Mineral wool slag is a by-product derived from the production of thermal insulating products. Mineral wool is often defined as any fibrous glassy substance made from minerals (typically natural rock materials such as basalt or diabase) or mineral products such as slag and glass.
Most mineral wool manufactured today is produced from slag or a mixture of slag and rock. Most of the slag used by the industry is generated from integrated iron and steel plants as a blast furnace byproduct from pig iron production.
The first step in the process involves melting the mineral feed. The raw material (slag and rock) is loaded into a cupola in alternating layers with coke at weight ratios of about 5 to 6 parts mineral to 1 part coke. As the coke is ignited and burned, the mineral charge is heated to the molten state at a temperature of 1300 to 1650°C (2400 to 3000°F). Combustion air is supplied through tuyeres located near the bottom of the furnace.
The molten slag, rich in Fe, is tapped from the bottom of the furnace and cooled in place. It is then moved to the processing area for size reduction.
On visual inspection, it appears to be made up of irregular shapes. The max weight of each piece is up to 1 ton. A bespoke preparation or a further crushing might be required, before recycling it in an electric arc furnace.
Its chemical composition is homogeneous and stable with Fe contents in the range of 85-95% and P contents between 0.5% and 3.5%, S around 0.5 and 1% and C% around 1.5 to 2.5%.
Average chemical composition. Please note that these data are believed to be accurate and representative of the average composition.
The mineral wool slag derives from the manufacturing of mineral wool. Rock wool insulation is composed principally of fibres manufactured from a combination of aluminosilicate rock (usually basalt), blast furnace slag, and limestone or dolomite. Binders may or may not be used, depending on the product. Typically, rock wool insulation is comprised of a minimum of 70 - 75 percent natural rock. The byproduct is a ferrous slag which can be utilised in an electric arc furnace to produce crude steel.