Dynamic Simulation of CO2 Absorption in a Packing Tower

The removal of CO₂ from gaseous streams is a very important industrial technology with applications to mitigate greenhouse gas emissions from flue gases in coal-fired power plants and removal of radioactive C₁₄ in the nuclear industry, among others.  One of the well-known technological alternatives for CO₂ capture is absorption/stripping with aqueous solvents, such as alkanolamines and their mixtures.

A dynamic model of the absorption process for dilute carbon dioxide mixtures in high alkaline solutions is proposed. Chemical reactions between CO₂ and the high pH solution have been included in the model through the use of an enhancement factor for chemical absorption. Interfacial equilibrium constants have been calculated based upon Henry’s constant values for the different gas phase species calculated using fugacity ratios obtained by the Peng-Robinson equation of state. Mass and energy balances have been derived for all the species in vapor and liquid phases. Numerical techniques have been used to calculate the resulting species concentrations and temperature axial profiles in both phases. The dynamic behavior has been compared to steady-state solutions. The model has been validated using experimental data available in literature for different columns, packing materials, and operating conditions. Simulations under different operating variables and dynamic inputs have been conducted. These results show the potential of the proposed model to optimize operation and control of these separation processes.