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First Thermal and Fluids Engineering Summer Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

Numerical Study of Turbulent Gas Flow and CO2 Absorption in Porous Media

DOI: 10.1615/TFESC1.prm.012861
pages 2265-2294

Amit Patil
Department of Mechanical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250

Frank Wang
Green Technology, Ltd, Co, 311 Townepark Circle Ste 101, Louisville, KY 40243

Liang Zhu
Department of Mechanical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250; Centennial High School, Ellicott City, MD, 21042

Ronghui Ma
Department of Mechanical Engineering, University of Maryland, Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250


KEY WORDS: CO2 absorption, turbulent gas flow, porous media

Abstract

Chemical absorption of CO2 in Monoethnol Amine (MEA) solutions has been used extensively in removal of carbon dioxide from flue gases generated in coal-burning thermal power plants. The removal of CO2 by chemical absorption involves turbulent flow through a porous packing material, physical absorption at the /liquid interface, and chemical reactions in the liquid phase on the wetted surface of the packing material. The treated flue is nearly CO2 free and the CO2-rich chemical solution is delivered to a striping facility to liberate CO2. The rate of absorption is dependent on local gas velocity, temperature and mass transfer between the gas and liquid phases. The ratio of liquid/gas flow rates and the type of packing material have substantial influence on the performance and energy consumption of the CO2 capture process.
In this study, we have developed a two-dimensional model for simulating absorption of CO2 using water-based MEA with the consideration of turbulent flow through a porous medium, physical and chemical absorption of CO2, mass transfer of CO2 and MEA, and heat transfer between the gas and liquid phases. Specifically, the Brinkman-Forchheimer equation is used to describe high velocity gas flow through porous packing materials, and a two-film theory is used for simulating mass transfer between the gas and liquid phases. This model is used to study the distributions of gas velocity, pressure, CO2 absorption flux, CO2 and MEA concentrations, and temperature in the absorption column for various operating liquid/gas ratios and packing materials. This model is also used to verify the validity of the assumptions made in one-dimensional model, such as plug flow and linear pressure drop along the axial centerline of the column. Our results show that the distributions of velocity, CO2 and MEA concentrations, and temperature vary substantially in the axial directions in a cylindrical absorption column of a large aspect ratio. The performance of various packing materials is evaluated. The relationship between the liquid flow rate and CO2 absorption rate is obtained for different packing materials.

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