Modeling carbon capture using MEA and extended UNIQUAC: Validation and analysis of underlying physical phenomena

A rate-based process model for post-combustion CO 2 absorption using aqueous monoethanolamine (MEA) was evaluated against a broad dataset consisting of pilot and industrial scale absorbers. The model is based on a differential formulation for adiabatic packed columns and employs the extended UNIQUAC thermodynamic framework to describe phase and reaction equilibrium. Validation was performed using six independent campaigns, comprising 75 operating conditions and spanning wide ranges of liquid-to-gas ratios, inlet CO 2 concentrations, absorber heights, packing types, and MEA mass fractions (13–30 wt.%). The model successfully reproduces key absorber characteristics, including temperature (RMSE=3.69 ∘ C), gas-phase CO 2 (RMSE=1.6 mol%), and liquid-phase loading (RMSE=0.033 𝑚 ⁢ 𝑜 ⁢ 𝑙 𝐶 ⁢ 𝑂 2 𝑚 ⁢ 𝑜 ⁢ 𝑙 𝑀 ⁢ 𝐸 ⁢ 𝐴 ) profiles. Rich solvent loading is predicted with an overall AAD of 0.0106 𝑚 ⁢ 𝑜 ⁢ 𝑙 𝐶 ⁢ 𝑂 2 𝑚 ⁢ 𝑜 ⁢ 𝑙 𝑀 ⁢ 𝐸 ⁢ 𝐴 across all pilots. In addition to these, extended UNIQUAC performance within the absorption column is evaluated in terms of speciation and equilibrium partial pressure of CO 2 (p * 𝐶 ⁢ 𝑂 2 ). Temperature bulge analysis over the entire dataset reveals that, for the same operating conditions, lowering feed streams temperatures up to 15 ∘ C infers the migration of temperature bulge downwards. We suggest that this can be attributed to limiting, at low temperatures, water evaporation. Case study analysis demonstrates that locations of maximum CO 2 flux and temperature bulge do not necessarily coincide and focuses on mechanisms that define them.