We have developed a 200kW multifuel-type phosphoric acid fuel cell (PAFC) power plant for liquefied propane gas (LPG) and for town gas 13A, which is made from natural gas. It was made by partially reconstructing a one-fuel (town gas 13A) type PAFC power plant. LPG and town gas 13A were steamreformed in the same reformer to form hydrogen, which is necessary for the fuel-cell reaction. Double-layer catalyst beds were used in the reformer. These beds consisted of Ru-Al
2O
3 catalyst layers located at low-temperature areas on the gas-inlet sides of the beds and Ni-Al
2O
3 catalyst layers located at high-temperature areas on the gas-outlet sides. Steam-reforming LPG needs more steam than that for town gas 13A, but the new catalyst beds reduced the amount of steam needed for reforming LPG so that it was kept within the maximum steam-supply level of the plant without resulting in carbon deposition.
The developed plant generated a maximum AC 200 kW output power by using either fuel. At AC 200 kW power generation, the steam-to-carbon (S/C) ratio in the feed was 3.40 for steam reforming of LPG and 2.56 for steam reforming of town gas 13A. The S/C ratio for steam reforming of LPG was also decreased to 2.80. Fuel switching from town gas 13A to LPG and vice versa was performed without decreasing the output power by adjusting the fuel and steam supplies to the reformer depending on whether the output power remained constant, changed, or was interrupted. Power generation continued stably and the fuel was switched by stopping the town-gas supply even when the fuel-switching trigger pressure of the town-gas supply was set at 100 mmAq, which is the guaranteed minimum pressure. Sufficient heat for LPG vaporization was obtained from the plant exhaust. The fuel-cell DC output power at the same AC power level generated by LPG and by town gas 13A was, therefore, the same. 8.39kW of the parasitic-power consumption for the heat source of the LPG vaporizer was decreased by using the exhaust heat from the plant to vaporize LPG, when the power was generated at AC 200kW using LPG.
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