Date of Award
Doctor of Philosophy
This work aimed to evaluate the subsystems of a novel mediated oxycombustion system and determine the expected final conditions of the integrated subsystems. The subsystems included a cerium based oxygen transport membrane, transport membrane coatings to assist in the pickup and release of oxygen, and a molten intermediary oxygen carrier. Various doping levels of yttrium and zirconium were investigated, both as singular dopants and in a co-doped scheme. Regression analysis was performed to quantitatively evaluate how each dopant affected the material properties. Zirconium was not found to have statistically significant effects, although an effect was clearly noted on pure ceria. Functions of the doping level of yttrium were found for relative density, hardness, and the contributing factors of electrical conductivity. Chemical looping combustion experiments were performed to determine viable candidates for oxygen pickup and release coatings. It was discovered that a release coating was not necessary due to the use of a reactive fluid, and iron showed promise as a pickup coating but short of showing statistical significance. The ability of antimony oxide to react with hydrocarbon fuels and be regenerated by oxygen was investigated to determine the reaction rates. It was discovered that a co-doping scheme of yttrium and zirconium at a level of 8.33% (1/12th) each achieved the highest oxygen flux with a value of 3.671x10-7 mol O/s/cm2. All of the subsystems were we analyzed and a complete, theoretical system was described. It is recommended that the shape of the oxygen transport membrane be of a single-closed-end cylinder. This allows the increase of oxygen permeation with a smaller device footprint. It was found that the system would be capable of combusting 6.699 grams of carbon based fuel per minute per square meter of footprint. This equates to a heat rate of 3.6 kilowatts per square meter when utilizing a medium volatile bituminous coal. This value will continue to be improved as further research is conducted into the components of the system.
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