Effect of hydrogen permeation and operating parameters on thermochemical performance of solar-driven steam methane reforming membrane reactor

Abstract

When the steam methane reforming membrane reactor is coupled with trough solar collector to achieve solar thermochemical energy storage, the dimension of the membrane reactor is enlarged and the catalyst filling amount increases dramatically. As a results, the hydrogen permeation property should be well addressed to match the permeation and the reaction characteristics for a better energy storage performance. In the present paper, the effect of hydrogen permeation, including the effective permeation area and the membrane permeance was investigated by numerical simulations. Results show that the sensitivity factors of the membrane surface area on CH4 conversion, H2 yield and H2 recovery are 0.379, 0.325 and 2.196 respectively while that of membrane permeance are 0.007, 0.009 and 0.488 respectively. This indicates that influence of membrane surface area is more remarkable and H2 recovery is the most sensitive to the hydrogen permeation. The reactor with a membrane tube diameter of 50 mm and a permeance of 1.07 × 10−2 mol/(m2·s·Pa0.62) can achieve best reaction performance. Besides the reaction performance, a solar thermochemical system is proposed and a solar-to-fuel efficiency is defined to evaluate the thermochemical performance. Again the aforementioned reactor has the highest solar-to-fuel efficiency which can exceed 70 %. Furthermore, for a better thermochemical performance, lower inlet mass flow rate and higher inlet temperature are recommended, but too small or too high values should be avoided to maintain the operating temperature of the membrane. A suitable combination of pressures in the reaction side and the permeating side is also suggested. The results of the present paper reveal the role of hydrogen permeation and helps the reactor design.