Ladle skim dross, also called ladle slag or ladle foam slag, is a typical dross generated during steelmaking process. It is also an important type of steelmaking slag.
Ladle skim dross is generated when the liquid steel is processed in the ladle refining and steelmaking furnace, especially when un-deoxigated molten steel is present in addition to forging and blowing up the required oxygen, nitrogen and other elements. The chemical composition of the dross depends on the steelmaking process, such as the oxygen content of the steel, the nitride content and the amount of Si, C and scrap. When the nitrogen content of the steel is about 0.01%, the amount of ladle skim dross will be larger.
Slag is usually dumped from the ladle from the slag hole in the bottom of the ladle and solidifies into flat pieces which are dug up from the slag dump and goes to the slag warehouse.
The chemical composition of ladle skim dross is complex and varies greatly [7]. The major chemical components of the ladle skim dross are taken as main ingredients of slag tap - water, CaO, SiO2, FeO, MgO, P2O5 and some other components such as Al2O3, TiO2, MnO etc. In addition, ladle skim dross also contains flux elements and a certain amount of metal (mainly iron) inclusions which can be used as reducing agent or alloy elements in the steelmaking process.
The properties of ladle skim dross have strong influence on the performance of the steelmaking process and steel products; the beneficial effects of ladle skim dross in steelmaking performances such as deoxidation, removal of harmful elements like P, S and Mn and improving slag floatability have been documented in [6].
Ladle skim dross can be used as a slag modifier in steelmaking and as an additive in smelting and refining processes. It can also be used to produce slag cement, as a refractory material, and for other applications.
In steelmaking process, the main function of ladle skim dross is to reduce energy consumption, improve quality and efficient of the products, and contribute to reducing environmental pollution. It is increasingly used by steelmakers as a flux-transform material to reduce energy consumption and improve the quality of steel.
However, ladle skim dross is a hazardous waste that is difficult to dispose of. Ladle skim dross contains high content of phosphorous and sulfur, as well as heavy metals, while these materials tend to volatilize in water and cause environmental pollution. Therefore, it is important to develop appropriate environmental technology to dispose ladle skim dross, such as chemical stabilization and physical and chemical combination treatment. Moreover, to reduce the pollution from ladle skim dross and to make the process more efficient and cost-effective, it is necessary to closely monitor the fume and emissions generated in the steelmaking process, and for proper disposal of the dross materials.
