JP2013058340A - Fuel cell system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel cell system that promotes water self-sufficiency and heat self-sufficiency and improves power generation efficiency.SOLUTION: A fuel cell system 10 includes a condensing device 14 that has: an air-cooled condenser 44 that uses oxidant gas as a cooling medium; and a water-cooled condenser 46 that uses hot water stored in a hot water storage tank 18, as the cooling medium. Between the air-cooled condenser 44 and the water-cooled condenser 46, a thermoelectric conversion section 60 is provided that performs thermoelectric conversion by use of a temperature difference between exhaust gas and the oxidant gas. The fuel cell system 10 also includes a control device 16 that adjusts at least either a flow rate of the exhaust gas supplied to the air-cooled condenser 44 or a flow rate of the exhaust gas supplied to the water-cooled condenser 46, based on at least either the result of a comparison of supply power and demand power or the result of a comparison of the amount of supply heat and the amount of demand heat.

Description

  The present invention condenses water vapor in the exhaust gas by heat exchange between a fuel cell module that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, and the exhaust gas discharged from the fuel cell module and a refrigerant body. The present invention relates to a fuel cell system including a condenser device that collects and supplies condensed water to the fuel cell module.

  Usually, a solid oxide fuel cell (SOFC) uses an oxide ion conductor, for example, stabilized zirconia, as a solid electrolyte. An electrolyte / electrode assembly in which an anode electrode and a cathode electrode are disposed on both sides of the solid electrolyte is sandwiched between separators (bipolar plates). This fuel cell is usually used as a fuel cell stack in which a predetermined number of electrolyte / electrode assemblies and separators are laminated.

  As the fuel gas supplied to the fuel cell, hydrogen gas generated from a hydrocarbon-based raw fuel by a reformer is usually used. In a reformer, generally, after obtaining a reforming raw material gas from a hydrocarbon-based raw fuel such as fossil fuel such as methane or LNG, the reforming raw material gas is subjected to, for example, steam reforming. The reformed gas (fuel gas) is generated.

  In this type of fuel cell, the operating temperature is relatively high, and the exhaust gas containing the fuel gas and oxidant gas used for the power generation reaction is also at a high temperature. For this reason, it is desired to make effective use of exhaust gas. For example, a fuel cell system disclosed in Patent Document 1 is known.

  As shown in FIG. 9, this fuel cell system includes a solid oxide fuel cell 1a, a heat exchanger 2a for exchanging heat between the exhaust gas from the solid electrolyte fuel cell 1a and water, and a hot water storage tank 3a for storing water. And between the bottom of the hot water storage tank 3a and the heat exchanger 2a and between the upper part of the hot water storage tank 3a and the heat exchanger 2a, respectively, and between the hot water storage tank 3a and the heat exchanger 2a A circulation pipe 4a for circulating water between them, a circulation pump 5a forcibly circulating water, and a temperature detector 6a for detecting the inlet water temperature and the outlet water temperature of the heat exchanger 2a, 7a and a control device 8a for controlling the output of the circulation pump 5a so that the outlet water temperature of the heat exchanger 2a is equal to or higher than the inlet water temperature.

  Further, as shown in FIG. 10, the fuel cell system disclosed in Patent Document 2 includes a solid electrolyte fuel cell 1b and a heat exchanger 2b for exchanging heat between exhaust gas and water from the solid electrolyte fuel cell 1b. A hot water storage tank 3b for storing water, a circulation pipe 4b for circulating water between the hot water storage tank 3b and the heat exchanger 2b, a circulation pump 5b provided in the circulation pipe 4b, and the amount of hot water used. And a control device 6b for controlling the fuel utilization rate during power generation of the solid oxide fuel cell 1b.

  Furthermore, the fuel cell system and the cogeneration system disclosed in Patent Document 3 include a fuel cell unit, an exhaust gas combustion unit, and a first heat exchange unit, and the fuel cell unit is connected to an electrical load, Fuel cell power as electric power is generated by the fuel gas and the oxidant gas and supplied to the electric load. The exhaust gas combustion unit burns the fuel gas and the oxidant gas used in the fuel cell unit to generate combustion exhaust gas. The 1st heat exchange part collects the amount of heat of combustion exhaust gas with a heat carrier.

  The fuel cell unit is continuously operated at a preset temperature or higher so that fuel cell power can be supplied to the electric load even when the electric load is zero. . The amount of heat is supplied to a heat utilization facility that uses the heat medium.

  Moreover, the cogeneration apparatus disclosed in Patent Document 4 includes a thermoelectric generator 1c, a power storage device 2c, a heat storage device 3c, and a control device 4c, as shown in FIG. The electric power generated and output by the thermoelectric generator 1c is supplied to and stored in the power storage device 2c. Similarly, the heat generated and output by the thermoelectric generator 1c is given to the heat storage device 3c and stored. Therefore, the load 5c that requires energy is supplied with electric power from the power storage device 2c and is also supplied with heat from the heat storage device 3c.

JP 2006-24430 A International Publication No. 2007/052633 Pamphlet Japanese Patent Laid-Open No. 2003-187843 JP 2002-48004 A

  However, in the above-mentioned Patent Document 1, when the water in the hot water storage tank 3a becomes high temperature, the supply of the hot water is stopped or the supply of the exhaust gas is stopped, and the high temperature exhaust gas is discharged wastefully. Will be. In addition, there is a problem that it is difficult to fully circulate (water self-sustained) water necessary for reforming by condensing moisture in the exhaust gas.

  Moreover, in said patent document 2, the fuel utilization rate during electric power generation is controlled. For this reason, when the hot water stored in the hot water storage tank 3b is full or when the temperature becomes high, the water self-sustained operation, the supply of the required power load and the maintenance of the hot water are not intended.

  Furthermore, Patent Document 3 intends to improve energy efficiency even in a time zone in which the power load and the heat load are small. Therefore, when the hot water is full or at a high temperature, it is not possible to cope with water self-sustained operation, supply of required power load and maintenance of hot water.

  Moreover, in patent document 4, the electrical storage apparatus 2c and the thermal storage apparatus 3c are provided, and there exists a problem that the whole thermoelectric supply apparatus enlarges. In addition, it is difficult to achieve water independence and to maintain the operating temperature of the fuel cell only with heat generated by itself without applying heat from the outside (thermal independence).

  The present invention solves this type of problem, and an object thereof is to provide a fuel cell system that can promote water self-sustainability and heat self-sustainability and can improve power generation efficiency.

  The present invention condenses water vapor in the exhaust gas by heat exchange between a fuel cell module that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas, and the exhaust gas discharged from the fuel cell module and a refrigerant body. The present invention relates to a fuel cell system including a condenser device that collects and supplies condensed water to the fuel cell module.

  In this fuel cell system, the condensing device includes an air-cooled condensing mechanism that uses an oxidant gas as a refrigerant body, a water-cooled condensing mechanism that uses hot water stored in a hot water storage section as the refrigerant body, and the air-cooled condensing mechanism. And a thermoelectric conversion mechanism that is disposed between the water-cooled condensing mechanism and performs thermoelectric conversion by a temperature difference between the exhaust gas and the oxidant gas.

  Then, the fuel cell system can at least flow the exhaust gas supplied to the air-cooled condensing mechanism or the water-cooled condensing based on either the comparison result between the supplied power and the demand power or the comparison result between the supplied heat quantity and the demanded heat quantity. A control device for adjusting any one of the flow rates of the exhaust gas supplied to the mechanism is provided.

  In this fuel cell system, the control device includes at least a power comparison unit that compares the supplied power with a preset demand power range, and a heat quantity comparison unit that compares the supply heat amount with a preset demand heat range. It is preferable to have an exhaust gas flow rate adjusting unit that adjusts the flow rate of the exhaust gas supplied to the air-cooled condensation mechanism and the flow rate of the exhaust gas supplied to the water-cooled condensation mechanism.

  For this reason, the flow rate of the exhaust gas supplied to the air-cooled condensing mechanism and the flow rate of the exhaust gas supplied to the water-cooled condensing mechanism are selectively or simultaneously adjusted based on the comparison results by the power comparing unit and the calorific value comparing unit. Therefore, when electric power is required, the heat energy of the exhaust gas can be recovered as electric energy, and the power generation efficiency is effectively improved. On the other hand, when the amount of heat is required, the heat energy of the exhaust gas can be recovered as the heat energy of hot water. Thereby, the energy efficiency can be easily improved.

  Furthermore, in this fuel cell system, it is preferable that the exhaust gas flow rate adjustment unit increases the flow rate of the exhaust gas supplied to the air-cooled condensing mechanism when the power comparison unit detects that the supplied power is less than the demand power range. . For this reason, the quantity which collect | recovers the heat energy of waste gas as electric energy (electric power) is increased, and supply electric power can be brought close to demand electric power. Therefore, it is possible to easily improve the power generation efficiency according to the demand power.

  Furthermore, in this fuel cell system, the exhaust gas flow rate adjustment unit can maintain the flow rate of the exhaust gas supplied to the air-cooled condensing mechanism when the power comparison unit detects that the supplied power is within the demand power range. preferable. Thereby, since the quantity which collect | recovers the heat energy of waste gas as electric energy is maintained, it becomes possible to make supply electric power close to demand electric power. For this reason, it is possible to easily improve the power generation efficiency in accordance with the demand power.

  Further, in this fuel cell system, it is preferable that the exhaust gas flow rate adjusting unit decreases the flow rate of the exhaust gas supplied to the air-cooled condensing mechanism when the power comparison unit detects that the supplied power exceeds the demand power range. . Therefore, since the amount of recovering the heat energy of the exhaust gas as electric energy is reduced, the supplied power can be brought close to the demand power. Thereby, the improvement of the power generation efficiency according to demand electric power is achieved easily.

  Further, in this fuel cell system, it is preferable that the exhaust gas flow rate adjustment unit increases the flow rate of the exhaust gas supplied to the water-cooled condensation mechanism when the heat quantity comparison unit detects that the heat supply amount is less than the demand heat quantity range. . For this reason, since the quantity which collect | recovers the heat energy of waste gas as the heat energy of hot water is increased, it becomes possible to make supply heat quantity close to demand heat quantity. Therefore, it is possible to easily improve the thermal efficiency according to the amount of heat demand.

  Furthermore, in this fuel cell system, the exhaust gas flow rate adjusting unit can maintain the flow rate of the exhaust gas supplied to the water-cooled condensing mechanism when the calorific value comparing unit detects that the supplied heat amount is within the demand heat amount range. preferable. Thereby, since the quantity which collect | recovers the heat energy of waste gas as the heat energy of hot water is maintained, supply heat quantity can be brought close to demand heat quantity. For this reason, the improvement of the thermal efficiency according to the amount of heat demand is facilitated.

  In this fuel cell system, the exhaust gas flow rate adjusting unit may reduce the flow rate of the exhaust gas supplied to the water-cooled condensing mechanism when the heat quantity comparison unit detects that the supplied heat quantity exceeds the demand heat quantity range. preferable. Therefore, the amount of recovered heat energy of the exhaust gas as the heat energy of hot water is reduced, so that the amount of supplied heat can be made close to the amount of demand heat. Thereby, the improvement of the thermal efficiency according to the amount of heat demand is facilitated.

  Further, in this fuel cell system, in the fuel cell module, the power comparison unit detects that the supplied power exceeds the demand power range, and the heat quantity comparison unit detects that the supply heat amount exceeds the demand heat range. It is preferable to reduce the output or transmit power to the power system.

  For this reason, the quantity which collect | recovers the thermal energy of waste gas as an electrical energy, and the quantity which collects the thermal energy of the said waste gas as the thermal energy of hot water are each reduced. Therefore, it is possible to bring the supplied power closer to the demand power and to make the supply heat amount closer to the demand heat amount, and the overall efficiency according to the demand power and the demand heat amount can be easily improved.

  Furthermore, in this fuel cell system, the fuel cell module includes a fuel cell in which an electrolyte / electrode assembly configured by sandwiching at least an electrolyte between an anode electrode and a cathode electrode, and a separator, and a plurality of the fuels In order to produce a fuel cell stack in which the cells are stacked, a heat exchanger that heats the oxidant gas before being supplied to the fuel cell stack, and a mixed fuel of raw fuel and steam mainly composed of hydrocarbons, It is preferable to include an evaporator that evaporates water and a reformer that reforms the mixed fuel to generate fuel gas.

  Thereby, it can be optimally applied to a fuel cell module that performs steam reforming in particular, and a good effect can be obtained.

  In this fuel cell system, the fuel cell module is preferably a solid oxide fuel cell module. For this reason, it becomes possible to use optimally for a high temperature type fuel cell system, and a good effect is acquired.

  According to this invention, the thermoelectric conversion part which performs thermoelectric conversion by the temperature difference of waste gas and oxidant gas is arrange | positioned between the air cooling condensation mechanism and the water cooling condensation mechanism. For this reason, the structure of the whole fuel cell system is easily made compact. In addition, since the temperature difference (thermal energy) between the exhaust gas and the oxidant gas can be recovered as electric energy, the power generation efficiency is effectively improved.

  Further, the exhaust gas temperature is reduced, and the water vapor in the exhaust gas can be condensed and recovered, thereby suppressing waste heat and promoting water independence. Furthermore, since the temperature of the oxidant gas is increased, it becomes possible to easily promote thermal self-sustainment.

  Here, water self-supporting means that the entire amount of water necessary for the operation of the fuel cell system is supplied from within the fuel cell system without being supplied from the outside. Further, the heat self-sustainment means that the operating temperature of the fuel cell system is maintained only by the heat generated by itself without adding the whole amount of heat necessary for the operation of the fuel cell system.

  Furthermore, based on the comparison result between the supplied power and the demand power, or the comparison result between the supply heat amount and the demand heat amount, the flow rate of the exhaust gas supplied to the air-cooled condensation mechanism and the flow rate of the exhaust gas supplied to the water-cooled condensation mechanism are: Adjusted selectively or simultaneously. Therefore, when electric power is required, the thermal energy of exhaust gas can be recovered as electric energy, while when the amount of heat is required, the thermal energy of exhaust gas can be recovered as the thermal energy of hot water. Can be easily improved.

  In addition, since the air-cooled condensing mechanism and the water-cooled condensing mechanism are used selectively or simultaneously, it becomes possible to efficiently recover the thermal energy of the exhaust gas. Thereby, water independence is achieved and the exhaust gas temperature can be reduced.

1 is a schematic configuration explanatory diagram of a fuel cell system for carrying out a control method according to a first embodiment of the present invention. It is explanatory drawing of the condensing apparatus which comprises the said fuel cell system. 4 is a flowchart illustrating a control method of the fuel cell system. It is a control map of the said control method. It is explanatory drawing of the relationship between the temperature difference of a thermoelectric conversion element, and an output. It is a schematic structure explanatory drawing of the fuel cell system concerning the 2nd Embodiment of this invention. It is front explanatory drawing of the condensing apparatus which comprises the said fuel cell system. FIG. 8 is a cross-sectional perspective view taken along line VIII-VIII in FIG. 7 of the condensing device. 2 is an explanatory diagram of a fuel cell system of Patent Document 1. FIG. 2 is an explanatory diagram of a fuel cell system of Patent Document 2. FIG. It is explanatory drawing of the cogeneration apparatus of patent document 4.

  The fuel cell system 10 for carrying out the control method according to the first embodiment of the present invention is used for various purposes such as in-vehicle use as well as stationary use.

  As schematically shown in FIG. 1, the fuel cell system 10 includes a fuel cell module 12 that generates electricity by an electrochemical reaction between a fuel gas (hydrogen gas) and an oxidant gas (air), and an exhaust from the fuel cell module 12. As a result of the heat exchange between the exhaust gas and the refrigerant body, the water vapor in the exhaust gas is condensed and recovered, and the condensing device 14 for supplying condensed water to the fuel cell module 12, the control device 16, and the refrigerant body And a hot water storage tank (storage part) 18 in which the stored water is stored.

  The fuel cell module 12 includes a fuel gas supply device (including a fuel gas pump) 20 that supplies raw fuel (for example, city gas) to the fuel cell module 12 and an oxidation that supplies an oxidant gas to the fuel cell module 12. An agent gas supply device (including an air pump) 22 and a water supply device (including a water pump) 24 for supplying water to the fuel cell module 12 are connected.

  Although not shown, the fuel cell module 12 is, for example, an electrolyte / electrode joint configured by sandwiching a solid electrolyte (solid oxide) composed of an oxide ion conductor such as stabilized zirconia between an anode electrode and a cathode electrode. A solid oxide fuel cell 30 in which a body 26 and a separator 28 are stacked, and a solid oxide fuel cell stack 32 in which a plurality of the fuel cells 30 are stacked in a vertical direction (or a horizontal direction). Prepare.

  On the lower end side (or upper end side) of the fuel cell stack 32 in the stacking direction, a heat exchanger 34 that heats the oxidant gas before supplying it to the fuel cell stack 32, a raw fuel mainly composed of hydrocarbons, and steam In order to generate the mixed fuel, an evaporator 36 for evaporating the water and a reformer 38 for reforming the mixed fuel to generate a fuel gas (reformed gas) are provided.

The reformer 38 contains higher hydrocarbons (C ₂₊ ) such as ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ), and butane (C ₄ H ₁₀ ) contained in the city gas (fuel gas), This is a pre-reformer for steam reforming to a fuel gas mainly containing methane (CH ₄ ), and is set to an operating temperature of several hundred degrees Celsius.

  The operating temperature of the fuel cell 30 is as high as several hundred degrees C. In the electrolyte / electrode assembly 26, methane in the fuel gas is reformed to obtain hydrogen, and this hydrogen is supplied to the anode electrode.

  The heat exchanger 34 exchanges heat by flowing a used reaction gas (hereinafter also referred to as exhaust gas or combustion exhaust gas) discharged from the fuel cell stack 32 and air that is a fluid to be heated in opposite directions. The exhaust gas after the heat exchange is discharged to the exhaust pipe 40, while the air after the heat exchange is supplied to the fuel cell stack 32 as an oxidant gas.

  The outlet of the evaporator 36 is connected to the inlet of the reformer 38, and the outlet of the reformer 38 communicates with a fuel gas supply communication hole (not shown) of the fuel cell stack 32. A main exhaust pipe 42 is provided to discharge the exhaust gas supplied to the evaporator 36. The main exhaust pipe 42 is integrated with the exhaust pipe 40.

  The condenser 14 includes an air-cooled condenser (air-cooled condensation mechanism) 44 that uses an oxidant gas as a refrigerant body, and a water-cooled condenser (water-cooled condensation mechanism) that uses hot water stored in the hot water storage tank 18 as the refrigerant body. 46. The air-cooled condenser 44 and the water-cooled condenser 46 have, for example, a rectangular tube shape with a square cross section.

  The exhaust pipe 40 extending from the fuel cell module 12 is provided with a regulating valve 48, and exhaust gas passages 50 a and 50 b branch on the outlet side of the regulating valve 48. An air-cooled condenser 44 is connected to the exhaust gas passage 50a, while a water-cooled condenser 46 is connected to the exhaust gas passage 50b.

  The adjustment valve 48 can individually adjust the flow rate of the exhaust gas supplied to the air-cooled condenser 44 and the flow rate of the exhaust gas supplied to the water-cooled condenser 46. The exhaust gas may be supplied to the air-cooled condenser 44 only, to the water-cooled condenser 46 only, or to the air-cooled condenser 44 and the water-cooled condenser 46 at a predetermined flow rate. .

  The adjustment valve 48 can also adjust the exhaust gas flow rate supplied to the exhaust gas passages 50a and 50b by changing the distribution flow rate of the exhaust gas to the exhaust gas passages 50a and 50b. At that time, in the control described later, it is necessary to increase / decrease the exhaust gas flow rate distributed to the exhaust gas passages 50a, 50b by increasing / decreasing the output of the fuel cell module 12 to increase / decrease the exhaust gas supply amount.

  Exhaust gas passages 52a and 52b for discharging exhaust gas are provided on the outlet side of the air-cooled condenser 44 and the water-cooled condenser 46, and a condensed water passage 56a for supplying condensed water to the water container 54. , 56b are provided. The water container 54 stores condensed water and is connected to the water supply device 24 via the water flow path 58. The exhaust gas passages 52 a and 52 b can discharge exhaust gas to the outside of the condensing device 14 after joining.

  As shown in FIGS. 1 and 2, a thermoelectric conversion mechanism 60 that performs thermoelectric conversion by a temperature difference between exhaust gas and oxidant gas is disposed between the air-cooled condenser 44 and the water-cooled condenser 46. The thermoelectric conversion mechanism 60 includes a first thermoelectric converter 60a provided on the air-cooled condenser 44 side and a second thermoelectric converter 60b provided on the water-cooled condenser 46 side.

  As shown in FIG. 2, the first thermoelectric converter 60 a includes one flat outer surface (high temperature side) 44 a of the air-cooled condenser 44 and a rectangular tube-shaped air circulation pipe (air oxidizing gas) is circulated ( A plurality of thermoelectric conversion elements 64a attached to the low temperature side) 62 are provided. The second thermoelectric conversion unit 60 b includes a plurality of thermoelectric conversion elements 64 b attached between one flat outer surface (high temperature side) 46 a of the water-cooled condenser 46 and the air circulation pipe (low temperature side) 62. The thermoelectric conversion elements 64a and 64b have a function of generating an electromotive force by causing a temperature difference between both ends (described later).

  The volume of the several thermoelectric conversion element 64a which comprises the 1st thermoelectric conversion part 60a is set larger than the volume of the several thermoelectric conversion element 64b which comprises the 2nd thermoelectric conversion part 60b. The thermoelectric conversion temperature of the thermoelectric conversion element 64a is set higher than the thermoelectric conversion temperature of the thermoelectric conversion element 64b.

  Specifically, the thermoelectric conversion element 64a uses a material having a high thermoelectric conversion efficiency in a relatively high temperature range, while the thermoelectric conversion element 64b uses a material having a high thermoelectric conversion efficiency in a relatively low temperature range. For example, in the temperature range from room temperature to 500K, bismuth and tellurium (Bi-Te system), in the temperature range from room temperature to 800K, lead and tellurium (Pb-Te system), and in the temperature range from room temperature to 1000K, silicon. Germanium-based (Si-Ge-based) can be used.

  As shown in FIG. 1, an air supply pipe 66 provided with an oxidant gas supply device 22 is connected to the air circulation pipe 62. The air supply pipe 66 passes the oxidant gas as a refrigerant through the air circulation pipe 62 and supplies the oxidant gas heated by exchanging heat with the exhaust gas to the fuel cell stack 32.

  The water-cooled condenser 46 is provided with a circulation pipe 68 connected to the hot water storage tank 18. The circulation pipe 68 exchanges heat with the exhaust gas through the hot water stored in the hot water storage tank 18 as a refrigerant in the water-cooled condenser 46, and returns the heated hot water to the hot water storage tank 18.

  The control device 16 includes at least a power comparison unit 70 that compares the supply power W with a preset demand power range, a heat comparison unit 72 that compares the supply heat amount Q with a preset demand heat range, and air-cooled condensation An exhaust gas flow rate adjusting unit 74 that adjusts the flow rate of the exhaust gas supplied to the vessel 44 and the flow rate of the exhaust gas supplied to the water-cooled condenser 46. The exhaust gas flow rate adjustment unit 74 controls the adjustment valve 48 to perform a desired adjustment function. For example, the exhaust gas flow rate adjustment unit 74 may be provided with valves (not shown) individually disposed in the air-cooled condenser 44 and the water-cooled condenser 46, respectively. You may control simultaneously.

  The hot water storage tank 18 includes a water level meter (hot water level detector) 80 for detecting the hot water level and a thermometer (hot water temperature detector) 82 for detecting the hot water temperature. The water container 54 includes a water level meter (condensed water level detector) 84 for detecting the condensed water level in the water container 54.

  A water supply pipe 86 for supplying city water from the outside, a drain pipe 88 for draining water, and a hot water supply pipe 90 for supplying hot water at a desired temperature are connected to the hot water storage tank 18. Valves 92, 94, and 96 are disposed on the water supply pipe 86, the drain pipe 88, and the hot water supply pipe 90, respectively.

  The operation of the fuel cell system 10 configured as described above will be described below.

Under the driving action of the fuel gas supply device 20, raw fuel such as city gas (including CH ₄ , C ₂ H ₆ , C ₃ H ₈ , and C ₄ H ₁₀ ) is supplied to the evaporator 36. . On the other hand, under the driving action of the water supply device 24, water is supplied to the evaporator 36 and the heat exchanger 34 is supplied with oxidant gas via the oxidant gas supply device 22, for example, air. Is supplied through the thermoelectric conversion mechanism 60.

In the evaporator 36, steam is mixed with the raw fuel to obtain a mixed fuel, and this mixed fuel is supplied to the inlet of the reformer 38. The mixed fuel is steam reformed in the reformer 38, and C ₂₊ hydrocarbons are removed (reformed) to obtain a fuel gas mainly composed of methane. This fuel gas is introduced into the fuel cell stack 32 from the outlet of the reformer 38. Therefore, methane in the fuel gas is reformed to obtain hydrogen gas, and the fuel gas containing the hydrogen gas as a main component is supplied to an anode electrode (not shown).

  On the other hand, when the air supplied to the heat exchanger 34 moves along the heat exchanger 34, heat exchange is performed with exhaust gas described later, and the air is preheated to a desired temperature. The air heated by the heat exchanger 34 is introduced into the fuel cell stack 32 and supplied to a cathode electrode (not shown).

  Therefore, in the electrolyte / electrode assembly 26, power generation is performed by an electrochemical reaction between fuel gas and air. The high-temperature (several hundred degrees Celsius) exhaust gas discharged to the outer periphery of each electrolyte / electrode assembly 26 exchanges heat with air through the heat exchanger 34, and heats the air to a desired temperature. A drop is triggered. The exhaust gas is supplied to the evaporator 36 to evaporate water. The exhaust gas that has passed through the evaporator 36 is sent from the main exhaust pipe 42 to the condensing device 14 through the exhaust pipe 40.

  Next, the control method according to the first embodiment in the condenser 14 will be described below along the flowchart shown in FIG. 3 and the control map shown in FIG.

  First, the demand power upper limit value Wmax and the demand power lower limit value Wmin are set as the demand power range for the supply power W of the fuel cell module 12. Further, as the demand heat quantity range for the supply heat quantity Q, a demand heat quantity upper limit value Qmax and a demand heat quantity lower limit value Qmin are set.

  In FIG. 4, the electric mode is a mode in which the amount of heat energy recovered as electric energy by the thermoelectric conversion mechanism 60 is increased or decreased. Specifically, the flow rate of the exhaust gas supplied into the air-cooled condenser 44 is increased or decreased. . On the other hand, the heat mode is a mode for increasing or decreasing the amount of recovered heat energy of the exhaust gas as the heat energy of hot water. Specifically, the flow rate of the exhaust gas supplied into the water-cooled condenser 46 is increased or decreased.

  In FIG. 4, the other is control that reduces the output or transmits power to the power system when the supplied power W exceeds the power demand range and the heat supply Q exceeds the power demand range. is there.

  Therefore, in the control device 16, the supplied power W is compared with a preset demand power range via the power comparison unit 70. When it is determined that the supplied power W is equal to or less than the demand power upper limit Wmax (YES in step S1), the process proceeds to step S2.

  If it is determined in step S2 that the supplied power W is greater than or equal to the demand power lower limit value Wmin (YES in step S2), the process proceeds to step S3, where the fuel cell module 12 is supplied via the heat quantity comparison unit 72. The heat quantity Q is compared with a preset demand heat quantity range. When it is determined that the supplied heat quantity Q is equal to or less than the demand heat quantity upper limit Qmax (YES in step S3), the process proceeds to step S4.

  In step S4, if it is determined that the supplied heat quantity Q is equal to or greater than the demand heat quantity lower limit Qmin (YES in step S4), the process proceeds to step S5 and process E is performed. That is, the supply power W of the fuel cell module 12 is within the demand power range, and the supply heat quantity Q of the fuel cell module 12 is within the demand heat quantity range. At that time, the flow rate of the exhaust gas supplied into the air-cooled condenser 44 is maintained, and the flow rate of the exhaust gas supplied to the water-cooled condenser 46 is maintained. For this reason, the supplied power W and the supplied heat quantity Q are maintained.

  In Step S4, when it is determined that the supplied heat quantity Q is less than the demand heat quantity lower limit Qmin (NO in Step S4), the process proceeds to Step S6 and the process D is performed. In the process D, the adjustment valve 48 is operated under the action of the exhaust gas flow rate adjustment unit 74. That is, the flow rate of the exhaust gas supplied into the air-cooled condenser 44 is maintained, while the flow rate of the exhaust gas supplied to the water-cooled condenser 46 is increased. Accordingly, while the supplied power W is maintained, the amount of recovered heat energy of the exhaust gas as the heat energy of the hot water increases, so that the supplied heat amount Q is increased.

  In that case, the 2nd thermoelectric conversion part 60b is provided in the water-cooled condenser 46 side, and the flow volume of the waste gas supplied to the said water-cooled condenser 46 is increased. In the water-cooled condenser 46, heat exchange between the exhaust gas and the hot water is performed, and then thermoelectric conversion is performed. Therefore, the electrical energy recovered by the thermoelectric conversion element 64b does not increase more than necessary. The same applies to other processes described below.

  Furthermore, if it is determined in step S3 that the supplied heat quantity Q exceeds the demand heat quantity upper limit Qmax (NO in step S3), the process proceeds to step S7, and the process F is performed. In this process F, the flow rate of the exhaust gas supplied into the air-cooled condenser 44 is maintained under the action of the exhaust gas flow rate adjusting unit 74, while the flow rate of the exhaust gas supplied to the water-cooled condenser 46 is reduced. Thereby, while the supplied power W is maintained, the amount of recovered heat energy of the exhaust gas as the heat energy of the hot water is reduced, so that the supplied heat amount Q is reduced.

  If it is determined in step S2 that the supplied power W is less than the demand power lower limit value Wmin (NO in step S2), the process proceeds to step S8, and whether the supplied heat quantity Q is equal to or less than the demand heat quantity upper limit value Qmax. It is determined whether or not. When it is determined that the supplied heat quantity Q is equal to or less than the demand heat quantity upper limit Qmax (YES in step S8), the process proceeds to step S9.

  In step S9, if it is determined that the supplied heat quantity Q is equal to or greater than the demand heat quantity lower limit Qmin (YES in step S9), the process proceeds to step S10 and process B is performed. In this process B, the flow rate of the exhaust gas supplied into the air-cooled condenser 44 is increased under the action of the exhaust gas flow rate adjusting unit 74, while the flow rate of the exhaust gas supplied to the water-cooled condenser 46 is maintained.

  Therefore, as shown in FIG. 2, in the first thermoelectric conversion unit 60 a, the plurality of thermoelectric conversion elements 64 a attached between the outer surface 44 a of the air-cooled condenser 44 and the air circulation pipe 62 are on the high-temperature side. As the exhaust gas flow rate flowing through the condenser 44 increases, the temperature difference between both ends increases. As shown in FIG. 5, the thermoelectric conversion element 64 a increases the output power as the temperature difference between both ends increases, and the amount of recovered heat energy of the exhaust gas as electrical energy increases. For this reason, the supply power W is increased, while the supply heat quantity Q is maintained.

  In step S9, when it is determined that the supplied heat quantity Q is less than the demand heat quantity lower limit Qmin (NO in step S9), the process proceeds to step S11 and the process A is performed. In this process A, the flow rate of the exhaust gas supplied into the air-cooled condenser 44 is increased and the flow rate of the exhaust gas supplied to the water-cooled condenser 46 is increased under the action of the exhaust gas flow rate adjusting unit 74. Accordingly, the supplied power W and the supplied heat quantity Q are increased.

  In Step S8, when it is determined that the supplied heat quantity Q exceeds the demand heat quantity upper limit Qmax (NO in Step S8), the process proceeds to Step S12 and the process C is performed. In the process C, the flow rate of the exhaust gas supplied into the air-cooled condenser 44 is increased under the action of the exhaust gas flow rate adjusting unit 74, while the flow rate of the exhaust gas supplied to the water-cooled condenser 46 is decreased. As a result, the supply power W is increased while the supply heat quantity Q is decreased.

  Furthermore, when it is determined in step S1 that the supplied power W exceeds the demand power upper limit Wmax (NO in step S1), the process proceeds to step S13. In this step S13, when it is determined that the supplied heat quantity Q is equal to or less than the demand heat quantity upper limit Qmax (YES in step S13), the process proceeds to step S14. In this step S14, when it is determined that the supplied heat quantity Q is equal to or greater than the demand heat quantity lower limit Qmin (YES in step S14), the process proceeds to step S15 and the process H is performed.

  In this process H, the supply power W of the fuel cell module 12 exceeds the demand power upper limit Wmax, and the supply heat quantity Q of the fuel cell module 12 is within the demand heat quantity range. At that time, the flow rate of the exhaust gas supplied into the air-cooled condenser 44 is reduced under the action of the exhaust gas flow rate adjusting unit 74, while the flow rate of the exhaust gas supplied to the water-cooled condenser 46 is maintained. For this reason, the supplied power W is reduced, while the supplied heat quantity Q is maintained.

  If it is determined in step S14 that the supplied heat quantity Q is less than the demand heat quantity lower limit Qmin (NO in step S14), the process proceeds to step S16 and the process G is performed. In this process G, the flow rate of the exhaust gas supplied into the air-cooled condenser 44 is decreased under the action of the exhaust gas flow rate adjusting unit 74, while the flow rate of the exhaust gas supplied to the water-cooled condenser 46 is increased. For this reason, the supplied power W is reduced, while the supplied heat quantity Q is increased.

  In Step S13, when it is determined that the supplied heat quantity Q exceeds the demand heat quantity upper limit Qmax (NO in Step S13), the process proceeds to Step S17 and the process I is performed. That is, the supply power W of the fuel cell module 12 exceeds the demand power upper limit value Wmax, and the supply heat amount Q of the fuel cell module 12 exceeds the demand heat amount upper limit value Qmax.

  Therefore, in the process I, control is performed to reduce the output or transmit power to the power system. The output reduction is performed by decreasing the flow rates of the fuel gas and the oxidant gas supplied to the fuel cell module 12. On the other hand, the supplied power W can be consumed by supplying the power to a place where power is required via the power system.

  In this case, in the first embodiment, the condensing device 14 includes an air-cooled condenser 44 in which an oxidant gas is used as a refrigerant body, and a water-cooled condenser in which hot water stored in the hot water storage tank 18 is used as the refrigerant body. 46. Between the air-cooled condenser 44 and the water-cooled condenser 46, a thermoelectric conversion mechanism 60 that performs thermoelectric conversion by a temperature difference between the exhaust gas and the oxidant gas is disposed.

  For this reason, the structure of the whole fuel cell system 10 is easily made compact. Moreover, as shown in FIG. 2, the temperature difference (thermal energy) between the exhaust gas flowing through the air-cooled condenser 44 and the exhaust gas flowing through the water-cooled condenser 46 and the oxidant gas can be recovered as electrical energy. As a result, the power generation efficiency can be effectively improved.

  In addition, the exhaust gas temperature is reduced, and it becomes possible to condense and recover the water vapor in the exhaust gas, thereby suppressing waste heat and promoting water independence. Furthermore, since the temperature of the oxidant gas is increased, it becomes possible to easily promote thermal self-sustainment.

  Here, water self-sustainment means that the entire amount of water necessary for the operation of the fuel cell system 10 is supplied from within the fuel cell system 10 without being supplied from the outside. In addition, the heat self-sustainment means that the operating temperature of the fuel cell system 10 is maintained only by the heat generated by itself without adding all the heat necessary for the operation of the fuel cell system 10 from the outside.

  In the fuel cell system 10, the control device 16 supplies at least the air-cooled condenser 44 based on either the comparison result between the supply power W and the demand power or the comparison result between the supply heat amount Q and the demand heat amount. It has a function of adjusting either the flow rate of the exhaust gas to be discharged or the flow rate of the exhaust gas supplied to the water-cooled condenser 46. Therefore, when electric power is required, the thermal energy of exhaust gas can be recovered as electric energy, while when the amount of heat is required, the thermal energy of exhaust gas can be recovered as the thermal energy of hot water. Can be easily improved.

  Thus, since the air-cooled condenser 44 and the water-cooled condenser 46 are used selectively or simultaneously, the thermal energy of the exhaust gas can be efficiently recovered. For this reason, water independence is achieved, and the exhaust gas temperature can be reduced. Moreover, the power generation output is not affected by the state of the hot water, that is, the amount of the hot water, and the demand power can be supplied reliably.

  Furthermore, the fuel cell module 12 does not depend on the capacity of the hot water storage tank 18 and can be started and stopped to a minimum, and the power generation efficiency can be easily improved.

  Furthermore, the control device 16 includes a power comparison unit 70 that compares at least the supplied power W and a preset demand power range, and a heat quantity comparison unit 72 that compares the supply heat amount Q and a preset demand heat range. And an exhaust gas flow rate adjusting unit 74 that adjusts the flow rate of the exhaust gas supplied to the air-cooled condenser 44 and the flow rate of the exhaust gas supplied to the water-cooled condenser 46.

  Thereby, based on the comparison result by the electric power comparison part 70 and the calorie | heat amount comparison part 72, the flow volume of the waste gas supplied to the air cooling condenser 44 and the flow volume of the said waste gas supplied to the water cooling condenser 46 are selectively or simultaneously. It has been adjusted. For this reason, when electric power is requested | required, the thermal energy of waste gas can be collect | recovered as electrical energy, and electric power generation efficiency improves effectively. On the other hand, when the amount of heat is required, the heat energy of the exhaust gas can be recovered as the heat energy of hot water. Therefore, energy efficiency can be easily improved.

  Further, the exhaust gas flow rate adjusting unit 74 increases the flow rate of the exhaust gas supplied to the air-cooled condenser 44 when the power comparison unit 70 detects that the supplied power W is less than the demand power range. Thereby, the quantity which collect | recovers the heat energy of waste gas as electric energy (electric power) is increased, and supply electric power W can be brought close to demand electric power. For this reason, it is possible to easily improve the power generation efficiency in accordance with the demand power.

  Further, the exhaust gas flow rate adjusting unit 74 maintains the flow rate of the exhaust gas supplied to the air-cooled condenser 44 when the power comparison unit 70 detects that the supplied power W is within the demand power range. Accordingly, since the amount of recovering the thermal energy of the exhaust gas as electric energy is maintained, the supplied power W can be brought close to the demand power. Thereby, the improvement of the power generation efficiency according to demand electric power is achieved easily.

  Furthermore, the exhaust gas flow rate adjusting unit 74 reduces the flow rate of the exhaust gas supplied to the air-cooled condenser 44 when the power comparison unit 70 detects that the supplied power W is beyond the demand power range. For this reason, since the quantity which collect | recovers the thermal energy of waste gas as an electrical energy is reduced, the supplied electric power W can be brought close to demand electric power. Therefore, it is possible to easily improve the power generation efficiency according to the demand power.

  Further, the exhaust gas flow rate adjusting unit 74 increases the flow rate of the exhaust gas supplied to the water-cooled condenser 46 when the heat quantity comparison unit 72 detects that the supplied heat quantity Q is less than the demand heat quantity range. Thereby, since the quantity which collect | recovers the heat energy of waste gas as the heat energy of hot water is increased, it becomes possible to make supply heat quantity Q close to demand heat quantity. For this reason, the improvement of the thermal efficiency according to the amount of heat demand is facilitated.

  Further, the exhaust gas flow rate adjustment unit 74 maintains the flow rate of the exhaust gas supplied to the water-cooled condenser 46 when the heat quantity comparison unit 72 detects that the supply heat quantity Q is within the demand heat quantity range. Therefore, since the quantity which collects the heat energy of exhaust gas as the heat energy of hot water is maintained, supply heat quantity Q can be brought close to demand heat quantity. Thereby, the improvement of the thermal efficiency according to the amount of heat demand is facilitated.

  Furthermore, the exhaust gas flow rate adjustment unit 74 reduces the flow rate of the exhaust gas supplied to the water-cooled condenser 46 when the heat quantity comparison unit 72 detects that the supplied heat quantity Q is beyond the demand heat quantity range. For this reason, since the quantity which collect | recovers the heat energy of waste gas as the heat energy of hot water is reduced, the supplied heat quantity Q can be brought close to the demand heat quantity. Therefore, it is possible to easily improve the thermal efficiency according to the amount of heat demand.

  In the fuel cell module 12, the power comparison unit 70 detects that the supplied power W exceeds the demand power range, and the heat amount comparison unit 72 detects that the supply heat amount Q exceeds the demand heat amount range. At the time, the output is reduced or transmitted to the power system.

  Thereby, the quantity which collects the thermal energy of exhaust gas as electric energy, and the quantity which collects the thermal energy of the exhaust gas as thermal energy of hot water are decreased, respectively. For this reason, it is possible to bring the supplied power W closer to the demand power and to make the supplied heat quantity Q closer to the demand heat quantity, and the overall efficiency according to the demand power and the demand heat quantity can be easily improved.

  Further, the fuel cell module 12 includes a fuel cell stack 32, a heat exchanger 34, an evaporator 36, and a reformer 38. Therefore, it can be optimally applied to the fuel cell module 12 that performs steam reforming in particular, and a good effect can be obtained.

  Furthermore, the fuel cell module 12 is composed of a solid oxide fuel cell (SOFC) module. As a result, it can be optimally used in a high-temperature fuel cell system, and a good effect can be obtained.

  FIG. 6 is an explanatory diagram of a schematic configuration of a fuel cell system 100 according to the second embodiment of the present invention.

  Note that the same components as those of the fuel cell system 10 according to the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As shown in FIGS. 7 and 8, the fuel cell system 100 includes one or more, for example, two air cooling fans 102 attached across the air cooling condenser 44 and the water cooling condenser 46. The air cooling fan 102 integrally supplies cooling air to the plurality of thermoelectric conversion elements 64 a mounted on the outer surface 44 a of the air cooling condenser 44 and the plurality of thermoelectric conversion elements 64 b mounted on the outer surface 46 a of the water cooling condenser 46. .

  Accordingly, in the air-cooled condenser 44 and the water-cooled condenser 46, the exhaust gas discharged from the fuel cell stack 32 is cooled by the outside air (oxidant gas) that is forcibly supplied from the air-cooling fan 102, and a plurality of thermoelectric conversion elements. A temperature difference can be generated between 64a and 64b.

  Thereby, in 2nd Embodiment, the heat energy of the waste gas which distribute | circulates the inside of the air-cooled condenser 44 and the exhaust gas which distribute | circulates the inside of the water-cooled condenser 46 can be favorably collect | recovered as an electrical energy, and electric power generation efficiency improves. The same effects as those of the first embodiment can be obtained.

DESCRIPTION OF SYMBOLS 10,100 ... Fuel cell system 12 ... Fuel cell module 14 ... Condensing device 16 ... Control device 18 ... Hot water storage tank 20 ... Fuel gas supply device 22 ... Oxidant gas supply device 24 ... Water supply device 26 ... Electrolyte / electrode assembly 28 ... separator 30 ... fuel cell 32 ... fuel cell stack 34 ... heat exchanger 36 ... evaporator 38 ... reformer 40 ... exhaust pipe 44 ... air-cooled condenser 46 ... water-cooled condenser 48 ... regulating valve 54 ... water container 60 ... thermoelectric Conversion mechanism 60a, 60b ... thermoelectric conversion unit 62 ... air circulation piping 64a, 64b ... thermoelectric conversion element 66 ... air supply pipe 70 ... power comparison unit 72 ... heat quantity comparison unit 74 ... exhaust gas flow rate adjustment unit 80, 84 ... water level meter 82 ... Thermometer 102 ... Air cooling fan

Claims (11)

A fuel cell module that generates electricity by an electrochemical reaction between a fuel gas and an oxidant gas;
A condenser that condenses and collects water vapor in the exhaust gas by heat exchange between the exhaust gas discharged from the fuel cell module and the refrigerant, and supplies condensed water to the fuel cell module;
A fuel cell system comprising:
The condensing device includes an air-cooled condensing mechanism in which the oxidant gas is used as the refrigerant body,
A water-cooled condensing mechanism in which hot water stored in the hot water storage section as the refrigerant body is used;
A thermoelectric conversion mechanism that is disposed between the air-cooled condensation mechanism and the water-cooled condensation mechanism, and performs thermoelectric conversion by a temperature difference between the exhaust gas and the oxidant gas;
With
The fuel cell system has at least a flow rate of the exhaust gas supplied to the air-cooled condensing mechanism based on at least a comparison result between supplied power and demand power, or a comparison result between supplied heat amount and demand heat amount, or A fuel cell system comprising a control device for adjusting any of the flow rates of the exhaust gas supplied to the water-cooled condensing mechanism. 2. The fuel cell system according to claim 1, wherein the control device compares at least supply power with a preset demand power range;
A calorific value comparing unit that compares the supplied calorific value with a preset demand calorific value range;
An exhaust gas flow rate adjusting unit for adjusting the flow rate of the exhaust gas supplied to the air-cooled condensing mechanism and the flow rate of the exhaust gas supplied to the water-cooled condensing mechanism;
A fuel cell system comprising:   3. The fuel cell system according to claim 2, wherein the exhaust gas flow rate adjusting unit is supplied to the air-cooled condensing mechanism when the power comparison unit detects that the supplied power is less than the demand power range. A fuel cell system characterized by increasing the flow rate of the fuel cell.   3. The fuel cell system according to claim 2, wherein the exhaust gas flow rate adjusting unit is supplied to the air-cooled condensing mechanism when the power comparison unit detects that the supplied power is within the demand power range. A fuel cell system that maintains the flow rate of the fuel cell.   3. The fuel cell system according to claim 2, wherein the exhaust gas flow rate adjusting unit is supplied to the air-cooled condensing mechanism when the power comparison unit detects that the supplied power exceeds the demand power range. A fuel cell system that reduces the flow rate of the fuel cell.   6. The fuel cell system according to claim 2, wherein the exhaust gas flow rate adjustment unit is configured to perform the water cooling when the heat quantity comparison unit detects that the supply heat quantity is less than the demand heat quantity range. A fuel cell system characterized in that the flow rate of the exhaust gas supplied to the condensing mechanism is increased.   6. The fuel cell system according to claim 2, wherein the exhaust gas flow rate adjustment unit is configured to perform the water cooling when the heat quantity comparison unit detects that the supply heat quantity is within the demand heat quantity range. A fuel cell system characterized by maintaining a flow rate of the exhaust gas supplied to a condensing mechanism.   6. The fuel cell system according to claim 2, wherein the exhaust gas flow rate adjustment unit is configured to perform the water cooling when the heat quantity comparison unit detects that the supply heat quantity exceeds the demand heat quantity range. A fuel cell system, wherein the flow rate of the exhaust gas supplied to the condensing mechanism is reduced.   3. The fuel cell system according to claim 2, wherein in the fuel cell module, the power comparison unit detects that the supply power exceeds the demand power range, and the heat amount comparison unit determines that the supply heat amount is the demand. A fuel cell system, characterized in that when it is detected that the amount of heat exceeds the heat range, the output is reduced or transmitted to an electric power system. 10. The fuel cell system according to claim 1, wherein the fuel cell module includes an electrolyte / electrode assembly configured by sandwiching at least an electrolyte between an anode electrode and a cathode electrode, and a separator. A fuel cell stack in which a plurality of the fuel cells are stacked; and
A heat exchanger that heats the oxidant gas before supplying it to the fuel cell stack;
An evaporator for evaporating water in order to produce a mixed fuel of raw fuel mainly composed of hydrocarbon and water vapor;
A reformer for reforming the mixed fuel to produce the fuel gas;
A fuel cell system comprising:   The fuel cell system according to any one of claims 1 to 10, wherein the fuel cell module is a solid oxide fuel cell module.

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