This chapter gives an overview on the issue of aerosol-based emissions observed in post-combustion CO2 capture. Firstly, the evidence of aerosol-based emissions obtained from different pilot plant tests is presented. Unlike vapor-based emissions, which can be quantified and predicted based on the vapor pressure of the component, aerosol-based emissions are difficult to predict as it depends on several parameters. The key elements identified to explain the observation of aerosol-based amine emissions in PCC are discussed here. As the issue is being better understood, several countermeasures have been tested. Their efficiency in reducing aerosol-based emissions and possible disadvantages are summarized. The remaining knowledge gaps both from an understanding point of view as well as from a countermeasures point of view are outlined, and can serve as a basis for future research on this topic.

Aqueous amino acid salt solutions that precipitate due to CO2 absorption are a relatively novel and promising class of solvents. Although the presence of solids in the process stream requires adequate measures related to slurry handling and crystallization control, precipitation also increases the solvent CO2 capacity and the energy performance of the stripper. By using an additional solid–liquid separation step to concentrate the slurry before it is sent to the stripper, known as the DECAB+ process, the energy performance can be further improved. Most of the current experimental work on these systems focuses on the amino acids taurine, α- and β-alanine, sarcosine, glycine, and proline, neutralized with equimolar amounts of potassium hydroxide. Investigated properties include the CO2 concentration at which precipitation is first observed, which is closely related to the solubility of the amino acid, the composition of the precipitate, and the CO2 absorption rate. The precipitate typically contains pure amino acids and/or bicarbonate, depending on the amino acid solubility. Shortcut process simulations have been used to estimate the energy performance of absorption processes using precipitating amino acids, so far focusing on 4M KOH + taurine (K-tau) and 4M KOH + α-alanine (K-α-ala) solutions. Specific regeneration duties below 2 GJ/ton CO2 seem possible for the DECAB+ process when using K-α-ala and lean vapor compressor (LVC). Compared to a conventional process using 30 wt % monoethanolamine and LVC, this corresponds to a reduction of 35% in the regeneration duty. Future research should focus on more-detailed process simulations, based on a predictive thermodynamic model that consistently describes the vapor–liquid–solid equilibria of the system. Demonstration of the DECAB+ process on a pilot scale is also highly recommended, with a special focus on the crystallization and slurry handling process steps and units