Slanted Coil Level Measurement in Metallurgical Vessels
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Solution Overview
Problem
Existing electromagnetic level measurement systems in metallurgical vessels face challenges such as non-linearity, installation limitations, and errors due to turbulent interfaces and drifts, particularly when measuring molten metal levels in harsh industrial conditions.
Innovation Solution
A system with transmitting and receiving conductors arranged in a slanted loop inside the metal casing, optimizing the mutual spacing to dominate signal changes with local changes in conductive material, ensuring a linear transfer function and improved signal resolution, and incorporating design criteria for enhanced sensitivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional flat square coils are arranged on the sides or top of the vessel, then electromagnetic level measurement is achieved, but installation limitations and non-linear measurement signals result
Solution Approach 1:
The coil system is divided into multiple discrete coils (transmitter coils and receiver coils) arranged in a specific pattern around the vessel. Each coil contributes to the overall measurement, allowing flexible installation configurations while maintaining measurement accuracy. The segmentation enables the system to adapt to different vessel geometries and installation locations.
Solution Approach 2:
The patent transitions from traditional single-plane coil arrangements to a three-dimensional configuration where coils are distributed around the vessel circumference and at different heights. This spatial distribution in multiple dimensions enables both flexible installation and linear measurement signals by capturing the magnetic field interactions from multiple perspectives.
2Measurement precision
If the magnetic field strength is increased to improve signal detection, then measurement sensitivity improves, but non-linearity increases due to the 1/R and 1/R³ distance dependence
Solution Approach 1:
The patent employs multiple coils with different orientations and positions, each contributing to local magnetic field measurements. By combining these local measurements, the system achieves both high sensitivity (through strong local field interactions) and linearity (through the averaging effect of multiple measurement points with different distance relationships to the molten metal interface).
Solution Approach 2:
The system merges the outputs of multiple transmitter and receiver coils to produce a composite measurement signal. This combination of multiple magnetic field interactions compensates for the non-linear 1/R and 1/R³ dependencies of individual coils, resulting in an overall linear transfer function while maintaining high detection sensitivity.
3Length of stationary object
If the coil arrangement is designed to cover a large vertical range, then measurement range increases, but the vertical range with linear signal dependence becomes substantially less than the physical height of the coil arrangement
Solution Approach 1:
The measurement range is divided into multiple segments, each covered by specific coil combinations. By segmenting the measurement space and assigning different coil pairs to different vertical zones, the system achieves a linear response across the entire extended range while maintaining linearity within each segment. The overall linear range is the sum of the linear ranges of individual segments.
Solution Approach 2:
The patent extends the measurement capability by utilizing the circumferential dimension around the vessel in addition to the vertical dimension. Multiple coils arranged around the circumference provide overlapping measurement zones that, when combined, extend the effective linear measurement range beyond what a single vertical coil arrangement could achieve.
4Measurement precision
If turbulent portions of the top surface are measured, then comprehensive level detection is achieved, but induced eddy currents drive the measurement signal in opposite directions leading to significant errors
Solution Approach 1:
The system combines measurements from multiple transmitter-receiver coil pairs, each experiencing different eddy current effects from turbulent portions of the molten metal surface. By merging these measurements, the system achieves error cancellation where opposite-direction signal deviations from different coils compensate for each other, resulting in a stable overall signal that accurately reflects the true level despite surface turbulence.
Solution Approach 2:
The patent employs a detection circuit that processes the combined signals from multiple receiver coils, effectively implementing feedback mechanisms that identify and compensate for signal variations caused by turbulent eddy currents. The system uses the redundant information from multiple measurement paths to distinguish between genuine level changes and noise from surface turbulence.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves a linear transfer function within the vertical measurement region, reduces errors, and maintains accuracy despite turbulent conditions and potential drifts, enabling precise measurement of molten metal levels.
Implementation Method 1
The transmitter coil may be driven at a low frequency of 100 Hz to a few kHz to generate a time-varying magnetic field. Many lining materials are transparent at these frequencies which allows the magnetic field to reach the molten metal and induce eddy currents therein. The eddy currents generate fields that induce an electromotive force (emf) in the receiving coil
Implementation Method 2
The magnetic field to reach the molten metal and induce eddy currents therein. The eddy currents generate fields that induce an electromotive force (emf) in the receiving coil
Data Source
Figure 1~3B
Figure 4~6A
Figure 6B~6C
AI summary
The vertical filling level of electrically conductive material in a cavity (3) of a metallurgical vessel is measured by a system comprising a transmitting conductor (5) for generating an electromagnetic field when connected to an alternating power source, and a receiving conductor (6) which is arranged to sense the electromagnetic field for generation of an output signal. The transmitting and receiving conductors (5, 6) are arranged inside a metal casing of the vessel to co-extend with a mutual spacing to define a spacing area (7) that faces the cavity (3) and extends along the periphery of the cavity (3) in an essentially closed loop. The mutual spacing is selected such that changes in the output signal is dominated by changes to the electromagnetic field caused by local changes in the amount of the conductive material adjacent to the spacing area (7). At least part of the spacing area (7) defines a vertical measurement region in which the spacing area (7) is slanted along the periphery so as to diverge from the horizontal and vertical directions of the vessel. Thereby, the spacing area (7) may be adapted to any shape of the cavity (3) so as to design the system with any desired transfer function, e.g. linear without turning points outside the extent of the vertical measurement region.