KR100813245B1 - Electric generating system of fuel cell - Google Patents

Abstract

The present invention provides a fuel cell system that can improve the electrical efficiency of the system and at the same time simplify the overall configuration of the apparatus. The provided fuel cell system is disposed adjacent to a fuel cell stack such that the thermally transferable interlocked thermally transfer medium is in thermal communication with all or a portion of the plurality of cells stacked on the fuel cell stack, and the thermally transfer medium is in thermal communication with the thermally transfer medium. And a second steam generator for generating water vapor based on heat supplied through the heat transfer medium.

Description

Fuel cell power generation system {Electric generating system of fuel cell}

1 is a schematic view showing a configuration of a fuel cell stack according to a first embodiment of the present invention.

2 is a plan view showing a schematic configuration of a fuel cell stack and a second evaporation generator according to the first embodiment of the present invention;

3 is a structural diagram showing a heat transfer medium according to the first embodiment of the present invention,

4 is an enlarged view and configuration diagram showing another aspect of a fuel cell power generation system according to an embodiment of the present invention;

4 is a block diagram showing a schematic configuration of a stationary fuel cell power generation system according to an embodiment of the present invention;

5 is a flowchart showing a startup operation performed in the stationary fuel cell power generation system according to the embodiment of the present invention;

6 is a flowchart showing a startup operation performed in the stationary fuel cell power generation system according to the embodiment of the present invention;

7 is a schematic view showing the structure of a fuel cell stack according to a second embodiment of the present invention, which is a block diagram showing the structure of a conventional fuel cell main body and a stationary fuel cell power generation system structure;

8 is a plan view showing a schematic configuration of a fuel cell stack and a second evaporation generator according to a second embodiment of the present invention;

9 is a schematic view showing the structure of a conventional fuel cell stack,

10 is a block diagram showing the structure of a conventional stationary fuel cell power generation system.

* Description of Signs of Major Parts of Drawings *

1, 50, 90... … Fuel cell stack

2, 52... … Solid polymer electrolyte membrane

3, 53... … Fuel electrode

4, 54... … Oxidant electrode

6, 56... … Separator for fuel gas

8, 58... … Separator for oxidant gas

9, 59... … Fuel cell

11... … Cold plate

20, 70... … Fuel cell system

22... … Pure tank

23... … Water bath

24... … Reformer

25... … Shift reactor

31... … (First) Steam generator

36... … Combustion section

51... … Second steam generator

60, 92... … Heat transfer medium

61, 91... … Insulation sheet

72, 77... … Shut-off valve

73... … Bypass valve

74... … Bypass line

Japanese Patent Laid-Open No. 11-214017

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell power generation system, and more particularly, to a fuel cell power generation system that realizes effective use of stack heat generation in a medium temperature fuel cell stack having a stack operation temperature of 100 ° C or higher.

9 shows the structure of a conventional fuel cell stack 1. In the conventional fuel cell stack 1, a plurality of fuel cell cells 9 are stacked, and a cooling plate having a cooling medium flow path 10 for each predetermined fuel cell cell 9 or alternately with the fuel cell cell 9 ( 11) is arranged and configured.

The fuel cell 9 includes a sheet-like solid polymer electrolyte membrane 2, a fuel electrode 3, an oxidant electrode 4, and the electrode bonded to each of both surfaces of the solid polymer electrolyte membrane 2; The separator 6 for fuel gas which has the fuel gas flow path 5 provided in each of (3, 4) and the oxidant gas separator 8 which has the oxidant gas flow path 7 are provided.

Heat is generated when a fuel gas containing hydrogen as the main fuel and an oxidant gas such as air or oxygen react electrochemically with the solid polymer electrolyte membrane 2 interposed therebetween. The cooling plate 11 discharges this reaction heat, and is arrange | positioned in order to keep the temperature of the fuel cell 9 constant. In addition, water is mainly used as a cooling medium supplied to the cooling plate 11.

The structure of the conventional fuel cell power generation system 20 in which this fuel cell stack 1 is mounted is shown in FIG. The cooling medium supplied to the cooling plate 11 in the fuel cell stack 1 is configured to circulate between the cooling plate 11 and the pure water tank 22 by the power of the circulation pump 21 or the like. have. The pure water tank 22 is heat-exchanged with an external heat utilization device, for example, a hot water tank 23, so that the coolant discharged from the cooling plate 11 and the temperature is high is cooled to a predetermined temperature, and then again. The system configuration is supplied to the cooling plate 11 and circulated.

Specifically, the fuel cell system of the present invention receives a supply of source gas from the outside, and reformers 24 for reforming the source gas to hydrogen-rich reformed gas, and a shift to reduce carbon monoxide in the reformed gas to produce fuel gas. Reactor 25 and CO selective oxidation unit 26, fuel cell stack 1 that receives the supply of fuel gas and air, and generates electricity by electrochemical reaction, cooling water and hot water tank 23 of fuel cell stack 1 Heat exchanger 27 for performing heat exchange with the low temperature water of the < RTI ID = 0.0 >), < / RTI > DC / DC converter 28 for adjusting the voltage and current of the DC power from the fuel cell stack 1 and converting it into desired DC power, and the converted An inverter 29 for converting direct current power into alternating current power having the same phase as that of the electric device and supplying power to the electric device is provided.

In addition, pure water stored in the pure water tank 22 is supplied to the steam generator 31 through the pure water supply pump 30, and further, to the inlet of the reformer 24 through the steam control valve 32. The pure water tank 22, the pure water supply pump 30, and the reformer 24 are arranged in series so as to be supplied. In the reformer 24 and the shift reactor 25, the source gas supplied through the desulfurizer 34 and the control valve 35 to remove the boosting pump 33 and the sulfur content from the source gas line, and the pure water tank 22. The hydrogen-rich reforming gas is produced by the steam reforming reaction and the shift reaction of the following formulas (1) and (2) by means of the steam whose flow rate is regulated by the control valve 32 through the steam generator 31. .

CH ₄ + H ₂ O-> CO + 3H ₂ … … (One)

CO + H ₂ O-> CO ₂ + H ₂ … … (2)

The reformer 24 is provided with a combustion section 36 for supplying heat necessary for such a reaction and heat necessary for generating steam in the steam generator 31. The combustion side 36 is supplied with the anode side exhaust gas of the fuel cell stack 1, so that unreacted hydrogen in the anode side exhaust gas can be used as the fuel.

Therefore, in the power generation system 20 using a conventional low-temperature solid polymer fuel cell (operating temperature of 100 ° C. or less), the amount of hydrogen required by the fuel cell stack 1 and the combustion unit 36 are determined. In order to maintain at a predetermined temperature of about 700 ° C., a source gas corresponding to the total amount of hydrogen required had to be supplied to the power generation system.

Here, Equation (3) shows the power generation efficiency of the fuel cell power generation system.

eta g = (DELTA G _H2 x 4) / DELTA H _CH4 x ηref x Uf x (V / V ₀ ) x ηinv. … (3)

Where ΔH _CH4 is the heat of methane reaction, ΔG _H2 is the free energy of hydrogen, ηref is the reforming rate (of the methane supplied, the reformed rate), and Uf is the fuel utilization rate The ratio of the amount of hydrogen supplied to 50), V is the voltage at the rated load operation, V ₀ is the theoretical voltage, and ηinv is the inverter efficiency.

At present, the generation efficiency of the low-temperature solid polymer fuel cell power generation system leased in Japan is about 32% (HHV), which is lower than the average power generation efficiency of about 37%. Since the heat recovery efficiency exceeds 40%, it is a system that exceeds the overall efficiency of 70% (HHV).

Therefore, it can exert its superiority in cogeneration operation of all kinds of thermoforms, but the demand for hot water supply decreases during the summer season, and thus the superiority in terms of overall efficiency is not established. Since the operating time of the type solid polymer fuel cell power generation system is shortened, there is a problem that the advantage of reducing the annual operating cost is reduced. For this reason, in order to commercialize and spread the polymer electrolyte fuel cell power generation system, it is required to increase the power generation efficiency to be equal to or higher than the average power generation efficiency of the electric power.

In response to these demands, in order to facilitate effective use of heat in a system in recent years, a medium temperature type having an operating temperature of 100 ° C or higher (in this text, a fuel cell having an operating temperature of 100 ° C or lower is a low temperature type, and an operating temperature of 100 to 250 ° C). Is defined as mid-temperature type). Research and development of a polymer electrolyte fuel cell is underway. In this mesophilic type polymer electrolyte fuel cell, the temperature of water, which is a cooling medium of the fuel cell stack, is also 100 ° C. or higher, so that the saturated vapor pressure is increased. Therefore, the refrigerant pipe requires a pressure resistance standard.

In particular, since the internal pressure standard of the cooling water circulation pump 21 (FIG. 10) is selected from an industrial pump with a large capacity, it is inevitably connected to an increase in power consumption and size, so that a small capacity for the purpose of home use (e.g., For example, in the design of a fuel cell power generation system of 5 kW or less, there is a problem that commercialization is difficult because the design of the system is not established in terms of the efficiency of the system and the size of the system.

In this case, in order to lower the internal pressure specification of the cooling line, an alternative to using a high boiling point refrigerant such as silicone oil may be considered. However, since these high boiling point refrigerants have much lower thermal conductivity than water, the flow rate of the cooling medium is increased. In addition to the increase of the power of the circulation pump, the heat recovery in the heat recovery of the fuel cell power generation system for the purpose of cogeneration has also caused a decrease in the thermal efficiency, there is a problem that does not establish a competitive commercialization.

As a solution to the problem of the breakdown voltage standard of the cooling line, the patent document uses a plate-shaped heat pipe having a structure larger than the area of the laminated cross section of the fuel cell in the cooling plate and protruding from the laminated cross section as a heat dissipation structure. By enabling air cooling of the battery stack, it is unnecessary to install a circulation pump for cooling the fuel cell, a cooling circulation water pipe, or the like, and also requires pump power for circulating the cooling medium, and management of water as a cooling medium. The present invention discloses a method for achieving a miniaturization and low cost of an apparatus, improving efficiency during power generation, and providing a fuel cell with easy maintenance.

However, the method described in the patent literature is limited to the cooling of the fuel cell stack, and although it is an effective means in the use of portable fuel cells and the like, it is applied to a fuel cell power generation system for the purpose of cogeneration which effectively utilizes the heat generation of the fuel cell stack. Is difficult.

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and it is an object of the present invention to provide a fuel cell system capable of improving the electrical efficiency of the system and at the same time simplifying the overall configuration of the apparatus and reducing the power of the auxiliary equipment.

In order to solve this problem, in the present invention, a cell composed of an electrolyte and a pair of electrodes composed of an anode and a cathode interposed therebetween, and a fuel gas containing hydrogen to the anode are supplied and discharged to the cathode. A fuel cell stack in which a pair of separators having a gas flow path for supplying and discharging oxygen-containing oxidant gas are alternately stacked, a fuel reforming system for generating a fuel gas supplied from a source gas to a fuel cell main body, and In a fuel cell power generation system having a pure water system for supplying pure water to a first steam generator for supplying steam required for a reforming reaction in a fuel reforming system, and for effectively utilizing heat emission, Thermally conductive and engaged with all or a portion of the plurality of cells stacked on the fuel cell stack With heat transfer medium,

And a second steam generator disposed adjacent to the fuel cell stack such that the heat transfer medium is in thermal communication with the heat transfer medium, the second steam generator generating water vapor with heat supplied through the heat transfer medium.

In addition, the present invention, the first steam generator and the second steam generator is installed between the first shut-off valve;

A steam control valve disposed in a line connecting said second steam generator to an inlet of said fuel reforming system; And

And a second shut-off valve installed in a recovery line between the second steam generator and the pure water system.

The heat transfer medium transfers the heat of the steam remaining in the second steam generator by supplying the steam generated by the first steam generator to the second steam generator with the first shut-off valve open during system startup. Imparted to the fuel cell stack through a temperature increase,

After the temperature rise of the fuel cell stack is completed, the steam control valve is opened when a system load is applied, and the steam generated by the first steam generator is supplied to the fuel reforming processing system through the second steam generator. Go to system load operation,

After the load operation is stabilized, the first shutoff valve is closed and at the same time the second shutoff valve is opened to switch to the independent operation of the second steam generator.

In the present invention, the heat transfer medium is inserted into the plurality of cells stacked on the fuel cell stack every predetermined number of sheets or alternately with each of the cells. In addition, the heat transfer medium is a plate, the meander customs is disposed or formed inside the plate, the customs is characterized in that the meander custom tubular heat pipe structure is filled with the working fluid which is a heat transport medium therein. do.

In addition, the heat transfer medium is characterized in that the electrically insulating inclusions are arranged on and in contact with each other on at least one surface of the stacked sections of the plurality of cells.

In particular, in the medium-temperature fuel cell power generation system, the fuel cell stack and the first steam generator are disposed adjacent to each other through a heat transfer medium for cooling or heating the fuel cell stack, thereby directly generating heat from the fuel cell stack during power generation operation. It is used for the steam generation heat source for heat, On the other hand, it is characterized in that the heat obtained from the first steam generator is used for heating the fuel cell stack during system startup.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(1) First embodiment

(1-1) Structure of Fuel Cell Stack

FIG. 1 illustrates a structure of a fuel cell stack 50 showing an embodiment of the present invention, and FIG. 2 illustrates a structure in which the fuel cell stack 50 is disposed adjacent to the second steam generator 51. . Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2.

In the fuel cell stack 50 of the present invention, a plurality of fuel cell cells 59 are stacked, and each of the plurality of fuel cell cells 59 protrudes from a stacked end surface of the fuel cell cells 59. The configuration is interposed.

The fuel cell 59 has a sheet-like solid polymer electrolyte membrane 52, a fuel electrode 53 and an oxidant electrode 54 bonded to each of the two main surfaces of the solid polymer electrolyte membrane 52, and the electrode. A fuel gas separator 56 having a fuel gas flow path 55 provided on each of both outer surfaces of the 53 and 54 and an oxidant gas separator 58 having an oxidant gas flow path 57 are provided. The protruding portion of the heat transfer medium 60 is covered with an insulating sheet 61 so as to prevent a short circuit at the time of connection with the second steam generator 51.

The connection between the heat transfer medium 60 and the second steam generator 51 via the insulating sheet 61 is such that the heat transfer medium 60 is pinned in the second steam generator 51 to facilitate heat transfer. It is arranged to form a structure. In addition, the connection between the heat transfer medium 60 and the 2nd steam generator 51 is not limited to a fin structure, The structure by which heat exchange between both is effective is preferable. Moreover, around the fuel cell stack 50, the heat transfer medium 60, and the 2nd steam generator 51, the heat insulating material 62 for preventing heat dissipation is provided so that the whole may be covered.

Here, the rough calculation of the calorific value of the calorific value required for generation of the reformed steam required for the fuel cell stack 50 to perform the reforming reaction during the rated load operation and the reforming reaction during the rated operation will be described below. Shown in

Home condition

1) System capacity: Household 1kW power generation system (gross output 1.3kW)

2) Fuel cell rated performance: 0.3A / cm ² At load current, cell voltage 0.75V / cel1,

Cell effective area 100 cm ² , cell number 45cel1

3) Reformer performance: Reformer conversion efficiency 90%, fuel utilization Uf = 80%,

Steam / Carbon Ratio = 3

4) Heat dissipation = 0 (above)

The heat balance in the case of calculating on the assumption conditions of the above 1) -4) is as showing in following Table 1.

Calorific value of 1kW class stack at rated operation (gross output 1.3kW) 0.89 kW The amount of heat required to generate reformed steam at rated operation 0.41 kW

As described above, even in consideration of heat dissipation and transient response from the results in Table 1, the amount of heat generated by the reformed steam can be sufficiently supplied by the heat generation amount of the stack.

According to the rated operation of the fuel cell power generation system of the above-described embodiment, the heat generated by the medium temperature fuel cell stack 50 having an operating temperature of 100 ° C. or higher is moved to the adjacent second steam generator 51, and the steam required for the reforming reaction. Since it can be used for production, the steam reforming is carried out by the first steam generator 31 (FIG. 10) installed in the fuel reforming system used in the conventional low temperature type (operating temperature of 70 to 80 ° C) solid polymer fuel cell power generation system. It is not necessary to provide a considerable amount of heat necessary for generation, and it is possible to reduce the source gas to be introduced into the fuel cell power generation system. As a result, operation of a higher fuel utilization becomes possible, and thus high electrical efficiency of the fuel cell power generation system can be achieved.

(1-2) Detailed structure of the heat transfer medium

Next, the heat transfer medium 60 used by this invention is demonstrated using FIG.3 (A) and (B). The heat transfer medium 60 has a plate-type heat pipe structure, a loop meandering tubular tube 65 is disposed or formed in a conductive metal plate, and a working liquid which is a heat transfer medium is enclosed in the tubular tube. As the conductive plate, a metal or carbon material having excellent conductivity and workability, such as aluminum, stainless steel, and copper, is used. In particular, the reason why conductivity is required for the heat transfer medium 60 of the present invention is that the fuel cell cells 59 sandwiching the heat transfer medium 60 are electrically connected in series.

As the working liquid, HFC134a (alternate chlorofluorocarbon) or butane (Bu) -based working liquid or the like adapted to the operating temperature range of the fuel cell stack 50 of the present invention is used. It is enclosed in the inside. The characteristic of the heat transfer medium 60 having the plate-type heat pipe structure is that there is no large change in the heat transfer capacity due to the application posture, so that the heat-receiving portion and the heat dissipating portion can be exchanged at both ends of the heat transfer medium 60. Therefore, heat can be input and output in both directions between the fuel cell stack 50 and the second steam generator 51. An example of the performance of the heat transfer medium 60 which has a commercially available plate type heat pipe structure is shown below.

Bottom hit Top hit level Vertical horizontal (※) 343 271 296 295

AL-EX heat lane plate TM (product made by TEX Hitronics)

Performance Heat Transport per Area of Flow Section [W / cm ² ]

An article name: HLB50-200 working fluid: Butane

(※) Vertical horizontal means the state which made thickness T the base side toward the longitudinal direction (L).

With respect to the heat generation amount 0.89 kW of the 1 kW class fuel cell stack shown in Table 1, the configuration of the fuel cell stack 50 (for example, the heat transfer medium is inserted) in the heat transfer capacity performance of one example of the heat transfer medium 60 shown in Table 2 reviewing the calculation) in the contact area 100cm ² at the time of the fuel cell stack (heat transfer medium, even considering the temperature profile reduction in 5O), for example, Chapter 9 (in inserted every one sheet of the sheet cell 5) (60) By inserting N, it is possible to realize a predetermined heat balance in the fuel cell power generation system without operational problems.

As described above, when the heat transfer medium 60 of the described embodiment is used, the heat transfer medium 60 has a plate-type heat pipe structure, so that the heat generation of the fuel cell stack 50 operates inside the heat transfer medium 60. The heat is transferred to the liquid, and the working liquid becomes steam bubbles of high temperature and high pressure, and rapidly flows into the second steam generator 51 by the circulation phenomenon or vibration phenomenon of the working liquid toward the low temperature second steam generator 51 side. Heat transfer.

As a result, even in a medium temperature fuel cell power generation system having an operating temperature of 100 ° C. or more, no equipment such as a circulation pressure pump or a cooling circulation water pipe of a pressure resistance standard required when water is used as a conventional heat transfer medium is required. The heat of the battery stack 50 is moved to the second steam generator 51 quickly and efficiently to generate steam.

(1-3) Configuration of fuel cell power generation system

Next, the configuration of the fuel cell power generation system of the present invention will be described. 4 is a block diagram showing a schematic configuration of a fuel cell power generation system according to an embodiment of the present invention. The fuel cell power generation system 70 of the embodiment receives a supply of source gas from the outside as illustrated, and reformers 24 for reforming the source gas into hydrogen-rich reformed gas, and reduce the carbon monoxide in the reformed gas to reduce the fuel. The shift reactor 25 made of gas, the fuel cell stack 50 which receives the supply of fuel gas and air, and generates electricity by an electrochemical reaction, the cooling water of the fuel cell stack 50 and the low temperature water of the hot water tank 23 Heat exchanger 71 for performing heat exchange with the DC, DC / DC converter 28 for adjusting the voltage and current of the DC power from the fuel cell stack 50 and converting it into desired DC power, and the converted DC power An inverter 29 is provided which converts into AC power having the same phase as the device and supplies power to the electric device.

In addition, the pure water stored in the pure water tank 22 is supplied to the first steam generator 31 through the pure water supply pump 30, and is supplied to the second steam generator 51 through the shutoff valve 72. It is arranged to be supplied to the inlet of the reformer 24 through the steam control valve (32). In addition, after the piping branched downstream of the pure water supply pump 30 and the bypass valve 73 is disposed, the bypass line 74 of the first steam generator 31 connected downstream of the shutoff valve 72. Is installed. In addition, the second steam generator 51 is provided with a level gauge 75 and a pressure gauge 76 for measuring the liquid level and pressure in the second steam generator 51, and receiving the signals to provide a predetermined liquid level. And a recovery line 78 to the pure water tank 22 in which the shutoff valve 77 is disposed to be controlled by the pressure.

In the reformer 24 and the shift reactor 25, the source gas supplied through the desulfurizer 34 and the control valve 35 to remove the boosting pump 33 and the sulfur content from the source gas line, and the pure water tank 22. Steam reforming and shift reactions of the above formulas (1) and (2) by means of steam whose flow rate is regulated by the regulating valve 32 via the first steam generator 31 and the second steam generator 51 It is configured to produce a reformed gas rich in hydrogen. The reformer 24 is provided with a combustion section 36 for supplying heat required for such a reaction. The combustion section 36 is supplied with an exhaust gas on the anode side of the fuel cell stack 50, and an anode off gas. Unreacted hydrogen in can be used as a fuel.

The fuel cell stack 50 generates electricity by an electrochemical reaction by hydrogen in fuel gas from the shift reactor 25 and oxygen in air from the air blower 79. As described above, by arranging the heat transfer medium 60 between the fuel cell stack 50 and the second steam generator 51, the heat transfer between the fuel cells stack 50 and the second steam generator 51 can be efficiently performed.

Here, for example, according to Table 1 showing the heat resin of the 1 kW class fuel cell power generation system, (heat value of the 1 kW class stack during rated operation)> (heat amount required for generating reformed steam during rated operation). … (4)

Since the relationship between is established, the discharge flow rate of the pure water supply pump 30 and the pressure in the second steam generator 51 are operated to return the calorie value of the difference in the above formula (4) to the pure water tank 22. It is comprised so that a part of heat_generation | fever of the fuel cell stack 50 may be moved to the pure water tank 22 by controlling the shutoff valve 77 arrange | positioned at the recovery line 78. FIG. In addition, a heat exchanger 71 is provided in the pure water tank 22, and the pump 80 is discharged from the hot water tank 23 by heat exchange with pure water which receives a part of heat generated by the fuel cell stack 50 and is heated. It is configured so that the low temperature water supplied by the temperature is raised to be stored in the hot water tank (23).

According to the polymer electrolyte fuel cell power generation system 70 of the present embodiment described above, the second steam generator 51 generates the calorific value of the fuel cell stack 50 operated at 100 ° C. or higher through the heat transfer medium 60. As a result, the second steam generator 51 can generate about twice as much steam as the reformed steam required for the rated power generation operation (assume that the heat dissipation out of the system is "0").

In the fuel cell power generation system 70 of the present embodiment, since the shutoff valve 72 is closed and the shutoff valve 73 is opened at the rated operation, the pure water supplied from the pure water pump 30 is the first steam generator 31. Is bypassed and supplied directly to the second steam generator 51. Thus, during the rated operation, since the second steam generator 51 using only the heat generated by the fuel cell stack 50 is operated alone, the conventional low-temperature solid polymer fuel cell power generation system 20 (FIG. 10) has been implemented. The generation of the reformed steam by the first steam generator 31 using the combustion heat of unreacted hydrogen in the anode off gas can be stopped. As a result, it is possible to reduce the feed gas input amount of the heat amount used for steam generation in the first steam generator 31, thereby increasing the power generation efficiency. (Increasing the fuel utilization rate Uf in the above formula (3). Thereby increasing power generation efficiency)

(1-4) Startup operation of fuel cell power generation system

Next, operation at the start of the fuel cell power generation system 70 of the present invention will be described. 5 and 6 are flowcharts showing an example of a startup operation performed in the present invention.

When the start command of the fuel cell power generation system 70 is executed, the air blower 79 is operated to supply air to the combustion section 36. Thereafter, the boosting pump 33 of the raw material gas line is operated, and the raw material gas having passed through the desulfurization unit 34 is supplied to the combustion unit 36 through a pipe (not shown). Next, by igniting the burner 36A disposed in the combustion section 36, the supplied air and source gas heat the inside of the combustion section 36, and the reformer 24 and the adjacent shift reactor 25 and the first The temperature of the steam generator 31 is increased.

When the combustion part 36 is heated up to the predetermined temperature which can generate | occur | produce steam enough in the 1st steam generator 31, the pure water supply pump 30 is operated and it is from the pure water tank 22 to the 1st steam generator 31. FIG. Supply pure water. At this time, since the shutoff valve 72 is open, the steam generated by the first steam generator 31 is supplied to the second steam generator 51 connected in series.

The steam supplied to the second steam generator 51 is heated by the fuel cell stack 50 by applying heat to the fuel cell stack 50 through the heat transfer medium 60. In the second steam generator 51, the supplied steam condenses after supplying heat to the fuel cell stack 50, and the condensation level rises. When the level gauge 75 detects and exceeds the predetermined level, A shutoff valve 77 is opened to control the liquid level of the second steam generator 51 by operating the condensate to be returned to the pure water tank 22 through the recovery line 78.

When the fuel cell stack 50 reaches a predetermined operating temperature, for example, 150 ° C, the pressure gauge 76 detects a vapor pressure corresponding to the temperature, and the shutoff valve 77 opens to recover the steam. By operating to discharge to the pure water tank 22 through the line 78, the temperature of the second steam generator 51 and the fuel cell stack 50 is controlled to a predetermined temperature. When the temperature raising operation of the reformer 24 and the fuel cell stack 50 is performed above and both reach | attain predetermined temperature, it moves to fuel gas introduction mode.

Steam remaining in the second steam generator 51 is supplied to the reformer 24 by leaving the steam control valve 32 open. Thereafter, the control valve 35 disposed downstream of the desulfurizer 34 is opened to supply the raw material gas to the reformer 24. As a result, the steam reforming reaction shown in formula (1) and the shift reaction shown in formula (2) occur in the reformer 24 and the shift reactor 25, respectively, so that the anode of the fuel cell stack 50 is rich in hydrogen. Fuel gas is supplied. Thereafter, by opening the control valve 81 and supplying air to the cathode of the fuel cell stack 50, the fuel cell stack 50 moves to the power generation operation standby state, and load input to the electric machine is executed.

Next, the load increase is performed at the stage where the hydrogen-rich fuel gas and air equivalent to the rated operation are supplied, and the process moves to the rated load operation. After reaching the rated load operation, the shutoff valve 72 disposed downstream of the first steam generator 31 is shut off, and arranged in a bypass line 74 that bypasses the first steam generator 31. By keeping one shutoff valve 73 open, pure water of the pure water tank 22 is directly supplied to the second steam generator 51. As a result, the pure water supplied from the pure water tank 22 is converted into steam in the second steam generator 51 by the heat generation of the fuel cell stack 50 which has moved through the heat transfer medium 60, thereby reforming ( It is used as reforming steam fed to 24). Therefore, in the rated load mode, the reformed steam supply to the reformer 24 is continued by the independent operation of the second steam generator 51.

According to the start-up operation method of the polymer electrolyte fuel cell power generation system 70 of the present embodiment described above, a part of combustion heat generated in the combustion section 36 of the reformer 24 is obtained during system startup, and the first steam generator ( Using the steam generated in 31), the heat transfer operation of the fuel cell stack 50 is performed by heat transfer through the heat transfer medium 60 disposed in the second steam generator 51. In the transient state, since the amount of heat transfer from the fuel cell stack 50 to the second steam generator 51 is still insufficient, the reformed steam supply to the second steam generator 51 alone cannot be realized. The steam continuously generated from the steam generator 31 is controlled to be supplied to the reformer 24 as reformed steam.

As a result, even in the medium-temperature fuel cell stack 50 having an operating temperature of 100 ° C. or more, facilities such as a circulation pressure pump and a cooling circulation pipe of a pressure resistance standard required when water is used as a conventional heat transfer medium are not required. In addition, the temperature increase operation of the fuel cell stack 50 can be completed quickly and efficiently.

(2) Second Embodiment

(2-1) Structure of Fuel Cell Stack

7 and 8 show the configuration of the fuel cell stack 90 according to the second embodiment of the present invention. As shown in Fig. 7, in the present invention, a flat polymer electrolyte membrane having a flat shape, a fuel electrode and an oxidant electrode bonded to each of both surfaces of the solid polymer electrolyte membrane, and a fuel gas flow path on each of the outer both surfaces thereof. A plurality of fuel cell cells including a separator for fuel gas and a separator for oxidant gas having an oxidant gas flow path are stacked, and a fuel cell stack 90 having a flat laminated cross section is formed.

On the two stacking side surfaces corresponding to the long sides of the stacking cross sections of the fuel cell stack 90, one or a plurality of plate-shaped heat transfer media 92 are arranged in parallel via the insulating sheet 91, and One end of the heat transfer medium 92 protrudes from the stacking side of the fuel cell stack 90 and is arranged in a shape to sandwich the second steam generator 51 as shown in FIG. 8.

The connection between the heat transfer medium 92 and the fuel cell stack 90 via the insulating sheet 91 and the second steam generator 51 facilitate the movement of heat by reducing the contact thermal resistance. In order to make it, it arrange | positions by predetermined contact surface pressure. In addition, a heat insulating material (not shown) is disposed around the fuel cell stack 90, the heat transfer medium 92, and the second steam generator 51 to prevent heat radiation.

In the fuel cell power generation stack 90 of the present embodiment, heat generated in the fuel cell during the power generation operation is thermally conducted in adjacent separators, and moves to the heat transfer medium 92 in contact with the stack side. In this case, since the heat generation of the fuel cell stack 90 passes through the edge section of the long side of the separator having a flat shape, the thickness and the flat shape (aspect ratio) of the separator are designed to be suitable for thermal movement. Cooling design can be achieved.

For example, assuming that the separator thickness of the 1 kW fuel cell stack 90 is 3 mm long, 30 cm long, and 50 sheets, the total area of the two sides of the long side stacking side of the fuel cell stack 90 is 900 cm ^2. Becomes Although considering the heat conduction loss according to the thermal resistance between the fuel cell stack 90 and the heat transfer medium 92, if the heat transfer medium 92 having the performance shown as an example in Table 2 is employed, a 1 kW class fuel cell stack ( A heating value of 0.89 kW (see Table 1) of 90) may be transferred to the second steam generator 51 to be used for generating steam required for the reforming reaction.

As described above, according to the configuration of the fuel cell stack of the embodiment described above, since the heat transfer medium 92 is disposed outside the laminated cross section of the fuel cell stack 90, a gas seal required when disposed within the laminated cross section. ) Structure and a manifold structure arranged to be discharged to each of the stacked fuel cell cells, so that the cost of the structure of the heat transfer medium 92 can be reduced, and the fuel cell stack 90 can be manufactured. In this case, an advantage of shortening the time can be obtained. Further, since the heat transfer medium 92 is disposed outside the laminated cross section of the fuel cell stack 90, the heat transfer medium 92 does not need to be limited to a conductive material, and if a non-conductive material is used, When used, the insulating sheet 91 can be omitted.

INDUSTRIAL APPLICABILITY The present invention can be applied to a fuel cell system that realizes effective stack heat generation in a medium temperature fuel cell stack having a stack operation temperature of 100 ° C or higher.

As described above, according to the fuel cell power generation system according to the present invention, since the heat generated in the middle temperature type fuel cell stack having an operating temperature of 100 ° C. or more can be moved to an adjacent second steam generator, it can be used to generate steam necessary for the reforming reaction. The first steam generator installed in the fuel reforming system, which is used in the conventional low-temperature (operating temperature 70 to 80 ° C.) solid polymer fuel cell power generation system, does not need to provide the necessary heat for reforming steam generation. In addition, it is possible to reduce the source gas introduced into the fuel cell power generation system. As a result, operation of a higher fuel utilization becomes possible, and thus high electrical efficiency of the fuel cell power generation system can be achieved.

In addition, since the heat transfer medium for moving the heat generation of the fuel cell stack to the second steam generator is a plate-type heat pipe having excellent thermal conductivity, a circulation pump having a pressure resistance standard required when water is used as a conventional heat transfer medium, Since equipment such as a cooling circulating water pipe can be omitted, it is possible to reduce the size of the device, reduce the cost, and reduce the power of the auxiliary equipment.

Further, according to the method of starting the fuel cell power generation system according to the present invention, during the system startup, a part of the combustion heat generated in the combustion section of the reformer is obtained, and the steam generated in the first steam generator is used to be placed in the second steam generator. The heat transfer operation of the fuel cell stack is carried out by heat transfer through one heat transfer medium, and the heat transfer amount from the fuel cell stack to the second steam generator is still insufficient during the transient state of the load input and the rated load movement. The reformed steam supply to the steam generator alone is not feasible, and since the steam generated from the first steam generator is controlled to continue to be supplied as reformed steam to the reformer, a medium temperature fuel cell stack having an operating temperature of 100 ° C or higher. Even in the case of using water as a conventional heat transfer medium, the circulation of the pressure resistance standard required There is no need for equipment such as a pump or cooling circulation water pipe, and the temperature increase operation of the fuel cell stack can be completed quickly and efficiently, and the transient state until the rated operation can be smoothly completed.

From the above, the reformed steam is generated by using the heat generated in the medium temperature fuel cell stack to improve the electrical efficiency of the fuel cell power generation system and to omit the conventional fuel cell stack cooling water circulation line, thereby reducing the cost of the apparatus. In addition, it is possible to provide a fuel cell power generation system for reducing power of auxiliary equipment.

Claims (5)

A cell composed of an electrolyte and a pair of electrodes composed of an anode and a cathode interposed therebetween, a fuel gas containing hydrogen is supplied to and discharged from the anode, and an oxidant gas containing oxygen is supplied to and discharged from the cathode. A fuel cell stack in which a plurality of separators having a gas flow path are alternately stacked are stacked, a fuel reforming system for generating a fuel gas supplied from a source gas to a fuel cell body, and a reforming reaction is caused in the fuel reforming system. In a fuel cell power generation system having a pure water system for supplying pure water to a first steam generator for supplying necessary steam and for effectively utilizing heat discharge, A thermal transfer medium engaged with all or a portion of the plurality of cells stacked on the fuel cell stack and having thermal conductivity; And a second steam generator disposed adjacent to the fuel cell stack such that the heat transfer medium is in thermal communication with the heat transfer medium, the second steam generator generating water vapor with heat supplied through the heat transfer medium. The method of claim 1, A first shut-off valve installed between the first steam generator and the second steam generator; A steam control valve disposed in a line connecting said second steam generator to an inlet of said fuel reforming system; And a second shut-off valve installed in a recovery line between the second steam generator and the pure water system. The heat transfer medium transfers the heat of the steam remaining in the second steam generator by supplying the steam generated by the first steam generator to the second steam generator with the first shut-off valve open during system startup. Imparted to the fuel cell stack through a temperature increase, After the temperature rise of the fuel cell stack is completed, the steam control valve is opened when a system load is applied, and the steam generated by the first steam generator is supplied to the fuel reforming processing system through the second steam generator. Go to system load operation, After the load operation is stabilized, the first shutoff valve is closed, the second shutoff valve is opened, and the fuel cell power generation system is switched to independent operation of the second steam generator. . The method according to claim 1 or 2, And said heat transfer medium is inserted into said plurality of cells stacked on said fuel cell stack every predetermined number of sheets or alternately with each said cell. The method of claim 3, The heat transfer medium is a plate, A meander customs pipe is disposed or formed inside the plate, and the customs pipe is a meander custom pipe-type heat pipe structure in which a working liquid as a heat transport medium is enclosed therein. The method according to claim 1 or 2, And said heat transfer medium are arranged in contact with each other by arranging electrically insulating inclusions on at least one or more surfaces of the stacked cross-sections of the plurality of cells.

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