Kinetics of reactions between magnetite and carbon monoxide between 723 and 823 K

Abstract

The kinetics of some reactions between carbon monoxide and magnetite were investigated between 723 and 823 K. Gas-phase mass-transfer effects within and near the porous samples and surface-reaction kinetics were considered. The experiments were done on sintered magnetite disks whose void fraction was 15 to 20 pct. A continuously weighed rotating disk reactor provided uniform mass transfer to the sample faces. The reacted disks were analyzed by Mössbauer spectroscopy and other methods. The only product species found were cementite and carbon, which suggested the existence of two reactions: the formation of cementite and carbon dioxide directly from magnetite and carbon monoxide, and the disproportionation of carbon monoxide to carbon dioxide and free carbon. These reactions were modeled mathematically. The surface kinetic data for both reactions were found to be compatible with rate expressions which were directly proportional to the square of the partial pressure of carbon monoxide and approximately inversely proportional to the partial pressure of product carbon dioxide.