falls in the range of silt, but it has better soil engineering characteristics than general soils of same grain size. For example, the permeability, shearing strength, CBR, and consolidation properties match to that of sandy soils, moreover, strengthening by hydration can be expected with the lapse of year because of CaO presence in the components. So, utilizing those coal ashes in a productive way as reclamation or banking materials is expected.

• Korean Chemical Engineering Research
• /
• v.52 no.1
• /
• pp.133-140
• /
• 2014

The experiment was designed to compare the char combustion kinetics of pulverized Indonesia coals commonly utilized in Korea power plants. The reaction rate of coal char has been formulated using the external and internal effectiveness factors to describe the diffusion effect quantitatively. The Random Pore Model (RPM) was used for applying internal specific surface area as a function of carbon conversion ratio. Reaction rate was obtained from reaction time using the Wire Heating Reactor (WHR) which can heat and measure the char particle temperature at the same time. BET and TGA were used to obtain physical properties such as internal specific surface area and structural parameter. Three kinds of Indonesia Sub-bituminous coals "BARAMULTI, ENERGYMAN, AGM" were used in order to derive the activation energy and pre-exponential factor. The results of this study showed that the effect of internal diffusion than that of external diffusion is the dominant as comparison of kinetics was reflected in external and internal effectiveness factors. For three kinds of coal char, finally, activation energy of intrinsic kinetics indicates 110~118 kJ/mol.

• KSBB Journal
• /
• v.11 no.2
• /
• pp.238-245
• /
• 1996

Microbial desulfurization characterlstics of a bituminous coal have been determined by using Thiobacillus ferrooxidans. The effects of process variables (such as coal pulp density, particle size and addition of surfactants) on pyrite removal have been investigated in both shake and airlift-bioreactor culture experiments. In shake experiments, pyrite could be removed over 78% for pulp densifies below 20% (w/v) and removed below 40% for pulp densities over 30% (w/v) in 8 days. Pyrite removal decreased with increasing pulp densities, and it also decreased sharply with increasing particle sizes. In airlift bioreactor experiments, pyrite at 50% (w/v) pulp density could be removed about 50%. Its value is much higher than 15% at the same pulp density in a shake experiment. With addition of surfactants, pyrite removal was enhanced in shake experiments significantly, whereas it was slightly decreased in an airlift bioreactor experiment.

• Korean Journal of Soil Science and Fertilizer
• /
• v.31 no.4
• /
• pp.373-379
• /
• 1998

Fly ash application with a rate 0, 50, 100, $150Mg\;ha^{-1}$ in clay loam paddy, which had properties of pH 5.3 and low contents of silicate, gave a positively residual effects on the growth of rice crop subsequent to malting barley. The responses of rice yields to fly ash application were in the order of bituminous coal fly ash(BCFA) 100 > 150 > 50 > anthracite fly ash(AFA) 50 > 100 > none > AFA $150Mg\;ha^{-1}$. As a result, yields responses of milled rice were ranged from $6.2(50Mg\;ha^{-1}){\sim}14.4%(100Mg\;ha^{-1})$ by BCFA and from $-0.6(150Mg\;ha^{-1}){\sim}6.6%(50Mg\;ha^{-1})$ by AFA showing maximum yields of 5.084 and $4.738Mg\;ha^{-1}$ by the former and the latter, respectively. Rice plant showed lodging indices ranging from $20(50Mg\;ha^{-1}){\sim}40%(150Mg\;ha^{-1})$ by BCFA and from $1.3(150Mg\;ha^{-1}){\sim}15%(50Mg\;ha^{-1})$ by AFA at harvesting stage. In especial, soils applicated with BCFA contained a good fertility in terms of pH, available $P_2O_5$ and $SiO_2$, and exchangeable Ca and Mg etc. so that possibly harbored 3yr-residual effects of the fly ash on crop subsequent to this rice.

• Applied Chemistry for Engineering
• /
• v.33 no.1
• /
• pp.28-37
• /
• 2022

The lignite and bituminous coal are mainly used in thermal power plant. They exhaust green house gas (GHG) such as CO₂, and become deplete, thus require alternative energy resources. To solve the problem, the hydrochar production from biomass is suggested. In this study, both hydrothermal carbonization (HTC) and solvothermal carbonization (STC) were used to produce high quality hydrochar. To improve the reactivity of water solvent process in HTC, STC process was conducted using ethanol solution. The experiments were carried out by varying the solid-liquid ratio (1:4, 1:8, 1:12), reaction temperature (150~300 ℃) and retention time (15~120 min) using kenaf. The characteristic of hydrochar was analyzed by EA, FT-IR, TGA and SEM. The carbon content of hydrochar increased up to 48.11%, while the volatile matter decreased up to 39.34%. Additionally, the fuel characteristic of hydrochar was enhanced by reaction temperature. The results showed that the kenaf converted to a fuel by HTC and STC process, which can be used as an alternative energy source of coal.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.33 no.11
• /
• pp.876-885
• /
• 2009

Char oxidation experiments were performed with a sub-bituminous roto-middle coal in the Drop Tube Furnace (DTF) at atmospheric pressure condition. While temperatures varied between 900, 1100, 1400 $^{\circ}C$, particle size, mass, particle temperature, and CO/$CO_2$ concentration were obtained to be used for kinetic analysis of the char oxidation. This study addresses several different methods to analyze the char consumption rate, which are classified as energy balance method, ash-traced mass method, flue-gas based method, and particle size based method. The char consumption rate obtained with such methods was compared with the results of Monson et al.$^{(24)}$ While there are some differences between them because of differences in experimental apparatus and parameters to be measured, the kinetic results seems to be reasonable enough to be incorporated in a numerical modeling of coal combustion.

• Journal of the Korean Applied Science and Technology
• /
• v.16 no.3
• /
• pp.217-221
• /
• 1999

This study was carried out to synthesis the zeolite using the bituminous coal fly ash emitted from power plant that occurs several environmental problems. In spite of fly ash has contained high content of $SiO_2$ and $Al_2O_3$, it disposed mainly landfill. If the effective methods to recover the $SiO_2$ and $Al_2O_3$ were developed, the fly ash could be utilized valuable raw materials. In this study, fly ash was used as raw material to synthesize the zeolite by pressurized hydrothermal reaction. Also, experimental parameters included temperature($70{\sim}110^{\circ}C$, and pressure($140{\sim}200$ psi) of crystallization were investigated. The more crystallization pressure was increased, the more Zeolite 4A was synthesized at 70 and $90^{\circ}C$. Zeolite 4A of metastable phase tend to be transformed into sodalite of stable phase at $110^{\circ}C$.