JPS59149664A - Fuel-cell system - Google Patents

Abstract

PURPOSE:To enable a fuel-cell system to be safely driven by preventing any local explosion which might be caused due to fuel gas or oxygen by controlling the quantity of air exhaust gas flowing into the gas mixer of a recycle system by means of an oxygen-concentration controlling means. CONSTITUTION:Fuel exhaust gas and air exhaust gas exhausted from a cell body 7 are diluted and mixed with recycle gas in a gas mixer 23. Since oxygen and hydrogen concentrations in mixture gas are made zero in the reformer 15 of a recycle system, oxygen and hydrogen concentrations respectively become only around 1.5% and 3% even after the mixture gas is mixed with exhaust gas causing no possibility of explosion. An oxygen concentration detector 27 opens the control valve 28 of a bypass tube 29 branching from a fuel gas exhaust tube 22 when oxygen concentration in recycle gas flowing into the gas mixer 23 becomes over zero % so as to control the quantity of air exhaust gas flowing into the gas mixer 23 and to restrict oxygen concentration in an upper stream from the reformer 15 to around 1.5%, thereby preventing any local explosion.

Description

[Detailed description of the invention] The present invention relates to improvements in fuel cell devices.

[Technical background of the invention]

Fuel 'il'j /ll1. is used to directly convert the chemical energy of fuel into electrical energy. It has been known. This fuel tank usually has a pair of porous electrodes sandwiching the electrolyte, and one 'tb;
The electrical energy generated by the electrochemical reaction that occurs when the back of the electrode is brought into contact with a gas (such as hydrogen or other fuel), and the back of the electrode is brought into contact with oxygen contained in the air as an oxidizing agent. is taken out from the pair of electrodes.

In the above, electrolytes include molten salt, alkaline solution,
Acidic solutions and the like are used, with phosphoric acid being particularly typical.

The principle of a fuel cell using phosphoric acid as an electrolyte will be explained below with reference to FIG. In FIG. 1, symbol ``No'' is an electrolyte made by impregnating a fibrous sheet or mineral powder with phosphoric acid. In this electrolyte 1, two electrodes as an anode and an electrode 2B as a cathode are placed facing each other. This electrode? A,,? B is made of porous carbonaceous material, and one surface in contact with the electrolyte 1 is coated with platinum as a catalyst. Further, on the other side of the electrodes 2A and 2B, a fuel gas supply chamber 3, which is a chamber into which fuel gas such as hydrogen flows, and an air supply chamber 4, which is a chamber into which air as an oxidizer (oxygen) flows, are opposed to each other. It is provided.

In a fuel cell with such a configuration, hydrogen gas flows into the fuel gas supply chamber 3, and hydrogen gas as a source gas diffuses into the gap between the two porous electrodes (H'l). It reaches the catalyst to the positive electrode 2. Here, the hydrogen gas is ionized into hydrogen ions and ?L atoms by the action of the catalyst. Expressed in the reaction formula, Ii2→2
H″1+2e.Hydrogen ions 2H+ enter the electrolyte 1 and migrate toward the electrode 2B due to the action of electromotive force and concentration diffusion.On the other hand, the electrons 2e move to the electrode 2B with j:1]Ω5, The electrode 2B is charged with a negative potential. On the catalyst surface of the electrode 2B, the hydrogen ions 2H+ and the porous electrode 2B supplied to the air supply chamber 4 are
A reaction occurs between the oxygen that passes through the void of 1F4 and the oxygen that has come from electrode 2A through external power load R to electrode 2B.

Expressed as a reaction formula, 4, H++ 4 e + 02-) 2H20.

Here, a reaction in which hydrogen is oxidized to become water and a reaction in which the chemical energy at this time is converted into electrical energy occur, and the electrical energy is muffled by the electric power load R.

At this time, part of the electrical energy is 'Pl'! ．． ) In property 1, it is consumed by the internal resistance of the fuel cell. Therefore, in order to increase the efficiency of the combustion battery, the electrolyte 1 is designed to be extremely thin, shortening the migration distance of hydrogen ions and reducing internal resistance.

The fuel gas and air supplied as raw materials for the trench are normally pressurized to several atmospheres in order to speed up the reaction rate and improve efficiency.

The electrolyte 1 that separates the fuel gas from the air in the fuel cell is made of a fiber sheet or mineral powder impregnated with phosphoric acid and has a thickness of 0.5 mm, in order to ensure electrochemical reaction characteristics above a certain value. It is made of an extremely thin member of about 1 mm.

However, due to load fluctuations in the electrical system, pressure fluctuations occur in the supplied fuel gas and air due to flow rate fluctuations, and a large amount of stress may act on the electrolyte I.

There is a possibility that the electrolyte 1 may be damaged due to this stress effect, and the fuel gas and air may come into contact and mix momentarily within the fuel cell, leading to a local explosion 1- and the destruction of the entire device. was there.

In order to prevent local explosions within the fuel cell, a fuel cell device has been proposed in which the fuel cell shown in FIG. 1 is provided with a fuel gas and air supply section and a discharge section as shown in FIG. There is. That is, water vapor and the natural gas compressed by the pump 5 are subjected to the following (
1) Formula CH4+ 2H20-+ Co2+4H2...
(1) Perform a reaction to generate fuel gas containing high concentration of hydrogen, and electrolyze 741. Electrodes 2A, 2B, fuel gas supply chamber 3. The compressed air is supplied to the fuel gas supply chamber 3 of the battery main body 7 equipped with an air supply ♀4, while the compressed air is supplied to the air supply chamber 4 of the battery main body 7. The fuel gas and air supplied to the fuel gas supply chamber 3 and the air supply chamber 4 generate DC power and moisture through an electrochemical reaction, and then are converted into fuel exhaust gas and air exhaust gas 7 to the battery body, respectively. 7. The fuel exhaust gas discharged from the battery body 7 has moisture removed in a steam/water separator 8, and then supplied with the thermal energy necessary for reforming in the burner section 6B of the reformer 6. After the hydrogen component contained in the battery is burned, it flows into the gas mixer 9. On the other hand, moisture is removed from the air exhaust gas 10 discharged from the battery main body 7, and then the above-mentioned gas is removed by the gas mixer 9. After mixing with the fuel exhaust gas and matching the flow pressure, the exhaust gas is transferred to the turbine section 8 of the turbine compressor 8.
At B, a turbine is turned and the gas is released into the atmosphere.

The pressure fluctuations between the fuel exhaust gas and the air exhaust gas that occur during normal operation in the fuel cell device with the above configuration are handled by the steam separator 8,
This is caused by the difference in pressure drop in the fuel cell 10 and the pressure drop caused by combustion of the fuel exhaust gas in the burner section 6B of the reformer 6.

In this case, it is easy to prevent pressure fluctuations occurring in the steam and water separators 8 and 10, which do not directly respond to the electrochemical reaction within the battery body 7, since this allows flexibility in design.

However, preventing the pressure drop of the fuel exhaust gas caused by combustion in the burner section 6B of the reformer 6 is an essential condition for safely supplying the thermal energy essential for reforming. I can't do it.

The pressure drop of the fuel exhaust gas in the burner section 6B reaches several thousand micrometers in the water column. Therefore, burner part 6B
The pressure fluctuations in the fuel exhaust gas and air exhaust gas caused by the pressure drop at This resulted in a local explosion between fuel gas and air.

Depending on the amount of fuel and air supplied to the battery body 7 and the conditions of the exhaust section of the combustion exhaust gas and air exhaust gas discharged from the battery body 7, the oxygen component in the air exhaust gas may hydrogen component in the fuel exhaust gas misfires,
Local explosions could occur in piping systems.

[Purpose of the invention]

The present invention has been made based on the above circumstances, and its purpose is to provide a fuel that maintains high properties and prevents local explosions due to fuel gas and air, thereby allowing safe operation. The purpose of the present invention is to provide a battery device.

[Summary of the invention]

The fuel cell device according to the present invention uses the fuel gas and air discharge section as a recycling system, mixes the fuel exhaust gas and the air exhaust gas in a gas mixer, and transfers the mixed exhaust gas to the low-field side flow path and high temperature. After passing through the low temperature side flow path of the reverse heat exchanger having a side flow path, and after being used as a thermal energy supply source for reforming of the reformer, the high temperature side flow path of the reverse heat exchanger is used. After being circulated and cooled by a heat exchanger, it is caused to flow into the gas mixer by a recycle blower, and excess gas is discharged by a pressure regulating means so as to maintain the circulation pressure in the recycle system at a constant value. The above object is achieved by controlling the flow rate of air exhaust gas flowing into the mixer by means of oxygen concentration control means.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a configuration diagram showing the first embodiment of the fuel cell device according to the present invention. The same parts as in FIGS. Only parts will be explained.

In FIG. 3, compressed air in the consolestor section 8A of the turbine compressor 8 flows into the air supply chamber 4 of the battery main body 7 through an air supply pipe 12 having an air supply amount adjustment valve 11 on the pipe. . Fuel gas containing methane CH4, such as natural gas, is preheated by the heat exchanger 13, mixed with water vapor that has flowed in from the outside in the mixer 14, and flows through the reforming pipe 15A of the reformer 15 to form CH4+H2O.
-+CO+3H2 and cH4+2H2o->co2+4
A reaction of H2 occurs, and a fuel gas containing a mixture of hydrogen, carbon monoxide, and carbon dioxide is generated, and the above -carbon oxide is converted into CO+H20→Co2+■(2
As a result of the reaction, the hydrogen is converted into carbon dioxide and its hydrogen concentration is increased, and it flows into the fuel gas supply chamber 3 of the battery main body 7 via a fuel gas supply pipe (8) having a fuel gas supply amount adjustment valve 17 on the pipe. In the battery body 7, DC power is generated by an electrochemical reaction between the supplied fuel gas and air, and the fuel exhaust gas and the air exhaust gas are separated by a steam separator 19. The fuel gas flows into the gas mixer 23 through the fuel gas exhaust pipe 21 and the air exhaust pipe 22 having the following characteristics. Fuel exhaust gas and air exhaust gas are mixed in a gas mixer 23, and this mixed gas is heated to approximately 200°C.
enters the low temperature side flow path 24A of the reverse heat exchanger 24, which has a low temperature side flow path 24A and a high temperature side flow path 24B, and is preheated to about 650°C, and then the catalyst layer of the reformer 15. 15B generates reaction heat due to the catalytic action of hydrogen and oxygen contained in the mixed gas, heats the reforming pipe 15k, and supplies reforming thermal energy necessary to reform the fuel gas. After that, the concentration of hydrogen and oxygen is reduced to zero, and a mixed gas of about 700°C is passed through the high temperature side flow path 24 of the reverse heat exchanger 15.
After passing through B and heating the low temperature side flow path 24k, it flows into the heat exchanger 13 as a mixed gas at about 350°C. The mixed gas at approximately 350° C. that has entered the heat exchanger 13 preheats the natural gas containing methane before reforming. The mixed gas that flows out after releasing heat in the heat exchanger 13 has a temperature of about 300°C, and flows into the gas mixer 23 as a recycle gas via the recycle blower 25.
It becomes 00℃.

The fuel exhaust gas and air exhaust gas discharged from the battery main body 7 are treated. Gas mixer 23° Reverse heat exchanger 2
4. The reformer 11) + heat exchanger 13 and recycle blower 25 constitute a series of cycle systems. 2 in the diagram
Reference numeral 6 denotes a pressure control valve, which releases excess gas as necessary to keep the mixed gas flowing through the recycling system constant. In the figure, 27 is a concentration detector that detects the oxygen temperature, and when the oxygen concentration of the recycled gas flowing into the gas mixer 23 becomes equal to or higher than zero, a control valve 28 branched to the fuel gas discharge pipe 22 is activated. The control valve 28 of the bypass pipe 29 having the above-mentioned structure is opened to control the amount of air exhaust gas flowing into the gas mixer 23.

In the above, the exhaust gases released through the pressure control valve 26 and the pipe 29 both rotate a turbine in the turbine portion 8B of the turbine compressor 8 and are released into the atmosphere.

Next, the operation of the fuel cell device configured as described above will be described. That is, the air supply amount adjustment valve 11 and the fuel gas supply amount adjustment valve 17 are controlled to supply air to the battery body 7 in excess of the fuel gas, so that the electrochemical reaction within the battery body 7 can be performed satisfactorily. . The fuel exhaust gas and air exhaust gas discharged from the battery main body 7 are separated by a steam separator 19 having flow resistance.
After a slight pressure drop at 2θ, the gas is diluted and mixed with the recycle gas in the gas mixer 23. As mentioned above, the oxygen and hydrogen concentrations in the mixed gas are brought to zero in the reformer 15 of the recycling system including the gas mixer 23, and the concentration of oxygen and hydrogen in the mixed gas is reduced to zero.
3. Therefore, the recycled gas from the recycling system has zero oxygen and hydrogen concentration, so even if it is mixed with fuel exhaust gas and air exhaust gas, the oxygen concentration is about 15 parts, the hydrogen concentration is about 3 parts, and nitrogen and carbon dioxide are mixed. It is a mixed gas and will not explode. Since the reverse heat exchanger 24 is still performing highly efficient heat exchange of the mixed gas, the reformer 15 is effectively supplied with reforming thermal energy.

In this embodiment, when the concentration detector 27 provided in the recycling system detects that the oxygen concentration in the recycling system is equal to or higher than zero candy, the opening side valve 28 is opened and the amount of air exhaust gas supplied to the gas mixer 23 is controlled. The oxygen concentration control means is provided with a feedback control function to limit the oxygen concentration.

Therefore, before flowing into the gas mixer 23, the oxygen concentration at the 0 part in the figure is about 0%, and the oxygen concentration at the part (■), that is, the upstream side of the reformer 15, is about 15%, and (0 In other words, no local explosion occurs on the downstream side of the reformer 15.There is no possibility that the catalyst in the catalyst layer 15B in the reformer 15 will deteriorate due to the local explosion.

Next, the differential pressure control characteristics according to this embodiment will be explained. In FIG. 3, the fuel exhaust gas and the air exhaust gas are mixed in the gas mixer 23, so that their pressures are the same. From here, to the battery body 7, there is a flow resistance of the steam and water separator 19 at the fuel gas discharge section, and a flow resistance of the steam and water separator 20 at the air discharge section, as shown in Fig. 2. Firearms from the burner section never enter the fuel discharge section. Unlike a firearm such as a burner, the steam/water separator 19, 2θ having flow resistance has a small differential pressure, about 1001 parts m of water column. However, the pressure loss characteristic also becomes a square law characteristic as shown in Figure 4.
At each rated flow rate (air supply/discharge section: Fa, fuel gas supply/discharge section: Ff), it is easy to set the differential pressure ΔPo to several tens of water columns.

In addition, when there is a change in the power load, the flow rate (air supply/
Discharge section: Fa' + fuel gas supply/discharge section: Ff
By controlling Ff'/Ff=F a '7'F a as shown in FIG. 4, the differential pressure ΔP' can be made smaller than the differential pressure ΔPo at the rated flow rate.

The problem is, even if this differential pressure control cannot cope with excessive movement, the overall differential pressure is 100 threshold in the water column at the rated time, so even in the worst case, the load fluctuation differential pressure will be 1003 in the water column. . Therefore, the stress in the battery body 7 due to this differential pressure (100 rnm in water column) will not damage the electrolyte 1 and cause the fuel gas and air gas to mix and explode.

Next, a second embodiment of the present invention will be described with reference to FIG. In FIG. 3, the same parts as those in FIG. 3 are given the same reference numerals, and the explanation thereof will be omitted, and only the different parts will be explained here. L (1) In FIG. 5, the feed bank control function in FIG. An air exhaust gas flowmeter 31 is provided in the air exhaust pipe 22 to measure the fuel exhaust gas as described in the first embodiment.

Gas mixer 23 consisting of air exhaust gas and recycled gas
The flow rate of air exhaust gas flowing into the gas mixer 23 is controlled by the control valve 28 so that the oxygen concentration of the mixed gas becomes about 15%.
It is configured to be controlled by

With the above configuration, constant value control of oxygen concentration and differential pressure control between fuel gas and air within the battery body 7 can be executed extremely effectively due to the synergistic effect of the feedback control function and the feedford control function.

The present invention is not limited to the above-mentioned embodiments. For example, the pressure control valve 26 that controls the flow pressure of the mixed gas in the recycling system may be connected to the high temperature side flow path 24 of the reverse heat exchanger 24.
Predetermined control can be performed even if it is provided on the outlet side of B or the inlet side of the recycled gas in the gas mixer 23. This invention can be modified and implemented in various ways without changing the gist.

〔Effect of the invention〕

As described above, according to the present invention, the fuel gas and air discharge section is used as a recycling system, and the fuel exhaust gas and the air exhaust gas are mixed in the gas mixer, and the mixed exhaust gas is transferred to the low temperature (1111 channel). and a high temperature side flow path, and after being used as a thermal energy supply source for reforming of the reformer, the high temperature side flow of the reverse heat exchanger is used as a reforming thermal energy supply source of the reformer. After being cooled by a heat exchanger, the excess gas is flowed into the gas mixer by a recycle blower, and the excess gas is discharged by a pressure regulating means so as to maintain the circulation pressure in the recycle system at a constant value. Furthermore, since the flow rate of the air exhaust gas flowing into the mixer is controlled by the oxygen flow 5 degree control means, localized 1iuA emission is prevented by the fuel gas and air while ensuring high characteristics, thereby making it safe. Therefore, it is possible to provide a fuel cell device that can be operated in a variety of ways.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the principle of a fuel cell, FIG. 2 is a configuration diagram showing conventional fuel conversion and other devices, and FIG. 3 is a configuration diagram showing a first embodiment of a fuel cell device according to the present invention. FIG. 4 is a characteristic diagram for explaining the operation of the same embodiment, and FIG. 5 is a configuration diagram showing a second embodiment of the present invention. 1. Electrolyte 1. ? A, 2B... Electrode, 3... Fuel gas supply chamber, 4... Air supply chamber, 7... Battery body, 8
゛°゛Turbine congressor, 11... Air supply amount adjustment valve, 12... Air supply pipe, 13... Heat exchanger, 14
... Mixer, 15... Reformer, 16... Carbon oxide shift converter, 17... Fuel gas supply amount adjustment valve, 18...
Fuel gas supply pipe, 19, 2θ...Steam water separator, 2-
...Fuel gas discharge pipe, 22...Air discharge pipe, 23...
Gas mixer, 24... Reverse heat exchanger, 25...
Recycle blower 126・Pressure control valve, 27・Concentration detector, 28・Control valve, 29・Bypass pipe, 30
... Fuel exhaust gas flow meter, 31... Air exhaust gas flow meter. Applicant's Representative Patent Attorney Takehiko Suzue 3 Figure 4] Dish-shaped and --

Claims (4)

[Claims] (1) Receive fuel gas oxidant gas from a fuel gas supply section and an oxidant gas supply section that have a reformer that converts fuel gas into a high-concentration hydrogen component, and combine the fuel gas and oxidant gas. In a fuel cell device that generates DC power through an electrochemical reaction and discharges fuel exhaust gas and oxidant gas to a fuel gas and oxidant gas discharge section, the fuel gas and oxidant gas discharge section is configured to discharge the fuel exhaust gas and oxidant gas and oxidizer exhaust gas are mixed in a gas mixer, and the mixed exhaust gas is passed through a low temperature side flow path of a reverse heat exchanger having a low temperature side flow path and a high temperature side flow path, and then the reforming process is performed. a recycle system that is used as a thermal energy supply source for reforming of the reactor, is then passed through the high-temperature side flow path of the reverse heat exchanger, is cooled by the heat exchanger, and then flows into the gas mixer by a recycle blower; It is characterized by comprising a pressure regulating means for discharging surplus gas to the outside so as to maintain the circulation pressure of the recycling system at a constant value, and an oxygen concentration controlling means for controlling the flow rate of air exhaust gas flowing into the gas mixer. A fuel cell device. (2) The oxygen concentration control means has a function of detecting the oxygen concentration of the recycling system and controlling the flow rate of air exhaust gas flowing into the gas mixer according to the detected value. The fuel cell device according to item (1). (3) The oxygen concentration control means controls the air exhaust gas flowing into the gas mixer to the outside by an excess amount of oxygen in accordance with the supply amount of the fuel gas and air supplied from the fuel gas supply section and the air supply section. Claim No. 1, which has a control function to cause air exhaust gas containing nearly the same amount of oxygen to be discharged into a gas mixer to burn the hydrogen component contained in the fuel exhaust gas. The fuel cell device described in Section 1. (4) The oxygen concentration control means controls the air exhaust gas flowing into the force mixer to the outside by an excess amount of oxygen in accordance with the amount of fuel gas and air supplied from the fuel gas and air supply section. a control function for causing air exhaust gas containing nearly an equal amount of oxygen to flow into the gas mixer to burn the hydrogen component contained in the fuel exhaust gas by discharging it;
The fuel according to claim (1), which has a function of detecting the oxygen concentration of the recycling system and controlling the flow rate of air exhaust gas flowing into the gas mixer according to the detected value. “Battery device”.