Abstract: The U-typed reduction chamber is the core reaction device of the iron suspension roaster. In order to study the fluidization characteristics， a cold experiment system of U-typed reduction chamber was established. Based on the experimental data collected by pressure fluctuation method， the following conclusions were drawn. Aeration velocity and particle size were the main factors affecting the initial fluidization velocity， while the initial bed height had little effect. With the increasing of initial bed height and aeration velocity， the pressure fluctuation in fluidization chamber became lower， but opposite result was obtained for particle size. Besides， power spectrum analysis revealed that the formation， coalescence and fragmentation of bubbles were the fundamental reasons for pressure fluctuation. The results would provide theoretical support for the design and optimization of the operating parameters during suspension magnetization roasting experiments.

Key words: fluidization, granular materials, initial fluidization velocity, pressure fluctuation, two-phase flow, bubble