Material selection and process design for adsorptive CO2 capture

  • Author / Creator
    Rajagopalan, Ashwin Kumar
  • Carbon dioxide capture using adsorption based separation processes has shown promise but has not been exploited to full potential to be implemented on a commercial scale. This thesis examines two key stages in the development of adsorption based carbon dioxide capture processes, namely adsorbent selection and process design. The first part of the thesis lays the foundation for screening and ranking adsorbents for CO2 capture using process optimization techniques. Recent interest in carbon dioxide capture has led to the development of hundreds of adsorbents. The selection of the adsorbents and the analysis of their performance for a given process is a challenging task. Usually, the expected performances of these adsorbents are evaluated by inspecting the isotherms and using simple adsorbent metrics (selectivities, working capacities, figures of merit). A process optimization based approach to screen adsorbents for post-combustion CO2 capture using vacuum swing adsorption is presented. Four different adsorbents (Mg-MOF-74, Zeolite 13X, UTSA-16 and activated carbon) were chosen as test materials and were subjected to process-scale studies on a 4-step PSA cycle with light product pressurization (LPP). The study highlights that most commonly used metrics do not correctly rank the performance of these processes. A systematic study to evaluate the process performance for hypothetical adsorbents to understand the effect of adsorption equilibria is presented. A graphical method to illustrate the non-linearity of CO2 and N2 isotherms along with the purity-recovery contours for the hypothetical adsorbents is put forward. It was shown that process performance is more sensitive to the affinity of N2 than that of CO2 adsorption capacity. The second part of the thesis deals with CO2 capture from an integrated gasification combined cycle (IGCC) based power plants. The IGCC based power plants is attractive as it provides better conditions for CO2 capture (high operation pressure of 35 bar and CO2 composition of 30-40 %). Adsorption equilibria for CO2 on an activated carbon based adsorbent were described using an empirical model and was used to design pressure swing adsorption cycles to concentrate the CO2 in excess of 95% with a recovery of 90%.

  • Subjects / Keywords
  • Graduation date
    Fall 2015
  • 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.