Thomas Echterhof

Nitrogen Oxide Formation in the Electric Arc Furnace—Measurement and Modeling

In this article, the results of pilot electric arc furnace (EAF) trials and model calculations regarding the formation of NOx in an electric arc furnace are presented. The results of these investigations confirm that the conditions within the electric arc furnace are favorable for the formation of NOx. During pilot furnace trials, a notable influence of the electric parameters on the NOx formation could not be established. The importance of the influence of the furnace atmosphere, especially the O2 and CO content, could be ascertained clearly. Thermodynamic equilibrium calculations concerning the furnace atmosphere were conducted during the course of the investigations. The results clearly show that the chemical reaction kinetics have a considerable influence on the NOx concentrations measured in the off-gas of electric arc furnaces. Therefore, in addition to the equilibrium calculations, a reactor network model of the EAF was developed subsequently. Using this model, it was possible to reproduce phenomena such as the NOx peak at arc ignition as well as to calculate NOx concentrations, which match measurement data within an order of magnitude.

Heat recovery from EAF off-gas for steam generation: analytical exergy study of a sample EAF batch

The high amount of latent and sensible enthalpy discharged from the melting process in an electric arc furnace (EAF) through the off-gas offers high potential for waste heat recovery. Evaporative cooling systems (ECSs) installed at dedusting systems of some EAFs are utilising this waste heat for steam generation and subsequent usage of steam for further applications. Within the following paper, further optimisation approaches of this waste heat recovery are examined comparatively by means of exergetic analysis. Thereby, the focus is on the excessive intake of false air into the dedusting system to ensure a complete CO post-combustion. While a sheer energetic examination of the enthalpy hardly shows any differences, the exergetic calculation confirms the significantly higher amount of generated steam with controlled false air ingress. For the calculated optimal reference case with stoichiometric post-combustion, between 50 and 70% more steam could be produced. Even though a stoichiometric post-combustion cannot be realised for safety reasons, the calculation shows the potential of controlled false air intake for CO post-combustion.

Increasing the sustainability of steel production in the electric arc furnace by substituting fossil coal with biochar agglomerates

Biochar fines from a wood gasification plant and from pyrolysis of agricultural residues were investigated as substitutes for fossil coal used in the steel production in the electric arc furnace (EAF). During previous tests biochar fines with high specific surface showed problematic burn-off behaviour. Therefore the agglomeration behaviour of the biochar fines was investigated. Different binary and ternary mixtures of biochar with water and binders were tested in a hydraulic stamp press and evaluated with regard to green strength and fatigue strength of the briquettes after 3 days. One selected mixture was used to produce pillow briquettes in a double roll press. The abrasion behaviour of the produced briquettes was tested and compared to an anthracite reference coal (RC). Melting tests in a pilot EAF showed that the agglomerated biochar reacts similar to the RC. The briquetting leads to reduced reactivity and slower burn-off compared to the biochar fines.

Modeling and Simulation of the Off-gas in an Electric Arc Furnace

The following paper describes an approach to process modeling and simulation of the gas phase in an electric arc furnace (EAF). The work presented represents the continuation of research by Logar, Dovžan, and Škrjanc on modeling the heat and mass transfer and the thermochemistry in an EAF. Due to the lack of off-gas measurements, Logar et al. modeled a simplified gas phase under consideration of five gas components and simplified chemical reactions. The off-gas is one of the main continuously measurable EAF process values and the off-gas flow represents a heat loss up to 30 pct of the entire EAF energy input. Therefore, gas phase modeling offers further development opportunities for future EAF optimization. This paper presents the enhancement of the previous EAF gas phase modeling by the consideration of additional gas components and a more detailed heat and mass transfer modeling. In order to avoid the increase of simulation time due to more complex modeling, the EAF model has been newly implemented to use an efficient numerical solver for ordinary differential equations. Compared to the original model, the chemical components H2, H2O, and CH4 are included in the gas phase and equilibrium reactions are implemented. The results show high levels of similarity between the measured operational data from an industrial scale EAF and the theoretical data from the simulation within a reasonable simulation time. In the future, the dynamic EAF model will be applicable for on- and offline optimizations, e.g., to analyze alternative input materials and mode of operations.

Verwendung von Biomassekarbonisaten

Die Verwendungsmoglichkeiten von Biomassekarbonisaten sind sehr vielfaltig. Dabei ist darauf hinzuweisen, dass sich die Anwendung von Biomassekarbonisaten bisher fast ausschlieslich auf pyrolytisch erzeugte Produkte beschrankt. Fur Karbonisate aus der HTC existieren noch kein Produktionsanlagen im Dauerbetrieb und dementsprechend auch kein Markt. Auserdem sind die HTC-Karbonisate fur manche Einsatzgebiete, wie z. B. als Medizinalkohle oder in der Landwirtschaft, nicht zugelassen.

Application of genetic algorithm to improve an electric arc furnace freeboard model based on practical data

Electric arc furnaces are applied to produce steel by melting scrap in a batch process. Despite of the significant role of the off-gas in the electric arc furnace environmental and energy feature, limited research has been carried out specifically on the modelling of the electric arc furnace freeboard. In this research, a reactor base model for electric arc furnace with burner and without burner is extended by considering more inputs to approach real conditions. There are some uncertainties in the measurement or calculation of electric arc furnace inputs due to different constraints. Regarding the multi objective problem and the conflicting nature of objectives, a genetic algorithm is applied to improve the model accuracy. The genetic algorithm found the optimum input parameters in the validated range based on the best compatibility with actual off-gas data. The comparison among different results illustrates the effective performance of genetic algorithm for this problem. This accurate model can be applied in the study of recycling, storage condition and control of the electric arc furnace off-gas for final purpose of energy saving and environmental protection.