Scale-up of Amine-Containing Membranes for CO2 Capture and Separation

Scale-up of Amine-Containing Membranes for CO₂ Capture and Separation

Witopo Salim¹, Varun Vakharia¹, Dongzhu Wu¹, Yuanxin Chen¹, Lin Zhao¹, Yang Han¹, and W.S. Winston Ho^1,2

¹William G. Lowrie Department of Chemical and Biomolecular Engineering, The Ohio State University, 151 West Woodruff Avenue, Columbus, OH 43210-1180, USA

²Department of Materials Science and Engineering, The Ohio State University, 2041 College Road, Columbus, OH 43210-1178, USA

Abstract

Amine-containing membranes for CO₂ capture and separation were scaled up to fabricate 14-inch wide membranes by using a continuous roll-to-roll machine equipped with a thin-film-coating assembly.  Aided by a material balance equation, three variables, including the coating knife gap setting, substrate rolling speed, and coating solution concentration, were identified as the critical factors to control the membrane selective layer thickness.  For the CO₂ separation from a synthesis gas stream containing CO₂ and H₂S, i.e., pre-combustion CO₂ capture in IGCC (integrated gasification combined cycle) technology or hydrogen purification for fuel cells, the thicker amine-containing membranes with around 15 ± 2 microns of selective layer thicknesses were fabricated by using a gap setting of 17 mils, a rolling speed of 0.5 ft/min (set by the drying capacity of the drier, i.e., its length), and an amine coating solution of 18 wt%.  For the post-combustion CO₂ capture from flue gas, the same thin-film-coating assembly machine was used to fabricate thinner amine containing membranes with < 250 ± 20 nm of selective layer thicknesses by using various rolling speeds and amine-containing solution concentrations at a fixed gap setting of 0.45 mils.  The fabrication of thinner membranes was improved further by using an insert in the coating solution trough to control the coating solution delivery rate and a smooth coating knife base to reduce the thickness variation.  From the gas transport measurements, the flat-sheet samples of the scale-up membranes for both applications exhibited similar performances compared to the membranes synthesized in lab scale.  CO₂ permeance of approximately 200 GPU and CO₂/H₂ selectivity > 180 for the thicker membranes for the purification of hydrogen and synthesis gas along with CO₂ capture (e.g., pre-combustion capture), and CO₂ permeance of about 800 GPU and CO₂/N₂ selectivity > 140 for the thinner membranes for CO₂ capture from flue gas.  Techno-economic analysis of the post-combustion CO₂ capture membrane process using the thin membrane resulted in about $41/tonne CO₂ captured (based on 2007 dollar).  The scale-up membranes can be used to prepare pilot-scale membrane modules, either as spiral-wound or plate-and-frame configuration, for testing with the acid gas mixtures or flue gas.