Accurate screening of amines by the Wetted Wall Column

To screen amine solvents accurately for CO2 capture, a Wetted Wall Column (WWC) was used to measure equilibrium CO2 partial pressure and CO2 absorption/desorption rate at variable CO2 loading from 40 to 100 °C. The solvents included 10 m diglycolamine (DGA®), 4.8 m 2-amino-2-methyl-propane (AMP), 8 m N-methyl-1,3-propanediamine (MAPA), 7 m/2 m and 5 m/5 m methyldiethanolamine (MDEA)/piperazine (PZ). With a semi-empirical VLE model assuming a lean/rich CO2 loading corresponding to 500 Pa/5000 Pa CO2 partial pressure, cyclic capacity and heat of CO2 absorption was determined. Liquid film mass transfer coefficients are reported for each solvent, which allows estimation of packing area required for 90 removal via a simple absorber design. The results show that the capacity of DGA® and MAPA is 10–20% less than 7 m MEA with a 5 to 15% slower rate. 4.8 m AMP has a capacity twice as great as 7 m MEA, but the rate is lower by 45%. 7 m/2 m MDEA/PZ has a similar capacity to 8 m PZ but slightly slower rate. 5 m /5 m MDEA/PZ has a capacity 20% greater than 8 m PZ and a comparable rate. The heat of CO2 absorption in the primary amines is about 80 kJ/mol CO2. The value for PZ and its blend with MDEA is about 70 kJ/mol CO2.