Microstructural Stability of Tailored CaMn_0.875−xFe_xTi_0.125O_3−δ Perovskite Oxygen Carrier Materials for Chemical Looping Combustion

Abstract

CaMn1−xTixO3−δ are state‐of‐the‐art perovskite‐type oxygen‐carrier materials (OCMs) used in gaseous fluidized‐bed chemical looping combustion (CLC), which is currently undergoing upscaling and demo campaigns in several large pilot plants around the world. CLC requires control of oxygen release and uptake by the oxygen‐carrier material. The flexibility of the perovskite's structure allows a wide range of substitutions, which can be beneficial for tuning the properties. In this study, we investigate the beneficial effect of iron substitution on the microstructural stability of tailored CaMn0.875−xFexTi0.125O3−δ perovskite oxygen carrier materials for chemical looping combustion. The redox performances of the substituted compounds under different reducing atmospheres are discussed. During operation in a fixed‐bed reactor, methane conversion occurred without any soot formation. It was demonstrated that iron substitution improved the spontaneous release of oxygen and the oxygen‐transfer capacity of the material for moderate iron substitution close to x=0.15. Iron substitution also effectively limited the degradation of the microstructure of the particles during redox cycling.

Highly Stable Dual‐Phase Membrane Based on Ce0.9Gd0.1O2–δ—La2NiO4+δ for Oxygen Permeation under Pure CO2 Atmosphere

“…Oxygen has been recognized as an essential chemical for power plants based on fossil fuel consumptions such as integrated gasification combined cycle and oxy‐fuel combustion, which have been recognized as the most realistic clean energy technologies for energy production with carbon capture and storage. Unfortunately, the current industrial tonnage oxygen production is still mainly achieved by the conventional cryogenic distillation technology, a very expensive technique .…”

Fabrication process parameters significantly affect the perovskite oxygen carriers materials (OCM) performance in chemical looping with oxygen uncoupling (CLOU)

“…On A-site doping, partial substitution of the calcium by strontium, barium and lanthanum [12,13] is reported, as well as A-site-deficient compounds [14,15]. More relevant and interesting is the doping of the transition metal on the B-site, with partial substitution of manganese by magnesium, iron, titanium, or a combination of two or more of them [14][15][16][17][18][19][20][21][22][23][24][25]. Although it has limited miscibility in the perovskite structure, magnesium has positive catalytic effect on the methane reforming.…”

“…Furthermore, it has been shown that it has good chemical stability and shows small dimensional changes upon redox cycling [30]. It is also observed that the re-oxidation is faster for Ti-substituted CaMnO 3 at high temperatures [22], and additional Fe doping positively influences the reduction reaction rate and broadened the operation window of the OCM to lower temperatures as well as improve microstructural stability during redox cycling [16]. Although Ti-doping does not assist with the known sulfur intolerance of CaMnO 3 [14, 20,21], remedial technologies for reactivation of the poisoned OCM in situ (in the fuel reactor) are already developed [31].…”

Manufacturing of Perovskite Oxygen Carriers by Spray Granulation for Chemical Looping Combustion

“…It has been demonstrated that CaMn 0.875 Ti 0.125 O 3− δ (CMT) is a promising OCM . Furthermore, it has been shown that iron substitution improves the spontaneous release of oxygen (later called chemical looping oxygen uncoupling, CLOU) as well as providing higher conversion and less degradation of the microstructure . The method of manufacturing the OCM is the second decisive factor.…”

“…Two types of self‐supported OCMs, based on the promising calcium manganite titanate perovskite were investigated: Ca 0.98 Mn 0.875 Ti 0.125 O 3 (CMT) and Ca 0.98 Mn 0.75 Fe 0.125 Ti 0.125 O 3 (CMTF125) with 12.5 % iron on the B‐site of the perovskite. The performance characteristics of these two materials as OCMs for fluidized‐bed CLC were published separately . CMTF125 was also coated on α‐alumina (CMTF125@alumina).…”