DEVICE FOR CONTROLLING TEMPERATURE IN ROLL CHAMBER OF VERTICAL TYPE PLURAL PASS DIRECT-FIRING HEATING FURNACE

摘要

PURPOSE:To suppress effectively oxidation of a steel strip in a furnace even if multiple stages of heating chambers are used by burning non-stoichiometrically the waste combustion gas after after-burning by reducing burners, decreasing the temp. of the same combustion gas with a heat exchanger and blowing said gas into roll chambers. CONSTITUTION:A steel strip 1 enters the inside of a furnace from a sealing device 3, is directionally changed by upper and lower rolls 6, 5 and passes through the inside of three preheating chambers 4 and clean furnace heating chambers 7. The waste combustion gas of the direct firing burners 7a in the chambers 7 heat the strip 1 while said gas flows from the chambers 7 through the chambers 4 to a chimney 17. The after-burner 18 in the upper part of the chamber 4 adjacent to the chamber 7 burns completely the unburned component from the burners 7a. A part of the waste combustion gas to the chimney 17 is fed through recirculating lines 19-21 to a heat exchanger 13 by which said gas is cooled. The cooled gas is increased in pressure by a blower 14 and is fed to roll chambers 12', 12'' to control the temp. thereof. On the other hand, the gas is burned with rich fuel by a reducing burner 16 provided to the line 21 to control the CO value of the gas to be blown to the chamber 12' to a specified value thereby preventing oxidation of the strip 1.