Effect of the burner position on an austenitizing process in a walking-beam type reheating furnace

Highlights: • Burner position has a great effect on efficiency and heating characteristics. • Efficiency varied up to 18 percentage points by changing the burner position. • Cold air leaks were responsible for the lower efficiencies and billet heating problems. • The most appropriate burner configuration depends on the geometry of the furnace. -- Abstract: An analysis of the effect of burner location on the performance of a walking-beam type reheating furnace for an austenitizing process is presented in this work. Four configurations were evaluated, where the main difference was the position of four high-speed self-recuperative burners. The analysis was done through computational fluid dynamics (CFD) simulations, using a set of models suitable, and previously validated, to consider combustion, heat transfer, and billet heating, all in a 3D steady-state calculation. The self-recuperative burners were modeled by programming a custom user-defined-function (UDF) for the specific burner. This UDF calculates air preheating temperature in each burner as a function of air mass flow rate and the flue gas temperature entering the burner recuperator. The efficiency of the heating process, the billet heating characteristics, and the heat transfer rate to the billets for the different configurations were analyzed and compared. The results show that position and type of burners have a great effect on the furnace performance. The entrance of cold air through the furnace openings was responsible for the lower efficiencies and some billet heating problems observed. The configuration with the burners staggered on the sidewalls presented the best results in terms of energy efficiency and the billet heating characteristics required for an austenitizing process (heating rate, austenitizing temperature, holding time, and temperature uniformity).