Low-emission technology in the furnace of (CFB)circulating fluidized bed boiler

China's primary energy coal-based structure will not change in the future. Achieving efficient and clean utilization of coal is an important goal of China's energy development. At the same time, it is also an important starting point for safeguarding China's energy security and winning the "blue sky defense war." As an important technology for coal utilization, circulating fluidized bed combustion technology has outstanding advantages such as good fuel adaptability and low pollutant emissions, and is especially suitable for treating inferior fuels such as slime and coal gangue. In recent years, with the increasingly strict environmental protection requirements of the country, the main air pollutants for coal-fired boilers will fully implement ultra-low emission standards. That is, the NOx emission concentration is lower than 50 mg/m3, the SO2 emission concentration is lower than 35 mg/m3, and the dust emission concentration is lower than 10 mg/m3. The circulating fluidized bed boilers currently in operation cannot basically achieve the ultra-low emission of pollutants directly. The addition of additional flue gas treatment devices has made the circulating fluidized bed boilers lose their traditional environmental advantages and pose great challenges in terms of technological development and market competitiveness.

The Institute of Engineering Thermophysics of the Chinese Academy of Sciences undertook the project “Study on Low Emission Technology in 660MW Efficient Ultra Supercritical Circulating Fluidized Bed Furnace” in the National Key Research and Development Program “Ultra-supercritical Circulating Fluidized Bed Boiler Technology R&D and Demonstration”. Breakthrough in the technology of nitrogen oxide and sulfur dioxide depth control in circulating fluidized bed boilers.By improving the gas-solid flow characteristics of fluidized combustion, establishing a large-scale combustion space reduction atmosphere, optimizing key components of the boiler, and successfully developing a low-emission technology suitable for circulating fluidized bed boilers.

The technical achievements have been successfully applied to the 150 t/h CFB boiler of Xiangyu Biochemical Company through enterprise cooperation. In July 2018, Liaoning Provincial Boiler Performance and Quality Inspection Center was commissioned by the Institute to carry out operation inspection of the boiler. The results show that the NOx emission concentration at the outlet of the furnace is 38.3 mg/m3 and the SO2 emission concentration is 15.4 mg/m3. The original discharge of the boiler directly meets the ultra-low emission standard.

The successful validation of low-emission technology in CFB boilers has realized that the nitrogen oxides and sulphur dioxide at the outlet of boilers can directly meet the ultra-low emission standards. Without adding additional flue gas treatment devices, the technology meets the increasingly stringent national environmental protection standards and greatly improves the market competitiveness of CFB boilers. The research results will also provide technical support for the development and demonstration of 660MW high-efficiency ultra-supercritical circulating fluidized bed boilers in the national key R&D projects.