By-products gain new life in rubber

Iron powder can be produced by making a so-called sponge iron which is ground into a powder. Sponge iron is a porous iron product that is produced in tunnel kilns at Höganäs AB. During production, the by-product tunnel kiln lime is also formed.

A waste of tunnel kiln lime

Höganäs annually produces 20 000 tonnes of tunnel kiln lime and much of this is transported to landfills, despite it being usable in other areas.

“Because the by-product is rich in calcium, we’re looking for areas in which it can replace regular calcium,” explains Björn Haase, responsible for non-metallic products at Höganäs.

Waste recycled in rubber

A new application area for the by-product is as filling material in EPDM rubber (ethylene propylene rubber).

Swerim has already performed studies in which the filling material has been replaced with tunnel kiln lime, and the results showed that the same properties are achieved as when traditional filling materials are used.

“The primary benefit for us is that we avoid having to deposit the material in landfills, which is also in line with the company’s vision of zero waste. But the benefit is doubled since the extraction of virgin lime can also be reduced,” says Björn Haase.

EPDM rubber

A synthetic rubber material that is used in packaging, conveyor belts and cooling hoses, for example. The rubber is resistant to aging, weather, ozone and high temperatures. Filling material is added to reduce costs and to improve mechanical properties. Examples of filling materials are carbon black, calcium and chalk.