Smelting unit for steel production with a tap weight of between 60 t and 350 t

A smelting unit (1) for steel production with a tap weight between 60 t and 350 t, comprising:

• a lower furnace (2),
• wherein the lower furnace (2) is refractory-lined and includes a tapping hole (3),
• wherein a receptacle bottom (4) of the lower furnace (2) substantially corresponds to a spherically shaped shell section,
• wherein a sphere from which the spherically shaped shell section originates geometrically has a radius≥5 m and ≤15 m, and
• wherein a distance (dS) between a lowest point of the receptacle bottom (4) in the lower furnace (2) and a surface (6) of a melt (7) located therein in an operating state is ≥0.5 m and ≤1.5 m;
• an upper furnace (8),
• wherein the upper furnace (8) is substantially cylindrical and water-cooled, and
• wherein a height (hO) of the upper furnace (8) is ≥3 m and a radius (rO) of the upper furnace (8) is ≥2 m;
• a first cover (9) closing the upper furnace (8) at a top, having an exhaust gas nozzle (10) and at least one opening (11) for inserting a top lance (12) into the smelting unit (1)
• wherein the top lance (12) can be brought into a working position through the opening (11) in the first cover (9), and
• wherein the top lance (12) is rotatable around a longitudinal axis (17) of the top lance (12), is rotatable around a vertical axis (18), and/or is pivotable around a horizontal axis (19) during operation of the smelting unit (1), and
• wherein a distance (hS) between the surface (6) of the melt (7) and a tip (20) of the top lance (12) can be varied;
• a second cover (13) closing the upper furnace (8) at the top, having at least one opening (14) for passage of one or more electrodes (27),
• wherein the lower furnace (2) and the upper furnace (8) are designed for operation both with and without a melt current, and
• wherein the first cover (9) can be exchanged for the second cover (13) during operation of the smelting unit (1);
• a plurality of side wall injectors (15) arranged radially circumferentially in the upper furnace (8) for injecting a process gas,
• wherein the side wall injectors (15) can be pivoted horizontally and/or vertically by up to ±5°;
• and
• a process gas control (16) for adjusting a pressure and/or a volume flow of the process gas for the top lance (12) and the side wall injectors (15).

A method, comprising:

• providing smelting unit (1) for steel production with a tap weight between 60 t and 350 t, including
• a lower furnace (2),
• wherein the lower furnace (2) is refractory-lined and includes a tapping hole (3),
• wherein a receptacle bottom (4) of the lower furnace (2) substantially corresponds to a spherically shaped shell section and
• wherein a sphere from which the spherically shaped shell section originates geometrically has a radius≥5 m and ≤15 m, and
• wherein a distance (dS) between a lowest point of the receptacle bottom (4) in the lower furnace (2) and a surface (6) of a melt (7) located therein in an operating state is ≥0.5 m and ≤1.5 m;
• an upper furnace (8),
• wherein the upper furnace (8) is substantially cylindrical and water-cooled, and
• wherein a height (hO) of the upper furnace (8) is ≥3 m and a radius (rO) of the upper furnace (8) is ≥2 m;
• a first cover (9) closing the upper furnace (8) at a top, having an exhaust gas nozzle (10) and at least one opening (11) for inserting a top lance (12) into the smelting unit (1)
• wherein the top lance (12) can be brought into a working position through the opening (11) in the first cover (9), and
• wherein the top lance (12) is rotatable around a longitudinal axis (17) of the top lance (12), is rotatable around a vertical axis (18), and/or is pivotable around a horizontal axis (19) during operation of the smelting unit (1), and
• wherein a distance (hS) between the surface (6) of the melt (7) and a tip (20) of the top lance (12) can be varied;
• a second cover (13) closing the upper furnace (8) at the top, having at least one opening (14) for passage of one or more electrodes (27),
• wherein the lower furnace (2) and the upper furnace (8) are designed for operation both with and without a melt current, and
• wherein the first cover (9) can be exchanged for the second cover (13) during operation of the smelting unit (1);
• a plurality of side wall injectors (15) arranged radially circumferentially in the upper furnace (8) for injecting a process gas,
• wherein the side wall injectors (15) can be pivoted horizontally and/or vertically by up to +5°;
• and
• a process gas control (16) for adjusting a pressure and/or a volume flow of the process gas for the top lance (12) and the side wall injectors (15);
• and
• operating the smelting unit by performing the following steps:
• a) creating the melt (7) having the surface (6);
• b) injecting the process gas onto the surface (6) by the side wall injectors (15);
• c) lowering the top lance (12) into a first working position (23) and injecting the process gas onto the surface (6) through the top lance (12);
• d) aligning the top lance (12) by rotating, changing the distance (hS), and/or pivoting the top lance (12) to a second working position (24), such that
• a core of an impact cavity (25) produced by the top lance (12) lies between two adjacent impact cavities (26) of the side wall injectors (15), or
• the core of the impact cavity (25) produced by the top lance (15) lies within a region of one of impact cavities (26) of the side wall injectors (15);
• e) adjusting volume flows of the process gas of the side wall injectors (15) and the top lance (12), such that a total required quantity or a total required volume flow of the process gas is applied to the surface (6).