Continuous High-Temperature Slab Preheating With Induction-Radiation Staging
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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, compactness, and uniformity, especially with varying slab dimensions and compositions, leading to energy loss and potential cracking.
Innovation Solution
A continuous preheating plant combining induction furnaces for initial heating and electric resistance radiation furnaces for final heating, with a specific arrangement to optimize compactness and efficiency, using removable panels and modular units for flexibility and temperature control, and inert gas protection to prevent oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If induction heating is used for high-temperature preheating, then heating speed is improved, but energy efficiency deteriorates due to radiation losses and water cooling requirements
Solution Approach 1:
The preheating process is divided into two distinct stages: a first induction heating stage for rapid temperature increase, and a second radiation resistance heating stage for efficient high-temperature maintenance. This segmentation allows each method to operate in its optimal efficiency range, resolving the contradiction between heating speed and energy efficiency.
Solution Approach 2:
The induction heating stage performs preliminary heating to raise the slab temperature to an intermediate level before transitioning to radiation resistance heating. This preliminary action enables the subsequent radiation heating stage to operate more efficiently, as it only needs to complete the heating from the intermediate temperature rather than from ambient conditions.
2Power
If induction heating coils are used, then heating capability is improved, but device complexity increases due to cooling systems and gap configurations
Solution Approach 1:
The patent extracts the cooling system requirement from the heating process by using radiation resistance heating panels that do not require water cooling. This eliminates the complex cooling infrastructure associated with induction coils while maintaining high heating capability through the two-stage approach.
Solution Approach 2:
The system dynamically transitions between two heating methods: using induction heating when rapid power delivery is needed, and switching to radiation resistance heating when energy efficiency and simplified equipment are advantageous. This dynamic approach optimizes both heating capability and device complexity.
3Loss of energy
If radiation resistance heating is used for high-temperature preheating, then energy efficiency is improved, but heating speed deteriorates
Solution Approach 1:
The induction heating stage performs preliminary heating to rapidly raise the slab temperature to an intermediate level before transitioning to radiation resistance heating. This preliminary action enables the subsequent radiation heating stage to operate more efficiently, as it only needs to complete the heating from the intermediate temperature rather than from ambient conditions.
Solution Approach 2:
The preheating process is divided into two distinct stages: a first induction heating stage for rapid temperature increase, and a second radiation resistance heating stage for efficient high-temperature maintenance. This segmentation allows each method to operate in its optimal efficiency range, resolving the contradiction between heating speed and energy efficiency.
4Temperature
If conventional preheating plants are designed for high temperature, then temperature capability is improved, but plant compactness deteriorates
Solution Approach 1:
The patent merges two different heating technologies (induction heating and radiation resistance heating) into a single integrated preheating plant. This combination allows the plant to achieve high temperature capability while maintaining compact dimensions, as each heating method contributes its strengths in a space-efficient configuration.
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, compact design, and prevents cracking while accommodating varying slab dimensions, ensuring uniform heating and reducing CO2 emissions.
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). The current flow inside the workpiece causes internal heating according to Joule's law.
Implementation Method 2
The current flow inside the workpiece causes internal heating according to Joule's law.
Implementation Method 3
Radiation resistance heating consists in using electric resistance elements to heat a closed heating chamber lined with refractory insulating material (e.g., 'electric furnace'), with the result that both the resistances and the refractory surface, heated at a high temperature, radiate their energy to the semi-finished product.
Implementation Method 4
in the absence of combustion, the free atmosphere present in the electrically heated furnace can cause increased oxidation of the semi-finished product
Data Source
AI summary
A continuous, high-temperature preheating plant for preheating flat semi-finished steel products has a conveying line suitable to transfer the flat semi-finished steel products from an inlet to an outlet of the continuous, high-temperature preheating plant, and a plurality of heating devices arranged along the conveying line to heat the semi-finished steel products from an inlet temperature to a predetermined final temperature. The plurality of heating devices has, arranged in sequence between the inlet and the outlet along the conveying line, a first induction furnace, a second induction furnace, and at least one electric resistance radiation furnace. The continuous, high-temperature preheating plant has a cutting apparatus suitable to cut a starting flat semi-finished steel product into a plurality of cut segments having a predetermined length less than a length of the starting flat semi-finished steel product. The cutting apparatus is arranged between the first induction furnace and the second induction furnace.