<div>The objective of this research was to develop an efficient simulation of an industrial reheating furnace with a flexible scale formation model and to apply the models to study various conditions within an industrial reheating furnace. This work focused on developing a model capable of considering many different key variables that influence scale formation. The scale formation model was incorporated into the computational fluid dynamics (CFD) software ANSYS Fluent © to solve a coupled steady-state and transient simulation. It was also generalized for a low-carbon steel product, so it may not be adequate to cover the effects of alloying metals on the oxidation process. In order to verify the accuracy of these models, baseline cases were simulated and validated against both industrial data and findings from experiments in published literature.</div><div><br></div><div>A parametric study with two levels of oxygen enrichment implementation in only the preheat zone was undertaken to study the effects on the heat transfer, scale formation, and fluid flow within the reheat furnace. A medium oxygen enrichment case of 46 vol% oxygen and an oxy-fuel case were used for study. Both oxygen enrichment cases showed largely increased heat transfer to the slab in the preheat zone and increased scale formation. Based on these results, 46 vol% oxygen enrichment is recommended for use in a typical industrial reheat furnace with additional firing rate drawback to reduce scaling and to reduce the chance of overheating the steel slab product.</div>

In this master thesis an implementation of an Organic Rankine Cycle (ORC) on a stepping furnace in a steel mill is modeled and proposed. The study is a case study at the company Štore&amp;STEEL d.o.o. with intentions of realization. In a steel mill a stepping furnace is used to preheat the steel billets for later forging. The stepping furnace is gas fired and already has recuperation of the inlet air implemented. Still there is high temperature of the stack after recuperation, which makes application of an ORC worth of researching and modeling.First the flue gas over one year of furnace operation is analyzed in terms of temperature and volumetric flow. Mass flow and heat capacity are calculated. A layout of an ORC is proposed and modeled in IPSEpro for different temperatures of the flue gas resulting in different output powers and efficiencies. For each temperature an economic viability calculation with the method of reference cost of electric energy is done.The results are presented and the best design and conditions are proposed. The results of the thesis proved that further detailed measurements and calculation are worthwhile , as the flue gas from the stepping furnace has satisfactory conditions to make an application of an Organic Rankine cycle viable. Also the least ammount of state support to fulfill the companies conditions on return of investment is calculated and presented. Finally there are additional measurements and calculations suggested.

<p dir="ltr">This thesis explores novel methods of steel reheating, simulating hydrogen as a cleaner fuel in the combustion furnace and magnetic induction heating as a viable alternative, by utilizing advanced numerical simulations, including Computational Fluid Dynamics (CFD) and Finite Element Analysis (FEA), to assess their performance and feasibility.</p><p dir="ltr">Hydrogen, known for its potential to significantly reduce carbon dioxide emissions, is examined as a substitute for natural gas. Simulations revealed that hydrogen combustion results in higher flame temperatures and heat fluxes. While the CFD model achieved a high level of accuracy, with a maximum temperature error of 3% and an average deviation of 7% from real-world data, hydrogen fuel caused an increase in heat flux by up to 12% and higher slab surface temperatures. These changes led to steeper thermal gradients and increased stress, with peak stress levels reaching 90% of material limit. This simulation approach provides valuable data on the performance of different furnace fuels, helping to identify optimal fuel blends and configurations that minimize the risk of material failure while enhancing furnace efficiency.</p><p dir="ltr">The impact of scale formation on steel surfaces during reheating was also investigated. A mathematical model based on linear-parabolic equations was integrated into CFD simulations to predict scale growth. This model was validated against experimental data, showing an average error of 6%. The presence of scale led to a reduction in core temperature by up to 31 K and a 7.6% decrease in heat flux, which negatively affected heating efficiency. Scale formation also caused a significant drop in thermal conductivity, impacting heat transfer and slab uniformity. Pre-heating zone contributed minimally to overall scale formation despite its extended duration whereas a majority of scale growth was observed in the heating zone. Applications of this model include improving reheat furnace model efficiency and optimizing furnace operation to minimize scale.</p><p dir="ltr">Magnetic induction heating was also explored as an alternative to combustion-based reheating, assessing its potential benefits and challenges. The simulation results, validated with an average error of approximately 7% compared to literature data. showed uniform temperature distribution, and reduced stress levels with optimal power settings around 80 kW. A 3D transient simulation modeled an adaptive power cycle to minimize thermal stress highlighting the effectiveness of adaptive soaking strategies over continuous soaking in managing thermal stress, improving heating efficiency and material integrity.</p>