| Summary: | 碩士 === 國立中興大學 === 環境工程學系所 === 100 === Hydrogen-rich gas mixtures can be obtained by through several biomass conversion technologies. The composition and concentration of the gas mixtures will influence the efficiencies of the separation and purification ability of the membrane. In addition, the operating temperature and pressure during penetration will also influence the results of purification. Therefore, the aim of this study explores the application of carbon molecules sieve (CMS) membranes at different hydrogen production processes by estimation of the synthesis gas permeability and selectivity. The relationships between the membrane structure and the transmission behavior in mixed gas of membrane are also in consideration. The approaching experiments of CMS membrane applications for gas separation and purification are as following steps: (1) Single gas; (2) Binary gases (H2 and CH4 mixtures); (3)Biomass gasification simulated gases mixture ratio; (4)Synthesis gases obtained from methanol steam reforming. In consequence, the experimental results are expected to have better understanding of the mixed gas permeation behaviors during the membrane separation process and the possibility of biomass hydrogen production technology combined with membrane separation and purification.
The experimental results of single gas separation are found that CMS membrane provides a better H2 permeability (1929.60 Barrer). On the other hand, the 1.0%PPO modified CMS membrane performed a high selectivity of H2/CH4 (182.02), but H2 permeability significantly decreases after modification (1255.75 Barrer). Moreover, the results of binary gases (H2 and CH4 mixtures) indicate that the gas permeability increases/decreases with increase/decrease of gas proportions. As the feeding ratio of H2/CH4 from 1/1 to 1/3, the CH4 permeability is from 13.84 to 31.48 Barrer at the same time.
The result of separation of biomass gasification simulated syngas illustrates that the best hydrogen permeability and H2/CH4 selectivity of CMS membrane are 175.70 Barrer and 50.82 at the feeding ratio of H2:CO2:CO:CH4:N2 is 5:12:10:3:70 condition, respectively. In addition, experimental results obtained from methanol steam reforming reaction indicated that the methanol conversion from 96.88% decreases to 86.61% with the reaction temperature increase, and the amount of gas production decreased from 1678×10-6 mol/h to 910×10-6 mol/h. The results present the methanol conversion decreases with temperature increases, and it is supposed that the inactivation effect of 7Ni2Cu/Al2O3 catalyst occurred due to system pressure exists in membrane separation system. Besides, higher H2/CO selectivity and hydrogen yield is 8.86 and 853×10-6 mol/h at 250 ℃are estimated during the application of CMS membrane in methanol reforming, respectively.
Consequently, the experimental results in this study indicated that the H2 permeability increases with increasing the proportion of H2 in mixed gas, however, the permeability of CMS membrane separation in mixed gas environment is lower than that in single gas condition.
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