AT525203A1 - Fuel cell system with a recombination device - Google Patents

Abstract

The present invention relates to a fuel cell system (100), comprising a fuel cell stack (110) with an anode section (120) and a cathode section (130), the anode section (120) having an anode feed section (122) for supplying anode feed gas (AZG) and has an anode discharge section (124) for discharging anode off-gas (AAG) and the cathode section (130) has a cathode feed section (132) for supplying cathode feed gas (KZG) and a cathode discharge section (134) for discharging cathode off-gas (KAG), further comprising the fuel cell stack (110) and at least in sections the anode feed section (122), the anode discharge section (124), the cathode feed section (132) and the cathode discharge section (134) are arranged within a thermally insulated insulating housing (140) and within the insulating housing (140) at least one catalytic recombination device (10) is arranged with a catalyst body (20) with a catalyst surface (22) for a catalytic recombination of at least one fuel gas (BG) of the fuel cell stack with an oxidizing gas (OG).

Description

Fuel cell system with a recombination device

The present invention relates to a fuel cell system with a recombination device for protection against an explosive atmosphere in an insulating

houses.

It is known that fuel cell systems are used in different constructions for the production of a fuel gas or for the production of electricity. A fuel gas is supplied to the fuel cell system for the production of electric power, while fuel gas is produced while consuming electric power. In both cases it is a flammable combustible gas such as hydrogen or methane. Also, it is known that a high-temperature fuel cell can be used as a construction of the fuel cell system. In order to be able to ensure the most efficient possible operation of such high-temperature fuel cells, thermally insulated insulating housings are usually provided, which can also be used as a hot box

be referred to, within which the fuel cell stack is arranged.

A disadvantage of the known solutions is that, in the case of high-temperature fuel cells, leakage within the hotbox cannot be completely ruled out. In particular, high temperature fluctuations between normal ambient temperature and operating temperatures of 400 C° to 900 C° can lead to small leaks in the lines and/or other components within the hotbox due to thermal expansion or wear. In extreme cases, this could lead to combustion gas escaping and accumulating via such a leak inside the housing. Since, in addition, there is a correspondingly high internal temperature in this insulating housing in a high-temperature fuel cell, there is a risk of this combustion gas igniting within the insulating housing above a defined ignition concentration. In order to avoid this, either a very high degree of accuracy and avoidance during assembly and the associated avoidance of leaks is necessary. It is also known that the gas flow of the fuel cell system is carried out under negative pressure, so that in the event of a leak no gas escapes into the hotbox, but rather gas is sucked from the interior of the hotbox into the line operated with negative pressure.

This reduces the operational variability of the fuel cell system.

It is also known to use such insulating housings with a complex active gas outlet

exchange in order to regularly ventilate the interior of the insulating

home to provide.

It is the object of the present invention to at least partially eliminate the disadvantages described above. In particular, it is the object of the present invention to provide explosion protection for a in a cost-effective and simple manner

To provide high-temperature fuel cell.

The above object is achieved by a fuel cell system having the features of claim 1 and a recombination device having the features of claim 12. Further features and details of the invention result from the dependent claims, the description and the drawings. Features and details that are described in connection with the fuel cell system according to the invention naturally also apply in connection with the recombination device according to the invention and vice versa, so that the disclosure of the individual aspects of the invention is always reciprocal

reference is or can be made.

A fuel cell system according to the invention has a fuel cell stack with an anode section and a cathode section. The anode section is provided with an anode supply section for supplying anode supply gas and an anode discharge section for discharging anode off-gas. The cathode section is equipped with a cathode supply section for supplying cathode supply gas and a cathode exhaust section for discharging cathode off-gas. In addition, the fuel cell stack and at least sections of the anode feed section, the anode discharge section, the cathode feed section and the cathode discharge section are arranged within a thermally insulated insulating housing. In addition, at least one catalytic recombination device is arranged within this insulating housing in a fuel cell system according to the invention. This recombination device has a catalyst body with a catalyst surface for a catalytic combination of at least one fuel gas of the fuel cell stack

an oxidizing gas.

lensystems, for example in the range between around 400 C° and up to 900 C°.

The core idea of the present invention is now to ensure explosion protection or protection against ignition of a combustible gas within the insulating housing. In the context of the present invention, a combustible gas is any gas which would ignite under the influence of a high temperature and/or an ignition spark from an ignition concentration and could lead to a combustion reaction and/or an explosion. An oxidizing gas is a gas that chemically oxidizes the fuel gas and in this way reduces the concentration of fuel gas again, in particular below the ignition concentration.

adorns

The core idea according to the invention is now based on the fact that leaks in the individual feed sections and discharge sections of the anode section and the cathode section can be accepted, since the fuel gas can be catalytically converted if it escapes through such a leak. It should also be pointed out that the fuel gas can be contained in one of the feed sections and/or in one of the discharge sections. For example, if the fuel cell system generates the fuel gas in electrolysis mode while consuming electricity, this fuel gas can be contained in one of the discharge sections and can escape into the interior of the insulating housing via corresponding leaks in this discharge section. If the fuel cell system is operated in power generation mode, the fuel gas can be contained in the anode feed section, for example, but also a residual amount of such a fuel gas in one of the discharge sections. In this case, too, the fuel gas can leak into the interior of the insulating housing via a leak in the feed section or the corresponding discharge sections.

get it.

exceeds.

In addition to explosion protection, a very cost-effective and simple implementation is possible in this way. Even a retrofitting of existing fuel cell systems with a recombination device according to the invention and explained later is fundamentally conceivable. It should also be pointed out that this is in particular a passive or essentially passive protection option. In comparison to active ventilation devices, as are known in the prior art, there is increased reliability here. Since the catalytic recombination essentially takes place automatically through chemical driving forces, this safety function is also control-free and therefore complete

chemical drive automatically guaranteed.

The catalyst body has a catalyst material for this catalytic effect. This can form the catalyst surface, for example as a catalyst material on the surface of the catalyst. Of course, the catalyst body can also be formed entirely or essentially entirely from such a catalyst material. In order, as will be explained later, to further increase the catalyst surface area and thus the catalytic effect, the catalyst body can have, for example, a honeycomb structure, a ribbed structure or a pore-like design, which can be suitably filled with catalyst material

coated as a catalyst surface. For example, ceramic components

to provide correspondingly enlarged catalyst surface.

It can be advantageous if, in a fuel cell system according to the invention, the at least one recombination device is arranged in a gas collection section of the insulating housing, in which the at least one fuel gas collects during operation of the fuel cell stack. This is, of course, fuel gas that has entered the interior of the insulating housing through a possible leak in the feed sections, the discharge sections or on the fuel cell stack itself. The gas collection section is based on the flow conditions within the insulating housing and the differences in density of the atmosphere of the insulating housing. If the fuel gas is, for example, a gaseous component with a lower density than the rest of the atmosphere inside the insulating housing, then the gas collection section will be arranged accordingly in an upper region of the insulating housing. In particular, several gas collection sections can also be defined in order to have different gas collection sections with one or even more recombination devices for different operating situations and/or different temperatures.

equipment.

A further advantage results when a defined amount of fresh oxidation gas is introduced into the insulating housing at a defined point and the recombination device is positioned in front of a defined outlet point. This arrangement and in combination with the forced convection can ensure that all fuel gas from a leak is also converted at the recombination device. In order to minimize possible heat losses,

Advantage also take place a heat exchange between outlet and inlet.

Further advantages can be achieved if, in a fuel cell system according to the invention, the catalyst body has at least in sections a geometry with an enlarged catalyst surface, in particular at least one of the following

the geometries: — rib geometry,

— honeycomb geometry,

— pore geometry.

The above list is a non-exhaustive list. Of course, different geometries can also be combined with one another. For example, a porous catalyst body can have a plurality of rib structures in order to be able to provide a further reinforced and enlarged catalyst surface. Depending on the choice of material for the catalyst body and in particular also the type of catalyst material, the most varied of geometries are conceivable here. The larger the catalyst surface is formed, the greater the catalytic effect and the associated conversion rates. In order to further increase safety, especially in large leakage situations, an enlarged catalytic converter surface can provide greater safety, so that the concentration of fuel gas remains below a predefined ignition concentration. Of course, the catalyst surfaces can also be at least partially on and/or in a wall of the insulating

be integrated into the house.

There are further advantages if, in a fuel cell system according to the invention, the recombination device has a vertical or essentially vertical flow direction for a flow of fuel gas and oxidizing gas in relation to a direction of gravity of the fuel cell system. This vertical orientation, in particular along a straight line, causes the fuel gas and the oxidizing gas to react with one another catalytically within the catalyst body, with heat usually being released. The reaction gas is heated by the heat released, creating a chimney effect within the catalyst body. This is fundamentally independent of the type and orientation of the inlets and outlets of the catalyst body, but can be further supported by the guide elements that will be explained later. The defined and in particular vertically aligned direction of flow not only leads to an improved flow through the catalyst body, but also leads to an actively forced circulation in the interior of the insulating housing. In addition to an improved flow and thus an increased catalytic effect, combustion gases from other sections of the insulating housing automatically become the recombination device, so to speak

circulated towards. The inventive effect of recombination increases further,

so that in particular a smaller configuration of the recombination device

and in particular the catalyst body for the same safety in explosion

protection is sufficient.

It is also advantageous if, in a fuel cell system according to the invention, the recombination device has guide elements, in particular in the form of guide walls, at least in sections, for guiding the fuel gas and the oxidizing gas along the flow direction. Such guide elements serve to reinforce the chimney effect even further, as explained in the preceding paragraph. For example, a lateral inflow is also conceivable in principle, but the guide walls preferably enclose the catalyst body in such a way that in particular a single defined inlet opening from the interior of the insulating housing to the catalyst body and a single defined outlet opening from the catalyst body to the interior of the insulating housing are formed. This reduces or even minimizes the lateral inflow, thus correspondingly the chimney effect according to the previous one

Paragraph can be further strengthened.

It is also advantageous if, in the case of the recombination device, in particular its catalyst body has a constant or essentially constant flow cross section along the flow direction. This flow cross section is in particular regular, preferably rotationally symmetrical, for example round. For example, a cylindrical design of the recombination device can have cylindrical wall sections, in the cavity of which the catalyst body, also of cylindrical design, is arranged. The hollow cylinder of the guide elements, i.e. the correspondingly designed piece of pipe, has a corresponding inlet and outlet opening at the lower and upper end, with the flow cross section, preferably as a round flow

flow cross-section, constantly extending between inlet and outlet.

Further advantages can be achieved if, in a fuel cell system according to the invention, the recombination device has at least one temperature

sensor has, for a detection at least one of the following temperatures:

— material temperature of the catalyst body,

— recombination device inlet temperature, — recombination device outlet temperature.

The above list is a non-exhaustive list. Of course, two or more different temperature sensors can also be combined with one another at different points. It is also possible that a temperature sensor for detecting the temperature in the interior of the insulating housing is provided at a distance from the recombination device. Because the temperature can be monitored, in the simplest case it can be monitored whether an ignition temperature is exceeded or not. By monitoring the heat development on the catalytic converter body, for example due to the material temperature or the difference between the outlet temperature and the inlet temperature at the recombination device, the catalytic effect that is currently being called up can be recorded. The stronger a conversion takes place in a catalyzed manner within the recombination device, the greater the heating effect, which in turn can be detected by the temperature sensor. It is thus possible to record the current recombination performance and, in particular over longer periods of time, not only to monitor whether the recombination is functional, but also to identify possible aging effects or wear and tear of the catalytic converter effect. This training is special

free of a gas sensor in the insulating housing.

There are also advantages if, in a fuel cell system according to the invention, the recombination device has at least one heating element for active heating of the catalyst body. This can be an electrical heating element, for example. Such an electrical heating element can either be integrated into the catalyst body or arranged in lateral guide elements. The active heating of the recombination device and/or the catalyst body means that the chimney effect already explained several times can be generated or intensified even during start-up processes of the fuel cell system or other cooler modes of operation at correspondingly low operating temperatures. The catalytic effect can also be made available by actively heating the recombination device

be when the temperature inside the insulating housing is still below the

catalytic active temperature of the catalyst material is. The recombination and

the protective effect is also available in cold operating situations

bar. For example, inductive heating elements and/or

of capacitive heating elements conceivable within the scope of the present invention.

It can also bring advantages if, in a fuel cell system according to the invention, the catalyst body has the heating element at least in sections according to the preceding paragraph. This leads to an integration of the heating element into the catalyst body or even to the formation of the heating element through the catalyst body. For example, the catalyst body can be designed to be at least partially electrically conductive, so that it is electrically conductive

Energization provides a resistance heater for the catalyst body.

Further advantages can be achieved if, in a fuel cell system according to the invention, recombination devices are arranged in at least two different positions in the insulating housing, with the flow directions of the recombination devices in particular being aligned parallel or essentially parallel. Preferably, at least two recombination devices are even aligned coaxially with one another, so that the chimney effect is passed on to the other recombination device and the overall circulation within the insulating housing is further increased. These different positions are preferably formed at different vertical heights within the insulating housing, so that the recombination devices are also at different

Small heights increase the forced circulation in the insulating housing.

It is also advantageous if, in a fuel cell system according to the invention, the insulating housing is designed as a vacuum housing in relation to the internal pressures in the anode feed section, the anode discharge section, the cathode feed section and/or the cathode discharge section. This means that even if you accept a possible leak, the feed sections and the discharge sections of the fuel cell stack can operate very freely, that is to say can be operated both in negative pressure mode and in positive pressure mode. The insulating housing as a vacuum housing is possible, since even in the vacuum

case, ie if fuel gas enters the insulating housing through a leak, the

10730

Iytische recombination effect of the recombination device is guaranteed.

Another object of the present invention is a recombination device for use in a fuel cell system according to the invention. Such a recombination device has a catalyst body with a catalyst surface for catalytic recombination of at least one fuel gas of the fuel cell stack with an oxidizing gas. A mounting interface for mounting in the insulating housing of the fuel cell system is also provided. A combination device according to the invention thus brings with it the same advantages as have been explained in detail with reference to a fuel cell system according to the invention. The recombination device is in particular according to the corresponding embodiments in the already

refined fuel cell system formed.

Further advantages, features and details of the invention result from the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawings. It show schematic

table:

1 shows an embodiment of a fuel cell system according to the invention, FIG. 2 shows a further embodiment of a fuel cell according to the invention

fabric cell system,

3 shows an embodiment of a recombination device according to the invention, FIG. 4 shows a further embodiment of a recombination device according to the invention

combination device,

Fig. 5 shows a further embodiment of a Recom-

combination device,

Fig. 6 shows a further embodiment of a Recom-

combination device,

11 FIG. 7 a further embodiment of a recombination device according to the invention, FIG. 8 the embodiment of FIG. 7 in a side view and FIG. 9 a further embodiment of a recombination device according to the invention

combination device.

FIG. 1 shows a schematic of a fuel cell system 100 with an insulating housing 140 designed as a hotbox. The anode section 120 receives anode feed gas AZG via an anode feed section 122 and produces anode off-gas AAG, which it discharges via anode discharge section 124 . Similarly, the cathode section 130 receives cathode supply gas KZG via the cathode supply section 132 and discharges cathode off-gas KAG via the cathode discharge section 134 . The two feed sections 122 and 132 as well as the two discharge sections 124 and 134 lead through the insulating housing 140 and can, for example, be discharged outside to the environment or be provided with corresponding further components in a fluid-communicating manner. The entire fuel cell system can, of course, have further components such as recirculation lines, reformer devices, heat exchanger devices, afterburner devices or the like. These are for the sake of clarity

not shown in FIG.

If, depending on the mode of operation of the fuel cell system 100, a leak occurs in one of the feed sections 122 and 132 or in one of the discharge sections 124 or 134 or even in the fuel cell stack 110 itself, through which fuel gas BG escapes, the lack of ventilation of the insulating housing 140 would Concentration of fuel gas BG within the insulating case 140 increase. Since the fuel cell system 100 is a high-temperature system, the temperatures within the insulating housing 140 are in the range between 400° C. and up to 900° C. If an ignitable ignition concentration of fuel gas BG is reached within the insulating housing 140, this would lead to the fuel gas igniting and thus either to damage to the fuel cell

systems 100 or even to destroy the same by explosion.

reduced and ensures that an ignition concentration is not exceeded.

FIG. 2 shows a similar solution, but here the gas collection section 142 is formed over the entire vertical height counter to the direction of gravity SR. Two identical recombination devices 10 are arranged here, one in the upper part and one in the lower part. The correspondingly designed through-flow direction of each recombination device 10 is parallel and here even coaxial to one another, so that circulation within the insulating housing 140 is made available in an increased manner. Combustion gas from other areas, in particular to the right of the fuel cell stack 110 in FIG.

Nations devices 10 are promoted.

FIGS. 3 to 9 show different embodiments of recombination devices 10 as can be used in fuel cell systems 100, for example according to FIGS. FIG. 3 shows a solution with a chimney effect, which has a round cross section. The catalyst body 20 is designed here as a porous ceramic and is surrounded by a tubular guide element 30 . The catalyst surface 22 is formed by the honeycomb or pore-shaped inner surfaces on the catalyst body 20 and can have a coating of catalyst material, for example. The flow cross-section SQ, which here through the radial extension of the

Catalyst body 20 is defined is substantially constant between the

inside the insulating housing 140.

FIG. 4 is based on the embodiment of FIG. 3. Three temperature sensors 40 are additionally arranged here, which can determine temperatures at three points. In the present embodiment, it is possible to determine the inlet temperature at the catalyst body 20, the outlet temperature of the catalyst body 20 and a material temperature of the catalyst body 20. The current catalytic reaction performance and thus the active recombination effect can thus be qualitatively or even quantitatively determined by the waste heat that can be detected in this way, so that the recombination performance can be checked or monitored

to protect against explosion damage.

FIG. 5 is also based on the embodiment of FIG. 3. A heating element 50 is integrated into the guide elements 30 here. In this way, lateral heating of the catalytic converter body 20, activated for example by electric current, is possible. FIG. 6 shows a similar possibility, in which the heating element 50 is integrated into the catalyst body 20 so that it can be flowed through. In both cases, the temperature of the catalyst body 20 can be actively increased, so that even in cold operating situations, for example when starting up the fuel cell system 100, the desired safety function can be achieved by recombination in a catalytic manner

can be guaranteed.

In Figures 7 and 8 is an alternative embodiment with a reduced

Chimney effect shown. Here, the catalyst body 20 has several

Individual components, which are arranged in ribs here. The individual

Parts of the catalyst body can also be porous again, but also as a solid material

be trained. The catalyst surface 22 is thereby at least through the rip

pen surfaces of the individual parts of the catalyst body 20 available

puts. However, a combination with porous catalyst

bodies 20 conceivable.

FIG. 9 develops the embodiment of FIG. 3 in that the flow cross section SQ is reduced along the flow direction DR. With the development of heat and the corresponding differences in density, the rise of the gases within the catalyst body 20 is further increased and in particular accelerated, so that not only the flow through, but also the external forced circulation in the insulating housing 140 is further reduced.

can be strengthened.

The above explanation of the embodiments describes the present one

Invention solely in the context of examples.

Reference List

10 recombination device 20 catalyst body

22 catalyst surface

30 guide elements

40 temperature sensor

50 heating element

60 attachment interface

100 fuel cell system 110 fuel cell stack 120 anode section

122 anode supply section 124 anode discharge section 130 cathode section

132 cathode supply section 134 cathode discharge section 140 insulating case

142 gas collection section

BG fuel gas

OG oxidizing gas

AZG anode feed gas AAG anode exhaust gas

KZG cathode feed gas KAG cathode exhaust gas

SR gravity direction

DR flow direction

SQ flow cross-section

Claims (1)

patent claims 1. Fuel cell system (100), comprising a fuel cell stack (110) with an anode section (120) and a cathode section (130), wherein the anode section (120) has an anode feed section (122) for supplying anode feed gas (AZG) and an anode discharge section (124) for discharging anode waste gas (AAG) and the cathode section (130) has a cathode feed section (132) for supplying cathode feed gas (KZG) and a cathode discharge section (134) for discharging cathode waste gas (KAG), the fuel cell stack (110) and at least the anode feed section (122), the anode discharge section (124), the cathode feed section (132) and the cathode discharge section (134) are arranged in sections within a thermally insulated insulating housing (140), characterized in that at least one catalytic recombination device ( 10) is arranged with a catalyst body (20) with a Catalyst surface (22) for catalytic recombination of at least one fuel gas (BG) of the fuel cell stack with an oxidizing gas (06). 2. The fuel cell system (100) according to claim 1, characterized in that the at least one recombination device (10) is arranged in a gas collection section (142) of the insulating housing (140), in which the at least one Fuel gas (BG) collects. 3. Fuel cell system (100) according to any one of the preceding claims, characterized in that the catalyst body (20) has at least partially a geometry with an enlarged catalyst surface (22) on has, in particular at least one of the following geometries: - rib geometry - honeycomb geometry — pore geometry points. 5. Fuel cell system (100) according to claim 4, characterized in that the recombination device (10) has guide elements (30) at least in sections, in particular in the form of guide walls, for guiding the fuel gas (BG) and the oxidizing gas (OG) along the flow direction (DR). 6. Fuel cell system (100) according to one of claims 4 or 5, characterized in that the recombination device (10), in particular its catalyst body (20) along the flow direction (DR) has a constant or substantially constant flow cross section (SQ) on points. 7. Fuel cell system (100) according to any one of the preceding claims, characterized in that the recombination device (10) has at least one temperature sensor (40) for detecting at least one ner of the following temperatures: - material temperature of the catalyst body (20) - inlet temperature of the recombination device (10) - outlet temperature of the recombination device (10) 8. Fuel cell system (100) according to any one of the preceding claims, characterized in that the recombination device (10) has at least one heating element (50) for active heating of the catalyst body (20). 10. The fuel cell system (100) according to any one of the preceding claims, characterized in that recombination devices (10) are arranged in at least two different positions in the insulating housing (140), the flow directions (DR) of the recombination devices (10) being aligned parallel or substantially parallel are. 11. Fuel cell system (100) according to one of the preceding claims, characterized in that the insulating housing (140) as a vacuum housing based on the internal pressures in the anode feed section (122), the anode discharge section (124), the cathode feed section (132) and/or the cathode discharge section ( 134) is formed. 12. recombination device (10) for use in a fuel cell system (100) having the features of one of claims 1 to 11, having a catalyst body (20) with a catalyst surface (22) for catalytic recombination of at least one fuel gas (BG) of the fuel cell stack (110) with an oxidizing gas (O0G) and a mounting interface (60) for mounting in the insulating housing (140) of the combustion fabric cell system (100). 13. recombination device (10) according to claim 12, characterized in net that this has the features of claims 3 to 10.