微粉炭焚きボイラの燃焼管理のための燃焼シミュレーション技術の開発

抄録

This paper describes a newly-developed simulation method for pulverized coal combustion, and examples of commercial power generation boiler optimization by using the method. Recently, a number of pulverized coals, especially low rank coal, are mixed and supplied for commercial pulverized coal firing boiler to reduce power generation costs. However, it causes ash deposition, and overheating of furnace wall and heat exchangers. Experience-based boiler optimization is difficult, because much type of coals is used and changed in short time, so simulation method for boiler optimization is needed. Simulation accuracy is strongly affected by the kinetic parameters for the pulverized coal oxidation. However, the kinetic parameters based on Arrhenius plots, which uses experimental data obtained in a simple drop-tube furnace, do not have enough accuracy to optimize practical boiler. A newly-developed method, called Inverse Analysis (IA) method, has developed to estimate the kinetic parameters more accurately, and used for numerical simulation of a test furnace and practical boilers. Simulations based on Arrhenius plots and IA methods are performed for CRIEPI's coal combustion test furnace, and are compared with experimental results. The IA method shows better prediction of unburned Carbon in Ash (CIA) compared with Arrhenius plots method. Simulations with the kinetic parameters from the IA method are performed for two pulverized coal-fired boilers, in which the low rank coal is mixed and fired with bituminous coal. An optimization method is proposed to reduce CO and CIA as well as ash deposition under high mixture ratio condition of low rank coal. It is found that optimization based on numerical simulation with IA method is valid procedure.