Technical and economic analysis of ionic liquid-based post-combustion Co2 capture process

Abstract

Post-combustion CO2 capture (PCC) is considered the most feasible and viable process for CO2 abatement in the power sector. Aqueous monoethanolamine (MEA) solvent, traditionally used in this process, brings along challenges, namely, huge energy requirement for solvent regeneration, huge solvent flow rate leading to large equipment sizes, and chemical and thermal degradability, among others. In this study, the prospects of replacing aqueous MEA solvent with a blend of ionic liquid (IL) and MEA are explored. IL is generally chemically and thermally stable among other encouraging properties but is however expensive. A blend of IL and MEA is predicted to have shared qualities of MEA and IL and therefore could hypothetically contribute to meaningful reduction in overall cost of the process. This hypothesis is investigated in this study by performing a technical and economic analysis of the process using aqueous blend of IL ([Bpy][BF4]) and MEA as solvent. A rate-based model of the process developed in Aspen Plus was used to perform the technical and economic studies. Technical and economic analysis of PCC with aqueous blend of IL and MEA as solvent have not been covered in existing studies. Also, reported models are derived using equilibrium-based approach. From the analysis, it is found that with about 5, wt% IL concentration, total solvent cost approximates closely to typical solvent cost for the MEA only process; higher IL concentration leads to significant increase in solvent cost. Also, the simulation results showed that the rate-based [Bpy][BF4]-MEA process can save about 7–9% regeneration heat duty and reduce the solvent flow rate by about 11.5–27% compared to the conventional MEA only process.