Effect of Elevated Pressure on Gas-Solid Flow Characteristics in a Circulating Fluidized Bed

Gas-solid fluidized beds are extensively applied because of their excellent heat and transfer properties. The pressurized Circulating Fluidized Beds (CFB) are found in some applications, e.g, the pressurized oxy-fuel combustion for CO₂ capture. The particle concentration profile and solid circulating rate are crucial parameters, which affect the design of pressurized CFB reactor. In the current study. A cold pressurized CFB experimental device is established. The inner diameter of the riser is 50 mm and the height is 3300 mm. Geldart B glass beads with an average particle size of 250 μm and a density of 2550 kg/m³ is used as material. The operation pressures ranges from 0.1 MPa to 0.6 MPa. The distribution of the particle concentration along the axial and radial directions in the riser is studied. The result shows that, as the pressure is increased, the particle concentration presents a slight increase in the top and middle parts of the riser, while the particle concentration in the bottom part of the riser does not change obviously. The particle concentration is generally higher near the wall under different pressures, but the particle concentration changes slightly along the radial direction under different pressures.

A further analysis of pressure fluctuation shows that the domain frequency of the particle concentration sequence signal is around 5 Hz based on the power spectrum density curves. The domain frequency increases with increasing pressure and decreases with increasing circulating flow rate. The average gas-solid slip velocity decreases at the same particle concentration conditions and particle circulation flow rate.