JP2005093127A - Fuel cell cogeneration system and its operation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell cogeneration system with a higher heat utilization rate than a prior art but more simplified, and easy to propagate in various houses including existing ones, to be installed in a given region or in apartment houses, as well as its operation method. <P>SOLUTION: The system comprises a dwelling-unit hot water storage tank 61 for storing exhaust heat of a fuel cell power generation device as hot water through a heat-collection circulating water pipe 62, a common hot water storage tank 77 installed inside a given area or an apartment house, a pipe 76 branching from the heat-collection circulating water pipe and guiding circulating water for heat collection above the common hot water storage tank, a pipe 82 for flowing back the circulating water for heat collection from lower part of the common hot water storage tank to a lower part of each dwelling-unit hot water storage tank, and a pipe 79 for flowing back the circulating water for heat collection from upper part of the common hot water storage tank to an upper part of each dwelling-unit hot water storage tank. When hot water temperature in each dwelling-unit hot water storage tank reaches a given value, the hot water is circulated form the heat-collection circulating water pipe to the common hot water storage tank to radiate heat through the common hot water storage tank, and the hot water inside the common hot water storage tank is effectively utilized. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a fuel cell cogeneration system installed in a predetermined area or an apartment house and an operation method thereof.

  In recent years, the spread of a fuel cell cogeneration system that effectively uses the exhaust heat of a fuel cell power generator for hot water supply is expected. 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.

  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).

  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.

  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 the combustion for catalyst heating for performing the 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.

  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.

  FIG. 3 is a system diagram showing an example of a conventional solid polymer electrolyte fuel cell power generation apparatus 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.

  In FIG. 3, the 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.

  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.

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.

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.

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. 3, the reforming water flow line to the CO converter 4 and the CO remover 5 is omitted.

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: 500-700 ° C, CO converter: 200-300 ° C, CO remover: 100-250 ° C.

  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 temperature of the CO transformer 4 and the CO remover 5 is raised 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 the CO remover to the air electrode of the fuel cell main body.

  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.

  Next, the cooling water system device 50 and the recovered water system device 30 of the fuel cell in FIG. 3 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.

  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. 3). Thereafter, the temperature is raised to, for example, about 60 ° C. to 70 ° C. via the cathode off-gas cooler 52 and the exhaust gas cooler 53 of the combustion exhaust gas, and is refluxed from the circulating water introduction line 57 to the hot water storage tank. The pure water tank 55 is provided with a liquid level gauge. When the liquid level reaches the lower limit, recovered water described later is intermittently replenished via the water treatment device 35.

  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.

  In this case, off-air containing steam and combustion exhaust gas are allowed to flow upward from the lower portion of the packed bed (not shown in FIG. 3), while the recovered water at about 40 ° C. cooled by the recovered water cooler 34 is sprinkled from above. 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.

  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.

  By the way, in recent years, from the viewpoint of promoting a new energy policy, development of a small-capacity polymer electrolyte fuel cell power generation device has progressed rapidly, and studies are being conducted to install it in homes, small-scale offices, and the like. At these installation locations, cogeneration is performed to store hot water of about 70 ° C that accompanies the generation of electric power by the small-capacity polymer electrolyte fuel cell power generator in the hot water storage tank and supply it to the bathhouse or kitchen. It is common to generate economic benefits.

  FIG. 2 is a diagram showing a schematic system configuration of a conventional fuel cell cogeneration system provided with a hot water storage tank installed in each dwelling unit. For convenience of explanation of the present invention, the hot water storage tank is related to the system similar to FIG. It is the schematic which paid its attention to the system | strain. In FIG. 2, members having the same functions as those shown in FIG. 3 are given the same reference numerals, and detailed descriptions thereof are omitted.

  Each dwelling hot water tank 61 that receives the city water supply from the city water pipe 73 derives the heat recovery water from the circulating water outlet line 56 by the hot water pump 63 and introduces the circulating water through the heat recovery circulation water pipe 62. It returns to each said residence hot water storage tank 61 from the line 57. FIG. This heat recovery water receives each exhaust heat from the fuel cell cooling water 66, the fuel cell exhaust air 68, and the reformer combustion exhaust gas 70 through the heat exchangers 51, 52, and 53, and becomes hot water. This hot water is usually introduced from the circulating water introduction line 57, stored in the dwelling hot water storage tank 61, and hot water is supplied via the hot water supply pipe 74.

  In the above system, when the thermometer 91 as the hot water tank circulating water temperature detector detects that the hot water temperature level of each dwelling hot water tank 61 has reached a certain value or more during power generation, The three-way control valve 71 switches the heat recovery water path of the heat recovery circulating water pipe 62 to a path that passes through the bypass line 72, and further operates the hot water cooler 64 to cool the heat recovery water, thereby The device is controlled so that it can be operated at an appropriate temperature.

  As described above, in a fuel cell cogeneration system equipped with a conventional hot water storage tank, when the demand for hot water supply is relatively small and the exhaust heat of the fuel cell power generator becomes excessive, the exhaust of the fuel cell power generator is reduced. It is necessary to release heat by the hot water cooler 64. In addition to such wasteful heat radiation, there is also a waste of energy for operating the hot water cooler 64, and there is a problem that the heat utilization efficiency is poor as a whole.

  As a cogeneration system for improving the heat utilization efficiency, the one described in Patent Document 2 is known. According to the description of the publication, the system disclosed in Patent Document 2 states that “commercial power supplied from an electric power company and electric power generated from a distributed power generator are used in combination, while A cogeneration system that uses waste heat for hot water supply, which uses gas supplied from a gas company as an energy source, and controls supply of electric power from the distributed generator, the distributed generator, and commercial power A power controller, a gas controller for controlling the supply of gas from a gas company, a hot water storage tank for storing hot water obtained by waste heat from the distributed power generator, and the distributed power generator, the power controller and the gas controller A cogeneration system with a system controller to control. "

  However, in the case of the system disclosed in Patent Document 2, the system controller centrally monitors all the electric power, gas, and hot water supply of each target household, thereby performing control that emphasizes economy as a whole. Since the management system is adopted, the equipment scale is large and the control system is complicated. In addition, considering the utility connection between the central management facility and each dwelling unit for the centralized management system, this centralized management system is difficult to apply to existing houses.

That is, the above system has a problem that the hurdles for dissemination are high when considering the diffusion of small-capacity fuel cell cogeneration systems to each unit.
JP 2002-124288 A (page 2-3, FIG. 3) JP 2002-281568 A (page 2-5, FIGS. 1 and 2)

  The present invention has been made in view of the above points, and an object of the present invention is a simplified system that has higher heat utilization efficiency than before, and is easy to spread to each dwelling unit including existing houses. Another object of the present invention is to provide a fuel cell cogeneration system installed in a predetermined area or apartment house and an operation method thereof.

  The above-mentioned subject is achieved by the following. That is, according to the first aspect of the present invention, when the exhaust heat of the fuel cell power generator is supplied to the hot water storage tank via the heat recovery circulating water pipe, and the hot water temperature in the hot water storage tank reaches a predetermined value, In the operation method of the fuel cell cogeneration system in which the fuel cell power generation device that radiates heat through a radiator is installed in each dwelling unit in a predetermined area or apartment house, in the predetermined area or apartment house, Each hot water tank installed in each dwelling unit (each dwelling hot water tank) is provided with a joint hot water tank connected by piping, and when the hot water temperature in each dwelling hot water tank reaches a predetermined value, Hot water is supplied to the common hot water storage tank from the circulating water pipe or each of the above-mentioned hot water storage tanks, and the heat of the hot water can be used outside the dwelling unit.

  As an embodiment of the invention of claim 1, the invention of claim 2 is preferable. That is, in the operation method according to claim 1, when the hot water temperature in the common hot water storage tank is compared with the temperature temperature in each of the dwelling hot water tanks, The hot water in the tank can be effectively used in each dwelling unit via each dwelling hot water tank.

  As described above, if the hot water in the common hot water tank can be effectively used in each dwelling unit via each dwelling hot water tank, the heat utilization efficiency is improved as a whole in the predetermined area or in the common housing. In addition, if the transfer of heat between each unit through the shared hot water tank is free, the control system becomes extremely simple, and the heat utilization efficiency is higher than before, but the system becomes a simplified system. Dissemination to dwelling units becomes easy. Details will be described later.

  Further, as an apparatus for carrying out the operation method, the inventions of the following claims 3 to 4 are preferable. That is, a fuel cell cogeneration system for carrying out the operation method according to claim 2, wherein each dwelling unit supplies the exhaust heat of the fuel cell power generation device via a heat recovery circulating water pipe and stores it as hot water. A hot water storage tank, a common hot water tank provided in the predetermined area or apartment house, a pipe branched from the heat recovery circulating water pipe and introducing the heat recovery circulating water above the common hot water tank, and the joint A pipe that circulates the circulating water for heat recovery from below the hot water storage tank to the lower part of each hot water storage tank, and a pipe that circulates the circulating water for heat recovery from above the joint hot water tank to the upper part of each hot water storage tank, Furthermore, a thermometer, a switching valve, and a control device for controlling the operation method according to claim 2 are provided (claim 3).

  The fuel cell cogeneration system according to claim 3, wherein the control device discharges heat by discharging the hot water in the common hot water tank when the hot water temperature in the common hot water tank reaches a predetermined value. (Claim 4).

  According to the fourth aspect of the invention, the hot water in the common hot water tank can be discharged and necessary heat radiation can be performed, so that the hot water cooler (64 in FIG. 2) in the conventional system can be omitted. Therefore, the apparatus provided in each dwelling unit is simplified, and the heat utilization efficiency can be improved as a whole in the predetermined area or the apartment house. In the case of a system that does not include a hot water cooler, the discharged hot water is not simply drained to the outside, but can be used effectively for heating a pool, a pond, etc., depending on the season.

  According to this invention, even when the hot water demand of hot water storage tanks conventionally installed in each dwelling unit is saturated and reaches a predetermined hot water temperature, power generation can be continued without wasting waste heat, In addition, by storing hot water in the common hot water storage tank, when hot water is insufficient in the hot water storage tank of each dwelling unit, hot water can be supplied by receiving supply of hot water from the common hot water storage tank. Moreover, it becomes possible to abbreviate | omit the hot water cooler installed in each dwelling unit by performing required heat dissipation from a common hot water storage tank.

  As described above, a fuel cell cogeneration system installed in a predetermined area or apartment house that has a higher heat utilization efficiency than the conventional one, but is simplified, and can be easily spread to each dwelling unit including existing houses, and its Driving method can be provided.

  Next, an embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic system diagram of a fuel cell cogeneration system according to an embodiment of the present invention. In FIG. 1, members having the same functions as those shown in FIG.

  1, main points different from FIG. 2 are a common hot water tank 77, a pipe 76 that branches from the heat recovery circulating water pipe 62 and introduces the heat recovery circulating water above the common hot water tank 77, and a joint. A pipe 82 for returning the circulating water for heat recovery from the lower side of the hot water tank 77 to the lower side of each of the hot water tanks 61 and a pipe for returning the circulating water for heat recovery from the upper side of the common hot water tank 77 to the upper side of each of the hot water tanks 61. 79 is provided. In addition, the reason for providing a vertical difference in the arrangement of the pipes is that there is an upper and lower temperature distribution based on natural convection in the hot water in each hot water storage tank. For example, the piping configuration is performed such that the lower temperature water in the common hot water storage tank 77 does not mix with the higher temperature hot water in each dwelling hot water tank 61.

  Further, FIG. 1 includes thermometers (92 and 93), switching valves (75 and 81), and a control device (not shown) for controlling the operation method according to claim 2. In addition, pumps (78 and 83) are provided as necessary. In addition, the part number 80 shows the hot water supply piping from the common hot water storage tank 77 to the dwelling unit different from the dwelling unit shown in FIG.

  According to the configuration of FIG. 1, the hot water storage destination is switched from each dwelling hot water storage tank 61 to the common hot water storage tank 77 by switching to the pipe 76 by the switching valve 75. Thereby, even when the hot water temperature of each dwelling hot water storage tank 61 reaches a predetermined temperature, the hot water is stored in the common hot water storage tank 77, and it is not necessary to throw away the exhaust heat in the hot water cooler 64. Will improve.

  Further, when the hot water is insufficient in the hot water storage tanks of each dwelling unit and the measurement value of the thermometer 93 is higher than the measurement value of the thermometer 92, the hot water stored in the common hot water storage tank 77 is supplied from the pipe 79 by the pump 78. It is supplied above each dwelling hot water tank. Thereby, the hot water of the common hot water tank 77 can be effectively used in each dwelling unit.

  Furthermore, by performing necessary heat radiation from the common hot water tank 77, the hot water cooler 64 installed in each dwelling unit can be omitted.

1 is a schematic system diagram of a fuel cell cogeneration system according to an embodiment of the present invention. Schematic system diagram of a conventional fuel cell cogeneration system. The system diagram which shows an example of the conventional solid polymer electrolyte type fuel cell power generation device.

Explanation of symbols

61 Each hot water storage tank 62 Circulating water piping for heat recovery 64 Hot water cooler 71, 75, 81 Switching valve 76, 79, 82 Piping 77 Joint hot water storage tank 91, 92, 93 Thermometer

Claims (4)

The fuel cell is configured to supply exhaust heat from the fuel cell power generator to a hot water storage tank through a heat recovery circulating water pipe, and to radiate heat through a radiator when the temperature of the hot water in the hot water storage tank reaches a predetermined value. In a method of operating a fuel cell cogeneration system in which a power generator is installed in each dwelling unit in a predetermined area or apartment house,
In each of the predetermined areas or apartment houses, a common hot water tank connected to each hot water tank (each hot water tank) installed in each of the dwelling units is provided, and the hot water temperature in each of the dwelling hot water tanks reaches a predetermined value. When the temperature reaches, the hot water is supplied from the circulating water piping for heat recovery or each hot water storage tank to the common hot water tank so that the heat of the hot water can be used outside the living room. How to operate the cogeneration system.   The operation method according to claim 1, wherein the hot water temperature in the common hot water tank is compared with the hot water temperature in each of the dwelling hot water tanks, and when the hot water temperature in the common hot water tank is high, Method of operating a fuel cell cogeneration system, wherein each hot water can be effectively used at each dwelling unit through each dwelling hot water tank.   A fuel cell cogeneration system for carrying out the operation method according to claim 2, wherein each of the dwelling hot water tanks stores the exhaust heat of the fuel cell power generation device through a circulating water pipe for heat recovery and stores it as hot water. A common hot water tank provided in the predetermined area or the apartment house, a pipe branched from the heat recovery circulating water pipe and introducing the circulating water for heat recovery above the common hot water tank, and the common hot water tank A pipe that circulates the circulating water for heat recovery from below the dwelling hot water tank, and a pipe that circulates the circulating water for heat recovery from above the joint hot water tank to the upper side of each dwelling hot water tank, A fuel cell cogeneration system comprising a thermometer, a switching valve, and a control device for controlling the operation method according to claim 2. 4. The fuel cell cogeneration system according to claim 3, wherein the control device has a function of discharging the hot water in the joint hot water tank to dissipate heat when the hot water temperature in the common hot water tank reaches a predetermined value. 5. A fuel cell cogeneration system.

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