| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 106 === In recent years, technologies for reducing carbon dioxide in atmosphere have received much attention. Converting captured CO2 into valuable chemicals such as syngas is one possible solution. Syngas is a universal intermediate and could be further converted into various valuable products depending on the H2/CO ratio in syngas. The conversion of CO2 into syngas could be realized by consuming methane (dry reforming) or hydrogen (reverse water gas shift). However, the H2/CO ratio in produced syngas from direct conversion of CO2 with methane is limited to around 1. The concept of combined reforming is to utilize the advantage of steam reforming and partial oxidation simultaneously, which could raise H2/CO ratio and mitigate coke formation on catalyst. This work attempts to use rigorous kinetic model to determine at which H2/CO ratio the process would convert more CO2 than produced, and to select the best combined reforming reactor. All production processes considered in this work are heat-integrated to recover energy from product. The CO2 emission of raw material production evaluated with Life Cycle Assessment data is also considered. Process for conversion of CO2 with hydrogen from polymer electrolyte membrane or from upstream steam reforming reactor is also discussed.
The result suggests that process with tri-reforming reactor when target H2/CO ratio lower than 1.5 would have ability to reduce CO2. CO2 conversion could be improved with addition of oxygen because combustion reaction could maintain high temperature in reactor. The sensitivity test for hydrogen cost on total annual cost of process shows that if cleaner hydrogen cost becomes lower than 3 USD/kg, conversion of CO2 with hydrogen is cost competitive with combined reactor process and performs even better in terms of CO2 reduction.
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