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Iron Refining in (pyro-)metallurgical plants

Many (pyro-)metallurgical plants produce liquid pig iron as a by-product which is casted into pig iron ingots. This pig iron often has a poor quality which requires refining steps to bring it into line with specifications. Küttner offers solutions for the following refining tasks using ladles as refining vessels and injection technology:

Recarburization (Re-C)
Depending on the melting process, the carbon content of the hot metal often has to be increased, especially for the production of casted pig iron. This is done by either feeding fine coal or char into the ladle while the melt is intensively stirred with gas or by injecting a carbon source into the melt.

Desulphurization (De-S)
Lime (CaO), magnesium (Mg), calcium carbide (CaC2), soda (Na2CO3) or mixtures thereof are injected as a gas/solid mixture in dense phase mode deep into the hot metal. The sulphur is captured in a generated slag, which is mechanically skimmed off from the bath surface.

Desiliconization (De-Si)
Desiliconization is an essential preconditional step before efficient dephosphorization can take place. A mixture of lime and iron oxide is injected into the ladle in order to oxidize the dissolved silicon into the slag. Additional soft blowing of oxygen can be used to support the process. Before proceeding with the next process step, the slag is mechanically skimmed off from the bath surface.

Dephosphorization (De-P)
Removal of phosphorous from the pig iron is applied by injecting a mixture of lime and iron oxide into the metal which binds the generated phosphorous oxide in the slag. Again the slag is mechanically skimmed off from the bath surface.

Resiliconization (Re-Si)
The production of pig iron ingots specify certain silicon contents in the final product. As the silicon content can be too low, in particular when dephosphorization has been applied, it has to be increased by adding a suitable source of silicon, typically FeSi, while intensive gas stirring is applied.

Chemical Heating
Chemical heating is applied to adjust the pig iron temperature in a suitable range for casting, in particular if dephosphorization has been applied and caused a significant temperature drop. Aluminum or silicon are used as fuels which are oxidized by pure oxygen.

Deslagging (De-Slag)
A proper mechanical skimming of the process slag from the bath surface is essential for the success of the process step as the slag contains the elements to be removed from the hot metal.

Refining stations which allow more than one of the above mentioned treatments are called multi-refining stations. Küttner is experienced in designing and supplying such small-scale highly integrated multi-refining station especially in existing plants with space constraints.