A BURNER EVAPORATOR FOR A FUEL CELL SYSTEM

Abstract

A fuel cell system comprising a fuel cell stack, an evaporator for evaporating a mixture of methanol and water to be forwarded through a catalytic reformer for producing portions of free hydrogen. The fuel cell stack being composed of a number of proton exchange membrane fuel cells each featuring electrodes in form of an anode and a cathode for delivering an electric current. The liquid fuel using a. pre-evaporator, which. partly evaporates the fuel, followed by a. nozzle, which atomizes the fuel into a fine mist, before being passed to the final evaporation zone. This configuration ensures that liquid fuel for producing thermal, neat is converted into a form that facilitates a burner to achieve a quick heating up of the fuel, cell system into production mode.

Claims

1. A fuel cell system, comprising: a fuel cell stack comprising a plurality of proton exchange membrane fuel cells each featuring electrodes in the form of an anode and a cathode for delivering an electric current, wherein a reaction of free hydrogen into ionic form with contact to the anode being proportional to a flow of electric current between the electrodes; a catalytic reformer; an evaporator for evaporating a mixture of methanol and water to be fed through the catalytic reformer for producing portions of free hydrogen; a fluid fuel burner for providing heat for heating the system to a temperature level at which the fuel cell system can enter a state of steady current production; a burner fuel evaporator for heating of liquid fuel for the burner, the burner fuel evaporator being arranged in proximity to the burner in such a way that the burner fuel evaporator can absorb energy in the form of thermal heat from the burner in order to accelerate evaporation of liquid fuel into a fine mist of fuel to be led to the burner for producing thermal heat.

2. The system according to claim 1, wherein the burner fuel evaporator comprises: a first section forming a pre-evaporator, which partly evaporates the liquid fuel into drops, droplets and mist followed by: a second section forming a nozzle, which atomizes the liquid fuel into a fine mist before being passed to a third section, the third section providing a path for further heating and stabilizing the liquid fuel into its gas phase.

3. The system according to claim 2, wherein the pre-evaporator is formed by at least one cavity with substantially vertical orientated walls within which cavity is arranged at least one protruding rod, the walls and the at least one protruding rod forming heating elements for heating the liquid fuel.

4. The system according to claim 3, wherein the liquid fuel is forced into the cavity because of gravity and ricochets between the walls to atomize and evaporate the drops of liquid fuel into drops, droplets and mist.

5. The system according to claim 3, wherein the at least one protruding rod forms heating elements and is arranged to protrude in all directions within the evaporator cavity.

6. The system according to claim 3, wherein the at least one protruding rod forms heating elements and is formed with a plurality of sides.

7. The system according to claim 3, wherein a shape of the sides of the at least one protruding rod forms heating elements and varies from being flat to a curved or concave form.

8. The system according to claims 3, wherein the walls and the at least one protruding rod have edges forming a nose adapted for letting remaining liquid fuel form drops that, because of gravity, collide with protruding parts in the evaporator cavity.

9. The system according to claim 3, wherein the at least one protruding rod forms heating elements that are arranged in a matrix within the evaporator cavity.

10. The system according to claim 3, wherein the at least one protruding rod forms heating elements that are arranged as a grate comprising at least one rod-formed heating element.

11. The system according to claim 10, wherein the grate is formed as a net with several rod-formed heating elements arranged side by side and arranged crossing each other.

12. The system according to claim 11, wherein the grate includes sets of rod-formed heating elements joined together to form joints where rod-formed heating elements cross each other.

13. The system according to claim 3, wherein the pre-evaporator is separated into a number of chambers, each chamber comprising a gap for passing the liquid fuel drop, a negative angled substantially vertical portion of a wall followed by a positive angled substantially vertical portion of a wall followed by a gap that leads to another one of the chambers.

14. The system according to claim 3 wherein the pre-evaporator chamber has at least two mirrored sets of walls and the rod-like heating elements are arranged between the walls.

15. The system according to claim 13, wherein the gap between the chambers is adapted for forming a pressure nozzle for two-phase atomization of the liquid fuel into another of the chambers having a lower pressure.

16. The system according to claim 2, wherein the nozzle which atomizes the liquid fuel into a fine mist is formed by a passage with decreased cross section followed by a passage with a larger cross section for providing a pressure drop that supports the atomization of liquid fuel into mist.

17. The system according to claim 3, wherein a pressure-reducing nozzle for two-phase atomization forms a last outlet of the pre-evaporator cavity.

18. The system according to claim 2, wherein the evaporator for heating of liquid fuel for being passed to the reformer is arranged in such a way that the evaporator for heating of liquid fuel can absorb energy in the form of thermal heat from the burner in order to accelerate evaporation of liquid fuel into a fine mist of fuel to be led to the reformer for facilitating a quick startup of the fuel cell system.

19. The system according to claim 1, wherein the reformer is operable to reform the liquid fuel into a syngas to be passed to the fuel cell stack and is arranged in such a way that the reformer can absorb energy in form of thermal heat from the burner for facilitating a quick startup of the fuel cell system.

20. The system according to claim 1, wherein a cooling system, for cooling the fuel cell stack, includes a radiator arranged in such a way that the radiator can absorb energy in form of thermal heat from the burner for facilitating a quick startup of the fuel cell system.

21. A fuel cell system, comprising: a fuel cell stack comprising a plurality of proton exchange membrane fuel cells, each fuel cell comprising an anode and a cathode to deliver an electric current, wherein a reaction of free hydrogen into ionic form when contacting the anode is proportional to a flow of electric current between the anode and cathode; a catalytic reformer; an evaporator to evaporate a mixture of methanol and water to be fed through the catalytic reformer to produce portions of free hydrogen; a fuel burner to heat the system to a temperature level at which the fuel cell system can enter a state of steady current production; a burner fuel evaporator to heat liquid fuel for the burner, the burner fuel evaporator being arranged in proximity to the burner so that the burner fuel evaporator absorbs thermal heat from the burner in order to accelerate evaporation of liquid fuel into a mist of fuel, the mist of fuel being delivered to the burner for producing heat.

Description

DESCRIPTION OF THE DRAWING

[0045] Embodiments of the invention will be described with reference to the accompanying drawing, in which:

[0046] FIG. 1, shows an illustration of a fuel cell system,

[0047] FIG. 2, shows an illustration of a reformer module, with a burner fuel evaporator facility for evaporating liquid fuel into mist suitable for being burned by the burner and

[0048] FIG. 3, shows a detailed part of the burner fuel evaporator facility,

[0049] FIG. 1, of the drawing shows a fuel cell system 1 comprising a fuel cell stack 2, a number of supporting modules for supplying the fuel cell stack 2 with a modified fuel enabling the fuel cell stack 2 to produce a steady flow of electrical current. The exceed gas supplied to the fuel cell stack 2 but not being converted into electrical current, is fed to the burner 3. The exhaust gas is under normal operating conditions in the temperature area of 500 degrees Celsius and the energy content is recycled for preparing the syngas for fueling the fuel cell stack 2. More detailed, the exhaust is forwarded through the heat exchanger module 4, which takes up the heat from the exhaust and transfer the heat to the neighboring module in the stack here being the evaporator module 5. Further, the heat exchanger module 4 includes a radiator for the transfer of thermal energy in form of heat to the cooling system.

[0050] The cooling system serves in the start up phase as to provide thermal energy in form of heat to the fuel cell stack 2 and when the system is up and running to take away excess heat from the fuel cell stack 2. The thermal energy is used for evaporating and reforming the liquid fuel and the surplus is disposed off.

[0051] The liquid fuel, a mixture of methanol and water, is processed into a syngas consisting of free hydrogen for use in the fuel cell stack 2. In the evaporator module 5, the fuel is atomized and evaporated into the two-phase stage of the liquid fuel. Further, the evaporated gas is forwarded to the catalytic reformer module 6 that reforms the evaporated gas into a syngas consisting largely of free hydrogen. The catalytic reformer module includes a catalyst including copper, which in addition to heat converts the evaporated liquid fuel into the syngas directly usable by the fuel cell stack 2. The exhaust heat of the fuel cell stack 2 and the waste gas burner 3 is led through channels in the evaporator module 5 and catalytic reformer module 6. The temperature demand in the catalytic reformer 6 is highest, so thus the catalytic reformer 6 is arranged directly behind the burner 3. At a later stage of the exhaust channel the evaporator module 5 takes up the heat from the exhaust in order to evaporate the liquid fuel into gas.

[0052] The catalytic reformer module 6, shown in FIG. 2 also includes a burner fuel evaporator facility 7 for evaporating liquid fuel into mist suitable for being burned by the burner 3.

[0053] A detailed view of the burner fuel evaporator facility 7 is shown in FIG. 3 of the drawing. The liquid fuel is supplied via the inlet hole 8 of the burner fuel evaporator facility 7. The first part of the burner fuel evaporator facility 7 is formed as a pre-evaporator 9 through which the liquid fuel falls forced by gravity. The pre-evaporator 9 is in the present embodiment separated into five chambers 10, which according to specific embodiments could be more or fewer chambers.

[0054] When the liquid fuel is supplied via the inlet hole 8, it drops down in the first chamber and is further forwarded to the next chamber via a gap 11. The drop splashes into the next chamber 10 where it will hit a protruding rod 12. The protruding rod 12 serves partly as a heating element, and partly to atomize and evaporate the liquid fuel into droplets and mist. Since the droplets because of gravity fall further down the pre-evaporator 9, more protruding rods 12 are hit and the effect of evaporation is increased. As can be seen, the walls 13 of the pre-evaporator 9 are vertically angled in order to embrace the protruding rods 12 in such a way that the travel of liquid fuel floating down the walls 13 is prolonged and as most as possible of the liquid fuel is atomized or evaporated. Since the liquid fuel, especially directly after the inlet hole 8, splashes down the pre-evaporator 9, the liquid fuel and the droplets will ricochet from wall 13 to wall 13 and eventually hit the protruding rods 12, the arrangement will help to fully atomize and evaporate the liquid fuel and as such be a fine substitute for a spray injector. It has to be noted that the walls 13 are also heated and forms heating elements for heating and evaporating the liquid fuel. The protruding rods 12, which serves as heating elements, are as well as the walls 13 specially adapted for atomizing the liquid fuel and prolonging the travel of liquid fuel when it floats down the pre-evaporator 9. Experiments have shown that the quadratic shape of the protruding rods 12 have a fine effect on the atomization and evaporation of the liquid fuel. Triangular shapes also works fine. However, more edges support the capture of the drop and thus the time the drop is being subject to heating. The shapes of the edges are thus forming a nose 20 adapted for letting the remaining liquid fuel drip and thus because of gravity collide with protruding parts in the evaporator cavity, this nose 20 being arranged either on a rod-like heating element or a wall. As can be seen from FIG. 3, the nose can be applied on the rod-like heating element and/or on the wall.

[0055] The gaps 11 also serve as nozzles that because of the increased pressure helps the liquid fuel to evaporate and to keep the gas phase through the travel of the channel of the burner fuel evaporator facility 7.

[0056] A special pressure nozzle 14 is provided as the outlet of the the pre-evaporator. Because of the small passage, the pressure nozzle 14 provides a pressure fall that serves to blow leftovers of atomized liquid fuel further into a vertical channel that is the pathway 15 to the evaporator labyrinth channel 16 in which the atomized and evaporated fuel is further heated into a homogeneous gas mist. Since the pressure through the pressure nozzle 14 is considerable high, the effect is that it serves as a spray injection unit for the evaporator but without the previously mentioned drawbacks since it is a completely integrated feature of the burner fuel evaporator facility 7. The outlet 17 of the burner fuel evaporator leads directly to a cavity 18 that encloses the burner. Small injection nozzles 19 are provided for jet streaming the evaporated fuel in front of the burner, here preferably being a monolith.

[0057] For the understanding of the system, the system components are build as modules that can be fixed together by conventional screws and bolts. Pathways for e.g. exhaust gas are forwarded from module to module in order to take out as much thermal energy as possible and get a high efficacy of the system. Thus the modules can be joined using gaskets in-between as can be seen in FIG. 1 between the evaporator module 5 and reformer module 6.

[0058] The modules can be made by machining of a bar of material or by extrusion, die-casting or sintering etc. In the present embodiment, the evaporator module is provided using a bar of aluminum and carving out the channels for the evaporator on a first side of the bar.

[0059] Provided by the invention is an enhanced system for evaporating the liquid fuel using a burner fuel evaporator facility 7, which partly evaporates the fuel, followed by a nozzle 14, which atomizes the fuel into a fine mist, before being passed to the final evaporation zone 16 and let to the burner via the injection nozzles 19.