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Theoretical Study and Experimental Test-Rig Implementation for Investigating Water-Gas Shift Conversion Processes for Coal-to-Hydrogen Energy Systems

The doctorate work has concerned the study, design, development, construction, setting up and blank experimentation of a laboratory-scale test-rig for two-stage water-gas shift conversion processes. A first analysis of the shift conversion process has been conducted (both chemical dynamics and kinetics), to predict the performance of the two reactors and the gas conversion achieved inside them. An in-depth thermal analysis has also been performed, to estimate the temperature distribution inside the reactors. The reactors have hence been designed and their general behaviour at design and off-design conditions predicted. The model has been of support for the detailed design of the entire set-up. Strong attention has also been directed to the instru-mentation of the test-rig, concerning both the measuring instrument selections and their calibration and arrangement in the set-up. The development of programmes for the data acquisition management has permitted to automate the data collection and storage. The blank tests performed have hence allowed to validate the solutions adopted during design and to prove the test-rig functionality. The set-up is currently used by the Department for further experimental studies of support for a full-scale Sardinian power plant, as well as for the work of various graduating engineering students and PhD students.

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1 Introduction Aim of the work Major industrialized countries have been engaged in a course of transformation of the present energy technologies based on fossil fuels towards new technologies founded on hydrogen. This action derives from the unbearableness of the present industrial politics pivots on the economy of fossil fuels and oil in particular, more and more in crisis for global extent problems, such as: the limited quantity, and therefore duration, of ascertained fossil fuel reserves, carbon dioxide accumulation in atmosphere caused by fossil fuel combustion and incidental increment of greenhouse effect, uncertainty of supplies and vulnerability of energy systems founded on oil. Time required to put into effect this transition process will last at least 50 years. A first phase, of nearly 20 years, should be characterized by conspicuous public investments for research and development activities, with the fulfilment of demonstrative and innovative systems of hydrogen production and utilization, and building of initial infrastructures. If in a long-term perspective hydrogen will be produced prevalently from water by means of thermal or electrolytic decomposition starting almost exclusively from renewable and nuclear energy sources, in a short and middle- term, the first phase of transition, it could be produced from renewable sources only in a minimum amount, due to high costs related to the use of these sources. Instead, it mostly will have to be produced from fossil fuels, through chemical processes of reforming (particularly steam methane reforming), partial oxidation and gasification (of coal, TAR, etc.), already available and mature at industrial level for other applications in chemical, petrochemical and energy sectors. These processes produce, even if with different modalities, a fuel gas which can be turned after various treatments to a hydrogen and carbon dioxide mixture, with subsequent final “sequestration” of the latter. Hydrogen produced with current technologies still presents rather high costs, that if are bearable for a use in process applications, they are not for employment as an energy carrier, related to the cost of fuels nowadays commonly used in civil, industrial and transport sectors. For this reason it is necessary an improvement of those technologies permitting the fulfilment of easier and more efficient plant solutions, in order to make hydrogen cost (in energy terms) comparable with that of other fuels. On the basis of U.S.A. and E.U. “outlooks” about the transition towards a hydrogen economy these solutions should be industrially mature by 2015.

Tesi di Dottorato

Dipartimento: Dipartimento di Ingegneria Meccanica

Autore: Stefano Sollai Contatta »

Composta da 147 pagine.

 

Questa tesi ha raggiunto 118 click dal 07/04/2011.

Disponibile in PDF, la consultazione è esclusivamente in formato digitale.