JP2013197037A - Reformer system, fuel cell system, and operation method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly efficient reformer system, a fuel system and an operation method therefor, for removing depositing carbon in a reforming catalyst according to the storage amount.SOLUTION: A fuel cell system 1 includes a reformer 2 and a solid oxide fuel cell 6, and the reformer 2 includes raw fuel gas supplying means 3, vapor supplying means 4, control means 5 for the above supplying means, first detecting means 7 for detecting temperature or pressure of unreformed gas G2, and second detecting means 8 for detecting temperature or pressure of reformed gas G3. On the basis of the temperature or pressure detected by the first and second detecting means, the raw fuel supplying means 3 and the vapor supplying means 4 are controlled so that a ratio S/C, where S is an amount of vapor S1 and C is an amount of raw material gas G1, becomes a normal value when a difference of temperatures or pressures between the unreformed gas G2 and the reformed gas G3 lies within a predetermined range, and that the ratio S/C becomes at least one type of a higher setting value larger than the normal value when the above difference lies outside the predetermined range.

Description

  The present invention relates to a reformer system, a fuel cell system, and an operation method thereof.

  In a fuel injection type solid oxide fuel cell, a reformed gas containing hydrogen is used as a fuel. The reformed gas is generated by bringing an unreformed gas, which is a mixed gas of raw fuel gas and water vapor, into contact with the reforming catalyst in the reformer.

  During the operation of the reformer, a phenomenon occurs in which carbon derived from the raw fuel gas is deposited on the reforming catalyst. When carbon deposits and accumulates on the reforming catalyst, the activity of the reforming catalyst decreases and deteriorates. For this reason, there has been a demand for a technique that can reduce the amount of carbon deposited on the reforming catalyst. For example, the ratio (O / C) between the number of oxygen atoms O supplied to the reformer and the number of carbon atoms C contained in the raw fuel supplied to the reformer is the steady state of the reformer. For removing carbon deposited on the reforming catalyst by controlling at least one of the supply amount of raw fuel and the supply amount of oxygen so as to take a value larger than the appropriate range during operation. A control method for a reformer characterized by performing a carbon removal process is known (Patent Document 1).

JP 2002-134151 A

  However, in the carbon removal treatment adopted by the method described in Patent Document 1, the amount of carbon accumulated in the reformer is calculated based on prediction according to the history of the operating state of the reformer, It did not necessarily indicate the amount of carbon accumulated. For this reason, even though the oxidative removal of the carbon is completed, the operation is continued with the high O / C value set to damage the reforming catalyst, or the carbon deposited on the reforming catalyst still remains. Regardless, there is a risk that the O / C may be returned to a low value.

  The present invention relates to a reformer system, a fuel cell system, and a fuel cell system operation method capable of operating with high efficiency while removing carbon deposited on the reforming catalyst by an operation according to the actual accumulated amount. The purpose is to provide.

  The present invention provides a reformer that generates a reformed gas used as a fuel for a solid oxide fuel cell by bringing an unreformed gas, which is a mixed gas of raw fuel gas and water vapor, into contact with a reforming catalyst. A reformer system comprising: a raw fuel gas supply means for supplying raw fuel gas to the reformer; a steam supply means for supplying water vapor to the reformer; the raw fuel gas supply means; and the water vapor Control means for controlling the supply means, first detection means for detecting the temperature or pressure of the unreformed gas, and second detection means for detecting the temperature or pressure of the reformed gas, The control means, when the temperature difference or pressure difference between the unreformed gas and the reformed gas is within a predetermined range based on the temperature or pressure detected by the first and second detection means The amount of water vapor supplied to the reformer When the ratio S / C of the amount of raw fuel gas supplied to the reformer C is a normal value and the temperature difference or pressure difference is outside the predetermined range, the S / C is the normal value. The present invention relates to a reformer system that controls the raw fuel gas supply means and the water vapor supply means so that at least one higher set value is set.

  The present invention relates to a reformer that generates a reformed gas by bringing an unreformed gas that is a mixed gas of raw fuel gas and water vapor into contact with a reforming catalyst, and a solid oxide that uses the reformed gas as a fuel. A fuel cell system comprising: a raw fuel gas supply means for supplying raw fuel gas to the reformer; a steam supply means for supplying water vapor to the reformer; and the raw fuel gas Control means for controlling the supply means and the water vapor supply means; first detection means for detecting the temperature or pressure of the unreformed gas; and second detection means for detecting the temperature or pressure of the reformed gas; The control means has a predetermined temperature difference or pressure difference between the unreformed gas and the reformed gas based on the temperature or pressure detected by the first and second detection means. If within range, supply to the reformer When the ratio S / C between the amount S of steam generated and the amount C of raw fuel gas supplied to the reformer is a normal value, and the temperature difference or pressure difference is outside the predetermined range, S / C The present invention relates to a fuel cell system that controls the raw fuel gas supply means and the water vapor supply means so that C becomes at least one high set value higher than the normal value.

  The present invention relates to a reformer that generates a reformed gas by bringing an unreformed gas that is a mixed gas of raw fuel gas and water vapor into contact with a reforming catalyst, and a solid oxide that uses the reformed gas as a fuel. A fuel cell system comprising: a fuel cell, wherein the reforming gas has a temperature difference or a pressure difference within a predetermined range between the unreformed gas and the reformed gas. The ratio S / C between the amount S of steam supplied to the reactor and the amount C of raw fuel gas supplied to the reformer is set to a normal value, and the temperature difference or pressure difference is outside the predetermined range. In some cases, the present invention relates to an operation method in which S / C is set to at least one high set value higher than the normal value.

  According to the present invention, a reformer system, a fuel cell system, and a fuel cell system that can be operated with high efficiency while removing carbon deposited on the reforming catalyst by an operation according to the actual accumulation amount. A driving method can be provided.

It is a figure showing the outline of the fuel cell system concerning one embodiment of the present invention. It is a graph which shows the relationship between S / C (ratio of the quantity S of the water vapor | steam supplied to a reformer, and the quantity C of the raw fuel gas supplied to a reformer), and the production amount of hydrogen or carbon monoxide. . It is a graph which shows the relationship between S / C and the selectivity (mol%) of each reaction product. It is a flowchart which shows operation | movement of the fuel cell system which concerns on one Embodiment of this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Fuel cell system]
First, a fuel cell system according to an embodiment of the present invention will be described with reference to FIG.
The fuel cell system 1 of the present embodiment includes a reformer 2, raw fuel gas supply means 3, water vapor supply means 4, control means 5, solid oxide fuel cell 6, and first detection means 7. And second detection means 8.

The reformer 2 generates the reformed gas G3 by bringing the unreformed gas G2 that is a mixed gas of the raw fuel gas G1 and the steam S1 into contact with the reforming catalyst.
The raw fuel gas supply means 3 supplies the raw fuel gas G 1 to the reformer 2.
The steam supply means 4 supplies the steam S 1 to the reformer 2.
The control means 5 controls the raw fuel gas supply means 3 and the water vapor supply means 4 based on the temperature or pressure detected by the first detection means 7 and the second detection means 8.
The solid oxide fuel cell 6 uses the reformed gas G3 generated by the reformer 2 as fuel.
The first detection means 7 detects the temperature or pressure of the unreformed gas G2.
The second detection means 8 detects the temperature or pressure of the reformed gas G3.

An unreformed gas supply line L1 and a reformed gas supply line L2 are connected to the reformer 2. The unreformed gas G2 is supplied to the reformer 2 through the unreformed gas supply line L1. Further, the reformed gas G3 is supplied from the reformer 2 to the solid oxide fuel cell 6 through the reformed gas supply line L2. The reformed gas G3 generated by the reformer 2 is a gas containing hydrogen generated by the steam reforming reaction between the raw fuel gas G1 and the steam S1. Examples of the reforming catalyst include a ruthenium catalyst and a nickel catalyst.
“Line” is a general term for a flow path, a path, a pipe line, and the like.

  Examples of the raw fuel gas G1 include a gas of a compound containing carbon and hydrogen in a molecule and a gas of a mixture composed of these compounds. More specifically, methane, ethane, propane, butane, LNG (liquefaction) Natural gas), LPG (liquefied petroleum gas), city gas, hydrocarbons such as gasoline, naphtha, kerosene and light oil, alcohols such as methanol and ethanol, and ethers such as dimethyl ether.

  A raw fuel gas supply line L3 is connected to the raw fuel gas supply means 3. The raw fuel gas supply line L3 is connected to the unreformed gas supply line L1 and a later-described steam supply line L4 at a junction J1. The raw fuel gas supply means 3 is connected to the reformer 2 via a raw fuel gas supply line L3 and an unreformed gas supply line L1. The raw fuel gas supply means 3 supplies the raw fuel gas G1 to the reformer 2 through the raw fuel gas supply line L3 and the unreformed gas supply line L1.

  A steam supply line L4 is connected to the steam supply means 4. The steam supply means 4 is connected to the reformer 2 through a steam supply line L4 and an unreformed gas supply line L1. The steam supply means 4 supplies the steam S1 to the reformer 2 through the steam supply line L4 and the unreformed gas supply line L1.

The control means 5 determines that the ratio S / C between the amount S of the steam S1 supplied to the reformer 2 and the amount C of the raw fuel gas G1 supplied to the reformer 2 is a normal value at a predetermined timing. And the raw fuel gas supply means 3 and the water vapor supply means 4 are controlled so as to switch between at least one high set value higher than the normal value.
In the present embodiment, the control means 5 is electrically connected to the raw fuel gas supply means 3, the water vapor supply means 4, the first detection means 7, and the second detection means 8. Then, the control means 5 determines that the temperature difference or pressure difference between the unreformed gas G2 and the reformed gas G3 is based on the temperature or pressure detected by the first detection means 7 and the second detection means 8. When it is within the predetermined range, the value of S / C becomes a normal value, and when the temperature difference or pressure difference is outside the predetermined range, the value of S / C is higher than the normal value. The supply amount of the raw fuel gas G1 by the raw fuel gas supply unit 3 and the supply amount of the water vapor S1 by the water vapor supply unit 4 are controlled so that at least one high set value is obtained.

  The solid oxide fuel cell 6 is connected to the reformer 2 via the reformed gas supply line L2. The solid oxide fuel cell 6 includes a plurality of stacked solid oxide fuel cells (not shown). This solid oxide fuel cell 6 uses the reformed gas G3 supplied from the reformer 2 through the reformed gas supply line L2 as fuel, and generates power by using a plurality of stacked solid oxide fuel cells. The solid oxide fuel cell includes an anode, a cathode, and an electrolyte layer provided between the anode and the cathode. The electrolyte layer conducts oxide ions at a temperature of 800 ° C to 1000 ° C. The anode generates electrons and water by reacting oxide ions with hydrogen in the reformed gas G3. The cathode reacts oxygen and electrons in the air to generate oxide ions.

  The first detection means 7 is provided in the middle of the unreformed gas supply line L1. The first detection means 7 transmits the result of detecting the temperature or pressure of the unreformed gas G2 to the control means 5.

  The second detection means 8 is provided in the middle of the reformed gas supply line L2. The second detection means 8 transmits the result of detecting the temperature or pressure of the reformed gas G3 to the control means 5.

Here, the terms “normal value” and “high setting value” of the ratio S / C used to describe the control means 5 will be described. FIG. 2 is a graph showing the relationship between the value of S / C and the amount of hydrogen or carbon monoxide produced. FIG. 3 is a graph showing the relationship between the S / C value and the selectivity (mol%) of each reaction product.
The normal value of S / C is high in hydrogen selectivity (ratio of hydrogen in the reaction product) when the equilibrium calculation of the steam reforming reaction is performed at various S / C values, and the unit It is determined as the S / C value that increases the amount of hydrogen produced per raw fuel gas.
On the other hand, the high setting value of S / C is the S / C value that can keep the selectivity of carbon low, although the hydrogen selectivity is lower than the normal value when the same equilibrium calculation is performed. As determined.

  Specifically, the normal value and the high set value of S / C are calculated by performing an equilibrium calculation of a steam reforming reaction at 800 ° C. between 1 kmol of methane, which is the raw fuel gas G1, and steam S1, and reacting with the value of S / C. It is determined based on the relationship between the amount of product produced and the relationship between the S / C value and the selectivity of the reaction product.

From the results shown in FIGS. 2 and 3, as the S / C value increases, the amount of hydrogen produced per unit raw fuel gas increases (see FIG. 2), but the hydrogen selectivity decreases (see FIG. 3). ). It can be seen that when the S / C value is less than 3, the increase in the carbon selectivity increases as the S / C value decreases, and carbon deposition tends to occur. On the other hand, when the S / C value is 3 or more, the carbon selectivity decreases as the S / C value increases.
Therefore, as a normal value of S / C, 2-3 is mentioned, for example, Preferably it is 2.5-3. On the other hand, as a high setting value of S / C, 3-7 are mentioned, for example, Preferably it is 5-6. When the normal value of S / C is within the above range, carbon is precipitated on the reforming catalyst, but hydrogen can be generated with a high yield using the reformer 2. Further, when the high set value of S / C is within the above range, the hydrogen selectivity is lowered, but the carbon deposited on the reforming catalyst can be removed by oxidation without interrupting the production of hydrogen. it can.

  Next, the operation of the fuel cell system according to one embodiment of the present invention will be described with reference to FIG.

  In step ST1 shown in FIG. 4, the control means 5 controls the raw fuel gas supply means 3 and the water vapor supply means 4 so that S / C becomes a normal value. Specifically, the control means 5 controls S / C to a normal value by controlling at least one of the supply amount of the raw fuel gas G1 by the raw fuel gas supply means 3 and the supply amount of the water vapor S1 by the water vapor supply means 4. Set to.

  In step ST2, the control means 5 determines the temperature difference or pressure between the unreformed gas G2 and the reformed gas G3 based on the temperature or pressure detected by the first detection means 7 and the second detection means 8. It is determined whether or not the difference is outside a predetermined range. In step ST2, when the control means 5 determines that the temperature difference or pressure difference is outside the predetermined range (YES), the process proceeds to step ST3. In step ST2, when the control means 5 determines that the temperature difference or pressure difference is not outside the predetermined range (NO), the process returns to step ST2.

  In step ST3, the control means 5 controls the raw fuel gas supply means 3 and the water vapor supply means 4 so that S / C becomes a high set value. Specifically, the control unit 5 sets S / C to a high level by controlling at least one of the supply amount of the raw fuel gas G1 by the raw fuel gas supply unit 3 and the supply amount of the water vapor S1 by the water vapor supply unit 4. Set to value.

  In step ST4, the control means 5 determines the temperature difference or pressure between the unreformed gas G2 and the reformed gas G3 based on the temperature or pressure detected by the first detection means 7 and the second detection means 8. It is determined whether or not the difference is within a predetermined range. In step ST4, when the control means 5 determines that the temperature difference or pressure difference is within a predetermined range (YES), the process returns to step ST1. In step ST4, when the control means 5 determines that the temperature difference or pressure difference is not within the predetermined range (NO), the process returns to step ST4.

  Here, the “predetermined range” in steps ST2 and ST4 will be described. The temperature difference or pressure difference between the unreformed gas G2 and the reformed gas G3 varies depending on the amount of carbon deposited on the reforming catalyst. That is, the steam reforming reaction is an endothermic reaction. However, when carbon is deposited on the reforming catalyst and the steam reforming reaction is less likely to occur, the endothermic amount is reduced and the temperature difference is reduced. Moreover, clogging occurs in the reforming catalyst due to the deposition of carbon, and it becomes difficult for gas to pass through the reforming catalyst. Therefore, the pressure of the unreformed gas G2 increases, and the pressure difference becomes larger. Therefore, the measured value of the temperature difference or pressure difference reflects the amount of carbon deposited on the reforming catalyst. In steps ST2 and ST4, examples of the predetermined range include the temperature difference or pressure difference range corresponding to the case where the amount of carbon deposited on the reforming catalyst is equal to or less than a predetermined threshold.

According to the fuel cell system 1 according to an embodiment of the present invention, for example, the following effects are exhibited.
As shown in FIG. 3, the smaller the value of S / C, the higher the hydrogen selectivity. Therefore, by operating the fuel cell system 1 with S / C set to a normal value, until the temperature difference or pressure difference between the unreformed gas G2 and the reformed gas G3 is outside a predetermined range. Power generation by the solid oxide fuel cell 6 can be performed with high efficiency while generating hydrogen with a high yield using the reformer 2. The carbon deposited on the reforming catalyst during that time is removed by oxidation after the temperature difference or pressure difference is outside the predetermined range and the S / C is switched from the normal value to the high set value. Compared with the case where the value of S / C is a normal value, when the value of S / C is a high setting value, the hydrogen selectivity is lowered, but hydrogen is generated, so that the solid oxide The carbon deposited on the reforming catalyst can be oxidized and removed without interrupting the power generation by the fuel cell 6.

  Thus, the fuel cell system 1 monitors whether carbon is actually deposited on the reforming catalyst based on the temperature difference or pressure difference between the unreformed gas G2 and the reformed gas G3. However, S / C switching can be performed. Therefore, even though the oxidative removal of carbon has been completed, the operation is continued with the S / C set to a high setting value, or the carbon deposited on the reforming catalyst still remains. The inconvenience of returning / C to the normal value can be solved.

  In FIG. 1, instead of using the first detection means 7 provided in the middle of the unreformed gas supply line L1, first detection means 7a (in the figure) provided in the middle of the raw fuel gas supply line L3. (It is not shown. It is a code | symbol for the convenience of description.), You may use the 1st detection means which consists of the 1st detection means 7b (not shown) provided in the middle of the water vapor | steam supply line L4. The first detection means 7a detects the temperature or pressure of the raw fuel gas G1, and the first detection means 7b detects the temperature or pressure of the water vapor S1. From the detection result of the temperature or pressure of the raw fuel gas G1 and the detection result of the temperature or pressure of the steam S1, the temperature or pressure of the unreformed gas G2, which is a mixed gas of the raw fuel gas G1 and the steam S1, is calculated. be able to. Thus, the first detection means may directly detect the temperature or pressure of the unreformed gas G2, or the detection result of the temperature or pressure of the raw fuel gas G1 and the detection result of the temperature or pressure of the steam S1. From the above, the temperature or pressure of the unreformed gas G2 may be detected by calculation.

  A plurality of high setting values of S / C may be set. Even if the fuel cell system 1 is operated at the lowest high setting value among a plurality of high setting values and the deposited carbon is removed by oxidation, after the predetermined time has elapsed, the unreformed gas G2 and the reformed gas G3 When the control means 5 determines that the temperature difference or pressure difference between them is not within the predetermined range, the fuel cell system 1 is operated by switching to a higher setting value, and the temperature difference or pressure difference is This operation may be repeated until the control means 5 determines that it is within the predetermined range.

[Reformer system]
A reformer system according to an embodiment of the present invention is a reformer system 10 shown in FIG. The reformer system 10 includes a reformer 2, raw fuel gas supply means 3, steam supply means 4, control means 5, first detection means 7, and second detection means 8. Included in the fuel cell system 1 according to an embodiment of the present invention.

[Operation method of fuel cell system]
According to the fuel cell system 1 according to an embodiment of the present invention, when the temperature difference or pressure difference between the unreformed gas G2 and the reformed gas G3 is within a predetermined range, S / C is normally set. When the temperature difference or the pressure difference is outside the predetermined range, the fuel cell system operating method can be implemented in which the S / C is set to a high set value.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 2 Reformer 3 Raw fuel gas supply means 4 Water vapor supply means 5 Control means 6 Solid oxide fuel cell 7 First detection means 8 Second detection means 10 Reformer system L1 Unreformed gas Supply line L2 Reformed gas supply line L3 Raw fuel gas supply line L4 Steam supply line

Claims (3)

A reformer that generates reformed gas G3 used as fuel for a solid oxide fuel cell by bringing unreformed gas G2 that is a mixed gas of raw fuel gas G1 and water vapor S1 into contact with a reforming catalyst. A reformer system comprising:
Raw fuel gas G1 supply means for supplying raw fuel gas G1 to the reformer;
Steam S1 supply means for supplying steam S1 to the reformer;
Control means for controlling the raw fuel gas G1 supply means and the water vapor S1 supply means;
First detection means for detecting the temperature or pressure of the unreformed gas G2,
Second detection means for detecting the temperature or pressure of the reformed gas G3;
With
Based on the temperature or pressure detected by the first and second detection means, the control means has a temperature difference or pressure difference between the unreformed gas G2 and the reformed gas G3 within a predetermined range. In this case, the ratio S / C between the amount S of the steam S1 supplied to the reformer and the amount C of the raw fuel gas G1 supplied to the reformer becomes a normal value, and the temperature difference or When the pressure difference is outside the predetermined range, the raw fuel gas G1 supply means and the steam S1 supply means are controlled so that S / C becomes at least one high set value higher than the normal value. Reformer system. A reformer that generates reformed gas G3 by bringing unreformed gas G2 that is a mixed gas of raw fuel gas G1 and water vapor S1 into contact with a reforming catalyst, and solid oxidation that uses the reformed gas G3 as fuel A fuel cell system comprising a physical fuel cell,
Raw fuel gas G1 supply means for supplying raw fuel gas G1 to the reformer;
Steam S1 supply means for supplying steam S1 to the reformer;
Control means for controlling the raw fuel gas G1 supply means and the water vapor S1 supply means;
First detection means for detecting the temperature or pressure of the unreformed gas G2,
Second detection means for detecting the temperature or pressure of the reformed gas G3;
With
Based on the temperature or pressure detected by the first and second detection means, the control means has a temperature difference or pressure difference between the unreformed gas G2 and the reformed gas G3 within a predetermined range. In this case, the ratio S / C between the amount S of the steam S1 supplied to the reformer and the amount C of the raw fuel gas G1 supplied to the reformer becomes a normal value, and the temperature difference or When the pressure difference is outside the predetermined range, the raw fuel gas G1 supply means and the steam S1 supply means are controlled so that S / C becomes at least one high set value higher than the normal value. Fuel cell system. A reformer that generates reformed gas G3 by bringing unreformed gas G2 that is a mixed gas of raw fuel gas G1 and water vapor S1 into contact with a reforming catalyst, and solid oxidation that uses the reformed gas G3 as fuel A fuel cell system comprising a physical fuel cell, comprising:
When the temperature difference or pressure difference between the unreformed gas G2 and the reformed gas G3 is within a predetermined range, the amount S of steam S1 supplied to the reformer and the reformer The ratio S / C with the amount C of the raw fuel gas G1 supplied to is set to a normal value, and when the temperature difference or the pressure difference is outside the predetermined range, the S / C is set to be lower than the normal value. An operation method in which at least one high set value is set.

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