News Date:2015-09-14
Slag is a partially vitreousby-productof the process ofsmeltingore, which separates the desiredmetalfraction from the unwanted fraction. Slag is usually a mixture of metaloxidesandsilicon dioxide. However, slags can contain metalsulfidesand metalatomsin the elemental form. While slags are generally used to remove waste in metal smelting, they can also serve other purposes, such as assisting in thetemperature controlof the smelting, and minimizing any re-oxidation of the final liquid metal product before the molten metal is removed from the furnace and used to make solid metal.
In nature, the ores of metals such asiron,copper,lead,nickeland other metals are found in impure states, oftenoxidizedand mixed in withsilicatesof other metals. During smelting, when the ore is exposed to high temperatures, these impurities are separated from the molten metal and can be removed. Slag is the collection of compounds that are removed. In many smelting processes, oxides are introduced to control the slag chemistry, assisting in the removal of impurities and protecting the furnacerefractorylining from excessive wear. In this case, the slag is termedsynthetic. A good example is steelmaking slag:quicklimeandmagnesiteare introduced for refractory protection, neutralising thealuminaandsilicaseparated from the metal, and assist in the removal of sulfur and phosphorus from the steel.
Ferrousandnon-ferroussmelting processes produce different slags. The smelting of copper and lead in non-ferrous smelting, for instance, is designed to remove the iron and silica that often occurs with those ores, and separates them as iron-silicate-based slags. Slag fromsteel millsin ferrous smelting, on the other hand, is designed to minimize iron loss and so mainly contains oxides of calcium,silicon,magnesium, and aluminium. Any sandy component or quartz component of the original ore automatically carries through the smelting process as silicon dioxide.
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 material, and gives the slag its 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 filters away and is returned to the system.
When the filtering process is complete, the remaining slag granules, which now give the appearance of coarse beach sand, can be scooped out of the filter bed and transferred t
Ground granulated slag is often used in concrete in combination withPortland cementas part of a blendedcement. Ground granulated slag reacts with water to produce cementitious properties. Concrete containing ground granulated slag develops strength over a longer period, leading to reduced permeability and better durability. Since the unit volume of Portland cement is reduced, this concrete is less vulnerable toalkali-silicaandsulfate attack.[citation needed]
This previously unwanted recycled product is used in the manufacture of high performance concretes, especially those used in the construction of bridges and coastal features, where its low permeability and greater resistance to chlorides and sulfates can help to reduce corrosive action and deterioration of the structure. The slag can also be used to create fibers used as an insulation material namedslag wool.
In the next time, we will have more share about the solution of the slag production line project.
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