JPS62272468A - Fuel cell power generating system - Google Patents

Abstract

PURPOSE:To increase heat efficiency as the whole system by recovering excess hydrogen in fuel gas exhausted from a fuel cell and effectively using the recovered hydrogen. CONSTITUTION:A gas reformed in a reformer 1 is supplied as fuel gas from a reforming gas reaction tube 3 to a fuel electrode of a fuel cell 30 and electrochemically reacts with the air supplied to an oxidizing agent electrode in the fuel cell 30 to generate electricity, and electric power is supplied to a load 50. The gas exhausted from the fuel cell 30 is sent to a burner 2 of the reformer 1 and used as fuel for generating reforming gas. A part of exhaust gas is sucked with a sucker 21 in accordance with a value of the load 50, and hydrogen is separated with a hydrogen recovering unit 20. The separated hydrogen is stored in a storage tank 25 and supplied to the burner 2 or the fuel cell 30 through an outlet pipeline 29 to use as fuel. Therefore, heat efficiency as the whole system is increased.

Description

[Detailed Description of the Invention] [Technical Field to which the Invention Pertains] The present invention relates to a fuel cell comprising a reformer that generates hydrogen-rich reformed gas and a fuel cell that uses the reformed gas as fuel gas. The present invention relates to a power generation device, and particularly to a fuel cell power generation device that supplies fuel gas discharged from a fuel cell to a burner of a reformer.

[Prior art and its problems]

ing. In Fig. 5, the reformer 1 has a case-like furnace body 1.
A burner 2 is installed in the upper part of the furnace body 1o, and a vaporizing tube 2 and a reaction tube 3 are installed in the furnace body 1o.A reforming material made of liquid fuel such as alcohol is supplied from a reforming material tank 31 to a supply pump 32. It is supplied to the electrification pipe 5 ◎ and the vaporization pipe 5
The reforming raw material flowing through it is electrified by the combustion heat of the fuel by the burner 2 and becomes vaporized gas9, and this vaporized gas is heated by the combustion heat in the reaction tube 3 filled with a reforming catalyst and becomes hydrogen. The rich reformed gas is supplied to the fuel cell 30 via a pipe 33 as a fuel gas as a reaction gas.

An oxidant gas, such as air, as a reactive gas is supplied to the fuel cell 30 through a pipe 35 and undergoes an electrochemical reaction together with the fuel gas within the cell, and the remaining air is discharged through a pipe 39. On the other hand, since the fuel gas still contains unreacted hydrogen after the electrochemical reaction is completed, the fuel gas discharged from the fuel cell (hereinafter referred to as off-gas) is supplied to the burner 2 through the pipe 34 and the reformer 1 It is used as fuel. Note that liquid fuel is also used as a supplement to this fuel gas. Furthermore, the combustion gas combusted in the burner 2 flows through the reformer 1 and is discharged to the outside through a duct 12.

By the way, in order to make the reformed gas rich in hydrogen by the action of the catalyst layer consisting of the reforming catalyst filled in the reaction tube,
It is necessary to maintain the catalyst layer within an appropriate operating temperature range using off-gas from the burner and the combustion heat of liquid fuel as fuel. However, if the required amount of reformed gas increases, it will naturally be necessary to supply it to the vaporization tube and reaction tube. Liquid fuels such as alcohol must be increased. Therefore, in order to maintain the temperature of the catalyst in the reaction tube within an appropriate range, it is necessary to increase the amount of combustion in the burner. For this purpose, the flow rate of liquid fuel and off-gas supplied to the burner may be adjusted to increase. In this case, adjustment of the supply flow rate of liquid fuel is easy since it is usually supplied by a pump or the like. However, since the fuel for the reformer is mostly off gas with a high calorific value, the liquid fuel for combustion is used for auxiliary combustion of the off gas that is the main flame, and as a pilot flame, so the flow rate of liquid fuel is essentially No adjustments have been made. Further, since the amount of off-gas is determined depending on the amount of power generated by the fuel cell, the flow rate of off-gas is not adjusted.

In any case, in conventional reformers, the amount of fuel supplied is not adjusted so as to maintain an appropriate temperature of the catalyst layer of the reaction tube with respect to the required amount of reformed gas.

FIG. 6 is a graph showing the relationship between the fuel cell load current, off-gas flow rate, and catalyst temperature under the above conditions, with time on the horizontal axis and fuel cell load current and off-gas flow rate (m3) on the vertical axis. /h), the temperature of the catalyst (°C) is shown. In the figure, the broken line P is load current and time, and the broken line Q
indicates the relationship between the off-gas flow rate and time, and the broken line R indicates the relationship between catalyst temperature and time. In the figure, when the power generation amount of the fuel cell, that is, the load current decreases from Pl to P2, the electrochemical reaction decreases, and the off-gas flow rate transiently increases from Ql to Q2.
increases to As a result, the amount of combustion due to off-gas increases,
The temperature of the catalyst increases from R1 to R2. Furthermore, in this case, since the amount of power generation decreases, the amount of reformed gas required also decreases, so the liquid fuel for the reformed gas supplied to the reaction tube also decreases, and the amount of liquid fuel supplied is adjusted and reduced. Therefore, the rise in the temperature of the catalyst is further promoted.As a result, when the catalyst temperature exceeds a predetermined temperature, there is a problem that the life of the catalyst itself is shortened. Note that it is possible to maintain the temperature of the reforming catalyst layer in the reaction tube within an appropriate range by burning only liquid fuel whose supply amount can be adjusted in a burner without using off-gas. However, since off-gas has a high calorific value, not using off-gas as fuel is disadvantageous in terms of improving the thermal efficiency of the fuel cell power generation device.

In addition, the reaction of reforming the reformed raw material into a hydrogen-rich gas in a reformer is generally an endothermic reaction, so in order to carry out the reaction, external thermal energy is used, for example from the burner mentioned above. Because combustion gas is provided as a heat carrier and there is a catalyst space to secure the amount of reforming catalyst necessary to promote the above reaction and convert it into reformed gas, The response speed for generating the amount of reformed gas in response to changes in the amount of raw material supplied is extremely slow. On the other hand, since the electrochemical reaction rate of a fuel cell is very fast, the reformer always generates a long reformed gas so that the fuel cell does not run out of fuel gas.

As a result, excess reformed gas is generated, which poses a problem of lowering the thermal efficiency of the fuel cell power generation device.

[Purpose of the invention]

In view of the above-mentioned points, the present invention is directed to recovering excess hydrogen from fuel gas discharged from a fuel cell and effectively utilizing the recovered hydrogen to improve the efficiency of the entire device. The purpose is to provide a fuel cell power generation device that can

[Summary of the invention]

According to the present invention, in a fuel cell power generation device that supplies fuel gas discharged from a fuel cell to a burner of a reformer, the present invention provides a suction device for taking out a part of the discharged fuel gas; a sending means for supplying hydrogen from the fuel tank to the burner or the fuel cell, an output detector for detecting the electrical output of the fuel cell, and an output signal of the output detector; This is achieved by providing a controller for controlling the amount of fuel gas.

[Embodiments of the invention]

The present invention will be described in detail below with reference to the drawings. FIG. 1 is a system diagram of a fuel cell power generation device according to an embodiment of the present invention. In FIG. 1 and FIGS. 2 to 4, which will be described later, parts that are the same as those in the conventional example shown in FIGS. do. What differs from the prior art in this embodiment is that a system is provided to extract a portion of the off-gas, recover hydrogen in the off-gas, and reuse it. That is, a suction device 21 such as a blower is installed in a pipe line 22 branched from an off-gas pipe line 34.
A hydrogen recovery device 20 is provided via the.

As shown in FIG. 2, the hydrogen recovery device 20 uses a thin tube 41 made of a hydrogen selective permeation membrane with good hydrogen permeability. For example, a polyimide membrane having micropentane rings is used as the hydrogen selective permeation membrane.The hydrogen permeation rate of this membrane can be determined by the relationship between the differential pressure in the pre-membrane permeation layer and the hydrogen permeation rate shown in Figure 3. and has a permeability coefficient C=3.5 at 100°C
x 10-9 (cd tan/1sec cmHg).

In FIG. 2, the hydrogen recovery device 20 attaches both ends of each of the plurality of thin tubes 41 to a tube plate 42 to form a tube bundle, stores this tube bundle in a cylindrical container 40, and connects the tube plate 42 and the end surface 40a of the cylindrical container, 40b are formed as an inlet chamber 44 and an outlet chamber 45 for off-gas, respectively.
4 is provided with an inlet pipe line 43, and the outlet chamber 45 is provided with an outlet pipe line 23. Also, on the side wall of the cylindrical container 40, hydrogen in the off-gas flowing through the capillary tube 41 permeates the pipe wall of the capillary tube 41. Returning to FIG. 1, an off-gas outlet pipe 2 of the hydrogen recovery device 20 is provided.
Narrow it down to 3! 123a is provided. This is because the amount of hydrogen that permeates through the hydrogen selective separation membrane forming the capillary tube 41 (see FIG. 2) is proportional to the differential pressure before and after the membrane, so the pressure of the off-gas flowing through the capillary tube 41 was maintained appropriately.

A storage tank 25 that stores hydrogen recovered by the hydrogen recovery device 20 is connected to the hydrogen recovery device 20 through a pipe 24 . The storage tank 25 is connected to a conduit 2 equipped with a regulating valve 26.
8 is connected to a feed pump 27 as a delivery means. An outlet line 29 of the feed pump 27 is connected to a line 33 that supplies reformed gas to the burner 2 or the fuel cell 30.

A circuit 53 connecting the fuel electrode and oxidizer electrode of the fuel cell 30
An electric load 50 is connected to the circuit 53, and a load current detector 51 as an output detector is provided in the circuit 53. A controller 52 is provided to which the output signal of the load current detector 51 is input. The amount of off-gas taken out through the process is controlled.

With such a system configuration, the reformed gas reformed in the reformer 1 is sent as a fuel gas from the reaction tube 3 to the fuel electrode of the fuel cell 30 via the pipe 33, and the fuel is sent together with the air sent to the oxidizer electrode. An electrochemical reaction occurs in the battery to generate electricity and supply power to the load 50. The off-gas from the fuel cell is then sent to the burner 2 of the reformer 1 via the pipe 34 and used as fuel for producing reformed gas. At this time, a part of the off-gas is sucked from the pipe line 34 by the suction device 21 according to the load of the electric load 50, and the hydrogen is separated by the hydrogen recovery device 20. The separated hydrogen is stored in storage tank 2.
5, and is supplied to the burner 2 or the fuel cell 30 as needed by the supply pump 27 via the outlet pipe 2°9, and is used to raise the temperature of the reformer or fuel when starting up the fuel cell' power generator. Used as fuel for batteries.

Next, control for sucking off gas by the suction device 21 in accordance with the above-mentioned electric power will be explained. The flow rate sucked from the υ pipe 34 by the suction device 21 is controlled by detecting the load current of the fuel cell 3o supplied to the electric load 50 with the load current detector 51, and detecting the output signal from the load current detector 51. Controller 52
After some time, the suction device 21 is controlled via the controller 52. This control progress will be explained in more detail with reference to the graph of FIG.

FIG. 4 is a graph showing the operating progress of the load current, off-gas flow rate, and catalyst temperature of the reaction tube during operation of the fuel cell power generation device. The horizontal axis represents time, and the vertical axis represents the fuel cell load current ( 2), off-gas flow rate (m3/h) and catalyst temperature (C) are shown.

In the figure, the broken line P is the load current, Ql is the flow rate of off-gas of the fuel cell, and the broken line (L-t is the flow rate of off-gas supplied to the reformer, and the broken line q2 is the flow rate of off-gas supplied to the hydrogen recovery device, and the operation progress. ◇The load on the fuel cell changes, for example, the load decreases, and as shown in Figure 4, the amount of power generated by the fuel cell, that is, the load current, decreases to Pl.
When Q1 decreases from Q2 to P2, the electrochemical reaction decreases and the off-gas flow rate increases from Q1 to Q2. When the load current decreases to P2, the suction device is controlled via a program-operated controller consisting of the relationship between the output signal of the load current detector and the off-gas flow rate q2 recovered in the hydrogen recovery device, and the off-gas flow rate is increased. q2 increases. Note that the off-gas flow rate q2 is obtained by subtracting the off-gas amount q1 supplied to the burner in order to generate the necessary reforming energy according to the load current of the fuel cell, that is, the necessary amount of combustion heat in the burner, from the off-gas flow rate Q. That is, Q=qt+qi. At this time, since the off-gas flow rate q1 can be calculated in advance according to the load current, the off-gas flow rate q2 can also be determined according to the load current.

As a result, the off-gas combusted in the burner supplies only the amount necessary for reforming energy, which prevents a rapid temperature rise of the reforming catalyst in the reaction tube, and increases the catalyst temperature R as shown in Figure 4. [Effects of the Invention] As is clear from the above explanation, according to the present invention, the off-gas of the fuel cell is collected in the reformer according to the load current of the fuel cell. By extracting off-gas other than the amount of off-gas required to generate reformed gas using a suction device, and separating and storing hydrogen in this off-gas using a hydrogen recovery device, the load on the combustion battery changes. However, since the amount of off-gas is supplied to the reformer according to the load and is burned, the temperature of the reforming catalyst can be maintained within an appropriate range, which has the effect of extending the life of the reforming catalyst. be. Furthermore, since the recovered hydrogen can also be reused, there is also the effect of improving the thermal efficiency of the fuel cell power generation device.

[Brief explanation of drawings]

FIG. 1 is a diagram of a fuel power generation device according to an embodiment of the present invention.
FIG. 5 is a system diagram of the conventional fuel cell power generation device, and FIG. 6 is a graph showing the operation progress of the fuel cell power generation device shown in FIG. 1: Reformer, 2: Burner, 3: Reaction tube, 20: Hydrogen recovery device, 21: Aspirator, 25: Storage tank, 27: Delivery means, 30: Fuel cell, 51: Output detector, 52: Control vessel. Fig. 1 Fig. 2 Cage pressure (kg/Crr12G) Fig. 3 Fig. 4

Claims (1)

[Claims] In a fuel cell power generation device that supplies fuel gas discharged from a fuel cell to a burner of a reformer, a suction device takes out a portion of the discharged fuel gas, and hydrogen in the fuel gas from the suction device is separated. a hydrogen recovery device for storing hydrogen from the hydrogen recovery device, a storage tank for storing hydrogen from the hydrogen recovery device, a delivery means for supplying hydrogen from the storage tank to the burner or the fuel cell, and an output detector for detecting the electrical output of the fuel cell. and a controller for controlling the amount of fuel gas taken out by the suction device based on the output signal of the output detector.