Numerical Simulation of a Pusher-Type Reheat Furnace for Optimizing Product Quality and Energy Efficiency
Abstract
Reheating furnaces are used by steel plants for the hot rolling process. The hot rolling stage transforms slabs produced by the steelmaking stage into the reheating process in order to preheat the slabs to the target rolling temperature. Different operating conditions could affect the combustion and flow field characteristics of the gas environment inside the furnace, which will eventually affect the slab temperature distribution. Furthermore, as the level of temperature uniformity of the slab at the discharge door will determine the products quality, the slab quality must be tracked during the whole heating process. In addition, slab heating process is critical to analyze due to some existing issues such as uneven temperature distribution on slab surface, the coiling edge of slab caused by extreme high temperature, and the low temperature effects of skids. However, experimental approaches are limited by the time requirements and the influence on the operating conditions. Methods to quickly predict the furnace environment and condition of the slab surface are required to help adjust practical operation. Therefore, a three-dimensional transient Computational Fluid Dynamics (CFD) model of an industrial pusher-type reheating furnace was developed to simulate the flow characteristics, combustion process, and multi-scale heat transfer inside the reheating furnace to investigate gas environment effects to the slab temperature. This furnace contains a preheating zone, heating zone, and soaking zones with several top and bottom burners. The model simulates the slab heating process during a certain time period with full load natural gas combustion. The operation process was modeled with specific slab line-ups and fuel input conditions. The model was validated with furnace thermocouple readings, laser species measurement, and industrial software. This model can predict the spatial and temporal gas temperature field in the furnace and the temperature evolution of the slab as it travels through the furnace. The characteristics of the slab heating process were investigated by correlating the gas environment and slab temperature. Parametric studies of different slab travel speeds, different sizes of supporting structures, and different skid temperature distributions were conducted to explore the causes and solutions for existing issues. It was found that the slab travel speed would affect the residence time of the slab in different zones. Thus, the slab temperature changes over time will be different due to different gas temperatures in different zones. The supports and skid structures significantly affect the flow field because of their locations and will even split the flames. The skid temperature distribution would directly affect the skid marks at the bottom surface of the slabs, which will cause unevenness of slab temperature. Based on the parametric studies, potential operation changes will be discussed for optimization.
Degree
M.S.M.E.
Advisors
Zhou, Purdue University.
Subject Area
Mechanical engineering
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