Pilot-scale evaluation of AMP/PZ to capture CO2 from flue gas of an Australian brown coal–fired power station

Abstract

Monoethanolamine (MEA) is a well-established absorption liquid used in post-combustion capture (PCC) technology that has a high rate of reaction with CO2. However, an absorption liquid with improved properties, such as less degradation, less corrosion and a lower energy requirement for solvent regeneration, would greatly benefit the PCC process. An alternative to MEA is an aqueous solution of 2-amino-2-methyl-1-propanol (AMP), promoted with piperazine (PZ). This absorption liquid is expected to improve CO2 recovery and reduce reboiler heat duty for solvent regeneration in PCC plants.This paper evaluates the pilot-scale performance of an aqueous mixture of 25wt% AMP and 5wt% PZ (AMP/PZ) with a total amine concentration of 30wt% compared with the baseline performance of aqueous MEA (30wt%). We evaluated the reboiler heat required for solvent regeneration and CO2 recovery for AMP/PZ and MEA as both a function of CO2-lean loading at a similar liquid to gas (L/G) ratio, and as a function of L/G ratio at a similar CO2-lean loading.Our results show that AMP/PZ is a promising alternative to MEA. At a similar L/G ratio, both MEA and AMP/PZ required lower reboiler heat duty when CO2-lean loading was reduced. At higher CO2-lean loadings, neither absorption liquid showed any changes in reboiler heat duty as a function of L/G ratio. One exception occurred for AMP/PZ at lower CO2-lean loadings (0.03 and 0.08mol CO2/mol amine), when reboiler heat duty dropped as the L/G ratio rose. In most experiments with AMP/PZ, the condenser heat and sensible heat were the major contributors to the reboiler heat duty at lower CO2-lean loadings (<0.1mol CO2/mol amine). For MEA, the condenser heat had the highest portion in the reboiler heat duty at a CO2-lean loading of <0.18mol CO2/mol amine. Increasing condenser heat was associated with an increase of heat for water evaporation to generate steam for CO2 stripping. The reboiler heat duty to capture ∼80% and ∼85% CO2 was similar for both absorption liquids; yet, to capture this proportion of CO2, AMP/PZ required a higher L/G ratio than MEA.