Applicability of Polyimide Membranes for Air Separation in Oxy-MILD Power Plants: Semi-Experimental Research

Abstract

The paper presents the results of experimental and computational research concerning the parameters of the separation process of N2/O2 mixture, regarding the composition of ambient air, using capillary polyimide membranes. The analysis focused on the potential applicability of polyimide membranes in oxy-MILD combustion units. The experimental data, collected using a sophisticated experimental test stand, was used to approximate continuous functions, describing the dependencies of essential parameters of the air separation process on variable operational conditions. These functions were used as fundamental blocks to develop a complete mathematical model of the membrane separation unit (MSU), including polyimide membranes and additional equipment, intended for use within oxy-MILD power generation units. Computational research was performed for three variants of MSU unit configuration, including: serial connection of membrane modules, multiple retentate recirculation and multiple permeate recirculation. Results, presented in the form of characteristic curves of investigated dependencies, indicate that the highest parameters of the separation process were gained for serial connection, whereas the lowest were for permeate recirculation. The collected data suggests that retentate recirculation might be beneficial for specific conditions, with limited application for continuous operation.