(321d) Syngas Production Via Chemical Looping

Authors: 
Bhavsar, S. K., US DOE-National Energy Technology Laboratory, Pittsburgh
Najera, M., US DOE-National Energy Technology Laboratory, Pittsburgh
Solunke, R. D., US DOE-National Energy Technology Laboratory, Pittsburgh
Veser, G., US DOE-National Energy Technology Laboratory, Pittsburgh


Chemical looping combustion is an emerging clean combustion technology with inherent CO2 capture in which an oxygen carrier (typically a metal) is exposed to cyclic oxidation/reduction with air and a fuel, respectively. By changing the nature of the oxidant, the chemical looping principle can be extended onto related fuel processing reactions. Specifically, by using steam as oxidant, fuel-cell ready hydrogen streams can be obtained as the effluent of the oxidizer reactor. Similarly, replacing air with CO2 as oxidant, CO is obtained as product of the carrier oxidation process. Using methane as fuel for these processes, the first process results in net steam reforming of methane, while the second process results in dry reforming, although in both cases the selectivities are significantly different from the conventional processes. For both of these chemical looping reforming (CLR) processes, significant challenges lie in the slower oxidation kinetics when using steam or CO2 as oxidants, as well as the high-temperature and mechanical stability of the carriers. We are reporting on a combined experimental and theoretical investigation, in which a range of metals was evaluated as carriers for CLR via thermodynamic screening, and select nanostructured carriers were synthesized and evaluated for their oxidation kinetics and high-temperature stability in CLR with pure CO2 and H2O, respectively, as well as mixed CO2 and H2O streams. The latter case results in the direct formation of syngas streams with tunable CO:H2 ratios. Finally, the feasibility of CLR in a periodically operated fixed-bed reactor was evaluated using a simplified pseudo-homogeneous reactor model.