JP2011131141A - Evaporator and fuel cell system using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaporator which can stably supply water vapor by surely and continuously evaporating water at a predetermined evaporation portion, and a fuel cell system using the evaporator. <P>SOLUTION: The evaporator 6 is installed in the middle of an exhaust gas lead-out passage 5 for discharging exhaust gas from a cell module. The tip 71 of a water supply pipe 7 laid outside the cell module is arranged adjacent to an evaporation surface 63 heated by the exhaust gas serving as a heat source, whereby water continuously moves on the evaporation surface 63 without growing to a droplet. The water supply pipe 7 is covered and insulated by a heat insulating material 8 to avoid water evaporation inside the water supply pipe 7. The evaporation surface 63 is formed to be a minutely uneven surface to increase wettability. Water vapor evaporated on the evaporation surface 63 is mixed into fuel gas in a fuel gas supply pipe inside the cell module by a water vapor supply pipe 64. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an evaporation apparatus and a fuel cell system using the same, and more particularly to a technique capable of stably generating water vapor.

  2. Description of the Related Art Conventionally, a polymer electrolyte fuel cell system has been proposed that includes a humidifier for heating and humidifying a fuel gas that is being supplied to a battery module. In this device, as a humidifier, the fuel gas flow channel is sandwiched between them, the off gas flow channel is disposed on one side, the cooling water flow channel of the fuel cell is disposed on the other side, and a moisture permeable film is interposed at the boundary between the heat and moisture. It is configured in combination so that they can be exchanged (see, for example, Patent Document 1).

  Further, as an evaporator used for evaporating the liquid to be evaporated such as water or hydrocarbon-based raw fuel and supplying it to the reformer, a groove is provided on the surface of the heat transfer substrate for heating the liquid to be evaporated, A structure in which a skin having a large number of holes communicating with the grooves is bonded to the surface of the heat transfer substrate has been proposed. In this case, the groove and the hole have a size of about 0.2 to 0.3 mm where the effect of capillary action can be expected, and a thin liquid film is supplied from the groove through the hole to the surface of the heat transfer surface to achieve a high heat transfer coefficient. Is maintained to make the evaporator core temperature uniform (see, for example, Patent Document 2).

JP 2004-31073 A JP 2005-233477 A

  By the way, in a solid oxide fuel cell (SOFC), steam reforming is performed by reacting a hydrocarbon fuel with steam under a high temperature condition to convert it into hydrogen and carbon monoxide. However, when the supply of steam for the steam reforming becomes unstable, various disadvantages are expected.

  For example, as shown in FIG. 6, an evaporation unit 202 is disposed in a housing 201 in a high temperature environment of the battery module 200. A fuel gas supply pipe 203 and water (pure water) In the case of a structure in which the supply pipe 204 is joined and water is evaporated in the evaporation section 202 heated to a high temperature in a high temperature environment to mix water vapor with the fuel gas, the following inconvenience is expected. .

  That is, there is a possibility that the water supply pipe 204 is also exposed to a high temperature environment higher than the boiling point of water in the housing 201 to evaporate even before the evaporation section 202 is reached. In this case, there is a possibility that the supply of water vapor becomes discontinuous due to an uncertain situation as to how much water is evaporated in which part. Further, the evaporating section 202 has a high temperature of, for example, 200 to 300 ° C. in a high temperature environment, which may cause a Leidenfrost phenomenon when water is evaporated in the internal space. As a result, the evaporation rate may become unstable. When the Leidenfrost phenomenon occurs, the evaporation of water is hindered and the evaporation itself becomes irregular, which not only causes evaporation and instability of water vapor, but also causes sudden and instantaneous evaporation of water, resulting in fuel The pressure loss on the gas flow rate side suddenly increases, causing a rapid decrease in the fuel gas flow rate. Due to the discontinuity or instability of the amount of water vapor mixed into the fuel gas as described above, the fuel gas flow rate to the downstream side may fluctuate discontinuously or the amount of water vapor supplied to the reformer may fluctuate. As a result, the steam / carbon ratio (S / C) value fluctuates and the catalyst inside the reformer deteriorates (carbon deposition), or the fuel gas flow rate to the cell decreases momentarily, resulting in durability of the cell. The situation that damages is also caused.

  The present invention has been made in view of such circumstances, and an object of the present invention is an evaporation apparatus capable of stably and continuously evaporating at a predetermined evaporation site and stably supplying water vapor. An object of the present invention is to provide a fuel cell system using an evaporation apparatus.

  In order to achieve the above object, the invention relating to the evaporation apparatus includes an evaporation section heated by a heat source, and a water supply pipe for supplying water to the evaporation surface of the evaporation section, at the tip of the water supply pipe. The opening is arranged close to the evaporation surface (claim 1).

  In the case of the present invention, since the tip of the water supply pipe is disposed close to the evaporation surface, it is possible to reliably move the water supplied from the tip with respect to the evaporation surface by the surface tension. Even if an extremely small flow rate of water is supplied to the evaporation surface through the water supply pipe, the occurrence of the Leidenfrost phenomenon can be prevented and suppressed. For this reason, it becomes possible to evaporate continuously and stably on the evaporation surface, and a continuous and stable supply of evaporated water vapor is realized. Here, as the “heat source”, in addition to an electric heater or the like, for example, high-temperature exhaust gas may be used for exhaust heat utilization. In addition, as described above, “adjacent” means proximity close to a minute interval to the extent that water supplied from the tip of the water supply pipe can be reliably moved with respect to the evaporation surface by surface tension. The tip of the tube may be brought into contact with the evaporation surface at one point or a part thereof.

  The water supply pipe in the present invention can be insulated so that heat transfer from the evaporation surface is blocked (Claim 2). By doing so, it is possible to reliably avoid the occurrence of a situation in which the water supplied by the water supply pipe evaporates in the middle of the supply other than the tip of the water supply pipe. By evaporating the entire amount on the evaporation surface, a more stable water vapor supply becomes possible. Here, in order to “heat-insulate”, for example, a heat insulating material may be used for heat insulation, or a water supply pipe may be constituted by a double pipe and heat insulated by a gas layer.

  Further, the evaporation surface in the present invention can be constituted by a fine uneven surface. By doing so, it becomes possible to increase the wettability of the evaporation surface, thereby making it possible to further prevent and suppress the occurrence of the Leidenfrost phenomenon. As a result, even if an extremely small flow rate of water is supplied through the water supply pipe, continuous and stable evaporation on the evaporation surface is further ensured, and continuous and stable supply of evaporated water vapor is further increased. It will surely be realized.

  On the other hand, in the invention relating to the fuel cell system, the evaporation unit is heated in the middle of the exhaust gas exhaust passage for exhausting the exhaust gas from the battery module to the outside using the exhaust gas in the exhaust gas exhaust passage as a heat source. Thus, the water vapor supply pipe is arranged so that the water vapor evaporated on the evaporation surface is mixed with the fuel gas in the fuel gas supply pipe.

  In the case of the present invention, since the water supply pipe is not disposed in the high temperature environment in the battery module but is disposed in the exhaust gas outlet flow path, the evaporation of water during the water supply by the water supply pipe is prevented. On the other hand, the exhaust gas in the exhaust gas outlet passage can be effectively used as a heat source for heating the evaporation surface. At this time, by making the water supply pipe insulated, it is possible to more reliably prevent water evaporation during the supply. Even if a very small flow rate of water is supplied to the high-temperature evaporation surface through the water supply pipe, the occurrence of Leidenfrost phenomenon can be prevented and suppressed, and the evaporation surface can be continuously and stably evaporated. Therefore, continuous and stable supply of water vapor to the fuel gas in the fuel gas supply pipe is realized. As a result, the steam / carbon ratio is also stably maintained, and there is no inconvenience that the catalyst deteriorates in the reformer that performs steam reforming, and the durability of the battery body decreases.

  In this fuel cell system, except for the tip of the water supply pipe, the water supply pipe can be piped through the inside of the fuel gas supply pipe so that heat transfer from the evaporation surface is blocked. ). By disposing the water supply pipe inside the fuel gas supply pipe, the fuel gas serves as a heat insulating material, and it becomes possible to realize the heat insulation of the water supply pipe without using a special heat insulating material. .

  As described above, according to the invention relating to the evaporation apparatus, since the tip of the water supply pipe is disposed close to the evaporation surface, the water supplied from the tip is reliably moved with respect to the evaporation surface by the surface tension. As a result, even if a very small amount of water is supplied to the high-temperature evaporation surface through the water supply pipe, the occurrence of the Leidenfrost phenomenon can be prevented / suppressed. For this reason, it can evaporate continuously and stably in an evaporation surface, and can implement | achieve the continuous and stable supply of the evaporated water vapor | steam.

  In particular, according to the second aspect, it is possible to reliably avoid the occurrence of a situation in which the water supplied by the water supply pipe evaporates in the middle of supply other than the tip of the water supply pipe. By evaporating the total amount of water on the evaporation surface, more stable water vapor supply can be realized.

  According to the third aspect of the present invention, the evaporating surface is composed of fine uneven surfaces, thereby increasing the wettability of the evaporating surface, thereby further preventing and suppressing the occurrence of the Leidenfrost phenomenon. Can be. For this reason, continuous and stable evaporation on the evaporation surface can be further ensured, and continuous and stable supply of evaporated water vapor can be realized more reliably.

  On the other hand, according to the invention relating to the fuel cell system, the water supply pipe is not disposed in the high-temperature environment in the battery module, but is disposed in the exhaust gas outlet flow path. While it is possible to avoid evaporation of water on the way, the exhaust gas in the exhaust gas outlet passage can be effectively used as a heat source for heating the evaporation surface. At that time, by adopting a configuration in which the water supply pipe is insulated, evaporation of water during supply can be more reliably prevented. Even if a very small amount of water is supplied to the high-temperature evaporation surface through the water supply pipe, the occurrence of the Leidenfrost phenomenon can be prevented and suppressed, and the evaporation surface can be continuously and stably evaporated. Therefore, continuous and stable supply of water vapor to the fuel gas in the fuel gas supply pipe can be realized. As a result, the steam / carbon ratio is also stably maintained, and it is possible to avoid the occurrence of inconveniences such as catalyst deterioration of a reformer that performs steam reforming and a decrease in durability of the battery body.

  In this case, in particular, according to the fifth aspect, the water supply pipe is disposed inside the fuel gas supply pipe, so that the fuel gas serves as a heat insulating material, and the water supply is performed without using a special heat insulating material. Insulation of the tube can be realized.

It is a schematic diagram which shows embodiment of the fuel cell system using the evaporation apparatus of this invention. FIG. 2 is an enlarged explanatory view of the evaporation apparatus of FIG. 1. 3A is an enlarged view of a portion A in FIG. 2, and FIG. 3B is an enlarged cross-sectional explanatory view taken along line BB in FIG. It is the elements on larger scale of FIG.3 (b). It is a figure corresponding to FIG. 2 which shows other embodiment. It is a schematic diagram which shows the example of the fuel cell system for showing the subject of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a fuel cell system using an evaporation apparatus according to an embodiment of the present invention. In this embodiment, an example of a solid oxide fuel cell system is shown. In the figure, reference numeral 2 is a battery module, 3 is a battery body constituting the battery module 2, 4 is a fuel gas supply pipe, 5 is an exhaust gas outlet passage for exhausting exhaust gas from the housing 20 of the battery module 2, and 6 is this The evaporator 6 is disposed in the middle of the exhaust gas discharge passage 5, and the evaporation device 6 evaporates water (pure water) using the exhaust gas in the exhaust gas discharge passage 5 as a heat source to form fuel gas in the fuel gas supply pipe 4. It is designed to be mixed. Hereinafter, each component will be described in detail.

  The battery body 3 includes a cylindrical cell 31, a reformer 32, and an air heat exchanger 33. The cell 31 is concentrically integrated with a small-diameter cylindrical anode (fuel electrode) 311 and a large-diameter cylindrical cathode (air electrode) 312 covering the outer peripheral side with an electrolyte 313 sandwiched therebetween. A cell stack is formed by standing a plurality of cells at predetermined intervals. That is, the cathode 312 is exposed to the internal space 314, and the anode 311 is shielded from the internal space 314 by the cathode 312 and the like. The anode 311 and the cathode 312 are both formed of ceramics containing a metal oxide such as Ni, and the electrolyte 313 is formed of a solid oxide such as YSZ (yttrium stabilized zirconia). . Although only one cell 31 is shown in FIG. 1 because of the principle illustrated, it is configured as a cell stack by a plurality of cells not shown.

  The fuel gas supplied from the reformer 32 is caused to flow from the lower end toward the upper end through the inner hole 315 formed by the inner peripheral surface of the anode 311 of the cell 31. Further, the outer peripheral surface of the cell 31 is constituted by the outer peripheral surface of the cathode 312, and the cathode air is jetted from the air heat exchanger 33 to the internal space 314 so as to be supplied to the outer peripheral surface of the cathode 312. Yes. At the cathode 312, oxygen in the cathode air becomes oxygen ions and passes through the electrolyte 313, and at the anode 311, it reacts with hydrogen of the fuel gas to generate water (water vapor), while electrons generated at that time pass through the circuit to the cathode 312 side. It is generated by repeating the process of re-ionizing oxygen once again. The fuel gas supplied to the inner hole 315 is used for the reaction while passing through the inner hole 315 upward, and then the off-gas discharged from the upper end of the fuel gas is guided to the reformer burner 321 for combustion. It has come to be used as fuel. Then, the exhaust gas from the reformer burner 321 is led out from the housing 20 to the exhaust heat recovery circuit (for example, exhaust heat recovery heat exchanger) outside the figure through the exhaust gas outlet flow path 5, and the heat recovery in this exhaust heat recovery circuit At this time, the water recovered by recovering moisture in the exhaust gas or the like is purified to pure water, and then used as part or all of the water supplied to the evaporator 6. Further, the inside of the housing 20 becomes a high-temperature environment (for example, 200 to 300 ° C.) due to heat radiation from the battery body 3 side and the exhaust gas.

  The fuel gas supply pipe 4 is extended from the outside of the housing 20 of the battery module 2 in order to supply fuel gas (for example, city gas 13A) to the reformer 32, and its downstream end is connected to the reformer 32. It is connected. The fuel gas in the fuel gas supply pipe 4 in the housing 20 is supplied with water vapor from a water vapor supply pipe 64 (to be described later) of the evaporator 6 and mixed.

  As shown in detail in FIG. 2, the evaporator 6 is interposed in the middle of the exhaust gas outlet passage 5 (between the outlet from the housing 20 and the exhaust heat recovery circuit outside the figure) in an internally fitted state. Yes, it is detachably fixed to the cylindrical wall constituting the exhaust gas outlet passage 5 at an appropriate position of the casing 61 of the evaporator 6 (for example, a mounting flange provided on the casing 61). The casing 61 is formed as an airtight container, and an inner surface on one side thereof is constituted by the evaporation surface 63 of the evaporation part 62, and an upstream end of a water vapor supply pipe 64 for supplying water vapor communicates with the upper surface on the other side. Connected. The downstream end of the water vapor supply pipe 64 is disposed so as to extend through the housing 20 (see FIG. 1) and open into the fuel gas supply pipe 4. On the other hand, in the casing 61, a water supply pipe 7 piped to the outside of the battery module 2 is disposed so as to penetrate from the outside of the casing 61 to the inside, and a tip 71 which is a downstream end thereof is close to the evaporation surface 63. Has been placed.

  More specifically, the evaporation surface 63 is disposed in a state of being exposed to be inclined obliquely downward facing the internal space of the casing 61, and the water supply pipe 7 is cut obliquely with respect to the evaporation surface 63. It is arranged so that the opening of the tip 71 faces and directly faces. The tip 71 of the water supply pipe 7 is in contact with the evaporation surface 63 at least at one point (part) of the opening, preferably at the lowest point, or as close as possible even with a minute gap. Is arranged. Even if the water is supplied at a very small flow rate (for example, 1 to 6.5 cc / min) to the water supply pipe 7 constituted by a thin tube (for example, a stainless steel pipe having an inner diameter of 8 mm), for example, FIG. As shown in FIG. 9, the limit is a minute interval α that does not form a droplet from the tip 71 but surely moves to the evaporation surface 63 by surface tension. As a result, the occurrence of the Leidenfrost phenomenon is prevented / suppressed.

  The back surface of the evaporation unit 62 on the opposite side of the evaporation surface 63 is exposed to the exhaust gas in the exhaust gas outlet passage 5 to become a heat receiving surface, but in order to collect heat from the exhaust gas more efficiently, As shown in FIG. 3B, the heat collecting members 65, 65,... The heat collecting members 65, 65,... Are configured by fin plates, for example, and absorb the heat from the exhaust gas (for example, 400 to 500 ° C.) in the exhaust gas outlet flow path 5 and transfer the heat to the evaporation unit 62, thereby evaporating the surface 63. Is heated to a high temperature state. Further, the surface of the evaporation surface 63 is formed to be a fine uneven surface 631 (see FIG. 4), thereby increasing the wettability and supplying water supplied from the tip 71 of the water supply pipe 7 (FIG. 4) is attached to the uneven surface 631 to prevent / suppress the occurrence of the Leidenfrost phenomenon.

  The outer peripheral surface of the water supply pipe 7 is covered with a heat insulating material (for example, glass wool) 8 so that it does not evaporate until the water inside reaches the tip 71. Note that the water supply pipe 7 may be formed of a double pipe spaced apart from each other and insulated by an air layer between the inner pipe and the outer pipe. Further, in the illustrated example, the insulation material 8 is coated on all but the tip 71 of the water supply pipe 7, but only on the inside of the evaporator 6 that is affected by high heat from the evaporation surface 63. You just have to do it.

  In the case of the above evaporation apparatus 6, the water supply pipe 7 is not disposed in the high temperature environment in the housing 20, and evaporation of water during the water supply by the water supply pipe 7 can be avoided. Since the exhaust gas outlet passage 5 is interposed, the exhaust gas in the exhaust gas outlet passage 5 can be effectively used as a heat source for heating the evaporation surface 63. At this time, by covering the water supply pipe 7 with the heat insulating material 8, the evaporation of water during supply can be prevented more reliably, while the heat collecting members 65, 65,. By doing so, the heat of the exhaust gas can be used more efficiently.

  In addition, since the tip 71 of the water supply pipe 7 is disposed close to the evaporation surface 63, the water supplied from the tip 71 can be reliably moved with respect to the evaporation surface 63 by the surface tension. Even if a very small amount of water is supplied to the high-temperature evaporation surface 63 by the water supply pipe 7, the occurrence of the Leidenfrost phenomenon can be prevented / suppressed. In addition, since the evaporation surface 63 is formed by the fine uneven surface 631, the wettability can be increased, thereby further ensuring the prevention / suppression of the above-described Leidenfrost phenomenon. Can do. As described above, even if a very small amount of water is supplied through the water supply pipe 7, it can be continuously and stably evaporated on the evaporation surface 63, and the evaporated water vapor can be passed through the water vapor supply pipe 64 in the fuel gas supply pipe 4. The fuel gas can be continuously and stably supplied. Thereby, the steam / carbon ratio is also stably maintained, and there is no inconvenience that the catalyst deterioration of the reformer 32 and the durability of the cell 31 are reduced.

<Other embodiments>
In addition, this invention is not limited to the said embodiment, Various other embodiments are included. That is, in the said embodiment, in order to avoid reliably the evaporation in the middle of the supply in the water supply pipe 7, it heat-insulates by coat | covering the heat insulating material 8, but it is not restricted to this, For example, the housing 20 Alternatively, the water supply pipe 7 may be inserted into the fuel gas supply pipe 4 that is piped outside, so that the water in the water supply pipe 7 is insulated by the fuel gas in the fuel gas supply pipe 4. For example, as shown in FIG. 5, the external fuel gas supply pipe 41 before being introduced into the housing 20 in the fuel gas supply pipe 4 is passed through the casing 61 of the evaporator 6, and its tip 411 is connected to the water vapor supply pipe 66. Insert inside and open. The water supply pipe 7 is passed through the external fuel gas supply pipe 41 passed through the casing 61, and the tip 71 of the water supply pipe 7 protrudes from the external fuel gas supply pipe 41 at a position near the evaporation surface 63 to form the evaporation surface 63. However, they are placed close to each other. The water vapor generated on the evaporation surface 63 passes through the inside of the water vapor supply pipe 66 and is mixed with the fuel gas at the junction 651 where the tip 411 of the external fuel gas supply pipe 41 is opened. Thereafter, the internal fuel gas supply in the housing 20 is supplied. The reformer 32 is supplied through the pipe 42. By doing so, it is possible to reliably prevent evaporation of water in the water supply pipe 7 in the middle of the supply while omitting the heat insulating material 8 and the like.

  Moreover, in the said embodiment, although exhaust gas is utilized as a heat source which heats the evaporation surface 63 of the evaporator 6, it is not restricted to this, For example, you may make it use an electric heater as a heat source. In this case, for example, an electric heater may be attached to the back surface of the evaporation unit 62. In this way, the evaporator 6 can be installed outside the housing 20 completely separated from the exhaust gas outlet passage 5. Alternatively, the present invention can be applied to a system different from the fuel cell system.

2 Battery module 4 Fuel gas supply pipe 5 Exhaust gas outlet flow path 6 Evaporator 7 Water supply pipe 8 Heat insulating material 62 Evaporating part 63 Evaporation surface 64, 66 Water vapor supply pipe 71 Tip

Claims (5)

An evaporation section heated by a heat source, and a water supply pipe for supplying water to the evaporation surface of the evaporation section,
The opening at the tip of the water supply pipe is disposed close to the evaporation surface,
An evaporation apparatus characterized by that. The evaporation apparatus according to claim 1,
The evaporation apparatus, wherein the water supply pipe is insulated so that heat transfer from the evaporation surface is blocked. The evaporation apparatus according to claim 1,
The evaporation apparatus, wherein the evaporation surface is constituted by a fine uneven surface. A fuel cell system that performs steam reforming on fuel gas,
In the evaporation apparatus according to any one of claims 1 to 3, the evaporation unit is heated using the exhaust gas in the exhaust gas discharge passage as a heat source in the middle of the exhaust gas discharge passage for exhausting the exhaust gas from the battery module to the outside. Intervened and
The water vapor supply pipe is arranged so that the water vapor evaporated on the evaporation surface is mixed with the fuel gas in the fuel gas supply pipe.
A fuel cell system. The fuel cell system according to claim 4, wherein
The fuel cell system, wherein the water supply pipe is piped through the inside of the fuel gas supply pipe so that heat transfer from the evaporation surface is cut off except for the tip.

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