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Primary Metallurgy and Metallurgical Processes – PMP



The process step "primary metallurgy" involves the processing of iron ore to hot metal or sponge iron and the further treatment to crude steel. Regarding energy- and emission-optimization in the steel industry, the exploratory focus concentrates on the issues of reduction- and steelmetallurgy. The results of the research activities are used for the enhancement of existing processes and for the implementation of new technologies. Further application areas are characterization and evaluation of raw materials and reducing agents for the various processes of ironmaking.

Reduction Metallurgy

Steelmaking Metallurgy

Head

Research Associates

Fields of research

Fine-ore reduction in fluidized bed reactor - Daniel Spreitzer

The reduction of iron ore fines by means of the fluidized bed technology has become an alternative route in the field of ironmaking. To investigate the reduction behavior of these ores and to improve fluidized bed processes, a lab scale fluidized bed facility has been installed. With this equipment, the process behavior of iron ores can be determined close to industrial applications. Up to 5 kg of fine ores can be charged and fluidized with a wide variety of gas mixtures, containing H2, H2O, CO, CO2, CH4 and N2. Additionally a subsampling system was installed which enables the sampling of material. The scientific comparison of raw ore, subsamples and final material leads to a new way of fine ore characterization. Based on industrial processes also standardized tests were developed. With these procedures, globally traded iron ore brands can be tested close to industrial conditions.

Fine-ore reduction in fluidized bed reactor & micro agglomeration - Lukas Schmidt

A fluidized bed reactor in a smelting reduction process represents a high sophisticated technology which enables operators to adapt to different requirements. It is possible to reduce fine iron ores without the energy-intensive process of sintering. The aim of this study is to determine the of ultra fine iron ore (< 63 µm) on a circulating fluidized bed in a cold testing model. Moreover, various binding concepts for a production of micro pellets are evaluated concerning their suitability for processing in a fluidized bed reactor. Fig. 1 shows a microsection of a reduced pellet which matches the critical parameters of reducibility and compressive strength.

Fig.1: Microsection of a micro pellet after reduction process: Fe - Metallic Iron; W - Wustite; Sl - Silica; G - Gangue; B – Binder accumulation (Sodium silicate)

Effect of alkaline elements on ironmaking process - Anrin Bhattacharyya

Alkalis like potassium and sodium are known as harmful elements with effect on burden and coke disintegration, destruction of the refractory material and the creation of scaffolds. Because of the higher input rates caused by low quality iron ore and fuels, the aim was focused on the effect of K & Na during the iron ore reduction. Therefore experimental and theoretical work is performed. According to a standardized methodology, the specific effect on ferrous burden materials has been determined by experiments (reduction, tumbling and softening/melting tests). Furthermore, a model was developed to predict the alkali distribution in ironmaking reactors. Based on thermochemical calculations regions with enriched contents of alkali-compounds can be determined. A multi-stage construction connects the gas-, temperature- and pressure- profiles with the thermochemical calculation of stable alkali-compounds. The model enables the prediction of the K/Na-distribution and circulation inside the processes as well as an overall alkali balance.

On the other hand, in order to achieve a deeper insight on the effects of alkaline elements on coke reactivity and strength, some industrial coke samples impregnated with different alkaline species(Na & K) in various amounts have been tested under standard conditions to find out their CRI and CSR values. A home-grown controlled method is developed to induce external alkali in coke structure. Scanning electron microscopy, petrographic and Raman Spectrometric investigations demonstrate the change of structural properties. The mechanism of catalysis has been postulated in terms of atomic radii.

A breakthrough was achieved by TEM analysis of alkali treated and reacted samples. Na and K species have been found to infiltrate in the graphitic structure creating enormous lattice distortion, which is the most probable reason of drastic deterioration of coke properties under the influence of alkaline elements. Presently, research is in progress for deeper in depth structural analysis.

Reduction of lumpy burden

Within this research field, a broad variety of either industrial scale processed or lab scale produced lump ferrous burden materials can be investigated. The description of a material’s ability regarding oxygen release and mechanical performance during reduction can be investigated either at standardized testing conditions as well as more sophisticated industrial scale processes conditions concerning temperature and gas composition. The reduction is performed within a vertical reduction aggregate and for mechanical characterization a rotating tumbling drum is set in the lab (see picture, both according to a wide range of standardized testing procedures).
Combined with the morphological characterization of the raw material and the structural evolution during reduction by means of light microscopic means an overall picture of the performance of an iron containing burden material can be given.

Characterization of coke and char - Anrin Bhattacharyya

Coke is the major fuel as well as the costliest raw material of the Blast Furnace (BF) ironmaking process. It is not only the major reductant of the process, but it also provides strength to the burden under BF conditions. Total cost of coke is around 60% of the hot metal production and 1/3rd of the steelmaking production cost in whole. As the world reserve of coking coal is gradually decreasing and price of coke increasing steadily, coking coal has been attributed as a ‘critical’ raw material for ironmaking. Therefore coke, a direct product from coking coals, requires careful investigation of its physical, chemical and mechanical properties for determining its suitability under operational requirements. Minimizing the specific coke consumption per ton of hot metal and maximizing the furnace efficiency are two big challenges for the BF operator.
A proper forecast for the behavior of raw materials under BF conditions is major task for ferrous process metallurgists. Coke properties such as reactivity and strength do not depend only on its composition, but also an exhaustive number of factors, such as maceral, microstructure, porosity,  structural order, crystallinity and even up to the nano-level domain of lattice parameters, only to name a few. An apposite knowledge about the coke properties in advance not only helps the metallurgists to select the proper quality of coke for the process, but also to foresee its behavior under continuously changing physical and chemical conditions of the blast furnace under real industrial conditions.
The chars generated from non-coking coals which are used in alternative smelting reduction processes (COREX® and FINEX®) should also have analogous properties for application in the melter-gasifier.
The focus of this research area is to demonstrate how it is possible to characterize cokes and chars aiming for a holistic forecast of their behaviors under actual process condition. It will not only enable us to select the proper reductant for the process, but also to minimize operation costs by more efficient process control, less coke(or coal) consumption and reduced CO2 generation.

Kinetics of lime and magnesium oxide dissolution in converter slag - Elizaveta Cheremisina

Kinetics of lime dissolution in model and industrial steelmaking slags has been investigated. Samples of lime in a cylinder shape of predetermined size were immersed for a fixed time in the molten slag at temperatures between 1400 - 1600°?. Considering the experimental data derived: mass of dissolved calcium oxide, linear dimensions of calcium oxide samples and the total mass balance of CaO in the liquid layer as well as contact area of the solid-liquid phases, mass transfer coefficients have been determined. The dependences of the dissolved CaO mass, linear rate of samples dissolution and content of CaO in the slag phase on the duration of the dissolution process have been obtained. Activation energy has been calculated with the value lower than 200 kJ per mol. The low activation energy value characterizes the diffusion limiting step in the process of lime dissolution in slag.

Modelling of the LD-process - Philip Bundschuh

The basic development of a thermodynamic and kinetic model of the converter steelmaking was completed by the predecessor Mag.Dr.mont. Y. Lytvynyuk in Phase I and II of the K1-Met. The first test calculations with the model showed qualitatively fair results considering the time trend for the bath temperature as well as concentration of elements in the metal bath and slag components. Further model improvements are related to the kinetic part of the model. A more realistic description of the interaction area between slag and metal is under development and will be verified by slag sample investigations. The effect of iron droplet formation during the blowing process is included in the calculation of the reaction area (Fig.1).

IntArea_VgL
P_Verlauf
Fig.1: Comparison of different interaction area approaches (left) and the influence on the trajectory of the phosphorus in the metal phase


Alternative model correlation for the bath agitation which is controlling the interfacial metal slag reaction will be tested and if necessary implemented. In order to adjust the model results with actual operation data from industrial plant model tuning parameters have to be modified. The objective within this project is the further verification and improvement of this model. The aim is to reduce the number of necessary tuning parameters and to develop look up tables for these parameters which are fitted by operation data. The sub-models of the metallurgical reactions should be further developed. Further a verification of the currently used thermodynamic data (e.g. heat capacities) is under progress. The effect of different cp-functions on the calculation demonstrates Fig.2.

Fig.2: Comparison of different heat capacity functions (left) and the influence on the trajectory of the carbon, phosphorus and manganese content in the metal phase

The research work on converter slag should be continued from Phase II of K1-Met where the basic understanding for the dissolution kinetic for CaO and MgO was elucidated. The objective of this project is the development of strategies to minimize the refractory wear on one hand and to optimize the metallurgical results with regard to Fe yield, P and Mn partition, end C content and tapping temperature for a converter heat on the other hand. A new methodology for the evaluation of the properties of slag additives should be developed. The objective is a standardized method for the quality control of converter additives which reflects the process conditions in the converter. Project includes development of experimental technique and application of kinetic models to calculate kinetic parameters of the process as well as verification of kinetic model.


Equipment of the working group

  • Scientific Staff

    Technical Staff

    Student Staff

    Running Master Theses

    Running Bachelor Theses