Reaction kinetics of direct reduction of mineral iron carbonate with hydrogen: Determination of the kinetic triplet

Astrid Loder, Simone Santner, Matthäus Siebenhofer, Andreas Böhm, Susanne Lux*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Direct reduction of mineral iron carbonate with hydrogen is a CO2-lean technology for the production of elemental iron from iron carbonate ore. In this study, the reaction mechanism and reaction kinetics were investigated by thermogravimetric analysis and in a fixed-bed tubular reactor. The degree of metallization increases with increasing temperature from 773 to 1023 K. At 1023 K, the degree of metallization is 93 wt%, with the remaining iron species being wüstite. The reduction proceeds via two reaction pathways: calcination of iron carbonate to wüstite with consecutive reduction of wüstite to elemental iron and direct reduction of iron carbonate to elemental iron. The reaction steps occur simultaneously. During the first hour of reaction, which corresponds to the heat-up phase, calcination of iron carbonate to wüstite adopts the dominant reaction path. Then wüstite reduction and direct iron carbonate reduction with hydrogen to elemental iron, become dominant, facilitated by the increasing porosity of the ore due to the release of CO2. Towards the end of the reduction process the remaining wüstite is reduced to elemental iron. The kinetic triplet – solid phase reaction kinetic model, activation energy and frequency factor – was determined for each reaction step. The reaction kinetics can be described by a combination of an Avrami-Erofeyev model (A3 model for iron carbonate calcination to wüstite), and reaction-order models (F2 model for the reduction of iron carbonate to elemental iron and F3 model for the reduction of wüstite to elemental iron).

Original languageEnglish
Pages (from-to)575-589
Number of pages15
JournalChemical Engineering Research and Design
Volume188
DOIs
Publication statusPublished - Dec 2022

Keywords

  • Avrami-Erofeyev model
  • Hydrogen reduction
  • Reaction-order model
  • Siderite ore
  • Solid-state kinetics

ASJC Scopus subject areas

  • General Chemistry
  • General Chemical Engineering

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