JP2009302010A - Fuel cell cogeneration system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel cell cogeneration system that stabilizes power generation reaction of a fuel cell, and uses heat of the system efficiently. <P>SOLUTION: The fuel cell cogeneration system recovers heat generated by power generation reaction of a solid oxide fuel cell (22), then uses the heat. The system includes a heating means (4) capable of heating each of a plurality of materials consisting of liquid or gas introduced into the fuel cell (22), and a high-temperature heat exchanger (5) exchanging heat of exhausted gas from the fuel cell (22) so as to give the heat to the materials introduced into the heating means (4). Moreover, it includes a low-temperature heat exchanger (6) exchanging heat of exhausted gas from the high-temperature heat exchanger (5) so as to give the heat to supply water, and a hot water tank (7) storing the supply water. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a fuel cell cogeneration system that recovers and uses heat generated by a power generation reaction of a solid oxide fuel cell.

  A solid oxide fuel cell (hereinafter referred to as SOFC) is a high-temperature operation type fuel cell, and many systems for recovering and using heat generated by a power generation reaction have been proposed.

  For example, in an SOFC using a fuel such as city gas or kerosene, the fuel is reformed into a gas such as hydrogen or carbon monoxide and then led to the fuel electrode to cause a power generation reaction. This reforming reaction (reforming reaction) is an endothermic reaction, and given the heat generated by the power generation reaction, which is an exothermic reaction, SOFC modules are known that aim at stable operation while increasing thermal efficiency. Yes.

  For example, in Patent Document 1, in an SOFC module including an SOFC and a reforming device including a reforming unit and an oxidation heating unit, not only exhaust heat generated from the SOFC in a reforming reaction in the reforming unit but also an oxidation heating unit Discloses an SOFC module including an oxidation autothermal reformer that uses a combination of heat generated in the above.

  There is also known an SOFC module for the purpose of performing a stable operation while increasing heat efficiency by using heat generated by a power generation reaction as another heat source.

  In Patent Document 2, air supplied to the SOFC is supplied to a regenerator, and heat exchange is performed with the combustion exhaust gas from the SOFC in this regenerator, and the heated air is supplied to the SOFC air electrode. A SOFC system to supply is disclosed.

  Furthermore, an SOFC module is also known that aims to perform stable operation while increasing the thermal efficiency by reusing fuel related to the power generation reaction, not the heat generated by the power generation reaction.

  In Patent Document 3, an exhaust fuel discharged from the SOFC is completely combusted in a combustor, air is preheated by exhaust gas discharged from the combustor, and then the heated air is introduced into the air electrode of the SOFC. Disclosure.

  Furthermore, for example, fuel that recovers heat generated by the power generation reaction of SOFC to generate hot water, temporarily stores this hot water in a heat storage means (hot water storage tank), and uses the thermal energy held by the hot water for various purposes Battery cogeneration systems have also been proposed.

  In the above-described Patent Document 2, heat is supplied to hot water storage water (clean water) from combustion exhaust gas after heat exchange with air, and the hot water storage water is stored in a hot water storage tank and used for hot water supply equipment and the like. It is disclosed.

Further, in Patent Document 4, a fuel cell coordinator that can change the thermoelectric ratio while maintaining the heat self-sustaining operation state of the fuel cell by controlling the power generation output of the SOFC and / or the exhaust gas temperature of the SOFC according to the heat demand A generation system is disclosed.
JP 2007-227237 A JP-A-2005-317489 JP 2003-17103 A JP 2006-73316 A

  As disclosed in Patent Document 4, in a fuel cell cogeneration system, control of the fuel cell system according to heat demand is effective. On the other hand, the power generation reaction of SOFC is very complicated because it is affected by many accompanying reaction systems such as fuel reforming reaction and desulfurization reaction, and the power generation reaction itself can be a multistage reaction. . Therefore, it is necessary to efficiently use the heat of the entire system while stably controlling these reactions.

  The present invention has been made in view of the situation as described above, and an object of the present invention is a fuel cell cogeneration system that recovers and uses heat generated by a power generation reaction of SOFC. To provide a fuel cell cogeneration system that stabilizes the power generation reaction of a battery and enables efficient heat utilization of the system.

  A system according to the present invention is a fuel cell cogeneration system that recovers and uses heat generated by a power generation reaction of a solid oxide fuel cell, wherein a plurality of raw materials composed of liquid or gas introduced into the fuel cell are used. A heating means capable of heating each of them, a high-temperature heat exchanger for exchanging heat to give the heat from the exhaust gas from the fuel cell to the raw material introduced into the heating means, and the high-temperature heat exchanger It includes a low-temperature heat exchanger that performs heat exchange so as to give heat from exhaust gas to clean water, and a hot water storage tank that stores the clean water.

  ADVANTAGE OF THE INVENTION According to this invention, each temperature of the some raw material introduce | transduced according to the operating condition of a solid oxide fuel cell can be controlled by a heating means, and the electric power generation reaction of a fuel cell can be stabilized. Further, the exhaust heat from the high-temperature heat exchanger can be used also in the low-temperature heat exchanger, and the system can efficiently use the heat.

  A system according to an aspect of the present invention is a fuel cell cogeneration system that recovers and uses heat generated by a power generation reaction of a solid oxide fuel cell, from a liquid or gas introduced into the fuel cell. A heating unit capable of heating each of the plurality of raw materials, a high-temperature heat exchanger that performs heat exchange so as to give heat from the exhaust gas from the fuel cell to the raw material introduced into the heating unit, and the high-temperature heat It includes a low-temperature heat exchanger that performs heat exchange so that heat generated by the exhaust gas from the exchanger is supplied to clean water, and a hot water storage tank that stores the clean water.

  According to this aspect, the temperature of each of the introduced raw materials can be controlled by the heating means in accordance with the operation status from the start of the solid oxide fuel cell to the stable operation. The control of the heating means may be feedback controlled from the output information of the fuel cell, or may be feedback controlled from the temperature information by arranging a temperature sensor around the fuel cell. Thus, since the temperature of the raw material to be supplied to the fuel cell can be controlled, the power generation reaction of the fuel cell can be stabilized. Furthermore, the exhaust heat from the high-temperature heat exchanger can be used in the low-temperature heat exchanger, and the system can efficiently use the heat.

  Here, in the above system, the raw material may be composed of water, an oxidant gas, and a hydrocarbon fuel. In the system using the hydrocarbon fuel, the fuel cell may include an electrode carrying a catalyst for reforming the hydrocarbon fuel. The reforming reaction of the hydrocarbon-based fuel by the catalyst is an endothermic reaction, but since the heat to be supplied to the fuel cell can be controlled by the heating means, the power generation reaction of the fuel cell can be stabilized. That is, even in the case of a direct internal reforming fuel cell that reforms fuel in the vicinity of the electrode, the system can efficiently use heat.

  Further, in the system using the direct internal reforming fuel cell, the hydrocarbon fuel may be a paraffinic liquid fuel synthesized and distilled from hydrogen and carbon monoxide. According to such a fuel, since the power generation reaction can be further stabilized even in a direct internal reforming type fuel cell, the system can efficiently use heat.

  By the way, in a system using water, oxidant gas, and hydrocarbon fuel as raw materials, the high temperature heat exchanger performs heat exchange with water in a part of the exhaust gas, and the rest of the exhaust gas. May be allowed to pass through without exchanging heat. By heating only water having a large amount of sensible heat and latent heat with a high-temperature heat exchanger and a low-temperature heat exchanger, efficient heat utilization of the system can be achieved.

  In the above system, the low temperature heat exchanger may be provided in an upper part of the high temperature heat exchanger. The heat from the high-temperature heat exchanger can be efficiently guided to the low-temperature heat exchanger, heat loss is reduced, and the system can efficiently use the heat.

  Moreover, the said system WHEREIN: The said heating means is good also as having the heating piping which heats each of the said raw material, and the passage piping which allows it to pass through without heating. Since the raw material sufficiently heated in the high-temperature heat exchanger can be quickly passed through the heating means and introduced into the fuel cell, fine control is possible and heat loss is reduced, so that the system can efficiently use heat.

  In the above system, the fuel cell may be housed in a heat insulating container, and the heating means may be provided in or near the heat insulating container. Since the raw material can be guided from the heating means to the fuel cell at a short distance and heat loss is reduced, the system can efficiently use the heat.

  In the above system, the heating means may combust a part of the exhaust gas from the fuel cell and send the combusted gas to the high temperature heat exchanger. Since the excess chemical energy of the exhaust gas can be converted into heat energy, it can be used more efficiently for the system.

[Example 1]
Next, a fuel cell cogeneration system using a solid oxide fuel cell (SOFC) according to one embodiment of the present invention will be described in detail with reference to FIGS.

  As shown in FIG. 1, the fuel cell cogeneration system 1 accommodates a fuel cell assembly 2 in which one or a plurality of SOFCs 22 are accommodated in a metal can 21, and is insulated so as to be insulated from the outside. A cylindrical heat insulating container 3, a heater 4 for heating the raw material introduced into the fuel cell assembly 2, and the raw material introduced into the fuel cell assembly 2 and the exhaust discharged from the fuel cell assembly 2 A high-temperature heat exchanger 5 for exchanging heat between gases, a low-temperature heat exchanger 6 for exchanging heat between exhaust gas discharged from the high-temperature heat exchanger 5 and clean water, and low-temperature heat exchange And a hot water tank 7 for storing clean water heated by the vessel 6.

  The heat insulating container 3 includes a cylindrical side heat insulating wall 33 such as a cylinder or a square tube, and an upper heat insulating wall 34 and a lower heat insulating wall 35 that close both upper and lower ends of the side heat insulating wall 33. The inside of the heat insulating container 3 is divided into two spaces by a partition heat insulating wall 32 extending along the axial direction of the side heat insulating wall 33, and the fuel cell assembly 2 is placed in one space (fuel cell space R 1). Contained. On the inner side surface of the heat insulating container 3 exposed in the space R1 surrounding the fuel cell assembly 2, a mirror finish or a radiant heat reflecting film is attached or coated so as to confine the radiant heat radiated from the assembly 2. Thereby, the radiant heat from the fuel cell assembly 2 can be efficiently confined in the fuel cell space R1, and the operation of the SOFC 22 can be stabilized. Moreover, since the overheating of the side heat insulating wall 33, the upper heat insulating wall 34, and the lower heat insulating wall 35 can be prevented, the life of the heat insulating container 3 can be improved.

  The heater 4 and the high-temperature heat exchanger 5 are accommodated in the other space (preheating part space R2) partitioned by the partition heat insulating wall 32. In the vicinity of the upper end of the partition heat insulating wall 32, a through hole P for connecting two spaces in the heat insulating container 3 is provided. The fuel cell assembly 2, heater 4 and high temperature heat exchanger 5 described later are connected. Each pipe to be connected goes through. The through hole P is large enough to allow each pipe to pass therethrough and is provided as small as possible.

  The side heat insulating wall 33, the upper heat insulating wall 34, and the lower heat insulating wall 35 are detachably combined with a clasp 37. The operator can remove the upper heat insulating wall 34 and the lower heat insulating wall 35 from the side heat insulating wall 33 by operating the clasp 37. Thereby, the maintenance of the fuel cell assembly 2, the heater 4, the high-temperature heat exchanger 5, and the like housed in the heat insulating container 3 can be easily performed.

  Referring also to FIG. 2, the can 21 of the fuel cell assembly 2 has a raw fuel inlet 24a, a water inlet 24b and an oxidant gas inlet 24c for introducing each heated raw material into the can 21. Is provided. From the inlets 24a, 24b, and 24c, each raw material is conveyed to the SOFC 22 by piping (not shown). On the other hand, the exhaust gas discharged from the SOFC 22 is discharged to the outside through an exhaust gas outlet 28 provided in the can body 21.

As shown in FIG. 3, the SOFC 22 is a so-called direct internal reforming type solid oxide fuel cell in which the reforming reaction (S1) is performed on the cell in addition to the power generation reaction (S3). A solid oxide electrolyte 25 made of yttria-stabilized zirconia (YSZ) or the like is sandwiched between a fuel electrode 26 and an air electrode 27 which are a pair of opposed electrodes. The air electrode 27 is a porous body made of lanthanum manganite (LaMnO ₃ ) or the like, and gas can pass through the inside of the porous body. The fuel electrode 26 is a porous body made of nickel zirconia (Ni—ZrO ₂ ) cermet or the like, and a catalyst such as platinum fine particles is supported inside the micropores by, for example, an impregnation method. (Not shown). The platinum catalyst may be fine particles made of other elements belonging to Group VIII, for example, elements such as iridium, osmium, ruthenium, rhodium and palladium.

  Here, the reaction in SOFC 22 will be described.

  As will be described later, raw fuel m1, water m2, and oxidant gas m3 are heated and guided to the fuel cell assembly 2 as gases. As the raw fuel m1, a known raw fuel such as methane gas or kerosene is appropriately used. In particular, a raw fuel suitable for reforming on the cell surface of SOFC22 is preferable. For example, a synthetic kerosene prepared by appropriately preparing a paraffinic chain hydrocarbon obtained by Fischer-Tropsch (FT) synthesis of carbon monoxide and hydrogen. Etc. are used. Such raw fuel (gas) m1 and water (steam) m2 are guided to the surface of the fuel electrode 26 as a mixed gas M1. When the mixed gas M1 comes into contact with a catalyst (not shown) supported in the fuel electrode 26, the mixed gas M1 is decomposed into a fuel gas M2 composed of carbon monoxide and hydrogen while causing a steam reforming reaction (S1).

  On the other hand, the oxidant gas m <b> 3 is guided to the surface of the air electrode 27. The oxygen in the oxidant gas m3 that has received electrons at the air electrode 27 becomes oxygen ions and moves to the fuel electrode 26 through the electrolyte 25 (S2).

  The oxygen ions that have reached the fuel electrode 26 react with the fuel gas M2 generated by the steam reforming reaction (S1), thereby generating water and carbon dioxide and releasing electrons to the fuel electrode 26 (S3). Here, water, carbon dioxide, unreacted mixed gas M1 generated by the reaction, and fuel gas M2 generated by the steam reforming reaction are discharged from the SOFC 22 as heated exhaust gas M3 (S4). . Although the steam reforming reaction (S1) is an endothermic reaction and the power generation reaction (S3) is an exothermic reaction, the exothermic amount is much larger than the endothermic amount.

  Referring again to FIG. 1 together with FIG. 2, the high-temperature heat exchanger 5 is a known heat exchanger such as a multi-tube type or a plate type, and is accommodated in the preheating part space R <b> 2 of the heat insulating container 3. . The high temperature heat exchanger 5 gives heat of the exhaust gas M3 discharged from the fuel cell assembly 2 to each raw material of the raw fuel m1, water m2, and oxidant gas m3 introduced into the fuel cell assembly 2. The high-temperature heat exchanger 5 is provided with a pair of raw fuel introduction ports 51a and outlet ports 52a connected by piping for introducing, heating, and discharging the raw fuel m1. Similarly, a pair of water inlet 51b and outlet 52b connected by a pipe for heating water m2, a pair of oxidant gas inlet 51c connected by a pipe for heating oxidant gas m3, and a lead. An outlet 52c is provided. On the other hand, a pair of exhaust gas inlets 53 and outlets 54 for introducing exhaust gas M3 discharged from the fuel cell assembly 2 and exchanging heat with the raw fuel m1, water m2, and oxidant gas m3 are provided. It has been. The exhaust gas inlet 53 and the exhaust gas outlet 28 of the fuel cell assembly 2 are connected to each other by a pipe 12 that passes through a through hole P provided in the partition heat insulating wall 32.

  The low temperature heat exchanger 6 is provided in the vicinity of the high temperature heat exchanger 5, preferably in the upper part, and is installed in a heat insulating container 65 that is heat shielded from the heat insulating container 3. The low temperature heat exchanger 6 is a known heat exchanger similar to the high temperature heat exchanger 5, and introduces the exhaust gas M <b> 3 after heat exchange in the high temperature heat exchanger 5 and is stored in the hot water tank 7. Heat is exchanged with the running water or directly with the drinking water. That is, heat recovery up to the cooling water level of clean water can be performed. The low-temperature heat exchanger 6 includes a pair of an exhaust gas inlet 61 for introducing the exhaust gas M3 that has passed through the high-temperature heat exchanger 5 and an exhaust gas outlet 62 for discharging the exhaust gas M3 to the outside. The exhaust gas inlet 61 is connected to the exhaust gas outlet 54 of the high-temperature heat exchanger 5 by a pipe 54a having a length as short as possible to reduce heat loss. Further, a cold water inlet 63 for guiding clean water from the hot water tank 7 and a hot water outlet 64 for heating the cold water and returning it to the hot water tank 7 are provided. These are respectively connected to the hot water tank 7 by piping.

  The hot water tank 7 stores the clean water heated by the low-temperature heat exchanger 6 and supplies the clean water to the outside as needed. The hot water storage tank 7 is a columnar container, and stores hot water in an upper portion and cold water in a lower portion with a temperature gradient. That is, the water supply port 71 for replenishing tap water or the like and the water discharge port 72 for discharging the clean water toward the low temperature heat exchanger 6 are heated by the low temperature heat exchanger 6 below the hot water tank 7. A hot water supply port 73 for introducing warm hot water and a hot water return port 74 for deriving warm water are provided on the upper side of the hot water tank 7 (see FIG. 1). In addition, a heating device (heater) 78 that heats water according to demands such as the temperature and amount of hot water is provided in the hot water tank 7 or outside the hot water outlet 74. Even when the temperature of the warm water is low, the warm water can be heated and supplied by the heating device 78 as necessary.

In addition, the magnitude | size of the low-temperature heat exchanger 6 and the hot water storage tank 7 is determined by the required amount of the water to supply. The hot water storage tank 7 has a size that can store hot water of about 0.5 to 2 m in the vertical direction and about 50 L to 1 m ³ , typically about 0.5 to 1 m in the vertical direction and about 50 to 300 L of hot water. As described above, the heating device 78 for heating the water may be provided therein.

  Finally, the heater 4 should be a high-temperature heat exchanger 5 in the vicinity of the fuel cell space R1 defined by the heat insulating container that accommodates the fuel cell assembly 2, that is, the partition heat insulating wall 32 and the side heat insulating wall 33. It is provided at a close position. Specifically, it is provided in the preheating part space R2 of the heat insulating container 3 and above the high temperature heat exchanger 5 and in the vicinity of the through hole P. The heater 4 can heat the raw fuel m1, the water m2, and the oxidant gas m3 derived from the high-temperature heat exchanger 5 as necessary. The heater 4 is provided with a pair of raw fuel inlets 41a and outlets 42a connected by piping for introducing and leading out the raw fuel m1. Similarly, a pair of water inlet 41b and outlet 42b connected by a pipe for heating water m2, a pair of oxidant gas inlet 41c connected by a pipe for heating oxidant gas m3, and a lead. An outlet 42c is provided.

  The raw fuel inlet 41a, the water inlet 41b, and the oxidant gas inlet 41c are connected to the raw fuel outlet 52a, the water outlet 52b, and the oxidant gas outlet 52c of the high-temperature heat exchanger 5 by piping. . The raw fuel outlet 42a, the water outlet 42b and the oxidant gas outlet 42c are connected to the raw fuel inlet 24a, the water inlet 24b and the oxidant gas inlet 24c of the fuel cell assembly 2, respectively. .

  Referring also to FIG. 4, a heating unit 4 a including burners 44 a, 44 b and 44 c for heating each raw material is provided inside the heater 4. The heater 4 is provided with an oxidant gas introduction port 43a for introducing the oxidant gas to each burner 44a, 44b and 44c of the heating unit 4a and a heating fuel introduction port 43b for introducing the heating fuel. . The amount of the heating fuel introduced from the heating fuel introduction port 43b is appropriately adjusted by adjusting the opening degree of the flow rate adjusting valves 45a, 45b, 45c provided in front of the burners 44a, 44b and 44c. Then, each heating power is controlled by being supplied to each burner 44a, 44b and 44c. As will be described later, the flow rate adjusting valves 45a, 45b, and 45c can be controlled based on a signal from a temperature sensor 46 provided in the vicinity of the SOFC 22.

  The heater 4 can be changed according to the control method. For example, a general valve (not shown) may be provided downstream of the heating fuel introduction port 43b. In such a case, the flow rate adjusting valves 45a, 45b, and 45c are fixed in advance so that the heating fuel flows at a predetermined flow rate or a predetermined distribution ratio. Thereby, only the opening degree of the general valve is adjusted based on the signal from the temperature sensor 46, or the full open / close operation is repeated, and the heating power of each burner 44a, 44b and 44c can be adjusted as necessary. According to this, control of a thermal power can be simplified more.

  Further, the heater 4 is provided with an exhaust gas outlet 49 for leading the combustion gas generated in the burners 44a, 44b and 44c to the outside as the exhaust gas M4. The exhaust gas outlet 49 is connected to the pipe 12 connecting the exhaust gas outlet 28 of the SOFC 22 and the exhaust gas inlet 53 of the high-temperature heat exchanger 5, and the exhaust gases M3 and M4 merge.

  Further, in the heater 4, the pipe connected to the raw fuel introduction port 41a branches into a heating pipe 11a that passes through the heating section 4a and a bypass pipe 11a ′ that does not pass through the heating section 4a. Are joined again to the raw fuel outlet 42a. A valve Va that opens and closes is provided near the branch point downstream of the heating pipe 11a and the junction point, and a valve Va ′ that operates reversely to the valve Va near the branch point downstream of the bypass pipe 11a ′. Is provided. That is, when the valve Va is opened, the valve Va 'is closed in reverse, and the raw fuel inlet 41a and the raw fuel outlet 42a are connected via the heating pipe 11a. On the other hand, when the valve Va is closed, the valve Va 'is opened in reverse, and the raw fuel introduction port 41a and the raw fuel outlet port 42a are connected via the bypass pipe 11a'.

  Similarly, pipes connected to the water inlet 41b and the oxidant gas inlet 41c are respectively connected to heating pipes 11b and 11c that pass through the heating part 4a and bypass pipes 11b ′ and 11c ′ that do not pass through the heating part 4a. Branch. Further, they merge again downstream of the heating unit 4a and are connected to the water outlet 42b and the oxidant gas outlet 42c, respectively. Valves Vb and Vc are provided in the vicinity of the branch point downstream of the heating pipes 11b and 11c and in the upstream of the junction. Valves Vb 'and Vc' are provided in the vicinity of the branch point downstream of the bypass pipes 11b 'and 11c'.

  Next, the operation of the fuel cell cogeneration system 1 will be described with reference to FIGS. 1 to 4.

  When the fuel cell cogeneration system 1 is activated, a predetermined warm-up operation for warming the SOFC 22 is performed. For example, the valves Va, Vb and Vc of the heater 4 are opened, while the valves Va ′, Vb ′ and Vc ′ are closed and the heater 4 is started. Here, in order to protect at least the fuel electrode 26 (see FIG. 3), the raw fuel m1 is not supplied during the warm-up operation. In this state, a predetermined warm air gas heated by the heater 4 is introduced into the fuel cell assembly 2 through a supply pipe (not shown) to warm up the SOFC 22. Details of the warm-up operation are omitted.

  When the raw fuel m1, the water m2, and the oxidant gas m3 are led to the heater 4 after the sufficient warm-up operation, the burners 44a, 44b, and 44c (see FIG. 4), these are sufficiently heated and gasified (vaporized) and guided to the SOFC 22 in the fuel cell assembly 2.

  As described in FIG. 3, at the fuel electrode 26 of the SOFC 22, the introduced raw fuel m1 and water m2 generate fuel gas M2 (carbon monoxide and hydrogen) in the presence of the catalyst (S1: steam reforming reaction). Further, the fuel gas M2 generates a power generation reaction (S3) while generating water. Since the amount of heat generated by the power generation reaction (S3) is much larger than the amount of heat absorbed by the steam reforming reaction (S1), the exhaust gas M3 from the SOFC 22 is discharged with heat.

  On the other hand, the exhaust gas M4 discharged from the heater 4 joins M3 and is led to the high temperature heat exchanger 5 as an exhaust gas M5 (see FIG. 6). In the high temperature heat exchanger 5, heat from the exhaust gas M5 is exchanged with the raw fuel m1, water m2, and oxidant gas m3. Thereby, the raw fuel m1, the water m2, and the oxidant gas m3 are heated and guided to the heater 4. That is, gradually, the temperature of the SOFC 22 can be maintained at a predetermined temperature without requiring much output from the heater 4. Further, when the raw fuel m1, water m2, and oxidant gas m3 are further heated by the heat from the exhaust gas M5, the temperature of the SOFC 22 can be kept at a predetermined temperature without requiring any heating output by the heater 4. become able to do. In this case, the valves Va, Vb and Vc of the heater 4 are closed and at the same time the valves Va ′, Vb ′ and Vc ′ are opened, and the heater 4a is bypassed all at once, and the raw fuel m1, water m2 and oxidant gas m3 are opened. May be led directly from the high temperature heat exchanger 5 to the SOFC 22.

  Note that radiation from the fuel cell assembly 2 is confined in the narrow fuel cell space R1, and a temperature drop of the fuel cell assembly 2 is prevented. Therefore, the temperature of the SOFC 22 quickly reaches a high temperature of 700 ° C. to 1000 ° C. by self-heating by the power generation reaction (S3).

  By the way, the output of the heater 4 is adjusted so as to stabilize the operation of the SOFC 22. For example, the temperature of the SOFC 22 can be monitored by the temperature sensor 46 and the output of the heater 4 can be adjusted so as to keep it constant. The heating power of each burner 44a, 44b, and 44c of the heater 4 can be adjusted independently by the opening degree of the flow rate adjusting valves 45a, 45b, and 45c that adjust the amount of heating fuel that flows through the burner. For example, for water m2, which has a large amount of sensible heat and latent heat, only the amount of heating fuel supplied to the burner 44b is increased in order to give a larger amount of heat than the raw fuel m1 and the oxidant gas m3. Can do. Moreover, only the supply amount of the heating fuel to the burners 44a and / or 44b can be adjusted so as to promote or suppress the steam reforming reaction.

  Further, when the temperature of the SOFC 22 is excessively increased, the heating power of each burner 44a, 44b and / or 44c can be adjusted by reducing the opening degree of the flow rate adjusting valves 45a, 45b, 45c. On the other hand, when the valves Va ′, Vb ′ and / or Vc ′ are opened simultaneously with closing the valves Va, Vb and / or Vc of the heater 4, the raw fuel m1, water m2 and / or oxidant gas m3 are The heating unit 4a can be bypassed all at once and led directly from the high-temperature heat exchanger 5 to the SOFC 22. Thus, the temperature can be adjusted more rapidly than the heating power of the burners 44a, 44b and / or 44c.

  The output of the heater 4 can also be controlled by other monitoring methods so as to stabilize the operation of the SOFC 22. For example, the power generation output of the SOFC 22 may be monitored and feedback controlled, or a temperature sensor may be provided downstream of the heating unit 4a of the heater 4 and monitored.

  By the way, the exhaust gas M5 used for heat exchange in the high temperature heat exchanger 5 is further introduced into the low temperature heat exchanger 6 to exchange heat with clean water. Here, in the low-temperature heat exchanger 6, heat exchange can be performed until the temperature of the exhaust gas M <b> 5 introduced from the exhaust gas inlet 61 reaches the temperature level of the clean water near the exhaust gas outlet 62. The clean water heated by the recovered heat (warm clean water) is stored in the hot water tank 7. On the other hand, the exhaust gas M5 exiting the low-temperature heat exchanger 6 is recovered and appropriately processed. The temperature of the hot water tank 7 is managed as necessary, and the amount of clean water circulating between the low temperature heat exchanger 6 and the hot water tank 7 is determined accordingly. In addition, the warm water stored in the hot water tank 7 is extracted from the hot water outlet 74 and used as necessary. In addition, when the amount of water in the hot water tank 7 decreases, tap water such as tap water is supplied from the water supply port 71. The amount of water in the hot water tank 7 is maintained substantially constant, but the water surface position can be managed as necessary.

  As described above, in this embodiment, the temperature of each of the plurality of raw materials to be introduced can be controlled by the heating means in accordance with the operation status from the start of the solid oxide fuel cell to the stable operation. Thus, since the temperature of the raw material to be supplied to the fuel cell can be controlled, the power generation reaction of the fuel cell can be stabilized. In addition, the exhaust heat from the high-temperature heat exchanger can be used also in the low-temperature heat exchanger, and the system can efficiently use the heat. That is, even if it is a direct internal reforming type solid oxide fuel cell, the power generation reaction (S3) can be stabilized, and the system can efficiently use heat.

[Example 2]
Next, a fuel cell cogeneration system according to another embodiment of the present invention will be described with reference to FIG. In addition, since it is the same as that of Example 1 except the high temperature heat exchanger 5, the detailed description is abbreviate | omitted.

  The high-temperature heat exchanger 5 is a known heat exchanger such as a multi-tube type or a plate type as in the first embodiment, and is accommodated in the preheating part space R2 of the heat insulating container 3 (see FIG. 1). The high temperature heat exchanger 5 gives the heat of the exhaust gas M3 exhausted from the fuel cell assembly 2 only to the water m2 introduced into the fuel cell assembly 2. It is possible to improve the stability of the operation of the fuel cell assembly 2 by preliminarily heating the water m2 having high sensible heat and latent heat and then introducing it into the heater 4. Therefore, the high-temperature heat exchanger 5 is provided with a pair of water inlets 51b and outlets 52b connected by piping for introducing, heating, and discharging water m2. On the other hand, the raw fuel m1 and the oxidant gas m3 are led directly to the raw fuel introduction port 41a and the oxidant gas introduction port 41c of the heater 4. Further, a pair of exhaust gas introduction ports 53 and a discharge port 54 through which the exhaust gas M3 is introduced from the exhaust gas outlet 28 of the fuel cell assembly 2 through the pipe 12 and discharged are provided. Further, the exhaust gas outlet 54 is connected to the exhaust gas inlet 61 of the low-temperature heat exchanger 6 by a pipe 54a.

  Here, in this embodiment, a pipe 12 ′ that bypasses a part of the exhaust gas M <b> 3 flowing through the pipe 12 to the pipe 54 a without passing through the high-temperature heat exchanger 5 is provided. A shunt 13 is provided at a connection point between the pipe 12 and the pipe 12 ′. The flow divider 13 is configured such that the flow dividing ratio thereof is adjusted corresponding to the temperature sensor 75 provided in the hot water tank 7.

  By the way, the operation of the fuel cell cogeneration system 1 of the present embodiment is substantially the same as that of the first embodiment. On the other hand, as described in the first embodiment, tap water such as tap water is supplied from the water supply port 71 to the hot water tank 7 due to the demand for hot water in the hot water tank 7. Therefore, when the overall temperature in the hot water tank 7 is lowered, the temperature sensor 75 detects this, and when the temperature in the hot water tank 7 is set high, the flow divider 13 causes the exhaust gas M3 to flow into the pipe 12 '. Operates to flow more. At this time, the decrease in the temperature of the water m2 is compensated by the heater 4, and the power generation reaction of the fuel cell can be stabilized.

  As described above, in this embodiment, even if it is a direct internal reforming type solid oxide fuel cell, the power generation reaction can be stabilized, and further the warm water in the fuel cell cogeneration system 1 can be stabilized. Efficient heat utilization is possible in response to demand.

  The control method of the flow divider 13 is not limited to the above. For example, in addition to the temperature of the warm water stored in the hot water tank 7, the amount of water and the amount of use are detected, and further, the operating temperature information of the SOFC 22 And may be controlled according to a preset table.

[Example 3]
Next, a fuel cell cogeneration system according to another embodiment of the present invention will be described with reference to FIG. In addition, since it is the same as that of Example 1 and / or Example 2 except the heater 4, the detailed description is abbreviate | omitted.

  The internal structure of the heater 4 is the same as that of the first embodiment. Here, a pipe 81 for branching and guiding the exhaust gas M3 of the fuel cell assembly 2 joins upstream of the heating fuel introduction port 43b. That is, the pipe 12 connecting the exhaust gas outlet 28 of the fuel cell assembly 2 and the exhaust gas inlet 53 of the high temperature heat exchanger 5 is provided with a flow divider 82, and the pipe 81 branched here is It is connected to the upstream side of the heating fuel inlet 43b. The flow divider 82 is configured such that the flow dividing ratio thereof is adjusted corresponding to the gas sensor 83 provided in the vicinity of the fuel battery cell 22. By the way, the operation of the fuel cell cogeneration system 1 of the present embodiment is substantially the same as that of the first and / or second embodiment. On the other hand, when the gas sensor 83 provided in the vicinity of the fuel cell 22 detects that the raw fuel m1 is not yet burned, the flow divider 82 converts a part of the exhaust gas M3 into the heating fuel for the heater 4. It is distributed to. That is, unburned raw fuel m1 is used as fuel for the burners 44a, 44b and 44c.

  As described above, in this embodiment, even if an excessive raw fuel m1 is introduced into the internal reforming reaction in the direct internal reforming type solid oxide fuel cell, this is used as the heating fuel for the heater. It can be used. Therefore, efficient heat utilization is possible.

  As mentioned above, although the typical Example by this invention and the modification based on this were described, this invention is not necessarily limited to these, For example, although the Example of the direct internal reforming type fuel cell was described. However, the present invention is not limited thereto, and materials such as electrodes, electrolytes, and catalysts can be appropriately changed by those skilled in the art. That is, those skilled in the art will be able to find various alternative embodiments and modifications without departing from the scope of the appended claims.

It is sectional drawing of the principal part of the system by this invention. It is a block diagram of the principal part of the system by this invention. It is sectional drawing of the principal part of the system by this invention. It is a block diagram of the principal part of the system by this invention. It is a block diagram of the principal part of the other system by this invention. It is a block diagram of the principal part of the other system by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fuel cell cogeneration system 2 Fuel cell assembly 3 Heat insulation container 4 Heater 5 High temperature heat exchanger 6 Low temperature heat exchanger 7 Hot water tank 22 SOFC
25 Solid oxide electrolyte 26 Fuel electrode 27 Air electrode

Claims (9)

A fuel cell cogeneration system that recovers and uses heat generated by a power generation reaction of a solid oxide fuel cell,
Heating means capable of heating each of a plurality of raw materials made of liquid or gas introduced into the fuel cell;
A high-temperature heat exchanger that performs heat exchange so as to give heat from the exhaust gas from the fuel cell to the raw material introduced into the heating means;
A low-temperature heat exchanger that performs heat exchange so that heat from the exhaust gas from the high-temperature heat exchanger is given to clean water;
And a hot water storage tank for storing the clean water.   2. The fuel cell cogeneration system according to claim 1, wherein the raw material comprises water, an oxidant gas, and a hydrocarbon fuel.   3. The fuel cell cogeneration system according to claim 2, wherein the fuel cell has an electrode carrying a catalyst for reforming the hydrocarbon fuel.   4. The fuel cell cogeneration system according to claim 3, wherein the hydrocarbon fuel is a paraffinic liquid fuel synthesized and distilled from hydrogen and carbon monoxide.   3. The fuel cell core according to claim 2, wherein the high-temperature heat exchanger exchanges heat with water in a part of the exhaust gas and allows the remainder of the exhaust gas to pass through without exchanging heat. Generation system.   The fuel cell cogeneration system according to claim 1, wherein the low-temperature heat exchanger is provided on an upper portion of the high-temperature heat exchanger.   2. The fuel cell cogeneration system according to claim 1, wherein the heating means includes a heating pipe for heating each of the raw materials and a passage pipe for allowing the raw materials to pass through without heating.   The fuel cell cogeneration system according to claim 1 or 7, wherein the fuel cell is housed in a heat insulating container, and the heating means is provided in or near the heat insulating container.   8. The fuel cell core according to claim 1, wherein the heating unit combusts a part of the exhaust gas from the fuel cell and sends the combusted gas to the high-temperature heat exchanger. 9. Generation system.