Slag is usually a mixture of metal oxides and silicon dioxide. However, slags can contain metal sulfides and elemental metals. Cleator Moor slag contained high concentrations of sulfides, and tragically resulted in the death of a family at Bowthorn.
During smelting, when ore is exposed to high temperatures, impurities are separated from the molten metal and can be removed.
As the slag is channeled out of the furnace, water is poured over it. This rapid cooling, often from a temperature of around 2,600 °F (1,430 °C), is the start of the granulating process. This process causes several chemical reactions to take place within the slag, and gives the material cementitious properties.
The water carries the slag in its slurry format to a large agitation tank, from where it is pumped along a piping system into a number of gravel based filter beds. The filter beds then retain the slag granules, while the water drains away and is returned to the system.
Workmen from Crowgarth Number 4 Pit, sat upon Slag |