Maximizing sorting and increasing scrap aluminum quality

According to TOMRA Sorting Recycling, the company's X-Ray Transmission (XRT) technology with X-TRACT and X-TRACT X6 FINES technology efficiently separates aluminum and aluminum alloys from heavy metals. 

This technology delivers consistent quality for resulting raw materials and products. According to TOMRA, the quality control of aluminum scrap used as secondary raw material in aluminum production is becoming increasingly stringent. For this reason, it is necessary to have first-class material. This quality is not always guaranteed for those aluminum manufacturers who, as is often the case, are dependent on buying recycled aluminum materials. 

"Aluminum has a bright future," says Carlos Manchado Atienza, regional director Americas for TOMRA Sorting Recycling.  "Its production is increasing, as the material largely replaces steel in many applications due to its strength and low weight. A primary example is the automotive sector, especially with electric cars, where weight reduction is crucial."

Therefore, when using recycled material, quality control is essential. This process starts with the scrap aluminum recyclers, as they supply raw materials to the aluminum producers. However, the latter must verify that the materials purchased meet the respective quality requirements. Both recyclers and producers must be involved in classification material improvements.

TOMRA's XRT technology, quality assurance and other benefits for scrap processors and secondary smelters

TOMRA Sorting Recycling's XRT technology facilitates the classification process and optimizes the efficiency of sorting secondary aluminum raw material. This applies to those who use aluminum scrap consisting of several alloys and heavy metals, including Copper (Cu), Zink (Zn), Iron (Fe), Magnesium (Mg), Silicon (Si), etc.

"Prior to melting secondary aluminum, our XRT technology separates the heavy metals from aluminum alloys containing more than 2% heavy metals," offers Eric Thurston, sales manager metals - recycling for TOMRA. 

"Each aluminum alloy contains a certain percentage of other metals, which must be controlled to ensure that the chemical composition of the product meets the required specifications. In this way, aluminum producers control the quality level before the material enters the furnace and avoid the loss of the melt, due to heavy metal peaks exceeding the maximum allowable content of these elements. TOMRA's technology becomes a second control barrier after the materials have been processed by the recyclers."

This secondary aluminum production using scrap material recycling has a fundamental positive role in the recycling economy. It increases recovery rates and delivers a high-quality end product with a lower carbon footprint, since it requires less energy and lower raw material costs compared to the primary aluminum smelting process. The latter uses bauxite ore as a raw material and requires high energy consumption and complicated physico-chemical processes.

TOMRA's XRT technology can compound the advantages when used by refiners and remelters. Adding sorting technology at this stage can lead to a lower purchase price for raw material (scrap), since strict material composition is not required, which requires less processing. Thus, lower quality scrap can be bought at a lower cost and subsequently cleaned by X-TRACT technology.

Thurston explains, "Secondary smelters, who are interested in separating scrap to pure fractions, now have the possibility of saving money for raw materials by sorting it with TOMRA's XRT technology to achieve the desired quality level." Apart from cleaning scrap, they can also produce new fractions. "For example, they can separate the crankcase from aluminum siding," he adds.

Commenting on the trend emerging from secondary smelters, Atienza mentions, "We believe aluminum producers will continue to develop their processes for separating raw materials. This has somewhat replaced the recycler's work in terms of material differentiation, creating new qualities that are always adapted to their needs".

Not using a technology, such as TOMRA's X-TRACT, involves several risks if the material does not meet the required specifications in terms of composition and grain size. The final product may not achieve the desired properties. To compensate for the quality deviation, prime materials must be added during the refining process.

"A process of dilution and/or addition of various additives may be required, which increases costs per ton of the final product produced," Thurston explains. "In addition, significant economic losses, greater instability and lack of control at the furnace entrance are to be expected."

What XRT technology means for remelters and refiners

Today, there are a variety of systems used by the aluminum industry or the supplying scrap companies to process the material: XRT technology, dense media separation, densimetric tables and manual separation. This range of possibilities leads to the creation of materials of very different origins and with a range of qualities.

In fact, many scrap processors have their own quality laboratories with melting furnaces, and results are often sent to the scrap customers to prove both traceability and compliance with the required quality standards. In this sense, TOMRA's XRT technology is a fundamental tool to achieve consistent product quality and to generate new fractions with higher added value, allowing the recyclers to sell their products at a much higher price per ton.

X-TRACT and X-TRACT X6 FINES from TOMRA, efficient sorting for aluminum producers and recyclers

TOMRA has two models that incorporate XRT technology: the X-TRACT and the X-TRACT X6 FINES. TOMRA X-TRACT recovers ready-to-melt aluminum fractions with a purity of 98-99%. With its XRT technology, it separates materials according to their atomic density, regardless of color and surface impurities.

TOMRA's X-TRACT X6 FINES identifies and classifies grain sizes that are almost half the size of those that could previously be processed (between 5 and 40 mm). In addition, the heavy metals separated with this device can be further separated by the COMBISENSE BELT system by color, brightness and shape.

The operating costs of TOMRA's sensor-based dry sorting systems are significantly lower compared to a system with dense media that uses water and additives. Additionally, dry sorting makes the necessity for water treatment obsolete.

"In short, these flexible XRT devices are fast and offer simple sorting program changes from the control panel. They offer agile operation and can be turn on/off without waiting, ideal for meeting the new challenges and needs of the market," offers Atienza. "They also control the percentage of heavy metals entering the melting process and final product quality. Therefore, they help smelters avoid exceeding the permitted limits of these heavy metals, which, if not controlled, could cause "non-conformity" of the melt, with great economic consequence."

The challenge lies in separating Aluminum and Magnesium

Both in the U.S. and Europe, scrap consumers are increasingly facing the challenge of producing pure aluminum end products that are free of not only heavy metals but also of light fractions, such as magnesium. "Magnesium makes up between 1% and 4% of typical scrap aluminum fractions and is regarded as an unwanted contaminant in the scrap mix, making it difficult for recyclers to sell," says Thurston. "Especially in the U.S., secondary aluminum smelters require Zorba to be magnesium free in order to sell it within domestic markets."

"Due to magnesium and aluminum being similar in density, technologies have difficulties in clearly differentiating between these materials in order to separate the," he adds. "To this end, removing magnesium from aluminum scrap is still a challenge that requires advanced technology."