A comparison between packed beds and rotating packed beds for CO2 capture using monoethanolamine and dilute aqueous ammonia solutions

• A model for the absorption of CO2 using NH3 solution in RPB and PB was developed.
• We compared the PB and RPB volumes based on various capture rate scales.
• The RPB can reduce the volume using both solvents on various capture rate scales.
• The reduction ratio is more significant when NH3 solution instead of MEA solution.

In this work, a model for the absorption of carbon dioxide using 3 wt% dilute aqueous ammonia solution in rotating packed bed and packed bed was developed and validated using experimental data. The model was then employed to design absorbers for different throughput rates, ranging from 0.01 to 1000 ton-CO2-capture/day. The solvent used is 3 wt% ammonia solution operating in the lean-to-rich loading range of 0.2–0.4. The results were compared to those obtained with a similar model using 30 wt% monoethanolamine solution operating in the lean-to-rich loading range of 0.35–0.49. It was found that the apparent intensification effect of the rotating packed bed is more significant for ammonia than for monoethanolamine solution. This is explained by the fact that the operating loading of the monoethanolamine solution is closed to saturation and the average reaction rate is low at this end. Improving mass transfer will increase the amount of CO2 transferred from gas to liquid resulting in an accumulation of free CO2, thus reducing the driving force. For the dilute ammonia process, there is still sufficient reaction rate to covert the free CO2 because the operating lean-to-rich loading is far from saturation.