Ilmenite–CO reduction kinetics. (1st February 2016)

• Record Type: Journal Article
• Authors: Perreault, Patrice; Patience, Gregory-S.
• Is Part Of: Fuel. Volume 165(2016)
• Page Start: 166
• Page End: 172
• Publication Date: 2016-02-01
• Subjects: Kinetics -- Chemical looping -- Ilmenite -- Preoxidation -- Mechanistic -- Modelling; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2015.10.066
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: Preoxidizing ilmenite reduces agglomeration but also its reactivity towards CO. Mechanistic kinetic model with external mass transfer. Model that accounts for more than 90% of the variance of the data. The kinetic model predicts sintering. Abstract: Secondary ilmenite is an inexpensive mineral that is a potential oxygen carrier for the chemical looping process. It has excellent mechanical stability, adequate heat capacity to transfer heat from the air reactor to the fuel reactor, and possesses a modest oxygen transfer capacity. Fresh and preoxidized ilmenite can transfer up to 1.7% and 1.2% oxygen on a mass basis, when reduced for 2 min with CO at 910 °C. Preoxidizing ilmenite reduces its tendency to agglomerate but it also reduced its reactivity towards CO. We characterized the kinetics of the reduction of preoxidized secondary ilmenite from South Africa with a mechanistic model. The model assumes CO reacts with surface oxygen atoms, and that bulk oxygen replenishes the surface oxygen. The model accounts for more than 90% of the variance in the data. The activation energies of the surface reduction and reoxidation steps are 51 kJ mol −1 and 89 kJ mol −1, respectively. The surface site density decreases with the reduction cycles via the simple power law expression because sintering deactivates the catalyst.