JPH01307175A - Small fuel battery type power generating system - Google Patents

Abstract

PURPOSE:To prevent misfire of a modifier burner by calculating the misfire timing of the burner upon reception of an output current increment signal and a modifier burner temp. drop signal, computing the amount of the aid fuel supplied on the basis of the result from calculations, and by driving the aid fuel supplying part when the burner temp. has sunk. CONSTITUTION:A misfire timing calculating part 31 calculates the misfire timing with the plant constant taken into considerations upon reception of the current increment signal emitted repeatedly from a main calculating part 20 at a certain timing and the temp. drop signal from the set value of the temp. of modifier burner 41. An aid fuel computing part 32 computes the incremental portion (aid fuel) of the modifier fuel at modifier burner 41 necessary for prevention of misfire on the basis of the result from calculation of misfire timing to be emitted repeatedly, and when the temp. of the modifier burner 41 has sunk below specified value, a control signal to drive the aid fuel supplying part is emitted. Accordingly supply of the modifier fuel to the modifier burner 41 is increased in an amount corresponding to the aid fuel. Thus the modifier burner 41 is prevented from misfire certainly.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a small fuel cell power generation system using a fuel reformer, and in particular to a small fuel cell power generation system with an AC output that can easily follow an increase in power load. .

[Conventional technology]

In a fuel cell power generation device IIt using a fuel reformer,
A fuel cell power generation system with AC output, which is small and used in applications where the power load fluctuates rapidly, has two main components: the amount of reforming material supplied to the fuel reformer and the amount of fuel supplied to the fuel cell section.
It is necessary to control the amount of air supplied according to the power load.

Conventional large-scale fuel cell power generation equipment has a fuel gas surge tank added in front of the fuel electrode side of the fuel cell in order to avoid delays in the reforming reaction of the fuel reformer. Hydrogen was supplied. However, in small power generation devices, due to space issues and the need to be able to operate independently for long periods of time, secondary batteries are used in the system to compensate for the delay of the fuel reformer.

[Problem that the invention attempts to solve]

Such small fuel '#j1. Pond power generation equipment had the following problems.

b) Depending on the load, a large capacity secondary battery is required.

Therefore, the size of the secondary battery becomes an impediment to miniaturization.

-・) When load fluctuations are severe, the secondary battery becomes over-discharged during operation and the output voltage decreases.

A part of the fuel gas supplied to the fuel cell is supplied as return gas to the fuel reformer burner and is consumed as thermal energy necessary for the reforming reaction of the raw fuel. Since most of the gas is consumed by the fuel cell, the reformer burner tends to misfire (go out), which accelerates overdischarge of the secondary battery.

The purpose of this invention is to have a function to prevent the burner of the fuel reformer from misfiring when the power load suddenly increases, thereby increasing the load followability of the fuel reformer and thereby increasing the capacity of the secondary battery. The objective is to reduce the number of fuel cells and obtain a more compact fuel cell power generation device.

[Means to solve the problem]

In order to resolve the above question, the present invention calculates the total output power of the fuel cell based on the detection of load power of the fuel cell, auxiliary power, secondary battery voltage, etc. In a device that is equipped with a main calculation section that controls the output current, momentarily calculates the flow rates of the reforming material, reformer fuel, auxiliary fuel air, etc. corresponding to the total output power, and issues a control signal. A misfire timing calculation section that calculates the misfire timing of the reformer burner based on the fuel output current increase signal of the pond and the reformer temperature decrease signal, which is outputted from the calculation section at a predetermined timing; an auxiliary fuel calculation unit that issues a signal to control the amount of auxiliary fuel supplied to the reformer burner based on the door-output signal when the temperature of the reformer reaches a predetermined level; and an output control signal of the auxiliary fuel calculation unit. and an auxiliary fuel control section that receives auxiliary fuel at a predetermined level and supplies the auxiliary fuel to the reformer burner.

[Effect]

In the above means, the misfire timing of the reformer burner depends on plant constants such as the volume of the fuel gas system of the fuel cell including piping, the increase level of the output current, and the temperature drop of the reformer burner,
In severe cases, misfires occur within a few seconds from the point at which the current increases, so we focused on the fact that misfires can be prevented by detecting this misfire timing early and increasing the amount of reformer fuel supplied to the reformer burner. It is constructed. That is, the misfire timing calculation section receives the current increase amount signal repeatedly output at predetermined timing from the main calculation section and the temperature decrease amount signal for the set value of the reformer burner temperature, and calculates the misfire timing taking into account the plant constants. Calculated. In addition, the auxiliary fuel calculation section calculates the amount of increase in the amount of reformer fuel for the reformer burner (hereinafter referred to as auxiliary fuel) necessary to prevent misfires based on the calculation results of the misfire timing outputted back. By issuing a control signal for driving the auxiliary fuel supply section when the reformer burner temperature falls below a predetermined temperature, the amount of reformer fuel supplied to the reformer burner is increased by the amount of the auxiliary fuel. Therefore, if the reformer burner temperature, which determines the timing to start supplying auxiliary fuel, is set to be much smaller than the amount of decrease in the reformer burner temperature that has the potential for OJ to misfire, misfires in the reformer burner can be prevented. This can be reliably prevented, and the consumption of the secondary battery associated with this button is prevented.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention. In the figure, 1 is a fuel reformer, 2 is a fuel cell, and the fuel reformer 1 is a reformer burner 41. A temperature detector 30f is provided, and the raw fuel 71 supplied from the reforming raw material control section 3 is reformed into fuel gas 81 by the reforming reaction of the reforming catalyst layer heated to a predetermined operating temperature, and is then supplied to the fuel cell 2. supply The fuel cell 2 directly generates electricity using the fuel gas 81 supplied to each unit cell and the reaction air supplied from a reaction air control section (not shown), and a portion of the fuel gas is sent to the reformer burner 41 as a return gas 82. It supplies the thermal energy necessary for the endothermic reforming reaction. Also, the reformer burner 4
1 generates necessary thermal energy by combusting the auxiliary combustion air 74 and reformer fuel 73 supplied from the auxiliary combustion air control section 4 and the reformer fuel control section 5, respectively.

The output circuit of the 10,000 fuel cell 1 includes a current control section 10°DC
A load 16 is connected via the /AC converter 11, and a secondary battery 17 is provided on the output side of the current control section 10 to supply current to the load 13 which has large fluctuations. The power consumption of the load 13 is determined by the load power calculator 24, which multiplies the output signals of the voltage detector 22 and the current detector 26, and its actual value is 24A.
is calculated, and the auxiliary power of each control unit 3, 4, 5.6, etc. is
The actual value 27A is determined by the auxiliary power calculator 27 which multiplies the output signals of the secondary battery voltage detector 25 and the current detector 26 of the auxiliary power source 14. In addition, the output voltage of the fuel cell 2 is 2 B A (Vfc), and the output current is 29 A (Vfc).
) is determined by the voltage detector 28 and current detector 29. Furthermore, the reformer temperature (burner temperature) 30A(T) is detected by a temperature detector 60.

20 is a main calculation unit, a load power calculator 24, an auxiliary power calculator 27, and an output voltage detector 28 of the fuel cell 2. Output signals 24A, 27A of the output current detector 29,
28A and 29A, the total electric power to be output by the fuel cell 2 is calculated, and based on this, a signal 10A is outputted to the current control unit 10 to instruct the control of the output current fc. Also, the raw fuel 71. necessary to output the output current fc and the output voltage Vfc. Auxiliary combustion air74. The supply amount of the reformer fuel 76 etc. is calculated and the control signals 3A, 4A,
5A is output to each control section 3, 4.5. Also,
Furthermore, the main calculation section 20 outputs a load power control signal (not shown in the figure) to the DC/AC converter, and the current control section 10. By controlling the mutual control of the DC/AC converter 11, the secondary battery 17 is charged when the shaft is loaded, and the secondary battery 17 is discharged when the load increases, so that the fuel cell 2 can control the consumption rate of the fuel gas 81. For example, it is controlled to generate electricity while keeping it at around 70%.

FIG. 2 is a voltage-current characteristic diagram of a fuel cell for explaining the control state of the device according to the embodiment, curves 100, 101,
102 has a fuel gas consumption rate of h70% and 50%, respectively.
The Vfc-Ifc characteristic curve at 100% or more is shown.

In the figure, the load power of the fuel cell, which is being operated at 0 current with a fuel consumption rate of 70%, increases and the main control unit 2
Assume that 0 issues a command to increase the output current of the fuel cell to . If the command to increase the current from 0 to 11 is slow, the increase in raw fuel supply will follow the increase in current, so the fuel cell will have control characteristics that change from point A to point B on curve 100. , and the drop in voltage from vO to vl is primarily compensated for by discharge of the secondary battery. However, if the current increase command is rapid due to unfavorable conditions such as a sudden increase in load current or a voltage drop in the secondary battery, the fuel cell consumes the fuel that should be sent to the reformer burner as return gas to generate electricity. As a result, the fuel consumption rate increases, and the output voltage of the fuel cell changes from point A to point C, as shown by the dotted line in the figure. If the supply of fuel gas from the reformer increases during this process, misfire of the reformer burner can be avoided, but the increase in the supply of fuel gas cannot keep up and the fuel consumption rate is higher than 100%. In the event of a fuel gas shortage that reaches near the point, a situation may occur in which the reformer burner misfires (goes out).

In FIG. 1, a misfire timing calculation section 61°, an auxiliary fuel calculation section 32. The auxiliary fuel control section 63 is a means for preventing misfire of the reformer burner, and the misfire timing calculation section 31 receives the output signal 3 of the temperature detector 30 from the main calculation section 20.
A temperature reduction amount signal 30B of the reformer burner based on 0A;
A signal 29B indicating the amount of increase in the output current is inputted from time to time, and the misfire timing from point A to point C in FIG. 2 is calculated based on the signals 29B and 30B and the plant constant. The auxiliary fuel calculation unit 32 receives the above calculation result 31A, calculates the supply i of auxiliary fuel, and outputs a control signal 32A to the auxiliary fuel control unit 33 when the output signal of the temperature detector 30 drops to a predetermined level. do. As a result, since the auxiliary fuel 75 is added to the reformer burner 41 in addition to the reformer fuel from the reformer fuel control section 5, the return gas 8
As a result, the reformer gas temperature rises and the amount of fuel gas 81 supplied increases, thereby preventing misfire of the reformer burner.

FIG. 3 is an explanatory diagram of the operation of the above-mentioned misfire prevention means.
II curve 110 shows the flow rate curve of the auxiliary fuel, and curve 111 shows the temperature curve of the reformer burner. In the figure, it is assumed that at time t1, the current increases, the fuel consumption rate increases based on this, and the reformer burner temperature begins to decrease. At time t2 when the reformer burner temperature T decreases by ΔT1, the auxiliary fuel calculation unit 62 outputs the control signal 32A, and the auxiliary fuel control unit supplies auxiliary fuel to the reformer burner 41, thereby reducing the reformer burner temperature. The temperature of the burner 41 is ΔT2T as shown by the 1IIll line 111.
When the amount of fuel gas decreases by 2, it starts to increase, and reaches equilibrium at time t3 when the amount of fuel gas supply catches up. As a result, misfires that would occur due to a drop in reforming burner temperature as shown by the dotted line in the figure when auxiliary fuel is not supplied are avoided by starting supply of auxiliary fuel earlier. In addition, auxiliary fuel flow curve 11
In the form of 0, the misfire timing calculation section 31 changes its output signal 31A based on the actual frequency of the input signals 29B and 30B that are inputted from time to time, and changes the control signal of the auxiliary fuel calculation section 32 based on this changed value. may be changed,
Control suitable for preventing misfires is performed.

[Effects of the Invention] As described above, the present invention provides a misfire timing calculation unit that calculates a misfire timing of a reformer burner in response to an increase in output current of a fuel cell and a signal of a decrease in a reformer burner temperature, and a result of this calculation. The present invention is configured to include an auxiliary fuel calculation unit that calculates the amount of auxiliary fuel supplied based on the auxiliary fuel supply amount and drives the auxiliary fuel supply unit when the temperature of the reformer burner decreases. As a result, it is possible to detect fuel gas shortages due to an increase in fuel cell output current at an early stage and increase the amount of reformed fuel, eliminating the problem of reformer burner misfires due to fuel gas shortages, which was a problem with conventional technology. This is prevented, and the followability of the small fuel 'Rt' pond, which has large load fluctuations, to load fluctuations is improved. In addition, by avoiding a misfire in the reformer burner, the discharge time of the secondary battery is shortened, making it possible to reduce the installed capacity of the secondary battery, and making it possible to reduce the size of the small fuel cell power generation system. This has the advantage of contributing to weight reduction and weight reduction.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a device according to an embodiment of the present invention, FIG. 2 is a characteristic diagram showing a control state of the device according to the 7I example, and FIG. 3 is an explanatory diagram of the operation of the device according to the embodiment. DESCRIPTION OF SYMBOLS 1... Fuel reformer, 2... Fuel cell, 20... Main calculation part, 30... Temperature detector, 61... Misfire timing calculation part, 32... Auxiliary fuel calculation part , 33... Auxiliary fuel control section, 41... Reformer burner. 7IJ 2nd figure 3

Claims (1)

[Claims] 1) Calculate the total output power of the fuel cell based on detection signals such as load power of the fuel cell, auxiliary power, secondary battery voltage, etc., control the output current of the fuel cell, and perform reforming corresponding to the total output power In a device equipped with a main calculation unit that momentarily calculates the flow rates of raw materials, reformer fuel, auxiliary combustion air, etc. and issues control signals, this increases the output current of the fuel cell that is output from the main calculation unit at a predetermined timing. a misfire timing calculation unit that calculates the misfire timing of the reformer burner based on the signal and the reformer temperature drop signal, and a misfire timing calculation unit that calculates the auxiliary fuel supply amount of the reformer burner based on the misfire timing calculation result an auxiliary fuel calculation unit that issues a control signal when the temperature decrease reaches a predetermined level; and an auxiliary fuel control unit that receives the output control signal of the auxiliary fuel calculation unit and supplies a predetermined amount of auxiliary fuel to the reformer burner. A small fuel cell power generation system characterized by comprising: