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Design of a novel reactor for the production of hydrogen from biofuels

By Παναγιώτης Κεχαγιόπουλος

Abstract

Pollution of the environment from the use of fossil fuels and the accelerating depletion of oil reserves have intensified research on alternative energy sources. Hydrogen, as a means for the production of electricity via fuel cells, has emerged as the energy carrier of the future. Environmental benefits can only be gained though when hydrogen is derived from renewable energy sources. Steam reforming of bio-oil is an attractive hydrogen production process which is characterized by severe coke production. Goal of the present study is the design of a proper reactor that in combination with active catalytic materials will lead to successful commercialization of the process. The entire experimental work took place in a pilot scale unit, aiming at realistic conditions. The performance of the process was studied elaborately in a fixed bed reactor using commercial reforming catalysts. Ethylene glycol, acetic acid and acetone were chosen as model compounds, while experiments were also carried out with the aqueous fraction of bio-oil. The monomeric compounds were successfully reformed with hydrogen yield reaching as high as 90%. The processing of the thermally unstable bio-oil proved a lot more problematic, exhibiting high coke deposition. Thus, lower hydrogen yield, fluctuating at 60%, was achieved. The use of a spouted bed reactor equipped with a feed injection system was investigated, in order to achieve fast atomization and contact between bio-oil and catalytic particles. Ethylene glycol and acetic acid reforming was investigated over sand, olivine and Ni/olivine catalysts. Implementation of the injection system was successful. The production of coke was drastically reduced due to the hydrodynamics of the bed. The fast and efficient mixing between particles and reactants, in conjunction with the continuous cyclic movement of the solids, reduces significantly the accumulation of coke deposits, while at the same time facilitates their gasification by transporting them to bed parts where gas composition is more appropriate. The implementation of the spouted bed reactor in the reforming of the aqueous fraction of bio-oil proved a lot more complex leading to the design of a new bio-oil injection system. Results indicate that the problem of coking can be efficiently handled in the particular type of reactor. Finally, a non-isothermal pseudo-homogeneous model of the spouted bed reactor was developed. The basic characteristics of the reactor are satisfactorily described.

Topics: Αναμόρφωση με ατμό, Ρευστοστερεά κλίνη με πίδακα αερίου, Βιοέλαια, Υδρογόνο, Καταλύτες Ni/Ολιβίνη, Πιλοτικές μονάδες, Μαθηματική προσομοίωση, Steam reforming, Spouted bed reactor, Bio-oil, Hydrogen, Ni/Olivine catalysts, Pilot scale unit, Mathematical modeling
Publisher: Aristotle University Of Thessaloniki (AUTH)
Year: 2008
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