JP2002343404A - Fuel supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel supply system capable of improving consumption efficiency of the fuel. SOLUTION: This fuel supply system comprises a fuel tank 1 for storing liquid fuel, a means 2 for extracting hydrogen gas containing steam from the liquid fuel, and a waste fuel tank 6 for storing the waste fuel, left after extraction of hydrogen gas; and has a gas-liquid separator 3 for separating the hydrogen gas from the waste fuel, while keeping steam in the hydrogen gas at a temperature which will not cause condensation thereof is arranged between the hydrogen gas extracting means 2 and the waste fuel tank 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a fuel supply system for a fuel cell.

[0002]

2. Description of the Related Art Various fuels have been studied as fuels for fuel cell systems for vehicles.

However, when hydrogen is used as a fuel, the high-pressure cylinder for storing hydrogen has a spherical shape, so that it is difficult to mount on a vehicle. Further, the amount of stored hydrogen is small, and the cruising distance per hydrogen supply is short. There is a problem that it is short.

[0004] When a liquid fuel such as gasoline or methanol is used, a so-called reformed fuel cell system is obtained in which the fuel is reformed to obtain hydrogen. In this case, the size of the fuel reformer is increased. In addition, it is necessary to reduce the weight and cost, and it is necessary to improve the startability and responsiveness of the reformer.

Further, a fuel cell system using sodium borohydride has been studied, and this system is shown in FIG.
(Source: “A novel Safe
Method for Storing / Gener
ating Hydrogen Gas uses A
queous NaBH4 Solution and
Supported Ru Catalyst ”,
p. 265-267, 2000 Fuel Semin
aor, October 30-November
2, 2000, Portland, Oregon, U.S.A.
S. A. ).

[0006] This system comprises a main fuel tank 100 for storing an aqueous sodium borohydride solution, a catalyst 200 for decomposing the aqueous sodium borohydride solution into a hydrogen gas containing water vapor and an aqueous sodium borate solution, and hydrogen and an aqueous sodium borate solution. Capacitor 300 for adjusting to a predetermined temperature
And waste fuel tank 4 for storing sodium borate aqueous solution
00. The reaction formula for decomposing the aqueous sodium borohydride solution into hydrogen gas containing water vapor and the aqueous sodium borate solution is an exothermic reaction represented by the following chemical formula.

[0007]

(Equation 1) The aqueous sodium borohydride solution supplied from the main fuel tank 100 is decomposed by the catalyst 200 into a hydrogen gas containing water vapor and an aqueous sodium borate solution. The hydrogen gas containing water vapor and the aqueous sodium borate solution are cooled to a predetermined temperature by a refrigerant in the condenser 300, and the hydrogen gas containing water vapor is supplied to a fuel cell (not shown) for power generation, cooled and condensed. The water and the aqueous sodium borate solution are collected in the waste fuel tank 400. The recovered water and the aqueous sodium borate solution are regenerated and supplied again as an aqueous sodium borohydride solution.

[0008]

However, in such a fuel supply system using an aqueous sodium borohydride solution, it is necessary to provide a waste fuel tank in addition to the main fuel tank, and the capacity of the main fuel tank is limited. There is a problem that is. Also, the cost of collecting and transporting the aqueous sodium borate solution to a recycle plant is expensive and expensive compared to other fuels that can use well-structured infrastructure.

It is an object of the present invention to provide a fuel supply system which solves the above problems.

[0010]

According to a first aspect of the present invention, there is provided a fuel tank for storing a liquid fuel, a means for extracting hydrogen gas containing water vapor from the liquid fuel, and storing waste fuel remaining after extracting the hydrogen gas. In a fuel supply system comprising a waste fuel tank, a gas is disposed between the hydrogen gas extracting means and the waste fuel tank and separates hydrogen gas and waste fuel by maintaining a temperature at which water vapor in the hydrogen gas is not condensed. A liquid separator is provided.

According to a second aspect of the present invention, in the first aspect, a condenser in which a hydrogen gas containing steam flows in from the gas-liquid separator to condense water from the steam, and stores condensed water from the condenser And a water tank.

[0012] In a third aspect based on the first or second aspect, the heat generated when the hydrogen gas extracting means extracts hydrogen gas is used as heat for maintaining the gas-liquid separator at the predetermined temperature. Used.

In a fourth aspect based on any one of the first to third aspects, the operating conditions of the gas-liquid separator are controlled in accordance with the operating environment of the fuel supply system.

According to a fifth aspect of the present invention, in any one of the first to third aspects, a flow path communicating the waste fuel tank and the water tank is provided, and the water in the water tank is provided in the middle of the flow path. A pump for supplying the fuel to the waste fuel tank is installed, and the operating conditions of the pump are controlled according to the operating environment of the fuel supply system.

[0015]

According to the first aspect of the present invention, the hydrogen gas containing the high-temperature steam extracted by the hydrogen extraction means is supplied to a gas-liquid separator installed downstream of the hydrogen gas, and the temperature is such that the steam in the hydrogen gas does not condense. The hydrogen gas and the waste fuel are separated by the gas-liquid separator maintained in the tank, and the waste fuel is stored in the waste fuel tank.The amount of waste fuel per consumed liquid fuel does not contain condensed water. The number can be reduced as compared with the conventional example. Therefore, the size of the waste fuel tank can be reduced, and the amount of waste fuel can be reduced, so that the cost for recovery can be reduced.

According to a second aspect of the present invention, there is provided a condenser into which hydrogen gas containing water vapor flows from the gas-liquid separator to condense water from the water vapor, and a water tank for storing condensed water from the condenser. Therefore, the water stored in the water tank can be used to humidify the polymer membrane of the fuel cell, and the water balance of the fuel cell system can be improved.

In the third invention, since the heat generated when the hydrogen gas extracting means extracts hydrogen gas is used as the heat for maintaining the gas-liquid separator at the predetermined temperature,
It is possible to prevent the efficiency of the system from lowering.

In the fourth invention, the operating conditions of the gas-liquid separator are controlled in accordance with the operating environment of the fuel supply system, thereby controlling the concentration of the waste fuel and preventing crystal deposition in the waste fuel tank. it can.

In the fifth aspect of the present invention, a pump for supplying water in the water tank to the waste fuel tank is provided in the middle of the flow path connecting the waste fuel tank and the water tank, and the operating condition of the pump is controlled by the fuel. By controlling according to the operating environment of the supply system, it is possible to prevent crystal precipitation in the waste fuel tank with a simple configuration and control.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of a fuel supply system according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a diagram for explaining the configuration of the first embodiment of the present invention. This system has a fuel tank 1 for storing a liquid fuel, for example, an aqueous solution of sodium borohydride.
And a catalyst 2 for decomposing the aqueous sodium borohydride solution into a hydrogen gas containing water vapor and an aqueous sodium borate solution;
A first gas-liquid separator 3 for gas-liquid separation of a hydrogen gas containing high-temperature steam and an aqueous sodium borate solution at a high temperature, and a hydrogen gas containing high-temperature steam and cooling the hydrogen gas containing water vapor. A first condenser 4 for separating water, a heat exchanger 5 for cooling an aqueous sodium borate solution, a waste fuel tank 6 for storing an aqueous sodium borate solution, and a water tank 7 for storing water separated by the first condenser 4 And a fuel cell 8 to which hydrogen gas containing water vapor is supplied to generate power.

Further, a pump 9 for supplying the fuel in the fuel tank 1 to the catalyst 2, a valve 10 for controlling the flow rate of the waste fuel (aqueous sodium borate solution) recovered in the waste fuel tank, and a recovery in the water tank 8 And a valve 11 for controlling the flow rate of the water to be supplied.

The aqueous sodium borohydride solution supplied from the fuel tank 1 causes the above-mentioned exothermic reaction at the catalyst 2,
It is decomposed into hydrogen gas containing high-temperature steam and an aqueous sodium borate solution, and sent to the first gas-liquid separator 3. In the first gas-liquid separator 3, the hydrogen gas containing water vapor in a gas phase and the aqueous sodium borate solution in a liquid phase are separated. The hydrogen gas containing the water vapor is sent to the first condenser 4, and the aqueous sodium borate solution is It is sent to the heat exchanger 5. The two-phase separation of gas and liquid using the gas-liquid separator is performed in a high temperature state, so that the waste fuel (sodium borate solution) is in a high concentration state (water vapor contained in hydrogen gas of the conventional example is condensed). Water-free state), and the capacity of the waste fuel tank can be reduced.

The heat source for maintaining the first gas-liquid separator 3 at a high temperature uses heat generated by the exothermic reaction of the catalyst 2 to prevent a decrease in system efficiency. .

In the first condenser 4, the hydrogen gas containing high-temperature steam is cooled by the refrigerant and separated into condensed water and hydrogen gas containing steam. Water is collected in the water tank 7 via the valve 11, and hydrogen gas containing water vapor is sent to the ejector 13 via the pressure regulating valve 12 and further supplied to the fuel electrode of the fuel cell 8.

The aqueous sodium borate solution sent to the heat exchanger 5 is cooled by a refrigerant and collected in a waste fuel tank 6 via a valve 10. The recovered sodium borate aqueous solution is a high-concentration waste fuel, and is regenerated again into a sodium borohydride aqueous solution at a regeneration plant or the like.

The air sent from the air supply source 14 is humidified to a predetermined humidity by a humidifier 15 and supplied to the air electrode of the fuel cell 8. The water recovered in the water tank 7 is supplied to the humidifier 15 by the pump 16 and is used to prevent the polymer membrane of the fuel cell 8 from drying, thereby improving the water balance of the fuel cell system.

In the fuel cell 8, power is generated by the hydrogen gas supplied to the fuel electrode and the air supplied to the air electrode.
Exhaust hydrogen after power generation is sent to a second gas-liquid separator 17 where it is separated into water and hydrogen.
And supplied to the fuel cell 8 again.

The exhaust air after the power generation is sent to the second condenser 18, the water in the exhaust air is condensed by the refrigerant, the condensed water is collected in the water tank 7, and the exhaust air is discharged to the outside.

As the aqueous sodium borohydride solution in the fuel tank 1 is consumed in the present system, the aqueous sodium borohydride solution in the fuel tank 1 decreases and the aqueous sodium borate solution in the waste fuel tank 6 increases. However, the amount of waste fuel (aqueous sodium borate solution) per consumed liquid fuel (aqueous sodium borohydride solution) does not contain condensed water, and thus can be reduced as compared with the conventional example. Therefore, when the waste fuel tank capacity is the same as the conventional example, the number of times of collecting the waste fuel decreases,
The cost for recovery can be reduced, and the price of the regenerated liquid fuel can be reduced. In addition, users of fuel cell vehicles who purchase fuel at the price per volume of liquid fuel and have them pick up at the price per volume of waste fuel,
A reduction in running costs can be expected.

Further, since the amount of waste fuel can be reduced, the size of the waste fuel tank can be reduced, and the capacity of the fuel tank can be increased accordingly. Can be extended. Alternatively, the total amount of liquid in the system (the amount of liquid fuel, waste fuel and water) can be reduced, so that the weight is reduced, and when mounted on a vehicle, the weight can be reduced, thereby improving fuel efficiency.

In the system of the prior art, one capacitor 300 is used.
Although the configuration corresponding to 00 is increased to two, that is, the heat exchanger 5 and the first condenser 4, the amount of heat for cooling the hydrogen supplied to the fuel cell 8 to an appropriate temperature is the same. The combined size of the heat exchanger 5 and the first condenser 4 is not necessarily larger than the conventional condenser.

FIG. 2 shows a second embodiment, which is different from the first embodiment in that the catalyst 2 and the first gas-liquid separator 3 are used.
A heat exchanger 19 is provided between the heat exchanger 19 and the medium for transmitting heat to the hydrogen gas containing water vapor discharged from the catalyst 2 and the aqueous sodium borate solution.
Is supplied via Further, a temperature sensor 21 for detecting the temperature of the first gas-liquid separator 3 and a pressure sensor 2 for detecting the pressure
2 is installed in the first gas-liquid separator 3. Further, a valve 23 for adjusting the pressure of the hydrogen gas containing water vapor discharged from the first gas-liquid separator 3 is provided. These sensors 21,
The output of the controller 22 is sent to the controller 30, and in conjunction with the signal from the outside air temperature sensor 24, the controller 30 controls the first gas-liquid separator according to the operating environment of the system (eg, operating location, outside air temperature, season, etc.) The operating conditions (temperature, pressure, etc.) of 3 are set, and the valves 20 and 2 are set to the set values.
By controlling 3, the concentration of the waste fuel or the crystallization temperature can be controlled. Therefore, it is possible to prevent the waste fuel from being deposited in the waste fuel tank 6 even in a cold region or the like.

The third embodiment shown in FIG. 3 is different from the first embodiment in that a flow path communicating the waste fuel tank 6 and the water tank 7 is provided, and a pump 25 is provided in the middle of the flow path. It is. The pump 25 is controlled by a controller 30 to which an outside air temperature signal is input from the outside air temperature sensor 24. When the outside air temperature at which the waste fuel in the waste fuel tank is crystallized, the pump 25 operates, and the water is discharged from the waste fuel tank 6. To prevent the precipitation of crystals. The operation of the pump 25 may be controlled not only by the outside air temperature but also by the season, the operation place, and the like.

A self-humidifying type fuel in which the polymer membrane of the fuel cell 8 is made of a material that does not require swelling with water, or has a structure in which water generated on the air electrode side is reverse-diffused. When the system does not require water in the battery, the water tank 7 is abolished, and only the fuel tank 1 and the waste fuel tank 6 are used, and the water collected by the first condenser 4 is discharged to the outside. By doing so, the configuration of the system can be simplified.

Although the present invention has been described with the embodiment using a fuel cell, the present invention is also applicable to a hydrogen supply system such as a hydrogen gas engine system. The fuel to be supplied is not limited to hydrogen, but may be applied to a fuel supply system that separates liquid fuel into gaseous fuel such as methane and waste fuel. Furthermore, an example has been described in which hydrogen is extracted from a liquid fuel using a catalyst.However, the present invention is not limited to a catalyst. If it is generated, it is applicable.

The liquid fuel for extracting hydrogen is LiBH ₄ , K instead of sodium borohydride.
An aqueous solution such as BH ₄ or CsBH ₄ may be applied.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a fuel supply system illustrating a first embodiment of the present invention.

FIG. 2 is a schematic diagram of a fuel supply system illustrating a second embodiment.

FIG. 3 is a schematic diagram of a fuel supply system illustrating a third embodiment.

FIG. 4 is a schematic diagram of a conventional fuel supply system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fuel tank 2 Catalyst 3 First gas-liquid separator 4 First condenser 5 Heat exchanger 6 Waste fuel tank 7 Water tank 8 Fuel cell 30 Controller

Claims (5)

[Claims] 1. A fuel supply system comprising: a fuel tank for storing liquid fuel; means for extracting hydrogen gas containing water vapor from the liquid fuel; and a waste fuel tank for storing waste fuel remaining after hydrogen gas extraction. A gas-liquid separator disposed between the hydrogen gas extracting means and the waste fuel tank and separating the hydrogen gas and the waste fuel while maintaining a temperature at which water vapor in the hydrogen gas is not condensed. Fuel supply system. 2. A condenser for flowing hydrogen gas containing water vapor from the gas-liquid separator and condensing water from the water vapor, and a water tank for storing condensed water from the condenser. The fuel supply system according to claim 1, wherein 3. The apparatus according to claim 1, wherein heat generated when said hydrogen gas extracting means extracts hydrogen gas is used as heat for maintaining said gas-liquid separator at said predetermined temperature. A fuel supply system as described. 4. The fuel supply system according to claim 1, wherein operating conditions of the gas-liquid separator are controlled according to an operating environment of the fuel supply system. 5. A pump having a flow path communicating the waste fuel tank and the water tank, and a pump for supplying water in the water tank to the waste fuel tank is provided in the middle of the flow path. The fuel supply system according to any one of claims 1 to 3, wherein the fuel supply system is controlled according to an operating environment of the fuel supply system.