• Environmental and Resource Economics Review
• /
• v.16 no.2
• /
• pp.337-361
• /
• 2007

Using the sample of bituminous coal prices, this study calculates the cash flows of selective procurement strategies compared to the previous routine procurement strategies, and analyzes the revenue-improvement and revenue-stabilization effects of different procurement strategies. In empirical analyses, these effects of routine and selective procurement strategies are compared by forecasting model and forecasting period. The revenue-improvement and revenue-stabilization effects are analyzed to compare the distribution of return flows, that is the means and standard deviations of procurement revenue flows. The revenue-improvement and revenue-stabilization effects of selective procurement strategies compared to the previous routine procurement strategies are as follows. Compared with routine procurement strategies, the selective procurement strategies turn out to yield higher means of returns (except for some forecasting periods and models). On the contrary, the standard deviations of returns decrease. With longer forecasting periods, the amounts of increases in the means become larger, but the degrees of decreases in the standard deviations vary. Although there exist some variations, some forecasting models outperform the others in terms of means and standard deviations.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1184-1189
• /
• 2004

Coking process is the thermal decomposition of bituminous coal with final temperature of about $900^{\circ}C$ Because coke plays important roles in ironmaking process in a blast furnace it's essential for developing modeling of coke oven. In this study, An unsteady 2-dimesional model is proposed to simulate coking process in a coke oven. In this model, gas and solid phase are assumed homogeneous continnum and solid bed is assumed as porous media . The model contains governing equations for the solid phase and the gas phase. Complicated phenomena such as swelling, softening, resolidification and shrinkage are neglected and mass loss by drying and devolatilization is reflected by generation of internal pores. Drying, devolatilization, heat transfer and generation of internal pores are also reflected in source terms. Calulated results are compared with experimental data

• Journal of Energy Engineering
• /
• v.11 no.3
• /
• pp.269-275
• /
• 2002

Experimental studies are carried out to find the behavior of sulfur compounds which are evolved during high temperature pyrolysis of coals at the smelting reduction process for iron ore. Three kinds of bituminous coals, such as Hunter & Mt. Thorley (Australia), and Ensham (South Africa) are used. And forms of sulfur compound and their amounts are analyzed at the temperature ranges of 800~110$0^{\circ}C$. Then H$_2$S is the major gas, but CS$_2$ and COS are minor gases. Sulfur compounds in three coals are distributed into the volatiles (gas & tar) and coal char as the ratio of approximately 50%：50%, respectively.

• Journal of the Korean Society of Combustion
• /
• v.8 no.2
• /
• pp.34-40
• /
• 2003

Analyses for concentration, surface phenomena, and crystal structure were performed to identify the causes of clinker formation in three type of pulverized coal fired boilers. Some clinkers had partially molten surface and more CaO and $Fe_2O_3$ as compared with fly ash, and the major crystalline phases identified in the clinker were mullite and quartz. Clinkers were formed in high temperature zone of the boiler according to the identification of mullite by XRD. Free $SiO_2$ in sand combined with K, Na and Ca in limestone served as a fluxing agent to form clinkers in a circulating bed boiler.

• Journal of environmental and Sanitary engineering
• /
• v.14 no.4
• /
• pp.165-171
• /
• 1999

A study on the synthesis of zeolite 4A using the bituminous coal fly ash from power plant was carried out. This study aims to investigate possibility for detergent builder with synthesized zeolite. It was examined at the crystallization conditions of atmospheric pressure and that of pressurization. The synthesized zeolite was proved to be Zeolite 4A type by means of the XRD and SEM analysis, and then the synthesized zeolite was used as an absorbent the remove the $Ca^{2+}$ ions in the water. In this study, commercial zeolite and synthesized zeolite reached equilibrium within 10 and 30 minutes respectively. The amount of $Ca^{2+}$ ions exchanged by the commercial zeolite, atmospheric pressure zeolite (zeolite A) and pressurized zeolite(zeolite PA) were 391mg/L(as $CaCO_3$), 323mg/L(as $CaCO_3$) and 355mg/L(as $CaCO_3$) respectively.

• Journal of Mechanical Science and Technology
• /
• v.15 no.2
• /
• pp.239-247
• /
• 2001

Measured radiative heat fluxes on the furnace exit plane of a heavy duty power boiler of steam output 1650 T/h are discussed. A high-ash pulverized bituminous coal was used. Such measurements are necessary to improve heat fluxes inside a steam boiler furnace was manufactured. An extra small heat radiation sensor was placed in the water cooled head of the probe. The sensor had no direct contact with furnace gases and measured only the radiant energy. There was no exposure to convective heat transfer. With the radiometric probe, one can obtain a spherical indicatrix of radiation intensity as well as hemispherical radiative heat flux incident on any surface passing through a measuring point inside the furnace. Thus, the quantity of radiation energy, passing through the furnace exit plane, to the convective heating surfaces and the quantity of radiation energy going in the opposite direction were measured. A formula for relative radiative heat flux on the furnace exit plane has been proposed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.04a
• /
• pp.159-162
• /
• 2000

The purpose of this study is to develope an accurate procedure for measuring the glass content of fly ash produced by bituminous coal to assist in predicting their behavior in concrete. Quantitative mineralogical compositions of fly ashes were obtained by internal standard method using powder X-ray diffraction analysis. In the X-ray diffraction method, the specimen and standard fluorite were cautiously mixed and pulverized to 22$\mu$m in wet process so as to avoid the prefered orientation of the crystal and microabsorption effect of X-ray. calibration curve were fitted for several references peaks of four phases:$\alpha$-quartz. mullite, magnetite, hematite. The amount of glass was calculated by subtracting the amount of crystal phase and loss on ignition from the total amount. Glass content determined with this method ranged from 66.7 to 75.wt%.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.11a
• /
• pp.729-732
• /
• 2006

Portland cement is presently the most widely used construction material. The process of manufacture of cement consists essentially of grinding the raw materials, mixing them intimately proportions and burning in a rotary kiln at a temperature of up to about $1450^{\circ}C$. Raw materials have used limestone, clay, silica, and iron oxide and fuel have used bituminous coal. Recently, A standpoint of the recycling of material resources, the production of cement use of industrial waste and residual products. Therefore, the final product of cement were included heavy metals such as $Cr^{+6}$ and Pb. The purpose of this study is standardization for $Cr^{+6}$ analysis in cement and concrete. From the comparative study of the examination method of $Cr^{+6}$ analysis, Japan cement association standard of $Cr^{+6}$ analysis is most suitable for the real state of affairs in korea.

• Applied Chemistry for Engineering
• /
• v.23 no.6
• /
• pp.529-533
• /
• 2012

In this study, we compare various physicochemical properties of solvent extracted coals obtained at both mild and high temperature conditions. In order to characterize the extraction behavior, experiments were performed using a sub-bituminous coal (Kideco) and a polar solvent (N-methyl-2-pyrrolidinone, NMP), where the extraction temperature and the effect of solvent recycling were evaluated. As the extraction temperature increased up to $350^{\circ}C$, an extraction yield and a calorific value of the extracted coal increased, while an ash content of the extracted coal decreased. FT-IR results revealed that the surface of the coal extracted at $350^{\circ}C$ was found to contain more amide, aromatic ester, and aliphatic ether groups than that at the lower temperatures. The result of MALDI-TOF/MS analysis confirmed that the smaller molecules with 300~500 m/z were extracted at a mild condition, while the bigger molecules in the range of 500~1500 m/z were extracted at the high temperature.

• Korean Journal of Soil Science and Fertilizer
• /
• v.30 no.3
• /
• pp.248-256
• /
• 1997

In order to establish a optimum level and proper method of fly ash application for soybean cultivation, the successive three years experiment was conducted in the field applied with four application levels of fly ash, 0, 30, 60, 90 MT/ha during the 1991 to 1993. Influence of successive application and residue of fly ash in soil on soybean growth and yield was discussed. Fly ash application had a favorable effect on soybean growth, however over application such as 90 MT/ha caused to turn the color into the brown of young leaf edge and eventually to have necrosis on the leaf. This symptom was prominent under the application of bituminous coal fly ash. In the 1st year cultivation of soybean, the highest yield was obtained at application level of 30 MT/ha. In the 2nd year, application of anthracite fly ash showed the highest yield at 60 MT/ha for successive application and at 90 MT/ha for the 1st year application followed by the 2nd year residue. Application of bituminous coal fly ash showed the highest yield at 60 MT/ha for the both successive application and residue. In the 3rd year, successive application of the both fly ash was given the highest yield at 30 MT/ha, respectively indicating the decrease of yield with increasing level of application. In case of residue plot, the highest yield by the application of anthracite fly ash was made at 90 MT/ha for the 1st year application followed by 2 years residue and at 60 MT/ha for the 1st and 2nd year application followed by the 3rd year residue. But in the residue plot of bituminous coal fly ash, yield was highest at 30 MT/ha showing the decrease of yield with increasing level of residue. Enhancement in growth and yield of soybean by application of fly ash was due to the fact that fly ash contained some plant nutrients such as phosphorus, silicon, and boron etc. and reformed soil pH that caused to increase availability of nutrients in soil.