Low-Temperature Dielectric Heating-Assisted CO2 Stripping/Solvent Regeneration of Aqueous Carbon-Rich Monoethanolamine, Piperazine, and 2-Amino-2-Methyl-1-Propanol Solvents

Global carbon dioxide (CO2) emissions rose by 0.9% to an all-time high of 36.8 Giga tons estimated by the International Energy Agency in 2022. Chemical-based CO2 absorption is one of the promising techniques where thermal energy is used to strip CO2 out of the solvents. The main purpose of this study is to regenerate the aqueous carbon-rich solvents, namely, monoethanolamine (MEA), piperazine (PZ), and 2-amino-2-methyl-1-propanol (AMP) using a microwave (MW) technique. The aim is to understand the MW exposure effects on carbon loading, CO2 stripping efficiency, stripping rate, cyclic capacity, energy demand, change in the physical properties such as pH, viscosity (μ), density (ρ), and surface tension (σ), and CO2 stripping kinetics. From the experimental investigation, the maximum stripping efficiency obtained with the higher nominal power input is observed to be 68.62% for MEA, 71.05% for PZ, and 67.74% for AMP. The temperature rise is very prompt within 2 min of MW exposure, where the solution reaches 80–88 °C, and in another 3 min, 92–100 °C was reached, indicating that the highest stripping rate of 7.88 × 10–4 kg/s was achieved in a short span of 2 min of regeneration for MEA at 30% power input level. AMP exhibits the highest cyclic capacity of 0.42 mol/mol, followed by MEA and PZ, and the corresponding energy consumption was 0.52 MJ/mol CO2. Increasing the MW power level has the direct influence on increased CO2 stripping, and this facilitates decreasing μ, ρ, and σ of the lean solvents. During regeneration, the pH of the lean solvent increases due to CO2 stripping. The desorption kinetic results revealed that CO2 stripping is kinetically controlled.