2011 Volume 52 Issue 6 Pages 1288-1293
A new process for producing ferromolybdenum powder master alloy without generating secondary pollutants by a two-step hydrogen reduction process involving MoO3 and mill scale has been developed. In this process, mill scale which is an iron byproduct generated from the steel rolling process is used as an iron source. Experimentally, ferromolybdenum powder master alloy was produced by a two-step hydrogen reduction process: The first hydrogen reduction stage was carried at a horizontal furnace for 60 min at 848 K under a hydrogen gas at a partial pressure of 101.3 kPa, and the second hydrogen reduction stage was done at the same furnace for 40 min at 1123 K under the same hydrogen partial pressure. In the process, the reduction reactions of MoO3 to MoO2 and mill scale to Fe proceed simultaneously in the first reduction step, and then the reduction reaction of MoO2 to Mo does in the second reduction step. The reaction rate of the second step in the two-step hydrogen reduction process of MoO3-Fe2O3 mixture was also measured under isothermal condition in hydrogen atmosphere using TGA equipment. As an example, at 1173 K under a hydrogen partial pressure of 101.3 kPa, almost 100% of MoO2 was reduced to Mo in 5 min. The nucleation and growth model were found to be applicable to the reaction rate. The reaction was first order with respect to hydrogen partial pressure and had an activation energy of 83.8 kJ/mol (20.1 kcal/mol).
