EP0927321B1 - Pre-vaporizing and pre-mixing burner for liquid fuels - Google Patents

Abstract

The invention concerns a pre-vaporizing and pre-mixing burner for liquid fuels which has a fuel feed line (56), a pump which pressurizes the fuel in the feed line, a mixing region (123) and a fuel valve (119) which opens out into the mixing region and by means of which the fuel is atomized and fed to the air for combustion (127). According to the invention, the fuel is vaporized in an optimum manner in that the fuel valve opens automatically as from a given fuel pressure, and a heating device (128) is associated with the fuel valve.

Description

The invention relates to a method for generating a flammable mixture of a liquid fuel and Combustion air and a pre-evaporating and premixing burner for liquid fuels, with a or several fuel heaters for heating the liquid Fuel before combustion. Such a method is already known from documents US-A-4 013 396 and DE-A-2 239 317.

It is known in the area of household and small consumption (HuK) Heating oil EL in a pressure atomizing burner for heating purposes or to burn for thermal process engineering purposes. The liquid heating oil EL is under high pressure (500 to 2000 kPA) transformed into a droplet mist by means of an atomizing nozzle and at the same time with the supplied combustion air mixed. There is also a process in which the heating oil EL is atomized using compressed air. Furthermore exist Evaporation burner designs where the liquid Fuel on the surface of a heated body by Combustion air is surrounded, evaporates.

The previous burners are based on the following problems: The liquid heating oil EL is used in conventional oil burners high pressure by means of an atomizing nozzle into a droplet mist transformed and at the same time with the supplied Combustion air mixed. The processes like atomization, Mixing, evaporation and gasification of the fuel as well as the Combustion of the gasified fuel runs out of order side by side and interact with each other. The individual drops of oil are surrounded by a flame envelope. The solve high temperatures near the drop at the same time the lack of air cracking processes in which soot is formed becomes.

Today 's blue burners avoid the formation of soot by the Evaporate fuel in the flame root before combustion. Hot flue gases returned from the flame zone evaporate here the oil spray emerging from a swirl nozzle. The The water content of the returned flue gases prevents formation Long chain hydrocarbons that only form soot let it burn. The method of exhaust gas recirculation lowers in addition to soot emissions, nitrogen oxide emissions. To one a sufficient amount of hot flue gas is added to the flame root promote is a correspondingly large induction effect of Fuel / air jet within the mixture preparation required. The induced mass flow is caused by the velocity of the mixture flow emerging as well influences the cross section of the free jet. Both parameters can only be varied within certain limits. A high Exit velocity leads to high flow noise, high blower output and larger burner dimensions. An enlargement of the outlet cross section, associated with a speed reduction already leads to that Ignition conditions exist in the evaporation area and so the intended to be decoupled from the combustion reaction Fuel vaporization does not occur. In addition, the Exchange of momentum between fuel and combustion air, which also negatively affects the mixture. A high The exit speed at the swirl generator is prevented in addition, the flame formation in the vicinity of the Mixing device and thus leads to a reduced thermal stress on these components. It follows from this that in previous mixture preparation processes for oil burners Reduction of pollutant emissions always related to stands for an increase in the combustion air speed and thus to an increase in noise emissions and required fan power leads.

A reduction in the fuel oil throughput is one Burner system with a combustion output of 15 kW conventional oil pressure atomizing nozzles not possible. For reasons reliability is the nozzle cross section for one Throughput reduction cannot be further reduced. Also the Pump pressure cannot be reduced arbitrarily, since the Atomization quality deteriorated significantly.

Conventional oil burners are heterogeneous System, i.e. the disperse phase heating oil EL and that Air dispersants exist as discrete phases side by side, and are separated by a phase boundary. The coarsely disperse created by atomization Fuel distribution does not allow fuel without to mix prior evaporation before the flame as the individual droplets of fuel under the influence of gravity sediment and deposit on the mixing chamber walls. For this reason it is a premix Surface burner construction, as in the field of Gas combustion is not possible.

Modern gas burner designs show that a reduction nitrogen oxide emissions most effectively through a Premix burner system is to be solved.

DE-C2-24 56 526 is a gasification device for Heating oil and kerosene and with DE-OS 14 01 756 is one Oil heater become known in which the fuel before the atomization is heated. Although the heating of the Fuel to better and finer atomization, however problems arise from deposits from cracked products, such as Clogging the lines, etc., on.

The above problems are solved by the in claim 1 listed features solved.

(a) Niedrige Emissionen (Ruß, Stickoxid, Kohlemonoxid) bei Anwendung eines Oberflächenverbrennungssystems;

(b) niedrige Geräuschemissionen;

(c) kleine Gebläseleistung;

(d) vollständiger Verzicht auf ein Verbrennungsluftgebläse möglich (atmosphärische Gemischbildung);

(e) kompakte Wärmeerzeugerkonstruktion durch direkte Ankopplung der Heizkreisseitigen Wärmetauscher an die räumlich exakt festlegbare Reaktionszone.

The advantages achieved by the invention consist in particular in the fact that, in the method on which the invention is based, a colloidally disperse or molecularly disperse fuel distribution occurs after the fuel atomization, depending on the degree of air preheating. A mixed form of both types of distribution is also conceivable. Due to the stability of the colloidally dispersed fuel, it is possible to mix the reactants before the flame without the fuel droplets being deposited on the walls of the mixing chamber. The mixture of the reactants is therefore completely spatially decoupled from the combustion reaction and not, as with conventional emission-reduced oil burners (so-called blue burners), only within a very small gasification zone upstream of the flame, which is in direct convective heat exchange with the flame via flue gas recirculation. Because the mixture of fuel and combustion air is no longer limited to the gasification zone upstream of the flame, the premix burner designs known from gas burner technology, which enable a very intensive mixing of the reactants, can now also be used for liquid fuels. The known advantages of this burner technology can now also be used for liquid fuels. These include:

(a) Low emissions (soot, nitrogen oxide, carbon monoxide) when using a surface combustion system;

(b) low noise emissions;

(c) small blower output;

(d) a combustion air blower can be completely dispensed with (atmospheric mixture formation);

(e) compact heat generator design by directly coupling the heating circuit side heat exchanger to the spatially precisely definable reaction zone.

Core of the pre-evaporating, premixing combustion technology puts the heating of the liquid heating oil under high pressure Evaporation of the heating oil only takes place at the nozzle outlet instead, unlike conventional evaporative burner designs, where the oil is almost pressureless on a hot Surface hits, with deposits less volatile Heating oil components are the result. Compliance with the aforementioned pressure condition in the operating phases in which heated heating oil is in the burner's hydraulic system, avoids these deposits. Both during the heating phase as well as during the cooling phase, the oil lines from the Pump to the heated fuel valve is sealed pressure-tight or the pressure in the system is determined by means of the oil pump or a Maintain expansion tank (e.g. metal bellows).

In the system according to the invention, a fuel valve is used "Atomization characteristic" used, that from a certain Pressure releases the nozzle opening. The by the pressure drop on Oil evaporation triggered by the valve causes extreme Volume increase and thus a significant reduction in throughput compared to the operation of the fuel valve with not preheated heating oil. When using a swirl nozzle, a Throughput reduction through the preheating of the Fuel-related decrease in viscosity. With the air core takes in increasing fuel temperature the nozzle opening and the fuel flow rate decreases. The extreme Preheating the fuel allows the nozzle opening significantly larger, especially with small throughputs design than with conventional pressure atomizing systems is possible. By using the swirl principle in one Return nozzle with integrated needle valve is the Burner output can be further reduced.

In a development of the invention it is provided that the Heating device of at least one electric heating element, Heating element or heating cartridge is formed. The heater is designed to operate at maximum fuel flow heated to the desired temperature. Can be beneficial the fuel valve additionally with a temperature sensor, e.g. B. a thermocouple or the like. So that its Temperature for regulating the heating output of the heating device is detectable.

A particularly simple embodiment provides that the Heating device is provided in the fuel valve. You can the individual heating cartridges or the like. B. in holes be used. However, it is also conceivable that the Heater can be attached to the fuel valve, e.g. B. can be flanged so that there is direct contact between Heating device and fuel valve exists.

In one embodiment, the fuel valve is as Simplex nozzle designed with a closing piston. The Locking piston outside or inside the Fuel valve are.

A further development provides that the fuel valve is a Has return opening and with a return line can be combined. In this way, a return system created, and the fuel valve serves as a return nozzle.

When designing the hydraulic system as a return system is one direct electrical heating of the valve or the valve body unnecessary. It is enough to put the fuel in one of the Fuel valve removed, upstream of the valve arranged electrically heated fuel heater heat. Pumping the fuel at low Pressure difference between supply and return pressure before opening of the valve causes the fuel volume to heat up inside the valve. An insufficiently preheated exit Fuel immediately after opening the fuel valve is avoided.

The return nozzle can e.g. an integrated needle valve have that the nozzle opening during the heating and Completes the cooling phase in a pressure-tight manner. The movement of the Valve tappet is determined by the pressure difference between pre and Return pressure allows. Pumping around the heating oil at low The pressure difference between the supply and return pressure prevents this Leakage of preheated heating oil. To cool the hot, returned oil mass flow can also be a Oil cooler that heats combustion air before the pump enters be provided. Depending on the degree of air preheating increases the proportion of the gaseous fuel in the fuel / air mixture. The exchange of impulses between combustion air and Fuel that affects the quality of the mixture takes also with increasing air temperature.

A further training provides that one in the return line adjustable flow resistance for pressure control as well as a adjustable shut-off valve are provided.

With a return line, which is only used as a leakage line serves are not a special measure to cool the very low oil mass flow necessary. For example, at Coaxial combination of the oil supply line and oil return line the cooling effect of the supplied oil mass flow. Finally Embodiments are also known in which a Return line is not required.

A burner with an immediately after the valve tappet The free-flowing fuel valve has the advantage that depending on the degree of air preheating, after the Fuel atomization is a colloidal or sets molecularly disperse fuel distribution. Due to the Stability of the colloidal or molecularly dispersed It is possible to pre-fuel the reactants Flame in a large volume area without mixing knock down the fuel droplets on the mixing chamber walls. The mixture of the reactants is therefore completely spatial decoupled from the combustion reaction possible and not how in conventional emission-reduced oil burners (so-called Blue burners) only within a very small flame upstream gasification zone, which via flue gas circulation in direct convective heat exchange with the flame. The low temperature of the quasi-homogeneous mixture of Burner according to the invention allows an intensive mixing in a large-volume mixing zone without the risk of self-ignition. The mixture of fuel and combustion air is now not more on the gasification zone upstream in the flame limited. In particular through the use of a return nozzle in Connection with an extreme fuel preheating at under Pressurized fuel is a small combustion output operationally feasible. It also has the big advantage achieves that deposits from cracked products are avoided, because fuel vaporization takes place in a free atmosphere and not on a hot like with film evaporation burners Surface in the presence of oxygen.

The heating zone is in the immediate vicinity of the Reaction body, but is spaced from it. At a another embodiment is the heating zone directly with the Reactor connected. With this configuration, the Fuel as it passes the heating zone, from the reaction body, which usually glows during operation, warms up. While the company therefore does not have separate heating devices required. The heating by radiation energy, by convection or by direct contact through heat conduction respectively.

In a particularly preferred embodiment, the Heating zone designed as a ring channel. In this way, one relatively large surface area for the inflowing fuel created so that this relatively quickly z. B. by radiation can be heated. The ring channel in particular surrounding sleeve-shaped reaction body is a very large Area available for heating.

In another embodiment it is provided that the Heating zone is formed as a coil. In this coiled tubing the fuel to be heated led, the coiled tubing is directly illuminated by the reaction body.

In the preheating phase before the burner starts, the Fuel warmed up by an electric immersion heater is provided, which is connected to the heating zone.

In particular, the heating zone lies directly on the heating cartridge, so that the heat of the heating cartridge by conduction on the Heating zone and is transferred from there to the fuel. Here can be used as a heating element or as a heating coil be trained.

In a preferred embodiment, the heating cartridge is in sections with a fuel-air mixture leading Area in connection, being in the direction of the mixture preparation flame arrester is provided. The heating cartridge also serves as in this embodiment Ignition device, the fuel-air mixture at the usually ignited glowing outer surface of the heating element. Separate ignition devices are therefore unnecessary.

Fig. 1:

eine schematische Darstellung eines vorverdampfenden, vormischenden Brenners für flüssigen Brennstoff;

Fig. 2:

ein Regelkonzept für die Brennstoffzuführung;

Fig. 3:

ein erstes Ausführungsbeispiel eines Brennstoffventils mit Schließkolben;

Fig. 4:

ein nach Art einer Simplexdüse ausgebildetes Brennstoffventil mit Schließkolben;

Fig. 5 bis 7:

Längsschnitte durch Ausführungsformen des erfindungsgemäßen Brenners; und

Fig. 6a:

ein Querschnitt gemäß Figur 6.

Further advantages, features and details emerge from the subclaims and from the following description, in which several particularly preferred exemplary embodiments and variants are described in detail with reference to the drawing. Show:

Fig. 1:

a schematic representation of a pre-evaporating, premixing burner for liquid fuel;

Fig. 2:

a control concept for the fuel supply;

Fig. 3:

a first embodiment of a fuel valve with a closing piston;

Fig. 4:

a fuel valve designed in the manner of a simplex nozzle with a closing piston;

5 to 7:

Longitudinal sections through embodiments of the burner according to the invention; and

Fig. 6a:

6 shows a cross section according to FIG. 6.

In Fig. 1, the fuel lines 113, the air-carrying Components 114, the components carrying the fuel / air mixture 115, the flue gas-carrying components 116 and the water pipes 117 of the heating circuit 144 is shown schematically.

1 consists of the functional units Air treatment 118, fuel treatment 119, air control 121, fuel control 122, mixing zone 123 and reaction zone 124.

The air treatment 118 consists of a heat exchanger Air preheating 125, the returned fuel 126 heat withdrawn and emits 127 to the supplied combustion air.

The fuel preparation 119 consists of an electric heated fuel heater 128, the heat exchanger 125 in the Return line 126, which is coupled to the air treatment 118 is and a heat exchanger 129, which is a part of the at Combustion reaction released heat to the Fuel preparation 119 transmits, and a return nozzle 130 with integrated needle valve.

The air control 121 consists of a fan 131 and a Air throttle 132, the electromechanical or mechanical is actuated, whereby an automatic adjustment of the promoted air mass flow to the current air demand of Firing is possible.

When the burner starts, the burner control switches the burner motor one with the oil pump 62 (FIG. 2) and the fan 131 is coupled. First, the shut-off valves 53, 54 and 55 closed. Then the electromechanically operated opens Shut-off valve 53 in the flow line 56 and that Shut-off valve 55, which can be actuated electromechanically, in the secondary branch 58 the return line 57. At the same time the Burner control the electrically operated heating element 133 in Fuel heater 128 a. The oil pump 62 delivers in this Operating phase the fuel through the fuel preparation 119 and the one coupled to the air treatment 118 Heat exchanger 125. The needle valve in the return nozzle 130 remains due to the low pressure difference between the Measuring points for supply pressure 33 and return pressure 134 locked. This pressure difference is due to the mechanical actuatable pressure control valves 60 and 59 variably adjustable. The minimum pressure in this system corresponds to the Measuring point for the return pressure 134 ascertainable pressure value. In all components flowed through by heated fuel thus an overpressure compared to atmospheric pressure. Thereby it is ensured that none during fuel heating evaporate low-boiling fuel components and the remaining high-boiling fuel components none Form deposits in the hydraulic system. Furthermore prevented pumping the fuel out early insufficiently preheated fuel from the return nozzle 130.

By opening the electromechanically operated shut-off valve 54 the return pressure drops when the required pressure is reached Oil temperature in the swirl chamber of the return nozzle 130 and that The needle valve releases the nozzle bore. This will make the Fuel atomizes and forms in the mixing chamber 123 combustible mixture with the supplied combustion air 127, the burns in reaction zone 124. To ignite the mixture is either a conventional high voltage ignition system or a electrically heated ignition element provided. Another Possibility is the high surface temperature of the electrically heated fuel heater 128 for igniting the Use mixture.

The return nozzle 130 is like a conventional one Pressure atomizer burner designed as a swirl nozzle. With growing The throughput decreases. The use of a Return nozzle 130 also has the advantage that Ratio between the amount of fuel returned and atomized fuel quantity at constant flow pressure above a large control range 1:10 by throttling the back pressure is changeable.

Preheating the fuel and using a The return nozzle enables the nozzle cross-section to be the same To choose oil throughput significantly larger than this in conventional Pressure atomizer burners is possible. This results in one low clogging of the nozzle opening and an increased Operational reliability of the system.

The heated, pressurized fuel is at this Process atomized within the dispersant air. On Part of the evaporated molecules condense into one colloid-disperse system, the rest remains as stable As with a gas burner, gas is obtained and forms a homogeneous one Mixing system. The proportion of colloidally dispersed oil droplets and homogeneously mixed molecules depends on the temperature and pressure-dependent chemical reactions (e.g. cracking reactions in the case of fuel heating oil EL) Fuel composition and the degree of air preheating.

The colloidally dispersed fuel is in this system aggregated to such large droplets that they delimited a phase boundary against the dispersant air are. On the other hand, the particles are so small that they are in their behavior largely corresponds to dissolved molecules.

This has the following advantages over one coarsely dispersed heating oil distribution conventional Pressure atomizing systems: (a) Distribute by Brownian motion colloidally dispersed oil droplets in the combustion air, until their concentration is the same in all locations of the system Has reached value; (b) excellent durability of the colloidal fuel; (c) the gaseous fraction of the Fuel forms immediately after mixing by molecular Transport a flammable mixture with the combustion air. For the colloidally dispersed portion of the fuel applies as with conventional oil pressure atomizing burners the laws of Spray combustion. The accelerated drop heating and - evaporation due to the small drop diameter and the Early combustion and related Temperature increase of that already in the gas phase Share of the fuel make it possible despite the in the liquid phase of the fuel portion of a "quasi homogeneous Combustion system "to speak.

In the burner's operating phase, this is electrical Heating element 133 switched off. The one for fuel heating necessary energy is coupled out of the reaction zone 124. The heat exchanger in reaction zone 129 and Fuel heaters 128 can be designed as a structural unit.

The burner control unit closes to switch off the burner the shut-off valve 54 in the return line 57 and that Shut-off valve 55 in the secondary branch 58 of the return line 57. This reduces the pressure difference between the forward and Return at measuring points 133 and 134 and the needle valve in the return nozzle 130 closes. The combustion reaction is thereby interrupted. The high pressure in the Fuel preparation 119 prevents evaporation of the hot fuel after burner shutdown. Finally the burner control closes the electromechanically operated one Shut-off valve 53 in the flow line 56 and switches the Burner motor.

FIG. 3 shows a first exemplary embodiment of a shown in total with 201 burner valve. This burner valve 201 has a housing 202 with a Valve nozzle bore 203, into which an opening 204 Feed line (not shown) opens out. Optionally, that can Provide fuel valve 201 with an additional opening 205 be, which also opens into the valve nozzle bore 203. On this additional opening 205 can be a return line (not shown), so that the fuel valve 201 both in a pure lead system and in one Return system is usable. When used in one Flow system is the opening 205 with a plug locked.

A valve nozzle 206 is located in the valve nozzle bore 203 screwed into which a valve lifter 207 is inserted. This valve lifter 207 is closed by means of a closing spring 208 held in a closed position. The pressure increases in the Valve nozzle bore 203 above a certain value, then opens the valve nozzle 206 automatically by the valve lifter 207 is pushed out.

In Figure 3 it can also be seen that in corresponding Bores or other recesses in the housing 202 Cartridges 209 are used. Will over these cartridge heaters 209, which are electrically operated, heats the housing 202, then that located in the valve nozzle bore 203 Fuel also heated. The valve nozzle bore 203 serves thus as a preheating chamber 210. That from the valve nozzle 206 escaping fuel is preheated, causing the above advantages mentioned.

Figure 4 shows a second embodiment of a A total of 211 fuel valve, which one has slightly changed structure. The preheating chamber 210 opens into a simplex nozzle 212, which from a valve lifter 213 is closed. Here, too, the valve disc 214 becomes Reaching a certain pressure of the fuel in the The preheating chamber 210 is lifted from the opening of the simplex nozzle 212. Since the features of a simplex nozzle are known, i. H. the inversely proportional relationship between throughput and The temperature of the fuel will not be discussed any further received. It should also be noted that the storage 215 of the Valve tappet 213 in FIG. 4 merely by way of example is reproduced. Other constructions are conceivable and should also be encompassed by the invention.

It is important, however, that the fuel valves 201 and 211 with a heating device 216 formed by heating cartridges 209 are provided, wherein in the embodiments Cartridges 209 are inserted into corresponding openings. It however, it is also conceivable that the heating device 216 positively mounted on fuel valves 201 and 211 are. The housing 202 of the Fuel valve 201 and 211 heated and over this housing 202 the fuel located in the preheating chamber 210. At Reaching a certain temperature or increasing the Pressure of the fuel in the preheating chamber 210 to one valve tappet 207 or 213 is lifted and it can fuel from the fuel valve 201 or 211 emerge. The heated fuel escaping under pressure nebulizes during relaxation and can optimally preheated combustion air can be mixed.

FIG. 5 shows a burner, designated overall by 301 shown, which has the structure described below. Within a rotationally symmetrical reaction body 302 there is a heat exchanger element 303, in which the Fuel is preheated. This is via a feed line 304 supplied to the heat exchanger element 303 and enters one Annular channel 305 formed by two concentric sleeves 306 and 307 is formed. The fuel is transferred into the ring channel 305 a connecting line 308 inserted or from the ring channel 305 led out via a line 309. Line 309 opens into a return nozzle 310 that goes from a certain one in the line 309 prevailing pressure opens and the fuel inside Mixing chamber 311 atomized. Open into this mixing chamber 311 also air channels 312 through which the combustion air is fed. This combustion air flows through it Heat exchanger element 303 via a line 313 and a Annular channel 314.

When the return nozzle 310 is closed or open, the overflow line 309 fuel supplied via a return line 315 returned to the tank. This return line 315 is located near line 313 so that over the Line 313 air flowing through in the return line 315 located fuel cooled or over this fuel the air is heated. With high returned A special oil cooler is provided for fuel quantities either from the supplied combustion air or from Mass flow of oil or both is flowed through.

The heat exchanger element 303 has a circumferential groove 316, in which is a heating element 317 in the form of a heating coil 318 is inserted. This heating coil 318 is in the start phase the inner sleeve 306 and this in the ring channel 305 itself fuel is preheated. The fuel is in the Ring channel 305 under pressure. The inner sleeve 306 is on the Heating coil 318 pressed on and welded on its end faces, which fixes and protects the heating coil 318. The Heating coil 318 can also be used with a (not shown) Thermocouple.

The return nozzle 310 is located in a union nut 319, so that if necessary, e.g. B. to repair or Maintenance purposes, can be removed quickly. At the back the valve tappet 320 of the nozzle 310 can be seen, which has a Compression spring 321 is biased. The fuel valve can too contain the spring as a structural unit.

The inner mixing chamber housing 322 is on the union nut 319 attached, which from the outer mixing chamber housing 323 is spread. Between the inner and the outer Mixing chamber housing is therefore another mixing chamber 324, which is used to further homogenize the fuel-air mixture serves. This becomes from this outer mixing chamber 324 Mixture supplied to the reaction body 302 and flows through it radially outwards. After igniting, the mixture burns outside of the reaction body 302, the reaction body 302 glows during operation. The radiant heat of the Reaction body 302 is radially inward on both the between the reaction body 302 and the heat exchanger element 303 fuel-air mixture as well as on the outer sleeve 307 transferred, whereby the mixture and the im Ring channel 305 located fuel are heated. While the operation is the heating element 317, which over the electrical lines 325 power is turned off or in order to maintain a certain temperature e.g. B. operated cyclically via a controller.

The flame monitoring on the outside of the reaction body 302 takes place via one in the firebox or in the Premixing area flicker detector 326 looking from below looks through the reaction body 302. A Flame control by means of an ionization electrode above of the reaction body is arranged or projects into it, is also possible.

The embodiment of a burner shown in Figure 5 has the main advantage that due to the low Distance of the oil film in the ring channel 305 to that of Reaction body 302 formed radiation source of the fuel within a very short time, especially in the start-up phase is heated. The heat flows radially from the oil film inside too. In burner operation, the radiant heat emission from the Reaction body on the outer sleeve of the ring channel. This gives the heat continues to the oil film. When the burner starts, the Accordingly, oil film heated radially from the inside, in The burner is operated by heating (Radiation, conduction) of the reaction body.

In addition, the ring channel 305 offers a large one Heat exchanger surface. Alternatively, the rotationally symmetrical Reaction body 302 can also be designed as a flat body, being immediately below this flat body of the ring channel 305 also a heat exchanger for the Heating of the fuel is to be provided.

In the exemplary embodiment in FIG. 6, this contacts Heat exchanger element 303 directly the reaction body 302, whereby the fuel in the connection line 308 is warmed up via heat conduction. The heating element 317 for Heating of the fuel in the starting phase is as a heating element 327 formed, which in a corresponding bore 328 (see Figure 6a) of the heat exchanger element 303 is used. This Bore 328 is segmental over part of its length broken open so that the heating element 327 in this area 329 is openly accessible. This area 329 is above one Outbreak 330 and a connecting line 331 with a chamber 332 in connection, which in turn via the ring channel 333 with the outer mixing chamber 324 is connected. This way you can at the end of the start phase, the fuel-air mixture, which is about the connecting line 331 can enter the cutout 330, Ignite on the glowing heating element 327 so that the flame Reaction body 302 can penetrate, whereby the burner 301 is started. The flame strikes back from the Outbreak 330 into chamber 332 is proportionate by the small cross section of the connecting line 331 and its length reached, which ensures a safe flame arrester is created. The high speed of the fuel-gas mixture and the small distance of the faces and the relative large length of the area (clearing distance) of the connecting line 331 prevent the mixture in the chamber 332 from igniting.

In the exemplary embodiment in FIG. 7, this is Heat exchanger element 303 wrapped in a coiled tube 333, in which the fuel is carried. This coiled tubing 333 is to both connection line 308 and line 309 connected, with the tube coil 333 in countercurrent is flowed through. This coiled tubing 333 is glowing Reaction body 322 illuminated, whereby the flowing therein Fuel is heated.

Claims (33)

1. Combustion process having generation of a combustible mixture of a liquid fuel and air of combustion and for the combustion thereof, in which:

   the liquid fuel is pressurised in a heat-up phase with the fuel valve (201, 211) closed,

   the pressurised liquid fuel is heated,

   after the heat-up phase the fuel valve (201, 211) is opened, and the pressurised, heated liquid fuel is atomised and vaporised by way of a nozzle,

   the vaporised fuel is mixed with the air of combustion, with at least part of the vaporised fuel condensing, such that there arises a colloidally and/or molecularly disperse fuel-air mixture,

   in order to terminate the combustion the fuel valve (210, 211) is closed, and

   with the fuel valve (210, 211) closed the pressurised, heated liquid fuel is cooled down.
2. Process according to Claim 1, characterised in that the air of combustion is heated before the mixing process.
3. Pre-vaporising and pre-mixing burner for liquid fuels, in particular in order to carry out a process according to one of the preceding claims, having one or more fuel heaters (128) in order to heat the liquid fuel, having a means of raising the pressure in the fuel, having a nozzle in order to atomise and vaporise the fuel and to mix the fuel with air of combustion, with at least part of the vaporised fuel condensing, such that there arises a colloidally and/or molecularly disperse fuel-air mixture, and with the burner having a hydraulic system which during a heat-up phase before combustion and also during a cooling-down phase after combustion holds the liquid fuel under pressure greater than ambient pressure and with the exclusion of air and has a shuttable fuel valve (201, 211) which in the heat-up phase, during combustion and also in the cooling-down phase holds the liquid fuel under pressure.
4. Burner according to Claim 3, characterised in that there is provided in order to atomise the heated fuel a swirl nozzle which is embodied as a return nozzle (130) having an integrated needle valve.
5. Burner according to Claim 3 or 4, characterised in that the swirl nozzle (130) has a needle valve which at a certain adjustable pressure difference between the forward and the return pressure unblocks the nozzle opening in the return nozzle.
6. Burner according to one of Claims 3 to 5, characterised in that the fuel pre-heating temperature is adjustable, depending on the fuel used, to a level such that the fuel is vaporisable under atmospheric conditions.
7. Burner according to one of Claims 3 to 6, characterised in that the heated fuel is virtually completely vaporisable by lowering of the pressure at the nozzle outlet and mixing with air of combustion which is pre-heated to the same temperature.
8. Burner according to one of Claims 3 to 7, characterised in that, as a result of lowering of the pressure at the nozzle outlet and mixing with air of combustion which is pre-heated only slightly or is not pre-heated, after the lowering of the pressure at the nozzle outlet part of the fuel forms with the supplied air of combustion a colloidally disperse system and the other part of the fuel forms a molecularly disperse system.
9. Burner according to one of Claims 3 to 8, characterised in that there is provided for the combustion of the fuel dispersed in the air of combustion a permeable reaction burner (124).
10. Burner according to one of Claims 3 to 9, characterised in that when an in particular electrically operated fuel heater (128) is coupled to the reaction zone (124) the fuel-air mixture is ignitable as a result of the surface temperature of the fuel heater (128).
11. Burner according to one of Claims 3 to 10, characterised in that there are provided for fuel preparation one or two fuel heaters (128), an air heater (125) and a return nozzle (130) having an integrated needle valve.
12. Burner according to one of Claims 3 to 11, characterised in that the pressure difference between the forward and the return pressure during a burner operation cycle (burner start-up, burner operation, burner switch-off) is modifiable by the burner control in step-less, step-wise or pulse-wise manner depending on the fuel regulation (122) used.
13. Burner according to one of Claims 3 to 12, characterised in that the lines which guide fuel are closable in pressure-tight manner by a needle valve integrated in the return nozzle (130) as well as by cut-off valves (53, 54, 55).
14. Burner according to one of Claims 3 to 13, characterised in that there is combusted a colloidally and/or molecularly disperse fuel-air mixture.
15. Burner according to Claim 3, characterised in that the closing force of the valve lifter (207, 213) during the burner start-up and switch-off phase is greater than the opposing force acting on the valve lifter (207, 213), which is brought about by the difference between the forward and the return pressure.
16. Burner according to one of Claims 3 to 15, characterised in that there is provided a circulating pump which during the burner start-up phase with a small pressure difference between the forward and the return pressure and with the burner valve closed pumps round the fuel in fuel preparation.
17. Burner according to one of Claims 3 to 16, characterised in that there is provided a fuel regulating device (122) which by lowering of the return pressure and/or raising of the forward pressure when the required fuel temperature is reached unblocks the nozzle bore by way of a needle valve in the return nozzle (130) and thus enables the mixture to form.
18. Burner according to Claim 16, characterised in that the fuel conveyed back to the fuel pump is usable in a heat exchanger (125) in order to pre-heat the air of combustion.
19. Burner according to one of Claims 3 to 18, characterised in that the fuel valve (301, 311) opens at a certain pressure difference between the pressure in the supply line and in a return line and/or opens above a certain temperature of the fuel located in the valve interior.
20. Burner according to one of Claims 3 to 19, characterised in that there is provided in the supply line a pressure compensation vessel, for example a bellows, in particular a metal bellows.
21. Burner according to one of Claims 3 to 20, characterised in that the fuel valve (311) is constructed as a simplex nozzle having a closing plunger (313).
22. Burner according to one of Claims 3 to 21, characterised in that when the fuel valve (301, 311) is open there arises an induction effect for the air of combustion in order to enable the burner to operate without assistance from a blower.
23. Burner according to one of Claims 3 to 22, characterised in that depending on the fuel regulating device used the fuel supply into the reaction zone (124) may be switched off by raising of the return pressure and/or lowering of the forward pressure to the level of the return pressure.
24. Burner according to one of Claims 3 to 23, characterised in that the fuel valve (301, 311) opens above a certain pressure difference between the valve internal pressure and atmospheric pressure and/or has a return opening (305) and is combinable with a return line, and in particular there is provided in the return line a settable flow resistance means, in particular a cut-off valve.
25. Burner according to one of Claims 3 to 24, characterised in that the hydraulic system has, arranged both in the forward line (56) and in the return line (57), an electromagnetically activatable cut-off valve and in particular an electromechanically activatable pressure regulating valve (60).
26. Burner according to one of Claims 3 to 25, characterised in that there is/are provided one or more mechanically or electromechanically activatable pressure regulating valves (59) in order to adjust the return pressure.
27. Burner according to one of Claims 3 to 26, characterised in that the fuel valve (301, 311) opens to the outside immediately downstream of the valve lifter (307, 313).
28. Burner according to one of Claims 3 to 27, characterised in that the fuel heater or the heating device (316) is formed by at least one electric heating rod, heating cartridge (309) or the like, in particular may be switched off shortly after combustion start-up.
29. Burner according to one of Claims 3 to 28, characterised in that the heating device (316) is provided in and/or on the fuel valve (301, 311).
30. Burner according to one of Claims 3 to 29, characterised in that there is provided an electric heating element (217) which is connected to the heating zone, is constructed in particular as a heating rod (227) or as a heating coil (218) and/or is connected section-wise to a region (230) which guides the fuel-air mixture, and there is provided in the direction of mixture preparation a flashback arrester (231).
31. Burner according to one of Claims 4 to 30, characterised in that the return line (215) is provided in the region of the supply line (213) for the air of combustion.
32. Burner according to one of Claims 3 to 31, characterised in that it has a supply line (204) for the fuel, a mixing zone (211) in which the fuel is mixed with the air of combustion and a fuel valve (210) which is connected to the supply line (204) and opens into the mixing zone (211), with the supply line (204) being provided with a heating zone (205) in which the supplied fuel is heated by a reaction body (202).
33. Burner according to Claim 32, characterised in that the heating zone (205) is arranged in the immediate vicinity of the reaction body (202) while being distanced therefrom and/or is connected directly to the reaction body (202) and is constructed as an annular channel (205) or as a coiled tube (233).

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