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Development of a Biogas Reformer for Production of Hydrogen for PEM Fuel Cells

Final Report Summary - BIO-HYDROGEN (Development of a Biogas Reformer for Production of Hydrogen for PEM Fuel Cells)

BIO-HYDROGEN aimed at the development of a cost effective biogas reforming system (6 kW hydrogen) for decentralised application with biogas from agricultural biogas plants, municipal waste water treatment plants and landfills. Costs of 1 EUR/kWh H2 were targeted. The first main objective was the development of reformer system which exhibits a better compatibility with biogas and hence shows an improved efficiency. The improvement of the heat and steam management for CO2 containing gas was targeted with the aid of simulation and modelling. A screening of the catalysts currently used for the reforming reaction was performed in order to evaluate and compare their stability, performance and durability when used for biogas reforming.

The second objective was the implementation of a cost effective cleaning unit for biogas. Biofiltration is believed to give good results in terms of cost-efficiency. Biofilters have been investigated for various applications but up to now their usage for siloxane removal has not been realised. Laboratory prototype will constitute the basis for the development of a biotrickling filter system capable to treat 1-2 m3/h biogas. This system will be integrated to the already developed biotrickling filter for H2S cleaning.

During the project catalyst tests were performed for the pre-reformer, the primary-reformer and the low temperature single shift. For comparison two different fuels were used for each catalyst stage. The pre- and the primary-reformer were operated with pure methane and a model biogas comprising 60 %-vol. methane and 40 %-vol. carbon dioxide, the low temperature shift catalyst was operated with model reformate gases from the methane and the biogas reforming, respectively. The pre-reformer as well as the primary-reformer catalyst were also tested for their sulphur tolerance by means of additional hydrogen sulphide in the feed gas. Furthermore, experiments were conducted with a non-commercial precious metal primary-reformer catalyst in order to investigate possible advantages with respect to sulphur resistance of the catalyst in comparison to the standard commercially available nickel based catalysts.

The results of the performed tests without sulphur impurities were all positive. The comparison between the operation with methane and the model methane reformate on the one side and the model biogas and the synthetic biogas reformate on the other side show the principal suitability of the tested catalysts for the application with purified biogas. Hence, there are no objections to use the tested commercially available catalysts in the biogas reformer prototype.

The tests with H2S contaminated gases confirmed the experiences given in the literature concerning the sulphur sensitivity of nickel based primary-reformer catalysts. It became clear that the tested primary-reformer catalysts, the nickel based as well as the precious metal based one, are not sulphur tolerant. Hence, the sulphur has to be removed from the input flow in front of the reformer reactor to prevent catalyst poisoning.

The result, based on the experimental experiences is, that commercially available standard reforming and shift catalysts could be used for the reforming of biogas. The reasons can be comprised as follows:
1. Good performance of the standard catalysts for pre-reforming, reforming and shift with respect to activity, selectivity and durability.
2. Proven since decades in different large-scale reformer systems (refinery applications) with lifetimes of about 40 000 hours and more.
3. Availability at constant quality.
4. Mass product with calculable cost for future purchasing and commercialising.
5. Available from different manufacturers.
These results could directly be used for the catalyst choice for existing reformer technology or for future reformer designs.

Long-term tests with the used system design should be performed, to check the performance, the stability and the durability of the catalysts at real operating conditions. The technical performance of the reformer, when operated with methane and different biogases, was investigated. The reformer has been measured with different input gases. As a conclusion of these experiments a modification of the reformer construction would not be necessary and the existing reformer technology could be used for the biogas operation.

During the project further experiments with real purified biogas will be performed to investigate the long-term stability of the used catalysts in combination with the reformer design. In the future the combination of the fuel processor technology with a CO fine purification (like preferential CO oxidation or pressure swing adsorption) and a PEM fuel cell, or only with high temperature PEM fuel cell with higher CO tolerance would be necessary, in order to demonstrate the functionality of hydrogen production from biogas for fuel cell application and to optimise the used technology.

The results of exploration in bio-gas reforming, showing the gaseous components before and after the reformer and bio-gas purification, and also showing the poisonous gas components for the PEM fuel cell stacks, especially the membrane, were undertaken.

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