Optimal heating and energy management for slabs in a reheating furnace

Optimal heating for slabs in a reheating furnace is investigated numerically to aid in managing energy consumption of the reheating furnace in a hot strip mill, where an arctangent function is applied as the heating curve. Particular attention is paid to the relationship among the temperature uniformity, discharging target temperature and retention time of the slabs. The results indicate that the temperature difference between the slab surface and the core increases rapidly in the initial period and the maximum value of the temperature difference is close to the inflection point of the heating curve. After that, the internal temperature tends to be uniform. For a given retention time of slabs, it is difficult to simultaneously reach the requirements of discharging target temperature and desired temperature uniformity. A method to evaluate the optimal heating time is thus developed, using the Newton scheme. Some correlations linking the desired temperature uniformity and optimal heating time are established. They suggest that heating thinner slabs in the reheating furnace can facilitate employing energy more efficiently in contrast to heating thicker slabs.