Twin AOD-L Converters for Stainless Steel Autogenous Heating
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Solution Overview
Problem
Existing methods for stainless steel production using AOD converters without electrical energy supply are limited to producing only ferritic steels due to energy constraints, preventing the production of austenitic stainless steel grades.
Innovation Solution
The method involves separating pretreated, slag-free liquid pig iron into two parallel Twin AOD-L converters, where heating, decarburization, and alloying processes are conducted using autogenous chemical energy, with opposite process steps in each converter to enable the production of all stainless steel grades, decoupling the need for electrical energy and improving temperature control and cost efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single AOD converter is used for stainless steel production without electrical energy supply, then ferritic steels can be produced, but austenitic stainless steel grades cannot be produced due to energy constraints
Solution Approach 1:
The single AOD converter is divided into two parallel converters (first AOD converter for heating and decarburization, second AOD converter for alloying and finishing). This segmentation allows the process to be split into distinct stages, with each converter optimized for specific functions, enabling sufficient temperature and energy management to produce both ferritic and austenitic stainless steel grades using only autogenous chemical energy
Solution Approach 2:
The first AOD converter performs preliminary heating and decarburization of the pig iron before the steel is transferred to the second AOD converter for alloying and final treatment. This preliminary action ensures that the steel reaches the necessary temperature and compositional state before alloying, enabling the production of austenitic grades that require higher temperatures and precise energy management
2Manufacturing precision
If pig iron quantity is reduced in each converter, then temperature control is enhanced and costs are lowered, but production capacity per converter is reduced
Solution Approach 1:
By segmenting the total pig iron charge into two parallel converters, each converter handles a smaller quantity of molten steel. This reduces the thermal mass in each converter, improving temperature control precision and reducing the energy required for heating and alloying operations, while the parallel configuration maintains overall production capacity
3Reliability
If DDD treatment is performed externally before AOD conversion, then phosphorus, silicon and sulfur are removed, but additional processing steps and equipment are required
Solution Approach 1:
The DDD (dephosphorization, desiliconization, desulfurization) treatment is extracted as a separate external processing step performed before the molten steel is charged into the AOD converters. This removes harmful impurities (phosphorus, silicon, sulfur) from the pig iron in advance, ensuring high-quality steel suitable for both ferritic and austenitic grades, while allowing the AOD converters to focus on heating, decarburization, and alloying functions
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 allows for the production of both austenitic and ferritic stainless steel grades while exclusively using autogenous chemical energy, reducing electrical energy demand, enhancing temperature control, and lowering costs and investment requirements by treating smaller pig iron quantities in each converter.
Implementation Method 1
The pig iron is heated to a desired temperature or the temperature required for the subsequent process steps by means of Si oxidation
Implementation Method 2
an oxygen/inert gas mixture is blown through the side nozzles and a top lance into and onto the pig iron
Implementation Method 3
the required chemical process steps (of heating, decarburization and alloying) are then carried out using autogenous chemical energy
Data Source
Figure 1~2
AI summary
The aim of the invention is to produce stainless steel for all stainless steel products both in the austenitic and the ferritic range, based on liquid pig-iron and FeCr solids, without using a supply of electrical energy. According to the invention, the liquid pig-iron, after being pre-treated in a blast furnace (1), is subjected to a DDD treatment (dephosphorisation, desiliconisation and desulphuration), is heated, finished or alloyed and deoxidated. The quantity of slag-free liquid pig-iron that has been pre-treated in the blast furnace (1) and a DDD device (2) is separated and introduced into two classic "twin" AOD-L converters (3, 4), where the required chemical process steps (of the heating, decarburisation and alloying stages) take place in parallel contrary processes using autogenous chemical energy, the heating stage being carried out first in the first twin AOD-L converter (3) and the decarburisation being carried out first in the second twin AOD-L converter (4).