JP2014229482A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system capable of preventing the S/C from becoming excessive in a fuel cell, while avoiding carbon deposition.SOLUTION: A fuel cell system includes a fuel reformer 44 generating fuel gas by reforming a hydrocarbon-based fuel by using steam, an internal reforming type fuel cell 10 outputting electric energy by electrochemical reaction of fuel gas and oxidant gas, and capable of internally generating fuel gas by reforming the fuel, fuel supply piping 4 for introducing fuel to the fuel reformer 44, water supply piping 5 for supplying steam to the fuel reformer 44, a water pump 52 provided in the water supply piping 5 and adjusting steam supply to the fuel reformer 44 so that the molar ratio of steam to carbon in the fuel supplied to the fuel reformer 44 is a predetermined reference value less likely to cause carbon deposition or more, and bypass piping 6 for introducing fuel directly to the fuel cell 10 without going through the fuel reformer 44.

Description

  The present invention relates to a fuel cell system including a fuel cell that outputs electric energy by an electrochemical reaction between a fuel gas and an oxidant gas.

  2. Description of the Related Art Conventionally, a fuel cell system including a solid oxide fuel cell (SOFC) includes a fuel reformer that reforms a hydrocarbon-based fuel (for example, methane) into fuel gas using water vapor (external modification). A quality type system) is known (for example, see Patent Document 1).

JP 2011-238363 A

  By the way, in steam reforming, as the carbon number of the hydrocarbon fuel increases, carbon tends to be deposited on the reforming catalyst during the reforming reaction. Carbon deposition in the fuel reformer is not preferable because it causes deterioration of catalyst performance and blockage of a supply path of fuel and the like.

  For this reason, in a general fuel cell system, the molar ratio (S / C: steam / carbon) of water vapor to carbon in the fuel supplied to the fuel reformer is a reference value (for example, 3) or more where carbon deposition hardly occurs. It is desirable that

  However, in the external reforming system, if the molar ratio (S / C) of water vapor to carbon in the fuel supplied to the fuel reformer is 3 or more, the water vapor to carbon in the fuel flowing into the fuel cell There is a problem that the molar ratio becomes excessive.

Explaining this point, in the fuel reformer, as shown by the following reaction formula, only about twice as much steam (H ₂ O) as that of the fuel (CH ₄ ) is consumed, and the fuel reformer This is because the amount of water vapor increases compared to the fuel that flows in.
CH ₄ + 2H ₂ O → CO ₂ + 4H ₂
For example, when the supply amount B1 of water vapor to the fuel reformer is set to about three times the supply amount A1 of fuel (B1≈3 × A1), and half of the supply amount A1 of fuel to the fuel reformer is consumed. Then, the inflow amount A2 of fuel that flows into the fuel cell without being consumed by the fuel reformer becomes about half of A1 (A2≈A1 / 2).

  On the other hand, if the supply amount B1 of water vapor to the fuel reformer is about twice as much as the supply amount A1 of fuel, the inflow amount B2 of water vapor that flows into the fuel cell without being consumed by the fuel reformer is , About “B1-2 × A2”. That is, the inflow amount B2 of water vapor flowing into the fuel cell is about four times the inflow amount A2 of fuel flowing into the fuel cell (B2≈4 × A2, S / C≈4).

  Excessive S / C in the fuel cell is not preferable because water vapor that does not contribute to power generation in the fuel cell causes a decrease in the Nernst voltage of the fuel cell and causes a reduction in power generation efficiency of the system.

  An object of the present invention is to provide a fuel cell system capable of suppressing S / C from becoming excessive in a fuel cell while avoiding carbon deposition.

  In order to achieve the above object, according to the first aspect of the present invention, a fuel reformer (44) for reforming a hydrocarbon-based fuel using steam to generate a fuel gas, and a fuel gas and an oxidant gas An internal reforming type fuel cell (10) capable of generating fuel gas internally by reforming the fuel, and a first fuel supply for guiding the fuel to the fuel reformer The molar ratio of water vapor to carbon in the fuel provided in the path (4), the water supply path (5) for supplying the steam to the fuel reformer, and the water supply path, and the fuel in the fuel reformer is carbon deposition. The water amount adjusting means (52) for adjusting the amount of water vapor supplied to the fuel reformer so as to be equal to or higher than a predetermined reference value, and the fuel is directly guided to the fuel cell without going through the fuel reformer. And a second fuel supply path (6).

  As described above, when the fuel is allowed to flow into the fuel cell through the second fuel supply path while ensuring a sufficient amount of water vapor that is unlikely to cause carbon deposition in the fuel reformer, the fuel is supplied to the fuel cell. The amount of inflow can be increased. Thereby, it can suppress that the molar ratio (S / C) of the water vapor which flows into the fuel cell with respect to the carbon in the fuel which flows into the fuel cell becomes excessive. In addition, by supplying the fuel directly to the fuel cell, it is possible to promote internal reforming of the fuel cell by using water vapor that flows into the fuel cell without being consumed by the fuel reformer.

  According to a second aspect of the present invention, in the fuel cell system according to the first aspect, the fuel adjusting means (61, 63) for adjusting the amount of fuel flowing into the fuel cell via the second fuel supply path. And a reforming temperature detecting means (44a) for detecting the temperature of the fuel reformer, and a control means (100) for controlling the fuel adjusting means in accordance with the temperature detected by the reforming temperature detecting means. The second fuel adjustment means is controlled so that the amount of fuel flowing into the fuel cell through the second fuel supply path increases as the temperature detected by the reforming temperature detection means increases. .

  Thus, if the configuration is such that the amount of fuel flowing into the fuel cell via the second fuel supply path is increased in accordance with the rise in the reforming temperature, the fuel cell with respect to carbon in the fuel flowing into the fuel cell. It can suppress more appropriately that the molar ratio (S / C) of the water vapor which flows into the water becomes excessive.

  In addition, the code | symbol in the parenthesis of each means described in this column and the claim shows an example of a correspondence relationship with the specific means described in the embodiment described later.

1 is an overall configuration diagram of a fuel cell system according to a first embodiment. It is a figure which shows the arrangement | positioning form of the fuel reformer which concerns on 1st Embodiment. It is a characteristic view which shows the correlation characteristic of the reforming temperature and reforming rate in a fuel reformer. It is a characteristic view which shows the correlation characteristic of S / C and OCV. It is a figure which shows the arrangement | positioning form of the fuel reformer which concerns on 2nd Embodiment. It is a whole block diagram of the fuel cell system which concerns on 3rd Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, the same or equivalent parts are denoted by the same reference numerals.
(First embodiment)
A first embodiment will be described with reference to the drawings. As shown in FIG. 1, the fuel cell system 1 includes a solid oxide fuel cell (SOFC) 10 whose operating temperature is high (for example, 500 ° C. to 1000 ° C.). For convenience of explanation, in FIG. 1, the fuel cell 10 is illustrated as a single power generation cell 10a.

  The fuel cell 10 of this embodiment has a stack structure in which a plurality of power generation cells 10a that output electric energy by an electrochemical reaction of a fuel gas and an oxidant gas (air in this embodiment) are stacked via separators 14 and 15. It has become. The cell shape of the power generation cell 10a may be either a flat plate type or a cylindrical type.

Each power generation cell 10 a includes a solid oxide electrolyte 11, an air electrode (cathode) 12, and a fuel electrode (anode) 13. The power generation cell 10a of the present embodiment uses hydrogen (H ₂ ) generated by reforming methane (CH ₄ ), which is a hydrocarbon fuel, and carbon monoxide (CO) as fuel gases. The fuel to be used may be other than methane as long as it is a hydrocarbon-based fuel.

  Here, the fuel electrode 13 of the power generation cell 10a includes nickel (Ni) that functions as a reforming catalyst. That is, the fuel cell 10 of the present embodiment is configured by an internal reforming type fuel cell that can reform fuel using nickel contained in the fuel electrode 13 as a reforming catalyst to generate fuel gas therein.

  The separators 14 and 15 have functions of electrically connecting the power generation cells 10a and supplying a reaction gas such as a fuel gas and an oxidant gas to the power generation cells 10a. The separators 14 and 15 are formed with a fuel gas passage (not shown) for supplying fuel gas to each power generation cell 10a and an air passage (not shown) for supplying air to each power generation cell 10a.

In each power generation cell 10a, electric energy is output by an electrochemical reaction of hydrogen and oxygen represented by the following reaction formulas [Chemical Formula 1] and [Chemical Formula 2].
(Fuel ^{_{electrode) 2H 2 + 2O 2- → 2H}} 2 O + 4e - ··· [ Formula 1]
(Air electrode) O ₂ + 4e ⁻ → 2O ²⁻ ..
In each power generation cell 10a, electric energy is output by an electrochemical reaction of carbon monoxide (CO) and oxygen represented by the following reaction formulas [Chemical Formula 3] and [Chemical Formula 4].
(Fuel _{^{electrode) 2CO + 2O 2- → 2CO 2}} + 4e - ··· [ of 3]
(Air electrode) O ₂ + 4e ⁻ → 2O ²⁻ .
An air supply pipe 3 that is an air supply path is connected to the air inlet side of the fuel cell 10. The air supply pipe 3 is provided with an air filter 31 that removes dust and the like, an air blower 32 that pumps air to the fuel cell 10, and an air preheater 33 in order from the upstream side.

  The air preheater 33 of the present embodiment heats the air pressure-fed from the air blower 32 by exchanging heat with combustion gas generated by a combustor 71 described later. The air preheater 33 reduces the temperature difference between the air supplied to the air electrode 12 of the fuel cell 10 and the high-temperature fuel gas supplied to the fuel electrode 13 to improve the power generation efficiency in each power generation cell 10a. Is provided.

  On the other hand, a fuel supply pipe 4 that is a fuel gas and fuel supply path is connected to the fuel gas and fuel inlet side of the fuel cell 10. The fuel supply pipe 4 includes, in order from the upstream side, a desulfurizer 41 that removes sulfur components contained in the fuel, a fuel pump 42 that pumps fuel to the fuel cell 10 side, a fuel preheater 43, and a fuel reformer 44. Is provided.

  The fuel preheater 43 heats the fuel pumped from the fuel pump 42 by exchanging heat with a combustion gas generated by a combustor 71 described later in order to promote the reforming reaction in the fuel reformer 44. .

The fuel reformer 44 heats the mixed gas, which is a mixture of the fuel heated by the fuel preheater 43 and water vapor, with heat exchange with the combustion gas, and performs a reforming reaction represented by the following reaction formula [Chem. 5]: The fuel gas (hydrogen, carbon monoxide) is generated by the shift reaction shown in the reaction formula [Chem. 6].
CH ₄ + H ₂ O → CO + H ₂ ..
CO + H ₂ O → CO ₂ + H ₂ [Chemical 6]
The fuel reformer 44 is connected to the water supply pipe 5 and is supplied with water vapor generated by the vaporizer 53 provided in the water supply pipe 5.

  Here, the water supply pipe 5 will be described. The water supply pipe 5 constitutes a water supply path for supplying water vapor to the fuel reformer 44. The water supply pipe 5 is provided with a pure water device 51, a water pump 52, and a vaporizer 53 in order from the upstream side, and the outlet side of the vaporizer 53 is connected to the fuel reformer 44. The water pump 52 supplies water vapor to the fuel reformer 44 via the vaporizer 53, and the vaporizer 53 uses the water supplied from the water pump 52 via the pure water device 51 as combustion gas and heat. It is an evaporator that exchanges and evaporates.

  Further, as shown in FIG. 2, the fuel reformer 44 of the present embodiment is disposed around the fuel cell 10 so as to absorb heat (radiant heat) released to the surroundings when the fuel cell 10 generates power. Has been. The fuel reformer 44 is constituted by a radiant heat type heat exchanger that can heat the fuel that has absorbed heat from the surroundings and circulated therethrough.

  The steam reforming in the fuel reformer 44 is an endothermic reaction, and has a characteristic that the reforming rate F (T) is improved under high temperature conditions as shown in FIG. The reforming rate F (T) is the ratio of the fuel used for steam reforming out of the entire supplied fuel.

  As in the present embodiment, the reforming rate F (T) of the fuel reformer 44 is increased by arranging the fuel reformer 44 in a high temperature environment capable of absorbing radiant heat generated during power generation of the fuel cell 10. Improvements can be made.

  Returning to FIG. 1, the fuel supply pipe 4 of the present embodiment is connected to a bypass pipe 6 that guides the fuel heated by the fuel preheater 43 to the fuel cell 10 without going through the fuel reformer 44. The bypass pipe 6 has an upstream side connected to a branch portion 4A provided between the fuel preheater 43 and the fuel reformer 44 in the fuel supply pipe 4 and a downstream side connected to the fuel reformer 44 in the fuel supply pipe 4. The fuel cell 10 is connected to a merging portion 4B provided between the fuel cell 10 and the fuel inlet side.

  The bypass pipe 6 of the present embodiment is provided to be branched from the fuel supply pipe 4, and a part of the fuel pressure-fed from the fuel pump 42 provided in the fuel supply pipe 4 is connected to the fuel cell via the bypass pipe 6. 10 is configured to flow in. According to this, the fuel pump 42 for supplying the fuel can be constituted by a single fuel supply means, and the fuel cell system 1 can be simplified.

  Further, the bypass pipe 6 of the present embodiment is provided with a fuel adjustment valve 61 that adjusts the amount of fuel flowing directly into the fuel cell 10 via the bypass pipe 6. The fuel adjustment valve 61 is composed of an electromagnetic valve that increases or decreases the passage opening of the bypass pipe 6 in accordance with a control signal from the control device 100 described later.

  In this embodiment, the fuel supply pipe 4 constitutes a first fuel supply path that leads the fuel to the fuel reformer 44, and the bypass pipe 6 serves as a second fuel supply path that leads the fuel directly to the fuel cell 1. It is composed. Further, the fuel adjustment valve 61 constitutes fuel adjustment means for adjusting the amount of fuel flowing into the fuel cell 10 via the bypass pipe 6.

  A reforming temperature sensor 44 a for detecting the reforming temperature T in the fuel reformer 44 is provided on the fuel gas outlet side of the fuel reformer 44. In the present embodiment, the reforming temperature sensor 44a constitutes a reforming temperature detecting means. The arrangement of the reforming temperature sensor 44 a is not limited to the fuel gas outlet side in the fuel reformer 44. For example, the reforming temperature sensor 44 a may be disposed on the surface of the fuel reformer 44 and the surface temperature of the fuel reformer 44 may be detected as the reforming temperature T.

  An air discharge path 7 a through which discharged air (oxidant gas off-gas) from the fuel cell 10 flows is connected to the air outlet side of the fuel cell 10, and discharged fuel ( A fuel discharge path 7b through which fuel gas (off gas) flows is connected. Each discharge path 7a, 7b is connected to a combustor 71.

  The combustor 71 burns a mixed gas, which is a mixture of exhaust fuel and exhaust air, as combustible gas, so that the combustor 71 is used as a heat source for preheating the air and fuel gas supplied to the fuel cell 10 (for example, 900 ° C.). ˜1000 ° C.).

  The combustor 71 is connected to a combustion gas path 7 for discharging high-temperature combustion gas. This combustion gas path 7 is connected to devices such as a fuel reformer 44, an air preheater 33, a carburetor 53, and a fuel preheater 43 in order from the upstream side in order to effectively use the heat of the combustion gas flowing inside. . Although not shown, a heat exchanger for heating hot water is provided on the downstream side of the fuel preheater 43 in the combustion gas path 7 so that the hot water is heated by the heat of the combustion gas. It has become. In addition, you may change the order which flows combustion gas to each apparatus 33, 43, 44, 53 according to the calorie | heat amount etc. which are required in each apparatus.

  Next, the control apparatus 100 which comprises the electronic control part in the fuel cell system 1 is demonstrated. The control device 100 includes a well-known microcomputer composed of storage means such as a CPU, ROM, and RAM, and its peripheral circuits. The control device 100 constitutes a control unit that performs various calculations and processes based on a control program stored in the storage unit and controls operations of various control devices connected to the output side.

  Various sensors such as a reforming temperature sensor 44 a are connected to the input side of the control device 100, and detection results of the various sensors are input to the control device 100.

  On the other hand, an air blower 32, a fuel pump 42, a water pump 52, a fuel adjustment valve 61, and the like are connected to the output side of the control device 100 as control devices. The operation of these control devices is controlled according to a control signal output from the control device 100.

  Here, when the molar ratio (S / C) of water vapor to carbon in the fuel supplied to the fuel reformer 44 is small, the inside of the fuel reformer 44 is caused by a thermal decomposition reaction of fuel, carbon monoxide or the like. Carbon deposition may occur. Specifically, carbon deposition tends to occur in a situation where water vapor is insufficient and reforming reaction or shift reaction is difficult to proceed inside the fuel reformer 44.

  For this reason, the control device 100 according to the present embodiment operates the water pump 52 so that the molar ratio of water vapor to carbon in the fuel supplied to the fuel reformer 44 is equal to or higher than a predetermined reference value at which carbon deposition hardly occurs. Is controlling. In the present embodiment, the configuration for controlling the water pump 52 and the water pump 52 in the control device 100 constitutes a water amount adjusting means for adjusting the amount of water vapor supplied to the fuel reformer 44.

The “predetermined reference value at which carbon deposition is unlikely to occur” refers to the mole of water vapor relative to the carbon in the fuel supplied to the fuel reformer 44 that is required to establish a reforming reaction or shift reaction that generates fuel gas. It is set to a value (for example, 3) obtained by adding a margin to the necessary minimum value of the ratio. Since the steam has a function of advancing the gasification reaction of carbon (C + H ₂ O → CO + H ₂ ) in the fuel reformer 44, the fuel reforming can be performed by adding a margin to the above-mentioned necessary minimum value. Carbon deposition in the vessel 44 can be appropriately avoided.

  Specifically, the control device 100 controls the water pump 52 so that the amount of water vapor supplied to the fuel reformer 44 is about three times the amount of fuel supplied to the fuel reformer 44. The number of revolutions is controlled. Note that the amount of fuel supplied to the fuel reformer 44 can be determined from the number of revolutions of the fuel pump 42 and the control signal to the fuel adjustment valve 61.

  Here, as shown in FIG. 4, the fuel cell 10 has a characteristic that the open circuit voltage OCV increases as the molar ratio of water vapor to carbon in the fuel flowing into the fuel cell 10 decreases, and high output is obtained. Therefore, it is necessary to suppress the molar ratio of water vapor to carbon in the fuel.

  However, if the operation of the water pump 52 is controlled so that the molar ratio of water vapor to carbon in the fuel supplied to the fuel reformer 44 becomes a value at which carbon deposition is unlikely to occur, the carbon in the fuel flowing into the fuel cell 10 is controlled. The molar ratio of water vapor to water becomes excessive.

  Further, according to the research conducted by the present inventors, the molar ratio of water vapor to carbon in the fuel flowing into the fuel cell 10 increases the reforming rate F (T) due to the high temperature of the fuel reformer 44. It turned out that it becomes remarkably large with conditions.

  Hereinafter, this point will be described with reference to FIG. In FIG. 2, “A1” is the amount of fuel supplied to the fuel reformer 44, “B1” is the amount of steam supplied, and “A2” is the fuel flowing into the fuel cell 10 via the fuel reformer 44. “B2” indicates the inflow amount of water vapor.

Further, the fuel reforming rate in the fuel reformer 44 is “F (T)”, and the ratio of the steam consumed for steam reforming to the fuel consumed in the fuel reformer 44 is “β”. In the fuel reformer 44, as shown in the following reaction formula [Chem. 7], about twice as much steam (H ₂ O) is consumed as fuel (CH ₄ ), so “β” is The value is about “2”.
CH ₄ + 2H ₂ O → CO ₂ + 4H ₂ [Chemical 7]
The molar ratio α of water vapor to carbon in the fuel supplied to the fuel reformer 44 satisfies the relationship represented by the following relational expression [Equation 1].
α = B1 / A1 [Equation 1]
Further, the amount of fuel consumed in the fuel reformer 44 is “A1 × F (T)”, so that it is not consumed by the fuel reformer 44 and flows into the fuel cell 10 via the fuel reformer 44. The fuel inflow amount “A2” can be defined by the following relational expression [Equation 2].
A2 = A1−A1 × F (T) (Equation 2)
On the other hand, since the consumption amount of water vapor in the fuel reformer 44 is “(A1-A2) × β”, it is not consumed in the fuel reformer 44 and is sent to the fuel cell 10 via the fuel reformer 44. The inflow amount “B2” of the inflowing steam can be defined by the following relational expression [Formula 3].
B2 = B1− (A1−A2) × β (Equation 3)
Summarizing the above [Expression 1] to [Expression 3], the ratio of the inflow amount of water vapor to the inflow amount of fuel flowing into the fuel cell 10 via the fuel reformer 44 is expressed by the following relational expression [Expression 4]. The relationship indicated by is established.
B2 / A2 = [beta] + ([alpha]-[beta]) / (1-F (T)) [Equation 4]
According to this relational expression [Equation 4], when the reforming rate F (T) of the fuel reformer 44 is high, the mole of water vapor relative to carbon in the fuel flowing into the fuel cell 10 via the fuel reformer 44. The ratio becomes excessive.

  On the other hand, in this embodiment, since the fuel is directly guided to the fuel cell 10 via the bypass pipe 6, the molar ratio of water vapor to carbon in the fuel flowing into the fuel cell 10 is excessive. Can be suppressed.

  Specifically, if the inflow amount of the fuel flowing into the fuel cell 10 via the bypass pipe 6 is “A3”, the ratio of the inflow amount of water vapor to the inflow amount of fuel flowing into the fuel cell 1 is “B2 / (A2 + A3) ". That is, by allowing the fuel to flow into the fuel cell 10 via the bypass pipe 6, the molar ratio of water vapor to carbon in the fuel flowing into the fuel cell 10 can be reduced.

  Here, the reforming rate F (T) of the fuel reformer 44 has a characteristic that it increases as the reforming temperature T of the fuel reformer 44 increases as described above. According to the relational expression [Equation 4], the ratio of the inflow amount “B2” of the steam to the inflow amount “A2” of the fuel flowing into the fuel cell 10 via the fuel reformer 44 is as follows. As the reforming rate F (T) increases, it significantly increases.

  Therefore, in the control device 100 of the present embodiment, the inflow amount “A3” of the fuel flowing into the fuel cell 10 via the bypass pipe 6 increases as the reforming temperature T of the fuel reformer 44 increases. In addition, the fuel adjustment valve 61 is controlled. Specifically, the control device 100 controls the fuel adjustment valve 61 so that the passage opening degree of the bypass pipe 6 increases as the temperature detected by the reforming temperature sensor 44a increases.

  Meanwhile, in the fuel cell 10, as shown in the reaction formula [Chemical Formula 1], water is generated by an electrochemical reaction of hydrogen and oxygen, so that carbon deposition is less likely to occur than in the fuel reformer 44.

  However, if the amount of fuel flowing into the fuel cell 10 via the bypass pipe 6 becomes excessive and the molar ratio of water vapor to carbon in the fuel flowing into the fuel cell 10 becomes too small, the carbon inside the fuel cell 10 is reduced. Precipitation is a concern.

For this reason, it is desirable to adjust the amount of fuel flowing into the fuel cell 10 via the bypass pipe 6 within a range satisfying the following relational expression [Equation 5], for example.
B2 / (A2 + A3)> 2 (Equation 5)
Next, the overall operation of the fuel cell system 1 according to the above configuration will be described. When the operation of the fuel cell system is started by a control command from an external controller (not shown), the control device 100 outputs a control signal instructing each control device to start operation.

  As a result, in the air supply pipe 3, after the air pressure-fed by the air blower 32 is heated to a desired temperature by the air preheater 33, the heated air is supplied to the fuel cell 10. .

  On the other hand, in the fuel supply pipe 4, the fuel supplied from the fuel pump 42 is heated to a desired temperature by the fuel preheater 43 and then mixed with the water vapor generated by the vaporizer 53 inside the fuel reformer 44. At the same time, it is reformed into fuel gas by steam reforming and supplied to the fuel cell 10.

  At this time, in addition to the fuel gas, a part of the fuel heated to a desired temperature by the fuel preheater 43 is supplied to the fuel cell 10 through the bypass pipe 6. The fuel supplied via the bypass pipe 6 is reformed into fuel gas by steam reforming inside the fuel cell 10.

  When fuel gas and air are supplied, the fuel cell 10 outputs electric energy by the electrochemical reaction shown in the above reaction formulas [Chemical Formula 1] to [Chemical Formula 4] using hydrogen and carbon monoxide as fuel gas.

  Each off-gas discharged from the fuel cell 10 is supplied to the combustor 71 through the discharge paths 7a and 7b. Each off gas supplied to the combustor 71 is combusted in the combustor 71. Thereafter, the high-temperature combustion gas generated in the combustor 71 flows to the fuel reformer 44, the air preheater 33, the vaporizer 53, and the fuel preheater 43 via the combustion gas path 7, and serves as a heat source in each device. It is discharged outside after being used.

  In the fuel cell system 1 of the present embodiment described above, the fuel reformer is configured so that the molar ratio of water vapor to carbon in the fuel supplied to the fuel reformer 44 is equal to or higher than a predetermined reference value at which carbon deposition is difficult to occur. The supply amount of water vapor to 44 is adjusted. For this reason, it is possible to secure an amount of water vapor that is unlikely to cause carbon deposition in the fuel reformer 44 and to suppress carbon deposition in the fuel reformer 44.

  In addition, in this embodiment, the fuel is directly introduced into the fuel cell 10 via the bypass pipe 6. Thereby, since the inflow amount of the fuel flowing into the fuel cell 10 increases, the molar ratio (S / C) of the water vapor flowing into the fuel cell 10 to the carbon in the fuel flowing into the fuel cell 10 becomes excessive. Can be suppressed. In addition, by supplying the fuel directly to the fuel cell 10, it is possible to promote internal reforming of the fuel cell 10 by using the water vapor that flows into the fuel cell 10 without being consumed by the fuel reformer 44. It becomes.

  Here, when the fuel supply amount in the entire system is constant, a part of the fuel bypasses the fuel reformer 44 via the bypass pipe 6, so that the fuel supply amount to the fuel reformer 44 is reduced. Therefore, the amount of water vapor supplied to the fuel reformer 44 can be reduced. As a result, the amount of heat required for generating water vapor can be reduced, so that the vaporizer 53 can be downsized.

  In the present embodiment, as the reforming rate F (T) in the fuel reformer 44 increases, the molar ratio of water vapor flowing into the fuel cell 10 to carbon in the fuel flowing into the fuel cell 10 becomes excessive. In view of this, the control apparatus 100 performs the following control. That is, the control device 100 controls the fuel adjustment valve 61 so that the amount of fuel flowing into the fuel cell 10 via the bypass pipe 6 increases as the temperature detected by the reforming temperature sensor 44a increases. .

  In this way, if the configuration is such that the amount of fuel flowing into the fuel cell 10 via the bypass pipe 6 increases as the reforming temperature T rises, the fuel cell for carbon in the fuel flowing into the fuel cell 10 It can suppress more appropriately that the molar ratio of the water vapor which flows into is excessive.

  In the present embodiment, the fuel reformer 44 is disposed around the fuel cell 10 so that the heat released from the fuel cell 10 can be absorbed. According to this, the reforming rate F (T) in the fuel reformer 44 can be improved by effectively utilizing the radiant heat from the fuel cell 10.

(Second Embodiment)
Next, a second embodiment will be described. In the present embodiment, description of the same or equivalent parts as in the first embodiment will be omitted or simplified.

  In the present embodiment, as shown in FIG. 5, the fuel reformer 44 is disposed adjacent to the combustor 71 so that the heat released from the combustor 71 can be directly absorbed. More specifically, the fuel reformer 44 is disposed so that the combustor 71 comes into contact with the side surface of the fuel reformer 44 opposite to the facing surface facing the fuel cell 10.

  According to this, the temperature of the fuel reformer 44 can be more effectively increased by the heat released from the combustor 71 in addition to the heat released from the fuel cell 10. Thereby, it is possible to further improve the reforming rate F (T) in the fuel reformer 44 by effectively utilizing the radiant heat from the fuel cell 10 and the heat of the combustor 71.

(Third embodiment)
Next, a third embodiment will be described. In the present embodiment, description of the same or equivalent parts as in the first and second embodiments will be omitted or simplified.

  In the present embodiment, as shown in FIG. 6, the bypass pipe 6 is not branched from the fuel supply pipe 4, and the sub-desulfurizer 62 and the sub-pump 63 are provided in the bypass pipe 6. That is, in the present embodiment, the fuel pumped from the sub pump 63 provided in the bypass pipe 6 flows into the fuel cell 10 via the bypass pipe 6.

  In the present embodiment, the amount of fuel flowing into the fuel cell 10 via the bypass pipe 6 is adjusted by changing the rotation speed of the sub pump 63. For this reason, in this embodiment, the sub pump 63 comprises the fuel adjustment means.

  Other configurations and operations are the same as those in the first embodiment. According to the configuration of this embodiment, in addition to the effects described in the first embodiment, the following effects can be obtained. That is, in this embodiment, since the dedicated sub pump 63 is added, the inflow of the fuel flowing into the fuel cell 10 through the bypass pipe 6 without changing the amount of fuel supplied to the fuel reformer 44. The amount can be easily adjusted.

  In the present embodiment, the fuel preheater 43 and the carburetor 53 may be integrally configured so as to simplify the fuel cell system 1.

(Other embodiments)
As mentioned above, although embodiment of this invention was described, this invention is not limited to the above-mentioned embodiment, In the range described in the claim, it can change suitably. For example, various modifications are possible as follows.

  (1) Although it is desirable to arrange the fuel reformer 44 around the fuel cell 10 so that the radiant heat from the fuel cell 10 can be absorbed as in the first embodiment described above, the present invention is not limited to this. When there is another heat source that raises the temperature of the fuel reformer 44, the fuel reformer 44 may be disposed outside the periphery of the fuel cell 10.

  (2) In the first embodiment described above, the example in which the upstream side of the bypass pipe 6 is connected between the fuel preheater 43 and the fuel reformer 44 in the fuel supply pipe 4 has been described, but the present invention is not limited to this. For example, the upstream side of the bypass pipe 6 may be connected between the fuel pump 42 and the fuel preheater 43 in the fuel supply pipe 4. In this case, the fuel preheater 43 and the carburetor 53 may be integrally configured to simplify the fuel cell system 1.

  (3) In the first embodiment described above, the example in which the fuel adjustment means is configured by the fuel adjustment valve 61 provided in the bypass pipe 6 has been described, but the present invention is not limited to this. For example, an electric three-way valve capable of adjusting the opening of the passage may be disposed in either the branching section 4A or the merging section 4B, and the three-way valve may function as the fuel adjusting means.

  (4) Although it is desirable to adjust the amount of fuel flowing into the fuel cell 1 in accordance with the reforming temperature T of the fuel reformer 44 as in the above-described embodiments, the reforming of the fuel reformer 44 Regardless of the temperature T, the amount of fuel flowing into the fuel cell 1 may be adjusted. For example, the amount of fuel supplied to the fuel reformer 44 and the fuel can be reduced by arranging a fixed throttle in the bypass pipe 6 or reducing the passage cross-sectional area of the bypass pipe 6 to be smaller than that of the fuel supply pipe 4. You may make it adjust the balance with the inflow amount of the fuel which flows in into the battery 1. FIG.

  (5) In each of the above-described embodiments, the example using the solid oxide fuel cell that operates at a high temperature as the fuel cell 10 has been described. However, the present invention is not limited thereto. A salt type fuel cell may be used.

  (6) The above-described embodiments are not irrelevant to each other, and can be appropriately combined unless the combination is clearly impossible.

  (7) In each of the above-described embodiments, elements constituting the embodiment are not necessarily indispensable unless specifically indicated as essential and clearly considered essential in principle. Needless to say.

  (8) In each of the above-described embodiments, when numerical values such as the number, numerical value, quantity, range, etc. of the constituent elements of the embodiment are mentioned, the specific number is clearly specified when clearly indicated as essential. It is not limited to the specific number except when limited to.

  (9) In each of the above-described embodiments, when referring to the shape, positional relationship, etc. of the constituent elements, etc., unless specifically stated or limited in principle to a specific shape, positional relationship, etc. It is not limited to shape, positional relationship, and the like.

10 Fuel cell 4 Fuel supply pipe (first fuel supply path)
5 Water supply piping (water supply route)
52 Water pump (water volume adjustment means)
7 Bypass piping (second fuel supply route)

Claims (4)

A fuel reformer (44) for reforming a hydrocarbon-based fuel using steam to generate fuel gas;
An internal reforming type fuel cell (10) capable of generating electrical energy by outputting electric energy by electrochemical reaction of the fuel gas and oxidant gas, and reforming the fuel to generate the fuel gas internally;
A first fuel supply path (4) for guiding the fuel to the fuel reformer;
A water supply path (5) for supplying the water vapor to the fuel reformer;
The fuel reformer is provided in the water supply path so that a molar ratio of the water vapor to carbon in the fuel supplied to the fuel reformer is equal to or higher than a predetermined reference value at which carbon deposition is difficult to occur. A water amount adjusting means (52) for adjusting the supply amount of the water vapor;
A second fuel supply path (6) for directing the fuel to the fuel cell without going through the fuel reformer;
A fuel cell system comprising: Fuel adjusting means (61, 63) for adjusting an inflow amount of the fuel flowing into the fuel cell via the second fuel supply path;
Reforming temperature detecting means (44a) for detecting the temperature of the fuel reformer;
Control means (100) for controlling the fuel adjusting means according to the temperature detected by the reforming temperature detecting means,
The control means controls the fuel adjustment means so that the amount of the fuel flowing into the fuel cell through the second fuel supply path increases as the temperature detected by the reforming temperature detection means increases. The fuel cell system according to claim 1, wherein the fuel cell system is controlled.   3. The fuel cell system according to claim 1, wherein the fuel reformer is disposed around the fuel cell so as to absorb heat released from the fuel cell. 4. A combustor (71) for combusting combustible gas to generate high-temperature combustion gas;
4. The fuel reformer according to claim 1, wherein the fuel reformer is disposed adjacent to the combustor so as to absorb heat released from the combustor. 5. Fuel cell system.

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