Greater hot metal yield increases production efficiency in steelmaking

In a project with SSAB, Swerim has shown how injection of reagents reduces hot metal losses.

Demand for steel with superior mechanical properties has increased dramatically. It is essential to minimize the content of impurities, such as sulphur, in the steel. Efficient desulphurization is therefore an important step in steelmaking.

Lost iron via slag raking

During desulphurization different reagents (chemical compounds) affect the amount of slag that is formed and how much iron is entrapped in the slag. The slag normally contains 50–70 % iron. When it is removed (via slag raking) much iron is lost. Some is entrapped in the slag and some is drawn off during slag raking.

The results of a project led by Swerim in collaboration with SSAB in Luleå show that iron losses are significantly reduced when nepheline syenite is added to the reagent calcium carbide during desulphurization.

25 percent of reduced losses

But since the slag is more fine-grained, it can be removed more effectively with more iron remaining in the melt. Hot metal losses after slag raking therefore decrease by about 25 %. Improved hot metal yield means better production efficiency and reduced intermediate storage.

“We have tried to establish a basis for meeting new quality requirements in conjunction with desulphurization and slag raking,” says Anna Carlsson Dahlberg of SSAB, Luleå.

“Together with Swerim, we have had the opportunity to fine tune our process and find new ways of reducing iron losses.”

The study has been funded by the Swedish Energy Agency via Jernkontoret. The other project partners are SKW Metallurgy Sweden, Sibelco Nordic and KTH.