With the progress in blast furnaces and direct methods of steel making, it has become necessary to make clear the mechanism of are reduction in bed. There are few data available for calculation of the reduction speed.
Thereupon the auther measured the reduction speed of are bed under the following conditions;
Ore: Self-fluxing sinter, Indian ore and Korean ore,
Weight: 200, 100, 50, 25, 12·5g.
Size: 1-2·5, 2·5-5, 5-10, 10-20, 20mm up
Bed; Dia: 4, 27, 20mm.
Thick: About 5, 10, 20, 40, 80mm.
Reducing gas. ; CO flow 0·25, 0·5, 1, 2, 3·2 Nl/mn.
N2 0, 70%. CO2 0, 10, 20%.
(The italics indicate the standard conditions.)
To indicate the reduction speed, it is advantageous to use “Reduction degree-CO2/ (CO+CO2) curve” for each contact time. At equilibrium, this curve has the steps whose heights indicate CO2/ (CO+CO2) of the equilibrium mixture over Fe-FeO, FeO-Fe3O4, and Fe3O4-Fe2O3.
At any contact time, the curve deviates lower than these steps. With charging are size and contact time, this curve follows the relation of potential function. At the same contact time, this curve is slightly affected by gas speed. But when its speed exceeds a certain value, the curve seems to be little affected by the speed.
Even with CO+N2 mixed gas, these relations hold. CO2 in CO gas little affects these relations in the range of 20% and at the contact time 0·23 second.