Completed Research
Carbon Dioxide Capture Using Aqueous MEA Solutions in a Countercurrent Adiabatic Packed-bed Absorber
Sudesna Banerjee, MS, 2020
(Thesis: University of Pittsburgh ETD)
A 5-components mathematical model was developed in Matlab (R2016a) for CO2 absorption from a gas mixture using aqueous MEA solutions in a countercurrent adiabatic packedbed absorber based on the gas absorption with chemical reaction method developed by Pandya [1]. The absorber was operated under conditions similar to CO2 capture in post-combustion applications. The model equations were derived, and their parameters were obtained from the literature. The Henry’s Law constant (He) and CO2 diffusivity in the aqueous MEA solutions were calculated using the N2O analogy. Also, a rate-based model for the system in the same absorber was developed in Aspen Plus (v.8.8). Both models were used to predict the experimental results of CO2 capture from a gas mixture using aqueous MEA solutions in a 0.10 m ID, 6.55 m height packed-bed absorber with 12.7 mm Berl Saddles reported by Tontiwachwuthikul et al. [2]. The experimental results include CO2 mole fraction, CO2 loading and liquid-phase temperature profiles for four different runs.
The Matlab model predictions indicated that under all operating conditions used, the reactions between CO2 and aqueous MEA were fast as enhancement factors greater than 10 were calculated, and consequently the overall mass transfer rates were dependent on the specific wetted gas-liquid interfacial areas (aw) and independent of the liquid-side mass transfer coefficients (kL). In the Matlab model, the correlations by Cho [3] were used to calculate the specific wetted area (aw) and the liquid-side mass transfer coefficient (kL); and the model predictions were in a good agreement with the experimental data. In the Aspen Plus model, the correlations by Billet and Schultes [4] were used to calculate (aw) and the liquid-side mass transfer coefficient (kL); and the model could not satisfactorily predict the experimental data. The reason for this behavior was attributed to the small aw values calculated using the correlations by these authors when compared with those using the correlations by Cho [3]. Therefore, an interfacial area correction factor was introduced into the Aspen Plus model; and as a result, a good agreement was possible between the corrected model predictions and the experimental data.