Fuel cell system and method of load following operation of the same

摘要

Provided is a fuel-cell system and a method of operating the fuel-cell system, wherein functions F=f(P) and P=f−1(F) of electrical output P and fuel flow-rate F required to output P are beforehand obtained, and a reformable fuel flow-rate FR is calculated from the temperature of reforming catalyst layer. When FR≧Fmin, if the output demand PD≦maximum output PM, and when f(PD)≦FR, F is set to f(PD); and when f(PD)>FR, the P is set to the maximum value within a range of less than PD amongst P calculated from
P=f1(FR), and F is set to FR. When PD>PM, and when f(PM)≦FR, the cell output is set to PM, andF is set to f(PM). When f(PM)>FR, the cell output is set to the maximum value amongst P calculated from P=f1(FR), and F is set to FR.

主权项

1. A method of load following operation of a fuel cell system comprising a reformer having a reforming catalyst layer, for reforming a hydrocarbon-based fuel to produce a reformed gas containing hydrogen, and a high temperature fuel cell for generating electric power using the reformed gas, the method comprises determining before start of the load following operation:
functions F=f(P) and P=f−1(F), where P is an electrical output of the fuel cell and F is a flow rate of the hydrocarbon-based fuel required to be supplied to the reforming catalyst layer in order to output the electrical output P from the fuel cell, P=f−1(F) is an inverse function of F=f(P), wherein flow rate F is uniquely determined for each value of P in the range of 0 to PM, wherein PM represents maximum electrical output of the fuel cell and wherein for at least one value of F there are plurality of P values; and
a minimum value of flow rate of the hydrocarbon-based fuel, which is represented as Fmin, said Fmin being a minimum value that is given by the function F=f(P) when P ranges in the range of 0 to PM,the load following method comprising:A) measuring a temperature of the reforming catalyst layer;B) calculating a reformable flow rate FR that is a flow rate of the hydrocarbon-based fuel capable of being reformed in the reforming catalyst layer, based on the measured temperature of the reforming catalyst layer;C) when the calculated reformable flow rate FR is smaller than the minimum value Fmin, stopping electric power generation in the fuel cell; andD) when the calculated reformable flow rate FR is equal to or more than the minimum value Fmin,performing step d1 if a fuel cell output demand value PD is equal to or less than the maximum electrical output PM, and performing step d2 if the fuel cell output demand value PD exceeds the maximum electrical output PM,d1) calculating a flow rate f(PD) of the hydrocarbon-based fuel required to be supplied to the reforming catalyst layer in order to output the fuel cell output demand value PD from the fuel cell, using the function F=f(P),if f(PD) is equal to or less than the calculated reformable flow rate FR, setting an electrical output of the fuel cell to PD, and setting a flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to f(PD), andif f(PD) exceeds the calculated reformable flow rate FR, setting the electrical output of the fuel cell to a P value that is the highest from amongst one or more P values calculated from P=f−1(FR), but which is lower than the PD value, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to FR,d2) calculating a flow rate f(PM) of the hydrocarbon-based fuel supplied to the reforming catalyst layer required to be supplied to the reforming catalyst layer in order to output the maximum electrical output PM from the fuel cell, using the function F=f(P),if f(PM) is equal to or less than the calculated reformable flow rate FR, setting the electrical output of the fuel cell to PM, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to f(PM), andif f(PM) exceeds the calculated reformable flow rate FR, setting the electrical output of the fuel cell to a P value that is the highest from amongst one or more P values calculated from P=f−1(FR), and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to FR,wherein output demand value PD fluctuates with time.