WO2006072363A1

WO2006072363A1 - Hearth furnace, method, and use of said hearth furnace for melting metals

Info

Publication number: WO2006072363A1
Application number: PCT/EP2005/013306
Authority: WO
Inventors: Peter Biedenkopf
Original assignee: Linde Aktiengesellschaft
Priority date: 2004-12-23
Filing date: 2005-12-12
Publication date: 2006-07-13
Also published as: DE102004062261A1

Abstract

The invention relates to a hearth furnace comprising a burner for melting metals, especially non-ferrous metals, and an oxygen lance (25) for the post-oxidation of carbonisation gases.

Description

description

Furnace hearth, process and use of the stove for melting metals

The present invention relates to a hearth furnace for melting metals and a corresponding method and the use of the hearth furnace for melting metals.

Industrial furnaces for molten metal with burners as heating have long been known and used in various embodiments. Frequently, the burners are mounted so that the flame of the burner is directed in the furnace operation in the furnace interior and this heat almost directly. Furnaces of this type exist in various designs, for example as hearth furnaces, rotary drum ovens, tilt rotary kilns, shaft kilns. To the hearth furnaces and younger types of hearth furnace are expected, for example, so-called closed-well ovens, twin-chamber ovens (twin chamber) or Dreikammeröfen.

The associated burners are usually operated with fossil fuels, mostly natural gas or oil. The burner is in addition to the fossil fuel air, oxygen-enriched air or oxygen supplied to enable combustion of the fuel. The heat transfer between the hot flame of the burner and the metal to be heated in the furnace can be convective and / or via radiant heating.

The melting of metals has u. a. Significance in the recycling or recycling of scrap, slag or sorted waste, especially in the non-ferrous metals such as Al, Cu, Pb and Zn. In this area rotary drum ovens and tilt rotary drum ovens are common.

The invention is based on the technical problem of specifying the design options for furnaces for melting metals, in particular non-ferrous metals, and to provide a structurally novel metal melting furnace with favorable operating properties. Furthermore, the invention is intended to provide a corresponding method for melting metals and a corresponding advantageous use of the furnace. The invention relates to a hearth furnace for melting metals, which is designed for a discontinuous operation and a horizontal charging and a burner whose flame is directed in operation in the interior of the hearth furnace, and an additional oxygen! for introducing oxygen into the interior of the hearth furnace,

and to a method for melting a metal charge of a hearth furnace, in particular according to one of the preceding claims, with the aid of a burner whose flame is directed into the interior of the furnace, wherein the furnace is operated intermittently lte and substantially horizontally charged and with Help oxygen lance during operation oxygen is introduced into the interior of the hearth furnace to cause by a local excess of oxygen in the interior of the furnace, a post-oxidation of exhaust gases, especially carbonization gases,

and to the use of the hearth furnace described for melting metals, in particular non-ferrous metals, in particular Al, Cu, Pb or Zn, preferably Al.

Preferred embodiments are specified in the dependent claims and are explained in more detail below.

The following description implicitly relates both to the hearth furnace according to the invention and to the method according to the invention and to the use of the furnace, without explicitly distinguishing between them.

The invention provides for the use of a hearth furnace for melting metals, ie a furnace with a substantially horizontal charging direction, and usually also a side door designed for discontinuous operation, ie discontinuous charging and discharging of a charge before re-cruising. For example, compared to shaft furnaces are in hearth furnaces, the aufzuschmelzenden materials distributed more in the area and less layered stove ovens are not rotated as turn and Drehkippöfen. Accordingly, they are structurally simpler and less expensive. However, the inventor assumes that hearth furnaces also favorably melt metals, in particular non-ferrous metals, although they are not commonly used for this purpose.

In addition, sol! . the hearth furnace according to the invention to a ^'problem which arises in particular when melting of Schratten, slags again to use waste and the like, adapted to: impurities in the starting material result in heating and melting such materials to environmentally harmful and / or hazardous exhaust gases, in particular for strong development of carbon monoxide and incompletely burnt hydrocarbons and other organic compounds. In the course of increasing environmental awareness, such exhaust gases are tolerated less and less. In individual cases, in addition to the health burden of the gases themselves, hazards to the persons involved may result from explosions.

Therefore, in addition to a burner for heating a charge, the invention provides an additional oxygen lance for introducing oxygen into the furnace interior. This oxygen lance should be provided separately from the burner; So here is not meant a device for supplying the oxygen or the air in the burner itself for combustion of the fuel. Rather, it is a separately delivered, own device for supplying pure oxygen or gas mixtures with oxygen, but preferably pure oxygen, to achieve a post-oxidation of problematic compounds by a local oxygen enrichment in the heated atmosphere over the charge.

It has been found that a separate supply of oxygen here is extremely effective and provides much better results than a superstoichiometric enrichment in the burner itself. Advantageously, a local oxygen enrichment, with neither an excess of stoichiometry in the flame itself _. a pronounced oxygen enrichment in the entire atmosphere in the burner interior is crucial. The oxygen lance according to the invention produces a pronounced oxygen excess and thus a high oxidation potential in certain areas. By a pronounced mixing of the atmosphere by the gas velocities generated by the burner and / or the oxygen lance, very substantial reductions of harmful gases can be produced. This is also without additional Energy expenditure possible; rather, the post-oxidation releases additional energy in the form of heat and can be used for the melting process.

The range of the oxygen introduced into the interior space by the oxygen lance can preferably not only be altered by adjusting the amount of oxygen per unit of time, but largely independently thereof. Thus, an optimization of the gas dynamics in the interior can be made, in particular to adjust the temperature distribution As already mentioned, energy is released by the post-oxidation If, for example, a relatively short-flame burner is used, it can be fitted with one at an opposite end of the stove On the other hand, the energy released as a result of the post-oxidation can also lead to fear of overheating, so that the range of the oxygen flow is set longer, and in some cases it can also be adapted to a specific charging form or a batch amount, gas dynamics varying by a particular furnace geometry or burner setting, or other circumstances.

This can be done with the help of swirl chambers. If the oxygen (or oxygen-containing gas) stream is swirled with the aid of a swirl chamber before entering the furnace interior, it tends more to widen and has a shorter range, it flows in untwisted, in particular by a nozzle which increases its velocity and concentrates its cross-sectional profile. so the range is bigger. Here also double-tube lances, in particular with an inner and an outer tube can be used, in which between a oxygen entry through a lance with turbulence and an oxygen entry through the other lance without Verwir- belung chosen and by adjusting the oxygen levels of the respective tubes also a infinite range adjustment can be done. Thus, transition states can be generated between short, bushy and wide flow formers and long narrow flow-forms. Particularly short flows can also be generated by the fact that the oxygen flows are swirled through both tubes, wherein a co-directional turbulence quiet currents and an opposite turbulence generates particularly short flow forms in the furnace interior. However, vortexing of the oxygen flow through one of two oxygen tube tubes is preferred. An additional or alternative possibility of range adjustment consists in a multi-tube lance, in particular double-tube lance, in which a tube, preferably an inner tube, has a nozzle opening into the interior and the other tube opens without a nozzle and with a comparatively larger cross-sectional area. Here, by dividing the oxygen flow to the two tubes also influencing the range of the flow in ^' the interior can be achieved without significant change in the amount of input per unit time.

It is further preferred that an exhaust gas analysis device is provided in an exhaust passage of the furnace or its mouth into the interior, by means of which the lance to be registered by the oxygen lance is controlled or regulated. Here, for example, the carbon monoxide value or, preferably, the oxygen content itself can be measured. Various methods which are already known per se can be considered, such as vibration absorption measurements with laser (carbon monoxide vibration or asymmetric oxygen vibration).

The oxygen flow generated by the oxygen lance in the furnace interior is preferably not in the same direction, but at least somewhat opposite to the flame direction. Preferably, an angle of more than 90 ° in between. An at least partial antidirectionality proves favorable for gas dynamics and mixing. In this case, the flame and the oxygen flow, even with directly opposite orientation, not be directed to each other directly. Incidentally, with a plurality of burners in the respective furnace chamber, this applies to at least one of the burners.

Furthermore, an arrangement of the oxygen lance in the vicinity of the exhaust duct is preferred, i. H. relative to the horizontal extent of the hearth furnace interior in the abgasgasseitigenseitigen half and particularly preferably relatively close to the mouth of the exhaust passage, as illustrated in the embodiment. The burner or at least one of a plurality of burners is preferably arranged in the respective other furnace half and relatively far away from the exhaust gas duct.

Finally, the oxygen unit is preferably arranged so that the oxygen flow is formed in an upper region of the hearth furnace, ie in an upper half relative to the vertical extension of the furnace interior. This can be done by arranging tion of the oxygen lance in this upper half and / or done by a certain upward inclination.

The foregoing and following embodiments are also and especially to read on multi-chamber hearth furnaces in which a separate Abschwelkammer is provided. The features of the invention then relate primarily to the Abschwelkammer, but can also be provided in other chambers in addition, about NEN to burn in a further heating of a charge for melting itself occurring in one of the Abschwelkammer downstream chamber exhaust gases.

Another preferred feature relates to adjustability of the flame length of the burner largely independent of the burner power. This should allow the gas dynamics to be adjusted additionally and also to optimize the geometric relationship of the flame with respect to the charge to be heated. In this case, the range of the oxygen flow in the manner already described can be adapted to changes in the flame length and, in particular, excessive superficial and residual oxidation of the metal by the oxygen flow can be avoided by appropriate adjustment. Often, however, the flame length of the burner will be adjusted especially as the charge melts and alters its geometry. In many cases, the main function of the oxygen lance according to the invention will then already be completed, because the carbonization gases arise, above all, in the initial heating process.

For adjustability of the flame length, an external mixing burner with a burner head, at least one fuel gas tube and at least one tube for an oxygen-containing gas may be provided, wherein the burner head has outlet openings from the fuel gas tube and from the tube for the oxygen-containing gas.

Gas supply lines for fuel gas and for oxygen-containing gas are provided,. each associated with a source of fuel gas or for oxygen-containing gas and at least one gas supply line eccentrically opens into a swirl chamber, which is mounted between the gas inlet and the fuel gas pipe and / or between the gas supply line and the tube for oxygen-containing gas. Preferably, at least one of the gas supply lines upstream of the swirl chamber divides into two lines, one of these lines being eccentric. opens into the swirl chamber and the other of these lines opens directly into the fuel gas pipe or into the tube for oxygen-containing gas.

^' 5

Particularly preferably valves are provided in the gas supply lines, in particular in the part of the gas supply lines, in which at least one gas supply line is already divided into two lines, and is a control or regulating device available, which controls or regulates the opening degrees of the valves, whereby the length the flame of the 0 burner is adjustable

Conveniently, the valves are designed as solenoid valves. These allow a gradually variable setting of the flame shape. For higher demands, the solenoid valves can be partially or completely replaced with control valves. These allow a continuously variable adjustment of the flame shape.

The swirl chamber preferably has a circular cross-section in a section perpendicular to the longitudinal axis of the fuel gas tube. Particularly preferably, the gas supply line opens tangentially into the swirl chamber. Through each of these embodiments, the friction for the swirl flow can be reduced and minimized together.

In this case, the fuel gas and / or the oxygen-containing gas can be registered eccentrically in a swirl chamber, in which the fuel gas or the oxygen-containing gas a swirl flow is impressed and the fuel gas or oxygen-containing gas 5 after leaving the swirl chamber the fuel gas pipe or the tube for oxygen-containing Gas is supplied.

Preferably, the per unit time via the swirl chamber and without the swirl chamber supplied to the burner amounts of fuel gas and oxygen-containing gas are controlled 0 or regulated, the fuel gas and the oxygen-containing gas are passed through valves whose degrees of opening are controlled or regulated so that the burner Produces flame, which has a desired length adjustable via the control or regulation. Preferably, a flow of Drail is impressed on the fuel gas stream. The advantage here is that a good mixing of the fuel with the oxygen with a slightly shortened flame arises.

According to another advantageous embodiment of the invention, a swirl flow is impressed on the flow of the oxygen-containing gas. This is advantageous because the flame aucfi shortens somewhat here and the burner can be structurally somewhat easier to manufacture.

According to a particularly preferred Äusführungsform of the invention, the combustion gas flow and the flow of the oxygen-containing gas to each other in the same direction swirl flows are impressed. The advantage here is that the flame is very short and quiet.

A further embodiment of the invention provides that opposing swirl flows are impressed on the fuel gas flow and the flow of the oxygen-containing gas. This is recommended in case an extremely short, bushy flame is needed.

A significant advantage of this embodiment of the invention is that the change in the flame length can be changed continuously (without changing the amount of fuel during operation). There are no changes to the burner (such as nozzle change) are made. Thus, the current flame length can be reduced to one third of its maximum length.

Another great advantage is that the change in the flame length is infinitely variable and during the operation of the burner, the impingement of a swirl flow can be started and also stopped again, without the burner would have to be turned off and without any structural changes, such as Changing a conventional swirl disk would be necessary. The change in the flame takes place via the change of at least one of the two gas flows solely by adjusting the opening degree of the described valves, which in turn takes place via the control or regulating device. Incidentally, if the flame is replaced by a second oxygen flow, the above explanation on the adjustability of the flame length also corresponds, mutatis mutandis, to the adjustability of the range of the oxygen flow with the aid of at least one drain chamber.

Furthermore, preferably the burner of the furnace should be aligned so that the flame is directed downwards to the metal to be heated. This can be an oblique orientation or a vertical orientation. The oblique orientation should form an angle between the main flame axis and the horizontal of at least 25 °, preferably at least 30 ° and more preferably at least 35 °. With this approach, the convective heat transfer is increased in the estate. With a burner whose flame length is adjustable, there is the possibility of determining the distance between the flame and the metal or, more generally, the geometric relationship between the flame. and the . To adjust metal to a certain extent.

In smelting furnaces for melting metals, the deterioration due to the flame is of particular importance. For metals, oxidation reactions can occur, which can be controlled by the adjustability of the flame length, and the range of the oxygen flow in the furnace according to the invention. In addition, it may be advantageous, for example, to achieve a rather uniform heat input into a heap of metal material with a significantly uneven ("heaped") surface by initially holding the flame for a short time, and then to lengthen the flame during the course of leveling the surface by increasing melting. Above all, however, the question of the contact between the gases in the flame and the metal is of concern. The same applies to the adjustability of the range of the oxygen flow, if this is not already directed into an (upper) region of the furnace interior, in which no harmful reactions can occur with the metal material.

Of particular interest is the invention for non-ferrous metals, in particular aluminum, copper, lead, zinc. The preferred area of application is in the melting of aluminum. Incidentally, here, the elemental information is meant in the technical and not necessarily chemically pure sense, ie at elemental proportions above about 60 wt.%. The term aluminum also also includes oxidically contaminated recycle material such as "scabies" with more than about 10 wt% Al.

As already mentioned above, the energy released by the afterburning can be considerable, especially in the case of stronger development of carbonization gases in carbonization chambers. Therefore, it is preferable that the burner power to the oxygen input through the

Adjust oxygen lance so that overall performance remains substantially constant. In addition to avoiding environmental damage and hazards to the

Employees can thereby profit economically from the actual oxygenation of the actual melting process.

Finally, the invention allows a stoichiometric operation of the burner, which is of interest for relatively nitrogen-containing fuels, for example, Dutch natural gas, to throttle nitrogen oxide production. Incidentally, this aspect, the invention speaks for a continued operation of the oxygen lance even after the onset of carbonization, d. H. during the actual melting process and / or in an actual melting chamber. For hearth furnaces, in which initially heated and then melted in the same chamber, so the oxygen lance would continue to operate, provided in Mehrkammeröfen another oxygen lance also in the melting chamber.

The invention will be explained in more detail below with reference to two exemplary embodiments, wherein the individual features can also be essential to the invention in other combinations and relate both to the apparatus and to the method character of the invention.

FIG. 1 shows a burner for use in a furnace according to the invention.

FIG. 2 shows a section along the line A-A in FIG. 1.

FIG. 3 shows a section along the line B-B in FIG. 1. FIG. 4 shows a schematic representation for explaining the flame length setting with the burner from FIGS. 1 to 3.

FIG. 5 schematically shows a double-tube oxygen lance for a furnace according to the invention. FIG. 6 shows a schematic representation of a hearth furnace according to the invention with a burner according to FIGS. 1-3 and an oxygen lance according to FIG. 4.

Before discussing the actual furnace according to the invention in more detail, a preferred embodiment of a burner for this furnace is first explained, which allows a particularly favorable adjustability of the flame length.

In detail, the figures show a burner 1 with a burner head 2, a tube 4 for an oxygen-containing gas and with a fuel gas tube 3 (not shown). The two tubes are arranged concentrically, in such a way that the fuel gas tube 3 is mounted within the tube 4. A burner 1 constructed in this way is also called a parallel-flow burner. For example, natural gas is used as fuel gas. An exemplary operation of the burner 1, in which both gas streams are twisted in the same direction, looks like this: Natural gas flows from the gas supply line 6 with open valve 10 via the line 6a in the swirl chamber 8. There, a swirl flow is impressed on the Ergas-. The valve 11 is closed.

Oxygen-enriched air passes via the gas supply line 7 and the line 7a into the swirl chamber 9. There, this gas flow is impressed by a swirl flow which is the same direction as the natural gas flow. In this case, the valve 12 is opened and the valve 13 is closed.

The flow of oxygen-enriched air leaves the swirl chamber and is introduced into the tube 4. The natural gas stream is introduced into the fuel gas tube 3.

At the burner head 2, the two gas streams mix and there is a characteristic flame. The shape and the length of the resulting flame depend directly on the setting of the valves 10, 11, 12 and 13.

For example, the flame lengthens when the fuel gas flow is added with the valve 11 open and the valve 10 closed, ie no swirling flow is imparted to the natural gas flow. It lengthens in comparison to the flame just described, in which two gas flows a swirl flow is impressed. Likewise, only the natural gas stream can be twisted and the flow of the oxygen-containing gas without ^' twist on the line 7b and the open valve 13 to the tube 4 are supplied.

By forming the valves 10, 11, 12 and / or 13 as control valves intermediate positions, ie adjustable degrees of opening of these valves are possible. As a result, the shape of the flame is infinitely adjustable. The change in the shape of the flame takes place without difficulty during the operation of the burner 1 by means of the control or regulating device for the valves 10, 11, 12, 13.

Boundary conditions for the shape of the flame are the supply amounts of fuel gas and oxygen-containing gas, the once selected supply quantities remain constant during operation of the burner. Only by the choice of valve positions for the valves 10, 11, 12, 13 a short, bushy and wide flame is generated up to a long, narrow flame.

Figure 4 shows a schematic representation of the above-mentioned short bushy flame above and the long narrow flame below. The burner 1 is thus shown twice here.

FIG. 5 shows the schematic structure of a double-tube oxygen lance. First of all, it should be noted that the oxygen lance has a substantially analogous structure to the explanation of FIGS. 1-4, wherein the natural gas flow and the oxygen-enriched air flow are each replaced by pure oxygen. Further, the swirl chamber 8, and thus the conduit 6a and the valve 10 can be omitted, so that the flow of oxygen through the inner tube 3 is not swirled. Finally, the inner tube 3 has an indicated in Figure 5 nozzle 23a, which is why the inner tube is provided in Figure 5 instead of the reference numeral 3 with the reference numeral 23. Accordingly, the outer tube of the oxygen lance is denoted by 24 in FIG.

This results overall in the possibility of an accelerated by the nozzle 23a and therefore in the interior of the furnace relatively far reaching oxygen flow through the inner tube 23 and a result of the larger opening cross-section of the outer. Tube 24 and the absence of a nozzle already slowed down, and therefore shorter Oxygen flow, which can be shortened by adjusting the valves 12 and 13 in Figure 1 and 2 corresponding valves by additional turbulence in terms of their range.

Figure 6 shows a schematic representation of a hearth furnace according to the invention in plan view and in section. The reference numeral 1 denotes the burner of Figures 1 - 4, the reference numeral 25, the oxygen lance of Figure 5, 26 an exhaust passage, 27 a charging door, 28 a removal door and 29 an oven interior. The furnace is substantially rectangular in plan and is loaded by the side loading door 27 and unloaded through the removal door 28. The material to be melted, namely aluminum scrap, is piled up on a substantially flat base of the oven interior 29 and heated by the burner 1 inclined downwards by about 45 ° to the plane of the paper, in the manner described first with a shorter flame length and then with increasing melting and thereby Lowering the aluminum scrap extended flame length is worked.

The carbonization gases produced during the initial heating are post-oxidized in the hot atmosphere above the aluminum scrap with the aid of a high oxygen concentration in the region of the oxygen flow from the oxygen lance 25 before they reach the exhaust gas channel 26. In this case, the flow length of the oxygen lance 25 exiting from the oxygen lance 25 into the furnace interior 29 can be adjusted in the manner already described in order to produce favorable gas dynamics.

An exhaust gas analysis device, not shown here, at the beginning of the exhaust duct 26 allows for an optimization of the gas dynamics, in particular the range adjustment of the oxygen flow, but also the flame geometry, and on the other hand, a regulation of the amount of oxygen depends on the oxygen concentration measured in the exhaust gas. Thus, an unnecessary oxygen consumption can be avoided and - at the same time an almost complete post-oxidation of harmful exhaust gas components can be achieved. Depending on the changing amount of oxygen, in turn, the performance of the burner 1 can be readjusted, in order to ensure an overall substantially constant furnace performance taking into account the energy released by the post-oxidation. The described furnace may also have a plurality of chambers. For example, it could be in the chamber shown in Figure 6 is a Abschwelkammer, which is connected upstream of an actual melting chamber. The oxygen source 25 is, as Figure 6 also does not show due to perspective, mounted with respect to the vertical extent of the interior space 29 at the top, approximately 75% of the height, to avoid excessive oxygen contact with the metal. The same applies to the exhaust duct 26, so that there is a relatively large proximity between the exhaust duct 26 and the oxygen lance 25, taking into account the height distribution.

Claims

claims

A hearth furnace for melting metals, which is designed for discontinuous operation and horizontal charging (27) and a burner (1), the flame in operation in the interior (29) of the

Stove oven is directed

and an additional oxygen lance (25) for introducing oxygen into the interior (29) of the hearth furnace.

2. hearth furnace according to claim 1 with means (23a, 23, 24) for adjusting the range of penetration of the oxygen from the oxygen lance (25) in the interior (29) of the furnace substantially independent of the amount of oxygen.

3. hearth furnace according to claim 2, wherein the means for adjusting the range of the oxygen has a swirl chamber (9).

4. hearth furnace according to claim 2 or 3, wherein the oxygen lance (25) is double-tube with a in an outer tube (24) arranged inner tube (23), wherein the inner tube (23) in a nozzle (23 a) ends , the outer tube (24) but ends without a nozzle.

5. hearth furnace according to one of the preceding claims with an exhaust gas analysis device and a control device for controlling the oxygen lance (25) introduced amount of oxygen in response to signals of the exhaust gas analysis device.

6. hearth furnace according to one of the preceding claims, wherein the oxygen lance (25) is aligned so that the oxygen flow in the inner space (29) of the furnace to the flame direction of the burner (1) forms an angle of about 90 °.

7. hearth furnace according to one of the preceding claims, wherein the oxygen lance (25) is arranged in relation to the horizontal extent of the interior (29) of the hearth furnace in a Abgaskanalseitigen half.

8. hearth furnace according to one of the preceding claims, wherein the oxygen! arranged (25) is arranged so that the generated oxygen flow with respect to the vertical extent of the interior space (29) of the hearth furnace in an upper half,

9. hearth furnace according to one of the preceding claims, which is designed as a multi-chamber furnace and having a Abschwelkammer in which the burner and the oxygen lance are arranged.

A hearth furnace as claimed in any one of the preceding claims, including means (6-13) for adjusting the flame length of the burner (1) which permits a flame length adjustment substantially independent of the power of the burner (1).

11. hearth furnace according to one of the preceding claims, wherein the burner (1) is oriented so that its flame is directed at an angle of at least 25 ° relative to the horizontal to the metal to be heated down.

12. hearth furnace according to one of the preceding claims, which is designed for melting non-ferrous metals, in particular Al, Cu, Pb or Zn, preferably Al.

13. A method for melting a metal charge of a hearth furnace, in particular according to one of the preceding claims, by means of a burner (1) whose flame is directed into the interior (29) of the furnace, wherein the furnace operated discontinuously and substantially horizontally ( 27) is charged and with the help of an oxygen lance (25) during operation oxygen is introduced into the interior (29) of the hearth furnace to cause by a local excess of oxygen in the interior (29) of the furnace post-oxidation of exhaust gases, especially carbonization gases ,

14. The method of claim 13, wherein the power of the burner (1) for compensation by the post-oxidation of energy released depending on the oxygen input through the oxygen lance (25) is reduced.

15. The method according to claim 13 or 14, wherein the burner (1) for reducing the nitrogen oxide attack in nitrogen-containing fuels (1) is operated with substoichiometric oxygen supply of the burner (1) itself.

16. Use of a hearth furnace according to one of claims 1 - 12 for melting metals, in particular non-ferrous metals, in particular _. Al, Cu, Pb or Zn, preferably Al.