(123f) Thermodynamic Modeling of Water-Acid Gases-Alkanolamine Systems

In the gas processing industry absorption with chemical solvents has been used commercially for the removal of acid gas impurities from natural gas. The currently preferred chemical solvent technology for carbon capture is the use of amine-based chemical absorbent. Alkanolamines, simple combinations of alcohols and ammonia, are the most commonly used category of amine chemical solvents for CO2 capture. Internationally many large oil and gas fields have high CO2 and H2S content (>50 mol%) and also traces of carbonyl sulfide (COS) and mercaptanes (RSH).

It is known that many of the most used thermodynamic models for the simulation of acid gas solubility in alkonolamines (Kent Eisenberg, Deshmuk-Mather, electrolyte-NRTL) may give large errors when extrapolated to high pressures, high wt% amine, mixed CO2 and H2S gasses, gasses with traces of COS, RSH. So accurate estimation of thermodynamic equilibrium between high pressure natural gasses (up to 100 bar) with high amounts of CO2 and H2S and alkonolamines such as MEA, MDEA and DEA is crucial for obtaining a good design of amine based acid gas removal processes.

In this work the Extended UNIQUAC model is used for representation of the behavior of acid gas-alkanolamine mixtures over an extensive pressure range, with emphasis on mixed acid gases and presence of carbonyl sulfide and mercaptanes. Model parameters are optimized from the available experimental data. As a foundation for this modeling, a large literature review on experimental works for water-acid gases-alkanolamine systems has been done.

Keywords: Alkanolamines, Acid gases, Thermodynamic model, Extended UNIQUAC