Study on the Dynamic Characteristic of the Circulating Fluidized Bed Whole Loop at Variable Load

Authors: Boyu Deng ^a, Man Zhang ^a, Yi Zhang ^a, Junfu Lyu ^a, Hairui Yang ^a and Mingming Gao ^b
a Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Energy and Power Engineering, Tsinghua University, Beijing, 100084, China
^b The State Key Laboratory of Alternate Electric Power System with Renewable Energy Sources, North China Electric Power University, Beijing, 102206, China

Source: This paper was published in the 13th International Conference on Fluidized Bed Technology in 2021.

Abstract: With more and more renewable energy power plants connecting to the power grid in China, to ensure the power quality and the security of the power grid, all thermal power units connected to the power grid are required to participate in the depth peak regulation, which proposes a high standard for the tracing performances to the load demand of all units. However, currently, the maximum load change rate of many circulating fluidized bed (CFB) units cannot satisfy the assessment criteria laid down by the power grid. To increase the ability of CFB units in load change and meet the ultra-low emission standard of China, it is necessary to first pay attention to the characteristic of the gas-solid flow in the CFB whole loop at variable load, which lays the foundation of other physical processes, to optimize the design and operation of CFB units. Aiming to develop a deeper understanding of the gas-solid flow in the CFB whole loop at variable load, a visual cold CFB test rig was built, which has a height of 10.3 m and a square section area of 0.1×0.1 m2. CFD models based on the test rig were also set up using CPFD Software Barracuda and were verified with experiments conducted on the same test rig at fixed and variable loads. The dynamic characteristic of the mass and pressure balance among the whole loop during the load changing process were studied by decreasing the fluidizing velocity in the riser. Results showed that the total particle mass in the standpipe decreased gradually whereas the pressure drop in the riser increased accordingly during the load reduction process.