110th Anniversary: Indirect Partial Oxidation of Methane Using a Counter-Current Moving-Bed Chemical Looping Configuration for Enhanced Syngas Production

Syngas is a valuable chemical intermediate for producing commodity chemicals, such as olefins, methanol, liquid fuels, etc. The chemical looping route for syngas production presents an attractive alternative to state-of-the-art technology, such as partial oxidation, autothermal reforming, and steam methane reforming. Out of the several chemical looping configurations, the co-current moving-bed reactor with iron titanium composite metal oxide particles has demonstrated a high-purity syngas production. In this study, an alternative reactor configuration (indirect chemical looping system) is proposed to the co current moving-bed reactor system (direct chemical looping system) to enhance the syngas yield. The indirect chemical looping system consists of a fuel reactor and a syngas generation reactor, both operated in countercurrent mode, with respect to the gas-solid flow, as opposed to just one co-current fuel reactor in the direct chemical looping system. This unique gas-solid contact pattern in the indirect chemical looping system aids in greater utilization of CO2 and H2O and improves the thermodynamic performance for syngas production. Thermodynamic simulations in Aspen Plus software are performed for system analysis and comparison under isothermal and autothermal conditions. Isothermal analysis at several different temperatures and pressures, with and without co-injection of CO2/H2O, is conducted to explain the behavior of the proposed system. Autothermal operation of the system under different pressures is also evaluated to determine the maximum syngas yield within the constraints of a practical system for syngas production to further produce liquid fuels via Fischer-Tropsch synthesis. The results from these simulations are compared against the direct chemical looping system to highlight the difference in thermodynamic constraints between the two processes. The oxidation behavior of reduced Fe2O3-MgAl2O4 with CO2 and H2O is experimentally tested at different pressures and temperatures to gain an understanding for the syngas generation reactor in the indirect chemical looping system.