Steel Slag Stabilization via Basicity and Aluminium Control
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Solution Overview
Problem
Steel slags disintegrate into fine powders due to the formation of γ-dicalcium silicate during slow cooling, making them unsuitable for use as aggregate in construction materials.
Innovation Solution
A method involving the production of mainly crystalline solidified steel slag by adjusting the basicity of the steel slag through the addition of a low basicity material and ensuring a minimum amount of aluminium oxide is present, thereby reducing the formation of γ-dicalcium silicate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If steel slag is slowly cooled to solidify it, then the solidification process is simple and energy-efficient, but γ-dicalcium silicate forms causing disintegration into fine powders
Solution Approach 1:
The invention changes the chemical composition parameters of the steel slag by controlling the basicity ratio (CaO/SiO2) to be between 0.8 and 1.2, and by ensuring aluminium oxide content is at least 5 wt%. These parameter changes prevent γ-dicalcium silicate formation during slow cooling, allowing simple solidification to produce stable slag without disintegration.
2Reliability
If borates or phosphates are added to stabilize steel slag and prevent disintegration, then the slag remains stable as aggregate, but toxic and expensive stabilizers are required
Solution Approach 1:
The invention replaces expensive and toxic stabilizers (borates, phosphates) with a composition adjustment approach using common steel slag components. By controlling basicity and aluminium oxide content, the slag stabilizes itself without requiring additional chemical additives, eliminating toxicity and extra costs.
Solution Approach 2:
The steel slag stabilizes itself through its own chemical composition rather than requiring external stabilizers. The controlled basicity ratio and aluminium oxide content enable the slag to prevent γ-dicalcium silicate formation inherently, making the system self-stabilizing without harmful additives.
3Reliability
If the basicity of steel slag is increased to prevent γ-dicalcium silicate formation, then slag stability improves, but the slag becomes less suitable for construction applications
Solution Approach 1:
The invention optimizes the basicity ratio to a specific range (0.8-1.2) that balances two competing requirements: high enough to prevent γ-dicalcium silicate formation and maintain stability, but not so high as to compromise construction applicability. This precise parameter control achieves both stability and versatility.
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 method effectively reduces the formation of fines in steel slag, allowing it to be used as a stable aggregate in construction materials without the need for toxic or expensive stabilizers like borates or phosphates.
Implementation Method 1
lowering the basicity of the liquid steel slag separated from the molten steel from said first basicity (B1) to a second basicity (B2) at least partially by dissolving at least one low basicity material in the liquid steel slag
Implementation Method 2
solidifying the liquid steel slag having said second basicity (B2) by cooling it down to produce said mainly crystalline solidified steel slag
Implementation Method 3
solidifying the liquid steel slag having said second basicity (B2) by cooling it down to produce said mainly crystalline solidified steel slag
Data Source
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AI summary
The present invention relates to a method for producing a mainly crystalline solidified steel slag to produce solid steel slag, in particular a solid steel slag which can be used, after crushing, as aggregate in construction. In order to avoid or reduce the formation of dicalcium silicate, or in other words in order to stabilize the steel slag, the basicity of the steel slag which is separated from the molten steel is reduced to a relatively small extent and, in combination therewith, a sufficient amount of aluminium is provided in the steel slag. Use is thus made of a low basicity material such as glass, which is added in a relatively small amount to the liquid steel slag after it has been separated from the molten steel, and of at least one aluminium rich material which is added to the steel furnace and/or to the liquid steel slag which is tapped from the steel furnace.