Magnesium removal

Tomra has enhanced the capability of its x-ray based metals sorting.

TOMRA has further enhanced X-TRACT units for magnesium removal, an x-ray-based solution which can separate magnesium from aluminum in products such as Zorba and Twitch.

With consistently high purity rates of up to 99% being achieved in field tests, the material can be treated and traded within North America, as it meets the stringent quality requirements of domestic customers for Low Magnesium Twitch.

The United States generates an estimated four million tons of Zorba annually, which typically contains between two and four percent magnesium. Historically, scrap metal processors exported the bulk of this material to China. Changes to China’s scrap import policies regarding purity and trade tariffs have created significant barriers to exporting over the past couple of years.

Limited export opportunities have resulted in a surplus of Zorba scrap in North America. A growing domestic market for furnace-ready material produced from Zorba offers scrap operations an opportunity to profit from this surplus. The challenge scrap metal processors face, however, is secondary aluminum smelters in domestic markets require the aluminum from Zorba to contain exceptionally low magnesium, well below 0.5% by weight.

Until now, the only way of treating Zorba for the removal of contaminants such as magnesium has been a two-stage sink-float operation. Initially, the heavy metals are separated from the shredder scrap, while the hollow aluminum scrap, magnesium and high-density plastics are floated out in an additional media stage. Sink-float processes have historically been difficult to manage, require a large footprint, can be relatively unstable and have a relatively high operating cost-per-ton.

Today, TOMRA’s upgraded X-TRACT for magnesium removal offers a reliable, robust and cost-effective alternative to sink-float separation. The system uses existing TOMRA XRT technology but in a new configuration with enhancements made to the software, firmware and hardware. The new X-TRACT for magnesium removal sorts material of different density levels and separates magnesium from aluminum to create furnace-ready products, including Low Magnesium Twitch, across the full Zorba size spectrum from 0.2-4.7 in (5-120mm).

This degree of fines separation consistency simply could not be achieved using the dense media plant sink-float separation process. Also, until now, it wouldn’t have been possible using sensor-based sorting technology, since magnesium is similar in density to aluminum, and the existing technology could not recognize the difference between the two materials. The capabilities and combination of the x-ray technology used in the new X-TRACT for magnesium removal makes it by far the most consistently accurate solution to date.

“We are thrilled to be the first company in the world to create furnace-ready products using sensor-based sorting, including Low Magnesium Twitch, across the full Zorba size spectrum, previously only accomplished through a two-stage float-sink process,” said Brian Gist, global sales director metals at TOMRA Sorting Recycling.

“With X-TRACT for magnesium removal, we have greatly reduced the commercial and operational barriers to sorting this material and can offer a proven alternative to replace dense media plant technology for separating magnesium from aluminum. The field test results to date have been extremely positive with regard to machine reliability, robustness and sorting stability.”