Steel Slag Reduction for Iron Recovery and Alite Binder
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Solution Overview
Problem
Current methods for processing steelworks slags fail to recover iron and produce a hydraulic mineral binder with high hardening potential, as the iron in the slags is not effectively recovered and the resulting products are not suitable for high-quality utilization due to the absence of significant alite formation.
Innovation Solution
A method involving the reduction of iron compounds in steelworks slag melts with reducing agents in a non-oxidizing atmosphere to achieve a lime standard of 90-110, followed by slow cooling and mechanical separation of elemental iron, which is then used as a hydraulic mineral binder with high alite content and reactivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If steelworks slag is processed using conventional oxidation methods, then a hydraulic binder can be produced, but iron cannot be recovered and the binder lacks high hardening potential
Solution Approach 1:
The patent applies parameter changes by switching from oxidation to reduction conditions, changing the atmosphere from oxidizing to non-oxidizing, and adjusting temperature parameters (1200-1800°C) to achieve simultaneous iron recovery and alite formation. This fundamental parameter change enables both iron metallization and production of high-hardening binder phases.
Solution Approach 2:
The patent utilizes phase transitions by melting the slag to form a liquid phase where reduction reactions occur, then controlling cooling to precipitate metallic iron and form crystalline alite phases. The controlled solidification from molten state enables separation of metallic iron droplets and formation of hydraulic binder minerals.
2Loss of substance
If steelworks slag is rapidly cooled, then iron can be separated, but significant amounts of alite phase are not formed
Solution Approach 1:
The patent employs periodic action through a two-stage cooling process: first rapid cooling to solidify the melt and separate iron, then controlled reheating and slow cooling to form alite phase. This periodic thermal treatment enables both iron separation and subsequent phase formation.
Solution Approach 2:
The patent applies preliminary action by first completing iron reduction and separation before proceeding to alite formation. The metallic iron is removed in advance, preventing interference with the subsequent phase transformation process and enabling pure alite crystallization.
3Loss of substance
If reducing agents are introduced to metallize iron, then elemental iron can be recovered, but the lime standard may deviate from optimal range
Solution Approach 1:
The patent applies feedback by continuously monitoring the lime standard during reduction and adjusting reducing agent addition rate and temperature to maintain lime standard between 90-110. This closed-loop control ensures optimal conditions for both iron recovery and alite formation despite process variations.
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 allows for the efficient recovery of elemental iron and the production of a highly reactive hydraulic mineral binder with a high alite content, suitable for high-quality binders, exhibiting enhanced hardening capacity and reactivity.
Implementation Method 1
introducing reducing agents into the melt to reduce the iron compounds
Implementation Method 2
the melt is then cooled in a defined manner, with the melt solidifying
Data Source
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AI summary
The invention relates to a method for the treatment of steelwork slag for producing a hydraulic mineral binder with high curing potential and for recycling iron. To this end and according to the invention, a source product containing steelwork slag and MnO is prepared. This source product is further processed as a melt by introducing reducing agents into the melt. The mineral content of the melt should reach a lime standard of between 90 and 110. The melt is then cooled under defined conditions and elemental iron is mechanically separated from the solidified melt. The solidified melt is then fed to be used as a hydraulic mineral binder. The invention further relates to a hydraulic mineral binder.