燃用典型低阶煤的积灰预测及在线监测

Coal will still be an important part of China's primary energy. As high-quality bituminous coal becomes less, it is more economical for power plants to burn low-rank coal. However, some types of low-rank coal rich in alkali and iron are prone to cause severe fouling inside boilers, and thus it is necessary to optimize the combustion technology based on coal property so that the overall benefits concerning boiler safety and plant profit are maximized. The key to this goal is to quantify the ash deposit characteristics and use advanced in situ monitoring techniques in boiler operation. To this end, this proposal is firstly devoted to investigating the initial deposited layer formed by low-rank coal. The transport of micro-particles in the turbulent flow will be simulated, and a population balance model in the boundary layer of heat transfer tubes will be developed to quantify the forming rate of initial deposited layer. Then, this proposal aims at studying the growth of deposited layer through an experimental investigation on the sticking probabilities for the high-temperature deposition of fly ash particles. Moreover, a camera-based RGB pyrometry will be applied for analyzing the surface temperature and heat transfer property of deposited layers. This fundamental work is expected to provide solid foundation for the ash deposition control technology in burning low-rank coal rich in alkali and/or iron.

煤炭仍将是我国一次能源的重要组成部分。随着优质烟煤资源趋于紧张，电厂燃用低阶煤具有成本优势，但一些高碱、高铁低阶煤的燃用易引发严重的炉内积灰问题，因此需要根据煤质优化燃用技术方案，实现锅炉安全性与电厂经济性的综合效益最大化。实现此目标的关键是将积灰特性定量化，并在运行中采用先进的积灰监测技术。为此，本项目首先针对低阶煤的积灰初始层，分析微米颗粒在流场内的输运过程，并建立管壁边界层内的群平衡模型，定量模拟积灰初始层生成速率。其次，针对积灰层的发展，通过机理实验研究飞灰颗粒高温沉积的粘附效率，并采用一种RGB相机三色测温方法研究沉积层的表面温度与传热特性。本项目的研究有望为燃用高铁、高碱低阶煤的积灰防控技术方案提供坚实基础支撑。