Continuous High-Temperature Slab Preheating With Induction-Radiation Zoning
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Solution Overview
Problem
Existing preheating technologies for flat semi-finished steel products, such as induction, direct resistance, and radiation resistance heating, face inefficiencies and challenges in achieving high temperature uniformity, compactness, and flexibility for varying slab dimensions and steel grades, leading to energy loss and increased carbon emissions.
Innovation Solution
A continuous preheating plant combining induction and electric resistance radiation furnaces, with a specific arrangement that includes a movable hearth furnace, allows for efficient and compact preheating by utilizing induction furnaces for initial heating and resistance radiation furnaces for final heating, ensuring temperature uniformity and flexibility for varying slab dimensions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If induction heating is used to heat slabs quickly, then heating speed is improved, but temperature uniformity deteriorates and energy efficiency decreases at high temperatures
Solution Approach 1:
The heating process is divided into multiple zones along the conveying line, with different heating devices (induction furnaces for rapid heating, resistance radiation furnaces for uniformity) assigned to different segments. This segmentation allows each zone to perform its specialized function while contributing to the overall heating objective.
Solution Approach 2:
The patent changes the heating parameters by transitioning from induction heating (high speed, lower uniformity) to resistance radiation heating (slower, high uniformity) as the slab progresses through the heating line. This parameter change optimizes both heating speed and temperature uniformity at different stages of the process.
2Speed
If induction heating is used to heat slabs quickly, then heating speed is improved, but energy efficiency deteriorates due to radiation losses and water cooling requirements
Solution Approach 1:
The heating system is segmented into induction heating zones (for speed) and resistance radiation heating zones (for efficiency), allowing the process to leverage the advantages of both methods while minimizing their respective disadvantages.
Solution Approach 2:
The heating method is changed from induction to resistance radiation as the slab progresses, optimizing energy efficiency for the final heating stages where radiation losses would be most problematic in induction systems.
3Temperature
If resistance radiation furnaces are used for final heating, then temperature uniformity and energy efficiency are improved, but plant compactness deteriorates
Solution Approach 1:
The patent merges induction heating and resistance radiation heating into a single integrated heating line, combining the rapid heating capability of induction with the uniformity and efficiency of resistance radiation in a compact configuration.
Solution Approach 2:
The heating devices are arranged along a conveying line in a linear configuration, utilizing the longitudinal dimension to provide both rapid and uniform heating without requiring a large volumetric footprint, thus maintaining plant compactness.
4Reliability
If preheating is performed to prevent slab cracking during cutting, then slab integrity is improved, but production time increases
Solution Approach 1:
The heating line performs preliminary heating of slabs before they reach the cutting apparatus, preventing thermal shock and cracking during cutting. This preliminary action is integrated into the main production flow, so it does not add separate production time.
Solution Approach 2:
The heating process operates continuously along the conveying line, with slabs being heated progressively as they move through the different heating zones, rather than requiring a separate batch preheating operation. This continuous action maintains production efficiency while ensuring slab integrity.
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 achieves high energy efficiency, prevents slab cracking, and maintains compactness while accommodating varying slab dimensions and steel grades, reducing carbon emissions by optimizing thermal power distribution between furnace types.
Implementation Method 1
Through induction heating, heat is generated directly in the material by the action of an eddy current. If the semi-product (= workpiece) is exposed to an alternating magnetic field, an eddy current will be generated close to its surface (alternating/sinusoidal current).
Implementation Method 2
The current flow inside the workpiece causes internal heating according to Joule's law.
Implementation Method 3
Direct resistance heating consists in flowing a high electric current inside the semi-finished product by direct contact with resistive elements
Implementation Method 4
Radiation resistance heating consists in using electric resistance elements to heat a closed heating chamber lined with refractory insulating material, with the result that both the resistances and the refractory surface, heated at a high temperature, radiate their energy to the semi-finished product.
Data Source
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AI summary
A continuous, high-temperature preheating plant (1) for preheating flat semi-finished steel products comprising: - a conveying line (10) suitable to transfer the flat semi-finished products from an inlet (2) to an outlet (3) of said plant (1); and - a plurality of heating devices (20, 30, 41, 42, 43, 44, 45, 46, 47, 48) which are arranged along said conveying line (10) to heat the semi-finished products from an inlet temperature (Te) to a predetermined final temperature (Tf). The plurality of heating devices comprises, arranged in sequence between said inlet (2) and said outlet (3) along said conveying line (10): - a first induction furnace (20); - a second induction furnace (30); - at least one electric resistance radiation furnace (41, 42, 43, 44, 45, 46, 47, 48). The plant comprises a cutting apparatus (50) which is suitable to cut a starting flat semi-finished product (MS) into a plurality of cut segments (CS) of flat semi-finished product having a predetermined length less than the length of the starting flat semi-finished product, wherein said cutting apparatus (50) is arranged between said first induction furnace (20) and said second induction furnace (30),