Abstract
ABSTRACT Chemical looping air separation (CLAS) is a novel and efficient method of producing high-purity oxygen because of its low-energy demands. Cu-based materials are suitable oxygen carriers (OCs) for CLAS. In the current study, Cu-based OCs in different particle sizes were prepared using various methods (viz., through mechanical mixing, impregnation, and coprecipitation) and different supporting materials (viz., ZrO2, SiO2, and Al2O3) and porosities (viz., in the mesopore range). This study evaluated the reactivity, reaction kinetics, and recyclability of these OCs by measuring their conversion rates for reduction (oxygen release) and oxidation (regeneration) in a thermogravimetric analyzer. CuO OCs on ZrO2 nanoparticles prepared through impregnation (CuZr-IM) exhibited almost complete conversion and the fastest reaction rates of all the OCs for reduction and oxidation. These characteristics are primarily attributable to the fine particles (100–250 nm) of the OCs. Furthermore, the CuO on the surface of the ZrO2 particles was distributed in a uniform pattern, as these fine particles displayed greater oxygen mobility and more rapid diffusion than the micrometer-sized particles paired with bulk materials. Kinetic analysis revealed that Avrami-Erofe’ev random nucleation and the subsequent growth reaction model with n = 2 (A2), with an observed activation energy of 140.2 kJ mol–1 in our study, is the optimal fitting for CuZr-IM OC conversion during reduction, and a long-term-stability test indicated that this OC is an appropriate candidate for CLAS.
Highlights
Oxy-fuel combustion is used for thermal power generation and as one of the carbon capture and storage technologies (Scheffknecht et al, 2011)
CuZr-IM oxygen carriers (OCs) can be classified as fine particles
The reactivity and conversion rates of novel Cu-based OCs prepared with various methods and different supporting materials for Chemical looping air separation (CLAS) were studied
Summary
Oxy-fuel combustion is used for thermal power generation and as one of the carbon capture and storage technologies (Scheffknecht et al, 2011). Oxy-fuel combustion is the process of burning fuel using pure oxygen instead of air. It produces exhaust, which primarily comprises CO2 and H2O. In the oxy-fuel combustion process, the required oxygen is produced through air separation (Smith and Klosek, 2001). The oxygen-specific power of the CAS process is 0.3–0.6 (kWh)ꞏ(m3 O2)–1 (Fan and Zhu, 2015). The oxygen-specific power of the PSA was approximately 0.4 (kWh)ꞏ(m3 O2)–1. Membrane separation is another favorable technology for oxygen separation from air. Compared to CAS and PAS methods, ITMs are usually applied to small volumes of O2 production (approximately 20 t d–1) and generate extremely high-purity oxygen (> 99%). Chemical looping process (CLP) has been developed over the past few years
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