BURNER SYSTEM, SYSTEM WITH SUCH A BURNER SYSTEM AND METHOD FOR PROVIDING THERMAL ENERGY BY MEANS OF SUCH A BURNER SYSTEM

Description

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

[0002] When fossil energy sources such as coal, gas and oil are burned, the carbon present is irreversibly converted into carbon dioxide, thus promoting the greenhouse effect, which leads to global warming.

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

[0004] Surface burners are increasingly being used for low-power burners, particularly those for domestic heating systems. With this principle, the burner head consists of a porous material. High-heat-resistant metal or ceramic fiber is typically used for this. Fuel and air are premixed and burn as they flow through the burner head. Due to the small flow channels, the reaction heat is easily convective to the burner head material. The heat radiates from the burner head to the boiler walls. The glow temperature of the burner head is between 700 °C and 900 °C. In this temperature range, the formation of thermal NO x is inhibited. The burners are therefore characterized by extremely low NO x emissions.

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

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

[0007] The Magma burner is known as a burner 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 greater heat resistance. The gas-air mixture is fed in a swirling pattern.

[0008] The Matrix burner features a hemispherical burner head. The surface is made of a high-alloy stainless steel wire mesh.

[0009] A fuel cell is a galvanic cell that converts the chemical reaction energy of a continuously supplied fuel and an oxidizer into electrical energy. The different types are classified based on the electrolyte (e.g., polymer electrolyte membrane fuel cell, PEMFC) and the fuel used (e.g., DMFC).

[0010] WO 2010 / 066900 A1 discloses a humidification unit for providing a carrier gas containing fuel and water vapor to supply a fuel cell. The humidification unit comprises a humidification chamber configured to receive a fuel-containing liquid, an inlet opening into the humidification chamber for supplying a fuel-containing liquid, and another inlet opening into the humidification chamber for supplying a carrier gas such that the carrier gas is in contact with the liquid in the humidification chamber. Furthermore, an outlet is provided for discharging the gaseous fuel-containing carrier gas, wherein a control device is provided that adjusts the fuel-containing liquid in the humidification chamber to a temperature below its boiling point.The control device is designed in such a way that the vapor pressures of the fuel and water vapor are regulated by adjusting the fuel concentration and the temperature of the fuel-containing liquid.

[0011] WO 2015 / 110545 A1 discloses a fuel cell system for thermally coupled reforming with reformate processing. This system comprises a fuel cell stack with an anode inlet, an anode outlet, a cathode inlet, and a cathode outlet, and a reformer device for steam reforming, thermally coupled to the fuel cell stack, for providing an anode fluid comprising reformed fuel, which reformer device is arranged upstream of the anode inlet.The fuel cell stack and the reformer device are thermally coupled in such a way that the waste heat of the fuel cell stack is transferred to the reformer device by means of thermal conduction and is used at least partially for the operation of the reformer device, and wherein at least one processing device arranged between the reformer device and the anode inlet is provided for removing and / or reforming non-reformed fuel and / or substances harmful to the fuel cell stack from the anode fluid, wherein an operating temperature of the fuel cell stack is in the range between 140°C and 230°C.

[0012] In order for fuel cell stacks to reach their operating temperature, an electrical heating device is usually provided.

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

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

[0015] Buderus has developed an oil vaporization burner. This involves injecting heating oil into highly preheated burner air. The surface area of ​​the heating oil is increased by atomization during injection via 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 comprises at least one reformer, one fuel cell and one burner arranged outside the fuel cell, such as a surface burner with a low flame height, e.g. a burner with a ceramic or metallic surface or a surface made of fiber materials, such as a ceramic fiber mat coated with silicon carbide, in order to heat the reformer and the fuel cell stack.

[0018] DE 199 10 387 A1 discloses a fuel cell battery with a stack and a heating device. The heat provided by the heating device is intended to be usable for heating the fuel cell stack. In this fuel cell battery, at least one process gas channel can be provided to provide thermal energy using a heat transfer medium. A heating device is any heatable space in which a heat transfer medium can be heated, also 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 heat sink is connected to a fuel and / or oxidant supply line in such a way that appropriate heat exchange can take place. This should make it possible to heat the fuel cell's gas / fluid streams with the waste heat from a cooling system.

[0020] DE 272 1 818 A1 describes a burner for burning liquid fuel with an evaporator. The evaporator is heated exclusively electrically.

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

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

[0023] DE 10 2012 101 580 A1 describes a liquid-fuel-operated, mobile burner with a primary and secondary combustion zone and an air guide device for recirculating the combustion air to ensure thorough mixing of the combustion air and fuel. Another such burner is also known from DE 10 2014 103 814 A1.

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

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

[0026] DE 10 2009 026 266 A1 discloses a mobile heating device in which a fuel jet is generated via an injector

[0027] CH 116 460 A, on which the two-part form of claim 1 is based, discloses a burner for an oil-fired furnace. DE 31 52 948 A1 describes a pressure vaporizer burner. JP S57 134606 A discloses a method for operating a burner system.

[0028] The object of the present invention is therefore to provide a burner system for generating thermal energy which is simple and cost-effective in construction and is safe and reliable in operation.

[0029] A further task is to provide an environmentally friendly and compact burner system that can be used flexibly.

[0030] This object is achieved with a device according to claim 1 and a method according to claim 8. Advantageous embodiments thereof are specified in the subclaims.

[0031] The present invention relates to a burner system for providing thermal energy comprisingan evaporator device for evaporating a liquid fuel to provide completely evaporated fuel, a burner air supply device for providing burner air, a surface burner for burning a fuel mixture comprising the completely evaporated fuel and the burner air to provide an exhaust gas stream, a shielding plate with openings for passing through and regulating the thermal energy of the exhaust gas stream of the surface burner, wherein the surface burner is coupled to the evaporator device via the shielding plate such that, during operation, the exhaust gas stream of the surface burner provides the thermal energy and the evaporation temperature required for complete evaporation of the fuel in the evaporator device, wherein the shielding plate is designed both for radiation shielding of the evaporator device,as well as for mixing the hot exhaust gas stream with a tertiary air in order to reduce a total exhaust gas temperature in order to cool it to a suitable level for complete evaporation, and a tertiary air supply device for supplying tertiary air to the exhaust gas stream in order to control a temperature of the exhaust gas stream by mixing with the tertiary air in order to form a hot gas stream.

[0032] The burner air supply device is also referred to below as the primary / secondary air device.

[0033] In the context of the present invention, complete evaporation of the fuel, preferably methanol, is understood to mean the complete phase transition of a liquid or a liquid mixture into the gaseous state at or above the boiling point of the liquid or the liquid mixture.

[0034] The evaporation temperature required for complete evaporation depends on the fuel used. In the case of methanol, for example, this is an evaporation temperature in the range between 64.7 °C and approximately 150 °C.

[0035] The tertiary air supplied by the tertiary air device enables regulation or control of the output temperature of the useful or hot gas flow during burner operation.

[0036] With the burner system according to the invention, fuel and burner air can be regulated or controlled independently of each other in order to make power adjustments or the temperature of the hot air flow both by changing the air lambda and via a constant air lambda when reducing (or increasing) the fuel and / or air.

[0037] In addition, the tertiary air can be used to cool another device, e.g. a fuel cell stack, when the burner device or the surface burner is not in operation.

[0038] A thermal sensor can be provided in front of a blower or fan of the tertiary air supply device to protect it from overheating.

[0039] The ambient air (tertiary air) conveyed via the tertiary air system is mixed with the exhaust gas in such a way that its temperature is cooled to both a desired initial temperature and a suitable level for evaporation.

[0040] With the burner device according to the invention, the temperature of the evaporator device can thus be actively controlled. Overheating of the evaporator can be prevented by supplying tertiary air.

[0041] In combination with the shielding plate or baffle plate (functional device), this design allows the use of highly thermally conductive materials such as aluminum in the evaporator unit. Furthermore, a controlled temperature of the evaporator unit can successfully prevent thermal decomposition of the fuel, which could otherwise lead to sooting and thus clogging of the evaporator unit and damage to the burner unit or the surface burner.

[0042] The shielding plate or baffle plate (functional device) itself is preferably a passive element; control takes place via the tertiary air (tertiary air device; tertiary air blower) or the gas flows. There is no exhaust gas recirculation. This is also not necessary because the surface burner fundamentally enables significantly cleaner combustion. In addition, no further preheating of the surface burner with exhaust gas is necessary during operation, since the fuel vapor is already sufficiently superheated in the evaporator device and sufficient energy is already conducted back from the burner surface via heat conduction. Furthermore, the baffle plate not only regulates the thermal energy input into the evaporator device but also the temperature level of the hot gas flow, which can then be used, for example, to heat a fuel cell stack.

[0043] The baffle plate and the tertiary air device are designed in such a way that both the temperature level of the hot gas supplied to the evaporator device can be adjusted and the outlet temperature of the burner can be controlled.

[0044] The surface burner does not require any special flame stabilization measures, as this can already be achieved via a metal fiber surface. The fuel vapor-air mixture can also be swirled in a burner screw, but this serves exclusively to mix and distribute the fuel gas across the cross-section of the burner surface.

[0045] The shielding plate is designed to thermally shield the evaporator device. Furthermore, it can be provided that the area of ​​the openings in the shielding plate can be changed by means of a corresponding adjustment device, or can be enlarged or reduced, in order to implement a corresponding control.

[0046] The shielding plate thus provides radiation shielding for the evaporator unit, as the surface burner operates in radiant mode. It also ensures that the hot burner exhaust gas is mixed with the tertiary air to reduce the overall exhaust gas temperature. This also ensures that the temperature exposed to the evaporator unit is not within the range of thermal decomposition of the fuel. The resulting controlled superheating of the fuel vapor allows for the use of more cost-effective valves and seals in the vapor line.

[0047] The shielding plate can be, for example, a stainless steel sheet of a suitable thickness.

[0048] The shielding plate can be part of an evaporator chamber of the evaporator device and thus an integral part of the evaporator device. In this case, the shielding plate or baffle plate has a particular effect on temperature distribution and homogenization toward the evaporator chamber.

[0049] In order to protect the downstream heat exchanger of the evaporator device from excessive heat input by radiation, the shielding plate can have heat sinks for absorbing radiant energy and bringing the heat input to a suitable level by dissipation via convection.

[0050] The functional device or the shielding plate is designed to shield and / or regulate a heat flow.

[0051] Without a shielding plate, there is a risk that the heat transfer by thermal radiation (the burner device is operated in radiation mode to ensure little burnout and a combustion chamber with a small depth in order to keep the installation space as small as possible) is so strong that the material of a heat transfer device surrounding the evaporation chamber would melt, even if the gas flowing through has already been lowered below the melting point by tertiary air.

[0052] The shielding plate itself can also be cooled using tertiary air, as otherwise, after some time, it too can begin to glow, and the radiation component of heat transfer increases again, leading to the same problem as without the shielding plate. Essentially, the shielding plate is a heat transfer transformer, absorbing heat energy in the form of high levels of radiation and low levels of convection, and dissipating heat energy with high levels of convection and low levels of radiation.

[0053] The evaporator device can be coupled to the burner device via the shielding plate in such a way that the thermal energy of the exhaust gas flow of the burner device is used during operation after a start-up phase to completely evaporate the liquid fuel in the evaporator device.

[0054] The fuel system according to the invention does not require a powerful fuel pump to atomize the fuel, nor does it require an injection nozzle to atomize the fuel. Therefore, the invention provides for the fuel to be completely evaporated in the evaporator device.

[0055] The evaporator device can preferably be designed as a closed device. In the context of the present invention, a closed evaporator device is understood to mean that the liquid fuel is evaporated in an evaporator chamber whose outlet is connected to an inlet of the burner device only via a line section (steam line). Liquid fuel is supplied to the evaporator chamber via a corresponding inlet; otherwise, the chamber is designed as a closed chamber.

[0056] The burner system according to the invention can supply the fuel to the evaporator chamber using a simply constructed fuel pump, since the evaporator device is able to ensure uniform evaporation in the event of inconsistent fuel supply.

[0057] The evaporator unit of the burner system requires only one evaporation branch, rather than two or more evaporation branches that must be controlled via valves. The evaporator unit can gradually deactivate an electric heater based on empirical values ​​(temperature detection is also possible). How such empirical values ​​can be determined is described in more detail below using the example.

[0058] Furthermore, in the burner system according to the invention, fuel and burner air can be controlled independently of each other in order to make performance adjustments both by changing the air lambda and by keeping the air lambda constant when reducing the fuel and air.

[0059] The above advantages are described in more detail in the embodiment.

[0060] The burner system may preferably be surrounded by a housing device that is slightly spaced from the components of the burner system.

[0061] The thermal energy of the exhaust gas stream can be provided in the form of tempered air (hot gas stream), whereby the thermal energy can be transferred directly or via a separate heat exchanger device to a device coupled to the burner system, whereby this device is an internal combustion engine or a fuel cell stack or a battery or an air duct device for heating a vehicle interior.

[0062] The tempered air is initially diluted exhaust gas, which can then be fed into an air-to-air heat exchanger to produce tempered air.

[0063] The following briefly lists the different types of fuel cells and their respective operating temperatures (BT) that can be heated in conjunction with the burner system according to the invention. Alkaline fuel cell (AFC); BT: 60 °C to 100 °C; Polymer electrolyte membrane fuel cell (PEMFC); BT: Low temperature: 70 °C - 90 °C; High temperature: 120 °C - 190 °C; Direct methanol fuel cell (DMFC); BT: 60 °C to 130 °C; Phosphoric acid fuel cell (PAFC); BT: 170 °C to 200 °C; Molten carbonate fuel cell (MCFC); BT: approx. 650 °C; Solid oxide fuel cell (SOFC); BT: 900 °C to 1000 °C;

[0064] The tempered air can be supplied to an oil circuit of a vehicle or an engine of a vehicle or a cooling circuit of a vehicle or can be coupled to it, e.g. via an air-to-air or an air-to-fluid heat exchanger, in order to preheat the engine, preferably an internal combustion engine.

[0065] This burner system can also form a thermal range extender, allowing battery vehicles to operate more independently of the charging infrastructure and increasing the range in the cold season while maintaining the usual level of comfort.

[0066] Furthermore, a vehicle interior can be heated with inexpensive methanol, which can also be produced renewably, instead of with electrical energy from an expensive battery.

[0067] For example, a vehicle interior can be heated via the burner system using an air-to-air heat exchanger. A similar structure to that described in EP 23 15 493 A1 can be provided, but this uses an electric resistance heating device instead of the burner system according to the invention.

[0068] By integrating it into a vehicle's cooling system, a vehicle battery can also be kept at operating temperature. The energy density of methanol is 35 times higher per kg than that of a lithium-ion battery.

[0069] In methanol engines, the burner system enables trouble-free starting without a dual fuel system.

[0070] By means of the burner system according to the invention, thermal energy is thus provided from clean liquid fuels. Within the scope of the present invention, alcohols such as methanol, ethanol, 2-propanol, 2-butanol, etc., are particularly envisaged as liquid fuels. The use of fuels such as gasoline or petroleum or other liquid fuels with boiling points up to 350°C is also possible.

[0071] In particular, the following advantages can be achieved with the burner system according to the invention: CO2-neutral operation with renewable methanol Operates with globally available methanol > 35% cheaper than diesel Quiet operation - under 35 dB(A) Continuous control of heating output and temperature Compact installation dimensions - high energy density, low burnout Low-emission operation through the combination of a surface burner and clean fuel Increases the range of battery-electric vehicles at low temperatures Suitable for continuous operation Easily adaptable to other fuels Keeps batteries at operating temperature even in demanding environments Based on a surface burner with fan, which is operated with methanol vapor Should be able to heat up and cool the fuel cell Defined output temperature of the hot gas is adjustable Low pressure loss for the use of simple, cost-effective fans Can be used with already qualified dosing pumps (intermittent delivery) Robust, reliable and safe operation

[0072] In order to optimize the competitiveness of fuel cell systems compared to conventional generators, it is now possible, in conjunction with the burner system according to the invention, to solve the problems mentioned above with regard to the start-up time and the electrical heating system, among other things, when heating a fuel cell stack.

[0073] For the start-up process, a fuel cell stack, e.g. of a HAT-PEM fuel cell system, is no longer heated electrically, but is heated by the exhaust gas flow of the burner system to 140°C to 230°C or to 160°C to 180°C and in particular to approximately 165°C.

[0074] According to the invention, the burner device is designed as a surface burner, which comprises a burner nosepiece and a metal fiber mesh connected thereto, a diffuser, an ignition device and preferably a flame monitoring device.

[0075] The surface burner has a cost and space advantage over a catalytic burner.

[0076] In addition, the surface burner offers more flexibility, as it can easily be operated with slightly more or less load without requiring the use of a more expensive catalyst. Furthermore, a catalytic reaction-based burner has tighter limits for power modulation (lower temperature limits (approx. 800°C), as the catalyst is damaged above this temperature; higher air lambda required, resulting in higher exhaust gas loss; catalyst-dependent upper limit for the ratio between catalyst comb volume and flow rate; if this limit is exceeded, the catalyst no longer fully converts the fuel gas).

[0077] Such a surface burner also has only a low burnout, with a combustion chamber measuring approximately 95 mm x 141 mm x 49 mm in height x width.

[0078] A further advantage of the surface burner is that it is very pulsation-free and quiet due to the laminar flow.

[0079] Mixture preparation preferably takes place upstream of the burner surface (premix burner). A mixing screw can be provided for this purpose.

[0080] In principle, the burner system is only suitable for gaseous fuels resulting from the complete vaporization of a liquid fuel. Completely vaporized methanol is preferred for this purpose.

[0081] For flame monitoring, known gas burner components can be provided in the form of a flame monitoring device.

[0082] The primary / secondary air supply device can be provided for supplying primary air to form the fuel mixture, which is supplied to the fuel vapor before combustion, and / or secondary air for cooling the burner device, in particular the diffuser and / or the combustion chamber and / or for afterburning.

[0083] The primary air is mixed with the vaporized fuel (methanol) to form a fuel mixture. Only a portion of this mixture is used if there is insufficient primary air available for complete primary combustion. The secondary air is mixed with the primary exhaust gases, and depending on the operation, a portion is either converted or used only as a mixed gas.

[0084] The fuel may only be partially used (rich mixture). The primary air is either fully used (lambda <= 1) or there is still oxygen left due to lean operation (lambda > 1).

[0085] The fuel-air ratio lambda (λ) can thus be adjusted through targeted fuel regulation and / or air regulation. In operating conditions λ<1, a rich mixture exists, and the fuel's energy may not be fully utilized. In operating conditions above λ>=1, all of the primary air (λ=1) is utilized, or oxygen molecules remain (λ>1). A corresponding control device can be provided for adjustment.

[0086] Depending on the operating mode, the secondary air provides the burner with air for any necessary post-combustion. The secondary air provides the burner with sufficient oxygen to ensure complete combustion, even with rich combustion on the primary side.

[0087] The secondary air cools the combustion chamber walls and the diffuser, allowing the use of silicone seals on the diffuser. This significantly reduces the thermal load on the combustion chamber housing.

[0088] The tempered hot gas flows through or around a heat exchanger device of the evaporator device or an evaporation chamber of the evaporator device in order to heat the evaporator device or to provide the energy for the evaporation.

[0089] The temperature can be measured with suitable temperature sensors upstream of the heat exchanger and / or in the exhaust gas line in order to provide appropriate regulation or control in order to achieve a suitable outlet temperature and to avoid overheating the evaporator device.

[0090] The hot gas is created by the mixing of the burner exhaust gas with the tertiary air in a flow direction immediately behind a shielding plate or the functional device and in front of the evaporator device.

[0091] To achieve uniform mixing and flow distribution across the entire evaporator cross-section, appropriately designed openings in the shielding plate are positioned so that they are directly adjacent to the inlet openings of a tertiary air duct into the mixing chamber. The two air streams thus meet at a 90° angle and mix. Mixing the tertiary air with the burner exhaust is advisable to prevent excessive overheating of the fuel vapor and to enable the use of cost-effective standard valves between the evaporator and burner.

[0092] The tertiary air duct can also be designed as a spiral through which the combustion air is directed. In addition to the two gas streams meeting at a 90° angle, the spiral also provides further mixing.

[0093] Evaporation in the evaporator device thus occurs via the burner waste heat or the thermal energy contained in the exhaust gas stream, saving electrical energy during operation. The hot gas flows through a heat transfer device in the evaporation chamber.

[0094] Furthermore, a fuel supply device or fuel pump for supplying liquid alcoholic fuel to the vaporizer device can be provided. In combination with a fuel cell system, this can be an existing anode pump of the fuel cell system or, preferably, a fluid pump.

[0095] The fuel supply device preferably comprises a fuel tank and a pump.

[0096] In addition, a mixing device can be provided in which the fuel vapor generated in the evaporator device through complete evaporation is mixed with the primary air. The mixing device is spiral-shaped (screw) and is integrally formed on the rear wall of a diffuser of the burner device.

[0097] By using the shielding plate in combination with the cooling of the burner exhaust gas via the tertiary air flow, aluminum with its good thermal conductivity properties can be used as a material for the evaporator without being damaged by the high combustion temperatures above the melting point of aluminum.

[0098] The following media flows can be provided in the burner system according to the invention: Burner air consists of: Primary air: Air that is used directly for combustion and is mixed with the fuel vapor before combustion. Secondary air: Air that flows into the combustion chamber around the diffuser at the edge to cool the diffuser and the combustion chamber. Is available for afterburning as required depending on the operating mode. The secondary air provides the burner with sufficient oxygen to ensure complete combustion, even with rich combustion on the primary side. Hot gas consists of: Exhaust gas: Entire gas flow that exits the combustion chamber consisting of the primary / secondary air components and the gases produced during combustion. Tertiary air: Ambient air conveyed by a second fan (tertiary air fan) which is mixed with the exhaust gas to cool its temperature both to a desired initial temperature and to a suitable level for evaporation.Fuel vapor: Fuel vapor created in the evaporator by complete evaporation, which is mixed with the primary air in a mixing device.

[0099] According to a preferred embodiment of the present invention, a 3 / 2-way valve is arranged in a line section that connects an outlet of the evaporator device to a fuel inlet or the mixing device of the burner device.

[0100] In this way, it is possible to interrupt the fuel supply from the evaporator device to the burner device in order to ensure that the flame is extinguished within three seconds, as required by the standard.

[0101] Since there is also liquid methanol in the lower area of ​​the evaporator device, switching off a fuel pump does not lead to a timely extinguishing of the flame, since the methanol would still completely evaporate due to the waste heat from the burner device.

[0102] By providing the 3 / 2-way valve, the evaporator outlet can be kept open during heating. The methanol remaining in the evaporator after the last operation can outgas without causing a pressure increase in the evaporator.

[0103] Since the internal pressure of the evaporator at the time the valve switches to the burner device is approximately equal to the ambient pressure, no pressure can be released into the burner device and it can be started up more gently with a controlled fuel / methanol-air mixture.

[0104] To prevent methanol loss to the environment, the methanol evaporating from the evaporator during the heating and cooling phases is recirculated to the burner system. The methanol flows through a hose connection into a phase separation or condensation unit, where it is condensed and returned to the system. The methanol evaporating is thus returned to the burner system. If the burner system is used in conjunction with a fuel cell system, the methanol evaporating is fed to the fuel cell system or a methanol tank in the system.

[0105] A further advantage of using the 3 / 2-way valve is that the methanol evaporates and outgassing during heating, which is used as a heat transfer medium to more evenly preheat the evaporator and the pipes, even in the upper section. Since a heating device is integrated into a lower section of the evaporator, this section is preheated accordingly, as the material's thermal conductivity is limited. However, the evaporating methanol provides an additional heat transfer mechanism. Methanol that condenses in cold areas of the evaporator can flow back down and evaporate again if the evaporator is installed in the normal position.

[0106] To enhance this effect, a limited amount of methanol is pumped into the vaporizer approximately 10 seconds before the valve switches to the burner, meaning it is already operating. The methanol vapor, which may still contain unevaporated, liquid methanol at this point, is then returned to the burner system.

[0107] This also makes it possible to eliminate the dead time of the evaporator device (the time between the entry of the liquid methanol and the exit of the gaseous methanol vapor) for the ignition phase of the burner device, since this has already been passed through before the start of the ignition phase. Furthermore, a method according to the invention for providing thermal energy is provided, which comprises the technical features and corresponding advantages explained above.

[0108] A method for providing thermal energy by means of a burner system as described above comprises the following steps: heating the evaporator device with an electric heating device during a start-up phase, completely evaporating the liquid fuel in the evaporator device, supplying the completely evaporated fuel to a burner device designed as the surface burner, and burning the evaporated fuel in the burner device to provide thermal energy in the form of an exhaust gas stream,

[0109] A portion of the thermal energy used in the burner system is used to vaporize the fuel in the vaporizer during operation, so that the energy for vaporization in the vaporizer is provided exclusively by the burner device. The diffuser can also be preheated and heated electrically. Preferably, a second heating device is provided for this purpose, which can be regulated or controlled independently of the heating device of the vaporizer device.

[0110] The thermal energy of the exhaust gas flow can be regulated or controlled between the burner device and the evaporator device via openings formed in a shielding plate or a functional device.

[0111] The burner device comprises a surface burner for gaseous fuels produced by complete evaporation of a liquid fuel, wherein the completely evaporated fuel is burned in the surface burner.

[0112] Primary air may be supplied to form a fuel mixture, wherein the primary air is supplied to the fuel vapor prior to combustion and / or secondary air may be supplied, which is provided for cooling a diffuser and / or a combustion chamber of the burner device and / or is used for afterburning, wherein the primary and secondary air are supplied by a burner air supply device, referred to as primary / secondary air device.

[0113] Tertiary air is supplied in order to adjust the temperature of the thermal exhaust gas flow by mixing it with the tertiary air, so that a hot gas flow is formed therefrom, wherein the outlet temperature of the hot gas flow during burner operation is regulated via the tertiary air. An outlet of the evaporator device can be kept open via a 3 / 2-way valve during a start-up phase, in particular during heating of the evaporator device, and / or, when operation of the burner device is terminated, any methanol remaining in the evaporator device can outgas via the 3 / 2-way valve without there being an increase in pressure in the evaporator device, wherein the internal pressure of the evaporator device at the time the valve switches over to the burner device approximately corresponds to the ambient pressure, so that no pressure is released in the burner device and it is started up with a controlled fuel-air mixture.

[0114] In addition, a mixing device (or its diffuser) can be preheated with an electric heating device during the start-up phase.

[0115] The invention is explained in more detail below with reference to the drawings, which show: Fig. 1 is a schematic representation of a fuel cell system that can be combined with a burner system according to the invention, Fig. 2 is a perspective exploded view of the burner system according to the invention, Fig. 3 is a schematic representation of the media flows of the burner system, Fig. 4 is a side view of the burner system with media flows, Fig. 5 is a further side view of the burner system with media flows, and Fig. 6 is a further side view of the burner system with media flows.

[0116] 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 advantages indicated above (Figure 1 ). This fuel cell system 1 essentially corresponds to the fuel cell systems described in WO 2010 / 066900 A1 and WO 2015 / 110545 A1.

[0117] WO 2010 / 066900 A1 discloses a humidification unit for providing a carrier gas containing fuel and water vapor to supply a fuel cell.

[0118] WO 2015 / 110545 A1 discloses a fuel cell system for thermally coupled reforming with reformate processing.

[0119] The fuel cell system 1 comprises a fuel cell stack 2. This is designed as an HT-PEMFC (High-Temperature Polymer Electrolyte Fuel Cell). This high-temperature fuel cell operates in a temperature range of 160°C–180°C. The required hydrogen is obtained from methanol through a reforming process and converted into electricity in the fuel cell 2.

[0120] The cell is supplied by a carrier gas stream saturated with water and methanol vapor, which is provided by a humidification unit 3. This enables water recovery from the exhaust gas through the water cycle. This eliminates the need for external water addition and the use of premixes.

[0121] The components and functionality of the fuel cell system 1 are explained using an anode circuit.

[0122] In the anode circuit, methanol is pumped from a methanol storage tank 13 and water into the humidification unit (media unit) 3 via two metering pumps 4 and 5. In the humidification unit 3, a carrier gas stream is enriched with methanol. The methanol storage tank 13 can also be used to supply the burner system 20.

[0123] The carrier gas stream is pumped by an anode or fuel pump 6 from an anode outlet to the humidification unit 3. Saturation of the carrier gas stream with water and methanol vapor occurs in a temperature range of approximately 80 °C; the saturated gas then flows to the internal and external reformer devices 7, 8.

[0124] During allothermal steam reforming, water and methanol vapor decompose into hydrogen, carbon dioxide, and carbon monoxide. The resulting reformate gas contains predominantly hydrogen and is passed on to fuel cell stack 2.

[0125] After the hydrogen has been converted into electricity in fuel cell stack 2, the reformate gas still contains a large portion of carbon dioxide. The depleted reformate gas flows out of the anode, and the cycle starts again, starting with the anode pump.

[0126] A cathode blower 9 supplies the fuel cell with oxygen (air). The air flow of the cathode blower 9 absorbs the water produced by the power generation, which is condensed in a heat exchanger and phase separator 14. The recovered water is pumped back to the humidification unit 3 by the dosing pump 5.

[0127] The humidification device 3 is heated by the hot exhaust gases from the reformer device 7, 8, a catalytic burner, and the cathode waste heat. To keep the fuel cell stack 2 at operating temperature, it is cooled by an air supply device 12. This air supply device 12 can be used as the tertiary air or burner air device of the burner system 20.

[0128] The burner system 20 according to the invention can be used as a heating system for fuel cell stacks 2 of fuel cell systems 1 and is described below ( Figures 2 to 6 ).

[0129] Since an HT-PEMFC requires a certain starting temperature, this temperature of approximately 165 °C can be achieved by heating the fuel cell stack 2 using the burner system 20.

[0130] Previously, the fuel cell stack was heated by an electric heating device. Heating plates were arranged around the fuel cell stack and insulated from the outside. These heating plates require electricity throughout the entire heating process. The heating process takes approximately one hour and requires a high electrical output. A connected battery is therefore first discharged to heat the fuel cell. Once the fuel cell reaches the right temperature, it charges the battery, and the electricity can be used.

[0131] A reduction in power consumption is possible through the burner system 20 in the form of a non-electrical energy source.

[0132] The burner system 20 preferably uses methanol in conjunction with a burner device 21 designed as a top or surface burner. In this way, only low NO x formation and high exhaust gas temperatures occur.

[0133] The generated heat is dissipated to the fuel cell 2 via a tertiary air device 16 with a fan.

[0134] The burner system 20 according to the invention is described in detail below ( Figures 2 to 6 ).

[0135] The burner system 20 has a housing assembly 23. The housing assembly 23 is formed by four interconnected plate modules, preferably made of vermiculite. These plate modules are connected to each other via threaded rods and braced with foam. Vermiculite has low thermal conductivity and can be designed as a non-combustible plate material. This product is offered worldwide under the brand names "Fipro," "Miprotec," "bro-TECT," "Vermilite 2000," and "Thermax." Vermiculite has a high melting point of 1315°C and is electrically non-conductive and insulating. Silcawool 115-36A board, for example, can be used instead of vermiculite. Generally, the functions can also be separated and a metal housing with additional insulation (e.g., high-temperature glass wool) can be manufactured. The housing assembly primarily performs the functions of insulation and media routing.

[0136] One of these plate modules represents an end plate 24. An air inlet and a support surface for a diffuser 25 of the burner device 21 are formed in the end plate 24.

[0137] In a side edge or upper wall of the end plate 24 lying vertically upwards, a rectangular recess is provided for the passage of a methanol line and an air line for supplying the diffuser 25.

[0138] A further plate module, representing a center plate 26, is mounted on the end plate 24. A side wall of the center plate 26 facing the end plate 25 is provided for receiving a burner nozzle 27 of the burner device 21, and the opposite side wall has a recess for receiving a baffle plate of an evaporator device 28. The baffle plate forms a functional device 29.

[0139] Like the end plate 24, this middle plate 26 has a recess for the methanol and air line.

[0140] In the area between the end plate 24 and the middle plate 26, a space for the combustion device 21 is thus formed.

[0141] An outlet plate 30 is connected to the center plate 26. A space for the evaporator device 29 is provided between the center plate 26 and the outlet plate 30.

[0142] A front plate 31 is connected to the outlet plate 30.

[0143] The housing device 23 is approximately cuboid-shaped due to its plate-like construction. A top plate 33 is attached to an upper wall of the housing device 23.

[0144] The top plate 33 accommodates the tertiary air device 16, a burner air supply device 41, a solenoid valve, and an air shaft. The burner air supply device 41 includes a metering orifice, appropriate tubing, and an air preheater (a heating element similar to a hot air dryer). Without the air preheater or diffuser preheater, the burner will not start or will start only poorly, as the methanol condenses in the diffuser. The heater itself is located in the diffuser.

[0145] Alternatively, the diffuser can also be preheated with a directly integrated heating cartridge. In this case, the burner system has two heating cartridges.

[0146] The hot exhaust gases are distributed via flow channels 33 formed in the front plate 31 and directed to the fuel cell stack 2. For optimal air flow of the hot exhaust gases, the flow channels 33 of the front plate 33 are coupled to the fuel cell stack 2.

[0147] All panel modules are made of vermiculite and are clamped with threaded rods using through holes on the sides of the panels.

[0148] The burner system also includes the evaporator device 28 and a heating cartridge. The methanol is evaporated in the evaporator device 28.

[0149] The evaporator device 28 comprises an inlet pipe 42, a trough-like upper and lower element, which are connected to each other via a heat transfer device 45 with a heat exchanger structure arranged therebetween, and an outlet pipe. The trough-like upper and lower elements and the heat transfer device 45 arranged therebetween form an evaporator chamber.

[0150] The inlet pipe 42 for introducing the liquid methanol opens into the lower element 44 of the evaporator device 28. The heating cartridge with a power of 250 W is integrated into the lower wall. A fuel pump 47 is provided for this purpose, which pumps methanol from a fuel storage tank 48.

[0151] When the evaporator device 48 is operated with the exhaust gas flow from the burner device 21, the heat transfer device 45 ensures effective heat transfer for evaporating the methanol. The evaporated methanol concentrates at the top and is conducted through a welded pipe via a solenoid valve to the diffuser. To increase the surface area of ​​the phase boundary, the heat transfer device 45 is filled with fine metal wool, preferably stainless steel wool. An upper tray (upper element) of the evaporator device 28 is also filled with stainless steel wool; a lower tray (lower element), into which the methanol flows first, is filled with a solid metal foam, which also accommodates the heating cartridge and ensures or improves heat conduction from the heating cartridge to the evaporator device 28.

[0152] Alternatively, the lower pan can be constructed from solid stainless steel, with the heating cartridge located in a separate bore that has no fluid connection to the methanol distribution chamber. The distribution chamber is preferably lined with metal foam.

[0153] The burner device 21 comprises, among other things, the burner goggles 27, the diffuser 25 and electrodes.

[0154] The burner frame 27 is made of a perforated stainless steel sheet with a metal fiber coating. Holes located along the edge of the burner frame 27 are provided for a secondary air flow 36. Mounting holes are also provided for attaching electrodes.

[0155] The fuel mixture flows through the primary holes formed in a curvature of the burner nose 27.

[0156] On the side of the burner nosepiece 27 facing the center plate 26, a metal fiber mesh or a porous ceramic structure is welded. This consists of a heat-resistant Fe-Cr-Al alloy that provides protection against oxidation and high temperatures. This provides effective protection against overheating and also prevents deformation and breakage of the burner.

[0157] When the metal fiber is operated at low heat output, combustion occurs on the metal surface, and the fibers glow brightly. The metal fiber is then operated in radiant mode.

[0158] The use of a metal fiber offers the following advantages: Precise combustion with significant noise reduction High flame stability without flashback Shape stability

[0159] The mixing of the gaseous fuel produced by the complete evaporation of a liquid fuel and the air by the starting burner fan is achieved by a diffuser incorporated in the end plate.

[0160] On an upper side of the diffuser 27 and the end plate there are inlet openings for the fuel and burner air supply 34.

[0161] The vaporized methanol is metered directly into a screw of the diffuser 27. The screw forms a mixing device 17. The air is passed through a non-return membrane and then divided into primary air 35 and secondary air 36. The primary air 35 mixes with the methanol vapor in the screw, and the secondary air 37 flows around the diffuser 25 into the secondary holes. The fuel mixture of gas and air accumulates in a combustion chamber and flows through the primary holes of the burner nozzle 27.

[0162] The primary air supply can be regulated by a stainless steel cover on the screw.

[0163] Furthermore, two electrodes (high-voltage (HV) and flame monitoring (FW)) are screwed to the diffuser via the burner nosepiece and extend into the combustion chamber over the primary area of ​​the burner nosepiece. The ignition spark is formed between the ignition electrode (HV) and the burner nosepiece, which is grounded to obtain a better flame monitoring signal.

[0164] Furthermore, the burner system 20 comprises the tertiary air device 16 and a measuring orifice.

[0165] The tertiary air device 16 includes a PWM (pulse width modulation)-capable radial fan. PWM enables precise adjustment of the fan speed and thus controlled tertiary air flow. A sensor line provides information about the current fan speed and can indicate a fan failure through a logic check.

[0166] In addition to cooling the fuel cell 2, the tertiary fan 16 heats the fuel cell 2 using the hot exhaust air (hot gas stream 39 comprising exhaust stream 38 and tertiary air 37) from the burner device 21. The fan enables sufficient cooling of a fuel cell system 1 at every power level.

[0167] Another fan forms a burner air device 41 for supplying burner air 34 (primary air 35 and secondary air 36). The burner air device 42, like the tertiary air device 16, is a radial fan that conveys air to the diffuser 25 via a flow meter. The three-pin connection allows for speed regulation via a corresponding control device.

[0168] A burner control unit provides the ignition spark and monitors the flame. This detects a flame failure within a maximum of 0.8 seconds. A flame failure triggers an internal fault, which also closes a solenoid valve for the fuel supply. The ignition periods are integrated into the burner control unit's electronics. The starting system uses an ignition phase of approximately 4 to 20 seconds to ensure reliable ignition of the fuel mixture. If the burner device 21 is not started within the ignition phase, the control unit issues an error message.

[0169] The 3 / 2-way valve 19 is used to open and close the burner's gas line and is located between the evaporator unit 28 and the diffuser 25. In the event of a malfunction, the valve closes within 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 malfunction. The valve is in the open state as soon as the burner control unit performs the ignition process and is closed in the basic state.

[0170] Another safety device is a safety temperature limiter. This is located in the combustion chamber, with the measuring sensor attached to the diffuser. The principle 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, opening the circuit and closing the solenoid valve. Ambient temperature influences are compensated by a bimetallic disc. The advantage of this component is its electromechanical design, which allows temperature measurement without additional auxiliary power. To reopen the circuit, the snap-action switch must be operated manually.

[0171] Alternatively, a fuse can be used. This is mounted in a designated recess on the back of the diffuser. If the permissible temperature is exceeded in the event of a burnback, this opens the circuit to the valve, which then closes. To close the circuit again, the fuse must be replaced. The corresponding fuse wire of the thermal fuse burns out irreversibly at approximately 200°C.

[0172] The burner device is spatially separated from the evaporator device by a functional device designed as a baffle plate with openings.

[0173] The basic concept of burner system 20 is based on a surface burner with a fan, which is operated with methanol vapor. The system also includes an evaporator to evaporate the liquid methanol. A high-flow radial fan is used to remove the hot or cold air.

[0174] The housing assembly 23 is constructed from four vermiculite plates that are clamped together by a clamping system. The vermiculite plates are pre-milled for the internal components and provide two exhaust ducts for the hot gas outlet. The evaporator assembly, the baffle plate of the functional assembly 29, and the burner assembly 21, including the diffuser 25 and the burner nosepiece 27, are arranged in the housing. Furthermore, a mounting device for the burner air assembly 41 with a solenoid valve is located on the top of the starting system.

[0175] The fresh air supply is ensured on the one hand by the burner air system (primary air 35 and secondary air 36) and on the other hand by the tertiary air system 16 (tertiary air 37). The burner air 34 flows over the diffuser 25 and is divided there into primary air 35 and secondary air 36. The primary air 35 is mixed with the gas flow from the evaporator device 28 and flows through a central area of ​​the burner nozzle. The secondary air is directed through the outer holes of the burner nozzle 27 and serves for cooling and additional oxygen supply to the combustion process.

[0176] In the following, a method for providing thermal energy using the burner system described above is explained ( Figure 3 ).

[0177] During the start-up process, liquid methanol is pumped from the tank into the evaporator device 28 by a pump and a 3 / 2-way valve 19. In the evaporator device 28, the liquid methanol is first evaporated by an electrically operated heating cartridge, passed through a solenoid valve, and mixed by means of a screw with primary air 35 provided by the primary / secondary air device or the burner air device 41.

[0178] The ignitable fuel-air mixture is then ignited in the combustion chamber and additionally supplied with oxygen by the secondary air 36.

[0179] One evaporator outlet is open and therefore pressureless during the heating phase, so no check valve is required to protect the pump. As soon as the 3 / 2-way valve is activated, a connection between the evaporator unit and the diffuser is opened, while the connection to the outlet is closed. Methanol escaping from the evaporator during the heating phase is recirculated within the system by being directed into a phase separator cathode condensate, similar to the overflow from the methanol reservoir. From there, it then flows into the humidification unit and is converted into electricity.

[0180] Regarding the design, arrangement and other advantages of the 3 / 2-way valve, please refer to the relevant paragraphs in the introduction to the description.

[0181] The hot exhaust gas 38 then passes through the baffle plate of the functional device 29, where it is mixed with the tertiary air to reduce its temperature. First, the tertiary air stream is mixed with the exhaust gas, and then the resulting hot gas or useful gas stream 39 flows through the evaporator device 29 and then on to the fuel cell stack. Otherwise, the evaporator could overheat. This eliminates the need for electrical heating of the evaporator device 28. In particular, the hot gas stream heats a heat exchanger structure of the fuel cell stack, warming it to operating temperature. As soon as the fuel cell stack has reached the desired operating temperature, a cooling process is initiated by means of the burner system.

[0182] The pump 6 or 47 and the primary / secondary air device 41 gradually shut down and the tertiary air device 16 cools the fuel cell stack 2 to the desired operating temperature.

[0183] The burner system 20 is operated with a liquid fuel, such as methanol. A phase transition of the liquid component into the gas phase must be ensured. This phase transition is necessary to ensure mixing of the energy carrier with the oxidizer.

[0184] This process, known as mixture preparation, leads to the reduction of pollutant emissions and takes place initially in the evaporator unit and then in a downstream mixing unit. The mixing unit is spiral-shaped (screw) and is integrally formed on the rear wall of a diffuser of the burner unit. The diffuser distributes the mixed fuel gas across the burner cross-section so that it can flow evenly through a primary area of ​​the burner nozzle. The burner nozzle also contributes to the even distribution of the fuel gas across the burner cross-section through the pressure loss during flow.

[0185] Four sub-steps are necessary for the thermal conversion of liquid fuels. Fuel preparation Evaporation of the fuel Mixture preparation Combustion (heat release) of the mixture

[0186] In the first sub-step, the liquid energy carrier is processed by increasing its surface area. This process is carried out using atomization or distribution systems. Atomization or distribution of the liquid fuel serves both to transport the fluid and to increase the specific surface area. Since the evaporation of a liquid energy carrier occurs at the phase interfaces, this can increase the reaction rate and thus minimize the time required for the process.

[0187] The evaporation of a liquid medium into a gaseous component is referred to as a phase transition. During evaporation in air, the fuel is mixed with air and evaporated. Direct evaporation initially involves the evaporation of the fuel, which can then be mixed with air in gaseous form. In the case of methanol evaporation, methanol is added to the evaporator, and the vaporous methanol is then mixed with air in the mixing device. Due to the spatial separation of evaporation and mixing, an ignitable mixture of fuel and air is only formed after mixture formation.

[0188] The energy to ignite a fuel mixture is provided by the ignition device.

[0189] In particular, the evaporator device 28 is designed such that the evaporated fuel is released with a uniform or constant volume flow and not in a pulsating manner.

[0190] The burner system 20 according to the invention prevents pulsating combustion or the resulting pulsating vaporization by 1. preventing condensation of the fuel in burner components due to overheating of the burner vapor. 2. compensating for pump pulsation with sponge-like structures in the vaporizer device (porous metal foam), which increase the surface area due to their low surface tension and capillary forces. The excess fuel from a pump stroke can be temporarily stored in the internal structure and continuously released as vapor. In this way, the fuel can also be supplied to the vaporizer device 28 using a simply constructed pump with an intermittent delivery rate.

[0191] Furthermore, the invention provides for the temperature of the thermal energy of the hot gas stream emitted by the burner system to be adjustable. Since the hot gas temperature to which, for example, a fuel cell 2 can be exposed is limited, cool ambient air (tertiary air 37) is supplied to the exhaust gas stream 38 via the tertiary air device 16 in order to adjust or regulate it to a predetermined temperature. By appropriately regulating the fan speed of the blower of the tertiary air device 16, the output temperature of the hot gas stream 39 can be adjusted or regulated very precisely (+ / - 2°C).

[0192] The burner device 21 is designed such that its thermal output (via temperature or volume flow) is adjustable or controllable. The required heating output can vary depending on the application of the burner system. To avoid unfavorable cycling of the burner device (on / off) of the burner system 20 with all its disadvantages (cooling losses, electrical losses due to preheating, poorer exhaust gas values ​​during start-up), the output of the burner device can be modulated largely independently of the initial temperature. This can be done either on a small scale by adjusting a combustion lambda with a constant burner air flow or over a wide range by keeping the burner lambda constant while simultaneously varying the burner air supply.The outlet temperature can still be kept constant within the capacity of the fan of the tertiary air system because the escaping gas mass flow varies depending on the desired temperature level, but not the delivered heating power.

[0193] The thermal power required to start the burner system 20 before it goes into operation and the evaporator device 28 is heated via the burner device 21 is provided by the heating cartridge. This is a simple and cost-effective solution.

[0194] In addition, the temperature in the evaporator device 28 can be measured via a thermocouple integrated into the heating cartridge.

[0195] This is designed to prevent overheating and damage to the heating element, and to reduce the risk of thermal decomposition of the fuel. During the start-up phase, the heating cartridge is regulated to a maximum temperature that is below the thermal decomposition temperature of the fuel used. For this purpose, the power supply to the heating cartridge is pulsed.

[0196] The evaporator unit can gradually deactivate an electric heater based on empirical values ​​(temperature detection is also possible). How such empirical values ​​can be determined is described below.

[0197] Preheat: The heating cartridge for electrical preheating of the evaporator can be controlled via pulse width modulation (PWM) with, for example, 50 ms intervals. Control in, for example, 10% increments is provided. To extend the service life of the heating cartridge, a maximum heating output of, for example, 80% is used, as this places less strain on the heating conductor due to the currentless phases. Furthermore, the temperature of the heating cartridge is recorded by a thermal sensor integrated into the cartridge and limited to a maximum of 500°C by the control system. If the limit temperature is reached or exceeded, the heating output of the cartridge is gradually reduced until the constant limit temperature is reached. As one of the indicators for burner ignition, the temperature of the heating cartridge must be above 450°C for more than 5 seconds (the others are preheating of the diffuser to at least 70°C and a heating time of at least 4 minutes).The maximum temperature limit of 500°C serves not only to protect the heating cartridge but also to prevent thermal decomposition of the methanol. The temperature limits are stored in the software and can be variably adjusted depending on the fuel used.

[0198] Turning off the heating: After successful ignition of the burner (fuel valve open for more than 20 seconds and an initial temperature of over 150°C), the heater is initially reduced to 30% power. The heating output is then reduced gradually (1% increments) until the heater is completely switched off. 32 system software cycles (500ms) are counted per step. Active power adjustment only occurs in, for example, 10% increments; the remaining steps in between only serve the simpler control strategy. Accordingly, the process starts at a control value of 39%, which corresponds to only 30% of the actual heating output. The number of system cycles required per step can be individually adjusted to the fuel used. In addition, the temperature measurement integrated in the heating cartridge can ensure that the temperature in the evaporator does not fall below the boiling point of the fuel used.This means that the heating shutdown steps can be delayed or reversed if necessary.

Claims

1. Burner system (20) for providing thermal energy comprising an evaporator device (28) for evaporating a liquid fuel to provide completely evaporated fuel, a burner air supply device (41) for providing burner air (34), a surface burner for burning a fuel mixture comprising the completely vaporized fuel and the burner air (34) to provide an exhaust gas stream (38), a shielding plate with openings for passing through and regulating the thermal energy of the exhaust gas stream (38) of the surface burner, wherein the surface burner is coupled to the evaporator device (28) via the shielding plate such that during operation the exhaust gas stream (38) of the surface burner provides the thermal energy and the evaporation temperature required for complete evaporation of the fuel in the evaporator device (28), wherein the shielding plate is designed both for radiation shielding of the evaporator device (28) and for mixing the hot exhaust gas stream (38) with a tertiary air (37) in order to reduce a total exhaust gas temperature in order to cool it to a suitable level for complete evaporation, and a tertiary air supply device for supplying tertiary air (37) to the exhaust gas stream (38) in order to adjust a temperature of the exhaust gas stream (38) by mixing with the tertiary air (37) in order to form a hot gas stream (39).

2. Burner system (20) according to claim 1, characterized in that the surface burner comprises a burner cover (27) and a metal or ceramic fiber mesh connected thereto, a diffuser (25), an ignition device and / or a flame monitoring device.

3. Burner system (20) according to claim 1 or 2, characterized in that the burner air supply device (41) is a primary / secondary air supply device which is provided for supplying primary air (35) to form the fuel mixture, wherein this is supplied to the fuel vapor before combustion, and / or which is provided for supplying secondary air for cooling the burner device (21), and / or the diffuser (25) and / or the combustion chamber and / or for afterburning.

4. Burner system (20) according to one of claims 1 to 3, characterized in that the shielding plate thermally shields the evaporator device (28) and / or wherein the functional device (29) is a component of the evaporator device (28).

5. Burner system (20) according to one of claims 1 to 4, characterized in that the evaporator device (28) is designed to be closed, wherein the evaporator device (28) comprises an evaporator chamber (46) for evaporating the liquid fuel, and wherein an outlet of the evaporator device is connected to an inlet of the burner device (21) only via a line section, and the evaporator device (28) has an inlet for supplying liquid fuel.

6. Burner system (20) according to a claim 5, characterized in that a 3 / 2-way valve (19) is arranged in the line section which connects the outlet of the evaporator device (28) with the fuel inlet of the burner device (21).

7. System comprising a burner system (20) according to one of claims 1 to 6 and a device coupled to the burner system (20), wherein this device is an internal combustion engine or a fuel cell stack (2) or a battery, wherein thermal energy of an exhaust gas stream (38) is able to be provided in the form of diluted exhaust gas by the burner system (20), and wherein this thermal energy is delivered in the form of temperature-controlled air to the device coupled to the burner system (20) directly or via a separately formed heat exchanger device.

8. Method for providing thermal energy with a burner system (20) according to one of claims 1 to 6 comprising the following steps: heating the evaporator device (28) with an electric heating device during a start-up phase, completely evaporating the liquid fuel in the evaporator device (28), supplying the completely evaporated fuel to the surface burner, and combustion of the vaporized fuel in the burner device (21) designed as the surface burner to provide thermal energy in the form of an exhaust gas stream (38), use of a portion of the thermal energy to vaporize the fuel in the evaporator device (28) during operation, so that the energy for vaporization in the evaporator device (28) is provided exclusively by the burner device (21).

9. Method according to claim 8, wherein regulation or control of the thermal energy of the exhaust gas flow between the surface burner and the evaporator device (28) takes place via openings (29) formed in a shielding plate of a functional device.

10. Method according to claim 8 or 9, wherein primary air (35) is supplied to form a fuel mixture, wherein the primary air (35) is supplied to the fuel vapor before combustion and / or is supplied by secondary air (36) which is provided for cooling a diffuser (25) and / or a combustion chamber of the burner device (21) and / or is used for afterburning, wherein the primary (35) and the secondary air (36) is preferably supplied by a burner air supply device (41), which is referred to as a primary / secondary air device.

11. Method according to one of claims 8 to 10, wherein tertiary air (37) is supplied in order to adjust a temperature of the thermal exhaust gas stream (38) by mixing with the tertiary air (37), so that a hot gas stream (39) is formed therefrom, wherein the output temperature of the hot gas stream (39) is regulated during burner operation via the tertiary air (37) independently of the combustion and the combustion air.

12. Method according to one of claims 8 to 11, wherein an outlet of the evaporator device (28) is kept open during a start-up phase via a 3 / 2-way valve (19) and / or that when the operation of the burner device (21) ends, methanol remaining in the evaporator device (28) can outgas via the 3 / 2-way valve (19) without there being an increase in pressure in the evaporator device (28), wherein an internal pressure of the evaporator device (28) at the time the valve is switched over to the burner device (21) corresponds approximately to the ambient pressure, so that no pressure is discharged in the burner device (21) and it is started up with a controlled fuel-air mixture.

13. Method according to one of claims 8 to 12, wherein liquid fuels with boiling temperatures up to 350°C, such as methanol, ethanol, 2-propanol, 2-butanol, or gasoline or petroleum are provided as fuel.