Slag Valorisation Furnace
The Slag Valorisation Furnace (SVF) has been developed by METIX in collaboration with the SMS Group. It involves the metallurgical transformation of slag to achieve desired properties and convert it into a valuable product. It allows the recovery of valuable metallic units from steelmaking slags and other waste streams such as mill scale, dust and sludges. The SVF can process molten slags from EAFs, open bath furnaces and ladle refining operations, as well as solid slags and fine dusts.
TECHNICAL DESCRIPTION
The SVF can be integrated into existing steelmaking plants, particularly those using the EAF process. The SVF decouples slag valorisation from steelmaking, allowing production of calcium alumina cement, granulated blast furnace slag, and other cementitious materials. It also supports recovery of metal oxides through reduction reactions. Configurations include AC or DC electrical setups and rectangular or circular geometries, each offering process efficiency benefits.
The SVF supports solid feed or molten charging, reducing energy requirements. Injection systems enable controlled carbon addition to promote reduction reactions and improve metal recovery. Current designs allow the treatment of up to 1,300,000 tons of slag per year using a six-in-line rectangular furnace (See information attached). Residence time is adjusted for brownfield integration, supporting efficient tapping cycles and carburisation for iron reduction.
Slag can be modified to achieve glass content suitable for clinker replacement. The system supports wet and dry granulation, as well as conventional slag tapping and crushing. Off-gas is processed through a waste heat boiler for energy recovery.
DEGREE OF MATURITY
The SVF technology has currently reached TRL7. Extensive mass and energy balance analyses, grounded in first principles, have established process design parameters, with successful pilot-scale testing up to 1 MW.
A recent study demonstrated that slag valorisation led to the production of a viable supplementary cementitious material exhibiting high cementitious performance with compressive strength comparable to or exceeding Portland cement.
The realisation of a commercial furnace design is underway, and it is expected that within 24 months (2028), a first SVF commissioning could be done.
CROSS-MEDIA EFFECTS
The implementation of the SVF technology introduces additional power requirements and the use of modifiers such as lime; however, these impacts are offset by broader environmental benefits. Water consumption for furnace cooling, while necessary, has been minimised through the advanced design of the METIX SVF system. These cross-media effects are compensated not only within steelmaking operations but also across the cement value chain.
BARRIERS TO IMPLEMENTATION
Although the technology has reached a commercial-ready stage (TRL7), the primary barrier to widespread adoption is the perceived increase in carbon footprint for steel producers due to additional power consumption (when renewable electricity is not available). The success of the SVF technology is heavily dependent on strong collaboration between the steel and cement industries to share the economic and environmental benefits.
Basic information about the technique
Participant Companies
Project partners
- SMS Group
Technology provider
- METIX
Under development / testing
Achieved
TRL
7
System prototype demonstration in operational environment
- Environmental purpose of the innovative technique
- Decarbonisation
- Circular economy (e.g. recovery/reuse/recycling of residues, industrial symbiosis)
- Relevant industrial sector
- Iron and Steel
- IED activity
- 2.2 Production of pig iron or steel (primary or secondary fusion) exceeding 2,5 tonnes per hour
Locations
Metix (Pty) Ltd
Environmental benefits
As compared to: Conventional uses of steelmaking slags (e.g. road and hydraulic construction, production of cement and concrete).
GHG Emission
One of the primary environmental benefits of the SVF is its contribution to reducing CO₂ emissions across the cement sector value chain. The transition from BF to EAF steelmaking, driven by decarbonisation initiatives, has decreased the availability of BF slag traditionally used as a clinker substitute in cement production. While this shift lowers the steel industry’s carbon footprint, it creates challenges for the cement sector in sourcing alternative clinker replacements.
Recovery/reuse/recycling of residues
Recovery/reuse/recycling of residues
The SVF also supports circular economy principles by processing diverse waste materials, reducing storage requirements, and improving the recovery of metallic components. Incorporating by-products such as mill scale, fine dust and other process residues into the SVF feed enhances mate-rial efficiency. Additionally, the extended refractory lifespan minimises spent refractory waste, which is difficult to dispose of.
Economics
The SVF technology provides economic advantages by improving the recovery of Fe units from slag, thereby increasing ore utilisation efficiency in steelmaking operations. The conversion of slag into cementitious material creates an additional revenue stream for steel producers while reducing environmental liabilities associated with slag storage. Collaboration with the cement industry lowers the carbon footprint of cement production and reduces input costs for cement manufacturers. The results of an economic analysis carried out to estimate the pay-back period for implementation of a SVF (as a function of the steel production capacity and the power requirement of the SVF) showed that for valorising slags produced in an EAF of 2 million tonnes / annum liquid steel production capacity, a SVF with 20 MW power is required with an associated CAPEX of about 120 million USD, and OPEX of 40 million USD / annum. In this case, the pay-back period of the SVF implementation is about 2 years.