JP3943406B2 - Fuel cell power generation system and operation method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel cell power generation system and an operation method thereof.
[0002]
[Prior art]
In recent years, a power generation system incorporating a fuel cell has been proposed as a cogeneration system in consideration of environmental problems. As this fuel cell, a cell constructed by stacking a plurality of single cells is known. As a single cell, an electrolyte membrane, an anode and a cathode sandwiching the electrolyte membrane, and fuel gas are supplied to the anode. In addition, a device is known that includes an oxidant gas supplied to the cathode and a separator that forms a partition wall between adjacent single cells. As fuel gas, hydrogen-rich gas obtained by reforming hydrocarbon fuel using steam in the reforming section is known.
[0003]
In such a fuel cell power generation system, it has been proposed to effectively recover waste heat. For example, Japanese Patent Application Laid-Open No. 2001-313053 proposes a system that recovers waste heat from the reforming unit using cathode off-gas discharged from the cathode of the fuel cell. Japanese Patent Application Laid-Open No. 6-132038 proposes a system for recovering heat and water vapor of off-gas discharged from a fuel cell with fuel gas supplied to the fuel cell.
[0004]
[Problems to be solved by the invention]
However, in the above publication, when the temperature of the hydrocarbon fuel to be supplied to the reforming unit is raised in consideration of the reforming reaction in the reforming unit, the amount of heat must be given to the hydrocarbon fuel from the outside. did not become. In addition, heat must be given from the outside in order to generate steam to be supplied to the reforming section. For this reason, system efficiency was not necessarily good.
[0005]
The present invention has been made in view of the above-described problems, and an object thereof is to improve system efficiency in a fuel cell power generation system including a reforming unit.
[0006]
[Means for solving the problems and their functions and effects]
In order to achieve the above-described object, a first fuel cell power generation system of the present invention includes:
A reforming section for reforming hydrocarbon fuel into hydrogen-rich fuel gas using steam;
A reforming raw material supply unit for supplying at least hydrocarbon fuel and steam to the reforming unit as a reforming raw material;
A fuel cell that generates electric power by an electrochemical reaction between a fuel gas supplied from the reforming unit and an oxidizing gas supplied from a predetermined oxidizing gas supply source;
A heat exchanging unit that transfers the heat of off-gas discharged from the fuel cell to the hydrocarbon-based fuel supplied to the reforming unit by the reforming raw material supply unit;
It is equipped with.
[0007]
In this fuel cell power generation system, the reforming raw material supply unit supplies at least a hydrocarbon-based fuel and steam to the reforming unit, and the reforming unit uses the steam to reform the hydrocarbon-based fuel into a fuel gas. Fuel gas is supplied to the fuel cell. On the other hand, the heat of the off-gas discharged from the fuel cell is transferred to the hydrocarbon fuel supplied to the reforming unit. As a result, the temperature of the hydrocarbon-based fuel supplied to the reforming section increases, and the reforming reaction in the reforming section proceeds favorably. In addition, when the amount of heat is given from the outside to the hydrocarbon fuel supplied to the reforming section, the amount of heat given from the outside can be reduced. Therefore, system efficiency is improved. The “off gas” may be an anode off gas exhausted from the anode side of the fuel cell or a cathode off gas exhausted from the cathode side of the fuel cell.
[0008]
In the first fuel cell power generation system of the present invention, the heat exchange unit may transfer the off-gas water vapor and heat to the hydrocarbon-based fuel supplied to the reforming unit by the reforming raw material supply unit. In this case, since the water vapor in the off-gas is also collected and supplied to the reforming section, the amount of steam generated in the reforming section can be reduced and the amount of heat can be reduced accordingly. , Improve system efficiency.
[0009]
Thus, in the configuration for recovering off-gas heat and water vapor, the first fuel cell power generation system of the present invention includes an evaporation unit that generates water vapor supplied to the reforming unit, and an amount of water vapor generated by the evaporation unit A water vapor amount adjusting unit that adjusts the amount of water vapor generated in the evaporator according to the amount of water vapor transferred from the off-gas to the hydrocarbon fuel in the heat exchange unit. Also good. By doing so, the amount of water vapor generated in the evaporator can be appropriately controlled, so that the system efficiency is further improved.
[0010]
The first fuel cell power generation system of the present invention includes a hot water storage tank for storing hot water, a hot water temperature raising section for transferring the heat of the off gas to the hot water in the hot water tank and raising the temperature of the hot water, and the off gas for the heat exchange section. And a passage switching unit that switches between a first passage that leads to the second passage and a second passage that guides the off-gas to the hot water temperature raising unit. In this way, for example, when there is no need to raise the temperature of the hot water in the hot water tank, the system can be improved by switching to the first passage by the passage switching unit and transferring off-gas water vapor and heat to the hydrocarbon fuel. When it is necessary to raise the temperature of the hot water in the hot water storage tank, the passage switching unit can switch to the second passage, efficiently recover off-gas water vapor and heat with hot water, and raise the temperature of the hot water early.
[0011]
Thus, in the configuration including the hot water storage tank, the hot water temperature raising unit, and the passage switching unit, the first fuel cell power generation system of the present invention switches the passage switching unit according to the hot water temperature or the hot water amount of the hot water storage tank. A passage switching control unit may be provided. If it carries out like this, it can control appropriately whether it switches to a 1st channel | path or a 2nd channel | path according to the hot water temperature or the amount of hot water of a hot water tank. For example, when the hot water temperature or the amount of hot water is outside a predetermined range (a range where hot water is required to be raised), the system is switched to the first passage to improve system efficiency. When the hot water temperature or the hot water amount is within the predetermined range, The heat may be efficiently recovered by hot water by switching to the second passage.
[0012]
Further, in the configuration including the hot water storage tank, the hot water temperature raising unit, and the passage switching unit in this way, the first passage has a downstream side of the heat exchange unit on an upstream side of the hot water temperature raising unit in the second passage. It may be connected. By doing so, even when the passage switching unit is switched to the first passage, the heat remaining after the off-gas water vapor and heat are recovered by the heat exchange unit can be recovered by the hot water temperature raising unit.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
[First embodiment (Reference example) ]
FIG. 1 is a configuration diagram showing an outline of the configuration of the fuel cell power generation system 10 of the first embodiment. This fuel cell power generation system 10 mainly includes a reformer 12 that reforms city gas into hydrogen-rich reformed gas, and a CO selective oxidation unit 16 that reduces carbon monoxide in the reformed gas and uses it as fuel gas. , A mixer 34 that supplies a mixture of city gas and steam to the reformer 12, a fuel cell 40 that generates electricity by an electrochemical reaction between the fuel gas and the oxidizing gas, and the fuel cell 40 The steam / heat exchanger 35 that recovers off-gas water vapor and heat and the cooling water heat exchanger 42 recover the heat of the fuel cell 40, and the off-gas condenser 55 recovers the heat of the off-gas of the fuel cell 40. A hot water storage tank 44 for storing the heated water, a system linkage package 70 for converting the DC power from the fuel cell 40 into AC power and supplying it to the outside, and an electronic control unit for controlling the entire system And a door 60.
[0024]
The reformer 12 supplies the mixture of the city gas and steam introduced from the mixer 34 to the steam reforming reaction and the shift reaction of the following equations (1) and (2), thereby improving the hydrogen-rich reforming. Generates quality gas. The reformer 12 is provided with a combustion section 14 for supplying heat necessary for such a reaction. The combustion section 14 is supplied with city gas from a gas pipe 22 via a booster pump 28 and is not shown. Air required for combustion is supplied through the path, and further, the anode off-gas after passing through the off-gas condenser 55 is supplied. In other words, in order to effectively use the anode off gas, unreacted hydrogen in the anode off gas can be used as the fuel for the combustion unit 14. Moreover, the combustion exhaust gas discharged from the combustion unit 14 is piped so as to be discharged to the outside after the amount of heat is given to the evaporator 33. That is, it is configured such that the calorific value of the combustion exhaust gas can be effectively used to generate water vapor in the evaporator 33.
[0025]
[Expression 1]
CH _Four + H ₂ O → CO + 3H ₂ (1)
CO + H ₂ O → CO ₂ + H ₂ (2)
[0026]
The mixer 34 passes through the control valve 24 and the booster pump 26 from the gas pipe 22, and then the city gas after the sulfur is removed by the desulfurizer 27 and further through the steam / heat exchanger 35, and from the water tank 30 to the water pump 31. The steam vaporized by the evaporator 33 after passing through the control valve 32 is mixed at an appropriate ratio and supplied to the reformer 12. Purified water is supplied to the water tank 30 from a water purifier (not shown) that purifies and purifies tap water.
[0027]
The CO selective oxidation unit 16 is modified by a carbon monoxide selective oxidation catalyst (for example, a catalyst made of an alloy of platinum and ruthenium) that receives supply of air from a pipe (not shown) and selects and oxidizes carbon monoxide in the presence of hydrogen. Carbon monoxide in the gas is selectively oxidized to obtain a hydrogen-rich fuel gas having a very low carbon monoxide concentration (about several ppm in this embodiment).
[0028]
The fuel cell 40 is configured as a solid polymer fuel cell in which a plurality of single cells 410 (see FIG. 2) are stacked. The single cell 410 includes an electrolyte membrane 412 and the electrolyte membrane 412 as shown in FIG. A separator having an anode 414 and a cathode 416 sandwiching the electrolyte membrane 412, a separator 418 having a fuel gas supply path 415 for supplying fuel gas to the anode 414, and an oxidizing gas supply path 417 for supplying oxidizing gas to the cathode 416 is provided. The separators 418 and 420 form a partition wall with the adjacent single cell 410. The anode 414 includes a catalyst electrode 414a and a gas diffusion electrode 414b, and the cathode 416 includes a catalyst electrode 416a and a gas diffusion electrode 416b. The fuel gas is supplied from the CO selective oxidation unit 16 to the anode 414 of each single cell 410, and the air as the oxidizing gas is supplied from the blower 41 to the cathode 416 of each single cell 410 via a humidifier (not shown). Thus, power is generated by an electrochemical reaction between hydrogen in the fuel gas and oxygen in the oxidizing gas. An output terminal (not shown) of the fuel cell 40 is connected to the outside via an inverter (not shown) in the system linkage package 70, and DC power from the fuel cell 40 is converted into AC power and supplied to the outside.
[0029]
The steam / heat exchanger 35 uses an off-gas passage 36 and a city gas passage 37 that are separated by a hollow fiber membrane having a high water vapor selective permeability, and is discharged from the anode of the fuel cell 40 to a high-temperature anode off-gas containing steam. By making counter current contact with the city gas that has passed through the desulfurizer 27, the water vapor and heat of the anode off-gas are transferred to the city gas. Specifically, utilizing the difference in water vapor partial pressure generated between the anode off gas containing water vapor and the city gas not containing water vapor, the water vapor of the anode off gas passes through the hollow fiber membrane and moves to the city gas. The heat of the hot anode off gas is transferred to the city gas at room temperature through the hollow fiber membrane. The anode off-gas that has passed through the water vapor / heat exchanger 35 passes through the off-gas condenser 55 to condense and condense the latent heat of condensation in the hot water in the hot water storage tank 44, and is then supplied to the combustion unit 14 for combustion. A humidity sensor 38 for detecting the humidity of the city gas, that is, the amount of water vapor, is attached to the outlet of the city gas passage 37 in the water vapor / heat exchanger 35.
[0030]
The cooling water heat exchanger 42 performs heat exchange between the cooling water of the fuel cell 40 and the water stored in the hot water storage tank 44. During system operation, that is, when the fuel cell 40 generates power, the cooling water circulating through the cooling water circulation path 48 takes the heat of the fuel cell 40 and the hot water stored in the hot water storage tank 44 is used as the cooling water heat to the cooling water heat exchanger 42. It is collected and stored in the hot water storage tank 44.
[0031]
The hot water storage tank 44 is a tank of a predetermined capacity, and the hot water circulation path 45 that leads from the lower inside through the hot water storage pump 46, the off-gas condenser 55 and the cooling water heat exchanger 42 to the upper inside, and the tank is constantly filled with tap water. And a replenishment path (not shown) for replenishing as described above. The hot water circulating through the hot water circulation path 45 is heated by recovering the latent heat of condensation of the anode off gas after passing through the steam / heat exchanger 35 by the off gas condenser 55 and further cooled by the cooling water heat exchanger 42. The fuel cell 40 is cooled and the temperature of the heated cooling water is recovered and raised.
[0032]
The electronic control unit 60 is configured as a microprocessor centered on a well-known CPU, ROM, and RAM. The electronic control unit 60 includes an output voltage from a current sensor of an inverter (not shown) in the system linkage package 70, an output current from the voltage sensor of the inverter, the humidity of city gas from the humidity sensor 38, that is, the amount of water vapor, and the like. Is entered. The electronic control unit 60 also drives the solenoids of the control valve 24 and the control valve 32, and drives the boost pumps 26 and 28, the water pump 31, the blower 41, the cooling water pump 43, the hot water storage pump 46, and the like. A signal, a switching control signal to an inverter (not shown) in the system linkage package 70, and the like are output.
[0033]
When one of the high, middle, and low operation modes is determined, the electronic control unit 60 uses the power determined in accordance with the operation mode as the target output power and the DC power from the fuel cell 40 as the system linkage package 70. The power generation amount of the fuel cell 40 is controlled so that the AC power converted by the inverter (not shown) becomes the target output power. Here, the control of the power generation amount of the fuel cell 40 refers to, for example, the reformer by controlling the city gas regulating valve 24 and the booster pump 26, or controlling the water pump 31 and the regulating valve 32 of the water tank 30. 12, the amount of fuel gas produced at 12, that is, the amount of fuel gas supplied to the fuel cell 40 is controlled, or the amount of oxidizing gas supplied to the fuel cell 40 is controlled by controlling the blower 41.
[0034]
Next, the operation of the fuel cell power generation system 10 thus configured will be described. FIG. 3 is a flowchart showing an example of the water vapor amount adjustment processing program. This program is recorded in a ROM (not shown) of the electronic control unit 60, and is read out and executed by a CPU (not shown) of the electronic control unit 60 at every predetermined timing. . When this program is started, the electronic control unit 60 first calculates the water vapor supply amount H * corresponding to the target output power (step S100). That is, the power determined according to the operation mode is set as the target output power, the supply amount of the fuel gas and the oxidizing gas corresponding to the target output power is obtained, and the city used for the reforming reaction according to the supply amount of the fuel gas A gas amount and a water vapor amount are obtained, and the water vapor amount at that time is defined as a water vapor supply amount H *. Subsequently, the amount of water vapor Hg contained in the city gas after passing through the water vapor / heat exchanger 35 is read from the humidity sensor 38 (step S110). The amount of water vapor Hg contained in the city gas corresponds to the amount of water vapor transferred from the anode off gas to the city gas by the water vapor / heat exchanger 35. Subsequently, the amount of water vapor Hs generated by the evaporator 33 is calculated (step S120). The water vapor amount Hs is a value obtained by subtracting the water vapor amount Hg contained in the city gas from the water vapor supply amount H *. Thereafter, the amount of water supplied to the evaporator 33 is controlled by the water pump 31 and the control valve 32 so that the evaporator 33 generates the water vapor amount Hs (step S130), and this program is terminated.
[0035]
Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. The reformer 12 and the CO selective oxidation unit 16 of the present embodiment correspond to the reforming unit of the present invention, and each part from the gas pipe 22 to the mixer 34 and each part from the water tank 30 to the mixer 34 are reforming raw materials. The water vapor / heat exchanger 35 corresponds to a heat exchange unit, the evaporator 33 corresponds to an evaporation unit, and the electronic control unit 60 corresponds to a water vapor amount adjustment unit.
[0036]
According to the present embodiment described in detail above, the temperature of the city gas supplied to the reformer 12 is transferred in order to transfer the heat of the anode offgas discharged from the fuel cell 40 to the city gas supplied to the reformer 12. As a result, the reforming reaction in the reformer 12 proceeds well, and the system efficiency is improved. In addition, when the structure which gives calorie | heat amount to the city gas supplied to the reformer 12 from the exterior is employ | adopted, the calorie | heat amount given from the outside can be reduced. Further, since the water vapor in the anode off-gas is also collected and supplied to the reformer 12, the amount of water vapor collected from the anode off-gas when the water vapor supply amount H * required by the reformer 12 is generated by the evaporator 33. The amount of generation can be reduced by Hg, the amount of heat in the evaporator 33 can be reduced by that amount, and the system efficiency is improved.
[0037]
Note that the condensed water recovered by the off-gas condenser 55 may be supplied to the reformer 12. In that case, since noble metal, catalyst deteriorated powder, and the like are eluted in the condensed water, the ion exchange resin is used. And pass through a water purifier such as a filter. On the other hand, when the steam recovered by the steam / heat exchanger 35 is supplied to the reformer 12 as in the above-described embodiment, it is recovered by the off-gas condenser 55 because it is recovered as steam instead of water. Compared with the case where condensed water is collected, even if the water purifier is not required or passed through the water purifier, the burden is reduced.
[0038]
[Second Embodiment]
FIG. 4 is a configuration diagram showing an outline of the configuration of the fuel cell power generation system of the second embodiment. In the second embodiment, a bypass passage 51 is provided outside the steam / heat exchanger 35 in parallel with the off-gas passage 36 through which the anode off-gas of the steam / heat exchanger 35 passes, and upstream of the passages 36, 51. The first three-way valve 53 is provided with a second three-way valve 54 on the downstream side. The anode off-gas introduced into the first three-way valve 53 passes through either the off-gas passage 36 or the bypass passage 51 and then passes through the second three-way valve 54. The temperature sensor 44a for detecting the temperature of hot water stored in the hot water storage tank 44 is installed in the pipe connected so as to be led to the off-gas condenser 55, and the electronic control unit 60 is a temperature sensor. It is the same as that of 1st Embodiment except the point which inputs the temperature of the hot water of the hot water storage tank 44 from 44a, and outputs a drive signal to each solenoid of the 1st three-way valve 53 and the 2nd three-way valve 54. , The same components as the first embodiment are denoted by the same reference numerals, and a description thereof will be omitted. In FIG. 4, the city gas path to be introduced into the city gas path 37 of the water vapor / heat exchanger 35 is omitted. However, as in the first embodiment, the control pipe 24 and the booster pump 26 are provided from the gas pipe 22. The gas is introduced into the city gas passage 37 through the desulfurizer 27.
[0039]
Next, the operation of the fuel cell power generation system configured as described above will be described. FIG. 5 is a flowchart showing an example of the passage switching processing program. This program is recorded in a ROM (not shown) of the electronic control unit 60, and is read and executed by a CPU (not shown) of the electronic control unit 60 at predetermined timings. When this program is started, the electronic control unit 60 first reads the temperature of the hot water in the hot water tank 44 from the temperature sensor 44a (step S200), and the temperature and a predetermined predetermined temperature increase request range (hot water). (Step S210). When the temperature is within the required temperature increase range, the first and second three-way valves 53 and 54 are communicated with the bypass passage 51. 2 The solenoids of the three-way valves 53 and 54 are controlled (step S220), and this program is terminated. The temperature increase request range is determined to be, for example, 60 ° C. or less. As a result, when the temperature of the hot water in the hot water storage tank 44 decreases and enters the temperature increase request range due to a large amount of hot water used, the anode off-gas discharged from the fuel cell 40 passes through the steam / heat exchanger 35. Without being introduced to the off-gas condenser 55, the temperature of the hot water is quickly raised in order to effectively recover the heat of the anode off-gas (condensation latent heat, sensible heat, etc.) by the hot water in the hot water storage tank 44. On the other hand, when the temperature of the hot water in the hot water storage tank 44 is outside the temperature increase request range, the solenoids of the first and second three-way valves 53 and 54 are controlled so that the first and second three-way valves 53 and 54 communicate with the off-gas passage 36. (Step S230), and this program is terminated. Thus, when the hot water temperature in the hot water storage tank 44 is high and exceeds the temperature increase request range due to a small amount of hot water used, the anode off-gas discharged from the fuel cell 40 passes through the water vapor / heat exchanger 35. After transferring the steam and heat to the city gas, the remaining heat is recovered by the off-gas condenser 55.
[0040]
Here, the correspondence between the components of the present embodiment and the components of the present invention will be clarified. The off-gas condenser 55 of the present embodiment corresponds to the hot water temperature raising unit of the present invention, the first and second three-way valves 53 and 54 correspond to the passage switching unit, and the electronic control unit 60 corresponds to the passage switching control unit. .
[0041]
According to the embodiment described in detail above, when it is not necessary to raise the temperature of the hot water in the hot water storage tank 44, the anode off gas is switched so as to pass through the steam / heat exchanger 35, and the city gas is supplied with the steam and heat of the anode off gas. The system efficiency can be improved by the transfer, while the anode off gas is introduced into the off gas condenser 55 without passing through the steam / heat exchanger 35 when the temperature of the hot water in the hot water storage tank 44 needs to be raised. Thus, the heat can be efficiently recovered by hot water and the temperature of the hot water can be raised. In addition, since the anode off gas passage is switched in accordance with the temperature of the hot water in the hot water storage tank 44, switching control can be appropriately performed. Further, since the downstream side of the off-gas passage 36 of the steam / heat exchanger 35 is connected to the upstream side of the off-gas condenser 55, the anode off-gas is switched to pass through the steam / heat exchanger 35. However, the offgas heat and the heat remaining after the steam is recovered by the steam / heat exchanger 35 can be recovered by the offgas condenser 55.
[0042]
[Third Embodiment (Reference example) ]
FIG. 6 is a configuration diagram showing an outline of the configuration of the fuel cell power generation system of the third embodiment. In the first embodiment, the anode off-gas of the fuel cell 40 is guided to the off-gas passage 36 of the steam / heat exchanger 35 (see FIG. 1). In the third embodiment, the anode off-gas is generated by the reformer 12 and the CO selective oxidation unit 16. The fuel gas rich in hydrogen is guided to the fuel gas passage 136 of the water vapor / heat exchanger 35 and is introduced into the anode of the fuel cell 40 after passing through the fuel gas passage 136. Further, the anode off gas of the fuel cell 40 is supplied to the combustion unit 14 via the off gas condenser 55. Since the other configuration is the same as that of the first embodiment, the same components as those of the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In FIG. 1 round When 1 round , Round 2 When Round 2 Shall be connected to each other.
[0043]
Next, in the fuel cell power generation system configured in this way, the heat of fuel gas on the way from the CO selective oxidation unit 16 to the anode of the fuel cell 40 is removed by the desulfurizer 27 and supplied to the reformer 12. Move to city gas. Thereby, the temperature of the city gas supplied to the reformer 12 rises, and the reforming reaction in the reformer 12 proceeds well. Therefore, system efficiency is improved. In addition, when heat is given to the city gas supplied to the reformer 12 from the outside, the heat supplied from the outside can be reduced. Further, since the water vapor in the fuel gas on the way from the CO selective oxidation unit 16 to the anode of the fuel cell 40 is also recovered by the city gas and supplied to the reformer 12, the water vapor generated by the evaporator 33 is generated accordingly. The amount can be reduced, the amount of heat can be reduced by that amount, and the system efficiency is improved.
[0044]
In the system configuration of this embodiment, when the amount of water vapor in the fuel gas from the CO selective oxidation unit 16 is large and the fuel cell 40 is likely to be flooded, or when the temperature of the fuel gas from the CO selective oxidation unit 16 is It is suitable for use when the temperature tends to be higher than the desired temperature. In the present embodiment, as shown in FIG. 7, a bypass passage 61 is provided outside the steam / heat exchanger 35 in parallel with the passage 62 through which the fuel gas from the CO selective oxidation unit 16 passes the steam / heat exchanger 35. The first three-way valve 63 is provided on the upstream side of the passages 61 and 62, the second three-way valve 64 is provided on the downstream side, and the fuel gas introduced into the first three-way valve 63 passes through either of the passages 61 and 62. After passing, piping is conducted so as to be led from the second three-way valve 64 to the anode of the fuel cell 40, and a humidity sensor 65 for detecting the humidity of the fuel gas is detected in the vicinity of the outlet of the CO selective oxidation unit 16, and the temperature of the fuel gas is detected. A temperature sensor 66 may be provided, and the electronic control unit 60 may determine which of the passages 61 and 62 is switched based on the detection value of the humidity sensor 65 or the temperature sensor 66. Specifically, as shown in FIG. 8, the electronic control unit 60 reads the detection values of both sensors 65 and 66 (step S300), and the humidity of the fuel gas does not cause a flooding phenomenon in a predetermined humidity range. If it is within the predetermined humidity range, it is determined whether or not the temperature of the fuel gas is within the predetermined desired temperature range (step S320), and the humidity of the fuel gas is determined. Is controlled within the predetermined humidity range and the temperature is also within the predetermined desired temperature range, the solenoids of the first and second three-way valves 63 and 64 are controlled so that the first and second three-way valves 63 and 64 communicate with the bypass passage 61. (Step S330), when the humidity of the fuel gas is not within the predetermined humidity range, that is, when the flooding phenomenon may occur or the temperature of the fuel gas is within the predetermined desired temperature range. If not, the solenoids of the first and second three-way valves 63 and 64 are controlled so that the first and second three-way valves 63 and 64 communicate with the passage 62 in the steam / heat exchanger 35 (step S340). Also good. This prevents the fuel cell 40 from flooding because the water vapor of the fuel gas supplied to the fuel cell 40 is reduced by the water vapor / heat exchanger 35 when there is a possibility of the flooding phenomenon occurring in the fuel cell 40. Can do. In addition, even if the temperature of the fuel gas from the CO selective oxidation unit 16 increases as it exceeds the introduction temperature range, the temperature of the city gas supplied to the reformer 12 is raised using the heat, so that the system efficiency is improved. improves.
[0045]
It should be noted that the present invention is not limited to the above-described embodiment, and can of course be implemented in various forms within the scope belonging to the technical scope of the present invention.
[0046]
For example, in the above-described embodiment, steam and heat are transferred from the anode off-gas of the fuel cell 40 to the city gas in the steam / heat exchanger 35, but instead of or in addition to this, the cathode of the fuel cell 40 is used. You may comprise so that water vapor | steam and heat may be transferred from off gas to city gas.
[0047]
Further, in the above-described embodiment, the steam / heat exchanger 35 is exemplified by using a hollow fiber membrane, but other than the hollow fiber membrane can be adopted as long as the same function is achieved. For example, a honeycomb rotor carrying a hygroscopic agent is rotatably supported between a passage through which the anode off gas passes and a passage through which the city gas passes, and water vapor contained in the anode off gas is adsorbed in the passage through which the anode off gas passes. However, the water vapor adsorbed in the passage through which the city gas passes may be desorbed. Or you may employ | adopt the airtight container set in the state which folded the water vapor permeable film in the shape of a bellows.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing an outline of a configuration of a fuel cell power generation system according to a first embodiment.
FIG. 2 is a cross-sectional view of a single cell constituting a fuel cell.
FIG. 3 is a flowchart of a water vapor amount adjustment process.
FIG. 4 is a configuration diagram showing an outline of a configuration of a fuel cell power generation system according to a second embodiment.
FIG. 5 is a flowchart of a path switching process.
FIG. 6 is a configuration diagram showing an outline of a configuration of a fuel cell power generation system of a third embodiment.
FIG. 7 is a partial configuration diagram of a modification of the third embodiment.
FIG. 8 is a flowchart of flooding control and gas temperature control.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Fuel cell power generation system, 12 ... Reformer, 14 ... Combustion part, 16 ... CO selective oxidation part, 22 ... Gas piping, 24 ... Control valve, 26 ... Booster pump, 27 ... Desulfurizer, 28 ... Booster pump, DESCRIPTION OF SYMBOLS 30 ... Water tank, 31 ... Water pump, 32 ... Control valve, 33 ... Evaporator, 34 ... Mixer, 35 ... Steam / heat exchanger, 36 ... Off gas passage, 37 ... City gas passage, 38 ... Humidity sensor, 40 DESCRIPTION OF SYMBOLS ... Fuel cell, 41 ... Blower, 42 ... Cooling water heat exchanger, 43 ... Cooling water pump, 44 ... Hot water storage tank, 44a ... Temperature sensor, 45 ... Hot water circulation path, 46 ... Hot water storage pump, 48 ... Cooling water circulation path, 51 ... Bypass passage, 53 ... First three-way valve, 54 ... Second three-way valve, 55 ... Off-gas condenser, 60 ... Electronic control unit, 70 ... System linkage package. 410 ... single cell, 412 ... electrolyte membrane, 414 ... anode, 415 ... fuel gas supply path, 416 ... cathode, 417 ... oxidizing gas supply path, 418, 420 ... separator.

Claims (4)

A reforming section for reforming hydrocarbon fuel into hydrogen-rich fuel gas using steam;
A reforming raw material supply unit for supplying at least hydrocarbon fuel and steam to the reforming unit as a reforming raw material;
A fuel cell that generates electric power by an electrochemical reaction between a fuel gas supplied from the reforming unit and an oxidizing gas supplied from a predetermined oxidizing gas supply source;
A heat exchanging unit that transfers steam and heat of off-gas discharged from the fuel cell to the hydrocarbon-based fuel supplied to the reforming unit by the reforming raw material supply unit;
An evaporation section for generating water vapor to be supplied to the reforming section;
A water vapor amount adjusting unit that adjusts the amount of water vapor generated by the evaporator according to the amount of water vapor transferred from the off-gas to the hydrocarbon fuel in the heat exchange unit;
A hot water storage tank for storing hot water,
A hot water temperature raising unit for transferring the heat of the off-gas to the hot water in the hot water tank and raising the temperature of the hot water;
A passage switching unit that switches between a first passage that guides the off gas to the heat exchange unit and a second passage that guides the off gas to the hot water temperature raising unit;
A passage switching control unit that switches the passage switching unit according to the hot water temperature or amount of hot water in the hot water storage tank;
Fuel cell power generation system equipped with. The passage switching control unit controls the passage switching unit so that the off-gas is guided to the hot water temperature raising unit when the hot water temperature of the hot water tank is within a predetermined temperature increase request range, and the hot water temperature of the hot water tank is increased. There when it exceeds the predetermined temperature increase request range, that controls the passage switching unit so that the off-gas is led into the heat exchange section,
The fuel cell power generation system according to claim 1. The off gas that has passed through the first passage is led to the hot water temperature raising unit after passing through the heat exchange unit,
The fuel cell power generation system according to claim 1 . A reforming unit that reforms a hydrocarbon-based fuel into a hydrogen-rich fuel gas using steam; and a reforming material supply unit that supplies at least hydrocarbon-based fuel and steam as reforming materials to the reforming unit; A fuel cell that generates electricity by an electrochemical reaction between a fuel gas supplied from the reforming unit and an oxidizing gas supplied from a predetermined oxidizing gas supply source, and is supplied to the reforming unit by the reforming material supply unit A heat exchange unit that transfers steam and heat of off-gas discharged from the fuel cell to the hydrocarbon-based fuel, an evaporation unit that generates steam supplied to the reforming unit, a hot water storage tank for storing hot water, and the off-gas A hot water temperature raising part for transferring the heat of the hot water to the hot water in the hot water tank, and a first passage for leading the off gas to the heat exchange part and a second passage for guiding the off gas to the hot water temperature raising part. A passage switching unit for switching A method of operating a fuel cell power generation system,
The passage switching unit is switched according to the hot water temperature or the amount of hot water in the hot water tank, and the amount of water vapor generated by the evaporator is adjusted according to the amount of water vapor transferred from the off gas to the hydrocarbon fuel at the heat exchange unit. Operation method of fuel cell power generation system.

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