燃煤循环流化床锅炉烟气污染物超低排放的基础研究

Circulating fluidized bed (CFB) coal-fired boiler technology has unique merits in active emission control against other types of coal-fired combustion technologies, with excellent cost-effectiveness. A few latest engineering practices found that changing the fluidization status in the CFB boiler could significantly reduce the formation of the flue gas pollutants (SO2 and NOx). For some CFB boilers, the concentrations of flue gas pollutants (SO2 and NOx) at the furnace exit even met or were close to the ultra-low emission standards, which were set for the natural gas fired devices. However, the associated fundamental studies are much behind, and the mechanisms of the two phase flow on the emission are still unclear. The studies are demanded for facilitating the maturation of ultra-low emission CFB coal-fired technology. In this project, via the combined method of experimental study and the modeling, the influence of fluidization status and gas-solid structure on heat and mass transfer, chemical reaction in the bottom dense bed and upper dilute bed will be assessed, and thereby formation and destruction mechanisms for the pollutants of sulfur and nitrogen oxides under full spectrum scale, including the particle scale, cluster scale and the reactor scale for the coal-fired CFB boiler will be studied. The effect of the fluidization status adjustment, via such as size distribution of feeding particles, bed inventory and solid flow rate on the chemical kinetics of pollutants are to be assessed. Based on the results, the flexibility and the control mechanism for the ultra-low emission of the sulfur and nitrogen oxides are to be reconfirmed, and the key conditions to reach the ultra-low emission are to be identified. In the last, the control scheme for the ultra-low emission is to be found and the theory will be developed for the ultra-low emission of a coal-fired CFB boiler. The results are useful to accelerate the development and maturation of the ultra-low emission technology for coal-fired CFB boilers. They will be also the fundamentals for the clean coal technologies to resolve the severe haze problem that the entire China is facing at.

循环流化床燃煤技术与其他煤燃烧技术相比具有独特和优异的污染物排放控制性能，最新工程实践发现改变炉内气固流化状态可以显著强化其脱硫脱硝能力，使烟气污染物硫氮氧化物（SO_2和NOx）原始排放浓度达接近甚至达到燃气轮机相当超低排放水平，然而，相关基础研究尚有重大不足。本项目以实验和模型研究相结合的方法，系统全面地揭示循环流化床锅炉流化状态对床内二个区域（密相区和稀相区）和三个尺度（颗粒微尺度、团絮结构介尺度和反应器宏尺度）的气固流动结构及其与床内传热、传质、燃烧及污染物化学动力学的耦合作用；揭示流化状态调整（如给料粒度分布，床层高度，固体循环流率等）对硫氮氧化物生成和降解的影响机制；总结归纳通过流化状态调整实现烟气污染物超低排放的可行机制和控制策略；形成燃煤循环流化床锅炉实现硫氮氧化物超低排放的理论。研究成果将促进循环流化床锅炉超低排放技术成熟化，为治理雾霾提供理论基础。

循环流化床燃煤技术与其他煤燃烧技术相比具有独特和优异的污染物排放控制性能，在立项之前的最新工程实践发现改变炉内气固流化状态可以显著强化其脱硫脱硝能力，使烟气污染物硫氮氧化物（SO_2和NOx）原始排放浓度达接近甚至达到燃气轮机相当超低排放水平，然而，相关基础研究尚有重大不足。本项目采用实验和模型研究相结合的方法，系统全面地揭示了循环流化床锅炉流化状态对床内二个区域（密相区和稀相区）和三个尺度（颗粒微尺度、团絮结构介尺度和反应器宏尺度）的气固流动结构及其与床内传热、传质、燃烧及污染物化学动力学的耦合作用；揭示了流化状态调整（如给料粒度分布，床层高度，固体循环流率等）对硫氮氧化物生成和降解的影响机制；总结归纳了通过流化状态调整实现烟气污染物超低排放的可行机制和控制策略；丰富了燃煤循环流化床锅炉实现硫氮氧化物超低排放的理论。研究成果将促进循环流化床锅炉超低排放技术成熟化，为治理雾霾提供理论基础。