Modelling of the rotating packed bed for post-combustion carbon capture using Eulerian porous medium approach

The rotating packed bed (RPB) has shown promising advantages for post-combustion carbon capture (PCC), such as its high mass transfer rate and compact structure. However, there is limited understanding of the hydrodynamics and mass transfer performance within the RPB, including the liquid dispersion in the packing region, CO2 capture in the outer cavity zone, etc., when comparing with the conventional packed bed (CPB). This is largely because there is not an appropriate computational method that can simulate the fluid flows and the carbon capture processes in a full scale RPB in 3D due to the multiscale of the problem. These restrict the commercial application of the RPB technologies. The objectives of this thesis is to effectively investigate the hydrodynamics and mass transfer in the multi-scale RPB by employing the Eulerian porous medium approach and developing associated necessary process specific sub-models. The liquid dispersion and CO2 capture processes are respectively studied in a lab-scale and a pilot-scale RPB, and the CO2 capture performance in the RPB is compared with CPB. Firstly, a 3D Eulerian porous medium model is established coupled with the appropriate interfacial, drag and dispersion forces formulations for investigating the effect of the liquid dispersion in a practical lab-scale RPB. The sensitivity of the parameters employed in these formulations is thoroughly analyzed. New forms of the porous resistance model and the effective interfacial area correlation are developed for the non-uniform two-phase flows. The simulation results show that the effect of the capillary pressure and mechanical dispersion forces on the liquid flow distribution and holdup in the RPB is clear and important. In addition, increasing the number of the liquid nozzles from 1-4 could improve the liquid distribution and liquid holdup in the packing region substantially. Secondly, a full 3D CFD model, including the packing and the inner and outer cavity zones, is established based on a pilot-scale RPB, employing the Eulerian porous medium method. The CO2 capture processes, including the hydrodynamics, thermodynamics, and mass transfer, are examined within the entire RPB. The CO2 capture performance in the packing and outer cavity zones has been quantitatively analyzed under different operating conditions. The simulation results show good agreement with the experimental data, and the contribution of the outer cavity zone to the CO2 capture of the RPB is in the range of 28 %-42 % in this established RPB. Thirdly, a large-scale RPB is established computationally according to a design procedure and the experimental parameters from a CPB pilot plant. The CO2 capture processes in the RPB are effectively and extensively investigated by employing the Eulerian porous medium method and various sub-models developed. Furthermore, the RPB and CPB have been critically compared under different operating conditions. The simulation results show that compared with the CPB, the liquid flow rate could be saved by 40% when using a 50% MEA concentration solution instead of 30%, and the volume of the packed bed in the RPB could be reduced by a factor of 20. This thesis provides a new and effective approach to simulate the hydrodynamics and CO2 capture processes in full-scale RPBs, and it also provides important information for the scaling up and operation of RPBs for PCC, highlighting the important potential of RPBs for industrial applications.