Abstract
Alumina supported Fe2O3 was prepared to evaluate its feasibility as an oxygen carrier for chemical looping using a thermogravimetric analyzer (TGA) and fixed bed reactor. Fe2O3/Al2O3 particles containing 60 wt% Fe2O3 and sintered at 1300°C demonstrated reasonable oxygen conversion. The reduction mechanism of Fe2O3/Al2O3 oxygen carriers was proposed based on the thermogravimetric analysis and XRD characterization. FeAl2O4 is formed and can serve as a supporting material as well as oxygen carrier in practical operations by using a moving bed reactor. The prepared Fe2O3/Al2O3 oxygen carriers demonstrated high CO2 yields in relation to syngas and methane combustion in the fixed bed reactor operated at temperatures higher than 500 and 850°C, respectively. Moreover, hydrogen generation was demonstrated to be feasible by steam oxidation with reduced Fe2O3/Al2O3 oxygen carriers for experiments conducted at temperatures above 800°C. The crush strength and TGA of Fe2O3/Al2O3 were examined, and the results showed that they had an appropriate crush strength and reasonable reactivity as oxygen carriers for use in a chemical looping process.
Highlights
Carbon dioxide (CO2) as one of the anthropogenic GHGs has been rapidly grown by 39% above pre-industrial levels at the end of 2010 (IPCC, 2011)
The crush strength and thermogravimetric analyzer (TGA) of Fe2O3/Al2O3 were examined, and the results showed that they had an appropriate crush strength and reasonable reactivity as oxygen carriers for use in a chemical looping process
For experiments conducted with Fe2O3/Al2O3 oxygen carriers sintered at temperature lower than 1000°C, the conversions of oxygen were independent on sintering temperature
Summary
Carbon dioxide (CO2) as one of the anthropogenic GHGs has been rapidly grown by 39% above pre-industrial levels at the end of 2010 (IPCC, 2011). The performance of prepared Fe2O3/Al2O3 oxygen carriers on CO2 yield with syngas and methane combustions, and on H2 generation by H2O oxidation were determined in a fixed bed reactor. The procedure of redox cycling was replicated for 50 times with Fe2O3 and Fe2O3/Al2O3 pellets to evaluate the reactivity and recyclability with respect to practical moving bed operation of chemical looping process. For reduction of Fe2O3/Al2O3 oxygen carriers with methane and syngas, 1.5 L/min reducing gas was introducing into the fixed bed reactor at various temperatures, ranging from 100 to 900°C. For H2 generation by steam oxidation of reduced Fe2O3/Al2O3 oxygen carriers, 50 mmol/min of steam was introduced into the fixed bed reactor at various temperatures, ranging from 500 to 900°C. Where FCO2, FCO, FH2 and FCH4 are the molar flow rates of CO2, CO, H2 and CH4 in the outlet stream, respectively
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