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Process Evaluation of Fluorinated Ionic Liquids as F‑Gas Absorbents

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journal contribution
posted on 08.09.2020 by Julio E. Sosa, Rubén Santiago, Daniel Hospital-Benito, Margarida Costa Gomes, João M. M. Araújo, Ana B. Pereiro, José Palomar
The environmental impact of fluorinated gases (F-gases) necessitates the development of green technologies to mitigate them. Fluorinated ionic liquids (FIL/ILs) emerged as an alternative absorbent due to their unique and exceptional properties. In this work, a COSMO-based/Aspen Plus methodology was used to evaluate the performance of FIL/ILs as absorbents in the process scale of two F-gases: 1,1,1,2-tetrafluoroethane (R-134a) and difluoromethane (R-32). Results of the absorption column in equilibrium mode revealed that the behavior of FIL/ILs is similar under the same conditions, reaching higher efficiencies in the case of absorbing R-134a at a high F-gas partial pressure. Rate-based calculations in packing column demonstrated a kinetic control with highly viscous FIL/ILs, revealing higher performance differences between FIL/IL absorbents. The regeneration stage was also evaluated in near-industrial conditions. Operating conditions of the absorption column were optimized with a column of height 10 m and diameter ranging from 1.1 to 1.2 m at 10 bar total pressure, reaching 90% F gas recovery with an L/G range of 6–10. Finally, preliminary economic analysis revealed operating costs to recover 90% of F-gas of 70 $/ton (R-134a) and 130 $/ton (R-32) with the FIL/IL that revealed the best behavior, 1-ethyl-3-methylimidazolium triflate.