Emissions with Various Water Wash Configurations during Pilot Plant Testing of Aqueous Piperazine for CO₂ Capture

Five wash configurations were tested for 800 hours at a pilot plant campaign at the National Carbon Capture Center (NCCC): (1) a single-stage water wash (WWC), (2) a trickle bed alone, (3) the WWC + trickle bed, (4) the WWC + a third bed with structured packing (Bed 3 + WW), and (5) the WWC converted to an acid wash + the third bed (AW + Bed 3). Gas-phase analysis by PTR-ToF-MS (proton transfer reaction–time-of-flight–mass spectrometry) quantified outlet emissions of more than 38 species including ammonia, piperazine (PZ), 1-methylpiperazine (MPZ), acetaldehyde, and formaldehyde. The acid wash reduced ammonia to less than 10 ppb. Two-stage wash configurations reduced PZ and other amines to less than 0.1 ppb. The total listed hazardous air pollutants (HAPs) including aldehydes were not effectively removed by any of the wash configurations but were less than 10 tons/year when scaled to a 460 MW facility. All non-PZ emissions, including HAPs, were significantly reduced by thermal reclaiming of the solvent.