x-ray magnesium
The Tomra X-Tract for magnesium removal produces a low-magnesium twitch from zorba using senor-based sorting.
Tomra Sorting Recycling

Tomra technology targets magnesium

The new X-Tract for magnesium removal produces a low-magnesium twitch from zorba using senor-based sorting.

April 28, 2020

Tomra Sorting Recycling says it has further enhanced its X-Tract X-ray-based sensor sorting units to remove magnesium from aluminum in products such as zorba and twitch. This enables these materials to be treated and traded within North America because the final product meets domestic customers’ quality requirements for low-magnesium twitch.

According to a news release from the company about the new technology, consistently high purity rates of in line with Institute of Scrap Recycling Industries (ISRI) specifications have been achieved in field tests.

Brian Gist, the U.K.-based global sales director at Tomra Sorting Recycling, says by incorporating this technology, auto shredder operators with downstream nonferrous sorting operations won’t just be able to add a couple of cents per pound to their aluminum by producing twitch rather than zorba, they will be able to move their stock domestically.

The United States generates an estimated 4 million tons of zorba annually, according to Tomra, which typically contains from 2 percent to 4 percent magnesium. Historically, scrap metal processors exported the bulk of this material to China, but trade tariffs and changes to China’s scrap import policies regarding purity have created significant barriers in recent years. This has led to a surplus of zorba in North America. However, secondary aluminum smelters in domestic markets require the aluminum from zorba to contain exceptionally low levels of magnesium, well below 0.5 percent by weight.

tomra x-tract
© Tomra Sorting Recycling
The Tomra X-Tract features updated hardware, software and firmware to produce a low-magnesium twitch. 

Traditionally, to produce a low-magnesium twitch, zorba had to be processed with a two-stage sink-float method, which Tomra describes as “difficult to manage … relatively unstable,” and having “a relatively high operating cost per ton.”

Previously in his career, Gist ran a heavy-media plant in the U.K. and knows the instability of the process well, he says. With the Tomra X-tract, he says, an operation can turn the machine on in the morning and make the same material at the same quality consistently throughout the day.

“What smelters in the aluminum industry love is repeatable quality. That is where this comes in,” he says of the Tomra X-tract for magnesium removal.

Additionally, Gist says, “It’s game-changing from an operational cost standpoint.”

The company says its upgraded X-Tract for magnesium removal “offers a reliable, robust and cost-effective alternative to sink-float separation.”

The system uses the Tomra’s XRT technology but with enhancements to the software, firmware and hardware. The new X-Tract for magnesium removal sorts material of different densities and separates magnesium from aluminum to create furnace-ready products, including low-magnesium twitch, across the full zorba size spectrum from 0.2 to 4.7 inches (5 to 120 millimeters).

Tomra also says the degree of fines separation consistency the unit provides cannot be achieved using dense media plants. It was also a challenge for sensor-based sorting technology until now because magnesium is similar in density to aluminum, and the existing technology could not recognize the difference between the two materials.

“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,” Gist says. “The field test results to date have been extremely positive with regard to machine reliability, robustness and sorting stability.”

Eric Thurston, North American sales manager metals – recycling for Tomra Sorting Recycling, says the domestic market for low-magnesium twitch is strong, but the high purity requirements of secondary aluminum smelters previously hampered metal processors’ access to the market.

“Beyond accessing new and growing domestic markets, adding X-Tract for magnesium removal to the sorting line increases the market value of the aluminum, minimizes material losses and greatly reduces reliance on costly and risky manual sorting,” he says. “Our new X-Tract technology is an ideal solution for both small and large operators. Rather than selling material at a lower price to larger operators for further processing, smaller scrap yards can invest in just one machine and trade furnace-ready aluminum on the domestic market. This expands the company’s customer base and allows it to increase its profitability.”  

Gist says the Tomra X-Tract for magnesium removal can be employed offline from an existing nonferrous separation plant or integrated into the line. “It depends on how you design your plant.”

He adds, “Every shredder who makes zorba should have a machine.”

With the addition of the sorter, Gist says operators could garner 2 to 5 cents more per pound in addition to opening up new markets for their low-magnesium twitch.  

Gist says newer Tomra X-Tracts that have been in the field for roughly less than two-and-a-half years may be able to be upgraded to incorporate the new technology. However, he recommends a consultation with a representative from Tomra or plant builder first to make sure upgrading versus a new unit is the right solution to meet a company’s production needs. 

From a management perspective, he says, Tomra Insight reports on the unit’s functionality and performance. In some cases, Tomra technicians can access the machine remotely with this technology and advise operators on adjustments that will help to ensure peak performance.

Tomra Sorting Recycling designs and manufactures sensor-based sorting technologies for the global recycling and waste management industry. More than 6,000 systems have been installed in more than 100 countries worldwide.

Tomra Sorting Recycling is part of Tomra Sorting Solutions, which also develops sensor-based systems for sorting, peeling and process analytics for the food, mining and other industries. Tomra Sorting is owned by Norwegian company Tomra Systems ASA.