The production and processing of iron and steel involve precisely tuned steps in a resource-intensive process chain. Conversion of materials through chemical and metallurgical reactions using solid and liquid input materials and auxiliaries plays a key role in ensuring resource efficiency, equipment efficiency and product quality. The various process stages normally generate liquid and solid main products and by-products along with residuals and process gases. In its efforts to reduce the consumption of resources during production of its main output while also increasing the value of its liquid and solid by-products, residuals and process gases, the steel industry is supported by the BFI with its cross-sectoral perspective. In performing this role, the BFI focuses on developing and implementing new methods, components and modes of operation that enable more resource-efficient conversion of materials and alternative uses of solid and liquid by-products, residuals and process gases. Its activities lie mainly in the following areas:

Analytics and Flow-Sheet Modelling

Recovering valuable constituents from residuals in a targeted way and increasing the efficiency of the materials demand precise knowledge of the physical and chemical properties of the materials involved. The BFI maintains a laboratory equipped with the latest measuring technology that allows the Institute to determine all material parameters of liquid and solid media relating to the production and processing of steel. Predictions on resource demand and on optimisation of product-specific resource consumption are generated by means of flow-sheet modelling and balances of different kinds.

 

 

 

Segregation and recovery of reusable substances

Using magnetic separation techniques, steel mill slag was fractioned at the BFI into a phosphorus-rich fraction for the fertiliser sector and an iron-rich fraction that can be fed back into metallurgical processes. Ultrasound processes are also used to accelerate the transition of materials to the liquid phase when leaching out recoverables from slags.

A magnetic drum separator developed by the BFI to extract magnetisable particles and recoverables from liquid media such as cooling water, emulsions, oils and polymer quenching baths is being used with great success and is currently being implemented as a product.

 

Working with partners in the steel industry, the BFI has developed a patented process for chemical recycling of valuable compounds such as titanium carbide from hard metal processing operations. This method allows titanium carbides, costing as much as €30,000/tonne, to be recycled almost residue free and returned to the manufacturing process. Developments are underway to transfer the recovery method to tungsten carbides.

 

For the recovery of reusables from processing lines in steel production, such as tin or zinc from rinsing water or valuable metals from phosphating baths, the BFI uses membrane filtering methods that are adapted as appropriate to the needs of each industry.

 

 

 

 

 

 

 

Conditioning and recycling of raw materials, by-products and residuals

Before residuals can be reused, they generally require to be conditioned first – by drying, agglomeration or leaching – to ensure they have the right properties for the recycling process. The BFI has a number of pilot plants for conditioning these materials (pelletising and granulating equipment, briquetting presses, etc.)

The subsequent recycling is tested and optimised in existing industrial plants and in purpose-designed pilot and demonstration plants. One example of this is the recovery of metal from zinc-containing dusts by injection into a melt.

In the area of CO₂ mitigation, the BFI is working on hydrogen technologies as well as biological and chemical methods for recycling process gases. These investigations are also considering cross-sectoral solutions.

 

Increasing resource efficiency through closed-loop recycling

When treating liquid media such as cooling and gas scrubbing water as well as the different kinds of process water, closed-loop recycling is the main approach. To achieve this, treatment methods are being developed or improved to ensure that dissolved salts such as chlorides, sulphates and nitrates can be separated out and other components such as cyanide or organic compounds can be converted.

In addition to the dissolved substances, particulate matter is also separated out of liquid media such as acids, emulsions, rinsing and washing waters as well as cooling waters so that all of these fluids can be recirculated. The separation method is selected and adapted according to the respective process needs, and the BFI has mobile test systems that can be used for demonstrations under the local industrial conditions.