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

摘要

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 kWth) 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–γAl, Ni21–γAl, Ni18–αAl and Fe20–γAl. The oxygen carriers were prepared by impregnation on γ- and α-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–γAl and Ni18–αAl fulfill all the requirements to successfully conduct a CLC process and almost 100% CO2 capture efficiency was obtained. On the contrary, the Ni21–γAl 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 °C) would be necessary to make use of the Fe20–γAl material feasible.