JP4404559B2 - Fuel cell power generation system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell power generation system, and more particularly to a fuel cell power generation system capable of appropriately processing flammable gas (for example, reformed gas, anode off gas, etc.) remaining in the fuel cell power generation system during a stop operation.
[0002]
[Prior art]
In the conventional fuel cell power generation system, the release of the reformed gas remaining in the reformed gas system in the fuel processor and the reformed gas system in the fuel cell stack during the stop operation is specially treated. It was often done without doing.
[0003]
[Problems to be solved by the invention]
However, even though it is temporarily performed in a small amount during stop operation, releasing flammable gas as it is to the environment releases not only dangers such as fire but also toxic gases such as carbon monoxide. In particular, there is a possibility of danger in a small fuel cell power generation system that may be installed indoors.
[0004]
Accordingly, the present invention provides a safe fuel cell power generation system capable of processing the combustible gas in the reformed gas system after the supply of the reforming raw material gas is stopped and greatly reducing the amount released to the environment. With the goal.
[0005]
[Means for Solving the Problems]
  In order to achieve the above object, a fuel cell power generation system 1 according to a first aspect of the present invention includes, as shown in FIG. 1, for example, a first inlet 71 for introducing a reforming raw material h, and the introduced reformer. A reforming unit 21 that reforms the raw material h into a reformed gas g, a selective oxidation unit 23 that selectively oxidizes carbon monoxide contained in the reformed gas g with the selective oxidation air k1, and a selective oxidation unit. 23, the outlet 74 for deriving the reformed gas g, the first inlet 71, the reforming unit 21, the selective oxidation unit 23, and the outlet 74 are connected to the reforming raw material h or the reforming h. A fuel treatment device 2 having a reformed gas system line 76 for guiding the quality gas g, and a burner section 25 for burning at least the anode off-gas f and heating the reforming section 21; using the derived reformed gas g Fuel that generates power and discharges the anode off-gas f to the burner section 25 A cell stack 3; (B1) for combustion material m is supplied to the burner section 25or notWhen the combustion raw material m is not supplied to the burner unit 25, the supply of the combustion raw material m to the burner unit 25 is started, and then the introduction of the reforming raw material h is stopped (C1 ) A control unit 4 that introduces a first incombustible fluid n that pushes the combustible gas remaining in the reformed gas system line 76 to the burner unit 25 from the first introduction port 71.
[0006]
If comprised in this way, since the fuel processing apparatus 2, the fuel cell stack 3, and the control part 4 are provided, it is for reforming in the state by which the raw material for combustion m is supplied to the burner part 25 by the control part 4. Since the supply of the raw material h is stopped, the combustion in the burner unit 25 can be maintained even after the supply of the reforming raw material h is stopped. Since the first incombustible fluid n is supplied to the reformed gas system line 76, the reforming raw material h or the reformed gas g in the reformed gas system line 76 is pushed out to the burner section 25 to be eliminated, and the combustion raw material m It can be made to burn by the burner part 25 by which combustion is maintained by supply of. As described above, the residual combustible gas in the fuel cell power generation system 1 can be safely processed and purged. The residual combustible gas is a concept that generally includes the reforming raw material h, the reformed gas g, the anode offgas f, and the combustion raw material m remaining in the fuel cell power generation system 1.
[0007]
The supply of the combustion raw material m to the burner unit 25 may be performed after power generation of the fuel cell stack 3 is stopped. In this way, after the power generation of the fuel cell stack 3 is stopped, it is ensured that the combustion is reliably performed by the combustion raw material m in the burner portion 25, and the combustible gas pushed out to the burner portion 25 is reliably burned. Thus, the residual combustible gas in the fuel cell power generation system 1 can be safely processed and the fuel cell power generation system 1 can be stopped. After the control of (C1), the supply of the selective oxidation air k1 may be stopped. In this way, the reformed gas system line 76 can be filled with the first incombustible fluid n, and the purging of the combustible gas with the first incombustible fluid can be performed more efficiently. The supply of the combustion raw material m may be stopped after the control of (C1) or after the supply of the selective oxidation air k1 is stopped. If it does in this way, the burner part 25 can be filled with the 1st nonflammable fluid n, the raw material for modification | reformation h can be extruded, and the purge of combustible gas can be performed more efficiently.
[0008]
The supply of the combustion raw material m is stopped after the reforming raw material h and the reformed gas g are sufficiently removed from the reformed gas system in the fuel processing device 2 and the fuel cell stack 3 by the first incombustible fluid n. Is desirable.
[0009]
In the control of (C1) by the control unit 4, the residual reformed gas g remaining in the reformed gas system line 76 of the fuel processor 2 may be mixed into the burner unit 25. The supply of the raw material h is stopped and the supply of the first incombustible fluid n is started. At the same time, the flow rate of the combustion air k4 is increased to increase the air ratio (air ratio to the combustion raw material), and the residual reformed gas g is sufficient. It is good to make it burn. In addition, after the control of (C1), the supply of the selective oxidation air k1 is stopped, the supply of the combustion raw material m is stopped, and then the burner unit 25 is purged using the combustion air k4. Good. In this way, a small amount of combustion raw material m remaining in the burner portion 25 can be purged.
[0010]
When the first incombustible fluid n contains water vapor or is water vapor, the water remaining in the burner unit 25 is removed by the supply of the first incombustible fluid n by purging with the combustion air k4, and the next burner unit 25 Ignition can be performed smoothly. When the first incombustible fluid n is water vapor and a cooler 77 (FIG. 5) for cooling the reformed gas g exiting the selective oxidation unit 23 is further installed, the water vapor cooler 77 Since the downstream purge is not performed, the burner portion 25 is purged by the combustion air k4, and the residual combustible gases h and g can be removed from the burner portion 25.
[0011]
A fuel cell power generation system 1 according to a second aspect of the present invention is the fuel cell power generation system according to the first aspect, wherein the derived reformed gas g is conveyed to the fuel cell stack 3 as shown in FIG. A reformed gas line 16 having a second inlet 53 for introducing bleed air k2 for further oxidizing carbon monoxide remaining in the derived reformed gas g; Then, the process water p evaporated in the reforming unit 21 and used as reforming steam is introduced from the first introduction port 72, and the process water p is introduced in the control of (C1), and reforming is performed. The process water p evaporated by the part 21 is used as the first incombustible fluid p, and further, the flared air is used as the second incombustible fluid for pushing the combustible gas remaining in the reformed gas line 16 to the burner part 25. The k2 is introduced from the second inlet 53.
[0012]
In the control (C1), the process water p is introduced from the first introduction port 72 and the process water p evaporated in the reforming unit 21 is used as the first incombustible fluid. Residual combustible gas remaining in the reformed gas system line 76 can be pushed out to the burner unit 25 by the evaporated process water p while being supplied to the burner unit 25. Furthermore, since the bleed air k2 is introduced from the second introduction port 53 as the second incombustible fluid, the combustible gas remaining in the reformed gas line 16 can be pushed out to the burner section 25. In particular, when the cooler 77 for cooling the reformed gas g is installed in the reformed gas line 16, it is difficult to purge the downstream of the cooler 77 with the evaporated process water p. The residual combustible gas remaining in the reformed gas line 16 can be pushed out to the burner section 25 by purging with bleed air k2 from the side.
[0013]
A fuel cell power generation system 1 according to a third aspect of the present invention is the fuel cell power generation system according to the first or second aspect, wherein, for example, as shown in FIG. 1, FIG. 3, and FIG. Before the control of B1), the control of (A1) for stopping the power generation of the fuel cell stack 3 is performed, and further, in the control of (A1), the stack current Is generated by the fuel cell stack 3 is decreased with a predetermined gradient. Then, the power generation is stopped by setting it to 0, and the supply amount of the reforming raw material h is reduced to a predetermined flow rate and held.
[0014]
With this configuration, the supply amount of the reforming raw material h can be gradually reduced, and after the power generation is stopped, the reformed gas system line of the fuel processing device 2 is supplied by the supply of the first incombustible fluid n. The reforming raw material h and the reformed gas g in the fuel cell stack 3 and the reformed gas g can be smoothly purged, and the combustion gas m can be reliably burned by the combustion in the burner portion 25. The decrease in the supply amount of the reforming raw material h is typically advanced simultaneously with the decrease in current. The predetermined gradient is a decreasing gradient such that excessive anode off gas f is not supplied to the burner section 25, and is typically about 1 L / min.
[0015]
A fuel cell power generation system 1 according to a fourth aspect of the present invention is the fuel cell power generation system according to any one of the first to third aspects, wherein, for example, as shown in FIG. Residual hydrogen remaining in the battery stack 3 is configured to be consumed by discharging the stack residual voltage of the fuel cell stack 3;
The control unit 4
(E1) The discharge is caused simultaneously with the control of (C1),
(F1) When the cell voltage of any one of the fuel cell stacks 3 becomes a predetermined value or less, the discharge is stopped,
(G1) When the cell voltage that has fallen below the predetermined value has recovered to a predetermined value, the discharge is caused to occur again;
The control of (E1), the control of (F1), and the control of (G1) are repeated a predetermined number of times or until no cell voltage recovery occurs.
[0016]
With this configuration, the first incombustible fluid n is supplied to the reformed gas system line 76, and the reforming raw material h and the reformed gas g in the reformed gas system line 76 and in the fuel cell stack 3 are burnered. Since the hydrogen remaining in the fuel cell stack 3 is consumed by discharge, the combustible gases h and g in the fuel cell power generation system 1 are shortened. Can be reliably removed in time.
[0017]
For example, as shown in FIG. 2, the fuel cell stack 3 includes a DC / DC converter 81 that transforms an output DC voltage to a predetermined DC voltage, and a DC / DC converter inrush current prevention resistor R1, or In addition, the control unit 4 consumes residual hydrogen in the fuel cell stack 3, and therefore discharge by the DC / DC converter standby power, or discharge by the stack residual voltage discharging resistor R2, or It is preferable to cause discharge by the DC / DC converter inrush current preventing resistor R1.
[0018]
When the residual power in the fuel cell stack 3 can be consumed in a sufficiently short time with the standby power of the DC / DC converter 81, the discharge by the standby power is performed. In order to cope with the case where the consumption current is large, the inrush prevention resistor R1 is arranged in series with the DC / DC converter 81, thereby increasing the electric resistance and suppressing the consumption current to discharge at an appropriate consumption rate, and the residual hydrogen in the stack Can consume minutes. Further, since the stack residual voltage discharging resistor R2 is provided to cope with the case where the current consumption is insufficient, the residual hydrogen content in the fuel cell stack 3 can be consumed by discharging using the resistor R2.
[0019]
The fuel cell power generation system 101 according to claim 4 further includes a reformed gas line 16 for guiding the derived reformed gas g to the fuel cell stack 3 and power generation by the fuel cell stack 3 as shown in FIG. A gas line including an anode off-gas line 17 that guides the reformed gas g that has not been used in the fuel cell stack 3 to the burner unit 25; the gas line supplies the derived reformed gas g to the burner unit The control unit 104 may be configured to perform switching by the switching unit 68 after the control (A1) and before the control (B1). Good.
[0020]
With this configuration, the reformed gas g derived during normal operation is guided to the fuel cell stack 3 through the reformed gas line 16, and the reformed gas g that has not been used for power generation in the fuel cell stack 3 is converted into the anode. It can be led from the fuel cell stack 3 to the burner unit 25 via the off gas line 17. On the other hand, at the time of stop operation, after the power generation of the fuel cell stack 3 is stopped, switching is performed by the switching means 68 so that the derived reformed gas g is directly sent to the burner unit 25, and the reformed gas to the fuel cell stack 3 is Residual hydrogen remaining in the fuel cell stack 3 can be consumed by cutting off the supply of g and discharging the stack residual voltage of the fuel cell stack 3. In addition, sending directly to the burner unit 25 means sending to the burner unit 25 without passing through the fuel cell stack 3. At this time, when the combustion raw material m is not supplied to the burner unit 25, the supply may be started, and then the supply of the reforming raw material h may be stopped.
[0021]
  The fuel cell power generation system 1 according to the invention of claim 5 includes, as shown in FIG. 1, for example, first introduction ports 71 and 72 for introducing a reforming raw material h and process water p, and the introduced process water. The reforming unit 21 that reforms the reforming raw material h into the reformed gas g by evaporating p and using it as the reforming steam, and the carbon monoxide contained in the reformed gas g by the selective oxidation air k1 A selective oxidation unit 23 that selectively oxidizes, and a lead-out port 74 that leads out the reformed gas g exiting the selective oxidation unit 23YesA reforming gas line 16 that conveys the derived reformed gas g, and introduces a bleed air k2 that further oxidizes carbon monoxide remaining in the derived reformed gas g. 2 a reformed gas line 16 having an inlet 53; a fuel cell stack 3 that generates electricity using a reformed gas g obtained by oxidizing carbon monoxide with bleed air k2; and (B2) a first raw material for reforming h. After stopping the introduction from the introduction port 71, after a predetermined time has elapsed, the introduction of the process water p from the first introduction port 72 is stopped, and (C2) the control unit that introduces the bleed air k2 from the second introduction port 53 With 4The predetermined time is a sufficient time that the reforming raw material h or the reformed gas g remaining in the fuel processing apparatus 2 can be pushed out by the reforming steam and removed.
[0022]
If comprised in this way, since the fuel processor 2, the reformed gas line 16, the fuel cell stack 3, and the control part 4 are provided, after the introduction of the reforming raw material h is stopped by the control part 4, After the predetermined time has elapsed, the introduction of the process water p can be stopped and the bleed air k2 can be introduced.
[0023]
Since the introduction of the process water p is stopped after a lapse of a predetermined time after the introduction of the reforming raw material h is stopped, the process water p is introduced for a predetermined time after the introduction of the reforming raw material h is stopped. As a result, the process water p is evaporated in the reforming unit 21, and the evaporated water vapor can be used as a purge gas for extruding the reforming raw material h and the reformed gas g remaining in the fuel processing apparatus 2. Since the introduction of the process water p is stopped and the bleed air k2 is introduced, the water vapor remaining in the reformed gas line 16 can be further pushed out by the bleed air k2, and the residual water due to the condensation of the water vapor can be avoided. it can. The predetermined time referred to here is a sufficient time during which the reforming raw material h and the reformed gas g remaining in the fuel processing apparatus 2 can be pushed out and removed by the water vapor obtained by evaporating the process water p.
[0024]
In addition, since the fuel processing apparatus 2 typically has the burner unit 25, in this case, moisture remaining in the burner unit 25 is removed by purging with the bleed air k2, and the next fuel cell power generation system 1 is started. The burner part 25 can be ignited smoothly. Further, when the cooler 77 for cooling the reformed gas g exiting the selective oxidation unit 23 is installed in the reformed gas line 16, it is difficult to purge downstream of the cooler with water vapor. The burner section 25 can be purged by the bleed air k2 downstream of the section 23 and upstream of the cooler 77. By this purge, the combustible fluid n remaining in the reformed gas line 16 can be removed. Further, the burner unit 25 may be purged using combustion air k4.
When the bleed air k2 is supplied in (C2), the flow rate of the combustion air k4 may be decreased by the flow rate of the bleed air k2 in order to keep the air ratio constant. Note that the supply of the process water p is typically stopped before the temperature of the portion of the fuel processing apparatus 2 in contact with the water vapor becomes equal to or lower than the boiling point of moisture.
[0025]
In claim 5, for example, as shown in FIG. 1, after the control unit 4 stops (A2) power generation of the fuel cell stack 3, the introduction of the bleed air k2 is stopped, and (B2) the reforming raw material After stopping the introduction of h from the first introduction port 72, the introduction of the process water p from the first introduction port 72 is stopped after a lapse of a predetermined time, and (C2) from the second introduction port 53 of the bleed air k2 (D2) After a predetermined time has elapsed, the introduction of the bleed air k2 may be stopped again.
[0026]
In this way, after the power generation of the fuel cell stack 3 is stopped, the combustible gases h and g remaining in the fuel processing device 2 are purged from the fuel processing device 2 by the evaporated process water p, and the fuel cell power generation system 1 is stopped. can do. In particular, after the supply of the bleed air k2 is stopped, the purge is performed by the process water p introduced from the first introduction port 72 and evaporated, so that the purge in the fuel processing apparatus 2 can be performed more efficiently.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the mutually same or equivalent member, and the overlapping description is abbreviate | omitted.
[0028]
The configuration of the fuel cell power generation system 1 according to the first embodiment of the present invention will be described with reference to the block diagram of FIG. The fuel cell power generation system 1 includes a fuel treatment device 2, a fuel cell stack 3 that is a solid polymer electrolyte fuel cell, a control device 4, a fuel supply line 11, a selective oxidation air supply line 12, and process water. Supply line 13, combustion gas supply line 14, combustion air supply line 10, or reformed gas transport line 16 as a reformed gas line, anode offgas line 17, and bleed air supply as a bleed air line The line 18 includes a stack air supply line 19, a nitrogen gas supply line 20, and a switching line 67.
[0029]
The fuel supply line 11 includes a blower 31 as a fluid booster, a control valve 32 as a flow control device, and a flow meter 47 as a flow measurement device, and the selective oxidation air supply line 12 includes a blower 33 and a control valve 34. And a flow meter 48. The process water supply line 13 includes a pump 35 as a fluid booster, a control valve 36, and a flow meter 49, and the combustion gas supply line 14 includes a blower 37, a control valve 38, and a flow meter 50. The combustion air supply line 10 includes a blower 64, a control valve 65, and a flow meter 66. A bleed air inlet 53 as a second inlet for introducing bleed air k2 into the reformed gas carrier line 16 is formed in the reformed gas carrier line 16, and the bleed air inlet line 53 has a bleed air supply line 18. Is connected. The bleed air supply line 18 includes a blower 41, a control valve 42, and a flow meter 51, and the stack air supply line 19 includes a blower 43, a control valve 44, and a flow meter 52. The nitrogen gas supply line 20 includes a nitrogen cylinder (not shown) as a nitrogen gas supply source, a control valve 62, and a flow meter 63.
[0030]
The fuel processing apparatus 2 includes a reforming unit 21, a shift unit 22, a selective oxidation unit 23, a burner unit 25, a fuel introduction port 71 as a first introduction port, and a process water introduction port as a first introduction port. 72, the selective oxidation air inlet 73, the reformed gas outlet 74, the fuel inlet 71, the reformer 21, the shifter 22, the selective oxidizer 23, and the reformed gas outlet 74 are communicated. A quality gas system line 76 is provided.
[0031]
The fuel supply line 11 is connected to the fuel inlet 71. The reforming raw material gas h as the reforming raw material introduced from the fuel supply line 11 to the fuel introduction port 71 is supplied to the reforming unit 21. The reforming unit 21 reforms the supplied reforming raw material gas h to form a reformed gas g containing hydrogen as a main component (for example, about 70 to 75% in terms of hydrogen component). Is done. In the shift unit 22, a CO shift reaction of the reformed gas g is performed. The selective oxidation air supply line 12 is connected to the selective oxidation air introduction port 73. The selective oxidation air k <b> 1 introduced from the selective oxidation air supply line 12 to the selective oxidation air introduction port 73 is supplied to the selective oxidation unit 23. In the selective oxidation unit 23, the selective oxidation of the carbon monoxide gas remaining in the reformed gas by the selective oxidation air k1 is performed. A process water supply line 13 is further connected to the fuel inlet 71. The process water p introduced from the process water supply line 13 to the fuel introduction port 71 is supplied to the reforming unit 21. The process water p supplied to the reforming unit 21 is evaporated to become reforming steam. A combustion gas supply line 14 is connected to the burner unit 25, and a combustion gas m as a burner gas or a combustion raw material is supplied to the burner unit 25. A combustion air supply line 10 is further connected to the burner unit 25 to supply combustion air k <b> 4 to the burner unit 25. Further, an anode off gas line 17 is connected to the burner unit 25 as will be described later, and an anode off gas f is supplied. The burner unit 25 burns the combustion gas m with the combustion air k4 and supplies heat necessary for the reforming reaction and the transformation reaction. The reforming raw material may be a liquid. In this case, a pump (not shown) is used instead of the blower 31.
[0032]
The control unit 4 sends the flow rate control signal i1 to the control valve 32, the control valve 34, the control valve 36, the control valve 38, and the control valve 62 individually. Receiving the flow control signal i1 from the control unit 4, the adjustment valve 32 adjusts the supply amount of the reforming raw material gas h to the reforming unit 21, and the adjustment valve 34 selects the selective oxidation unit 23 of the selective oxidation air k1. The control valve 36 adjusts the supply amount of the process water p to the reforming unit 21, the control valve 38 adjusts the supply amount of the combustion gas m to the burner unit 25, The regulating valve 65 regulates the supply amount of the combustion air k4 to the burner unit 25. The control valve 62 adjusts the supply amount of the nitrogen gas n as the first incombustible fluid or incombustible gas to the reforming unit 21.
[0033]
The blower 31, the blower 33, the pump 35, the blower 37, and the blower 64 are driven by a motor (not shown) and are respectively a reforming raw material gas h, selective oxidation air k1, process water p, combustion gas m, and combustion air. k4, nitrogen gas n which is an inert gas is supplied, and the rotational speed is substantially constant in a steady state. These may be driven by, for example, a steam turbine (not shown), and the flow rate may be controlled by rotation speed control. In this case, the regulating valves 32, 34, 36, 38, 65, 62 need not be installed.
[0034]
The flow meter 47 measures the flow rate of the reforming raw material gas h supplied to the reforming unit 21, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5. The flow meter 48 measures the flow rate of the selective oxidation air k1 supplied to the selective oxidation unit 23, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5. The flow meter 49 measures the flow rate of the process water p supplied to the reforming unit 21, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5. The flow meter 50 measures the flow rate of the combustion gas m supplied to the burner unit 25, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5. The flow meter 66 measures the flow rate of the combustion air k4 supplied to the burner unit 25, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5. The flow meter 63 measures the flow rate of the nitrogen gas n supplied to the reforming unit 21, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5.
[0035]
The reformed gas transport line 16 connects the outlet 74 of the fuel processor 2 and the fuel cell stack 3 and transports the reformed gas g exiting the selective oxidation unit 23 from the outlet 74 to the fuel cell stack 3. A three-way switching valve 68 is installed in the reformed gas transfer line 16. A switching signal i6 for switching the three-way switching valve is sent from the control unit to the three-way switching valve 68. The anode off gas line 17 connects the fuel cell stack 3 and the burner unit 25, and conveys an anode off gas f described later from the fuel cell stack 3 to the burner unit 25 for supply. One end of a switching line 67 is connected to the three-way switching valve 68, and the other end of the switching line 67 is connected to the anode off gas line 17.
[0036]
The three-way switching valve 68 is open on the a1 side during normal operation, and the reformed gas g exiting the selective oxidation unit 23 flows from the fuel processing device 2 through the reformed gas transport line 16 to the stack battery 3 side. When the three-way switching valve 68 is switched to the b1 side at the same time as the stop operation is started, the reformed gas g exiting the selective oxidation unit 23 passes from the reformed gas transfer line 16 through the switching line 67 to the anode off gas line. 17 is sent to the burner unit 25. A check valve 69 is installed upstream of the junction of the anode off-gas line 17 and the switching line 67 so that the reformed gas g flowing into the anode off-gas line 17 does not flow back to the fuel cell stack 3.
[0037]
The fuel cell stack 3 has a multiple structure in which fixed polymer membranes (not shown) and separators (not shown) are alternately stacked, and the supplied reformed gas g and stack air k3 are reacted electrochemically. As a result, the anode off-gas f (unused reformed gas) is generated. Here, the anode off gas f is a surplus reformed gas after hydrogen is used for power generation in the fuel cell stack 3, and for example, 80 percent (mole percent) of the hydrogen contained in the reformed gas g is used for power generation. When used, it is a so-called hydrogen-rich gas containing the remaining 20 percent (mole percent) equivalents of hydrogen.
[0038]
The fuel cell stack 3 includes a cell voltage detector 75 that detects each cell voltage. Each cell voltage detected by the cell voltage detector 75 is sent to the control unit as a voltage signal i3. In the figure, only one voltage signal i3 sent from the cell voltage detector 75 is shown, and the others are omitted.
[0039]
The bleed air supply line 18 is connected to the reformed gas transport line 16 as described above, and supplies the bleed air k2 to the reformed gas transport line 16. In the reformed gas g, the remaining CO gas is oxidized by the bleed air k2. The stack air supply line 19 is connected to the fuel cell stack 3 and supplies the stack air k3 to the fuel cell stack 3. The control unit 4 sends the flow control signal i1 to the control valves 42 and 44 individually. The adjustment valve 42 adjusts the supply amount of the bleed air k2 to the reformed gas transfer line 16, and the adjustment valve 44 adjusts the supply amount of the stack air k3 to the fuel cell stack 3. The blowers 41 and 43 are driven by a motor (not shown), and the rotation speed is substantially constant in a steady state. These may be driven by, for example, a steam turbine (not shown), and the flow rate may be controlled by rotation speed control. In this case, the control valves 42 and 44 may not be installed. The flow meter 51 measures the flow rate of the bleed air k2 supplied to the reformed gas transfer line 16, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5. The flow meter 52 measures the flow rate of the stack air k3 as the oxidant gas supplied to the fuel cell stack 3, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5.
[0040]
The fuel cell stack 3 is electrically connected to a load 5 (any electrical device). The fuel cell stack 3 includes a stack voltage detector 45 that detects the stack voltage Vs and a stack current detector 46 that detects the stack current Is. The stack voltage Vs detected by the stack voltage detector 45 is sent to the control unit 4 as a voltage signal i3. The stack current Is detected by the stack current detector 46 is sent to the control unit 4 as a current signal i4.
[0041]
Next, the operation during normal operation of the fuel cell power generation system 1 will be described. The combustion gas m conveyed by the blower 37 at the time of start-up and auxiliary combustion is supplied from the combustion gas supply line 14 to the burner unit 25. The control valve 38 installed in the combustion gas supply line 14 receives the flow control signal i1 from the control unit 4, and is controlled to a predetermined opening so as to flow the combustion gas m having a flow rate corresponding to the flow control signal i1. The The control valve 65 installed in the combustion air supply line 10 receives the flow control signal i1 from the control unit 4 and is controlled to a predetermined opening degree so that the combustion gas m having a flow rate corresponding to the flow control signal i1 flows. The The flow rate of the combustion gas m is measured by the flow meter 50, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5. During normal operation, the anode offgas f is supplied to the burner unit 25 from the fuel cell stack 3 via the anode offgas line 17. The combustion heat generated in the burner unit 25 is used for the reforming reaction heat in the reforming unit 21, and a reforming catalyst (not shown) filled in the reforming unit 21 and a CO shift catalyst charged in the shift unit 22. (Not shown) is used to maintain a predetermined temperature suitable for the reaction.
[0042]
The reforming raw material gas h is conveyed by the blower 31 and supplied to the reforming unit 21 through the fuel supply line 11. The control valve 32 installed in the fuel supply line 11 receives a flow rate control signal i1 from the control unit 4, and is controlled to a predetermined opening so as to flow the reforming raw material gas h having a flow rate corresponding to the flow rate control signal i1. The The flow rate of the reforming raw material gas h is measured by the flow meter 47, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5.
[0043]
The process water p is conveyed by the pump 35 and supplied to the reforming unit 21 through the process water supply line 13. The control valve 36 installed in the process water supply line 13 receives the flow control signal i1 from the control unit 4, and is controlled to a predetermined opening so that the process water p having a flow rate corresponding to the flow control signal i1 flows. The flow rate of the process water p is measured by the flow meter 49, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5. The process water p supplied to the reforming unit 21 evaporates in the reforming unit 21 and is used as reforming steam s. That is, in the reforming unit 21, when the reforming raw material gas h is methane, the reforming catalyst performs CH₄+ H₂O → CO + 3H₂  A steam reforming reaction expressed by the following formula is performed to obtain a reformed gas g. Where H₂O is reforming steam.
[0044]
The reformed gas g is sent from the reforming unit 21 to the shift unit 22, and in the shift unit 22, CO + H is generated by a CO shift catalyst.₂O → CO₂+ H₂  The transformation reaction represented by Further, the reformed gas g is sent from the shift unit 22 to the selective oxidation unit 23. The selective oxidation air k <b> 1 is conveyed by the blower 33 and is supplied from the selective oxidation air supply line 12 to the selective oxidation unit 23. The control valve 34 installed in the selective oxidation air supply line 12 receives the flow control signal i1 from the control unit 4 and has a predetermined opening degree so as to flow the selective oxidation air k1 having a flow rate corresponding to the flow control signal i1. Be controlled. The flow rate of the selective oxidation air k1 is measured by the flow meter 48, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5.
[0045]
The CO gas remaining in the reformed gas g is selectively oxidized by the selective oxidization section 23 with the selective oxidation air k1, and CO + (1/2) O.₂→ CO₂  The reaction represented by The reformed gas g from which the CO gas has been removed is supplied toward the fuel cell stack 3 through the reformed gas transport line 16.
[0046]
The CO gas contained in the reformed gas g being transported in the reformed gas transport line 16 is oxidized by the bleed air k2 supplied into the reformed gas transport line 16.
The bleed air k <b> 2 is transported by the blower 41 and supplied from the bleed air supply line 18 to the reformed gas transport line 16. The control valve 42 installed in the bleed air supply line 18 receives the flow control signal i1 from the controller 4, and is controlled to a predetermined opening degree so that the bleed air k2 having a flow rate corresponding to the flow control signal i1 flows. The flow rate of the bleed air k2 is measured by the flow meter 51, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5.
[0047]
The fuel cell stack 3 is supplied with the stacking air k3 conveyed by the blower 43 through the stacking air supply line 19. The control valve 44 installed in the stack air supply line 19 receives the flow control signal i1 from the control unit 4, and is controlled to a predetermined opening so that the stack air k3 having a flow rate corresponding to the flow control signal i1 flows. The The flow rate of the stacking air k3 is measured by the flow meter 52, and the measured flow rate is sent to the control unit 4 as a flow rate signal i5.
[0048]
In the fuel cell stack 3, the reformed gas g and the stack air k <b> 3 are electrochemically reacted to generate power and supply power to the load 5. A part of the reformed gas g supplied to the fuel cell stack 3 is not used for power generation, leaves the fuel cell stack 3, is sent to the burner unit 25 as the anode off-gas f, and is burned in the burner unit 25.
During the normal operation, the control valve 62 receives the flow rate control signal i1 so as to make the opening degree 0 from the control unit 4 and maintains the closed state, and the nitrogen gas n is not supplied during the normal operation.
[0049]
As shown in FIG. 2, the load 5 includes a DC / DC converter 81, an inverter 82, and a load body 5A in series in this order. On the input side of the inverter 82, a smoothing capacitor 83, a switch SW1 including three contacts aa1, bb1, and cc1 and a switch SW2 including two contacts aa2 and bb2 are installed.
[0050]
When the power generation of the fuel cell stack 3 is terminated, the switch SW1 is connected to the contact aa1, the switch SW1 is turned off, and the inverter 82 and the load body 5A are disconnected from the DC / DC converter 81 and the fuel cell stack 3.
When power generation by the fuel cell stack 3 is started, the switch SW1 is connected to the contact bb1, the inverter 82 and the load 5A are connected to the DC / DC converter 81 and the fuel cell stack 3 via the inrush current preventing resistor R1, When shifting to steady power generation, the switch SW1 is connected from the contact bb1 to the contact cc1.
[0051]
During steady power generation, the switch SW2 is connected to the contact aa2, and the switch SW2 is off. When discharging the stack residual voltage at the time of power generation suspension, the switch SW2 is connected to the contact bb2, and the stack residual voltage is discharged by the residual voltage discharging resistor R2. After the end of the discharge, the switch SW2 is connected to the contact aa2 and turned off.
[0052]
Next, a stop operation method by the control unit 4 of the fuel cell power generation system 1 of the first embodiment will be described with reference to FIGS. 3 and 4 and FIG. 1 as appropriate. In FIG. 3, the horizontal axis represents the passage of time, and the vertical axis represents the flow rate (the unit is gas NL / min). In FIG. 4, the horizontal axis represents the passage of time, and the vertical axis represents the flow rate (unit L / min) and the current (unit A).
[0053]
In FIG. 3, the broken line R1 (solid line) indicates the flow rate of the combustion air k4, the broken line R2 (long two-dot chain line) indicates the flow rate of the reforming raw material gas h, and the broken line R3 (short alternate long and short dash line) indicates the combustion gas m. The broken line R4 (short two-dot chain line) represents the flow rate of the nitrogen gas n, and the broken line R5 (broken line) represents the flow rate of the bleed air k2. In FIG. 4, the broken line R6 (solid line) represents the flow rate of the process water p, and the broken line R7 (solid line) represents the stack current Is.
[0054]
At time t0, the normal operation of the fuel cell power generation system 1 is performed. At time t0, the flow rate of the combustion air k4 is constant at 20 NL / min, and the flow rate of the reforming raw material gas h is constant at 4.5 NL / min. The flow rate of the combustion air k4 is about 1.2 times the flow rate required for complete combustion of the combustion gas m and the anode off-gas f (the air ratio is about 1.2). The flow rate of the reforming raw material gas h is a flow rate corresponding to the stack current Is of the fuel cell stack 3, and the reformed gas g necessary for the fuel cell stack 3 to generate electric power commensurate with the load 5 is treated with fuel. This is the flow rate required for the device 2 to generate.
[0055]
Similarly, at the time t0, the flow rate of the process water p is constant at 0.011 L / min. The flow rate of the process water p is a flow rate at which the ratio of the molar flow rate of steam obtained from the flow rate of the process water p and the carbon to molar flow rate obtained from the flow rate of the reforming raw material gas h is about 2.8. . The flow rate of the bleed air k2 is constant at 0.7 NL / min. The flow rate of the bleed air k2 is an amount sufficient to oxidize the carbon monoxide remaining in the selectively oxidized reformed gas g.
[0056]
Although not shown in FIG. 3, the constant oxidation air k1 and the stacking air k3 are also supplied at a constant flow rate at time t0. As the flow rate of the selective oxidation air k1, a flow rate necessary for selectively oxidizing carbon monoxide in the reformed gas is supplied. A flow rate corresponding to the current load of the fuel cell stack 3 is supplied to the stack air k3. At time t0, the flow rate of the combustion gas m is zero. Therefore, no combustion is performed in the burner unit 25, and combustion is performed using only the anode off-gas f. Further, at the time t0, the flow rate of the nitrogen gas n is also zero.
[0057]
At time t1, a stop signal (not shown) of the fuel cell power generation system 1 is sent to the control unit 4, and the control unit 4 starts to decrease the value of the stack current Is and shifts to a stop operation. At the same time, the flow rate of the reforming raw material gas h is decreased in correspondence with a decrease in the stack current Is (for example, at a rate of 57 A to 10 A / min). The flow rate of the reforming raw material gas h is a flow rate expressed as a function of the stack current Is. The flow rate of the reforming raw material gas h is controlled so as not to decrease to 1 NL / min or less. The reason why it does not fall below 1 NL / min is to maintain the combustion stability in the burner section 25 that is burning by the anode off gas f. The decrease rate of the stack current Is is set to 10 A / min because the rapid decrease of the stack current Is results in a rapid decrease of the consumed reformed gas flow rate, and the pressure of the reformed gas transport line 16 increases rapidly. In the fuel processing apparatus 2, the back pressure fluctuation due to the change in the flow rate of the reformed gas g causes the amount of CO in the reformed gas g to increase, and the flow rate of the reformed gas g changes suddenly. The sudden change in the flow rate of the anode off gas f due to the above causes incomplete combustion in the burner portion 25. At time t1, the flow rate of the combustion air k4 also starts to decrease.
[0058]
Similarly, at the time t1, the process water p and the bleed air k2 start to decrease at the same reduction rate as the reduction rate of the flow rate of the reforming raw material gas h.
Although not shown in FIG. 3, at the same time t1, the selective oxidation air k1 and the stacking air k3 also start to decrease at the same reduction rate as the reduction rate of the flow rate of the reforming raw material gas h.
[0059]
The stack current Is simply continues to decrease from the time t1 to the time t2 (for example, 5.7 minutes have elapsed from the time t1), and at time t2, the stack current Is becomes 0, and the power generation is stopped. The flow rates of the reforming raw material gas h and the process water p also simply decrease from the time t1 to the time t2, and reach the minimum supply flow rates of 1.0 NL / min and 0.003 L / min, respectively, at the time t2. . The bleed air k2 also simply continues to decrease from time t1 to time t2. The combustion air k4 also simply decreases from time t1 to time t2, and at time t2, the flow rate becomes 10 NL / min.
[0060]
Although not shown in FIG. 3, the selective oxidation air k <b> 1 and the stacking air k <b> 3 similarly simply decrease from the time t <b> 1 to the time t <b> 2.
Further, at time t2, the three-way switching valve 68 is switched from the a1 side to the b1 side, and the reformed gas g exiting the selective oxidation unit 23 is sent from the reformed gas outlet 74 and the reformed gas transport line 16 to the three-way switching valve 68, The gas is supplied to the burner unit 25 through the switching line 67 and the anode off gas line 17. Therefore, the reformed gas g is not supplied to the fuel cell stack 3. The supply of the stacking air k3 stops at time t2 (not shown in FIG. 3).
[0061]
Further, at time t2, it is checked whether or not the combustion gas m is supplied to the burner unit 25 (not shown in FIG. 3). This is performed based on the flow signal i5 from the flow meter 50. When the combustion gas m is not supplied to the burner unit 25 (this embodiment corresponds to this case), supply of the combustion gas m to the burner unit 25 is started. The supply of the combustion gas m is started at a time t21 after a slight elapse of the time t2. The flow rate of the combustion gas m is 1.2 NL / min. At the same time, the flow rate of the combustion air k4 is increased to 28.9 NL / min. The flow rate of the combustion air k4 is determined so that the air ratio is set to 1.2 in consideration of the flow rates of the combustion gas m, the reforming raw material gas h, and the reformed gas g supplied to the burner section 25. It is.
[0062]
After the time t2, the flow rate of the reforming raw material gas h is 1 NL / min, and the flow rate of the process water p is maintained at a certain amount of 0.003 L / min, but a time slightly before the time t3. At t23, the supply of the reforming raw material gas h and the process water p is stopped. At the same time, the flow rate of the combustion air k4 is reduced to 13.5 NL / min.
[0063]
The selective oxidation air k1 (not shown in FIG. 3) and the bleed air k2 continue to decrease at time t2. The flow rate of the bleed air k2 becomes 0 at an intermediate time t22 between time t2 and time t3 described later.
The reason why the flow rate of the bleed air k2 is set to 0 at time t22 is to ensure that the bleed air k2 is supplied when the stack is separated.
[0064]
When the flow rate of the reforming raw material gas h is decreased during the stop operation, the flow rate of the reformed gas g is also decreased. Therefore, the flow rates of the process water p, the bleed air k2, the selective oxidation air k1, and the stack air k3 need to be similarly reduced (not shown in FIG. 3).
[0065]
Next, the supply of the reforming raw material gas h and the process water p is stopped at a time t23 slightly before the time t3. At the same time, the flow rate of the combustion air k4 is reduced to 13.5 NL / min. The flow rate of the combustion gas m is maintained at 1.2 NL / min.
[0066]
At time t3, supply of nitrogen gas n at a flow rate of 5 NL / min to the reformed gas system line 76 is started. Nitrogen gas n is a combustible gas remaining in the reforming gas system line 76, the reforming gas transport line 16 (except the downstream side of the three-way switching valve), and the switching line 67 in the fuel processing apparatus 2 (reforming raw material). h and the reformed gas g) and the reforming vapor from which the process water p has evaporated, and the combustible gas (anode offgas f) remaining in the anode offgas line 17 (excluding the upstream side of the connection portion of the switching line). ) And the combustible gases h, g, f, and reforming steam are pushed out toward the burner section 25 and eliminated. The excluded combustible gases h, g, and f are burned in the burner unit 25. The flow rate of the combustion air k4 is about 20% higher than the flow rate determined on the assumption that the air ratio is 1.2 based on the flow rate of the combustion gas m and the flow rate of the combustible gas pushed out to the burner section 25. . The reason why the flow rate is set in this way is to suppress the generation of unburned combustible gas and carbon monoxide as much as possible by causing the burner unit 25 to efficiently burn the residual combustible gas.
[0067]
The supply of the selective oxidation air k1 is stopped at time t31 which is an intermediate time between time t3 and time t4 described later (not shown in FIG. 3). The reason why the supply amount of the selective oxidation air k1 is stopped at the time t31 is to ensure that the selective oxidation air k1 is supplied when the supply of the reforming raw material gas h is stopped, so that the CO in the reformed gas g This is to reduce the amount.
[0068]
After the period t3, the flow rates of the nitrogen gas n, the combustion gas m, and the combustion air k4 are kept constant, but the supply of the combustion gas m is stopped at a time t32 slightly before the time t4. At the same time, the flow rate of the nitrogen gas n is increased to 15 NL / min, and at the same time, the flow rate of the combustion air k4 is increased to 20 NL / min. As a result, the reformed gas system line 76, the reformed gas transfer line 16 (excluding the three-way switching valve 68 side of the fuel cell stack 3), the switching line 67, and the anode off-gas line 17 (the switching line 67) The combustible gases h and g are replaced by the nitrogen gas n in the connecting portion (excluding the fuel cell stack 3 side), and the combustible gas is completely replaced by the nitrogen gas n and the combustion air k4 in the burner portion 25.
[0069]
At time t4, the flow rate of the combustion gas m becomes zero. At this time, the flow rates of the nitrogen gas n and the combustion air k4 are increasing.
[0070]
At time t41, which is slightly before time t5 (for example, 5 minutes after time t4), the supply of nitrogen gas n and combustion air k4 is stopped, and the fuel cell power generation system 1 is stopped. First, the flow rate of nitrogen gas becomes zero, and then the flow rate of combustion air k4 becomes zero at time t5.
[0071]
At time t2, the remaining stack voltage is discharged by at least one of the following methods, and hydrogen in the reformed gas g remaining in the fuel cell stack 3 is consumed.
(1) Discharge due to standby power of the DC / DC converter 81 (FIG. 2)
(2) Discharge by stack residual voltage discharge resistor R1 (FIG. 2)
(3) Discharge by DC / DC converter inrush prevention resistor R2 (FIG. 2)
Discharge is stopped when any one of the cell voltages detected by the cell voltage detector 75 falls below the first predetermined value (0.4V). When the cell voltage that has fallen below the predetermined value is restored to the second predetermined value (0.5 V) or higher and there is no cell voltage that is equal to or lower than the first predetermined value, the aforementioned discharge is resumed. The process is repeated until the cell voltage of a certain cell is decreased, the cell voltage is recovered, and the discharge is restarted a predetermined number of times (for example, three times) or until the cell voltage is not recovered.
[0072]
The first predetermined value is a value of the cell voltage when hydrogen in a portion in contact with the cell is reduced and there is a possibility that the catalyst or the like may be adversely affected by discharge. The second predetermined value is a value of the cell voltage that does not adversely affect the catalyst even if discharge is performed because hydrogen diffuses in the portion in contact with the cell, hydrogen increases in the portion, and the cell voltage increases. The predetermined number of times is the number of times that the voltage recovery after the stop of the discharge, which is caused by the fact that the diffusion rate of hydrogen in the stack is slower than the hydrogen consumption rate due to the discharge, can be sufficiently suppressed.
[0073]
When the discharge is performed in this manner, the residual hydrogen remaining in the fuel cell stack 3 is consumed by the discharge, so that the reforming raw material gas h and reformed gas g in the fuel cell power generation system 1 are reliably removed in a short time. can do.
[0074]
When the supply of the reforming material gas h is stopped, the gas velocities of the reforming material gas h and the reformed gas g in the reformed gas system line 76 of the fuel processing device 2 are reduced. For this reason, the reforming reaction proceeds, carbon monoxide cannot be sufficiently removed from the reformed gas g, and a reformed gas having a high carbon monoxide concentration may be generated although the amount is small. By operating the three-way switching valve 67, it is possible to prevent the reformed gas g having a high carbon monoxide concentration from entering the fuel cell stack, and the solid polymer membrane (not shown in FIG. 1) of the fuel cell stack 3 can be prevented. ) Carbon monoxide poisoning can be prevented.
[0075]
After stopping the power generation of the fuel cell stack 3 at time t2, the selective oxidization air k1 is supplied until time t31 (not shown in FIG. 3), but the selective oxidation is performed by operating the three-way switching valve 67 at time t2. The air k1 can be prevented from being mixed into the fuel cell stack, and the selective oxidation air k1 is formed from the residual hydrogen in the fuel cell stack 3 and the catalyst portion on the solid polymer membrane (not shown in FIG. 1). Therefore, it is possible to avoid shortening the life of the fuel cell stack 3 due to the combustion reaction.
[0076]
According to the fuel cell power generation system 1 of the first embodiment, the stack current Is is decreased to 0, the power generation of the fuel cell stack 3 is stopped, and the combustion source gas m is supplied to the burner unit 25. Since the supply of the reforming source gas h is stopped, the combustion source gas m can be supplied to the burner unit 25 and the combustion in the burner unit 25 can be maintained even after the supply of the reforming source gas h is stopped. it can. Since the nitrogen gas n is supplied to the reformed gas system line 76, the reforming raw material gas h and the reformed gas g in the reformed gas system line 76 are replaced, pushed out to the burner section 25, removed, and pushed out. The raw material gas h and the reformed gas g can be burned in the burner section 25. Next, since the supply of the selective oxidation air k1 (not shown in FIG. 3) and the bleed air k2 is stopped, the reformed gas system line 76 can be filled with the nitrogen gas n. Next, since the supply of the combustion source gas m is stopped, the burner part 25 can be filled with the nitrogen gas n, and a small amount of unburned combustion source gas m can be pushed out. Therefore, the release of the reforming raw material gas h and the reformed gas g remaining after the stop of the fuel cell power generation stack 1 to the environment can be greatly reduced. The supply of the combustion raw material gas m is desirably stopped after the reformed gas g and the like are sufficiently removed from the reformed gas system line 76 by the nitrogen gas n.
[0077]
In the first embodiment described above, nitrogen gas n is supplied to the reformed gas system line 76 as the first incombustible fluid, but air is used as the first incombustible fluid instead of the nitrogen gas n. Even if it is supplied to the system line 76, the same effect can be obtained.
[0078]
The configuration of the fuel cell power generation system 101 according to the second embodiment of the present invention will be described with reference to the block diagram of FIG. Only differences from the first embodiment (see FIG. 1) will be described below. Other points not described are the same as in the first embodiment.
[0079]
The fuel cell power generation system 101 does not include a nitrogen gas supply line that supplies the reformed gas system line 76 with the nitrogen gas n as the first incombustible fluid. Instead, the process water p supplied to the reformed gas system line 76 is used as the first incombustible fluid. The process water p supplied to the reforming unit 21 evaporates in the reforming unit 21 and becomes water vapor as an incombustible gas. Therefore, a control signal for controlling the flow rate of nitrogen gas is not output from the control unit 104 included in the fuel cell power generation system 101, and a flow rate signal indicating the flow rate of nitrogen gas is not input to the control unit 104. .
A cooler 77 for cooling the reformed gas g is installed on the downstream side of the bleed air introduction port 53 of the reformed gas transport line 16, and the reformed gas g leaving the fuel processing device 2 and going to the fuel cell stack 3 is installed. Reduce the temperature. The entering temperature of the cooler 77 of the reformed gas g is about 90 ° C., and the exit temperature of the cooler 77 is about 55 ° C.
[0080]
Next, a stop operation method by the control unit 104 of the fuel cell power generation system 101 according to the second embodiment will be described with reference to FIGS. Only differences from the stop operation method by the control unit 4 of the first embodiment will be described below. Since the fuel cell power generation system 101 does not include a nitrogen gas supply line, the supply of the process water p is maintained without stopping the supply of the process water p at the stage where the nitrogen gas is to be supplied. Use instead of.
[0081]
In FIG. 6, the broken line R11 (solid line) is the flow rate of the combustion air k4, the broken line R12 (long two-dot chain line) is the flow rate of the reforming raw material gas h, and the broken line R13 (short dashed line) is the combustion gas m. The broken line R15 (broken line) represents the flow rate of the bleed air k2. In FIG. 6, the broken line R16 (solid line) represents the flow rate of the process water p, and the broken line R17 (solid line) represents the stack current Is. In FIG. 6, the horizontal axis represents the passage of time, and the vertical axis represents the flow rate (unit: NL / min). In FIG. 7, the horizontal axis represents the passage of time, and the vertical axis represents the flow rate (unit L / min) and the current (unit A).
[0082]
The time t0 to the time t3 are the same as the stop operation method of the fuel cell power generation system 1 described above except that the supply of the process water p is not stopped at the time t3 but the supply is maintained. Therefore, the description from time t0 to time t3 is omitted. Further, in the stop operation method of the fuel cell power generation system 1 described above, the time between the time t3 and the time t4 is 5 minutes, but in the stop operation method of the fuel cell power generation system 101, it is 10 minutes.
[0083]
Since the supply of the process water p is stopped at a time t31 ′ slightly before the time t3 ′ (elapsed 5 minutes from the time t3) between the time t3 and the time t4, the process water p is supplied from the time t3 to the time t31 ′. It will be supplied continuously. Therefore, the supplied process water p evaporates in the reforming unit 21 to become steam, but this steam does not work as reforming steam after stopping the supply of the reforming raw material gas h, The flammable gas (reforming raw material gas h and reformed gas g) remaining in the reformed gas system line 76 in the fuel processing device 2 is replaced and pushed out toward the burner section 25 to be removed. Here, the process water p and the water vapor from which the process water has evaporated are the first incombustible fluid of the present invention. The combustible gas pushed out to the burner unit 25 is similarly combusted by the combustion of the combustion gas m in the burner unit 25. At this time (time t31 '), the combustion gas m and the combustion air k4 are continuously supplied, so that the burner unit 25 is combusted.
[0084]
The supply of the process water p is stopped at time t31 ', and the supply of the bleed air k2 once stopped is restarted at time t31'. The flow rate of the bleed air k2 at this time is 1 NL / min. Here, the bleed air k2 is supplied because the water vapor from which the process water p has evaporated cannot be sufficiently replaced with the combustible gas because the downstream side of the cooler 77 is condensed by cooling of the water vapor. k2 is supplied to the downstream side of the cooler 77 (the reformed gas transfer line 16 (excluding the fuel cell stack 3 side of the three-way switching valve), the switching line 67, the downstream side of the cooler 77 of the anode offgas line 17 (switching). Except for the fuel cell stack 3 side of the connecting portion of the line 67))), the combustible gas can be replaced. Here, the bleed air k2 is the second incombustible fluid of the present invention.
Slightly before time t3 '(after time t31'), the flow rate of combustion air k4 decreases from 13.5 NL / min to 12.5 NL / min. This decrease is due to the resumption of the supply of bleed air k2.
[0085]
At time t33 'slightly before time t4 (5 minutes after time t3'), the supply of combustion gas m and the supply of bleed air k2 are stopped, and the flow rate of combustion air k4 is increased to 20 NL / min. This is to ensure the ignitability of the burner portion 25 when moisture is completely removed from the burner portion 25 and the fuel cell power generation system 101 is next started.
[0086]
At time t4, the flow rates of the combustion gas m and the bleed air k2 become zero.
[0087]
At time t41, which is slightly before time t5 (for example, 5 minutes after time t4), the supply of combustion air k4 is stopped, and at time t5, the flow rate of combustion air becomes 0, and the fuel cell power generation system 1 is stopped. To do. At time t2, the remaining stack voltage is discharged by at least one of the methods (1), (2), and (3), and hydrogen in the reformed gas g remaining in the fuel cell stack 3 is consumed.
[0088]
According to the fuel cell power generation system 101 of the second embodiment, the stack current Is is decreased to 0 to stop the power generation of the fuel cell stack 3, and the combustion source gas m is supplied to the burner unit 25. Since the supply of the reforming source gas h is stopped, the combustion source gas m can be supplied to the burner unit 25 and the combustion in the burner unit 25 can be maintained even after the supply of the reforming source gas h is stopped. it can. Since the process water p is supplied even after the supply of the reforming source gas h is stopped, the reforming source gas h and the reformed gas g in the reformed gas system line 76 are replaced with water vapor evaporated from the process water p. The reforming raw material gas h and the reformed gas g which have been pushed out to the burner unit 25 and eliminated, can be burned in the burner unit 25. Next, since the supply of the bleed air k2 is started, the flammable gas on the downstream side of the cooler 77 that cannot be replaced with the water vapor from which the process water p has evaporated can be replaced with the bleed air k2. Therefore, the release of the reforming raw material gas h and the reformed gas g remaining after the stop of the fuel cell power generation stack 101 to the environment can be greatly reduced.
[0089]
[Effect of the invention]
As described above, according to the present invention, since the fuel processing device, the fuel cell stack, and the control unit are provided, the control unit stops power generation of the fuel cell stack, and the combustion raw material is supplied to the burner unit. In this state, since the supply of the reforming raw material is stopped, the combustion raw material can be supplied to the burner portion and the combustion in the burner portion can be maintained even after the supply of the reforming raw material is stopped. Since the first incombustible fluid is supplied to the reformed gas system line, the reforming raw material in the reformed gas system line pushes out the reformed gas to the burner section, and combustion is maintained by supplying the combustion raw material. It can be burned in the burner part. In this way, the residual combustible gas in the fuel cell power generation system can be safely processed and purged, and the system can be stopped.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a fuel cell power generation system according to a first embodiment.
2 is a block diagram illustrating details of a load of the fuel cell power generation system of FIG. 1. FIG.
FIG. 3 is a graph showing a stop operation method of the fuel cell power generation system of FIG. 1;
4 is a graph showing a stack current and process water temporal changes in the stop operation of the fuel cell power generation system of FIG. 1; FIG.
FIG. 5 is a block diagram showing a configuration of a fuel cell power generation system according to a second embodiment.
6 is a graph showing a stop operation method of the fuel cell power generation system of FIG. 5. FIG.
7 is a graph showing a temporal change in stack current and process water in the stop operation of the fuel cell power generation system of FIG. 5. FIG.
[Explanation of symbols]
1, 101 Fuel cell power generation system
2 Fuel processor
3 Fuel cell stack
4,104 Control unit
5 Load
11 Fuel supply line
12 Air supply line for selective oxidation
13 Process water supply line
16 Reformed gas transfer line
17 Anode off-gas line
21 reformer
22 Metamorphosis Department
23 Selective oxidation part
25 Burner
32, 34, 36, 38, 42, 44 Control valve
39 Temperature detector
45 Stack voltage detector
46 Stack current detector
47-52 flow meter
53 Bleed air inlet
54 Voltage Current Data Storage Unit
55 Transformer proper temperature storage unit
f Anode off gas
g Reformed gas
h Fuel
i1 Flow control signal
i2 Temperature signal
i3 voltage signal
i4 current signal
i5 Flow signal
i6 switching signal
Is stack current
k1 Selective oxidation air
k2 bleed air
k3 stack air
n Combustion gas
p Process water
Vs Stack voltage

Claims (5)

A first inlet for introducing a reforming raw material;
A reforming section for reforming the introduced reforming raw material into a reformed gas;
A selective oxidation unit that selectively oxidizes carbon monoxide contained in the reformed gas with air for selective oxidation;
An outlet for deriving the reformed gas exiting the selective oxidation unit;
A reformed gas system line that communicates the first inlet, the reformer, the selective oxidation unit, and the outlet, and guides the reforming raw material or the reformed gas;
A fuel processor having at least a burner section for burning the anode off gas and heating the reforming section;
A fuel cell stack that generates electric power using the derived reformed gas and discharges the anode off-gas to the burner section;
(B1) Check whether or not the combustion raw material is supplied to the burner unit, and if the combustion raw material is not supplied to the burner unit, supply the combustion raw material to the burner unit. Start, then stop the introduction of the reforming raw material,
(C1) including a control unit that introduces a first incombustible fluid that pushes combustible gas remaining in the reformed gas system line to the burner unit from the first introduction port;
Fuel cell power generation system. A reformed gas line that conveys the derived reformed gas to the fuel cell stack, and has a second inlet for introducing bleed air that further oxidizes carbon monoxide remaining in the derived reformed gas. Equipped with a quality gas line;
The control unit introduces process water which is evaporated in the reforming unit and used as reforming steam from the first introduction port,
In the control of (C1), the process water is introduced, and the process water evaporated in the reforming unit is used as the first incombustible fluid.
Furthermore, the bleed air is introduced from the second introduction port as a second non-combustible fluid that pushes the combustible gas remaining in the reformed gas line to the burner portion;
The fuel cell power generation system according to claim 1. The control unit performs the control (A1) to stop the power generation of the fuel cell stack before the control (B1).
Further, in the control of (A1), the stack current generated by the fuel cell stack is reduced by a predetermined gradient to zero, the power generation of the fuel cell stack is stopped, and the supply amount of the reforming raw material is predetermined. Reduced to a flow rate of
The fuel cell power generation system according to claim 1 or 2. The fuel cell stack is configured such that residual hydrogen remaining in the fuel cell stack is consumed by discharging a stack residual voltage of the fuel cell stack;
The controller is
(E1) The discharge is caused simultaneously with the control of (C1),
(F1) The discharge is stopped when any cell voltage of the fuel cell stack becomes a predetermined value or less,
(G1) When the cell voltage that has fallen below the predetermined value has recovered to a predetermined value, the discharge is caused to occur again;
The control of (E1), the control of (F1), and the control of (G1) are repeated a predetermined number of times or until no cell voltage recovery occurs;
The fuel cell power generation system according to any one of claims 1 to 3. A first inlet for introducing the raw material for reforming and process water;
A reforming section for evaporating the introduced process water and using it as reforming steam to reform the reforming raw material into a reformed gas;
A selective oxidation unit that selectively oxidizes carbon monoxide contained in the reformed gas with air for selective oxidation;
A fuel processor for chromatic and guide outlet deriving the reformed gas leaving the selective oxidation unit;
A reformed gas line for conveying the derived reformed gas, the reformed gas line having a second inlet for introducing bleed air for further oxidizing carbon monoxide remaining in the derived reformed gas;
A fuel cell stack for generating electricity using a reformed gas obtained by oxidizing carbon monoxide with the bleed air;
(B2) After stopping the introduction of the reforming raw material from the first inlet, after the predetermined time has elapsed, the introduction of the process water from the first inlet is stopped,
(C2) including a control unit that introduces the bleed air from the second introduction port ;
The predetermined time is a sufficient time for extruding the reforming raw material or the reformed gas remaining in the fuel processing apparatus by the reforming steam ;
Fuel cell power generation system.

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