CO2Absorption Rate into Concentrated Aqueous Monoethanolamine and Piperazine

The CO 2 equilibrium partial pressure and liquid film mass transfer coefficient ( k g ′) in (7, 9, 11, and 13) m monoethanolamine (MEA) and (2, 5, 8, and 12) m piperazine (PZ) were measured in a wetted wall column. Also examined was 7 m MEA/2 m PZ. Absorption and desorption experiments were performed at (40, 60, 80, and 100) °C over a range of CO 2 loading. Amine concentration does not affect the CO 2 partial pressure of PZ or MEA solutions as a function of CO 2 loading with less than 0.45 mols CO 2 /mol alkalinity. Changes in amine concentration and temperature often do not affect the measured value of k g ′. At higher temperature and CO 2 loading in PZ, the diffusion of reactants and products limits CO 2 transfer, and k g ′ is depressed. PZ (8 m) exhibits a 70 % greater CO 2 capacity than 7 m MEA and a 50 % greater CO 2 capacity than 11 m MEA. k g ′ decreases by a factor of 30 in aqueous MEA with 0.23 to 0.50 CO 2 loading. k g ′ decreases by a factor of 20 in aqueous PZ with 0.21 to 0.41 CO 2 loading. PZ is shown to absorb CO 2 2 to 3 times faster than MEA.