Optimization of solvent properties for post-combustion CO₂ capture using process simulation

Great efforts are underway to develop improved absorbents for post-combustion CO₂ capture. Regardless of the solvent composition, the absorbent can be represented by a series of sub-models for physicochemical properties. The purpose of this paper is to identify the solvent characteristics that play crucial roles in the total cost of CO₂ separation. Aqueous monoethanolamine (MEA) was selected as the reference solvent system, and a robust process model to describe its behavior was validated. The impact of various properties on the capture performance was evaluated separately via flowsheet simulations. The solvent viscosity, volatility, heat capacity, CO₂ solubility, enthalpy of solution, solvent strength and absorption kinetics have been identified to be important factors, that have however a combined effect on CO₂ separation cost. Compared with an optimized MEA-based capture plant, a lower capture cost of 52.19 €/ton CO₂ could be achieved with a low-volatile solvent. To show a clear target for further solvent development, sensitivity analyses of solvent properties were employed. Taking the assumed absorbent as a reference, an increase in CO₂ solubility, solvent strength or absorption kinetics, or a decrease in liquid volatility or viscosity can further improve solvent performance to some extent.