DE102021114407A1 - Bubble detection device and method for detecting bubbles in an electrically conductive melt - Google Patents

Abstract

According to various embodiments, a bubble detection device (100) and a method for detecting bubbles are provided, the bubble detection device (100) having: a transmitting coil (110) for transmitting a signal, a receiving coil (120) for receiving a signal, the transmitting coil (110 ) and the receiving coil (120) are set up in such a way that at least one coupling region (130) is formed in which the transmitting coil (110) and the receiving coil (120) are inductively coupled to one another such that when the transmitting coil (110) and the Receiver coil (120) are in an electrically conductive melt, a signal emitted by the transmitter coil (110) can be received by the receiver coil (120).

Description

Various embodiments relate to a bubble detection device and a method for detecting bubbles in a melt.

In general, two-phase flows of one or more gases in a melt (e.g., a liquid metal, semiconductor melt, molten salt, or alloy) can be important in many technologies, e.g., metallurgy, metal recycling, power engineering processes, and/or the semiconductor industry . For example, in metallurgy, gas can be used to process molten materials with large melting volumes (e.g. more than 100 l), e.g. for stirring, mixing and/or homogenizing. In these processes, a size, speed, residence time and/or distribution of the bubbles can be important, e.g., to be able to stir effectively and/or to promote the chemical reactions. Gas can be introduced or injected during the continuous casting of steel, e.g. to prevent clogging of the dip tube and/or to separate non-metallic inclusions. In the case of unfavorable flows and/or bubble distributions, bubbles can remain in the steel during solidification, which can reduce the quality of an end product, for example. In energy technology, the production of hydrogen is relevant, among other things. In addition to electrolysis from water, hydrogen can also be extracted from methane, for example. Here, methane can be blown into a column reactor filled with liquid tin. On the way through the reactor, the methane can be separated into hydrogen and elemental carbon without producing carbon dioxide. A residence time, a size and a distribution of the methane bubbles within the liquid tin can be important in order to allow the chemical reaction to proceed optimally and/or to generate a high throughput rate.

In general, gas bubbles in water, and/or poorly conducting media, and/or opaque media can be detected using various measurement techniques. These methods can be unsuitable for use in a melt. For example, optical methods cannot be used in an opaque melt. For example, current resistive or capacitive grid sensors may not be suitable for a melt, e.g. due to a high electrical conductivity or a high temperature of the melt.

For example, bubbles in a melt can be detected using one of the following methods. However, the following methods have disadvantages, for example the above-mentioned properties of the bubbles can only be determined indirectly by means of these. For example, in metal melts in industrial plants, eg in steel secondary metallurgy, gas bubbles can be evaluated using an impact area on the visible surface. For example, various properties of gas bubbles in melts and/or two-phase flow regimes can be visualized using X-rays. However, the massive elements (e.g. Bi, Ga, Fe, In, etc.), which can typically occur in melts, can weaken the X-rays to such an extent that only thin containers, e.g. with a width of less than 15 mm, can penetrate with reasonable effort can become. As a result, this method can be unsuitable for large volumes (eg more than 1 liter). For example, wider containers (eg with a width of more than 15 mm) can be irradiated using a neutron-based method or a gamma radiography method. However, the effort can be increased by these methods. In addition, an achievable image contrast and/or a temporal resolution of the measurement may be insufficient. For example, ultrasonic methods can be based on a reflection of the pulses emitted by a sensor at an interface between a bubble surface and the melt. This allows the distance between a sensor and the bubble surface to be determined. Tomographic methods can detect the shape, position and speed of the bubble. However, evaluating the data can become very difficult if there are many bubbles (eg more than 3) in the measurement window at the same time. For example, the bubbles that are closer to the sensor than other bubbles can shield signals from the other bubbles. In addition, coupling the ultrasonic signal into the melt can be difficult with this method, especially at temperatures above 200 °C. For example, when used in particularly high temperatures, the measuring depth can be limited using ultrasonic waveguides. In addition, oxides can be deposited at a coupling point of the signal, which can reduce the signal quality. This can cause the sensors to deliver unusable signals. For example, bubbles can be detected using needle probes. A transit time of a bubble can be measured locally at the tip of one of the needle probes. For example, if the bubble reaches the tip of the needle probe, the resistance of the needle probes may increase. For example, in order to determine a spatial distribution and/or a size of a bubble, it may be necessary to arrange a large number of needle probes (eg more than 10) in the melt. In addition, a spatial resolution can be determined by a distance between the needle probes. For example, a choice of insulation and of a material for a needle probe tip may be important to reduce corrosive effects during measurement. For example, oxides can build up on the tip of the needle probe, reducing signal fidelity. Due to the needle probes within the melt, flow disturbances that cannot be neglected can occur. For example, gas bubbles can show a tendency to avoid flow obstructions, such as needle probes. As a result, measured values can be subject to very large errors. For example, inductive methods, in which the magnetic field sensors are positioned outside the melt, can enable bubbles to be detected. However, an accurate spatial distribution and/or an accurate determination of the bubble size can be difficult because, for example, a mathematical non-linear inverse problem or an ill-posed non-linear inverse problem has to be solved.

According to various aspects, an apparatus for detecting bubbles (i.e., gas bubbles) in an electrically conductive melt is provided. The melt can be opaque to visible light.

According to various aspects, a device is provided that can continuously detect one or more properties (e.g., a spatial distribution, a size, a velocity, etc.) of gas bubbles. According to various aspects, an apparatus is provided that can detect a plurality of gas bubbles, e.g., simultaneously. The gas bubbles can be detected, for example, in so-called bubble chains and/or in bubble swarms. According to various aspects, an apparatus is provided that can detect small diameter (e.g., less than 3 mm) and large diameter (e.g., greater than 10 mm, 30 mm, 60 mm, and greater than 100 mm) bubbles.

According to various aspects, an apparatus is provided that has high temporal and/or high spatial resolution compared to conventional bubble detection systems.

According to various aspects, a device is provided whose measured values can be evaluated with little computational effort. According to various aspects, an apparatus is provided in which additional information about the bubble and melt can be determined with high computational effort (e.g. solving an inverse problem). According to various aspects, a device is provided which has a structure which is easy to implement and/or adapt, and/or which is suitable for containers with large diameters (e.g. more than 20 cm).

According to various aspects, a device is provided which can be used in a wide range of geometries, in particular the geometry of the device can be adapted to a use or a use location.

According to various aspects, a device is provided which is at least partially brought into contact with media having a high temperature, e.g., above 300°C, 500°C, or above 1000°C.

According to various aspects, a device is provided that is robust to one or more reactive fluids, e.g., one or more chemically aggressive fluids.

According to various aspects, a bubble detection device for detecting bubbles in an electrically conductive melt is provided, the bubble detection device having: a transmitting coil for transmitting a signal, a receiving coil for receiving a signal, the transmitting coil and the receiving coil being set up in such a way that at least one coupling region is formed in which the transmission coil and the reception coil are inductively coupled to one another in such a way that when the transmission coil and the reception coil are in an electrically conductive melt, a signal emitted by the transmission coil can be received by the reception coil.

Clearly, a bubble detection device is provided that has at least two coils that can be positioned in a melt. At least one coil can be used to transmit a signal (a so-called transmitter coil or excitation coil) and at least one coil can be used to receive a signal (a so-called receiver coil or receiver coil). By means of a chosen frequency of the transmitted signal, a spatially resolved output can be provided without solving an inverse problem. The bubble detection device provided allows a high spatial and/or temporal resolution of the distribution, size and speed of bubbles in the electrically conductive melt, for example in liquid metals. The spatial resolution of the bubble detection device can be achieved by adding a plurality of transmitting coils and/or receiving coils. A high frame rate compared to conventional systems can be provided by means of the bubble detection device due to a high frequency. The ability to measure the velocity of bubbles can be achieved by adding one or more additional measurement planes. The bubble detector provided tion device can, for example, be set up in such a way that it is not limited by the temperature of the melt, any corrosion that may occur and/or by a special requirement for a coupling layer.

According to various aspects, a method for detecting bubbles in a melt is provided, the method comprising: positioning at least one transmission coil and one reception coil in an electrically conductive melt, the transmission coil and the reception coil being inductively coupled to one another in a coupling region. Sending a signal using the transmitting coil, receiving a measurement signal generated by the transmitted signal using the receiving coil, determining a value which represents one or more properties of the melt with or without gas bubble(s), based on the received measurement signal.

According to various aspects, a method for detecting bubbles in a melt is provided, the method comprising: positioning a plurality of transmission coils and a plurality of reception coils in an electrically conductive melt, the plurality of transmission coils and the plurality of reception coils having a spatial arrangement of coupling regions, in each of which one of the multiple transmitting coils is inductively coupled to one of the multiple receiving coils. Sending a transmission signal by means of one of the several transmission coils, receiving a respective measurement signal by means of each of the several reception coils, the respective measurement signal being generated by the transmission signal. Determination of a value, which represents one or more properties of the melt with or without gas bubble(s), based on the received measurement signals.

According to various aspects, a bubble detection device is provided that includes one or more coils, wherein the one or more coils are configured to be placed in a liquid metal. In various aspects, the one or more coils may each have one or more turns.

According to various aspects, a bubble detection device can have one or more measurement planes, for example to detect time dependencies over a distance between directly adjacent measurement planes, e.g. speed over time differences.

According to various aspects, a bubble detection device may include multiple receiving coils (e.g., 2, 3, 4, 5, 6, 7, 8, 16, 32, or more than 32) configured to sense an induced magnetic field simultaneously, e.g., in a parallel measurement, or at different times, e.g. in a serial measurement.

According to various aspects, a method is provided that allows for a quick and precise measurement of the amplitude and/or the phase of an induced voltage. Furthermore, an effective and accurate algorithm for demodulation can be used.

According to various aspects, a method is provided for influencing the size of the coupling region via different frequencies, the frequencies can be superimposed and/or generated with a time offset.

Embodiments are shown in the figures and are explained in more detail below.

• 1A bis 2B schematisch eine Blasendetektionsvorrichtung gemäß verschiedenen Aspekten;
• 3 eine beispielhafte schematische Darstellung einer Blasendetektionsvorrichtung gemäß verschiedenen Aspekten, die mehrere Sendespulen und mehrere Empfangsspulen aufweist;
• 4 einen beispielhaften Zeitverlauf eines demodulierten Signals einer Empfangsspule;
• 5A eine schematische Blasendetektionsvorrichtung gemäß verschiedenen Aspekten;
• 5b eine beispielhafte Sensitivitätsmatrix einer Blasendetektionsvorrichtung gemäß verschiedenen Aspekten;
• 6 beispielhaft einen schematischen Aufbau einer Blasendetektionsvorrichtung gemäß verschiedenen Aspekten;
• 7 eine Fotografie einer Blasendetektionsvorrichtung gemäß verschiedenen Aspekten entsprechend der schematischen Darstellung nach 2A/2B;
• 8 eine Fotografie einer Blasendetektionsvorrichtung gemäß verschiedenen Aspekten, die in einen Behälter, der mit einem Flüssigmetall gefüllt ist, eingetaucht ist; und
• 9 in einer Fotografie schematisch eine mögliche Anordnung einer Blasendetektionsvorrichtung gemäß verschiedenen Aspekten.

Show it

• 1A until 2 B schematically a bubble detection device according to various aspects;
• 3 an exemplary schematic representation of a bubble detection device according to various aspects, which has a plurality of transmitting coils and a plurality of receiving coils;
• 4 an exemplary time course of a demodulated signal of a receiving coil;
• 5A a schematic bubble detection device according to various aspects;
• 5b an exemplary sensitivity matrix of a bubble detection device according to various aspects;
• 6 by way of example, a schematic structure of a bubble detection device according to various aspects;
• 7 1 shows a photograph of a bubble detection device according to various aspects according to the schematic representation 2A /2 B;
• 8th 14 is a photograph of a bubble detection device according to various aspects immersed in a container filled with a liquid metal; and
• 9 in a photograph schematically a possible arrangement of a bubble detection device according to various aspects.

In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. Because components of embodiments can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. It is understood that the features of the various exemplary embodiments described herein can be combined with one another unless specifically stated otherwise. The following description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.

In various aspects, one or more components may be in contact with a melt. Here, a melt is understood to be a material or a mixture of materials that is neither solid nor gaseous. A melt can have a process temperature at which bubbles within the melt are to be detected. The process temperature can also be referred to below as a temperature of the melt. It goes without saying that the process temperature can cover a temperature range. For example, the process temperature of the material or the process temperature of the material mixture can be greater than its respective melting point. For example, in the case of a material mixture comprising a plurality of materials, the process temperature can be lower than a melting point of at least one of the plurality of materials in the material mixture. For example, the melt can include or be a salt melt and/or a semiconductor melt and/or a metal melt, a so-called liquid metal. For example, the melt can have one or more metals and/or one or more ionic solutions and/or one or more semiconductors.

According to various aspects, one or more components and/or a melt can be electrically conductive. The one or more components or the melt are referred to as being electrically conductive if the respective electrical conductivity a is greater than 10 ² S/m, for example greater than 10 ³ S/m, 10 ⁴ S/m, 10 ⁵ S/m. m, 10 ⁶ S/m, 10 ⁷ S/m, or greater than 10 ⁸ S/m. It goes without saying that the electrical conductivity relates to the electrical conductivity at a temperature at which the respective component can be used (eg functionally) or at which the melt can be examined, eg at the process temperature.

In various aspects, one or more components may be electrically isolating. An electrically insulating component is, for example, not electrically conductive or only poorly conductive.

For example, the electrical conductivity of an electrically insulating component can be less than 10 ² S/m. It can be of particular importance that the conductivity of the insulating component is at least one order of magnitude lower than that of the electrical conductor

In various aspects, a component may be referred to as a transmit coil. The transmitter coil can be a coil that has one or more turns. The transmitter coil can be a rod. The transmission coil can be set up to transmit a signal. For example, the signal can be sent at a predetermined frequency. For example, an alternating current with the specified frequency can be applied to the transmission coil for this purpose. For example, the predetermined frequency may be greater than 10 Hz, e.g. greater than 100 Hz, 200 Hz, 500 Hz, 1 kHz, 2 kHz, 5 kHz, 10 kHz, 20 kHz, 50 kHz, 100 kHz, 200 kHz, 500 kHz, 1MHz, 2MHz, 5MHz, 10MHz or greater than 20MHz. For example, the transmission coil can be set up to transmit one or more further signals. For example, the one or more further signals can have predefined frequencies that are different or the same as one another. For example, the signal and the one or more other signals can be sent in a predetermined order. For example, the transmission coil can be set up to transmit the signal continuously and/or at specific intervals (e.g. at time intervals). In particular, the transmission coil can be set up to transmit each of the one or more further signals in a respective predefined time interval. For example, the transmission coil can be designed in such a way that it influences (e.g. disturbs) a flow within the melt as little as possible. For example, a cross section of a coil conductor of the transmission coil can be as small as possible without impairing the function of the bubble detection device. For example, the transmitter coil can be as large as necessary to meet mechanical strength requirements.

In various aspects, a component may be referred to as a receiving coil. The receiving coil can be a coil with one or more turns. The receiving coil can be a rod. The receiving coil can be set up to receive a signal. The signal can have or be a current and/or a voltage and/or a frequency, for example. The receiving coil can be set up, for example, to receive the signal continuously or only at predetermined intervals. For example, the receiving coil can receive the signal in a time-resolved manner. For example, the receiving coil can be designed in such a way that it affects a flow within the melt as little as possible flows (e.g. disturbs). For example, a cross section of a coil conductor of the reception coil can be as small as possible without impairing the function of the bubble detection device. For example, the receiver coil can be as large as necessary to meet mechanical strength requirements.

According to various aspects, a signal (e.g. a transmitted signal, a received signal, a measurement signal, a transmission signal) can have a signal characteristic. A signal characteristic can be defined by or represent one or more of the following properties: an intensity, and/or a frequency, and/or a signal duration, and/or a pulse duration, and/or a pulse number, and/or a time, and/or a phase. Intensity includes the current and voltage of the signal. For example, a first signal and a second signal may have different (i.e. different) signal characteristics from each other. This can clearly mean that a signal characteristic of the first signal differs from a signal characteristic of the second signal in at least one of the above-mentioned properties of the signal characteristic. For example, a first signal and a second signal can have the same signal characteristics, i.e. they do not differ in any of the aforementioned properties. Signals with the same signal characteristics can also be understood as the same signals.

A bubble detection device may include one or more transmit coils and one or more receive coils.

Coils can each be arranged in such a way that one or more coupling regions can be formed between the one or more transmission coils and the one or more reception coils. In each of the one or more coupling areas, a respective transmission coil can be inductively coupled to a respective reception coil.

1A shows a schematic plan view of a bubble detection device 100 and 1B 12 shows a schematic side view of the bubble detection device 100 with a coupling area 130. The bubble detection device 100 can have a transmitting coil 110 and a receiving coil 120. FIG. The transmitting coil 110 and the receiving coil 120 can be positioned such that the coupling region 130 is formed. In the coupling area, the transmission coil 110 and the reception coil 120 can be coupled to one another in such a way that they are inductively coupled to one another within an electrically conductive melt. For example, the transmission coil 110 and the reception coil 120 can have a distance from one another in the coupling region that is less than a predetermined value. For example, in the 1A and 1B a coupling region 130 is shown. In the top view ( 1A ) and side view ( 1B ) shows, for example, that the transmission coil 110 and the reception coil 120 can be arranged in different planes. The coupling area 130 can be, for example, the area in which the transmission coil 110 is closest to the reception coil 120 . For example, the coupling area in a projection can be a crossing point of the transmission coil 110 and the reception coil 120 .

It goes without saying that the coils can also be arranged in such a way that the transmission coil 110 can be arranged entirely or partially inside the receiving coil 120 or the receiving coil 120 can be arranged entirely or partially inside the transmitting coil 110 .

2A shows a schematic plan view of a bubble detection device 100 and 2 B 12 shows a schematic side view of the bubble detection device 100 with a plurality of coupling regions 130. The bubble detection device 100 can have a transmitting coil 110 and a receiving coil 120. FIG. The transmitting coil 110 and the receiving coil 120 can be positioned such that a plurality of coupling regions 130 are formed. In the top view ( 2A ) and side view ( 2 B ) shows, for example, that the transmission coil 110 and the reception coil 120 can be arranged in different planes. For example, the multiple coupling regions in a projection can each be a crossing point of the transmission coil 110 and the reception coil 120 . In contrast to the 1A and 1B For example, the transmission coil 110 and the reception coil 120 can each be rotated by 90° along a Y-axis. It goes without saying that a rotation along the Y-axis at an angle other than 90° can also be possible. For example, the angle can be more than 0°, eg more than 1°, 2°, 3°, 4°, 5°, ..., 85°, 86°, 87°, 88° or by more than 89°. It is further understood that the transmitting coil 110 and the receiving coil 120 can be rotated about the Y-axis independently of one another and/or at different angles from one another.

It goes without saying that the transmission coil 110 and/or the reception coil 120 can also be rotated as desired with respect to a Z-axis. For example, a rotation with respect to the Z-axis can be carried out analogously to a previously described rotation with respect to the X-axis or the Y-axis.

In the 1A and 2A the transmitting coil 110 and the receiving coil 120 can be in one 90° angle to each other. It goes without saying that arrangements with an angle not equal to 90° can also be possible. For example, the angle can be 0° or more than 0°, e.g. more than 1°, 2°, 3°, 4°, 5°, ..., 85°, 86°, 87°, 88° or more than 89 °.

In order to detect bubbles, the transmission coil 110 can be set up to transmit a signal at a predetermined frequency. The receiving coil 120 can receive this, for example, in the coupling area, e.g. via the inductive coupling. For example, the received signal may be different when there is a bubble within and/or near the coupling region compared to the received signal when only the melt (or melt) is present within and/or near the coupling region. no bubble) is located.

The transmitting coil 110 and the receiving coil 120 can each be surrounded at least in sections by an electrically insulating material, e.g. in order to separate the respective coil from the electrically conductive melt. For example, the electrically insulating material should have a melting temperature that is greater than the temperature of the melt in which the bubble detection device is to be used. For example, the electrically insulating material prevents an electrical short circuit between the transmitting coil 110 and the receiving coil 120 (e.g. in a coupling region 130). For example, the electrically insulating material can be arranged so that the respective surrounded coil does not melt during use of the bubble detection device 100 . For example, the transmission coil 110 and/or the reception coil 120 and/or the respective electrically insulating material can be coupled to a cooling device.

For example, the transmitting coil 110 and/or the receiving coil 120 can be constructed in such a way that they operate for a predefined time interval (e.g. within 600 s, e.g. within 300 s, 180 s, 120 s, 60 s, 50 s, 40 s, 30 s, 20 s, 10 s, 5 s, or within 1 s) fulfill their respective function and thereafter dissolve and/or fuse in the melt. For example, the materials from which the transmitting coil 110 and/or the receiving coil 120 are formed can be contained in the melt. For example, the materials may have a similar melting temperature (e.g. 200°C more or less) than the melt.

The bubble detection device 100 can have a transmission circuit, for example. For example, the transmission circuit can be coupled to the transmission coil 110 . The transmission circuit can be set up to apply an alternating current with a frequency for transmission of the signal to the transmission coil 110 . For example, an additional frequency can be equal to or a multiple (e.g. 2 times, 3 times, 5 times, 10 times, etc. or also a non-integer multiple) of the frequency of the transmission signal and can be superimposed on it. For example, the transmit circuitry may apply an AC voltage to transmit coil 120 at a frequency for transmitting a signal. For example, the transmitted signal can have a frequency and/or an intensity. For example, the transmission circuit can provide multiple alternating currents for transmitting signals from the transmitting coil 120, wherein the multiple alternating currents can have different frequencies and/or current strengths and/or voltages from one another. For example, the transmission circuit can have a multiplexer. For example, the multiplexer can be coupled to the transmit coil 110 to provide a signal to be transmitted. For example, the transmission circuit can be set up to carry out a measurement of a current in the transmission coil 110 . For example, the transmission circuit can have a current measuring device and/or a voltage measuring device. For example, the transmission circuit can have a power amplifier and/or a special power current amplifier.

The bubble detection device 100 may include a receiver circuit, for example. For example, receiver circuitry may be coupled to receiver coil 120 . The receiver circuit can be set up, for example, to receive and/or process and/or store the signal that was transmitted by the receiving coil 120 . For example, the receiving coil 120 can also be set up to receive the one or more further signals from the transmitting coil 110 . For example, the receiver circuit can be set up to measure a current and/or a voltage of the receiving coil 110 . For example, the receiver circuit can have a current measuring device and/or a voltage measuring device. For example, the receiver circuit can have a voltage preamplifier and/or a current amplifier and/or a current preamplifier.

The bubble detection device 100 can have a control unit, for example. The transmitter circuit and/or the receiver circuit can be part of the control unit. The control unit can be set up, for example, to control the receiver circuit and/or the transmission circuit. For example, the Bubble detection device 100 and/or the transmission unit may be set up to assign a signal that was transmitted by the transmission coil to a signal that was received by the reception coil. For example, the control device can be set up to output a data record. The data set can, for example, contain information about a respective transmitted signal and/or an associated received signal. The data set can, for example, contain information about whether the signal was received or sent, and/or in which coil, and/or with which voltage, and/or with which current, and/or with which phase, and/or with which frequency , and/or at what time the signal was sent or received.

3 12 shows an exemplary schematic illustration of a bubble detection device 100 which has a plurality of transmission coils 110 and a plurality of reception coils 120. FIG. For example, the plurality of transmission coils 110 and the plurality of reception coils 120 can be arranged in such a way that each transmission coil forms two coupling regions with each reception coil. For example, the coupling regions 130 can be arranged in a matrix arrangement.

The multiple transmission coils 110 can each be connected to a transmission circuit 210 . The transmission circuitry 210 may include an AC power source. The transmission circuit can be set up to provide an alternating current with a constant frequency at each transmission coil 110 . For example, the alternating current can be provided at the multiple transmission coils at the same time. For example, the alternating current can be provided to the transmitter coils in a predetermined order (e.g. sequentially or alternately).

The multiple receive coils may be coupled to a receiver circuit 220 . The receiver circuitry may be configured to operate the multiple receiver coils simultaneously and/or in a predetermined order (e.g., sequentially). The receiver circuit 220 can have a signal amplifier 221 and/or an analog/digital converter 222, for example. Receiver circuitry 220 may be coupled to a controller 230 (e.g., a real-time computer system). The receiver circuit and/or the control unit 230 can be set up to process the received signal, e.g. to output the received signal, and/or to split the received signal into one or more partial signals (e.g. by means of signal demodulation), and/or to correct the received signal (e.g. by means of an error correction and/or an attenuation correction), and/or to smooth the received signal. The receiver circuit and/or the control unit 230 can be set up to process signals received from the multiple receiving coils in a time-resolved manner. For example, the control unit 230 can be set up to process more than 10 received signals per second, e.g. more than 50, 100, 200, 500, 1000, 2000, 5000, or more than 10000 signals per second, e.g. to process them individually. For example, the control unit 230 can be set up to transmit the received signal and/or the processed signal to the data processing unit 240 (e.g. personal computer).

The bubble detection device 100 can be positioned in a melt. Several bubbles 11 can be located in the melt. The bubbles 11 can move past one of the coupling regions 130 or through one of the coupling regions 130, for example. For example, a bladder 11 is shown in a docking area 130 in an enlarged view. The presence of the bubble 11 can change a signal received by a receiving coil. For example, the impedance of the receiving coil can change. For example, the impedance of the transmission coil can change.

4 shows an exemplary time course of a demodulated signal of a receiving coil 120 when passing the bubbles 11 or through a coupling region 130. In the upper part of 4 a real part of the demodulated signal (vertical axis) is shown as a function of time (horizontal axis). In the lower part of 4 An imaginary part of the demodulated signal (vertical axis) is shown as a function of time (horizontal axis). When a bubble passes the vicinity of the coupling region, an amplitude of the real part and imaginary part of a demodulated signal of the receiving coil can change. This clearly means that the presence of a bubble can be determined via an amplitude of the signal. For example, negative deflections of the real part and/or positive deflections of the imaginary part can indicate the presence of a bubble. For example, information about the location of the bubble in the coupling area can be given via the signs of the deflections of the imaginary and real parts. For example, a standard deviation and/or peak value detection can be used as a measure of the presence of bubbles that is easy to visualize or evaluate. For example, the existence or a presence of a bubble can be determined via a wavelet transformation. For example, by means of an arrangement of several coupling areas (coupling areas arranged next to one another and/or one above the other), and/or with at least two measurements, the have a small time interval between each other (eg less than 0.5 ms), a size and/or a speed of a bubble can be determined. For example, the size can be determined using the spacing of the coupling regions that detect a bubble. For example, a speed of the bubble can be determined when a plurality of coupling regions are arranged along the moving direction of the bubble, using respective points in time at which a bubble is detected at a respective coupling point and a distance of the respective coupling points from one another. A spatial arrangement can be determined by means of the spatial arrangement of the coupling regions, a detection time and/or a duration in which a bubble is detected.

wobei σ eine elektrische Leitfähigkeit der Schmelze darstellt,µ eine absolute Permeabilität der Schmelze und ƒ die Frequenz des gesendeten Signals (z.B. die Frequenz des Wechselstroms). Da sich die Leitfähigkeit des Gases innerhalb einer Blase von der Leitfähigkeit der Schmelze unterscheidet, verändert sich die Form und Intensität des Wirbelstroms (z.B. Dicke δ, ein Verlauf, eine Stromstärke) bei Anwesenheit der Blase. Die Veränderung des Wirbelstromes kann durch eine Änderung des durch die Empfangsspule empfangenen Signals ermittelt werden, wie beispielsweise in 4 dargestellt. Anschaulich erlaubt die Nutzung von geringen Skin-Tiefen durch die hohe Frequenz ein lokales Messen, ohne ein inverses Problem lösen zu müssen. Für eine hohe zeitliche und/oder örtliche Auflösung sollte eine genaue Stromquelle und/oder eine präzise Strommessung (z.B. mit einer Ungenauigkeit von weniger als 10% eines gemessenen Stromwerts, z.B. weniger als 5%, 1%, 0,5%, 0,1%, 0,05% oder weniger als 0,01%) für die genutzte Frequenz verwendet werden.Clearly, the coupling area can be an area in which bubbles can be detected. A size of the coupling region can be estimated using the skin effect. The signal sent by the transmitter coil 110 can cause an eddy current with a thickness δ around the transmitter coil 110 in the conductive melt, with the thickness δ being estimated as follows: $$\delta =\sqrt{\frac{1}{\pi \mu ƒ\sigma }},$$

where σ represents an electrical conductivity of the melt, µ an absolute permeability of the melt and ƒ the frequency of the transmitted signal (eg the frequency of the alternating current). Since the conductivity of the gas within a bubble differs from the conductivity of the melt, the shape and intensity of the eddy current (eg thickness δ, a course, a current strength) changes in the presence of the bubble. The change in the eddy current can be determined by a change in the signal received by the receiving coil, as for example in 4 shown. Clearly, the use of low skin depths due to the high frequency allows local measurement without having to solve an inverse problem. For a high temporal and/or spatial resolution, an accurate current source and/or a precise current measurement (e.g. with an inaccuracy of less than 10% of a measured current value, e.g. less than 5%, 1%, 0.5%, 0.1 %, 0.05% or less than 0.01%) for the frequency used.

A bubble detection device 100 with two transmitting and two receiving coils can be used, for example, for a clear representation of boundaries of one or more coupling regions 130 (i.e. of one or more sensitive regions of the bubble detection device 100).

5a FIG. 12 schematically shows a bubble detection device 100 according to FIG 2A / 2B having a transmission coil 110 and a reception coil 120. The transmission coil can be coupled to the reception coil in a first coupling region 131, in a second coupling region 132, in a third coupling region 133 and a fourth coupling region 134.

5b FIG. 12 shows an exemplary sensitivity matrix of a measurement arrangement of the bubble detection device 100 according to FIG 5A arranged in a melt. For example, bubbles may pass through the bubble detection device 100 at predetermined points and an output of the bubble detection device 100 is sampled at the respective point. The bubble detection device 100 can detect bubbles present in the respective coupling regions 131-134. A respective size of the coupling areas 131-134 in which bubbles can be detected is in 6B shown schematically by dashed lines. In 5B For example, a sensitivity of the bubble detection device 100 can be represented by a larger sensitivity value 701—clearly a darker area—within the coupling regions 131-134. For example, all of the coupling areas 131-134 of a sensor can be collectively referred to as a sensor surface.

6 shows an example of a schematic structure of an embodiment of a bubble detection device 100. The bubble detection device 100 can have a transmitting coil 110 and a receiving coil 120. FIG. The transmitting coil 110 and the receiving coil 120 can form a coupling region 130 in which bubbles can be detected. The transmit coil 110 may be coupled to a transmit circuit 210 . the transmission circuit 210 can have a digital-to-analog converter 211, a controllable current source 212 and/or a current measuring device 213. For example, the controllable current source 212 can be set up to supply the transmission coil with a constant current. The controllable current source can provide the current at a predetermined frequency to the transmission coil 110 . The receiving coil 120 can be coupled to a receiver circuit 220 . The receiver circuit can have a voltage preamplifier and/or an analog/digital converter. The bubble detection device 100 may further include a control unit 230 and a data processing unit 240 . The control unit 230 can be set up to demodulate the signal received by the receiving coil 120 . For example, the received signal can be demodulated in a time-resolved manner, for example in real time. For example, the received signal and/or the demodulated signal can be presented and/or visualized and/or processed and/or stored by the data processing unit 240, eg in real time. In 6 shows, for example, how the demodulated signal 241 and the spatially resolved signal can be shown 242. For example, the demodulated signal can be shown using an oscilloscope.

7 FIG. 12 shows a photograph of a bubble detection device 100 according to the schematic illustration, for example 5A .

8th 12 shows a photograph wherein the bubble detection device 100 of FIG 7 immersed in a container filled with a liquid metal. The liquid metal can be, for example, GaInSn, which is liquid at room temperature. The bubble detection device 100 can be positioned within the liquid metal, for example by means of one or more holders. For example, the bubble detection device 100 can be positioned at a predetermined distance from a surface of the liquid metal. A gas supply line, eg a metal tube, can be placed below the bubble detection device 100 . The metal tube can be moved to any position under the sensor using a traverse. One or more gases can be injected via the metal tube, so that individual bubbles 11 can rise.

9 12 schematically illustrates in a photograph how the bubble detection device 100 according to FIG 8th can be arranged in a melt 10. One or more gases 13 can be introduced into the melt 10 from the gas supply line 12 . The one or more gases 13 can move within the melt in the form of bubbles 11 , eg rise to the bubble detection device 100 . If there is a bubble in the coupling area (ie in a sensitive area of the bubble detection device 100), the bubble can be detected by means of the signal received by the receiving coil.

According to various aspects, a device and a method for detecting and/or characterizing gas bubbles in electrically conductive melts, e.g. in metal melts, can be provided. For example, the device or the method can be used to detect gas bubbles in a two-phase flow that can contain a liquid metal, e.g. in metallurgy, in the recycling of metals, and in energy technology. For example, a gas can be used in metallurgy, e.g., for stirring, mixing and homogenizing large melt volumes. Bubble parameters such as size, speed, residence time and spatial distribution of the bubbles can play an important role. According to various aspects, a device and a method are provided which allow the bubble parameters of gas bubbles in electrically conductive and/or optically opaque melts to be characterized in a structurally simple, uncomplicated and/or continuous manner. For example, they allow characterizing the bubble parameters under aggressive conditions such as high process temperatures with high temporal and spatial resolution.

For example, the device can have an excitation coil and a receiver coil, which are introduced together into a melt to be characterized. The two coils can be electrically insulated from the melt by means of a protective sheath. For example, their coil axes can form an angle of 90°. The excitation coil can be subjected to an alternating electrical excitation signal, as a result of which eddy currents can be induced in the melt. The voltages induced in the receiver coil can be measured. If there is a bubble (e.g. a gas bubble) in the measuring range, eddy currents induced by the transmitter coil can be influenced or distorted by the bubble, which can be noticeable in the influence of a voltage induced in the receiver coil. Based on the voltage signal induced at the receiver coil, the gas bubbles can be detected and characterized. For example, the bubble detection device can enable bubble characterization for optically opaque fluids.

Due to the high frequencies used for the excitation signal and the resulting skin effect, the eddy currents can be limited to a small spatial area in the vicinity of the excitation coil, which means that the spatial resolution can be given solely by the sensor geometry. For example, a high spatial resolution can thus be achieved through a corresponding sensor geometry. Due to a strong localization, the recorded measurement signals can always be assigned to a locally defined measurement position, so that an evaluation does not require a solution of an ill-posed non-linear inverse problem and can therefore be carried out in an uncomplicated manner. Due to the strong localization, measurements at different measuring positions (e.g. using several excitation coils and/or receiver coils) can also be or be carried out independently of one another, so that simultaneous characterization at several different measuring positions can be carried out in an uncomplicated manner, from which, for example, conclusions can be drawn about the size or speed of movement of the bubbles. By using a high sampling frequency (eg at the excitation coils), the measurement can be carried out with a high temporal resolution.

For example, the bubble detection device may be suitable for use in metallurgy (e.g. during stirring or continuous casting). For example, the bubble detection device may be suitable for use in power engineering (e.g. during the extraction of hydrogen from methane). For example, the bubble detection device can be suitable for use during recycling processes. For example, the bubble detection device can be suitable for early detection of defects in a liquid metal/water heat exchanger (e.g. the heat exchanger between sodium and water in a solar power plant).

Some examples are described below that relate to what is described herein and shown in the figures.

Example 1 is a bubble detection device for detecting bubbles in an electrically conductive melt, the bubble detection device can have: a transmitting coil for transmitting a signal, a receiving coil for receiving a signal, wherein the transmitting coil and the receiving coil can be set up in such a way that at least one coupling region is formed in which the transmission coil and the reception coil are inductively coupled to one another in such a way that when the transmission coil and the reception coil are in an electrically conductive melt, a signal emitted by the transmission coil can be received by the reception coil. For example, the bubble detection device and/or the coupling area can be set up in such a way that molten metal can flow through the bubble detection device and/or the coupling area. For example, the transmission coil and the reception coil can cross in a projection of the coupling area. For example, the transmission coil can have one or more turns. For example, the receiving coil can have one or more turns. For example, the at least one coupling area can be exactly one coupling area.

Example 2 is a bubble detection device according to example 1, wherein the transmitting coil and/or the receiving coil can largely have or consist of one or more of the following materials: tungsten, aluminum, copper, platinum, gold, molybdenum, tantalum, niobium, titanium, chromium and rhenium. For example, the transmitting coil and/or the receiving coil can largely consist of or have a titanium-zirconium-molybdenum alloy and/or a tungsten-copper alloy.

Example 3 is a bubble detection device according to Example 1 or 2, wherein the transmitting coil is encased in a first material and the receiving coil is encased in a second material. For example, the first material can be the same as the second material. For example, the first material can be different from the second material. For example, the first or second material can be an electrical insulator. For example, the first or second material can have a conductivity that is at least one order of magnitude lower at a temperature of the melt (or process temperature) (i.e. have poorer electrical conductivity) at which the bubbles in the molten metal are to be detected. For example, the first or second material may include or be a ceramic, a glass, an organic material (e.g. a resin) and/or porcelain and/or polyetheretherketone (PEEK) and/or polytetrafluoroethylene (PTFE). For example, it could also be a poorer conductor, i.e. with an electrical conductivity that is at least one order of magnitude lower. For example, the first or second material can be selected in such a way that the melting temperature of the material is greater than a temperature of the melt at which bubbles in the molten metal are to be detected. For example, the first or second material can be selected in such a way that the coil covered by the material does not melt within the molten metal.

For example, the first or the second material can be selected in such a way that the first material or the second material can dissolve in the melt and/or fuse with the melt after a predefined time interval. For example, the transmitting coil or the receiving coil can be selected in such a way that the transmitting coil or the receiving coil can dissolve in the melt and/or fuse with the melt after a predefined time interval.

Example 4 is a bubble detection device according to one of Examples 1 to 3, wherein the melt has an electrical conductivity σ greater than 10 ² S/m, eg greater than 10 ³ S/m, 10 ⁴ S/m, 10 ⁵ S/m , 10 ⁶ S/m, 10 ⁷ S/m, or greater than 10 ⁸ S/m. For example, the melt can include or be a salt melt and/or a semiconductor melt and/or a liquid metal and/or a metal melt. For example, the melt can contain one or more metals and/or an alloy and/or one or more ionic Solutions, and / or have one or more semiconductors.

Example 5 is a bubble detection device according to any one of Examples 1 to 4, wherein the transmitting coil may be coupled to a transmitting circuit. The transmission circuit can be set up to transmit a first signal at a predetermined first frequency by means of the transmission coil in order to evaluate a measurement result based on the first signal. The transmission circuit can be set up to transmit a second signal by means of the transmission coil in order to evaluate a measurement result based on the second signal. For example, the first signal and the second signal can be the same (i.e. all properties of the signal characteristic are the same) and/or have different signal characteristics (i.e. differ in at least one property of the signal characteristic). For example, a signal characteristic can have or be one or more of the following properties: an intensity and/or a frequency and/or a signal duration and/or a pulse duration and/or a pulse number and/or a time and/or a phase. For example, the transmission circuit can be set up to transmit the first signal and the second signal in a predetermined order, e.g. one after the other or alternately. For example, the transmission circuit can be set up to transmit the first signal with a time offset from the second signal. For example, the transmission circuit can be set up to send more than two signals in order to evaluate a measurement result based on the more than two signals.

Example 6 is a bubble detection device according to example 5, wherein the first signal or the second signal can have a frequency of more than 10 Hz, e.g. more than 100 Hz, 200 Hz, 500 Hz, 1 kHz, 2 kHz, 5 kHz, 10kHz, 20kHz, 50kHz, 100kHz, 200kHz, 500kHz, 1MHz, 2MHz, 5MHz, 10MHz or greater than 20MHz.

Example 7 is a bubble detection device according to any one of Examples 1 to 6, wherein the receiving coil may be coupled to a receiver circuit. The receiver circuit can be set up to receive a measurement signal by means of the receiving coil. For example, the receiver circuit can be set up to receive the measurement signal in a time-resolved manner. For example, the receiver circuit can be set up to receive the measurement signal during one or more predefined time intervals. For example, the one or more time intervals may be arranged in a predetermined order. For example, the one or more time intervals may include a range of time intervals. A series of time intervals may include, for example: a first time interval, a second time interval, and a third time interval. The receiver circuit can be configured to first receive a first measurement signal in the first time interval, then a second measurement signal in the second time interval, and then a third measurement signal in the third time interval. The series can then be repeated. A number of rows per second can be referred to as a measurement frequency. For example, the measurement frequency can be more than 10 Hz, for example more than 100 Hz, 500 Hz, 1 kHz, 10 kHz, 100 kHz, 1 MHz or more than 10 MHz. It is understood that a series can also have more or less than 3 time intervals, e.g. 1, 2, 4, 5, 6, 7, 8, 9 or more than 9 time intervals.

Example 8 is a bubble detection device according to example 7, wherein the measurement signal can be a current and/or a voltage and/or an impedance and/or a frequency.

Example 9 is a bubble detection device according to any one of Examples 1 to 8, optionally further comprising a control unit. For example, the transmission circuit and/or the receiver circuit can be part of the control unit or can be coupled to the control unit. The control unit can be set up, for example, to control the receiver circuit and/or the transmission circuit. For example, the control unit can be set up to demodulate the signal received by the receiving coil. For example, the control unit can be set up to control and/or detect a current intensity, a voltage and/or a frequency from the transmission coil and/or the reception coil.

Example 10 is a bubble detection device according to any one of Examples 1 to 9, optionally further comprising a data processing unit. For example, the data processing unit can be set up to process (e.g. represent, process, store, divide (e.g. into one or more partial signals) a signal that represents the received signal (e.g. a received signal, a transmitted signal and/or a measurement signal). ), and/or compare (e.g., to a predetermined value) to generate data representing a presence of a bubble in the coupling region. A property to be calculated may be, for example, one of the following properties: an impedance, and/or a frequency. The Signal can be, for example, a transmitted signal, for example from the transmitting coil.The signal can be, for example, a received signal, for example from the receiving coil.For example, the signal can be a demodulated signal.The data processing unit can have or be a processor and/or an oscilloscope, for example . For example the data processing unit can be set up to correct a signal by means of a correction value or a correction term, eg to remove a known error or a known measurement uncertainty.

Example 11 is a bubble detection device according to any one of Examples 1 to 10, further optionally comprising one or more further transmitter coils. The one or more further transmission coils and the receiving coil can form a plurality of further coupling regions. For example, in each of the additional coupling areas, a respective additional transmission coil of the one or more additional transmission coils can be inductively coupled to the reception coil in such a way that when the respective additional transmission coil and the reception coil are in an electrically conductive melt, a signal is emitted by the respective additional transmission coil can be received by the receiving coil. For example, the respective further transmission coil and the receiving coil can cross in a projection of the respective further coupling area. For example, the transmission coil can be set up to transmit a first signal. For example, a first additional transmission coil of the one or more additional transmission coils can be set up to transmit a second signal. For example, a transmission characteristic of the first signal and a transmission characteristic of the second signal can be the same or different from one another. For example, the transmission coil and the first further transmission coil can be set up to transmit their respective signals simultaneously. For example, the first transmission coil and the second transmission coil can be set up to transmit their respective signals one after the other.

Example 12 is a bubble detection device according to any one of Examples 1 to 10, further optionally comprising one or more further receiving coils. The transmitting coil and the one or more additional receiving coils can form multiple additional coupling areas. For example, in each of the additional coupling areas, the transmission coil can be inductively coupled to a respective additional reception coil of the one or more additional reception coils in such a way that when the transmission coil and the respective additional reception coil are in an electrically conductive melt, a signal emitted by the transmission coil can be detected by means of the respective further receiving coil can be received. For example, the transmission coil and the respective further receiving coil can cross in a projection of the respective further coupling area.

For example, the receiving coil can be set up to receive a first signal. For example, at least a first additional receiving coil of the one or more additional receiving coils can be set up to receive a second signal. For example, the first or second received signal can be referred to as the first or second measurement signal. For example, the reception coil can receive the first measurement signal at the same time as the reception of the second measurement signal by the first additional reception coil. For example, the receiving coil can receive the measurement signal before (or after) the first further receiving coil receives the second measurement signal. For example, a signal characteristic of the first measurement signal can be the same as or different from a signal characteristic of the second measurement signal.

Based on Examples 11 and 12, it is understood that the bubble detection device can also have a plurality of transmitting coils and a plurality of receiving coils. Each coil of the plurality of transmission coils or of the plurality of reception coils can each be configured according to one of the examples mentioned above. In addition, the further features can also be transferred to a bubble detection device with a plurality of transmitting coils and a plurality of receiving coils. A few selected examples are described below for better understanding.

Example 13 is a bubble detection device for detecting bubbles in an electrically conductive melt, the bubble detection device may have: a plurality of transmitting coils for transmitting one or more signals, a plurality of receiving coils for receiving one or more signals, wherein the plurality of transmitting coils and the plurality of receiving coils can be set up in such a way that a plurality of coupling regions is formed, wherein in each coupling region of the plurality of coupling regions one transmitting coil of the plurality of transmitting coils and one receiving coil of the plurality of receiving coils can be inductively coupled to one another in such a way that, if the respective transmission coil and the respective reception coil are in an electrically conductive melt, a signal emitted by the respective transmission coil can be received by the respective reception coil. For example, each transmission coil of the plurality of transmission coils can have one or more turns. For example, each receiving coil of the plurality of receiving coils can have one or more turns.

Example 14 is a bubble detection device according to Example 13, wherein each transmission coil of the plurality of transmission coils, and/or each reception coil of the plurality of reception coils is large may include or consist of one or more of the following materials: tungsten, aluminum, copper, platinum, gold, molybdenum, titanium, tantalum, niobium, chromium, and rhenium. For example, the transmitting coil and/or the receiving coil can largely consist of or have a titanium-zirconium-molybdenum alloy and/or a tungsten-copper alloy. For example, a material composition of a first and a second transmission coil of the plurality of transmission coils can be the same as or different from one another. For example, a first and a second transmission coil of the plurality of transmission coils can be structurally identical. For example, a material composition of a first and a second receiving coil of the plurality of receiving coils can be the same as or different from one another. For example, a first and a second receiving coil of the plurality of receiving coils can be structurally identical.

Example 15 is a bubble detection device according to Example 13 or 14, wherein one, more, or all of the transmit coils of the plurality of transmit coils are encased in a first material, and wherein one, more, or all of the plurality of receive coils are encapsulated in a second material. For example, the first and the second material can be configured according to example 3.

Example 16 is a bubble detection device according to any one of Examples 13 to 15, wherein the plurality of transmit coils may be coupled to a transmit circuit. The transmission circuit can be set up to transmit one or more signals via the plurality of transmission coils in order to evaluate a measurement result based on the one or more signals. For example, the transmission circuit can be set up to transmit a first signal of the one or more signals at a predetermined first frequency using at least one first transmission coil of the plurality of transmission coils to evaluate a measurement result based on the first signal. For example, the transmission circuit can be set up to transmit at least a second signal of the one or more signals by means of the first transmission coil in order to evaluate a measurement result based on the second signal. For example, the transmission circuit can be set up to transmit at least one second signal by means of at least one second transmission coil of the plurality of transmission coils in order to evaluate a measurement result based on the second signal. For example, the first signal and the second signal can be the same (i.e. all properties of the signal characteristic are the same) and/or have different signal characteristics (i.e. differ in at least one property of the signal characteristic). For example, a signal characteristic can have or be one or more of the following properties: an intensity and/or a frequency and/or a signal duration and/or a pulse duration and/or a pulse number and/or a time and/or a phase. For example, the transmission circuit can be set up to transmit the first signal and the second signal in a predetermined order, e.g. one after the other or alternately. For example, the transmission circuit can be set up to transmit the first signal with a time offset from the second signal. For example, the transmission circuit can be set up to send more than two signals in order to evaluate a measurement result based on the more than two signals.

Example 17 is a bubble detection device according to any one of Examples 13 to 16, wherein the plurality of receiving coils may be coupled to a receiver circuit. The receiver circuit can be set up to receive one or more measurement signals by means of the plurality of receiving coils. For example, the receiver circuit can be set up to receive the one or more measurement signals in a time-resolved manner. For example, the receiver circuit can be set up to receive at least one measurement signal of the one or more measurement signals during one or more predefined time intervals. For example, the one or more time intervals may be arranged in a predetermined order. For example, the one or more time intervals may include a range of time intervals. The receiver circuit can be configured to first receive a first measurement signal in the first time interval, then a second measurement signal in the second time interval, and then a third measurement signal in the third time interval. For example, the first measurement signal can be received with a first receiving coil of the plurality of receiving coils. For example, the second measurement signal can be received with a second receiving coil of the plurality of receiving coils. For example, the third measurement signal can be received with a third receiving coil of the plurality of receiving coils. For example, the first, and/or second, and/or third receiving coil can receive the respective first, second, or third measurement signal simultaneously or one after the other.

Example 18 is a bubble detection device according to any one of Examples 13 to 17, optionally further comprising a control unit. For example, the transmission circuit and/or the receiver circuit can be part of the control unit or can be coupled to the control unit. The control unit can be set up, for example, to control the receiver circuit and/or the transmission circuit to control circle. For example, the control unit can be set up to demodulate the one or more signals (eg measurement signals) received by the receiving coil. For example, the control unit can be configured to individually demodulate each received signal from each coil.

Example 19 is a bubble detection device according to any one of Examples 13 to 18, optionally further comprising a data processing unit. For example, the data processing unit may be configured to process one or more signals representing the one or more received signals to create data representing a presence of one or more bubbles in the plurality of coupling regions. A property to be calculated can be one of the following properties, for example: an impedance and/or a frequency. The one or more signals may be, for example, one or more transmitted signals, e.g., from the plurality of transmit coils. The one or more signals may be, for example, one or more signals received, e.g., from the plurality of receiving coils. For example, the data processing unit can be set up to correct the one or more signals by means of a correction value or a correction term, e.g. to remove a known error or a known measurement uncertainty. For example, the correction value or correction term can be specific to a specific coupling area of the plurality of coupling areas.

Example 20 is a method for detecting gas bubbles in a melt, the method may include: positioning at least one transmitting coil and one receiving coil in an electrically conductive melt, wherein the transmitting coil and the receiving coil may be inductively coupled to one another in a coupling region, sending a signal by means the transmitting coil, receiving a measurement signal generated by the transmitted signal by means of the receiving coil, determining a value, which can represent one or more properties of the melt, based on the received measurement signal. For example, the determined value can be a real part or an imaginary part of an impedance, e.g., of a coil that received or transmitted the signal. For example, the determined value can be a frequency and/or phase and/or an intensity. For example, the output value can correspond to a size and/or a speed and/or a size of a bubble.

Example 21 is a method for detecting gas bubbles in a melt, the method may include positioning multiple transmitting coils and multiple receiving coils in an electrically conductive melt, wherein the multiple transmitting coils and the multiple receiving coils have a spatial arrangement of coupling areas, in each of which one of the multiple transmitting coils can be inductively coupled to one of the plurality of receiving coils. Sending a transmission signal by means of one of the several transmission coils, receiving a respective measurement signal by means of each of the several reception coils, it being possible for the respective measurement signal to be generated by the transmission signal, determining a value which can represent one or more properties of the melt, based on the measurement signals received.

Example 22 is a bubble detection device that can be configured to generate eddy currents in a melt through a time-varying field using an excitation coil. The excitation coil, which can also be referred to as the transmission coil, can be immersed in an area to be measured. The eddy currents can be distorted by a bubble that is close to the bubble detection device because the bubbles have little or no electrical conductivity. A receiving coil can be immersed in the melt and placed close to the excitation coil. The distortion of the eddy currents can be measured by the receiving coil. In this case, the receiving coil can be rotated through an angle (eg 90°) to the excitation coil. As a result, sensitive areas for bubble detection can arise at or around the crossing points of the transmitting coil and the receiving coil, which can also be referred to as the coupling area. The voltage induced in the receiver coil can be measured as a received signal. The amplitude and the phase (eg a state of aggregation, an electrical state) of the measured signal can be extracted (eg read out) together with the excitation frequency. Both amplitude and phase may include (eg, include) information about the eddy current distorted by the bubble and/or a magnetic field distorted by the bubble. For example, in order to only obtain information from bubbles that rise at the crossing points of the two coils, an excitation frequency of the excitation coil of the order of 1 kHz to 1 MHz can be selected. Due to the skin effect, the eddy currents in the fluid can only form locally around the conductor of the excitation coil. Depending on the selected frequency and conductivity of the fluid, the eddy currents can hardly be detected from a certain distance inside and outside the coil. This means, for example, that only bubbles that are close to the excitation coil are taken into account. Thus, the amplitude and phase measured by the excitation coil can be used directly to determine the existence of a bubble at the cross point of the coils, or in the sensitive area around the crossing point, without having to solve an ill-posed non-linear inverse problem afterwards. Thus, the spatial resolution can depend only on the geometry of the bubble detection device. A further advantage of the high excitation frequency, which can also be referred to as the carrier frequency, can be that the measurement can be carried out with a high temporal resolution. Due to this locality of the measurement, several receiver coils can be arranged along the transmitter coil, for example, so that the existence of the bubbles can be determined at several points along the excitation coil. By choosing the high excitation frequency, the measurements of the individual receiver coils can be independent of one another due to the skin effect. If a number of excitation coils are additionally used, a lattice structure can result which, for example, allows a surface to be scanned. For example, the voltages induced by the bubbles can be small, so that a precise current source and a so-called lock-in analysis method can be necessary. The method enables, for example, a very precise demodulation of the amplitude and phase using quadrature demodulation. If several excitation coils are used, the excitation coils can either be controlled via a multiplexer or different frequencies can be used, which can further increase the temporal resolution of the measurement.

Example 23 is one possible arrangement of a bubble detection device. An excitation coil and a receiving coil can be arranged horizontally or perpendicularly to one another, for example. Both coils can be electrically isolated from each other and from the melt in order to avoid unwanted leakage currents. Such insulation can be achieved up to around 250 °C using special materials such as PEEK. At higher melt (or process) temperatures, ceramic materials can be used to insulate the coils. The thickness of the insulated wires should be as thin as possible in order to disturb the flow as little as possible.

Claims (16)

Bubble detection device (100) for detecting bubbles (11) in an electrically conductive melt, the bubble detection device (100) having: a transmitting coil (110) for transmitting a signal; and a receiving coil (120) for receiving a signal, wherein the transmitting coil (110) and the receiving coil (120) are set up in such a way that at least one coupling region (130) is formed in which the transmitting coil (110) and the receiving coil (120) are inductively coupled to one another such that when the transmitting coil (110) and the receiving coil (120) are in an electrically conductive melt, a signal emitted by the transmitting coil (110) can be received by the receiving coil (120). Bubble detection device (100) according to claim 1 , wherein the transmitting coil (110) and/or the receiving coil (120) largely has or consists of one or more of the following materials: tungsten, aluminum, copper, platinum, gold, molybdenum, tantalum, niobium, chromium, titanium, zirconium , molybdenum and rhenium. Bubble detection device (100) according to claim 1 or 2 , wherein the transmitting coil (110) is coated with a first material and wherein the receiving coil (120) is coated with a second material. Bubble detection device (100) according to claim 3 , wherein the first material and / or the second material has one or more of the following properties: the first or second material is an electrical insulator, and / or the first or second material is selected such that the transmission coil (110) or the Receiver coil has a temperature below their respective melting point during the measurement. Bubble detection device (100) according to claim 3 , wherein the transmitting coil (110) and/or the receiving coil (120) dissolves in the melt after a predefined time interval and/or fuses with the melt. Bubble detection device (100) according to any one of Claims 1 until 5 , wherein the melt has a specific conductivity of more than 10 ² S/m, in particular the melt is a salt melt and/or a semiconductor melt and/or a liquid metal and/or a metal melt and/or an alloy. Bubble detection device (100) according to any one of Claims 1 until 6 , wherein the transmission coil (110) is coupled to a transmission circuit (210), and wherein the transmission circuit (210) is set up to send a plurality of signals for evaluating a measurement result based on the plurality of signals. Bubble detection device (100) according to claim 7 , wherein the plurality of signals either have the same signal characteristics or different signal characteristics from one another. Bubble detection device (100) according to any one of Claims 1 until 8th , wherein the receiving coil (120) is coupled to a receiver circuit (220), wherein the receiver circuit (220) is set up to receive a measurement signal by means of the receiving coil (120), and wherein the receiver circuit (220) is set up in particular to To receive measurement signal during one or more predetermined time intervals. Bubble detection device (100) according to claim 9 , wherein the measurement signal is a current and/or a voltage and/or an impedance and/or a frequency. Bubble detection device (100) according to any one of Claims 1 until 10 , further comprising a data processing unit (240) configured to process the received signal or a measurement signal representing the received signal to create data representing a presence of a bubble in the coupling region (130). Bubble detection device (100) according to any one of Claims 1 until 11 , further comprising: one or more further transmission coils (110), wherein the one or more further transmission coils (110) and the receiving coil (120) form a plurality of further coupling regions (130), and wherein in each of the further coupling regions (130) a respective further Transmission coil (110) of the one or more further transmission coils (110) is inductively coupled to the reception coil (120) in such a way that when the respective further transmission coil (110) and the reception coil (120) are in an electrically conductive melt, one of the respective further transmission coil (110) emitted signal can be received by the receiving coil (120). Bubble detection device (100) according to any one of Claims 1 until 12 , one or more additional receiving coils (120), wherein the one or more additional receiving coils (120) and the transmitting coil (120) form multiple additional coupling areas (130), and wherein in each of the additional coupling areas (130) a respective additional receiving coil (120 ) of the one or more further receiving coils (120) is inductively coupled to the transmitting coil (110) in such a way that when the respective further receiving coil (120) and the transmitting coil (110) are in an electrically conductive melt, one of the transmitting coil (110 ) emitted signal can be received by means of the respective further receiving coil (120). Bubble detection device (100) for detecting bubbles (11) in an electrically conductive melt, the bubble detection device (100) having: a plurality of transmission coils (110) for transmitting one or more signals, a plurality of receiving coils (120) for receiving one or more signals, wherein the plurality of transmission coils (110) and the plurality of reception coils (120) are set up in such a way that a plurality of coupling regions (130) is formed, with one transmission coil (110 ) of the plurality of transmission coils (110) and in each case one reception coil (120) of the plurality of reception coils (120) are inductively coupled to one another in such a way that when the respective transmission coil (110) and the respective reception coil (120) are in an electrically conductive melt , a signal emitted by the respective transmitting coil (110) can be received by means of the respective receiving coil (120). Method for detecting bubbles (11) in a melt: Positioning at least one transmission coil and one reception coil in an electrically conductive melt, the transmission coil and the reception coil being inductively coupled to one another in a coupling region; Sending a signal using the transmitter coil (110), receiving a measurement signal generated by the transmitted signal by means of the receiving coil (120), Determination of a value, which represents one or more properties of the melt, based on the received measurement signal. Method for detecting bubbles (11) in a melt: Positioning a plurality of transmission coils and a plurality of reception coils in an electrically conductive melt, the plurality of transmission coils and the plurality of reception coils generating a spatial arrangement of coupling regions in which one of the plurality of transmission coils is inductively coupled to one of the plurality of reception coils; Sending a transmission signal by means of one of the several transmission coils (110), Receiving a respective measurement signal by means of each of the several reception coils (120), the respective measurement signal being generated by the transmission signal, Determination of a value, which represents one or more properties of the melt, based on the received measurement signals.

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