Introduction
Due to dynamic conditions in the LD converter (LD = Linz-Donawitz), it is a challenge to obtain stable blowing and to achieve a required steel composition and temperature simultaneously at the end point. Within the current project, it is planned to predict the progress of the blow by means of thermodynamic and kinetic modeling of the converter operation in order to enable an improved process control. The LD process should be modelled in a comprehensive manner and the evolution of variables such as temperature and slag composition in time and space must be simulated. The occurring reactions depend on parameters like oxygen flow rate and post combustion rate. The interaction of the metal droplets with the gas phase and the slag also plays an important role. In addition, the post-combustion zone should be investigated, and slopping should be prevented.
Further downstream the steelmaking process chain, steel cleanness is one of the key quality factors for high performance steels whose significance is constantly increasing. Steel cleanness is defined by number, type, composition and morphology of so-called non-metallic inclusions in the steel matrix. To achieve a defined cleanness level, secondary metallurgical processes are decisive. A profound process model to describe and track steel cleanness, while processing through secondary metallurgy is also a part of this project.
Objectives and Motivation
- Thermodynamic description of the driving force in quinary systems (CaO-SiO2-FeO-MgO-MnO)
- Development of a kinetic model to describe the dissolution of Calcium and Magnesium containing additives in converter slag
- Modeling on the behaviors of non-metallic inclusions during the secondary refining process
Literature studies, numerical and thermodynamic modelling and experimental campaigns are part of the planned methodology. The development of a dissolution model for the slag forming additives in quinary slag systems should be conducted. Thermodynamic modeling should be applied for the clarification of the dissolution process kinetics. A comprehensive dissolution test procedure will be developed in lab-scale using a high-temperature vertical tube furnace to study the dissolution kinetics of Calcium and Magnesium under industrial gas conditions. Accompanying mineralogic investigations of the used additives and the slag after the experiments complete the experimental part. The derived results from the experiment and modeling should be compared and validated.
Another part of the modelling activities is focused on the validation of a currently used post combustion sub model and, based on that, on the creation of alternative post combustion models and heat transfer models. The validation of the model will be supported by plant data e.g. the current converter design and gas analysis devices of the industrial project partner.
On the secondary metallurgical side, the modeling work will combine fast computing reactor models from chemical engineering with thermodynamic databases and kinetic calculations. The models will be validated by the plant trials from the industrial partners. The developed model should finally be applied for specifically adapted questions.
The expected results comprise the thermodynamic description of the quinary system (CaO-SiO2-FeO-MgO-MnO). Furthermore, it is planned to develop a kinetic model of the dissolution of Calcium and Magnesium containing additives in converter slag by combining sophisticated experimental trials and thermodynamic modeling. Further thermodynamic quantities, e.g. Gibbs energies as function of temperature and composition will be required to formulate the kinetics of the dissolution process within a thermodynamically consistent formalism. Furthermore, the derived results will be validated for a final application to the industry.
The reliable determination of the LD converter model results (e.g. decarburization rate) and post-combustion model are expected. Furthermore, the improvement of the kinetic parameters, which are connected to the interaction area and the gas phases inside the LD converter should be executed. Finally, a thorough literature review summarizing the gas measuring methods and slopping detection mechanism is expected.
A validated thorough model on secondary refining process is expected. Identification of the influence of the process parameters and operations on steel cleanness should be quantified. Finally, solutions should be proposed to specific questions and innovative aspects from the involved industrial partners.
