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Modeling and Control of Three-Phase Submerged Arc Furnaces for Performance Improvement

Mohammadpour, Amir | 2024

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 58248 (05)
  4. University: Sharif University of Technology
  5. Department: Electrical Engineering
  6. Advisor(s): Parniani, Mostafa
  7. Abstract:
  8. Nowadays, submerged arc furnaces (SAFs) have gained considerable attention due to their lower energy consumption compared to electric arc furnaces. A submerged arc furnace typically consists of a shallow pot-shaped body made of a steel shell that withstands high temperatures and various chemical reactions. The steel casing enables the furnace to endure high temperatures and diverse chemical reactions. The required energy for the desired chemical reactions is supplied through three vertical carbon electrodes submerged under the arc within the charge materials. These electrodes are powered by three-phase alternating current from furnace transformer. The energy generated in the form of heat from the electric arc between the electrode tips and the charge materials facilitates the chemical reactions. SAFs are widely used in the ferroalloy industry for smelting calcium carbide, ferro-nickel, ferro-chrome, ferro-manganese, ferro-silicon, and other essential materials required for product manufacturing. Concurrently with the increasing application and capacity of SAFs, the development of DC types has also been introduced, offering advantages such as reduced voltage drops, increased power factor at AC side, and achieving three-phase balance. With the increasing use of SAFs in industries, it is crucial to pay special attention to their power consumption and the quality of their products. The objective of this thesis is to model, analyze, and improve the performance of a three-phase SAF for silicon production by proposing an appropriate closed-loop control system to regulate electrode heights. Silicon in submerged arc furnaces is produced using electric current, which provides the necessary heat for endothermic chemical reactions. The physical processes in SAFs are interrelated and vary across different time scales. As a result, SAF modeling often neglects one or more of the chemical, thermal, and electrical effects. This thesis aims to present a comprehensive and yet simple model that addresses all these effects. A new simplified model for electric arcs in SAFs is proposed, where radiative heat transfer is considered the primary mechanism for thermal losses, based on dimensional analysis of a magnetohydrodynamic (MHD) model. To account for the effects of alternating and sinusoidal feeding, this arc model is integrated into an equivalent circuit model for the SAF electrical system. After words, closed loop control of the SAF electrodes elevation is designed using the proposed model and PID control, for the purpose of its performance improvement and regulation. It is then evaluated using various simulations
  9. Keywords:
  10. Loss Reduction ; Electric Arc Furnaces ; Efficiency Maximization ; Submerged Arc Furnace Control ; Submerged Arc Furnace ; Electric Arc Furnaces Modeling

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