Abstract
Authors presented the following empirical equation on the rate of reducing reaction. dW/d t=-K (W0-w)
where W0 is oxygen volume combined with iron in are (g/cm3), w is oxygen volume combined with iron in are after reduction for some time (g/cm3), W is oxygen volume removed per unit time with reduction (g/min), K is reaction rate constant, and t is time (min), so that W is equal to W for t=0.
Authors have studied on the fluidized bed reduction of iron are powder by hydrogen gasunder atmospheric or increased pressure with a laboratory scale apparatus.
On the basis of the above equation, the mechanism of fluidized reduction was discussed.
The results are as follows.
1) For fluidized bed reduction under atmospheric pressure at less than 500°C, the reduction rate is considered to be controlled by its reaction rate. Meanwhile it is controlled by diffusion rate over 600°C. In the intermediate temperature region, the reduction is affected by both these rates.
2) The reduction under increased pressure is controlled by the reaction rate near 400°C, while it is controlled by the diffusion rate over 5000°C.
3) The effect of gas film on the surface of particles becomes important with a decreasing flow rate, especially below 20l/min for 50mm ∅; bed.
