Structure and Reactivity of Brazilian Iron Ores as Low-Cost Oxygen Carriers for Chemical Looping Combustion

Abstract

Chemical looping combustion (CLC) is one of the most efficient and advantageous CO2 capture technologies from an economic and energy point of view. An important key factor in this process is the oxygen carriers (OCs) used to transfer oxygen from the air to the fuel. In this work, three natural iron ores from Brazil were selected as interesting oxygen carriers for the CLC process due to their low cost and abundance in nature. Their chemical composition, redox properties, and structural evolution when submitted to a reactivity test in a thermobalance with 15% CH4 and H2 were investigated. The OCs (ItaHP-MG, ItaHP-RN, and ItaLP-RN) revealed good resistance to fracture, and their reactivity increased after the first reaction cycle due to the occurrence of an activation process, leading to a gain in reactivity in the following cycles. The reactivity tests showed that for all OCs, the reactivity with hydrogen was higher when compared to methane, highlighting ItaHP-MG oxygen carrier with relevant rate index values for both fuels (9.60%/min and 3.55%/min for H2 and CH4, respectively). However, OCs performed differently depending on the degree of use of the Fe2O3 phase. Interestingly, ItaHP-MG, with a high Fe2O3 content (96.5%), showed a regeneration of only 60%, while ItaLP-RN, whose Fe2O3 content is 41.5%, presented a degree of use above 85%. This effect is the result of preferential gas–solid interaction on the surface of the OC.

Performance Evaluation of Torrefaction Coupled with a Chemical Looping Gasification Process under Autothermal Conditions: Flexible Syngas Production from Biomass

“…As an essential intermediate product, syngas is used in many applications. For example, syngas can be converted into liquid fuels using Fischer–Tropsch technology, it can be used to produce methanol or glycol, and it can be a vital fuel for solid oxide fuel cells. , However, different applications require different syngas H 2 /CO ratios. For example, during methanol synthesis, syngas’s H 2 /CO ratio is usually 2.0; during Fischer–Tropsch synthesis, syngas’s H 2 /CO ratio varies from 0.6 to 2.0 depending on the catalyst; and the methanation reaction requires a H 2 /CO ratio of 3.0 .…”

Evaluation of Brazilian Iron-Based Ore and Industrial Waste as Low-Cost Oxygen Carriers for Chemical Looping Process

“…The CRJ OC also presented magnetite (Fe 3 O 4 ) and silica (SiO 2 ) phases that can act as support for the active phase, promoting greater chemical stability through successive redox cycles. 14,24 A lower percentage of the manganese dioxide (MnO 2 ) crystalline phase was also identified in the CRJ and ISR OCs. There are only crystalline phases of iron oxides in different oxidation states in the MSR sample diffractogram, with the presence of magnetite (Fe 3 O 4 ) and wustite (FeO) phases.…”

Chemical Looping Combustion and Gasification: A Review and a Focus on European Research Projects

“…The study of affordable, locally available natural ores as OCs is also important for the sustainability of CLC. Barros do Nascimento et al 103 investigated the suitability of three natural and locally abundant Brazilian Fe ores as OCs, by means of TGA redox tests at 950 °C.…”