Colloquia

Summary

The carbon dioxide concentrations are rising in the atmosphere, affecting global warming and causing changes in climates all over the world. With large social impacts on life and economies, one of the major challenges also arises from large dependency on fossil fuels. Direct air capture (DAC) is one of the solutions to remove the CO2 to become net zero or negative in the future. However, with current carbon pricing and the large energy consumption required in DAC, it is not yet financially viable.

This research looks into a novel regeneration technique of amine-functionalized solid sorbents using a vacuum steam-assisted multi-stage fluidized bed (MSFB) desorber column. A heat integration system has been designed and modeled, which together with a model for a MSFB showed potential to significantly reduce the specific energy consumption. Experiments were conducted to determine some of the fluidization properties of the solid sorbent under different vacuum levels. The results showed differences to relations obtained from literature, including an unexpected observation of a difference between the minimal fluidization and bubbling velocity.

First a single-stage fluidized bed and later a three-stage fluidized bed setup was tested on feasibility and performance. Both designs showed to be feasible to operate continuously. The performance was tested on sorbent working capacity of both H2O and CO2. Moreover, the wall-to-bed heat transfer and thermal gradient inside the bed were assessed using the data collected during the experiments.

This work has shown that a vacuum steam-assisted single- or multi-stage fluidized bed for solid sorbent is feasible and could improve the scalability and energy efficiency of regeneration of carbon dioxide from the sorbents.