Method for operating an electric melter

Abstract

The invention relates to a method for operating an electric melter according to claim 1.

Description

[0001] The invention relates to a method for operating an electric melter.

[0002] The use of so-called Söderberg electrodes in electric melters has been state of the art for decades. Self-firing electrodes, or Söderberg electrodes named after their inventor "Söderberg," consist of a steel housing, essentially a ribbed cylinder made of thin sheet metal, into which carbon-containing electrode material is placed. This material can be clamped into position in an electric melter within a Söderberg device, for example, using a holding fixture. In this way, the upper end of the Söderberg device is filled with raw material. The resulting electrode, which protrudes from the lower end of the Söderberg device, is continuously consumed in the melter. The Söderberg electrode formed in the device can flow downwards during operation, requiring the replacement of the consumed material.During this process, the electrode material flows through a zone of increasing temperature and is baked by the heat of the melter. The material in the Söderberg device thus consists of an upper section, in which the electrode is assembled with interconnected steel housings and filled with electrode material, thus functioning as a moving mass; a lower section in the form of a hard, baked electrode; and an intermediate section in which the material gradually transforms from a moving mass to a hard, baked electrode. For the sake of simplicity, these three sections will nevertheless be referred to as the electrode below, although only the baked lower section functions like an electrode.

[0003] The Söderberg device is designed so that the electrode moves gradually at a predetermined speed and is successively guided downwards, particularly by loosening the clamped receiving device and due to its own mass, so that unbaked sections of the material are heated to increasingly higher temperatures as they approach the melter. The receiving device is located outside the electric melter. The electrode is preferably repositioned under full load, so that the electrode's operation can be maintained while the electric melter is running, allowing current to continue flowing through the electrode. Electrical contact between the receiving device and the electrode housing can be provided by means of suitable contact jaws.

[0004] The steel housing of the Söderberg electrodes used is predominantly round and features a series of inwardly projecting lamellae extending radially towards the center of the electrode to provide mechanical strength. The lamellae and the housing are generally made of standard steel or thin sheet metal.

[0005] The structure and operating principle of a Söderberg electrode, or the corresponding Söderberg device, are familiar to those skilled in the art. For example, a Söderberg electrode consists of interconnected ring-shaped sheet metal sheath elements in its upper section, which is filled with electrode material. Due to the application of current and / or heat, the lower section of the Söderberg electrode is in a baked state and, during operation, burns away successively at its lower end. This allows the Söderberg electrode to be successively reattached at a specific cycle time, with further sheet metal sheath elements being successively connected to its upper end and filled with electrode material.

[0006] From EP 1 209 243 A1, it is known to pass an electric current of known intensity and frequency through a central conductor element in the upper section of an electrode in order to collect a response signal via contact plates arranged in this upper section. In this way, the current generated at a specific frequency and voltage is introduced through the aforementioned central conductor element in the upper section of the electrode and passed through it until it reaches the contact plate after traversing a carbon paste. The condition of the electrode in its individual areas is then determined by comparing the transmitted and received signals.

[0007] The object of the present invention is to provide an alternative method for operating an electric melter that is simpler compared to the prior art.

[0008] This problem is solved by a method having the features of claim 1. Further embodiments are listed in the dependent claims.

[0009] The first teaching of the invention relates to a method for operating an electric melter, wherein the electric melter comprises at least one Söderberg electrode for melting feed materials in the electric melter, wherein the Söderberg electrode is formed in its upper section from annular sheet metal jacket elements connected to one another and is filled with carbon-containing electrode mass, wherein the Söderberg electrode is in a baked state in its lower section by application of current and / or heat and is successively burned off at its lower end, so that the Söderberg electrode is successively added and further sheet metal jacket elements are successively connected at its upper end and filled with electrode mass.

[0010] The inventors have discovered that by measuring the vibrations of at least one Söderberg electrode, at least one state variable relating to the Söderberg electrode can be determined.

[0011] Every operational or existing system, as well as individual components within systems, including Söderberg electrode(s) used in electric melters, generates vibrations that can be analyzed for specific operating conditions using vibration analysis. Under optimal or normal operating conditions, the at least one Söderberg electrode oscillates within a specific frequency range. During operation, the at least one Söderberg electrode thus generates its own characteristic vibration profile. This vibration profile or the vibrations themselves change when conditions deviate from normal or optimal operating conditions, i.e., when external and / or internal circumstances affect the at least one Söderberg electrode.

[0012] The feedstocks to be melted are preferably iron-containing materials, such as sponge iron and / or scrap, which are preferably melted with slag formers to form an iron melt and a slag floating on the iron melt.

[0013] According to a preferred embodiment, the electric melter comprises at least three Söderberg electrodes, and the vibrations of each individual Söderberg electrode are measured. These measurements are used to determine at least one state variable pertaining to the respective Söderberg electrode. In this way, each individual Söderberg electrode operated in the electric melter can be subjected to a vibration analysis, and it can be verified whether the characteristic vibration profile of the respective Söderberg electrode is within the "optimal" range. The number of Söderberg electrodes used can be four, five, six, and up to ten, particularly up to nine, preferably depending on the dimensions of the electric melter in which the Söderberg electrodes are used. Both round and rectangular melters can be used.

[0014] Depending on external and / or internal conditions, vibrations or vibration profiles result, which are compared with known vibration profiles that may be stored specifically for the respective Söderberg electrode, for example in an evaluation unit, in order to identify problems indicated by "bad" vibrations or vibration profiles that deviate from the "optimal" vibrations or vibration profiles.

[0015] According to a preferred embodiment, at least one state variable indicates a baking state in the lower section of at least one Söderberg electrode or of each individual Söderberg electrode. Depending on the baking state, different vibrations or vibration profiles result. If these deviate from the "optimal" and known values ​​(vibrations, vibration profiles), information about the baking state of the Söderberg electrode in its lower section is provided, for example, by corresponding values ​​stored in the evaluation unit. This information can be acquired, for example, through operational tests and / or determined operating data and stored with specific information in the evaluation unit.

[0016] According to one embodiment, at least one vibration sensor for measuring vibrations can be arranged on the at least one Söderberg electrode or on each individual Söderberg electrode. In particular, at least one accelerometer known to the relevant field can be used as the vibration sensor, which can be brought into contact with the Söderberg electrode either continuously or temporarily. Continuous contact allows for the successive repositioning or lowering of the Söderberg electrode, and the accelerometer can thus remain permanently in the same measuring position on the Söderberg electrode. Alternatively, for the duration during which repositioning or lowering of the Söderberg electrode is not required, contact can be established with the accelerometer, for example, by means of an adjustable manipulator.In particular, at least one vibration sensor head can be arranged in the upper and / or middle section of the Söderberg electrode. This allows the vibrations in the upper and / or middle section of the Söderberg electrode to be measured. Specifically, the accelerometer(s) used should not exhibit resonant vibrations during the "optimal" operating mode of the Söderberg electrode. Processes such as the attachment of additional ring-shaped sheet metal sheath elements and the filling with electrode material can be filtered out at the respective time, for example, using digital filters (low-pass, band-pass).

[0017] According to an additional or alternative embodiment, at least one non-contact vibrating sensor head can be positioned in the direction of the at least one Söderberg electrode, or at least one non-contact vibrating sensor head can be positioned in the direction of each individual Söderberg electrode to measure the vibrations. In particular, at least one vibrometer or laser vibrometer known to the trade can be used as the vibrating sensor head, which is directed at a measurement position on the Söderberg electrode. Thus, continuous recording of a measurement position is not disturbed even by successive repositioning or lowering of the Söderberg electrode. In particular, the measurement position can be located in the upper and / or middle section of the Söderberg electrode. The upper and / or middle section is located outside the melter. Therefore, the vibrations in the upper and / or middle section of the Söderberg electrode can be measured.Processes such as attaching further ring-shaped sheet metal casing elements and filling with electrode mass can be filtered out at the respective time using digital filters (low-pass, band-pass).

[0018] The at least one vibration sensor (accelerometer, vibrometer) is connected to an evaluation unit in which the measured vibrations or vibration profiles are processed and compared with stored vibrations or vibration profiles, and corresponding information is provided. Thus, information about at least one state variable of the at least one Söderberg electrode is available, preferably about the baking state.

[0019] The current actual value, corresponding to the vibrations measured by the vibration sensor head or the measured vibration profile, can be compared with target values ​​stored in the evaluation unit. Control and / or regulation signals can be stored in the evaluation unit for each vibration profile or for each vibration corresponding to a predefined target value. According to one embodiment, if the state variable deviates from a predefined target value, control and / or regulation signals can be output to change the electric current flowing through the Söderberg electrode. According to an alternative or additional embodiment, if the state variable deviates from a predefined target value, control and / or regulation signals can be output to change the cycle time of the successive repositioning of the Söderberg electrode.

[0020] By changing the electric current flowing through the Söderberg electrode and / or changing the cycle time of the successive repositioning of the Söderberg electrode, the baking process of the Söderberg electrode can be improved, and thus the baking condition can be positively influenced.

[0021] Vibrations or vibration profiles deviating from target values ​​can occur, for example, due to incompletely baked electrodes. This can cause the Söderberg mass (electrode mass) to run down from the electrode into the melter in liquid form, a so-called electrode breakdown. This must be prevented at all costs, as no power can be transferred to the furnace via the electrode in this case. Furthermore, the power input through the electrode via the slag can be optimized by adjusting the position of the electrode tip relative to the metal or iron bath surface. However, if the electrode is immersed too deeply, the slag is heated only very locally; conversely, if the electrode is not immersed deeply enough, energy losses can also occur due to arcing.

[0022] It is conceivable, especially in addition to the "monitored" baking state, that further characteristic state variables can also be measured or determined using the vibrations or vibration profiles, such as the burning of the Söderberg electrode, the position of the electrode tip to the melt / slag and the enveloping of the arc.

[0023] According to a further teaching, the invention relates to a method for monitoring a baking state at at least one Söderberg electrode, wherein vibrations of the Söderberg electrode are measured, wherein the measured vibrations are compared with target values ​​and, if the target values ​​are undershot or exceeded, control and / or regulation signals are output to change an electric current flowing through the Söderberg electrode and / or to change a cycle time for successively repositioning the Söderberg electrode.

[0024] To avoid repetition, reference is made to the details of the first teaching. Corresponding features of the first teaching are therefore also applicable and / or implementable in the subsequent teaching and thus comprehensible to the person skilled in the art. Consequently, all combinations of individual features of the first teaching with the subsequent teaching are also disclosed.

[0025] The invention is explained in more detail with reference to the following exemplary embodiments in conjunction with the Figure 1 .

[0026] The invention relates, firstly, to a method for operating an electric melter, wherein the electric melter comprises at least one Söderberg electrode (1) for melting feed materials in the electric melter, wherein the Söderberg electrode (1) is formed in its upper section from annular sheet metal sheath elements connected to one another and is filled with carbon-containing electrode mass, wherein the Söderberg electrode (1) is in a baked state in its lower section by application of current and / or heat and successively burns off at its lower end, so that the Söderberg electrode (1) is successively added and further sheet metal sheath elements are successively connected at its upper end and filled with electrode mass, wherein vibrations of the at least one Söderberg electrode (1) are measured during operation, with the help of which at least one state variable relating to the Söderberg electrode (1) is determined.Secondly, the invention relates to a method for monitoring a baking state at at least one Söderberg electrode (1), wherein vibrations of the Söderberg electrode (1) are measured, wherein the measured vibrations are compared with target values ​​and, if the target values ​​are undershot or exceeded, control and / or regulation signals are output to change an electric current flowing through the Söderberg electrode (1) and / or to change a cycle time to successively reposition the Söderberg electrode (1).

[0027] In a schematic view in Figure 1At least one Söderberg electrode (1) is shown, which is arranged in an electric melter (not shown), which may be of type OBF or SAF or type EAF. Preferably, the electric melter (not shown) may comprise at least three Söderberg electrodes (1), wherein the vibrations of each individual Söderberg electrode (1) can be measured, with the aid of which at least one state variable relating to the respective Söderberg electrode (1) can be determined. Preferably, the at least one state variable indicates at least a baking state in the lower section (not shown) of the at least one Söderberg electrode (1) or of each individual Söderberg electrode (1).

[0028] At least one non-contact vibrating measuring head (2) can be arranged in the direction of the at least one Söderberg electrode (1) or at least one non-contact vibrating measuring head (2) can be arranged in the direction of each individual Söderberg electrode (1) for measuring the vibrations, see. Figure 1 , top left. At least one vibrometer (2) or one laser vibrometer can be used as the vibration measuring head.

[0029] Alternatively or additionally, at least one vibration measuring head (3) can be arranged on the at least one Söderberg electrode (1) or on each individual Söderberg electrode (1) for measuring the vibrations, see. Figure 1 , bottom left. In this case, at least one accelerometer (3) can be brought into contact with the Söderberg electrode (1) either sliding or temporarily as a vibrating measuring head.

[0030] Preferably, the vibrations are measured in the upper and / or middle section of the Söderberg electrode (1).

[0031] The at least one vibration sensor head (2, 3) is connected to an evaluation unit (4) in which the measured vibrations or vibration profiles are processed and compared with stored vibrations or vibration profiles, and corresponding information is provided. Thus, information about at least one state variable of the at least one Söderberg electrode (1) is available, preferably about the baking state.

[0032] The current actual value, which corresponds to the vibrations measured by the vibration sensor head (2, 3) or the measured vibration profile, can be compared with target values ​​stored in the evaluation unit (4). Control and / or regulation signals can be stored in the evaluation unit for each vibration profile or for each vibration that corresponds to a predefined target value. This allows, for example (not shown here), control and / or regulation signals to change the electric current flowing through the Söderberg electrode (1) and / or control and / or regulation signals to change the cycle time of the successive repositioning of the Söderberg electrode (1) if the state variable deviates from a predefined target value.

[0033] The aforementioned operating method allows for the early or timely detection of defects in the Söderberg electrode (1) or in its lower section during the baked state.

Claims

1. A method for operating an electric melter, wherein the electric melter comprises at least one Söderberg electrode (1) for melting feed materials in the electric melter, wherein the Söderberg electrode (1) is formed in its upper section from interconnected ring-shaped sheet metal sheath elements and is filled with carbon-containing electrode mass, wherein the Söderberg electrode (1) is in a baked state in its lower section by application of current and / or heat and successively burns off at its lower end, so that the Söderberg electrode (1) is successively added and further sheet metal sheath elements are successively connected at its upper end and filled with electrode mass, characterized by the fact that During operation, vibrations of at least one Söderberg electrode (1) are measured, with the help of which at least one state variable relating to the Söderberg electrode (1) is determined.

2. Method according to claim 1, wherein the electric melter comprises at least three Söderberg electrodes (1) and the vibrations of each individual Söderberg electrode (1) are measured, with the help of which at least one state variable relating to the respective Söderberg electrode (1) is determined.

3. Method according to one of the preceding claims, wherein the at least one state variable indicates at least a baking state in the lower section of the at least one Söderberg electrode (1) or of each individual Söderberg electrode (1).

4. Method according to one of the preceding claims, wherein at least one vibration measuring head (3) for measuring the vibrations is arranged on the at least one Söderberg electrode (1) or on each individual Söderberg electrode (1).

5. Method according to claim 4, wherein the at least one acceleration sensor (3) is brought into contact with the Söderberg electrode (1) in a sliding or temporary manner.

6. Method according to one of the preceding claims, wherein at least one non-contact vibrating measuring head (2) is arranged in the direction of the at least one Söderberg electrode (1) or at least one non-contact vibrating measuring head (2) is arranged in the direction of each individual Söderberg electrode (1) for measuring the vibrations.

7. Method according to claim 6, wherein at least one vibrometer (2) is used.

8. Method according to one of the preceding claims, wherein the vibrations are measured in the upper and / or middle section of the Söderberg electrode (1).

9. Method according to one of the aforementioned claims, wherein, in the event of a deviation of the state variable from a predetermined setpoint value, control and / or regulation signals are output to change an electric current flowing through the Söderberg electrode (1).

10. Method according to one of the aforementioned claims, wherein, in the event of a deviation of the state variable from a predetermined setpoint value, control and / or regulation signals are output to change a clock time of the successive repositioning of the Söderberg electrode (1).

11. Method for monitoring a baking state at at least one Söderberg electrode (1), characterized by the fact thatVibrations of the Söderberg electrode (1) are measured, the measured vibrations are compared with target values ​​and, if the target values ​​are undershot or exceeded, control and / or regulation signals are output to change an electric current flowing through the Söderberg electrode (1) and / or to change a cycle time to successively reposition the Söderberg electrode (1).

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