Desulfurization Process, Dephosphorization, and Secondary Refining

Performance of Tecnosulfur Products

The search for efficiency in the desulfurization process (reduction in the sulfur content) of pig iron led to new procedures and equipment innovations, which significantly increased the final quality of steel and reduced the consumption of power, in addition to turning toxic waste into inert material. Current desulfurization processes use highly reactive desulfurization agents consisting of calcium oxide, calcium carbide, metallic magnesium, and other elements that react with the metal’s sulfur by turning it into sulfide and converting it into slag.

Since the reducing environment is an essential factor for the desulfurization reaction, the processes require, in addition to balanced compounds, a controlled, continuous, homogenous addition of the agents to the metal. For that purpose, an inert gas (Nitrogen) carries and supplies the desulfurization agent. Tecnosulfur desulfurization operations include everything from the simple process of adding the agent into the pig iron ladle to the more sophisticated method of deep injection through the immersion of a refractory rotary spear in torpedo cars or ladles.

The dephosphorization processes (reduction in the phosphorus content) of pig iron consist of oxidizing the phosphorus and combining it with calcium and other components, which are injected into the hot metal deeply, resulting in compounds transferred to the slag and, thus, removed from the metal.

Complementary desulfurization treatments, final adjustments of the chemical composition, and control of inclusions occur in the secondary refining of steel. Typically used equipment allows for the electric (ladle furnace) or chemical (CAS-OB, AHF, or IRUT) heating or simply bubbling inert gas. The chemical composition is adjusted by adding alloys through silos or wires. Ancillary injection equipment can be used to employ micropulverized desulfurization agents.

Molten pig iron is the primary raw material in steel manufacturing and requires increasing resistance and applicability. As a result, demand for desulfurization and dephosphorization processes is growing. High contents of phosphorus, sulfur, and other non-metallic inclusions in the steel lead to more hot shortness and less resistance to impacts, among other losses.

Tecnosulfur products perform throughout transforming pig iron into molten steel, beginning with reducing the content of sulfur found in the pig iron at the Desulfurization Station. Afterward, the dephosphorization agent is applied to the pig iron at the Dephosphorization Station using initial refining to reduce the phosphorus content. Then the pig iron goes to the still mill’s converters or electric furnaces and is transformed into steel. Next, the steel goes to the ladle furnace, the bubbling station, or chemical heating to apply synthetic slag as second refining or have a micropulverized desulfurization agent injected. The next step is vacuum degassing to refine steel for the third time using other synthetic slag specifications. Finally, the steel goes to the rolling/drawing chain.