Improvement of Reducibility by Pre-reduction in Low Temperature

Abstract

Self-fluxing sinter, basic pellet and acidic pellet were pre-reduced at low temperatures (500, 600 or 700°C) for several minutes, then heated quickly and reduced again at a high temperature (900°C). The gas utilization coefficient at the same reduction degree was increased by the pre-reduction. This effect was the largest in the case that the pre-reduction temperature was 600°C and the pre-reduction degree was 11%.
Using the parallel model with 3 interface reductions, reaction rate constants for wustite, magnetite and hematite reduction were calculated from these experimental data by electronic computer. The reaction rate constant on the reduction from magnetite to wustite, K_ma and that from hematite to magnetite, K_he were increased by pre-reduction at low temperature, but that from wustite to iron, K_wu, was remained unchanged. In the case of sinter, K_ma and K_he were increased about 3 times on the pre-reduction at 600°C, and about 2 times at 500°C and 700°C.
This effect may be considered with the calculation of countercurrent reduction of descending ore bed.