DK180247B1

DK180247B1 - Fuel cell system, its use and method of its operation

Info

Publication number: DK180247B1
Application number: DKPA201870763A
Authority: DK
Inventors: Bang Mads; Risum Korsgaard Anders
Original assignee: Blue World Technologies Holding ApS
Priority date: 2018-11-20
Filing date: 2018-11-20
Publication date: 2020-09-14
Also published as: DE112019005805B4; DE112019005805T5; DK180453B1; DK201970390A1; CN113056837B; CN113056837A; DK201870763A1

Abstract

In a fuel cell system, for example HTPEM fuel cells. a valve system is employed by selectively guiding exhaust gas from the burner either to the reformer for heating the reformer, especially during normal operation, or to a heat exchanger while bypassing the reformer in startup situations in order to heat the fuel cell stack before starting heating the reformer. Optionally, a compact burner/reformer unit is provided where the heat from the burner is reaching the reformer by conduction of heat through the intermediate walls.

Description

DK 180247 B1 1 Fuel cell system, its use and method of its operation

FIELD OF THE INVENTION The present invention relates to a fuel cell system according to claim 1, especially HTPEM fuel cells, and its use for a vehicle as well as a method of operating such fuel cell system.

BACKGROUND OF THE INVENTION When generating electricity with fuel cell systems, also heat is generated as a by- product, which is removed by cooling-liquid that is circulating through channels in the fuel cell. The temperature is adjusted by flow of cooling-liquid, for example based on glycol, through heat exchangers and radiators for optimized function of the fuel cell.

On the other hand, the coolant can be used for heating the fuel cells during startup conditions. As example thereof is disclosed in WO2016/008486, in which a compact fuel cell system comprises a burner, the exhaust gas of which is passed along the outer wall of a reformer for heating it to a temperature necessary for its production of syngas on the basis of evaporated fuel. Once, the exhaust gas, also called flue gas, from the burner has passed the reformer for transfer of heat to the reformer, the gas transfers heat to a heat exchanger downstream of the reformer. The heat exchanger transfers thermal energy to the cooling-liquid in the cooling system for heating it in startup situations where the fuel cell stack shall be activated quickly. During start-up of the fuel cell system, a quick rise in temperature is desired in order to get the fuel cell system into operation quickly. However, a quick startup requires aggressive use of the burner and high temperature of the exhaust gas. To a certain ex- tent this is advantageous in that efficient use of the burner at high temperature implies so-called clean burning. However, the inventors of the present invention have realized that during optimum burning in start-up situations, the temperature of the exhaust gas

DK 180247 B1 2 may become so high that there is a risk for degradation of the reformer by the heat of the exhaust gas. Accordingly, it would be desirable, if there could be found a balance between quick startup and protection of the reformer against overheating. This prob- lem appears not to have having been solved satisfactory in the prior art, especially not for compact burner/reformer combinations. EP 3311911 Al discloses a fuel reforming device that generates hydrogen by reform- ing a hydrocarbon based raw material. The device comprises a gas injection inlet, a burner, a combustion chamber and a reforming reactor. Further the device can be used in a fuel cell system. The exhaust gas generated in the combustion chamber may sup- ply heat to the reforming reactor while moving to the top of the casing. WO2018/189375 discloses a burner inside a tubular reformer. The thermal energy is provided by thermal conduction through the wall therein between as well as through the heating of the gas in heat exchanger. Although, the reformer/burner unit is com- pact, it lacks a thermal protection for the reformer. As it reads on page 11 lines 14-18 in WO2018/189375, there is a good transport of heat from the burner to the reformer due to the reformer is surrounded by the reformer-catalyzer along all of its length. Under aggressive start-up, however, the reformer is correspondingly heated by the thermal conductivity through the wall between the burner, and the reformer is not properly protected against degradation by overheating.

US5019463 discloses a fuel cell system with a burner upstream of a reformer where the exhaust gas from the heater is guided around the reformer and discharged through an exhaust pipe and through atmospheric gas outlet. For startup, the gas is selectively guided by a valve to pipe to heat the air ports and cooling jacket of the fuel cell. Alt- hough, there is a selective diversion of gas, it does not protect the reformer under quick aggressive startup heating, as the diversion is downstream of the reformer.

US5998053 discloses a fuel cell system in which exhaust gas can be selectively guid- ed by a valve to the fuel cell system, which also includes the reformer, or to a heating system for a room. Although, there is a selective diversion of gas upstream of the re- former, it does not protect the reformer under quick aggressive startup heating.

DK 180247 B1 3 It would be desirable to provide a better way of protecting the reformer against over- heating in startup situation.

DESCRIPTION / SUMMARY OF THE INVENTION It is an objective of the invention to provide an improvement in the art. In particular, it is an objective to provide a fuel cell system with a burner/reformer unit and including heat protection of the reformer during startup of the fuel cell system by heat from the exhaust gas of the burner. This objective is achieved with a system and method as described in the following.

The invention differs from the above disclosures in that a valve system is employed for selectively guiding exhaust gas from the burner either to the reformer for heating the reformer, especially during normal operation, or to a heat exchanger while bypass- ing the reformer in startup situations in order to heat the fuel cell stack before starting heating the reformer.

In view of EP 3311911 Al, the subject matter disclosed differs in specifying a fuel cell system comprises a bypass valve in communication with the burner-chamber and configured for regulating flow of the flue gas between a) flow along the reformer walls, and b) flow out of the burner-chamber through a flue gas outlet conduit, bypass- ing the reformer walls for preventing it from flowing along the reformer walls.

The system and method is particular useful in a compact burner/reformer unit where the heat from the burner is reaching the reformer by conduction of heat through the intermediate walls.

Optionally, the valve system is be configured for regulating the exhaust gas from the burner to only partially pass the reformer so that the temperature of the reformer can be regulated, for example continuously regulated by adjusting the opening of the valve for the partial flow to the reformer. The remaining part of the how flue gas flow is

DK 180247 B1 4 advantageously guided to the downstream heat exchanger which transfers heat to the cooling circuit. A gradual regulation of the partial bypass is useful in start-up situa- tion, as the reformer can be heated gently and controlled.

In order to prevent the reformer from overheating during the aggressive startup, the reformer is at least partially thermally insulated from the burner. For example, the reformer walls are provided at a distance from the burner wall. In order to regulate such thermal insulation additionally, some embodiments comprise an air flow regula- tion in which ambient air is guided along a space between the burner and the reformer so that increased air flow along the reformer thermally insulates the reformer catalyzer from the hot walls of the central burner.

The invention is explained in more detail in the following.

The fuel cell system comprises a fuel cell, typically a fuel cell stack. Herein, the term fuel cell is used for a single fuel cell as well as for multiple 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, differentiating HTPEM fuel cell from low temper- ature PEM fuel cells, the latter operating at temperatures below 100 degrees Celsius, for example at 70 degrees Celsius. The operating temperature of HTPEM fuel cells is the range of 120 to 200 degrees Celsius, for example in the range of 160 to 170 de- grees Celsius. The electrolyte membrane in the HTPEM fuel cell is mineral acid based, typically a polymer film, for example polybenzimidazole doped with phosphor- ic acid. HTPEM fuel cells are advantageous in being tolerant to relatively high CO concentration and are therefore not requiring PrOx reactors between the reformer and the fuel cell stack, why simple, lightweight and inexpensive reformers can be used, which minimizes the overall size and weight of the system in line with the purpose of providing compact fuel cell systems, for example for automobile industry.

DK 180247 B1 The fuel cell is used to create electricity, for example for driving a vehicle. In order to provide a buffer for the produced electricity, typically a battery system is provided in electrical connection with the fuel cell.

5 A cooling circuit is provided for recirculating coolant through the fuel cell for adjust- ing the temperature of the fuel cell with the coolant. During normal operation, the cooling circuit is taking up heat from the fuel cell in order to keep the temperature stable and in an optimized range. For example, the temperature of the fuel cell is 170 degrees Celsius, and the coolant has a temperature of 160 degrees Celsius at the en- trance of the fuel cell. A reformer with a catalyzer is used for catalytic conversion of fuel into syngas used in the fuel cell for production of electricity. Accordingly, the reformer is conduit- connected to the anode side of the fuel cell. The reformer comprises a catalyzer inside a reformer housing, which has reformer walls. For the catalytic reaction in the reformer, the provided liquid fuel is evaporated in an evaporator that is conduit-connected on its downstream side by a fuel vapor conduit to the reformer. The upstream side of the evaporator is conduit-connected to a liquid fuel supply, for example for receiving a mix of liquid methanol and water. For heating the reformer to the proper catalytic conversion temperature, for example in the range of 250-300 degrees Celsius, flue gas, for example at a temperature in the range of 350-400 degrees Celsius, is provided from a burner. The burner comprises a burner-chamber inside burner walls and is configured for providing the flue gas by burning fuel or off-gas from the anode or both. Typically, the burning is a catalytic burning by a burner-catalyzer, for example in the form of pellets. The burner-chamber is in fluid-flow communication with the reformer walls so that the flue gas is flowing from the burner-chamber to and along the reformer walls and transferring heat from the flue gas to the reformer walls for heating the catalyzer by heat transfer through the reformer walls. In normal operation, the flue gas from the burner is passing along the reformer walls and heats them. After the transfer of the thermal energy from the flue gas to the re-

DK 180247 B1 6 former walls, remaining thermal energy can be used for heating other components, for example batteries that are used to store the electrical energy of the fuel cell, or for heating a vehicle cabin.

For example, the reformer walls are tubular and surround the burner walls. Such con- figuration results in a compact configuration useful for vehicles, as the available space is usually small.

During startup of the fuel cell system, the fuel cell has to be heated up for reaching a steady state electricity-producing state. Especially for use in vehicles, the start-up pro- cedure should be fast. For this reason, the burner is used strongly in the start-up phase, transferring its heat to the fuel cell. Typically, this is done in practice by transferring the heat from the flue gas to the coolant in the cooling cycle which during start-up is used as heating fluid, instead, to heat up the fuel cell to a temperature suitable for normal operation. However, as discussed above, a quick startup requires aggressive use of the burner and high temperature of the exhaust gas, which is advantageous in that efficient use of the burner at high temperature implies so-called clean burning, but which implies the risk for degradation of the reformer by overheating. In the following, different tech- nical solutions are given to this problem. A first method of preventing overheating of the reformer is achieved by providing a bypass valve in communication with the burner-chamber. The bypass valve is and configured for regulating flow of the flue gas between flow along the reformer walls and flow out of the burner-chamber through a flue gas outlet conduit, bypassing the reformer walls for preventing it from flowing along the reformer walls. By operating the bypass valve, the flow of the flue gas between flow along the reformer walls and flow that is bypassing the reformer walls is regulated.

For example, by the bypass valve, an exhaust path is selectively established in which a bypass-quantity of the flue gas is guided out of the burner-chamber through a flue gas outlet conduit, bypassing the reformer walls. The bypass quantity, which is a portion or all of the flue gas, is thus prevented from flowing along the reformer walls.

DK 180247 B1 7 For example for start-up, the bypass valve is set into a start-up configuration where all or most of the flue gas in the start-up phase is bypassing the reformer and the thermal energy from the flue gas is used instead to heat the fuel cell. This leads to a quick start-up procedure. After the start-up, the bypass valve is switched such that the flue gas is flowing along the reformer walls. In practical embodiments, the downstream side of the flue gas outlet conduit is in flow-communication with a heat exchanger for transfer of thermal energy from the flue gas to the coolant in the cooling circuit for transfer of thermal energy to the cool- ant. A bypass-quantity of more than half of the flue gas from the burner, for example all or substantially all of the flue gas is bypassing the reformer in start-up situation and reaches the heat exchanger for transfer of a majority of the thermal energy of the flue gas to the coolant and not to the reformer in order to heat the fuel cell to a normal op- eration temperature. Then, after the start-up, the bypass valve is set into a normal operation configuration, closing for bypassing the reformer and causing all of the flue gas to flow along the reformer walls for heating of the reformer catalyzer during normal operation.

In some embodiments, the bypass quantity can be changed during start-up of the fuel cell system for regulating the amount of thermal energy transferred from the burner to the reformer. For example, instead of first causing all flue gas to bypass the reformer and reach the heat exchanger until normal operation temperature of the fuel cell is reached, a minor portion is used for moderately heating the reformer during start-up, especially in the late phase of the start-up procedure. In case that the bypass valve is variable adjustable with respect to the amount of flue gas that bypasses the reformer, the temperature profile for heating the reformer during start-up can be regulated pre- cisely.

In principle, it is even possible to provide and regulate a bypass quantity during nor- mal operation.

DK 180247 B1 8 Optionally, in order to provide one way of a compact burner/reformer unit, the re- former walls are tubular and surround the burner walls. However, this is not strictly necessary, and a side-by-side configuration of the burner/reformer or a configuration of a burner sandwiched between two sections of the reformer is also possible.

Related to such configurations, a second method of preventing overheating of the re- former is explained in the following and suitable for combination with the first meth- od of preventing overheating, which was explained above. In this second method, an insulation space, for example filled with insulation material, is provided between the reformer walls and the burner walls for thermal insulation. Optionally, an air supply is provided for supplying air, optionally ambient air, into the insulation space for flow of the air through the insulation space. For example, the air- flow is along the walls of the reformer and not only insulate the reformer walls from the burner walls but also remove heat from the insulation space. It can even cool the reformer when heated by radiation from the burner wall. A further general improvement is mentioned in the following, which finds application not only with the above embodiments but which is useful as a general principle in fuel cells that use water for the fuel cell, such as a mix of methanol and water as explained above for the HTPEM fuel cell. In this improvement, the water from the fuel cell and/or from the burner is recycled. In some practical embodiments, the liquid fuel supply comprises a methanol reservoir for supplying methanol as well as a water supply for supplying water and for mixing the water with the methanol at a mixing point upstream of the evaporator, and the wa- ter supply is configured for supply of water that is recycled from the flue gas of the burner. For example, the water supply is part of a recycling circuit from the mixing point, through the evaporator, through the reformer, through the anode side of the fuel cell, through the burner, through a condenser, and back to the mixing point.

DK 180247 B1 9 Optionally, the recycling circuit is configured for adding water from the outlet of the cathode side of the fuel cell. In concrete embodiments, water and methanol are supplied to the mixing point, the mix of water and methanol are evaporated in an evaporator, the evaporated mix is fed as fuel into the reformer and catalytically reacted to syngas, which is then fed into the anode side of the fuel cell for producing off-gas. The off-gas from the anode is fed into the burner and burned, typically catalytically burned, to flue-gas, which is fed into a condenser for condensing water out of the flue gas. The water is fed back to the mix- ing point for repeating the cycle. Optionally, water from the outlet of the cathode side of the fuel cell is added to the recycling circuit. Optionally, in order to use the waste heat, the fuel cell system comprises a further heat exchanger for transfer of thermal energy from the coolant to air upstream of the burn- er. This is used for increasing the temperature of the air prior to entering the burner- chamber, which increases the energy efficacy of the fuel cell system.

SHORT DESCRIPTION OF THE DRAWINGS The invention will be explained in more detail with reference to the drawing, where FIG. 1 illustrates the compact burner/reformer unit in steady state operation; FIG. 2 illustrates a compact burner/reformer unit in start-up condition; FIG. 3 illustrates a flow diagram for the fuel cell system.

DETAILED DESCRIPTION / PREFERRED EMBODIMENT FIG. 1 illustrates a fuel cell system 1 with a fuel cell 16, typically fuel cell stack, and a burner/reformer unit 10 comprising a burner 7 and a reformer 6. The burner 7 com- prises a burner-chamber 7a for producing thermal energy for heating the reformer 6. Inside the burner-chamber 7a, typically, a burner-catalyser is provided, which howev- er is not shown for simplicity in FIG. 1 and 2.

DK 180247 B1 10 For example, the burner 7 is sandwiched between two layers of a heat exchange chamber 10b, inside which the reformer 6 is located. Alternatively, the burner 7 is of cylindrical shape and surrounded by a cylindrical tubular heat exchange chamber 10b, inside which a tubular cylindrical reformer 6 is arranged. Especially, the cylindrical configuration is compact, which is advantageous when using it in an automobile, where space is scarce. With reference to the configuration for normal operation as illustrated in FIG. 1, an air inlet 31 provides an air flow 32 into the burner-chamber 7a. Methanol is supplied to the burner 7 via a methanol dosing valve 21 (see FIG. 2 for a start-up situation). Through off-gas inlet 3 and injection-manifold 4, off-gas 3a from the anode of the fuel cell 16 enters the burner-chamber 7a and is used as fuel in the burner 7, as the off-gas contains fuel remains even after the reaction in the fuel cell 16. The flue gas 13a from the burning in the burner-chamber 7a is flowing into the heat exchange chamber 10a in which the reformer 6 is located. Containing substantial heat, the flue gas 13a heats the outer walls 6b of the reformer 6 by flowing along them. By conduction of thermal energy through the walls 6b, typical metal walls, of the reformer 6, the thermal energy is transferred to the catalyser 6a inside the space enclosed by the reformer walls 6b.

The heated catalyser 6a receives a mix of water and methanol from a mixing point 38 to which water has been supplied from a dosing supply 19 and methanol through a methanol dosing valve 20. The mix is catalysed into syngas that is fed into the anode of the fuel cell 16. The cathode is fed with air from a compressor 17 for providing oxygen.

After transfer of thermal energy from the flue gas 13a to the reformer 6, the flue gas 13a exits the burner/reformer unit 10 through flue gas conduit 9 into flue gas chamber

13. The cooled coolant in the cooling circuit 22 upstream of the fuel cell 16 receives further thermal energy from the flue gas 13b by heat exchange in the heat exchanger 14 downstream of the flue gas chamber 13.

From the cathode of the fuel cell 16, through connection 33, air and water steam is entering the flue gas chamber 13 and mix with the flue gas 13a before reaching the

DK 180247 B1 11 heat exchanger 14 for transfer of thermal energy to the coolant in the cooling circuit 22, through which the cooling-liquid is pumped by pump 15. After cooling the fuel cell 16 by take up of further thermal energy from the fuel cell 16, the coolant enters a further heat exchanger 18, through which heat is used for heat- ing other components, for example the battery in the vehicle or the cabin. Typical temperatures in centigrade for a HTPEM fuel cell stack during steady state operation: Fuel cell: 170 degrees Celsius Cooling-liquid: 160 degrees Celsius Catalyser in reformer: 280 degrees Celsius Flue gas: 350-400 degrees Celsius Whereas FIG. 1 illustrates the configuration during steady state operation, FIG. 2 il- lustrates a start-up situation. Special attention is drawn to the bypass valve 8 with a closure-member 8a that is regulated by an actuator 11 and which is used to direct the flue gas 13a such that the reformer 6 is bypassed in start-up situations.

As illustrated in FIG. 2, the closure-member 8a of the bypass valve 8 has been brought to a configuration where the closure-member 8a has been withdrawn from the valve seat 8b and the bypass valve 8 is fully open, so that the burner-chamber 7a is connect- ed to the flue gas chamber 13 for flow of the flue gas 13a from the burner-chamber 7a to the flue gas chamber 13 while bypassing the heat exchange chamber 10a that con- tains the reformer 6.

In the start-up situation, methanol 2a is received through a methanol inlet 2 and inject- ed into the burner-chamber 7a through methanol injection nozzle 5. For the burning, typically catalytic burning by a burner catalyser, air 32 is entering through air inlet 31.

As illustrated, the burner walls 7b are not abutting the reformer walls 6b, but an insu- lation space 10b is provided there between, preventing direct heat conduction from the burner-chamber walls 7b to the reformer walls 6b.

DK 180247 B1 12 As an option, in order to further protect the reformer 6 from the heat of the burner 7, a bypass airflow 12a can be established through air bypass-orifice 12, creating an air- flow from the air inlet 31 and along outer side of the burner-chamber 7a in the insula- tion space 10b between the burner-chamber and the reformer wall 6b. The airflow 12a not only further insulates the reformer 6 from the hot burner walls 7b of the burner- chamber 7 but also potentially removes heat from the reformer walls 6b. In the illus- trated embodiment, the bypass airflow 12a leaves the heat exchange chamber 10a and combines with the flue gas 13a in the flue gas chamber 13.

Optionally, it is possible to only partially open the bypass valve 8, in which case the closure-member 8a is only slightly withdrawn from the valve seat 8b. In this case, a portion of the flue gas 13a is passing through the heat exchange chamber 10a and an- other portion through the bypass valve 8. This is useful for adjusting the temperature of the reformer 6 and its catalyser 6a while preventing overheating of it. For example, in start-up situation, the bypass valve 8 is fully open initially for aggressive and quick heating of the fuel cell 16, followed by a partially closure of the bypass valve 8 in or- der to gradually and gently heat the reformer 6, until a sufficiently high temperature has been reached for the components to go into a normal steady state fuel cell opera- tion, and the bypass valve 8 is closed.

It is in principle possible to use the bypass valve 8 for regulating and optimizing, for example continuously, the heat transfer to the reformer 6 also during steady state op- eration of the fuel cell system.

FIG. 3 illustrates some of the flows through the fuel cell system. From the methanol tank 23, methanol 2a flows through methanol dosing valve 20 for being mixed with water from the water supply 19 at the mixing point 38. After evaporating in evapora- tor 28 downstream of the mixing point 38, the evaporated air/methanol mix is fed through inlet 24 into the reformer 6 for catalytic conversion into syngas which is then fed into the anode side of the fuel cell 16.

After catalytic reaction in the fuel cell for providing electricity, the partially converted syngas is exiting the anode side of the fuel cell as off-gas, which is entering the burn-

DK 180247 B1 13 er-chamber 7a through burner off-gas inlet 3 and used as fuel in the burner 7. Air is provided to the burner 7 through air inlet 31. The catalytically converted syngas/air mix in the burner-chamber 7a exits the burner as flue gas 13a through flue gas chamber 13 and mixes with water steam and remain- ing air from the cathode at mixing point 33. The hot mix leaves the flue gas chamber 13 and transfers heat in the heat exchanger 14 to the liquid in the cooling circuit 22. The steam is then condensed in condenser 27 and the water recycled for mixing with methanol 2a at mixing point 38 before entering the reformer 6.

Notice that, in the illustrated example, the steam from the cathode as well as the flue gas 13a, either directly from the burner or after heat transfer to the reformer 6, is recy- cled and mixed with methanol at mixing point 38 downstream of the condenser 27 for subsequent production of syngas. This implies that the water cycle for the fuel cell is a closed circuit.

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

Optionally, a secondary cooling circuit 35 through cooler 26 is provided for adjusting the temperature of other equipment, for example for heating and/or cooling the batter- ies 37 in a vehicle or for heating a cabin of a vehicle. As illustrated, for heating or cooling purposes, a heat exchanger 18 is provided for thermal energy exchange be- tween the primary cooling circuit 22 and the secondary cooling circuit 35. The heat from the coolant in the secondary cooling circuit 35, which is pumped by pump 36, is transferred through a corresponding heat exchanger 18 in order to keep the battery 37 at an advantageous fixed temperature, for example heated during start-up and cooled during steady state operation.

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

DK 180247 B1 14 A heat exchanger 30 upstream of the burner 7 is used for preheating air before enter- ing the burner 7, which is of advantage in order to increase the up-start speed and also for increasing the efficacy of the burner 7. Air is also heated in a different heat ex- changer 29 upstream of the cathode side of the fuel cell 16 for providing a temperature adjustment of the air from the compressor 17. Reference numbers 1) Fuel cell system 2) Methanol inlet for burner 7 2a) Methanol flow from methanol inlet 2 to chamber 7a 3) Burner inlet for off gas from the anode of the fuel cell 16 3a) Anode off gas 4) Injection manifold for injecting off gas or fuel into burner 7 5) Methanol injection nozzle 6) Reformer 6a) Catalyst in reformer 6 for Methanol to Hydrogen reforming methanol to hydrogen 7) Burner 7a) Burner-chamber 7b) Burner walls 8) Bypass valve 8a) Closure member of bypass valve 8 9) Flue gas outlet conduit 10) Burner/reformer unit 10a) Heat exchange chamber with reformer 6 10b) Insulation space between burner walls 7b and reformer walls 6b 11) Actuator for bypass valve 8 12) Air bypass orifice (optional) 13) Flue gas chamber 13a) Flue gas 14) Heat exchanger for heat exchange between flue gas 13a and cooling circuit 22 15) Circulation pump for liquid in cooling loop 2 16) Fuel cell 17) Air compressor 18) Auxiliary heat exchanger for example for heating of battery

DK 180247 B1 15 18a) Auxiliary heat exchanger for example for heating of cabin or other equipment 19) Water dosing supply for reformer 20) Methanol dosing valve for reformer 21) Methanol dosing valve for start-up burner 7 22) Primary cooling circuit for fuel cell

23) Methanol tank 24) Methanol/water mix inlet in reformer for syngas production 25) Cooling loop radiator 26) Battery cooler

27) Condenser 28) Evaporator for evaporating methanol/water mix for reformer 29) Heat exchanger for preheating air for cathode 30) Heat exchanger for preheating air for burner 7 31) Air inlet for burner 7

32) air flow from air inlet 31 to burner-chamber 7a 33) Connection for mixing air and steam from cathode to flue gas 13a 34) expansion container 35) Secondary cooling circuit for battery 37 and other purposes 36) Pump for battery cooling circuit 35

37) Battery 38) Mixing point for methanol and water

Claims

DK 180247 B1 1 PATENTKRAV

A fuel cell system comprising: - a fuel cell (16); - a cooling circuit (22) for recirculating refrigerant through the fuel cell (16) to adjust the temperature of the fuel cell (16) with the refrigerant; a reformer (6) comprising a catalyst (6a) enclosed by reformer walls (6b) and arranged for catalytic conversion of evaporated fuel to synthesis gas, the reformer (6) being tubularly connected to the anode side of the fuel cell (16) for providing synthesis gas to the fuel cell (16); - an evaporator (28) adapted to evaporate liquid fuel and tubed to the reformer (6) to provide the evaporated fuel to the reformer; - a fuel supply for liquid fuels (2, 19), which is piped to the evaporator, to provide liquid fuel to the evaporator; a burner (7) comprising a burner chamber (7a) within burner walls (7b), the burner chamber (7a) being arranged to provide combustion gas (13a) by burning anode flue gas or fuel, or both, wherein the burner the chamber (7a) is in fluid flow communication with the reformer walls (6b) for flowing the combustion gas (13a) from the burner chamber (7a) to and along the reformer walls (6b) for transferring heat from the combustion gas (13a) to the reformer walls ( 6b), to heat the catalyst (6a) by heat transfer through the reformer walls (6b); characterized in that the fuel cell system comprises a bypass valve (8) connected to the burner chamber (7a) and arranged to regulate flow of the combustion gas (13a) between a) flow along the reformer walls (6b), and b) flow out of the burner chamber (7a ) through a flue gas passage (9) which leads past the reformer walls (6b) to prevent the combustion gas from flowing along the reformer walls (6b).

Fuel cell system according to claim 1, wherein the fuel gas duct (9) on its downstream side is in flow communication with a heat exchanger (14) for the transfer of thermal energy

DK 180247 B1 2 from the combustion gas (13a) to the refrigerant in the refrigeration circuit (22), for the transfer of thermal energy to the refrigerant; wherein the bypass valve (8) is arranged to switch between a start-up setup mode during start-up of the fuel cell system and a normal operating mode after start-up, wherein the bypass valve in the start-up phase is configured to cause a bypass amount of more than half of the combustion gas (13a) from the burner is bypassed by the reformer (6) and to the heat exchanger (14) for transferring a majority of the thermal energy from the combustion gas (13a) to the coolant and not to the reformer (6), to heat the fuel cell to normal operating temperature, and where the pass valve (8) in the normal operating mode is configured to close the diverter of the reformer (6) and cause the combustion gas (13a) to flow along the reformer walls (6b), to heat the reformer catalyst (6a) after start-up.

A fuel cell system according to claim 2, wherein the bypass valve (8) is arranged to gradually adjust the bypass amount of the combustion gas (13a), which is diverted to the reformer (6), wherein the bypass amount ranges from a minimum amount to a maximum amount, where the minimum amount is less than 20% and the maximum amount is greater than 80% in relation to the total amount of combustion gas produced by the burner (7).

A fuel cell system according to any one of the preceding claims, wherein the reformer walls (6b) are tubular and enclose the burner walls (7b), and wherein an insulation gap (10b) is provided between the reformer walls (6b) and the burner walls (7b) for thermal insulation.

The fuel cell system of claim 4, wherein an air supply (12) is provided into the insulation gap (10b) for flow of air (12a) through the insulation gap (10b) to dissipate heat from the insulation gap (12a) during start-up conditions.

A fuel cell system according to any one of the preceding claims, wherein the fuel cell (16) is a high temperature proton electrolyte membrane, HTPEM, fuel cell (16) configured to operate at a temperature between 120 -200 degrees Celsius, and where the liquid fuel is a mixture of methanol (2a) and water.

DK 180247 B1 3

A fuel cell system according to any one of the preceding claims, wherein the supply of liquid fuel comprises a methanol reservoir (2) for supplying methanol (2a) as well as a water supply (19) for supplying water and for mixing the water with methanol at a mixing point (38) which is upstream of the evaporator (28), the water supply (19) being configured to supply water recirculated from the combustion gas (13a) of the burner (7).

A fuel cell system according to claim 7, wherein the water supply (19) is part of a recirculation circuit from the mixing site (38), through the evaporator (28), through the reformer (6), through the anode side of the fuel cell (16), through the burner (7), through a capacitor (27), and back to the mixing site (38).

The fuel cell system of claim 8, wherein the recirculation circuit is configured to supply water from the outlet of the cathode side of the fuel cell (16).

A fuel cell system according to any one of the preceding claims, comprising an additional heat exchanger (30) for transferring thermal energy from the coolant to air upstream of the burner (7), in order to increase the temperature of the air before it enters the combustion chamber (7a ).

A fuel cell system according to any one of the preceding claims, wherein the cooling circuit (22) is a primary cooling circuit, and wherein the fuel cell system comprises a secondary cooling circuit (35) with coolant separated from the coolant in a primary cooling circuit (22). ; wherein the fuel cell system comprises a secondary heat exchanger (18) for transferring thermal energy between the primary cooling circuit (22) and the secondary cooling circuit (35), the secondary cooling circuit (35) being thermally connected to a battery (37) and is configured to regulate the temperature of the battery (37).

Use of a fuel cell system according to any one of the preceding claims for an automobile.

A method of operating a fuel cell system, the fuel cell system comprising: - a fuel cell (16);

DK 180247 B1 4 - a cooling circuit (22) for recirculating coolant through the fuel cell (16) to adjust the temperature of the fuel cell (16) with the coolant; a reformer (6) comprising a catalyst (6a) enclosed by reformer walls (6b) and arranged for catalytic conversion of evaporated fuel to synthesis gas, the reformer (6) being tubularly connected to the anode side of the fuel cell (16) for providing synthesis gas to the fuel cell (16); - an evaporator (28) adapted to evaporate liquid fuel and tubed to the reformer (6) to provide the evaporated fuel to the reformer; - a fuel supply for liquid fuels (2, 19), which is piped to the evaporator to provide liquid fuel to the evaporator; a burner (7) comprising a combustion chamber (7a) within burner walls (7b), the combustion chamber (7a) being arranged to provide combustion gas (13a) by burning excess anode gas or fuel or both, the combustion chamber (7a) ) is a fluid flow connection with the reformer walls (6b) for flowing the combustion gas (13a) from the combustion chamber (7a) to and along the reformer walls (6b) for transferring heat from the combustion gas (13a) to the reformer walls (6b), for heating the catalyst (6a) by heat transfer through the reformer walls (6b); characterized in that the fuel cell system comprises a bypass valve (8) connected to the combustion chamber (7a) and arranged to regulate flow of the combustion gas (13a) between a) the flow along the reformer walls (6b), and b) the flow out of the combustion chamber (7a) ) through a flue gas duct (9) which is passed past the reformer walls (6b) to prevent it from flowing along the reformer walls (6b); and wherein the method comprises operating the bypass valve (8) and regulating the flow of combustion gas (13a) between flow along the reformer walls (6) and flow directed past the reformer walls (6b) as a result of the operation of the relief valve (8).

DK 180247 B1

The method of claim 13, wherein the method of starting the fuel cell comprises setting the bypass valve (8) in a start-up configuration and at the bypass valve (8) causing a bypass amount of more than half of the combustion gas (13a) from the burner (7) is bypassed around the reformer (6). 5

A method according to claim 14, wherein the fuel gas duct (9) on its downstream side is in flow communication with a heat exchanger (14) for transferring thermal energy from the combustion gas (13a) to the refrigerant in the refrigerant circuit (22) for transferring thermal energy to the refrigerant; wherein the method comprises causing a bypass amount of more than half of the combustion gas (13a) from the burner to be diverted to the reformer (6) and reaching the heat exchanger (14) for transferring a majority of thermal energy from the combustion gas (13a) to the refrigerant and not to the reformer (6), to heat the fuel cell to a normal operating temperature.

A method according to claim 14 or 15, wherein the method after start-up comprises setting up the bypass valve (8) in a normal operating configuration and closing the bypass of the combustion gas (13a) around the reformer (6), and causing all the combustion gas (13a) to flow along the reformer walls (6b) for heating the reformer catalyst (6a) during normal operation.

A method according to any one of claims 14-17, wherein the reformer walls (6b) are tubular and enclose the burner walls (7b), and wherein an insulating gap (10b) is provided between the reformer walls (6b). and the thermal insulation burner walls (7b), wherein an air supply (12) is provided into the insulation gap (10b) for flowing air (12a) through the insulation gap (10b) to dissipate heat from the insulation gap (10b) during start-up conditions. , the method during start-up comprising providing an air flow through the air supply (12) and into and along the insulation gap (10b) to dispose of heat from the insulation gap (12a).

A method according to any one of claims 14-17, wherein the fuel cell (16) is a high temperature proton electrolyte membrane, HTPEM, fuel cell (16) and the method comprises controlling the fuel cell at a temperature of between 120 ° C.

DK 180247 B1 6 200 degrees Celsius and to provide the liquid fuel as a mixture of methanol (2a) and water.

A method according to any one of claims 14-18, wherein the supply of liquid fuel comprises a methanol reservoir (2) for supplying methanol (2a) as well as a water supply (19) for supplying water and for mixing the water with methanol at a mixing point (38) which is upstream of the evaporator (28), where the water supply (19) is part of a recirculation circuit from the mixing point (38), through the evaporator (28), through the reformer (6), through the fuel cell (16) anode side, through the burner (7), through a condenser (27), and back to the mixing site (38), the method comprising supplying water and methanol to the mixing site (38), evaporating the mixture of water and methanol in an evaporator (28), supplying the evaporated mixture as fuel into the reformer (6) and catalytically converting the fuel to synthesis gas, supplying the synthesis gas into the anode side of the fuel cell (16) and producing excess gas, supplying the excess gas into a burner ( 7) and br turn the excess gas into combustion gas, supply the combustion gas into a condenser (27) and condense the water out of the combustion gas, supply the condensed water back to the mixing point (38) to repeat the cycle.

The method of claim 19, wherein the method comprises supplying water from the discharge of the cathode side of the fuel cell (16) to the recirculation circuit.

A method according to any one of claims 14-20, wherein the fuel cell system comprises an additional heat exchanger (30) for transferring thermal energy from the coolant to air upstream of the burner (7) and the method of the coolant comprises increasing the temperature before it enters the burner chamber (7a), to increase the energy efficiency of the fuel cell system.