(211c) Solar Thermochemical Reforming of Natural Gas Via Metal Oxide Based Redox Reactions
AIChE Spring Meeting and Global Congress on Process Safety
Wednesday, April 29, 2015 - 4:30pm to 5:00pm
Emission of greenhouse gases resulting from the combustion of fossil fuels such as petroleum oil, coal and natural gas is believed to be the major cause of global warming. CH4 and CO2 are the two most significant greenhouse gases contributing to global warming. Reforming of CH4 with CO2 converts them into syngas (a mixture of H2 and CO) which has a wide range usage in synthetic chemistry. Although CO2 reforming of CH4 is very attractive process, the energy required to carry out the reforming reaction is one of the major drawbacks which needs to be addressed. To resolve this issue, a metal oxide based two-step solar driven thermochemical CH4 reforming process can be a feasible option. In this process, the first step belongs to the solar reforming of CH4 (with and without CO2) producing syngas and the second step corresponds to solar water-splitting which yields into H2. The metal oxide material will be carbothermally reduced during the first step and reoxidized with the help of O2 from water in the second step. Hence, this material is not consumed during the reforming and water-splitting steps and the same ferrite material can be reused for multiple solar thermochemical cycles. In this study, thermodynamic analysis of the two-step metal oxide based solar thermochemical reforming of CH4 (first step) and water splitting (second step) was investigated in two sections with the help of commercial thermodynamic softwares such as HSC Chemistry and FactSage. In the first section, the thermodynamic equilibrium compositions for the metal oxide based solar thermochemical CH4 reforming and water splitting steps were determined at different experimental conditions and for various metal oxide systems. In addition, variations in the reaction enthalpy and Gibbs free energy and conversion of CH4 and H2O into syngas and H2 during solar thermochemical cycles were also studied in detail. In the second section, solar reactor analysis of the metal oxide based solar thermochemical reforming of CH4 and water-splitting reactions was performed by following the thermodynamic second law analysis. Effects of various process parameters were studied and the solar-to-fuel conversion efficiency for the process was determined. All the results obtained during this investigation will be presented in detail.
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