JP5164449B2 - Air return mechanism and stationary fuel cell system - Google Patents

Description

  The present invention relates to an air return mechanism and a stationary fuel cell system, and more particularly to an air return mechanism that is provided between a water tank and a pump and removes air in water sent to the pump, and a stationary apparatus including the air return mechanism. The present invention relates to a type fuel cell system.

  Fuel cell systems equipped with fuel cells, etc., that reform raw gas such as gasoline, natural gas, city gas, etc. into hydrogen gas and generate electricity using hydrogen, are developed, especially for household use. Battery systems are gradually penetrating the market. In particular, a fuel cell system is highly expected as a trump card for popularizing cogeneration.

  Generally, a fuel cell system is included in a fuel cell body, a reformer that generates reformed gas containing hydrogen, carbon dioxide, and carbon monoxide from a raw material gas, and the reformed gas from the reformer. A CO converter that converts carbon monoxide into carbon dioxide and a CO remover that removes unmodified carbon monoxide from the CO converter are provided.

  This reformer includes a burner, mixes the fuel gas and the steam steamed by the internal heat exchanger, preheats and activates the catalyst by generating a reformed gas. The water that forms the water vapor is supplied to the reformer by a pump. In order for the reformer to stably generate hydrogen, it is necessary to increase the accuracy of the amount of water supplied from the pump.

  FIG. 3 is a schematic configuration diagram of the water tank 71 and the water pump 72 in the conventional fuel cell system. As shown in the figure, the pure water stored in the water tank 71 is supplied to the water pump 72 through the suction pipe 73. The water pump 72 supplies a desired amount of pure water to the reformer via the discharge pipe 74. At this time, if bubbles (air) are generated in the pure water, the pump unit 75 of the water pump 72 cannot supply an appropriate amount of pure water to the reformer. Even if bubbles are not included when entering the pure water from the water tank 71 to the suction pipe 73, bubbles may be generated in the path to reach the water pump 72.

  As a technique for removing bubbles contained in the liquid, the bubbles are removed by passing the fuel from the top to the bottom through a bubble separation membrane provided above the pump and installed horizontally inside the pump. There is a bubble removing device to perform (see Patent Document 1). That is, it is a device that returns bubbles to the tank using the return passage of surplus fuel. In this apparatus, fine bubbles gather on the bubble separation membrane, and the bubbles gradually increase and move upward.

  Further, in the fuel filter provided below the fuel tank, the fuel is generated in the downstream space (downstream chamber) due to a change in environmental temperature or a reduced pressure after passing through the filter body provided vertically within the filter. There is also a technique for guiding vapor to a fuel tank from a deaeration pipe provided above (see Patent Document 2).

Furthermore, in the fuel filter of the natural downstream type fuel supply device of the diesel engine, the liquid that has passed through the filter body provided in the vertical direction is guided to the outside (pump) in a substantially horizontal direction at the upper part inside, and the filter There is a technique in which an air vent passage for a filter that guides vapor contained in liquid that has passed through a main body vertically upward is provided (see Patent Document 3).
JP-A-5-157014 JP 2002-168155 A Japanese Utility Model Publication No. 4-19659

  By the way, in the technique disclosed in Patent Document 1, petroleum-based fuel is assumed as a liquid, and once the generated vapor is removed, it is unlikely that vapor will be generated again in the subsequent process. Moreover, when water is assumed as the liquid, there is a high possibility that even if air bubbles are captured once, they are continuously generated in the subsequent processes. And since the path | route after passing a fuel filter is not disclosed, when water is made into a target as a liquid, it is difficult to apply this technique as it is. The technique disclosed in Patent Document 2 still has the same problem. Further, when the filter is clogged, air may be sucked in from the air return passage. Furthermore, since the air is separated into the air return passage after passing through the filter, there is a problem that bubbles generated after passing through the filter cannot be sufficiently removed. Furthermore, in the technique disclosed in Patent Document 3, since the filter air vent passage for removing the vapor is close to the path leading to the pump, fuel in a state where the vapor is not sufficiently removed is supplied to the pump. there is a possibility. Furthermore, similarly to Patent Document 2, there is a possibility of air suction due to filter clogging.

  The pumps disclosed in Patent Documents 1 to 3 are fuel pumps, and generally do not control the amount of fuel supplied, but control the pressure of fuel supplied to the fuel injection nozzle to a desired pressure. doing. On the other hand, in the pure water supply device in the stationary fuel cell system, it is necessary to control the amount of pure water supplied from the pump to the reformer. Therefore, even if the amount of bubbles allowed in the technology in which fuel is assumed as a liquid is not allowed in a system that supplies pure water to a reformer of a stationary fuel cell system.

  The present invention has been made in view of the above situation, and an object thereof is to provide a technique for suitably removing bubbles contained in water, which is a liquid supplied to a water pump in a stationary fuel cell system. There is.

The apparatus according to the present invention relates to an air return mechanism. This air return mechanism is used in a stationary fuel cell system, and is provided between a suction pipe communicating with a tank and a reformer pump to which water is supplied from the tank via the suction pipe. An air separation chamber that communicates with the suction pipe and is provided below the suction port that communicates with the suction pipe, a reformer pump communication portion that communicates with the reformer pump, and the air separation chamber. An air return pipe provided above the tank and communicated with the tank , wherein the air separation chamber has first and second spaces separated by a partition wall having a communication port below. The space is provided with the suction port provided above the communication port of the partition wall and communicating with the suction pipe,
The second space includes the reformer pump communication portion that is provided above the communication port of the partition wall and is a discharge port that communicates with the reformer pump, and the air return pipe includes the first return pipe. It extends upward from the upper part of the space, communicates with the tank, and further communicates with the suction pipe via the first space.
Yet another apparatus of the present invention relates to a fuel cell system. This fuel cell system includes the air return mechanism described above .

  ADVANTAGE OF THE INVENTION According to this invention, the technique which removes suitably the bubble contained in the water which is the liquid supplied to a water pump in a stationary fuel cell system can be provided.

  Next, the best mode for carrying out the present invention (hereinafter simply referred to as “embodiment”) will be specifically described with reference to the drawings. Here, in a stationary fuel cell system generally used for home use, in order to stably and accurately supply pure water to the reformer, bubbles contained in pure water are sucked into the pump by pure water. Remove immediately before This fuel cell system is a stationary fuel cell system with a relatively small output, for example, an output of 1 kWh, which is assumed to be installed and used mainly in homes, and is naturally limited to home use. It is not intended to be used for business purposes.

  FIG. 1 is a functional block diagram showing a schematic configuration of a fuel cell system 10 according to the present embodiment. The fuel cell system 10 is, for example, a polymer electrolyte fuel cell, and includes a fuel cell main body 16, a reformer 14 that generates hydrogen gas to be supplied to the fuel cell main body 16, natural gas that is a raw material for hydrogen gas, The fuel supply unit 12 supplies fuel gas such as city gas and propane gas, and the water supply unit 30 supplies pure water to the reformer 14.

  The reformer 14 evaporates the pure water supplied from the water supply unit 30 and reacts with the fuel gas supplied from the fuel supply unit 12 to generate a gas having a high hydrogen concentration, so-called hydrogen rich gas. The reformer 14 supplies the generated hydrogen rich gas to the fuel cell main body 16.

  The water supply unit 30 includes a water treatment unit 32, a water tank 34, a water pump 36, and an air return mechanism 40.

  The water treatment unit 32 purifies city water, such as tap water, into pure water by using, for example, an ion exchange resin membrane. The purified pure water is stored in the water tank 34.

  The water pump 36 sucks pure water stored in the water tank 34 and supplies it to the reformer 14 by the pump unit 67 (see FIG. 2). The amount of pure water supplied to the reformer 14 is controlled with high accuracy from the relationship between the drive control value for the drive means of the pump unit 67 and the actual discharge amount for the drive control value. The water pump 36 supplies, for example, several ml to several tens ml of pure water per minute to the reformer 14 with high accuracy.

  By the way, if the pure water sucked by the water pump 36 contains bubbles, the pump unit 67 cannot properly control the discharge amount of the pure water to the reformer 14. That is, the flow rate of the water pump 36 decreases, and a desired amount of pure water cannot be supplied to the reformer 14.

  As described above, bubbles may naturally occur in the path through which pure water is supplied from the water tank 34 to the water pump 36. In particular, when pure water is warm water, bubbles are likely to be generated. In addition, since the amount of bubble generation cannot be predicted, control taking the amount of generation into consideration is not realistic. This phenomenon occurs regardless of the type of the water pump 36.

  Therefore, in the present embodiment, an air return mechanism 40 that removes bubbles is provided in the middle of the path connecting the water tank 34 and the water pump 36. Specifically, as shown in the configuration diagram of FIG. 2, an air return mechanism 40 is provided at the suction port 65 of the water pump 36, and bubbles A in the pure water are discharged immediately before the pure water is sucked into the water pump 36. Remove. Hereinafter, the air return mechanism 40 will be described.

  The air return mechanism 40 includes an air separation unit 42 and an air return pipe 62.

  The air separation part 42 is hollow and has a substantially cylindrical shape with a predetermined depth, and forms a pure water flow path in the internal cavity. This internal cavity is called an air separation chamber 50.

  A suction port 51 is formed in the upper portion of the side surface of the air separation chamber 50, and the suction port 51 communicates with a tank outlet 35 formed at the bottom of the water tank 34 through a suction pipe 61. Note that the suction port 51 of the air separation chamber 50 is located below the tank outlet 35 of the water tank 34. A discharge port 52 for supplying pure water to the water pump 36 is formed on the side opposite to the suction port 51.

  In addition, a separation wall 54 is formed in the ceiling portion of the air separation chamber 50 so as to extend downward, and the air separation chamber 50 is discharged from the suction side separation chamber 57 on the suction port 51 side and the discharge side on the discharge port 52 side. It is separated into two spaces in the side separation chamber 58. A separation chamber communication port 55 that connects the suction side separation chamber 57 and the discharge side separation chamber 58 is formed in the lower portion of the separation wall 54.

  Further, an air outlet 53 is formed in the ceiling portion of the suction side separation chamber 57, and one end of an air return pipe 62 extending upward is attached. The other end of the air return pipe 62 is attached to an air return port 37 formed above the water tank 34. The formation position of the air return port 37 is higher than the water level W of pure water stored in the water tank 34.

  In the air return mechanism 40 having such a configuration, the pure water taken into the suction side separation chamber 57 from the suction port 51 enters the discharge side separation chamber 58 through the separation wall 54 toward one end downward, and then, It goes upward and is supplied to the water pump 36 from the discharge port 52.

  When pure water that has entered from the suction port 51 is directed downward by the separation wall 54, the bubbles A contained in the pure water do not go downward due to buoyancy, and the air return pipe 62 from the air outlet 53. Head to. The bubbles A are discharged from the water surface in the air return pipe 62 and returned to the water tank 34 from the air return port 37. That is, the bubble A is trapped in the air separation chamber 50. If the discharge amount of the water pump 36 is several ml to several tens ml per minute as described above, the flow rate of pure water in the air separation chamber 50 is such that the bubble A is discharged from the suction side separation chamber 57 to the discharge side separation chamber 58. It will be a level that is not drawn into.

  Therefore, even when bubbles A are generated in the pure water in the suction pipe 61, the bubbles A in the pure water are appropriately removed by the air return mechanism 40 before reaching the water pump 36. Further, since the air separation chamber 50 is directly connected to the water pump 36, the pure water supplied to the water pump 36 does not include the bubbles A. As a result, the water pump 36 can supply pure water to the reformer 14 with high accuracy.

  Note that one end of the air return pipe 62 attached to the air return port 37 of the water tank 34 only needs to be open to the atmospheric pressure, and is not limited to the configuration connected to the water tank 34. However, in the case of a configuration open to the atmosphere, it is preferable to provide a filter or the like in order to prevent impurities from being mixed into the pure water in the air return pipe 62.

  The present invention has been described based on the embodiments. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

  For example, in the above-described embodiment, the air trap in the air separator 42 is trapped only once, but the air separator 42 may be configured to be trapped a plurality of times. That is, it is good also as a structure where the above-mentioned air separation part 42 continues. The air separation unit 42 may be configured integrally with the water pump 36 as a component of the water pump 36. In addition, the air separation chamber 50 may not be directly connected to the water pump 36, but the air separation chamber 50 can be formed in order to eliminate the possibility of bubbles being generated in the path between the air separation chamber 50 and the water pump 36. It is preferable to install it as close to the water pump 36 as possible.

  Further, a gas-liquid separation filter may be provided at the entrance of the discharge side separation chamber 58. Furthermore, instead of part or all of the separation wall 54, the gas A may be prevented from flowing into the water pump 36 by a gas-liquid separation filter.

It is a functional block diagram which shows schematic structure of the fuel cell system based on this embodiment. It is a figure which shows the structure which provided the air return mechanism in the middle of the path | route which connects a water tank, a water pump, and a water tank and a water pump based on this embodiment. It is a figure which shows the structure of the water tank and water pump based on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell system 12 Fuel supply part 14 Reformer 16 Fuel cell main body 30 Water supply part 32 Water treatment part 34 Water tank 36 Water pump 37 Air return port 40 Air return mechanism 42 Air separation part 50 Air separation chamber 51 Inlet 52 Discharge port 53 Air outlet 54 Separation wall 55 Separation chamber communication port 57 Suction side separation chamber 58 Discharge side separation chamber 61 Suction piping 62 Air return piping 63 Discharge piping 65 Suction port 66 Discharge port 67 Pump section

Claims (2)

An air return mechanism used in a stationary fuel cell system, provided between a suction pipe communicating with a tank and a reformer pump to which water is supplied from the tank via the suction pipe,
An air separation chamber that communicates with the suction pipe and is provided below the suction port that communicates with the suction pipe ;
A reformer pump communication portion communicating with the reformer pump;
An air return pipe provided above the air separation chamber and communicated with the tank ;
Equipped with a,
The air separation chamber has first and second spaces separated by a partition wall having a communication port below.
The first space includes the suction port that is provided above the communication port of the partition wall and communicates with the suction pipe;
The second space includes the reformer pump communication portion which is a discharge port which is provided above the communication port of the partition wall and communicates with the reformer pump,
The air return pipe extends upward from an upper part of the first space, communicates with the tank, and further communicates with the suction pipe via the first space. Air return mechanism. A stationary fuel cell system comprising the air return mechanism according to claim 1.

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