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崔尙丁,李孝眞,吳明淑 弘益大學校 科學技術硏究所 2001 科學技術硏究論文集 Vol.12 No.-
As the number of coal fired power plants in the domestic power industry continues to increases, the amount of fly ash produced is also increasing, making the reutilization of fly ash a vital issue. Various methods to reutilize the fly ash from coal power plants have been investigated, and one of such areas with the potential to grow is the usage as light weight sintered construction materials. Sintered fly ash aggregates are produced in two steps; the first is the pellet formation step, during which the fly ash particles containing unburnt carbons were made into a pellet using caking components, and the second the pellet sintering by the combustion heat of the carbons. During the sintering process, the combustion rate of the carbon affects the characteristics of sintered pellets. The combustion of carbon occurs via adsorption of O₂ on the active sites, and desorption of CO/CO₂. The parameters which affect the rate of adsorption, desorption, and transfer of O₂ and CO/CO₂ include the O₂ partial pressure and flow rate, the pellet size, the porosity, the pore tortuosity, the pore size distribution, the carbon content and distribution. This study investigated the combustion of carbon during the production of sintered fly ash through modeling. A simple combustion model using Langmuir isotherm is used to calculate the pellet temperature. The oxygen diffusion through the pores is ignored. At the temperatures of sintering, the desoption process is a rate limiting process, making the overall rate sensitive to the desoption kinetic parameters. In addition, it was found that the carbon content and the heat capacity of the pellet affected both the rate of the reaction and the final pellet temperature, while the area of active sites only affect the reaction rate. The future work will include the combustion modeling with external and internal diffusion of O₂, and the model confirmation through experimentation.