Mechanistic analysis of post-combustion CO₂ capture performance during amine degradation

Degradation of amine is often regarded as a major problem for amine-based post-combustion CO₂ capture. However, the observed regeneration energy in long-term pilot plant operations does not necessarily increase, regardless of the accumulation of degradation compounds. This paper provides a mechanistic explanation for this seemingly paradoxical behavior by focusing on the influence of heat stable salts and the CO₂ loading range on solution properties. Post-combustion CO₂ capture using degraded amine solution was simulated in Aspen Plus®, and the influence of heat stable salts on CO₂ loading, solution properties, and regeneration energy were analyzed. Results indicate that the alteration of the operational CO₂ loading range and the physical properties of heat stable salts themselves cause changes in solution properties that dictate overall energy consumption, such as viscosity, vapor liquid equilibrium, and specific heat capacity. These effects often offset each other to some extent, thereby obscuring the influence of individual factors on regeneration energy. These counteracting effects can largely explain the seemingly paradoxical behavior of post-combustion capture maintaining relatively low energy consumption even when amine degradation proceeds.