Kinetic analysis of the reduction of hematite fines by cold hydrogen plasma

Abstract

This study deals with the reduction of hematite fines by cold hydrogen plasma in the temperature range of 360–450 °C. It aims to examine the rate-controlling processes of fine hematite reduction by hydrogen plasma. The gaseous reduction was also performed for comparison. The reduction experiments were performed in a DC pulsed plasma reactor and the phases were characterized by X-ray diffraction. Reacted fraction curves were obtained by using the gravimetric technique. The kinetic analysis suggests that the controlling step of the hematite reduction process by cold hydrogen plasma was the nucleation and growth of iron on the magnetite substrate. The controlling step for the gaseous reduction process was found to be the chemical reaction at the magnetite–gas interface. The activation energy values obtained for cold plasma and gaseous hydrogen reduction processes were 68.5 and 87.2 kJ/mol.

Keywords

• Iron oxide reductions
• Hydrogen plasma
• Cold plasma
• Kinetic model
• Solid-state reaction
• Avrami-Erofe'ev equation