Completed Research
Modeling of CO2 Absorption from Gas Mixtures Using Chemical Absorbents in Adiabatic Packed-Beds
Rui Wang, MS, 2019
(Thesis: University of Pittsburgh ETD)
A five-components comprehensive mathematical model for CO2 absorption from different gaseous mixtures by aqueous solutions of AMP (2-amino-2-methyl-1-propanol) and sodium glycinate (Na Gly) in a countercurrent adiabatic packed-bed absorber was developed. The model was implemented in MATLAB 2017b and used to predict, among others, the profiles of CO2 absorption efficiency, CO2 loading, and gas-phase and liquid-phase temperatures. The model predictions were first validated using four different runs of the AMP experimental data by Tontiwachwuthikul et al. (1992). In general, the model predicted the experimental data with good accuracy.
The validated model was used to predict the behavior of a small-scale (0.1 m ID) packed-bed absorber with (13 mm ceramic Berl Saddle) for CO2 capture from a CO2-air gaseous mixture using SG under identical inlet conditions to those of AMP. A direct comparison between the two absorbents showed that AMP has higher CO2 absorption efficiency and CO2 loading than those of SG due to the former’s greater reaction rate constant (k2) under similar temperatures.
The validated model was also used to conduct a parametric study to investigate the behavior of a large-scale (1.5 m ID) absorber packed with 13 mm ceramic Berl Saddle for CO2 capture from CO2-N2 gaseous mixtures using AMP and SG. The system pressure, liquid temperature, superficial liquid and gas velocities, CO2 mole fraction and packing type were varied in this study. The model predictions indicated that increasing system pressure, liquid temperature, superficial liquid and gas velocities, and CO2 mole fraction led to increasing the CO2 absorption efficiency and CO2 loading by both absorbents. This behavior was related respectively to the increase of the gas-residence time, reaction rate constants, gas-liquid mass transfer coefficients and the wetted specific area of the packing used. Among these variables, system pressure appeared to have the strongest effect on CO2 absorption efficiency. Also, the Metal Pall Ring 25 mm random packing with the largest specific wetted area showed the highest CO2 absorption efficiency when compared with those of the other four packings used.