Variation of Ladle Eye Size Using Image Analysis

ABSTRACT Inert gas bubbling through purge plugs is often used to stir molten steel in ladles to ensure compositional and thermal uniformity, as well as enhancing chemical reactions between slag and steel phases. The rising gas bubbles generate a drag force on the liquid steel, forming a gas-liquid plume. The plume travels with a velocity high enough to penetrate the slag, causing exposed liquid steel to appear at the top. This exposed bare steel at the surface is referred to as the ‘ladle eye’. The formation of the ladle eye and its size has significant implications on the quality of the steel. Ladle furnace operators observe the size of the ladle eye and judge the amount of stirring taking place in the melt and the actual gas flow rate. In this plant study, images of the ladle eye were captured and analyzed. MATLAB was used to analyze the images and measure dimensions in pixels. It was found that the variation in the ladle eye size throughout a heat is large. Its size can increase by up to 100% for a set flowrate into the element depending on operating conditions and the age of the bubbling element. The results show that dynamic measurement of the ladle eye is required to control the ladle eye effectively. Various measurement options of sound, image and vibration are found in literature. The inherent working conditions of a steel plant cause interference with all signals, the interference is less for image signals.