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Title
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Chemical kinetics modeling of non-equilibrium and thermal effects in vibrationally active CO2 plasmas
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Author
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Abstract
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| The problem of global climate change due to the emission of greenhouse gasses has accelerated the transition from fossil fueled energy sources to renewable ones. However, the intermittency of these energy sources makes their implementation challenging. Hence, there is an urgent need for more research on methods to store this excess electrical energy at peak production. Plasma technology has been shown to efficiently convert CO2 to CO (and oxygen), which can then be used to synthesize hydrocarbons through the Fischer-Tropsch process. However, more insight is needed in the importance of the underlying chemistry, and the different dissociation pathways. In our research, we aim to reveal the conditions at which the most energy efficient dissociation of CO2 takes place, for plasmas in which both vibrational induced dissociation and thermal dissociation become important. First, a supersonic flow microwave plasma model is investigated. This model reveals the effect of the flow on the plasma performance. The results reveal that the time delay for vibrational induced dissociation to take place, as well as the maximum specific energy input that can be added before the flow is choked are the main limitations to reaching high energy efficiency. Next, it is shown that pulsing the plasma can increase the vibrational-translational non-equilibrium, that is needed for efficient vibrational induced dissociation. The maximum improvement is reached when the plasma pulse time equals the time at which the vibrational temperature reaches a maximum value, and for long interpulse times, so that the gas can cool down before the next pulse starts. Finally, the effect of thermal quenching on the plasma performance is investigated for warm and cold plasmas at different specific energy inputs. It is shown that quenching can increase the final CO2 conversion by reducing the recombination mechanisms, and that high efficiencies are reached for thermal plasmas in combination with quenching. This PhD thesis increases our knowledge of the kinetics in CO2 plasmas, and gives valuable insight for experimentalists. |
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Language
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English
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Publication
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Antwerpen
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Universiteit Antwerpen
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2020
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Volume/pages
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207 p.
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Note
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Bogaerts, Annemie [Supervisor]
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Full text (open access)
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