Configuration screening of combined stationary/rotating packed beds using MDEA/PZ mixture from a techno-economic perspective for enhanced CO₂ capture

Rotating packed beds (RPBs) offer cost advantages over packed beds (PBs) in CO₂ capture but face scale-up limitations. This work proposes combined RPB or PB absorbers as scalable alternatives. Rate-based models for PB and RPB using blended N-methyldiethanolamine and piperazine (MDEA/PZ) solvents were developed in Aspen Plus. High-gravity mass transfer correlations for RPBs were implemented through Fortran programming and validated against experimental data. The scale-up design was conducted using 25 wt% MDEA/5 wt% PZ solvents for various configurations combining PB or RPB, as well as for single PB and RPB, aiming to absorb 90% of CO₂ from 240 kg/h coal-fired flue gas. Results show that the volume required for the RPB + RPB in series is the smallest, approximately one-third that of the single PB. This space-saving effect is is essentially comparable to that of the single RPB. The designed absorbers were integrated with PB strippers into complete CO₂ capture processes for techno-economic analysis. The specific total CO₂ capture energy of the PB + PB in series process is the lowest, while the specific cooling duty is minimized in the series RPB + PB process. The RPB + PB also represents the most economical combination containing RPBs. The sensitivity analysis of the combined processes indicates that the absorber capital expenditure has the most significant impact on the estimated capture cost. A further orthogonal test was performed on the RPB + PB to clarify the primary and secondary factors affecting energy consumption and cost. This work offers novel insights for extending the application of RPB-based processes.