CO2 absorption into amine solutions: a novel strategy for intensification based on the addition of ferrofluids

Abstract

AbstractBACKGROUND: In this paper a novel approach for increasing the mass transfer coefficient in gas/liquid mass transfer is reported and applied to the industrially important system of CO2 absorption. The approach makes use of a ferrofluid additive to the liquid phase. To demonstrate this strategy, a wetted wall column has been built and experiments have been conducted on the CO2/methyl diethanolamine (MDEA) system. This reaction system allows the absorption to be carried out in the transition regime between slow and fast regimes, so that the mass transfer coefficient (kL) and interfacial area (ai) can be measured independently, in the presence and absence of ferrofluids. A surfactant‐coated aqueous magnetic fluid was prepared and shown to be stable in MDEA solutions.RESULTS: The experimental results, with this fluid, show that there is an enhancement in mass transfer in the presence of ferrofluids, the extent of which depends on the amount of ferrofluid added. The enhancement in mass transfer coefficient was 92.8% for a volume fraction of the fluid of about 50% (solid magnetite volume fraction of about 0.39%). Experiments were also carried out to further enhance the mass transfer rates by employing a periodic oscillating magnetic field. Under the conditions employed, there was no further impact of magnetic field on mass transfer rates.CONCLUSIONS: Magnetic nanoparticles are able to significantly enhance gas/liquid mass transfer rates when added to the liquid phase. The reasons for this striking effect are under investigation. It is possible for significantly higher enhancements to be produced by the action of an external field, but this requires special fluids to be formulated which are not affected by the chemical solvent used. These results have significance for the absorption of CO2 in industrial absorbers using amine solutions. Copyright © 2008 Society of Chemical Industry