Investigation of a methanol reformer concept considering the particular impact of dynamics and long-term stability for use in a fuel-cell-powered passenger car

A methanol reformer concept including a reformer, a catalytic burner, a gas cleaning unit, a PEMFC and an electric motor for use in fuel-cell-powered passenger cars was investigated. Special emphasis was placed on the dynamic s and the long-term stability of the reformer. Experiments on a laboratory scale were performed in a methanol steam reformer consisting of four differ ent reactor tubes, which were separately balanced. Due to the endothermy of the steam reforming reaction of methanol, a sharp drop in the reaction tem perature of about 50 K occurs at the beginning of the catalyst bed. This ag -rees well with the high catalytic activity at the entrance of the catalyst bed. Forty-five percent of the methanol was converted within the first 10 cm of the catalyst bed where 12.6 g of the CuO/ZnO catalyst was located. Fu rthermore, CO formation during methanol steam reforming strongly depends on methanol conversion. Long-term measurements for more than 700 h show that the active reaction zone moved through the catalyst bed. Calculations, on t he basis of these experiments, revealed that 63 g of reforming catalyst was necessary for mobile PEMFC applications, in this case for 400 W-el at a sy stem efficiency of 42% and a theoretical specific hydrogen production of 5. 2 m(n)(3)/(h kg(Cat)). This amount of catalyst was assumed to maintain a hy drogen production of at least 80% of the original amount over an operating range of 3864 h. Cycled start-up and shut-down processes of the methanol st eam reformer under nitrogen and hydrogen atmospheres did not harm the catal ytic activity. The simulation of the breakdown of the heating system, in wh ich a liquid water/methanol mixture was in close contact with the catalyst, did not reveal any deactivation of the catalytic activity. (C) 2000 Elsevi er Science S.A. All rights reserved.