Separation of nitrous oxide from aqueous solutions applying a micro porous hollow fiber membrane contactor for energy recovery

Abstract

Abstract Nitrous oxide (N 2 O) is a potent green-house gas, but has also recently been acknowledged as sustainable energy source that can intentionally be produced by bioreactor systems such as the C oupled A erobic-anoxic N itrous D ecomposition O peration (CANDO). In this study, the application potential of a porous hollow fiber membrane contactor has been assessed at expected conditions of an operating CANDO system in shell-side liquid feed operation for N 2 O removal. At varying feed concentrations, liquid and gas flow rates, off-gas concentrations, removal efficiencies, trans-membrane fluxes and mass-flows have been assessed and compared to previous studies on CO 2 . Under the applied operational conditions, the gas flow rate had no significant effect on the results. Removal efficiencies up to 77% of the module feed load demonstrated a high application potential for the CANDO process and indicate a promising removal potential greater 90% in reference to typical initial substrate loads in an operating CANDO system. Additionally, considerably higher off-gas concentrations compared to recently published results applying conventional stripping technology of 3700 ppmv were generated reducing sweeping gas demand by 70%. The mass transfer was dominated by the superficial velocity on the liquid side and its behavior could be well described by Sherwood correlations. However, previously published mass transfer correlations over-estimated the results. Hence, a more appropriate correlation is presented to describe the observations of this study.