JP4003130B2 - Fuel cell power generator and its operation method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell power generator including a reformer that converts hydrocarbon-based raw fuel gas into hydrogen-rich reformed gas using a catalyst, in particular, a solid polymer electrolyte fuel cell provided with a reformed gas bypass line, and It relates to the driving method.
[0002]
[Prior art]
There are various types of fuel cells incorporated in the fuel cell power generator, depending on the type of electrolyte, the type of reforming raw material, and the like. For example, a solid polymer membrane is used as the electrolyte, and the operating temperature is about 80 ° C. A solid polymer electrolyte fuel cell is well known as a relatively low type fuel cell.
[0003]
This solid polymer electrolyte fuel cell is similar to a phosphoric acid fuel cell, for example, in hydrogen and air in a fuel gas obtained by steam reforming a hydrocarbon-based raw fuel such as methane gas (city gas). Oxygen is supplied to the fuel electrode and the air electrode of the fuel cell, respectively, and electricity is generated based on the electrochemical reaction. Further, when reforming raw fuel into fuel gas, a method is adopted in which steam is added to the raw fuel and reforming is promoted by a catalyst in a fuel reformer (the basic system configuration is, for example, Patent Document 1).
[0004]
In order to perform the reforming constantly, it is necessary to constantly replenish the required amount of water vapor, and it is necessary to constantly replenish the water vapor supply device with water corresponding thereto. The water to be used needs to be high-purity water, and ion-exchanged water from which impurities have been removed by an ion-exchange type water treatment device is usually used.
[0005]
On the other hand, in the electrochemical reaction of the fuel cell, power generation product water is generated, and in the fuel reformer, combustion product water is generated with combustion for catalyst heating for performing a steam reforming reaction which is an endothermic reaction constantly. These generated waters have fewer impurities than normal tap water, and if these generated waters are used as raw water, the load on the water treatment device can be reduced. Therefore, a recovery water tank and an exhaust gas cooler are added. A method of recovering these generated waters to obtain supply water for generating reformed steam is usually employed.
[0006]
Further, in the electrochemical reaction of the fuel cell, heat is generated along with the reaction, and a part of the exhaust heat energy is stored as hot water in a hot water storage tank and supplied for hot water supply or heating.
[0007]
FIG. 4 is a system diagram showing an example of a conventional solid polymer electrolyte fuel cell power generation device using city gas as a raw fuel. Compared with that disclosed in Patent Document 1, battery cooling water system equipment and recovered water are shown. A more detailed system configuration is shown by adding devices and the like.
[0008]
In FIG. 4, a fuel cell 1 schematically shown includes a cooling plate 1c having a cooling pipe or a cooling groove (not shown) arranged and stacked each time a plurality of unit cells each having a fuel electrode 1a and an air electrode 1b are stacked. It is comprised by doing.
[0009]
The raw fuel is first supplied to the reformer 3 together with the reforming steam, and reformed into hydrogen and carbon monoxide by the following reaction. As the reforming catalyst, a noble metal catalyst or a nickel catalyst is used.
[0010]
CH ₄ + H ₂ O → 3H ₂ + CO (endothermic reaction)
Thereafter, the reformed gas is supplied to the CO converter 4, and the carbon dioxide in the reformed gas is reduced to about 1% by the following reaction. As the CO conversion catalyst, a noble metal catalyst or a copper-zinc catalyst is used.
[0011]
CO + H ₂ O → H ₂ + CO ₂ (exothermic reaction)
After that, carbon monoxide in the reformed gas is reduced to about 10 ppm by the following reaction that is further supplied to the CO remover 5 and selectively oxidized with air supplied by a selective oxidizing air blower (not shown). It is supplied to the fuel electrode 1a of the fuel cell.
[0012]
CO + 1 / 2O ₂ → CO ₂ (exothermic reaction)
As described above, when the reforming reaction is performed in the reformer 3, it is necessary to supply water vapor. In the polymer electrolyte fuel cell power generator, the sensible heat of the combustion exhaust gas from the reformer 3 and CO conversion are used as the heat source. In general, the heat of reaction of the vessel 4 and the CO remover 5 is used. Therefore, the reforming water supply line 25 for sequentially flowing the reforming water supplied by the battery cooling water circulation pump 54 through the reactors of the CO converter 4, the CO remover 5, and the steam generator 24 in series is provided. It is configured to receive heat from each of the reactors into steam, mix the steam and raw fuel, and introduce the steam into the reformer 3 from the reforming steam supply line 25. In FIG. 4, the reforming water flow line to the CO converter 4 and the CO remover 5 is omitted.
[0013]
In addition, since each of the reactors performs a chemical reaction using a catalyst, it is necessary to raise the temperature to an appropriate temperature in advance when the fuel cell power generator is started.
Appropriate temperatures for each reactor are as follows. Reformer: 500 to 700 ° C, CO converter: 200 to 300 ° C, CO remover: 100 to 250 ° C.
[0014]
For this reason, the reformer 3 is normally heated by burning the hydrogen supplied from the exhaust hydrogen supply line 19 of the fuel cell with a burner installed in the reformer. The temperature is raised by burning the raw fuel with a burner. In addition, the steam generator 24 is also heated by the combustion exhaust gas from the reformer. On the other hand, the CO transformer 4 and the CO remover 5 are heated by an electric heater (not shown) provided individually. Combustion air is introduced into the burner by a combustion air blower 6. Reference numeral 7 denotes a reaction air blower for supplying reaction air and CO selective oxidation air in a CO remover to the air electrode of the fuel cell main body.
[0015]
Further, the city gas is first introduced into the desulfurizer 2 by the city gas booster 27, and after the sulfur component contained in the city gas is removed, the city gas is introduced into the catalytic reactor of the reformer 3, and the combustion exhaust gas. As a result, the fuel gas is reformed while being supplied with heat, and becomes a hydrogen-rich fuel gas.
[0016]
Next, the cooling water system device 50 and the recovered water system device 30 of the fuel cell in FIG. 4 will be described below. The coolant system device 50 includes a battery coolant cooler 51, a cathode offgas cooler 52, an exhaust gas cooler 53 for combustion exhaust gas, a pure water tank 55, a battery coolant circulating pump 54, and other piping.
[0017]
The fuel cell 1 is operated at about 80 ° C. as described above, cooled by the water flowing from the pure water tank 55 by the battery cooling water circulation pump 54, and removed by the battery cooling water cooler 51. The battery cooling water cooler 51 is supplied with, for example, about 50 ° C. water supplied from a circulating water lead-out line 56 connected to a hot water storage tank (not shown in FIG. 4). Thereafter, the temperature is raised to, for example, about 60 ° C. via the cathode off-gas cooler 52 and the exhaust gas cooler 53 for the combustion exhaust gas, and is returned to the hot water storage tank from the circulating water lead-out line 57. The pure water tank 55 is provided with a liquid level gauge. When the liquid level reaches the lower limit, recovered water, which will be described later, is intermittently replenished via the water treatment device 35.
[0018]
Next, the recovered water system device 30 will be described. The recovered water system device 30 includes a recovered water tank 31, a recovered water pump 33, a recovered water cooler 34, and the like. Off-air and combustion exhaust gas cooled by the cathode off-gas cooler 52 and the combustion exhaust gas cooler 53 are introduced into the upper part of the recovered water tank 31, and the water content contained in the air and gas is sprinkled in the upper part. By condensing the cooling water from the apparatus, it is condensed and recovered in the lower part of the recovered water tank 31. The recovered water is cooled by the recovered water cooler 34 and introduced into the watering device. A cooling water direct contact type condenser having a packed bed such as a Raschig ring may be provided at the subsequent stage of the watering device.
[0019]
In this case, off-air containing steam and combustion exhaust gas are allowed to flow upward from the lower part of the packed bed (not shown in FIG. 4), while the recovered water at about 40 ° C. cooled by the recovered water cooler 34 is sprinkled from the upper part. Thus, the gas and the cooling water are brought into direct contact with each other in the packed bed portion, and the water and the water vapor in the gas are condensed and recovered, and there is an advantage that the recovery efficiency is improved with a simple structure.
[0020]
As described above, the recovered water is purified by a water treatment device and used as makeup water. A liquid level gauge is also provided at the bottom of the recovered water tank 31, and when the water in the recovered water tank is insufficient, city water (tap water) is supplied as make-up water. It is purified by.
[0021]
By the way, when starting and generating the fuel cell power generator as described above, it is necessary to start the power generation after raising the temperature of the reformer, the fuel cell main body, and the like. The outline of the process to raise the temperature of the reforming system and steady operation is listed below.
(1) The temperature of the catalyst of the reforming system is raised by the heat obtained by burning the raw fuel such as city gas with the burner and the heat obtained by energizing the electric heater.
(2) After the temperature of the reforming catalyst rises to a certain value, raw gas such as city gas is introduced into the reforming catalyst, and the generated reformed gas (hydrogen rich gas) is burned by the burner of the reformer. Meanwhile, each reforming catalyst is heated to a temperature at which a gas suitable for power generation is generated. At this time, the generated reformed gas bypasses the fuel cell main body.
(3) After detecting that the temperature of each reforming catalyst, fuel cell main body, etc. is appropriate for power generation, the reformed gas is introduced into the fuel cell main body, and the power generation state is reached.
[0022]
In the above item (2), the reason for introducing the reformed gas into the reformer burner by bypassing the fuel cell main body is that the reformed gas at this point is passing through the reforming equipment on the way of raising the temperature. Therefore, the gas composition is not sufficiently prepared, and carbon monoxide CO, which is a poisoning substance of the fuel cell catalyst, is contained in the gas at a high concentration of several percent to several thousand ppm. CO, even on the order of several tens of ppm, acts on the platinum catalyst of the fuel cell main body and significantly impedes power generation performance. Therefore, a reforming gas bypass line that bypasses the fuel cell main body is usually provided, The high CO concentration reformed gas that has passed is designed not to be introduced into the fuel cell body.
[0023]
However, since the reformed gas bypass line merges with the fuel electrode outlet piping of the fuel cell main body at or before the burner portion of the reformer, the high CO concentration gas diffuses through the fuel electrode outlet piping, When this diffusion gas reaches the battery body, an adverse effect on power generation performance is unavoidable. Therefore, in order to prevent this diffusion, a system that introduces an inert gas such as nitrogen between the fuel electrode outlet of the fuel cell main body and the reformed gas bypass line junction in the fuel electrode outlet piping of the fuel cell main body. Alternatively, the inventors of the present application have considered these systems in the past, considering that it is preferable to use a system that closes with an electromagnetic valve.
[0024]
FIG. 2 shows an example of a schematic system configuration of a conventional fuel cell power generation apparatus that introduces the inert gas, and FIG. 3 shows an example of a schematic system configuration that is closed by the electromagnetic valve. 2 and 3, members having the same functions as those in FIG. 4 are given the same reference numerals, and detailed descriptions thereof are omitted. Further, some of the cooling water system equipment, the recovered water system equipment, etc. in FIG. 4 are shown in a simplified manner.
[0025]
In FIG. 2, components different from those in FIG. 4 are a battery bypass valve 10, a reformed gas bypass line 18, a CO diffusion prevention nitrogen introduction line 13, and a nitrogen electromagnetic valve 11.
[0026]
In the figure, a CO diffusion prevention nitrogen introduction line 13 is connected to an exhaust hydrogen supply line 19 as shown in the figure, and exhaust hydrogen discharged from the fuel cell main body 1 is supplied to the reformer 3 by the exhaust hydrogen supply line 19. It is configured to be supplied to the burner.
[0027]
In the above-described configuration, the high CO concentration reformed gas generated during the reforming apparatus temperature rise bypasses the fuel cell main body 1 by the battery bypass valve 10 and is introduced into the burner portion of the reformer 3. By purging a small amount of inert gas such as nitrogen from the diffusion preventing nitrogen introduction line 13, it is possible to prevent the high CO concentration reformed gas from diffusing into the outlet of the fuel electrode 1 a of the fuel cell body 1.
[0028]
Next, FIG. 3 will be described. 3 differs from FIG. 2 in that a CO diffusion prevention valve 15 and a safety valve 16 are provided on the exhaust hydrogen supply line 19 instead of the CO diffusion prevention nitrogen introduction line 13 in FIG. is there. In FIG. 3, the CO diffusion preventing valve 15 (solenoid valve) can prevent the high CO concentration reformed gas from diffusing into the outlet of the fuel electrode 1a of the fuel cell body 1. The safety valve 16 is provided from the viewpoint of maintaining the fuel cell main body 1 and ensuring the safety of the power generation device because there is a risk that an excessive pressure is applied to the fuel cell main body when the CO diffusion prevention valve 15 malfunctions.
[0029]
[Patent Document 1]
JP 2002-124288 A (page 2-3, FIG. 2)
[0030]
[Problems to be solved by the invention]
Incidentally, the conventional fuel cell power generators that have been studied so far as shown in FIGS. 2 and 3 have the following problems.
[0031]
In the case of the above-described conventional apparatus, it is necessary to install an inert gas facility or an expensive safety valve in order to protect the fuel cell main body from the diffusion of the high CO concentration reformed gas. Regular maintenance is required. Therefore, when it is assumed that fuel cell power generation devices will be installed in homes and small-scale stores where fuel cell power generation devices are expected to become popular in the future, the costs and maintenance system related to the installation and maintenance of the inert gas facilities and safety valves are improved. May become a problem, and these may become a factor that hinders the spread.
[0032]
The present invention has been made in view of the above problems, and an object of the present invention is to prevent the diffusion of a high CO concentration reformed gas into the fuel cell main body, and has excellent maintainability and an inexpensive fuel cell power generation. It is to provide an apparatus and a method for operating the apparatus.
[0033]
[Means for Solving the Problems]
In order to solve the above-described problems, in the present invention, a reformer that converts a hydrocarbon-based raw fuel gas into a hydrogen-rich reformed gas using a catalyst, and an electrochemical reaction between the reformed gas and an oxidant gas. A fuel cell body that generates electricity based on the fuel cell, a waste hydrogen supply line that supplies exhaust hydrogen discharged from the fuel cell body to the burner for the reformer, and fuel reformed gas containing high-concentration CO before power generation is started And a reformed gas bypass line provided for bypassing the fuel cell main body so as not to be introduced into the battery main body, and the fuel cell power generator having a configuration for introducing the bypassed reformed gas into the exhaust hydrogen supply line In the driving method of
An air introduction line is connected to the fuel cell main body side from the bypass reformed gas introduction part on the exhaust hydrogen supply line,
Before the start of power generation, air is introduced from the air introduction line so that the reformed gas containing high-concentration CO is not introduced into the fuel cell body, and after the start of power generation, the introduction of the air is stopped, and the fuel cell Waste hydrogen discharged from the main body is supplied to the burner for the reformer (invention of claim 1).
[0034]
Further, as an apparatus for carrying out the above method, the inventions of the following claims 2 to 5 are preferable. That is, a fuel cell power generator for carrying out the operation method according to claim 1, wherein the reformer, the fuel cell body, the exhaust hydrogen supply line, and the reformed gas bypass line having a battery bypass valve. An air introduction line connected to the fuel cell main body side from the bypassed reformed gas introduction section on the exhaust hydrogen supply line, an air blower for sending air to the air introduction line, and before starting power generation and And a control device for switching between start and stop of air introduction from the air introduction line after the start (invention of claim 2).
[0035]
As described above, in the present invention, in order to protect the fuel cell main body from the diffusion of the high CO concentration reformed gas, the power generation system is maintained by introducing the air sent from the air blower before the start of power generation. It is possible to reduce the cost.
[0036]
As an embodiment of the invention of claim 2, the invention of claim 3 is preferable. That is, in the fuel cell power generation device according to claim 2, the air blower is incorporated in the fuel cell power generation device and also serves as an air blower provided for other purposes than the air blower provided exclusively for the air delivery. (Invention of claim 3).
[0037]
Further, in the fuel cell power generator according to claim 3, the combined air blower is one of a reaction air blower for a fuel cell main body, a combustion air blower for a reformer, and a selective oxidation air blower for a CO remover. Any of them (the invention of claim 4). As a result, the apparatus can be rationalized and the cost can be further reduced.
[0038]
Furthermore, in the fuel cell power generator according to any one of claims 2 to 4, the control device that switches the start and stop of the introduction of the air includes an electromagnetic valve provided on the air introduction line. (Invention of claim 5) Thereby, air can be sent out only when necessary by opening / closing control of the solenoid valve, and the reformed gas can be prevented from flowing back to the blower side.
[0039]
DETAILED DESCRIPTION OF THE INVENTION
Examples of the present invention will be described below with reference to the drawings.
[0040]
FIG. 1 is a schematic system diagram showing an embodiment relating to the present invention. Constituent members having the same functions as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.
[0041]
The difference between FIG. 1 and FIG. 2 is that, in FIG. 1, an air introduction line 17 is provided on the exhaust hydrogen supply line 19 instead of the nitrogen introduction line 13 and the nitrogen solenoid valve 11 for preventing CO diffusion in FIG. And the air solenoid valve 12 is provided.
[0042]
According to the configuration of FIG. 1, the fuel cell body 1 of high CO reformed gas is sent by sending air from the air blower 14 during the reforming equipment temperature raising process before power generation in which high CO reformed gas is generated. Gas diffusion into the can be prevented. Further, by providing the solenoid valve 12 in the air introduction line 17, it is possible to send air only when necessary and to prevent the reformed gas from flowing back to the air blower 14 side.
[0043]
With the above configuration, it is possible to provide a safe and highly reliable fuel cell power generation apparatus without installing an inert gas that requires maintenance, and also installing an expensive safety valve that also requires maintenance. The air blower 14 can also be used as another air blower essential for constituting a fuel cell power generator, that is, a combustion air blower 6, a reaction air blower 7, and a selective oxidation air blower (not shown). By branching and introducing a part of the air sent from the air blower built in the fuel cell power generation device, the device can be rationalized and the cost can be reduced.
[0044]
【The invention's effect】
As described above, according to the present invention, a reformer that converts a hydrocarbon-based raw fuel gas into a hydrogen-rich reformed gas using a catalyst, and power generation based on an electrochemical reaction between the reformed gas and an oxidant gas. Fuel cell main body, exhaust hydrogen supply line for supplying exhaust hydrogen discharged from the fuel cell main body to the reformer burner, and reformed gas containing high-concentration CO before power generation is introduced into the fuel cell main body And a reformed gas bypass line provided to bypass the fuel cell main body so that the bypassed reformed gas is introduced into the exhaust hydrogen supply line. An air introduction line is connected to the fuel cell main body side from the bypassed reformed gas introduction section on the exhaust hydrogen supply line, and before the start of power generation, the reformed gas containing the high concentration CO Air is introduced from the air introduction line so as not to be introduced into the fuel cell body, and after the start of power generation, the introduction of the air is stopped and the exhaust hydrogen discharged from the fuel cell body is supplied to the burner for the reformer. To do and
Further, as an apparatus for carrying out the method, the reformer, the fuel cell main body, the exhaust hydrogen supply line, the reformed gas bypass line having a battery bypass valve, and the exhaust hydrogen supply line are provided. An air introduction line connected to the fuel cell main body side from the bypassed reformed gas introduction part, an air blower for sending air to the air introduction line, and air from the air introduction line before and after the start of power generation Because it is equipped with a control device that switches between start and stop of introduction,
It is possible to provide a low-cost fuel cell power generator and an operation method thereof that prevent diffusion of a high CO concentration reformed gas into the fuel cell main body and that are excellent in maintainability.
[Brief description of the drawings]
FIG. 1 is a schematic system diagram related to an embodiment of a fuel cell power generator according to the present invention. FIG. 2 is a schematic system diagram showing an example of a conventional fuel cell power generator. Schematic system diagram showing an example. Fig. 4 System diagram showing an example of a conventional solid polymer electrolyte fuel cell power generator.
1: fuel cell main body, 3: reformer, 4: CO converter, 5: CO remover, 6: combustion air blower, 7: reaction air blower, 10: battery bypass valve, 12: solenoid valve for air, 14 : Air blower, 17: Air introduction line, 18: Reformed gas bypass line, 19: Waste hydrogen supply line.

Claims (5)

From a reformer that converts hydrocarbon-based raw fuel gas into hydrogen-rich reformed gas using a catalyst, a fuel cell body that generates electricity based on an electrochemical reaction between the reformed gas and an oxidant gas, and a fuel cell body An exhaust hydrogen supply line for supplying exhaust hydrogen exhaust to the reformer burner, and for bypassing the fuel cell body so as not to introduce reformed gas containing high-concentration CO into the fuel cell body before the start of power generation A reformed gas bypass line provided in the fuel cell power generation apparatus having a configuration for introducing the bypassed reformed gas into the exhaust hydrogen supply line,
An air introduction line is connected to the fuel cell main body side from the bypass reformed gas introduction part on the exhaust hydrogen supply line,
Before the start of power generation, air is introduced from the air introduction line so that the reformed gas containing high-concentration CO is not introduced into the fuel cell body, and after the start of power generation, the introduction of the air is stopped, and the fuel cell An operation method of a fuel cell power generator, characterized in that exhaust hydrogen discharged from a main body is supplied to a burner for the reformer. A fuel cell power generator for carrying out the operation method according to claim 1, wherein the reformer, the fuel cell main body, a waste hydrogen supply line, a reformed gas bypass line having a battery bypass valve, An air introduction line connected to the fuel cell main body side from the bypassed reformed gas introduction section on the exhaust hydrogen supply line, an air blower for sending air to the air introduction line, and before and after the start of power generation And a control device for switching between start and stop of the introduction of air from the air introduction line. 3. The fuel cell power generator according to claim 2, wherein the air blower is incorporated in the fuel cell power generator and is also used as an air blower provided for other purposes other than the air blower provided exclusively for air delivery. A fuel cell power generator. 4. The fuel cell power generator according to claim 3, wherein the combined air blower is any one of a reaction air blower for a fuel cell main body, a combustion air blower for a reformer, and a selective oxidation air blower for a CO remover. A fuel cell power generator characterized by that. 5. The fuel cell power generator according to claim 2, wherein the control device that switches start and stop of the introduction of air includes an electromagnetic valve provided on the air introduction line. 6. A fuel cell power generator.

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