Gas-solid hydrodynamic steady-state operation is the operating basis in a chemical looping dual-reactor system. This study reported the experimental results on the steady-state operation characteristics of gas-solid flow in a 15.5 m high dual circulating fluidized bed (CFB) cold test system. The effects of superficial gas velocity

static bed material height and solid returning modes on the steady-state operation characteristics between the two CFBs were investigated. Results suggest that the solid distributions in the dual CFB test system was mainly determined by the superficial gas velocity and larger solid inventory may help to improve the solid distributions. Besides

cross-returning mode coupled with self-returning is good for steady-state running in the dual-reactor test system.