KR100448692B1 - Fuel feed system for fuel cell - Google Patents

Abstract

The present invention relates to a fuel supply apparatus of a fuel cell system, and the present invention also relates to a main fuel tank in which a fuel supply unit for supplying fuel to a fuel electrode of a fuel cell stack part is filled with liquid fuel, and arranged on one side of the main fuel tank. Auxiliary fuel tank filled with liquid fuel, a fuel supply pipe connecting the main fuel tank and the auxiliary fuel tank to the fuel electrode of the fuel cell stack in parallel, and the fuel cell stack unit are connected between the fuel electrode stack of the fuel electrode and the main fuel tank. And a fuel switching valve for circulating the fuel back to the main fuel tank after the reaction of the fuel cell, and a fuel switching valve for connecting the main fuel tank or the auxiliary fuel tank with the anode of the fuel cell stack by installing the fuel circulation pipe between the fuel supply pipe and the fuel circulation pipe, respectively. Fuel pump to pump fuel from each fuel tank to the anode, and between the main fuel tank and the auxiliary fuel tank. And a supplementary fuel tank having a fuel filler valve to supplement the fuel used in the auxiliary fuel tank from the new main fuel tank to the auxiliary fuel tank during the replacement of the main fuel tank. And auxiliary tanks are used to replace the main fuel tanks and the casting tanks so that the auxiliary fuel tanks and the auxiliary tanks can be used to supply fuel without interruption and thus to continuously obtain electrical energy.

Description

FUEL FEED SYSTEM FOR FUEL CELL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power generation system that obtains electrical energy by using a fuel cell. In particular, a plurality of fuel tanks filled with liquid fuel may be provided to be used alternately, and thus portable and continuously generate electricity even when the fuel tank is replaced. The present invention relates to a fuel supply apparatus for a fuel cell system.

Most of the energy that humans are using comes from fossil fuels. However, the use of such fossil fuel has a serious adverse effect on the environment, such as air pollution, acid rain, global warming, and low energy efficiency.

In order to solve the problems caused by the use of fossil fuels, fuel electric systems have recently been developed.

A fuel cell is a battery system that generates power by supplying fuel (hydrogen gas or hydrocarbon) to a cathode different from a normal battery (secondary battery) and oxygen to an anode from an external source.

The power generation method using a fuel cell is a method of directly converting an energy difference before and after the reaction into electrical energy through an electrochemical reaction between hydrogen and oxygen without undergoing combustion (oxidation) reaction of the fuel.

These fuel cells are NOx and SOx generation, noise and vibration-free system, thermal efficiency is more than 80% combined with the amount of electricity generation and heat recovery, but can be said to be a clean power generation system that does not generate harmful gases such as NOx or SOx.

Conventionally known fuel cell systems include a fuel cell stack 10 having a fuel electrode 11 and an air electrode 12 to generate electrical energy by an electrochemical reaction between hydrogen and oxygen, as shown in FIG. Fuel supply unit 20 for producing hydrogen (H2) from the LNG to supply to the anode 11 of the fuel cell stack 10, and the air supply unit for supplying oxygen to the cathode 12 of the fuel cell stack (10) 30), the electric energy output unit 40 for supplying the electric energy generated by the fuel cell stack unit 10 to the load, and each of the above-described units 10, 20, 30, 40 to properly adjust It consists of a control part (not shown).

The fuel supply unit 20 is provided with a relatively bulky device, usually called a reformer 25, between the fuel cell stack 10 and the fuel supply source 21. That is, the reformer 25 includes a desulfurizer 26 for removing sulfur (S) from LNG as a fuel, a reformer 27 for producing hydrogen by contact with water vapor, and CO 2, CO, N 2, The CO converter 28 and the CO remover 29 for separating H 2 O and the like are formed in series.

In the drawings, reference numeral 22 denotes a fuel pump, 31 an air compressor, 32 a humidifier, 41 an inverter, and 42 a rod.

The conventional fuel cell system as described above operates as follows.

That is, when a control unit (not shown) issues an operation command, LNG, which is fuel, is passed through a desulfurizer 26, commonly referred to as a reformer 25, a reformer 27, a CO converter 28, and a CO remover 29 in that order. H2 is generated and supplied to the anode 11 of the fuel cell stack 10.

At the same time, air is supplied to the cathode 12 of the fuel cell stack 10 through the air supply unit 30 to generate electrical energy while causing an oxidation reaction and a reduction reaction together with the fuel supplied to the anode 11. It was.

Such a conventional fuel cell system has a large volume and complexity of the hydrogen generating unit, which can be fixed and installed in a general household power generation system, but it is a fact that it is burdensome in terms of volume and cost to carry it outdoors. In view of this, in the related art, in order to remove a hydrogen generating part having a large volume and a complicated structure in a fuel cell system, a hydrogen cylinder 50 having compressed and stored hydrogen gas is detachably connected to the fuel electrode 11 of the fuel cell stack 10. The method is known.

However, in the conventional fuel cell system as described above, when all of the hydrogen gas filled in the hydrogen cylinder 50 is used, it must be replaced or refilled, which is not only a very difficult and dangerous task for the general public, but also replaces the hydrogen cylinder 50. During or while filling, there was an inconvenience in using the electrical appliance that had to be turned off.

The present invention has been made in view of the problems of the conventional fuel cell system as described above, and can not only safely carry the fuel cell system but also continuously supply fuel to produce fuel in a fuel cell system without interruption. It is an object of the present invention to provide a feeding device.

1 and 2 are schematic diagrams each showing an example of a conventional fuel cell system.

Figure 3 is a system diagram showing an example of the fuel cell system of the present invention.

4 is a cross-sectional view of the fuel cell stack.

Figure 5 is a schematic diagram showing the main part of a modification of the fuel cell system of the present invention.

** Description of symbols for the main parts of the drawing **

110: fuel cell stack 113: fuel electrode

114: cathode 120: fuel supply unit

121: main fuel tank 122: auxiliary fuel tank

123: fuel supply pipe 124: fuel circulation pipe

125a, 125b: fuel switching valve 126: fuel pump

127: fuel supply pipe 130: air supply unit

140: air humidifier 141: humidifier

142: water supply pipe 145: casting tank

146: auxiliary tank 147: three-way valve for supply (water switching valve)

150: water circulation 151: water circulation tube

152: gas-liquid separator 160: electrical energy output unit

In order to achieve the object of the present invention, a fuel cell stack unit having an electrolyte membrane and a fuel electrode and an air electrode stacked on both sides with the electrolyte membrane interposed therebetween to generate electricity by an electrochemical reaction between fuel and air supplied to each pole. A fuel supply section for supplying liquid fuel to the anode of the fuel cell stack, an air supply section for supplying air to the cathode of the fuel cell stack section, an air humidifying section for humidifying the air in the middle of the air supply section, and a fuel cell stack. A fuel cell system including an electrical energy output unit for supplying electrical energy generated by a part to a load, comprising: a main fuel tank having a concentration sensor configured to fill a liquid fuel, detect the concentration of the fuel, and inform the fuel replacement time; Auxiliary fuel tank, which is also located on one side of the main fuel tank and filled with liquid fuel, the main fuel tank and the auxiliary fuel A fuel supply pipe connecting the fuel cell stack to the anode of the fuel cell stack in parallel; a fuel circulation pipe connecting the fuel electrode stack to the anode and the main fuel tank to circulate the fuel back to the main fuel tank after the reaction at the fuel cell stack; Fuel switching valve is installed between the fuel supply pipe and the fuel circulation pipe, and the main fuel tank or the auxiliary fuel tank is connected with the anode of the fuel cell stack and the fuel switching valve is connected to the fuel switching valve to pump fuel from the fuel tank to the anode. And a fuel supplement pipe having a fuel supplement valve installed between the main fuel tank and the auxiliary fuel tank to supplement the amount of fuel used in the auxiliary fuel tank with the auxiliary fuel tank from the new main fuel tank during the replacement of the main fuel tank. It provides a fuel supply device of the fuel cell system including a.

In addition, the main fuel tank is filled with a liquid fuel to detect the concentration of the fuel and to inform the time of replacement of the fuel, and the auxiliary fuel tank, which is also located on one side of the main fuel tank and filled with liquid fuel; The fuel supply pipe connects the main fuel tank and the auxiliary fuel tank to the anode of the fuel cell stack in parallel, and connects the fuel between the fuel pole and the main fuel tank of the fuel cell stack to return the fuel after the reaction at the fuel cell stack. A fuel switching valve which is installed in the middle of the fuel circulation pipe circulating to the fuel supply pipe and the fuel circulation pipe, and connects the main fuel tank or the auxiliary fuel tank with the anode of the fuel cell stack, and is connected to the fuel switching valve to connect each fuel. A fuel pump that pumps fuel from the tank to the anode and is installed between the main fuel tank and the auxiliary fuel tank to assist during the replacement of the main fuel tank. A fuel supply pipe having a fuel supplement valve to refill the amount of fuel used in the fuel tank from the new main fuel tank to the auxiliary fuel tank, a water supply pipe having a water pump to supply water to the air supply unit, and a constant amount of water; A casting tank that contains water from the tank and detachably installed in the water supply pipe; Water switching valve installed in the water supply pipe between the tanks to temporarily connect the auxiliary tank and the air supply unit when replacing the casting tank, and installed between the casting tank and the auxiliary tank, and the amount of water used in the auxiliary tank during the casting tank replacement. A water fill pipe with a water fill valve to refill the new foundry tank with the auxiliary tank Provides a fuel supply system of the fuel cell system.

Hereinafter, a fuel cell system according to the present invention will be described in detail with reference to an embodiment shown in the accompanying drawings.

3 is a system diagram showing an example of the fuel cell system of the present invention, FIG. 4 is a sectional view of the fuel cell stack, and FIG. 5 is a system diagram showing a main part of a modification of the fuel cell system of the present invention.

As shown in the drawing, the fuel cell system according to the present invention includes a fuel cell stack 110 for generating electrical energy by an electrochemical reaction between hydrogen and oxygen, and a liquid fuel including hydrogen (H 2). The air supply unit 120 for supplying air to the 110, the air supply unit 130 for supplying air to the fuel cell stack 110, and the air humidifying unit for humidifying the air installed in the air supply unit 130 ( 140, the water circulation unit 150 for circulating the water passing through the cathode 114 of the fuel cell stack unit 110 back to the air supply unit 140, and the electricity generated by the fuel cell stack unit 110 An electric energy output unit 160 for supplying energy to the load, and a control unit (not shown) for appropriately adjusting the above-described units 110, 120, 130, 140, 150, 160.

The fuel cell stack 110 is a stack of a plurality of single cells (111) as shown in Figure 4, each single cell 111 is an electrolyte membrane 112, and the electrolyte membrane 112 The fuel electrode 113 and the air electrode 114 which are stacked on both sides of the fuel electrode 113 and the air electrode 114, which are stacked between the fuel electrode 113 and the air electrode 114, are laminated to the outside of the fuel electrode 113 and the air electrode 114, respectively. It consists of a separator (115, 116) to allow circulation. The fuel cell stack 110 is formed by stacking current collectors 117 and 118 which form current collector electrodes on the outer sides of the separators 115 and 116, respectively.

As the electrolyte membrane 112, it is preferable to use a membrane made of a polymer that transfers H +, such as a polymer ion exchange membrane that exhibits electrical conductivity in a wet state.

The anode 113 and the cathode 114 are composed of a support and a catalyst layer laminated on both sides of the support, wherein the support is formed of porous carbon paper or carbon cloth, and the catalyst layer is hydrogen oxide and oxygen. It is preferable to use platinum suitable for the reduction reaction. The catalyst layer is formed in the form of coating fine platinum particles on the surface of the fine carbon particles in order to increase the effective surface area of the catalyst.

The separators 115 and 116 use a metal material such as graphite having good electrical conductivity and high corrosion resistance, and a fuel flow path through which fuel liquid passes through each inner surface of the separator 113 and the cathode 114. A fuel channel (Cf) and an air channel (Co) are formed. In addition, the separators 115 and 116 provided between the single cells 111 are formed using a fuel passage Cf at one side and an air passage Co at the other side, and end portions at both sides of the fuel cell stack 110. The separators 115 and 116 provided in the above are formed by forming the fuel passage Cf or the air passage Co only on the inner side. The fuel passages Cf and the air passages Co of the separators 115 and 116 provided in the fuel cell stack 110 are connected in parallel by manifolds.

The current collectors 117 and 118 are used for finally extracting electrical energy from the fuel cell stack 110 and are preferably formed of an electrical conductor such as a copper material used as a conventional terminal.

The fuel supply unit 120 fills a predetermined amount of liquid fuel and arranges the primary fuel tank 121 and the auxiliary fuel tank 122 and the liquid fuel of each of the fuel tanks 121 and 122 in the fuel cell stack. A fuel supply pipe 123 connecting the respective fuel tanks 121 and 122 and the fuel electrode stack 113 of the fuel cell stack 110 in parallel to supply the fuel electrode 113 of the fuel cell stack 110; A fuel circulation pipe 124 connecting the fuel electrode 113 and the main fuel tank 121 of 110 to circulate the fuel back to the main fuel tank 121 after the reaction in the fuel cell stack 110; Installed in the middle of the fuel supply pipe 123 and the fuel circulation pipe 124, the fuel conversion to switch the main fuel tank 121 or auxiliary fuel tank 122 and the fuel electrode stack 110 of the fuel cell stack 110 A fuel pump 126 connected to the valves 125a and 125b and a fuel switching valve 125a and 125b to pump fuel from each fuel tank 121 and 122 to the anode 113. The.

In addition, the amount of fuel used in the subsidiary fuel tank 122 during the replacement of the main fuel tank 121 by installing between the main fuel tank 121 and the subsidiary fuel tank 122 is supplementary fuel in the new main fuel tank 121. It is made by installing a fuel filler pipe 127 having a fuel filler valve 127a so as to replenish the tank 122.

Main fuel tank 121 and the auxiliary fuel tank 122 is preferably formed integrally with a pair of the casting tank 145 and the auxiliary water tank 146 of the air humidifier 140 to be described later, as shown in FIG. .

In addition, the main fuel tank 121 is provided with a concentration sensor 128 having a display unit to detect the concentration of the liquid fuel and to inform the replacement time of the main fuel tank 121, each fuel tank 121, 122 At the inlet and the outlet of the main fuel tank 121, the fuel control valves (129a) and 129b for circulating fuel to the auxiliary fuel tank (122) and appropriately adjusting the amount of fuel during fuel supply are respectively installed. .

The air supply unit 130 includes an air compressor 131 for pumping air in the atmosphere, and an air supply pipe 132 connecting the air compressor 131 to the cathode 114 of the fuel cell stack 110. An air filter 133 is provided at the inlet side of the air compressor 132 to purify the sucked air.

In the middle of the air supply pipe 132, that is, the outlet side of the air compressor 131, a humidifier 141, which will be described later, is provided to properly humidify the air passing through the air supply pipe 132, and the humidifier 141 is provided. The check valve 134 is installed on the inlet side of the air to prevent the reverse flow of air, while the air control valve 135 is installed on the outlet side.

The air humidifier 140 includes a humidifier 141 installed in the middle of the air supply pipe 132, a water supply pipe 142 connecting the humidifier 141 and a water supply source, and a water supply pipe 142 in the middle. The installation consists of a water pump 143 pumping water to the humidifier 141. In addition, the water supply pipe 142 is provided with a water supply valve 144 to supply water to the humidifier 141 from the water supply source.

The humidifier 141 is made of a conventional ultrasonic type, bubble type, heating type and the like.

The water supply source is connected to a constant water when used for home use, and when used as a portable device according to the present embodiment, each of the fuel tanks 121 and 122 and one to one are stored by storing a certain amount of water. It consists of a casting tank 145 and an auxiliary tank 146 to be used.

The casting tank 145 and the auxiliary tank 146 are connected to the water supply pipe 142 with a three-way valve 147 for supplying water switching valve therebetween.

In addition, the casting tank 145 and the auxiliary tank 146 may be used in pairs with the respective fuel tanks 121 and 122 and then replaced with the appropriate volume ratio in consideration of the amount of fuel and water used. It is preferable to form integrally with each fuel tank 121, 122.

In addition, when the casting tank 145 is replaced between the casting tank 145 and the auxiliary tank 146, the amount of the casting tank 145 supplied from the auxiliary tank 146 is returned from the new casting tank 145. Water refill pipe 148 and the water refill valve 149 to be installed.

The water circulation unit 150 includes a water circulation pipe 151 and a water circulation pipe connecting the cathode 113 and the water supply pipe 142 of the fuel cell stack 110 to the three-way valve 153 for water circulation. It is installed in the middle of 151 and consists of a gas-liquid separator 152 for circulating the water in the water and air passing through the fuel cell stack 110, the humidifier 141.

The gas-liquid separator 152 is provided with a water level sensor (not shown) to open and close the three-way valve 153 for water circulation according to the amount of separated water.

Reference numeral 154 in the drawing indicates an exhaust pipe.

The operation and effect of the fuel cell system of the present invention as described above are as follows.

When the control unit issues an operation command, the fuel pump 126 of the fuel supply unit 120 is driven and pumps liquid fuel from the main fuel tank 121 to supply the anode 113 of the fuel cell stack 110 to the air compressor. While driving 131, the air is sucked and supplied to the cathode 114 of the fuel cell stack 110 to generate electrical energy through the electrochemical reaction between the fuel and the air.

Looking at the process of generating electricity in more detail as shown in Figure 4 the liquid fuel is supplied through the fuel flow path (Cf) formed in the separator (115, 116) of the fuel cell stack 110 through the fuel supply pipe 123 and air The air control valve 135 of the supply unit 130 is opened so that air in the atmosphere is supplied through the air passage Co formed in the separators 115 and 116 of the fuel cell stack 110 through the air supply pipe 132.

At this time, the water supply valve 144 is opened and the water pump 143 is driven so that the water in the casting tank 145 is supplied to the humidifier 141 through the water supply pipe 142, the air from the humidifier 141 The water vapor is made to be supplied to the fuel cell stack 110.

As such, the liquid fuel and the air supplied to the fuel passage Cf and the air passage Co of the separators 115 and 116 come into contact with the anode 113 and the cathode 114, respectively, to generate electrical energy by an electrochemical reaction.

That is, on the anode 113 side, the electrochemical oxidation reaction of H + supplied from the fuel

H2 → 2H + + 2e-

Is generated, the electrolyte membrane 112 transfers ions generated by the oxidation / reduction reaction, and in the cathode 114, an electrochemical reduction reaction of the supplied air (oxygen) is performed.

4H + + O2 + 4e- → 2H2O

Is generated.

Accordingly, an electromotive force is generated between the anode 113 and the cathode 114, and the electromotive force is provided through current collectors 117 and 118 installed at both ends of the fuel cell stack 110 in which a plurality of single cells 111 are stacked. The current output from the current collectors 117 and 118 is supplied to the load.

On the other hand, the fuel passing through the fuel electrode 113 of the fuel cell stack 110 is recovered to the main fuel tank 121 through the fuel circulation pipe 124 and then supplied by the fuel pump 126 to the supply side fuel switching valve ( 125a) and a series of processes to be resupplied to the anode 113 of the fuel cell stack 110 through the fuel supply pipe 123 is repeated.

In this process, the fuel is lowered in concentration, and the concentration sensor 128 senses this and informs the replacement time of the main fuel tank 121. The user who received this closes the fuel control valve 129a toward the main fuel tank 121, and the auxiliary fuel tank 122 is connected to the fuel electrode 113 of the fuel cell stack 110 so that the main fuel tank ( Replace 121).

At this time, both the supply side fuel switching valve 125a and the circulation side fuel switching valve 125b open the auxiliary fuel tank 122 and close the main fuel tank 121 to close the fuel passing through the fuel cell stack 110. Temporary circulation to the auxiliary fuel tank (122).

In addition, as the casting tank 145 which supplies the water to the humidifier 141 is also exhausted, the water is supplemented by adjusting the three-way valve 147 for supply so that the humidifier 141 and the auxiliary water tank 146 are connected. The tank 146 is supplied to the humidifier 141. Subsequently, the casting tank 145 together with the main fuel tank 121 should also be replaced. When the main fuel tank 121 and the casting tank 145 are integrally formed as shown in FIG. 5, the main fuel tank 121 and Casting tank 145 can be replaced together to facilitate the replacement operation.

Next, after replacing both the main fuel tank 121 and the casting tank 145, each of the fuel switching valves 125a and 125b and the three-way valve 147 for supplying the auxiliary fuel tank 122 and the auxiliary water tank At 146, the main fuel tank 121 and the casting tank 145 are changed so that fuel and water are normally supplied. At this time, the fuel supplement pipe 127 installed between the main fuel tank 121 and the auxiliary fuel tank 122 is the auxiliary fuel tank 122 while the fuel supplement valve 127a is opened and the main fuel tank 121 is replaced. In the main fuel tank 121 is supplemented by the amount of fuel used instead. When the auxiliary fuel tank 122 is completely filled, the fuel supplement valve 127a is closed to supply fuel only to the fuel cell stack 110.

In addition, the water filling valve 148a between the casting tank 145 and the auxiliary tank 146 is also opened and a predetermined amount of water is transferred from the replaced casting tank 145 to the auxiliary tank 146 through the water filling pipe 148. Replenish.

Here, water is mixed in the air passing through the cathode 114 of the fuel cell stack 110 and discharged to the gas-liquid separator 152 through the water circulation pipe 151, among which air is passed through the exhaust pipe 154. While the water is discharged as it is, the water is circulated to the humidifier 141 by the humidification water pump 143 when the three-way valve 153 for circulation closes the casting tank 145 and opens the gas-liquid separator 152. Supplied. At this time, the water level sensor (not shown) provided in the gas-liquid separator 152 determines the amount of water stored in the gas-liquid separator 152 and the amount is enough to replace the casting tank 145. The controller (not shown) is connected to the humidifier 141 alone.

In this way, fuel can be smoothly supplied without a separate reformer, thereby preventing the volume increase and the cost of the system generated by the reformer.

In addition, by allowing the removable fuel tank to be filled with the liquid fuel to be used, not only can it be portable, but also it can reduce the risk of use and increase convenience.

In addition, while replacing the main fuel tank and the casting tank, it is possible to supply fuel and water normally by using the auxiliary fuel tank and the auxiliary tank can generate electrical energy without interruption.

In addition, it is also possible to use a water tank that can be attached and detached in addition to the constant humidification water for humidifying the air, especially in the case of using a water tank, the water tank is formed integrally with the fuel tank, fuel tank and water The tanks can be replaced together for greater ease of use.

In addition, by circulating the water discharged with air from the cathode of the fuel cell stack to the humidifier to humidify the air with pre-heated water, especially when using a heated humidifier, the humidification effect is increased with a small amount of heat, so energy is more efficiently used. Can be used.

As described above, according to the present invention, the auxiliary fuel tank and the auxiliary tank are provided in the main fuel tank and the casting tank, respectively, so that the fuel can be supplied without interruption by using the auxiliary fuel tank and the auxiliary tank when the main fuel tank and the casting tank are replaced. The electrical energy can be obtained continuously.

In addition, the fuel tank and the water tank for humidifying the air can be formed in a removable structure so that the fuel cell system can be used as a portable device, and the fuel tank and the water tank can be replaced by integrally forming the fuel tank and the water tank. Can be unified.

In addition, energy loss can be prevented by circulating water that has passed through the air electrode and recycling it to air humidification.

The present invention is not limited only to the above-described embodiments, and various modifications are possible within the spirit and scope of the present invention.

Claims (4)

delete A fuel cell stack unit having an electrolyte membrane and a fuel electrode and an air electrode stacked on both sides with the electrolyte membrane interposed therebetween to generate electricity by an electrochemical reaction between fuel and air supplied to each pole, and a liquid fuel on the fuel electrode of the fuel cell stack unit. A fuel supply unit for supplying air, an air supply unit for supplying air to the cathode of the fuel cell stack unit, an air humidifier unit installed in the middle of the air supply unit to humidify the air, and electric energy generated by the fuel cell stack unit for supplying the load. In a fuel cell system comprising an electrical energy output unit, A main fuel tank with a concentration sensor to fill the liquid fuel and detect the concentration of the fuel to inform the time of fuel replacement; an auxiliary fuel tank which is arranged on one side of the main fuel tank to fill the liquid fuel; The fuel supply pipe connects the tank and the auxiliary fuel tank to the anode of the fuel cell stack in parallel, and connects between the anode and the main fuel tank of the fuel cell stack to circulate the fuel back to the main fuel tank after the reaction at the fuel cell stack. A fuel switching valve installed between the fuel circulation pipe, a fuel supply pipe, and a fuel circulation pipe, respectively, for switching the main fuel tank or the auxiliary fuel tank to the anode of the fuel cell stack; and a fuel switching valve connected to the fuel switching valve for fuel in each fuel tank. Fuel pump that pumps fuel to the anode and between the main fuel tank and the auxiliary fuel tank, and the auxiliary fuel tank during the replacement of the main fuel tank. A fuel supply device of a fuel cell system including a fuel tube having a fuel supplement supplementary valve to compensate for the use as fuel in the auxiliary fuel tanks at a new primary fuel tank. A fuel cell stack unit having an electrolyte membrane and a fuel electrode and an air electrode stacked on both sides with the electrolyte membrane interposed therebetween to generate electricity by an electrochemical reaction between fuel and air supplied to each pole, and a liquid fuel on the fuel electrode of the fuel cell stack unit. A fuel supply unit for supplying air, an air supply unit for supplying air to the cathode of the fuel cell stack unit, an air humidifier unit installed in the middle of the air supply unit to humidify the air, and electric energy generated by the fuel cell stack unit for supplying the load. In a fuel cell system comprising an electrical energy output unit, A main fuel tank with a concentration sensor to fill the liquid fuel and detect the concentration of the fuel to inform the time of fuel replacement; an auxiliary fuel tank which is arranged on one side of the main fuel tank to fill the liquid fuel; The fuel supply pipe connects the tank and the auxiliary fuel tank to the anode of the fuel cell stack in parallel, and connects between the anode and the main fuel tank of the fuel cell stack to circulate the fuel back to the main fuel tank after the reaction at the fuel cell stack. A fuel switching valve installed between the fuel circulation pipe, a fuel supply pipe, and a fuel circulation pipe, respectively, for switching the main fuel tank or the auxiliary fuel tank to the anode of the fuel cell stack; and a fuel switching valve connected to the fuel switching valve for fuel in each fuel tank. Fuel pump that pumps fuel to the anode and between the main fuel tank and the auxiliary fuel tank, and the auxiliary fuel tank during the replacement of the main fuel tank. A fuel supplement pipe having a fuel supplement valve to supplement the used fuel amount from the new main fuel tank to the auxiliary fuel tank, a water supply pipe for supplying water to the air supply unit, and a water supply tube connected to the humidifier, and a predetermined amount of water Between the casting tank and the auxiliary tank that temporarily supplies water to the air supply during replacement of the casting tank by connecting to the water supply pipe in parallel with the casting tank. Water casting valve installed in the water supply pipe to temporarily connect the auxiliary tank and the air supply unit when replacing the casting tank, and installed between the casting tank and the auxiliary tank, and as much as the water used in the auxiliary tank while replacing the casting tank. A fuel cell comprising a water replenishment pipe having a water replenishment valve to replenish with an auxiliary water tank in the System fuel supply. The method of claim 3, A fuel supply system for a fuel cell system, wherein the main fuel tank, the casting tank, and the auxiliary fuel tank and the auxiliary tank are integrally formed in pairs in consideration of appropriate amounts of fuel and water.