Abstract: [Objectives] When a large circulating fluidized bed (CFB) boiler is involved in deep peaking, the fluidization quality in the furnace decreases. In order to enhance the fluidization effect of particles in CFB boilers during peaking, the concept of a pulsed hood has been proposed. [Methods] By adding a Helmholtz oscillating chamber to the inlet duct of the hood, the outlet airflow can be made to show a certain frequency of pulse variation and the pulsed hood to be designed can be obtained. Based on the visualization test bench, the cold state test research of a single impulse hood is carried out. By analyzing the time-domain and frequency-domain variation rules of the pressure at different positions of the hood, its pulse characteristics are obtained. Obtain the resistance characteristics based on the variation of pressure drop between the inlet and outlet of the hood. The fluidization characteristics are obtained by analyzing the particle disturbance range and gas-solid flow around the hood.[Results] The pulse frequency is concentrated at 18~24 Hz, and there is still some pulse intensity when the load is less than 40%. The pressure drop at both ends of the pulsed hood increased with the increase of load, and the full load was 2.2 kPa. Compared with the bell-type hood, the disturbance range of the pulsed hood for large particles increased by 8.0%, 11.1%, and 15.7%, and the pile-up height of the large particles decreased by 2.1%, 2.5%, and 2.9%, respectively, at the loads of 40%, 70%, and 100%.[Conclusions] The addition of Helmholtz oscillating chamber can make the outlet of the hood to produce pulse airflow, strengthening the gas-solid contact, thus increasing the disturbance of the bed material particles, reducing the accumulation height of large particles, and significantly improving the fluidization quality of the particles.

Key words: circulating fluidized bed (CFB) boiler, deep peaking, hood, impulse characteristics, drag characteristics, fluidization characteristics, gas-solid flow