Intensification of a Carbon Capture Process for Onboard Application

Process Intensification (PI) has emerged as a promising approach to reducing energy consumption and production costs in chemical processes. This study investigates a carbon capture process with a focus on PI, aiming to address the spatial limitations of shipboard applications. The key objective is to minimize the size of large equipment involved in the carbon capture process, ensuring its feasibility for maritime applications while accounting for the energy constraints onboard. A rotating packed bed (RPB) was evaluated as an alternative to large traditional packed columns for carbon capture. The study used a 17 MW cargo ship as a case study, referencing earlier work where a conventional carbon capture system was designed for the same vessel. This research compared the size and energy demand of the RPB-based system with those of the conventional approach. To assess the potential size reductions, a model was developed to simulate CO2 absorption using a Monoethanolamine (MEA) solution in an RPB. The results indicated that the RPB could significantly decrease the size of traditional absorption columns while maintaining the same CO2 removal efficiency. Similar modelling was conducted for CO2 absorption using other solvents, such as piperazine (PZ), piperazine-methyldiethanolamine (MDEA), and diethanolamine (DEA)-potassium carbonate aqueous solutions. The modeling results were validated using experimental data available in the literature, and ultimately, the sizes of RPBs required with different absorbents to achieve the same removal efficiency were compared. A detailed analysis of gas flow in RPB was conducted using CFD simulations. The high gas flow rates in large-scale RPBs with wire mesh packing were simulated under different operating conditions. Two case studies with different bed specifications were analysed. A CFD-aided pressure drop correlation was developed and incorporated into absorption and regeneration models to predict pressure variations within the rotating beds. The regeneration of the solvent was modelled, and the influence of various parameters on the efficiency of stripper units was analysed. The findings revealed that the RPB had minimal impact on the regeneration of the absorbent, with most of the regeneration being carried out by the reboiler. However, given the high heat transfer rate in the RPB and its substantial size reduction compared to conventional packed columns, the RPB was identified as a promising alternative. Finally, an RPB-based absorption-stripper cycle was modelled to assess the overall efficiency of the intensified process in comparison to conventional carbon capture methods. The results indicated that while the intensified process could reduce the size by more than three times, it would also lead to a significant increase in power demand. The impact of various parameters on system efficiency was examined to identify the optimal design and operating conditions. The results suggested that, although optimizing the design and operating conditions can significantly reduce the system's power demand, some additional energy consumption for the RPB-based carbon capture process, compared to the conventional design, is unavoidable.