JP2015109149A - Solid oxide type fuel cell and shutdown and storage method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid oxide type fuel cell capable of maintaining a performance of a desulfurizer in the case of storage after stopping power generation while ensuring cost reduction and energy loss reduction.SOLUTION: The solid oxide type fuel cell includes: a modifier 1 which performs water vapor modification on raw material gas to produce fuel gas; a desulfurizer 2 provided in the middle of a raw material gas supply path 7 at an upstream side of the modifier 1; an evaporator 3 that is provided in the middle of the raw material gas supply path 7 at the upstream side of the modifier and a downstream side of the desulfurizer 2, evaporates water supplied through a water supply path 20 and mixes atomized water vapor with the raw material gas supplied through the raw material gas supply path 7; and a cell stack 5 including a plurality of fuel battery cells 4 for generating power by oxidizing and reducing the fuel gas and an oxidant. In the solid oxide type fuel cell, a folded-back part K is provided which is folded back in such a manner that the middle of the raw material gas supply path 7 between the desulfurizer 2 and the evaporator 3 is projected downward, to store water.

Description

  The present invention relates to a reformer that steam-reforms a hydrocarbon-based raw fuel gas supplied through a raw fuel gas supply path to generate fuel gas, and a raw fuel gas supply path upstream of the reformer. Provided in the middle of the desulfurizer that performs desulfurization treatment on the raw fuel gas and the raw fuel gas supply path upstream of the reformer and downstream of the desulfurizer, and supplied through the water supply path The vaporized water and the vaporizer that mixes the vaporized water vapor and the raw fuel gas supplied through the raw fuel gas supply path, and the oxidation and reduction of the fuel gas and oxidant generated in the reformer The present invention relates to a solid oxide fuel cell including a cell stack having a plurality of fuel cells that generate power, and a method for stopping and storing the same.

  Conventionally, a solid oxide fuel cell including a cell stack having a plurality of fuel cells using a solid electrolyte as a membrane for conducting oxide ions is known. In a solid oxide fuel cell, zirconia doped with yttria is generally used as a solid electrolyte, and a fuel electrode for oxidizing a fuel gas (for example, hydrogen) is provided on one side of the solid electrolyte. Provided on the other side is an air electrode for reducing an oxidant (for example, oxygen in the air). In the solid oxide fuel cell, the operating temperature of the cell stack is as high as about 700 ° C. to 1000 ° C. Under such a high temperature, the hydrogen gas as the fuel gas and the oxygen in the air as the oxidant undergo an electrochemical reaction. Power is generated by causing

  Fuel gas such as hydrogen is generated by reforming a hydrocarbon-based raw fuel gas with a reformer (for example, steam reforming using steam). The raw fuel gas such as city gas and LP gas supplied to the reformer contains an odorant (odorant) component containing sulfur so that it can be perceived when gas leaks. Since the sulfur component in the odorant causes deterioration of the performance of the reforming catalyst accommodated in the reformer, the odorant in the raw fuel gas, especially its It is necessary to remove the sulfur component. For this reason, in a system generally equipped with a fuel cell, a desulfurizer is disposed upstream of the reformer, and after the sulfur component in the raw fuel gas is removed by the desulfurizer, the desulfurizer is supplied to the reformer. The

For desulfurizers, room-temperature desulfurization agent system that removes using physical adsorption performance at room temperature and ultra-high order that adds a small amount of hydrogen to convert odorant into hydrogen sulfide and removes it using chemical adsorption performance There is a desulfurization method. In the former, although the piping system is simple, the adsorption capacity is small compared to the latter, so the volume occupied by the desulfurizer is too large to mount a desulfurizing agent equivalent to the life of a solid oxide fuel cell. And the cost increases. On the other hand, the latter method requires a separate piping system for taking out part of the hydrogen to be added from the downstream side of the reformer and returning it to the desulfurizer, and the temperature of the desulfurizer is, for example, 200 ° C. to 300 ° C. Although installation considerations such as around 0 ° C. are necessary, the capacity of the desulfurizer can be small, and the entire equipment cost is lower than that of the room temperature desulfurization method even if the piping system is included.
As an example of applying an ultra-high order desulfurization method to a solid oxide fuel cell, there is Patent Document 1 described later.

In the ultra-high order desulfurization method, for example, a copper-zinc-based desulfurizing agent, a copper-zinc-aluminum-based desulfurizing agent, or the like is used. And a desulfurizer is installed in the position where a desulfurization agent will be 200-300 degreeC during a driving | operation of a solid oxide fuel cell. In order to make this desulfurizing agent usable in ultra-high order desulfurization, the desulfurizing agent itself needs to be subjected to high-temperature heat treatment (preliminary reduction treatment) in advance under the flow of a reducing gas containing H ₂ . After incorporation into the solid oxide fuel cell through this preliminary reduction treatment, the desulfurization agent accommodated in the desulfurizer must basically maintain the reduced state.

If air or the like enters the desulfurizer during stoppage or the like, oxidation (exothermic reaction) of the desulfurization agent proceeds. In that case, at the next start-up, even if an amount of hydrogen necessary for ultra-high order desulfurization is added to the raw fuel gas, the hydrogen is consumed for the reduction purpose for re-reducing the oxidized portion on the surface of the desulfurization agent. Therefore, the amount of hydrogen that can be used for sulfur desulfurization is reduced. Therefore, the raw fuel gas that has passed through the desulfurizer with the surface of the desulfurizing agent being oxidized contains a sulfur content in the SOx state, and there is a high possibility of causing performance deterioration of the reforming catalyst in the subsequent stage. .
In view of these problems, it is important that the desulfurizer always maintains a constant low oxygen partial pressure even after storage of the solid oxide fuel cell is stopped after starting to use the desulfurizer. It becomes.

  In Patent Document 1 describing a solid oxide fuel cell employing an ultrahigh-order desulfurization method, the raw fuel gas after exiting the desulfurizer (22) is cooled by a cooling heat exchanger (42), and electromagnetic After passing through the valve (44), it is supplied to the vaporizer (12) and the reformer (4). The electromagnetic valve (44) is for opening and closing the raw fuel gas supply path (14) for supplying the raw fuel gas to the vaporizer (12) and the reformer (4), and the fuel gas when opened. The supply of the raw fuel gas through the supply flow path (14) is permitted, and the cell stack (6) is closed after power generation is stopped, and the water vapor is supplied from the vaporizer (12) through the raw fuel gas supply path (14). Is prevented from flowing back. That is, when the solid oxide fuel cell finishes power generation and enters a stopped state, the internal gas contracts as the temperature of the desulfurizer (22) decreases, resulting in a negative pressure. For this reason, when there is no solenoid valve (44), a gas containing oxygen or the like is drawn from the open end of the cell stack (6), and in some cases, the desulfurization agent may be oxidized and deteriorated. In order to prevent this, it is necessary to switch the solenoid valve (44) to the closed state after the power generation of the cell stack (6) is stopped. Further, in the technology disclosed in Patent Document 1, if the raw fuel gas flows through the electromagnetic valve (44) in a high temperature state, the electromagnetic valve (44) may be broken. Therefore, the cooling heat exchanger (42) It is installed for the purpose of cooling the raw fuel gas after the desulfurization treatment to the guaranteed heat resistance range of the solenoid valve (44).

JP 2011-159485 A

  However, as described in Patent Document 1, cooling the high-temperature raw fuel gas after the desulfurization process in the desulfurizer and feeding it to the vaporizer is also loss in energy and cost reduction. From the viewpoint, it is not preferable to provide such a heat exchanger for cooling and a solenoid valve at a stage after the desulfurizer.

  The present invention has been made in view of the above problems, and its object is to provide a desulfurizer for storage after power generation of a solid oxide fuel cell is stopped in a state where low cost and low energy loss are ensured. It is in providing a solid oxide fuel cell capable of maintaining the performance of the above and a method for stopping and storing the same.

In order to achieve the above object, the solid oxide fuel cell according to the present invention is characterized in that the hydrocarbon-based raw fuel gas supplied through the raw fuel gas supply passage is steam reformed to generate fuel gas. The genitalia
A desulfurizer that is provided in the middle of the raw fuel gas supply path upstream of the reformer and that performs a desulfurization process on the raw fuel gas;
Provided in the middle of the raw fuel gas supply path upstream of the reformer and downstream of the desulfurizer, the water supplied through the water supply path is vaporized, and the vaporized water vapor and the raw fuel gas A vaporizer that mixes the raw fuel gas supplied through the supply path;
A solid oxide fuel cell comprising a fuel gas generated in the reformer and a cell stack having a plurality of fuel cells that generate power by oxidation and reduction of an oxidant,
A point is provided with a turn-back portion configured to be folded back so as to have a convex shape in the middle of the raw fuel gas supply path between the desulfurizer and the vaporizer and to store water.

According to the above characteristic configuration, the solid oxide fuel cell includes the folded portion, and the folded portion is configured to be folded so that the middle of the raw fuel gas supply path has a downwardly convex shape and store water. Has been. That is, in the middle of the raw fuel gas supply path, when a folded portion having the above structural features is provided, water (for example, condensed water) is generated at the folded portion or water is supplied to the folded portion. The water is collected by gravity and stays in the folding part. When the amount of water staying in the turn-up portion becomes the amount that blocks the raw fuel gas supply path, the gas flow in the raw fuel gas supply path between the desulfurizer and the vaporizer is interrupted, so the cell stack is opened. Even if oxygen enters the raw fuel gas supply path through the end or the like, the oxygen is blocked between the desulfurizer and the vaporizer and does not reach the desulfurizer. As a result, oxidation of the desulfurization catalyst accommodated in the desulfurizer is prevented.
Further, in this feature configuration, the structural feature of the turn-back portion can create a state in which the raw fuel gas supply path between the desulfurizer and the vaporizer is blocked by stagnant water. In addition, a special device such as a solenoid valve is not required, and a measure for cooling the raw fuel gas is not required to protect such a special device.
Accordingly, a solid oxide fuel cell capable of maintaining the performance of the desulfurizer during storage after power generation of the solid oxide fuel cell is stopped with low cost and low energy loss secured is provided. it can.

  Another characteristic configuration of the solid oxide fuel cell according to the present invention is that, in the cold stop state after the power generation in the cell stack is stopped, the folded portion retains water in the raw fuel gas supply path. Therefore, it functions as a gas shut-off mechanism capable of shutting off the gas by being blocked.

In the cold stop state after the power generation in the cell stack is stopped, the temperature of the raw fuel gas supply path gradually decreases, so that water may be condensed inside the raw fuel gas supply path.
In this feature configuration, since the folding portion is provided in the middle of the raw fuel gas supply path between the desulfurizer and the vaporizer, the desulfurizer and the vaporizer are in a cold stop state after power generation in the cell stack is stopped. When condensed water is generated in the middle of the raw fuel gas supply path to the vessel, the condensed water is collected by gravity toward the folded portion due to the structure of the folded portion. Then, the collected water stays in the raw fuel gas supply path and the raw fuel gas supply path is closed, so that the turning portion functions as a gas shut-off mechanism capable of shutting off the raw fuel gas supply path. Can do.

  Still another feature of the solid oxide fuel cell according to the present invention is that the water supplied to the vaporizer through the water supply path is in a cold stop state after power generation in the cell stack is stopped. It is configured to flow into the raw fuel gas supply path between the desulfurizer and the vaporizer, and to be at least a part of the accumulated water staying in the raw fuel gas supply path at the turning portion. In the point.

When the temperature in the vicinity of the desulfurizer falls below the carburetor side in the cold stop state after the power generation in the cell stack is stopped, the raw fuel gas is supplied from the carburetor side toward the desulfurizer. Gas begins to flow through the road.
In this feature configuration, gas flows from the vaporizer side toward the desulfurizer in the cold stop state after power generation in the cell stack is stopped, and water is condensed in the middle of the raw fuel gas supply path. Take advantage of what happens. That is, the water previously supplied to the carburetor through the water supply passage is caused to flow into the raw fuel gas supply passage between the desulfurizer and the vaporizer and be condensed, so that the raw fuel gas at the turn-back portion. It can be utilized as at least a part of the staying water staying in the supply path.

Still another characteristic configuration of the solid oxide fuel cell according to the present invention includes a water supply path capable of supplying water to the raw fuel gas supply path between the desulfurizer and the vaporizer,
In the cold stop state after power generation in the cell stack is stopped, the water supplied from the water replenishment path to the raw fuel gas supply path stays in the raw fuel gas supply path at the turning portion It is in the point comprised so that it may become at least one part of water.

  According to the above characteristic configuration, the water supplied from the water replenishment path to the raw fuel gas supply path without passing through the water vaporization step in the vaporizer is retained in the raw fuel gas supply path at the turn-back portion. It can be at least part. That is, water can be stored at the turn-back section regardless of the temperature of the vaporizer.

Still another characteristic configuration of the solid oxide fuel cell according to the present invention is that the folded portion includes a sealed container constituting a part of the raw fuel gas supply path, and a part of the raw fuel gas supply path. A first piping portion configured to be inserted from the desulfurizer side into the sealed container and a part of the raw fuel gas supply path to be inserted from the vaporizer side into the sealed container A second opening position of the second piping section inside the sealed container is more than a first opening position of the first piping section inside the sealed container. Is also in the lower position,
The first opening position is located on the gas phase side and the second opening position is located on the liquid phase side in a state where water stays in the folded portion.

  According to the above characteristic configuration, the second opening position of the second piping part inserted from the vaporizer side with respect to the sealed container is the second opening position of the first piping part inserted from the desulfurizer side with respect to the sealed container. Since the first opening position is located below the first opening position, the first opening position is located on the gas phase side and the second opening position is located on the liquid phase side in a state where water stays in the sealed container serving as the folding portion. Can happen. That is, the second piping part inserted from the vaporizer side into the sealed container without touching the first opening position of the first piping part inserted from the desulfurizer side with respect to the sealed container. Only the second opening position can be immersed in water. As a result, the space above the liquid level of the accumulated water is relatively large, so that the water between the desulfurizer and the vaporizer is secured while ensuring that water does not flow into the desulfurizer through the first pipe portion. The circulation of the gas in the fuel gas supply path can be blocked by the staying water.

  Still another characteristic configuration of the solid oxide fuel cell according to the present invention is that the cross-sectional area of the sealed container at the second opening position is larger than the cross-sectional area of the sealed container at the first opening position. In order to reduce the size, the hermetic container is tapered downward.

  According to the above characteristic configuration, even if the amount of staying water present in the sealed container is small, the level of the staying water in the sealed container becomes relatively high. That is, the 2nd opening position of the 2nd piping part inserted from the vaporizer side with respect to an airtight container will be located in a relatively deep water depth. As a result, the water head (for example, the first submerged in the stagnant water from the surface of the stagnant water) is inserted into the sealed container from the vaporizer side and partially submerged in the stagnant water. (Corresponding to the length of up to 2 opening positions) becomes longer, so that the gas (oxygen or the like) on the vaporizer side hardly flows into the desulfurizer side.

  Still another characteristic configuration of the solid oxide fuel cell according to the present invention is that the folded portion is provided below the lowermost surface of the desulfurizer.

  According to the above characteristic configuration, by making the potential energy in the desulfurizer larger than the potential energy in the folding portion, it is difficult for the object to move from the folding portion to the desulfurizer side. As a result, even if the desulfurizer is cooled and becomes a negative pressure state in which the pressure in the desulfurizer becomes relatively low, it is possible to suppress the staying water from flowing into the desulfurizer side from the folded portion.

A characteristic configuration of a method for stopping and storing a solid oxide fuel cell according to the present invention includes: a reformer that steam-reforms a hydrocarbon-based raw fuel gas supplied through a raw fuel gas supply path to generate a fuel gas; A desulfurizer that is provided in the middle of the raw fuel gas supply path upstream of the reformer and performs desulfurization treatment on the raw fuel gas; and upstream of the reformer and more than the desulfurizer Vaporization is provided in the middle of the raw fuel gas supply path on the downstream side, vaporizes water supplied through the water supply path, and mixes the vaporized water vapor with the raw fuel gas supplied through the raw fuel gas supply path. And a storage method for a solid oxide fuel cell, comprising a fuel cell and a cell stack having a plurality of fuel cells that generate power by oxidation and reduction of the fuel gas and oxidant generated in the reformer. And
The solid oxide fuel cell is configured to be folded so that water is stored by being folded so that a middle portion of the raw fuel gas supply path between the desulfurizer and the vaporizer has a downwardly convex shape. Part
After the power generation in the cell stack is stopped, when the temperature of the vaporizer and the temperature of the desulfurizer are equal to or higher than the boiling point of water and the temperature of the folded portion is lower than the boiling point of water, the vaporization is performed. And a step of supplying water to the vessel through the water supply path.

According to the above characteristic configuration, after the power generation in the cell stack is stopped, the temperature at which the temperature of the vaporizer and the temperature of the desulfurizer are equal to or higher than the boiling point of water, and the temperature of the folded portion is lower than the boiling point of water. Under the conditions, a process of supplying water through the water supply path to the vaporizer is performed, so that water is vaporized in the vaporizer. Further, when the water (steam) vaporized by the vaporizer flows into the raw fuel gas supply path between the desulfurizer and the vaporizer, the temperature of the folded portion is lower than the boiling point of water. Condensation can occur. In addition, the condensed water is collected in one place by gravity due to the structural features of the folded portion and becomes retained water. In addition, since the temperature of a desulfurizer is more than the boiling point of water, water does not condense in a desulfurizer. In other words, while ensuring that no condensation of water occurs in the desulfurization section, water that is at least part of the staying water staying in the raw fuel gas supply path at the turning section is supplied to the vaporizer through the water supply path. can do. Then, by retaining the water in the turning portion, the raw fuel gas supply path is blocked by the retained water, and the gas flow in the raw fuel gas supply path between the desulfurizer and the vaporizer is blocked. it can. As a result, even if oxygen enters the raw fuel gas supply path through the open end of the cell stack after power generation in the cell stack is stopped, the oxygen is blocked between the desulfurizer and the vaporizer, Since it does not reach the desulfurizer, the desulfurization catalyst accommodated in the desulfurizer is prevented from being oxidized.
In addition, in this feature configuration, a state in which the raw fuel gas supply path between the desulfurizer and the vaporizer is blocked can be created by the structural features of the turn-up portion. Thus, a special device such as the above is not required, and a measure such as cooling the raw fuel gas is not required to protect such a special device.
Therefore, the shutdown of the solid oxide fuel cell that can maintain the performance of the desulfurizer at the time of storage after the power generation of the solid oxide fuel cell is stopped with the low cost and low energy loss secured A storage method can be provided.

Another feature of the method for stopping and storing a solid oxide fuel cell according to the present invention is a reforming process for generating a fuel gas by steam reforming a hydrocarbon-based raw fuel gas supplied through a raw fuel gas supply path. A desulfurizer that is provided in the middle of the raw fuel gas supply path upstream of the reformer and that performs desulfurization treatment on the raw fuel gas, and upstream of the reformer and the desulfurizer Provided in the middle of the raw fuel gas supply path on the downstream side, vaporizes water supplied through the water supply path, and mixes vaporized water vapor with the raw fuel gas supplied through the raw fuel gas supply path And a solid oxide fuel cell stop-and-store method comprising: a vaporizer for generating a gas and a cell stack having a plurality of fuel cells that generate power by oxidizing and reducing fuel gas and oxidant generated in the reformer Because
The solid oxide fuel cell is configured to be folded so that water is stored by being folded so that a middle portion of the raw fuel gas supply path between the desulfurizer and the vaporizer has a downwardly convex shape. And
A water supply path capable of supplying water to the raw fuel gas supply path between the desulfurizer and the vaporizer;
After the power generation in the cell stack is stopped, when the temperature of the folding part is less than the boiling point of water, water is supplied from the water supply path to the raw fuel gas supply path to supply water to the folding part. It has the process of storing.

According to the above characteristic configuration, after the power generation in the cell stack is stopped, the raw fuel gas supply path between the desulfurizer and the vaporizer is placed under a temperature condition that the temperature of the turning portion is lower than the boiling point of water. Since the process of supplying water from the water supply path that can supply water to the raw fuel gas supply path and storing the water in the return section is performed, the supply section does not vaporize the supplied water and stores it as it is. Become. In addition, the water that has reached the turn-back portion remains in one place by gravity due to the structural features of the turn-back portion and becomes stagnant water. Further, since the water supplied from the water supply path does not pass through the vaporizer, this process is not affected by the temperature of the vaporizer. Moreover, since the temperature of the folding part is lower than the boiling point of water, when gas flows into the folding part from the vaporizer side, water can be condensed in the folding part. As a result, the condensed water becomes part of the accumulated water at the turn-back section, and the raw fuel gas supply path is blocked by the above-mentioned retained water, and the gas in the raw fuel gas supply path between the desulfurizer and the vaporizer is Can be blocked. For this reason, even if oxygen enters the raw fuel gas supply path through the open end of the cell stack after power generation in the cell stack is stopped, the oxygen is blocked between the desulfurizer and the vaporizer. The desulfurization catalyst accommodated in the desulfurizer is prevented from being oxidized without reaching the desulfurizer.
In addition, in this feature configuration, a state in which the raw fuel gas supply path between the desulfurizer and the vaporizer is blocked can be created by the structural features of the turn-up portion. Thus, a special device such as the above is not required, and a measure such as cooling the raw fuel gas is not required to protect such a special device.
Therefore, the shutdown of the solid oxide fuel cell that can maintain the performance of the desulfurizer at the time of storage after the power generation of the solid oxide fuel cell is stopped with the low cost and low energy loss secured A storage method can be provided.

It is a figure which shows the structure of the solid oxide fuel cell of 1st Embodiment. It is a graph which shows the temperature change of each part of the solid oxide fuel cell after the power generation in a cell stack is stopped, and a suitable water supply timing. It is a figure which shows the example of the folding | turning part which functions as a gas interruption | blocking mechanism. It is a figure which shows the structure of the solid oxide fuel cell of 2nd Embodiment. It is a figure which shows the structure of the solid oxide fuel cell of 3rd Embodiment. It is a figure which shows the structure of the solid oxide fuel cell of 4th Embodiment. It is a figure which shows the structure of the solid oxide fuel cell of 5th Embodiment.

<First Embodiment>
The configuration of the solid oxide fuel cell according to the first embodiment will be described below with reference to the drawings.
FIG. 1 is a diagram showing a configuration of the solid oxide fuel cell according to the first embodiment. As shown in the figure, a solid oxide fuel cell includes a reformer 1 that steam-reforms a hydrocarbon-based raw fuel gas supplied through a raw fuel gas supply path 7 to generate a fuel gas, and a reformer. A desulfurizer 2 that is provided in the middle of the raw fuel gas supply path 7 upstream of 1 and performs desulfurization processing on the raw fuel gas; and upstream of the reformer 1 and downstream of the desulfurizer 2 A vaporizer 3 provided in the middle of the raw fuel gas supply path 7 for vaporizing water supplied through the water supply path 20 and mixing the vaporized water vapor with the raw fuel gas supplied through the raw fuel gas supply path 7. And a cell stack 5 having a plurality of fuel cells 4 that generate power by oxidation and reduction of the fuel gas and oxidant generated in the reformer 1. In addition, the solid oxide fuel cell of the present embodiment is folded back so that the middle of the raw fuel gas supply path 7 between the desulfurizer 2 and the vaporizer 3 has a downwardly convex shape, and stores water. The folding part K comprised in this way is provided. In other words, the folded portion K has a downwardly convex shape, so that when liquid is present, the liquid remains on the bottom portion by gravity.

  The raw fuel gas supply path 7 is a gas flow path from a supply source of hydrocarbon-based raw fuel gas such as methane to the reformer 1. In the example shown in FIG. 1, an on-off valve 14, a zero governor 15, a flow meter 16, a gas pump 17, a desulfurizer 2, and a vaporizer 3 are provided in this order from the upstream side in the raw fuel gas supply path 7. The on-off valve 14 is a valve that switches between opening and closing the flow path of the raw fuel gas supply path 7. The operation of the on-off valve 14 is controlled by the control device C. The zero governor 15 keeps the pressure of the downstream raw fuel gas at substantially the atmospheric pressure regardless of the pressure of the upstream raw fuel gas (that is, keeps the differential pressure from the atmospheric pressure at substantially zero). is there. The flow meter 16 is a device that measures the flow rate of the raw fuel gas flowing through the raw fuel gas supply path 7. The detection result of the flow meter 16 is transmitted to the control device C. The gas pump 17 is a device that flows gas toward the desulfurizer 2. The control device C controls the output of the gas pump 17 so that the gas flow rate detected by the flow meter 16 becomes a predetermined flow rate value.

  The desulfurizer 2 is a device that performs a desulfurization process on the raw fuel gas. For example, city gas and LP gas mainly composed of methane, propane, and the like contain an odorant (odorant) component containing sulfur so that it can be perceived when gas leaks. Since the sulfur component in the odorant causes deterioration of the performance of the reforming catalyst accommodated in the reformer 1 described later, the sulfur component in the odorant is added to the raw fuel gas before being fed to the reformer 1. It is necessary to remove the odorant, particularly its sulfur component. Further, the desulfurizer 2 of the present embodiment is an ultra-high order desulfurization system that adds a trace amount of hydrogen to the raw fuel gas, converts the odorant into hydrogen sulfide, and removes the hydrogen sulfide using chemical adsorption performance. Is adopted. As the ultra-high order desulfurizing agent accommodated in the desulfurizer 2, for example, a copper-zinc-based desulfurizing agent, a copper-zinc-aluminum-based desulfurizing agent, or the like can be used.

  In the present embodiment, hydrogen to be added to the raw fuel gas is obtained from a fuel gas (that is, a gas containing hydrogen as a main component) generated by the reformer 1 described later. Specifically, the fuel gas supply path 8 through which the fuel gas obtained by the reforming process in the reformer 1 flows branches the recycle gas supply path 9 between the reformer 1 and the gas manifold 6. The recycle gas supply path 9 joins the raw fuel gas supply path 7 between the flow meter 16 and the gas pump 17, whereby hydrogen is added to the raw fuel gas supplied to the desulfurizer 2. . In the middle of the recycle gas supply path 9, an orifice 10 for limiting the flow rate, an on-off valve 11 for opening and closing the flow path, and a gas-liquid separator 12 are provided. The operation of the on-off valve 11 is controlled by the control device C. Then, the liquid (that is, condensed water) obtained in the gas-liquid separator 12 is discharged out of the apparatus through the drainage passage 13, and the gas (hydrogen) obtained in the gas-liquid separator 12 is supplied to the raw fuel gas supply passage 7. Supplied.

  The raw fuel gas after being desulfurized by the desulfurizer 2 is supplied to the vaporizer 3. Water is supplied to the vaporizer 3 through the water supply path 20, and the water is vaporized. In the vaporizer 3, the vaporized water vapor and the raw fuel gas supplied through the raw fuel gas supply path 7 are mixed. An opening / closing valve 21 for opening and closing the flow path and a water pump 22 for adjusting the flow rate of water in the water supply path 20 (the amount of water supplied to the vaporizer 3) are provided in the middle of the water supply path 20. The operation of the on-off valve 21 and the operation of the water pump 22 are controlled by the control device C.

  The reformer 1 receives a supply of a mixed gas of raw fuel gas and steam from the vaporizer 3 and performs steam reforming of the raw fuel gas to generate fuel gas (a gas containing hydrogen as a main component). . The fuel gas generated in the reformer 1 is supplied to the gas manifold 6 through the fuel gas supply path 8. The fuel cell 4 is connected to the gas manifold 6, and the fuel gas supplied to the gas manifold 6 is distributed to each fuel cell 4.

  The cell stack 5 includes a fuel flow portion (not shown) through which the fuel gas generated by the reformer 1 flows and an air flow portion (not shown) through which air (that is, an oxidant (oxygen)) flows. And a plurality of solid oxide fuel cells 4 are electrically connected in series. Although illustration is omitted, the fuel cell 4 is configured in a solid oxide form having a solid electrolyte layer between the fuel electrode and the air electrode. In each fuel cell 4, the fuel gas is supplied to the entire fuel electrode by flowing the fuel gas upward through the fuel flow portion, and the air is flowed upward through the air flow portion. Air is supplied to the whole, and fuel gas and air are used for the power generation reaction. Then, the exhaust fuel gas after being subjected to the power generation reaction is discharged from the discharge port at the upper end of the fuel flow passage, and the exhaust air after being subjected to the power generation reaction is discharged from the discharge port at the upper end of the air flow passage. The

  Combustion for burning off-gas (that is, exhaust fuel gas discharged from the fuel flow portion of each fuel cell 4 and exhaust air (that is, oxygen) discharged from the air flow portion) above the cell stack 5. A space (that is, the combustion part B) is formed. That is, the combustion section B is realized by the cell stack 5. In addition, the vaporizer 3 and the reformer 1 are provided adjacent to the combustion space above the cell stack 5 that functions as the combustion section B. As a result, the vaporizer 3 and the reformer 1 are heated by the combustion heat generated in the combustion section B.

  As shown in FIG. 1, the solid oxide fuel cell according to the present embodiment accommodates a vaporizer 3, a reformer 1, a gas manifold 6, a cell stack 5, an orifice 10, and the like in a metal casing 18. doing. Although not shown, the power generation reaction air described above is supplied to the internal space of the metal casing 18. Then, air in the space inside the metal casing 18 is supplied to the air flow portions of each of the plurality of fuel cells 4 through the air supply holes, and each air flow portion is passed from the lower side to the upper side. To be used for power generation reaction.

  The solid oxide fuel cell of the present embodiment is configured such that water is stored by being folded back so that the middle of the raw fuel gas supply path 7 between the desulfurizer 2 and the vaporizer 3 has a downwardly convex shape. The folded portion K is provided. The turn-back portion K and the desulfurizer 2 are housed inside the hot module 19 through which heat released from the metal housing 18 is transmitted, although it is outside the metal housing 18. For example, when power generation is performed in the cell stack 5, the temperature of the cell stack 5 inside the metal casing 18 is 600 ° C. to 750 ° C., and the temperature of the desulfurizer 2 provided adjacent to the metal casing 18 is increased. The temperature can be from about 200 ° C to about 300 ° C. This temperature is a temperature range suitable for ultra-high-order desulfurization, and conversely, it can be said that the desulfurizer 2 is installed by selecting a place in such a temperature range. Since the folded portion K is provided at a position farther from the metal casing 18 than the desulfurizer 2, its temperature is higher than the temperature of the desulfurizer 2 even when the solid oxide fuel cell is operating. Also lower. For example, the temperature of the folded portion K is 200 ° C. to 250 ° C.

  During power generation in the cell stack 5, the inside of the raw fuel gas supply path 7 is at a high temperature and the raw fuel gas is constantly flowing. Absent. Further, even if water enters the folded portion K, it is vaporized and discharged downstream. On the other hand, in the cold stop state after the power generation in the cell stack 5 is stopped, the raw fuel gas does not flow into the raw fuel gas supply path 7 (gas molecule diffusion may occur), and the raw fuel gas Since the temperature inside the supply path 7 is lowered, the moisture in the gas is condensed, and the condensed water is stored at the bottom of the folded portion K.

  That is, in the solid oxide fuel cell according to the present embodiment, the turn-back portion K is blocked because water stays in the raw fuel gas supply path 7 in the cold stop state after the power generation in the cell stack 5 is stopped. It functions as a gas shut-off mechanism S that can shut off the gas. That is, since the turning portion K is provided in the middle of the raw fuel gas supply path 7 between the desulfurizer 2 and the vaporizer 3, the desulfurizer is in a cold stop state after power generation in the cell stack 5 is stopped. When condensed water is generated in the middle of the raw fuel gas supply path 7 between 2 and the vaporizer 3, the condensed water is collected by gravity toward the folded portion K due to the structure of the folded portion K. Then, the collected water stays in the raw fuel gas supply path 7 and the raw fuel gas supply path 7 is closed, so that the turn-off portion K can shut off the gas in the raw fuel gas supply path 7. It can function as S. The desulfurizer 2 is isolated from the cell stack 5, the reformer 1, and the vaporizer 3 with the closed portion (folded portion K) interposed therebetween, so that oxygen and water do not enter the desulfurizer 2. It becomes like this.

  In addition, when the folding | turning part K like this embodiment is not provided, even if water condensation occurs in the raw fuel gas supply path 7 in the cold stop state after the power generation in the cell stack 5 is stopped. Since the condensed water does not always stay in one place, the raw fuel gas supply path 7 is not blocked. Therefore, the desulfurizer 2 remains in a state in which gas can flow between the cell stack 5, the reformer 1, and the vaporizer 3, and oxygen or water vapor may enter the desulfurizer 2. .

  As the origin of the accumulated water staying in the raw fuel gas supply path 7 at the turn-back portion K in the cold stop state after the power generation in the cell stack 5 is stopped, the water supply path 20 passes through the water supply path 20 during the power generation in the cell stack 5. There is water being supplied to the vaporizer 3. For example, when power generation is performed in the cell stack 5, the gas downstream of the vaporizer 3 contains water vapor. Therefore, when the internal temperature of the raw fuel gas supply path 7 such as the desulfurizer 2 is lowered in the cold stop state after the power generation in the cell stack 5 is stopped, the water vapor flows back toward the desulfurizer 2 and turns back. It may condense in part K and become retained water (condensed water).

  Alternatively, water can be positively supplied to the vaporizer 3 so that condensed water (residual water) is intentionally generated in the vicinity of the turn-back portion K. That is, the water supplied to the vaporizer 3 through the water supply path 20 is the raw fuel gas supply path between the desulfurizer 2 and the vaporizer 3 in the cold stop state after the power generation in the cell stack 5 is stopped. 7 and may be configured to become at least part of the staying water staying in the raw fuel gas supply path 7 at the turn-back portion K. This method will be described below.

  FIG. 2 is a graph showing a temperature change of each part of the solid oxide fuel cell after the power generation in the cell stack 5 is stopped and a suitable water supply timing. Specifically, FIG. 2A is a graph showing temperature changes in the desulfurizer 2, the vaporizer 3, and the turning portion K when the power generation of the cell stack 5 is urgently stopped. When the power generation of the cell stack 5 is stopped urgently, the supply of the raw fuel gas is stopped by closing the on-off valve 14 provided in the raw fuel gas supply path 7 almost simultaneously with the stop of the power generation. The supply of cathode air to is stopped, and the on-off valve 21 provided in the water supply path 20 is closed, whereby the supply of water is stopped. As shown in FIG. 2 (a), immediately after the stop process, the temperature rises remarkably in the vaporizer 3 and the desulfurizer 2, and then gradually begins to decrease. The cause of the temperature rise is that the temperature distribution that has been formed by the gas and air flows at the time of power generation goes through a process of soaking as the gas and air flows stop. In particular, in the vaporizer 3, the temperature change is large. In the folded portion K located farther from the metal casing 18 than the desulfurizer 2, the temperature rise is smaller than these.

In this figure, the time when the turning portion K is less than 100 ° C. and the vaporizer 3 and the desulfurizer 2 are at 100 ° C. or higher, that is, at the timing after about 670 minutes have elapsed from the stop of power generation. 3 may be supplied with water. If water is supplied to the vaporizer 3 during this time period, the water vapor generated in the vaporizer 3 reaches the turn-back portion K due to diffusion as the temperature decreases, and a flow in which condensation of the water vapor occurs there. it can. That is, the reverse flow of water vapor from the vaporizer 3 to the folded portion K can be effectively performed.
However, when about 750 minutes have passed since the power generation was stopped, that is, when the temperature of the desulfurizer 2 is also lower than 100 ° C., the condensation of water in the desulfurizer 2 may also proceed. It is desirable to complete the closed state of the raw fuel gas supply path 7 by the staying water in the part K.

  That is, when the temperature of the desulfurizer 2 is lowered and becomes a negative pressure state in the cold stop state after the power generation in the cell stack 5 is stopped, the raw fuel gas is supplied from the vaporizer 3 side toward the desulfurizer 2. A state in which gas flows through the path 7 is reached. In the stopped storage method of the solid oxide fuel cell according to the present invention, the control device C detects the temperature of the vaporizer 3 with the temperature sensor T1 in anticipation that such a state occurs, and the desulfurizer. 2 is detected by the temperature sensor T2, the temperature of the turn-back portion K is detected by the temperature sensor T3, and after the power generation in the cell stack 5 is stopped, the temperature of the vaporizer 3 and the temperature of the desulfurizer 2 are water. When the temperature is equal to or higher than the boiling point and the temperature of the folded portion K is lower than the boiling point of water, a step of supplying water through the water supply path 20 to the vaporizer 3 is performed. As described above, the water previously supplied to the vaporizer 3 through the water supply passage 20 is caused to flow into the raw fuel gas supply passage 7 between the desulfurizer 2 and the vaporizer 3 and condensed. The folded portion K can be used as at least a part of the staying water staying in the raw fuel gas supply path 7. Then, when the closed state of the raw fuel gas supply path 7 by the condensed water is completed at the turn-back portion K, air and water do not enter the desulfurizer 2 thereafter.

  FIG. 2B is a graph showing temperature changes in the desulfurizer 2, the vaporizer 3, and the turning portion K when the power generation of the cell stack 5 is normally stopped. When the power generation of the cell stack 5 is normally stopped, the supply of the raw fuel gas is continued by maintaining the open state of the on-off valve 14 provided in the raw fuel gas supply path 7 even after the power generation is stopped. The supply of cathode air to the inside of the water supply is continued, and the supply of water is continued by maintaining the open state of the on-off valve 21 provided in the water supply path 20. As described above, by continuing the supply of the raw fuel gas, the cathode air, and the reforming water even after the power generation is stopped, the temperature decrease of the solid oxide fuel cell is promoted. In the example shown in FIG. 2B, the supply of the raw fuel gas and the reforming water is stopped when 100 minutes have elapsed since the power generation was stopped.

  As in FIG. 1, immediately after the stop step, the vaporizer 3 and the desulfurizer 2 are remarkably increased in temperature, and then start to decrease rapidly. The turning portion K becomes 100 ° C. or lower when about 270 minutes have elapsed since the stop of power generation. At this time, the vaporizer 3 and the desulfurizer 2 exceed 100 ° C. Therefore, it is preferable to supply water to the vaporizer 3 at a timing after about 270 minutes have elapsed since the power generation was stopped.

Next, a method for removing the water staying in the turning portion K will be described.
When water stays in the folded portion K in the raw fuel gas supply path 7 in the cold stop state after the power generation in the cell stack 5 is stopped by the method described above, the power generation in the cell stack 5 is next performed. In order to resume, it is necessary to remove the accumulated water. Therefore, the control device C opens the on-off valve 14 and operates the gas pump 17 to perform a step of applying gas pressure by the raw fuel gas to the raw fuel gas supply path 7 on the downstream side of the desulfurizer 2. As a result, the water staying in the folded portion K on the downstream side of the desulfurizer 2 can be pumped further to the vaporizer 3 on the downstream side by the gas pressure.

Next, a specific example of the folding portion K that functions as the gas cutoff mechanism S will be described.
FIG. 3 is a diagram illustrating an example of the folding portion K that functions as the gas cutoff mechanism S.

  FIG. 3A shows an example in which the folded portion K is configured with the raw fuel gas supply path 7 having a downwardly convex U-shaped pipe structure. This example corresponds to the shape of the folded portion K of the raw fuel gas supply path 7 shown in FIG.

  FIG. 3B shows that the folded portion K forms a part of the raw fuel gas supply path 7 and a part of the raw fuel gas supply path 7 and a part of the raw fuel gas supply path 7. A first piping part 7a inserted from the desulfurizer 2 side and a second piping part 7b constituting a part of the raw fuel gas supply path 7 and inserted from the vaporizer 3 side into the sealed container 23 It is an example in the case of having. In this example, the partition plate 24 in contact with the top surface of the hermetic container 23 is mounted inside the hermetic container 23 with an opening provided on the bottom surface of the hermetic container 23. In FIG. 3 (b), a broken line indicates a virtual raw fuel gas supply path 7, and as shown in the figure, the raw fuel gas supply path 7 is folded back into a convex shape so that water is stored. It is configured.

FIG. 3 (c) shows that the folded portion K forms a part of the raw fuel gas supply path 7 and a part of the raw fuel gas supply path 7 and forms a part of the raw fuel gas supply path 7. A first piping part 7a inserted from the desulfurizer 2 side and a second piping part 7b constituting a part of the raw fuel gas supply path 7 and inserted from the vaporizer 3 side into the sealed container 23 And the second opening position 26 of the second piping part 7 b inside the sealed container 23 is located below the first opening position 25 of the first piping part 7 a inside the sealed container 23. It is configured. Also in FIG. 3 (c), the virtual raw fuel gas supply path 7 is indicated by a broken line, and the raw fuel gas supply path 7 is folded back into a convex shape as shown in the drawing to store water. It is configured as follows. Then, in a state where water stays in the folded portion K, the first opening position 25 opened at the tip of the first piping portion 7a inserted from the desulfurizer 2 side is on the gas phase side, from the vaporizer 3 side. A second opening position 26 that opens at the tip of the inserted second piping part 7b is positioned on the liquid phase side.
By making the folding part K in such a configuration, the sealed container 23 can be closed without touching the first opening position 25 of the first piping part 7a inserted into the sealed container 23 from the desulfurizer 2 side with water. 23, it is possible to create a state in which only the second opening position 26 of the second piping portion 7b inserted from the vaporizer 3 side is immersed in water. As a result, since the space is relatively large above the liquid level of the staying water inside the sealed container 23, while ensuring that water does not flow into the desulfurizer 2 side through the first piping portion 7a, The circulation of the gas in the raw fuel gas supply path 7 between the desulfurizer 2 and the vaporizer 3 can be blocked by the staying water.

In FIG. 3D, the folded portion K forms a sealed container 23 that forms part of the raw fuel gas supply path 7 and a part of the raw fuel gas supply path 7 that A first piping part 7a inserted from the desulfurizer 2 side and a second piping part 7b constituting a part of the raw fuel gas supply path 7 and inserted from the vaporizer 3 side into the sealed container 23 And the second opening position 26 of the second piping part 7 b inside the sealed container 23 is located below the first opening position 25 of the first piping part 7 a inside the sealed container 23. It is configured. Also in FIG. 3 (d), the broken line shows a virtual raw fuel gas supply path 7, and the raw fuel gas supply path 7 is folded back into a convex shape as shown in the figure to store water. It is configured as follows. Further, the sealed container 23 is tapered downward so that the cross-sectional area of the sealed container 23 at the second opening position 26 is smaller than the cross-sectional area of the sealed container 23 at the first opening position 25. It has a shape.
By configuring the folded portion K in such a configuration, even if there is a small amount of accumulated water in the sealed container 23, the water level in the sealed container 23 is relatively high. The 2nd opening position 26 of the 2nd piping part 7b inserted from the vaporizer 3 side with respect to the container 23 will be located in a relatively deep water depth. As a result, the water head (for example, submerged from the surface of the accumulated water into the accumulated water) is inserted into the sealed container 23 from the vaporizer 3 side and partly submerged in the accumulated water. (Corresponding to the length up to the second opening position 26), the gas on the vaporizer 3 side (oxygen or the like) hardly flows into the desulfurizer 2 side.

  As described above, the solid oxide fuel cell according to the present embodiment includes the folded portion K, and the folded portion K is folded so that the middle portion of the raw fuel gas supply path 7 has a downwardly convex shape. Is configured to accumulate. That is, when water (for example, condensed water) is generated in the turning portion K by providing the turning portion K having the structural features as described above in the middle of the raw fuel gas supply path 7, the water is It is collected by gravity and stays at the turn-back portion K. When the amount of water staying in the turn-back portion K becomes an amount that blocks the raw fuel gas supply path 7, the gas flow in the raw fuel gas supply path 7 between the desulfurizer 2 and the vaporizer 3 is blocked. Even if oxygen enters the raw fuel gas supply path 7 through the open end of the cell stack 5, the oxygen is blocked between the desulfurizer 2 and the vaporizer 3 and does not reach the desulfurizer 2. As a result, the desulfurization catalyst accommodated in the desulfurizer 2 is prevented from being oxidized. In addition, the structural feature of the turn-back portion K can create a state in which the raw fuel gas supply path 7 between the desulfurizer 2 and the vaporizer 3 is blocked by stagnant water. A special device such as a solenoid valve is not necessary, and a measure such as cooling the raw fuel gas is not required to protect such a special device.

Second Embodiment
The solid oxide fuel cell according to the second embodiment is different from the first embodiment in the form of water supplied to the turning portion K that functions as the gas shut-off mechanism S. The configuration of the solid oxide fuel cell according to the second embodiment will be described below, but the description of the same configuration as the above embodiment will be omitted.

  FIG. 4 is a diagram showing the configuration of the solid oxide fuel cell according to the second embodiment. As shown in the figure, the solid oxide fuel cell according to the second embodiment includes a water replenishment path 27 that can replenish water in the raw fuel gas supply path 7 between the desulfurizer 2 and the vaporizer 3. Then, in the cold stop state after the power generation in the cell stack 5 is stopped, the water supplied from the water replenishment path 27 to the raw fuel gas supply path 7 stays in the raw fuel gas supply path 7 at the turn-back portion K. It is comprised so that it may become at least one part of the staying water. Specifically, the branching portion 30 in the middle of the water supply path 20 is supplied with water that can supply water to the raw fuel gas supply path 7 between the desulfurizer 2 and the vaporizer 3 without using the vaporizer 3. A path 27 is connected. The branch portion 30 is located in the middle of the water supply path 20 on the downstream side of the water pump 22. The water supply path 27 is connected to a merging section 31 in the vicinity of the turning section K in the middle of the raw fuel gas supply path 7. In this case, the control device C operates the open / close valve 21 in the open state, operates the open / close valve 28 provided in the water supply path 20 between the branch portion 30 and the vaporizer 3 in the closed state, and supplies water. By opening the on-off valve 29 provided in the middle of the path 27 and operating the water pump 22, the water supply path 27 is not supplied to the carburetor 3 while supplying water to the turn-back portion K. Water can be supplied via

  Also in the present embodiment, it is preferable that water is replenished to the folded portion K at the timing when the temperature of the folded portion K is less than 100 ° C. as illustrated in FIG. That is, in the case of this embodiment, water can be replenished to the folding part K without going through the vaporizer 3, so the temperature of the vaporizer 3 need not be considered.

  As described above, in the method for stopping and storing the solid oxide fuel cell according to the present embodiment, the control device C detects the temperature of the folded portion K with the temperature sensor T3 and the power generation in the cell stack 5 is stopped. When the temperature of the turning portion K is lower than the boiling point of water, a step of supplying water from the water replenishment passage 27 to the raw fuel gas supply passage 7 and storing water in the turning portion K is performed. When such a process is performed, the folded portion K can be directly closed by the water supplied to the folded portion K. That is, in this embodiment, the water vaporization process in the vaporizer 3 as described in the above embodiment is not performed, and the temperature of the vaporizer 3 is independent of the temperature of the vaporizer 3 (that is, the temperature of the vaporizer 3 vaporizes water. Water that is supplied from the water replenishment passage 27 to the raw fuel gas supply passage 7 and at least part of the retained water that stays in the raw fuel gas supply passage 7 at the turn-back portion K. can do. As a result, air and water will not enter the desulfurizer 2 thereafter.

<Third Embodiment>
The solid oxide fuel cell according to the third embodiment is characterized by the positional relationship between the folded portion K and the desulfurizer 2. The configuration of the solid oxide fuel cell according to the third embodiment will be described below, but the description of the same configuration as the above embodiment will be omitted.

FIG. 5 is a diagram showing the configuration of the solid oxide fuel cell according to the third embodiment. As shown in the drawing, the folded portion K is provided below the lowermost surface of the desulfurizer 2. Here, the “folded portion K” to be compared with the lowermost surface of the desulfurizer 2 is the position of the highest water level of the accumulated water.
By adopting such a configuration, the potential energy in the desulfurizer 2 becomes larger than the potential energy in the folded portion K. Therefore, it becomes difficult for the object to move from the folded portion K to the desulfurizer 2 side. As a result, even if the desulfurizer 2 is cooled and becomes a negative pressure state in which the pressure in the desulfurizer 2 is relatively low, it is possible to prevent the accumulated water from flowing into the desulfurizer 2 side from the folded portion K. .

<Fourth embodiment>
The solid oxide fuel cell according to the fourth embodiment is different from the above-described embodiment in that the stagnant water discharge path 32 is connected to the folded portion K. The configuration of the solid oxide fuel cell according to the fourth embodiment will be described below, but the description of the same configuration as the above embodiment will be omitted.

  FIG. 6 is a diagram showing the configuration of the solid oxide fuel cell according to the fourth embodiment. As shown in the figure, a stagnant water discharge path 32 is connected to the folding portion K, and an open / close valve 33 that switches between opening and closing of the flow path is provided in the middle of the stagnant water discharge path 32. The operation of the on-off valve 33 is controlled by the control device C.

In the above embodiment, when it is time to start the solid oxide fuel cell, the control device C causes the water remaining in the folded portion K downstream of the desulfurizer 2 to be further vaporized further downstream by the gas pressure. The example which excludes stagnant water from the folding | turning part K by pumping to 3 was demonstrated.
On the other hand, in the present embodiment, the control device C opens the on-off valve 33 provided in the accumulated water discharge path 32 when it is time to start the solid oxide fuel cell. As a result, even if water stays in the turning portion K, it is drained through the staying water discharge passage 32 while the on-off valve 33 is opened, and the raw fuel gas flows in the raw fuel gas supply passage 7. Is possible. At this time, the control device C may perform the closing operation of the opening / closing valve 33 after opening the opening / closing valve 33 for a period sufficient to drain the accumulated water.

<Fifth Embodiment>
The solid oxide fuel cell according to the fifth embodiment is different from the above-described embodiment in that a heating means 34 capable of heating the accumulated water in the folded portion K is provided. The configuration of the solid oxide fuel cell according to the fifth embodiment will be described below, but the description of the same configuration as the above embodiment will be omitted.

  FIG. 7 is a diagram showing the configuration of the solid oxide fuel cell of the fifth embodiment. As shown in the figure, the solid oxide fuel cell includes a heating unit 34 that can heat the accumulated water in the folded portion K. As the heating means 34, for example, an electric heater that generates Joule heat by energization can be used. The operation of the heating means 34 is controlled by the control device C.

  The control device C heats the heating means 34 when it is time to start the solid oxide fuel cell. As a result, even if water stays in the folded portion K, the staying water is vaporized by the heat transmitted from the heating means 34. At this time, the control device C may cause the raw fuel gas to flow from the desulfurizer 2 to the turning portion K. By doing so, it is possible to prevent the water vapor evaporated by the heating means 34 from flowing toward the desulfurizer 2. At this time, the control apparatus C should just stop the heating operation of the heating means 34, after heating the heating means 34 only for the period sufficient to vaporize stagnant water.

<Another embodiment>
<1>
In the said embodiment, although the specific example was given and demonstrated about the structure of the solid oxide fuel cell, the structure can be changed suitably.
For example, FIG. 4 illustrates a configuration in which the opening / closing valve 28 is provided on the downstream side of the branch portion 30 of the water supply passage 20 and the opening / closing valve 29 is provided in the middle of the water supply passage 27. An apparatus configuration different from the configuration provided with 29 may be adopted. For example, by providing a three-way valve in the branch part 30 without providing the on-off valves 28 and 29, water supply through the water supply path 27 to the turn-back part K is performed without supplying water to the vaporizer 3. You may employ | adopt the structure to perform.

<2>
In the said 2nd Embodiment, although the water supply to the folding | returning part K demonstrated the example performed only from the water supply path 27 not via the vaporizer | carburetor 3, the water supply to the folding | returning part K via the vaporizer | carburetor 3 and The water supply to the turn-back portion K via the water supply path 27 may be performed together. For example, in the solid oxide fuel cell shown in FIG. 4, after the power generation in the cell stack 5 is stopped by the control device C, the temperature of the vaporizer 3 and the temperature of the desulfurizer 2 are equal to or higher than the boiling point of water. And, when the temperature of the folded portion K is lower than the boiling point of water, after supplying water through the water supply path 20 to the vaporizer 3, and after the power generation in the cell stack 5 is stopped, When the temperature of the turning part K is lower than the boiling point of water, the step of supplying water from the water supply path 27 to the raw fuel gas supply path 7 and storing the water in the turning part K may be performed.

<3>
In the above embodiment, as a method of removing the water staying in the turn-back portion K, a method of pumping further to the downstream vaporizer 3 by the gas pressure as described in the first embodiment, in the fourth embodiment Although the method of draining through the stagnant water discharge path 32 as described above and the method of vaporizing by the heating means 34 as described in the fifth embodiment have been described separately, these methods are used in combination to the folded portion K. The remaining water may be excluded.

<4>
In the above-described embodiment, when the number of times that the middle portion of the raw fuel gas supply path 7 between the desulfurizer 2 and the vaporizer 3 is folded downward is one in the folding portion K (that is, However, the folded portion K may be formed so that the number of times of folding is plural (the number of convex portions is plural). That is, the folded portion K may be formed so that the shape of the raw fuel gas supply path 7 has a waveform (that is, a shape in which a valley portion and a mountain portion are repeated to form a waveform).

<5>
In the said embodiment, although the desulfurizer 2 demonstrated the example in the case of having a super high-order desulfurization agent using a copper-zinc type desulfurization agent, a copper-zinc-aluminum type desulfurization agent, etc., it has another desulfurization agent. A desulfurizer can also be used in the solid oxide fuel cell according to the present invention. For example, a sulfur compound is reacted with hydrogen on a catalyst (Ni—Mo system, Co—Mn system) to convert it into hydrogen sulfide (250 ° C. to 400 ° C.), and the hydrogen sulfide is taken into zinc oxide and removed (350 A desulfurizer employing a so-called hydrodesulfurization method (such as a temperature of 400 ° C. to 400 ° C.) can also be used in the solid oxide fuel cell according to the present invention.

  The present invention provides a solid oxide fuel cell capable of maintaining the performance of a desulfurizer during storage after power generation of the solid oxide fuel cell is stopped in a state where low cost and low energy loss are ensured. And can be used for its suspended storage method.

DESCRIPTION OF SYMBOLS 1 Reformer 2 Desulfurizer 3 Vaporizer 4 Fuel cell 5 Cell stack 7 Raw fuel gas supply path 7a First piping part 7b Second piping part 20 Water supply path 23 Sealed container 25 First opening position 26 Second opening Position 27 Water supply path K Folding section S Gas shut-off mechanism

Claims (9)

A reformer for steam-reforming hydrocarbon-based raw fuel gas supplied through the raw fuel gas supply path to generate fuel gas;
A desulfurizer that is provided in the middle of the raw fuel gas supply path upstream of the reformer and that performs a desulfurization process on the raw fuel gas;
Provided in the middle of the raw fuel gas supply path upstream of the reformer and downstream of the desulfurizer, the water supplied through the water supply path is vaporized, and the vaporized water vapor and the raw fuel gas A vaporizer that mixes the raw fuel gas supplied through the supply path;
A solid oxide fuel cell comprising a fuel gas generated in the reformer and a cell stack having a plurality of fuel cells that generate power by oxidation and reduction of an oxidant,
A solid oxide fuel cell including a folded portion configured to be folded so that a middle portion of the raw fuel gas supply path between the desulfurizer and the vaporizer has a downward convex shape and store water. .   The folding portion functions as a gas shut-off mechanism capable of shutting off gas when water stays in the raw fuel gas supply path and is blocked in the cold stop state after power generation in the cell stack is stopped. The solid oxide fuel cell according to claim 1.   The water supplied to the carburetor through the water supply path is in the raw fuel gas supply path between the desulfurizer and the vaporizer in a cold stop state after power generation in the cell stack is stopped. 3. The solid oxide fuel cell according to claim 1, wherein the solid oxide fuel cell is configured to flow into at least a part of the staying water that flows in and stays in the raw fuel gas supply path at the turn-up portion. A water supply path capable of supplying water to the raw fuel gas supply path between the desulfurizer and the vaporizer;
In the cold stop state after power generation in the cell stack is stopped, the water supplied from the water replenishment path to the raw fuel gas supply path stays in the raw fuel gas supply path at the turning portion The solid oxide fuel cell according to any one of claims 1 to 3, wherein the solid oxide fuel cell is configured to be at least part of water. The folded portion is inserted from the desulfurizer side into the sealed container constituting a part of the raw fuel gas supply path and the sealed container constituting a part of the raw fuel gas supply path. A first piping section and a second piping section that constitutes a part of the raw fuel gas supply path and is inserted from the vaporizer side into the sealed container; The second opening position of the second piping part is lower than the first opening position of the first piping part inside the sealed container,
Solid oxidation as described in any one of Claims 1-4 in which the said 1st opening position is located in the gaseous-phase side, and the said 2nd opening position is located in the liquid phase side in the state which the water stagnated in the said folding | turning part. Physical fuel cell.   The sealed container is tapered downward so that a cross-sectional area of the sealed container at the second opening position is smaller than a cross-sectional area of the sealed container at the first opening position. The solid oxide fuel cell according to claim 5.   The solid oxide fuel cell according to any one of claims 1 to 6, wherein the folded portion is provided below a lowermost surface of the desulfurizer. A reformer that steam-reforms hydrocarbon-based raw fuel gas supplied through the raw fuel gas supply passage to generate fuel gas, and a middle portion of the raw fuel gas supply passage upstream of the reformer. A desulfurizer for desulfurizing the raw fuel gas, and provided in the middle of the raw fuel gas supply path upstream of the reformer and downstream of the desulfurizer, and through the water supply path A vaporizer that vaporizes the supplied water and mixes the vaporized water vapor and the raw fuel gas supplied through the raw fuel gas supply path, and oxidation of the fuel gas and oxidant generated in the reformer And a method for stopping and storing a solid oxide fuel cell comprising a cell stack having a plurality of fuel cells that generate electricity by reduction,
The solid oxide fuel cell is configured to be folded so that water is stored by being folded so that a middle portion of the raw fuel gas supply path between the desulfurizer and the vaporizer has a downwardly convex shape. Part
After the power generation in the cell stack is stopped, when the temperature of the vaporizer and the temperature of the desulfurizer are equal to or higher than the boiling point of water and the temperature of the folded portion is lower than the boiling point of water, the vaporization is performed. A method for stopping and storing a solid oxide fuel cell comprising a step of supplying water to the vessel through the water supply path. A reformer that steam-reforms hydrocarbon-based raw fuel gas supplied through the raw fuel gas supply passage to generate fuel gas, and a middle portion of the raw fuel gas supply passage upstream of the reformer. A desulfurizer for desulfurizing the raw fuel gas, and provided in the middle of the raw fuel gas supply path upstream of the reformer and downstream of the desulfurizer, and through the water supply path A vaporizer that vaporizes the supplied water and mixes the vaporized water vapor and the raw fuel gas supplied through the raw fuel gas supply path, and oxidation of the fuel gas and oxidant generated in the reformer And a method for stopping and storing a solid oxide fuel cell comprising a cell stack having a plurality of fuel cells that generate electricity by reduction,
The solid oxide fuel cell is configured to be folded so that water is stored by being folded so that a middle portion of the raw fuel gas supply path between the desulfurizer and the vaporizer has a downwardly convex shape. And
A water supply path capable of supplying water to the raw fuel gas supply path between the desulfurizer and the vaporizer;
After the power generation in the cell stack is stopped, when the temperature of the folding part is less than the boiling point of water, water is supplied from the water supply path to the raw fuel gas supply path to supply water to the folding part. A method for stopping and storing a solid oxide fuel cell having a storing step.

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