Ciencias Exactas y Ciencias de la Salud

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Study of heat transfer in tubular-panel and spray cooling systems applied to the electric arc furnace walls
(Instituto Tecnológico y de Estudios Superiores de Monterrey, 2018-05-15) Contreras-Serna, Josué; Rivera Solorio, Carlos Iván; García Cuéllar, Alejandro Javier; López Salinas, José Luis
This project consists in a heat transfer study in the electric arc furnace (EAF) walls, focused in the tubular-panel and spray cooling systems for the EAF located at Ternium-Guerrero plant, in the northeastern region of Mexico. The tubular-panel system is the one currently used to keep the walls cooled, composed of a total of 14 tubular panels. More dangerous accidents in the EAF operation, are the water steam explosions, which occur due to water leaks in the piping system inside the furnace. Spray cooling is given from the outside of the EAF, reducing the possibility of water directly impacting molten steel. The main purpose of this research is to know the operational conditions of both systems, verifying if the spray cooling system could be as good as the tubular system for the removal of heat on walls, efficiency and keeping the walls at low temperatures. The following procedures were used to estimate the water flow distribution in the cooling systems and the heat transfer in the walls. Piping network configurations are proposed for both systems. Models that consider surface-energy balances between different layers of the EAF’s walls and the heat radiated onto the walls by the electric arc and the molten-slag surface are developed herein. Conventional correlations were used for determining the heat transfer coefficients inside the tubular panels (Internal convection) and alternate correlations for determining the heat transfer coefficients for the external convection (spray cooling). Additional scenarios were done trying to improve the operational conditions and heat removal of each system. Water flow regulation by valves in each panel in tubular system and jet nozzles are used instead of spray nozzles in the spray system to verify the effectiveness of the spray cooling. The study was conducted via a parametric analysis in which the principal factors governing the process—the arc coverage and slag-layer thickness adhering to the walls—were varied. The results of the tubular-panel system were compared with experimental measurements of the outlet water temperature in each panel, showing a good approximation; allowing us to predict the operational conditions of the furnace. For both systems the optimal operating condition of the EAF, is when the arc is completely covered and the maximal thickness of the slag-layer that can be reached is around to 4.5 cm, it does that energy losses to decrease significantly and to keep walls at low temperatures. The minimal temperature difference between the inlet and final flow is around to 3 K. The spray cooling system operates with a lower heat removal capacity and pressure than the tubular-panel, causing that inner wall surface temperature to be approximately 20 degrees higher than when using the tubular system for critical operating conditions. Under optimal operating conditions each nozzle removes approximately 8.5 kW of thermal power. It is concluded that each cooling system has different temperatures and heat-removal capacity, which are highly dependent on the water flow within them. It is proved that slag-layer thickness and arc-coverage factors significantly affect the safe operation of the EAF, as well as its energy efficiency. This is a semi-analytical study; the equations of models were obtained analytically, and an equation-solver program is necessary to treat the non-linear equations obtained. Relatively few computational resources are required for this method.
Implementation of a transient approach for the mass and energy balance in an electric arc furnace.
(Instituto Tecnológico y de Estudios Superiores de Monterrey) Camacho, Alejandra; Montesinos, Alejandro; Campus Monterrey; Campus Monterrey; Campus Monterrey; Trejo, Eder
On this work, an implementation of a transient approach for the mass and energy balance in an electric arc furnace is presented. Real operation conditions were included, such as the dynamic material and energy additions and continuous inlets and outlets. Also, several inherent phenomena were characterized, such as the melting rate of scrap, the chemical reaction mechanisms and the residence time of bubbles in the slag. With all these elements, the estimation of the distribution of mass and energy flows at any time of the “heat” process was performed. The main contributions of this work are to provide a prediction of mass and energy distribution at any time of the EAF process, and to be a guideline for a dynamic optimization model which can be useful to improve the efficiency of the furnace by operation protocol modifications, therefore, the net cost per ton of liquid steel can be reduced.
Implementation of a thermo energetic model of an electric arc furnace using static approach.
(Instituto Tecnológico y de Estudios Superiores de Monterrey) Torres Vázquez, Armando; 784401; López Salinas, José Luis; Campus Monterrey
In this work two mathematical models that describe the performance of an Electric Arc Furnace (EAF) are presented: Mass and energy balances and the heat rate transfer model. The mass and energy balances use real data taken from a process of a siderurgical and is able to calculate the amount of products of the actual process. The objective of this model is to make a diagnostic of the energetic performance of the EAF and to perform a detailed description of the energy distribution within the furnace. The mass and energy balance models were validated comparing the amount of hot heel and slag calculated with the obtained during the process. In order to the model works properly, it is necessary that the input data be accurate enough. The heat transfer model predicts the temperature distributions and energy flows between the diferent elements of the EAF, from the input energy rates and mass flows of the process. This model has an analytical approach and considers the different mechanisms of heat transfer: conduction, convection and radiation. The robustness and flexibility of the model was tested varying the electric power supplied to the furnace, the arc coverage index, the slag layer thickness and the process time. The model produces similar results to the results presented in other works. Both models require relatively few computational resources for their operation.

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