EP2327802B1 - Determination of the bath level in metallurgical containers - Google Patents

Description

The invention relates to a method and a device for accurate and rapid determination of the constant at the same bath volume by the wear of the refractory lining from batch to batch and within a batch changing level of a bath covered with a slag layer metal bath in a metallurgical vessel, for example in a converter a blow-molder.

When using metallurgical vessels for steel production, the refractory vessel lining is exposed to a constant wear by the metal and slag melt through which its inner volume increases accordingly and the bath level drops while a constant bath volume. The knowledge of this lowering of the bath level is important for the operation of the metallurgical vessel, since, for example, a defined distance of the lance position to the melt must be maintained for an optimal process. It is therefore necessary to determine the height of the bath level at regular intervals, so that, for example, the blowing position of the lance and the sampling position of the sublance can each be redefined. To determine the height of the bath level, various methods are known.

An easy way is to attach a wooden handle to the blower or sublance and drive into the steel bath. After a short residence time, the height of the bath level can be determined mathematically by burning off the wooden handle. The method is very personal and time-consuming and not very accurate, since the burning of the wooden stem through the melt and the slag takes place.

Another method of determining the level of the bath is a sub-level probe that registers the temperature difference between the steel bath and the slag layer. The height of the bath surface is then determined via the travel path of the sublance probe. However, this option is only possible in steelworks equipped with a sublance.

Furthermore, it is known to determine the bath level height of a converter via a radar measurement. In this case, radar waves are transmitted to the bath surface via an opening in the exhaust system of the converter. The height of the bath surface can then be calculated over the wave time. The negative aspect of this method is that the measurement results are negatively influenced by the slag layer, which can lead to measurement inaccuracies. In addition, the installation effort is disadvantageous because the measuring system must be swiveled over the existing lance dome for measurement. Regular maintenance leads to additional costs and production downtime.

From the DE 102 07 395 B4 For example, a method for determining the current level of the bath level in an electric arc furnace or in a liquid steel converter is known wherein a measuring probe is lowered down to the bath level and forms an electrical measuring circuit with the metallic vessel shell. The electrical measuring circuit is tuned to conductivity values of the slag layer, the liquid metal and the refractory material. Depending on the distance traveled by the measuring probe per unit time and a change in the electrical conductivity of slag and / or liquid metal occurring when the slag layer and / or the liquid metal is touched, the measuring probe generates a measuring signal, whereby the level of the bath level is displayed.

Also WO 2005/059527 discloses a method for analyzing a melt.

In the DE 103 52 628 A1 discloses a method and apparatus for determining the molten bath height of successive pig iron charges in one Electric arc furnace described in the manufacture of steel from pig iron, wherein the underfloor furnace provided from batch to batch receives different volumes of pig iron and is operated with an oxygen Aufblaslanze, wherein to adjust the distance of the oxygen Aufblaslanze to the molten bath mirror the process-related distance between the lance head and the Schmelzbadhöhe is determined by the fact that the Schmelzbadspiegel the respective batch detected by tilting the electric arc furnace and after tilting back into the operating position by optical measurement or at least by estimating the tilt angle and determines the Schmelzbadhöhe and then the distance is adjusted.

Finally, out of the DE 38 22 705 C2 a method for measuring the height of the bath level, the oxygen partial pressure and the temperature of a below a slag layer metal bath in a container, in particular known in a converter, one consisting of an EMF cell for measuring the oxygen partial pressure and a thermocouple, by a protective cap protected measuring probe is immersed in the metal bath from a starting position located outside the container to a predetermined depth as a fixed point and after the melting of the protective cap, the oxygen partial pressure and the temperature of the metal bath are measured. During the upward movement of the measuring probe at a slower speed, the oxygen partial pressure and the temperature are measured as a function of the distance traveled by the measuring probe in the metal bath from the selected fixed point and until a change in the measured oxygen partial pressure and Temperature from the fixed point traveled distance is recorded as a measure of the Badstandshöhe.

Based on this described prior art, it is an object of the invention to provide an independent of other equipment system for determining the height of the bath level in metallurgical vessels, with at Optimized accuracy production loss is reduced by the measurement and maintenance of the known methods and devices and can be used in all known metallurgical vessels.

The object is achieved with the characterizing features of claim 1, characterized in that the determination of the height of the bath level during a batch with a wireless transmitter-receiver system according to the RFID method (Radio Frequency Identification) is performed by measuring the radio wave Signal strength between at least one battery-powered RF transmitter, which is integrated in a floating on the metal bath measuring body and at least one fixed above the metallurgical vessel RF receiver, wherein the increasing distance between the RF transmitter and the RF receiver reduction takes place Radio wave signal strength is used for the current distance determination.

An apparatus for carrying out the method is specified in claim 4.

The measuring body with integrated battery-operated RF transmitter can either be placed manually from above, for example via the doghouse door, or via a material supply system or via the sublance robot, into the metallurgical vessel and onto the metal bath. This task and the subsequent determination of the current Badspielgelhöhe is advantageously carried out at an optimal time at the end of the metallurgical treatment time at which all additives and the scrap used are melted and a bath calming has occurred.

According to the invention consists of the RF transmitter enveloping measuring body made of a heat-resistant ceramic material, including refractory materials count and is designed as a sphere, its density is selected so that the ball floats exactly on the dividing line between the metal bath and the slag layer, the bath mirror.

Due to the extreme conditions prevailing inside the metallurgical vessel, the measuring body and the integrated RF transmitter are designed for a single measurement with a relatively short service life, so that they are destroyed during their residence time on the metal bath. Any existing remains are removed by the slag from the metallurgical vessel with. Higher service life of the measuring body are not economical, since they can only be achieved with higher quality expensive materials, leaving open whether the RF transmitter is then still functional for a second batch and at what cost the measuring body can be removed from the metallurgical vessel again.

The RF receiver required for receiving the radio waves emanating from the RF transmitter and their signal strength is installed stationarily above the metallurgical vessel, for example in the exhaust system. Due to the stationary position of the RF receiver, the change in the signal strength emanating from the freely movable measuring body with its RF transmitter, converted to a distance calculation between the measuring body and the RF receiver and thus the height of the bath level can be determined. In conjunction with a vessel profile measuring system then the exact determination of the instantaneous amount of melt is feasible.

Further details of the invention are explained in more detail below on an embodiment shown in a drawing figure.

The drawing figure shows a sectional view of a plant scheme with a arranged in a "Doghouse" 5 serving as a metallurgical vessel converter 1. The converter 1 is delivered with a refractory lining 2 and in the illustrated operating state in its lower part with a Metal bath 3, which is covered with a slag layer 4. Above the converter 1 is an exhaust system 6 with a lower opening 11 for receiving the exhaust gases generated in the converter 1. In the lower part of the exhaust system 6, a filler neck 12 is arranged with a funnel 13, through which the measuring body 9 passes into the exhaust system and can be fed through the lower opening 11 in free fall directly to the metal bath 3. In addition to the manual task in the hopper 13 more task options are available.

In the drawing figure on the top right, a material addition system is used for the measuring object, consisting of a bottom open container 17 with a plurality of measuring bodies 9, a conveyor belt 15 and a chute 14, with each one or more measuring body 9 in the transport direction 7, 7 ', 7 " can be promoted to the funnel 13.

If available, the sublance robot 8 shown in the drawing figure at the top left can also be used to discharge the measuring body 9 into the funnel 13, wherein the sublance robot 8 removes a measuring body from the container 16 which is arranged in reach and drops it into the funnel 13.

The introduced by one of the possibilities shown in the converter 1 measuring body 9 is arranged according to its set density below the slag layer 4 in a stable floating position on the bath level 20 of the metal bath 3, as shown in the drawing figure. To receive the radio waves radiated by the RF transmitter in the measuring body 9, an RF receiver 10 is installed fixed above the converter 1 in the lower part of the exhaust system 6. During the entire service life of a measuring body 9 with RF transmitter, the signal arriving at the RF receiver 10, depending on the distance between the measuring body 9 and the RF receiver 10 different signal strength, registered and converted in an (not shown) evaluation unit in a current distance value.

The invention is not limited to the illustrated embodiment. Depending on the metallurgical process to be carried out and the size of the metallurgical vessel, it may be necessary to use several measuring bodies during a batch, which is why a corresponding supply of measuring bodies should be present. Also, depending on local circumstances, installation of more than one RF receiver could prove useful to eliminate the sources of interference affecting the signal strength of the radio wave signal. But even then, the simple system structure according to the invention makes possible a use for all metallurgical vessels.

LIST OF REFERENCE NUMBERS

1

converter

2

Refractory lining of the converter

3

metal

4

slag layer

5

Doghouse

6

exhaust system

7, 7 ', 7 "

transport direction

8th

Sublanzenroboter

9

Measuring body with integrated RF transmitter

10

RF receiver

11

lower opening of the exhaust system

12

filler pipe

13

funnel

14

slide

15

conveyor belt

16

open top container

17

bottom open container

20

Bathroom mirror

Claims (6)

1. Method for precise and rapid determination of the bath level height, which with a concurrently constant bath volume changes due to wear of the refractory cladding from charge to charge and within a charge, of a metal bath (3), which is covered with a slag layer (4), in a metallurgical vessel, characterised in that determination of the height of the bath level (20) during a charge is carried out by a cable-free transmitter/receiver system according to the RFID (Radio Frequency Identification) method by measuring the radio-wave signal strength between at least one battery-operated RF transmitter integrated in a measuring body (9) floating on the metal bath (3) and at least one RF receiver (10) arranged above the metallurgical vessel, wherein the reduction, which takes place with increasing spacing between the RF transmitter and RF receiver (10), of the radio-wave signal strength is used for determination of instantaneous spacing.
2. Method according to claim 1, characterised in that the measuring body (9) is delivered from above into the metallurgical vessel and onto the metal bath (3) either manually or by way of a material delivery system or by way of a sub-lance robot (8).
3. Method according to claim 2, characterised in that the delivery of the measuring body (9) and the determination subsequent thereto of the instantaneous bath level height is carried out at an optimum point of time at the end of the metallurgical treatment time at which all additives and the introduced scrap have melted and bath quiescence has set in.
4. Device for precise and rapid determination of the bath level height, which with a concurrently constant bath volume changes due to wear of the refractory cladding from charge to charge and within a charge, of a metal bath (3), which is covered with a slag layer (4), in a metallurgical vessel, for example in a converter (1), particularly for carrying out the method according to any one of claims 1 to 3, characterised by an installed cable-free transmitter/receiver system according to the RFID (Radio Frequency Identification) method,

   - with at least one RF receiver (10) arranged in stationary position above the metallurgical vessel, for example above the converter (1) in the doghouse region,

   - an evaluating system connected with the RF receiver (10) and

   - together with each charge at least one freely movable measuring body (9) with an integrated RF transmitter.
5. Device according to claim 4, characterised in that the measuring body (9) is made of a heat-resistant ceramic material, which includes refractory materials, and is constructed as a sphere, wherein the density thereof is so selected that the sphere (9) floats exactly on the interface between the metal bath (3) and the slag layer (4), i.e. the bath level (20).
6. Device according to claim 4 or 5, characterised in that the measuring body (9) and the integrated RF transmitter are designed only for a single measurement with short duration so that they can be destroyed during their dwell time on the metal bath (3), wherein any residues present are removable by the slag removal from the metallurgical vessel.

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