Kinetics of the low-temperature hydrogen reduction of single-crystal magnetite

Abstract

The hydrogen reduction of plates made from synthetic magnetite single crystals is studied in the temperature range 400–570°C. A mathematical model is developed and applied to describe the kinetics of gaseous reduction of plane finite objects. The following time contributions of individual process stages are distinguished with the least squares method and numerical integration: the nucleation of an iron phase, a chemical interaction of magnetite with hydrogen, and external and internal mass transfer. The diffusion and kinetic reduction parameters are calculated. The activation energy of the chemical stage (87.5 kJ/mol) is determined. An equation for the rate constant of the interaction of magnetite with hydrogen is proposed for temperatures below 570°C. A significant effect of the processes of consolidation and sintering of reduced iron on the internal diffusion parameters is detected in the low-temperature range.