CFD MODELING OF MULTIPHASE COUNTER-CURRENT FLOW IN PACKED BED REACTOR FOR CARBON CAPTURE

Packed bed reactors with counter-current, gas-liquid flows have been considered to be applicable in CO2 capture systems for post-combustion processing from fossil-fueled power production units. However, the hydrodynamics within the packing used in these reactors under counter-current flow has not been assessed to provide insight into design and operational parameters that may impact reactor and reaction efficiencies. Hence, experimental testing of a laboratory-scale spherical ball, packed bed with two-phase flow was accomplished and then a meso-scale 3D CFD model was developed to numerically simulate the conditions and outcomes of the experimental tests. Also, the hydrodynamics of two-phase flow in a packed bed with structured packing were simulated using a meso-scale, 3D CFD model and then validated using empirical models. The CFD model successfully characterized the hydrodynamics inside the packing, with a focus on parameters such as the wetted surface areas, gas-liquid interactions, liquid distributions, pressure drops, liquid holdups, film thicknesses and flow regimes. The simulation results clearly demonstrated the development of and changes in liquid distributions, wetted areas and film thicknesses under various gas and liquid flow rates. Gas and liquid interactions were observed to occur at the interface of the gas and liquid through liquid entrainment and droplet formation, and it became more dominant as the Reynolds numbers increased. Liquid film thicknesses in the structured packing were much thinner than in the spherical ball packing, and increased with increasing liquid flow rates. Gas flow rates had no significant effect on film thicknesses. Film flow and trickle flow regimes were found in both the spherical ball and structured packing. A macro-scale, porous model was also developed which was less computationally intensive than the meso-scale, 3D CFD model. The macro-scale model was used to study the spherical ball packing and to modify its closure equations. It was found that the Ergun equation, typically used in the porous model, was not suitable for multi-phase flow. Hence, it was modified by replacing porosity with the actual pore volume within the liquid phase; this modification successfully accounted for liquid holdup which was predicted via a proposed equation

CFD modelling of post-combustion carbon capture with amine solutions in structured packing columns

The scope of the present thesis is the development of a Computational Fluid Dynamics model to describe the multiphase flow inside a structured packing absorber for postcombustion carbon capture. The work focuses mainly on two flow characteristics: the interface tracking and the reactive mass transfer between the gas and the liquid. The interface tracking brings the possibility of studying the liquid maldistribution phenomenon, which strongly affects the mass transfer performance. The development of a user-defined function to account for the reactive mass transfer between phases constitutes the second major concept considered in this thesis. Numerical models found in the literature are divided into three scales due to the current computational capacity: small-, meso- and large-scale. Small-scale has usually dealt with interface tracking in 2D computational domains. Meso-scale has usually been considered to assess the dry pressure drop performance of the packing (considering only the gas phase). Large-scale studies the liquid distribution over the whole column assuming that the structured packing behaves as a porous medium. This thesis focuses on small- and meso-scale. The novelty of this work lies in expanding the capabilities of the aforementioned scales. At small-scale, the interfacial tracking is implemented in a 3D domain, instead of 2D. The user-defined function that describes the reactive mass transfer of CO2 into the aqueous MEA solution is also included to assess the influence of the liquid maldistribution on the mass transfer performance. At the meso-scale, the Volume of Fluid method for interface tracking is included (instead of only the gas phase) to describe flow characteristics such as the liquid hold-up, the interfacial area and the mass transfer. At the theoretical level, this model presents the particularity of including both a mass and a momentum source term in the conservation equations. A comprehensive mathematical development shows the influence of the mass source terms on the momentum equation

Design of Packed Column for C02 Absorption from NG at Reserves Using FLUENT

Nowadays, the high composition of CO2 at the gas reserves has incurred problem to the existing treatment system inthe gas processing plant. Assolution anadditional treatment plant can bebuilt at the gas reserves to reduce CO2 composition before the gas enters the processing plant. The option to use a packed column in this additional treatment plant is investigated. This dissertation explain the background, problem statement, objective, methodology and the finding of the modeling simulation present computational fluid dynamics model built in FLUENT in order to simulate the CO2 removal from high pressure natural gas using a specially designed solvent. The purpose for this simulation model is to study the behavior of mass diffusion of in the reactive absorption process with packing material as the contacting device in counter current absorption process. The packing area represent by a porous medium with 0.9 porosity. This research investigate the gas distribution throughout the column with 17ft packing height, at range of 1- 80 Bar operating pressure and the effect of liquid loading range from 50 - 150 mVm2h to the decrease ofC02 content. In the study involving gas distribution, height of the column also increase from 14ft to 17ft in order to observe the effect to packing area to the gas distribution.

Modelling of CO2 absorption in a rotating packed bed using an Eulerian porous media approach

The rotating packed bed (RPB) is a promising reactor for CO2 capture with liquid amine because of its high mass transfer rate and energy and space savings. The CFD simulations of RPBs generally use the volume of fluid (VOF) method, but this method is prohibitively expensive for 3D simulations, in particular for large-scale reactors. The Eulerian method is a promising and effective method; however, there are still several difficulties, such as the settings for the porous media models in the gas-liquid counter-current flow and the interfacial area between the gas and liquid. To overcome these difficulties in the Eulerian method, this paper uses a new porous media model, a novel liquid generation-elimination model for numerically investigating the gas-liquid counter-current flow in RPBs and a new interfacial area model derived from the VOF simulation. These new models, incorporating the two-film reaction-enhancement mass transfer model, have successfully simulated the CO2 capture process with monoethanolamine (MEA) solutions in a RPB under both low (30 wt%) and high (90 wt%) concentration conditions. The results show that the overall gas phase mass transfer coefficient (KGa) increases with increasing the rotation speeds and the liquid to gas mass flow rate (L/G ratio). The simulations were validated by the experimental data and the results were analysed and discussed

Investigating the Advantages and Limitations of Modeling Physical Mass Transfer of CO2 on Flat Plate by One Fluid Formulation in OpenFOAM

One fluid formulation is an approach used for modeling and analysis of mass transfer between two immiscible phases. In this study we implement and analyze the advantages and limitations of this approach for CO2 physical mass transfer into MEA. The domain is a flat plate and gas liquid flow is counter current. The analysis was carried for operating parameters like liquid phase Reynolds number, MEA mass fraction and the angle of inclination of flat plate. The results clearly show that the model effectively captures the deviation in liquid side mass transfer coefficient due to the surface instabilities and liquid properties which are generally neglected by standard correlations. Also the model shows that the standard Higbie correlation is preferable at low Reynolds number at any angle of inclination. The grid independent studies show that a size of 6.25 µm is required in the interface region for effectively using this approach. The computational resource time at this resolution was found as the only limitation for using this approach and we suggest a procedure to overcome this limitation. The present simulation results can help CFD researchers investigating immiscible gas-liquid mass transfer using OpenFOAM

Direct effect of solvent viscosity on the physical mass transfer for wavy film flow in a packed column

The interphase mass transfer plays a critical role in determining the height of packed column used in absorption process. In a recent experiments2, the direct impact of viscosity on the physical mass transfer coefficient was observed to be higher in a packed column as compared to the wetted wall column. We offer a plausible mechanism involving the wavy film and eddy enhanced mass transfer in a packed column to explain underlying physics via analytical and numerical studies. The analytically derived mass transfer coefficient matches well with experimental observation in a packed column. The countercurrent flow simulations in a packed column with both uniform and wavy films also confirm this behavior. The predicted k_L shows steep variation with for a wavy film than a uniform film, further confirms the proposed theory. A similar relation for a wavy film is also observed in theoretical, experimental and numerical studies

Parametric Study of Experimental and CFD Simulation Based Hydrodynamics and Mass Transfer of Rotating Packed Bed: A Review

The emission of CO2 into the atmosphere is one of the major causes of the greenhouse effect, which has a devastating effect on the environment and human health. Therefore, the reduction of CO2 emission in high concentration is essential. The Rotating Packed Bed (RPB) reactor has gained a lot of attention in post-combustion CO2 capture due to its excellent rate of mass transfer and capture efficiency. To better understand the mechanisms underlying the process and ensure optimal design of RPB for CO2 absorption, elucidating its hydrodynamics is of paramount importance. Experimental investigations have been made in the past to study the hydrodynamics of RPB using advanced imaging and instrumental setups such as sensors and actuators. The employments of such instruments are still challenging due to the difficulties in their installation and placement in the RPB owing to the complex engineering design of the RPB. The hydrodynamics of the RPB can be affected by various operational parameters. However, all of them cannot be evaluated using a single instrumental setup. Therefore, the experimental setups generally result in a partial understanding of the flow behavior in the RPB. The cons and pros of experimental methods are reported and critically discussed in this paper. Computational Fluid Dynamics (CFD), on the other hand, is a powerful tool to visually understand the insights of the flow behavior in the RPB with accurate prediction. Moreover, the different multiphase and turbulence models employed to study the hydrodynamics of RPB have also been reviewed in-depth along with the advantages and disadvantages of each model. The models such as Sliding Mesh Model (SMM) and rotating reference frame model have been adopted for investigating the hydrodynamics of the RPB. The current research gaps and future research recommendations are also presented in this paper which can contribute to fill the existing gap for the CFD analysis of Rotating Packed Bed (RPB) for CO2 absorption

CFD modelling of carbon capture in large-scale for structured packed bed column.

In this Ph.D. thesis, a novel 3D numerical model is developed to solve multiphase flow problem for carbon capture. The model solves the Navier-Stokes equations with commercial solver Ansys Fluent with higher accuracy and much better prediction. The proposed model was at first developed to solve the hydrodynamics problem inside the structured packed bed. In the hydrodynamic part, viscous resistance and inertia resistance for both gas and liquid were taken into account and were implemented by the User Defined Function (UDF). The structured mesh was done using ICEM-CFD. In this part, dispersion forces were also included by UDF. Hydrodynamics of the structured packed bed was validated in terms of liquid volume fraction and, a higher degree of accuracy was achieved. This achievement was done by implementing drag law in a novel way. Dispersion of the liquid inside the packed bed was modelled both by mechanical dispersion and by spread tensor. Pressure drop is a very important part of designing structured packing and, it has to be kept to a minimum. In the hydrodynamics study, this pressure drop was kept minimum, and a good distribution of gas and liquid was achieved. The second part of the model is the chemical reactions. In this case, all the five reactions that occur in carbon capture were taken into account along with the hydrodynamics. Few studies like the effect of solvent concentration, the effect of pressure were studied by using this part of the model. Another novel aspect of the model is that it can predict gas-liquid interfacial area and enhancement factor for chemical reactions. As a result, it has become much easier to understand chemical reactions and calculate carbon removal easily. The third part of the model is the heat transfer effect. Heat transfer effect was included by changing gas and liquid temperature and it was found that liquid temperature has a wider impact on carbon capture. All the contributions to the knowledge were summarized in Chapter 7.PhD in Energy and Powe

Performance of multiphase packed-bed reactors and scrubbers on offshore floating platforms: hydrodynamics, chemical reaction, CFD modeling and simulation

Les systèmes flottants de production, stockage et de déchargement (FPSO) ont été introduits dans les secteurs d'exploitation des hydrocarbures offshore en tant qu'outils facilement déplaçables pour l’exploitation de champs de pétrole et de gaz de petites ‘a moyenne tailles ou lorsque ceux-ci sont éloignés des côtes ou en eaux profondes. Ces systèmes sont de plus en plus envisagés pour les opérations de traitement et de raffinage des hydrocarbures à proximité des sites d'extraction des réservoirs sous-marins en utilisant des laveurs et des réacteurs à lit fixe embarqués. De nombreuses études dans la littérature pour découvrir l'hydrodynamique de l'écoulement polyphasiques dans des lits garnis ont révélé que la maîtrise de tels réacteurs continue d’être un défi quant à leur conception /mise à l'échelle ou à leur fonctionnement. De plus, lorsque de tels réacteurs sont soumis à des conditions fluctuantes propres au contexte marin, l'interaction des phases devient encore plus complexe, ce qui entraîne encore plus de défis dans leur conception. Les travaux de recherche proposés visent à fournir des informations cruciales sur les performances des réacteurs à lit fixes à deux phases dans le cadre d'applications industrielles flottantes. Pour atteindre cet objectif, un simulateur de mouvement de navire de type hexapode avec des mouvements à six degrés de liberté a été utilisé pour simuler les mouvements des FPSO tandis que des capteurs à maillage capacitif (WMS) et un tomographe à capacitance électrique (ECT) couplés avec le lit garni ont permis de suivre en ligne les caractéristiques dynamiques locales des écoulements diphasiques. L'effet des inclinaisons et des oscillations de la colonne sur le comportement hydrodynamique des lits garnis biphasiques a été étudié, puis les résultats ont été comparés à leurs analogues terrestres correspondants (colonne verticale immobile). De plus, des stratégies opérationnelles potentielles ont été proposées pour atténuer la maldistribution des fluides résultant des oscillations du lit ainsi que pour intensifier le processus de réactions dans les réacteurs à lit fixe. Parallèlement aux études expérimentales, un modèle Eulérien CFD transitoire 3D a été développé pour simuler le comportement hydrodynamique de lits garnis polyphasiques sous des inclinaisons et des oscillations de colonnes. Enfin, pour compléter le travail expérimental, une étude systématique a été réalisée pour étudier les performances de capture de CO2 à base d'amines d’un laveur à garnissage (en vrac et structuré) émulant une colonne à bord des ...Floating production storage and offloading (FPSO) systems have been introduced to offshore hydrocarbon exploitation sectors as readily movable tools for development of small or remote oil and gas fields in deeper water. These systems are increasingly contemplated for onboard treatment and refining operations of hydrocarbons extracted from undersea reservoirs near extraction sites using embarked packed-bed scrubbers and reactors. Numerous efforts in the literature to uncover the hydrodynamics of multiphase flow in packed beds have disclosed that such reactors continue to challenge us either in their design/scale-up or their operation. Furthermore, when such reactors are subjected to marine conditions, the interaction of phases becomes even more complex, resulting in further challenges for design and scale-up. The proposed research aims at providing important insights into the performance of two-phase flow packed-bed reactors in the context of floating industrial applications. To achieve this aim, a hexapod ship motion simulator with six-degree-of-freedom motions was employed to emulate FPSO movements while capacitance wire mesh sensors (WMS) and electrical capacitance tomography (ECT) coupled with the packed bed scrutinized on-line and locally the two-phase flow dynamic features. The effect of column tilts and oscillations on the hydrodynamic behavior of multiphase packed beds was investigated and then the results were compared with their corresponding onshore analogs. Moreover, potential operational strategies were proposed to diminish fluid maldistribution resulting from bed oscillations as well as for process intensification of heterogeneous catalytic reactions in packed-bed reactors. In parallel with the experiment studies, a 3D transient Eulerian CFD model was developed to simulate the hydrodynamic behavior of multiphase packed beds under column tilts and oscillations. Ultimately, a systematic experimental study was performed to address the amine-based CO2 capture performance of packed-bed scrubbers on board offshore floating vessels/platforms. Apart from gaining a comprehensive knowledge on the influence of translational and rotational movements on multiphase flows in porous media, oil and gas sectors and ship industry would benefit from the results of this work for design and scale-up of industrial reactors and scrubbers.Unité flottante de production, de stockage et de déchargemen