During the process of solids circulation establishment in circulating fluidized beds (CFBs)

the solids circulation goes through a transition from an unstable state to a stable one. In this work

the stability of solids circulation in a CFB with limited bed inventory is studied by using a pressure transducer and a digital camera. The work reveals an interesting phenomenon

termed as oscillation circulation behavior of solids transportation between the riser and the downer through a solid control valve. Two important features are noted from the experimental results. Firstly

the gas-solid flow pattern in the riser and the downer is in transition between various fluidization regimes. Secondly

the pressure drop of the riser and the downer fluctuates periodically alternating between pd>pr and pd<pr. The calculation model of oscillation cycle is deduced by force analysis of oscillation process. Further study shows that solids oscillation behavior is controlled by the gas flow and valve opening. With a constant bed inventory

the oscillatory behavior is only initiated by the critical gas flow or valve opening. The oscillation cycle decreases with the decrease in gas flow but remains constant with varying solid control valve opening. The amount of solid transfer decreases with the decrease in gas flow and valve opening

while the pressure drop fluctuation decreases.