Products

Steel and iron slag

Oxide dusts, sludges, scales, slags and spent refractories are co-products of the iron and steel manufacturing process.
These residues generally represent 6-7% of the whole steel production.
Their production arises from the conversion of ores to iron, hot iron to steel, and from melting scrap in an electric arc furnace or from the subsequent treatment of crude steel.

These by-products, especially in the past, were classified as “waste” and often stocked and or disposed in landfills, although they could be a valuable secondary raw material when recycled and properly reused. If treated correctly, they can be utilized both in metallurgical processes and in other industrial applications.


Each year, millions of tonnes of these by-products are generated in Europe as per the tab below:

BLAST FURNACE
IRON GENERATION
 
BLAST FURNACE SLAG
< 2% Iron Content
FLUE DUST
10 to 35% Iron Content
Carbon Content
(30-75% under the form of coke brezee)
SLUDGE
10 to 48% Iron
 
BASIC OXIGEN FURNACE
STEEL GENERATION
 
SLAG
20- 25% Iron Content
DUST
60-67% Iron Content
SLUDGE
50-80% Iron Content
 
ELETRIC ARC FURNACE
STEEL GENERATION
 
EAF SLAG
20- 25% Iron Content
EAF DUST
20 - 40% Iron Content
 
FINISHING AND LAMINATION
 
MILL SCALE
60-74% Iron Content
SLUDGE
30-60 % Iron Content
PICKLE LIQUOR
(Hazardous Waste)
1.5lb/gallon Kg Fe2O3
The slags can basically be distinguished in BLAST FURNACE SLAG and STEELMAKING SLAG. The chemical properties of different types of ferrous slag vary depending on the specific production process within they are generated. They can be defined as non-metallic by-products consisting essentially of compounds of silica, alumina, lime, magnesia, iron oxides and manganese oxides, developed during the refining of crude iron products to steel. They are averagely made up by 90% oxides therefore calcium oxide (CaO) and silica (SiO2) are their primary components. Other components include alumina (Al2O3) and magnesium oxide (MgO).
 
   
Here below summarized the different slag typologies:
BLAST FURNACE SLAG: is the result of the thermo-chemical reduction in the blast furnace. The slag is separated by the hot metal due to their density difference and tapped at 1500°C .
• GRANULATED BLAST FURNACE SLAG (GBFS): it is granular glassy product (0-5mm), with latent hydraulic properties. Since it is an amorphous, coarse sand sized material exhibiting hydraulic cementations features in can be prepared and then used for the production of Portland Cement and Blast Furnace
• AIRCOOLED BLAST FURNACE SLAG (ABS): formed when the liquid slag is allowed to cool under atmospheric conditions. The material can then be sized to produce aggregates for concrete production and aggregates for infrastructure.

STEELMAKING SLAG:
• ELETRIC ARC FURNACE SLAG: is produced within the EAF during the production of steel. This slag contains low percentage of amorphous silica and high content of FEO and P2O5 and consequently has lower basicity and pozzolanic activities in comparison with Blast Furnace Slag (BFS). This cubic shape material has an excellent affinity to bitumen since it is a resistant and no porous material and ideal for the adding as an aggregate in the asphalt
• SECONDARY METALLURGICAL SLAG (SECS): is generated in secondary metallurgical making procedure during the production and refining of high-quality steels. It has a high CaO-contents and low oxidation levels. It is usually recycled in other metallurgical processes.
• BASIC OXYGEN FURNACE SLAG (BOS): is generated within a basic oxygen furnace (Linz-Donawitz process) during the production of hot metal. Basic oxygen furnace slag confers strength and skid resistance and thus makes it an ideal aggregate for road constructions and surface layers for high skid resistance.
 
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