Amine Solutions for Biogas Upgrading: Ideal versus Non-Ideal Absorption Isotherms

Amine solutions were applied in carbon dioxide removal from a model mixture of biogas, carried out in a loop reactor system. In addition, the effect of CO₂ absorption acceleration in the presence of piperazine was confirmed and quantified, relating the obtained CO₂ loading with the piperazine concentration. Further, the interactions of CO₂ and water in aqueous amine solutions were discussed. The obtained acid gas loadings were accurately described taking into account the effect of the dissolved CO₂ on the equilibrium constant. A logarithmic absorption isotherm that follows from such considerations and a saturation-type isotherm were compared. In describing the experimental data, advantages and disadvantages of both approaches are discussed.