DE112019005805B4 - Compact combustor/reformer unit for a fuel cell system and its use and method of operating the unit - Google Patents

Abstract

A burner/reformer unit (10) for a fuel cell system (1); wherein the burner/reformer unit (10) comprises a reformer (6) with a catalyst (6a) for the catalytic conversion of fuel vapor into synthesis gas for a fuel cell (16), a housing (39) enclosing the reformer (6), and a burner (7) for transferring thermal energy to the reformer (6) to heat the catalyst (6a); the reformer (6) comprising an inner wall (6c) and an outer wall (6d) between which the catalyst is sandwiched (6a) and by which the catalyst is enclosed;wherein the combustor (7) is configured to produce combustor exhaust gas (13a) by burning anode exhaust gas or fuel or both and comprises a tubular combustor wall (7b), the inner wall (6c) of the reformer (6) encloses the burner wall (7b) and is spaced from the burner wall (7b), creating a space (10b) between the inner wall (6c) and the burner wall (7b), the burner chamber (7a) being separated by a The burner exhaust duct (12) is in fluid flow communication with the space (10b); the housing (39) enclosing the reformer (6), with a further space (10c) between the outer wall (6d) of the reformer (6) and the housing ( 39) is created; the space (10b) and the further space (10c) being connected at the first end (40a) by a connecting front-end chamber (50);wherein the burner/reformer unit (10) for flow of burner exhaust gas (13a) from the burner chamber (7a) through the burner exhaust duct (12) into the space (10b) and then along the inner cylindrical wall (6c) to the first end (40a) of the reformer (6) without re-entering the combustor chamber (7a) is configured for heat transfer from the burner exhaust ( 13a) to the inner wall (6c) for heating the catalyst (6a) by heat conduction through the inner wall (6c), and further for flow of the burner exhaust gas (13a) from the first end (40) of the reformer (6) through the front-end chamber (50) into the further space (10c) and out of the burner/reformer unit (10) through a burner exhaust gas outlet duct (9), the reformer (6) having a fuel vapor inlet (24a) at the first end (40a) and a outlet (24b) for synthesis gas at the second end (40b) and having a reformer flow direction on average unidirectional from the first end (40a) to the second end (40b) and that the flow direction of the burner exhaust gas in the space (10b) is counter to the reformer flow direction; characterized in that the inner wall (6c) and the outer wall (6d) are cylindrical and form a hollow cylinder having a central axis (43) and a reformer length L when measured in a direction along the central axis (43), the hollow cylinder a first end (40a) and a second end (40b), the first end being spaced a distance equal to the reformer length L from the second end (40b);wherein the combustor/reformer unit (10) is configured to have combustor exhaust gas (13a ) in the further space (10c) along the outside of the outer wall (6d) flows for heat transfer from the burner exhaust gas (13a) to the catalyst (6a) through the outer wall (6d) for the catalytic reaction in the reformer (6).

Description

FIELD OF THE INVENTION

The present invention relates to fuel cell systems, in particular HTPEM fuel cells, with a burner and a reformer and their use for a vehicle and methods for operating such a fuel cell system. In particular, the invention relates to a burner/reformer unit according to the preamble of claim 1 and its use for a vehicle, as well as a method for operating a burner/reformer unit according to the preamble of claim 11.

BACKGROUND OF THE INVENTION

Power generation with fuel cell systems also generates heat as a by-product, which is removed by cooling liquid circulating through channels in the fuel cell. The temperature is adjusted by flowing cooling liquid, e.g. based on glycol, through heat exchangers and coolers in order to optimize the function of the fuel cell.

On the other hand, the coolant can be used to heat the fuel cells during start-up conditions.

An example of this is in WO2016/008486A1 discloses a compact fuel cell system comprising a burner whose exhaust gas is passed along the outer wall of a reformer to heat it to a temperature required for its production of syngas from vaporized fuel. Once the exhaust gas, also called flue gas, from the burner has passed through the reformer to transfer heat to the reformer, the gas transfers heat to a heat exchanger downstream of the reformer. The heat exchanger transfers thermal energy to the coolant liquid in the cooling system to heat it up in start-up situations where the fuel cell stack needs to be activated quickly.

During start-up of the fuel cell system, a rapid temperature rise is desirable in order to get the fuel cell system up and running quickly. However, a quick start requires aggressive use of the burner and high temperature of the exhaust gas. To a certain extent this is advantageous in that efficient use of the burner at high temperatures entails so-called clean burning.

However, the inventors of the present invention have recognized that during optimal combustion in starting situations, the temperature of the exhaust gas can become so high that there is a risk of the reformer being worn out by the heat of the exhaust gas. Therefore, it would be desirable if a balance could be struck between fast start-up and protecting the reformer from overheating. This problem does not appear to have been satisfactorily solved in the prior art, particularly for compact combustor/reformer combinations.

When generating power with fuel cell systems in vehicles, it is important that the fuel cell system is compact and efficient. On the other hand, it is also important that the system is robust and durable. One of the components that needs to be compact is the combustor/reformer combination, where the combustor is used to provide thermal energy to the reformer to make the reforming process efficient.

WO2018/189375A1 discloses a combustor in a tubular reformer. The thermal energy is supplied by conduction through the intervening wall and by heating the gas in the heat exchanger. Although the reformer/burner unit is compact, thermal protection for the reformer is lacking. As on page 11, lines 14-18 in WO2018/189375A1 can be read, there is good heat transport from the burner to the reformer, since the reformer is surrounded by the reformer catalyst over its entire length. However, with an aggressive start, the reformer will be appropriately heated due to thermal conductivity through the wall, and the reformer is not adequately protected against wear from overheating.

Heat transfer through the wall between burner and reformer is also discussed in KR1020060065779A and in US8617269B2 revealed by Son on behalf of Samsung, as well US9238781B2 in von Du, the latter disclosing a helical wall section from the combustor extending into the reformer. A similar section of wall extending into the reformer is in the Korean KR100988470B1 disclosed, on behalf of Korea Mach and Materials Inst.

The system offers protection against overheating WO2016/008486A1 in which a compact fuel cell system comprises a combustor whose exhaust gas is passed along the outer wall of a reformer to heat it to a temperature required for its production of syngas from vaporized fuel. Although the arrangement is compact, the energy transfer is not optimized. For example, the radiant energy of the burner, which otherwise contains a significant amount of energy, is not used.

US5998053A discloses transmission of both radiant energy and thermal energy from the gas through the wall. Thermal energy is supplied only from the outer cylindrical wall of the reformer, which is surrounded by a burner.

US5019463A discloses a fuel cell system having a combustor in front of a reformer, wherein the exhaust gas from the heater is bypassed around the reformer and discharged to the atmosphere through an exhaust pipe and a gas outlet. For start-up, the gas is selectively routed from a valve to the tube to heat the fuel cell's air vents and cooling jacket. Although there is selective by-pass of gas, it does not protect the reformer under rapid aggressive start-up heat since the by-pass is downstream of the reformer.

Flow along one side of the reformer is not optimally efficient. The US patent US6936567B2 von Ueda discloses a burner with a central tubular burner in a central cavity of a reformer, which is designed as a hollow cylindrical tube. The combustor is spaced from a first end of the reformer where the reformer receives the raw fuel for reforming, and the combustor exhaust gas in a combustor chamber flows to the first end and makes a 180 degree U-turn and then flows along the reformer wall in the same direction like the reformer gas. Both the reformer gas and the burner exhaust make a 180 degree turn and both flow to the first end where both the reformed gas and the combustion exhaust are released. Since the burner exhaust gas follows the flow direction of the reformed gas, it only heats the reformed gas on one side of the reformed gas flow through the reformer. It is therefore not optimized in terms of heat transfer. A similar configuration can be found in US2013/0195736A1 by fishermen and in JPH07223801A on behalf of Fuji Electric Co.

US5998053A discloses a fuel cell system in which exhaust gas can be selectively routed through a valve to the fuel cell system that also includes the reformer or to a heating system for a room. Although selective gas bypass occurs before the reformer, it does not protect the reformer during rapid, aggressive start-up heat.

It would be desirable to provide a better way of protecting the reformer from overheating in a start-up situation.

There is also a constant need for optimization for fuel cell systems, particularly in the automotive industry.

DESCRIPTION/SUMMARY OF THE INVENTION

It is an object of the invention to provide an improvement in the art. In particular, it is an aim to provide a fuel cell system with a combustor/reformer unit in which the exhaust gas from the combustor is efficiently used for heating the reformer, including the thermal protection of the reformer during the start-up of the fuel cell system. This goal and other goals are achieved with a fuel cell system, a combustor/reformer unit and a method as described below and in the claims.

As explained below, various principles are presented in order to achieve thermal protection of the reformer despite compactness and at the same time optimize the thermal efficiency.

A combustor/reformer assembly is provided for use in a fuel cell system and includes a reformer having a catalyst for catalytically converting fuel vapor to syngas for a fuel cell. In operation, it is line connected to the anode side of the fuel cell to supply synthesis gas to the fuel cell. In addition, a burner supplies thermal energy to the reformer to heat the catalyst. The combustor is configured to generate combustor exhaust by combusting anode exhaust or fuel, or both. In some practical embodiments, the burner/reformer unit also includes a housing around the reformer. Optionally, the burner/reformer unit is made compact by arranging the burner in the reformer.

A first technical solution for thermal protection differs from the above prior art in that a valve system is used to selectively route the exhaust gas from the burner either to the reformer to heat the reformer, particularly during normal operation, or to a heat exchanger, wherein the reformer is bypassed in start-up situations to heat the fuel cell stack before starting to heat the reformer. The system and method are particularly useful in a compact combustor/reformer unit in which heat from the combustor passes through the baffles to the reformer by conduction.

For example, the valve is an on/off valve for switching between flow along the reforming wall and flow out of the combustor chamber.
Optionally, the valve system is configured so that the exhaust gas from the combustor is only partially routed through the reformer so that the temperature of the reformer can be controlled, for example continuously controlled by adjusting the opening of the partial flow valve to the reformer. The remaining part of the burner exhaust gas flow is advantageously routed to the downstream heat exchanger, which transfers the heat to the cooling circuit. Gradual control of the partial bypass is useful in the start-up situation where the reformer can be warmed up gently and in a controlled manner.

In order to prevent the reformer from overheating during the aggressive start, it has proved advantageous that the reformer is at least partially thermally insulated from the combustor. For example, the reformer walls are provided at a distance from the burner wall.

For this reason, a second technical solution is provided, which is advantageously but not necessarily combined with the first technical solution, which provides a space between the burner and the reformer through which burner exhaust gas flows for controlled heating of the reformer. Thus, the burner walls do not conduct heat directly into the reformer.

To further regulate such thermal isolation, some embodiments include air flow control in which ambient air is directed past a space between the combustor and the reformer such that the increased air flow past the reformer thermally isolates the reformer catalyst from the hot walls of the central combustor.

Various aspects of the first and second technical solution, possibly in combination, are explained in more detail below.

Fuel cell options

The fuel cell system includes a fuel cell, typically a fuel cell stack. The term fuel cell is used here both for a single fuel cell and for a plurality of fuel cells, for example a fuel cell stack.

For example, the fuel cells are high-temperature proton exchange membrane fuel cells, also called high-temperature proton electrolyte membrane (HTPEM) fuel cells, which operate above 120 degrees Celsius, which distinguishes HTPEM fuel cells from low-temperature PEM fuel cells, the latter operating at temperatures below 100 degrees Celsius, for example Example at 70 degrees Celsius, work. The operating temperature of HTPEM fuel cells is in the range of 120 to 200 degrees Celsius, for example in the range of 160 to 170 degrees Celsius. The electrolyte membrane in the HTPEM fuel cell is based on mineral acid, typically a polymer film, for example polybenzimidazole doped with phosphoric acid. HTPEM fuel cells are advantageous because they have a tolerance to relatively high CO concentration and therefore do not require PrOx reactors between the reformer and the fuel cell stack, allowing the use of simple, lightweight and inexpensive reformers, reducing the overall size and weight of the system be minimized in line with the purpose of providing compact fuel cell systems, for example for the automobile industry.

The fuel cell is used to generate electricity, for example, to drive a vehicle such as an automobile. In order to provide a buffer for the electricity generated, a battery system is typically provided in electrical communication with the fuel cell.

A cooling circuit is provided for circulating the coolant through the fuel cell to adjust the temperature of the fuel cell with the coolant. During normal operation, the cooling circuit absorbs heat from the fuel cell to keep the temperature stable and within an optimized range. For example, the temperature of the fuel cell is 170 degrees Celsius and the coolant temperature at the inlet of the fuel cell is 160 degrees Celsius.

A reformer with a catalyst is used to catalytically convert fuel into synthesis gas, which is used in the fuel cell to generate electricity. Accordingly, the reformer is connected to the anode side of the fuel cell. The reformer includes a catalyst in a reformer housing with reformer walls.

For the catalytic reaction in the reformer, the supplied liquid fuel is vaporized in an evaporator connected at its downstream side to the reformer by a fuel vapor line. The upstream side of the evaporator is connected to a liquid fuel supply, for example to receive a mixture of liquid methanol and water.

In order to heat the reformer to the correct catalytic conversion temperature, for example in the range of 250 to 300 degrees Celsius, burner exhaust gas, for example at a temperature in the range of 350 to 400 degrees Celsius, is supplied from a burner.

In normal operation, the burner exhaust gas from the burner flows along the reformer walls and heats them up. After thermal energy is transferred from the combustor exhaust to the reformer walls, the remaining thermal energy can be used to heat other components, such as batteries used to store fuel cell electrical energy, or to heat a vehicle cabin.

During the start-up process of the fuel cell system, the fuel cell must be heated in order to reach a stationary, power-generating operating state. The starting process should be fast, especially for use in vehicles. For this reason, the burner is used heavily during the start-up phase and transfers its heat to the fuel cell.

Typically this is done in practice by transferring the heat from the combustor exhaust to the coolant in the cooling circuit, which is used instead as a heating fluid during start-up to heat the fuel cell to a temperature suitable for normal operation.

In practical embodiments, the downstream side of the combustor exhaust outlet duct is in flow communication with a heat exchanger for transferring thermal energy from the combustor exhaust to the coolant in the cooling loop for transferring thermal energy to the coolant.

In some practical embodiments, the liquid fuel supply includes a methanol reservoir for supplying methanol and a water supply for supplying water and mixing the water with the methanol at a mixing point upstream of the evaporator, the water supply being configured to draw the water to the supply from the combustor exhaust of the burner is recycled.

In specific embodiments, water and methanol are fed to the mixing point, the mixture of water and methanol is vaporized in an evaporator, and the vaporized mixture is fed as fuel to the reformer and catalytically converted to synthesis gas, which is then fed to the anode side of the fuel cell to generate exhaust gas becomes. The exhaust gas from the anode is fed to the combustor and combusted, typically catalytically combusted, into combustor exhaust gas, which is then fed to a condenser to condense water from the combustor exhaust gas.

operation of the fuel cell

As explained above, a fast start requires an aggressive application of the burner and a high temperature of the exhaust gas, which is advantageous in that an efficient use of the burner at high temperature leads to a so-called clean combustion, but with the risk of wearing out the reformer leads to overheating. Various technical solutions to this problem are given below.

A first method of preventing overheating of the reformer is achieved by providing a bypass valve in communication with the combustor chamber. The bypass valve is configured to regulate the flow of combustor exhaust gas between flowing along the reformer walls and flowing out of the combustor chamber through a combustor exhaust outlet passage, the latter bypassing the reformer walls to prevent it from flowing along the reformer walls flows. By operating the bypass valve, the flow of combustor exhaust gas is regulated between the flow along the reformer walls and the flow bypassing the reformer walls.

For example, an exhaust gas path is selectively established by the bypass valve in which a bypass amount of the combustor exhaust gas is directed out of the combustor chamber through a combustor exhaust gas outlet passage, bypassing the reformer walls. The bypass flow, which includes part or all of the burner exhaust gas, is thus prevented from flowing along the reformer walls.

For example, the start-up bypass valve is placed in a start-up configuration where all or most of the combustor exhaust bypasses the reformer during start-up and the thermal energy from the combustor exhaust is instead used to heat the fuel cell. This results in a fast boot process. After the start, the bypass valve is switched in such a way that the burner exhaust gas flows along the reformer walls.

In practical embodiments, the downstream side of the burner exhaust gas outlet duct is in flow communication with a heat exchanger for transferring thermal energy from the Burner exhaust on the coolant in the cooling circuit to achieve a transfer of thermal energy to the coolant. A bypass quantity of more than half of the combustor exhaust from the combustor, for example all or substantially all of the combustor exhaust, bypasses the reformer in the starting situation and reaches the heat exchanger for transfer of a majority of the thermal energy of the combustor exhaust to the coolant and not to the Reformer to heat the fuel cell to a normal operating temperature.

Then, after start-up, the bypass valve is placed in a normal operating configuration, closing the bypass around the reformer and causing all combustor exhaust to flow along the reformer walls to heat the reformer catalyst during normal operation.

In some embodiments, the amount of bypass may be changed during startup of the fuel cell system to regulate the amount of thermal energy transferred from the combustor to the reformer. For example, instead of first causing all of the combustor exhaust to bypass the reformer and reach the heat exchanger until the fuel cell's normal operating temperature is reached, a small portion is used to moderately heat the reformer during startup, particularly in the later stages of startup. If the bypass valve is variably adjustable in relation to the amount of burner exhaust gas that bypasses the reformer, the temperature profile for heating the reformer during start-up can be precisely controlled.

In principle, it is even possible to provide and regulate a bypass quantity during normal operation.

Optionally, the reformer walls are tubular and surround the combustor walls to provide a compact combustor/reformer option. However, this is not strictly necessary and a configuration of the combustor/reformer side by side or a configuration of a combustor located between two sections of the reformer is also possible.

Aspects with a space between burner and reformer

With respect to such compact configurations, a second method for preventing overheating of the reformer, which is suitable for combination with the first method for preventing overheating using a valve as already explained above, will be explained below.

In this second method, an insulating space is provided between the reformer walls and the burner walls, which is filled with, for example, insulating material to thermally insulate heat from the burner walls against conduction, but which is used to direct the burner exhaust gas along the reformer.

An air supply is optionally provided in order to direct air, possibly ambient air, into the insulating space so that the air can flow through the insulating space. For example, the airflow runs along the walls of the reformer and not only insulates the reformer walls from the burner walls, but also removes heat from the insulating space. It can even cool the reformer when it is heated by radiation from the burner wall.

Advantageously, the reformer includes reformer walls and a catalyst enclosed by the reformer walls. The reformer walls are tubular and include an inner cylindrical wall and an outer cylindrical wall forming a hollow cylinder having a central axis and a reformer length L when measured in a direction along the central axis. The hollow cylinder includes a first end and a second end, the first end being spaced apart from the second end by the reformer length L . In some embodiments, the burner is provided in a central cavity of the reformer, which is designed as a hollow cylinder.

In some aspects, the combustor includes a tubular combustor wall. Advantageously, the inner wall of the reformer surrounds and is spaced from the burner wall, thereby creating a space between the inner wall and the burner wall, the combustor chamber being in fluid flow communication with the space through a burner exhaust passage.

A housing encloses the reformer, with another space provided between the outer wall of the reformer and the housing. The space and the further space are connected at the first end by a connecting front end chamber and form a heat exchange chamber. Heating from opposite sides of a cylindrical reformer increases heating efficiency while preventing thermal overload.

In some aspects, the reformer includes a fuel vapor inlet at the first end and a syngas outlet at the second end and a reformer flow direction from inlet to outlet that is one-way on average from first end to second end. In this case, the flow direction of the burner exhaust gas in space is opposite to the flow direction of the reformer.

• - von der Brennerkammer durch den Brennerabgaskanal in den Raum, der Teil der Wärmetauschkammer um den Reformer herum ist,
• - dann entlang der zylindrischen inneren Wand des Reformers bis zum ersten Ende des Reformers (vorteilhafterweise ohne erneutes Eintreten in die Brennerkammer), wodurch Wärme vom Brennerabgas auf die innere Wand übertragen wird, um den Katalysator durch Wärmeleitung durch die innere Wand zu erwärmen,
• - dann durch die Vorderendkammer in den weiteren Raum und
• - dann entlang der äußeren Wand zum zweiten Ende des Reformers und
• - aus der Brenner/Reformer-Einheit durch einen Brennerabgas-Auslasskanal,

Insbesondere für den Fall, dass der Brenner zum Starten und entsprechend aggressiven Brennen verwendet wird, verhindert der Raum zwischen der Brennerwand und der inneren zylindrischen Wand eine Überhitzung des Reformers.Burner exhaust gas flows for operation

• - from the burner chamber through the burner exhaust duct to the space that is part of the heat exchange chamber around the reformer,
• - then along the cylindrical inner wall of the reformer to the first end of the reformer (advantageously without re-entering the combustor chamber), whereby heat from the combustor exhaust gas is transferred to the inner wall to heat the catalyst by conduction through the inner wall,
• - then through the front end chamber into the further room and
• - then along the outer wall to the second end of the reformer and
• - from the burner/reformer unit through a burner exhaust gas outlet duct,

In particular, in the event that the burner is used for starting and correspondingly aggressive burning, the space between the burner wall and the inner cylindrical wall prevents the reformer from overheating.

Although the space insulates against direct contact between the burner wall and the reformer wall, heat radiation from the burner wall can reach the reformer wall. This thermal radiation contributes to thermal energy transfer without risk of overheating of the reformer.

For example, the combustor includes an injection manifold for injecting exhaust gas or fuel into the combustor, the injection manifold being provided closer to the first end of the reformer than the second end to transmit radiant energy primarily to the reformer at or near the first end. Most of the energy is required at the first end, but without overheating the reformer, so adding radiant energy to this first end is beneficial.

However, the main heat transfer from the burner to the reformer is achieved by transporting thermal energy with the burner exhaust gas.

It is noted that the flow of burner exhaust gas within the space between the burner and the inner cylindrical wall of the reformer is in a direction opposite to the direction of flow of the reformer gas through the reformer, while the flow in the wider space extending between the outer cylindrical wall of the reformer and the housing is in the same direction as the flow of the reformer gas in the reformer. It is emphasized that the reformer gas in the reformer is subject to turbulence and possibly even a helical path, therefore the term "direction" in relation to the gases should be understood as an average direction. For example, even if the flow inside the reformer is along a helical path, it is on average along a line from the inlet to the outlet without changing the average direction toward the inlet.

In some embodiments, no bypass valve as discussed above is provided. In such embodiments, all of the combustor exhaust gas is bypassed from the combustor around the reformer so that the combustor exhaust gas can only exit through the combustor exhaust gas outlet passage provided downstream of the further space on the outside of the outer cylindrical wall of the reformer. Particularly for this purpose, a partition wall is provided between the burner chamber and the burner exhaust gas outlet duct and between the space and the burner exhaust gas outlet duct in order to prevent the burner exhaust gas from bypassing the wider space between the housing and the outer cylindrical wall, and instead the Forcing burner exhaust to always flow around the reformer. These embodiments are provided without a bypass valve. However, other embodiments also include such a bypass valve, as described above.

The following optional advantageous embodiments are useful to optimize the heat transfer profile to the reformer. For example, the burner exhaust gas duct is provided in the burner wall. Optionally, the combustor exhaust duct is provided for combustor exhaust flow from the combustor chamber to the heat exchange chamber at a distance from the second end, the distance being in the range of 10%-50% of L, the distance being measured along a central axis of the reformer. Optionally, the combustor exhaust duct for combustor exhaust flow from the combustor chamber to the heat exchange chamber extends a length in the range of 5% to 60% of L, the length being measured along a central axis of the reformer. Optionally, the sum of distance and length is in the range of 15% - 80% of L.

In some embodiments, the reformer includes a helical wall extending between the first and second ends and between between the inner and outer cylindrical walls, the helical wall defining a helical flow path through the reformer. The helical wall extends the length of the flow path through the reformer that is greater than direct flow along the distance from the first end to the second end. Such a helical path has the advantage over the prior art that it lengthens the flow path in the reformer without having to generate a counterflow in two directions through the reformer. In addition, the helical path improves the mixing of the gas in the reformer.

For example, the reformer catalyst is provided as granules between turns of the helical wall to enable efficient reforming.

Optionally, a heating profile can be optimized by adjusting the position of the release of hot combustor exhaust from the combustor to the walls of the reformer. Optionally, more than one burner exhaust duct is provided, with multiple burner exhaust ducts being provided at various locations along the length of the reformer to optimize the temperature profile within the reformer.

aspects of water recycling

Another general improvement is mentioned below, which not only applies to the above embodiments, but is useful as a general principle in fuel cells that use water for the fuel cell, such as a mixture of methanol and water, as above for the HTPEM fuel cell explained. This improvement recycles the water from the fuel cell and/or burner.

In some practical embodiments, the liquid fuel supply includes a methanol reservoir for supplying methanol and a water supply for supplying water and mixing the water with the methanol at a mixing point upstream of the evaporator, and the water supply is for a supply of water derived from the burner exhaust of the burner is reused.

For example, the water supply is part of a recycle loop from the mix point, through the evaporator, through the reformer, through the anode side of the fuel cell, through the combustor, through the condenser, and back to the mix point.

Optionally, the recycle loop is configured to add water from the outlet of the cathode side of the fuel cell.

In specific embodiments, water and methanol are fed to the mixing point, the mixture of water and methanol is vaporized in an evaporator, the vaporized mixture is fed as fuel to the reformer and catalytically converted to synthesis gas, which is then fed to the anode side of the fuel cell for generation of exhaust gas. The exhaust gas from the anode is fed to the combustor and is combusted, typically catalytically combusted, into combustor exhaust gas, which is then fed to a condenser to condense water from the combustor exhaust gas. The water is returned to the mixing point to repeat the cycle. Optionally, water from the outlet of the cathode side of the fuel cell is fed into the recycling loop.

Optionally, the fuel cell system includes a further heat exchanger for the transfer of thermal energy from the coolant to air upstream of the burner in order to use the waste heat. This is used to increase the temperature of the air before it enters the combustor chamber, which increases the energy efficiency of the fuel cell system.

ASPECTS

A number of aspects are explained below that are related to one another and can be combined with the other aspects mentioned here.

• eine Brennstoffzelle;
• einen Kühlkreislauf zum Umwälzen von Kühlmittel durch die Brennstoffzelle zum Einstellen der Temperatur der Brennstoffzelle mit dem Kühlmittel;
• einen Reformer, der einen Katalysator umfasst, der von Reformerwänden umschlossen und für die katalytische Umwandlung von Brennstoffdampf in Synthesegas konfiguriert ist, wobei der Reformer mit der Anodenseite der Brennstoffzelle zur Erzeugen von Synthesegas für die Brennstoffzelle verbunden ist;
• einen Verdampfer, der zum Verdampfen von flüssigem Brennstoff konfiguriert und mit dem Reformer leitungsverbunden ist, um den verdampften Brennstoff dem Reformer bereitzustellen;
• eine Flüssigbrennstoffversorgungsleitung, die mit dem Verdampfer verbunden ist, um dem Verdampfer flüssigen Brennstoff zuzuführen;
• einen Brenner mit einer Brennerkammer innerhalb der Brennerwände, wobei die Brennerkammer zum Erzeugen von Brennerabgas durch Verbrennen von Anodenabgas oder Brennstoff oder beidem konfiguriert ist, wobei die Brennerkammer mit den Reformerwänden für die Strömung des Brennerabgases von der Brennerkammer zu und entlang der Reformerwände in Fluidströmungsverbindung steht zur Übertragung von Wärme vom Brennerabgas zu den Reformerwänden zur Erwärmung des Katalysators durch Wärmeübertragung durch die Reformerwände; dadurch gekennzeichnet, dass das Brennstoffzellensystem ein Bypassventil umfasst, das mit der Brennerkammer in Verbindung steht, und zur Regulierung des Abgasstroms zwischen

1. a) Strömung entlang der Reformerwände und
2. b) Strömung aus der Brennerkammer heraus durch einen Brennerabgas-Auslasskanal (9) unter Umgehung der Reformerwände zur Verhinderung der Strömung entlang der Reformerwände konfiguriert ist.

Aspect 1. A fuel cell system, comprising:

• a fuel cell;
• a cooling circuit for circulating coolant through the fuel cell to adjust the temperature of the fuel cell with the coolant;
• a reformer comprising a catalyst enclosed by reformer walls and configured for catalytic conversion of fuel vapor to syngas, the reformer being connected to the anode side of the fuel cell for generating syngas for the fuel cell;
• a vaporizer configured to vaporize liquid fuel and in line communication with the reformer to provide the vaporized fuel to the reformer;
• a liquid fuel supply line connected to the vaporizer for supplying liquid fuel to the vaporizer;
• a combustor having a combustor chamber within the combustor walls, the combustor chamber configured to produce combustor exhaust gas by combusting anode exhaust gas or fuel, or both, the combustor chamber being in fluid flow communication with the reformer walls for the flow of combustor exhaust gas from the combustor chamber to and along the reformer walls transferring heat from the combustor exhaust to the reformer walls to heat the catalyst by heat transfer through the reformer walls; characterized in that the fuel cell system comprises a bypass valve communicating with the combustor chamber and for regulating the flow of exhaust gas between

1. a) Flow along the reformer walls and
2. b) flow out of the combustor chamber is configured through a burner exhaust gas outlet passage (9) bypassing the reformer walls to prevent flow along the reformer walls.

Aspect 2. The fuel cell system according to aspect 1, wherein the combustor exhaust gas outlet passage is in fluid communication, on its downstream side, with a heat exchanger for transferring thermal energy from the combustor exhaust gas to the coolant in the cooling circuit for transferring thermal energy to the coolant; wherein the bypass valve is configured to transition between a start-up configuration state during start-up of the fuel cell system and a normal operating state after start-up, wherein in the start-up configuration the bypass valve is configured to cause a bypass amount of more than half of the combustor exhaust gas from the combustor, bypassing the reformer and reaching the heat exchanger to transfer much of the thermal energy of the combustor exhaust to the coolant and not to the reformer, thereby heating the fuel cell to a normal operating temperature, and wherein the bypass valve is so configured in the normal operating condition that it stops the reformer bypass and allows the burner exhaust to flow along the reformer walls to heat the reformer catalyst after start-up.

Aspect 3. The fuel cell system according to aspect 2, wherein the bypass valve is configured to gradually adjust the bypass amount of the combustor exhaust gas passed through the reformer, the bypass amount ranging from a minimum amount to a maximum amount, wherein the minimum amount is less than 20% and the maximum amount is greater than 80% relative to the total amount of burner exhaust gas produced by the burner.

Aspect 4. The fuel cell system according to any preceding aspect, wherein the reformer walls are tubular and surround the combustor walls, and wherein an insulating space is provided between the reformer walls and the combustor walls for thermal insulation.

Aspect 5. The fuel cell system according to aspect 4, wherein an air supply is provided in the insulating space for air flow through the insulating space to remove heat from the insulating space during start-up conditions.

Aspect 6. The fuel cell system of any preceding aspect, wherein the fuel cell is a high temperature proton electrolyte membrane, HTPEM, fuel cell configured to operate at a temperature in the range of 120 to 200 degrees Celsius, and wherein the liquid fuel is a mixture of methanol and water is.

Aspect 7. The fuel cell system according to any one of the preceding aspects, wherein the liquid fuel supply comprises a methanol reservoir for supplying methanol and a water supply for supplying water and for mixing the water with the methanol at a mixing point upstream of the evaporator, the water supply for supplying water , which is reused from the burner off-gas from the burner.

Aspect 8. The fuel cell system of aspect 7, wherein the water supply is part of a recycle loop from the merging point, through the evaporator, through the reformer, through the anode side of the fuel cell, through the combustor, through the condenser, and back to the merging point.

Aspect 9. The fuel cell system according to aspect 8, wherein the recycle loop is configured to add water from the cathode side outlet of the fuel cell.

Aspect 10. A fuel cell system according to any preceding aspect, comprising a further heat exchanger for transferring thermal energy from the coolant to air upstream of the combustor to increase the temperature of the air prior to entering the combustor chamber.

Aspect 11. The fuel cell system according to any one of the preceding aspects, wherein the cooling circuit is a primary cooling circuit and wherein the fuel cell system comprises a secondary cooling circuit with coolant that is separate from the coolant in the primary cooling circuit; wherein the fuel cell system includes a secondary heat exchanger for transferring thermal energy between the primary cooling circuit and the secondary cooling circuit, the secondary cooling circuit being in thermal communication with a battery and configured to regulate the temperature of the battery.

Aspect 12. Use of a fuel cell system according to any one of the preceding as aspects for an automobile.

• eine Brennstoffzelle;
• einen Kühlkreislauf zum Umwälzen von Kühlmittel durch die Brennstoffzelle zum Einstellen der Temperatur der Brennstoffzelle mit dem Kühlmittel;
• einen Reformer, umfassend einen Katalysator, der von Reformerwänden umschlossen ist und für die katalytische Umwandlung von Brennstoffdampf in Synthesegas konfiguriert ist, wobei der Reformer mit der Anodenseite der Brennstoffzelle verbunden ist zur Versorgung der Brennstoffzelle mit Synthesegas;
• einen Verdampfer, der zum Verdampfen von flüssigem Brennstoff konfiguriert und mit dem Reformer verbunden ist, um dem Reformer verdampften Brennstoff zuzuführen;
• eine Flüssigbrennstoffversorgung, die mit dem Verdampfer leitungsverbunden ist, um dem Verdampfer flüssigen Brennstoff zuzuführen;
• einen Brenner mit einer Brennerkammer innerhalb der Brennerwände, wobei die Brennerkammer zur Versorgung von Brennerabgas durch Verbrennen von Anodenabgas oder Brennstoff oder beidem konfiguriert ist, wobei die Brennerkammer in Fluidströmungsverbindung mit den Reformerwänden steht für die Strömung des Brennerabgases von der Brennerkammer zu und entlang der Reformerwände zur Übertragung von Wärme vom Brennerabgas zu den Reformerwänden zur Erwärmung des Katalysators durch Wärmeübertragung durch die Reformerwände; dadurch gekennzeichnet, dass das Brennstoffzellensystem ein Bypassventil umfasst, das in Verbindung mit der Brennerkammer steht und zur Regulierung des Abgasstroms zwischen

1. a) Strömung entlang der Reformerwände und
2. b) Strömung aus der Brennerkammer heraus durch einen Brennerabgas-Auslasskanal (9) unter Umgehung der Reformerwände zur Verhinderung der Strömung entlang der Reformerwände konfiguriert ist;

und wobei das Verfahren das Betreiben des Bypassventils umfasst und als Folge des Betreibens des Bypassventils die Strömung des Brennerabgases zwischen der Strömung entlang der Reformerwände und der die Reformerwände umgehende Strömung reguliert wird.Aspect 13. A method for operating a fuel cell system, the fuel cell system, comprising:

• a fuel cell;
• a cooling circuit for circulating coolant through the fuel cell to adjust the temperature of the fuel cell with the coolant;
• a reformer comprising a catalyst enclosed by reformer walls and configured for catalytic conversion of fuel vapor to synthesis gas, the reformer being connected to the anode side of the fuel cell for supplying synthesis gas to the fuel cell;
• a vaporizer configured to vaporize liquid fuel and connected to the reformer to supply vaporized fuel to the reformer;
• a liquid fuel supply in line communication with the vaporizer for supplying liquid fuel to the vaporizer;
• a combustor having a combustor chamber within the combustor walls, the combustor chamber configured to supply combustor exhaust gas by burning anode exhaust gas or fuel or both, the combustor chamber being in fluid flow communication with the reformer walls for flow of combustor exhaust gas from the combustor chamber to and along the reformer walls transferring heat from the combustor exhaust to the reformer walls to heat the catalyst by heat transfer through the reformer walls; characterized in that the fuel cell system comprises a bypass valve which is in communication with the combustor chamber and for regulating the flow of exhaust gas between

1. a) Flow along the reformer walls and
2. b) flow out of the combustor chamber is configured through a burner exhaust gas outlet passage (9) bypassing the reformer walls to prevent flow along the reformer walls;

and wherein the method comprises operating the bypass valve and, as a result of operating the bypass valve, the flow of the combustor exhaust gas is regulated between the flow along the reformer walls and the flow bypassing the reformer walls.

Aspect 14. The method of aspect 13, wherein the method comprises adjusting the bypass valve during startup of the fuel cell to a startup configuration and causing a bypass amount greater than half of the combustor exhaust from the combustor to bypass the reformer.

Aspect 15. The method of aspect 14, wherein the burner exhaust gas outlet passage (9) is in flow communication on its downstream side with a heat exchanger for transferring thermal energy from the burner exhaust gas to the coolant in the cooling circuit for transferring thermal energy to the coolant; the method providing for bypassing the reformer with a bypass amount of more than half of the combustor exhaust from the combustor to reach the heat exchanger for transferring a majority of the thermal energy of the combustor exhaust to the coolant and not to the reformer to convert the fuel cell to a normal operating temperature.

Aspect 16. The method of aspect 14 or 15, wherein the method comprises after start-up placing the bypass valve in a normal operating configuration and closing the combustor exhaust bypass to bypass the reformer and flowing all of the combustor exhaust along the reformer walls to bypass the Heat reformer catalyst during normal operation.

Aspect 17. The method of any one of aspects 14 to 17, wherein the reformer walls are tubular and surround the combustor walls, and wherein an insulating space is provided between the reformer walls and the combustor walls for thermal insulation, with an air supply into the insulating space for air flow through the insulating Space is provided to remove heat from the insulating space during start-up conditions, the method during start-up including creating an air flow through the air supply and in and along the insulating space for dissipating heat from the insulating space.

Aspect 18. The method according to any one of aspects 14 to 17, wherein the fuel cell is a high temperature proton electrolyte membrane, HTPEM, fuel cell and the method comprises operating the fuel cell at a temperature in the range of 120 to 200 degrees Celsius and a supply of liquid fuel as Mixture of methanol and water.

Aspect 19. The method of any one of aspects 14 to 18, wherein the liquid fuel supply comprises a methanol reservoir for supplying methanol and a water supply for supplying water and mixing the water with the methanol at a mixing point upstream of the vaporizer, the water supply for the supply of water reused from the combustor exhaust gas, the water supply being part of a recycle loop from the mix point, through the evaporator, through the reformer, through the anode side of the fuel cell, through the combustor, through the condenser, and back to the mix point is, the method comprising feeding water and methanol to the mixing point, and evaporating the mixture of water and methanol in an evaporator, feeding the vaporized mixture as fuel in the reformer and catalytically converting the fuel to synthesis gas, feeding the synthesis gas into the anode side of the fuel cell and generating off-gas, feeding the off-gas to the combustor and combusting the off-gas to become combustor off-gas, feeding the combustor off-gas to a condenser and condensing water from the combustor off-gas, feeding the condensate of the water back to the mixing point to complete the cycle to repeat.

Aspect 20. The method of aspect 19, wherein the method comprises adding water from the outlet of the cathode side of the fuel cell to the recycle loop.

Aspect 21. The method of any one of aspects 14 to 20, wherein the fuel cell system includes a further heat exchanger for transferring thermal energy from the coolant to air upstream of the combustor, and the method includes increasing the temperature of the air prior to entry into the combustor chamber by the coolant to increase the energy efficiency of the fuel cell system.

character list

• 1 ein Beispiel eines Brennstoffzellensystems darstellt;
• 2a eine alternative Ausführungsform mit einem Ventil darstellt, bei dem sich die kompakte Brenner/Reformer-Einheit im stationären Betrieb befindet;
• 2b die alternative Ausführungsform im Startzustand darstellt;
• 3 ein Flussdiagramm für das Brennstoffzellensystem darstellt;
• 4a, 4b, 4c und 4d alternative Ausführungsformen mit versetzten Brennerabgaskanälen veranschaulichen;
• 5a eine beispielhafte kompakte Brenner/Reformer-Einheit mit einem Reformer zeigt, der eine wendelförmige Strömungsführung in perspektivischer Ansicht umfasst;
• 5b eine Querschnittslinienzeichnung des Reformers mit der wendelförmigen Strömungsführung zeigt.

The invention will be explained in more detail with reference to the drawing, in which

• 1 Figure 12 illustrates an example of a fuel cell system;
• 2a Figure 12 shows an alternative embodiment with a valve in which the compact burner/reformer unit is in steady state operation;
• 2 B Figure 12 shows the alternative embodiment in the starting state;
• 3 Figure 12 illustrates a flowchart for the fuel cell system;
• 4a , 4b , 4c and 4d illustrate alternative embodiments with offset burner exhaust passages;
• 5a Figure 12 shows an exemplary compact combustor/reformer unit with a reformer incorporating a helical flow guide in perspective view;
• 5b Figure 12 shows a cross-sectional line drawing of the reformer with the helical flow guide.

DETAILED DESCRIPTION / PREFERRED EMBODIMENT

1 shows a fuel cell system 1 with a fuel cell 16, typically a fuel cell stack, and a burner/reformer unit 10, which comprises a burner 7 and a reformer 6. The burner 7 comprises a burner chamber 7a for generating burner exhaust gas with thermal energy for heating the reformer 6. A burner catalyst is typically provided inside the burner chamber 7a, but for the sake of simplicity in 1 and 2 is not shown.

For example, the burner 7 is arranged between two layers of a heat exchange chamber 10b in which the reformer 6 is located.

Alternatively, the burner 7 has a cylindrical shape and is surrounded by a cylindrical tubular heat exchange chamber 10a formed as a hollow tube with an internal cavity and an annular cross-section. In particular, the cylindrical configuration is compact, which is advantageous when used in an automobile where space is limited.

The cylindrical reformer 6 is provided inside the reformer walls 6b, which includes an inner cylindrical wall 6c and an outer one cylindrical wall 6d coaxial with the inner cylindrical wall 6c.

An air inlet 31 provides air flow 32 into the combustion chamber 7a. Through the exhaust gas inlet 3 and the injection manifold 4, the exhaust gas 3a from the anode of the fuel cell 16 enters the combustor chamber 7a and is used as fuel in the burner 7, since the exhaust gas contains fuel residues even after the reaction in the fuel cell 16. The burner exhaust gas 13a out of combustion in the combustion chamber 7a flows into the heat exchange chamber 10a.

Since the burner exhaust gas 13a contains considerable heat, it heats the outsides of the walls 6b of the reformer 6 by flowing along them. Due to conduction of thermal energy through the walls 6b, typically metal walls, the thermal energy from the burner exhaust gas 13a is transferred to the catalyst 6a in the space enclosed by the reformer walls 6b.

The heated catalyst 6a in the reformer 6 receives a mixture of water and methanol from an evaporator 28 downstream of the mixing point 38 to which water is supplied from a metering feed 19 and methanol via a methanol metering valve 20 . The mixture enters the reformer 6 through the inlet 24a at a first end 40a of the cylindrical reformer 6 .

In the reformer 6 the mixture is catalyzed into synthesis gas which exits the reformer 6 through an outlet 24b at a second end 40b of the cylindrical reformer 6 from which it is fed to the anode of the fuel cell 16 . The cathode is supplied with air from a compressor 17 to supply oxygen.

like it in 1 is illustrated, the walls 7b of the combustion chamber 7a do not lie against the reformer walls 6b, in particular not against the inner wall 6c of the reformer 6, but there is a space 10b between them which isolates and direct heat conduction from the combustion chamber walls 7b to the reformer walls 6b prevented. This advantageously prevents overheating of the reformer 6.

In contrast to the prior art, the reformer 6 does not have a second stage which diverts the reformed gas into a counterflow to the first end 40a of the cylindrical reformer 6 . Instead, the averaged reformer flow is one way from a first end 40a to a second end 40b of the reformer 6 as indicated by an arrow.

The burner exhaust gas 13a inside the burner 7 has a direction towards the second reformer end 40b and then enters the heat exchange chamber 10a through a burner exhaust gas channel 12 at the partition wall 52 .

The partition wall 52 is provided at the second end 40b of the reformer and is continuous and extends across the hollow chamber containing the combustion chamber 7a and defined by the inner wall 6c. The partition wall 52 separates the burner 7 and the upstream part of the heat exchange chamber 10a from the burner exhaust gas outlet duct 9 and from the burner exhaust chamber 13, so that the only way for the burner exhaust gas to reach the burner exhaust chamber 13 is to flow around the reformer 6. How in 1 shown by way of example, the upstream end of the heat exchange chamber 10a is located approximately at the downstream second end 40b of the reformer 6.

When the burner exhaust gas 13a enters the heat exchange chamber 10a through the burner exhaust gas duct 12 at the end of the burner chamber 7a, it changes direction to an oppositely directed counterflow in the heat exchange chamber 10a towards the first end 40a of the reformer 6 and along the inner cylindrical wall 6c, which is in the Compared to the flow in the combustion chamber 7a and the direction of the reformed gas in the reformer 6 is opposite. Upon reaching the first end 40a, the combustor exhaust gas 13a flows around the first end 40a of the reformer 6 and again changes direction within the casing 39 to flow along the outer cylinder wall 6d of the reformer 6 parallel and in the same direction as the flow in the Combustion chamber 7a and the reformer 6.

After the transfer of thermal energy from the burner exhaust gas 13a to the reformer 6, the burner exhaust gas 13a, after reaching the second end 40b of the reformer 6, leaves the heat exchange chamber 10a at the second end 40b through the burner exhaust gas duct 9 into the burner exhaust gas chamber 13.

The advantage of this configuration is the heat transfer for the catalytic reaction in the reformer 6 not only from the inner cylindrical wall 6c but also from the outer cylindrical wall 6d, which allows the reaction inside the reformer 6 to be heated more evenly from both sides even if the reformer has a relatively large diameter. If only the inner cylindrical wall 6c or only the outer cylindrical wall 6d is heated, the heat transfer is not optimal.

Prior art configurations in which only one side of the reformer is heated attempted to overcome the lack of sufficient To improve heat by extending the walls of the combustor into the reformer through a helical wall structure. However, this principle of the prior art entails that the wall of the combustor conducts the heat through the metal walls into the reformer by conduction. This requires the burner to be used only at moderate heat, otherwise the heat transfer will be too aggressive. The consequence of this in the prior art is that the burner cannot be used with high efficiency, so that clean burning is prevented. In the invention, this disadvantage has been overcome.

All in all, in comparison between the illustrated embodiments and the prior art, the indirect heat transfer through the flow of the burner exhaust gas 13a flowing along the reformer walls 6b causes a more moderate heating than the heat transfer directly through the metal walls from the burner walls 7b to the reformer walls 6b, while at the same time a large and optimized total amount of heat is provided, since the heat is transferred to both the inner cylindrical wall 6c and the outer cylindrical wall 6d.

Optionally, radiant energy from burner 7 is added through burner walls 7b to increase efficiency.

Optionally, the cooled coolant in the cooling circuit 22 upstream of the fuel cell 16 receives further thermal energy from the burner exhaust gas 13a through heat transfer in the heat exchanger 14 downstream of the burner exhaust gas chamber 13.

From the cathode of the fuel cell 16, air and water vapor enter the burner exhaust gas chamber 13 via the connection 33 and mix with the burner exhaust gas 13a before they reach the heat exchanger 14 for the transfer of thermal energy to the coolant in the cooling circuit 22, through which the cooling liquid with of the pump 15 is pumped.

After cooling the fuel cell 16 by absorbing further thermal energy from the fuel cell 16, the coolant enters another heat exchanger 18, through which heat is used to heat other components, such as the battery in the vehicle or in the cabin.

• Brennstoffzelle: 170 Grad Celsius
• Kühlflüssigkeit: 160 Grad Celsius
• Katalysator im Reformer: 280 Grad Celsius
• Brennerabgas: 350-400 Grad Celsius

Typical temperatures in Celsius for a HTPEM fuel cell stack in steady-state operation:

• Fuel cell: 170 degrees Celsius
• Coolant: 160 degrees Celsius
• Catalyst in the reformer: 280 degrees Celsius
• Burner exhaust: 350-400 degrees Celsius

Optionally, in start-up situations, the same burner 7 can be used as the initial heat-up burner. In this case, methanol is received by a corresponding methanol metering valve 21 through a methanol inlet 2 and injected through the methanol injection nozzle 5 into the combustor chamber 7a. Air 32 enters through air inlet 31 for combustion, typically catalytic combustion by a combustor catalyst.

The combustor exhaust transfers the greatest amount of heat to the inner cylindrical wall 6c at the point where the combustor exhaust 13a exits the combustor chamber 7a and approaches the reformer wall 6b. Gradually, the temperature of the burner exhaust gas 13a is lowered as it flows along the inner cylindrical wall 6c toward the first end 40a. However, this does not necessarily mean that the inner cylindrical wall 6c at the first end 40a receives the lowest total amount of heat. This is because radiant energy is added from the combustor wall 7b to the inner cylindrical wall 11c, particularly at the first end 40a, since the temperature in the combustor chamber 7a is highest at the nozzle 5.

A further development is in 2a and 2 B shown, the latter showing only part of the fuel cell system for ease of illustration. Particular attention is drawn to the bypass valve 8 with a shutter element 8a controlled by an actuator 11 and used to direct the burner exhaust gas 13a into the burner exhaust chamber 13 so that the reformer 6 is bypassed in start-up situations.

The system inside 2a shows a similar situation as the system in 1 , since the valve 8 is closed, replacing the partition 52. In this embodiment shows 2a the configuration during stationary operation, and 2 B shows a starting situation.

As in 2 B As shown, the closure member 8a of the bypass valve 8 is placed in a configuration in which the closure member 8a is retracted from the valve seat 8b and the bypass valve 8 is fully opened so that the combustor chamber 7a communicates with the combustor exhaust chamber 13 so that the combustor exhaust gas 13a from the combustor chamber 7a to the burner exhaust chamber 13 while bypassing the heat exchange chamber 10a containing the reformer 6.

In the starting situation, methanol 2a is received through a methanol inlet 2 and injected through the methanol injection nozzle 5 into the combustor chamber 7a. Air 32 enters through air inlet 31 for combustion, typically catalytic combustion by a combustor catalyst.

As illustrated and discussed, the burner walls 7b do not abut the reformer walls 6b, but there is an insulating space 10b therebetween which prevents direct heat conduction from the burner chamber walls 7b to the reformer walls 6b. Optionally, to further protect the reformer 6 from the heat of the combustor 7, a bypass airflow 42A can be established through the air bypass opening 42, allowing airflow 42A from the air inlet 31 and along the outside of the combustor chamber 7a into the insulating Space 10b is generated between the burner walls 7b and the inner reformer wall 6b. The airflow 42A not only further isolates the reformer 6 from the hot combustor walls 7b of the combustor chamber 7, but also potentially extracts heat from the reformer walls 6b. In the illustrated embodiment, the bypass airflow 42A exits the heat exchange chamber 10a through the valve 8 and joins the burner exhaust gas 13a in the burner exhaust chamber 13. Optionally, the bypass opening can be closed to regulate the bypass airflow.

It is optionally possible to only partially open the bypass valve 8, in which case the closure element 8a is only slightly pulled back from the valve seat 8b. In this case, part of the burner exhaust gas 13a flows through the heat exchange chamber 10a and another part through the bypass valve 8. This is useful for adjusting the temperature of the reformer 6 and its catalyst 6a while preventing overheating. For example, in a start-up situation, the bypass valve 8 is initially fully open to aggressively and rapidly heat the fuel cell 16, followed by a partial closing of the bypass valve 8 to gradually and gently heat the reformer until a sufficiently high temperature is reached at which the components go into normal stationary fuel cell operation and the bypass valve 8 is closed.

In principle it is possible to use the bypass valve 8 also during stationary operation of the fuel cell system for controlling and optimizing, for example continuous controlling and optimizing, the heat transfer to the reformer 6 .

3 shows some of the flows through the fuel cell system. From the methanol tank 23, methanol 2a flows through the methanol metering valve 20 to be mixed with water from the water supply 19 at the mixing point 38. After vaporization in vaporizer 28 downstream of mixing point 38, the vaporized air/methanol mixture is fed through inlet 24a into reformer 6 for catalytic conversion to synthesis gas, which then exits reformer 6 through outlet 24b and into the anode side of fuel cell 16 is fed.

After the catalytic reaction in the fuel cell to produce electricity, the partially converted synthesis gas exits the anode side of the fuel cell as exhaust gas, which enters the combustor chamber 7a through the combustor exhaust gas inlet and is used as fuel in the combustor 7 . Air is supplied to the burner 7 through the air inlet 31 .

It will now open 3 referenced. When valve 8 is open, as in 1 shown, the catalytically converted synthesis gas/air mixture in the burner chamber 7a leaves the burner as burner exhaust gas 13a through the valve 8 into the burner exhaust gas chamber 13 and, as in FIG 3 shown, mixes with water vapor and remaining air from the cathode at mixing point 33. The hot mixture exits the burner exhaust chamber 13 and transfers heat in heat exchanger 14 to the liquid in cooling circuit 22. The vapor is then condensed in condenser 27 and the water is mixed with it Methanol 2a recycled at mixing point 38 before entering reformer 6.

When the valve 8 is open, only a very small part of the burner exhaust gas finds its way around the reformer 6 due to the resistance in the flow through the heat exchange chamber 10a. However, if the valve 8 is closed, as in 2 As shown, the burner exhaust gas is forced from the burner 7a into the heat exchange chamber 10a and around the reformer 6 and exits the reformer 6 through the outlet duct 9 into the burner exhaust chamber 13. In each intermediate position of the valve 8 between fully closed and open, a corresponding portion of the burner exhaust gas flows through the heat exchange chamber 10a and exits the reformer 6, and another part exits the burner 7a into the burner exhaust chamber 13.

It should be noted that in the illustrated example of 3 the vapor from the cathode as well as the burner exhaust gas 13a is returned to the reformer 6 either directly from the burner or after heat transfer and is mixed with methanol at the mixing point 38 downstream of the condenser 27 to subsequently produce synthesis gas. This implies that the water circuit for the fuel cell is a closed circuit.

In the primary cooling circuit 22 , a fuel cell cooler (FC cooler) is used for adjusting the temperature of the coolant pumped by the coolant pump 15 .

Optionally, a secondary cooling circuit 35 is provided up to the radiator 26 to adjust the temperature of other devices, for example for heating and/or cooling the batteries 37 in a vehicle or for heating a cabin of a vehicle. As shown, a heat exchanger 18 is provided for thermal energy transfer between the primary cooling circuit 22 and the secondary cooling circuit 35 for heating or cooling purposes. The heat from the coolant in the secondary cooling circuit 35 pumped by the pump 36 is transferred through an appropriate heat exchanger 18 to maintain the battery 37 at a favorable fixed temperature, e.g. heated during start-up and cooled during steady-state operation .

Optionally, a further cooling circuit exchanges thermal energy with the primary cooling circuit 22 via a further heat exchanger 18a, for example for cabin heating in a vehicle.

A heat exchanger 30 upstream of the burner 7 is used to preheat air before it enters the burner 7, which is advantageous in order to increase the start-up speed and also to increase the burner 7's effectiveness. Air is also heated in another heat exchanger 29 downstream of the cathode side of the fuel cell 16 to achieve temperature adjustment of the air from the compressor 17 .

In relation to 1 and 2a For example, the amount of heat delivered at the reformer second end 40b from the direct combustor gas relative to the amount of heat delivered at the first end 40a by the combination of combustor exhaust gas and radiant heat from the combustor wall 7b at the first end 40a with a configuration such as that described in connection with 4 is explained, can be adjusted better.

In this case, the burner exhaust gas duct 12 for the burner exhaust gas 13a from the burner chamber 7a is provided as a number of openings 12' in the cylindrical burner wall 7b at a distance 45 from the second end 40b of the reformer 6, so that the burner exhaust gas 13a enters the heat exchange chamber 10a at a distance to the second end 40b of the reformer 6 enters. Depending on the exact configuration, the distance 45 will be adjusted. The extension 46 of the burner exhaust gas duct 12 along the central axis of the reformer 6 can also be adjusted for optimization.

As an alternative to a number of orifices, a single orifice 12' in the burner exhaust duct could be used, such as a slotted orifice extending a distance 46 measured along the cylinder axis. For example, the single opening is a helical slot. The distance 45 is then measured similarly as for the orifice, namely from the position of the orifice closest to the second end, measured along the central axis of the reformer 6.

As a further alternative, multiple zones of openings 12' that act as burner exhaust passage 12 may be placed between first end 40a and second end 40b for optimization. An example in which the burner exhaust gas channel 12 is supplemented by a further spaced-apart burner exhaust gas channel 12A is shown in FIG 4d shown.

In the exemplary representation of 4a the burner end wall 7c is provided at the second end 40b of the reformer 6 and is integrated in the partition wall 52. However, this need not be the case, as in 4b shown where the end wall 7c of the combustor 7 is spaced from the bulkhead 52 at the second end 40b of the reformer 6.

Optionally, the burner end wall 7c is provided at the end of the burner exhaust gas duct 12, as shown in FIG 4c . For example, the burner end wall 7c forms the end of the burner exhaust gas duct 12.

It should be noted that the combustor chamber 7a as well as the space 10b are sealed and separated from the burner exhaust duct 9 so that the burner exhaust gas 13a flows around the reformer 6 at the front end 40a and through the further space 10c between the outer cylindrical wall and the housing 39 must flow before it flows through the burner exhaust channel 9 into the burner exhaust chamber 13.

However, the configurations in which the burner exhaust passage 12 is offset from the second end 40b of the reformer 6 can be used with the embodiment of FIG 2 be combined with the valve 8.

An example of a burner/reformer unit is in 5a shown in a shaded semi-transparent representation and in a dashed drawing in 5b . The injection manifold 4 is not shown, but may be that of FIG 1 and 2 similar and is used in the combustion chamber 7a. A burner catalyst is typically also provided in the burner chamber 7a, for example in the form of granules, which, however, are not shown for the sake of simplicity.

Within the reformer 6, a helical flow guide 44 forces the reformer gas to helically move within the reformer 6 between the inner cylindrical wall 6c and the outer cylindrical wall 6d. It should be noted that the average flow direction of the gas within the reformer is unidirectional despite the helical motion of the gas from inlet 24a to outlet 24b.

As it is more detailed in 5b is shown, the burner exhaust gas 13a in the burner 7 exits the burner chamber 7a through the burner exhaust gas duct 12, which in the exemplary illustration consists of a plurality of openings 12' distributed over a length 46 of the burner exhaust gas duct 12, which is a fraction of the total length L of the Reformers 6, for example in the range from 5% to 50%.

The burner exhaust duct 12 is provided a distance 45 from the second end 40b of the reformer 6, the distance 25 being typically in the order of 10 to 60% of L .

Overall length 45+46 is typically less than 80% of L and typically greater than 15% of L.

When the burner exhaust gas 13a has left the burner chamber 7a through the burner exhaust channel 12, the burner exhaust gas 13a moves in the heat exchange chamber 10a in the space 10b between the outside of the burner wall 7b and the inner cylindrical wall 6c of the reformer 6. While the burner exhaust gas 13a travels along the inner cylindrical wall 6c of the reformer 6, it transfers heat to the inner cylindrical wall 6c and also absorbs new heat from the hot burner cylindrical wall 7b. Furthermore, radiant energy is transmitted from the burner wall 7b to the inner cylindrical wall 6c of the reformer 6. Accordingly, the heat transfer between the burner 7 and the reformer 6 is complex.

The burner exhaust gas 13a in the heat exchange chamber 10a in the space 10b between the outside of the burner wall 7b and the inner cylindrical wall 6c of the reformer 6 flows to the first end 40a of the reformer 6 and changes direction in the annular burner exhaust gas front-end chamber 50 and flows in the heat exchange chamber 10a further in the direction of the second end 40b of the reformer 6 in the further space 10c between the housing 39 and the outer cylindrical wall 6d of the reformer 6. At the second end 40b of the reformer 6, the burner exhaust gas 13a flows through the burner exhaust gas outlet channel 9 to the burner exhaust gas chamber 13 .

A probe 47 is used to monitor the temperature in the reformer 6 and another probe 48 is used to monitor the exhaust gas temperature 13a in the combustor 7.

• - Reformerdurchmesser: 50-200 mm
• - Reformerlänge: 300-1000 mm
• - Brennerdurchmesser: 20-40% des Reformerdurchmessers
• - Breite der Wärmetauschkammer 10a: 1-4 mm
• - Dicke der Wände des Brenners und / oder der Wände des Reformers: 05-1,5 mm (typischerweise Metall)

Possible example dimensions are as follows:

• - Reformer diameter: 50-200 mm
• - Reformer length: 300-1000 mm
• - Burner diameter: 20-40% of the reformer diameter
• - Width of the heat exchange chamber 10a: 1-4 mm
• - Thickness of the walls of the burner and / or the walls of the reformer: 05-1.5 mm (typically metal)

• - einen Raum 10b zwischen der Brennerwand 7b und der inneren zylindrischen Wand 6c des Reformers 6;
• - eine Wärmetauschkammer 10a in dem Raum 10b zwischen der Brennerwand 7b und der inneren zylindrischen Wand 6c des Reformers 6 zum Abströmen des Brennerabgases 13a entlang der inneren zylindrischen Wand 6c;
• - Verlängerung der Wärmetauschkammer 10a um das erste Ende 40a des Reformers 6 und zur äußeren zylindrischen Wand 6d des Reformers 6 in den weiteren Raum 10c zwischen der äußeren zylindrischen Wand 6d und dem Gehäuse 39;
• - Bereitstellung des Brennerabgaskanals 12, wo das Brennerabgas die Brennerkammer 7a verlässt, wobei der Brennerabgaskanal 12 zwischen dem ersten und dem zweiten Ende 40a, 40b des Reformers 6 und im Abstand zum zweiten Ende 40b vorgesehen ist, wenn entlang der Mittelachse 43 des Reformers 6 gemessen wird;
• - eine wendelförmige Strömungsführung 44 innerhalb des Reformers 6.

The embodiment of 5 comprises a combination of various factors, namely:

• - a space 10b between the burner wall 7b and the inner cylindrical wall 6c of the reformer 6;
• - a heat exchange chamber 10a in the space 10b between the burner wall 7b and the inner cylindrical wall 6c of the reformer 6 for outflow of the burner exhaust gas 13a along the inner cylindrical wall 6c;
• - Extension of the heat exchange chamber 10a around the first end 40a of the reformer 6 and to the outer cylindrical wall 6d of the reformer 6 into the further space 10c between the outer cylindrical wall 6d and the housing 39;
• providing the burner exhaust duct 12 where the burner exhaust exits the burner chamber 7a, the burner exhaust duct 12 being provided between the first and second ends 40a, 40b of the reformer 6 and spaced from the second end 40b when measured along the central axis 43 of the reformer 6 becomes;
• - a helical flow guide 44 within the reformer 6.

The space 10b between the burner wall 7b and the inner cylindrical wall 6c of the reformer 6 prevents the reformer 6 from being overheated by the burner 7. However, it must still be ensured that sufficient thermal energy is transferred from the burner 7 to the reformer 6. This is particularly so in the case of the helical flow guide 44 which lengthens the flow path of the reformer gas within the reformer 6. The helical flow guide 44 is advantageous because it increases the efficiency of the conversion while keeping the reformer 6 compact, but on the other hand there is a need for more thermal energy as a straight line from the first end 40a to the second end 40b of the reformer. In order to increase thermal energy transfer without overheating, the combustor exhaust gas 13a is guided along both the inner cylindrical wall 6c and the outer cylindrical wall 6d, thereby achieving thermal energy transfer from both sides of the hollow cylindrical reformer. During the one-way route from the inlet 24a to the outlet 24b, the gas inside the reformer 6 is heated from both sides. Furthermore, the temperature profile can be optimized by positioning the burner exhaust duct 12 between the first and second ends 40a, 40b of the reformer 6 and at a distance from the second end 40b. By adjusting the position of the burner exhaust duct 12 and optionally one or more further burner exhaust ducts, more thermal energy can be supplied in the upstream part of the reformer 6 near the first end 40a, where the thermal energy requirements are highest, while at the second end 40b of the reformer 6 less thermal energy is supplied where the energy demand is lower since most of the gas has already been converted. However, the energy supply at the first end must be matched to the radiant energy from the burner walls 7b as this is also highest at the first end where the burner manifold is located and where the combustion reaction begins. Accordingly, the various factors interact closely and lead to a synergistic effect in terms of optimization.

Even when used individually in burner/reformer systems, such as in prior art burner/reformer systems, these factors can also produce improvements even though they are not used in conjunction with all of the other factors mentioned above.

Reference List

1)

fuel cell system

2)

Methanol inlet for burner 7

2a)

Methanol flow from methanol inlet 2 to chamber 7a

3)

Burner inlet for exhaust gas from fuel cell anode 16

4)

Injection manifold for injecting gas or fuel into the burner 7

5)

methanol injector

6)

reformer

6a)

Catalyst in methanol to hydrogen reformer 6, wherein methanol is reformed to hydrogen

6b)

reformer wall

6c)

cylindrical inner wall of the reformer

6d)

cylindrical outer wall of the reformer 6

7)

burner

7a)

combustion chamber

7b)

burner walls

7c)

burner end wall

8th)

bypass valve

8a)

Bypass valve locking element 8

9)

Burner exhaust outlet duct

10)

Burner/reformer unit

10a)

Heat exchange chamber between burner walls 7b and inner reformer wall 6c

10b)

Space between burner walls 7b and inner reformer wall 6c

10c)

Additional space between the housing 43 and the outer reformer wall 6d

11)

Bypass valve actuator 8

12)

Exhaust duct from the combustion chamber 7a into the heat exchange chamber 10a

12')

Openings in the exhaust duct 12

12A)

Another gas channel

13)

burner exhaust chamber

13a)

burner exhaust

14)

Heat exchanger for heat exchange between burner exhaust gas 13a and cooling circuit 22

15)

Circulation pump for liquid in the cooling circuit 2

16)

fuel cell

17)

air compressor

18)

Additional heat exchanger for heating the battery, for example

18a)

Additional heat exchanger for heating the cabin or other equipment, for example

19)

Water dosing supply for reformers

20)

Methanol metering valve for reformers

21)

Methanol metering valve for starting burner 20

22)

Primary cooling circuit for fuel cell

23)

methanol tank

24a)

Reformer inlet for methanol/water mixture for synthesis gas production

24b)

Syngas reformer outlet

25)

cooling circuit cooler

26)

battery cooler

27)

capacitor

28)

Evaporator for evaporating methanol/water mixture for reformers

29)

Heat exchanger to preheat the air for the cathode

30)

Heat exchanger for preheating the air for the burner 7

31)

Air inlet for burner 7

32)

Air flow from air inlet 31 to burner chamber 7a

33)

Port for mixing air and vapor from cathode with burner exhaust 13a

34)

expansion tank

35)

Secondary cooling circuit for battery 37 and other purposes

36)

Battery cooling circuit pump 35

37)

battery

38)

Mixing point for methanol and water

39)

Housing

40a)

First end of the reformer 6

40b)

second end of reformer 6

42)

Bypass opening (optional)

42A)

bypass airflow

42)

Mix evaporator for methanol and water

43)

Central axis of the reformer 6

44)

Helical flow guidance

45)

Distance from the burner exhaust gas duct 12, 12' to the second end 40b of the reformer 6

46)

Width of the burner exhaust gas channel 12, 12'

47)

Sensor probe in the reformer 6

48)

Sensor probe in burner 7

49)

Length L of the reformer 6

50)

Exhaust front end chamber

52)

Partition wall separating the space 10c of the heat exchange chamber 10a from the burner exhaust gas outlet duct 9

Claims (13)

A burner/reformer unit (10) for a fuel cell system (1); wherein the burner/reformer unit (10) comprises a reformer (6) with a catalyst (6a) for the catalytic conversion of fuel vapor into synthesis gas for a fuel cell (16), a housing (39) enclosing the reformer (6), and a burner (7) for transferring thermal energy to the reformer (6) to heat the catalyst (6a); wherein the reformer (6) comprises an inner wall (6c) and an outer wall (6d) between which the catalyst (6a) is located and by which the catalyst is enclosed; wherein the combustor (7) is configured to generate combustor exhaust gas (13a) by burning anode exhaust gas or fuel or both and comprises a tubular combustor wall (7b), the inner wall (6c) of the reformer (6) enclosing the combustor wall (7b) and is spaced from the burner wall (7b), thereby creating a space (10b) between the inner wall (6c) and the burner wall (7b), the burner chamber (7a) being in fluid flow communication with the space (10b ); the casing (39) enclosing the reformer (6) with a further space (10c) being created between the outer wall (6d) of the reformer (6) and the casing (39); the space (10b) and the further space (10c) being connected to each other at the first end (40a) by a connecting front-end chamber (50); the burner/reformer unit (10) for flow of burner exhaust gas (13a) from the burner chamber (7a) through the burner exhaust duct (12) into the space (10b) and then along the cylindrical inner wall (6c) to the first end (40a) of the reformer (6) without re-entering the combustor chamber (7a) is configured for heat transfer from the combustor exhaust gas (13a) to the inner wall (6c) for heating the catalyst (6a) by conduction of heat through the internal wall (6c), and further for flow of the combustor exhaust gas (13a) from the first end (40) of the reformer (6) through the front-end chamber (50) into the further space (10c) and out of the burner/reformer unit (10) through a burner exhaust gas outlet duct (9), wherein the reformer (6) has a fuel vapor inlet (24a) at the first end (40a) and a syngas outlet (24b) at the second end (40b) and an average unidirectional running from the first end (40a) to the second end (40b). Has reformer flow direction, and that the flow direction of the burner exhaust gas in the space (10b) is opposite to the reformer flow direction; characterized in that the inner wall (6c) and the outer wall (6d) are cylindrical and a hollow cylinder with a center axis (43) and a reformer length L when measured in a direction along the central axis (43), the hollow cylinder comprising a first end (40a) and a second end (40b), the first end having a distance corresponding to the has reformer length L from the second end (40b); wherein the burner/reformer unit (10) is configured such that burner exhaust gas (13a) flows in the further space (10c) along the outside of the outer wall (6d) for heat transfer from the burner exhaust gas (13a) to the catalyst (6a) through the outer wall (6d) for the catalytic reaction in the reformer (6). A burner/reformer unit (10) after claim 1 , wherein the burner exhaust gas channel (12) for the flow of burner exhaust gas from the burner chamber (7a) into the space (10b) has a first channel spacing (45) from the second end (40b), the first channel spacing (45) being in the range of 10 % to 50% of the reformer length L, the first channel spacing being measured along the central axis (43). A burner/reformer unit (10) after claim 2 , wherein the burner exhaust gas channel (12) for the flow of burner exhaust gas from the burner chamber (7a) into the space (10b) extends over a first channel length (46) in the range of 5% - 60% of the reformer length L, the first channel length ( 46) is measured along the central axis (43) in extension of the first channel spacing (45) and in the direction of the burner (7). A burner/reformer unit (10) after claim 3 , wherein the sum of the first channel spacing (45) and the first channel length (46) is in the range of 25% to 80% of L. A combustor/reformer unit (10) as claimed in any preceding claim, wherein the combustor exhaust duct (12) is provided as a first set of openings (12') in the combustor chamber. A burner/reformer unit (10) after claim 5 wherein another burner exhaust passage (12A) is provided as a second group of openings (12') in the burner chamber (7a); the further burner exhaust duct (12A) being closer to the first end (40A) than the burner exhaust duct (12); wherein adjacent openings (12') in the first group are spaced a first distance from each other; and wherein a group spacing between the first and second groups is at least 10 times the first spacing; and wherein the further burner exhaust passage (12A) has a different total flow area than the burner exhaust passage (12). A combustor/reformer unit (10) as claimed in any preceding claim, wherein the combustor (7) includes an injection manifold (4) for injecting gas or fuel into the combustor (7), the injection manifold (4) being inside the combustor chamber (7a) closer to the first end (40a) of the reformer than to the second end (40b) to supply radiant energy to the reformer (6) mainly at the first end (40a). A burner/reformer unit (10) according to any one of the preceding claims, wherein a partition wall (52) between the burner chamber (7a) and the burner exhaust gas outlet duct (9) and between the space (10b) and the burner exhaust gas outlet duct (9) is provided to prevent the burner exhaust gas (13a) from bypassing the reformer (6) and instead to force the burner exhaust gas (13a) to flow into the space (10b) and the further space (10c). A combustor/reformer unit (10) as claimed in any preceding claim, wherein the reformer (6) includes a helical flow guide (44) extending between the first and second ends (40a, 40b) and between the inner and outer cylindrical wall (6c, 6d), the helical flow guide (44) defining a helical flow path through the reformer (6) to increase the length of the flow path through the reformer (6) relative to a distance from the first end (40a) to the second end (40b) when measured along the central axis (43), the catalyst (6a) being provided between turns of the helical flow guide (44). A combustor/reformer unit (10) according to any one of the preceding claims, wherein the fuel cell system comprises a bypass valve (8) communicating with the combustor chamber (7a) and configured to regulate the flow of combustor exhaust gas (13a) between: a) Flow along the reformer walls (6b) and b) Flowing out of the combustor chamber (7a) through a combustor exhaust outlet duct (9), bypassing the reformer walls (6b) to prevent it from flowing along the reformer walls (6b). Method for operating a burner / reformer unit (10) according to one of Claims 1 until 7 ; the method comprising: causing burner exhaust (13a) to flow from the burner chamber (7a) through the burner exhaust duct (12) into the space (10b) and then along the inner cylindrical wall (6c) to the first end (40a) of the reformer (6) without re-entering the entering the combustor chamber (7a), and heat transfer from the combustor exhaust gas (13a) to the catalyst (6a) through the inner wall (6c), and then through the front end chamber (50) into the further space (10c) and then along the outer wall (6c) to to the second end (40b) of the reformer (6) and heat transfer from the burner exhaust gas (13a) to the catalyst (6a) also through the outer wall (6d) for the catalytic reaction in the reformer (6) and out of the burner/reformer unit (10 ) out through a burner exhaust gas outlet duct (9), characterized in that the method comprises: providing the reformer (6) with an inlet (24a) for fuel vapor at the first end (40a) and an outlet (24b) for synthesis gas at the second end (40b) and causing a flow direction from the inlet (24a) to the outlet (24b) that is unidirectional on average from the first end (40a) to the second end (40b) and a flow direction of the combustor exhaust gas in the space (10b) opposite to the reformer flow direction. Use of a burner/reformer unit (10) according to any one of Claims 1 until 10 for a fuel cell system in an automobile. use after claim 12 wherein the fuel cell system (1) comprises an HTPEM fuel cell (16) configured to operate at a temperature in the range of 120 to 200 degrees Celsius with a liquid fuel that is a mixture of methanol (2a) and water.

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