PURPOSE: To lower the temperature near a furnace wall brickwork, solidify molten sludge, prevent slag deposit to the furnace wall, and make it possible to operate continuously by blowing in low pressure steam from the furnace top section of the combustion exhaust gas outlet section of a melting furnace.

CONSTITUTION: The periphery of a combustion gas discharge port 3 is at about 1400°C and the slag is in molten state. In this state slag deposit 7 are attached to the combustion gas discharge port 3 and it will finally close the combustion gas discharge port 3 of a melting furnace. Now, if the brick faces are cooled by blowing low pressure steam of an exhaust gas heat boiler from a stem pipe 6 provided through the brickwork of the combustion gas discharge port 3, the temperature near the furnace wall at the combustion gas discharge port 3 drops by about 200°C and it is possible to avoid the slag deposit and it is possible to operate the furnace continuously.