کد مقاله کد نشریه سال انتشار مقاله انگلیسی نسخه تمام متن
637906 1456157 2008 9 صفحه PDF دانلود رایگان
عنوان انگلیسی مقاله ISI
High pressure performance of thin Pd–23%Ag/stainless steel composite membranes in water gas shift gas mixtures; influence of dilution, mass transfer and surface effects on the hydrogen flux
موضوعات مرتبط
مهندسی و علوم پایه مهندسی شیمی تصفیه و جداسازی
پیش نمایش صفحه اول مقاله
High pressure performance of thin Pd–23%Ag/stainless steel composite membranes in water gas shift gas mixtures; influence of dilution, mass transfer and surface effects on the hydrogen flux
چکیده انگلیسی

The hydrogen permeation and stability of tubular palladium alloy (Pd–23%Ag) composite membranes have been investigated at elevated temperatures and pressures. In our analysis we differentiate between dilution of hydrogen by other gas components, hydrogen depletion along the membrane length, concentration polarization adjacent to the membrane surface, and effects due to surface adsorption, on the hydrogen flux. A maximum H2 flux of 1223 mL cm−2 min−1 or 8.4 mol m−2 s−1 was obtained at 400 °C and 26 bar hydrogen feed pressure, corresponding to a permeance of 6.4 × 10−3 mol m−2 s−1 Pa−0.5. A good linear relationship was found between hydrogen flux and pressure as predicted for rate controlling bulk diffusion. In a mixture of 50% H2 + 50% N2 a maximum H2 flux of 230 mL cm−2 min−1 and separation factor of 1400 were achieved at 26 bar. The large reduction in hydrogen flux is mainly caused by the build-up of a hydrogen-depleted concentration polarization layer adjacent to the membrane due to insufficient mass transport in the gas phase. Substituting N2 with CO2 results in further reduction of flux, but not as large as for CO where adsorption prevail as the dominating flow controlling factor. In WGS conditions (57.5% H2, 18.7% CO2, 3.8% CO, 1.2% CH4 and 18.7% steam), a H2 permeance of 1.1 × 10−3 mol m−2 s−1 Pa−0.5 was found at 400 °C and 26 bar feed pressure. Operating the membrane for 500 h under various conditions (WGS and H2 + N2 mixtures) at 26 bars indicated no membrane failure, but a small decrease in flux. A peculiar flux inhibiting effect of long term exposure to high concentration of N2 was observed. The membrane surface was deformed and expanded after operation, mainly following the topography of the macroporous support.

ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Membrane Science - Volume 316, Issues 1–2, 15 May 2008, Pages 119–127
نویسندگان
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