• Lelivelt, D. W. J.
• Hessels, Conrad
• Finotello, Giulia
• Stevens, N. C.
• Deen, Niels G.
• Tang, Yali

Abstract

The fluidization and reduction behavior of micron-sized iron oxide powder, produced by iron combustion, is studied in a lab-scale cylindrical fluidized bed. The minimum fluidization velocity u mf is found to stabilize above normalized static bed heights of 0.5 H/D (static bed height divided by the bed diameter). u mf is measured as a function of temperature between 280 and 860 K for both H 2 and N 2 as fluidizing gas. The experimental results start to deviate from the Ergun correlation at temperatures above 560 K, both for N 2 and H 2 . A new correlation, taking the cohesive inter-particle solid bridge force into account, is proposed in this work to predict the minimum fluidization velocity at high temperature. Reduction experiments are carried out for a total time of 5 h at constant excess velocity with 50, 75 and 100 vol% of H 2 and temperatures between 623 and 823 K. Gradual defluidization occurs when the operating temperature exceeds 800 K. A maximum reduction degree of 61% is obtained at 807 K and 100 vol% H 2 .

Topics

• impedance spectroscopy
• experiment
• combustion
• iron
• iron powder