With the industry trend moving away from dumping waste residues, Birkenmayer, one of Africa’s leading process engineering firms and the sole supplier of Eirich industrial mixers locally, has developed ways of viably recycling them back into the production line. By re-using these ‘wastes’, large industrial plants are able to boost efficiency and profitability, and extract valuable by-products.

The key enabler of recycling efficiency is the Eirich industrial mixer’s ability to thoroughly homogenise raw mineral-containing material before entering it into various extraction processes. Since homogenisation improves material’s porousness, it allows for even heat distribution, predictable melting/evaporation temperatures, exceptional energy savings and greater extraction ratios.

Sinter plant dust recycling

To recycle basic oxygen furnace dust (BOF), high in iron and quicklime, without the risk of an exothermic iron reaction, the mixer used to agglomerate the dust needs to be charged using nitrogen, and should be configured to function as an evaporative cooler.  This process also requires a lot of water for wetting dust-loaded particles before settling the dust into stable and manageable pellets – which can then be fed back into a plant’s first-phase processes.

“We have successfully designed and tested an Eirich industrial mixer to suit this application in Austria,” says Birkenmayer’s Business Development Manager, Louis Eksteen. “The Eirich mixer is capable of operating in a closed cycle – without any emissions into the environment, while efficiently maintaining nitrogen and water levels.”

For BOF recycling, Birkenmayer offers the Eirich mixer with a built-in, fully-automatic cleaning system, as well as an automatic water addition system. “As a supplier of complete process engineering systems, any additional scrubbers, pelletisers, and other ancillary equipment is worked into the system’s original design and specification,” says Eksteen.

Zinc recycling

The patented Waelz kiln process – which recovers zinc from industrial residues by vaporising it at 1 200°C in a rotary kiln and then filtering the process air in tube coolers – can improve its metallic zinc output by up to 20% with an Eirich industrial mixer.

“If used to pre-homogenise and pre-pelletise the raw process material, Eirich industrial mixers can help to increase the kiln’s oxidisation rate by up to 30%, while lowering energy requirements and CO₂ emissions by as much as 40%,” says Eksteen.

Eirich’s intensive mixing principle

Maximum energy is directed into the mix by a set of rotating mixing tools and a rotating pan. These components efficiently separate the transportation process from the high-speed mixing, making the Eirich industrial mixers ideal for use in various applications ranging from ore processing and iron carbon residues, to blast furnace sludges and mill scale sludges that require true homogenisation for efficient recycling.

Birkenmayer will analyse and design complete industrial mixing processes for its clients to determine optimal mixing speeds, tilt angles and other aspects which affect final mix quality. Complete mixing solutions include the mixer’s feeding systems, measurement devices and other process-related technologies.