Reduction and oxidation kinetics of Fe–Mn-based minerals from southwestern Colombia for chemical looping combustion

8 Figuras, 8 TablasThe oxygen carrier (OC) is the main component of the chemical looping combustion (CLC), process. Most OCs have been developed synthetically using an active metal oxide combined with an inert material. When solid fuels are used, the OC becomes mixed with the ashes generated during the CLC process and has to be removed, thereby increasing costs. As a result, there is growing interest in the use of low-cost OCs based on manganese and iron. Given the widespread use of coal to produce energy, there is a trend toward the study of the CLC process using solid fuels, since this process has the lowest energy penalties of all the combustion methods involving CO2 capture. Coproducts from the exploitation of Mn and Fe ores have been studied. These materials were selected from a group of eight minerals with Fe and Mn present in their composition, extracted from mines located in southwestern Colombia. The material selection process was based on crushing strength analysis and reactivity in thermographic analysis (TGA), using CH4 as fuel. Two materials were selected, one based on Fe and another based on Mn, which presented the best behavior in their respective group. It was found that the studied two materials were more reactive with H2 and CO than with CH4. This was demonstrated by performing a kinetic study using a shrinking core model (SCM). The selected Mn-based oxide was evaluated to identify whether it had the properties required for chemical looping with oxygen uncoupling (CLOU), commonly found in Mn minerals with a high silica content. However, no evidence to this effect was found in experiments at 1000 °C using N2 for OC decomposition and air as an oxidizing gas. The Mn ore showed the highest reactivity of all the studied materials, with a rate index of 11.9%/min in experiments at 950 °C using H2 as the reducing gas. Finally, it can be concluded that the presence of silica improves the reactivity of the Mn ore, making it a promising carrier for use in in situ gasification chemical looping combustion (iG-CLC) technology.This research was conducted with financial support from Unión Temporal Incombustion (Temporary Joint Working Group) and Colciencias through Recoverable Assistance Agreement RC 0852-2012. We are grateful for the collaboration shown by Instituto de Carboquímica, Zaragoza (Project ENE2016-77982-R and European Regional Development Fund (ERDF)).Peer reviewe