JPH0311504B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a fuel cell system, and particularly to a fuel cell system equipped with a refueling device suitable for improving load response.

[Background of the invention]

First, a conventional fuel cell system will be explained with reference to FIG.

Figure 3 is a system diagram of a conventional fuel cell system.
Thick solid arrows indicate natural gas and reaction gas paths;
The one-dot chain arrow shows the air path, the two-dot chain arrow shows the exhaust gas path, the broken line arrow shows the water vapor path, and the thin solid line arrow shows the cooling water path.

In FIG. 3, 1 is a fuel cell main body, which is composed of a hydrogen electrode 1a, an oxygen electrode 1b, and a cell cooling device 1c. 2 is a reformer for reforming fuel such as natural gas, and is composed of a reaction section 2a and a combustion section 2b. 3 is a shift converter, 4 is an ejector (or mixer), 13 is a main fuel control valve, and 14 is an auxiliary fuel control valve.

The re-boomer 2 is equipped with a piping system that connects these main fuel control valve 13, ejector 4, re-boomer 2, and shift converter 3 and supplies fuel gas to the hydrogen electrode 1a of the fuel cell main body 1, and an auxiliary fuel control valve 14.
A fuel supply system is constituted by a piping system that supplies natural gas to the combustor 2b.

Reference numeral 12 denotes a blower for supplying air; a pipe equipped with a cathode air adjustment valve 15 is connected to the oxygen electrode 1b of the fuel cell main body 1, and a pipe equipped with a burner air amount adjustment valve 16 is connected to the combustion section of the reformer 2. 2b
is connected to constitute an air supply system.

5 is a steam generator, 7 is a cooling water heat exchanger, 10
1 is a cooling water pump, and the cooling water pipes connecting these pumps are connected to the battery cooling device 1c of the fuel cell main body 1 to form a cycle of the battery cooling system.

8 is a heat exchanger for exhaust gas, which exchanges heat with the exhaust air from the oxygen electrode 1b of the fuel cell main body 1 and the exhaust gas from the combustion part 2b of the refoamer 2 with circulating water, etc., and constitutes an exhaust gas and water recovery system. ing. 9'
1 is a water tank for the recovered water, and 11 is a water supply pump that supplies water to the battery cooling system.

6 is an inverter provided on the output side of the combustion battery main body 1.

The main functions of the fuel cell system having such a configuration will be explained below.

Fuel such as natural gas is mixed with water vapor by the ejector 4 as shown by the thick solid line,
The gas is supplied to the reaction section 2a, where it is reformed into a so-called hydrogen-rich gas containing a large amount of hydrogen. Subsequently, the gas is introduced into the shift converter 3, where carbon monoxide in the gas reacts with water and is converted into carbon dioxide and hydrogen. Then, if there is excess water in the gas,
After removing this, the hydrogen electrode 1 of the fuel cell main body 1
About 80% of the hydrogen is consumed here, and the remaining 20% hydrogen-containing hydrogen electrode exhaust gas is sent to Refomar 2.
It is returned to the combustion section 2b and used as part of the combustion heat required for the reforming reaction.

The pressure of the air is increased by the blower 12, and the air is pumped to the oxygen electrode 1b of the fuel cell main body 1 as shown by the dashed line arrow.
and is supplied to the combustion section 2b of the re-former 2.

The exhaust air from the oxygen electrode 1b of the fuel cell main body 1 and the exhaust gas from the combustion section 2b of the re-former 2 are guided to the exhaust gas heat exchanger 8 where they join together as shown by the two-dot chain arrow, and are then cooled by circulating water or the like. Exhaust heat recovery and moisture recovery are performed by cooling the exhaust gas until the moisture is condensed. The recovered water is led to a water storage tank 9' and reused.

The pressure of the cooling water is increased by the cooling water pump 10,
It is supplied to the cell cooling device 1c of the fuel cell main body 1 as indicated by the thin solid line arrow, and after removing the generated heat from the fuel cell main body 1, it is flushed by the steam generator 5. Here, a part of the cooling water becomes water vapor, the flow rate of which is adjusted by the steam amount control valve 17, and guided to the ejector 4 as indicated by the broken line arrow. The remaining cooling water joins the makeup water from the water supply pump 11 and is led to the cooling water pump 10 again.

Excess heat generated in the battery cooling system is recovered in the form of hot water or the like by the cooling water heat exchanger 7.

In such conventional fuel cell system devices, the power load connected to the fuel cell system suddenly increases, for example.
Consider the case where the load increases from 25% to 100%.

In order to cope with this increase in load, it is necessary to quickly increase the gas supplied to the hydrogen electrode 1a of the fuel cell main body 1, but for this purpose, the main fuel amount control valve 13, the auxiliary fuel amount control valve 14, It is necessary to rapidly increase the opening degrees of valves such as the cathode air amount control valve 15, the burner air amount control valve 16, and the steam amount control valve 17.

However, even if the valve is relatively small, the valve control system is accompanied by an element of time delay, so it usually takes 2 to 30 minutes.
There will be a delay of about 18 seconds. This means that the fuel cell system cannot follow the load during the delay in operation, and this state is schematically shown in FIG.

FIG. 4 is a diagram showing load response, and a shows a state in which the load increases in a step function manner, with time on the horizontal axis and load on the vertical axis.

b shows the change in the output power from a conventional fuel cell system in comparison with a, with the horizontal axis representing time and the vertical axis representing the output power.

It can be seen that because the fuel cell system has a time delay _T1 , the output power is insufficient in the shaded area A.

This means that on-site fuel cell systems that are used independently of the general grid power (isolated operation) experience severe load fluctuations.
This was a particularly big problem.

As described above, fuel cell-based devices are required to have excellent load responsiveness, and in particular, improving the responsiveness of the amount of fuel supplied to the fuel cell main body is an important issue.

As a prior art corresponding to this, for example, the one described in JP-A-58-82478 is known.

In the invention disclosed in the publication, when the load increases and the output voltage decreases, the output detector immediately detects this and sends the signal to the control circuit. The control circuit sends a current proportional to the voltage fluctuation to the proportional control valve to widen the opening of the valve and increase the amount of gas supplied to keep the output voltage constant. In order to eliminate the time delay during this time, the control circuit is equipped with a differential and integral circuit.

In order to improve the load response in this way, special means such as a detection means and a fuel control means are required in the control system.

[Purpose of the invention]

The present invention was made to solve the problems of the prior art described above, and the control system has a simple configuration.
The object of the present invention is to provide a fuel cell system device with excellent load followability, which automatically replenishes fuel gas to the fuel cell main body when the load increases.

[Summary of the invention]

The structure of the fuel cell system device according to the present invention includes a fuel cell main body, a fuel supply system for the fuel cell main body, an air supply system, a cell cooling system, an exhaust gas and water recovery system, and ancillary devices. , a gas storage tank is provided which can be connected to the piping of the fuel supply system to replenish fuel, and the bottom of the gas storage tank is connected to the water storage membrane installed in the exhaust gas and moisture circuit system via a communication pipe. At the same time, the water level of the water storage membrane during steady state is located above the water level at the bottom of the gas storage membrane, and the head difference due to this water level difference allows the storage gas membrane to be sent to the piping of the fuel supply system when the load increases. It is made to be moisturized.

As an additional note, the present invention stores the hydrogen-rich gas necessary for power generation in the fuel cell during steady operation, and when the load increases, uses the difference in the head of water stored in the tank to perform the above-mentioned operation. By forcibly pushing out the accumulated gas and quickly replenishing it to the fuel cell itself, the system attempts to cope with temporary fuel shortages due to increased load.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIGS. 1, 2, and 4.

FIG. 1 is a system diagram of a fuel cell system according to an embodiment of the present invention, and FIG. 2 is a detailed view of the main parts of FIG. 1, showing details of the fuel replenishment device. Components with the same reference numerals as in FIG. 3 are the same parts as those in the prior art, so their explanation will be omitted.

Furthermore, the types of arrows indicating the paths of each fluid are also the same as in FIG. 3 above.

In the figure, 20 is a part of the fuel supply piping,
This is a pipe that connects the hydrogen electrode 1a of the fuel cell main body 1 and the shift converter 3, and is the same as the conventional device.

21 is a gas storage tank connected to the pipe 20 and storing fuel gas.

9 is a water storage tank installed in the exhaust gas and moisture recovery system, and is replaced by water storage tank 9' in Fig. 3, which was conventionally used to store water recovered from the exhaust gas and make-up water for the battery cooling system. It is equivalent.

24 is a communication pipe connecting the water storage tank 9 and the bottom of the gas storage tank 21, and the connection position of the communication pipe 24 to the water storage tank 9 is set to be lower than the full water level in the normal state.
It is lower by a water level difference h corresponding to the water volume corresponding to the stored gas volume of 1.

25 is a pipe connecting the upper part of the gas storage tank 21 and the pipe 20 of the fuel supply system.

The pressure at the portion connecting the gas storage tank 21 and the pipe 20 is set to be approximately several hundred mmAq higher than atmospheric pressure.

As shown in FIG. 2, it is installed so that the water level of the water storage tank 9 filled with water is ΔH higher than the water level of the gas storage tank 21 during steady state. At this time, if ΔH is set smaller than the gauge pressure of the pipe 20, the gas storage tank 21 is filled with fuel gas, ie, hydrogen-rich gas, until the stopper float 22 closes the water outlet 23 at the bottom during steady state.

Next, the operation of the fuel cell system having such a configuration when the load increases will be explained.

Suppose now that the load connected to the fuel cell system suddenly increases. As the load increases, an attempt is made to increase the amount of fuel gas from the fuel supply system, but as explained earlier in the prior art, there is a time delay in each control valve, etc., so this increase in load must be responded to immediately. Fuel gas cannot be supplied. As a result, the supply of fuel gas to the hydrogen electrode 1a of the fuel cell body 1 is delayed, resulting in a fuel shortage condition, and the pipe 2
0 pressure decreases.

Therefore, as the pressure in the pipe 20 decreases, the fuel gas stored in the gas storage tank 21 during normal operation is absorbed to compensate for the decrease in pressure, and
Using the head difference ΔH due to the water level difference between the water storage tank 9 and the storage gas tank 21, water becomes a working fluid and the fuel gas is forcibly fed to the pipe 20 via the pipe 25.

That is, a replenishment action is performed so that the supply of hydrogen-rich gas to the hydrogen electrode 1a of the fuel cell main body 1 does not become insufficient.

The water moving from the water storage tank 9 into the gas storage tank 21 via the communication pipe 24 ranges from the full water level to h.
This water level difference h is a water level difference corresponding to the gas storage volume of the gas storage tank 21 as described above, and the water is
This prevents the liquid from flowing into the pipes 25 and 20.

FIG. 4 schematically shows the effects of this example.

FIG. 4c shows changes in the outputtable power from the fuel cell system according to an embodiment of the present invention, with time on the horizontal axis and outputtable power on the vertical axis.

In this case, compared to the conventional technology shown in FIG. 4b, the outputtable power is increased by the portion corresponding to B, and as a result, the time delay is reduced to T ₂ (T ₂ < T ₁ ), Load response has been significantly improved.

In this way, according to this embodiment, even if the load connected to the fuel cell system increases rapidly, the gas storage tank 21
The fuel gas stored in the tank 9 can be quickly replenished to the fuel cell main body 1 by the difference in the head of water stored in the water tank 9 to compensate for the shortage of supplied fuel gas, thereby reducing the load on the fuel cell system equipment. This has the effect of increasing responsiveness.

In particular, in this embodiment, unlike the devices known in the prior art, the fuel control means is actuated in response to load fluctuations by a signal from the detection means, and the valve opening of a proportional control valve equipped with a differential and integral circuit is controlled, for example. Responds to pressure fluctuations in the fuel supply system piping 20 to the fuel cell main body 1 without requiring procedures such as expansion,
Since fuel gas is automatically replenished, the control system has a simple configuration and is advantageous in terms of cost.

〔Effect of the invention〕

As described above, according to the present invention, a fuel cell system with a simple control system configuration, which automatically replenishes fuel gas to the fuel cell main body when the load increases, and which has excellent load followability is provided. can be provided.

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a fuel cell system according to an embodiment of the present invention, Fig. 2 is a detailed view of main parts of Fig. 1 showing details of the fuel replenishment system, and Fig. 3 is a conventional Fig. 4 is a diagram showing the load response, where a is a state in which the load increases in a step function manner, and b is the power that can be output from a conventional fuel cell system in response to the load increase. The change in c indicates the change in the output power from the fuel cell system according to an embodiment of the present invention. 1...Fuel cell main body, 1a...Hydrogen electrode, 1b...
...Oxygen electrode, 1c...Battery cooling device, 2...Refoma, 2a...Reaction section, 2b...Combustion section, 3...
Shift converter, 7...Cooling water heat exchanger, 8
...Exhaust gas heat exchanger, 9...Water tank, 12...
Blower, 20... Fuel supply system piping, 21... Gas storage tank, 22... Stopper float, 23... Water outlet, 24... Communication pipe, 25... Piping.

Claims (1)

[Claims] 1. A fuel cell main body, a fuel supply system for the fuel cell main body, an air supply system, a cell cooling system, an exhaust gas,
In a fuel cell system consisting of a water recovery system and ancillary equipment, a gas storage tank is provided that can be connected to the piping of the fuel supply system to supply fuel, and the bottom of the gas storage tank is connected to the exhaust gas and water. In addition to connecting the water storage tank installed in the recovery system via a communication pipe,
The water level of the water storage tank during steady state is located above the water level at the bottom of the gas storage tank, and the head difference caused by this water level difference allows the gas in the storage gas tank to be sent to the piping of the fuel supply system when the load increases. A fuel cell system device characterized by comprising: 2. In what is stated in claim 1,
A fuel cell system in which the connection position of the communication pipe to the water storage tank is lower than the normal water level by a water volume corresponding to the gas storage capacity of the gas storage tank.