Adsorption and Chromatographic Processes: Modeling and Optimization

  • Author / Creator
    Subraveti, Sai Gokul
  • High pressure carbon dioxide adsorption processes are employed in applications such as carbon dioxide capture and supercritical fluid chromatography (SFC). Carbon dioxide capture using adsorption has gained wide attention because of the promising materials that are developed for this application. On the other hand, supercritical fluid chromatography is one of the most prominent techniques for chiral separations in the pharmaceutical and food industry. Supercritical fluids (such as carbon dioxide), when compared to liquid solvents, have low viscosities and high solute diffusion coefficients. This allows for operations at high flow rates with low pressure drops (hence high productivities). The thesis addresses the design and evaluation of adsorption processes for carbon dioxide capture and development of modeling tools to understand the SFC processes. The first part of the thesis deals with pre-combustion carbon dioxide capture using pressure swing adsorption (PSA) process in an integrated gasification combined cycle (IGCC) power plant. IGCC power plants provide favorable conditions for carbon dioxide capture (high operating pressures around 35 bar and high carbon dioxide compositions of 30-40 %). A variety of PSA cycle configurations that were earlier designed based on a modified activated carbon, are subjected to a process optimization so as to maximize the performance of the PSA process. A multi-objective optimization framework is developed using an evolutionary algorithm with objective functions as carbon dioxide purity-recovery, parasitic energy and productivity of the PSA process. The study presents the formulation of an extensive model for the parasitic energy and a systematic analysis to understand the effect of low pressure and carbon dioxide purity. The Pareto curves obtained at the end of optimizations are examined for the process feasibility. The second part of the thesis focuses on developing a comprehensive axi-symmetric computational fluid dynamics (CFD) model in order to understand the dynamics of a plug introduced through a mixed-stream injection in supercritical fluid chromatographic columns. Two main phenomena contribute to chromatographic band distortions: the different retention behaviors of solute in the plug and in the mobile phases; and viscous fingering, a phenomenon where less viscous mobile phase penetrates into more viscous plug. The aim of this study is to confirm the existence of viscous fingering and explain the peak distortions arising due to large-volume injections in SFC columns. The model takes into account of key phenomena that influence peak shapes in SFC, namely, the injection of fluids with different viscosities, variation of solute retention with local mobile phase composition and pressure. Finally, the simulated elution peaks of solute are compared against the experiments.

  • Subjects / Keywords
  • Graduation date
    Fall 2017
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.