Molten Metal Desulfurization With Controlled Current Density

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Solution Overview

Problem

Conventional methods for desulfurizing molten metal face challenges in controlling the desulfurization reaction effectively due to unclear specifications for current or voltage application, leading to potential facility damage and inefficiencies in reducing sulfur concentration and process time.

Innovation Solution

A method involving a direct-current power source to apply a potential difference between molten slag and metal using electrodes, with current density determined by equilibrated sulfur concentration to achieve a target concentration without excessive current, enhancing the overall mass transfer coefficient.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If constant-voltage control is applied to the slag-metal interface, then the desulfurization reaction is promoted, but when molten iron contacts the electrode due to level fluctuation, an extremely high current flows causing facility damage risk

Engineering Contradiction:

Improvedesulfurization reaction speedVSAvoidfacility safety

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the control parameter from constant voltage to constant current. By controlling the current to flow at a predetermined constant value rather than maintaining constant voltage, the system prevents extreme current surges when molten iron contacts the electrode, while still promoting the desulfurization reaction through sustained current application.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements feedback control by monitoring the actual current flow and adjusting the voltage to maintain a predetermined constant current value. This feedback mechanism detects when molten iron contacts the electrode and automatically adjusts to prevent excessive current, ensuring facility safety while maintaining desulfurization effectiveness.

Inventive Principle:

Principle #23Feedback

2Productivity

If conventional desulfurization methods are used with controlled slag composition and gas agitation, then the desulfurization reaction proceeds at a certain speed, but further improvement is difficult due to tolerable limits of reoxidation and nitrogen pickup

Engineering Contradiction:

Improvedesulfurization reaction speedVSAvoidreoxidation and nitrogen pickup

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the mechanical gas agitation method with an electrochemical approach. Instead of using gas bubbles to enhance mass transfer (which causes reoxidation and nitrogen pickup), the patent applies current to the slag-metal interface to drive the desulfurization reaction electrochemically, achieving improved desulfurization speed without the harmful side effects of mechanical agitation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If higher current density is applied to accelerate desulfurization, then the sulfur concentration reduces faster, but power consumption increases

Engineering Contradiction:

Improvedesulfurization speedVSAvoidpower consumption

Core Design Contradiction:

ProductivityVSUse of energy by moving object

Solution Approach 1:

The patent employs dynamic current density control rather than fixed high current density. The current density is adjusted based on process conditions, sulfur concentration levels, and slag composition to optimize the balance between desulfurization speed and power consumption, avoiding unnecessary energy waste while maintaining effective desulfurization rates.

Inventive Principle:

Principle #15Dynamics

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

Efficient desulfurization of molten metal to lower concentrations in shorter times with controlled current density, reducing power consumption and production costs, applicable to refining processes with electrochemical interface reactions.

Implementation Method 1

the desulfurization reaction is regarded as an electrochemical reaction in which electrons are exchanged at the interface, applying a current voltage to the slag-metal interface from the outside allows further progress of the reaction

Methodology Applied

Scientific EffectElectrochemical reaction: Electrolysis

Data Source

PatentEP4265743B1Method for desulfurizing molten metal

Publication Date: 2025.09.03 JFE STEEL CORP

Figure 1(a)~1(b)
Figure 2~3

AI summary

Proposed is a method for efficiently desulfurizing molten metal in a short time without passing an excessive current when applying a potential difference between slag and metal. Using a direct-current power source, this method for desulfurizing molten metal applies a potential difference between molten slag and molten metal through electrodes, of which one electrode contacting the molten metal serves as a negative electrode and the other electrode contacting only the molten slag serves as a positive electrode. An applied current density Ja is determined according to an equilibrated S concentration [S]e0 before application of a potential difference such that an equilibrated S concentration [S]ea when a potential difference is applied becomes equal to or lower than a target S concentration [S]εε.