CO2 capture efficiency and heat duty of solid acid catalyst-aided CO2 desorption using blends of primary-tertiary amines

Abstract

This study evaluated improvements in the CO2 capture process in terms of cyclic capacity, absorption efficiency and heat duty caused by using a primary amine (5 M MEA) blended with a tertiary amine (2 M MDEA or 1.25 M DEAB) and a catalyst-aided desorber loaded with two different solid acid catalysts (γ-Al2O3 or HZSM-5) in a bench scale full cycle CO2 capture plant. The absorber and desorber were stainless steel pipes with inside diameter of 0.05 m and height of 1.50 m. The desorber was loaded with varying amounts of solid acid catalyst at an average bed temperature of 85 °C. The two mixed amine solvents tested, were compared with 5 M MEA each with a circulation rate of 0.06 L/min. Simulated flue gas, 15% CO2 in N2, was used at a total flow rate of 15 SLPM. The results showed that in 5 M MEA system, cyclic capacity and absorption efficiency increased while heat duty decreased when the catalyst amount was increased. In the case of mixed primary and tertiary amines, catalysts contribute to slight improvements. The increase in absorption efficiency was found to be in the order of 5 M MEA: γ-Al2O3 < 5 M MEA: HZSM–5 < 5 M MEA: 2 M MDEA: γ-Al2O3 < 5 M MEA: 2 M MDEA: HZSM–5 < 5 M MEA: 1.25 M DEAB: γ-Al2O3 < 5 M MEA: 1.25 M DEAB: HZSM-5. The relative reduction in heat duty of the system was found to be in the order of 5 M MEA: 1.25 M DEAB: HZSM–5 < 5 M MEA: 2 M MDEA: HZSM–5 < 5 M MEA: 1.25 M DEAB: γ-Al2O3 < 5 M MEA: 2 M MDEA: γ-Al2O3 < 5 M MEA: HZSM-5 < 5 M MEA: γ-Al2O3.