Regeneration of CO2 Solvents with Polymeric Membranes

      The capture and storage of CO₂ is considered a potential mitigation to global climate change caused by greenhouse gases. Extensive research has been conducted to develop membrane-based systems for CO2 capture from fixed sources, such as coal-fired power plants,  due to the operational simplicity, reliability, and energy efficiency of membranes. Rather than focus on CO₂ capture directly from flue gas, our work seeks to evaluate membranes as a means to regenerate CO₂ from absorption solvents such as monoethanolamine (MEA).

      A membrane evaluation system was designed and built to study the permeability and selectivity of various membrane materials for the recovery of CO2 from MEA solutions. The feed consisted of an aqueous MEA solution (15% wt) saturated with CO2 and continuously circulated through a membrane module.  On the permeate side of the membrane a sweep gas was used to maintain a low CO₂ partial pressure. The permeate gas composition was measured by gas chromatography (GC) and a non-dispersive infrared (NDIR) detector. The performance of several porous and nonporous membrane materials, including polyester (PE), polypropylene (PP), polyamide, and polytetrafluoroethylene (PTFE), was measured and compared. The effects of feed flow rate, sweep gas rate, and temperature on CO₂ permeability were studied, as was the ability of these membranes to perform in long-term, continuous operation. Membrane porosity, swelling, and surface morphology was characterized by optical and electron microscopy.