| Summary: | 碩士 === 國立臺南大學 === 綠色能源科技研究所碩士班 === 98 === In this study, two topics of hydrogen production are explored. The first part focuses on the water gas shift reaction (WGSR) in an environment with high gravity; the second part is on the thermal characteristics of methanol autothermal reforming.
In the first part, to perform the WGSR with high centrifugal force, a rotating packed bed (RPB), embedded by a Cu-Zn-based catalyst, with elevated temperatures is conducted where the rotor speed is in the range of 0-1800 rpm. Meanwhile, the reaction temperature and the steam/CO ratio range from 250 to 350°C and 2 to 8, respectively. A dimensionless parameter, the G number, is derived to account for the effect of centrifugal force on the enhancement of the WGSR. With the rotor speed of 1800 rpm, the induced centrifugal force in the RPB acting on the reactants is as high as 234g on average. As a result, the CO conversion from the WGSR is promoted up to 70% compared with that without rotation. This clearly reveals that the centrifugal force is conducive to hydrogen production, resulting from intensifying mass transfer and elongating residence time of the reactants in the catalyst bed. From Le Chatelier''s principle, a higher reaction temperature or a lower steam/CO ratio disfavors CO conversion; however, under such a situation the enhancement of the centrifugal force on hydrogen production from the WGSR tends to become more significant. Accordingly, a correlation between the enhancement of CO conversion and the G number is established. As a whole, the higher the reaction temperature and the lower the steam/CO ratio, the higher the exponent of the G number function.
In the second part, a vertical heating oven is constructed to carry out the autothermal reforming of methanol where a reaction tube is embedded. A commercial catalyst (Sud Chemie, MDC-3) is used to trigger the reaction and energy consumption of the reaction system is recorded automatically. The important parameters of O2/C ratio, S/C ratio and reaction temperature are in the ranges of 0-0.5, 1-2 and 250-300°C, and the residence time of the reactants in the catalyst bed is fixed at 0.05s. The experiments clearly indicate that increasing O2/C ratio decreases the frequency of heat supply, implying that a higher O2/C ratio is able to decrease energy consumption. On the other hand, hydrogen yield decreases with increasing O2/C ratio, whereas varying S/C ratio merely has a slight effect on energy consumption. As a whole, the methanol conversion is always higher than 97% and the theoretical hydrogen yield is beyond 95% in this study.
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