in Wiley InterScience (www.interscience.wiley.com).A rigorous rate-based model for acid gas absorption was developed and validated against mass-transfer data obtained from a 3-month campaign in a laboratory pilot-plant absorber in which the experimental gas-liquid material balance was within an average of 6%. The mass-transfer model is based on the penetration theory where the liquid film is discretized using an adaptive grid. The model was validated against all data and the deviation between simulated and averaged gas and liquid side experimental mass-transfer rates yielded a total variability of 6.26%, while the total average deviation was 6.16%. Simpler enhancement factor mass-transfer models were also tested, but showed slight over-prediction of masstransfer rates. A sensitivity analysis shows that the accuracy of the equilibrium model is the single most important source of deviation between experiments and model, in particular at high loadings.

The partial pressures of carbon dioxide (CO2) over a 30 mass % aqueous solution of monoethanolamine (MEA) and a 50 mass % aqueous solution of methyldiethanolamine (MDEA) were measured. The range of partial pressures of CO2 measured at 120 °C over 30 mass % MEA was from (7 to 192) kPa with loadings from (0.16 to 0.42). The partial pressures of CO2 ranging from (66 to 813) kPa with loadings from (0.17 to 0.81) over 50 mass % MDEA were also measured at the temperatures (55, 70, and 85) °C. An approximate value of the enthalpy of solution of CO2 in the aqueous MDEA solution was estimated using the solubility data.

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This work focuses on the experimental determination and thermodynamic modeling of the solubility of carbon dioxide (CO2) in an aqueous solution of 30 mass % 2-((2-aminoethyl)amino)ethanol (AEEA), with AEEA being a potentially new solvent for postcombustion CO2 capture by absorption. The vapor−liquid equilibrium (VLE) experiments were performed over a range of temperatures from 40 to 120 °C and for partial pressures of CO2 ranging from 0.01 to 220 kPa. The results obtained were then modeled by use of a modified Deshmukh−Mather thermodynamic model. The model provides a very good representation of the experimental data over the whole temperature range. In addition, 1H and 13C 1D NMR spectra were acquired for species identification and quantitative analysis of the major species distribution. The predicted speciation obtained from the model was also found to be in agreement with the speciation from the NMR data. Protonation constants (pK a) for AEEA were obtained by titration.

The performance of a laboratory-scale membrane contactor was investigated for the case of CO2 absorption into separate aqueous solutions of monoethanolamine (MEA) and methyldiethanolamine (MDEA). The variation in the flux of the CO2 absorption rate with the CO2 partial pressure, liquid CO2 loading, liquid velocity, and temperature was studied individually in an apparatus giving well-defined and controlled experimental conditions. A two-dimensional diffusion−reaction model was developed and used to predict the results of the experiments. Initial and boundary conditions for the concentrations of chemical species were calculated by an equilibrium speciation model based on the solution method given by Astarita et al. (Gas Treating with Chemical Solvents; Wiley:  New York, 1983). Corrections for nonideality were introduced by using a salting-out correction and by tuning the model to experimental VLE data. It was found that the diffusion of the ionic reaction products had a significant rate-limiting contribution to the observed fluxes and these diffusivities were regressed from parts of the experimental data.