The current energy scenario demands a paradigm shift from fossil fuels-based to renewable fuels-based energy system to counter the challenges due to global warming. Among the renewable fuels, biogas is an environmentally friendly and sustainable fuel that faces a major challenge in processing due to the high amount of CO₂ present.
The current study reports biogas to liquid fuels process via chemical looping single moving bed reactor system using on Calcium Iron (CaFe) oxygen carrier. As-received biogas is directly fed to the top of moving bed reactor, while a mixture of CO₂ and H₂O is inlet from the bottom. While the biogas reacts with downward moving CaFe, the mixture of CO₂ and H₂O react countercurrently with the reduced CaFe, and the product syngas exits from the middle. Parametric studies have been conducted herein to study the effect of biogas composition, temperature, pressure, support to active material ratio, CO₂/H₂O ratios, etc on the outlet syngas quality to find the optimal operating conditions based on the quality of biogas received. Further, heat exchanger network has been designed to operate the system auto-thermally, meaning it can sustain without need of any external heat supply in steady state of operation. Exergy analysis has been conducted to compare the system with baseline systems.
To check feasibility, thermogravimetric studies have been conducted under the conditions suggested by process simulations. Previously, it has been found that doping Ni can increase the affinity of CaFe towards methane. For enhancing the regeneration kinetics, dopants have been screened by DFT simulations. Based on the DFT results, cobalt shows the maximum increase in the performance for CO₂ oxidation. Consequently, materials containing 1%, 2%, 5% and 10% Co haven been synthesized and tested in the TGA for reactivity and recyclability. Based on the results, 5% Co enhances the activity by maximum amount and gives a steady performance over prolonged number of cycles as well as increases the CO₂regeneration reaction kinetics. XRD and SEM analysis has been performed on the material before and after the redox tests to confirm the results.

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Lindsay Isom

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