JP2000012061A - Fuel cell power generating system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell power generating system using simple available and easy to handle hydrocarbon base fuel, utilizing all hydrogen obtained by reforming in power generation, and which is a partial load corresponding type capable of flexibly corresponding to load variation in non-control and highly efficient. SOLUTION: Reformed fuel, produced in a fuel reformer 2, is sent to a hydrogen separation device 6. A hydrogen storage alloy 7 filled in a pressure container within the hydrogen separating device 6 is cooled with a cooling device 8, and only hydrogen is selectively stored in the alloy. Cases other than hydrogen in the reformed fuel is exhausted by switching a gas flow outlet switching valve 10 to an atmospheric exhaust 11. A gas flow inlet valve 5 of the hydrogen separation device 6 is closed, the gas flow outlet valve 10 is switched from the atmospheric exhaust 11 to a fuel cell 13, the hydrogen storage alloy 7 within the hydrogen separating device 6 is heated with a heating device 8, and pure hydrogen stored is compressed and supplied to the fuel cell 13 whose terminal of a fuel supply line is closed. This operation is repeated in two or more lines to alternately conduct hydrogen absorption/releasing so as to keep the continuity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for continuously supplying high-purity hydrogen obtained by using a hydrogen storage alloy to a fuel cell for a reformed fuel mainly comprising hydrogen produced from a hydrocarbon fuel. And how to generate electricity.

[0002]

2. Description of the Related Art Generally, when power is generated by a fuel cell, it is necessary to use hydrogen as a fuel. FIG. 4 shows an example of a conventional system in which hydrogen is directly supplied to a fuel cell to generate power. When supplying only high-purity hydrogen, if the end of the fuel supply system in the fuel cell, that is, the gas flow path outlet in the fuel cell is closed (closed system) and appropriate pressurized conditions are set, the hydrogen used for power generation Because the pressure inside the fuel cell is reduced by the amount, hydrogen is automatically supplied continuously and can be used efficiently without waste (for example, the portable fuel cell FCP-1000KH manufactured by Sanyo Electric Co., Ltd.). As a storage method related to hydrogen supply, there are cases of high-density filling as a compressed gas using a hydrogen cylinder, a case using a hydrogen storage alloy and low liquid hydrogen.

[0003] On the other hand, a method for producing hydrogen by reforming a hydrocarbon fuel such as natural gas (mainly methane), gasoline (mainly octane), methanol, etc., which is easily available, is used for automobiles or households. Development of portable fuel cell power generators such as Mitsubishi Electric Technical Report, Vo
l.70, No. 9, "Polymer fuel cell portable power supply system", 1996). FIG. 5 shows an example of this conventional method. In this method, the fuel utilization must be set lower than 100% (about 80% in many cases) to prevent reverse reaction (water electrolysis reaction) in the fuel cell due to insufficient hydrogen, and it was not used. In order not to waste the fuel off-gas, various measures have been taken such as using it as a heat source fuel for a fuel reformer.

[0004]

However, the infrastructure for supplying hydrogen as secondary energy has not been established, and it is generally not easy to obtain hydrogen itself.

[0005] In addition, since reformed fuel contains a large amount of CO2 and the like in addition to hydrogen serving as fuel, the fuel supply system of the fuel cell is opened (open system) and constantly flows continuously for a predetermined amount or more. There is a need. For this reason, hydrogen that is not used in the open state is released to the atmosphere, wasting fuel, and the fuel flow needs to be controlled in accordance with the load demand, that is, the fluctuation of the power generation amount. As shown in FIG. 5, even when the fuel is used as efficiently as possible, the system becomes complicated and complicated and delicate control is required to perform the partial load operation.

[0006] When the fuel cell is operated at the rated value while avoiding the partial load operation, efficient operation cannot be performed unless an energy storage device such as a battery is added as a buffer for absorbing output fluctuation to the load. .

[0007] In order to use the fuel cell power generator for consumer use with the above-mentioned conventional techniques, it cannot be said that the operability, controllability, economy, etc. are very favorable.

[0008]

SUMMARY OF THE INVENTION The present invention uses a fuel that is widely used in handling natural gas, gasoline, and the like, and can use the hydrogen in the reformed fuel without waste.
Another object of the present invention is to construct a high-efficiency fuel cell power generation apparatus that can flexibly respond to a partial load operation according to a load change without control.

[0009]

SUMMARY OF THE INVENTION In view of the current situation that solid polymer fuel cells are being actively developed as small power sources for automobiles and homes, the present inventor has made efficient use of both partial load operation and the use of various fuels. As a result of researching both methods of software and hardware in terms of a method that satisfies the requirements, we focused on the fact that the hydrogen storage alloy had the function of selectively storing only hydrogen at high speed and in large quantities and at high density, and came to the present invention. .

The main system of the present device has a basic configuration in which a hydrogen separator using a hydrogen storage alloy is disposed downstream (downstream) of the fuel reformer, and a fuel cell is disposed further downstream. In the fuel connection between the hydrogen separation device and the fuel cell, a switching valve for releasing impurity gas is provided on the way to discharge unnecessary gas during the hydrogen storage step.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows the basic configuration of the present invention. Fuel reformer 2 for producing hydrogen fuel from hydrocarbon-based raw fuel
Uses the conventional steam system or the recently developed partial oxidation system. The reformed fuel leaving the fuel reformer 2 includes hydrogen (H2), CO2, H2O, N2, O2,
There are gases such as CO. Since these gases are in a high temperature state, they are adjusted to an appropriate temperature in the heat exchanger 4 and then sent to the hydrogen separator 6. When the hydrogen storage alloy 7 filled in the pressure vessel in the hydrogen separator 6 is cooled by the cooling / warming device 8, the hydrogen storage alloy 7 selectively stores only hydrogen in the alloy.

Since gases other than hydrogen do not react, the gas flow path outlet switching valve 10 is left as it is to the atmosphere release side and discharged from the atmosphere release 11 or CO2 which is a greenhouse gas is not discharged to the atmosphere. , CO2 recovery equipment 1
Collect at 2.

Next, the gas flow path inlet valve 5 of the hydrogen separation device 6 is closed, and the gas flow path outlet switching valve 10 is set to the atmosphere release 11 or C.
After switching the connection from the O 2 recovery device 12 to the fuel cell 13, the hydrogen storage alloy 7 in the hydrogen separation device 6 is cooled by the heating / cooling device 8.
Hydrogen stored in the fuel cell 13 with high purity
To supply. The fuel supply system in the fuel cell 13 is kept closed (closed system). At this time, while controlling the pressurization to some extent by temperature adjustment by the temperature controller 9,
Hydrogen is supplied for a relatively long time according to the amount of stored hydrogen.

When a large supply of hydrogen to the fuel cell 13 is not required, the fuel reforming device 2 is operated by using the fuel flow control valve 1.
The supply of the raw fuel to the fuel reformer 2 is stopped, and the fuel reformer 2 performs a flexible control like stopping the other fuels, thereby contributing to the improvement of the overall energy efficiency.

If a small amount of impurity gas accumulates in the fuel cell 13 due to long-term use and the power generation capacity is reduced, the leak valve 14 disposed at the end of the fuel supply system is opened to open the fuel cell 13. Releases impurity gas.

FIG. 2 shows an embodiment in which hydrogen is continuously supplied for practical use, and consideration is given to achieving excellent controllability and high energy efficiency. Hydrogen storage alloy 7 in hydrogen separator 6
By installing two or more systems, hydrogen can be selectively stored and released alternately, and hydrogen can be continuously supplied to the fuel cell 13. Further, at this time, since the hydrogen storage reaction is an exothermic reaction and the hydrogen releasing reaction is an endothermic reaction, heat is exchanged between the two by using a heat pump device 8 'such as a Peltier element, thereby contributing to energy saving. In addition,
FIG. 3 summarizes this operation method as a table.

The amount of hydrogen stored in the hydrogen separator 6, that is, the capacity of the hydrogen storage alloy 7, is ensured so that the amount of hydrogen supplied in one cycle is sufficient to absorb load fluctuations in the fuel cell 13.

Although it is assumed that the hydrogen storage alloy of the present invention does not poison impurities other than hydrogen, CO2, O2 and H2O are rare earth alloys such as LaNi5 and LaNi5.
MmNi4.5Al0.5 (Mm: misch metal [rare earth metal mixture]) is highly resistant to poisoning and CO
iFe0.85Mn0.15 is said to be resistant to poisoning. Since CO is relatively small in the reformed fuel gas, if a CO converter 3 is provided between the fuel reformer 2 and the hydrogen separator 6 to completely remove CO, the rare earth alloy The use of is preferred. However, technology development to prevent the poisoning of impurity gases by alloy microencapsulation is underway, and this is not always the case when it is put to practical use.

All of the above examples of the hydrogen storage alloy operate at around normal temperature. Since the reactions in the fuel reformer 2 and the CO converter 3 are performed at a high temperature, when using these, the reformed fuel is adjusted to an appropriate operating temperature by the heat exchanger 4 before entering the hydrogen separator 6. There must be.

Some types of hydrogen storage alloys, such as Mg2Ni (about 250 ° C.), operate at relatively high temperatures. Therefore, there is also a possibility of an apparatus that realizes high-purity hydrogen supply by the present method while keeping the reformed fuel at a relatively high temperature.

It is said that the hydrogen storage alloy has a reduced hydrogen storage and release capability due to many hydrogen storage and release cycles and poisoning, but is recovered by a simple process of heating in a vacuum. Therefore, the hydrogen separation and occlusion performance can be maintained by regular maintenance without replacement with a new one.

In addition to the present method using a hydrogen storage alloy, the hydrogen separation method includes an absorption method, a cryogenic separation method, an adsorption method, and a membrane diffusion permeation method. It is also possible to configure the present fuel cell power generation device by using

[0023]

The device of the present invention has the following advantages over the conventional fuel cell power generator. 1) Hydrocarbon fuel that is generally available and easily handled, such as natural gas and gasoline, can be used, and hydrogen as a fuel for a fuel cell can be converted to power generation without any waste. 2) A hydrogen separation device using a hydrogen storage alloy also has an energy buffer function as hydrogen storage. Therefore, it is not necessary to change the operation state of the former stage of the hydrogen separator such as the fuel reformer in response to the fluctuation of the power supplied by the fuel cell, and it is possible to always perform the steady optimal operation. 3) Since it is a pressurized supply system to a fuel cell using only high-purity hydrogen, there is no need to control the supply flow rate of hydrogen even for partial load operation according to load fluctuation, and flexible and fast-response power generation is achieved. it can. 4) It is easy to prevent atmospheric release by attaching a recovery device to separate CO2, which is a greenhouse gas. 5) Unlike the conventional fuel cell power generation system, there is no need to provide equipment to use hydrogen, which was not used for power generation to improve efficiency, as a heat source for the fuel reformer. Control can be simplified, and a stable power generation device resistant to disturbances can be obtained. 6) In the hydrogen separation process, a simple operation of alternately switching two or more hydrogen storage alloys alternately supplies hydrogen to the fuel cell without interruption, thus guaranteeing continuous power generation and using different types of raw fuel in parallel. It is also possible. Further energy savings can be expected by using the heat generated at the time of hydrogen storage for the heat absorption at the time of hydrogen release. 7) Since the pressurization when supplying hydrogen to the fuel cell is controlled by temperature, control is simple and high safety is ensured. 8) By storing hydrogen when the generator is stopped, power generation can be started in an extremely short time without waiting for the fuel reformer to be in operation. 9) It is a device without dynamic elements, has excellent quietness, is compact and lightweight, and requires little maintenance for long-time use, and is highly reliable. As described above, the present invention can be an inexpensive and high-performance power supply as a small consumer-use power supply for automobiles and homes.

[0024]

[Brief description of the drawings]

FIG. 1 Basic configuration diagram

FIG. 2 shows an embodiment of an apparatus for continuously supplying hydrogen to a fuel cell.

FIG. 3 shows a method of operation in the embodiment of FIG.

FIG. 4 is an embodiment of a conventional fuel cell power generator that directly supplies hydrogen.

FIG. 5 shows an embodiment of a conventional fuel cell power generator for reforming a hydrocarbon fuel.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fuel flow control valve 2 Fuel reformer 3 CO transformer 4 Heat exchanger 5 Gas flow path inlet valve 6 Hydrogen separator 7 Hydrogen storage alloy 8 Cooling heater, 8 'Heat pump device (for example, Peltier device) 9 Temperature controller 10 Gas flow path outlet switching valve 11 Atmospheric release 12 CO2 recovery device 13 Fuel cell 14 Leak valve 15 Gas flow path inlet valve (equivalent to 5 gas flow path inlet valve) 16 Gas flow path inlet valve (equivalent to 5 gas flow path inlet valve) 17) Gas passage outlet switching valve (corresponding to 10 gas passage outlet switching valve) 18 Gas passage outlet switching valve (corresponding to 10 gas passage outlet switching valve) 19 Temperature / pressure sensor 20 Hydrogen cylinder

Claims (3)

[Claims] 1. A hydrocarbon-based fuel such as natural gas, gasoline or methanol is converted into a reformed fuel containing hydrogen by a steam reforming method or a partial oxidation method, and the fuel is converted to a fuel containing hydrogen by a selective hydrogen storage function of a hydrogen storage alloy. Separates high-purity hydrogen gas from reformed fuel and separately discharges or recovers major impurity gases such as CO2, H2O, and N2, and pressurizes and supplies only hydrogen gas to a fuel cell with a closed fuel supply system. A fuel cell power generator characterized by the above-mentioned. 2. A method for continuously supplying hydrogen to a fuel cell by having a plurality of high-purity hydrogen separation systems using a hydrogen storage alloy and alternately performing a cycle of hydrogen storage and release at predetermined time intervals. The fuel cell power generator according to claim 1, wherein: 3. A cooling / heating function of a heat pump device between a plurality of high-purity hydrogen separation systems controls hydrogen storage (hydrogen storage) / release (hydrogen supply to a fuel cell) and heat required at the time of hydrogen release. 3. The fuel cell power generator according to claim 2, wherein energy is supplied from heat generated during storage of hydrogen to save energy.