• 한국연소학회:학술대회논문집
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• 2001.11a
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• pp.153-160
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• 2001

The combustion test used DTF was performed to obtain the characteristics of NOx emission and reduction. In this test, major factor of NOx emission was a stoichiometric air ratio. At the onset of combustion to be rich oxygen, NOx was produced rapidly. Optimum condition for NOx reduction was formed under about AR:0.7 in the combustion test of Alaska coal. Investigations were undertaken with 200KW(th) test combustor. In combustion test, the major variables were coal feed ratio of center/outer, stoichiometric air ratio at the onset of combustion. The lowest NOx emission, 182ppm(6% O2 base), was achieved at about AR:0.6 of the first combustion stage with low NOx burner. Also, unburned carbon content of char collected in this combustion condition was about 1wt%.

• Korean Journal of Environmental Agriculture
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• v.19 no.5
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• pp.401-418
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• 2000

1. Production of the artificial zeolite from coal ash Coal fly ash is mainly composed of several oxides including $SiO_2$ and $Al_2O_3$ derived from inorganic compounds remained after burning. As minor components, $Fe_2O_3$ and oxides of Mg, Ca, P, Ti (trace) are also contained in the ash. These components are presented as glass form resulting from fusion in the process of the combustion of coal. In other word, coal ash may refer to a kind of aluminosilicate glass that is known to easily change to zeolite-like materials by hydrothermal reaction. Lots of hot seawater is disposing near thermal power plants after cooling turbine generator periodically. Using seawater in the hydrothermal reaction caused to produce low price artificial zeolite by reduction of sodium hydroxide consumption, heating energy and water cost. As coal ash were reacted hydrothermally, peaks of quartz and mullite in the ash were weakened and disappeared, and new Na-Pl peaks were appeared strengthily. Si-O-Si bonding of the bituminous coal ash was changed to Si-O-Al (and $Fe^{3+}$) bonding by the reaction. Therefore the produced Na-Pl type zeolite had high CEC of 276.7 $cmol^+{\cdot}kg^{-1}$ and well developed molecular sieve structure with low concentration of heavy metals. 2. Utilization of the artificial zeolite in agro-environment The artificial zeolite(1g) could remove 123.5 mg of zinc, 164.7 mg copper, 184.4 mg cadmium and 350.6 mg lead in the synthetic wastewater. The removability is higher 2.8 times in zinc, 3.3 times in copper, 4.7 times in cadmium and 4.8 times in lead than natural zeolite and charcoal powder. When the heavy metals were treated at the ratio of 150 $kg{\cdot}ha^{-1}$ to the rice plant, various growth inhibition were observed; brownish discoloration and death of leaf sheath, growth inhibition in culm length, number of panicles and grains, grain ripening and rice yield. But these growth inhibition was greatly alleviated by the application of artificial zeolite, therefore, rice yield increased $1.1{\sim}3.2$ times according to the metal kind. In addition, the concentration of heavy metals in the brown rice also lowered by $27{\sim}75%$. Artificial Granular Zeolites (AGZ) was developed for the purification of wastewater. Canon exchange capacity was 126.8 $cmol^+{\cdot}kg^{-1}$. AGZ had Na-Pl peaks mainly with some minor $C_3S$ peaks in X-ray diffractogram. In addition, AGZs had various pore structure that may be adhere the suspended solid and offer microbiological niche to decompose organic pollutants. AGZ could remove ammonium, orthophosphate and heavy metals simultaneously. Mixing ratio of artificial zeolite in AGZs was related positively with removal efficiency of $NH_4\;^+$ and negatively with that of $PO_4\;^{3-}$. Root growth of rice seedling was inhibited severely in the mine wastewater because of strong acidity and high concentration of heavy metals. As AGZ(1 kg) stayed in the wastewater(100L) for 4days, water quality turned into safely for agricultural usage and rice seedlings grew normally.

• Resources Recycling
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• v.5 no.1
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• pp.3-8
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• 1996

CZS(2Ca0 , SiO\ulcorner) phase of cement clinkcr was obtaincd by melting mixcd four indnstrial wasles of limestone sludge, waste Foundry sand, coal lly ash fiorn power plants and chernicas glasses. The effect ot mixing ratio of four rvastc mater~als ou the composnlg phascs in melled slag was investigated. Thc mixed wastes were meltcd to slag by heat under a constant basicity at 1370C. The shg consisted of p -CIS and C,AS(2CaO - A I P , . SiO,). The ratio of two phases was varied with mixing ~atioo f the waste materials. In order Lo increasc the amount ot j -C2S phase, the coal fly ash content should be reduced, while amount of the chemical glass be increased. The coal fly ash contcnt was the most imporlant factor in controlling phases of thc melted-slag.

• Korean Chemical Engineering Research
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• v.47 no.5
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• pp.580-586
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• 2009

In this study, co-combustion characteristics of Chinese bituminous coal and North Korean anthracite were investigated using a 2 MWe scale circulating fluidized bed power plant. At first, the combustion efficiency of bituminous coal of China and Australia as a function of excess air ratio and temperature were observed. The results showed that the combustion efficiency was influenced by particle size and volatile content of coal, the combustion efficiency of Chinese bituminous coal was over 99.5%. The unburned carbon particles from fly ash and bottom ash were a content 5~7% and 0.3%, respectively. The combustion efficiency with the mixture ratio 20% of bituminous coal and anthracite decreased over 5% because of the increase of entrained particles by a small average particle size of anthracite in the combustor. However, the outlet concentration of $SO_2$ and $NO_x$ was not changed remarkably. The concentrations of the typical air pollutants such as $NO_x$ and $SO_2$ were 200~250 ppm($O_2$ 6%), 100~320 ppm($O_2$ 6%) respectively. The outlet concentration of $NO_x$ was decreased to 30~65% with $NH_3$ supplying rate of 2~13 l/min in SCR process. The $SO_x$ removal efficiency was up to 70% by in-furnace desulfurization using limestone with Ca/S molar of approximately 6.5. With wet scrubbing using $Mg(OH)_2$ as absorbent, the $SO_x$ removal efficiency reached 100% under near pH 5.0 of scrubbing liquid.

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

• Korean Chemical Engineering Research
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• v.52 no.2
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• pp.233-239
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• 2014

The slagging which generated from ash deposition on furnace wall and tube in boiler reduces the heat transfer efficiency and damages to safety of boiler. The slag flow behavior in boiler is affected by melting temperature which is related to ash compositions. In this study, the behavior of slag is researched by using ash fusibility test, called TMA (Thermo-Mechanical Analysis). The technique measures the percentage shrinkage as the function of temperature, T25%, T50%, T75%, T90%. These temperatures indicate different stages of melting. Then, the effect of ash chemical compositions measured from XRF (X-ray Fluorescence Spectrometer) to ash fusion temperatures is discussed. Among the chemical compositions, refractory and fluxing influence on ash fusibility is described. High levels of refractory component and limited amount of fluxing components ($Fe_2O_3$, $K_2O$, CaO) increase overall melting temperatures. High $SiO_2/Al_2O_3$ ratio decrease high melting temperatures (T75%, T90%). Meanwhile, the presence of reasonable levels of fluxing components reduces overall melting temperature. A presence of fluxing component such as $K_2O$ and CaO is found to decrease the T25% values significantly. From this research, it is possible to make a reasonable explanation and prediction of ash fusion characteristic from analysis of TMA results and ash chemical compositions.

• Journal of the Korean Society of Combustion
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• v.15 no.2
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• pp.34-40
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• 2010

The effect of co-firing with pulverized coal and wood biomass on ignition and burn-out temperature was investigated at air and oxy-fuel conditions by thermo gravimetric analyzer(TGA). Three kinds of coal(shenhua, adaro, wira) were selected and mixing ratios of coal and wood biomass was set to 1, 0.5, and 0.8. The ignition temperature depended on the amount of volatile matter of blended fuel, while the burn-out temperature was dominated by the oxidant ingredients. The oxy-fuel condition with an oxygen ratio(Ofr,o) of 0.3 showed similar tendency with air condition in the heat flow measurement. Volatile matter reaction, however, became dominant when oxygen ratio exceeded 0.8 for co-firing combustion of wood biomass and pulverized coal.

• Journal of environmental and Sanitary engineering
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• v.12 no.1
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• pp.49-58
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• 1997

A study on the synthesis of zeolite from bituminous coal ESP fly ash as a raw material, which was emitted from the power plant, was carried out to reduce environmental problems and reuse of the industrial wastes. Bituminous coal fly ash was used as the source of silica and alumina. Zeolite was synthesized by hydrothermal reaction in aqueous NaOH solution with sodium aluminate as additive. The objective of this study is to elucidate the effect of several experimental variables on the synthesis of zeolite. The effects of preroasting temperature, mixing speed, leaching alkalinity, and molar ratio of Na$_{2}$O/SiO$_{2}$ and SiO$_{2}$/Al$_{2}$O of the products were investigated. The synthesized zeolite was proved to be NaA, which is known as 4A type, by comparing with SEM images, and X-ray diffraction analysis. And also we know that the transformation of zeolite A take places into other types of zeolites, i.e. Hydroxysodalite, zeolite P, with the variation of leaching alkalinity.

• Particle and aerosol research
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• v.9 no.4
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• pp.239-246
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• 2013

The purpose of this study is to determine the feasibility of dry-type desulfurization process for actual application to coal-fired power plant. We used actual exhaust gas from Facility Y, Plant #2 to fabricate a demo-scale testing device to attempt to improve the efficiency of desulfurization. A spout-bed circulating dry scrubber convergence system connecting turbo reactor with bag filter was devised, then analyzed for performance characteristics of $SO_2$ removal for Ca/S mole ratio, superficial gas velocity, and ammonia injection, and for secondary reaction characteristics of the non-reactive sorbent at the bag filter. As a result, the installation of spout-bed circulating dry scrubber convergence system showed better economy and efficiency for removing sulfur than the existing wet/semidry-type desulfurization process. In addition, the best efficiency for desulfurization occurred when connected to the bag filter, with differential pressure maintained at 150 $mmH_2O$.

• Journal of the Korean Applied Science and Technology
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• v.32 no.2
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• pp.240-247
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• 2015

Zeolite A was prepared from coal fly ash upon NaOH fusion treatment, followed by hydrothermal treatment. The effects of treatment conditions such as NaOH/ash ratio, fusion temperature, the amount of sodium aluminate added, hydrothermal treatment temperature and time on the type and the crystallinity of zeolites were investigated. The optimal NaOH/ash weight ratio and fusion temperature to produce high crystalline zeolite A were 1.2 and $550^{\circ}C$, respectively. The dissolution of $Si^{4+}$ and $Al^{3+}$ from the fused fly ash was not affected by stirring time. The type of synthetic zeolites was found to be dependent on the amount of sodium aluminate added. The low amount of sodium aluminate favored zeolite X, while a single phase zeolite A was produced by increasing the amount sodium aluminate. Zeolite A was transformed into hydroxysodalite with increasing hydrothermal treatment time and temperature. A high crystalline zeolite A could be obtained by decreasing the temperature increasing time up to the reaction temperature.