Browsing by Author "Sebastia-Saez, Daniel"

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    Micro-scale CFD modeling of reactive mass transfer in falling liquid films within structured packing materials
    (Elsevier, 2015-02) Sebastia-Saez, Daniel; Gu, Sai; Ranganathan, Panneerselvam; Papadikis, Konstantinos
    Post-combustion carbon capture in structured packing columns is considered as a promising technology to reduce greenhouse gas (GHG) emissions because of its maturity and the possibility of being retrofitted to existing power plants. CFD plays an important role in the optimization of this technology. However, due to the current computational capacity limitations, the simulations need to be divided into three scales (i.e. micro-, meso- and macro-scale) depending on the flow characteristics to be analyzed. This study presents a 3D micro-scale approach to describe the hydrodynamics and reactive mass transfer of the CO2-MEA chemical system within structured packing materials. Higbie's penetration theory is used to describe the mass transfer characteristics whereas enhancement factors are implemented to represent the gain in the absorption rate attributable to the chemical reaction. The results show a detrimental effect of the liquid load on the absorption rate via a decrease in the enhancement factor. The evolution of the wetted area for MEA solutions is compared to the case of pure water highlighting the differences in the transient behavior. The CO2 concentration profiles are examined showing the capability of the model to reproduce the depletion of the solute within the bulk liquid ascribed to the high value of the Hatta number. Also, several approaches on the reaction mechanism such as reversibility and instantaneous behavior are assessed. The results from micro-scale are to be used in meso-scale analysis in future studies to optimize the reactive absorption characteristics of structured packing materials.
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    Micro-scale CFD study about the influence of operative parameters on physical mass transfer within structured packing elements
    (Elsevier Science B.V., Amsterdam, 2014-09-01T00:00:00Z) Sebastia-Saez, Daniel; Gu, Sai; Ranganathan, Panneerselvam; Papadikis, Konstantinos
    In this work a VOF-based 3D numerical model is developed to study the influence of several operative parameters on the gas absorption into falling liquid films. The parameters studied are liquid phase viscosity, gas phase pressure and inlet configuration, liquid-solid contact angle and plate texture. This study aims to optimize the post-combustion CO2 capture process within structured packed columns. Liquid phase viscosity is modified via MEA (i.e. monoethanolamine) concentration. The results show that an increase in liquid viscosity reduces the diffusivity of oxygen within the liquid film thus hindering the efficiency of the process. Higher pressure carries an absorption improvement that can be attractive to be applied in industry. The simulations show that enhanced oxygen absorption rates can be achieved depending on the velocity of the gas phase and the flow configuration (i.e. co- and counter-current). Also, the importance of wetting liquid-solid contact angles (i.e. less than 90°) is highlighted. Poor liquid-solid adhesion has similar effects as surface tension in terms of diminishing the spreading of the liquid phase over the metallic plate. Finally the influence of a certain geometrical pattern in the metallic surface is also assessed.