Aerosol based emissions have been reported from several Post-Combustion CO₂ capture (PCCC)pilot plants. These are known to pose a significant challenge in large scale implementation of PCCC processes. The aerosol nuclei are in the form of H₂SO₄ droplets or Na₂SO₄ particles, typically less than 0.1 μm and 0.255 μm, respectively. A wet electrostatic precipitator (WESP)is considered to be a potential counter-measure for removing these ultrafine aerosol nuclei from the flue gas. However, it has been observed that at certain operating conditions of the WESP, additional particles are formed which can act as aerosol nuclei. This study was performed to find out the specific operating conditions in terms of feed SO₂ concentration and applied WESP voltage, at which WESP results in generation of new particles. In the absence of SO₂, no additional particles are formed for the entire range of applied WESP voltage. At the lowest SO₂ concentration of 9 ppmv, additional particles were generated beyond 10 kV. The smallest size fractions contribute to more than 99% of the total number of particles, with 0.006 μm contributing to more than 80%. At the outlet of the absorber, although majority of the particles are of 0.006 μm (>60%)and 0.0158 μm (ca. 5%), larger particles of sizes 0.0945 to 0.945 μm, contributes to the remaining 35% of the total number. The shift in number distribution results in increase of aerosol mass from about 10⁻⁴ to 5 × 10^-3 mg/m³ to 0.2 to 0.5 mg/m³, from the inlet to the outlet of the absorber, respectively. Aerosol based MEA emissions were observed for the lowest SO₂ concentration of 9 ppmv and a voltage of 16 kV. Total MEA emissions were in the range of 600–1050 mg/Nm³. Based on these tests, industrial scale WESPs are likely to result in additional particles which can act as aerosol nuclei even at a SO₂ concentration as low as 9 ppmv. Additional tests aimed at SO₂ concentration lower than 9 ppmv in the feed gas, combinations of varying H₂SO₄ aerosol and SO₂ in feed gas, and varying flue gas velocity needs immediate attention to define the operating limits for WESP.

Potential production and emission of nitrosamines during post-combustion CO₂ capture has drawn some attention due to their toxicity and potential carcinogenicity. One of the possible ways to reduce the concentration of nitrosamines is irradiation of the liquid streams of the capture plant with UV light. This paper shows experimental results of the degradation of nitrosamines such as N-nitroso-diethanolamine (NDELA) and N-mononitroso- piperazine (MNPZ) in different solvent matrices. These solvent matrices include water and laboratory grade monoethanolamine (MEA) aqueous solutions, as well as aqueous MEA solution and wash water that had been used in a CO₂ capture pilot plant connected to a coal-fired power plant. Experiments were conducted in dedicated batch set-ups and in a continuous mini CO₂ capture plant. Results show that the UV absorbance of impurities (degradation products and/or dissolved metals) present in MEA solvent that had been used in a pilot plant significantly reduces the UV degradation rate of nitrosamines. Furthermore, UV light seems to accelerate the degradation of the capture solvent itself. For these reasons, if UV light treatment is to be used in full-scale post-combustion CO₂ capture plants, suitable locations would be the absorber's washing section or the stripper's condensate. At these locations, less interference of degradation products can occur and there is less solvent to be degraded.