KR101324112B1 - Fuel cell system - Google Patents

Abstract

The present invention relates to a fuel cell system.
According to an aspect of the invention the first mixing unit for mixing steam and fuel gas; A fuel cell stack including a fuel electrode and an air electrode; A reformer for absorbing heat generated from the anode to reform fuel gas into hydrogen; And a second mixing unit which mixes the exhaust gas discharged from the fuel electrode and the fuel gas provided by the first mixing unit and supplies the mixed gas to the reformer.

Description

Fuel cell system

The present invention relates to a fuel cell system.

The world is focusing on the development of energy to replace fossil fuels as the depletion of fossil fuels such as petroleum and coal becomes increasingly real. Alternative energy refers to an energy source that replaces an energy source that depends heavily on oil.

Renewable energy refers to hydrogen, fuel cell, solar, solar, bioenergy, wind, geothermal, ocean and waste, among which fuel cell converts chemical energy of fuel into electricity directly through electrochemical reaction. to be. Fuel cells are similar to batteries in that they generate electricity by chemical reaction. However, since hydrogen and oxygen, which are reactants, are supplied from the outside, unlike batteries, they do not require charging and can continuously produce electricity as long as fuel is supplied There are advantages.

The fuel cell may be classified according to the type of electrolyte because the type of ions flowing inside the electrolyte is different according to the type of electrolyte. For example, fuel cells may be classified into polymer electrolyte type and alkaline type fuel cells, phosphoric acid type fuel cells, molten carbonate fuel cells, and solid oxide fuel cells.

Among these, molten carbonate fuel cell is a fuel cell using carbonate melted in liquid state as an electrolyte. It is operated at about 650 ° C, and has high power generation efficiency and excellent environmental friendliness by direct power generation by supplying fuel. have.

The molten carbonate fuel cell may be classified into an internal reforming type for reforming hydrogen required for the reaction inside the stack and an external reforming type reforming outside the stack.

Among them, the internal reforming molten carbonate fuel cell has high utilization efficiency by using heat generated in the anode for reforming reaction. Specifically, heat generated while hydrogen reacts in the anode is supplied to a reformer provided adjacent to the anode, and this heat can be used for the reaction in which methane is reformed into hydrogen. Therefore, it is not necessary to separately supply heat required for the reforming reaction.

However, such an internally reformed molten carbonate fuel cell has a problem that it is difficult to control the load once it starts to operate normally. This problem leads to the limitation that the internally reformed molten carbonate fuel cell is difficult to apply in other fields, especially where the required amount of power is variable, rather than where a constant level of power generation is required such as a power plant.

Recently, in order to improve this, a technology for controlling the amount of fuel gas supplied to a fuel cell has been proposed, and the present applicant has also proposed such a technology as Korean Patent Application No. 10-2011-0029522.

However, the above prior art has the following problems.

By adjusting the amount of fuel gas to control the load of the fuel cell, the amount of reaction at the anode which generates heat required for the endothermic reaction in the reformer is reduced or excessive, so that adequate heat for methane reforming cannot be supplied. Therefore, it is impossible to properly adjust the load according to the amount of fuel gas, and the thermal balance inside the stack may be broken, which may cause serious obstacles to the operation of the fuel cell.

Embodiments of the present invention to provide a fuel cell system capable of stably adjusting the load.

According to an aspect of the invention the first mixing unit for mixing the fuel gas; A fuel cell stack including a fuel electrode and an air electrode; A reformer for absorbing heat generated from the anode to reform fuel gas into hydrogen; A second mixing unit for mixing the exhaust gas discharged from the fuel electrode and the fuel gas provided from the first mixing unit and supplying the reformed gas to the reformer; An exhaust gas heating unit heating the exhaust gas generated from the fuel electrode; And an exhaust gas storage unit configured to store the exhaust gas discharged from the anode in front of the exhaust gas heating unit.

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The fuel cell system may further include an exhaust gas catalytic combustion unit disposed between the exhaust gas heating unit and the second mixing unit.

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In addition, the exhaust gas heating unit may provide a fuel cell system, characterized in that the heat exchanger for heat exchange between the exhaust gas and the air discharged from the cathode.

The fuel cell system may further include a fuel gas heating unit provided between the first mixing unit and the second mixing unit to heat the fuel gas.

In addition, the fuel gas heating unit may provide a fuel cell system, characterized in that the heat exchanger for heat exchange between the fuel gas and the exhaust gas.

In addition, the first valve disposed in the front end of the second mixing portion for adjusting the amount of fuel gas supplied to the second mixing portion; And a second valve disposed at the front end of the second mixing unit and configured to adjust an amount of the exhaust gas supplied to the second mixing unit.

The apparatus may further include a control unit controlling the first valve and the second valve.

In addition, when the first valve reduces the amount of fuel gas supplied to the second mixing section, the second valve provides a fuel cell system, characterized in that to increase the amount of exhaust gas supplied to the second mixing section. can do.

In addition, the present invention includes a first valve for controlling the amount of fuel gas supplied to the anode; An exhaust gas circulation line for heating exhaust gas discharged from the anode and sending the exhaust gas back to the anode; And a second valve disposed on the exhaust gas circulation line and adjusting the amount of exhaust gas supplied to the anode.

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In addition, the exhaust gas circulation line may provide a fuel cell system, characterized in that a filter for removing foreign matter contained in the exhaust gas discharged from the anode.

In addition, the fuel gas supplied from the first valve and the exhaust gas supplied from the second valve may be provided in the fuel cell system characterized in that the mixture is supplied at the front end of the stack and supplied to the stack.

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Embodiments of the present invention can stably adjust the load of the fuel cell by utilizing the exhaust gas generated from the fuel electrode of the fuel cell as a heat source for the reforming reaction.

1 is a view showing the configuration of a fuel cell system according to a first embodiment of the present invention.
2 is a view showing the configuration of a fuel cell system according to a second embodiment of the present invention;

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

In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

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

Referring to FIG. 1, the fuel cell system 10 according to the first embodiment of the present invention includes a fuel cell stack 300 that generates electricity through a chemical reaction, and a fuel required for the chemical reaction in the stack 300. It may include a fuel supply unit 110 for supplying the air supply unit 210 for supplying the air required for the chemical reaction in the stack 300.

The fuel cell system 10 is a fuel cell system using heat generated in a chemical reaction in a reforming reaction of hydrogen. For example, the fuel cell system 10 may be an internal reforming molten carbonate fuel cell. In this embodiment, an internal reforming molten carbonate fuel cell in which a reformer and an anode are formed adjacent to the inside of the stack 300 will be described as an example.

The fuel supply unit 110 is a device for supplying fuel that is not reformed with hydrogen to the stack 300, and may be a device for supplying natural gas having methane as a main component. For example, the fuel supply unit 110 may be connected to an LNG storage tank, and may use natural gas (BOG) generated from the LNG storage tank or regasify LNG. In the present embodiment, the fuel supply unit 110 will be described taking the supply of natural gas to the stack 300 as an example.

The natural gas supplied from the fuel supply unit 110 passes through the desulfurization unit 120 and is introduced into the first mixing unit 130 after the sulfur component is removed. The first mixing unit 130 mixes the natural gas supplied from the fuel supply unit 110 and the steam supplied from the steam supply unit 150 at an appropriate ratio. Here, the gas mixed with steam in the first mixing unit 130 may be referred to as fuel gas.

The fuel gas provided from the first mixing unit 130 may be supplied to the second mixing unit 450 after being heated while passing through the fuel gas heating unit 160. At this time, a portion of the fuel gas passes through a preliminary reformer (not shown) and may be reformed into hydrogen in advance.

The amount of fuel gas provided from the first mixing unit 130 to the second mixing unit 450 may be adjusted by the first valve 510. The first valve 510 adjusts the amount of fuel gas to correspond to the load required by the fuel cell system 10.

The second mixing unit 450 mixes the exhaust gas to be described later and the fuel gas supplied from the first mixing unit 130 to supply the reformer 310 of the stack 300. In this case, the second mixing unit 450 may supply only the fuel gas supplied from the first mixing unit 130 to the reformer 310 according to whether the exhaust gas is supplied.

Meanwhile, the stack 300 includes a reformer 310 for reforming methane contained in fuel gas with hydrogen, a fuel electrode 320 supplied with hydrogen delivered from the reformer 310, and air from the outside. It may include a cathode 340 to be supplied, and an electrolyte 330 interposed between the anode 320 and the cathode 340.

The stack 300 may generate electricity by electrolytically reacting hydrogen supplied from the reformer 310 into hydrogen ions and electrons, and the chemical reaction mechanism of the anode 320 and the cathode 340 may be Since it is a well-known technique, detailed description is abbreviate | omitted.

In this case, the reformer 310 may be installed adjacent to the anode 320 in the stack 300 to reduce energy loss by allowing the reformer 310 and the anode 320 to exchange heat with each other. Specifically, the reaction in which hydrogen is separated into hydrogen ions and electrons in the anode 320 is an exothermic reaction, and the reaction in which the methane is reformed into hydrogen in the reformer 310 is an endothermic reaction. When the reformers 310 are installed to exchange heat with each other, the heat generated from the anode 320 may be used in the reformer 310.

In the present embodiment, the reformer 310 is installed adjacent to the anode 320 and heat exchanged (indirect internal reforming, IIR) has been described as an example, but the scope of the present invention is not limited thereto. . For example, the reformer 310 and the anode 320 may be physically formed as a single device so that methane is reformed into hydrogen and used for a chemical reaction (direct internal reforming, DIR: Direct). Internal Reforming).

On the other hand, in a normal operation state of the stack 300, the stack 300 should be maintained at about 650 ℃.

The exhaust gas discharged from the fuel electrode 320 may be discharged through the exhaust gas discharge unit 170. The exhaust gas discharged from the anode 320 is mainly composed of nitrogen, and has a temperature of about 300 ° C. or more, so that waste heat may be consumed while passing through a boiler or the like before being discharged to the exhaust gas discharge unit 170.

In this case, a part of the exhaust gas discharged from the anode 320 may be mixed with the fuel gas and used to adjust the load of the stack 300.

In detail, a part of the exhaust gas discharged from the anode 320 may be branched through the third valve 530, pass through the filter 410, and then stored in the exhaust gas storage unit 420. The filter 410 may filter out a small amount of pollutants contained in the exhaust gas.

The exhaust gas storage unit 420 serves to temporarily store the exhaust gas to smoothly control the load, and when the flow rate is directly controlled in the third valve 530 and the second valve 520 to be described later May be omitted.

The exhaust gas passing through the exhaust gas storage unit 420 may be heated in the exhaust gas heating unit 430 and then pass through the exhaust gas catalytic combustion unit 440 to consume components that can be used as fuel. The exhaust gas heating unit 430 may be a heater, and exhaust gas passes through the exhaust gas heating unit 430 and the exhaust gas catalytic combustion unit 440 and is required for reforming reaction in the reformer 310. Heated to a level sufficient to provide.

The exhaust gas passing through the exhaust gas catalytic combustion unit 440 is supplied to the second mixing unit 450 and mixed with the fuel gas supplied from the fuel gas heating unit 160.

In this case, a second valve 520 is provided at the front end of the second mixing part 450 to adjust the supply amount of the exhaust gas.

Here, the flow path for heating the exhaust gas discharged from the fuel electrode 320 and supplying it back to the fuel electrode 320 may be referred to as an exhaust gas circulation line, and the exhaust gas circulation line is an exhaust gas discharged from the fuel electrode 320. By circulating the gas serves to supply heat required for the reaction in the reformer 310. In the present exemplary embodiment, the exhaust gas circulation line includes the third valve 530, the filter 410, the exhaust gas storage unit 420, the exhaust gas heating unit 430, and the exhaust gas catalytic combustion unit ( 440, the second valve 520, and the second mixing unit 450 are sequentially disposed.

The control unit 600 controls the first valve 510 and the second valve 520 to adjust the amount of fuel gas and exhaust gas supplied to the second mixing unit 450 to control the stack 300 of the stack 300. The load can be adjusted. In addition, the controller 600 may also control the third valve 530.

On the other hand, the air supply unit 210 may suck air from the outside to supply air to the cathode 340 at a constant pressure. The air supply unit 210 may be, for example, a blower, and the air supplied through the air supply unit 210 is heated while passing through the air heating unit 220 and the air catalytic combustion unit 230, and thus the air electrode 340. Can be supplied to.

The air whose reaction is completed in the cathode 340 may be discharged to the outside through the air discharge unit 240.

Hereinafter, the operation of the fuel cell system 10 according to the first embodiment of the present invention having the configuration as described above will be described.

When it is not necessary to adjust the load of the fuel cell system 10, the controller 600 controls the first valve 510 to mix fuel gas mixed with steam supplied from the first mixing unit 130. All may be supplied to the reformer 310. In addition, the controller 600 controls the third valve 530 to discharge the exhaust gas generated from the anode 320 to the exhaust gas discharge unit 170 or the exhaust gas storage unit 420. ) To be prepared for future load regulation.

In this case, the heat generated from the anode 320 and the heat absorbed by the reformer 310 may achieve a thermal equilibrium in the stack 300.

On the other hand, when the load control of the fuel cell system 10 is necessary, in particular, when the load of the stack 300 is reduced to reduce the amount of power generation, the control unit 600 and the steam flowing into the second mixing unit 450 and Adjust the flow of mixed fuel gas. If the amount of hydrogen supplied to the anode 320 is reduced, the amount of power generation is also reduced.

Specifically, in order to reduce the load of the stack 300, the amount of fuel gas supplied to the reformer 310 and the anode 320 needs to be reduced, so that the controller 600 controls the first valve 510. Thereby reducing the amount of fuel gas supplied to the second mixing unit 450. In this case, the amount of heat generated by the anode 320 is also reduced.

In addition, the controller 600 may control the second valve 520 to increase the exhaust gas to the second mixing unit 450. Since the exhaust gas supplied to the second mixing unit 450 moves along the exhaust gas circulation line and is heated in the exhaust gas heating unit 430 and the exhaust gas catalytic combustion unit 440, a predetermined amount of heat is generated. Has

On the other hand, the control unit 600 may supply a portion of the exhaust gas to the exhaust gas circulation line by adjusting the third valve 530 to supply the exhaust gas as described above.

The second mixing unit 450 mixes the fuel gas supplied through the first valve 510 and the heated exhaust gas supplied through the second valve 520 and supplies the mixed gas to the reformer 310.

In the reformer 310, methane is reformed to hydrogen, in which part of the required heat may be obtained from the anode 320, and some of the heat may be obtained from the exhaust gas. Since the exhaust gas is mostly nitrogen, it may be circulated again along the exhaust gas circulation line without reacting at the anode 320.

By the above operation, even if the amount of fuel gas is reduced to adjust the load, the thermal equilibrium inside the stack 300 can be maintained. That is, the stack 300 may maintain about 650 ° C. in a normal operating state by supplying heated exhaust gas. In other words, even if the amount of heat supplied from the anode 320 decreases as the amount of hydrogen supplied decreases, the fuel cell system 10 can stably generate power by heating and circulating the exhaust gas.

Moreover, since waste heat contained in the exhaust gas can be used in the endothermic reaction, it is also advantageous in that energy consumption can be reduced.

Hereinafter, a fuel cell system according to a second embodiment of the present invention will be described with reference to the drawings. However, since the second embodiment has a difference in the exhaust gas heating unit and the fuel gas heating unit as compared with the first embodiment, only the differences will be described, and the same reference numerals and reference numerals are used for the same parts. .

2 is a view showing the configuration of a fuel cell system according to a second embodiment of the present invention.

Referring to FIG. 2, the fuel gas heating unit 160 ′ and the exhaust gas heating unit 430 ′ of the fuel cell system 10 according to the second embodiment of the present invention may be provided in the form of a heat exchanger.

Specifically, the exhaust gas heating unit 430 ′ may be a heat exchanger that heats the exhaust gas by exchanging the exhaust gas with the air discharged from the cathode 340, and the fuel gas heating unit 160 ′ may be The exhaust gas heater 430 ′ may be a heat exchanger that heat-exchanges the air gas exchanged with the fuel gas supplied from the first mixing unit 130.

Of course, the exhaust gas heating unit 430 ′ and the fuel gas heating unit 160 ′ may further include a heater that auxiliaryly heats the exhaust gas or the fuel gas.

According to the above structure, since waste heat contained in the air discharged from the cathode 340 may be utilized, energy may be further saved.

As described above as a specific embodiment of the fuel cell system according to the embodiment of the present invention, this is only an example, the present invention is not limited to this, and should be construed as having the broadest range in accordance with the basic idea disclosed herein. do. Skilled artisans may implement a pattern of features that are not described in a combinatorial and / or permutational manner with the disclosed embodiments, but this is not to depart from the scope of the present invention. It will be apparent to those skilled in the art that various changes and modifications may be readily made without departing from the spirit and scope of the invention as defined by the appended claims.

10: fuel cell system 110: fuel supply unit
120: desulfurization unit 130: first mixing unit
150: steam supply unit 160: fuel gas heating unit
170: exhaust gas discharge unit 210: air supply unit
220: air heating unit 230: air catalyst combustion unit
240: air outlet 300: stack
310: reformer 320: fuel electrode
330 electrolyte 340 air cathode
410: filter 420: exhaust gas storage unit
430: exhaust gas heating unit 440: exhaust gas catalytic combustion unit
450: second mixing unit 510: first valve
520: second valve 530: third valve
600:

Claims (18)

A first mixing unit mixing fuel gas;
A fuel cell stack including a fuel electrode and an air electrode;
A reformer for absorbing heat generated from the anode to reform fuel gas into hydrogen;
A second mixing unit for mixing the exhaust gas discharged from the fuel electrode and the fuel gas provided from the first mixing unit and supplying the reformed gas to the reformer;
An exhaust gas heating unit heating the exhaust gas generated from the fuel electrode; And
And an exhaust gas storage unit configured to store the exhaust gas discharged from the fuel electrode in front of the exhaust gas heating unit. delete The method of claim 1,
The fuel cell system further comprises an exhaust gas catalytic combustion unit disposed between the exhaust gas heating unit and the second mixing unit. delete The method of claim 1,
The exhaust gas heating unit is a fuel cell system, characterized in that the heat exchanger for heat exchange between the exhaust gas and the air discharged from the cathode. The method of claim 1,
And a fuel gas heating unit provided between the first mixing unit and the second mixing unit to heat fuel gas. The method according to claim 6,
The fuel gas heating unit is a fuel cell system, characterized in that the heat exchanger for heat exchange between the fuel gas and exhaust gas. The method according to any one of claims 1, 3, 5, 6 or 7,
A first valve disposed at a front end of the second mixing part to adjust an amount of fuel gas supplied to the second mixing part; And
And a second valve disposed at a front end of the second mixing unit and configured to adjust an amount of exhaust gas supplied to the second mixing unit. The method of claim 8,
And a control unit for controlling the first valve and the second valve. The method of claim 8,
And when the first valve reduces the amount of fuel gas supplied to the second mixing portion, the second valve increases the amount of exhaust gas supplied to the second mixing portion. The method of claim 1,
A first valve controlling an amount of fuel gas supplied to the anode;
An exhaust gas circulation line for sending exhaust gas discharged from the anode back to the anode; And
And a second valve disposed on the exhaust gas circulation line and controlling an amount of exhaust gas supplied to the anode. delete delete delete delete The method of claim 11,
The exhaust gas circulation line is provided with a filter for removing the foreign matter contained in the exhaust gas discharged from the anode. The method of claim 11,
And a fuel gas supplied from the first valve and an exhaust gas supplied from the second valve are mixed at the front end of the stack and then supplied to the stack. delete

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