Method for controlling furnace temperature of multi-zone heating furnace

For use with a multi-zone heating furnace having a plurality of zones, zone temperature sensors for sensing the zone temperatures, zone temperature control means for controlling the zone temperatures based on deviations of the output signals of the zone temperature sensors from set values of the zone temperatures, fuel flow rate control means for controlling flow rates of fuel supplied to burners in the respective zones in response to the output signals of the zone temperature control means, a method of controlling furnace temperatures comprising the steps of:

• (a) computing flow rates of fuel in a plurality of slab temperature rise patterns in which at least one of slabs to be charged into the furnace or remaining in the furnace will be heated to a predetermined slab temperature at discharge;
• (b) selecting a slab temperature rise pattern which results in the minimum one of the fuel flow rates computed in the preceding step;
• (c) predicting a desired discharge temperature of a slab at a predetermined later time from the present point of time based on the slab temperature rise pattern selected in the preceding step;
• (d) performing prediction computation of a slab temperature at a predetermined later time based on the slab temperature at the present point of time;
• (e) finding a deviation between the desired discharge temperature predicted in step (c) and the slab temperature computed in step (d);
• (f) correcting a set point temperature of an associated zone based on the deviation in temperature obtained in step (e);
• and
• (g) controlling the associated zone temperature so as to cause same to correspond to the set point temperature thus corrected.