JPS6269469A - Fuel cell power generation equipment - Google Patents

Abstract

PURPOSE:To attain a reformation ratio of about 100% even if the temperature of reformation is lowered, by providing an external and an internal reformers. CONSTITUTION:In a complex-reformation fuel cell power generation equipment, fuel is reformed by an external reformer 8 and an internal reformer 7 provided in the anode chamber of the equipment. If the equipment is of the molten carbonate type and operates at a temperature of 650 deg.C, the operation temperature of the external reformer 8 is set about 650 deg.C to reform about 60$ of the initial fuel therein (the ratio of reformation is about 60%), and the rest of the fuel is reformed by the internal reformer 7 in the anode chamber of the equipment, namely, about 40% of the initial fuel is reformed by the internal reformer, so that the ratio of reformation of all the fuel is about 100%. The operation temperatures of he external and the internal reformers can thus be made lower so that the reforming reaction load on reforming catalysts is reduced. This results in lengthening the total life of the reformers.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a fuel cell power generation device, and more particularly to a fuel cell power generation device that operates at high temperatures using molten carbonate or the like as an electrolyte, and includes an external reformer and an internal reformer. Regarding those equipped with a reformer.

[Background of the invention]

Conventional fuel cell power generation apparatuses have been equipped with two types of reformers based on reforming methods, such as an external reformer type and an internal reformer type.

External reforming type reformers literally produce the hydrogen required in the anode chamber of a fuel cell power generation system using equipment other than the fuel cell power generation system. On the other hand, an internal reformer produces hydrogen directly or indirectly in an anode chamber inside a fuel cell power generation device. These two reformers are.

When used in a fuel cell power generation device, it has the following features.

In an external reformer, a reformer is provided separately in addition to the cell stack that is the main body of the fuel cell power generation device. This reformer increases the fuel reforming rate by 5o
The mainstream is a so-called steam reformer that reformes a fuel such as a hydrocarbon with steam using a catalyst at a high temperature of about 30°C to obtain hydrogen.

This type of steam reformer has traditionally been used in the chemical industry, has a higher track record than fuel cell power generators, and has a certain level of practicality in terms of technology and reliability. It is believed that the standard has been reached.

However, in the case of this external reforming type reformer, in addition to the issue of extending the life of the reforming catalyst, the reforming section and the power generation section are separate structures, so it is difficult to use it in a fuel cell power generation device. However, there are problems in that the plant area becomes large and the equipment configuration becomes complicated. In particular, since the reforming reaction is carried out at high temperatures, the life of the catalyst is inevitably shortened and the catalyst must be replaced. Therefore, operation of the fuel cell power generator may be stopped while the catalyst is replaced.

On the other hand, an internal reformer has a reforming section inside the anode chamber of the fuel cell power generation device.

Compared to the external reforming type, the number of components can be reduced, the equipment is simpler and more compact, and when reforming fuel that involves an endothermic reaction, the heat generated by the cell reaction can be used effectively to cool the cell at the same time. It has the following advantages. However, if an attempt is made to carry out the reforming reaction using only the internal reformer, both the cell reaction and the reforming reaction must be carried out in the anode chamber, which may result in the 7-node chamber becoming larger and ultimately causing the battery itself to become larger. . Furthermore, since the anode chamber becomes larger, there is also the problem that the strength of the anode chamber must be increased. Furthermore, since it becomes difficult to regenerate and replace the reforming catalyst in the anode chamber, there is a problem in terms of improving the reliability of the fuel cell power generation device as a whole and shortening the life of the device.

The schematic configuration of the external reforming type and internal reforming type systems as described above is described in [Internal Reforming System].
orNatural Gas Fueled Molt
en CarbonateFuel CeN5 ()
RI-801012B, December 1981.

Energy l(, search corp,
p, 2-p, 8 J As seen in this document, external reformer and internal reformer have different positions and concepts, and conventionally, external reformer and internal reformer are There is no idea of a combination of a reforming type reformer and an internal reforming type reformer. This fact is.

The process of development has been based on the idea that external reformers are closer to practical use, and internal reformers can be realized with a simple system configuration. Based on this position of thinking,
Its development is based on a different background.

As mentioned above, internal reformer and external reformer have different advantages and disadvantages, and if each is used alone, the catalyst must be replaced. The problem is that the reliability of the fuel cell power generation system as a whole is not sufficient in terms of operating efficiency, etc. due to problems such as battery operation stoppage due to oxidation and complication of the battery configuration such as in internal reformer type reformers. was there.

[Purpose of the invention]

The present invention provides a reformer that eliminates the disadvantages of the external reformer and internal reformer, incorporates the advantages of each, and improves the reliability of the entire device. Our objective is to provide a fuel cell power generation device that will

[Summary of the invention]

The present invention provides a fuel cell power generation device in which a reforming catalyst is held, a fuel containing hydrocarbons, etc. is passed through the reforming catalyst, and the fuel is reformed into hydrogen-enriched gas through a reforming reaction. a reforming device, which is provided inside the anode chamber, holds a reforming catalyst, flows the hydrogen-enriched gas through the reforming catalyst, and converts unreformed gas contained in the hydrogen-enriched gas through a reforming reaction. This is a fuel cell power generation device characterized by comprising an internal reformer for reforming hydrogen gas into hydrogen gas.

In the present invention, the maximum value of the fuel reforming rate in a fuel cell power generation device equipped with an external reformer is uniquely determined by temperature, pressure, etc. under thermodynamic chemical equilibrium. Since the reforming rate cannot exceed that value, the operating conditions of the reformer are adjusted to 5o in order to maintain the maximum fuel reforming rate.
On the other hand, in a fuel cell power generation system equipped with an internal reformer that uses molten carbonate as an electrolyte, hydrogen is consumed in the anode chamber. The chemical equilibrium changes, and as a result, even at a temperature of about 650C, which is the operating temperature of the battery, the reforming rate of the fuel can exceed the maximum value of the reforming rate at the chemical equilibrium at that temperature. This is a composite reforming fuel cell power generation device constructed by combining two parts. That is, in this combined reforming type fuel cell power generation device, the reforming of the fuel is divided into two departments: an external reformer and an internal reformer in the anode chamber of the fuel cell power generation device. As a result.

For example, in the case of a molten carbonate-deaf fuel cell power generation system that operates at 650C, the operating temperature of the external reformer is also about 65L, and about 60% of the initial fuel is reformed here = reformation rate of about 60%), the remaining fuel is reformed in the internal reforming section of the anode chamber of the fuel cell power generation device. In other words, by reforming about 40% of the initial fuel in the reforming section of the anode chamber, an overall reforming rate of about 100% can be achieved. Therefore, the operating temperature of the external and internal reformers is low, and the load on the reforming catalyst due to the reforming reaction is reduced, so that the life of the reformer as a whole is extended. In addition, for fuel cell power generation devices that use the anode chamber as the reforming section, that is, internal reforming type fuel cell power generation devices, the load on the reforming catalyst due to the reforming reaction is reduced, which improves the lifespan and reduces the activity of the reforming catalyst. Maintenance such as regeneration and replacement can be entrusted to the external reformer. Therefore, it is possible to prevent the device from shutting down due to catalyst replacement and from complicating the device configuration, and the reliability of the fuel cell power generation device is improved.

[Embodiments of the invention]

Next, embodiments of the fuel cell power generation device according to the present invention will be described in detail with reference to the accompanying drawings. In the following example, a molten carbonate fuel cell power generation device using molten carbonate as an electrolyte and having a cell operating temperature of approximately 650C will be described. Also, a case will be described in which methane is used as the fuel and a steam reformer is used as the reformer, where ``is steam'' and reformes the methane into hydrogen gas. It should be noted that the present invention can be implemented in the same manner as in the following examples in the case of other raw materials or reforming methods.

FIG. 1(a)ti is a system diagram showing a first embodiment of the present invention.

In FIG. 1(a), an anode 3 and a cathode 4 sandwiching an electrolyte plate 2 in a fuel cell power generation device 1ri, and a busy anode 3
It consists of an anode chamber 5 surrounding the cathode 4, and a cathode chamber 6 surrounding the cathode 4.

An internal reformer 7 is provided within the anode chamber 5 in which a reforming catalyst is held to promote the reforming of methane and water vapor into hydrogen-rich gas.

For example, Ni can be used as the reforming catalyst.

On the other hand, the external reformer 8 has a reaction tube 9 therein, and is equipped with pipes 11 and 12 through which a heat medium for heating one reaction tube 9 flows. The reaction tube 9 has an anode chamber 5
As in the case of , a reforming catalyst 10 is maintained which rapidly reforms methane and steam to hydrogen-rich gas. Also, piping 14 for fluidly connecting one end of the reaction tube 9 of the external reformer 8 and one end of the internal reformer 7.
is provided. The other end of the reaction tube 9 of the external reformer 8 is provided with a reservoir pipe 13 into which a raw material gas containing a mixture of methane and steam flows.

On the other hand, on the other end side of the external reformer 8 of the anode chamber 5 of the fuel cell power generation device 1, a pipe 15 for discharging the exhaust gas from the anode is provided. In the configuration of this embodiment, each of the reaction tubes 9 and the anode chambers 5 may be composed of a single unit or a plurality of units.

As a configuration of the external reformer 8 that comes inside the anode chamber 5, the second
As shown in the figure, there are a direct type (a) diagram and an indirect type (b) diagram. In the direct type, the reforming catalyst is held as it is in the anode chamber 5, and the hydrogen-enriched gas 30 obtained by further reforming the reformed gas 14 with the reforming catalyst is supplied directly to the anode 3.

On the other hand, in the case of an indirect type, a space 32 for hydrogen-enriched gas circulation is provided between the anode 3 and the layer holding the reforming catalyst, and the gas 14 reformed in the external reformer 8 is further reformed. The resulting hydrogen-enriched gas 30 is once passed through a space 32, from which the hydrogen-enriched gas 30 is supplied to the anode 3.

Next, the operation of this embodiment will be explained. (b) in Figure 1
The figure shows the relationship between the reaction fluid temperature and the methane reforming rate at the displacement of the reaction fluid shown in FIG. 1(a). Symbols A to E indicate each of the six points, and one reaction fluid refers to a series of fluids from the raw material gas to the anode gas. In addition, the methane reforming rate refers to a value obtained by subtracting the amount of methane remaining after reforming from the amount of methane supplied, dividing the result by the amount of methane supplied, and multiplying the result by 100, expressed as a percentage.

First, the operating conditions are a pressure cuff ata, a steam carbon ratio (Hto/CHa molar ratio) of the feed material, and a raw material is transferred to the external reformer 8 through the pipe 13 with the inlet gas temperature of the external reformer 8 being approximately 480 °C. It is made to flow into the reaction tube 9.

Approximately 1,000 yen from the pipe 11 installed in the external reformer 8
A high-temperature heat medium of C or higher flows into the external reformer 8 and supplies heat to the reaction tube 9 of the first reactor. Some of the reaction gas that entered the reaction tube 9 is converted into the following α) in the presence of the reforming catalyst 10.
The reactions occur as shown in equations and (2), and the steam reforming of methane is promoted while being endothermic as a whole.

CHa+Hs04CO+3Hz-”49.3kcal/
mot-α)CO+Hz04COz+Hz+9.8kc
at/mot" (2) At this time, the high temperature heating medium flowing into the external reformer 8 from the pipe 11 causes the above reaction (1),
While providing heat for (2), the temperature gradually decreases, and the pipe 1
2 and flows out of the external reformer 8. The route is the first
Figure Φ) is shown by the DE curve in the figure. On the other hand, the reaction gas flowing through the reaction tube 9 gradually rises in temperature as shown in the middle path of the AB curve in FIG. , the temperature is further increased slightly, and it exits from the external reformer 8 through the pipe 14. At this time, a methane reforming rate of about 55% is obtained. The reactant gas cools down slightly due to some heat loss while passing through the pipe 14, and then flows into the internal reformer in the anode chamber 5 of the fuel cell power generator 1. In the fuel cell power generation device 1 as a whole, a water production reaction from hydrogen and oxygen (equation (3)), that is, an exothermic reaction occurs, and some cooling means must be taken.

If the operating temperature of the fuel cell power generation device is 650C, the temperature of the power generation device will rise above 650C, but the residual methane and water vapor will react as described above in the internal reformer 7 holding the reforming catalyst.
The battery operating temperature is maintained at about 650 C due to the reactions of formulas 1) and (2) occurring and absorbing heat, and the heat removal effect of the air, which is an oxidizing gas, flowing through the canard chamber 6. The temperature change at this time is as shown in the Be curve in Figure 1). In addition, residual methane in the anode gas flowing in the anode chamber 5 is reformed by steam in the presence of the reforming catalyst in the internal reformer 7, as shown by the curve of the methane reforming rate X in the figure. Almost 100% modified. Then, the anode gas that has completed the cell reaction flows out of the fuel cell power generation device 1 from the anode chamber 5 through the pipe 15, and an electrical output is taken out from the fuel cell power generation device 1.

According to this embodiment, the operating temperature level of the reformer and the fuel cell power generation device can be made almost the same.

The advantage is that there is no need for a heat exchanger to lower the temperature of the high temperature hydrogen-rich gas obtained from the reformer before it flows into the fuel cell power generation device, and external reformer gas is used as the anode gas required in the anode chamber 5. Since the reformed gas (approximately 5 soc) in the device 8 is available, no preheater is required to preheat the anode gas. In addition, in the external reformer 8, the reforming temperature is approximately 6500°C, so the heat resistance of the reformer can be relaxed, and as a result, the cost of reaction tube materials etc. of the reformer can be lowered. There is an effect that it can be done.

Next, another embodiment of the present invention will be described based on FIG. Note that differences from FIG. 1(a) will be explained.

In this embodiment, the heat medium flowing from the pipe 11 to heat the reaction tube 9 in the external reformer 8 is the combustion gas from the combustor 16 . This combustor 16 may be of either a burner type or a catalytic combustion type). The combustor 16 is connected to the pipe 11
is connected to the external reformer 8 and also to the combustor 1.
6 includes a pipe 17 for supplying air and an anode chamber 5
A pipe 18 is connected to the pipe 15 which is provided at one end and which is connected to a pipe 15 that guides the anode exhaust gas. Note that each pipe may be provided with a pulp at an appropriate position to control the flow rate of the flowing reaction fluid. Further, when starting up this combined reforming fuel cell power generation device, the pipe 17 may also serve as a passage for guiding the fuel of the combustor 16, and as a result, the pipe 17 can function as a passage for air and fuel. Furthermore, there is no piping 11,
A configuration in which the external reformer 8 and the combustor 16 are integrated may also be used.

Next, the operation of this embodiment in steady state will be explained.

The external reformer 8 and the fuel cell power generator 1 are both about 6
It operates at about 50C, and the reaction tube 9 of the external reformer 8
The heating medium for heating is the combustion gas obtained by combusting in the combustor 16 air led through the pipe 17 and anode exhaust gas containing unreacted hydrogen that is led to the pipe 15 after the battery reaction in the anode chamber 5. be. After this combustion gas supplies heat to the reaction tube 9, it is transferred to the piping 1 provided in the reformer 8.
2 and flows out of the reformer 8. Other operations are similar to those shown in FIG. 1(a).

According to this embodiment, in addition to the effects explained in FIG. 1(a), the anode exhaust gas can be used as fuel for heating the reaction tube 9 of the reformer 8, so that the thermal efficiency of the entire power generation device can be improved. There are effects that can be improved.

A third embodiment of the present invention will be explained with reference to FIG.

Points different from FIG. 2 will be explained.

In this embodiment, there is a pipe 12 that guides the combustion gas that has finished supplying heat to the reaction tube 9 of the external reformer 8 to the outside of the reformer 8, and a pipe that leads air, which is the oxidizing gas, to be supplied to the cathode 4. 1
9 is connected to one end of the cathode chamber 6 of the fuel cell power generation device 1, and a pipe 21 through which cathode gas flows out is provided at the other end of the cathode chamber 6.

The operation of this embodiment will be explained by adding the operation of the reaction fluid on the cathode side to the operation described in FIG. 3. That is, the composition of the cathode gas flowing into the cathode chamber 6 of the fuel cell power generation device 1 is required to contain several percent to several tens of percent carbon dioxide, while the reaction tube 9 of the external reformer 8 is heated. Since the combustion gas from the combustor 16 that has finished burning contains a considerable amount of carbon dioxide generated by the combustion reaction, the combustion gas flowing through the pipe 12 and the pipe 19
The gas containing carbon dioxide and oxygen is mixed with the flowing air and sent to the cathode via piping 20. Then, the cathode exhaust gas that has completed the reaction at the cathode 4 is discharged to the outside of the fuel cell power generation device 11 through the pipe 21.

According to this embodiment, the carbon dioxide required for the cathode is obtained from the combustion gas from the combustor for heating the reaction tube 9 of the reformer 8, so a special carbon dioxide generator is not required. In addition, since the gas supplied to the cathode is mixed with combustion gas, it is preheated.

FIG. 5 shows a fourth embodiment of the present invention. The differences from FIG. 1(a) will be explained.

One feature of this embodiment is that a hydrogen gas separation device 22 is provided which is fluidly connected to an external reforming device [8]. The external reformer 8 has a reaction tube 9 therein, and piping 11 and 12 for circulating a heat medium for heating the reaction tube 9 are provided. In the reaction tube 9, there is a reforming catalyst 10 for quickly reforming methane and water vapor into hydrogen-rich gas.
is retained. At the midpoint of the reaction tube 9 in the axial direction, there are pipes 23 and 2 for extracting the reaction gas in the reaction tube 9.
5, and piping 24 and 26 for returning a portion of the extracted gas into the reaction tube, respectively. The other ends of the reforming bag fIt8 of these pipes 23, 24° 25 and 26 are connected to the hydrogen gas separation bag [22]. The hydrogen gas separation bag f22 is further provided with a pipe 27 for guiding the hydrogen gas obtained by separation.
The other end of the pipe 27 is provided to join the pipe 14 that connects the reaction tube 9 of the reforming bag f8 and the internal reformer 7 in the anode chamber 5 of the fuel cell power generation device 1. .

Next, the operation of this embodiment will be explained. The mixed reaction gas of methane and water vapor that has flowed into the reaction tube 9 of pipe 13 and reformer f;
While being supplied with heat from the heat medium flowing into the reactor tube 9, a reforming reaction occurs under the reforming catalyst 10 held in one reaction tube 9, resulting in a hydrogen-enriched gas. A part of the hydrogen-containing gas is transferred to a pipe 23 provided at a midpoint in the axial direction of the reaction tube 9.
The hydrogen gas is guided through the hydrogen gas separation device 22 and separated into hydrogen gas and gases other than hydrogen gas. The separated hydrogen gas is fed into the pipe 27 by the hydrogen gas separation device 22, and gases other than hydrogen gas are returned into the reaction tube 9 through the pipe 24. Here, the gas composition in the reaction tube 9 is separated and the equilibrium of the reactions in equations (1) and (2) described above shifts by the amount of hydrogen gas that is removed, and the reaction in the direction of producing more hydrogen is promoted. Ru. Similarly, a part of the gas in the reaction tube 9 is led to the hydrogen gas separation device 22 through a pipe 25 provided at another midpoint in the axial direction of the reaction tube 9, and is separated into hydrogen gas and gases other than hydrogen gas. The separated hydrogen gas is sent to the pipe 27, and gases other than the hydrogen gas are returned to the reaction tube 9 through the pipe 26. As a result of this, the above-mentioned (1), (
2) The reaction in the equation shifts to the right, and the generation of hydrogen gas is promoted. The hydrogen-enriched gas thus obtained as a result of the reforming rate exceeding the equilibrium reaction rate at the operating temperature of the external reformer 8 and separated from unreacted methane flows through the pipe 27 .

It is obtained in the reaction tube 9, merges with the reformed gas passing through the pipe 14, and is supplied to the internal reformer 7 in the anode chamber. As a result, the gas is further subjected to a reforming reaction to become a hydrogen-enriched gas that has undergone nearly 100% reforming, and this hydrogen-enriched gas is used as an anode gas.

Note that the better the separation performance of the hydrogen gas separation device 22, the higher the reforming rate can be. Further, the external reformer 8 and the hydrogen gas separation device 22 may be integrally configured, and the number of pipes for extracting one reaction gas is not limited to the number in this embodiment.

According to this embodiment, in addition to the effects of the embodiment shown in FIG. Option 1: It is possible to generate more hydrogen gas than during reaction equilibrium. In addition, by operating the hydrogen gas separation device, it is possible to control the reforming rate of the reaction and the sharing ratio of the reforming reaction between the reformer and the fuel cell device, increasing the operating range of the fuel cell power generation device. In other words, a flexible fuel cell power generation device can be achieved. Furthermore, the separated hydrogen can also be used for other purposes.

〔Effect of the invention〕

As explained above, according to the fuel cell power generation device according to the present invention, since the external reformer and the internal reformer are combined, the reforming rate can be maintained at almost 100% even if the reforming temperature is lowered. Obtainable. Therefore, since the operating temperature of the reformer can be lowered, [F] the life and reliability of the heat resistance of the constituent materials of the reformer can be improved;
■The burden of the reforming reaction on the reforming catalyst is reduced, extending the catalyst life and preventing the fuel cell power generation system from stopping due to catalyst regeneration and replacement. ■Regeneration and replacement due to deterioration of the reforming catalyst's activity. Since this can be mainly entrusted to the external reformer, it has various effects such as reducing the frequency of regeneration and replacement of the reforming catalyst in the internal reformer, which has a complicated structure. The lifespan and reliability of the battery power generator as a whole can be improved.

Furthermore, compared to a fuel cell power generation device having only an external reformer, the required amount of catalyst can be reduced, so the cost of manufacturing the power generation device can be reduced.

In addition, compared to a fuel cell power generation system that only has an internal reformer, ■ instead of supplying raw materials directly to the internal reformer in the anode chamber, hydrogen-enriched gas obtained from an external reformer is supplied. As a result, differences in current density distribution and temperature distribution at the anode are reduced. ■The first stage of fuel reforming is performed in an external reformer, which further prevents carbon deposition in the anode chamber. It has various effects and can improve overall lifespan and reliability.

Furthermore, since the hydrogen-enriched gas that has been reformed in the external reformer and introduced into the internal reformer is heated during the reforming reaction, it is difficult for the cell reaction of the fuel cell to proceed effectively. No preheater is required to preheat the anode gas. Therefore, maintenance of the fuel cell power generation device becomes easier.

[Brief explanation of drawings]

FIG. 1(a), FIG. 3 to FIG. 5 are system diagrams of each embodiment of the fuel cell power generation device according to the present invention, and FIG. 1(b) shows the reaction fluid displacement in FIG. 1(a). A graph showing reaction fluid temperature and methane reforming rate. FIG. 2 is a cross-sectional configuration diagram showing an example of the structure of an anode chamber equipped with an internal reforming device. 1... Fuel cell power generation device, 5... Anode chamber, 6...
... Cando chamber, 7.10... Reforming catalyst, 8... Reformer, 9... Reaction tube, 11.12.13, 14, 1
5゜17.18, 19, 20.21...Piping%16・
...Combustor, 22...Hydrogen gas separation device.

Claims (1)

[Scope of Claims] 1. A battery stack is constructed by stacking a plurality of unit batteries each consisting of an anode and a cathode facing each other with an electrolyte plate sandwiched between them, with a separator in between, and the gas between the anode and the separator is stacked. Electricity is generated by supplying hydrogen gas, which is a fuel, to an anode chamber formed by a flow path groove, and supplying an oxidizing gas to a cathode chamber formed by the cathode and the gas flow groove of the separator. In the fuel cell power generation device, an external reformer that holds a reforming catalyst, distributes fuel containing hydrocarbons, etc. to the reforming catalyst, and reforms the fuel into hydrogen-enriched gas through a reforming reaction. a reforming device, which is provided inside the anode chamber, holds a reforming catalyst, flows the hydrogen-enriched gas through the reforming catalyst, and converts unreformed fuel contained in the hydrogen-enriched gas through a reforming reaction. A fuel cell power generation device comprising: an internal reformer for reforming hydrogen gas into hydrogen gas. 2. In claim 1, a hydrogen gas separation device for separating hydrogen gas from unreformed fuel in the reformed reaction gas is provided, and the reformed fuel reformed in the external reformer is provided with a A fuel cell power generation device characterized in that hydrogen gas is separated by introducing a quality gas into the hydrogen gas separation device, and the separated hydrogen gas is introduced into the internal reforming device. 3. In claim 2, the unreformed fuel separated by the hydrogen gas separation device is extracted to an external reformer and reformed, and the reformed reaction gas is sent to the hydrogen separation device. A fuel cell power generation device characterized in that it is introduced.