Abstract
The PolyActive™ thin film composite membrane (TFCM) has already been successfully applied for CO2 separation tasks at feed pressures up to 10 bar. To investigate the applicability at higher pressures, measurements were undertaken with C2H4 containing gas mixtures with a composition comparable to the product stream of the oxidative coupling of methane process, as well as single gases up to a feed pressure of 30 bar. Furthermore, the permeances of the conducted gas mixture experiments were simulated. The results show a strong swelling influence of CO2 on the used membrane depending on the CO2 fugacity. This swelling effect leads to a pronounced decrease in selectivity. The observed membrane behavior at high pressures could not be predicted by the Free Volume Model (FVM). Two different simulations were conducted: one based on parameters calculated from single gas data measured at pressures up to 2 bar; and a second based on parameters calculated from single gas data measured at pressures from 2 to 30 bar. The two simulations differ in their prediction accuracy. However, they confirm that it is possible to predict the measured permeances in the pressure range up to an average CO2 fugacity of 6 bar.
Highlights
Membrane processes are constantly becoming more significant in the field of gas separation.A requirement for the introduction of a membrane process is a reliable membrane material, which preferably has a high gas selectivity as well as a high permeability
The results indicated that the Free Volume Model (FVM) used for the calculation of the a mini plant module were compared for pilot plant investigations at 10 and 20 bar feed pressures [5]
The data sets for the determination of the FVM parameters were obtained from single gas transport experiments carried out at low and high pressures
Summary
A requirement for the introduction of a membrane process is a reliable membrane material, which preferably has a high gas selectivity as well as a high permeability. Those membrane materials can be implemented as selective layers of composite membranes installed in a membrane module. There are several processes, which require the separation of CO2 from permanent gases and C1 –C3 hydrocarbons at higher pressures. One of those processes is the separation of CO2 from a C2 H4 containing multi-component gas mixture. This separation task occurs in the purification step after the oxidative coupling of methane, Membranes 2018, 8, 27; doi:10.3390/membranes8020027 www.mdpi.com/journal/membranes
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