An investigation of the critical influence of potassium on the reduction of wustite

Abstract

An investigation of the influence of potassium on the reduction of wustite single crystals has been carried out at temperatures ranging from 600 to 1000 °C in 30 pct CO-10 pct CO₂-3 pct H₂-57 pct N₂, a gas composition close to that of the reserve zone of the blast furnace. Three doping techniques have been used in order to perform either an insertion of potassium in the wustite lattice, by annealing, by surface doping at room temperature, or a doping by a potassium loaded reducing gas during the reduction. Regardless of which doping technique is used, no potassium has been detected in the wustite lattice. All dopings affect only the surface of the particles before the reduction. Potassium markedly increases the rate of reduction of wustite. This is explained first by the change in the morphology of the iron produced. In addition, potassium also acts on the chemical stage of the reduction by changing the nucleation and the growth of the iron. Another important result is the following: when potassium is added to partly reduced wustite, it changes the iron properties in the course of a subsequent reduction (this iron becomes much more permeable to the gas, increasing the transfer of the reactants).