KR101276677B1 - Fuel cell system - Google Patents

Abstract

The present invention is formed to produce hydrogen using a hydrocarbon-based fuel, water and air, and is disposed between an autothermal reforming reactor that causes a reforming reaction and a hot water gas shift reactor that reduces carbon monoxide generated in the autothermal reforming reactor. A fuel reformer having a heat exchanger and a second heat exchanger disposed between the hot water gas shift reactor and a cold water gas shift reactor having a lower operating temperature than the hot water gas shift reactor, and a plurality of valves from the water pump. It provides a fuel cell system including a valve assembly that is configured to individually control the flow rate of water supplied to the first and second heat exchanger.

Description

Fuel cell system {FUEL CELL SYSTEM}

The present invention relates to a fuel cell system having a fuel reformer.

The fuel reformer used in the fuel cell system refers to a device for producing hydrogen from hydrocarbon-based fuels such as natural gas, methane, gasoline, and diesel. Hydrogen generated in the fuel reformer is supplied to the fuel cell, and the supplied hydrogen reacts with oxygen in the air in the fuel cell stack to generate electricity.

Fuel reformers can be classified into steam reforming, partial oxidation reforming, and autothermal reforming depending on the reaction method. Steam reforming is an endothermic reaction in which a hydrocarbon-based fuel and water are fed to a reactor to cause a catalytic reaction. Therefore, the temperature of the reactor can be maintained only by supplying additional heat from the outside. Partial oxidation reforming is an exothermic reaction in which a hydrocarbon-based fuel and air are supplied to a reactor to cause a catalytic reaction. Therefore, the heat must be removed through an external cooling system to maintain the reactor temperature. Autothermal reforming is a method of mixing the steam reforming and the partial oxidation reforming and catalyzing the reaction by supplying hydrocarbon-based fuel, water and air together to the reactor. Therefore, the heat generated by the catalytic reaction can be controlled by the amount of water and air, so the designer can operate the reactor at the desired temperature.

Products modified by autothermal reforming, steam reforming, and partial oxidation reforming contain large amounts of carbon monoxide. In the case of a polymer electrolyte fuel cell, since a large amount of platinum catalyst is used in an electrode membrane assembly (MEA), the catalyst is poisoned when carbon monoxide is introduced. When the catalyst is poisoned, the performance of the fuel cell stack drops drastically. Therefore, the carbon reformed product in the fuel reformer should be kept at a ppm or less unit, so after the autothermal reformer, steam reformer or partial oxidation reformer, an additional reactor for reducing carbon monoxide (HTS) is used. gas shift reactors, low temperature water gas shift (LTS) reactors, and Preferential Oxidation (PrOx) reactors are required. However, in the case of high temperature polymer electrolyte fuel cells (PEMFC), molten carbonate fuel cells (MCFC), and solid oxide fuel cells (SOFC), temperatures of more than 150 degrees Celsius It may be unnecessary to use a selective oxidation reactor because

As described above, autothermal reforming reactions require water and air together with hydrocarbon-based fuels. The fuel, water, and air supplied to the reactor may be expressed as a steam to carbon ratio (SCR), which is a ratio of water to fuel, and an oxygen to carbon ratio (OCR), which is a ratio of air to fuel. Optimum SCR and OCR are required for the autothermal reforming reactor to produce a large amount of hydrogen while maintaining a constant temperature at a desired temperature. Normally air is supplied through the blower to the required amount of air. Water can also be supplied in the desired amount via a pump. The optimum reaction temperature of autothermal reformer varies depending on the fuel, but it is generally operated at 650 ~ 850 degrees Celsius, and hydrocarbon-based fuel is decomposed into reactants composed of a large amount of hydrogen, a small amount of carbon monoxide and carbon dioxide by catalytic reaction.

In order to increase the efficiency of the fuel reformer, it is necessary to recover the energy through the medium of air and water supplied to the fuel reformer to dissipate unnecessary heat between the reactors. Usually, water is used as a secondary fluid of a heat exchanger because it has a higher specific heat than air.

In the design of the fuel reformer, the path of water and air supplied to the autothermal reforming reactor, that is, the path of water and air passing through the heat exchanger, is one of the important variables. Many patents and papers have been proposed.

However, in most fuel reformers, the heat exchangers mounted between the reactors are thermally connected in series via water and air piping. Because of this connection structure, it was difficult to simultaneously satisfy the inlet temperature of each reactor. Since the temperature control points of all the heat exchangers were linked, it was difficult to control the reactor temperature alone because changing the flow rate supplied to the heat exchanger to change the temperature of one reactor changed the flow rate to the other heat exchanger. In particular, it is difficult to apply a control algorithm that maintains a constant temperature in the event of a malfunction in the blower or pump. In addition, when the temperature of the external atmosphere changes, the temperature of each reactor also had to change because the temperature of water and air supplied to the autothermal reforming reactor also changed. As such, when the temperature of the reactor is not properly controlled, a situation in which hydrogen and carbon monoxide concentrations in the product of the fuel reformer are changed may not supply hydrogen to the fuel cell stack.

It is an object of the present invention to provide a fuel cell system capable of independently controlling the temperature of each reactor in a fuel reformer.

The fuel cell system according to an embodiment of the present invention for realizing the above object, in the autothermal reforming reactor and the autothermal reforming reactor is formed to produce hydrogen using a hydrocarbon-based fuel, water and air A first heat exchanger disposed between the high temperature water gas shift reactor and a second low temperature water gas shift reactor having a lower operating temperature than the high temperature water gas shift reactor. A fuel reformer having a heat exchanger, and a valve assembly configured to individually control the flow rates of water supplied from the water pump to the first and second heat exchangers through a plurality of valves.

In addition, the fuel cell system includes a fuel cell stack configured to generate electricity using hydrogen generated in the fuel reformer and oxygen in air, and a fuel cell stack configured to burn fuel remaining unreacted in the fuel cell stack. ATO (Anode Tail-gas Oxidizer), and the reactant is a mixture of the air supplied from the blower, the water vapor heated up through the first and second heat exchanger and the water bypassed to the outside of the fuel reformer through the valve assembly The heat exchanger may further include a third heat exchanger configured to supply heat to the fuel reformer while heat-exchanging with the gas passed through.

According to an example related to the present invention, the fuel cell system may control opening and closing of each of the plurality of valves to control temperatures of the autothermal reforming reactor, the high temperature water gas shift reactor, and the low temperature water gas shift reactor, respectively. It further comprises a control unit.

The fuel cell system may further include a temperature sensor installed at each inlet of the high temperature water gas shift reactor and the low temperature water gas shift reactor to sense a temperature, and the control unit measures the temperature sensor. It can be formed to control the opening and closing of the plurality of valves using the temperature.

The controller may be configured to control the water bypassed to the outside of the fuel reformer as a buffer.

According to another example related to the present invention, the fuel cell system includes a desulfurizer disposed between the autothermal reformer and the first heat exchanger to remove sulfur, and between the autothermal reformer and the desulfurizer. And a fourth heat exchanger disposed and controlled to control the flow rate of the water supplied by the valve assembly.

The fuel cell system may further include a fifth heat exchanger disposed between the low temperature water gas shift reactor and the fuel cell stack and configured to control a flow rate of water supplied by the valve assembly.

The fuel cell system may further include a selective oxidation reactor disposed between the fifth heat exchanger and the fuel cell stack.

According to another example related to the present invention, the fuel reformer further includes a mixer configured to mix the reactant heated through the third heat exchanger with a hydrocarbon-based fuel supplied from a fuel pump.

In addition, the present invention is formed to produce hydrogen using a hydrocarbon-based fuel, water, and air, and are sequentially connected to the autothermal reforming reactor, the first heat exchanger and the high temperature water gas shift reactor, the second heat exchanger and the low temperature water gas shift reactor And a fuel reformer having a third heat exchanger, a fuel cell stack configured to generate electricity by using hydrogen generated in the fuel reformer and oxygen in air, and to burn fuel left unreacted in the fuel cell stack. ATO (Anode Tail-gas Oxidizer) and a portion of the water supplied from the water pump through a plurality of valves to each of the first to third heat exchangers are formed to bypass the rest of the fuel reformer A valve assembly, and each of which is heated up through the air supplied from the blower and the first to third heat exchangers. It proposes a water vapor and a fuel cell system in which the reactants are mixed outside the reaction water was bypassed to the fuel reformer with the heat generated in the heat exchange ATO sikimyeo elevated temperature comprising a fourth heat exchanger configured to be supplied to the fuel reformer.

In addition, in order to realize the above object, the present invention is formed to produce hydrogen using a hydrocarbon-based fuel and water, a high temperature water gas to reduce the carbon monoxide generated in the steam reforming reactor and the steam reforming reactor to cause a reforming reaction. A fuel reformer having a first heat exchanger disposed between a conversion reactor and a second heat exchanger disposed between the hot water gas conversion reactor and a low temperature water gas conversion reactor having a lower operating temperature than the hot water gas conversion reactor, and a plurality of Disclosed is a fuel cell system including a valve assembly configured to individually control a flow rate of water supplied from a water pump to the first and second heat exchangers through a valve of.

The fuel cell system configured as described above has the advantage that it can effectively maintain the temperature of the reactor compared to the conventional fuel reformer structure, and also effectively increase the temperature of the reactants. In addition, even if the SCR or OCR changes due to disturbance due to blower and pump malfunction, or changes in external temperature conditions such as summer and winter, the temperature of the reactor may be kept constant by the fuel cell system proposed in the present patent. Can be. In addition, since heat can be effectively recovered at the same time, an increase in efficiency of the fuel cell system can be expected.

In particular, according to the present invention, since the temperature of the reactor can be effectively controlled during dynamic operation such as load tracking, starting, stopping, etc. of the fuel reformer, high stability and operability of the fuel reformer can be expected.

1 is a conceptual diagram showing an example of a fuel cell system related to the present invention.
2 is a conceptual view showing another example of a fuel cell system related to the present invention.

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

In the present specification, the same or similar reference numerals are given to different embodiments in the same or similar configurations. As used herein, the singular forms "a", "an" and "the" include plural forms unless the context clearly indicates otherwise.

1 is a conceptual diagram illustrating an example of a fuel cell system 100 according to the present invention.

Referring to FIG. 1, the configuration and operation of the fuel cell system 100 are as follows.

The fuel pump 110 and the water pump 120 are configured to supply the hydrocarbon-based fuel 11 and water 12 to the fuel reformer 140, respectively. In addition, the blower 130 is configured to supply the air 13 to the fuel reformer 140 in addition to this, it is shown that the fuel reformer 140 is configured to cause an autothermal reforming reaction.

The fuel reformer 140 is supplied with fuel 11, water 12 and air [13, air 13 may be excluded if the fuel reformer 140 is configured to cause a steam reforming reaction] to enrich the hydrogen. It is formed to make the product 14. The fuel reformer 140 includes a reforming reactor 142, a first heat exchanger 190a, a high temperature water gas shift reactor 144, a second heat exchanger 190b, and a low temperature water gas shift reactor 145 sequentially connected to each other. Equipped. In this figure, the reforming reactor 142 shows an auto-thermal reformer (ATR). However, the present invention is not limited thereto, and the reforming reactor 142 may be configured as a steam reformer (SR).

The hot water gas shift reactor 144 installed at the rear end of the autothermal reforming reactor 142 is a reactor that converts carbon monoxide generated after the autothermal reforming reaction into water and converts it into hydrogen and carbon dioxide. It operates at temperatures as low as 100 to 200 degrees Celsius. Therefore, a first heat exchanger 190a is installed between the autothermal reforming reactor 142 and the high temperature water gas shift reactor 144 to adjust the inlet temperature at which the high temperature water gas shift reactor 144 operates while recovering heat. . Water is supplied to the secondary side of the first heat exchanger 190a to satisfy the inlet temperature of the desired high temperature water gas shift reactor 144, and the water is evaporated with heat removed from the rear end of the autothermal reforming reactor 142. It is formed to be.

The rear end of the high temperature water gas shift reactor 144 is equipped with a low temperature water gas shift reactor 145 performing the same function as the high temperature water gas shift reactor 144 at a lower temperature in order to further lower the concentration of carbon monoxide. Since the low temperature water gas shift reactor 145 has a lower operating temperature than the high temperature water gas shift reactor 144, a second heat exchange is performed to remove heat between the high temperature water gas shift reactor 144 and the low temperature water gas shift reactor 145. The machine 190b is installed. Like the first heat exchanger 190a, water is supplied to the secondary side of the second heat exchanger 190b to adjust the inlet temperature of the low temperature water gas shift reactor 145 connected to the rear end of the high temperature water gas shift reactor 144. It is configured to be fed.

Flow rates of the water supplied to the first and second heat exchangers 190a and 190b may be individually controlled by the valve assembly 150. Specifically, the valve assembly 150 is formed to individually control the flow rate of the water supplied from the water pump 120 to the first and second heat exchangers 190a and 190b through opening and closing of the plurality of valves 151. . For example, the valve assembly 150 is composed of flipper valves connected to the first and second heat exchangers 190a and 190b, respectively, and correspond to each of the heat exchangers 190a and 190b at predetermined times. The valve to be opened and closed may be set.

The valve assembly 150 supplies a portion of the water 12 supplied from the water pump 120 to the first and second heat exchangers 190a and 190b and bypasses the other portion to the outside of the fuel reformer 140. It can be formed to be.

The control unit 160 is connected to the valve assembly 150. The controller 160 is configured to control the opening and closing of the plurality of valves 151 to control the temperatures of the autothermal reforming reactor 142, the high temperature water gas shift reactor 144, and the low temperature water gas shift reactor 145, respectively. In addition, the inlet of the high temperature water gas shift reactor 144 and the low temperature water gas shift reactor 145 is provided with a temperature sensor 147, respectively, to detect the temperature of each reactor inlet, the control unit 160 detects the temperature It may be configured to control the opening and closing of the plurality of valves 151 using the temperature measured by the sensor 147.

Meanwhile, the hydrogen-rich product 14 is supplied to the anode 171 of the fuel cell stack 170. At this time, the stack blower 172a is configured to supply the air 15 to the cathode 172. The fuel cell stack 170 is formed to generate electricity by reacting hydrogen and oxygen. The remaining fuel 16 which is not subjected to the electrochemical reaction in the fuel cell stack 170 is configured to combust in the ATO 180 (Anode Tail-gas Oxidizer).

The gas raised to high temperature by combustion in the ATO 180 is supplied to the third heat exchanger 190c, and the third heat exchanger 190c is configured to exchange heat between the hot gas 17a and the reactant 18a. . At this time, the reactant 18a is fuel reformer 140 through the steam 13 and the valve assembly 150 heated up through the air 13 supplied from the blower 130 and the first and second heat exchangers 190a and 190b. The water bypassed to outside may be mixed. The high-temperature gas 17a becomes a low-temperature gas 17b after heat exchange and is discharged to the atmosphere, and the heated reactant 18b is configured to be supplied to the fuel reformer 140.

The total amount of water 12 supplied through the water pump 120 may include up to the first and second heat exchangers 190a and 190b, and in some cases, the fourth and / or fifth heat exchangers 190d and 190e to be described later. The amount of water supplied to the fuel reformer 140 and the amount of water bypassed to the outside of the fuel reformer 140. The controller 160 controls the fuel reformer through the valve assembly 150 to control the temperature of each reactor. 140 may be configured to intensively control the amount of water supplied to the heat exchanger inside, and to control the water bypassed to the outside of the fuel reformer 140 as a buffer to maintain the total amount of water 12. Such control In order to satisfy the strategy, it is important that the amount of water bypassed to the outside of the fuel reformer 140 does not become “0”.

If necessary, a desulfurizer 143 (HDS: Hydrodesulfurization) may be installed between the autothermal reformer 142 and the first heat exchanger 190a to remove sulfur present in the hydrocarbon-based fuel 11. . In addition, a fourth heat exchanger 190d is disposed between the autothermal reforming reactor 142 and the desulfurization unit 143. The fourth heat exchanger 190d is formed to satisfy the inlet temperature of the desulfurizer 143 using water whose flow rate is controlled by the valve assembly 150.

In addition, a selective oxidation reactor 146 may be further installed at a rear end of the low temperature water gas shift reactor 145. The selective oxidation reactor 146 serves to lower the carbon monoxide concentration to 10 ~ 100ppm level. Usually, the operating temperature of the selective oxidation reactor 146 is about 80-220 degrees Celsius. A fifth heat exchanger 190e may be installed between the low temperature water gas shift reactor 145 and the selective oxidation reactor 146 for the same purpose. The fifth heat exchanger 190e is configured to satisfy the inlet temperature of the selective oxidation reactor 146 by using the water whose flow rate supplied by the valve assembly 150 is controlled.

Meanwhile, the mixer 141 may be installed at the front end of the autothermal reforming reactor 142. The reactant 18b heated up through the third heat exchanger 190c is mixed with the hydrocarbon-based fuel 11 supplied from the fuel pump 110 in the mixer 141 and then supplied to the autothermal reforming reactor 142. .

2 is a conceptual diagram illustrating another example of a fuel cell system 200 according to the present invention.

Comparing FIG. 2 with FIG. 1, when the fuel reformer 240 is connected to a high temperature polymer electrolyte fuel cell, it is not necessary to remove carbon monoxide to a level of 10 ppm, so that the selective oxidation reactor 146 is not necessary. 2 is a configuration example of the fuel cell system 200 in which the selective oxidation reactor 146 is removed. Even if these configurations are removed, the fuel reformer 240 can be operated identically or similarly.

On the other hand, when the fuel reformer 240 is connected to a molten carbonate fuel cell, a solid oxide fuel cell, etc., a higher carbon monoxide concentration allows the hot water gas shift reactor 244 and the low temperature water gas shift reactor 245 to be removed. . In addition, in the case of using the hydrocarbon-based fuel 21 in which sulfur is sufficiently removed, the desulfurizer 243 may also be removed. In this case, the valve assembly 250 is connected in parallel to a heat exchanger disposed between a plurality of reactors provided in the fuel reformer 240, respectively, and configured to individually control each flow rate supplied to the heat exchanger.

The fuel cell system configured as described above has the advantage that it can effectively maintain the temperature of the reactor compared to the conventional fuel reformer structure, and also effectively increase the temperature of the reactants. In addition, even if the SCR or OCR changes due to disturbance due to blower and pump malfunction, or changes in external temperature conditions such as summer and winter, the temperature of the reactor may be kept constant by the fuel cell system proposed in the present patent. Can be. In addition, since heat can be effectively recovered at the same time, an increase in efficiency of the fuel cell system can be expected.

In particular, according to the present invention, since the temperature of the reactor can be effectively controlled during dynamic operation such as load tracking, starting, stopping, etc. of the fuel reformer, high stability and operability of the fuel reformer can be expected.

The fuel cell system described above is not limited to the method and configuration of the embodiments described above. The present invention can be applied variously within a range in which technical ideas are protected.

Claims (11)

The first heat exchanger is formed between a hydrocarbon-based fuel, water, and air to produce hydrogen, and is disposed between the autothermal reforming reactor causing the reforming reaction and the hot water gas shift reactor which reduces the carbon monoxide generated in the autothermal reforming reactor. And a second heat exchanger disposed between the high temperature water gas shift reactor and the low temperature water gas shift reactor having a lower operating temperature than the high temperature water gas shift reactor. And
And a valve assembly configured to individually control a flow rate of water supplied from the water pump to the first and second heat exchangers through a plurality of valves. The method of claim 1,
A fuel cell stack configured to generate electricity by using hydrogen generated in the fuel reformer and oxygen in air;
An anode tail-gas oxidizer (ATO) configured to combust remaining fuel that fails to react in the fuel cell stack; And
Heat-reacting a reactant mixed with air supplied from a blower, water vapor heated up through the first and second heat exchangers, and water bypassed to the fuel reformer through the valve assembly, with the gas passed through the ATO, And a third heat exchanger configured to supply the reactant to the fuel reformer. The method of claim 2,
And a control unit for controlling opening and closing of each of the plurality of valves to control temperatures of the autothermal reforming reactor, the high temperature water gas shift reactor, and the low temperature water gas shift reactor. The method of claim 3,
Further comprising a temperature sensor is installed at the inlet of the high temperature water gas shift reactor and the low temperature water gas shift reactor to sense the temperature,
The control unit is configured to control the opening and closing of the plurality of valves using the temperature measured by the temperature sensor. The method of claim 3,
The control unit is a fuel cell system, characterized in that formed to control the water bypassed to the outside of the fuel reformer as a buffer. The method of claim 2,
A desulfurizer disposed between the autothermal reformer and the first heat exchanger to remove sulfur; And
And a fourth heat exchanger disposed between the autothermal reforming reactor and the desulfurizer, the flow rate of the water supplied by the valve assembly being controlled. The method according to claim 6,
And a fifth heat exchanger disposed between the low temperature water gas shift reactor and the fuel cell stack and configured to control a flow rate of water supplied by the valve assembly. The method of claim 7, wherein
And a selective oxidation reactor disposed between the fifth heat exchanger and the fuel cell stack. The method of claim 2,
The fuel reformer further comprises a mixer configured to mix the reactant heated up through the third heat exchanger with a hydrocarbon-based fuel supplied from a fuel pump. It is formed to produce hydrogen using hydrocarbon-based fuel, water, and air, and is sequentially connected to the autothermal reforming reactor, the first heat exchanger, the high temperature water gas shift reactor, the second heat exchanger, the low temperature water gas shift reactor, and the third heat exchanger. Fuel reformer provided;
A fuel cell stack formed to generate electricity by using hydrogen generated in the fuel reformer and oxygen in air;
An anode tail-gas oxidizer (ATO) configured to burn fuel left unreacted in the fuel cell stack;
A valve assembly configured to supply a portion of the water supplied from the water pump to the first to third heat exchangers through a plurality of valves, and to bypass the remaining portion to the outside of the fuel reformer; And
Heat reactant mixed with air supplied from a blower and water vapor heated up through the first to third heat exchangers and water bypassed to the outside of the fuel reformer with heat generated in the ATO, and the heated reactant reacts with the fuel And a fourth heat exchanger configured to be supplied to the reformer. The first heat exchanger is formed between a hydrocarbon-based fuel and water to produce hydrogen, and is disposed between a steam reforming reactor causing a reforming reaction and a high temperature water gas shift reactor for reducing carbon monoxide generated in the steam reforming reactor. A fuel reformer having a second heat exchanger disposed between the hot water gas shift reactor and the cold water gas shift reactor having a lower operating temperature than the hot water gas shift reactor; And
And a valve assembly configured to individually control a flow rate of water supplied from the water pump to the first and second heat exchangers through a plurality of valves.

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