Recycling of industrial and municipal waste as slag foaming agent in EAF (RIMFOAM): final report

High electric energy and coal prices in combination with carbon dioxide taxes have driven European steelmakers to look for alternative chemical energy resources other than primary coal to remain competitive on the global steel market. This fact requires higher flexibility in the steel production route regarding raw material preparation and melting operation. This project has investigated to partly substitute carbon and oxygen with industrial and/or municipal waste (ASR, rubber tyres, plastics, biomass waste and by-products, EAF dust and mill scale) for slag foaming purposes in the EAF. The goal was to find cost and energy-effective alternative slag foaming agents while maintaining or improving the slag foaming intensity, preserving the liquid steel quality and keeping emissions at a low level. The work includes characterisation of a large number of waste materials, model calculations. The results show that it is technically possible to partly replace carbon and oxygen with industrial and/or municipal waste while retaining a sufficient slag foaming. An environmental assessment of the investigated concept shows that the environmental impact is manageable as the dioxin level and heavy metal concentration in the off-gas was not affected. It is a challenge to perform an economic assessment of the investigated utilisation of waste materials as foaming agents in the EAF. Firstly, there is a need to assess the cost difference between the secondary waste material and the cost of injection grade anthracite. Then it is also needed to assess the cost for extra treatment of the melted steel depending impurities such as sulphur in the waste material. The pre-treatment cost of the waste material also provides a challenge for the implementation of the new concept.