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Compact methanol reformer test-design construction and operation of a 25 kW unit


In the future, drive systems for vehicles with polymer electrolyte membrane fuel cells (PEMFC), may be the environmentally most acceptable alternative to conventional drives with internal combustion engines. The energy carrier is neither gasoline nor diesel as in combustion engines today, but methanol, which is converted on-board into a hydrogen-rich synthesis gas in a reforming reaction with water. After removal of carbon monoxide in a gas-cleaning step, the conditioned synthesis gas is converted into electricity in the fuel cell using air as the oxidant. The electric energy thus generated, serves to supply the electric drive system of the vehicle. On the basis of the overall process design, a compact methanol reformer (CMR) was designed. A test facility was prepared and assembled at Forschungszentrum J?lich. Siemens constructed and supplied a 1 kW PEMFC. Final function tests with the PEMFC and the integrated CMR were carried out to determine the performance and the dynamic behaviour. With regard to the 50-Kw H(2)-compact methanol reformer, a special technical design of a catalytic burner was made. The burner units, with a total power output of 16 kW were constructed and tested under different stages of constant and alternating load. When selecting a specific catalyst loading of 40 g Pt/m(2), the burner emissions are below the SULEV standard. The stationary performance test of the CMR shows a specific hydrogen production of 6.7 m(3) N/(kg cat hour) for a methanol conversion rate of 95% at 280 degrees Celsius. Measurements of the transient behaviour of the CMR clearly show a response time of about 20 seconds reaching 99% of the demanded hydrogen flow due to the limited performance of the test facility control system. Thin palladium membranes deposited on ceramic tubes have been prepared. The measured hydrogen permeability through the Pd-layer has been as high as 150 Nm(3)/m(2)/hr/bar0.5. The best membranes were only 3-4 microns thick. The adhesion of the Pd-film to the ceramic support is very good, even after 1000 hours on stream. Pinholes in the membranes lead to a small amount of CO in the permeate, but the complete elimination of this has been demonstrated by selective CO methanation employing space velocities above 1,000,000 hours(-1) at 200 degrees Celsius.