Novel scrubbing system for post-combustion CO₂ capture and recovery: Experimental studies

Power plant emissions of flue gas to the atmosphere releases considerable CO₂ which is considered to be the main contributor to global warming. Several gas absorption techniques are being investigated to reduce the capital and operating costs for CO₂ capture from post-combustion flue gas. Conventional method of CO₂ capture by an aqueous solution of monoethanolamine (MEA) and its subsequent stripping in a separate tower with steam at 120°C is highly energy intensive. The low partial pressure of CO₂ in the flue gas inhibits the application of CO₂-selective membranes unless methods are employed to increase the CO₂ partial pressure in the flue gas to be treated. An absorption-stripping technique to potentially bypass the shortcomings of many existing approaches is described here. Bench-scale CO₂ capture and recovery from simulated flue gas with and without moisture was demonstrated using an advanced hollow fiber membrane contactor. This was achieved by the use of a novel non-volatile absorbent, consisting of the ionic liquid [bmim][DCA] containing 20wt% polyamidoamine (PAMAM) dendrimer Gen 0. We have employed a simulated humidified flue gas containing around 14% CO₂ and demonstrated successful removal of bulk of the CO₂ and its recovery in a CO₂-concentrated stream; the CO₂ concentration achieved in the stripper out stream was ~92vol%. An estimate of the overall volumetric mass transfer coefficient (K_la) for the current CO₂-IL-PAMAM Gen 0 system has been obtained.