Modelling oxy-combustion dynamics in rotary kilns for sustainable silicon production: A Case Study from the SisAl Project

This paper deals with the mathematical modelling and numerical simulation of the rotary gas furnace used at Fundiciones Rey for the preparation of SiO2-CaO slag, a crucial step in the silicon production process of the SisAl Pilot project. The model is structured in three stages to capture the critical thermal and physical processes involved. First, a steady-state combustion model evaluates the wall heat flux from the oxy-gas flame under varying temperature conditions, taking into account the heat exchange between the refractory wall and the furnace load. A simplified transient thermal model then predicts the temperature evolution in the refractory lining between casts during a whole week of operation, with the aim of providing realistic initial conditions for the subsequent model. Finally, the melting model uses these results to simulate the melting process in the furnace, incorporating additional phenomena previously neglected. The numerical results, validated against in-plant measurements of iron and slag melting times and temperature in the external wall of the furnace, demonstrate good agreement with experimental data, supporting the reliability of the model for optimizing furnace operations and energy efficiency.