Comprehensive CFD Model toward the Optimization of the Batch Annealing Cycle

摘要

Batch annealing is one of the critical unit operations involved in the production of cold rolled and annealed flat steel coils. It influences the key plant performance parameters such as energy, productivity, and product Quality. In the batch annealing process, a typical set of 4-5 steel coils separated by a convector plate are piled on a work base. Sealed inner cover encloses the coils where an inert gas is circulated during the annealing process. The coils are heated due to the radiation from the cover wall and convection from the circulated gases in addition to the conduction within the coil body. High speed fan is used to circulate the inert gases to force convection in order to provide an acceptable temperature growth of the outer and inner side of the coils within the process time. During the batch annealing process due to the mass weight of the coil, a hot and cold spots would be generated near the coil surface and at the coil core respectively. The cycle design is all about controlling the temperature evolution to minimize the variation between the hot and cold spots temperature within the coil, which control the product quality and mechanical properties. Increasing the soaking time would homogenous the coil temperature and reduce the microstructural and mechanical properties variation, however, it would dramatically affect the furnace productivity. Annealing cycle is usually long due to the mass weight of the processed steel coils which would consume lot of energy and processing time. Therefore, any reduction in in heating cycle time would lead to great energy savings. Therefore, the development of a mathematical simulation model would help to optimize the process and lead to valuable energy saving.