Pure hydrogen from pyrolysis oil by the steam-iron process

The steam-iron process is an old process, which was used for the production of hydrogen from cokes at the beginning of the twentieth century. In this thesis the steam-iron process is used to produce pure hydrogen from pyrolysis oil. Pyrolysis oil, obtained from the pyrolysis of biomass, is used to facilitate transportation and to simplify gasification and combustion processes, before being processed to hydrogen. The benefit of the steam-iron process compared to other thermo-chemical routes of biomass, is that hydrogen can be produced in a two step redox cycle, without the need of any purification steps (like HT-shift, LT shift and PSA). Experimental studies are performed in a fluidized bed in which the simultaneous gasification of pyrolysis oil and reduction of iron oxide and the consecutive oxidation of the reduced iron oxide with steam are taking place. During oxidation the steam is partly converted to hydrogen, which can be easily separated from the steam by condensation. Results with different iron oxides showed that the temperature and conversion degree of the iron oxide strongly determine the oil to hydrogen efficiency in the redox cycle. Rapid deactivation of the iron oxide occurs during subsequent cycling of the iron oxide. The observed deactivation, mainly caused by the swelling and shrinking of the iron oxide in the redox cycles, is a result of the decrease of the external surface area of the iron oxide. The observed deactivation with iron oxide are studied in a packed bed set-up and could be described with a sinter and particle model. A final process design study revealed that the efficiency of the steam-iron process is comparable to other biomass to hydrogen routes when an equilibrium oil and steam conversion is achieved in the reduction and oxidation.