Chrome-Containing Slag Basicity Control for Desulfurization
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Solution Overview
Problem
The use of CaF2-free slag in electric furnace operations for producing chrome-containing steel results in reduced chrome yield and poor desulfurization, leading to increased sulfur content in molten iron, which complicates the production of low-sulfur stainless steel.
Innovation Solution
Mechanically stirring chrome-containing molten iron and CaF2-free slag with an impeller in a refining vessel, adding a metal Al-containing substance and CaO to control the slag basicity, facilitating chrome reduction and collection while promoting desulfurization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If CaF2-free slag is used in electric furnace operations, then environmental compliance and slag utilization are improved, but chrome yield rate deteriorates and desulfurization capability worsens
Solution Approach 1:
The invention changes the basicity parameter of the slag from the conventional range (0.7-1.7 for CaF2-free slag) to a higher range (1.9-3.0) by adding CaO. This parameter change restores the chrome-reducing reaction capability and desulfurization function while maintaining the CaF2-free composition, thus resolving the contradiction between environmental compliance and chrome yield rate.
Solution Approach 2:
The invention introduces CaO as an intermediary substance to mediate between the CaF2-free slag and the molten iron. CaO acts as a bridge that enhances the basicity of the slag, enabling it to perform chrome reduction and desulfurization functions without requiring CaF2, thus resolving the contradiction between using CaF2-free slag and maintaining reliable chrome yield.
2Object-affected harmful factors
If CaF2-free slag is used, then environmental restrictions are satisfied, but slag flowability and basicity deteriorate
Solution Approach 1:
The invention changes the basicity parameter of the slag from the conventional range (0.7-1.7 for CaF2-free slag) to a higher range (1.9-3.0) by adding CaO. This parameter change improves slag flowability and basicity while maintaining the CaF2-free composition, thus resolving the contradiction between environmental compliance and slag operability.
3Reliability
If mechanical stirring with impeller is used, then chrome reduction and desulfurization are promoted, but energy consumption and process complexity increase
Solution Approach 1:
The invention makes the slag system multi-functional by adjusting its basicity to simultaneously perform chrome reduction, desulfurization, and flowability improvement. This reduces the need for separate stirring operations, as the chemical reactions are promoted by the slag composition itself rather than requiring intensive mechanical stirring, thus resolving the contradiction between chrome reduction efficiency and energy consumption.
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
This method effectively reduces and collects chrome from slag, preventing chrome yield reduction and decreasing sulfur content in molten iron, thereby enhancing the desulfurization process and allowing for the reuse of CaF2-free slag.
Implementation Method 1
2Al + (Cr2O3) = (Al2O3) + 2[Cr]
Implementation Method 2
mechanically stirring chrome-containing molten iron produced in an electric furnace and electric furnace slag formed during the molten iron production, with mixing blades (impeller) in a refining vessel
Data Source
Figure 1
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AI summary
[Problem] To provide a means for reducing and collecting chrome from slag with simultaneously promoting desulfurization of molten iron, as directed to chrome-containing molten iron and slag to be obtained in electric furnace operation using CaF2-free slag. [Means for Resolution] In mechanically stirring a chrome-containing molten iron produced in an electric furnace and having a Cr content of from 8.0 to 35.0% by mass, and a CaF2-free electric furnace slag formed during the molten iron production, including Cr2O3, SiO2 and CaO as the constituent components and having a basicity CaO/SiO2 of from 0.7 to 1.7, with an impeller in a refining vessel, a metal Al-containing substance and CaO are put into the vessel before the end of stirring to thereby control the basicity of the slag after the end of stirring to at least 1.9.