INVESTIGATIONS TO IMPROVE THE ENERGY EFFI CIENCY AND TEMPERATURE HOMOGENEITY IN REHEATING FURNACES

Within the scope of extensive experiments, the flow conditions at roof -mounted jet burners were first of all examined. Based upon this, simu lation experiments were conducted using physical rolling mill furnace models. These yielded universal valid information about the energy con sumption and the temperature homogeneity inside the furnace as well as inside the slab and transfer bar. With the aid of the model supported calculations and special measurements at the walking-beam furnaces of a hot strip mill it was possible, in a second step, to selectively ch ange the furnace operating mode. Important elements of the new control strategy included an additionally installed thermocouple at the centr e of the lower furnace and an airfuel ratio setpoint independent of th e furnace capacity. Both permitted a more effective mode of furnace op eration. It was possible, particularly when throughputs were low, to d emonstrate a lower energy consumption, a more homogeneous slab tempera ture, and an improved quality of combustion.