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Title: Hydrodynamics and mass transfer of rotating packed beds for CO2 capture
Author: Xie, P.
ISNI:       0000 0004 7964 5556
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2019
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Post-combustion CO2 capture (PCC) is an important technology for meeting the greenhouse gas control target. Rotating packed beds (RPBs), as a type of process intensification technology, have been proposed as an emerging technology to be used for PCC from the flue gas, and this is because of its high mass transfer coefficient and compact structure which may lead to energy and space savings. The purpose of this thesis is to investigate the hydrodynamics and mass transfer performance of RPBs for CO2 capture through using CFD modelling methods. CFD models with different scales are developed to study the hydrodynamics of RPBs, and finally a multiscale modelling method is proposed to predict the performance of large-scale RPBs. First of all, a 2D VOF-based CFD model with fine grids is built for analysing the characteristics of liquid flow within a laboratory-scale RPB. This model successfully captured the distinct liquid flow patterns in the entrance region and the bulk region of the RPB. The simulation results indicate that increasing the rotational speed dramatically decreases the liquid holdup and increases the degree of the liquid dispersion. Increasing the solvent concentration increases the liquid holdup but the degree of the liquid dispersion decreases. In addition, a 3D representative elementary unit (REU) based mesoscale CFD model is built, which can be used to investigate the hydrodynamics of RPBs in greater detail and accuracy. The REU is used to study the flow at different locations within an RPB, so that the overall flow characteristics within the RPB can be assembled. The proposed approach enables the detailed prediction of the liquid holdup, droplets formation, effective interfacial area, wetted packing area and specific surface area of the liquid within real 3D packing structures throughout the bed. Based on the data from the CFD simulations, new correlations to predict the liquid holdup and gas-liquid interfacial area in the RPB are proposed. Finally, an Eulerian porous media CFD model is developed to analyse the CO2 absorption by MEA solutions in an RPB. The new porous media model, the gas-liquid drag model, the reactive mass transfer model, the heat transfer model and the interfacial area model are integrated into the Eulerian model, and this model successfully simulates the CO2 capture from the flue gas by MEA solutions in the RPB. The results obtained show that KGa increases significantly with the increasing of the liquid flow rate, MEA concentration, and the liquid inlet temperature, while it only increases slightly with the increasing of the rotational speed and the gas flow rate. In addition, the pressure drop significantly increases with the increasing of the rotational speed and the gas flow rate. In this thesis, the CFD modelling is realised though using the ANSYS® Fluent software with user-defined functions (UDFs). For the VOF model, the settings of the inlet boundary conditions and the acquisition of the detailed parameters in the calculation domains are achieved through writing UDFs. For the Eulerian model, the specified submodels for RPBs, such as the porous media model, the gas-liquid drag model, the mass transfer model, the interfacial area model, etc. are implemented in ANSYS® Fluent through writing UDFs.
Supervisor: Ma, Lin ; Ingham, Derek ; Pourkashanian, Mohamed Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available