(209g) High-Purity Nitrogen Production from Air By Pressure Swing Adsorption Combined with SrFeO3 Redox Chemical Looping for Trace Oxygen Removal

This work focuses on the production of high purity nitrogen from air via a combination of pressure swing adsorption (PSA) with a downstream redox chemical looping cycle used as a deoxygenation unit. The non-stoichiometric perovskite SrFeO_3−δ was selected for the redox chemical looping cycle because of its favorable thermodynamics, rapid oxidation kinetics and intermediate reduction temperatures. A first principles analysis of the system showed that this combined process could improve upon both the energy balance and production capacity of a PSA system. The chemical stability of the material was demonstrated over 250 redox cycles via thermogravimetry with less than 1 % degradation in the chemical storage capacity. The oxidation kinetics were also measured at 523 K over a range of oxygen concentrations, and fit with a suitable kinetic model. The kinetics were then incorporated into a 1D convection-diffusion model of a packed bed reactor. The model indicates that, for a targeted oxygen impurity of x_O2 < 3 × 10^−6, a chemical looping unit added downstream to a PSA system could approximately triple the capacity and reduce the energy demand to 14 kJ/mol of N₂ [Bulfin et al. 2020]. The results are promising for further study, with the goal of bridging the gap between PSA and cryogenic systems in terms of scale, purity and cost.

Bulfin, B., Buttsworth, L., Lidor, A., & Steinfeld, A. (2020). High-purity nitrogen production from air by pressure swing adsorption combined with SrFeO3 redox chemical looping. Chemical Engineering Journal, 127734.

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