Evaluation of amine-blend solvent systems for CO2 post-combustion capture applications

This work evaluates amine-blend solvent systems for CO2 post-combustion capture applications for a 600 MWe conventional coal-fired power plant. The equilibrium-based Aspen Plus® absorption/desorption simulation tool was used for this evaluation. The total amine blends concentration was kept at the value of 30wt% for all different systems. Monoethanolamine (MEA) and diethanolamine (DEA) of weight variation of 3, 5, 10 and 15% are blended with 2-amino-2-methylpropanol (AMP), and methyldiethanolamine (MDEA). Fixed cross heat exchanger approach temperature of 10 °C and stripper bottom temperature of 120 °C are used as design specifications. These design specifications are used to screen each blend without CO2 loading through sensitivity analysis. The AMP with 3, 5, 10 and 15wt% blended DEA (the activator) was found to require lesser reboiler duty in comparison with 30wt% MEA, with lowest value of 3.17GJth/tonCO2 for 5wt% DEA activation. The promising four blends are further optimized using varying CO2 loadings. The blend of 5wt% DEA and 25wt% AMP with lean loading of 0.07 molCO2/molblend requires the lowest reboiler duty of 3.03GJth/ton-CO2 and lowest recirculation rate of 14.882m3/ton. Absorber temperature profiles indicate temperature changes depend significantly on the lean loading. Stripper temperature profile shows that temperature swing is pronounced at the bottom, suggesting that CO2 desorption takes place more at the lower stages.