Vacuum Converter Ferro-Alloy Decarburization
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Solution Overview
Problem
Conventional methods for producing ferroalloys with low carbon content, such as in AOD and CLU converters, are limited by long treatment times and high coolant requirements due to high initial silicon and carbon contents, and the VODC process has slow decarburization under low mixing energy.
Innovation Solution
A two-stage process in a single unit where desiliconization and main decarburization occur under atmospheric conditions with oxygen and CO2, followed by deep decarburization under vacuum, using annular gap nozzles with CO2 and inert gases to reduce coolant needs and enhance mixing energy, and utilizing CO2 for Boudouard reactions to achieve low carbon levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional AOD or CLU converter processes are used for decarburization, then ferroalloys can be produced, but treatment times are very long and carbon content can only be reduced to limited levels (approx. 1.0%)
Solution Approach 1:
The decarburization process is divided into two distinct stages: a first stage under atmospheric pressure for desiliconization and main decarburization, and a second stage under vacuum for deep decarburization. This segmentation allows each stage to operate under optimal conditions, achieving carbon contents below 0.05% without excessively long treatment times.
Solution Approach 2:
The process changes the pressure parameter from atmospheric (first stage) to vacuum (second stage) to enhance decarburization efficiency. The vacuum condition in the second stage shifts the Boudouard reaction equilibrium, enabling much deeper carbon removal and achieving carbon contents < 0.05% that are not attainable with conventional atmospheric processes alone.
2Quantity of substance
If large amounts of coolant are added during desiliconization and main decarburization in conventional converters, then high Start Si and Start C contents can be handled, but this increases process complexity and operational difficulty
Solution Approach 1:
The process changes the pressure parameter from atmospheric to vacuum in the second stage, which fundamentally alters the decarburization mechanism. This parameter change reduces dependence on coolant addition for carbon removal, simplifying operational control and reducing the quantities of coolant and other additives required.
Solution Approach 2:
The process replaces the mechanical/chemical approach of using large amounts of coolant for decarburization with a physical approach using vacuum pressure. The vacuum environment enables carbon removal through equilibrium shift in the Boudouard reaction, substituting the need for excessive coolant addition and simplifying the operational system.
3Manufacturing precision
If VODC converter is used with oxygen blowing under vacuum, then decarburization can occur, but the process progresses very slowly due to low blowing rates and low mixing energy
Solution Approach 1:
The process segments the decarburization into two stages with different pressure conditions. The first stage under atmospheric pressure provides high mixing energy and vigorous reaction for main decarburization, while the second vacuum stage completes the deep decarburization. This segmentation avoids the slow single-stage vacuum process while achieving the same carbon reduction目标.
Solution Approach 2:
The process uses periodic alternation between atmospheric pressure (high mixing energy phase) and vacuum pressure (deep decarburization phase). This periodic action combines the advantages of both pressure conditions: high productivity during atmospheric phase and deep carbon removal during vacuum phase, overall increasing decarburization speed compared to continuous vacuum operation.
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 approach significantly reduces coolant requirements, shortens treatment times, increases decarburization speed, and enhances production capacity with lower refractory and operational costs, achieving higher yields and flexibility in ferroalloy production.
Implementation Method 1
In particular, the CO2 or the carbon hydrates cause a strongly endothermic reaction when they come into contact with the liquid ferroalloys.
Implementation Method 2
when CO2 is used, the Boudouard reaction (the carbon content of the melt is still well over 1% in this phase) to use.
Implementation Method 3
The partial pressure reduction of CO takes place by blowing in inert gas and, in parallel, by reducing the pressure in the vessel.
Data Source
AI summary
The invention relates to a method for the production of ferro-alloys, particularly FeCr and FeMn alloys, with low carbon content in a vacuum converter. In the first stage, the melt is subjected to desiliconization and principal decarburization in the vacuum converter on the basis of the converter method under atmospheric conditions, wherein oxygen is injected into the melt via a top lance and oxygen and CO2 are injected into the melt via the nozzles, particularly annular gap nozzles, under the bath and subsequently, in a second stage, in the same converter the deep carburization phase takes place under a vacuum, wherein CO2 or CmH2m+2 is additionally injected on the protective gas side of the under-bath nozzles.