Aerosol measurement and mitigation in CO₂ capture by amine scrubbing




Beaudry, Matthew Robert

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Amine solvent losses are a significant issue for CO₂ capture by amine scrubbing. Solvent lost through aerosol emission represents an environmental hazard with adverse economic implications. This research focuses on developing analytical systems to quantify amine aerosol emissions. Fourier Transform Infrared Spectrometry quantified amine emissions and Phase Doppler Interferometry determined aerosol size and concentration. Baghouse pretreatment of the flue gas significantly reduced amine emissions through collection of aerosol nuclei. A baghouse at the National Carbon Capture Center (NCCC) reduced monoethanolamine (MEA) emission by over a factor of 10. An SO₃ generator was built to facilitate bench and pilot scale aerosol experiments by reacting SO₂ in air over vanadium pentoxide catalyst at 520 °C. Aerosol generation at UT-SRP produced up to 1.7 grams per minute of SO₃, with conversion exceeding 81 %. Bench scale experiments achieved conversion greater than 97 % and aerosol concentration up to 7E4 cm⁻³. SO₃ increased piperazine (PZ) emission by up to 7.6 mol PZ/ mol SO₃. SO₂ increased PZ emission by 1 mol/ mol SO₂, and increased MEA emissions by 3.9 mol/ mol SO₂. H₂SO₄ increased PZ emission by 3 mol/ mol H₂SO₄. PZ resisted aerosol emissions with lower SO₃ content; this is because a low inlet aerosol nuclei concentration results in rapid aerosol growth and subsequent collection by impaction. Higher process temperatures correlated with decreasing PZ emission, supporting the growth and capture theory. Increasing the solvent PZ content was shown to strongly correlate with increasing PZ emission. In bench scale experiments, PZ emission and aerosol size both increased as the PZ content in the solvent increased. Lowering the temperature bulge stage reduced PZ emission and the aerosol size. Increasing the inlet CO₂ correlated with larger aerosol. Increasing the solvent CO₂ loading and the inlet SO₃ resulted in greater aerosol concentration. Operations with a blower upstream of the absorber increased MEA aerosol emission. The upstream blower resulted in larger aerosol in greater quantities, containing a greater quantity of MEA Reduced MEA emission with an intermediate blower are probably due to collection of aerosol through impaction within the blower.


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