The furnace or convertor slag is held back during tapping, as far as possible, or removed by deslagging after tap. The residual tapping slag is treated with aluminium pellets to reduce any reducible oxides.Synthetic slag is added to bring the top slag composition within the required range for effective desulphurisation.

The ladle is located in the treatment station, and then sealed as far as possible by a ladle cover. The ladle cover serves two functions, the first being to capture and remove fume generated during the process. The fume is removed by a duct which connects the ladle cover to a fabric filter duct cleaning unit. The scond function of the ladle cover is to minimize atmospheric contract with the surface of the steel, which would cause oxidation and nitrogen pick up. For this reason, the ladle cover design is relatively sophisticated.Fluxing of the ladle top slag is done by argon stirring, either by top lance or bottom porous plug. When the top slag is in the required condition, desulphurisation by injection begins.

A lime fluospar mixture, which may be prefused is injected into the steel through an immersed lance. Argon is used as a carrier gas. To increase the effectiveness, the lance tips is close to the bottom of the ladle. Calcium compounds are also injected, either in combination with lime-spar (co-injection) or separately (mono or sequential injection).

The amount of reagent injected is obviously dependant on the initial sulphur level and final required level. Calcium is also used to modify the shape of the remaining sulphides. Both the total amount and the rate of injection are predetermined and controlled.

At the end of the injection the lance is automatically retracted, and a sample is taken. The ladle cover is than raised and the ladle removed.

The desulphurisation process is obviously to steel grades where low sulphur content and /or controlled sulphide shape are important. This is particularly true of heavy plate grades and certain pipeline steels.

Any grade of steel where uniform mechanical properties in all direction is important would benefit from this process.