Recycled Material & By-Products in Ferrochrome & Stainless Steel Production

Tornio operations include steel melting shop, hot and cold rolling plants as well as ferrochrome works and Kemi mine nearby – the only chrome mine in the EU. Even though Tornio is situated far from the markets, both customers and raw material suppliers, the operations of Outokumpu are very efficient. In the plant area Outokumpu operates the harbor, enabling convenient transport of the products and raw materials.

Building future from the past

Outokumpu’s business is based on recycling – recycled content in the steel is over 87 %. The most important raw material used by Outokumpu in producing stainless steel is recycled steel. The most important alloying material, material that makes steel “stainless”, chromium as ferrochrome is produced onsite. Together with metals recovered from waste products and by-products of the production process, it enables the recycled content of stainless steel produced by Outokumpu to be raised to high level compared to global industry average which is 50–60%.

As recycled materials replace virgin raw materials that would otherwise have been required, the resulting effects extend to the whole supply chain. Taking the entire product life-cycle into account, a 20% increase in recycled content avoids 1.2 tonnes of CO2 emissions per tonne of stainless steel. Stainless steel is 100 % recyclable and suffers no degradation during reprocessing. Its constituents (including iron, chromium and nickel) can therefore be reused indefinitely in producing new stainless steel. These excellent recycling characteristics mean that stainless steel is well positioned to meet the demands of a future sustainable society.

Turning waste into profit

In Tornio Outokumpu produces vast amounts of by-products: FeCr slag ~700 000 t/a and stainless steel slag ~400 000 t/a. Every working day an amount of 60-80 big trucks of slag have to be treated, metals recovered, slag products crushed and produced according to quality standards and loaded to external transport for customers.

Outokumpu’s expertise in utilization of by-products is outstanding.  For instance, the side streams from the ferrochrome production have been utilized since the Tornio plant first started operating in 1968. Over the years, the use of the slag products have saved over 20 000 000 m3 natural gravel in northern Finland. Outokumpu’s slag products have several standardized commercial uses, such as part of asphalts, neutralization in industrial processes and making refractory bricks for fireplaces and ovens. Most typically, however, they are used in road and building construction.

In civil engineering under northern European cold conditions by using slag products, the road structure can be built thinner than when using natural aggregates due to better physical properties. This means less digging, less load for ground soil, less transportation, cost savings, lower emissions than using natural sand, less deformations of the structure and better quality of the road. Annual use of Tornio FeCr slag in road and basement construction saves 1 000 000 tonnes of natural materials and 350 000 tonnes of CO2 emissions.