The TOP lance is an assembly that performs several tasks relevant to the process and procedure. These include:
- heating of the vacuum vessel by means of fuel gas and oxygen after vessel changing or during treatment breaks and
- melting down skulls inside the vessel.
Besides the burner function, the TOP lance can be equipped with an oxygen line. This opens up further possibilities:
- inflating oxygen to adjust the [C]:[O] ratio for optimum decarburization, especially at higher carbon content
- inflating oxygen for alumino-thermal heating of the melt
Furthermore, solids can be injected with the TOP lance. This serves:
- to support the decarburization reaction in order to achieve an extremely low carbon content if required
- for partial reduction of the S-content (in special cases).
Usually TOP lances are driven into the vessel via a traversing device up to the working position. If the lance is not needed during treatment, it takes up a parking position in the vessel.
The functions oxygen bubbles, powder bubbles and gas burner are combined in a multi-function TOP lance. Video cameras can be installed in the lance tip to monitor the process. A short lance design allows oxygen to be blown up at a greater distance even in systems with limited height.