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In-situ experimental investigation on the growth of aerosols along the absorption column in post combustion carbon capture

Journal article - S. Harsha, S. Harsha, Purvil Khakharia, Arjen Huizinga, Juliana Monteiro, Earl Goetheer, T.J.H. Vlugt

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 ...

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.@en

Lab scale investigation on the formation of aerosol nuclei by a wet electrostatic precipitator in the presence of SO2 in a gas stream

Journal article - Purvil Khakharia, Arjen Huizinga, Henk Trap, Juliana Monteiro, Earl Goetheer

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, typic ...

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.@en