A Thermodynamic Model for Estimating Acid Gas Solubility in Aqueous Alkanolamines

Partial pressures of carbon dioxide (CO2) and hydrogen sulfide (H2S) over aqueous solutions of monoethanolamine (MEA) and diethanolamine (DEA) have been correlated using a simple approach where only a few chemical equilibrium reaction is taken into account assuming ideal gas and ideal solution. The approach contains the Henry’s law constant and the chemical reaction equilibrium constants for the formation of carbamate and amine protonation for CO2-amine system with 4 adjustable parameters and H2S-amine system with just 2 adjustable parameters, resulting in an explicit expression for calculating the partial pressure of CO2/H2S over an aqueous alkanolamine solution. Accurate values for the partial pressure of CO2/H2S are obtained for a wide range of loading (0-1), temperature, amine concentration and pressure that is useful in modeling, design and handy calculations. The values derived from the model agree well with experimental data.