Method of heating up furnace bottom, and burner lance used in the method

A burner lance, characterized in that

• the burner lance has a double tube structure including an inner tube and an outer tube through which gas passes,
• the burner lance is provided with a cap for covering ends of the inner tube and the outer tube, the cap having a structure in which, when the cap exists, gas blown in from the inner tube is discharged from the outer tube without leaking to outside, or the gas blown in from the outer tube is discharged from the inner tube without leaking to the outside, and when the cap does not exist, the gas blown in from the inner tube or the outer tube is discharged from an end of the inner tube or the outer tube to the outside of the burner lance, wherein
• when the burner lance is installed in a burner lance insertion hole, and when a gap between the installed burner lance and a furnace exterior side of a tap hole is filled with a refractory, the cap has a function of cooling the burner lance by passing gas through the inner tube or the outer tube in a state where the cap exists, and after the gap between the installed burner lance and the furnace exterior side of the tap hole is filled with the refractory, the cap is configured to be removed, the cap has a function of heating up the furnace bottom by blowing in the gas for heating into the furnace from the burner lance after the cap is removed,
• wherein the cap is removable by melting the cap with heat in the furnace, or by passing oxidizing gas from the inner tube or the outer tube to melt the cap with heat generated by oxidization of the cap.