Pedro VILLARIM1, Jaouad ZEMMOURI 2, Leila MOURA3
1Université du Littoral Côte d'Opale, Dunkerque, France
2Terrao, Coudekerque-Branche, France
3Queen’s University Belfast, Belfast, United Kingdom
Abstract
We are currently witnessing an increase in biogas production in the context of fossil fuel decline and the future circular economy. Biogas is nowadays considered alternative renewable energy. However, raw biogas contains undesirable compounds such as hydrogen sulfide, volatile organic compounds (VOCs) and carbon dioxide (CO2) that should be removed to upgrade biogas to biomethane to be used as vehicle fuels or injected into the natural gas grid. Biogas upgrading with physical absorbents, such as water and other commercial organic solvents, is simple, efficient and with low energy requirements for regeneration. Also, absorption is an effective method to capture undesirable compounds from biogas1.
In this work, the feasibility of biogas upgrading using three hydrophobic DESs, based on fatty acid (C8:C12, C9:C12 and C10:C12) as well as conventional solvents (glycerol, propylene glycol and propylene carbonate) as absorbent was studied. Three major volatiles compounds found as biogas impurities were selected (toluene, limonene and octamethylcyclotetrasiloxane) to evaluate the efficiency of these absorbents. The influence of different parameters like temperature, water content and VOC concentration was investigated. To this aim, we determined the vapor–liquid partition coefficient (K) of the VOCs in the studied DESs and conventional solvents. The absorption capacities of absorbent were also evaluated using the screening method for gas absorption with (CO2 and CH4) besides dynamic set-up simulating an industrial absorption column. This set-up allows the flow rate of VOCs, CO2 and CH4 to be modified2,3. Both static and dynamic results are in good agreement.
The results show a decrease in K value for all solvents compared to water, with hydrophobic DESs being the most effective solvents with a K value up to 646-fold lower for toluene, 20000 for limonene and 13648 for octamethylcyclotetrasiloxane4,5. The obtained results indicate that efficient VOCs and CO2 absorption can be achieved by the proposed hydrophobic DESs and conventional solvent also providing easy recycling and recovering process.
References
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Acknowledgements
P.V acknowledges the financial support from Dunkerque l’Energie Creative project (PIA3), Starklab and Région Hauts-de-France.