E166 - Inst. f. Verfahrenstechnik, Umwelttechnik und Techn. Biowissenschaften
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PEM Brennstoffzelle; BioH2; Biomassevergasung
PEM Fuel Cell; BioH2; Biomass gasification
Today, hydrogen is mostly produced from fossil fuels like methane and coal. In order to decrease the world's carbon dioxide emissions several sustainable ways of hydrogen generation exist. One of them is electrolysis of water. If it is powered by renewable electricity like solar, hydro or eolic energy it can depict an environmentally friendly and carbon dioxide emission poor way to produce hydrogen with a high purity. Another possibility for sustainable hydrogen production is from biomass. Especially, wood gasi fication with further gas processing seems to be a promising technology which could be realized with the current and proven technology (water gas shift, absorption, membrane separation and adsorption). For gasifi cation, the already industrially applied dual fluidized bed technology has shown advantages which still has room for improvement by means of sorption enhanced reforming (SER). Fuel cells are devices which are able to convert hydrogen directly into electricity and heat without the limits of the Carnot cycle. Several fuel cell technologies exist with its own advantages and disadvantages. A proton exchange membrane (PEM) fuel cell, MobixaneTM, was tested in experiments with Alphagaz 1TM H2 hydrogen (pure hydrogen from a gas cylinder), from Air LiquideTM, and BioH2 acquired from wood gas from biomass gasifi cation. The wood gas from the biomass gasifi cation plant was subsequently processed in a water gas shift unit, in a RME gas scrubbing unit and in a pressure swing adsorption unit in order to achieve high purity BioH2. The experimental results showed that the operation with those two different hydrogen sources made no differences regarding the performance of the PEM fuel cell. A flawless fuel cell operation with BioH2 was possible. The experimental approach with detailed information is part of two papers which can be reviewed in Appendix C of this work. Past experiments using a process chain employing a RME scrubbing unit, a membrane separation unit and a pressure swing adsorption unit showed that a more than 100 hours lasting flawless operation of a PEM fuel cell with hydrogen generated from wood gas was possible. Today hydrogen is needed for several applications. Therefore storage of hydrogen is an important aspect, especially in context with Power to Gas concepts. Different possibilities exist like storage in pressure vessels, storage as liquid and in metal hydrids. A future project for hydrogen is the addition to the natural gas grid in order to reduce dependence of energy imports. This could be realized without issues because the Wobbe index of natural gas and hydrogen is quite similar. If the materials for hydrogen applications are chosen properly no signi cant damages or risks are expected. Several car manufacturers see fuel cells fed by hydrogen as possible future for locomotion being an alternative to combustion engines which could also be powered by hydrogen. Another possible hydrogen application is the utilization in households by fuel cells for satisfying heat and electricity demands which would enhance fuel use efficiency. This seems to be especially the case if several fuel cells are interconnected to a Virtual Power Plant" which is assumed to be able to replace large centralized power plants. Furthermore, hydrogen is an substance which is also needed in very high amounts in re neries, metal and chemical industry.
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