Melting method for an electric arc furnace with alternative sources of energy and relative electric arc furnace

摘要

Melting method for an electric arc furnace with alternative sources of energy for the melting of iron-based alloys, the electric furnace (10) including tuyéres (13) positioned on the bottom to deliver oxygen, at least one tuyére (15) to deliver coal dust which works in the area of contact between the bath of molten metal (16) and the layer of slag (22), at least one supersonic lance (12) cooperating with a lance (29) to deliver coal dust, these lances (12, 29) having a working position (12c, 29c) in which the supersonic lance (12) is positioned in close proximity to the surface of the molten metal (16) and the lance (29) to deliver coal dust is positioned in the vicinity of the surface of the layer of slag (22), and a plurality of burners (28) positioned on the cooled sidewalls (31) of the furnace (10) and delivering oxygen-based gases and combustible substances, whereby at least two first burners (28) work with the action of one burner supporting the action of the next one, the furnace (10) being charged with one or more charges which provide for a first step of start-up of the melting and a second step of melting, a refining step and a tapping step being included, in which method in the first step of start-up of the melting at least one second burner (28e) collaborates in freeing quickly the path of introduction of the supersonic lance (12) and of the lance (29) to deliver coal dust, at least one third burner (28a) is directed towards the centre of the furnace (10) in cooperation with the area of the emerging of the oxygen delivered by an oxygen tuyére (13) to the surface of the bath, the burners (28) work in the first step as burners and in the second step as subsonic oxygen lances and in the third step are substantially shut off, the oxygen tuyéres (13) deliver oxygen in a great quantity and at a low pressure, the delivery of the carbonaceous substances is directed towards the centre of the furnace (10) and takes action in cooperation with the slag (22) both above the slag and between the slag and the molten metal, the reactions Fe + O = FeO, FeO + C = Fe + CO are caused to take place within the bath of molten metal (16) just above the surface of the molten metal (16) and at about the thickness of the slag (22), which is processed to be foamy slag, and the reaction CO + O = CO2 is caused to take place just above the surface of the molten metal (16) and at about the thickness of the slag (22). Electric arc furnace which carries out the above method.