Increasing energy efficiency in chemical looping combustion of methane by in-situ activation of perovskite-based oxygen carriers

• Published in: Applied energy Vol. 287; p. 116557
• Main Authors: Cabello, Arturo, Abad, Alberto, Gayán, Pilar, García-Labiano, Francisco, de Diego, Luis F., Adánez, Juan
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2021
• Subjects: Activation; Chemical looping combustion; CO2 capture; Energy efficiency; Methane; Perovskites; Methane; Perovskites; Activation; Energy efficiency; CO2 capture; Chemical looping combustion
• ISSN: 0306-2619; 1872-9118
• DOI: 10.1016/j.apenergy.2021.116557

[Display omitted] •Activation of a CaMn-perovskite achieved in a chemical looping unit.•Combustion efficiency improved with activated material.•Flexible attrition and activation depending on variation in solids conversion.•Suggestions for the scale-up of the activation process are given.•Activation has implications on energy efficiency. CaMnO3-based perovskites are attractive for use as oxygen carriers in chemical looping combustion (CLC) because they are made from cheap materials (manganese, calcium). However, these materials show low reactivity with methane, and high oxygen carrier-to-fuel ratios (ϕ) are required to achieve complete fuel combustion. It is believed that energy efficiency in the chemical looping process would be improved if the reactivity of these materials were higher. In this work, the increase in reactivity of a perovskite (CaMn0.775Mg0.1Ti0.125O2.9-δ) material is evaluated during its in-situ activation under determined operating conditions in a 0.5 kWth CLC pilot plant. The combustion efficiency of methane over 60 h of continuous operation was analysed taking into consideration the effect of operating conditions on the activation process for increasing the reactivity of the perovskite. The material increased in reactivity as the ϕ ratio decreased to below 6, improving combustion efficiency. Moreover, the material was pre-activated by being fully reduced in the CLC plant. The conversion of methane with the pre-activated material was subsequently higher than the conversion achieved before the activation process, and almost complete combustion was achieved at a lower ϕ ratio. Characterization of the particles after the combustion tests showed good stability of the material with the operating time, although a negative effect on the crushing strength was observed when the particles were highly reduced. The impact of the perovskite material activation on the energy efficiency of the process is discussed.