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Amine-based absorption−desorption processes are considered to be the state-of-the-art technology for CO 2 capture. However, the typical amines used are susceptible to oxidative and thermal degradation. Ammonia is formed as a result of oxidative solvent degradation. Because of the volatility of ammonia, significant emissions of ammonia can occur. Emission countermeasures such as water washing and use of demisters are ineffective against highly volatile components such as ammonia. The aim of this study is to demonstrate acid washing as a countermeasure for ammonia emissions. The tests were carried out at TNO's CO 2 capture plant at Maasvlakte, The Netherlands. Aqueous monoethanolamine (MEA, 30 wt %) was used as the absorption liquid. Typical ammonia emissions at the water wash outlet were in the range of 15−20 mg/Nm 3 , as measured by Fourier transform infrared (FTIR) spectroscopy. An acid wash scrubber using sulfuric acid was installed downstream of the water wash. Parametric tests based on changing the pH and flow rate of the acid liquid and the temperature of the treated flue gas were performed to assess the efficiency of the acid wash scrubber. Additional ammonia (up to 150 mg/Nm 3 ) was spiked in the treated flue gas to test the acid wash scrubber, even under extreme conditions. The results from the experiments were compared with a model made in Aspen Plus. The experimental results indicated that it was possible to reduce ammonia emissions below 5 mg/Nm 3 at a pH of 6 for both spiking and nonspiking experiments. The modeling results were in good agreement with the experimentally measured ammonia emissions. The breakthrough of ammonia capture, defined as less than 20% capture efficiency, was found to be at lower pH, 6.8 for nonspiking experiments and 8.1 for spiking experiments, than for the model, which predicted breakthrough at pH 8.7 for nonspiking experiments and 9.7 for spiking experiments. Changes in the acid liquid and treated flue gas temperature did not have an impact on the capture of ammonia. MEA emissions were also below 3 mg/Nm 3 at the acid wash scrubber outlet. It is estimated that the purchased equipment cost of an acid wash is about €3.75 million for an 800-MW e -scale postcombustion CO 2 capture plant.

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 5.25ppm and 12.5 vol.% in the flue gas, MEA emissions at the top exit of the column were recorded as 1051mg/Nm 3 (with vapour emissions of 381mg/Nm 3 ). In the absence of SO3 in the flue gas, inlet particle concentration was 2.71 x 10 7 /cm 3 and resulting MEA emissions reduced by 63.5% to 383mg/Nm 3 . 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/Nm 3 . 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 6.24x10 7 /cm 3 and 2.3x10 7 /cm 3 respectively, while total particle mass is 2.22mg/m 3 at inlet and 1.32mg/m 3 at outlet. Particles with a dimeter below 0.006µm contribute the most to total particle concentration both at the inlet (50%) and outlet (32%), while particles with diameter of 0.087µm 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 1mg/m 3 . This is much lower than the expected aerosol mass emissions, in the order of magnitude of 1 g/Nm 3 based on FTIR emissions. No particles larger than 0.147µm 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.