Design and study of catalytic tube layer system for hydrogen production via ethanol steam reforming and water gas shift reaction

Abstract

In this study numerical simulation was conducted to analyze the effects of a new ethanol steam reforming (ESR) catalytic tube system design on hydrogen production and CO reduction The optimization method was also applied to evaluate the best relative angles between water gas shift reaction (WGSR) catalytic tubes in the combination of ESR and WGSR system The study was divided into two parts In the first part of this research a new design of the catalytic tube system with a crossflow configuration featured by low catalyst usage with low cost is developed in this study The simulation of ESR by using a new catalytic system is conducted by the computational fluid dynamics (CFD) model The effects of four parameters on ethanol conversion and H2 yield are evaluated by varying the catalyst thickness the ratio of tube diameter to channel width the molar ratio of steam to ethanol (S/E ratio) and the number of tubes The results indicate that the enhancement of the ratio of catalyst thickness and tube diameter can effectively improve the ethanol conversion and H2 yield stemming from the diminish of gas hourly space velocity (GHSV) and can be obtained 100% conversion when the value equal to 0 33; the greater ratio of tube diameter to channel width also give the lower GHSV resulting in better performance of the catalytic tube system (130 % improvement in ethanol conversion averagely) In addition increasing the number of tubes has the ability to rise the ethanol conversion and attain 97% conversion ratio when using four tubes In the second part of this research In order to reduce the high CO concentration form the ESR catalytic layer tube reactor for further application the ESR followed by WGSR in the single catalytic layer tube system is investigated The result reports that the low temperature is conducive to the hydrogen production for this system and the optimal S/E ratio is found to be 3 which is the theoretical value that would create the highest hydrogen yield and CO reduction improvement Furthermore it is discovered that the changing of tube diameter is better than changing the catalyst thickness because the same CO reduction improvement can be attained with lower catalyst cost (33% off) Lastly the optimization tool Bound Optimization by Quadratic Approximation (BOBYQA) is used for finding the best tubes arrangement It can be observed that the tubes are evenly distributed in the flow after optimization and the better performance in terms of H2 yield and CO reduction improvement (38%) can be achieved compared to the single catalytic layer tube system

Date of Award	2020
Original language	English
Supervisor	Wei-Hsin Chen (Supervisor)