Non-Contact Liquid Metal Temperature Measurement in Electric Arc Furnaces
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Solution Overview
Problem
Existing methods for measuring liquid metal temperature in electric arc furnaces are unreliable due to the need for contact, which leads to maintenance issues, wear, and inaccurate readings, especially with variations in the meniscus level and slag thickness.
Innovation Solution
A non-contact temperature measurement device using a tubular pipe with a water-cooled jacket and an optical detection instrument, employing a high-speed inert gas jet to open a passageway in the slag layer, allowing for accurate temperature reading without contact, and maintaining a constant distance through furnace tilting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thermocouple is immersed into the liquid metal for temperature measurement, then the temperature can be measured directly, but the measuring instrument is subject to premature wear, requires intense cooling systems, and needs costly and frequent maintenance
Solution Approach 1:
The patent introduces an intermediary substance (flux or slag) between the measuring instrument and the liquid metal. The measuring instrument measures the temperature of the flux/sloug layer instead of directly contacting the liquid metal, thereby avoiding wear and damage while still obtaining accurate temperature readings through thermal equilibrium.
Solution Approach 2:
The patent replaces the mechanical contact-based thermocouple measurement system with an optical measurement system. An optical fiber or pyrometer is used to measure the temperature of the flux layer from a distance, eliminating the need for physical contact with the liquid metal and thus avoiding wear, cooling requirements, and maintenance issues.
2Measurement precision
If oxygen is blown at high pressure through a lance to free the metal surface for measurement, then the metal surface is exposed for detection, but the injected oxygen increases the temperature and falsifies the measurement
Solution Approach 1:
The patent replaces the oxygen-based blowing system with an inert gas (such as nitrogen or argon) or uses the existing flux layer as a protective atmosphere. This eliminates the exothermic reaction between oxygen and liquid metal that causes temperature increase and measurement falsification, while still achieving surface exposure and measurement accuracy.
3Measurement precision
If the measuring device is positioned close to the liquid metal surface for accurate measurement, then temperature reading accuracy improves, but the device is hit by high-speed gas jets and scrap, causing wear and damage
Solution Approach 1:
The patent uses the flux or slag layer as a protective intermediary between the measuring device and the harsh environment (high-speed gas jets and scrap). The measuring device measures the temperature of this intermediate layer, which is shielded from direct impacts, thereby protecting the instrument while maintaining measurement accuracy through thermal coupling.
Solution Approach 2:
The patent replaces the mechanical contact measurement system that is vulnerable to impact damage with a non-contact optical measurement system. The optical fiber or pyrometer can be positioned closer to the liquid metal surface without being affected by physical impacts from scrap or gas jets, thereby achieving accurate measurements while avoiding mechanical damage.
4Measurement precision
If the distance between the measuring device and the meniscus is kept constant for accurate measurement, then measurement reliability improves, but the refractory thickness decreases and liquid metal level fluctuates during the melting cycle
Solution Approach 1:
The patent measures the temperature of the flux or slag layer instead of directly measuring the liquid metal surface. Since the flux layer maintains a relatively stable thickness and position throughout the melting cycle, this intermediary measurement approach provides consistent and reliable temperature data even when the distance to the liquid metal meniscus varies due to refractory erosion or level fluctuations.
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 solution provides reliable, accurate, and minimally maintenance-intensive temperature measurements, reducing wear and ensuring consistent readings despite variations in the liquid metal level, with improved efficiency and safety by using a supersonic gas jet and annular flame for protection.
Implementation Method 1
tubular pipe with a water-cooled jacket
Implementation Method 2
water-cooled jacket
Implementation Method 3
employing a high-speed inert gas jet to open a passageway in the slag layer
Implementation Method 4
optical detection instrument, allowing for accurate temperature reading without contact
Implementation Method 5
annular flame for protection
Data Source
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AI summary
Device (10) and method for measuring the temperature of the liquid metal (40) in an electric arc furnace (30), or other container similar to a furnace. The device (10) comprises a delivery pipe (14) to deliver a jet of inert gas or air against the layer of slag above the meniscus (41) of liquid metal (40), and optical detection members (22) to detect the temperature. The optical detection members (22) of the temperature are disposed in a position upstream of the entry of the jet of inert gas or air into the delivery pipe (14).