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The knowledge of vapour-liquid equilibrium (VLE) of the carbon dioxide-alkanolamine-water system at high pressure plays a critical role in the design of natural gas sweetening systems. Semi-empirical thermodynamic models have been widely used to estimate the VLE at high pressure. However, the understanding of their correlation behaviour at high pressure is limited. Therefore, this study reviews the chronological development and analyse the performance of the two types of semi-empirical equilibrium models for the high pressure-high gas loadings. The effect of process parameters is first analysed on a theoretical basis and then modelled with use of correction factors, defining the systematic contribution of different parameters used in such models. The analysis shows that their VLE require small corrections for good correlation at high pressure, if the equilibrium constants are well-determined. Therefore, the study reports both reliable and improved values of equilibrium constants for alkanolamines, where applicable. In addition, the combined equilibrium constant based semi-empirical models are modified for estimating high pressure VLE of the said system, which were previously limited to low pressure equilibria and low loadings only. The study presents a comprehensive review of the semi-empirical equilibrium models, highlighting their key issues, challenges and future recommendations.

The accurate design of a packed column is largely dependent upon the accurate calculation of the effective mass transfer area (ae ) of a packing. The experimental and the modelling study for the packed column with CO2-Monoethanolamine (MEA) system has been reported by employing Sulzer DX packing. The model validation results revealed that the modification in the available simple ae correlations is necessary to attain the reliable results using Sulzer DX packing. Recently, a new simple ae correlation suitable for Sulzer DX packing with MEA-CO2 system has been reported. Therefore, in the present study, the rate-based model is developed using the newly developed ae correlation for the packed absorption column with Sulzer DX structured packing for CO2-MEA system. The model has been successfully validated with the experimental data. Overall results depict good accuracy (AAD < 15%) of predicted CO2 concentration profiles due to the reliable ae calculations. However, the relative accuracy is low at high liquid flowrates (> 8 m3/m2h) due to the design limitations of the ae correlation. Therefore, in this study, the adopted ae mass transfer correlation is found suitable for the reliable modelling of the packed absorption column with Sulzer DX packing.