AEIFOROS S.A. is an industrial by-products- and wastes- recycling company which offers solutions for the valorization of these materials as secondary resources, raw materials and solid fuels for other industries according to the principles of circular economy while promoting industrial symbiosis.
Ladle furnace slag is a by-product of carbon steel manufacturing produced during the second stage of steelmaking in the ladles where the chemical composition of steel is adjusted prior to casting of steel semi-finished products. The slag produced in the ladle has a high content of calcium (around 40%) due to addition of calcium-containing fluxes. Other metallic oxides contained in the ladle furnace slag in significant amounts are iron oxides and silicon oxides. Calcium, iron and silicon oxides are sought by cement industry, which assesses raw materials, including natural resources from mining, according to their content in oxides. Therefore, AEIFOROS saw an opportunity to introduce ladle furnace slag to the cement factories located in the vicinity of the slag processing plants, while the cement industry was eager to substitute natural resources with secondary raw materials as a mean to reduce their environmental footprint and their CO2 emissions.
The processing of ladle furnace slag in order to produce a material of stable quality suitable for use by the cement factories requires successive phases of downsizing through crushing and screening as well as metallic iron separation.
The use of ladle furnace slag as a secondary raw material in the cement industry brings advantages to both industries, the waste producer (steel industry) and the end user (cement industry):
- For the steelmaking plants, the former waste material is now upgraded to the status of by-product with a stable market and a positive economic value. Prior to use in cement industry, ladle furnace slag was stored for years at the premises of the steelmaking plant because of the lack of viable waste management solutions. Today about 25.000 tons per year are valorised by the cement industry in Greece.
- For the cement producer, a valuable secondary raw material is now available in close vicinity, providing substantial savings in procurement, alternatively to raw calcium carbonate, as well as transportation costs.
- For both industries, the environmental footprint is reduced: no landfilling or on- site storage, less natural resources, less CO2
Industrial symbiosis ultimately translates into a more sustainable environment for companies and society.
The main challenge was to persuade the cement industry regarding their benefits, both environmental and economic, in order to change their raw material mix and partially substitute calcium carbonate with ladle furnace slag.
However, steel makers and slag processors should continue development of more uses of ladle furnace slags such as in soil additives as a pH adjustment agent in acidic soils, so that possible shutdowns of cement plants do not affect steelmaking plants’ continuous operation.
For this to be possible, another challenge is the acceptance by the Member State Environmental Authorities that industrial by-products fulfilling the relevant criteria set by the European Waste Framework Directive and satisfying the “further use” specific technical requirements can be indeed regarded as by-products and put on the market as such.