Page 54 - Hub-4 Magazine Issue 63

Recycling
TOMRA Sorting Recycling technology maximises sorting efficiency and increases scrap aluminium quality
The quality control of aluminium scrap used as secondary raw material in aluminium production is becoming increasingly stringent. As such, having the highest quality material is essential. This is not always guaranteed for those aluminium manufacturers who often depend on buying in recycled aluminium materials. TOMRA Sorting Recycling's X-Ray Transmission (XRT) technology, which includes its X-TRACT and X-TRACT X6 FINES units, is highly recommended for efficiently separating aluminium and aluminium alloys from heavy metals, consistently delivering high quality input for the resulting raw materials and products.
"Aluminium is a light metal with a bright future, and its production is increasing as it is increasingly used as a replacement for steel in many applications thanks to its strength and low weight. The automotive sector is a good example, particularly in electric vehicles where weight reduction is crucial," says Brian Gist, TOMRA Sorting Recycling’s Sales Director Metals and Head of TOMRA UK.
Quality control is therefore essential when using recycled material. This process starts with the scrap aluminium recyclers as they supply raw materials to the aluminium producers. However, the latter must verify that the materials they have purchased meet the respective quality requirements. Both recyclers and producers must, therefore, play their part in improving the classification of materials.
TOMRA's XRT technology, quality assurance and other benefits for scrap processors and secondary smelters
TOMRA Sorting Recycling's XRT technology optimises the efficiency of sorting secondary aluminium raw material. This applies to those who use aluminium scrap consisting of several alloys and heavy metals, including Copper (Cu), Zink (Zn), Iron (Fe), Magnesium (Mg), Silicon (Si), etc.
"Prior to melting the secondary aluminium, our XRT technology separates the heavy metals from aluminium alloys containing more than 2% heavy metals before the aluminium alloys enter the furnace. Each aluminium alloy contains a certain percentage of other metals, which must be constantly controlled to ensure that the chemical composition of the product meets the required specifications. In this way, aluminium producers control the material’s quality before it enters the furnace and avoid the loss of castings due to heavy metal peaks exceeding the maximum allowable content of these elements," Gist points out. "In short, TOMRA’s technology becomes a second control barrier after the materials have been processed by the recyclers."
Using recovered alumium in secondary aluminium production plays a fundamental role in the recycling economy as it is an infinitely recyclable product. It increases recovery rates and delivers a high quality end product with a lower carbon footprint as it requires less energy and has lower raw material
costs compared to the primary aluminium smelting process. The latter uses bauxite ore as a raw material and requires high energy consumption and complicated physico-chemical processes.
The advantages of TOMRA’s XRT technology are even greater when used by refiners and remelters. Using the sorting technology in the process can lead to a reduction in the purchase costs of the raw materials (scrap), firstly because the materials do not require an excessively strict composition and secondly because less material is processed. Thus, a lower quality scrap can be bought at a lower price and subsequently cleaned by the X-TRACT technology. "Secondary smelters who are particulary interested in separating scrap to achieve cleaner fractions can now buy raw materials at a lower price and use TOMRA’s XRT technology to sort them to achieve the desired quality for their furnace requirements,” clarifies Gist.
In addition to cleaning the scrap, the XRT technology can also produce new fractions, for example, by separating the crankcase from the profile.
Gist explains: "We believe the trend today is for aluminium ingot producers to continue to develop their processes for separating raw materials.The use of XRT technology has even partially replaced the work of the recyclers in terms of material differentiation, creating new qualities that can always be adapted to meet aluminium ingot producers’ furnace needs."
There are several risks associated with not using a technology such as TOMRA’s XRT. The material might not meet the required specifications in terms of composition and grain size. The final product may not achieve the desired properties. Furthermore, in order to compensate for this quality deviation, other types of materials may have to be added during the refining process. For example, a process of dilution and/or addition of various additives may be required, which results in very high costs per tonne for producing the final product. In short, significant economic losses, as well as greater instability and lack of control at the kiln entrance are to be expected if XRT equipment is not used.
What XRT technology means for remelters and refiners
Today, there are a variety of systems used by the aluminium industry or by the supplying scrap companies to process the material: XRT technology, dense media separation, densimetric tables and even manual separation. This range of systems leads to the creation of materials of very different origins and of very varying qualities. In fact, many scrap processors have their own quality laboratories with melting furnaces, with results often sent to the scrap customers to prove both traceability and compliance with the required quality standards. In this regard, TOMRA's XRT technology is a fundamental tool to achieve consistent product quality and to generate new fractions with higher added value, allowing recyclers to sell their products at a much higher price per tonne.
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www.hub-4.com July/August 2020 - Issue 63