High-Frequency Induction Heating of DRI for Uniform Transfer Temperature
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Solution Overview
Problem
Existing methods fail to efficiently and effectively heat DRI to the desired temperature for further processing, such as in the electric arc furnace or other compaction or melting plants, due to endothermic carburization and heat losses, resulting in suboptimal DRI temperature for downstream processing.
Innovation Solution
A method using induction coils with alternating current frequencies of at least 10 kHz to heat DRI in a conduit system, adjusting frequency and power to maintain or raise DRI temperature to the Curie point of iron (768°C) for efficient and uniform heating, preventing further temperature increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If induction coils are used to heat DRI, then DRI temperature increases, but energy consumption increases
Solution Approach 1:
The patent applies parameter changes by optimizing the alternating current frequency to at least 10 kHz and adjusting power levels to efficiently heat DRI to the Curie point while minimizing energy consumption. This frequency parameter change enables resonant heating that reduces overall energy requirements compared to conventional heating methods.
Solution Approach 2:
The patent replaces conventional thermal heating systems with an electromagnetic induction heating system. By using alternating magnetic fields generated by induction coils to directly induce currents in the DRI, the system achieves more efficient energy transfer and reduced energy losses compared to traditional contact-based heating methods.
2Productivity
If DRI is heated to higher temperatures, then downstream processing efficiency improves, but risk of overheating and material degradation increases
Solution Approach 1:
The patent employs feedback control by monitoring the DRI temperature during induction heating and adjusting the alternating current frequency and power levels in real-time. When the DRI approaches the Curie point (768°C), the system automatically modulates heating parameters to prevent overheating, ensuring optimal temperature for downstream processing without material degradation.
Solution Approach 2:
The patent utilizes the Curie point phase transition of iron (from ferromagnetic to paramagnetic state at 768°C) as a natural temperature limit. By heating DRI to this critical phase transition point, the system achieves maximum processing efficiency while the phase change itself provides a built-in safety mechanism that prevents excessive temperature rise and material degradation.
3Device complexity
If conventional heating methods are used, then equipment complexity is reduced, but heating uniformity and efficiency deteriorate
Solution Approach 1:
The patent applies oscillating electromagnetic fields at high frequency (at least 10 kHz) to induce rapid oscillating currents within the DRI particles. This high-frequency vibration effect ensures uniform heat distribution throughout the material, achieving superior heating uniformity compared to conventional static heating methods, while the modular coil design keeps system complexity manageable.
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
Achieves efficient, uniform, and controlled heating of DRI to the desired temperature range for downstream processing, minimizing energy consumption and preventing overheating, with reduced wear and maintenance.
Implementation Method 1
Induction coils are used as heating elements, providing a magnetic flux through which the DRI moves. This induces an electric current in the DRI, which in turn generates heat due to the electrical resistance of the DRI
Implementation Method 2
This induces an electric current in the DRI, which in turn generates heat due to the electrical resistance of the DRI, so that the DRI is heated by the induction coils without physical contact
Implementation Method 3
Induction is accompanied by two essential electrical effects that are characteristic of the heating principle: firstly, the skin effect (current displacement effect), and secondly, the proximity effect
Implementation Method 4
adjusting frequency and power to maintain or raise DRI temperature to the Curie point of iron (768°C) for efficient and uniform heating
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention relates to a method for heating DRI (abbreviation for "Direct Reduced Iron", also known as sponge iron) between a direct reduction plant and a processing plant, wherein the DRI (2) is conveyed as a DRI current (3) from the direct reduction plant to the processing plant by means of a conductor arrangement (1), and the conductor arrangement (1) comprises one or more induction coils (4) as a heating element for contactless heating of the DRI current (3) conveyed through the conductor arrangement (1), wherein the induction coil(s) (4) are operated with alternating current. The invention is characterized in that the frequency of the alternating current is specified and/or set to a frequency of at least 10 kHz.