Oxy-fuel burner system

A method of modifying an electric arc furnace to include a plurality of oxy-fuel burners which assist in the melting of scrap metal, said furnace including a bottom wall extending to a generally cylindrical side wall, and centrally located electrode means, comprising the steps of:

• (a) providing a plurality of gas burners operable to emit hot combustion gases for melting scrap metal, each of said burners having a firing rate in the range of from about 175,000 to about 350,000 BTU/hr. per ton of furnace capacity;
• (b) securing mounting means to said furnace to adjustably mount each of said burners to said furnace to flow combustion gases into the furnace along a firing direction extending downwardly at an angle of about 45 degrees and across an associated furnace cold spot, said mounting means being adjustable to laterally vary the firing direction of each of said burners toward and away from the center of said furnace and to vertically vary the firing direction of each of said burners upwardly and downwardly;
• (c) selecting a burner firing rate for each of said burners within said firing rate range and operating each of said burners for a firing time of sufficient duration to provide a total heat energy output of from about 250,000 to about 350,000 BTU per ton of furnace capacity;
• (d) operating said furnace to determine the occurrence of any side wall wear locations and unmelted scrap metal locations and the burner primarily affecting such location;
• and
• (e) adjusting said mounting means to substantially eliminate said side wall wear and unmelted scrap metal locations determined in step (d) by varying the lateral alignment of said firing direction of said burner primarily affecting said location and, if such side wall wear or unmelted scrap location persists upon further operation of the furnace, then varying the vertical alignment of said firing direction of the next adjacent upstream burner, and thereby mounting said burners to said furnace and aligning their firing directions to flow combustion gases into said furnace.

A method of melting scrap metal in a burner-assisted electric arc furnace including centrally located electrode means, a side wall and a plurality of oxy-fuel burners arranged to provide a circular flow of combustion gases within said furnace and a melt trench within scrap metal to be melted, said furnace being of the type that receives its total scrap metal charge per heat in a plurality of fractional charges of scrap metal which are each melted during a predetermined charge melting period, said burners being arranged to operate during each charge melting period at a firing rate and time which provide a total heat energy output of from about 250,000 to about 350,000 BTU per ton of furnace capacity, said electrode means being adapted to melt primarily scrap metal located adjacent the furnace center and said burners being adapted to melt primarily scrap metal located adjacent the furnace side wall, comprising the steps of:

• (a) delaying the firing of said burners for a predetermined initial portion of each of said charge melting periods while said electrode means melts a portion of said scrap metal charge;
• (b) firing said burners substantially continuously during the remaining portions of said charge melting periods to complete the melting of substantially all of the side wall scrap metal at substantially the end of each of said charge melting periods as said electrode means completes the melting of substantially all of the center scrap metal to thereby provide an even melt.

A method of melting scrap metal in a burner-assisted electric arc furnace including centrally located electrode means, a side wall and a plurality of oxy-fuel burners arranged to provide a circular flow of combustion gases within said furnace and a melt trench within scrap metal to be melted, said furnace being of the type that receives its total scrap metal charge per heat in a plurality of fractional charges of scrap metal which are each melted during a predetermined charge melting period, said burners being arranged to operate during each charge melting period at a firing rate and time which provide a total heat energy output of from about 250,000 to about 350,000 BTU per ton of furnace capacity, said electrode means being adapted to melt primarily scrap metal located adjacent the furnace center and said burners being adapted to melt primarily scrap metal located adjacent the furnace side wall, comprising performing the following steps in each of said charge periods:

• (a) advancing said electrode means with melting through at least a portion of the total depth of said scrap metal charge at the beginning of said charge melting period before firing said burners;
• and
• (b) firing said burners substantially continuously during the remainder of said charge melting period as said electrode means moves to its final melt position and also continues to operate to melt scrap metal during the remainder of said charge melting period, said burners and electrode respectively completing the melting of substantially all of said side wall and center scrap metal at substantially the end of said charge melting period to provide an even melt.