Characterizing Adsorbents for Pre- and Post-Combustion Carbon Capture

  • Author / Creator
    Wilkins, Nicholas S.
  • Anthropogenic carbon dioxide emissions are driving climate change. The largest sources of emitted carbon dioxide are coal and fossil fuel power plants. One proposed solution to mitigate emissions is to capture carbon dioxide from fossil fuel power plants and store it underground. This is the basis of carbon capture and storage (CCS). There are two main carbon capture processes that are utilized in industry: pre- and post-combustion capture. In post-combustion capture, the fuel is combusted to generate power and then carbon dioxide is separated afterwards. In pre-combustion capture, a fuel is gasified and catalytically converted to mostly carbon dioxide and hydrogen; the hydrogen is then combusted to generate power. Adsorption has been suggested as a possible mechanism to capture carbon dioxide. In early design stages it is practical to simulate an adsorbent using a process model. This cuts costs and time associated with physical experiments. This thesis characterized and built models for adsorptive pre- and post-combustion processes. TDA Research Inc. (Wheat Ridge, CO, USA) has developed an activated carbon adsorbent called TDA 2015 (a pseudonym for patent protections) for pre-combustion carbon capture. A series of dynamic column breakthrough experiments were performed to determine equilibrium loadings and to build a model in our in-house adsorption simulator. These experiments were performed at approximately 160, 200 and 240 degrees Celsius and approximately 2.5, 4.5, 6.5, 8.5 and 10.5 bar of carbon dioxide. Additional equilibrium loadings were measured using volumetry at 30, 60, 120 and 160 degrees Celsius from vacuum to 1.2 bar. At this time hydrogen was not characterized, but it known to be very weakly adsorbing on TDA 2015. A LRC isotherm was fit to the equilibrium data and utilized in the adsorption simulator. At approximately 2.5, 4.5 and 6.5 bar of carbon dioxide the experimental and simulated results were in good agreement. However, at 8.5 and 10.5 bar of carbon dioxide, the LRC isotherm could quantitatively predict the loading, but not qualitatively predict the concentration or thermal breakthrough shape. A case study was performed to determine possible explanations to this behavior. For post-combustion capture, a premium (Z10-02ND) and standard (Z10-02) zeolite 13X were obtained from Zeochem (Uetikon am See, Switzerland) and studied. Water adsorbs very strongly on zeolite 13X. Due to this fact it usually neglected in adsorptive post-combustion capture studies. For this study, post-combustion flue gas is considered as a mixture of carbon dioxide, water and nitrogen. Carbon dioxide and nitrogen equilibrium loadings were measured from 0 to 150 degrees Celsius and 0 to 5 bar using volumetry and gravimetry. Equilibrium data was fit to a dual-site Langmuir isotherm for all components. A series of single component carbon dioxide and water breakthrough experiments were measured on both zeolite 13X samples at 22 degrees Celsius and 1.02 bar. These were modeled and simulated with the in-house adsorption simulator. The simulator predicted breakthrough behavior well for all materials and components. Competitive carbon dioxide and water breakthrough experiments were then performed at 22 degrees Celsius and 1.02 bar. The competitive breakthrough experiments were also simulated with the breakthrough simulator. However, the dual-site Langmuir isotherm was not able to capture the nonideality of the carbon dioxide and water mixture well.

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  • Degree
    Master of Science
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    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.