Lpg

Tertiary coolant q j > >

Secondary coolant

Exhaust gas

Flow control valve

Shut-down valve my

© Heat pgp exchanger

Fig. 1 Main flow diagram of a 200kW multi-fuel type PAFC power plant my

Flow control valve

Shut-down valve

© Heat pgp exchanger

Fig. 1 Main flow diagram of a 200kW multi-fuel type PAFC power plant control valves are always regulated matching the plant output at that time to avoid shutdown of the plant caused by a transitional shortage of fuel in fuel switching. Fuel switching from pipeline town gas to LPG is carried out by opening the shut-down valve in the LPG supply line and then by closing the shut-down valve in the pipeline-town-gas supply line.

Pipeline town gas and LPG are steam-reformed to form hydrogen, which is necessary for the fuel cell reaction, in the same reformer. Steam reforming of LPG requires much more steam than steam reforming of pipeline town gas to avoid carbon deposition when a conventional Ni-Al203 catalyst bed is adopted in a reformer. In the developed multi-fuel type PAFC power plant, it is impossible to supply steam which is sufficient to suppress carbon deposition in steam reforming of LPG. A double-layer catalyst bed is therefore adopted in the reformer of this plant. Figure 2 shows the function of the double-layer catalyst bed. The new catalyst bed consists of a Ru-Al203 catalyst layer located at the gas-inlet side of the catalyst bed and a Ni-Al203 catalyst layer located at the gas-outlet side of the catalyst bed. This double-layer catalyst bed is designed so that LPG is steam-reformed completely on the Ru-Al203 catalyst layer. O11 a Ru-Al203 catalyst, carbon deposition does not occur in steam reforming of LPG even when the steam supply is suppressed and the steam-to-carbon ratio (S/C) is decreased to 2.0. The methane which forms by the methanation reaction on the Ru-Ai203 catalyst layer is steam-reformed on the Ni-Al203 catalyst layer. Carbon deposition in steam reforming of LPG can be therefore suppressed by adopting the double-layer catalyst bed.

Waste heat from the plant was utilized to vaporize LPG. The tertiary coolant was supplied to the hot water tank in the LPG vaporizer. The recycled hot water in the vaporizer was then heat-exchanged for this tertiary coolant and heated up. LPG was vaporized by heat-exchange for this recycled hot water.

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