JPH0482169A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To prevent a cell from being damaged by calculating a proper flow rate of fuel gas to a generated current value on the basis of a hydrogen gas measured by means of a hydrogen densitiometer thereby adjusting the flow rate of the fuel gas at a proper value. CONSTITUTION:A raw fuel gas 21 and a steam 20 are supplied to a fuel reforming equipment 24 at a specified rate. The flow rate of the raw fuel gas is adjusted by a raw fuel gas flow rate adjusting valve 22. In order to supply the fuel gas corresponding to the power used to a fuel cell, from a current detector 32 provided in a d.c. load circuit, a hydrogen concentration detector 27 provided in a fuel electrode exhaust gas 28 and a flow rate detector 23 provided in a raw fuel gas system are operated to detect respective values, a load signal 35, hydrogen concentration signal 36 and flow rate signal 37 are transmitted to an arithmetic controller 34. The controller 34 is operated to output a flow rate adjusting signal 38 for controlling a raw fuel gas valve 22.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel cell power generation system, and particularly to improvement of the fuel gas flow rate with respect to the generated current related to battery loss imbalance.

[Conventional technology]

Figure 3 is a system diagram showing a conventional fuel cell power generation system disclosed in, for example, Japanese Patent Application Laid-Open No. 1-286259. It is a single battery. (3) is a matrix impregnated with phosphoric acid, (4M and (4F) on both sides are an oxygen electrode and a hydrogen electrode, respectively. (5) is a current detector, (6) is a circuit breaker, and (7) is a load ]9) and QOJ are the fuel gas and oxidant gas supplied to the fuel cell (1), respectively, and (11) and (12) are
A flow rate sensor is provided in each of the supply paths of the ff1ll gas and the oxidizing gas.

Next, the operation will be explained. A fuel cell (1
), if the flow rate of the fuel gas (9) to be supplied is a little below the rated flow rate due to a malfunction in the reforming system, for example, the decrease in the fuel gas flow rate is detected moment by moment by the flow rate sensor (1) and its output is is input to the judgment circuit (13). On the other hand, the rated current ■ is detected by the current detection circuit (5) and the judgment circuit (
13), and the lower limit value of the flow rate is calculated. At this time, when the actual flow rate falls below the calculated lower limit value of the flow rate, a cutoff signal is output from the judgment circuit (13) and the circuit breaker (6) is opened. The above explanation deals with the case where the fuel flow rate decreases due to a malfunction in the reforming system, but gas shortages can also occur when the flow rate of the oxidizing gas system decreases or when the load current ■ suddenly increases due to circumstances on the load side. However, in this case as well, the load current is cut off by the above-described operation.

[Problem to be solved by the invention]

Conventional fuel cell power generation systems are configured as described above, so when the gas composition of the fuel supplied from the reforming system changes and the hydrogen concentration decreases, the hydrogen concentration is
Since control decisions are made based on the lower limit gas flow rate calculated only based on the load current, the system is essentially operated at a lower limit of the required amount of hydrogen, causing damage to the battery.

In addition, in this operating method, the lower limit gas flow rate calculated based on the load current is compared with the actual flow rate detected moment by moment, and if the gas amount is insufficient, the load is cut off and stopped, so the system can be used independently from the grid power supply. In such a case, when a load is applied, the load current responds instantaneously compared to the slow response of the gas flow rate, so it is calculated that there is a gas shortage and the load is cut off, making it impossible to operate. Furthermore, even if a time lag is included in the calculation and determination of gas shortage in order to eliminate the inoperability, if the time lag is too long, the actual required amount of hydrogen will fall below the lower limit value, causing damage to the battery.

Fluctuations in the gas composition of the fuel supplied from the reforming system mentioned above can also be caused by malfunctions in some parts of the equipment, but even if the equipment is operating normally, for example, when the temperature is raised by steam ventilation in the reforming system at startup, After the catalyst is oxidized by the steam, the raw material gas is introduced and reforming starts, and for a while the hydrogen in the reformed gas is consumed by the reduction of the oxidized catalyst and the concentration decreases. decreases. This phenomenon can be observed by changes in the hydrogen concentration in the gas at the outlet of the fuel electrode of the cell main body and by the temperature of the reformer catalyst layer when the exhaust gas of the fuel electrode of the cell main body is combusted. Figure 4 shows an example of this change.

Further, in the case where the battery is used independently from the grid power source, which is another problem mentioned above, an example of changes in the battery current and the supply gas flow rate when the load is suddenly changed is shown in FIG. It can be seen that although the current increases rapidly, the supply gas flow rate increases slowly.

This invention was made in order to solve the above-mentioned problems, and provides a fuel cell that can detect and calculate the gas flow rate that is substantially required for the battery body, and that can control operation based on the above calculation results to prevent damage to the battery. The purpose is to obtain a power generation system.

[Means to solve the problem]

The fuel cell power generation system according to the present invention is provided with a hydrogen concentration meter for detecting the hydrogen concentration of the fuel gas in the fuel gas transfer system of the fuel cell main body, and detects the amount of hydrogen gas based on the measured value of the hydrogen concentration meter. It is configured to use the standard as a reference, calculate the appropriate fuel gas flow rate for the generated current value, and adjust it to the appropriate flow rate.

According to claim 2, a hydrogen concentration meter for detecting the hydrogen concentration of the fuel gas is provided in the fuel gas transfer system of the fuel cell main body, and when the hydrogen concentration becomes lower than a set limit value, the current generated in the fuel cell main body is cut off. It is composed of an operation control means for controlling the

[Effect]

The hydrogen concentration meter in the fuel cell power generation system of the present invention detects the hydrogen concentration of the fuel gas and provides substantially necessary data on the fuel gas flow rate.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (2m) is steam, (2nd season is raw fuel gas, (22) is the increase in flow rate m to make raw fuel gas the appropriate flow rate,
(23) is a flow rate detector that detects and transmits the flow rate of the raw fuel gas to be supplied to the fuel gas reforming device (24). (2
4) converts the raw fuel gas (21) into hydrogen-rich reformed fuel gas (25) in a fuel gas reforming processing device. (
26) is the fuel cell main body, (26a) fuel electrode and (26c)
It consists of an air electrode. (27) is a hydrogen concentration detector that detects and transmits the hydrogen concentration in the fuel electrode exhaust gas (28). (29) is supplied with air to the air electrode (26e). (30) is the air electrode exhaust gas. (31) is a DC load circuit that connects the battery body (26) and the orthogonal conversion device (33). (32) is a current detector, which is provided in the middle of (31) the DC load circuit.

(34) is the operation and limiter that make up the judgment@path (35)
The receiver calculates the load signal of (36) and the hydrogen concentration signal (37) of the raw fuel gas flow rate signal and transmits a control signal.

(38) A flow rate control signal 1 is output from the arithmetic controller (34) and controls the raw fuel gas control valve (22). (3
9) is an AC electrical output, which is output from the orthogonal transformer (33).

(40) is the load cutoff signal for operation control that cuts off the generated current, and (34) calculation control l! Released from I1m (33) I!
Drives the AC converter and cuts off the load.

Next, the operation will be explained. At startup, the temperature of the fuel gas reformer is raised using nitrogen or steam (20). When the temperature conditions necessary for reforming are reached, the raw fuel gas (21) and steam (20) are supplied at a constant rate to the fuel reformer (24). At this time, the raw fuel gas flow rate is adjusted by the raw fuel gas flow rate control valve (22). The raw fuel gas (21) and steam (20) are converted into hydrogen-rich reformed fuel gas (25) in the fuel gas reformer (24), and then the fuel cell main body (
26) is supplied to the fuel electrode (26a).

Then, air (29) is supplied to the air electrode (26c), and the fuel cell main body (26) starts generating electricity. The electric power passes through a DC load circuit (31), is converted from DC to AC by an orthogonal converter (33), and is used as an AC electrical output (39). In order to supply fuel gas to the fuel cell according to the power used, a current detector (32) is installed in the DC load circuit, and a hydrogen concentration detector (27) is installed in the fuel electrode exhaust gas (28).
, and the flow rate detector (23) installed in the raw fuel gas system, detect the respective values, and send the load signal (35), hydrogen concentration signal (36) and flow rate signal (37) to the arithmetic controller (
34). Calculation control # (34) is the calculation result,
The flow rate adjustment signal (38) is output and the raw fuel gas flow rate adjustment valve (2
2). The first claim constitutes the above system. FIG. 2 shows the operation flow in this configuration, and the signal sent to the calculation side @M<34) operates according to the flow shown in FIG. In the figure, the load signal (35),
I is calculated based on the conversion rate of reformed hydrogen/raw fuel determined in the design, the hydrogen utilization rate of the fuel cell = η, etc., and the required gas flow rate: Qc is determined. (For example, Qc is expressed as: Here, N is the number of cells, and if the unit of ■ is A, then Qc is NM3/H.) Qc is compared with the flow rate signal: Q+n, and Q m < In the case of Q c,
If flow rate increase signal: aieQIrl>Qc, output flow rate decrease signal: b. In addition, the hydrogen concentration signal: CIn is determined by the operational design value of the fuel cell: the hydrogen concentration of the fuel electrode exhaust gas:
Compared with Ct (for example, when the hydrogen concentration of reformed fuel gas is 78% and the hydrogen utilization rate is 80%, Ct=41°5%), Cm>Ct
If CJeCrn<Ct, output a flow rate increase signal: d. Flow rate increase signals a and d are OR
The flow rate decrease signals (i) and (c), which increase under the condition, are adjusted to decrease under the AND condition. In the second claim, the hydrogen concentration limit value: Cc (for example, C
c-15%), and if Cm < Cc, a load shedding signal (40) is issued to cut off the load and, if necessary, stop the power generation system.

Note that in the above embodiment, the flow rate detector (23) is provided in the raw fuel gas (21) system upstream of the fuel reformer (24), but the flow rate detector (23) )
It may also be provided in the reformed fuel gas (25) system downstream of. Further, in the above embodiment, the orthogonal converter (33) is provided in the load circuit, but it can also be used as a DC load, and in this case, the orthogonal converter (33) is not required and a circuit breaker is simply used to interrupt the load. By changing to , the same effect as the above example can be obtained. In addition, in the above embodiment, the hydrogen concentration detector (
27) is installed in the fuel electrode exhaust gas (28) on the downstream side of the fuel cell main body (26), but it should also be installed in the reformed fuel gas (25) on the same upstream side, or on both the upstream and downstream sides. It may be provided. In this case, if the reformer is provided upstream, it will be easier to determine if there is an abnormality in the reformer (24). Further, in the example in which the fuel cells are provided on both sides, abnormalities in the reforming processing device (24) and the fuel cell main body (26) can be separated and easily determined.

Further, although the fuel system is described in the above embodiment, the air system can also be controlled by detecting the concentration of the reactant gas oxygen in a similar manner to prevent abnormal operation.

〔Effect of the invention〕

As described above, according to claim 1 of the present invention, a hydrogen concentration meter for detecting the hydrogen concentration of the fuel gas is provided in the fuel gas transfer system of the fuel cell main body, and the amount of hydrogen gas is determined based on the measured value of the hydrogen concentration meter. It is configured to use the standard as a reference, calculate the appropriate fuel gas flow rate for the generated current value, and adjust it to the appropriate flow rate. According to claim 2 of the present invention, a hydrogen concentration meter for detecting the hydrogen concentration of the fuel gas is provided in the fuel gas transfer system of the fuel cell main body, and when the hydrogen concentration becomes lower than a set limit value, the fuel Since it is configured as an operation-side splitting means that cuts off the current generated by the cell main body, a fuel cell power generation system that can prevent damage to the fuel cell because there is no substantial fuel gas shortage in the fuel cell main body can be obtained. There is.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a fuel cell power generation system according to an embodiment of the present invention, Fig. 2 is a control flow diagram showing the operational flow in the configuration of Fig. 1, and Fig. 3 shows a conventional fuel cell power generation system. System diagrams, Figures 4 to 7 are data diagrams for explaining problems in conventional equipment, and Figures 4 and 5 show examples of fuel electrode hydrogen concentration changes and reformer catalyst humidity changes at system startup. FIG. 6 and FIG. 7 show examples of load changes and fuel gas flow rate changes during load in independent operation. In the figure, (22) is a fuel gas flow rate control valve, (26)
is the fuel cell body, (27) is the hydrogen concentration meter, (34) +
(40) is a load shedding signal. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (2)

[Claims] (1) In a fuel cell power generation system that has a fuel gas flow rate detection function in the fuel gas transfer system of the fuel cell main body, and is equipped with a judgment circuit that compares and calculates the fuel gas flow rate and the current value generated by the fuel cell main body, The fuel gas transfer system is provided with a hydrogen concentration meter that detects the hydrogen concentration of the fuel gas, and the judgment circuit determines the appropriate fuel gas flow rate for the generated current value based on the hydrogen gas amount based on the measured value of the hydrogen concentration meter. A fuel cell power generation system that calculates and adjusts the flow rate to an appropriate level. (2) In a fuel cell power generation system that has a fuel gas flow rate detection function in the fuel gas transfer system of the fuel cell main body, and is equipped with a judgment circuit that compares and calculates the fuel gas flow rate and the current value generated by the fuel cell main body, A hydrogen concentration meter for detecting the hydrogen concentration of the fuel gas is provided in the fuel gas transfer system, and an operation control means is provided to cut off the current generated by the fuel cell main body when the hydrogen concentration becomes lower than a set limit value. A fuel cell power generation system characterized by: