WO2001006021A1

WO2001006021A1 - Melting plant with burner heated furnace vessel and charge preheater

Info

Publication number: WO2001006021A1
Application number: PCT/GB2000/002753
Authority: WO
Inventors: Reuben Trevor Kenning; Frank Norman Spedding; Peter Moxon; Jonathan Paul Harris
Original assignee: Fuchs Services Limited
Priority date: 1999-07-20
Filing date: 2000-07-18
Publication date: 2001-01-25
Also published as: AU6001400A

Abstract

A melting plant is provided for the production of molten metals, and in particular steel, primarily from metallic scrap or similar. The plant comprises a furnace with a closed furnace vessel (1) and at least one fuel burner (9, 10). The vessel (1) defines a lower portion (3) for containing a bath (8) of molten metal and an upper portion (4) located centrally of the lower portion (3) above the level of the bath (8) and through which waste gases produced by the burner or burners (9, 10) pass for discharge from the vessel (1). The upper portion (4) is adapted to form a preheating chamber (13) to retain temporarily a charge of material (14, 14') for subsequent release into the lower portion (3) of the vessel (1). In this way the heat of the waste gases from the burner or burners (9, 10) is used to preheat the charge of material (14, 14') within the chamber (13). In an extension of the invention, the preheating chamber (13) can be replaced by a hermetically sealed hood (22) to enable the melt to be refined and/or converted whilst the melt is still in situ within the vessel (1) prior to tapping.

Description

MELTING PLANTWITHBURNERHEATED FURNACE VESSEL AND CHARGEPREHEATER

The present invention relates to a melting plant and to a method for the production of molten metals, in particular steel, primarily from metallic scrap or similar.

In a conventional open hearth furnace, pig iron together with metallic scrap is deposited in the furnace. A mixture of air and gas is then combusted over the charge material to enable the melting process. The gas burned in the furnace is preheated using a regenerative firing system. In this system, the air and gas required for combustion is preheated in a refractory lined chamber at one side of the hearth before being combusted over the charge material. After combustion over the charge material, the hot waste gases are passed through another refractory lined chamber at the other side of the hearth. The hot waste gases heat the latter refractory lined chamber before being transferred to an off-gas cleaning equipment, prior to exhausting to atmosphere. The system is then reversed so that the continual preheating of the air and gas mixture can be maintained. The preheating of the combustion air and gas mixture allows elevated combustion temperatures to be achieved improving the efficiency of the system.

Open hearth furnaces have several disadvantages. The construction of a hearth furnace is complex and expensive. In addition, the regeneration system requires large preheating chambers where energy losses are high and large amounts of refractory materials are consumed. Also, material charging into the furnace is difficult and relatively slow. Open hearth furnaces are therefore uneconomical when compared to some other types of furnace.

Carbon and alloy steels of high purity can also be processed using an electric arc furnace. In this process, the primary heat source required to melt the charge material is produced by an electric current, specifically by using an electric arc. The arc is formed by passing electric current through graphite electrodes and controlling the relationship between the electrodes and the charge material. The electric arc furnace is essentially a melting process where scrap metal is generally used for the charge material.

To assist in the melting process, electric arc furnaces are equipped with secondary energy sources such as oxygen/gas burner systems. In addition, they can also be equipped with oxygen injection facilities to promote exothermic reactions from oxidizing elements within the furnace charge materials.

To reduce electrical energy consumption, the furnace can be charged with material through a preheating system utilizing energy recovery from the hot off-gases.

In EP-A-0 385 434 is described an electric arc furnace which has an attached shaft-like charging material preheater. By a horizontal movement of the furnace vessel away from the holding structure of the shaft, charge material can be discharged directly into the furnace vessel and into different regions of the furnace vessel. In this way, a more even distribution of the charge material can be achieved over a substantial cross-section of the vessel. The reason for this is to afford protection of the furnace structure when operating with ultra-high power electric arcs.

However, in an electric arc furnace such an arrangement still has the disadvantage that the charging shaft must be eccentrically mounted with respect to the centre of the furnace vessel because the central region is reserved for positioning of the electrodes. In addition, the relative horizontal movement between the furnace vessel and the holding structure for the shaft requires the cover of the furnace vessel to be raised from the bath with the possibility of the release of polluting waste gases into the atmosphere .

In addition, and more generally, electric arc furnaces also have disadvantages. They are dependent on a non- interruptible strong mains electric supply system, which may not always be available in developing countries. Even in highly technologically developed countries the cost of electricity generation can be relatively high, which makes the production of molten metals by such furnaces expensive. Also, electricity generation for such a furnace may in itself cause environmental pollution.

The object of the present invention is to overcome or substantially mitigate the aforementioned disadvantages of both open hearth and electric arc furnaces by providing a melting plant and a method of producing molten metal which use burners, such as fossil fuel gas or oil burners, and which make use of advantageous features developed for electric arc furnaces.

According to a first aspect of the present invention there is provided a melting plant comprising a furnace with at least one fuel burner characterised in that it comprises a closed furnace vessel defining a lower portion for containing a bath of molten metal and an upper portion located centrally of the lower portion above the level of the bath and through which waste gases produced by the burner or burners pass for discharge from the vessel, the upper portion being adapted to form a preheating chamber to retain temporarily a charge of material for subsequent release into the lower portion of the vessel whereby the heat of the waste gases from the burner or burners is used to preheat the charge of material within the chamber. Preferably, the lower portion of the vessel defines a substantially rounded base and tapering side walls, which define an upwardly reducing horizontal cross-sectional area to the interior of the lower portion of the vessel.

Advantageously, the tapering side walls are used to support the burner and at least one oxygen injection lance.

Preferably also, the lower portion of the vessel containing the bath is movable relative to the upper portion.

Preferably also, a vessel tapping system is provided in the base of the lower portion of the vessel. This may comprise a syphonic tapping system.

Alternatively, means are provided to tilt the lower portion of the vessel with respect to its vertical axis to facilitate tapping of the vessel via the tapping system.

Such an arrangement also has the additional considerable advantage that vacuum refining of the melt or steel conversion can take place whilst the melt is still in si tu within the vessel. Conventionally, the melt must be tapped from a furnace into a ladle and thence transferred into either a degassing tank or a converter vessel before such refining or converting can take place.

Hence, advantageously, the lower portion of the vessel comprises at least one gas injection means and a hood linked to a gas extraction means is provided which can be secured to the lower portion of the vessel in place of the upper portion comprising the preheating chamber whereby refining and/or conversion of the molten bath can be achieved prior to tapping of the bath from the vessel. Preferably, the hood can be releasably hermetically attached to the lower portion of the vessel.

Preferably also, the vessel comprises a neck which is located between the lower portion of the vessel and the preheating chamber and which forms a funnel through which hot waste gases from the lower portion of the vessel are drawn.

The neck of the vessel is preferably formed in two parts, a lower part being formed integrally with the lower portion of the vessel and an upper part being fixedly attached to the preheating chamber.

Preferably also, the preheating chamber is provided with a charge holding mechanism which operates to retain the charge of material within the chamber and when desired discharge it into the central portion of the lower portion of the vessel via the neck. Advantageously, the charge holding mechanism comprises at least one cantilevered finger, which is mounted at the base of the preheating chamber. The cantilevered finger can either pivot downwardly into the flared portion of the neck or, alternatively, can be withdrawn sideways from the interior of the preheating chamber through a wall of the vessel.

Advantageously, the lower portion of the vessel is capable of being tilted with respect to the upper portion of the vessel.

Preferably also, the upper portion of the vessel is closed by a removable cover, which provides access into the top of the preheating chamber.

According to a second aspect of the present invention there is provided a method of producing molten metal wherein a first batch of metal charging material is melted in a lower portion of a closed furnace vessel using the heat of at least one fuel burner, and characterised in that it comprises the further steps of filling a preheating chamber located in an upper portion of the furnace vessel with a second batch of metal charging material; funnelling waste gases produced by the burner or burners during melting of the first batch of material upwardly from the lower portion of the furnace vessel through the preheating chamber to heat the second batch of material; tapping molten metal from the lower portion of the furnace vessel; and discharging the second batch of material centrally into the lower portion of the furnace vessel for melting.

Preferably, the method comprises an initial step of preheating the first batch of metal charging material in the preheating chamber by firing up at least one fuel burner prior to the presence of charging material in the lower portion of the vessel.

Preferably also, the method comprises the additional step of refining the molten metal prior to tapping by replacing the pre-heating chamber with a hood that is hermetically sealed to the lower portion of the vessel above the molten first batch of metal, injecting gas into the molten bath to create turbulence therein, and extracting gases from the interior of the lower portion of the vessel above the molten bath.

Alternatively or in addition, the method comprises the additional step of converting a molten iron bath into steel by replacing the pre-heating chamber with a hood that is hermetically sealed to the lower portion of the vessel above the molten first batch of metal, blasting a jet of oxygen into the vessel to convert the molten iron to steel, and extracting waste gases from the interior of the vessel above the molten bath. Preferably, the molten metal is tapped from the lower portion of the vessel by means that do not require tilting of the lower portion of the vessel by more than 20° with respect to its vertical axis.

Advantageously, the method also comprises the step of retaining a residue of molten metal in the lower portion of the furnace vessel after tapping.

The present invention will now be described by way of example with reference to the accompanying drawings, in which Figs. 1 to 8 are sectional side views of a melting plant according to the invention showing the configuration of the plant at various times during a melting operation, as will be described.

The melting plant of the invention comprises a closed furnace vessel 1, which incorporates burners using fossil fuels in a conventional manner. The whole of the vessel 1 has a refractory lining 2 and in addition, or in parts of the vessel 1 as an alternative, may be provided with water, air or gas cooling systems (not shown) .

The vessel 1 comprises lower and upper portions 3 and 4 respectively. Optimally, the lower portion 3 of the vessel 1 is substantially pear-shaped with a rounded base 5 with side walls 6 that taper towards its apex. The tapering side walls 6 therefore define an upwardly reducing horizontal cross- sectional area to the interior of the lower portion 3 of the vessel 1. The upper portion 4 of the vessel 1 comprises a neck 7 that is centrally located above the lower portion 3 and therefore above a bath of molten metal 8 which in use is formed in the base 5 of the lower portion 3 (see Figs 3 and 4) . In the side walls 6 of the lower portion 3, either above or below the level of the bath 8, are located oxygen or fossil fuel burners 9 and oxygen injection lances 10. Tuyeres (not shown) may also be provided in the base 5 of the vessel 1, again either above or below the level of the bath 8. In order to provide support for the burners 9 and lances 10, the tapering side walls 6 of the lower portion 3 are preferably provided with water-cooling systems (not shown) . These water- cooled portions of the vessel 1 are then covered with thermal insulation in order to reduce heat losses from the lower portion 3 of the vessel 1. The thermal insulation may be designed either to minimize such heat losses or to achieve an optimized compromise between mechanical stability with maximum operational life and minimum heat losses.

A vessel tapping system 11 is also provided in the base of the lower portion 3 of the vessel 1.

The neck 7 of the vessel 1 forms a funnel through which hot waste gases from the melting process are drawn for discharge from the closed lower portion 3 of the vessel 1. At its top, the neck 7 comprises an outwardly flared portion 12 above which may be located a preheating chamber 13 for containing charging material 14. The top of the chamber 13 is closed by a removable cover 15, which it will be appreciated closes the vessel 1 as a whole. At the base of the chamber 13 between it and the flared top portion 12 of the neck 6 is a charge holding mechanism 16.

The charge holding mechanism 16 preferably comprises a plurality of cantilevered fingers 17 which project into the lower portion of the chamber 13 to form an openwork platform on which the charging material 14 can rest but which permit passage of the hot waste gases produced within the lower portion 3 of the vessel 1 therethrough. The fingers 17 may be pivotally mounted as at 18 at their ends adjacent the walls of the vessel 1 in order that they can be pivoted downwardly into the flared top portion 12 of the neck 7 to release the charging material 14 and permit it to fall into the lower portion 3 of the vessel 1. Alternatively, the fingers 17 may be adapted to be capable of withdrawal from the preheating chamber 13 through the walls of the vessel 1. To prevent the hot waste gases from adversely affecting the fingers 17, they are preferably each provided with their own internal water cooling system (not shown) .

Hence, charging material 14 which is retained in the chamber 13 during a melting operation will be heated by the hot waste furnace gases which are drawn upwardly from the lower portion 3 of the vessel 1 through the neck 7 and thence through the chamber 13 prior to discharge. This discharge takes place through a fume cleaning arrangement (not shown) .

The lower portion 3 of the vessel 1 containing the bath 8 is movable relative to the upper portion 4 in order to facilitate both slag removal and tapping of the molten metal and also to enable the upper portion 4 to be replaced for a time during a melting operation with a refractory-lined hood 22 to enable refining and/or conversion of the melt comprising the bath 8 to take place. As shown in the drawings, the neck 7 of the vessel 1 is formed in two parts, a lower part 23 being formed integrally with the lower rounded portion 3 of the vessel 1, whereas an upper part 24 is formed integrally with the flared top portion 12 and therefore fixedly attached to the preheating chamber 13. The lower portion 3 of the vessel 1 is thus capable of being tilted relative to the upper portion 4, as shown in Figs. 6 and 7, for slag removal and tapping of the molten metal via the tapping system 11. However, tipping of the lower portion 3 of the vessel 1 is always kept to a minimum and preferably it should be tipped at no more than 20° with respect to its vertical axis. This is unlike a conventional converter- vessel, for example, which is tilted significantly more than 20°, typically during filling, slag removal and discharge of the melt.

Alternatively, a syphonic tapping system could be provided for the vessel 1, which would enable the lower portion 3 of the vessel 1 to remain completely static during tapping.

If refining or conversion of the melt is to take place within the vessel 1, the upper portion 4 of the vessel 1 is removed and replaced for a time during a melting operation, as is described below, by the hood 22. The hood 22 is attached to the top of the lower part 23 of the neck 7 with a seal 25 being located therebetween to form a hermetically sealed joint. In embodiments of the plant where a hood 22 is going to be used, the vessel 1 is provided with one or more gas injectors 26 or other gas entry ports, such as tuyeres, through which stirring gases can be injected into the molten bath 8. The hood 22 is also provided with one or more outlet ports 27 through which gases can be extracted from the interior of the vessel 1 via one or more vacuum pump arrangements 28 at the same time as gases are injected into the bath 8.

A melting operation will now be described with reference to Figs. 1 to 8 sequentially to demonstrate operation of the vessel 1 throughout a melting cycle.

Fig. 1 shows the cover 15 removed from the top of the preheating chamber 13 to enable the latter to be filled with cold charging material 14. This charging material 14 is retained in the chamber 13 by the cantilevered fingers 17 which are at this period of the melting cycle held horizontal to form a platform to hold the material 14. The cover 15 is then replaced over the chamber 13 to close the vessel 1, as shown in Fig. 2, and the oxygen or fuel burners 9 are fired up to produce waste combustion gases which are funnelled upwardly through the neck 7 and thence through the chamber 13.

These waste combustion gases may be used to heat the cold material 14 to some extent but often the initial batch of charge material 14 is simply deposited directly into the lower portion 3 of the vessel 1. Hence, either after the charge material 14 has been sufficiently heated or, in the alternative, immediately after firing, the charge holding mechanism 16 is activated to discharge the material 14 into the lower portion 3 of the vessel 1, as shown in Fig. 3. To this end, the cantilevered fingers 17 may either be pivoted downwardly or be withdrawn. The oxygen or fuel burners 9 then commence melting of the material 14 directly. The oxygen injection lances 10 may also be used to support melting of the charge.

Once direct heating of the first batch of charging material 14 has commenced, the preheating chamber 13 can be used to commence heating of the next batch. Hence, as shown in Fig. 4, the cantilevered fingers 17 are returned back into position, projecting into the lower portion of the chamber 13, and the cover 15 is again removed from the top of the chamber 13 in order to enable it to be filled with a further batch 14' of cold charging material from a batch container or conveyor (not shown) . The cover 15 is then replaced to close the chamber 13 and heating of the material 14' by the hot waste gases from the vessel 1 then commences. During this time, heating of the first batch by the burners 9 and the injection lances 10 is reducing it into a molten bath 8, as shown in Fig. 5. Once melting is completed within the vessel 1, the burners 9 and the injection lances 10 are turned off and the molten metal can either be tapped directly, as shown in Fig. 7, or it can be refined or converted, as shown m Fig. 6.

If refining or conversion of the melt is to take place, the upper portion 4 of the vessel 1 is removed and replaced by the hood 22. It will be appreciated that to assist in this operation, the plant will be provided with pivoting support arms and gantries which can be used either to slide the upper portion 4 sideways or to raise it away from the lower portion 3 of the vessel 1 to enable the hood 22 to be located m position and then attached to the lower part 23 of the neck 7. During the time the chamber 13 is separated from the lower portion 3 of the vessel 1, the preheated charging material 14' can be retained within the chamber 13 by the fingers 17.

Once the hood 22 has been secured m position, in a refining process the injectors 26 are used to inject stirring gases such as argon, nitrogen, hydrogen or a halogen gas, directly into the bath 8 whilst gases are extracted from the interior of the vessel 1 above the bath via the outlet port or ports 27 in the hood 22. The injection of such stirring gases, which creates turbulence in the bath, enables tramp elements, such as copper, tin or nitrogen, to be removed from the melt as they react with the injected gases to create gaseous fumes which are then extracted from the vessel 1. The melt is thus refined. In order to ensure that refining of the melt occurs throughout the bath 8, it is important that sufficient turbulence in the bath 8 is created. The shape of the vessel 1 is an advantage here as it is designed such that a sufficiently large volume is available for considerable swirling of the melt, and therefore turbulence, to be achieved during the gas injection process. If the melt is to be converted, the oxygen lances 10 are used in place of or in addition to the injectors 26 to blast oxygen on to the bath of molten iron. In this way, the melt can be converted or both refined and converted to steel.

Conventionally, in order to control the temperature of a bath of molten iron during conversion, scrap material is often added to it. This can take place either before or after blasting with oxygen. In the present invention, in order to add scrap material to the bath 8, the hood 22 is released from its attachment to the lower portion 3 of the vessel 1 and replaced by the chamber 13 containing scrap charging material 14, as shown in Fig. 2. Once in position, the fingers 16 of the chamber 13 are either pivoted downwardly or withdrawn to discharge the material 14 into the lower portion 3 of the vessel 1, as shown in Fig. 3. If further oxygen blasting is then required, the chamber 13 can then be removed and replaced by the hood 22, as shown in Fig. 6, and the oxygen lances 10 employed again.

After refining and/or conversion has taken place, the hood 22 can be uncoupled from the lower portion 3 of the vessel 1 and moved away to be replaced by the upper portion

4, as before. Thereafter, any slag can be removed and the molten metal can be tapped.

During tapping, as shown in Fig. 7, the lower portion 3 of the vessel 1 can be tilted to pour the molten metal out of the vessel 1 via the tapping system 11 into a refractory lined ladle 21 or other receiving vessel. Alternatively, the vessel 1 may remain stationary and tapping achieved by syphonic means. During this time, the preheated charging material 14' is again retained within the chamber 13 by the fingers 17.

Once the tapping has been completed, the tapping system can be prepared for reception of the next batch, as shown in

Fig. 8. The lower portion 3 of the vessel 1 can then be returned back into an upright position ready to receive the next batch 14' of preheated charging material which has been retained within the chamber 13. If necessary, during the tapping operation, as shown in Fig. 6, a residue of molten metal 22 can be retained within the vessel 1 to facilitate melting of the material 14'. In this case, because the preheating chamber 13 is centrally located with respect to the lower portion 3 of the vessel 1, the material 14' is evenly discharged into the residue 22 and overheating of or the formation of hot spots within the subsequently formed bath 8 can be avoided or at least substantially mitigated.

When used for melting steel, the charging material 14, 14' will typically comprise metallic scrap. However, to enable the plant to be used for melting different types of scrap, the chamber 13 can be separated internally into different compartments to hold different types of material. These compartments are each associated with their own charge holding mechanism 16 in order that they can be separately discharged into the lower portion of the vessel 1. It will be appreciated that in this case, the charge material 14, 14' is still discharged substantially into the central portion of the lower portion 3 of the vessel 1 via the centrally located neck 7.

The shape and dimensions of the vessel 1 can be varied dependent on several factors. In particular, the height and cross-sectional area of the vessel 1 can be varied dependent upon the distribution of burners 9 and lances 10 to be employed; the dynamic characteristic of the burner flames and the lance stream; the type of fuel available; the characteristics of the scrap to be melted; and the degree of turbulence required during refining.

In addition, the melting plant may also be provided with facilities for other conventional ancillary components such as de-slag facilities, alloy additions, automatic temperature and sample taking, off-gas monitoring and control, and inert gas/electromagnetic stirring of the bath 8.

Claims

1. A melting plant comprising a furnace with at least one fuel burner (9, 10) characterised in that it comprises a closed furnace vessel (1) defining a lower portion (3) for containing a bath (8) of molten metal and an upper portion (4) located centrally of the lower portion (3) above the level of the bath (8) and through which waste gases produced by the burner or burners (9, 10) pass for discharge from the vessel (1), the upper portion (4) being adapted to form a preheating chamber (13) to retain temporarily a charge of material (14, 14') for subsequent release into the lower portion (3) of the vessel (1) whereby the heat of the waste gases from the burner or burners (9, 10) is used to preheat the charge of material (14, 14') within the chamber (13) .

2. A melting plant as claimed in Claim 1, characterised in that the lower portion (3) of the vessel (1) defines a substantially rounded base (5) and tapering side walls (6) which define an upwardly reducing horizontal cross-sectional area to the interior of the lower portion (3) of the vessel (1) •

3. A melting plant as claimed in Claim 2, characterised in that the tapering side walls (6) are used to support the burner (9) and at least one oxygen injection lance (10) .

4. A melting plant as claimed in any one of Claims 1 to 3, characterised in that the lower portion (3) of the vessel (1) containing the bath (8) is movable relative to the upper portion (4) .

5. A melting plant as claimed in any one of Claims 1 to 4, characterised in that a vessel tapping system (11) is provided in the base (5) of the lower portion (3) of the vessel (1) .

6. A melting plant as claimed in Claim 5, characterised in that means are provided to tilt the lower portion (3) of the vessel (1) with respect to its vertical axis to facilitate tapping of the vessel (1) via the tapping system (11) .

7. A melting plant as claimed in any one of Claims 1 to 5, characterised in that it comprises a syphonic tapping system.

8. A melting plant as claimed in any one of Claims 1 to 7, characterised in that the lower portion (3) of the vessel (1) comprises at least one gas injection means (26) and in that a hood (22) linked to a gas extraction means (28) can be secured to the lower portion (3) of the vessel (1) in place of the upper portion (4) comprising the preheating chamber (13) whereby refining and/or conversion of the molten bath (8) can be achieved prior to tapping of the bath (8) from the vessel (1) .

9. A melting plant as claimed in Claim 8, characterised in that the hood (22) can be hermetically attached to the lower portion (3) of the vessel (1).

10. A melting plant as claimed in any one of Claims 1 to 9, characterised in that the vessel (1) comprises a neck (7) which is located between the lower portion (3) of the vessel (1) and the preheating chamber (13) and which forms a funnel through which the waste gases formed in the lower portion (3) of the vessel (1) are drawn.

11. A melting plant as claimed in Claim 10, characterised in that the neck (7) of the vessel (1) is formed in two parts (23, 24), a lower part (23) being formed integrally with the lower portion (3) of the vessel (1) and an upper part (24) being fixedly attached to the preheating chamber (13) . - 1 !

12. A melting plant as claimed n Claim 10 or Claim 11, characterised m that at its top the neck (7) comprises an outwardly flared portion (12) that is connected to the preheating chamber (13) .

13. A melting plant as claimed in Claim 11, characterised in that the lower part (23) of the neck (7) can be hermetically attached to the hood (22) after removal therefrom of the upper part (20) and the preheating chamber (13).

14. A melting plant as claimed in any one of Claims 10 to 13, characterised in that the preheating chamber (13) is provided with a charge holding mechanism (16) which operates to retain the charge of material (14,14') within the chamber (13) and when desired discharge it into the central portion of the lower portion (3) of the vessel (1) via the neck (7) .

15. A melting plant as claimed in Claim 14, characterised in that the charge holding mechanism (16) comprises at least one cantilevered finger (17) which is mounted (18) at the base of the preheating chamber (13) .

16. A melting plant as claimed in Claim 15, characterised in that the cantilevered finger (17) can pivot downwardly into the flared portion (12) of the neck (7) .

17. A melting plant as claimed in Claim 15, characterised in that the cantilevered finger (17) can be withdrawn sideways from the interior of the preheating chamber (13) through a wall of the vessel (1) .

18. A melting plant as claimed in any one of Claims 1 to 17, characterised m that the upper portion (3) of the vessel (1) is closed by a removable cover (15) which provides access to the top of the preheating chamber (13) .

19. A method of producing molten metal wherein a first batch (14) of metal charging material is melted in a lower portion (3) of a closed furnace vessel (1) using the heat of at least one fuel burner (9,10), and characterised in that it comprises the further steps of filling a preheating chamber (13) located in an upper portion (4) of the furnace vessel (1) with a second batch (14') of metal charging material; funnelling waste gases produced by the burner or burners (9,10) during melting of the first batch (14) of material upwardly from the lower portion of the furnace vessel (1) through the preheating chamber (13) to heat the second batch

(14' ) of material; tapping molten metal (8) from the lower portion (3) of the furnace vessel (1) ; and discharging the second batch (14' ) of material centrally into the lower portion (3) of the furnace vessel (1) for melting .

20. A method as claimed m Claim 19, characterised in that it comprises the initial step of preheating the first batch (14) of metal charging material in the preheating chamber by firing up at least one fuel burner (9,10) prior to the presence of charging material in the lower portion (3) of the vessel (1) .

21. A method as claimed in Claim 19 or Claim 20, characterised in that it comprises the additional step of refining the molten metal prior to tapping by replacing the pre-heating chamber (13) with a hood (22) that is hermetically sealed to the lower portion (3) of the vessel (1) above the molten first batch of metal, injecting gas into the molten bath (8) to create turbulence therein, and extracting gases from the interior of the lower portion (3) of the vessel (1) above the molten bath (8) .

22. A method as claimed in Claim 21, characterised in that it comprises the addition step of converting a molten iron bath into steel by blasting a jet of oxygen into the vessel

(1) to convert the molten iron to steel in addition to the injection of gas into the bath (8) .

23. A method as claimed in Claim 19 or 20, characterised in that it comprises the additional step of converting a molten iron bath into steel by replacing the pre-heating chamber (13) with a hood that is hermetically sealed to the lower portion (3) of the vessel (1) above the molten first batch of metal, blasting a jet of oxygen into the vessel (1) to convert the molten iron to steel, and extracting waste gases from the interior of the vessel (1) above the molten bath (8).

24. A method as claimed in any one of Claims 19 to 23, characterised in that the molten metal (8) is tapped from the lower portion (3) of the vessel (1) by means that do not require tilting of the lower portion (3) of the vessel (1) by more than 20° with respect to its vertical axis.

25. A method as claimed in any one of Claims 19 to 24, characterised in that it comprises the step of retaining a residue (22) of molten metal in the lower portion (3) of the furnace vessel (1) after tapping.