Ca_0.9Mn_0.5Ti_0.5O_3−δ: A Suitable Oxygen Carrier Material for Fixed-Bed Chemical Looping Combustion under Syngas Conditions

Abstract

Power generation using chemical looping combustion (CLC) technology has emerged as a promising CO 2 -capture-based alternative to conventional technology. In this study, the performance of a Ca 0.9 Mn 0.5 Ti 0.5 O 3−δ perovskite-type oxygen carrier material for use in fixed-bed CLC reactors is investigated. The main focus of the study is on the material's oxygencarrying capacity and reactivity with and conversion of syngas in the fixed-bed reactor. Pressurized thermogravimetric analysis in model gases indicates neither Boudouard coking nor reactivity of the oxygen-carrier material toward CO 2 . A fuel gas conversion of 95% was achieved in the fixed-bed reactor using this oxygen-carrier material.

Ca1−A MnO3 (A = Sr and Ba) perovskite based oxygen carriers for chemical looping with oxygen uncoupling (CLOU)

“…Up to 8.8% decrease in initial decomposition temperature was reported for perovskite supported mixed metal oxides. As a standalone oxygen carrier, perovskites of the CaMnO 3 family are extensively studied for CLOU and CLC applications [20,[29][30][31][32][33][34][35][36][37][38][39]49,[57][58][59][60][61]. While its oxygen uncoupling capacity is smaller than copper oxides, CaMnO 3 , which can be synthesized from abundantly available manganese ores and Ca precursors [29,60], has been reported to be active for solid fuel conversions [29,31,34,36].…”

“…Pishahang et al investigated Ca 1Ày Mn 1Àx Ti x O 3Àd oxygen carriers under fixed bed conditions using syngas as the fuel [38]. The authors reported that adding Ti and decreasing the Ca content increased stability of the oxygen carrier.…”

Microstructural Stability of Tailored CaMn0.875−xFexTi0.125O3−δ Perovskite Oxygen Carrier Materials for Chemical Looping Combustion

“…For instance, too‐early release of oxygen in the loop‐seal (the chamber filled with steam separating the air and fuel reactors) should be limited, and oxygen should be released as quickly as possible in the fuel reactor of a circulating fluidized bed (CFB) CLC system. This aspect is even more critical in the case of a fixed‐bed CLC reactor, in which oxygen release during inert flushing should be prevented . In addition to kinetics, the OCM must retain several qualities during the reduction/oxidation (redox) cycles such as high oxygen capacity, high redox kinetics, and good mechanical properties such as low fragmentation, low attrition, and low agglomeration.…”

“…For CLC applications, substitution of calcium by strontium and barium has been considered. Furthermore, the substitution of manganese by magnesium, titanium, or a combination of both has been investigated. Substantial improvements from iron substitution were reported .…”

Performance of Perovskite‐Type Oxides as Oxygen‐Carrier Materials for Chemical Looping Combustion in the Presence of H2S

“…On the other hand, for gas‐based CLC, sophisticated OCMs with longer lifetimes are of greater interest. OCMs with perovskite‐type structures are attracting increasing interest thanks to their redox tunability by controlling various dopants in the structure . Perovskites are normally formulated as ABO 3− δ , in which A is a large alkaline earth or rare earth and B is a smaller transition‐metal cation .…”