Melter Slag (MS)

Brief Description

Melter Slag is a co-product of the steel making process that converts iron sand to iron by adding coal and limestone. Melter slag differs from other slags in that the major oxides (calcium oxide and magnesium oxide) do not occur in their free form in the slag. Unlike conventional blast furnace slag (BFS), the iron sand-based material can not be granulated, which precludes its use as a cement replacement in concrete manufacture.

Physical Description

The chemistry of melter slag differs from other variants of slag. This product consists of a high percentage of titanium and quantities of magnesium oxide and alumina typically higher than the industry norm. In contrast, the material has a characteristically low amount of silica, calcium oxide and sulphur.

Method of Manufacture

Iron sands are mined using conventional earthmoving equipment before being separated magnetically, by creating a slurry and running it over magnetic drums. This is followed by gravimetric separation through a series of cones and spiral separators, where the heavier iron-bearing materials gravitate toward the centre, while residual clays and silts gravitate outwards. The slurry is then pumped 18 kilometres to the steel mill through an underground pipeline, where it is finally dewatered and stockpiled.

To convert the iron, a direct reduction process is used, adding coal and limestone to the irons before pre-heating them in four multi-hearth furnaces. This drives off the volatile constituents of the coal. The material then enters one of four rotary kilns where the direct reduction takes place over a period of eight hours. The directly reduced product is then melted in one of two large electric melters.

Diagram of Manufacture

Applications

Typical uses for Melter Slag include:

• Filtration aggregate
• Road base course and sub bases
• Skid resistant surfacing for asphalt and chip seals
• Drainage and water filtering media
• Hardfill for civil construction
• Rural driveway and farm track construction