Burner system and method for providing thermal energy

Abstract

The present invention relates to a burner system for providing thermal energy, comprising: an evaporator device for evaporating a liquid alcohol fuel; a combustion air supply device; a burner device for burning a fuel mixture containing evaporated fuel and combustion air to provide an exhaust gas flow; a functional device for regulating the thermal energy of the exhaust gas flow, wherein the burner device provides the thermal energy for evaporation in the evaporation device during operation.

Description

Technical Field

[0001] The present invention relates to a burner system and method for providing thermal energy. Background Art

[0002] In the case of fossil energy sources such as coal, natural gas and oil, the carbon present is irreversibly converted into carbon dioxide during combustion, thereby contributing to the greenhouse effect, which leads to global warming.

[0003] An alternative to these energy sources is methanol. Methanol is a very widely used industrial chemical that is less popular as a fuel in Europe and the United States. In addition to its use as a fuel, methanol can also be used as energy storage through chemical reactions. The function of energy storage is based on its controlled absorption of a certain amount of energy, which can be released again with a time delay.

[0004] Surface burners are increasingly used for low-power burners, especially for domestic heating. According to this principle, the burner head consists of a porous material. Highly heat-resistant metals or ceramic fibers are usually used for this purpose. The fuel and air are premixed and burned while flowing through the burner head. Due to the small flow channels, the heat of the reaction is well convected to the material of the burner head. The heat is radiated from the burner head to the wall of the boiler. The annealing temperature of the burner head is set between 700°C and 900°C. In this temperature range, the formation of thermal NOx is suppressed. Therefore, the burner is characterized by extremely low NOx emissions.

[0005] According to the shape of the burner head, burners are divided into flat burners, cylindrical burners and hemispherical burners.

[0006] "Ceramic foam burner" is known as a flat burner head. In this burner, the gas-air mixture flows through the burner head made of ceramic foam and ignites on its inner surface. Combustion takes place on the porous surface.

[0007] Magma burners are known as burners with a cylindrical head. Its head consists of a stainless steel screen surrounded by a ceramic fiber layer. The fine-grained ceramic layer contains aluminum silicate inclusions to achieve higher heat resistance. The gas-air mixture is supplied in the form of a kink.

[0008] The burner head with a hemispherical shape is a matrix burner. The surface consists of a high-alloy stainless steel wire mesh.

[0009] Fuel cells are self-generating cells that convert the chemical reaction energy of a continuously supplied fuel and an oxidant into electrical energy. Different types are classified based on the electrolyte on the one hand (e.g. polymer electrolyte membrane fuel cell PEMFC) and on the other hand on the fuel used (e.g. DMFC).

[0010] WO 2010 / 066900 A1 discloses a humidifying unit for supplying a carrier gas containing fuel and water vapor to supply a fuel cell. The humidifying unit includes a humidifying space designed to receive a liquid containing fuel, an inlet leading to the humidifying space to supply the liquid containing fuel, and another inlet leading to the humidifying space to supply the carrier gas, so that the carrier gas contacts the liquid in the humidifying space. In addition, an outlet for discharging the carrier gas containing gaseous fuel is provided, and a control device is provided, which sets the liquid containing fuel in the humidifying chamber to a temperature below its boiling temperature. The control device is designed so that the vapor pressure of the fuel and water vapor is adjusted by adjusting the fuel concentration and temperature of the liquid containing fuel.

[0011] WO 2015 / 110545 A1 discloses a fuel cell system for thermally coupled reforming and reformate processing. The system includes a fuel cell stack having an anode inlet, an anode outlet, a cathode inlet and a cathode outlet, and a steam reforming reformer thermally coupled to the fuel cell stack to provide an anode fluid containing reformed fuel, the steam reforming reformer being connected upstream of the anode inlet. The fuel cell stack and the reformer device are thermally coupled so that the waste heat of the fuel cell stack is transferred to the reformer device by heat conduction and is partially used to operate the reformer device, and at least one processing device arranged between the reformer device and the anode inlet is provided for removing and / or reforming unreformed fuel and / or substances harmful to the fuel cell stack from the anode fluid, and the operating temperature of the fuel cell stack is in the range between 140°C and 230°C.

[0012] In order to bring the fuel cell stack to its operating temperature, electrical heating means are usually provided.

[0013] EP 2 706 052 A3 discloses a method and a device for using methanol in an internal combustion engine. The corresponding system can be heated by means of a parking heater in order to start the system.

[0014] US 5 372 115 A discloses a fuel system for a diesel internal combustion engine which can be operated with methanol and other liquid fuels in the manner of a dual-fuel system.

[0015] An oil vaporizing burner from the company Buderus is known. Here, it is intended to inject heating oil into the strongly preheated burner air. The surface area of ​​the heating oil is increased by atomization during injection by means of an injection valve, and the energy required for vaporization is provided by the introduction of hot air.

[0016] EP 1 703 578 A1 discloses a gas powered starting system for a reformer fuel cell system.

[0017] This includes at least one reformer, a fuel cell and a burner arranged outside the fuel cell, such as a low flame height surface burner, for example, a burner having a ceramic or metal surface or a surface made of a fiber material (such as a ceramic fiber mat coated with silicon carbide), to heat the reformer and the fuel cell stack.

[0018] DE 199 10 387 A1 describes a fuel cell with a battery and a heating device. The heat provided by the heating device can be used to heat the fuel cell stack. In the fuel cell, at least one process gas channel can be provided in order to provide thermal energy by means of a heat transfer medium. The heating device is defined as any heatable space in which a heat transfer medium can also be heated using a heat exchanger. The heating device preferably comprises a heating element, such as a catalytic burner and / or an electric heating element or a reformer.

[0019] DE 199 31 061 A discloses a fuel cell system with a cooling circuit. A radiator is connected to the supply lines of the fuel and / or oxidant so that a corresponding heat exchange can take place. Thus, it should be possible to heat the gas / fluid flow of the fuel cell with the waste heat of the cooling system.

[0020] DE 272 1 818 A1 shows a burner for burning liquid fuels with an evaporator. The evaporator is heated only electrically.

[0021] DE 10 2008 057 146 B4 discloses a fuel-operated vehicle heater having a jet pump for the combustion air.

[0022] An evaporator burner with an evaporator is known from DE 10 2011 050 368 A1.

[0023] In DE 10 2012 101 580 A1, a mobile burner operated with liquid fuel has a primary combustion zone and a secondary combustion zone and an air guide device for recirculating combustion air in order to achieve a good mixing of combustion air and fuel. Another such burner is also known from DE 10 2014 103 814 A1.

[0024] EP 23 15 493 A1 discloses a resistance heating device for heating air supplied to a vehicle interior.

[0025] US 9,285,114 B2 relates to a diesel particulate filter (DPF).

[0026] DE 10 2009 026 266 A1 discloses a mobile heating device in which a fuel propellant jet is generated via an injector. Summary of the invention

[0027] It is therefore an object of the present invention to provide a burner system for generating thermal energy which is simple and inexpensive in design and safe and reliable in operation.

[0028] A further object was to provide an environmentally friendly and compact burner system which could be used flexibly.

[0029] This object is achieved by a device according to claim 1 and a method according to claim 9. Advantageous embodiments are indicated in the dependent claims.

[0030] The present invention relates to a burner system for providing thermal energy, comprising

[0031] an evaporator device for evaporating a liquid fuel,

[0032] Burner air supply,

[0033] a surface burner for combusting a fuel mixture comprising vaporized fuel and burner air to provide an exhaust gas flow,

[0034] a shielding plate having openings for transferring and controlling the heat energy of the exhaust gas stream, the burner device providing the heat energy and vaporization temperature required for complete vaporization of the fuel in the evaporator device in operation, and

[0035] A tertiary air supply device is used to supply tertiary air to control the temperature of the exhaust gas flow by mixing with the tertiary air to form a hot gas flow.

[0036] The burner air supply device is also referred to below as primary / secondary air device.

[0037] In the context of the present invention, complete vaporization of the fuel (preferably methanol) is understood to be a complete phase change of the liquid or liquid mixture from the boiling temperature of the liquid or liquid mixture or above its boiling temperature to the gaseous aggregate state.

[0038] The evaporation temperature required for complete evaporation depends on the fuel used. For example, in the case of methanol, the evaporation temperature ranges between 64.7°C and about 150°C.

[0039] The surface burner can also be designed as another suitable burner device, such as a volume burner or a catalytic burner with ceramic or metal foam, whereby the catalytic coating can be applied to the ceramic, metal monolith or also to the foam or sheet.

[0040] The tertiary air supplied by the tertiary air device makes it possible to adjust or control the output temperature of the useful or hot gas flow during operation of the burner.

[0041] With the burner system according to the invention, the fuel and the burner air can be adjusted or controlled independently of one another in order to adjust the power or the temperature of the hot air flow both by changing the air λ and via a constant air λ when reducing (or increasing) the fuel and (and / or) the air.

[0042] Additionally, when the burner assembly or surface burner is not operating, the tertiary air may be used to cool another assembly, such as a fuel cell stack.

[0043] A thermal sensor may be provided in front of a blower or fan of the tertiary air supply device to prevent the tertiary air supply device from overheating.

[0044] Ambient air (tertiary air) delivered via the tertiary air device is mixed with the exhaust gas so that its temperature is cooled both to the desired initial temperature and to a level suitable for evaporation.

[0045] By means of the burner arrangement according to the invention, therefore, the temperature of the evaporator arrangement can be actively controlled.Overheating of the evaporator can be prevented by supplying tertiary air.

[0046] In combination with the shielding plate or baffle (functional device), this design allows the use of very thermally conductive materials, such as aluminum, in the evaporator device. In addition, the controlled temperature of the evaporator device can also successfully prevent thermal decomposition of the fuel, which would otherwise lead to soot production and thus to clogging of the evaporator device and damage to the burner device or surface burner.

[0047] The shielding plate or baffle (functional device) itself is preferably a passive element, the control being carried out via tertiary air (tertiary air device; tertiary air blower) or air flow. There is no exhaust gas recirculation. Such recirculation is also not necessary, since the surface burner enables a cleaner combustion. In addition, there is no need to further preheat the surface burner by exhaust gas during operation, since the fuel vapor is already sufficiently superheated in the evaporator device and sufficient energy is already returned from the burner surface via heat conduction. In addition, the baffle not only controls the thermal energy input into the evaporator device, but also controls the temperature level of the hot gas flow, which can then be used, for example, to heat the fuel cell stack.

[0048] The dampers and tertiary air device are designed so that the temperature level of the hot gas applied to the evaporator device can be adjusted and the output temperature of the burner can be controlled.

[0049] Surface burners do not require any special flame stabilization measures, as this can already be accomplished with the metal fiber surface. The fuel-steam-air mixture can also be provided with swirl in the burner's spiral, but this only serves to mix and distribute the fuel gas over the cross section of the burner surface.

[0050] The shielding plate or baffle comprises an opening for transferring and regulating or controlling the heat energy of the exhaust gas flow and / or can be designed to be used for heat shielding the evaporator device. In addition, it can be proposed that the area of ​​the opening of the shielding plate can be changed or enlarged or reduced by means of a corresponding adjustment device in order to carry out a corresponding control.

[0051] Thus, the shield plate provides radiation shielding to the evaporator device, as the surface burners are operated in radiation mode and the hot burner exhaust is mixed with tertiary air in order to reduce the overall exhaust temperature. This also has the effect that the temperature applied to the evaporator device is not within the range of thermal decomposition of the fuel. In this way, controlled superheating of the fuel vapor enables the use of cheaper valves and seals in the vapor line.

[0052] The shielding plate may be, for example, a stainless steel plate having a suitable thickness.

[0053] The shielding plate can be part of the evaporator chamber of the evaporator device and is therefore an integral part of the evaporator device. In this case, the shielding plate or baffle has an influence on the temperature distribution and uniformity towards the evaporator chamber.

[0054] In order to protect the downstream heat exchanger of the evaporator device from excessive heat input by radiation, the shielding plate may have fins to absorb the radiation energy and bring the heat input to a suitable level by dissipating the heat via convection.

[0055] Functional devices or shielding plates are designed to shield and / or control heat flow.

[0056] In the absence of a shielding plate, there is a risk that the heat transfer by thermal radiation (the burner arrangement is operated in radiation mode to form a low combustion consumption and has a combustion chamber of shallow depth to keep the installation space as small as possible) is so strong that the material of the heat transfer arrangement surrounding the evaporation space will melt even if the gases flowing through have been reduced to below the melting point by the tertiary air.

[0057] The shield itself can also be cooled by means of tertiary air, otherwise it will start to glow after a while and then the radiation part of the heat transfer increases again and can lead to the same problems as without the shield. The shield is basically a heat transfer heat exchanger, where heat energy is absorbed in the form of more radiation and less convection, and heat energy is emitted in the form of more convection and less radiation.

[0058] The evaporator device can be coupled to the burner device via the shielding plate so that the thermal energy of the exhaust gas flow of the burner device is used in operation after a start-up phase to completely evaporate the liquid fuel in the evaporator device.

[0059] In the fuel system according to the invention, neither a powerful fuel pump nor a nozzle for atomizing the fuel is provided. Therefore, according to the invention, it is intended to completely vaporize the fuel in the evaporator device.

[0060] The evaporator device can preferably be of closed design. In the context of the present invention, a closed evaporator device means that the liquid fuel evaporates in an evaporator chamber, the outlet of which is connected to the inlet of the burner device only via a pipe section (steam pipe). The liquid fuel is supplied to the evaporator chamber via the corresponding inlet, which is otherwise closed.

[0061] The burner system according to the present invention can feed fuel to the evaporator chamber with a simply constructed fuel pump, because the evaporator device can ensure uniform evaporation in the case of unstable fuel delivery.

[0062] The evaporator device of the burner system only requires one evaporation branch, instead of two or more evaporation branches that must be controlled via valves. The electric heater in the evaporator device can be shut down in stages based on empirical values ​​(temperature detection can also be performed). How these empirical values ​​are determined is described in detail in the following example.

[0063] Furthermore, in the burner system according to the invention, fuel and burner air can be controlled independently of one another in order to carry out power regulation by varying the air lambda and by keeping the air lambda constant while reducing fuel and air.

[0064] The above advantages are described in more detail in the following examples.

[0065] The burner system may preferably be surrounded by a housing arrangement which is slightly spaced apart from the components of the burner system.

[0066] The thermal energy of the exhaust gas flow can be provided in the form of conditioned air (hot gas flow), whereby the thermal energy can be delivered directly or via a separate heat exchanger device to a device coupled to the burner system, whereby the device is an internal combustion engine or a fuel cell stack or battery or airway device for heating the interior of the vehicle.

[0067] The conditioned air is initially still diluted exhaust gas, which can then be fed to an air-to-air heat exchanger device to form conditioned air.

[0068] The following briefly lists various types of fuel cells that may be heated in conjunction with the burner system according to the present invention and their corresponding operating temperatures (OT).

[0069] -Alkaline fuel cell (AFC); OT: 60℃ to 100℃;

[0070] -Polymer electrolyte membrane fuel cell (PEMFC); OT: low temperature: 70℃ to 90℃; high temperature: 120℃ to 190℃;

[0071] - Direct methanol fuel cell (DMFC); OT: 60℃ to 130℃;

[0072] -Phosphoric acid fuel cell (PAFC); OT: 170°C to 200°C;

[0073] - Molten carbonate fuel cell (MCFC); OT: about 650°C;

[0074] -Solid oxide fuel cell (SOFC); OT: 900°C to 1000°C;

[0075] The conditioning air may be delivered or coupled to an oil circuit of the vehicle or an engine of the vehicle or a cooling circuit of the vehicle, for example via an air-to-air heat exchanger or an air-to-fluid heat exchanger, in order to preheat the engine, preferably an internal combustion engine.

[0076] Such a burner system may also form a thermal range extender and enable battery-powered vehicles to operate more independently of charging infrastructure and increase range in cold weather with general comfort.

[0077] Additionally, the car interior could be heated with cheap, also renewable, methanol rather than using electricity from expensive batteries.

[0078] For example, the vehicle interior can be heated via a burner system by means of an air-air heat exchanger. In this case, a similar construction as in EP 23 15 493 A1 can be provided, however, it uses a resistance heating device instead of a burner system according to the invention.

[0079] By integrating it into the vehicle's cooling system, the vehicle battery can also be kept at operating temperature. Compared to lithium-ion batteries, methanol has an energy density 35 times higher per kilogram.

[0080] In methanol engines, the burner system allows trouble-free starting without the need for a dual-fuel system.

[0081] With the burner system according to the invention, heat energy is thus provided by a clean liquid fuel. In the context of the invention, alcohols such as methanol, ethanol, 2-propanol, 2-butanol, etc. are particularly envisaged as liquid fuels. Fuels such as gasoline or paraffin or other liquid fuels with a boiling temperature of up to 350° C. can also be used.

[0082] In particular, the following advantages can be achieved using the burner system according to the invention:

[0083] -CO2 neutralization operation with renewable methanol

[0084] -Working with globally available methanol is >35% cheaper than diesel

[0085] - Quiet operation, less than 35dB(A)

[0086] -Stepless adjustment of heating power and temperature

[0087] -Compact installation size, high energy density, low fuel consumption

[0088] - Low emission operation due to surface burners combined with clean fuels

[0089] -Increase the range of battery electric vehicles in cold temperatures

[0090] -Suitable for continuous operation

[0091] -Easily adaptable to other fuels

[0092] -Keep batteries at operating temperature even in harsh environments

[0093] - Based on a surface burner with fan operated with methanol vapor

[0094] -Besides heating, it can also cool the fuel cell

[0095] - The output temperature of the hot air can be adjusted

[0096] - Low pressure loss when using simple, low-cost fans

[0097] -Can be used with already qualified metering pumps (discontinuous delivery)

[0098] - Robust, reliable and safe operation

[0099] In order to optimize the competitiveness of the fuel cell system compared to conventional generators, the problems mentioned at the outset regarding the start-up time and the electrical heating system when heating the fuel cell stack can now be solved, among other things, in conjunction with the burner system according to the invention.

[0100] For the start-up process, the fuel cell stack, for example of an HT-PEM fuel cell system, is no longer heated electrically but is heated to 140 to 230° C. or to 160 to 180° C. and in particular to approximately 165° C. by means of the exhaust gas flow of the burner system.

[0101] The burner arrangement can be designed as a surface or area burner and comprises a burner screen and a metal fiber mesh connected together, a diffuser, an ignition device and preferably a flame monitoring device.

[0102] Surface burners have cost and installation space advantages over catalytic burners.

[0103] In addition, the surface burner offers more freedom here, since it can be easily operated at slightly higher or lower loads without using more expensive catalysts. In addition, burners based on catalytic reactions have narrower power modulation limits (lower temperature limit (about 800° C.), since the catalyst is damaged at temperatures above this; higher air lambda required, and therefore higher exhaust gas losses; catalyst-dependent upper limit of the ratio between catalyst volume and volume flow, if this catalyst-dependent upper limit is exceeded, the catalyst no longer completely converts the fuel gas).

[0104] This surface burner has low fuel consumption, with the combustion chamber measuring height x width x depth = about 95 mm x 141 mm x 49 mm.

[0105] Another advantage of surface burners is that they are very pulsation-free and low-noise due to the laminar flow.

[0106] The mixture preparation preferably takes place before the burner surface (premix burner). For this purpose, a mixing spiral can be provided.

[0107] In principle, the burner device is suitable only for gaseous fuels. Preferably, completely vaporized methanol is provided for this purpose.

[0108] Known gas burner components in the form of flame monitoring devices may be provided for flame monitoring.

[0109] The primary air supply / secondary air supply may be provided for supplying primary air to form a fuel mixture which is supplied to the fuel vapor before combustion and / or for providing secondary air for cooling the burner arrangement, in particular the diffuser and / or the combustion chamber and / or for after-combustion.

[0110] The primary air is mixed with the vaporized fuel (methanol) to form a fuel mixture. If not enough primary air is available for complete primary combustion, only a portion of it is used. The secondary air is mixed with the primary exhaust gas and, depending on the operation, a portion is then converted or used only as a mixed gas.

[0111] The fuel can only be partially used (rich mixture). The primary air is either fully utilized (λ≤1) or there is still oxygen left due to lean operation (λ>1).

[0112] Therefore, the fuel-air ratio λ (λ) can be adjusted by specific fuel regulation and / or air regulation. At operating conditions λ<1, there is a rich mixture and the energy of the fuel may not be fully utilized. In operating conditions above λ≥1, the entire primary air is used (λ=1) or the oxygen molecules are kept above (λ>1). Corresponding control devices can be provided for adjustment.

[0113] Depending on the operating mode, secondary air provides the burner equipment with air for any necessary post-combustion. Secondary air provides the burner with sufficient oxygen to ensure complete combustion, even with rich combustion on the primary side.

[0114] The secondary air cools the combustion chamber walls and the diffuser, which allows the use of silicone seals on the diffuser. In this way, the thermal load on the combustion chamber housing is significantly reduced.

[0115] The temperature-controlled hot gas flows through or around the heat exchanger device of the evaporator or the evaporation chamber of the evaporator to heat the evaporator or provide energy for evaporation.

[0116] The temperature upstream of the heat exchanger and / or in the exhaust line may be measured with suitable temperature sensors in order to provide appropriate regulation or control to achieve the proper output temperature and not overheat the evaporator device.

[0117] The hot gases are generated by mixing the burner exhaust gas with the tertiary air directly behind the shielding plate or functional device and in front of the evaporator device in the flow direction.

[0118] In order to achieve a uniform mixing and flow distribution over the entire evaporator cross section, the correspondingly designed openings in the shielding plate are positioned so that they are directly located at the inlet opening of the tertiary air channel to the mixing chamber. The two air flows thus meet and mix at an angle of 90°. The tertiary air is mixed with the burner exhaust gas in order not to overheat the fuel vapor too much and to enable the use of low-cost standard valves between evaporator and burner.

[0119] The tertiary air channel can also be designed as a spiral, into which the combustion air is fed. In addition to the two air flows meeting at a 90° angle, further mixing can also be achieved in the spiral.

[0120] The evaporation in the evaporator device is thus performed via burner waste heat or via thermal energy contained in the exhaust gas flow, in order to save electrical energy during operation.The hot gas flows through the heat transfer device of the evaporation chamber.

[0121] Furthermore, a fuel supply device or a fuel pump may be provided for supplying the evaporator device with liquid alcohol fuel. In conjunction with the fuel cell system, this may be an existing anode pump or preferably a fluid pump of the fuel cell system.

[0122] The fuel supply preferably includes a fuel tank and a pump.

[0123] In addition, a mixing device may be provided in which fuel vapor generated in the evaporator device by complete evaporation is mixed with primary air. The mixing device is designed in a spiral shape and is integrally formed on a rear wall of a diffuser of the burner device.

[0124] By using shielding plates in combination with cooling of the burner exhaust gases via a tertiary air flow, aluminum with its good thermal conductivity properties can be used as material for the evaporator without being damaged by high combustion temperatures above the melting point of aluminum.

[0125] The following medium flows can be provided in the burner system according to the invention:

[0126] - Burner air, which consists of:

[0127] - Primary air: air that is used directly for combustion and that has been mixed with fuel vapor before combustion.

[0128] -Secondary air: air that flows around the diffuser at the edges into the combustion chamber to cool the diffuser and the combustion chamber. It can be used for secondary combustion, which may be necessary depending on the operating mode. Secondary air provides the burner with enough oxygen to ensure complete combustion, even with rich combustion on the primary side.

[0129] - hot gas consisting of:

[0130] - Exhaust gas: The total gas flow leaving the combustion chamber consisting of the primary air component / secondary air component and the gases produced during combustion.

[0131] - Tertiary air: Ambient air delivered via a second fan (tertiary air fan) which mixes with the exhaust air to cool its temperature to the desired initial temperature and a level suitable for evaporation.

[0132] - Fuel vapor: Fuel vapor is generated in the evaporator by complete evaporation and is mixed with the primary air in the mixing device.

[0133] According to a preferred embodiment of the invention, the 3 / 2-way valve is arranged in a pipe section which connects the outlet of the evaporator device to the fuel inlet or the mixing device of the burner device.

[0134] In this way, the fuel supply from the evaporator unit to the burner unit can be interrupted to ensure that the flame is extinguished within three seconds as required by the standard.

[0135] Since there is still liquid methanol in the lower region of the evaporator assembly, shutting down the fuel pump does not extinguish the flame in time, since the methanol still evaporates completely due to the existing waste heat from the burner assembly.

[0136] By providing a 3 / 2 way valve, the outlet of the evaporator can be kept open during heating.Methanol remaining in the evaporator after the last operation can be degassed without causing an increase in the evaporator pressure.

[0137] Since the internal pressure of the evaporator is approximately the same as the ambient pressure when the valve switches to the burner arrangement, there is no pressure discharge into the burner arrangement and the burner arrangement can be started correspondingly more gently with a controlled fuel / methanol / air mixture.

[0138] In order not to lose any methanol to the environment, the methanol degassed from the evaporator during the heating and cooling phases is returned to the burner system. The methanol is connected via a hose to a phase separation or condensation unit, where it is condensed and returned to the system. The degassed methanol is thus returned to the burner system. If the burner system is used in conjunction with a fuel cell system, the degassed methanol is fed to the fuel cell system or to the methanol tank of the system.

[0139] Another advantage of using a 3 / 2-way valve is that the evaporated and degassed methanol is used as a heat transfer medium during heating to preheat the evaporator and the pipes in the upper section more evenly. Since the heating device is integrated in the lower section of the evaporator, this section is correspondingly preheated to a greater extent, since the heat conduction of the material is limited. However, the evaporated methanol adds an additional heat transfer mechanism. If the evaporator is installed in the normal position, the methanol that is condensed again in the cold area of ​​the evaporator can flow back downwards and evaporate again.

[0140] To enhance this effect, a limited amount of methanol has been pumped into the evaporator system about 10 seconds before the valve switches to the burner, i.e. the evaporator system is already in operation. The methanol vapor that may still contain unvaporized liquid methanol then returns to the burner system accordingly.

[0141] This also makes it possible to eliminate the dead time of the evaporator device (the time between the entry of liquid methanol and the exit of gaseous methanol vapor) during the ignition phase of the burner device, since the evaporator device has already been passed before the ignition phase begins.

[0142] In addition, a method for providing thermal energy according to the present invention is provided, which includes the above-mentioned technical features and corresponding advantages.

[0143] A method for providing thermal energy comprises the following steps:

[0144] During the start-up phase, the evaporator device is heated by means of an electric heating device.

[0145] Completely vaporize the liquid fuel in the evaporator device,

[0146] feeding the fully vaporized fuel to a burner device, preferably a surface burner, and

[0147] combusting the vaporized fuel in a burner device to provide heat energy in the form of an exhaust gas stream,

[0148] During operation a portion of the thermal energy is used in operation of the burner system to vaporize the fuel in the evaporator device, so that the energy for vaporization in the evaporator is provided exclusively by the burner device.

[0149] The diffuser can also be preheated and electrically heated. Preferably, a second heating device is provided for this purpose, which can be regulated or controlled independently of the heating device of the evaporator.

[0150] The regulation or control of the thermal energy of the exhaust gas flow can take place between the burner device and the evaporator device via openings formed in the shielding plate or in the functional device.

[0151] The burner arrangement may comprise a surface burner for gaseous fuel, whereby completely vaporised fuel is combusted in the surface burner.

[0152] Primary air may be supplied to form the fuel mixture, the primary air being supplied to the fuel vapor prior to combustion, and / or

[0153] Secondary air may be supplied, which is provided for cooling the diffuser and / or the combustion chamber of the burner arrangement and / or for afterburning, wherein primary air and secondary air are supplied from a burner air supply arrangement, referred to as primary air / secondary air.

[0154] Tertiary air may be supplied to adjust the temperature of the hot exhaust gas flow by mixing with the tertiary air so that a hot gas flow is thereby formed, wherein control of the output temperature of the hot gas flow in burner operation is achieved via the tertiary air.

[0155] Via the 3 / 2-way valve, the outlet of the evaporator device can be kept open during the startup phase (heating of the evaporator device) and / or at the end of operation of the burner device, and the methanol remaining in the evaporator device can be degassed via the 3 / 2-way valve without causing a pressure increase in the evaporator device, wherein the internal pressure of the evaporator device corresponds approximately to the ambient pressure when the valve is switched to the burner device, so that no pressure is discharged in the burner device and the burner device is started with a controlled fuel-air mixture.

[0156] Alternatively, the mixing device (or its diffuser) can also be preheated during the start-up phase using an electrical heating device. BRIEF DESCRIPTION OF THE DRAWINGS

[0157] The present invention will be explained in more detail below with reference to the accompanying drawings. These contents are shown in the following figures:

[0158] Figure 1 Schematic representation of a fuel cell system which can be combined with a burner system according to the invention,

[0159] Figure 2 A perspective exploded view of a burner system according to the invention,

[0160] Figure 3 Schematic representation of the medium flow in a burner system,

[0161] Figure 4 Side view of a burner system with media flow,

[0162] Figure 5 Another side view of the burner system with media flow,

[0163] Figure 6 Another side view of the burner system with media flow. DETAILED DESCRIPTION

[0164] In the following, a fuel cell system 1 is first described, which can be combined with a burner system 20 according to the invention in order to achieve the above advantages ( Figure 1 ). The fuel cell system 1 corresponds essentially to the fuel cell systems described in WO 2010 / 066900 A1 and WO 2015 / 110545 A1, which are hereby fully incorporated by reference.

[0165] WO 2010 / 066900 A1 discloses a humidifying unit for providing a carrier gas containing fuel and water vapor to supply a fuel cell.

[0166] WO 2015 / 110545 A1 shows a fuel cell system for thermally coupled reforming and reformate production.

[0167] The fuel cell system 1 comprises a fuel cell stack 2 designed as a HT-PEMFC (High Temperature Polymer Electrolyte Fuel Cell). The high temperature fuel cell operates in a temperature range of 160° C. to 180° C. The required hydrogen is obtained from methanol by a reforming process and converted into electricity in the fuel cell 2 .

[0168] The carrier gas flow saturated with water and methanol vapor provided by the humidification unit 3 is used for powering the battery. This enables water to be recovered from the exhaust gas by means of a water cycle. This eliminates the need to add water externally and to use a premix.

[0169] The components and the mode of operation of the fuel cell system 1 are explained with reference to the anode circuit.

[0170] In the anode loop, two metering pumps 4, 5 deliver methanol from a methanol storage tank 13 and water to a humidification unit (media unit) 3. In the humidification unit 3, the carrier gas flow is enriched with methanol. The methanol reservoir 13 can also be used to supply a burner system 20.

[0171] The carrier gas flow is delivered from the anode outlet to the humidification unit 3 by the anode or fuel pump 6. The saturation of the carrier gas flow with water and methanol vapor is carried out in a temperature range of about 80°C, and then the saturated gas flows into the internal reformer unit 7 and the external reformer unit 8.

[0172] In the allothermen steam reforming process, water and methanol vapor are decomposed into hydrogen, carbon dioxide and carbon monoxide. The resulting reformed gas contains mainly hydrogen and is passed to the fuel cell stack 2.

[0173] After the hydrogen has been converted into electricity in the fuel cell stack 2, a large part of the reformed gas still contains carbon dioxide. The depleted reformed gas flows out of the anode and the cycle starts again with the anode pump.

[0174] The fuel cell is supplied with oxygen (air) by the cathode blower 9. The airflow of the cathode blower 9 absorbs water produced by power generation, which is condensed out in the heat exchanger and phase separator 14. The recovered water is pumped back to the humidification unit 3 by the metering pump 5.

[0175] The humidification device 3 is heated by the hot exhaust gas of the reformer devices 7, 8, the catalytic burner and the cathode waste heat. In order to keep the fuel cell stack 2 at operating temperature, the fuel cell stack is cooled by means of an air supply device 12. The air supply device 12 can be used as a tertiary air device or a burner air device of the burner system 20.

[0176] The burner system 20 according to the present invention can be used as a heating system for the fuel cell stack 2 of the fuel cell system 1 and is described below. Figures 2 to 6 ).

[0177] Since HT-PEMFC requires a certain starting temperature, this temperature of about 165° C. can be achieved by heating the fuel cell stack 2 by means of a burner system 20 .

[0178] Until now, the fuel cell stack has been heated by an electrical heating device. Heating plates are arranged around the fuel cell stack and are insulated from the outside. These heating plates require electricity throughout the heating process. The heating process takes about one hour and requires high electrical power. Therefore, the connected battery is first discharged in order to heat the fuel cell. Once the fuel cell has reached its temperature, it charges the battery and the electricity can be used.

[0179] Reducing power requirements through the burner system 20 is possible in the form of non-power supplies.

[0180] The burner system 20 preferably uses methanol in combination with a burner device 21 designed as an inline or surface burner. In this way, there is only low NOx generation and high exhaust gas temperatures.

[0181] The generated heat is dissipated to the fuel cell 2 via a tertiary air device 16 having a fan.

[0182] The burner system 20 ( Figures 2 to 6 ).

[0183] The burner system 20 has a housing device 23. The housing device 23 is formed by four interconnected plate modules, which are preferably made of vermiculite. These plate modules are connected to each other by threaded rods and supported by foam. Vermiculite has low thermal conductivity and can be formed as a non-combustible sheet material. The product is sold worldwide under the brand names "Fipro", "Miprotec", "bro-TECT", "Vermilite 2000" and "Thermax". Vermiculite has a high melting point of 1315°C and is non-conductive or electrically insulating. Silcawol 115-36A board can be used instead of vermiculite. Generally speaking, it is also possible to separate the functions and produce a metal housing with additional insulation (e.g., high-temperature glass wool). In particular, the housing device assumes the functions of insulation and medium guidance.

[0184] One of these plate modules is an end plate 24. An air inlet and a support surface for a diffuser 25 of the burner arrangement 21 are formed in the end plate 24.

[0185] Rectangular grooves for passage of the methanol line and the air line supplying the diffuser 25 are provided in the side edge or top wall of the end plate 24 which is located at the top in the vertical direction.

[0186] Another panel module forming a central panel 26 is mounted on the end panel 24. The side wall of the central panel 26 facing the end panel 25 provides a burner support 27 for receiving the burner arrangement 21 and the opposite side wall has a recess for receiving a baffle of an evaporator arrangement 28. The baffle forms a functional arrangement 29.

[0187] Like the end plates 24, the center plate 26 has grooves for the methanol and air lines.

[0188] Therefore, an installation space for the combustion device 21 is formed in a region between the end plate 24 and the center plate 26 .

[0189] The outlet plate 30 is connected to the center plate 26. A mounting space for the evaporator device 29 is provided between the center plate 26 and the outlet plate 30.

[0190] The front plate 31 is connected to the outlet plate 30 .

[0191] The housing device 23 is approximately in the shape of a rectangular parallelepiped due to the plate-shaped configuration. The top plate 33 is attached to the top wall of the housing device 23 .

[0192] The top plate 33 is used to place the tertiary air device 16, the burner air supply device 41, the solenoid valve and the air shaft. The burner air supply device 41 includes a metering orifice, a corresponding hose system and an air preheater (heating metal, equivalent to a hot air dryer). In the absence of an air preheater or a diffuser preheater, the burner cannot start or starts poorly due to condensation of methanol in the diffuser. The heater itself is located in the diffuser.

[0193] Alternatively, the diffuser can also be preheated with a directly integrated heating cartridge. In this case, the burner system has two heating cartridges.

[0194] The hot exhaust gas is divided and guided to the fuel cell stack 2 via the flow channels 33 formed in the front panel 31. The flow channels 33 of the front panel 31 are connected to the fuel cell stack 2 for optimal air guidance of the hot exhaust gas.

[0195] All panel modules are made of vermiculite and are supported with threaded rods using through holes on the sides of the panels.

[0196] Furthermore, the burner system comprises an evaporator device 28 and a heating cartridge. Methanol is vaporized in the evaporator device 28.

[0197] The evaporator device 28 includes an inlet pipe 42, a trough-shaped upper unit and a trough-shaped lower unit interconnected by a heat transfer member 45 having a heat exchanger structure disposed between the trough-shaped upper unit and the trough-shaped lower unit, and an outlet pipe. The trough-shaped upper member and the trough-shaped lower member and the heat transfer device 45 disposed therebetween form an evaporator space.

[0198] An inlet pipe 42 for injecting liquid methanol leads to the lower element 44 of the evaporator device 28. A heating cartridge with an output of 250 W is integrated into the lower wall. For this purpose, a fuel pump 47 is provided, which delivers methanol from a fuel tank 48.

[0199] When the evaporator device 48 is operated with waste heat or exhaust gas flow from the burner device 21, the heat transfer device 45 ensures good heat transfer for the evaporation of methanol. The evaporated methanol is concentrated at the top and conducted into the diffuser through the welded pipe via the solenoid valve. In order to increase the surface area of ​​the phase interface, the heat transfer device 45 is filled with fine metal wool, preferably stainless steel wool. The upper tank (upper element) of the evaporator device 28 is also filled with stainless steel wool, and the lower tank (lower element) into which the methanol first flows is filled with solid foam metal, which also includes the heating cartridge and ensures or improves the heat conduction from the heating cartridge to the evaporator device 28.

[0200] Alternatively, the lower tank can also be made of solid stainless steel material and the heating cartridge is located in an additional hole that is not fluidically connected to the methanol distribution chamber. The distribution chamber is preferably equipped with foamed metal.

[0201] The burner arrangement 21 comprises, among other things, a burner screen 27 , a diffuser 25 and electrodes.

[0202] The burner port 27 is made of a perforated stainless steel sheet with a metal fiber coating. The holes arranged in the edge region of the burner screen 27 are used for the secondary air flow 36. In addition, fastening holes are provided for fastening the electrodes.

[0203] The fuel mixture flows through the primary holes formed in the protrusions of the burner screen 27 .

[0204] A metal fiber mesh is welded or a porous ceramic structure is provided on the side of the burner screen 27 facing the center plate 26. This consists of a heat-resistant Fe-Cr-Al alloy, which provides oxidation resistance and high temperature resistance. This provides effective overheating protection and also prevents deformation and damage to the burner.

[0205] When the metal fiber is operated at low heat output, combustion occurs on the metal surface and the fiber glows brightly. The metal fiber is now operating in radiant mode.

[0206] Using metal fibers offers the following advantages:

[0207] -Precise combustion and significantly reduced noise

[0208] -High flame stability without flashback

[0209] -Dimensional stability / resistance to deformation

[0210] The mixing of gaseous fuel and air by the start-up burner fan is achieved through a diffuser located on the end plate.

[0211] On the upper side of the diffuser 27 and on the end plate there are inlets for the fuel and burner air supply 34 .

[0212] The evaporated methanol is directly added to the spiral of the diffuser 27. The spiral forms the mixing device 17. The air passes through the one-way membrane and is then divided into primary air 35 and secondary air 36. The primary air 35 is mixed with the methanol vapor in the spiral, and the secondary air 37 flows into the secondary holes around the diffuser 25. The fuel mixture of gas and air accumulates in the pre-combustion chamber and flows through the primary holes of the burner screen 27.

[0213] The primary air supply can be adjusted with the help of a stainless steel cap on the screw.

[0214] In addition, two electrodes (high voltage (HV) and flame monitoring (FW)) are screwed to the diffuser via the burner screen and extend in the combustion chamber onto the main area of ​​the burner screen. The ignition spark is positioned between the ignition electrode (HV) and the burner screen, which are electrically grounded to obtain a better flame monitoring signal.

[0215] Furthermore, the burner system 20 includes a tertiary air device 16 and a metering orifice.

[0216] The tertiary air device 16 comprises a radial fan with PWM (Pulse Width Modulation) support. PWM enables precise adjustment of the fan speed and therefore the controlled flow of the tertiary air. The sensor line provides information about the current fan speed and can indicate fan failures by means of a consistency check.

[0217] In addition to cooling the fuel cell 2, the tertiary fan 16 heats the fuel cell 2 by means of the hot exhaust gas of the burner arrangement 21 (comprising the exhaust gas flow 38 and the hot gas flow 39 of the tertiary air 37). The fan allows sufficient cooling of the fuel cell system 1 at any power level.

[0218] Another fan forms the burner air device 41 for supplying the burner air 34 (primary air 35 and secondary air 36). Like the tertiary air device 16, the burner air device 42 is a radial blower which delivers air via a flow metering device into the diffuser 25. The three-pin connection can adjust the speed via a corresponding control device.

[0219] An automatic burner control system is used to provide the ignition spark and detect the flame. Such an automatic burner control system detects a flame failure within a maximum of 0.8 seconds. A flame failure results in an internal error which also closes the solenoid valve for the fuel supply. The ignition cycle is integrated into the electronic system of the automatic burner control. For the start-up system, an ignition cycle of approximately 4 seconds to 20 seconds is used to ensure safe ignition of the fuel mixture. If the burner unit 21 has not started within the ignition phase, the control outputs an error.

[0220] The 3 / 2-way solenoid valve 19 is used to open and close the gas pipe of the burner and is located between the evaporator unit 28 and the diffuser 25. In the event of a fault, the valve closes in a very short time and stops the fuel supply to the burner unit. This ensures safe shutdown of the burner in the event of a fault. As soon as the automatic burner control unit operates the ignition process, the valve is in the open state, and the valve is closed in the basic state.

[0221] Another safety device is the safety temperature limiter. It is arranged in the pre-chamber, where the measuring sensor is fixed to the diffuser. The function is based on a temperature sensor filled with a liquid. If the set temperature range is exceeded, the liquid expands from the sensor via the transmission mechanism to the snap-action switch and the circuit is opened and the solenoid valve is closed. The influence of the ambient temperature is compensated by the bimetallic disk. The advantage of this component lies in its electromechanical design, which allows temperature measurement without additional auxiliary energy. To open the circuit again, the snap-action switch must be reset manually.

[0222] Alternatively, a thermal fuse can be used. For this purpose, it is mounted on the back of the diffuser in a provided recess. If the permissible temperature is exceeded in the event of a flashback, it opens the circuit to the valve, which then closes. To close the circuit again, the fuse must be replaced. The corresponding fuse of a thermal fuse melts irreversibly at approximately 200°C.

[0223] The burner device is spatially separated from the evaporator device by a functional device designed as a baffle with an opening.

[0224] Therefore, the basic concept of the burner system 20 is based on a surface burner with a fan that operates with methanol vapor. In addition, the system contains an evaporator to evaporate liquid methanol. A radial fan with a high throughput is used to dissipate hot or cold air.

[0225] The housing device 23 is made of four vermiculite plates which are supported together by means of a support system. The vermiculite plates have been ground for the internal components and provide two exhaust pipes for the outlet of the hot gases. The evaporator device, the baffle of the functional device 29 and the burner device 21 including the diffuser 25 and the burner screen 27 are positioned in the housing. In addition, a mounting device for the burner air device 41 with a solenoid valve is located on top of the starting system.

[0226] The fresh air supply is provided on the one hand by the burner air device (primary air 35 and secondary air 36) and on the other hand by the tertiary air device 16 (tertiary air 37). The burner air 34 flows through the diffuser 25 and is divided there into primary air 35 and secondary air 36. The primary air 35 is mixed with the air flow of the evaporator device 28 and flows through the central area of ​​the burner screen. The secondary air is guided through the outer holes of the burner screen 27 and is used to cool the combustion process and additionally supply oxygen to the combustion process.

[0227] The method of providing heat energy using the above-mentioned burner system is explained below. Figure 3 ).

[0228] During the start-up process, liquid methanol is supplied from the tank via a pump and a 3 / 2-way valve 19 to the evaporator device 28. In the evaporator device 28, the liquid methanol is first evaporated by an electric heating cartridge, passes through a solenoid valve and is mixed with the primary air 35 supplied by the primary / secondary air device or the burner air device 41 by means of a spiral.

[0229] The fuel-air mixture may be ignited and then ignited in the combustion chamber, with oxygen additionally supplied by secondary air 36 .

[0230] The evaporator outlet is open in the heating phase and is therefore pressure-free, whereby a check valve is not required as pump protection. As soon as the 3 / 2-way valve is actuated, the connection between the evaporator unit and the diffuser is opened, while the connection to the outlet is closed. The methanol escaping from the evaporator during the heating phase is returned to the system in the same way as the overflow from the methanol reservoir is fed into the phase separator cathode condensate. From there, it reaches the humidification unit and is converted into electricity.

[0231] With regard to the design orientation, arrangement and further advantages of the 3 / 2-way valve, reference is made to the corresponding paragraphs in the introduction of the description.

[0232] Subsequently, the hot exhaust gas 38 passes through the baffle of the functional device 29 and mixes with the tertiary air there to reduce its temperature. Thus, the tertiary air flow is first mixed with the exhaust gas, and then the hot gas or useful air flow 39 formed therefrom flows through the evaporator device 29 and then reaches the fuel cell stack. Otherwise, the evaporator may overheat. In this way, the evaporator device 28 no longer needs to be electrically heated. In particular, the hot air flow heats the heat transfer structure of the fuel cell stack and heats it to the operating temperature. Once the fuel cell stack has reached the required operating temperature, a cooling process is initiated with the help of the burner system.

[0233] The pump 6 or 47 and the primary / secondary air device 41 are gradually shut down and the tertiary air device 16 cools the fuel cell stack 2 to its desired operating temperature.

[0234] The burner system 20 is operated with a liquid fuel such as methanol. Thus, it is necessary to ensure a phase change of the liquid component into the gas phase. The phase change is necessary to ensure mixing of the energy carrier and the oxidant.

[0235] This process is called mixture preparation and leads to a reduction in pollutant emissions and is carried out first in the evaporator device and in the downstream mixing device. The mixing device is designed in the form of a spiral and is integrated into the rear wall of the diffuser of the burner device. The diffuser spreads the mixed fuel gas over the burner cross section so that it can flow evenly through the main area of ​​the burner screen. Due to the pressure loss when flowing through it, the burner screen also participates in the uniform distribution of the fuel gas over the burner cross section.

[0236] Thermal combustion of liquid fuels requires four sub-steps.

[0237] - Prepare fuel

[0238] - Evaporated fuel

[0239] -Preparation of mixture

[0240] - Combustion mixture (exothermic)

[0241] In a first substep, the liquid energy carrier is treated by surface amplification. This process is carried out using an atomization or spreading system. Atomization or spreading of the liquid fuel serves on the one hand for fluid transport and on the other hand for increasing the specific surface area. Since the evaporation of the liquid energy carrier takes place at the phase boundary surface, an increase in the reaction rate and thus a minimization of the treatment time can be achieved here.

[0242] The evaporation of a liquid medium into a gaseous component is called a phase change. In the case of vaporization in an air environment, the fuel is mixed with air and then vaporized. Direct vaporization first represents the vaporization of the fuel, which can then be mixed with air in gaseous form. In the case of the vaporization of methanol, methanol is added to the evaporator, and then the vaporized methanol is mixed with air in a mixing device. Due to the spatial separation of vaporization and mixing, an ignitable mixture of fuel and air exists only after the mixture has been formed.

[0243] The energy to ignite the fuel mixture is provided by the ignition control.

[0244] In particular, the evaporator device 28 is designed so that the evaporated fuel is discharged in a uniform or continuous volume flow rather than in a pulsating manner.

[0245] The burner system 20 according to the invention prevents the resulting pulsating combustion or pulsating evaporation by: 1. preventing the condensation of the fuel in the burner components due to the overheating of the burner vapor; 2. compensating the pump pulsation by a sponge-like structure (porous foam metal) in the evaporator device, which increases the surface area due to its low surface tension or capillary forces. Due to the pump stroke, the overflowing fuel can be temporarily stored in the internal structure and continuously released as vapor. In this way, the fuel can also be supplied to the evaporator device 28 at an unstable delivery rate by means of a simply constructed pump.

[0246] Furthermore, according to the invention, the temperature of the heat energy of the hot gas stream emitted by the burner system is adjustable. Since, for example, the hot gas temperature to which the fuel cell 2 can be subjected is limited, cold ambient air (tertiary air 37) is supplied to the exhaust gas stream 38 via the tertiary air device 16 in order to set or adjust it to a predetermined temperature. By controlling the fan speed of the fan of the tertiary air device 16 accordingly, the output temperature of the hot gas stream 39 can be controlled or adjusted very accurately (+ / -2°C).

[0247] The burner device 21 is designed so that its heat output (via temperature or volume flow) is adjustable or controllable. Depending on the application of the burner system, the required heating power may vary. In order to avoid the unfavorable cycle (on / off) of the burner device of the burner system 20 and all its disadvantages (cooling losses, electrical losses due to preheating, worse exhaust values ​​during startup), the power device of the burner can be widely modulated independently of the output temperature. This can be done on a small scale by adjusting the combustion λ with a constant burner air flow, or can be done on a large scale by keeping the burner λ constant while changing the burner air supply. However, the output temperature can be kept constant within the range of the delivery rate of the fan of the tertiary air device because the output gas mass flow varies according to the desired temperature level rather than the heat output.

[0248] The thermal power for starting the burner system 20 before it is put into operation and the evaporator device 28 is heated via the burner device 21 is provided by means of a heating cartridge. This is a simple and inexpensive solution.

[0249] In addition, the temperature in the evaporator device 28 can be detected via a thermocouple integrated in the heating cartridge.

[0250] This is done to avoid overheating of the heating element and thus damage to it, and to reduce the risk of pyrolysis of the fuel. During the start-up phase, the heating cartridge is adjusted to a maximum temperature below the pyrolysis temperature of the fuel used. For this purpose, the current supply to the heating cartridge is timed.

[0251] The evaporator unit can switch off the electric heater in stages with the aid of empirical values ​​(temperature detection is also possible). The following describes how to find such empirical values.

[0252] Preheat:

[0253] • The heating cartridge for electrical preheating of the evaporator can be controlled via pulse width modulation (PWM) control, for example with an interval of 50 ms.

[0254] • Adjustments are expected to be made in steps of, for example, 10%.

[0255] To extend the service life of the heating cartridge, use for example 80% of the maximum heating power, as this causes less strain on the heating conductor due to the currentless phase.

[0256] In addition, the temperature of the heating cylinder is detected by a thermal sensor integrated in the cylinder and is limited with the help of a control system to a maximum of 500° C. If the limit temperature is reached or exceeded, the heating power of the cylinder is gradually reduced until a constant limit temperature is reached.

[0257] One of the indicators for burner ignition is that the cartridge heater temperature must be above 450°C for more than 5 seconds (other indicators are preheating the diffuser to a minimum of 70°C and a heating time of at least 4 minutes).

[0258] The maximum temperature limit of 500°C is used not only to protect the heating cartridge but also to prevent the pyrolysis of methanol.

[0259] The temperature limits are stored in the software and can be adjusted variably depending on the fuel used.

[0260] To fade the heater:

[0261] - After the burner has successfully ignited (fuel valve open for more than 20 seconds and output temperature exceeds 150°C), heating is initially reduced to 30% power.

[0262] • Then, gradually reduce (1% increments) the heating power until the heating is completely switched off. Each step counts 32 system software clocks (500 ms).

[0263] · Thereby, the effective power adjustment is only carried out in steps of, for example, 10%, and due to the simpler control strategy, only the remaining steps in the middle are used. Thus, a control value of 39% is activated, which corresponds to an actual heating output of only 30%.

[0264] The number of system cycles required for each step can be adjusted individually depending on the fuel used.

[0265] In addition, the integrated temperature detection in the heating cartridge can be used to ensure that the temperature in the evaporator does not fall below the boiling temperature of the fuel used. This means that the heater shut-off procedure can also be delayed or reversed if necessary.

[0266] Reference numerals list

[0267] 1 Fuel Cell System

[0268] 2 Fuel cell stack

[0269] 3 Humidification unit

[0270] 4 Methanol metering pump

[0271] 5 Metering pump air

[0272] 6 Anode pump

[0273] 7 Internal Reformer

[0274] 8 External Reformer

[0275] 9 Cathode Blower

[0276] 10 Catalytic burner

[0277] 11 Cooling fins

[0278] 12 Air supply unit

[0279] 13 Methanol Storage Tanks

[0280] 14 Heat exchanger / phase separator 15

[0282] 16 Tertiary air device

[0283] 17 Mixing device 18

[0285] 19 3 / 2-way valve

[0286] 20 Burner System

[0287] 21 Burner equipment

[0288] 22 Tertiary air device

[0289] 23 Shell device

[0290] 24 End plate

[0291] 25 Diffuser

[0292] 26 Center Plate

[0293] 27 Burner Screen

[0294] 28 Evaporator device

[0295] 29 Functional Devices

[0296] 30 Exit plate

[0297] 31 Front panel

[0298] 32 Flow channels

[0299] 33 Top Panel

[0300] 34 Burner air

[0301] 35 Primary air

[0302] 36 Secondary Air

[0303] 37 Tertiary Air

[0304] 38 Exhaust Flow

[0305] 39 Thermals

[0306] 40 Methanol Flow

[0307] 41 Burner air supply unit

[0308] 42 Inlet pipe

[0309] 43 Top element

[0310] 44 subcomponents

[0311] 45 Heat transfer device

[0312] 46 Evaporator compartment

[0313] 47 Fuel Pump

[0314] 48 Methanol storage tanks.

Claims

1. A burner system for providing heat energy, comprising: an evaporator device for vaporizing a liquid fuel to provide a fully vaporized fuel, a burner air supply device for providing burner air, said burner air supply device being a primary / secondary air supply device which is arranged for supplying primary air in order to form a fuel mixture which is supplied to the fuel vapor before combustion and / or which is arranged for supplying secondary air for cooling the burner device and / or for after-combustion, a surface burner for combusting a fuel mixture comprising the fully vaporized fuel and the burner air to provide an exhaust gas flow, a shield plate having openings for transferring and controlling thermal energy of the exhaust gas flow of the surface burner, wherein: the surface burner is coupled to the evaporator device via the shield plate so that, in operation, the exhaust gas flow of the surface burner provides the thermal energy and evaporation temperature required for complete evaporation of the fuel in the evaporator device, and a tertiary air supply device for supplying the tertiary air to the exhaust flow to adjust the temperature of the exhaust flow by mixing with the tertiary air to form a hot air flow, wherein the shield plate provides radiation shielding to the evaporator device because the surface burner is operated in a radiation mode and the surface burner exhaust is mixed with the tertiary air to reduce the total exhaust temperature so that the total exhaust temperature is cooled to a desired level suitable for evaporation, and Therein, the supply of tertiary air is arranged between the shielding plate and the evaporator device.

2. The burner system according to claim 1, It is characterized in that The thermal energy of the exhaust gas flow can be provided in the form of diluted exhaust gas and delivered in the form of conditioned air via a separately designed heat exchanger arrangement to the burner system, which is an internal combustion engine or a fuel cell stack or battery.

3. The burner system according to claim 1, It is characterized in that The surface burner comprises a burner screen and a metal or ceramic fiber mesh, a diffuser, an ignition device and a flame monitoring device connected together.

4. The burner system according to claim 3, It is characterized in that The burner air supply device is provided for supplying secondary air for cooling the diffuser and / or the combustion chamber of the surface burner and / or for after-combustion.

5. The burner system according to any one of claims 1 to 3, It is characterized in that The evaporator device is of closed design, wherein the evaporator device comprises an evaporator space for evaporating the liquid fuel and wherein the outlet of the evaporator device is connected to the inlet of the surface burner only via a conduit section and the evaporator device has an inlet for supplying liquid fuel.

6. The burner system according to any one of claims 1 to 3, It is characterized in that A 3 / 2-way valve is arranged in a line section which connects the outlet of the evaporator device with the fuel inlet of the surface burner.

7. A method for providing thermal energy, comprising the following steps: During the start-up phase, the evaporator device is heated by means of an electric heating device. completely evaporating the liquid fuel in the evaporator device, feeding the fully vaporized fuel to the surface burners, and combusting the completely vaporized fuel in the surface combustor to provide thermal energy in the form of an exhaust gas stream, using a portion of the thermal energy to vaporize the fuel in the evaporator device during operation, so that the energy for vaporization in the evaporator device is provided solely by the surface burner, It is characterized in that regulation or control of the thermal energy of the exhaust gas flow between the surface burner and the evaporator device is carried out via openings formed in a shielding plate, supplying primary air to form the fuel mixture, the primary air being supplied to the fuel vapor prior to combustion, and / or providing secondary air for cooling the diffuser and / or the combustion chamber of the surface burner and / or using the secondary air for post-combustion, wherein the primary air and the secondary air are supplied from a burner air supply, referred to as primary / secondary air, supplying tertiary air in order to adjust the temperature of the hot exhaust gas flow by mixing with said tertiary air so that a hot gas flow is formed thereby, the output temperature of which in burner operation is controlled via said tertiary air independently of said combustion and combustion air, wherein the shield plate provides radiation shielding to the evaporator device because the surface burner is operated in a radiation mode and the surface burner exhaust is mixed with the tertiary air to reduce the total exhaust temperature so that the total exhaust temperature is cooled to a desired level suitable for evaporation, and Therein, the supply of tertiary air is arranged between the shielding plate and the evaporator device.

8. The method according to claim 7, It is characterized in that The outlet of the evaporator device is kept open via a 3 / 2-way valve during the startup phase and / or when operation of the surface burner ends, the liquid fuel remaining in the evaporator device can be degassed via the 3 / 2-way valve without a pressure increase occurring in the evaporator device, wherein the internal pressure of the evaporator device corresponds to the ambient pressure when the valve is switched to the surface burner, so that no pressure is discharged in the surface burner and the surface burner is started with a controlled fuel-air mixture.

9. The method according to claim 7 or 8, It is characterized in that A liquid fuel having a boiling temperature of up to 350° C. is provided as the fuel, the liquid fuel being methanol, ethanol, 2-propanol, 2-butanol, or gasoline or petroleum.

Images