Gas-liquid multiphase computational fluid dynamics (CFD) of amine absorption column with structured-packing for CO2 capture
Abstract The gas−liquid multiphase Eulerian computational fluid dynamics (CFD) model was used to investigate hydrodynamics and CO2 removal efficiency of a pilot-scale amine absorber with structured-packing. The structured-packing was represented by a porous media zone having porous resistance, gas−liquid interfacial drag force, and liquid dispersion force. This study aimed to find a reasonable way to identify four modification factors of the Ergun coefficient that determine the hydrodynamic characteristics of structured-packing. The two modification factors (a and b) for porous resistance were mainly related to the liquid holdup (hL) with respect to the liquid load. The other two factors (c and d) for gas−liquid interfacial drag force depended on the specific wet pressure drop (ΔPwet/L) versus the gas load factor. The hL and ΔPwet/L increased in parallel with the increase of a and c, respectively, while the slopes of hL and ΔPwet/L increased with b and d, respectively.
Mathematical modelling of mass-transfer and hydrodynamics in CO2 absorbers packed with structured packings
Abstract This paper presents a mechanistic model that can predict mass-transfer performance and provide an insight into dynamic behavior within structured packings used for CO 2 absorption. The model was built upon the kinetics and thermodynamics of the absorption system, as well as the liquid irrigation features and the geometry of packing elements. A computer program (Fortran 90) was written to simulate CO 2 absorption into aqueous solutions of sodium hydroxide (NaOH) and monoethanolamine (MEA) in a column packed with Gempak 4A, Mellapak 500Y and Mellapak 500X. The simulation gave essential information, including the concentration of CO 2 in gas-phase, concentration of reactive species in the liquid-phase, system temperature, mass-transfer coefficients ( k G and k L ), and effective interfacial area ( a e ) for mass-transfer at different axial positions along the absorption column. The simulation also provided liquid distribution plots representing the quality of liquid distribution or maldistribution across the cross-section of the column. Verification of the model was achieved by comparing simulation results with experimental data. Very good agreement was found for wide ranges of operating and design parameters, including liquid load and initial liquid distribution pattern.
Pilot plant study of post-combustion carbon dioxide capture by reactive absorption: Methodology, comparison of different structured packings, and comprehensive results for monoethanolamine
Abstract Post-combustion carbon capture (PCC) from fossil fuel power plants by reactive absorption can substantially contribute to reduce emissions of the greenhouse gas CO 2 . To test new solvents for this purpose small pilot plants are used. The present paper describes results of comprehensive studies of the standard PCC solvent MEA (0.3 g/g monoethanolamine in water) in a pilot plant in which the closed cycle of absorption/desorption process is continuously operated (column diameters: 0.125 m, absorber/desorber packing height: 4.25/2.55 m, packing type: Sulzer BX 500, flue gas flow: 30–110 kg/h, CO 2 partial pressure: 35–135 mbar). The data establish a base line for comparisons with new solvents tested in the pilot plant and can be used for a validation of models of the PCC process with MEA. The ratio of the solvent to the flue gas mass flow is systematically varied at constant CO 2 removal rate, and CO 2 partial pressure in the flue gas. Optimal operating points are determined. In the present study the structured packing Sulzer BX 500 is used. The experiments with the removal rate variation are carried out so that the results can directly be compared to those from a previous study in the same plant that was carried out using Sulzer Mellapak 250.Y. A strategy for identifying the influence of absorption kinetics on the results is proposed, which is based on a variation of the gas load at a constant L / G ratio and provides valuable insight on the transferability of pilot plant results.