Thermodynamic analysis of solar-driven chemical looping steam methane reforming over Cr2O3/Cr redox pair

Abstract

Thermodynamic analysis of the Cr2O3/Cr based CH4 reforming (MR) and water splitting (WS) cycle is conducted and the results obtained are reported in this paper. For this study, two process configurations are considered: a) CS process - Cr2O3/Cr based MR open process, and b) CSH process- Cr2O3/Cr based MR and WS semi-open process. The equilibrium compositions associated with the Cr2O3/Cr based MR are determined and the obtained results indicate that the appropriate methanothermal reduction (MTR) temperature to achieve maximum yield is 2050 K. Likewise, the WS reactions is feasible in the temperature range of TL = 500 up to 2050 K. The total solar energy required to drive the CS process (Q-solar-CS) rises by 1498.8 kW as the CH4/Cr2O3 molar ratio upsurges from 0.5 to 3. In case of the CSH process, when the TL increases from 500 to 1400 K, the Q solar CSH decreases by 54.5 kW and further surge in the TL from 1400 to 2050 K yields into upturn in the Q-solar-CSH by 108.5 kW. Both CS and CSH processes are further compared by considering the best-case scenario and the comparison shows that the CSH process possess higher solar to fuel CSH = 71.1% than the solar to fuel CS = 54.0%. The solar to fuel CSH and solar to fuel CS can be further escalated up to 78.9% and 57.8% by occupying 50% of the heat recuperated by the coolers and WS reactor.