• 한국신재생에너지학회:학술대회논문집
• /
• 2007.11a
• /
• pp.417-423
• /
• 2007

Oxy-gasification or oxygen-blown gasification, enables a clean and efficient use of coal and opens a promising way to CO2 capture. The coal gasification process of a slurry feed type, entrained-flow coal gasifier was numerically predicted in this paper. The purposes of this study are to develop an evaluation technique for design and performance optimization of coal gasifiers using a numerical simulation technique, and to confirm the validity of the model. By dividing the complicated coal gasification process into several simplified stages such as slurry evaporation, coal devolatilization, mixture fraction model and two-phase reactions coupled with turbulent flow and two-phase heat transfer, a comprehensive numerical model was constructed to simulate the coal gasification process. The influence of turbulence on the gas properties was taken into account by the PDF (Probability Density Function) model. A numerical simulation with the coal gasification model is performed on the Conoco-Philips type gasifier for IGCC plant. Gas temperature distribution and product gas composition are also presented. Numerical computations were performed to assess the effect of variation in oxygen to coal ratio and steam to coal ratio on reactive flow field. The concentration of major products, CO and H2 were calculated with varying oxygen to coal ratio (0.2-1.5) and steam to coal ratio(0.3-0.7). To verify the validity of predictions, predicted values of CO and H2 concentrations at the exit of the gasifier were compared with previous work of the same geometry and operating points. Predictions showed that the CO and H2 concentration increased gradually to its maximum value with increasing oxygen-coal and hydrogen-coal ratio and decreased. When the oxygen-coal ratio was between 0.8 and 1.2, and the steam-coal ratio was between 0.4 and 0.5, high values of CO and H2 were obtained. This study also deals with the comparison of CFD (Computational Flow Dynamics) and STATNJAN results which consider the objective gasifier as chemical equilibrium to know the effect of flow on objective gasifier compared to equilibrium. This study makes objective gasifier divided into a few ranges to study the evolution of the gasification locally. By this method, we can find that there are characteristics in the each scope divided.

• Resources Recycling
• /
• v.2 no.2
• /
• pp.39-44
• /
• 1993

This study was carried out to remove the water from low grade anthracite slurry produced at Eoryong coal mine by the oil agglomeration process. 80% of Anthracite as a coal oil mixture (COM) was separated from water by the difference of specific gravity. Then, the amount of kerosene, diesel oil, and heavy oil forming COM was 10% of the amount of sample, respectively. The recovery rate of combustibles and ash content of agglomerated anthracite were affected largely by the amount of added oil, pulp density, particle size, mixing time, and impeller speed. The recovery rate of combustibles was increased to 95% and ash content was decrea-sed from 30% to 13.5% under the optimum conditions.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2010.03a
• /
• pp.1018-1031
• /
• 2010

In order to investigate the applicability and suitability of the industrial by-products to landfill final cover, field pilot-scale lysimeter experiments were carried out. The mixture of loamy soil, bottom ash, and construction waste was placed as a cover material in lysimeter($2m{\times}6m{\times}1.2m$) which were constructed with cement brick, and then, volumetric water contents, pF value, and the quantity of runoff and seepage of treatment boxes filled with the mixture of loamy soil and the industrial by-products were monitored from July, 2007 to February, 2008. Among the cases tested, consequently, the case containing the mixture of bottom ash and loamy soil was most effective in engineering and hydrological properties and water retention ability.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.32 no.3C
• /
• pp.95-104
• /
• 2012

Due to current interest in creation of urban space and urban landscape, more emphasis has been placed on underground space development. With increasing number of underground power cables and its importance, a study of backfill materials for pipe is now imperative. Backfill materials require outstanding thermal characteristics since breakdown of cable insulation can be caused if heat generated from transmission of underground power cables had not been effectively discharged through backfill materials. Also, coal ash, which are industrial by-products, is being produced in high volume every year. Among them, ponded ash (PA) is not recycled and instead, mostly buried. Therefore in this study, thermal conductivity test based on mixture ratio (PA, ponded ash : FA, fly ash) was performed to evaluate the thermal conductivity characteristics of CLSM (controlled low strength materials) with coal ash. The results indicate that the mixture ratio (PA, ponded ash : FA, fly ash) of 80:20, water contents of 28~30%, and cement contents of 7-11% showed the highest conductivity at 0.796~0.884W/mK and thus, considered optimal in terms of recycling ponded ash (PA) as well as for maximizing utilization as backfill materials for pipe in underground.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.10
• /
• pp.1908-1914
• /
• 1992

A significant drag reduction in the turbulent flow of CWM(coal Water Mixture) adding minute amounts of high molecular weight polymer additives has been obtained and it was compared with pure CWM.However, the rate of drag reduction could come down with flow time, which is caused by polymer degradation, The rate of drag reduction and polymer degradation is affected by polymer type, concentration, molecular weight, and flow velocity. In the present investigation, these important parameters were evaluated for their influences on polymer degradation in order to find out stable conditions for CWM transportation with time. It was necessary to determine the more effective type of polymer additives to guarantee the optimum conditions for CWM transport. Experiments were undertaken with a test section of pipe diameter 9.8mm and pipe length 3500mm(L/D=357) in a closed loop, and polyacrylamide and polyetylene oxide were utilized as polymer additives. The tests were carried out under the conditions of 200, 400, 700ppm of polymer concentrations. CWM concentrations utilized were 5% and 10% with flow velocities of 4.9m/s and 6.1m/s. Experimental data show that polyehylene oxide degraded faster than polyacrylamide in CWM transport, and polyacryamide is considered to be a more effective candidate as additive for long time-CWM transport. Polymer degradation is also found to be more likely at lower polymer concentrations, at higher flow velocities, and higher CWM concentrations.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.30 no.5
• /
• pp.201-206
• /
• 2018

This study investigated the changes in pore water quality of polluted sediment by mixing ratio of granulated coal ash. The mesocosm experiments were carried out with 0%, 10%, 30% and 50%, respectively, of the material mixture ratio relative to the sediments. According to the results of the experiments, pH increased depending on the mixing ratio. Phosphate and ammonia concentrations were significantly decreased in the mixing ratio of 30% and 50% compared to the control (p < 0.05). The concentration of hydrogen sulfide was reduced by 72% at the mixing ratio of 10%, and it was not detected at the mixing ratio of 30% and 50%. This study was confirmed that granulated coal ash can change the pore water quality of polluted sediments in proportion to the amount of material. However, the effect of the mixing ratio between 30% and 50% was not significantly different, thus it is concluded that mixing of 30% of the volume of the sediment is economically feasible.

• Journal of Soil and Groundwater Environment
• /
• v.27 no.1
• /
• pp.39-49
• /
• 2022

Bottom ash generated from thermal power plants is mainly disposed in landfills, from which metals may be leached by infiltrating water. To evaluate the effect of metals in leachate on soil and groundwater, we characterized bottom ash generated from burning cokes, bituminous coal, the mixture of bituminous coal and wood pellets, and charcoal powder. The bottom ash of charcoal powder had a relatively large particle size, and its wood texture was well-preserved from SEM observation. The bottom ash of charcoal powder and wood pellets had relatively high K concentration from total element analysis. The eluates of the bottom ash samples had appreciable concentrations of Ca, Al, Fe, SO₄, and NO₃, but they were not a significant throughout the batch test. Therefore, it is considered that there is low possibility of soil and groundwater contamination due to leaching of metal ions and anions from these bottom ash in landfills. To estimate the trend of various trace elements, long-term monitoring and additional analysis need to be performed while considering the site conditions, because they readily adsorb on soil and aquifer substances.

• Journal of the Korean GEO-environmental Society
• /
• v.14 no.10
• /
• pp.29-37
• /
• 2013

In this study, we constructed the test embankment with four kinds of sections(2 kinds of bottom ash; tire shred-bottom ash mixture, weathered soil) in field and had been monitoring the behaviour of the test embankment and change of ground water quality for 1 year. In the geotechnical aspects, there was no relative difference of deformation in 4 test materials section and we could not see the possibility of the strength-reduction of coal ash materials by freezing inside of the embankment. In addition, no settlement was observed in the test sections because the base soil of the test sections was rigid enough that no consolidation was occurred. In the examination of water quality, all of the heavy metals and negative ions were detected below the drinking water standards except for sulfate($SO_4^{2-}$). In the beginning of measurement, higher concentrations of sulfate from 4 test sections were detected than drinking water standard for 20 days after beginning of the test but the concentrations decreased below the drinking water standard after 50 days after the tests.

• Journal of the Korean Geotechnical Society
• /
• v.26 no.1
• /
• pp.75-83
• /
• 2010

Controlled low strength material (CLSM) is a flowable mixture and does not need to be compacted. It is produced by mixing portland cement, fly ash, fine aggregates, water and chemical admixtures. Sand is the most commonly used fine aggregates in the conventional CLSM, but it is getting more and more difficult to obtain sand in Korea. In this study, the characteristics of unconfined compressive strength, flow and applicability of a new CLSM that is produced by mixing of pond ash, fly ash, water, cement are examined. An unconfined compressive strength satisfies the standard unconfined compressive strength (0.5~1.0 MPa) were obtained when the mixture ratio of pond ash and fly ash is 30:70~70:30, cement ratio is 3.0~5.0%, and water content is 31~34%. The results of flow test indicate that the mixture ratio of pond ash and fly ash which satisfy the standard How value (0.2 m) is 30:70~70:30.

• Journal of Environmental Science International
• /
• v.13 no.2
• /
• pp.143-148
• /
• 2004

In this paper, the properties of inter - locking block using fly ash are discussed in order to provide economical advantages and improve quality, and protect environment and recycle resources. Fly ash is the by-product of coal in thermal power plant. The experimental parameters are fly ash content, the amount of AE water - reducing agent and mixing proportion of cement mortar. According to the experimental results, the improvement of quality in the side of strength, absorption ratio and freeze - thaw resistance for manufacturing inter -locking block and the curtailment of cost can be achieved in case of 15% of fly ash and 0.3% of AE water- reducing agent are mixed into mortar mixture of 1 :6(C:S).