Humid Post-Combustion CO2 Capture By Vacuum Swing Adsorption Using CALF-20

• Author / Creator

  Nguyen, Tran Thanh Tai

• Carbon capture utilization and storage (CCUS) play a crucial contribution in reducing CO2 emissions and obtaining net-zero emission by 2050. Adsorbent-based technology offers an opportunity to separate CO2 under mild regeneration conditions. However, low CO2 concentration and water vapour in the flue gas make it challenging to separate CO2. In this thesis, CALF-20, a water-stable metal-organic framework (MOF), was characterized and demonstrated for humid post-combustion CO2 capture. Single-component CO2 and N2 isotherms were measured at various pressures and temperatures using volumetric and gravimetric methods. The dual-site Langmuir model was used to describe the CO2 and N2 isotherms. The adsorption equilibrium of water was measured from 0%-100% relative humidity (RH) at various temperatures using thermogravimetry analysis and volumetric methods. A hysteresis loop was observed from 8%-22% RH. The Quadratic-Langmuir model was used to describe water isotherms. The competitive loadings of CO2 and N2 were quantified by performing both adsorption and desorption dynamic column breakthrough (DCB) experiments. The CO2 loading barely changed under the competition of N2. The adsorption and desorption DCB of water were also performed. Multiple transitions corresponding to the shape of the isotherm were observed in the water DCB curves. A one-dimensional column model, including all dispersion, convection, heat transfer and pressure drop, was used to describe the adsorption dynamic in the column. The competitive loadings of CO2 and H2O were collected using both thermogravimetry analysis and dynamic column breakthrough techniques. At RH<40%, the competitive CO2 loadings barely changed. Water still exhibited a type V isotherm, but the inflection point shifted to higher RH, at 65% RH. The modified Langmuir isotherm model was used to describe the competitive CO2 loading. The framework of CALF-20 showed an extension under the presence of CO2. Basic four-step vacuum swing adsorption (VSA) and four-step VSA with light-product pressurization (LPP) cycles were used to evaluate the performance of CALF-20 under dry and wet conditions. Multi-objective optimizations were used to optimize process performances. Five points on the Pareto curves were chosen randomly to validate the model predictions. The adsorption of CO2 was not affected by water at RH<45%. Similar purity, recovery and productivity compared to the dry case were obtained. The CO2 separation at high RH (70%) was also demonstrated in this study. The results of this thesis showed that CALF-20 was capable of separating CO2 under both wet and dry conditions.

• Subjects / Keywords

  • CO2 capture
  • Adsorption
  • MOFs
  • DCB
  • VSA

• Graduation date

  Spring 2021

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-gy4k-yt42

• 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.