WO2017089396A1

WO2017089396A1 - A method and a system measuring liquid and solid materials in the process of converting iron to steel in metallurgical vessels or furnaces

Info

Publication number: WO2017089396A1
Application number: PCT/EP2016/078551
Authority: WO
Inventors: Klaas Richard KLOETSTRA; Joop Joseph Hendrik HARTOGS
Original assignee: Danieli Corus B.V.
Priority date: 2015-11-24
Filing date: 2016-11-23
Publication date: 2017-06-01
Also published as: EP3380818A1; JP2019501299A; CN108291831A

Abstract

The present disclosure relates to methods and a system (1) for converting iron to steel in a metallurgical container (3). A plurality of AC transmitting and receiving coils (11; 11T, 11R) is arranged in the walls (5) of the container (3) in different positions and orientations with respect to the container axis (A). A filling level (L1, L2) of an electrically conductive material and/or a dielectric material in the container (3) is determined on the basis of AC signal reception data.

Description

A METHOD AND A SYSTEM MEASURING LIQUID AND SOLID

MATERIALS IN THE PROCESS OF CONVERTING IRON TO STEEL IN METALLURGICAL VESSELS OR FURNACES

TECHNICAL FIELD

The present disclosure relates to methods and a system for converting iron to steel in metallurgical vessels or

furnaces, e.g. Basic Oxygen Furnaces and Electric Arc Furnaces, and measuring liquid and solid materials therein.

BACKGROUND

In a Basic Oxygen Furnace (BOF) or an Electric Arc Furnace (EAF) liquid steel is produced from hot metal and/or scrap. Modern steelmaking requires a good quality of slag which is needed for the process and for lining protection purposes. The slag is usually made by adding lime, dolomite and recycled slag to the steelmaking process.

During the steelmaking process iron (Fe) in particular iron droplets should be available in the slag to help oxidizing unwanted elements like Silicon, Titanium, Phosphorus, Manganese etc. and an adequate amount of Lime should be available to reduce acidity of the slag.

During the process -due to several reasons- the slag in the converter might start to "foam" and overflow the converter vessel. This effect is called slopping and it has significant negative side-effects:

- The steelmaking shop will lose efficiency due to the fact that the slag contains lots of Fe;

- The production time will be longer (the oxygen blowing speed must be reduced to stop the slopping) ;

- Environmental issues; - Extra cleaning of the converter area, also leading to loss of production.

In this document "slopping of converter slag" means processes involving escape of slag of the converter e.g. by floating and/or splashing, unless otherwise specified. A side effect of slopping, happening occasionally, might be the

creation of a fume of red dust flowing through the roof of the steel plant in a severe slopping event.

E.g. WO 2014/009367 Al discloses a method for measuring the liquid-metal surface level and the slag surface level in the crucible of a metallurgical shaft furnace comprising measuring, at one or more points on the external wall of the crucible, the following variables: the circumferential strain in said external wall by means of a number of strain-gauge sensors fixed to the armour of the external wall of the crucible; and the temperature of said external wall by means of one or more temperature sensors fixed to the armour of the external wall of the

crucible .

Thermal effects in the crucible wall are not well localised and may be slow compared to (changes in) the liquid- metal level and/or processes occurring in the crucible.

EP 0 419 104 A2 discloses a method of detecting the level of molten metal existing within a mold, the method

comprises the steps of disposing a transmission coil and a receiving coil to oppose to each other with the mold interposed therebetween, applying an AC voltage to the transmission coil to produce alternating magnetic flux so that at least a part of the magnetic flux passes through the mold and the molten metal, if any, and reaches the receiving coil, and determining the level of the molten metal on the basis of at least one of a voltage value and a phase of an AC signal induced in the receiving coil by the alternating magnetic flux, and an apparatus for carrying out the above method. Similarly, EP 0 115 258 Al discloses a method and apparatus for measuring the remaining amount of metal melt at the bottom of a container; US 4,441,541 discloses a method of and apparatus for determining the melt level in a continuous- casting mold. US 5,232,043 discloses a device for identifying the solid-liquid interface of a melt.

US 4,138,888 discloses an arrangement for electro- magnetically measuring level of and/or distance to molten metal contained in a container, particularly a torpedo ladle wagon. Separate transmitter and receiver coils are located displaced relative to each other at or in the container walls so that the molten metal forms an AC magnetic screen between the coils when reaching a predetermined level. Before the molten metal cuts off the alternating magnetic field from the transmitter coil to the receiver coil, the alternating magnetic field sensed by the receiver coil is increased due to alternating magnetic field generated by electric currents induced at the surface of the raising molten metal. The top amplitude of the signal obtained in the receiver coil increases as the wear and erosion of the container lining proceeds.

Similarly, EP 0 419 104 A2 discloses a method and apparatus for detecting a level of molten metal.

US 4,144,756 discloses a system for electromagnetically measuring level, distance or flow rate in connection with molten metal contained in a furnace, mould, channel or the like.

Separate coreless single or few-turn transmitter and receiver coils are used, the coils being essentially freely positionable relative to the walls of the furnace etc. At least two signal channels are included for signal processing and for producing counteraction between transmitter and- /or receiver signals so as to produce a basic measurement signal that is at least substantially balanced with regard to disturbing and unbalance signals, whereby the small variations of the signals induced in the receiver coil or coils due to changes of the level, distance or flow rate of the molten metal can be accurately detected.

Such systems are only sensitive to variations locally at the positions of the transmitter and receiver coils.

WO 2013/039446 Al discloses measuring the vertical filling level of electrically conductive material in a cavity of a metallurgical vessel by a system comprising a transmitting conductor for generating an electromagnetic field when connected to an alternating power source, and a receiving conductor which is arranged to sense the electromagnetic field for generation of an output signal. The transmitting and receiving conductor are wound around the vessel.

SUMMARY

In view of the foregoing, improvements are desired.

To that end, herewith a method and a system are

provided .

An aspect comprises a method for converting iron to steel in a metallurgical container comprising measuring liquid and/or solid materials in the metallurgical container. The container comprises one or more walls defining a containment volume extending along a container axis, wherein in particular the container axis may be normally vertical in operation. The method comprises:

the step of providing the container with at least three coils in the one or more walls, each coil having a coil axis and a surface area perpendicular to the coil axis, each coil

preferably extending parallel to the respective nearest wall or walls ;

and the step of at least one of

(a) transmitting an AC signal from one of the coils, measuring reception of the AC signal by the other two coils and determining reception data indicative of the measured reception, and (b) transmitting one or more AC signals from two of the coils and measuring reception of the AC signal or signals, respectively, by the third coil and determining reception data indicative of the measured reception,

wherein

at least two of the coils are arranged at a different angular orientation with respect to the container axis and/or in a different azimuthal position with respect to the container axis, such that the respective coil axes are directed into the containment volume at a nonzero angle to each other and/or at least part of the containment volume is enclosed between these coils, and

at least two of the coils are arranged in the container wall(s) in different axial positions with respect to the container axis;

and the step of determining a filling level of an electrically conductive material and/or a dielectric material in the container on the basis of the reception data.

By the arrangement of the different coils and the transmission of the AC signal between the coils, two different signal paths through the containment volume are sampled. A comparison of the reception data of the different signal paths, in particular two signal paths having one end point in common, enables accurate determination of differences between the paths, which may be indicative of the levels of one or more

electrically conductive materials and/or dielectric material and/or composition thereof, in particular of metal and of slag, in the container. A vertical path difference enables an early warning of a slopping event, which then may be preventable.

Further, different components, in particular molten metal and slag types of different compositions, may be

discerned, e.g. on a basis of criteria such as a content of iron droplets or metallic iron particles (even partly oxidized) , also in the presence of significant turbulence and uneven, possibly violently varying, levels of the components, as is common in conversion of iron to steel.

The container may be provided with more coils, wherein any combination of three coils or more coils may be employed as described above for of determining a filling level of an

electrically conductive material in the container on the basis of the reception data.

In particular in such case, different AC signal

frequencies may be employed for measuring and/or identifying at least one of different effects, different (combinations of) coils and/or different signal paths. Two or more different frequencies may be transmitted subsequently and/or

simultaneously in one or more signal paths. A transmitted AC signal may also be frequency modulated and/or amplitude

modulated e.g. for providing identification data of a signal and/or for other reasons, e.g. chirped signals may excite particular resonance frequencies container volume and any contents therein. A transmitted AC signal may be sinusoidal or have non-sinusoidal waveform portions, e.g. a triangular

waveform, a saw tooth waveform or a square wave. The signal may be pulsed once or repetitively at one or more desired pulse repetition rates, or (quasi-) continuous for extended periods of time, e.g. seconds to minutes or even up to hours.

One or more of the coils may conform to the shape of the respective wall portion, e.g. being generally flat with a significantly larger surface area than its extent along its respective coil axis. In a container having a lining, in

particular a lining of heat resistant refractory material, a coil may be embedded in the lining and/or be arranged between the lining and an outer (at least relative to the lining) container wall.

In an embodiment, two of the coils are arranged in wall portions on opposite sides of the containment volume. Thus, an average over the containment volume may be obtained. Also, local artefacts, e.g. due to inhomogeneous composition and/or temperature of the metal and/or slag, may be avoided or rather detected by a comparison of the respective signals.

The two coils need not be exactly opposite each other relative to a possible plane or axis of symmetry of the

container, e.g. exactly diametrically opposite each other. This prevents undesirable interference an intended signal path through the centre by an object permanently or occasionally located in a centre of the container, e.g. an oxygen lance, a sublance, a metal stream for filling the container, etc.

The reception data may comprise at least one of signal transmission time data, frequency data, phase data and amplitude data of the received AC signal, and possibly data associated with the transmitted AC signal, e.g. for quality control of transmitted AC signals and/or detailed comparison of data between received and transmitted signals. Frequencies, phases and amplitudes tend to be reliably identifiable in a periodic signal such as an AC signal. A phase shift may be indicative of a (possibly frequency dependent) impedance between the

transmitting coil and the receiving coil. Eddy currents induced or otherwise occurring in conductive materials, e.g. metals, may absorb signal energy and they may affect a phase shift in the signal. Frequency data analysis may allow identification of different signals, detection of resonance frequencies, detection of a Doppler shift for signalling a movement of a conductive object e.g. indicative of a level change, etc. Amplitude data may indicate absorption or reflection of a signal. Comparison of one or more measured signals with one or more transmitted signals can improve information retrieval from the received signals. A single coil may be used for both transmission and reception, e.g. to measure reflection and/or absorption of the signal . Reception data may be stored in a memory for establishing a time-dependent behaviour, for future reference, analysis and/or training purposes.

The transmitted AC signal may be adjusted to a frequency associated with one or more predetermined signal transmission characteristics through one or more portions of material (s) in the container. E.g. the frequency may be one for which conductive particles with predetermined conduction

characteristics, like iron droplets of a predetermined size and/or temperature, may be dispersive and/or absorptive at or below a predetermined value, or rather above a particular value. E.g. the frequency may be one for which (possibly: weakly) conductive particles may be essentially transparent, or

alternatively be essentially opaque. The frequency may be determined taking an electric shielding effect of the conductive droplets into account. Thus, the one or more portions of

material (s) in the container may be selectively identified.

The transmitted AC signal may have a frequency away from a power grid frequency and harmonics of the power grid frequency. This enables reduction of signal-to-noise ratios of the data, reduces noise artefacts in the signal and improves reliability of the method. The AC signal may have a frequency in a range of 90-5000 Hz, in particular 400-4000 Hz.

In another embodiment the AC signal may have a frequency in a range of 50-300 Hz, e.g. 50-70 Hz or 240-275 Hz.

In an embodiment, the container comprises a basic oxygen furnace converter vessel and the method comprises

identifying a level of a first component in the containment volume and a level of a second component in the containment volume, in particular of components having a separation zone, e.g. wherein one tends to float on the other, in particular a level of molten metal and a level of slag. Thus, relevant process control parameters can be gained and slag quality may be controlled. Further, slopping events may be predicted, possibly prevented and/or behaviour thereof may be analysed.

The method may comprise moving, in particular tilting, the container from an initial position and/or orientation, in particular a vertical orientation, to a new position and/or orientation and determining a level in at least the new position and/or orientation. A level may also be determined during the movement and/or tilting process. This may aid in prevention of slopping of metal and/or slag during the movement. It may also assist a casting operation.

The method may comprise converting iron to steel in the container .

In association with the above, herewith a system for performing at least one embodiment of the method described herein is provided.

An aspect comprises a system for converting iron to steel in a metallurgical container the container comprising one or more walls defining a containment volume extending along a container axis wherein in particular the container axis may be normally vertical in operation. The container is provided with at least three coils in the one or more walls, each coil having a coil axis and a surface area perpendicular to the coil axis, each coil preferably extending parallel to the respective wall or walls. The system comprises an AC signal generator connected with at least one of the coils for transmitting an AC signal from the respective coil or coils, and an AC signal detector connected with at least one of the coils configured for

determining reception data indicative of a received AC signal. At least two of the coils are arranged at a different angular orientation with respect to the container axis and/or in a different azimuthal position with respect to the container axis, such that the respective coil axes are directed into the

containment volume at a nonzero angle to each other and/or at least part of the containment volume is enclosed between these coils, and at least two of the coils are arranged in the

container wall(s) in different axial positions with respect to the container axis. The system is provided with a controller programmed to determining a filling level of an electrically conductive material and/or a dielectric material in the

container on the basis of the reception data. The system may be used and/or configured for performing one or more embodiments of the method herein described.

Two of the coils may be arranged in wall portions on opposite sides of the containment volume, not necessarily directly opposite and/or diametrically opposite as explained elsewhere .

The reception data may comprise at least one of frequency data, phase data and amplitude data of the received AC signal.

The AC signal generator may be configured to generate an AC signal having a frequency away from a power grid frequency and harmonics of the power grid frequency. The AC signal may have a frequency in a range of 90-5000 Hz, in particular 400- 4000 Hz. In another embodiment the AC signal may have a

frequency in a range of 50-300 Hz, e.g. 50-70 Hz or 240-275 Hz.

The container may comprise a basic oxygen furnace converter vessel or electric arc furnace, arranged for

containing molten metal and slag.

The container may be movably, in particular rotary, mounted for moving, in particular tilting, the container from an initial position and/or orientation to a new position and/or orientation .

The system may comprise an oxygen lance for blowing oxygen into the containment volume, wherein in particular the oxygen lance may have an adjustable position with respect to the container. The system may be used to determine a position of the lance relative to a metal level and/or a slag level. The system may comprise a memory for storing measurement data. The system may comprise a display for

displaying measurement data. The measurement data may comprise reception data, transmitted signal data and/or system property data, e.g. effects on detection data of temperature of the container, container contents and/or surroundings of the container .

BRIEF DESCRIPTION OF THE DRAWINGS

The above-described aspects will hereafter be more explained with further details and benefits with reference to the drawings showing a number of embodiments by way of example.

Fig. 1 indicates a system for measuring liquid and/or solid materials in an exemplary metallurgical container (shown in cross section) ;

Fig. 2 indicates a cross section view of the container of Fig. 1 towards the top, as indicated in Fig. 1 with "11";

Figs. 3 and 4 are signals from experimental setups. DETAILED DESCRIPTION OF EMBODIMENTS

It is noted that the drawings are schematic, not necessarily to scale and that details that are not required for understanding the present invention may have been omitted. The terms "upward", "downward", "below", "above", and the like relate to the embodiments as oriented in the drawings, unless otherwise specified. Further, elements that are at least substantially identical or that perform an at least

substantially identical function are denoted by the same numeral, where helpful individualised with alphabetic suffixes.

Figs. 1 and 2 indicate (parts of) a system 1 for measuring liquid and/or solid materials in a metallurgical container 3. The container 3 has walls 5 defining a containment volume V extending along a container axis A. The container axis A normally is vertical in operation. In the following, references with respect to the axis A are commonly made to the axis in cylindrical coordinates.

The container walls 5 comprise an outer wall 7, a bottom wall 8 and a heat-resistant lining 9, here comprising plural layers (only two layers 9A, 9B shown) . The shown

container 3 is a basic oxygen furnace converter vessel, arranged for containing molten metal and slag. Although not shown, the container 3 is mounted movably for translation and rotary for transporting and/or tilting container 5 from an initial position and/or orientation to a new position and/or orientation. By tilting the container liquid metal and/or slag may be cast from an open top 0 of the container 3 into a different container.

The container 3 is provided with a number of coils 11, embedded in the container wall 5, e.g. arranged between the lining 9 and the outer wall 7 or between different lining layers 9A, 9B as shown in Fig. 1. Each coil 11 comprises one or more turns of heat-resistant insulated electrically conductive wire, providing a coil axis C and a surface area of the coil (not indicated) perpendicular to the coil axis C. Here, each coil 11 extends parallel to the respective wall or walls accommodating the coil(s) with the respective coil axes C extending

perpendicular to the container wall 5 and into the containment volume V. More or less coils may be provided. Different coils may differ in one or more of size, shape, number of turns, position and orientation.

The system 1 comprises an AC signal generator 13 connected with a transmission coil 11T of the number of coils 11 for transmitting an AC signal from the transmission coil 11T into the containment volume V. In Fig. 1 an optional amplifier 15 is further provided. Also, the AC signal generator 13 is connected with only one transmission coil 11T but further coils 11 may be connected.

The system 1 comprises an AC signal detector 17 with one or more reception coils 11R of the number of coils 11 for receiving an AC signal from the containment volume V and determining reception data indicative of the received AC signal. In Fig. 1 an optional amplifier 19 is further provided.

Connections between the coils 11 and the AC signal generator 13 and the AC signal detector 17, respectively, may be positioned in a rotary joint for tilting the container 3 (not shown) .

A controller 21 and optional display 23, e.g. comprising an oscilloscope, are further provided. The controller 21 is programmed to determine a filling level of an electrically conductive material and/or a dielectric material in the

containment volume V of the container 5 on the basis of the reception data.

As seen from Fig. 1, in the system 1, two of the coils 11R are arranged in the container wall(s) in different axial positions with respect to the container axis A, being arranged one above the other. Further coils 11 may be arranged in further different axial positions (see dashed lines) . Thus, part of the containment volume is enclosed between the coils 11T, 11R and signals transmitted from the transmission coil 11T may pass in a straight line to the reception coils 11R along different signal paths (arrows S) through the containment volume V. In case a signal path S is interrupted by a liquid level L2 of a

conductive liquid in the container 3, the signal will be

affected and reduced. Also, part of the signal may be reflected and received in one or more other coils 11R aside of the

interrupted direct signal path S (not shown) . Such reflected signal portion may provide further information regarding the contents of the container 3. In case the container comprises different components that can float on each other, e.g. slag and steel, different liquid levels LI, L2 may be formed in the container 3, wherein each component affects a signal (path) detectably differently. Also, coils 11 may be arranged in different azimuthal positions with respect to the container axis A (Fig. 2, dashed) or at different angular orientations with respect to the

container axis A (not shown, e.g. the coil axes C pointing in different directions than the radial orientations that are shown in Fig . 2 ) .

Various numbers and/or sizes of turns may be used. A transmission coil with more turns may provide a stronger

transmitted signal, a transmission coil with more turns may provide a stronger transmitted signal, similar applies to reception coils. Suitable coils may have more than 10 turns. A relevant factor is that individual turns are electrically insulated from each other, also under the harsh conditions associated with steel-making, e.g. high temperatures, large thermal fluctuations, high mechanical stresses and long periods of operation. Mineral insulating materials may age and/or wear rapidly in such conditions, e.g. due to (re-) crystallisation, which may lead to the materials becoming brittle and/or

disintegrating. Therefore, adjacent turns of a coil embedded in lining material of a wall may be insulated by a mortar. The mortar may be used for embedding and fixing the coil in a recess in the lining material, but different types of mortar for insulation and fixation may be used. Also or alternatively, turns of a coil may be separated and insulated by the lining material, e.g. being positioned in separate recesses in the lining material. Placing and/or replacing a coil in the

container, with or without providing a recess in the lining material, may be included in maintenance operations. Providing a recess in the lining material may comprise assembling lining elements into an operative position (e.g. fixed to another wall portion) such that at least part of the recess is formed.

Providing a recess in the lining material may also or

alternatively comprise cutting at least part of the recess in a portion of lining material that has been fixed in an operative position. As indicated in Fig. 1, a coil 11 may be positioned in a recess in one lining material layer 9B closed by another lining material layer 9A.

Typically, magnesium oxide, in particular in combination with graphite, in the lining material of a converter vessel, in particular in combination with graphite in the lining material, may improve signal transmission. One or more of the coils may comprise a core of another material than material adjacent the coil on a radial outside of the coil, e.g. in which the core is embedded. Such core may be formed by providing lining material of a different composition, e.g. with a reduced MgO-content relative to surrounding lining material.

Pairs of coils determining a signal path may be sized to have a cross sectional size in a range of 1/10 to 1/5 of the separation between two coils as seen along their respective axes .

Experiments have successfully been performed with rectangular coils of 20-80 turns and about 1.2 m² surface area per coil. Figs. 3 and 4 show typical experimental signals, wherein transmitted AC signals Tx of just under 5 kHz are shown overlaid with the associated received signals Rx in one graph as indicated (ordinate: time, abscissa: voltage) with coils

separated by about 3.5 m (Fig. 3) and by about 7 m (Fig. 4) in air. In Figs. 3-4 the scale of the received signals Rx is 60 times expanded relative to that of the transmitted signals Tx. Clearly, in the received signals Rx changes relative to the transmitted signals Tx in amplitude, phase, noise and offset may readily be discerned, one or more of which may be related to variations in substances between the respective coils.

Some examples successfully employed, coils of 20-30 turns, typically 25 turns, with sizes in a range of 80 cm to 150 cm, typically rectangular coils of 80 cm x 150 cm. The coils may have a low resistance and be operated with AC voltages in a range of 20-50 V, typically 20-30 V ac peak-peak. It is noted that coils 11 extending parallel to each other and facing each other, e.g. with their coil axes C

pointing towards each other, may exhibit strongest coupling for a given separation of the coils 11. However, a balance may be found between the orientation and position of the coils

individually and in combination for reasons of signal strength and for other reasons e.g. mechanical robustness reasons, electrical noise-related reasons and/or interaction with metal production. An electromagnetic shielding may be provided around portions of wires outside of the coils, in particular outside of the container 3 to improve a signal to noise ratio.

The disclosure is not restricted to the above described embodiments which can be varied in a number of ways within the scope of the claims. For instance, the container may have a different shape. Thermal insulation layers may be arranged between a coil and the container wall. Further systems may be present. Control of and/or data connection with a transmission coil and/or a reception coil may be done by wireless

communication and/or wired. Additional sensors may be provided.

Various embodiments of controller programming may be implemented as a program product for use with a computer system, where the program(s) of the program product define functions of the embodiments (including the methods described herein) . In one embodiment, the program(s) can be contained on a variety of non- transitory computer-readable storage media, where, as used herein, the expression "non-transitory computer readable storage media" comprises all computer-readable media, with the sole exception being a transitory, propagating signal. In another embodiment, the program(s) can be contained on a variety of transitory computer-readable storage media. Illustrative

computer-readable storage media include, but are not limited to: (i) non-writable storage media (e.g., read-only memory devices within a computer such as CD-ROM disks readable by a CD-ROM drive, ROM chips or any type of solid-state non-volatile semiconductor memory) on which information is permanently stored; and (ii) writable storage media (e.g., flash memory, floppy disks within a diskette drive or hard-disk drive or any type of solid-state random-access semiconductor memory) on which alterable information is stored.

Elements and aspects discussed for or in relation with a particular embodiment may be suitably combined with elements and aspects of other embodiments, unless explicitly stated otherwise .

Claims

1. A method for converting iron to steel in a metallurgical container (3) comprising measuring liquid and/or solid materials in the metallurgical container (3), the

container comprising one or more walls (5) defining a

containment volume (V) extending along a container axis (A) , the method comprising:

the step of providing the container (3) with at least three coils (11; 11T, 11R) in the one or more walls, each coil having a coil axis (C) and a surface area perpendicular to the coil axis, each coil preferably extending parallel to the respective wall or walls;

and the step of at least one of

(a) transmitting an AC signal (S; Tx) from one of the coils (11T), measuring reception of the AC signal by the other two coils (11R) and determining reception data indicative of the measured reception, and

(b) transmitting one or more AC signals from two of the coils (11T) and measuring reception of the AC signal or signals, respectively, by the third coil (11R) and determining reception data indicative of the measured reception,

wherein

at least two of the coils (11; 11T, 11R) are arranged at a different angular orientation with respect to the container axis (A) and/or in a different azimuthal position with respect to the container axis (A) , such that the respective coil axes are directed into the containment volume (V) at a nonzero angle to each other and/or at least part of the containment volume (V) is enclosed between these coils, and at least two of the coils (11; 11T, 11R) are arranged in the container wall(s) (5) in different axial positions with respect to the container axis (A) ;

and the step of determining a filling level (LI, L2) of an electrically conductive material and/or a dielectric material in the container on the basis of the reception data.

2. Method according to claim 1, wherein two of the coils (11; 11T, 11R) are arranged in wall portions on opposite sides of the containment volume.

3. Method according to any preceding claim, wherein the reception data comprise at least one of frequency data, phase data and amplitude data of the received AC signal, and possibly data associated with the transmitted AC signal.

4. Method according to any preceding claim, wherein the transmitted AC signal has a frequency away from a power grid frequency and harmonics of the power grid frequency.

5. Method according to any preceding claim, wherein the container (3) comprises a basic oxygen furnace converter vessel, and wherein the method comprises identifying a level (LI) of a first component in the containment volume and a level (L2) of a second component in the containment volume (V) , in particular a level of molten metal and a level of slag.

6. Method according to any preceding claim, comprising moving, in particular tilting, the container (3) from an initial position and/or orientation, in particular a vertical

orientation, to a new position and/or orientation and

determining a level in at least the new position and/or

orientation .

7. Method according to any preceding claim, comprisi converting iron to steel in the container (3) .

8. A system (1) for converting iron to steel in a metallurgical container (3), the container (3) comprising one or more walls (5) defining a containment volume (V) extending along a container axis (A) , wherein

the container (3) is provided with at least three coils (11; 11T, 11R) in the one or more walls (5), each coil having a coil axis and a surface area perpendicular to the coil axis (C) , each coil preferably extending parallel to the respective wall or walls;

the system comprising an AC signal generator (13) connected with at least one of the coils (11T) for transmitting an AC signal from the respective coil or coils,

and an AC signal detector (17) connected with at least one of the coils (11R) configured for determining reception data indicative of a received AC signal;

wherein at least two of the coils (11; 11T, 11R) are arranged at a different angular orientation with respect to the container axis (A) and/or in a different azimuthal position with respect to the container axis (A) , such that the respective coil axes (C) are directed into the containment volume at a nonzero angle to each other and/or at least part of the containment volume (V) is enclosed between these coils (11; 11T, 11R) , and at least two of the coils (11; 11T, 11R) are arranged in the container wall(s) (5) in different axial positions with respect to the container axis (A) ;

and the system (1) is provided with a controller (21) programmed to determine a filling level (LI, L2) of an

electrically conductive material and/or a dielectric material in the container (3) on the basis of the reception data.

9. The system (1) according to claim 8, wherein two of the coils (11; 11T, 11R) are arranged in wall portions on

opposite sides of the containment volume (V) .

10. The system (1) according to any one of claims 8-9, wherein the reception data comprise at least one of frequency data, phase data and amplitude data of the received AC signal.

11. The system (1) according to any one of claims 8-10, wherein the AC signal generator (13) is configured to generate an AC signal having a frequency away from a power grid frequency and harmonics of the power grid frequency.

12. The system (1) according to any one of claims 8-11, wherein the container (3) comprises a basic oxygen furnace converter vessel, arranged for containing molten metal and slag.

13. The system (1) according to any one of claims 8-12, wherein the container (3) is movably, in particular rotary, mounted for moving, in particular tilting, the container from an initial position and/or orientation to a new position and/or orientation .

14. The system (1) according to any one of claims 8-13, comprising an oxygen lance for blowing oxygen into the

containment volume, wherein in particular the oxygen lance has an adjustable position with respect to the container.