Thermal tracking of ladles

S. FERRO; C. CICUTTI; P. GALLIANO

Toronto

Conferencia; STEELSIM 19 - 8th International Conference on Modeling and Simulation of Metallurgical Processes in Steelmaking; 2019

STEELSIM

Thermal evolution of the refractory lining in the ladles is calculated as they move through the different stations of the steel plant. Temperature equations are solved in the ladle wall, accounting for the properties of the different layers of lining. Different boundary conditions are imposed to the equations according to the process the ladle is undergoing. Temperature measurements performed in the steel shop were used to validate the modelKnowledge of the thermal condition of ladles becomes primarily relevant when deciding the treatment the heat is going to receive in the ladle furnace. A ladle that has been without steel for a long period before tapping requires a higher amount of electric energy since ?cold? refractories will withdraw more heat from the steel. Giving standard treatment to a ladle that is not in thermal regime leads to a cold heat with the consequent problems for the continuous caster: risk of freezing and the need to increase the casting speed. On the other hand, when special treatment is applied to a ladle which does not require additional energy, steel becomes unnecessarily hot. This means not only a waste of energy but also more complications for the caster where the risk of breakouts increases and the casting speed must be reduced. Complementary the tapping temperature is usually adjusted to the thermal status of the ladle. Steel is tapped at a higher temperature in an out-of-regime ladle than in a ladle in regime. In order to determine which ladles should be considered out of thermal regime, plants usually take into account only the time elapsed between casting and tapping. Ladles are regarded as out of regime if this time is longer than an established threshold time. This method ?which does take into account the main factor? has some drawbacks: On one hand, it does not consider the eventual actions of preheaters nor the presence/absence of a lid. Secondly, it does not consider events previous to last tapping. Finally, it does not provide a continuous indicator of thermal regime. For these reasons several authors [1-5] have studied the whole thermal cycle of the ladle (that is the thermal evolution of the temperature of the ladle as it moves from one station to another in the steel shop) in order to have a better indicator of its thermal status. In the present work, a methodology is presented to continuously track the thermal status of the ladle by solving the time dependent thermal equation in each station of the steel shop. The model receives information of events that are relevant from the thermal point of view (tapping beginning/end, pre-heaters ignition, lid placement, and so on) and updates the status of the ladle. This information could be used to decide the treatment to be given to the heat.