Study on the Fluidized Bed Reduction of Iron Ores

Abstract

The fluidized bed reduction of powdery iron ores has become the object of the authors' attention in view of special localized conditions in Japan and making practical use of domestic materials. In this experiment, fluidized bed reduction by hydrogen gas of one sample of hematite and magnetite was carried out on a laboratory scale.
The apparatus was designed so as to fluidize powdery iron are by flat perforated grids or funnel type grids in a stainless steel pipe. Samples were extracted through a sampling tube at proper time intervals to investigate the effects of various factors on the reduction rate.
The results obtained were as follows:
(1) The rate of reduction of hematite are under atmospheric pressure reached 90% in 20 minutes at 600°C, and over 90% in only 10 minutes at 700°C and 800°C.
(2) In the case of magnetite ore, the rate of reduction under atomospheric pressure reached 80% in 15 minutes at 600°C Contrary to the former case, it became more dificult to reduce the ore at above 600°C
(3) No distinct relation between the ore size and the reduction rate was observed.
(4) When the hydrogen gas amount was slightly over the minimum value enough to complete fluidization, the reduction rate was increased remarkably. But the effect of hydrogen gas amount was a little even when it was more increased.
(5) Using funnel type grids, the reduction time was shortend, therefore ore-treating capacities was increased. When the same quantity of ores was reduced, the rate of reduction with those grids reached the same as with flat perforated grids by using nearly one half of hydrogen gas amount.
(6) In fluidized bed reduction under increased pressure, the reduction rate reached nearly twice as much as under atmospheric pressure when a gauge pressure of 2kg/cm² was adopted at lower temperature.