Decentralized modular thermo-chemically conversion facilities for utilizing biogenic energy sources in fuel cells

The supply of the annually 2 % increasing energy demand through fossil fuels is not sustainable. Alternatively energy from biogas can be used. State of the art is the conversion of biogas into heat and electricity or its upgrading to bio-methane. More innovative is the conversion of biogas into H2. About 60 % of the world's annual demand (500 Mio.m³) of H2 is provided by the reforming of fossil fuels, while 40 % are by-products of industrial processes. Substitution with H2 from biogas is an important part of the H2 infrastructure development and the establishment of multi-purpose H2 utilization technologies. Within the scope of the project Green-FC a modular prototype was developed for the conversion of biogas into H2, which includes five modules: I gas supply, II gas purification, III gas reforming, IV gas utilization and V post-combustion. The modules were designed using CAD software and simulated with CFD software. For the simulation of gas reforming, the eddy dissipation model and reaction kinetics from De Smet et al., Numaguchi & Kikuchi and Hla et al. were used. The simulation results indicated a full conversion of methane, a maximum H2 yield and a low carbon monoxide concentration in the gas, which is suitable for HT-PEMFC. The instrumentation and heat utilization concept will be described in detail. The replacement of modules is possible so that alternative reactors for biogas conversion and the further use of this concept can be studied. The project aimed to develop a prototype, as a process chain and modular connected components, to study the conversion of biogas into hydrogen for HT-PEMFCs. Based on the overview of the state of the art in process steps, a flow diagram was identified, a built-up plan for the subsequent realization of the components was designed, and the components were dimensioned and simulated for implementation. The innovations are the continuous operation of dual cartridge filters for the removal of hydrogen sulfide and siloxanes, and the compact reformer employing catalysts for ideal gas conversion through optimum heat and mass flow utilization. The simulation of the individual apparatus (e.g. reformer, water-gas-shift-reactor and afterburner) indicates optimal methane utilization, maximum hydrogen yield, minimal carbon monoxide content and proper after-treatment of the exhaust fulfilling emission limits. The result is the concept of a prototype to study the biogas conversion, provided with all design and construction documents, process control concept and simulation results for the system operation.