PURPOSE: To heat low temp. heating materials and high temp. heating materials in the same furnace by disposing tubes which are divided to 2 pieces in the in- furnace flame injection positions in front of burners, and performing regulation of flame lengths and direct heating with flames by moving the tubes vertically.
CONSTITUTION: For example, three pieces of tubes 11, 11', 11" are disposed in the in-furnace flame injection positions in front of a burner 15. In the case of direct heating in the high temp. hedating stage, the tubes, 11, 11', 11" are moved downward with vertically moving devices 14, 14', 14" to remove the tubes 11, 11', 11" from the burner 15 to permit direct heating with flames. In the indirect heating stage, the whole of the tubes 11, 11', 11" or the tubes 11, 11' or only the tube 11 is moved upward with the devices 14, 14', 14", whereby the lengths of the tubes are changed according to required flame lengths.
YOSHIBE YASUMASA
MATSUKAWA TOSHIAKI
