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

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, wherein

• a plurality of electrical outputs Pi of the fuel cell (i is an integer of 1 or more and M or less, where M is an integer of 2 or more) and a flow rate Fi of the hydrocarbon-based fuel that corresponds to each Pi are set beforehand,
• where each Fi is a flow rate of the hydrocarbon-based fuel required to be supplied to the reforming catalyst layer in order to output a corresponding electrical output Pi from the fuel cell,
• each Pi is 0 or more, Pi increases with an increase of i, and each Fi is larger than 0,
• PM that is Pi when i is M is a maximum electrical output of the fuel cell, and
• a minimum value of all Fi is represented as Fmin,
• the method comprising:
• 1-A) measuring a temperature of the reforming catalyst layer;
• 1-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;
• 1-C) when the calculated reformable flow rate FR is smaller than the minimum value Fmin, stopping electric power generation in the fuel cell;
• and
• 1-D) when the calculated reformable flow rate FR is equal to or more than the minimum value Fmin,
• performing step 1-d1 if a fuel cell output demand value PD is equal to or less than the maximum electrical output PM, and performing step 1-d2 if the fuel cell output demand value PD exceeds the maximum electrical output PM,
• 1-d1) if there exists, amongst all Pi values, a Pi that is equal to the fuel cell output demand value PD, then setting Fi, that corresponds to Pi, that is equal to PD, as FDS;
• if there does not exist, amongst all Pi, a Pi that is equal to the fuel cell output demand value PD, then setting Fi, that is the not smaller value of the two Fi values, as FDS;
• one of said two Fi values corresponding to the smallest Pi that exceeds PD, and the other of said two Fi values corresponding to the largest Pi that is less than PD,
• when FDS 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 FDS, and
• when FDS exceeds the calculated reformable flow rate FR,
• if there exists a Pi that is less than the fuel cell output demand value PD and that corresponds to Fi, that is equal to or less than FR, then setting the electrical output of the fuel cell to the maximum value of Pi that is less than PD and that corresponds to Fi, that is equal to or less than FR;
• and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to Fi that corresponds to this maximum value, and
• if there does not exist a Pi that is less than the fuel cell output demand value PD and that corresponds to Fi, that is equal to or less than FR, then stopping electric power generation of the fuel cell, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to the reformable flow rate FR,
• 1-d2) when FM that is Fi, corresponding to the maximum electrical output 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 FM, and
• when FM that is Fi, corresponding to the maximum electrical output PM, exceeds the calculated reformable flow rate FR,
• if there exists a Pi that corresponds to Fi, that is equal to or less than FR, then setting the electrical output of the fuel cell to the maximum value of Pi that corresponds to Fi, that is equal to or less than FR, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to Fi corresponding to this maximum value, and
• if there does not exist a Pi that corresponds to Fi, that is equal to or less than FR, then stopping the electric power generation of the fuel cell, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to the reformable flow rate FR.

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, wherein

• a plurality of electrical outputs Pi of the fuel cell (i is an integer of 1 or more and M or less, where M is an integer of 2 or more) and a flow rate Fi of the hydrocarbon-based fuel that corresponds to each Pi are set beforehand,
• where each Fi is a flow rate of the hydrocarbon-based fuel required to be supplied to the reforming catalyst layer in order to output a corresponding electrical output Pi from the fuel cell,
• each Pi is 0 or more, Pi increases with an increase of i, and each Fi is larger than 0,
• PM that is Pi when i is M is a maximum electrical output of the fuel cell, and
• a minimum value of all Fi is represented as Fmin, and
• a plurality of temperatures Tj of the reforming catalyst layer (j is an integer of 1 or more and N or less, where N is an integer of 2 or more) and a flow rate Gj of the hydrocarbon-based fuel that corresponds to each Tj are set beforehand,
• where each Gj is a flow rate of the hydrocarbon-based fuel capable of being reformed in the reforming catalyst layer at a corresponding reforming catalyst layer temperature Tj, each Gj is larger than 0, and Gj is the same value or increases with an increase of j,
• the method comprising:
• 2-A) measuring a temperature T of the reforming catalyst layer;
• 2-B) adopting Gj corresponding to a largest Tj that is equal to or less than the temperature T as a reformable flow rate FR that is a flow rate of the hydrocarbon-based fuel capable of being reformed in the reforming catalyst layer at the temperature T;
• 2-C) when the reformable flow rate FR is smaller than the minimum value stopping electric power generation in the fuel cell;
• and
• 2-D) when the reformable flow rate FR is equal to or more than the minimum value Fmin,
• performing step 2-d1 if a fuel cell output demand value PD is equal to or less than the maximum electrical output PM, and performing step 2-d2 if the fuel cell output demand value PD exceeds the maximum electrical output PM,
• 2-d1) if there exists, amongst all Pi values, a Pi that is equal to the fuel cell output demand value PD, then setting Fi, that corresponds to Pi, that is equal to PD, as FDS;
• if there does not exist, amongst all Pi, a Pi that is equal to the fuel cell output demand value PD, then setting Fi, that is the not smaller value of the two Fi values, as FDS;
• one of said two Fi values corresponding to the smallest Pi that exceeds PD, and the other of said two Fi values corresponding to the largest Pi that is less than PD,
• when FDS is equal to or less than the 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 FDS, and
• when FDS exceeds the reformable flow rate FR,
• if there exists a Pi that is less than the fuel cell output demand value PD and that corresponds to Fi, that is equal to or less than FR, then setting the electrical output of the fuel cell to the maximum value of Pi that is less than PD and that corresponds to Fi, that is equal to or less than FR;
• and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to Fi that corresponds to this maximum value, and
• if there does not exist a Pi that is less than the fuel cell output demand value PD and that corresponds to Fi, that is equal to or less than FR, then stopping electric power generation of the fuel cell, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to the reformable flow rate FR,
• 2-d2) when FM that is Fi, corresponding to the maximum electrical output PM, is equal to or less than the 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 FM, and
• when FM that is Fi, corresponding to the maximum electrical output PM, exceeds the reformable flow rate FR,
• if there exists a Pi that corresponds to Fi, that is equal to or less than FR, then setting the electrical output of the fuel cell to the maximum value of Pi that corresponds to Fi, that is equal to or less than FR, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to Fi corresponding to this maximum value, and
• if there does not exist a Pi that corresponds to Fi, that is equal to or less than FR, then stopping the electric power generation of the fuel cell, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to the reformable flow rate FR.

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, wherein

• a plurality of electrical outputs of the fuel cell are represented as Pi (i is an integer of 1 or more and M or less, where M is an integer of 2 or more), and a flow rate of the hydrocarbon-based fuel that corresponds to each Pi is represented as Fi,
• where each Fi is a flow rate of the hydrocarbon-based fuel required to be supplied to the reforming catalyst layer to output a corresponding electrical output Pi from the fuel cell, each Pi is 0 or more, Pi increases with an increase of i, and each Fi is larger than 0,
• PM that is Pi when i is M is a maximum electrical output of the fuel cell, and
• a minimum value of all Fi is represented as Fmin,
• the system comprising:
• I) a means for measuring a temperature T of the reforming catalyst layer;
• II) a means for obtaining a reformable flow rate FR that is a flow rate of the hydrocarbon-based fuel capable of being reformed in the reforming catalyst layer at the temperature T;
• III) a means for, when the reformable flow rate FR is smaller than the minimum value Fmin, stopping electric power generation in the fuel cell;
• and
• IV) a means for, when the 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) if there exists, amongst all Pi values, a Pi that is equal to the fuel cell output demand value PD, then setting Fi, that corresponds to Pi, that is equal to PD, as FDS;
• if there does not exist, amongst all Pi values, a Pi that is equal to the fuel cell output demand value PD, then setting Fi, that is the not smaller value of the two Fi values, as FDS;
• one of the said two Fi values corresponding to the smallest Pi that exceeds PD, and the other of said two Fi values corresponding to the largest Pi that is less than PD,
• when FDS is equal to or less than the 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 FDS, and
• when FDS exceeds the reformable flow rate FR,
• if there exists a Pi that is less than the fuel cell output demand value PD and that corresponds to Fi, that is equal to or less than FR, then setting the electrical output of the fuel cell to the maximum value of Pi that is less than PD and that corresponds to Fi, that is equal to or less than FR;
• and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to Fi that corresponds to this maximum value, and
• if there does not exist a Pi that is less than the fuel cell output demand value PD and that corresponds to Fi, that is equal to or less than FR, then stopping electric power generation of the fuel cell, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to the reformable flow rate FR,
• d2) when FM that is Fi, corresponding to the maximum electrical output PM, is equal to or less than the 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 FM, and
• when FM that is Fi, corresponding to the maximum electrical output PM, exceeds the reformable flow rate FR,
• if there exists a Pi that corresponds to Fi, that is equal to or less than FR, then setting the electrical output of the fuel cell to the maximum value of Pi that corresponds to Fi, that is equal to or less than FR, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to Fi corresponding to this maximum value, and
• if there does not exist a Pi that corresponds to Fi, that is equal to or less than FR, then stopping the electric power generation of the fuel cell, and setting the flow rate of the hydrocarbon-based fuel supplied to the reforming catalyst layer to the reformable flow rate FR.