1981 Volume 67 Issue 11 Pages 1943-1951
Single basic hematite-pellets (porosity 24%) are reduced in two reactors of 54 and 156 mm I.D. over a temperature range from 600° to 1 000°C and a flow-rate range 0.1 to 20 Nl/min. In the initial stage of reduction, hydrogen is diluted by nitrogen which flows through a reactor until it reaches a set temperature, and the reaction retards especially at low flow rates. In the course of reduction, hydrogen is also diluted by the product gas (H2O). For these dilution processes, the dispersion model has been introduced into the unreacted-core shrinking model for one interface in consideration of the resistance due to the rate of gas flow proposed by Clair.
Contribution of this resistance, denoted by κ (0≤κ≤1, κ=0 and 1 imply the analyses without and with the resistance proposed by Clair, respectively), is examined by comparing calculated reduction curves with experimental ones: The value of κ increases as the flow rate decreases. With appropriate selection of kinetic constants, the modified model produces a greatly improved fit to experimental data.