JP6847736B2 - Solid oxide fuel cell system - Google Patents

Description

The present invention relates to a solid oxide fuel cell system, and more particularly, a solid oxide fuel that generates electricity by reacting a hydrogen gas obtained by steam reforming a raw material fuel gas containing a hydrocarbon with an oxidant gas. Regarding the battery system.

A solid oxide fuel cell (Solid Oxide Fuel Cell: also referred to as "SOFC") uses an oxide ion conductive solid electrolyte as an electrolyte, and has a fuel electrode and an oxidant gas electrode attached to both sides of the solid oxide fuel cell. A fuel cell that operates at a relatively high temperature by supplying fuel gas to the pole side and supplying oxidant gas (air, oxygen, etc.) to the other oxidant gas pole side.

In this way, the fuel cell cell supplies fuel gas to the fuel electrode side and supplies oxidant gas to the oxidant gas electrode side to perform power generation operation, but shifts from the power generation operation state to the stopped state. There is a risk that the oxidant gas (air) will come into contact with the fuel electrode in a high temperature state. It is known that when an oxidant gas comes into contact with a fuel electrode in a high temperature state, nickel contained in the fuel electrode reacts with the oxidant gas and oxidatively expands. This oxidative expansion of the fuel electrode may deteriorate the fuel cell itself or the sealing material for airtightly fixing the fuel cell, even if it is very small, and is a solid oxide fuel cell system. The problem arises that the useful life of the fuel cell is shortened.

Japanese Patent No. 4906242 (Patent Document 1) describes a method for stopping the operation of a fuel cell. In this method of stopping the operation of the fuel cell, after stopping the power generation of the fuel cell, the supply of air to the air electrode layer is continued, and the supply of raw material and fuel gas is also continued after reducing the supply amount. , The temperature of the reforming catalyst and the fuel cell is lowered. That is, by continuing to supply the raw material fuel gas even after the power generation by the fuel cell is stopped, the reformed raw material fuel gas or the unmodified raw material fuel gas is discharged to the fuel electrode of the fuel cell. It is sent in and the fuel electrode side is maintained in a reducing atmosphere. As a result, the temperature of the fuel cell can be lowered while preventing the air from flowing back from the air electrode side to the fuel electrode side and oxidizing the fuel electrode.

Japanese Patent No. 4906242

However, even when the stop step of lowering the temperature of the fuel cell while continuing the supply of raw material and fuel gas is executed as in the invention described in Patent Document 1, when this stop step is executed an extremely large number of times. The present inventor has found that some fuel cell cells are affected by oxidative expansion. That is, even in the stopping step as in the invention described in Patent Document 1, when this stopping step is repeatedly executed several hundred times or more, a part of the fuel cell cells arranged in large numbers is slightly damaged due to oxidative expansion. Was confirmed to occur. Although this damage is slight, when such damage occurs in the fuel cell, it becomes difficult to guarantee the long-term stable operation of the solid oxide fuel cell system for more than a dozen years.

Next, the effect of oxidation of the fuel electrode on the fuel cell will be described with reference to FIG. FIG. 11 is a graph schematically showing a change in the outer diameter of the fuel cell when the conventional solid oxide fuel cell system is normally started and stopped. In FIG. 11, the horizontal axis shows the temperature of the fuel cell, and the vertical axis shows the outer diameter of the fuel cell at that temperature. Further, in FIG. 11, the change in the outer diameter of the fuel cell 16 when the temperature of the fuel cell 16 is raised in the start-up process is shown by a broken line, and when the temperature of the fuel cell 16 is lowered in the stop step, the change is shown by a broken line. The change in the outer diameter of the fuel cell 16 is shown by a solid line.

First, the broken line a1 in FIG. 11 shows the change in the outer diameter of the fuel cell when the start-up step is executed and the temperature of the fuel cell is raised in the conventional solid oxide fuel cell system. In this case, the outer diameter of the fuel cell becomes monotonously large as the temperature rises due to thermal expansion. After the start-up process is carried out, the process shifts to the power generation process, and the temperature of the fuel cell is maintained substantially constant, so that the outer diameter of the fuel cell also remains substantially constant. Next, when the temperature is raised according to the broken line a1 and the fuel cell system is stopped after passing through the power generation step, the stop step is executed. The solid line b1 in FIG. 11 shows the change in the outer diameter of the fuel cell when the temperature is raised according to the broken line a1, the power generation process is performed, the stop process is executed, and the temperature of the fuel cell is lowered. In this case, the outer diameter of the fuel cell cell initially decreases monotonically with the temperature decrease, but during the temperature decrease, the outer diameter of the fuel cell is in the temperature range surrounded by the imaginary line in FIG. It started to increase once, and then decreased again.

The increase in the outer diameter of the fuel cell during this stopping process is due to the fact that the oxidant gas slightly diffuses from the oxidant gas electrode side to the fuel electrode side of the fuel cell and the fuel electrode undergoes slight oxidation. That is, when the oxidant gas diffuses to the fuel electrode side, the nickel component contained in the fuel electrode expands due to oxidation, and the outer diameter of the fuel cell increases. The oxidation of the fuel electrode is slight, and the increase in the outer diameter of the fuel cell (the difference between the outer diameter at the lower end of the broken line a1 in FIG. 11 and the outer diameter at the lower end of the solid line b1) due to one stop step is extremely large. It is very small and does not immediately affect the performance of the fuel cell. However, even with such a slight oxidative expansion, if the solid oxide fuel cell system is started and stopped many times due to long-term use, the adverse effects of the oxidative expansion accumulate and the service life of the system is limited. The result is that

Therefore, an object of the present invention is to provide a solid oxide fuel cell system capable of sufficiently suppressing deterioration of a fuel cell even when the stop step is repeatedly executed a large number of times.

In order to solve the above-mentioned problems, the present invention presents a solid oxide fuel cell system that generates power by reacting a hydrogen gas obtained by steam reforming a raw material fuel gas containing a hydrocarbon with an oxidizing agent gas. a is a solid electrolyte layer, a fuel cell having a solid electrolyte layer of the fuel electrode layer containing nickel provided on the inside, and the oxidizing gas electrode layer provided on the outer side of the solid electrolyte layer, a module case, the raw fuel gas by reforming by steam reforming to produce a fuel gas rich in hydrogen gas, a reforming section and supplies the fuel gas to the fuel electrode side of the fuel cell , A fuel supply device that supplies raw fuel gas to this reforming unit, an evaporation unit that evaporates the supplied water to generate steam for steam reforming, and supplies the generated steam to the reforming unit. A water supply device that supplies water for steam reforming to the evaporation part, an oxidant gas supply device that supplies oxidant gas to the oxidant gas electrode side of the fuel cell, and a fuel cell provided in the module case. It controls a combustion unit that passes through the fuel electrode side of the cell and burns residual fuel gas remaining unused for power generation at the upper end of the fuel cell, a fuel supply device, a water supply device, and an oxidant gas supply device. The controller has a controller that controls the extraction of electric power from the fuel cell, and the controller stops the extraction of electric power from the fuel cell and ends the power generation process, and then supplies the raw fuel gas by the fuel supply device. , And a stop step that lowers the temperature of the fuel cell while continuing to supply water by the water supply device, and the controller is further configured to perform a combustion flame of residual fuel gas at the top of each fuel cell. The S / C, which is the molar ratio of the amount of water vapor and the amount of carbon supplied to the reforming part, is higher than the S / C in the power generation process during the predetermined fire extinguishing promotion period during the shutdown process so that the extinction is promoted. It is configured to control the fuel supply and water supply devices to be higher, and the fire extinguishing promotion period is for all fuel cells from the time when the combustion flame of the residual fuel gas at the upper end of some fuel cell cells begins to disappear. Ri period der including period until the combustion flame at the upper end of the cell is lost, extinguishing promotion period, the temperature of the combustion portion, reignition is started after reduced to a temperature below that does not occur at the upper end of the fuel cell The controller is characterized in controlling the fuel supply device and the water supply device so that the S / C becomes high at the start of the fire extinguishing promotion period.

In the present invention configured as described above, the raw fuel gas supplied from the fuel supply device is supplied to the reforming section together with the steam obtained by evaporating the water supplied from the water supply device in the evaporation section. The fuel gas containing abundant hydrogen gas, which has been steam reformed in the reforming section, is supplied to the fuel pole side of a plurality of fuel cell cells housed in the module case. On the other hand, the oxidant gas supplied by the oxidant gas supply device is supplied to the oxidant gas electrode side of the fuel cell. The residual fuel gas that has passed through the fuel electrode side of the fuel cell and has not been used for power generation is burned at the upper end of the fuel cell in the combustion part in the module case. The controller controls the fuel supply device, the water supply device, and the oxidant gas supply device, and also controls the extraction of electric power from the fuel cell. In addition, after the controller stops the extraction of electric power from the fuel cell and ends the power generation process, the controller continues to supply raw fuel gas by the fuel supply device and water by the water supply device. Perform a stop step to reduce the temperature. Further, the controller controls the amount of water vapor and the amount of carbon supplied to the reforming unit during a predetermined fire extinguishing promotion period during the stop step so as to promote the extinction of the combustion flame of the residual fuel gas at the upper end of each fuel cell. The fuel supply device and the water supply device are controlled so that the molar ratio S / C of the above is higher than the S / C during the power generation process.

As described above, in the conventional fuel cell system, a stop step of lowering the temperature of the fuel cell while continuing the supply of raw fuel gas by the fuel supply device and the supply of water by the water supply device is executed. However, if the stop step is executed many times, the effect of oxidative expansion appears on the fuel electrode of the fuel cell. As a result of investigating the cause of this, it was found that this phenomenon is caused by the combustion state of the residual fuel at the upper end of the fuel cell during the stopping process. That is, during the stop process, the temperature of each fuel cell is lowered while reducing the flow rate of the fuel gas supplied to the fuel electrode of each fuel cell. Along with this, the flame of the residual fuel gas burned at the upper end of each fuel cell during the power generation process gradually shrinks and disappears as the temperature drops.

At this time, among the many fuel cell cells arranged in the module case, the flame at the upper end of the fuel cell with a low temperature is extinguished at an early stage, and the flame of the fuel cell with a high temperature remains for a long time without being extinguished. .. In this way, if the fuel cell in which the flame is extinguished and the fuel cell in which the flame remains are mixed for a long time, the temperature of the fuel cell in which the flame is extinguished drops sharply, but the flame remains. Since the temperature of the fuel cell cells is not so low, a large temperature unevenness occurs between the arranged fuel cell cells. In general, of a plurality of fuel cell cells arranged, the fuel cell located in the central part of the arrangement tends to have a high temperature, and the flame at the upper end remains for a long time, whereas the fuel in the peripheral part of the arrangement remains. Since the temperature of the battery cell becomes low, the flame is extinguished early. As a result, the temperature of the fuel cell in the central portion of the array becomes higher, the temperature of the fuel cell in the peripheral portion drops sharply, and the temperature unevenness between the fuel cell cells increases. Even if the fuel supply is continued due to such a large temperature unevenness between each fuel cell and a sudden pressure change when the locally remaining flame disappears, the oxidant gas electrode side Backflow of oxidant gas to the fuel electrode side is generated.

On the other hand, according to the present invention configured as described above, the S / C, which is the molar ratio of the amount of water vapor and the amount of carbon supplied to the reforming portion during the predetermined fire extinguishing promotion period during the stopping process, is determined. Since the fuel supply device and the water supply device are controlled so as to be higher than the S / C during the power generation process, the flame at the upper end of the fuel cell is likely to be extinguished, and temperature unevenness between the fuel cell cells is unlikely to occur. Become. That is, by increasing the S / C during the fire extinguishing promotion period, even if the fuel supply amount is the same, the concentration of the fuel in the fuel gas decreases, so that the flame at the upper end of the fuel cell is easily extinguished. Even if the flame is extinguished at high temperature, reignition is unlikely to occur. As a result, the flame at the upper end of each fuel cell in the module case is likely to be extinguished relatively early as a whole, temperature unevenness between each fuel cell can be suppressed, and backflow of oxidant gas is suppressed. can do.

Further, according to the present invention, the combustion flame at the upper end of all fuel cell cells disappears from the time when the combustion flame of the residual fuel gas at the upper end of the fuel cell begins to disappear during the fire extinguishing promotion period for increasing the S / C. It is set to include the period until it is done. Therefore, at least, it is possible to promote the extinguishing of the flames from the state in which the flames of some fuel cell cells begin to extinguish until the flames of all the fuel cell cells extinguish. Since the flame remains for a long time, it is possible to prevent the temperature unevenness between the fuel cell cells from expanding. The fire extinguishing promotion period is set to an arbitrary period including the period from the time when the flames of some fuel cell cells start to extinguish to the extinguishment of the flames of all the fuel cell cells after the start of the stop process. can do.

According to the present invention configured as described above, the fire extinguishing promotion period is started after the temperature of the combustion portion drops below the temperature at which reignition does not occur at the upper end of the fuel cell, so that the S / C is increased. As a result, after the flame at the upper end of the fuel cell is extinguished, the flame can be surely extinguished without spontaneous ignition again. Further, according to the present invention configured as described above, since the S / C is not increased in the temperature zone where reignition occurs, a large amount of water vapor is not unnecessarily supplied to the fuel cell. The risk of water vapor oxidation of the fuel electrode can be reduced.

In the present invention, the fire extinguishing promotion period is preferably started when the temperature of the combustion part drops to a temperature of 300 ° C. or higher and 400 ° C. or lower.
According to the present invention configured in this way, since the fire extinguishing promotion period is started in the temperature zone where the temperature of the combustion part is 300 ° C. or higher and 400 ° C. or lower, the flame at the upper end of the fuel cell that has once disappeared is reignited. It is possible to surely extinguish the flame while suppressing the temperature unevenness between the fuel cell cells.

In the present invention, preferably, the controller controls the fuel supply device and the water supply device so that the S / C during the fire extinguishing promotion period is 4 or more and 10 or less.
According to the present invention configured in this way, since the S / C in the fire extinguishing promotion period is set to 4 or more and 10 or less, it is possible to effectively promote the extinguishing of the flame at the upper end of the fuel cell and also It is also possible to suppress the occurrence of water vapor oxidation due to excessive water vapor.

In the present invention, it is preferable that the fuel gas further has a manifold connected to the lower end of each fuel cell, and the fuel gas reformed in the reforming portion is distributed to each fuel cell via the manifold.

When supplying fuel gas to a large number of fuel cell cells, it is generally advantageous to distribute the supplied fuel gas to each fuel cell via a manifold because the structure inside the module case can be simplified. is there. On the other hand, when the fuel gas is distributed to a large number of fuel cell cells via the manifold, it is difficult to supply the fuel gas of exactly the same flow rate to each fuel cell, and the flame at the upper end of each fuel cell disappears. Variations occur at the time of fueling, and temperature unevenness is likely to occur. According to the present invention configured as described above, since the S / C is increased during the fire extinguishing promotion period, the flames of all the fuel cell cells are extinguished in a relatively short time even when a configuration having a manifold is adopted. It is possible to suppress the oxidative expansion of the fuel electrode due to the occurrence of temperature unevenness.

In the present invention, preferably, the controller includes a fire extinguishing prediction circuit that predicts the time when the combustion flame of the residual fuel gas at the upper end of the fuel cell starts to disappear, and the controller has a fire extinguishing promotion period based on the prediction by the fire extinguishing prediction circuit. To start.

According to the present invention configured in this way, since the fire extinguishing prediction circuit predicts the time when the combustion flame starts to disappear, the controller can accurately set the fire extinguishing promotion period and surely suppress the occurrence of temperature unevenness. can do.

In the present invention, preferably, the fire extinguishing prediction circuit sets the start time of the fire extinguishing promotion period based on the time when the combustion flame of the residual fuel gas at the upper end of the fuel cell starts to disappear in the stop step executed in the past. decide.

According to the present invention configured in this way, the fire extinguishing prediction circuit determines the start time of the fire extinguishing promotion period based on the stop step executed in the past, so that the combustion flame of the residual fuel gas disappears more accurately. It is possible to predict when to start fire extinguishing and to set the fire extinguishing promotion period accurately.

In the present invention, preferably, the evaporative unit is configured to be heated based on the combustion heat of the residual fuel gas burned in the combustion unit, and the evaporative unit is further separated from the combustion heat of the residual fuel gas. It is equipped with a heating heater that heats the evaporative part.

According to the present invention configured in this way, since the evaporating part is heated based on the combustion heat of the residual fuel gas burned in the combustion part, the combustion heat of the residual fuel gas is effectively utilized to generate water vapor. Can be generated. In addition, since the evaporation unit is also equipped with a separate heater to heat it, it is definitely necessary even when a large amount of steam is required or when the temperature has dropped over time after the power generation has stopped. A large amount of water vapor can be generated.

According to the solid oxide fuel cell system of the present invention, deterioration of the fuel cell can be sufficiently suppressed even when the stop step is repeatedly executed many times.

It is an overall block diagram which shows the solid oxide fuel cell system (SOFC) by embodiment of this invention. It is a side sectional view which shows the fuel cell module provided in the solid oxide fuel cell system by embodiment of this invention. It is sectional drawing of the fuel cell module along the line III-III of FIG. It is a figure which shows the fuel cell which was provided in the solid oxide fuel cell system by embodiment of this invention. It is an enlarged sectional view of the end part of the fuel cell provided in the solid oxide fuel cell system according to the embodiment of this invention. It is a perspective view which shows the fuel cell stack provided in the solid oxide fuel cell system by embodiment of this invention. It is a block diagram which shows the solid oxide fuel cell system by embodiment of this invention. It is a time chart which shows an example of each supply amount of fuel and the like in the start-up process of the solid oxide fuel cell system by embodiment of this invention, and the temperature of each part. It is a time chart which shows an example of the temperature of the fuel cell stack in the stop process of the solid oxide fuel cell system according to the embodiment of this invention, and each supply amount of fuel and the like. It is a figure which shows typically the state of the combustion flame at the upper end of each fuel cell in the stop process of the solid oxide fuel cell system by embodiment of this invention. It is a graph which schematically shows the change of the outer diameter of a fuel cell when normal start and stop are executed in a conventional solid oxide fuel cell system.

Next, the solid oxide fuel cell system according to the embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is an overall configuration diagram showing a solid oxide fuel cell system (SOFC) according to an embodiment of the present invention.
As shown in FIG. 1, the solid oxide fuel cell system (SOFC) 1 includes a fuel cell module 2 and an auxiliary machine unit 4.

The fuel cell module 2 includes a housing 6, and a metal module case 8 is built in the housing 6 via a heat insulating material 7. In the power generation chamber 10 which is a lower part of the module case 8 which is a closed space, a fuel cell which performs a power generation reaction with a fuel gas and an oxidant gas (hereinafter, appropriately referred to as "air for power generation" or "air") is used. The cell stack 14 is arranged. In the present embodiment, in the fuel cell stack 14, all of the plurality of fuel cell cells 16 are connected in series.

A combustion chamber 18 as a combustion unit is formed above the power generation chamber 10 of the module case 8 of the fuel cell module 2, and in this combustion chamber 18, residual fuel gas and residual air not used in the power generation reaction are formed. Burns to produce exhaust gas (in other words, combustion gas). Further, the module case 8 is covered with the heat insulating material 7 to suppress the heat inside the fuel cell module 2 from being dissipated to the outside air. Further, above the combustion chamber 18, a reformer 120, which is a reformer for reforming fuel gas, is arranged, and the temperature at which the reformer 120 can be reformed by the combustion heat of the residual gas is reached. It is heating like.

Further, an evaporator 140 is provided in the heat insulating material 7 above the module case 8 in the housing 6. The evaporator 140 evaporates water to generate water vapor by exchanging heat between the supplied water and the exhaust gas, and a mixed gas of the water vapor and the raw fuel gas (hereinafter referred to as "fuel gas"). (Sometimes referred to as) is supplied to the reformer 120 in the module case 8.
Further, a hydrogenated desulfurizer 36 for removing a sulfur component from the raw material fuel gas is provided on the side surface of the module case 8. The hydrodesulfurizer 36 heats the catalyst built in the module case 8 to a predetermined temperature and reacts the raw fuel gas with the hydrogen gas supplied from the reformer 120, so that the raw fuel gas is contained. It is a hydrodesulfurization type desulfurizer that removes the sulfur component of the gas.

Next, the auxiliary machine unit 4 has a pure water tank 26 that stores water containing dew condensation of water contained in the exhaust from the fuel cell module 2 and turns it into pure water by a filter, and water supplied from the water storage tank. A water flow rate adjusting unit 28 (such as a "water pump" driven by a motor) for adjusting the flow rate of the water flow rate is provided. Further, the auxiliary machine unit 4 includes a gas shutoff valve 32 that shuts off the fuel supplied from the fuel supply source 30 such as city gas, and a fuel flow rate adjusting unit 38 that adjusts the flow rate of the fuel gas (“fuel driven by a motor”. It is provided with a "pump", etc.) and a valve 39 that shuts off the fuel gas flowing out of the fuel flow rate adjusting unit 38 when the power supply is lost. Further, the auxiliary machine unit 4 supplies the solenoid valve 42 that shuts off the air supplied from the air supply source 40, the air flow rate adjusting unit 45 for power generation (“air blower” driven by the motor, etc.), and the power generation chamber. It is provided with a heater 48 for heating the power generation air to be generated. The heater 48 is provided in order to efficiently raise the temperature at the time of startup, but it may be omitted.

In the present embodiment, when the fuel cell system 1 is started, the fuel gas is first burned at the upper end of each fuel cell 16 to heat the reformer 120 arranged above, and then the reformer 120. The SR step in which only the steam reforming reaction occurs is executed in 120, and the temperature of the fuel cell stack 14 is raised to a temperature at which a power generation reaction is possible. Further, from the POX process in which only the partial oxidation reforming reaction (POX) occurs in the reformer 120 after the combustion operation at the start of the fuel cell system, the partial oxidation reforming reaction (POX) and the steam reforming reaction (SR) ) May occur through the ATR step in which the autothermal reforming reaction (ATR) is mixed, and then the SR step in which only the steam reforming reaction occurs may be performed, or the POX step may be omitted and the SR step may be changed to SR. It may be configured to be transitioned to the process. In the configuration where the partial oxidation reforming reaction is generated in the reformer 120, it is necessary to provide a reforming air flow rate adjusting unit (not shown) for supplying reforming air to the reformer 120. ..

Next, the hot water production device 50 to which the exhaust gas is supplied is connected to the fuel cell module 2. Tap water is supplied to the hot water production apparatus 50 from the water supply source 24, and the tap water becomes hot water by the heat of the exhaust gas and is supplied to a hot water storage tank of an external water heater (not shown). Further, the fuel cell module 2 is provided with a control box 52 for controlling the supply amount of fuel gas and the like. Further, the fuel cell module 2 is connected to an inverter 54 which is a power extraction unit (power conversion unit) for supplying the electric power generated by the fuel cell module to the outside.

Next, the structure of the fuel cell module provided in the fuel cell system 1 according to the present embodiment will be described with reference to FIGS. 2 and 3.
FIG. 2 is a side sectional view showing a fuel cell module of a solid oxide fuel cell system, and FIG. 3 is a sectional view taken along the line III-III of FIG.

As shown in FIGS. 2 and 3, the fuel cell module 2 has a fuel cell stack 14 and a reformer 120 provided inside a module case 8 covered with a heat insulating material 7, and also has a module case 8. It has an evaporator 140 provided outside and inside the heat insulating material 7.

First, as shown in FIG. 2, the module case 8 has a substantially rectangular top plate 8a, a bottom plate 8c, and a pair of opposite side plates 8b (FIG. 2) connecting the side extending in the longitudinal direction (horizontal direction in FIG. 2). The tubular body made of 3) and the two opposing openings at both ends of the tubular body in the longitudinal direction are closed, and the sides extending in the width direction (horizontal direction in FIG. 3) of the top plate 8a and the bottom plate 8c are separated from each other. It consists of closed side plates 8d and 8e to be connected.

In the module case 8, the top plate 8a and the side plate 8b are covered with the air passage cover 160. The air passage cover 160 has a top plate 160a and a pair of side plates 160b facing each other (FIG. 3). An exhaust pipe 171 is penetrated through a substantially central portion of the top plate 160a. The top plate 160a and the top plate 8a, and the side plate 160b and the side plate 8b are separated by a predetermined distance. As a result, between the outside of the module case 8 and the heat insulating material 7, specifically, between the top plate 8a and the side plate 8b of the module case 8 and the top plate 160a and the side plate 160b of the air passage cover 160, oxidation occurs. Air passages 161a and 161b as agent gas supply passages are formed (FIG. 3).

At the lower part of the side plate 8b of the module case 8, a plurality of through holes 8f are provided. The air for power generation passes from the air introduction pipe 74 for power generation provided in the substantially central portion of the top plate 160a of the air passage cover 160 on the closed side plate 8e side of the module case 8 via the flow path direction adjusting portion 164. It is supplied in 161a (see FIG. 2). Then, the air for power generation is injected into the power generation chamber 10 from the outlet 8f toward the fuel cell stack 14 through the air passages 161a and 161b (see FIG. 3).

Further, plate fins 162 and 163 as heat exchange promoting members are provided inside the air passages 161a and 161b (see FIG. 3). The plate fins 162 are horizontally provided between the top plate 8a of the module case 8 and the top plate 160a of the air passage cover 160 so as to extend in the longitudinal direction and the width direction, and the plate fins 163 are provided on the side plates 8b of the module case 8. It is provided between the air passage cover 160 and the side plate 160b of the air passage cover 160 and extends in the longitudinal direction and the vertical direction at a position above the fuel cell 16.

The power generation air flowing through the air passages 161a and 161b is inside the module case 8 inside the plate fins 162 and 163 (specifically, along the top plate 8a and the side plates 8b) when passing through the plate fins 162 and 163. It will be heated by exchanging heat with the exhaust gas passing through the exhaust passage provided in the above. For this reason, the portions of the air passages 161a and 161b provided with the plate fins 162 and 163 function as heat exchangers (heat exchange portions).

Next, the evaporator 140 is fixed so as to extend in the horizontal direction on the top plate 8a of the module case 8. Further, a part 7a of the heat insulating material 7 is arranged between the evaporator 140 and the module case 8 so as to fill these gaps (see FIGS. 2 and 3).

Specifically, the evaporator 140 has a fuel supply pipe 63 that supplies water and raw fuel gas (may include reforming air) to one side end side in the longitudinal direction (left-right direction in FIG. 2). , An exhaust gas discharge pipe 82 (see FIG. 3) for discharging exhaust gas is connected, and an upper end portion of the exhaust pipe 171 is connected to the other end side in the longitudinal direction. The exhaust pipe 171 penetrates the opening formed in the top plate 160a of the air passage cover 160 and extends downward, and is connected to the exhaust port formed on the top plate 8a of the module case 8.

Further, as shown in FIGS. 2 and 3, the evaporator 140 has a substantially rectangular evaporator case 141 when viewed from above. The evaporator case 141 is formed by joining two low-height bottomed rectangular tubular upper cases 142 and lower cases 143 with an intermediate plate 144 sandwiched between them.

Therefore, the evaporator case 141 has a two-layer structure in the vertical direction, and an exhaust passage portion 140A through which the exhaust gas supplied from the exhaust pipe 171 passes is formed in the lower layer portion, and fuel is formed in the upper layer portion. An evaporation unit 140B that evaporates the water supplied from the supply pipe 63 to generate water vapor and a mixing unit 140C that mixes the water vapor generated by the evaporation unit 140B and the raw fuel gas supplied from the fuel supply pipe 63 are provided. Has been done.

As shown in FIGS. 2 and 3, the evaporation section 140B and the mixing section 140C are formed in a space in which the evaporator 140 is partitioned by a partition plate 145 in which a plurality of communication holes (slits) are formed. Further, the evaporation portion 140B is filled with alumina balls (not shown).
Further, the exhaust passage portion 140A is similarly partitioned into three spaces from the upstream side to the downstream side of the exhaust gas by two partition plates 146 and 147 having a plurality of communication holes. Then, the second space is filled with a combustion catalyst (not shown). That is, in the present embodiment, the evaporator 140 includes a combustion catalyst in the lower layer structure of the two-layer structure in the vertical direction.

In such an evaporator 140, heat exchange is performed between the water in the evaporation section 140B and the exhaust gas passing through the exhaust passage section 140A, and the water in the evaporation section 140B evaporates due to the heat of the exhaust gas. Water vapor will be generated. Further, heat exchange is performed between the mixed gas in the mixing section 140C and the exhaust gas passing through the exhaust passage section 140A, and the temperature of the mixed gas is raised by the heat of the exhaust gas. Further, around the evaporator 140, rod-shaped heaters 149 (FIGS. 2 and 3) are arranged so as to surround the three sides thereof. The heating heater 149 is energized during the start-up step and the stop-step of the solid oxide fuel cell system 1 to heat the evaporation unit 140B from the surroundings and promote the generation of water vapor in the evaporation unit 140B. It is configured as follows. The heater 149 may be omitted.

Further, as shown in FIG. 2, a mixed gas supply pipe 112 for supplying the mixed gas to the reformer 120 is connected to the mixing unit 140C. The mixed gas supply pipe 112 is arranged so as to pass through the inside of the exhaust pipe 171 and has one end connected to an opening formed in the intermediate plate 144 and the other end formed on the top surface of the reformer 120. It is connected to the mixed gas supply port. The mixed gas supply pipe 112 passes through the exhaust passage portion 140A and the exhaust pipe 171 and extends vertically downward to the inside of the module case 8, where it is bent by approximately 90 ° and extends horizontally along the top plate 8a. , It is bent downward by approximately 90 ° and connected to the reformer 120.

Next, the reformer 120 is arranged above the combustion chamber 18 so as to extend horizontally along the longitudinal direction of the module case 8 and is fixed to the top plate 8a. The reformer 120 has a substantially rectangular outer shape when viewed from above, but is an annular structure in which a through hole is formed in a central portion, and has a housing in which an upper case 121 and a lower case 122 are joined. There is. The through hole is located so as to overlap the exhaust port 111 formed in the top plate 8a in a top view, and preferably the exhaust port 111 is formed at the center position of the through hole.

On one end side (closed side plate 8e side of the module case 8) of the reformer 120 in the longitudinal direction, the mixed gas supply pipe 112 is connected to the mixed gas supply port provided in the upper case 121, and the other end side (closed). On the side plate 8d side), the fuel gas supply pipe 64 is connected to the lower case 122, and the hydrogen extraction pipe 65 for the hydrogenated desulfurizer extending to the desulfurizer 36 is connected to the upper case 121. Therefore, the reformer 120 receives the mixed gas (that is, the raw fuel gas mixed with steam (which may include reforming air)) from the mixed gas supply pipe 112, reforms the mixed gas internally, and reforms the mixed gas. It is configured to discharge the reformed gas (that is, the fuel gas) from the fuel gas supply pipe 64 and the hydrogen extraction pipe 65 for the hydrogenated desulfurizer.

The reformer 120 is divided into three spaces by two partition plates 123a and 123b, so that the reformer 120 receives the mixed gas from the mixed gas supply pipe 112 in the reformer 120. A reforming unit 120B filled with a reforming catalyst (not shown) for reforming the mixed gas, and a gas discharge unit 120C for discharging the gas that has passed through the reforming unit 120B are formed. (See FIG. 2). The reforming section 120B is a space sandwiched between the partition plates 123a and 123b, and the reforming catalyst is held in this space. The mixed gas and the reformed fuel gas can move through a plurality of communication holes (slits) provided in the partition plates 123a and 123b. Further, as the reforming catalyst, a catalyst in which nickel is added to the surface of an alumina sphere or a catalyst in which ruthenium is added to the surface of an alumina sphere is appropriately used.

The mixed gas supplied from the evaporator 140 via the mixed gas supply pipe 112 is ejected to the mixed gas receiving unit 120A through the mixed gas supply port. This mixed gas is expanded in the mixed gas receiving section 120A to reduce the ejection speed, passes through the partition plate 123a, and is supplied to the reforming section 120B.
In the reforming section 120B, the mixed gas moving at a low speed is reformed into a fuel gas by the reforming catalyst, and this fuel gas passes through the partition plate 123b and is supplied to the gas discharging section 120C.
In the gas discharge unit 120C, the fuel gas is discharged to the fuel gas supply pipe 64 and the hydrogen extraction pipe 65 for the hydrogenated desulfurizer.

The fuel gas supply pipe 64 as the fuel gas supply passage extends downward along the closing side plate 8d in the module case 8, is bent by approximately 90 ° near the bottom plate 8c, and extends in the horizontal direction, and extends in the horizontal direction of the fuel cell stack 14. It enters the manifold 66 formed below, and further extends horizontally in the manifold 66 to the vicinity of the closing side plate 8e on the opposite side. A plurality of fuel supply holes are formed on the lower surface of the horizontal portion 64a of the fuel gas supply pipe 64, and fuel gas is supplied into the manifold 66 from the fuel supply holes. A lower support plate 68 having a through hole for supporting the fuel cell stack 14 is attached above the manifold 66, and the fuel gas in the manifold 66 is supplied into each fuel cell 16. To. Further, an ignition device 83 for starting combustion of fuel gas and air is provided in the combustion chamber 18.
Further, the reformer 120 is arranged at a predetermined horizontal distance from the side plate 8b of the module case 8.

Next, the fuel cell 16 will be described with reference to FIGS. 4 and 5.
FIG. 4 is a diagram showing fuel cell cells constituting the fuel cell cell stack according to the embodiment of the present invention. FIG. 5 is an enlarged cross-sectional view of the end of the fuel cell.
As shown in FIG. 4, the fuel cell 16 includes a fuel cell main body 84 and caps 86 which are connection electrode portions connected to both ends of the fuel cell main body 84.

As shown in FIG. 5, the fuel cell main body 84 having a conductive support as a support is a tubular structure extending in the vertical direction, and has a cylindrical shape forming a fuel gas flow path 88 which is a gas passage inside. The inner electrode layer 90, which is the fuel electrode layer, the electrolyte layer 94, which is a cylindrical solid electrolyte layer provided on the outer periphery of the inner electrode layer 90, and the cylindrical air electrode (cylindrical air electrode) provided on the outer periphery of the electrolyte layer 94. An outer electrode layer 92, which is an oxidant gas electrode) layer, is provided. The inner electrode layer 90 is a porous body that functions as a support that constitutes the fuel cell main body 84 and also constitutes a gas passage through which fuel gas flows. The inner electrode layer 90 is a fuel electrode and has a (−) pole, while the outer electrode layer 92 is an air electrode in contact with air and has a (+) electrode.

The inner electrode layer 90 is composed of, for example, a mixture of Ni and zirconia doped with at least one selected from rare earth elements such as Ca, Y, and Sc, and Ni and ceria doped with at least one selected from rare earth elements. It is formed from at least one of a mixture, a mixture of Ni and a lantern garade doped with at least one selected from Sr, Mg, Co, Fe and Cu. In this embodiment, the inner electrode layer 90 is made of Ni / YSZ.
A porous insulating support can also be used as the support, and in this case, a fuel electrode layer is formed as an inner electrode layer on the outside of the insulating support.

The electrolyte layer 94 is formed over the entire circumference along the outer peripheral surface of the inner electrode layer 90, the lower end is terminated above the lower end of the inner electrode layer 90, and the upper end is below the upper end of the inner electrode layer 90. It is terminated. The electrolyte layer 94 includes, for example, zirconia doped with at least one selected from rare earth elements such as Y and Sc, ceria doped with at least one selected from rare earth elements, and lanthanum gallate doped with at least one selected from Sr and Mg. It can be formed from at least one of. In the present embodiment, the electrolyte layer 94 is formed by LSGM, which is a lanthanum gallate doped with Sr and Mg.

The outer electrode layer 92 is formed over the entire circumference along the outer peripheral surface of the electrolyte layer 94, the lower end is terminated above the lower end of the electrolyte layer 94, and the upper end is terminated below the upper end of the electrolyte layer 94. ing. The outer electrode layer 92 is, for example, a lanthanum manganate doped with at least one selected from Sr and Ca, and a lanthanum ferrite doped with at least one selected from Sr, Co, Ni and Cu, Sr, Fe, Ni and Cu. It is formed from at least one of lantern cobaltite, silver, etc. doped with at least one selected from.

Next, the cap 86 will be described. Since the caps 86 attached to the upper end side and the lower end side of the fuel cell main body 84 have the same structure, they are attached to the lower end side of the fuel cell main body 84 here. The cap 86 will be specifically described.

The cap 86 is provided so as to surround the upper and lower ends of the fuel cell body 84, and is electrically connected to the inner electrode layer 90 of the fuel cell body 84 as a connection electrode for pulling out the inner electrode layer 90 to the outside. Function. As shown in FIG. 5, the cap 86 provided at the lower end of the fuel cell main body 84 has a cylindrical first cylindrical portion 86a and an annular circle extending outward from the upper end of the first cylindrical portion 86a. It has a ring portion 86b and a second cylindrical portion 86c extending upward from the outer circumference of the ring portion 86b. A fuel gas flow path 98 communicating with the fuel gas flow path 88 of the inner electrode layer 90 is formed in the central portion of the first cylindrical portion 86a of the cap 86. The fuel gas flow path 98 is an elongated pipeline provided so as to extend from the center of the cap 86 in the axial direction of the fuel cell main body 84.

The cap 86 is made of ferritic stainless steel or austenitic stainless steel, and the inner peripheral surface and outer peripheral surface thereof _{are coated with chromium oxide (Cr 2} O _{3 in} this embodiment), and the outer peripheral surface is MnCo ₂ O. ₄ is coated. In addition, an Ag current collector film is provided on the outer peripheral surface of _{the coated MnCo 2} O _{4 layer.} In the present embodiment, the Ag current collector film is provided over the entire outer peripheral surface of the cap 86, but may be provided only on a part of the outer peripheral surface.

The silver paste 95 is arranged in the space between the inside of the second cylindrical portion 86c of the cap 86 and the outer peripheral surface of the end portion of the inner electrode layer 90 of the fuel cell main body 84. By firing after assembling the fuel cell 16, the silver paste 95 is sintered, and the inner electrode layer 90 and the cap 86 are electrically and mechanically coupled. Further, a glass seal 96 made of a glass material is provided between the inner peripheral surface of the second cylindrical portion 86c of the cap 86 and the outer peripheral surface of the lower end portion of the electrolyte layer 94. The space between the cap 86 and the inner electrode layer 90 is hermetically sealed with respect to the space outside the fuel cell 16 by the glass seal 96.

Next, the fuel cell stack 14 according to the embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a perspective view showing a fuel cell stack according to the present embodiment.

As shown in FIG. 6, the fuel cell stack 14 includes 128 fuel cell cells 16 arranged in a grid pattern, and 16 of these fuel cell cells 16 are arranged side by side in eight rows.
Each fuel cell 16 is supported by a rectangular lower support plate 68 whose lower end side is made of metal. The lower support plate 68 constitutes the ceiling surface of the manifold 66, and a through hole for allowing fuel gas to flow into the fuel gas flow path 88 of each fuel cell 16 is formed. Further, a substantially cylindrical ceramic spacer 100 is arranged between the cap 86 on the lower end side of each fuel cell 16 and the lower support plate 68, and the cap 86 and the lower support plate 68 are separated from each other. This ensures insulation.

Further, each fuel cell 16 is attached with a current collecting member 102 that electrically connects one fuel cell 16 to an adjacent fuel cell 16. The current collecting member 102 connects the cap 86, which is electrically connected to the inner electrode layer 90, which is a fuel electrode, and the outer peripheral surface of the outer electrode layer 92, which is an air electrode of an adjacent fuel cell 16. Is placed in. Further, since each current collecting member 102 is attached to the upper end portion and the lower end portion of each fuel cell 16, the fuel cell 16 adjacent to one fuel cell 16 is electrified by the two current collecting members 102. (These two current collecting members 102 are in parallel). In this way, all the fuel cell cells 16 constituting the fuel cell stack 14 are electrically connected in series by each current collecting member 102. A thin silver film is formed on the entire outer surface of the outer electrode layer 92 (air electrode) of each fuel cell 16 as an electrode on the air electrode side. When the current collecting member 102 comes into contact with the surface of the thin film, the current collecting member 102 is electrically connected to the entire air electrode.

Next, the sensors and the like attached to the solid oxide fuel cell system (SOFC) according to the present embodiment will be described with reference to FIG. 7. FIG. 7 is a block diagram showing a solid oxide fuel cell system according to an embodiment of the present invention.
As shown in FIG. 7, the solid oxide fuel cell system 1 includes a control unit 210 which is a controller, and the control unit 210 is operated by an operation such as “ON” or “OFF” for the user to operate. An operation device 212 equipped with a button, a display device 214 for displaying various data such as a power generation output value (wattage), and a notification device 216 for issuing an alarm (warning) in the event of an abnormal state are connected. There is.
Further, the control unit 210 contains a microprocessor, a memory, and a program (not shown above) for operating these, and by these, the auxiliary machine unit 4 is based on the input signal from each sensor. The inverter 54 and the like are controlled. The notification device 216 may be connected to a management center at a remote location and notify the management center of an abnormal state.

Next, signals from various sensors described below are input to the control unit 210.
First, the combustible gas detection sensor 220 is for detecting a gas leak, and is attached to the fuel cell module 2 and the auxiliary machine unit 4.
In the CO detection sensor 222, CO in the exhaust gas originally discharged to the outside through the exhaust gas discharge pipe 82 (FIG. 3) or the like is transferred to an external housing (not shown) that covers the fuel cell module 2 and the auxiliary machine unit 4. It is for detecting whether or not a leak has occurred.
The hot water storage state detection sensor 224 is for detecting the temperature and amount of hot water in a water heater (not shown).

The power state detection sensor 226 is for detecting the current and voltage of the inverter 54 and the distribution board (not shown).
The power generation air flow rate detection sensor 228 is for detecting the flow rate of the power generation air supplied to the power generation chamber 10.
The ignition air flow rate sensor 230 is for detecting the flow rate of the ignition air supplied to the reformer 120.
The fuel flow rate sensor 232 is for detecting the flow rate of the fuel gas supplied to the reformer 120.

The water flow rate sensor 234 is for detecting the flow rate of pure water supplied to the reformer 120.
The water level sensor 236 is for detecting the water level of the pure water tank 26.
The pressure sensor 238 is for detecting the pressure on the upstream side outside the reformer 120.
The exhaust temperature sensor 240 is for detecting the temperature of the exhaust gas flowing into the hot water production apparatus 50.

The power generation chamber temperature sensor 242 is provided on the front side and the back side in the vicinity of the fuel cell stack 14, detects the temperature in the vicinity of the fuel cell stack 14, and detects the temperature in the vicinity of the fuel cell stack 14 (that is, the fuel cell 16 itself). ) Is for estimating the temperature.
The combustion chamber temperature sensor 244 is for detecting the temperature of the combustion chamber 18.
The exhaust gas chamber temperature sensor 246 is for detecting the temperature of the exhaust gas of the exhaust pipe 171.
The reformer temperature sensor 248 is for detecting the temperature of the reformer 120, and calculates the temperature of the reformer 120 from the inlet temperature and the outlet temperature of the reformer 120.
The outside air temperature sensor 250 is for detecting the temperature of the outside air when the solid oxide fuel cell system (SOFC) is arranged outdoors. Further, a sensor for measuring the humidity of the outside air or the like may be provided.

The signals from these sensors are sent to the control unit 210, which is a controller, and the control unit 210 determines the water flow rate adjusting unit 28, the fuel flow rate adjusting unit 38, and the air flow rate adjusting unit for power generation based on the data obtained from these signals. A control signal is sent to 45 to control each flow rate in these units.

Next, the operation of the fuel cell module 2 provided in the solid oxide fuel cell system 1 according to the embodiment of the present invention will be described with reference to FIGS. 2 and 3.
As shown in FIG. 2, water and raw fuel gas (fuel gas) are placed in an evaporator 140B provided on the upper layer of the evaporator 140 from a fuel supply pipe 63 connected to one end side in the longitudinal direction of the evaporator 140. Will be supplied. The water supplied to the evaporation section 140B is heated by the exhaust gas flowing through the exhaust passage section 140A provided in the lower layer of the evaporator 140 to become steam. The steam and the raw fuel gas supplied from the fuel supply pipe 63 flow in the downstream direction in the evaporation section 140B and are mixed in the mixing section 140C. The mixed gas in the mixing portion 140C is heated by the exhaust gas flowing through the lower exhaust passage portion 140A.

The mixed gas (fuel gas) formed in the mixing unit 140C is supplied to the reformer 120 in the module case 8 through the mixed gas supply pipe 112. Since the mixed gas supply pipe 112 passes through the exhaust passage portion 140A and the exhaust pipe 171 in this order, the mixed gas in the mixed gas supply pipe 112 is further heated by the exhaust gas flowing through these passages.

The mixed gas flows into the mixed gas receiving section 120A in the reformer 120, passes through the partition plate 123a from here, and flows into the reforming section 120B. The mixed gas is reformed in the reforming section 120B to become a fuel gas. The fuel gas thus generated passes through the partition plate 123b and flows into the gas discharge unit 120C.

Further, the fuel gas branches from the gas discharge unit 120C into the fuel gas supply pipe 64 and the hydrogen extraction pipe 65 for the hydrogenated desulfurizer. Then, the fuel gas flowing into the fuel gas supply pipe 64 is supplied into the manifold 66 from the fuel supply hole 64b provided in the horizontal portion 64a of the fuel gas supply pipe 64, and is supplied from the manifold 66 into each fuel cell 16. Will be done.

Further, as shown in FIGS. 2 and 3, the power generation air is supplied from the power generation air introduction pipe 74 to the air passage 161a. When the air for power generation passes through the plate fins 162 and 163 in the air passages 161a and 161b, the exhaust gas passes through the exhaust gas formed in the module case 8 below the plate fins 162 and 163. Efficient heat exchange between them will result in heating. After that, the power generation air is injected into the power generation chamber 10 from both sides toward the lower side surface of the fuel cell stack 14 from the plurality of outlets 8f provided in the lower part of the side plate 8b of the module case 8. The heated power generation air heats the lower portion of each fuel cell 16.

Further, the fuel gas not used for power generation in the power generation chamber 10 flows out from the upper end of each fuel cell 16 and is burned in the combustion chamber 18 to become exhaust gas (combustion gas), which rises in the module case 8. To go. After that, the exhaust gas flows out from the exhaust port 111 formed in the center of the top plate 8a of the module case 8.

Then, the exhaust gas flowing out from the exhaust port 111 passes through the exhaust pipe 171 provided outside the module case 8 and flows into the exhaust passage portion 140A of the evaporator 140, passes through the exhaust passage portion 140A, and then evaporates. It is discharged from the vessel 140 to the exhaust gas discharge pipe 82. When the exhaust gas flows through the exhaust passage portion 140A of the evaporator 140, it exchanges heat with the mixed gas in the mixing portion 140C of the evaporator 140 and the water in the evaporator 140B as described above.

Next, control in the start-up process of the solid oxide fuel cell system 1 will be described with reference to FIG.
FIG. 8 is a time chart showing an example of the supply amount of fuel and the like in the start-up process and the temperature of each part. The scale on the vertical axis of FIG. 8 indicates the temperature, and each supply amount of fuel or the like roughly indicates an increase or decrease thereof.

The start-up process shown in FIG. 8 is executed by the control unit 210, which is a controller. The control unit 210 executes a start-up step of raising the temperature of the fuel cell stack 14 in a normal temperature state to a temperature at which power generation is possible. After the completion of this start-up step, electric power is taken out from the fuel cell stack 14 and a power generation step of supplying electric power to an external device of the solid oxide fuel cell system 1 is executed. Further, in the present embodiment, the start-up step includes a combustion step, an SR1 step, an SR2 step, and an SR2 step, which will be described later.

First, at time t0 in FIG. 8, the supply of power generation air, ignition air, and water is started (prepurge step). Specifically, the control unit 210 sends a signal to the power generation air flow rate adjusting unit 45, which is an oxidant gas supply device for power generation, to operate the signal. As described above, the power generation air is introduced into the fuel cell module 2 via the power generation air introduction pipe 74, and flows into the power generation chamber 10 through the air passages 161a and 161b and the outlet 8f. Further, the control unit 210 sends a signal to an ignition air flow rate adjusting unit (not shown), which is an oxidant gas supply device for ignition, to operate the unit. The ignition air introduced into the fuel cell module 2 flows into the inside of each fuel cell 16 via the reformer 120 and the manifold 66, and flows out from the upper end thereof.

Further, the control unit 210 sends a signal to the water flow rate adjusting unit 28, which is a water supply device, to operate the water flow rate adjusting unit 28. The pure water pumped from the water flow rate adjusting unit 28 reaches the evaporator 140 through the fuel supply pipe 63. At least from time t0 to a predetermined time (water filling period: t0 to t1), a small amount of water is arranged in the evaporator 140 from the water flow rate adjusting unit 28 through the fuel supply pipe 63. At time t0, since the fuel has not been supplied yet, the reforming reaction does not occur in the reformer 120. In the present embodiment, the supply amount of power generation air started at time t0 in FIG. 8 is about 50 L / min, the supply amount of ignition air is about 4.8 L / min, and the water supply amount is about 4.8 L / min. It is 2.5cc / min.

Next, at time t1 after a predetermined time from time t0 in FIG. 8, fuel supply is started and the supplied fuel is ignited. Specifically, the control unit 210 sends a signal to the fuel flow rate adjusting unit 38, which is a fuel supply device, to operate the signal. In the present embodiment, the fuel supply amount started at time t1 is about 4.0 L / min. The fuel introduced into the fuel cell module 2 flows into the inside of each fuel cell 16 via the reformer 120 and the manifold 66, and flows out from the upper end thereof. At time t1, since the temperature of the reformer 120 is still low, the reforming reaction does not occur in the reformer 120.

When igniting, the control unit 210 sends a signal to the ignition device 83 (FIG. 2) which is an ignition means to ignite the fuel flowing out from the upper end of each fuel cell 16.
Further, at time t1, since a small amount of water is arranged in the evaporator 140, the control unit 210 reduces the amount of water supplied to 2.06 cc / min. As a result, a small amount of water begins to be supplied to the evaporator 140 during the ignition process.

At time t2, the control unit 210 confirms by the combustion chamber temperature sensor 244 that the ignition is completed when the temperature of the combustion chamber 18 rises by a predetermined temperature. Then, the ignition process shifts to the combustion process. In the combustion step, the temperature of the reformer 120 is raised by the combustion heat of the remaining fuel that is not used for power generation (the total amount of the supplied fuel because the power generation reaction does not occur at this point).

When the ignition is completed, the control unit 210 stops the supply of ignition air at time t2 (supply amount 0.0 L / min).
Further, at time t2, the control unit 210 reduces the fuel supply amount to 3.14 L / min and increases the power generation air supply amount to about 70 L / min. The amount of water supplied is maintained at 2.06 cc / min, and is maintained at the minimum value during the start-up process, at least immediately after ignition and during the combustion process.

In the combustion process, the supplied fuel flows out from the upper end of each fuel cell 16 and is burned here. This combustion heat heats the reformer 120 arranged above the fuel cell stack 14. By raising the temperature of the evaporator 140, it becomes possible to generate water vapor in a short time after the start of off-gas combustion.

In this way, the temperature of the reformer 120 rises during the combustion step, and at time t3, the combustion step is shifted to the first steam reforming reaction step (SR1 step). In this SR1 step, a steam reforming reaction is generated by the fuel and steam that have flowed into the reformer 120 via the evaporator 140. This steam reforming reaction is an endothermic reaction represented by the following formula (1).
C _m H _n + xH ₂ O → aCO ₂ + bCO + cH ₂ (1)

Further, when the first steam reforming reaction step (SR1 step) is started at time t3, the amount of water consumed increases, so that the control unit 110 maintains the supply amounts of fuel and power generation air. , Only increase the water supply to 3.82cc / min.
In the time chart shown in FIG. 8, the reformer temperature at time t3 is about 250 ° C. The reformer temperature is the temperature detected by the reformer temperature sensor 248 (FIG. 7), which is the average temperature of the reformer 120. In fact, at time t3, the reformer 120 has partially reached a temperature at which a steam reforming reaction occurs.

In the present embodiment, the SR step (SR1 step, SR2 step and SR3 step) is configured to be performed after the combustion step in the start-up step. The SR step of the present embodiment is intended to generate an SR reaction without introducing air for reforming.

Next, when the temperature detected by the reformer temperature sensor 248 reaches about 450 ° C., at time t4 in FIG. 8, the first steam reforming reaction step (SR1 step) to the second steam reforming reaction step (SR2). Process). At time t4, the air supply for power generation is reduced to 59 L / min, and the water supply is further increased to 5.0 cc / min. In addition, the fuel supply amount will be maintained at the previous value. As a result, the S / C, which is the molar ratio of water vapor and carbon, is increased in the SR2 step as compared with the SR1 step.

Further, when the temperature detected by the power generation chamber temperature sensor 242 reaches about 550 ° C. at time t5 in FIG. 8, the second steam reforming reaction step (SR2 step) to the third steam reforming reaction step (SR3 step) Will be migrated to. Along with this, the fuel supply amount is reduced to 2.02 L / min, the air supply amount for power generation is further reduced to 47 L / min, and the water supply amount is reduced to 4.75 cc / min. As a result, in the SR3 step, the molar ratio S / C of steam and carbon is further increased as compared with the SR2 step, and the value is set to a value suitable for the steam reforming reaction.

Further, when the temperature detected by the power generation room temperature sensor 242 reaches about 600 ° C. after executing the SR3 step for a predetermined time, the fuel cell stack 14 is in a state where power can be generated, and thus shifts to the “power generation step”. .. In the power generation process, electric power is taken out from the fuel cell stack 14 to the inverter 54 (FIG. 7), and the electric power is output to an external device. Further, in the power generation process, the control unit 210 changes the fuel supply amount, the power generation air supply amount, and the water supply amount according to the output power required for the fuel cell module 2. In the present embodiment, the molar ratio S / C of water vapor to carbon during the power generation process is set to about 2.5, and the temperature inside the power generation chamber 10 changes between about 550 ° C and 750 ° C.

Next, the stop step of the solid oxide fuel cell system 1 according to the embodiment of the present invention will be described with reference to FIGS. 9 and 10.
FIG. 9 is a time chart showing an example of the temperature of the fuel cell stack 14 in the stop step and the supply amount of fuel and the like. The scale on the vertical axis in the upper part of FIG. 9 indicates the temperature, and each supply amount of fuel or the like roughly indicates the increase or decrease thereof. The lower part of FIG. 9 is a time chart with S / C as the vertical axis, which is the molar ratio of the amount of water vapor supplied to the fuel cell stack 14 and the amount of carbon in the raw fuel gas. FIG. 10 is a diagram schematically showing a state of a combustion flame at the upper end of each fuel cell 16 during the stopping process.

First, when the stop operation is performed at the time t301 of FIG. 9, the control unit 210 (FIG. 7) executes the stop step, and the extraction of electric power from the fuel cell module 2 is stopped. As a result, the generated current drops to zero. The power generation process was executed before the time t301 in FIG. 9, and in the power generation process, a required amount of current was taken out from the fuel cell module 2, and an amount of raw fuel gas corresponding to the generated current was generated. Power generation air (oxidant gas) and water are supplied to the fuel cell module 2. Further, during the power generation process, the temperature of the fuel cell stack 14 is maintained at about 600 ° C., which is a temperature at which a power generation reaction is possible, and the amount of steam supplied to the reformer 120 and the amount of carbon in the raw fuel gas. S / C, which is the molar ratio of S / C, is maintained at about 2.5.

Next, when the stop process is started at time t301, the supply amount of power generation air (however, power generation is not performed during the stop process) to the fuel cell module 2 is increased as compared with that during the power generation process, and the raw fuel gas. And the water supply is less than during the power generation process. In the example shown in FIG. 9, the supply amount of air for power generation is increased to 70 L / min, the supply amount of raw material fuel gas is reduced to 0.45 L / min, and the supply amount of water is also reduced to 1.05 cc / min. To. As described above, in the stop step in the present embodiment, even after the power extraction (power generation) from the fuel cell module 2 is stopped, the fuel cell stack 14 continues to be supplied with the raw fuel gas and the reforming water. This is a so-called down-heating stop process that lowers the temperature. When the stop process is started at time t301, the supply amounts of raw material fuel gas and water are reduced, respectively, but as shown in the lower part of FIG. 9, the S / C is 2 even after the supply amounts are reduced. It is maintained at about 5.5.

During the power generation process or immediately after the start of the stop process, the temperature inside the module case 8 is high, so the temperature of the exhaust gas is also high. Can be generated. On the other hand, when a certain amount of time has passed from the start of the stop process, the temperature inside the module case 8 is lowered, so that the temperature of the exhaust gas is also lowered, and the heat of the exhaust gas alone is sufficient for the evaporation section 140B to have a sufficient amount of water vapor. Becomes difficult to generate. In such a case, the heaters 149 (FIGS. 2 and 3) arranged around the evaporator 140 are appropriately energized to heat the evaporator 140 so that a required amount of steam can be obtained.

Further, during the stop step, the supply of a predetermined amount of raw fuel gas and steam is continued, and these are supplied to the fuel pole side of each fuel cell 16 via the reformer 120. Here, since the temperature of the reformer 120 is sufficiently high at the initial stage of the stop step, a steam reforming reaction occurs in the reformer 120, and the steam reformed fuel gas is supplied to each fuel cell 16. Will be done. On the other hand, at the end of the shutdown process, the temperature of the reformer 120 is lowered, so that a sufficient steam reforming reaction does not occur in the reformer 120, and the unreformed raw fuel gas is used. A mixed gas with steam is supplied to each fuel cell 16. When any of these gases is supplied, the fuel electrode side inside each fuel cell 16 is maintained in a reducing atmosphere, and oxidation of the fuel electrode is prevented.

Further, as described above, during the power generation process, the residual fuel gas remaining not used for power generation at the fuel electrode of the fuel cell 16 is the upper end of the fuel cell 16 as shown in FIG. 10A. Outflow from and burned there. The inside of the module case 8 is heated by the combustion of the residual fuel in the combustion chamber 18. Next, when the stop process is started, the supply amount of raw fuel gas is reduced, so that the residual fuel flowing out from the upper end of each fuel cell 16 (during the stop process, power is generated in the fuel cell 16). Because there is no fuel, the total amount of fuel supplied) is reduced. Further, in the stop step, the flow rate of air supplied to the air electrode side of each fuel cell 16 is increased. As a result, when the stop process is started at time t301, the temperature inside the module case 8 is lowered, and the temperature of the fuel cell stack 14 is also lowered as shown in FIG. However, as shown in FIG. 10B, the combustion of the residual fuel at the upper end of each fuel cell 16 is maintained for a predetermined period after the stop process is started, although the flame is smaller than that during the power generation process. Will be done.

After the stop process is started at time t301, when the temperature inside the module case 8 (combustion chamber 18) drops to some extent with the passage of time, the combustion of the residual fuel at the upper end of the fuel cell 16 is stopped and the flame is extinguished. Will be done. At this time, the flame at the upper end of each fuel cell 16 is not extinguished at the same time in all the fuel cell 16, but as shown in FIG. 10 (c), from some fuel cell 16 whose temperature has dropped. The flames are extinguished in sequence, and finally all the flames are extinguished as shown in FIG. 10 (d). Here, according to the experiment of the present inventor, the extinction of the flame at the upper end of the fuel cell 16 tends to occur in order from the fuel cell 16 arranged in the peripheral portion where the temperature tends to decrease in the module case 8. Admitted. Further, in the conventional solid oxide fuel cell system 1, after the flame is extinguished in the first fuel cell 16 among a large number of fuel cell 16, the flame in all the fuel cell 16 is extinguished. It was found that the time to loss was quite long.

In this way, if the combustion flame in some fuel cell 16 is extinguished during the stop process and the combustion flame in the other fuel cell 16 is maintained for a long time, the flame is extinguished. A large temperature difference occurs between the 16 and the fuel cell 16 in which the flame is maintained. That is, since the temperature of the fuel cell 16 in which the flame is maintained is high, the pressure on the fuel electrode side inside the fuel cell 16 is high, while the temperature of the fuel cell 16 in which the flame is extinguished is low and the fuel electrode is high. The pressure on the side also tends to be low. Due to such a temperature difference of each fuel cell 16, the pressure on the fuel electrode side of each fuel cell 16 varies. Due to such a variation in pressure on the fuel electrode side between the fuel cell 16, even if a small amount of fuel is continuously supplied, the inside of the fuel cell 16 having a low pressure (fuel electrode side). ), The phenomenon that a small amount of air flows back has been found by the present inventor. It has also been found that such backflow of air tends to occur at the moment when the flame of the fuel cell 16 remaining until the end is extinguished during the stopping process.

In order to prevent backflow of air due to such variation in the extinction time of the combustion flame, in the present embodiment, S / which is a molar ratio of the amount of water vapor and the amount of carbon during a predetermined fire extinguishing promotion period during the stopping process. C is set higher than S / C during the power generation process to promote the disappearance of residual gas combustion. That is, when the S / C value is high, even if the supply amount of the raw material fuel gas is constant, the ratio of water vapor contained in the gas flowing out from the upper end of the fuel cell 16 is large and the ratio of carbon is small. , The flame is easily extinguished.

In the present embodiment, as shown in FIG. 9, the fire extinguishing promotion period is started at time t302 when the temperature in the combustion chamber 18 (almost the same as the temperature of the fuel cell stack) drops to about 400 ° C., and the S / C The value of is increased from 2.5 to 6. That is, when the temperature detected by the combustion chamber temperature sensor 244 drops to about 400 ° C., the control unit 210 sends a signal to the fuel flow rate adjusting unit 38 and the water flow rate adjusting unit 28, and the S / C value becomes about 6. The supply amount of raw material fuel gas and water is adjusted so as to be. As a result, the flame at the upper end of each fuel cell 16 is such that the flames of all the fuel cell 16 are extinguished immediately after the flame of the first fuel cell 16 is extinguished, and the combustion is maintained for a certain period of time. The temperature difference between each fuel cell 16 based on the variation of the above is effectively suppressed.

In the present embodiment, as an example, the S / C is set to about 6 by setting the supply amount of raw material and fuel gas to 0.45 L / min and the supply amount of water to 2.53 cc / min. The S / C value during the fire extinguishing promotion period is preferably set to 4 or more and 10 or less. Further, the entire amount of the water supplied from the water flow rate adjusting unit 28 to the evaporation unit 140B is immediately evaporated to become steam, which is not sent to the reformer 120. Therefore, the value of S / C, which is the molar ratio of the amount of water vapor supplied to the reformer 120 and the amount of carbon in the raw material fuel gas, depends only on the respective supply amounts by the fuel flow rate adjusting unit 38 and the water flow rate adjusting unit 28. It is not specified, and is also affected by the temperature of the evaporation unit 140B and the evaporation capacity. For example, when the evaporator 140 is heated by energizing the heater 149 (FIGS. 2 and 3), a required amount of steam can be supplied by supplying a relatively small amount of water as compared with the case where the heater 140 is not heated. Can be generated. In the present embodiment, the supply amounts of the raw fuel gas and water are set so that the S / C value actually supplied to the reformer 120 during the fire extinguishing promotion period is about 6, and the heater 149 is used. In the case, the amount of heating by the heater 149 is adjusted together with the amount of water supplied.

Here, the fire extinguishing promotion period is set to include a period from the time when the flame at the upper end of each fuel cell 16 begins to extinguish to the extinguishment of the flame at the upper end of all the fuel cell. That is, after the flames in many fuel cell 16 are extinguished, the fire extinguishing promotion period is started, and even if the flames of all the fuel cell cells are extinguished in a short time after that, until the fire extinguishing promotion period is started. In addition, since a large temperature difference is generated between the fuel cell cells 16, it is not possible to obtain a sufficient effect of suppressing temperature unevenness. Further, if the fire extinguishing promotion period is terminated before the flames of all the fuel cell cells are extinguished, the flames that have not been extinguished may be maintained for a long time and a large temperature unevenness may occur, which is preferable. Absent. Further, when the fire extinguishing promotion period is started from a relatively high temperature of about 500 ° C. in the combustion chamber 18, the flame is extinguished by increasing the S / C value, and then the fuel cell is high. The upper end of the cell 16 may be reignited. In this way, if the fire extinguishing promotion period is started from a temperature range in which reignition is likely to occur, water vapor for increasing S / C and heat for generating water vapor are wasted, so that reignition does not occur. It is preferable to start the fire extinguishing promotion period after the temperature has dropped.

In the present specification, "the time when the combustion flame of the residual fuel gas at the upper end of the fuel cell 16 begins to disappear" means that the flame in the first fuel cell 16 of all the fuel cell 16 is the flame. It is assumed to mean an arbitrary time point from the moment of extinction until the flame of about 20% of the fuel cell 16 is extinguished. In the present embodiment, when the temperature in the combustion chamber 18 drops to about 300 ° C. to 400 ° C., which is the fire extinguishing start temperature range, in the stopping step, the flame of the first fuel cell 16 is extinguished. It is preferable to start the fire extinguishing promotion period from a temperature range of about 300 ° C. to 400 ° C. More preferably, by starting the digestion promotion period from the temperature range of 350 ° C. to 400 ° C., the S / C is set high before the time when the combustion flame starts to disappear, and the combustion in all the fuel cell 16 is promptly performed. The flame can be extinguished.

At time t302 in FIG. 9, after the fire extinguishing promotion period is started, the flame at the upper end of each fuel cell 16 is quickly extinguished, and the temperature of the fuel cell stack also decreases with the passage of time. When the temperature detected by the power generation room temperature sensor 242 drops to 100 ° C. at time t303, the control unit 210 sends a signal to the water flow rate adjusting unit 28 to stop the signal. As a result, the amount of water vapor supplied is reduced to zero, so that the S / C value becomes zero and the fire extinguishing promotion period ends. Further, when the temperature detected by the power generation room temperature sensor 242 drops to 50 ° C. at time t304, the control unit 210 sends a signal to the fuel flow rate adjusting unit 38 to stop the fuel flow rate adjusting unit 38. At this temperature, the fuel electrode is not oxidized even when a backflow of air from the air electrode side to the fuel electrode side occurs. Next, after stopping the fuel supply at time t304, at time t305 after a predetermined time has elapsed, the control unit 210 sends a signal to the power generation air flow rate adjusting unit 45 to stop the signal. As a result, the stop process is completed.

According to the solid oxide fuel cell system 1 of the embodiment of the present invention, during the predetermined fire extinguishing promotion period (time t302 to t303 in FIG. 9) during the stop step (time t301 to FIG. 9), the reformer The fuel flow adjustment unit 38 and water so that the S / C (≈6), which is the molar ratio of the amount of water vapor and the amount of carbon supplied to 120, is higher than the S / C (≈2.5) during the power generation process. Since the flow rate adjusting unit 28 is controlled, the flame at the upper end of the fuel cell 16 is likely to be extinguished, and temperature unevenness between the fuel cell 16 is less likely to occur.

Further, according to the solid oxide fuel cell system 1 of the present embodiment, the fire extinguishing promotion period (time t302 to t303 in FIG. 9) for increasing the S / C is the combustion of the residual fuel gas at the upper end of the fuel cell 16. It is set to include a period from the time when the flame starts to disappear until the combustion flame at the upper ends of all the fuel cell 16 is extinguished. Therefore, at least, it is possible to promote the extinguishing of the flames from the state in which the flames of some fuel cell 16 start to extinguish to the extinguishment of the flames of all the fuel cell cells. It is possible to prevent the temperature unevenness between the fuel cell cells 16 from expanding due to the fact that the flame remains for a long time.

Further, according to the solid oxide fuel cell system 1 of the present embodiment, the fire is extinguished after the temperature of the combustion chamber 18 drops to a temperature (for example, 500 ° C.) or less at the upper end of the fuel cell 16 where reignition does not occur. Since the promotion period is started, after the flame at the upper end of the fuel cell 16 is extinguished by increasing the S / C, the flame can be surely extinguished without spontaneous ignition again. Further, with this configuration, the S / C is not increased in the temperature zone where reignition occurs, so that a large amount of water vapor is not unnecessarily supplied to the fuel cell 16 and the fuel electrode is used. The risk of water vapor oxidation can be reduced.

Further, according to the solid oxide fuel cell system 1 of the present embodiment, the fire extinguishing promotion period is started when the temperature of the combustion portion drops to 400 ° C., so that the flame at the upper end of the fuel cell 16 once extinguished is re-released. It is not ignited, and the flame can be surely extinguished while suppressing temperature unevenness between the fuel cell 16.

Further, according to the solid oxide fuel cell system 1 of the present embodiment, since the S / C in the fire extinguishing promotion period is set to 6, it is possible to effectively promote the extinction of the flame at the upper end of the fuel cell 16. At the same time, it is possible to suppress the generation of water vapor oxidation due to excessive water vapor.

Further, according to the solid oxide fuel cell system 1 of the present embodiment, since the S / C is increased during the fire extinguishing promotion period, the flames of all the fuel cell 16 can be extinguished in a relatively short time. Even when the configuration of the fuel supply system is simplified by adopting the manifold 66 (FIG. 2), it is possible to suppress the oxidative expansion of the fuel electrode due to the occurrence of temperature unevenness.

Further, according to the solid oxide fuel cell system 1 of the present embodiment, the evaporator 140 is heated based on the combustion heat of the residual fuel gas burned in the combustion chamber 18, so that the combustion heat of the residual fuel gas Can be effectively used to generate water vapor. Further, since the evaporator 140 is separately provided with a heater 149 (FIGS. 2 and 3) for heating the evaporator 140, the temperature drops when a large amount of steam is required or when time elapses after the power generation is stopped. Even in such a situation, it is possible to surely generate the required amount of water vapor.

Although the preferred embodiment of the present invention has been described above, various modifications can be made to the above-described embodiment of the present invention. In particular, in the above-described embodiment, when the temperature in the combustion chamber 18 drops to about 400 ° C., the fire extinguishing promotion period is started and the S / C value is increased, but the detection data by any other sensor is used. It is also possible to determine when to start the fire extinguishing promotion period based on. For example, when combustion at the upper end of the fuel cell 16 is stopped, the amount of carbon monoxide that is exhausted without being burned increases. Therefore, for example, based on the detection value of the CO detection sensor 222 provided in the exhaust path, combustion is performed. It is possible to determine the presence or absence of disappearance. Alternatively, the disappearance of the combustion flame can be detected by providing a camera capable of capturing an image of the inside of the combustion chamber 18 and analyzing the images captured at predetermined time intervals in the stopping step.

Further, the start time of the fire extinguishing promotion period can be determined based on the elapsed time after the start of the stop process, not on the detection result by the sensor. That is, the present invention can be configured such that the time for the temperature in the combustion chamber 18 to drop to a predetermined temperature after the start of the stopping process is substantially constant, and the fire extinguishing promotion period is started after this time has elapsed. Most simply, the present invention can be configured so that the fire extinguishing promotion period starts immediately after the start of the stop process.

Alternatively, as a modification, a fire extinguishing prediction circuit (not shown) is provided in the control unit 210, and the fire extinguishing prediction circuit predicts the time when the combustion of the residual fuel gas starts to disappear, and the fire extinguishing promotion period starts from the predicted time. The present invention can also be configured to initiate. In the fire extinguishing prediction circuit (not shown), for example, the combustion of the residual fuel gas disappears based on the temperature in the combustion chamber 18 at the start of the stop process, the operating conditions of the power generation process immediately before the start of the stop process, the outside air temperature, and the like. It can be configured to predict when to start.
According to this modification, since the fire extinguishing prediction circuit (not shown) predicts the time when the combustion flame starts to disappear, the control unit 210 can accurately set the fire extinguishing promotion period and ensure the occurrence of temperature unevenness. Can be suppressed.

Alternatively, as another modification, fire extinguishing prediction is made based on the relationship between the temperature in the combustion chamber 18 at the start of the stop process and the time when the combustion of the residual fuel gas begins to disappear in the stop process executed in the past. The present invention can also be configured such that a circuit (not shown) determines the starting point of the fire extinguishing promotion period.
According to this modification, the fire extinguishing prediction circuit (not shown) determines the start time of the fire extinguishing promotion period based on the stop step executed in the past, so that the combustion flame of the residual fuel gas disappears more accurately. It is possible to predict when to start fire extinguishing and to set the fire extinguishing promotion period accurately.

1 Solid oxide fuel cell system 2 Fuel cell module 4 Auxiliary unit 6 Housing 7 Insulation material 8 Module case 8a Top plate 8b Side plate 8c Bottom plate 8d, 8e Closed side plate 8f Outlet 10 Power generation chamber 14 Fuel cell cell stack 16 Fuel cell Cell 18 Combustion chamber (combustion section)
24 Water supply source 26 Pure water tank 28 Water flow rate adjustment unit (water supply device)
30 Fuel supply source 36 Desulfurizer 38 Fuel flow rate adjustment unit (fuel supply device)
39 Valve 40 Air supply source 42 Solenoid valve 45 Air flow rate adjustment unit for power generation (oxidizer gas supply device)
48 Heater 50 Hot water production equipment 52 Control box 54 Inverter 63 Fuel supply pipe 64 Fuel gas supply pipe 64a Horizontal part 65 Hydrogen extraction pipe for watering desulfurizer 66 Manifold 68 Lower support plate 74 Air introduction pipe for power generation 82 Exhaust gas discharge pipe 83 Ignition Equipment (ignition heater)
84 Fuel cell body 86 Cap 86a First cylindrical part 86b Circular part 86c Second cylindrical part 88 Fuel gas flow path 90 Inner electrode layer (fuel electrode layer)
92 Outer electrode layer (oxidizing agent gas electrode layer)
94 Electrolyte layer (solid electrolyte layer)
95 Silver paste 96 Glass seal 98 Fuel gas flow path 100 Spacer 102 Current collector 111 Exhaust port 112 Mixed gas supply pipe 120 Reformer (reformer)
120A Mixed gas receiving part 120B Reforming part 120C Gas discharging part 121 Upper case 122 Lower case 123a, 123b Partition plate 140 Evaporator 140A Exhaust passage part 140B Evaporating part 140C Mixing part 141 Evaporator case 142 Upper case 143 Lower case 144 Intermediate plate 145 Partition plate 146, 147 Partition plate 149 Heating heater 160 Air passage cover 160a Top plate 160b Side plate 161a, 161b Air passage 162, 163 Plate fin 171 Exhaust pipe 210 Control unit (controller)
212 Operating device 214 Display device 216 Notification device 220 Combustible gas detection sensor 222 CO detection sensor 224 Hot water storage status detection sensor 226 Power status detection sensor 228 Power generation air flow detection sensor 230 Ignition air flow sensor 232 Fuel flow sensor 234 Water flow sensor 236 Water level sensor 238 Pressure sensor 240 Exhaust temperature sensor 242 Power generation room temperature sensor 244 Combustion room temperature sensor 246 Exhaust gas room temperature sensor 248 Reformer temperature sensor 250 Outside air temperature sensor

Claims (7)

A solid oxide fuel cell system that generates electricity by reacting hydrogen gas obtained by steam reforming a raw material fuel gas containing hydrocarbons with an oxidant gas.
Solid electrolyte layer, a fuel cell having a fuel electrode layer containing nickel provided on the inside of the solid electrolyte layer, and an oxidant gas electrode layer provided on the outer side of the solid electrolyte layer,
And a module case,
A reforming unit that reforms the raw fuel gas by steam reforming to generate a fuel gas rich in hydrogen gas and supplies the generated fuel gas to the fuel electrode side of the fuel cell.
A fuel supply device that supplies raw fuel gas to this reforming section,
An evaporation unit that evaporates the supplied water to generate steam for steam reforming and supplies the generated steam to the reforming unit.
A water supply device that supplies water for steam reforming to this evaporation unit,
An oxidant gas supply device that supplies oxidant gas to the oxidant gas electrode side of the fuel cell, and
A combustion unit provided in the module case, passing through the fuel electrode side of the fuel cell, and burning residual fuel gas remaining unused for power generation at the upper end of the fuel cell.
It has a controller that controls the fuel supply device, the water supply device, and the oxidant gas supply device, and also controls the extraction of electric power from the fuel cell.
The controller stops the extraction of electric power from the fuel cell and ends the power generation process, and then continues to supply the raw fuel gas by the fuel supply device and the water supply by the water supply device. It is configured to perform a stop step that lowers the temperature of the battery cell,
The controller further causes the steam supplied to the reforming unit during a predetermined fire extinguishing promotion period during the stop step so as to promote the extinction of the combustion flame of the residual fuel gas at the upper end of each fuel cell. The fuel supply device and the water supply device are configured to be controlled so that the S / C, which is the molar ratio of the amount to the amount of carbon, is higher than the S / C during the power generation process.
The fire extinguishing promotion period is a period including a period from the time when the combustion flame of the residual fuel gas at the upper ends of some of the fuel cell cells begins to disappear to the time when the combustion flames at the upper ends of all the fuel cell cells disappear. Oh it is,
The fire extinguishing promotion period is started after the temperature of the combustion unit drops to a temperature at which reignition does not occur at the upper end of the fuel cell, and the controller has an S / C at the start of the fire extinguishing promotion period. A solid oxide fuel cell system characterized in that the fuel supply device and the water supply device are controlled so as to be high. The extinguishing promotion period, the temperature of the combustion section, 300 ° C. or higher, a solid oxide fuel cell system of claim 1, wherein the start time was reduced to a temperature of 400 ° C. or less. The solid oxide fuel cell system according to claim 2 , wherein the controller controls the fuel supply device and the water supply device so that the S / C during the fire extinguishing promotion period is 4 or more and 10 or less. Further, claims 1 to 3 which have a manifold connected to the lower end of each fuel cell, and the fuel gas reformed in the reforming portion is distributed to each fuel cell via the manifold. The solid oxide fuel cell system according to any one of the above items. The controller includes a fire extinguishing prediction circuit that predicts the time when the combustion flame of the residual fuel gas at the upper end of the fuel cell starts to disappear, and the controller starts the fire extinguishing promotion period based on the prediction by the fire extinguishing prediction circuit. The solid oxide fuel cell system according to claim 1. The claim that the fire extinguishing prediction circuit determines the start time of the fire extinguishing promotion period based on the time when the combustion flame of the residual fuel gas at the upper end of the fuel cell in the stop step executed in the past begins to disappear. 5. The solid oxide fuel cell system according to 5. The evaporative unit is configured to be heated based on the combustion heat of the residual fuel gas burned in the combustion unit, and the evaporative unit further heats the evaporative unit separately from the combustion heat of the residual fuel gas. The solid oxide type fuel cell system according to claim 2, further comprising a heating heater for heating.

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