Post-combustion carbon capture using amine-based solvents faces challenges like oxidative degradation. O₂ is a ubiquitous component in flue gases and induces irreversible oxidation reactions in the amines, reducing CO₂ capture efficiency and increasing corrosion and maintenance costs. This study proposes monitoring dissolved O₂ (DO) to estimate the solvent oxidation behaviour, avoiding complex chromatographic methods. The approach assumes that oxygen is exclusively consumed by the initial amine during the oxidation process, linking the oxygen depletion kinetics with the amine-oxidation kinetics. DO measurements in monoethanolamine (MEA) reveal significant insights into the kinetics of the oxidative degradation process. CO₂ presence, investigated across different temperatures, accelerates O₂ depletion compared to unloaded samples, though there is no clear correlation between the amount of CO₂ loading and O₂ depletion rates. Making MEA more acidic accelerates oxygen depletion rates; still, the change in pH alone is unable to reproduce the DO rates observed in CO₂-loaded MEA. Higher temperatures accelerate the MEA oxidation. Metal contamination through iron sulphate and iron nitrate accelerates O₂ consumption rates, with the amount of iron being more relevant than the oxidation state of the iron in the original salt or the salt counterion. The influence of viscosity and chelators was studied by adding glycerol and chelating agents as additives, but the results were challenging to interpret. Initial measurements of MEA-Water-glycerol and MEA-Fe-chelating agent mixtures unexpectedly accelerate O₂ consumption, challenging assumptions about the glycerol's role as a non-reactive solvent and chelating agents as oxidation inhibitors. It is revealed through blank experiments that glycerol also oxidises in MEA mixtures, breaking the link between DO decay and MEA consumption, while the tested iron complexes act rather as oxidation catalysts.

The amine-based post combustion carbon capture process is one of the most advanced and preferred technologies to reduce CO2 emissions from point sources like power plants. The emissions of amine from capture plants is one of the biggest challenges faced by this technology. These emissions typically occur by means of aerosol/mist formation. To develop effective countermeasures, it is crucial to understand the dynamic behavior of aerosols within the column, which is currently not well understood. This manuscript presents the results from a study aiming to understand the mechanism of aerosol growth and its behavior along the absorber column in terms of particles number concentration, particle size distribution, and amine emissions. For that, a series of experiments were performed in TNO’s bench scale CO2 capture plant using 30 wt% monoethnolamine (MEA) as solvent. For a SO3 and CO2 concentrations of 5.25 ppm and 12.5 vol.% in the flue gas, MEA emissions at the top exit of the column were recorded as 1051 mg/Nm3 (with vapour emissions of 381 mg/Nm3). In the absence of SO3 in the flue gas, inlet particle concentration was 2.71 × 107/cm3 and resulting MEA emissions reduced by 63.5%–383 mg/Nm3.

From the bottom of the column until the point of maximum temperature, the MEA content in the vapour phase was consistent with the volatility of the solvent. After this point it drastically increases to 1051 mg/Nm3. Both the number of particles and the total particle mass has lowered from the bottom to the top of the column. For the benchmark test, inlet and outlet total particle concentration were found to be 6.24 × 107/cm3 and 2.3 × 107/cm3 respectively, while total particle mass is 2.22 mg/m3 at inlet and 1.32 mg/m3 at outlet. Particles with a dimeter below 0.006 μm contribute the most to total particle concentration both at the inlet (50%) and outlet (32%), while particles with diameter of 0.087 μm contributes the most to the total particle mass at inlet (47%) and outlet (55%). The measured total mass of particles was in the order of magnitude of 1 mg/m3. This is much lower than the expected aerosol mass emissions, in the order of magnitude of 1 g/Nm3 based on FTIR emissions.

No particles larger than 0.147 μm were recorded, which might explain the low total mass recorded. The cause for this is still under investigation, but it suggests that the sampling procedure may induce systematic errors to the measurements. Nonetheless, the observations from this study have given further insight into the aerosol dynamics in the absorber column and corresponding emissions.