Carbon Molecular Sieve Membranes for Selective CO₂/CH₄ and CO₂/N₂ Separation: Experimental Study, Optimal Process Design, and Economic Analysis

Abstract

Membrane technology is considered a high-efficiency separation and purification technology due to its low carbon footprint and low energy consumption. In this work, carbon molecular sieve (CMS) membranes for the selective separation of CO2 from methane and nitrogen were successfully fabricated. A gas permeation setup was employed to test CO2/N2, CO2/CH4 perm-selectivities, and CO2 permeances of the CMS membranes. To study the impact of temperature and pressure, the experiments have been carried out at a temperature range from 20 to 350 °C and pressure from 1 to 40 bar. Furthermore, a novel multistage membrane process design was proposed to test the feasibility of the fabricated membranes for CO2 separation from different sources of carbon emission. Three major sweetening processes are considered, including CO2 capture from coal-fired flue gas, biogas upgrading (BG), and natural gas (NG). A structural optimization approach is applied to determine the most efficient membrane strategy from the point of view of gas separation cost. By varying the membrane properties and separation targets, the effect of these parameters on capital expenditure (CAPEX), operating expenditure (OPEX), and energy consumption was studied. The economic assessment revealed a superior potential for CO2/N2 separation with a capture cost of 41.8 €/ton of CO2 and energy consumption of 1.9 GJ/ton CO2. The use of the optimal two-stage membrane configuration resulted in a competitive CO2/CH4 separation cost of 4.2 €/ton of sweet NG and 23 €/ton of BG for natural gas and biogas upgrading, respectively.

Carbon–Carbon Composite Membranes Derived from Small-Molecule-Compatibilized Immiscible PBI/6FDA-DAM-DABA Polymer Blends

“…Membrane-based gas separations have become an active research topic over the past few decades [1][2][3][4][5][6]. Among the different types of membrane systems studied, carbon molecular sieve membranes (CMSMs) are attractive due to their stability under harsh industrial conditions (e.g., high temperature), their chemical resistance, and their unprecedented gas separation performance [7][8][9][10]. The separation properties of CMSMs are critically dependent on the membrane microstructure, which reflects, in part, that of the precursor polymer [7].…”

Metal–Organic-Frameworks Based Mixed-Matrix Membranes for CO2 Separation: An Applicable-Conceptual Approach

“…Inorganic membranes such as carbon molecular sieves (CMSs), ceramic, metal or metal oxide, zeolite, and metal–organic framework (MOF) membranes have the merit of moderate permeability and outstanding selectivity (permselectivity) and possess potential advantages encompassing high stability against harsh temperature and pressure conditions . Despite the advantages mentioned above, inorganic membranes have not been fully developed because of the high cost, fragile nature and difficulty of fabrication, processability and obtaining a defect-free structure …”

Thin-Film-Composite Carbon Molecular Sieve Membranes for Efficient Helium and Hydrogen Separation

“…Among inorganic membranes, CMS membranes, which are normally fabricated via carbonization of polymeric precursors, have attracted much attention for gas separation applications due to their precise pore size for molecule sieving, superior thermal and chemical stabilities, and relatively lower cost compared to other inorganic membranes …”