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- 주제어 : freeboard (검색결과 3 건)
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石炭流動層 燃燒爐에서의 Freeboard 燃燒特性에 관한 硏究
In this study, combustion characteristics in the freeboard zone were investigated and a model for the carbon combustion reaction was also developed by setting up the entraiment mechanism of the unburned carbon and applying the related reaction kinetics. Domestic low calorific anthracite, heating value of which is 2,500kcal/kg, was used as e coal sample in the experiments, and major operating conditions included bed temperature, fluidizing velocity, particle size distribution of the coal sample, and recyle ratio of the fly ash. Experimental results showed that the parameters most affecting combustion in the freeboard zone included size distribution of the coal particles, recycle ratio, and temperature, and that, based upon the variations of these parameters, the fraction of carbon combustion in the freeboard zone varied from 0 to 20%, and that, depending on the axial height of the freeboard, carbon monoxide(CO) concentration increased in the range of 300-3,000 ppm, while oxygen (O₂) concentretion decreased in the renge of 0-4%. These results imply that the carbon load and temperature in the freeboard zone most affect the freeboard combustion, especially that the fly ash recycle most influences the combustion in the freeboard zone by improving the carbon load. Finally, the values calculated from the model were compared to the experimental values, which showed that the combustion reaction in the freeboard zone could be explained similarly to the actual reaction, under given conditions, by using this model.
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김현교 충북대학교 산업대학원 2025 국내석사
Due to the recent climate change, damages such as river levees and reservoir overflows, flooding of agricultural land, and landslides caused by typhoons and local heavy rains have frequently occurred. According to the 2022 Statistical Yearbook of Agricultural Production Base Maintenance (2023), 14,877 out of about 17,066 agricultural reservoirs have been built for more than over 50 years old, and it is unlikely to respond to rainfall events caused by recent abnormal climates. Four reservoirs with at least 30 years old of weather observation data were selected among small reservoirs located in Chungcheongbuk-do, and since there are differences in the observation timing of weather data for each observatory, this study selected a period from 1973 to 2023 (51 years) to compare and analyze the results during the same period. To calculate the design flood amounts, the K-HAS (KRC Hydrology & Hydrology Analysis System) provided by the Korea Rural Community Corporation (KRC) was utilized. Flood amounts were calculated, and reservoirs were tracked using this system. The appropriateness of the target reservoirs was examined based on changes in design flood amounts and reservoir tracking results according to the set period. As a result of analyzing the design flood increase/decrease rate by collecting meteorological data on the target reservoir of this study from 1973 to 2023 and classifying CASE into four categories, the largest increase rate was found in Satteo Reservoir Case 3 (-4.33%), Sojuk Reservoir Case 3 (23.77%), Neolakgol Reservoir Case 4 (15.18%), and Gojabae Reservoir Case 4 (72.58%). It can be seen that the rainfall is gradually increasing even considering the regional specificity. In addition, as a result of examining whether the height of the dam cest for each reservoir is adequate by performing flood tracking of the reservoir based on the design flood calculated to examine the hydrological stability of the target reservoir, it was confirmed that the dam cest height of the Satteo Reservoir Case 3 (-0.50m), Sojuk Reservoir Case 2 (-1.06m), Neolakgol Reservoir Case 4 (-0.53m), and Gojabae Reservoir Case 4 (-0.92m) were found to be the most insufficient. In all this study, the lack of height of the reservoir embankment due to changes in design standards and the increased precipitation is confirmed, and accordingly, measures and operational management measures need to be established to improve the hydrological stability of small reservoirs. Key words: Probability rainfall, aging reservoir, K-HAS, flood volume, dam cest, freeboard * A thesis for the degree of Master of Engineering in February 2025.
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