Degradation of amines is one of the most important issues to be addressed for absorption-desorption based post-combustion CO₂ capture. Several laboratory studies have been performed to identify the degradation products and understand the mechanisms of degradation. However, there seems to be a gap in knowledge from translating the lab scale studies to observations from the pilot campaigns. Moreover, the observations from different pilot plant campaigns can be quite different. The objective of this study is to compare the solvent degradation behavior from different campaigns and highlight their causes in terms of solvent metal content and ammonia emissions. Results from the following different pilot plants are evaluated: (a) TNO's CO₂ capture plant at Maasvlakte, the Netherlands, (b) EnBW's CO₂ capture plant at Heilbronn, Germany and (c) ENEL's CO₂ capture plant at Brindisi, Italy. The different rate of oxidative degradation are correlated to the different operating conditions and layout of the pilot plants. Along with these results, kinetic models based on laboratory studies are used to compare the pilot plant observations, highlighting the differences between lab-scale studies and pilot plant studies.

This study presents the results of two field tests that aimed at evaluating two countermeasures (WESP and GGH) to avoid acid mist formation. A WESP is shown to be very efficient for the removal of nuclei from the flue gas (100% efficient) and thus can prevent aerosol formation inside an amine based absorber. This is however only valid in the absence of SO₂ in the flue gas entering the WESP. A decreasing WESP efficiency is noted in the presence of SO₂ with increasing voltages as a result of newly formed aerosols inside the WESP. This implies that no or very low levels of SO₂ should be present in the flue gas entering the WESP. Since most of the amine carbon capture installations have a pre-scrubber (usually using NaOH to remove residual SO₂ in the flue gas leaving the power plant's Flue Gas Desulphurisation) in front of their amine absorber, the WESP must be installed behind this pre-scrubber and not in front of it. Having a Gas-Gas Heater (or any type of flue gas cooling such as a Low Temperature Heat Exchanger) installed upstream of the wet scrubbing may prevent homogenous nucleation and thus prevent the conversion of H₂SO₄ into sulfuric acid aerosols and consequently mist formation issues in the amine based carbon capture installation. Which option to choose amongst the two countermeasures presented in this study will depend on whether a new built installation is being considered or whether a carbon capture is planned as a retrofit into an existing installation. Published by Elsevier Ltd.

This study is to our knowledge the first to describe the effect of a Gas-Gas Heater (GGH) of a coal fired power plant's has on (i) the H₂SO₄ concentration and (ii) the particle/aerosol number concentration and particle size distribution present in the flue gas. In the absence of a GGH, homogenous nucleation takes places inside the Wet Flue Gas Desulphurisation (WFGD) converting the gaseous H₂SO₄ into aerosol H₂SO₄. This leads to a high aerosol number concentration behind the WFGD with 80% of the aerosols being smaller than 0.02μm. This implies that an amine based carbon capture (CC) installation treating this flue gas can suffer from amine mist formation due to the high amount of available nuclei (i.e., H₂SO₄ aerosols) resulting in high amine emissions. In contrast, in the presence of a GGH not only 70% of the H₂SO₄ is removed from the flue gas (measured at the Nijmegen powerplant), but also homogenous nucleation in the WFGD is prevented resulting in low particle number concentrations. The flue gas leaving the GGH will not create any mist formation issues in an amine based CC installation due to the low amount of nuclei present in the flue gas. It is not the reduction in H₂SO₄ concentration by 70% inside the GGH as such that prevents mist formation but absence of H₂SO₄ in its aerosol form. These results are most likely quite widely transformable to other power plants that burn low sulfur coal i.e., around 0.7 weight%. This information will serve future pilot and demo CC installation around the world; in particular when retrofitted on power plants that have a GGH.

Amine based solvent used for SO₄ capture can be lost during the process due to: degradation, vaporization, mechanical losses and aerosol (mist) formation. Only recently, studies have appeared pointing out that aerosols can dominate the total amine emission at pilot plant scale behind coal fired power plants. Future full scale amine scrubber installations will be imposed emission limit values (ELV) for a number of components including NH3 and the amine itself. Most likely these ELV will be expressed as maximum concentrations tolerated in the SO₄ poor flue gas leaving the stack so it is important to prevent or cure amine aerosol emission. The study presents a novel combination of two existing measurement techniques, that measure: (i) amine emissions from the top of the absorber using FTIR and (ii) PSD of the incoming flue gas using the ELPI+. The study is the first to show how combining these two measurement techniques allows to predict the presence or absence of mist formation. This hypothesis is based on information obtained during several measurement campaigns on different pilot plants.