A steam reforming process is one of the important composing elements of PAFC. It is desired that the process should become more compact and can supply hydrogen stably to cells for long periods (for example 40,000 hours) without exchanging catalysts. To meets these requirements, we have been developing an advanced steam reforming process for PAFC (1)(2).

Up to the present, the performance and the durability of the steam reforming process for more than twenty thousand hours have been confirmed by field monitor tests at 50 kW demonstration plants. Figure 1 shows the CHi concentration at the steam reformer outlet and CO concentration at the CO shift reactor outlet of the 50 kW plant. The CHi concentration is held at 1% or less even after 20,000 hours. The CO concentration is steadily maintained the desired value of 1.0% or less even after 20,000 hours. However, an evaluation of the catalyst for longer periods is necessary for practical use of PAFC.

As for the desulfurization process, we have already established to evaluate the life and to design the method and confirmed the required amount of desulfurization catalyst (2). This time we investigated a life evaluation method of the CO shift process which largely depends on the activity of catalyst and is essential to make a compact steam reforming process.

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