In Europe, the hot metal desulphurization (HMD) process has traditionally used an injection of either calcium carbide or a calcium carbide-magnesium mix. A recent development is to inject a mixture of quicklime and magnesium into the hot metal. .

Advantages

• the slag volume is reduced.
• the iron losses can be halved, thanks to the lower   viscosity of the slag.
• the cost of using milled lime is far lower than that of other reagents.
• the lime slag can be recycled.

Desulphurising with a lime-magnesium mix is therefore highly cost-effective.

Quicklime is an important active product in eliminating silicon and phosphorus. The lime combines with these impurities to form a basic slag. Lime quality is essential in producing a high quality slag which is easy to handle and treat, as well as being environmentally friendly.

It is also common practice to add soft- and hard-burned dolomite, either in its pure form or in a lime-dolime mix, as they are beneficial to the steel refining process. Indeed, dolime makes slag formation quicker which, in turn, makes foaming swifter and speeds up this stage of the process.

Calcined dolomite also extends the lifespan of refractory linings in converters, protecting them from the aggressive effect of certain impurities present in the hot metal. In fact, adding dolime will create MgO in solution in the slag, which provides an excellent buffering capacity as MgO particles in suspension provide excellent coating protection. Any excess MgO precipitates, protecting refractories and tap holes, reducing the need for gunning and repairs.

Tailored mixes, based on lime and dolime, have been specially developed for ladle metallurgy processes where they act as synthetic slags.

Quicklime is required for slag formation and further sulphur elimination. Dolime is used for swift slag formation and refractory protection.

The beneficial effects of dolime in the steel refining process lead to gains in several areas. The increased process speed boosts productivity and improves iron yield. Time and productivity are also gained through the reduction in downtime for repairs and maintenance of the refractories.

Effluent handling is a major issue for steelmakers. In several areas of the steel plant, fumes, water and by-products need to be treated so that they meet strict emission levels. NikiLime's steel and environmental specialists will work hand in hand with you to develop products which can help you to comply with this legislation effectively and economically.

Treatment of fumes

The very low emission levels which are being imposed for flue-gases, as well as for dioxins and furans, call for a highly effective reagent, and a process that can easily be incorporated into existing installations. For flus-gas treatment in a dry sorption system, SO₂ and other acid gases can be neutralised with hydrated lime.

To content with dioxins and furans, NikiLime delivers tailor-made mixtures of lime with activated carbon, lignite coke or bentonite, which that combine the neutralizing effect of lime and with the micro-pollutant capturing power of the additives. This formula means you avoid the negative side-effects associated with injection of pure activated carbon. Scrubbing fumes is an alternative process to dry sorption. The resulting acidic waters can be neutralized with lime.