1. Modeling the Adsorption of Mixed-Gases Based on Pure Gas Adsorption Properties Nir Tzabar, Harry J. Holland, Cris H. Vermeer, Marcel H.J. ter Brake Energy, Materials and Systems Faculty of Science and Technology University of Twente Enschede, Netherlands

2. CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 Outline 1.Motivation 2.Pure gas adsorption measurements 3.Sips isotherms 4.Mixed gas adsorption calculations 5.Summary

3. CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 1. Motivation  Joule-Thomson (JT) sorption cryocoolers have no moving parts; therefore, are free of vibrations and have potentially a long lifetime.  Mixed-Regrigerants allows lower operating pressures for JT cryocoolers (relative to pure gases) and higher COPs.  This study is a step in a research on mixed-refrigerant JT sorption cryocooling Developing an effective model to determine the adsorption of mixed gases out of pure gas adsorption isotherms for the research on JT sorption cryocoolers

4. CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 2. Pure gas adsorption measurements Experimental setup Connecting Tube Gas Source N 2 / CH 4 / C 2 H 6 / C 3 H 8 Coriolis Flow Controller PiPi P V Heater V3V3 V2V2 V1V1 Vacuum Pump Sorption Cell T Norit-RB2 Activated carbon, steam activated, extruded carbon.

5. CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 2. Pure gas adsorption measurements Experimental results 300 K 320 K 340 K 360 K 380 K 400 K Nitrogen Methane Ethane Propane

6. CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 3. Sips Isotherms C 0 – the saturated adsorption concentration a – the adsorption affinity n – adsorption heterogeneity parameter C – adsorption concentration p – pressure

7. CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 3. Sips Isotherms Linearization:

8. CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 3. Sips Isotherms

9. CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 3. Sips Isotherms 340 K 380 K 400 K 300 K 320 K 360 K Symbols – Experimental results Solid lines – Sips model

10. 3. Sips Isotherms Modified Sips model CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015

11. 3. Sips Isotherms Modified Sips model CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 Symbols – Experimental results Dashed lines – Modified Sips model

12. 3. Sips Isotherms CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015

13. 4. Mixed gas adsorption calculations The composition of the adsorbed phase: The adsorption selectivity: CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015

14. 4. Mixed gas adsorption calculations Nitrogen - Methane Nitrogen - Ethane Nitrogen - Propane 300 K x – molar fraction in the adsorbed phase y – molar fraction in the vapor phase = 0.22 @ 10 bar ij

15. CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 5. Summary  The adsorption of nitrogen, methane, ethane, and propane on Norit-RB2 activated carbon have been measured.  The Sips adsorption model is used to describe the adsorption isotherms, and a linearization method is used to determine the parameters out of the experimental results.  A modified Sips model that incorporates the temperature dependence is suggested.  The adsorption model is further developed for the adsorption of gas mixtures.  The adsorption selectivity is discussed and the results of nitrogen-methane, nitrogen- ethane, and nitrogen-propane are presented.  Future work: I.Pure gas adsorption measurements on other adsorbents II.Experimental verification of the mixed gases adsorption model III.Using the modified Sips model in a sorption compressor analysis

16. CEC-ICMC, Tucson AZ, Nir Tzabar, July 2015 Thank you for your attention