Multiphase porous medium adsorption/desorption model for CO2 capture applications
Denis Lukanin1*, Amit Halder2, and Ameya Joshi2
1Corning Science Center, Corning SNG, St.Petersburg (Russia)
2Modeling and Simulation Department, Corning Inc., Corning,
During the past decade, there has been much interest in CO2 capture and sequestration technologies due to emerging need for green-house gas mitigation. Adsorption of CO2 from gas mixtures by solid adsorbents gives one possible solution to the problem. Most widely used solid adsorbent reactors are conventionally based on packed beds loaded with various types of zeolite, activated carbon, or polymer adsorbent materials . A number of adsorption-regeneration strategies are used in industry, such as the Pressure Swing Adsorption (PSA), Vacuum Swing Adsorption (VSA), Temperature Swing Adsorption (TSA), carrier gas purge, and their combinations .
In this work, we present a comprehensive bed-scale numerical tool allowing for the simulation of packed-bed adsorption reactor operation. The model is developed on the basis of FLUENT® commercial fluid dynamics solver and involves computation of non-isothermal gas mixture flow through a packed bed, accompanied with the mechanism of CO2 extraction from feed mixture and its accumulation in the solid phase. We have also incorporated a thermal effect of adsorption in the model and developed an algorithm for separate computation of fluid- and solid-phase heat transfer, which was not readily available in the software. Various adsorbent regeneration (desorption) regimes can also be modeled with the developed tool.
For the verification of the model, we use experimental data on VSA CO2 adsorption cycle in 13X Zeolite-based packed beds borrowed from the papers by Xiao et al (2008)  and Zhang et al (2008) .
The model is based on numerical solution of Navier-Stokes equations describing mixture gas flow dynamics in the porous medium that represents the packed bed. The set of equations is accompanied with a transport equation for CO2 mass fraction. A separate CO2 accumulation equation in the solid phase is incorporated in the model.
Non-isothermal nature of flow in the packed bed is modeled with two separate energy equations for solid and gas phases. We account for the heat released during adsorption by incorporating the respective heat source term depending on the amount of adsorbed CO2 in the solid phase energy equaiton.
Results and Discussion
Verification of the model has been done using experimental data on CO2 adsorption taken from the paper  by Zhang et al. This reference contains time-evolution curves of outlet CO2 concentration for two adsorption experiments at different inlet flow rates: Q=115LPM and Q=66LPM. We used the first experiment to adjust unknown free parameters of the model. With these adjusted parameters we ran the simulation for the low flow rate and obtained pretty reasonable agreement between computed and experimental results.
1. Wei Liu et. al JOM Vol. 61 No. 4 36-44 (2009)
2. Penny Xiao et. al Adsorption 14 575–582 (2008)
3. Jun Zhang, Paul A. Webley, Penny Xiao, Energy Conversion and Management 49 346–356 (2008)