Steel manufacturing

Waste recycled for steel production

In a newly developed process, the salt slag from aluminium industry can be recycled as useable slag former for the steel industry. The process lowers energy consumption and is environmentally friendly.

Slag is a by-product formed when producing metals, where it is used to take up impurities. The processed slag can in many cases be used for new purposes, but the salt slag formed during aluminium production has no industrial application, and has therefore been deposited in landfills.

Recycling of slag

Swerea and Stena Aluminium have developed a process in which the salt slag can be recycled and converted into another type of slag, called premelted calcium aluminate, a material that can be used as a slag former in steel production. Using pre-melted calcium aluminate means shorter melting times, which saves energy and produces less environmental impact.

For Swedish steel mills there are potential yearly environmental savings of 23 000 tonnes of carbon dioxide and 50 000 megawatt hours of fossil fuel energy. A Swedish single-family house annually consumes an average of 25 megawatt hours of electricity.

23 000 tonnes decreased CO2 emissions

The new process has undergone both preliminary study and subsequent pilot testing. Aluminium maker Stena Aluminium sees major benefits with the process.

“Finding an environmentally sound solution for our salt slag is very important to us, and the opportunity to conduct tests on a pilot scale makes development work more efficient,” says Ola Falk, project manager at Stena Aluminium.