JP5439199B2 - Water reusable fuel cell system - Google Patents

Description

  The present invention relates to a fuel cell structure having a condensed water recovery function.

  In recent years, various types of fuel cells have been developed. One of them is a direct methanol fuel cell (hereinafter referred to as DMFC). The DMFC supplies a methanol aqueous solution as fuel to the anode pole of the power generation stack and supplies air to the cathode pole. The DMFC supplies power such as a pump and a blower to supply fuel and air. There are two main types: active type to be used and passive type that uses natural diffusion and natural convection without using any power.

  Of these, the active type often employs a circulation system in which the fuel in the built-in fuel tank is sent to the stack by the power of the pump, and the fuel not used for power generation is returned to the fuel tank. In this case, a high-concentration aqueous methanol solution and water are separately supplied from the outside to prevent depletion of the fuel in the fuel tank and to control the methanol concentration within a certain range. On the other hand, the air supplied to the cathode electrode using a blower contains water generated by a power generation reaction in the stack, and is basically discharged as water vapor from the stack exhaust port. By supplying this exhaust gas to a heat exchanger and condensing and reusing moisture contained in the exhaust gas, it is possible to eliminate the supply of water from the outside (for example, Patent Documents 1 to 4, non-patent documents). References 1, 2).

JP 2006-040787 A JP 2009-105060 A JP 2007-1000015 A JP 2009-218044

Toshio Sano et al. “Battery characteristics of direct methanol fuel cell system (YFC-100)” YUASA-JIHO NO. 95 OCTOBER 2003 Toshio Sano et al. “Development of 1 kW class DMFC system“ YFC-1000 ”” GS Yuasa Technical Report December 2004 Volume 1 Issue 1

  However, when the fuel cells described in these documents are viewed from the viewpoint of the equipment layout, in order to prevent the condensate from staying in the piping through which the water vapor flows, a heat exchanger is disposed below the stack, and the heat cell is further heated. A water recovery tank that receives condensed water must be placed in order under the exchanger, and the height of the entire system is required. Such a configuration reduces the size of the entire fuel cell or lowers the center of gravity. There was a problem of becoming an obstacle in case.

  FIG. 3 is a diagram showing a layout of devices constituting the main part of a conventional fuel cell. In the conventional fuel cell shown in FIG. 3, fuel is supplied to the stack 1 from the internal fuel tank 3 through the fuel feed pump 7. The fuel that has not been used for power generation in the stack 1 passes through the stack 1 and returns to the built-in fuel tank 3.

  As described above, in the conventional fuel cell, the power generation is continued by repeating the circulation. However, since methanol and water are consumed by the power generation, the fuel concentration and amount are reduced. On the other hand, the air supplied into the stack 1 by the air supply blower 8 is discharged from the exhaust port of the stack 1 in the state of water vapor containing water generated by the power generation reaction. And the discharged | emitted water vapor | steam is sent to the heat exchanger 5, and the water obtained by condensing after that is stored in the water collection | recovery tank 4, and is reused.

  In this case, when the fuel concentration and the remaining amount in the built-in fuel tank 3 become below a certain range, the high-concentration methanol aqueous solution feed pump 6 causes the high-concentration methanol aqueous solution tank 2 from the high-concentration methanol aqueous solution tank 2 outside the fuel cell system. The condensed water is sent from the water recovery tank 4 to the built-in fuel tank 3 by the condensed water feed pump 9. And the fuel concentration and quantity of the high concentration methanol aqueous solution and condensed water which were sent in this way are adjusted to the fixed range.

  In the conventional fuel cell layout, in the pipe through which the water vapor discharged from the stack 1 flows, the condensed water is collected as it is without being retained in the water collection tank 4. In this case, in order to finally send the condensed water to the built-in fuel tank 3, it is necessary to dispose the heat exchanger 5 below the stack 1 and dispose the water recovery tank 4 below that. As a result, the height of the stack 1, the heat exchanger 5, and the water recovery tank 4 itself is a constraint for lowering the center of gravity of the entire system.

  In terms of heat exchange performance, the heat exchanger is made of metal, but there is a problem that moisture in the exhaust from the stack and by-products from the power generation reaction corrode the heat exchanger. It was. Furthermore, the amount of condensed water recovered may not be sufficient for the operation of the fuel cell due to fluctuations in the ambient temperature around the stack, and there is a problem that continuous operation cannot be performed without supplying water from the outside for a long time. there were.

  As an improvement measure on this point, an increase in the amount of water recovered can be expected by providing the heat exchanger with a cooling function or a heater that raises the exhaust temperature. However, there is a problem in that the power consumption inside the system such as an auxiliary machine becomes large, and as a result, the capacity of the entire DMFC is reduced.

  The present invention has been made in view of the above-described problems, and provides a water reusable fuel cell system that is small in size and has a low center of gravity and can be continuously operated even when no external water is supplied. The purpose is to do. It is another object of the present invention to provide a water reusable fuel cell system that can prevent corrosion of a metal heat exchanger due to stack exhaust.

  In order to achieve the above-described object, a water reusable fuel cell system according to the present invention performs power generation by chemically reacting a liquid tank containing liquid fuel with the liquid fuel and oxygen, and by the chemical reaction. A stack for discharging the generated water vapor and the liquid fuel, a heat exchanger for exchanging heat by separating the water vapor into water and air, and a first for sending the liquid fuel discharged from the fuel tank to the stack A piping section, a second piping section for sending the steam discharged from the stack to the heat exchanger, and collecting condensed water generated in the process of sending the steam to the fuel tank, and discharging from the stack A third piping section that sends the liquid fuel to the fuel tank; a fourth piping section that sends the water separated from the heat exchanger by the heat exchanger to the fuel tank; The liquid fuel is adjusted to a predetermined concentration through the one piping section, the second piping section, the third piping section, and the fourth piping section, and the fuel tank, the stack, and the heat are adjusted. And a controller that circulates between the exchanger.

  According to the present invention, it is possible to provide a water reusable fuel cell system that is small in size and has a low center of gravity and that can be continuously operated even when no external water is supplied. Moreover, in such a water reusable fuel cell system, it is possible to provide a water reusable fuel cell system that can prevent corrosion of the metal heat exchanger due to stack exhaust.

It is an external view of ATM concerning this embodiment. It is a figure which shows the structure of the internal block of ATM. It is a figure which shows the example at the time of installing a sensor in the inside of the banknote storage in the banknote depositing / withdrawing mechanism shown in FIG.

  Embodiments of a water reusable fuel cell system according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a conceptual diagram showing a physical configuration of a water reusable fuel cell system 1000 according to the present embodiment. As shown in FIG. 1, a water reusable fuel cell system 1000 includes a stack 1, a high-concentration methanol aqueous solution tank 2, a built-in fuel tank 3, a water recovery tank 4, a heat exchanger 5, and a high-concentration methanol. The aqueous solution feeding pump 6, the fuel feeding pump 7, the air supply blower 8, the condensed water feeding pump 9, and the in-pipe condensed water recovery piping 10 are configured. The operations of these units of the water reusable fuel cell system 1000 are controlled by a controller 100 having an arithmetic unit such as a CPU (Central Processing Unit) provided outside the water reusable fuel cell system 1000. Yes.

  The stack 1 receives the air sent from the blower 8 and the high-concentration methanol aqueous solution after the concentration is adjusted inside the built-in fuel tank 3 by the fuel feed pump 7 from the built-in fuel tank 3. The stack 1 generates a power generation reaction with the received air and the high-concentration aqueous methanol solution after the concentration is adjusted by the catalyst (MEA: Membrane Electrode Assembly) formed in the stack 1. Then, a high-concentration methanol aqueous solution not used at that time is discharged to the built-in fuel tank 3. As described above, the high-concentration aqueous methanol solution circulates between the stack 1 and the built-in fuel tank 3 via the pipes connecting between them and the fuel feed pump 7 to continue power generation.

  On the other hand, the air sent from the blower 8 received by the stack 1 discharges water vapor containing water generated by the above-described power generation reaction from the exhaust port. The water vapor discharged in this way is sent to the heat exchanger 5, which separates the water vapor into air and condensed water, and the separated condensed water is passed through a condensed water feed pump 9 to a water recovery tank. 4 to discharge.

  When the built-in fuel tank 3 receives the condensed water and the high-concentration methanol aqueous solution discharged in this way, the controller 100 controls the concentration and amount of the high-concentration methanol aqueous solution inside the internal fuel tank 3 to be constant values. To do. At this time, if the fuel concentration and amount are below a certain range due to the consumption of methanol and water by the power generation of the stack 1, the controller 100 passes the high concentration methanol aqueous solution feed pump 6 through the high concentration methanol aqueous solution feed pump 6. Control is performed so that a high-concentration aqueous methanol solution is sent from the methanol aqueous solution tank 2, or condensate is sent from the water recovery tank 4 to the built-in fuel tank 3 via the condensate feed pump 9, so that the high concentration The fuel concentration and amount of aqueous methanol solution and condensed water are adjusted within a certain range.

  Although not shown in FIG. 1, the controller 100 detects the temperature sensor provided in the stack 1, the concentration sensor of the aqueous solution provided in various pumps (or pipes), and performs the above-described adjustment. It shall be.

  Further, the water reusable fuel cell system 1000 in the present embodiment is discharged from the stack 1 by the in-pipe condensed water recovery pipe 10 provided in a part of the pipe connecting the stack 1 and the heat exchanger 5. The condensed water when the water vapor is condensed can be directly returned to the built-in fuel tank 3 by its own weight. Therefore, as shown in FIG. 1, even when the stack 1 is arranged at the same height as the heat exchanger 5, the condensed water does not enter the pipe connecting the stack 1 and the heat exchanger 5. The water reusable fuel cell system 1000 can be downsized and the center of gravity can be reduced without stagnation.

  That is, the built-in fuel tank 3 contains the aqueous methanol solution, the stack 1 generates electricity by chemically reacting the aqueous methanol solution and oxygen, discharges the water vapor generated by the chemical reaction and the aqueous methanol solution, and the heat exchanger 5 The water is separated into water and air to exchange heat, and the first piping section sends the aqueous methanol solution discharged from the built-in fuel tank 3 to the stack 1 via the fuel feed pump 7, and the second piping section stacks. The steam discharged from 1 is sent to the heat exchanger 5, and the condensed water generated in the process of sending the steam is collected in the built-in fuel tank 3, and the third piping section uses the methanol aqueous solution discharged from the stack 1 as the built-in fuel. The water separated from the heat exchanger 5 by the heat exchanger 5 is sent to the internal fuel tank 3 through the water recovery tank 4 and the condensed water feed pump 9. The controller 100 adjusts the aqueous methanol solution to a predetermined concentration via the first piping unit, the second piping unit, the third piping unit, and the fourth piping unit, and the built-in fuel tank 3 and the stack 1. Since it circulates between the heat exchangers 5, it is small in size and has a low center of gravity, and continuous operation is possible even when no external water is supplied.

  By the way, in the water vapor | steam discharged | emitted from the stack 1 to the heat exchanger 5, since various by-products by an electric power generation reaction are contained in addition to a water | moisture content, when the heat exchanger 5 is metallic, the The corrosion of the heat exchanger 5 may be accelerated. However, in the water reusable fuel cell system 1000 according to the present embodiment, the metal corrosive component discharged from the stack 1 is formed on the inner wall of the pipe connecting the stack 1 and the heat exchanger 5 or on the whole. It has a resistant surface treatment and coating.

  Specifically, when the pipe connecting the stack 1 and the heat exchanger 5 is made of a stainless steel material, the pipe is coated with a fluorine material. The Fe component contained in the stainless steel material has an effect of reducing the elution amount by 90% or more. In addition, when the pipe connecting the stack 1 and the heat exchanger 5 is made of an aluminum material, it is included in the aluminum material by performing a fluorine-based coating treatment after performing a black alumite treatment. The AL component has an effect of reducing the elution amount by 80% or more, and the Fe component has an elution amount reduction effect of 95% or more. In the present embodiment, in order not to impair the heat exchange performance, the thickness of the coating made of a fluorine-based material on the pipe connecting the stack 1 and the heat exchanger 5 is set to 5 μm or less. In this way, the pipe connecting the stack 1 and the heat exchanger 5 is subjected to a surface treatment and a coating treatment that are resistant to the metal corrosive components discharged from the stack 1, so that the heat exchanger 5 corrosion can be prevented.

  Subsequently, in the water reusable fuel cell system 1000 configured as described above, it is necessary to control the water amount, blower air flow, and stack temperature in the water reusable fuel cell system 1000 within a certain range. The control method will be described. FIG. 2 is a diagram illustrating a relationship among the water amount, the blower air amount, the stack temperature, and the power generation efficiency when the water reusable fuel cell system 1000 is controlled by the controller 100. In the relationship shown in FIG. 2, when the relationship between the stack temperature S and the power generation efficiency W is seen, it can be seen that the power generation efficiency W tends to be higher as the stack temperature S is higher.

  As shown in FIG. 2, the air supplied from the air supply blower 8 to the stack 1 is also effective for controlling the temperature of the stack 1. That is, when the blower air volume Q is decreased by the control of the controller 100, the stack temperature S increases. The increase in the stack temperature S increases the exhaust temperature from the stack 1, and as a result, the temperature difference between the stack temperature S and the ambient temperature around the stack 1 increases, the heat exchange efficiency increases, and the condensed water The collection amount 12 increases. Therefore, the controller 100 decreases the blower air volume Q so as to increase the stack temperature S in this way.

  However, the stack temperature S needs to be set to a stack upper limit temperature 13 or less determined from the heat resistance temperature of the components constituting the stack 1 and to control to supply the stack 1 with the minimum amount of air necessary for power generation. Therefore, in order to satisfy these conditions, the minimum blower air volume necessary for power generation is Q0, the blower air volume at which the stack upper limit temperature 13 is reached is Q1, and the blower air volume at which the condensed water recovery amount 12 is greater than the water consumption amount 11 is set. In the case of Q2, the controller 100 controls the blower air volume Q so as to be within the range (in the region R) between the blower air volume Q1 and the blower air volume Q2 within the range of the stack upper limit temperature 13. Even in the region R, it is desirable to control the blower air volume so that the stack temperature S becomes higher.

  When the controller 100 performs the above-described control, the condensed water recovery amount 12 stably exceeds the water consumption amount 11. As a result, even if water from the outside is not supplied, the water reusable fuel cell system 1000 can be continuously operated.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above embodiments. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

DESCRIPTION OF SYMBOLS 1 Stack 2 High concentration methanol aqueous solution tank 3 Built-in fuel tank 4 Water recovery tank 5 Heat exchanger 6 High concentration methanol aqueous solution feed pump 7 Fuel feed pump 8 Air supply blower 9 Condensate feed pump 10 For collection of condensed water in piping Piping 11 Water consumption 12 Condensed water recovery 13 Stack upper limit temperature 100 Controller 1000 Water reusable fuel cell system.

Claims (4)

A fuel tank containing liquid fuel;
A stack that performs power generation by chemically reacting the liquid fuel and oxygen, and discharges the water vapor generated by the chemical reaction and the liquid fuel;
A heat exchanger for performing heat exchange by separating the water vapor into water and air;
A first piping section for sending the liquid fuel discharged from the fuel tank to the stack;
A second piping unit that sends the water vapor discharged from the stack to the heat exchanger and collects condensed water generated in the process of sending the water vapor to the fuel tank;
A third piping section for sending the liquid fuel discharged from the stack to the fuel tank;
A fourth piping section for sending the water separated from the heat exchanger by the heat exchanger to the fuel tank;
The liquid tank is adjusted to a predetermined concentration via the first piping section, the second piping section, the third piping section, and the fourth piping section, and the fuel tank and the stack are adjusted. A controller for circulating between the heat exchanger;
A blower for supplying the air to the stack,
The controller is equal to or greater than the amount of air at the heat-resistant temperature of the stack, and the amount of the condensed water is equal to or less than the amount of air that is greater than the amount of water consumed by the water reusable fuel cell system. So as to control the blower,
A water reusable fuel cell system characterized by the above. The inner wall of the second piping part is subjected to a resistance treatment against a metal corrosive component,
The water reusable fuel cell system according to claim 1. As the resistance treatment, a coating treatment with a fluorine-based material was performed, or the coating treatment was performed in addition to the black alumite treatment,
The water reusable fuel cell system according to claim 2. The controller controls the blower so that the temperature of the stack is close to the heat-resistant temperature of the stack.
The water reusable fuel cell system according to any one of claims 1 to 3, wherein:

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