Distillation studies in rotating packed bed with split packing

Comprehensive Analysis of Pressure Drop Phenomena in Rotating Packed Bed Distillation: An In-Depth Investigation

A rotating packed bed (RPB) is an innovative intensification technology that improves its separation capabilities in high-gravity conditions. This process increases efficiency with smaller equipment size and footprint than conventional packed columns. Although significant advancements have been made regarding RPBs, most studies only focused on single or dual rotor configurations in addressing dry pressure drop. Hence, multiple rotor systems in industrial settings can enhance economic efficiency by minimizing the necessity for numerous RPBs. This study investigated the pressure drops and holdup in a three-stage rotor-based RPB under actual process conditions using natural gas as the feed. A novel pressure drop correlation was introduced based on the nitrogen removal process from the natural gas in continuous RPB distillation operations. Consequently, the correlation between centrifugal acceleration, turbulent, and momentum effects demonstrated remarkable accuracy within ±15%. This outcome also highlighted the importance of meticulous design considerations in RPB-based applications due to the complex correlation between centrifugal forces, liquid holdup, and gas flow rates. The reflux feed ratio, liquid holdup, rotating speed, and F-factor effects were examined to comprehend the RPB distillation process. Overall, the correlations between the critical parameters offered crucial insights to prevent process upsets (such as flooding), contributing to advancing RPBs in practical industrial settings.

CFD simulation of gas pressure drop in porous packing for rotating packed beds (RPB) CO2 absorbers

Rotating packed bed (RPB) is a promising technology which can be used to intensify mass transfer in absorption processes. A better understanding of fluid dynamics is crucial to fill the gap in fundamental knowledge. Raising awareness on new technology and creating rules for process design and control are also very important. The experimental investigation of fluid in rotating beds is a very complex and difficult issue. What is more, the knowledge of the phase behavior in an RPB device is still insufficient. Therefore, an CFD (computational fluid dynamics) simulation is proposed as a tool for the study of gas phase flow inside porous packing. This study presents a three-dimensional numerical model for two fluid models: k-ε and RNG k-ε, for predicting dry pressure drop. The obtained simulation outcome was compared with the experimental results. The experimental dry pressure drop for porous packing was investigated for rotational speed in the range from 150 rpm to 1500 rpm and compared to the results from the CFD model. The comparison between the experimental and simulation results indicates very good consistency for the entire range of the rotational speed of interest. CFD modelling is recognised as an adequate tool leading to the better understanding of gas phase behaviour inside an RPB, filling an essential gap in our knowledge of the hydrodynamics of rotating packing, which allows to improve the design and performance of the process in RPB in terms of minimizing energy and material consumption.

Simultaneous removal efficiency of H2S and CO2 by high-gravity rotating packed bed: Experiments and simulation

This study explores the possibility of applying high-gravity rotating packed bed (HGRPB) in removing H2S and CO2 from biogas. Ca(OH)2 aqueous solution was used as the absorbent in this study. Different experimental conditions including solution pH, rotating speed (R S) of HGRPB, gas flow rate (Q G), and liquid flow rate (Q L) were investigated with respect to the removal efficiency (E) of H2S and CO2. The experimental and simulated results show that the optimal removal efficiency of H2S and CO2 using HGRPB achieved nearly the same as 99.38 and 99.56% for removal efficiency of H2S and 77.28 and 77.86% for removal efficiency of CO2, respectively. Such efficiencies corresponded with the following optimal conditions: a solution pH of 12.26, HGRPB reactor with the rotating speed of 1,200 rpm, the gas flow rate of 2.46 (L/min), and the liquid flow rate of 0.134 (L/min).

Degradation of nitrobenzene wastewater in an acidic environment by Ti(IV)/H2O2/O3 in a rotating packed bed

The rotating packed bed (RPB) as a continuous flow reactor performs very well in degradation of nitrobenzene wastewater. In this study, acidic nitrobenzene wastewater was degraded using ozone (O₃) combined with hydrogen peroxide and titanium ions (Ti(IV)/H₂O₂/O₃) or using only H₂O₂/O₃ in a RPB. The degradation efficiency of nitrobenzene by Ti(IV)/H₂O₂/O₃ is roughly 16.84% higher than that by H₂O₂/O₃, and it reaches as high as 94.64% in 30 min at a H₂O₂/O₃ molar ratio of 0.48. It is also found that the degradation efficiency of nitrobenzene is significantly affected by the high gravity factor, H₂O₂/O₃ molar ratio, and Ti(IV) concentration, and it reaches a maximum at a high gravity factor of 40, a Ti(IV) concentration of 0.50 mmol/L, a pH of 4.0, a H₂O₂/O₃ molar ratio of 0.48, a liquid flow rate of 120 L/h, and an initial nitrobenzene concentration of 1.22 mmol/L. Both direct ozonation and indirect ozonation are involved in the reaction of O₃ with organic pollutants. The indirect ozonation due to the addition of different amounts of tert-butanol (·OH scavenger) in the system accounts for 84.31% of the degradation efficiency of nitrobenzene, indicating that the nitrobenzene is dominantly oxidized by ·OH generated in the RPB-Ti(IV)/H₂O₂/O₃ process. Furthermore, the possible oxidative degradation mechanisms are also proposed to better understand the role of RPB in the removal of pollutants. Graphical abstract ᅟ.