Abstract
Rotating packed beds (RPBs) have been proposed as an emerging technology to be used for post-combustion CO2 capture (PCC) from the flue gas. However, due to the complex structure of the packing in RPBs, characteristics of the liquid flow within RPBs are very difficult to be fully investigated by experimental methods. Therefore, in this paper, a two-dimensional (2D) CFD model has been built for analysing the characteristics of liquid flow within an RPB. The volume of fluid (VOF) multiphase flow model is implemented to calculate the flow field and capture the interface between the gas and liquid phases in the RPB. The simulation results show good agreement with the experimental data. The distinct liquid flow patterns in different regions of an RPB are clearly observed. The simulation results indicate that increasing the rotational speed dramatically decreases the liquid holdup and increases the degree of the liquid dispersion. The increasing liquid jet velocity decreases the liquid residence time but slightly increases the liquid holdup. In addition, the liquid holdup increases and the degree of the liquid dispersion decreases with increasing MEA concentration, but the effects are weaker at a higher rotational speed. With the increasing of the contact angle, both the liquid holdup and the degree of the liquid dispersion are reduced. This proposed model leads to a much better understanding of the liquid flow characteristics within RPBs.
Highlights
The rotating packed bed (RPB), as a type of process intensification (PI) technology, was invented by Ramshaw and Mallinson (1981) for enhancing the gas–liquid mass transfer in chemical processes
The simulation results in this paper show that the effect of the rotational speed (Fig. 5(a)), the liquid jet velocity (Fig. 5(b)) and the liquid viscosity (Fig. 5(c)) on the liquid holdup is similar to those obtained by Yang et al (2015a) experimentally and the Burns correlation
This may be because the conductivity measurement method adopted in the experiments (Burns et al, 2000) cannot take into consideration of the free droplets, which take up an important percentage of liquid in the packing region of typical RPBs
Summary
The rotating packed bed (RPB), as a type of process intensification (PI) technology, was invented by Ramshaw and Mallinson (1981) for enhancing the gas–liquid mass transfer in chemical processes. In the RPB, liquid flow is injected radially from the centre of the bed and it is split continuously into discrete liquid ligaments, thin films and tiny droplets by the rotating porous packing. This can dramatically increase the interfacial area and promotes intensive mixing and mass transfer between the liquid phase and the gas phase that.
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