Experimental study on operating conditions and bubble behavior of bubbling fluidized bed in stable operation state

From the perspective of facilitating the design of fluidized hydrogen reduction reactors for iron ore powder and maintaining stable operation, the operational conditions and bubble behavior in stable state fluidization of multi-particle size systems were investigated through cold-state experiments. To facilitate the identification of bubble behavior, a two-dimensional bubbling bed cold-state experiment was carried out using iron ore powder with a narrow particle size distribution and glass beads. Initially, the multi-stage fluidization characteristics of iron ore powder were examined. Then, using Geldart B-type glass beads to simulate a multi-particle size composition system, the particle size range and superficial gas velocity range for stable operation of the multi-particle composition system were explored. When the mass percentage of 150-μm glass beads was 15%, the stable fluidization operational gas velocity range was found to be (1.05–1.21) u_mf, where u_mf is the minimum fluidization velocity; when the content was 20%, the stable fluidized superficial gas velocity range was (1.09–1.26) u_mf. Under stable fluidization operating conditions, the dynamic behavior of bubbles (average equivalent diameter, rising velocity, and lateral migration velocity) was studied, and the quantitative relationship between the average equivalent diameter of bubbles and bed height in multi-particle size systems under stable fluidization conditions was also corrected. Additionally, the correlation between bubble rising velocity and bubble average equivalent diameter was established.