Bioethanol combustion with CO2 capture in a 1 kWth Chemical Looping Combustion prototype: Suitability of the oxygen carrier

The use of a renewable liquid fuel, such as ethanol, in a Chemical Looping Combustion (CLC) process, in the context of carbon capture and sequestration (CCS) technologies can lead to carbon negative power system. This work presents experimental results obtained in a continuously operating CLC unit (1 kW(th)) using ethanol as fuel during more than 100 h. Complete ethanol conversion was reached under all operating conditions. The combustion efficiency as a function of the oxygen carrier to ethanol ratio was determined for four oxygen carriers: Cu14-gamma Al, Ni21-gamma Al, Ni18-alpha Al and Fe20-gamma Al. The oxygen carriers were prepared by impregnation on gamma- and alpha-Al2O3. The performance of these materials was evaluated on the basis of their reactivity with ethanol and its intermediate gaseous products. The suitability of the use of the oxygen carriers was finally decided by taking into account oxygen transport capacity and hydrodynamic criteria. Cu14-gamma Al and Ni18-alpha Al fulfill all the requirements to successfully conduct a CLC process and almost 100% CO2 capture efficiency was obtained. On the contrary, the Ni21-gamma Al oxygen carrier was discarded due to the low reactivity of the spinel NiAl2O4 at normal operating conditions. Iron-based materials are suitable for the CLC process, although higher Fe-content or higher operating temperatures (950 degrees C) would be necessary to make use of the Fe20-gamma Al material feasible. (C) 2015 Elsevier B.V. All rights reserved.