As soon as the sun is shining on Germany’s largest scrap yard, it starts to sparkle. The premises of DEUMU shine like silver and metal, like a precious treasure. This is not a false impression - every mountain of scrap here is worth several tenths of thousands of euros, even if the scrap price only amounts to 100 to 200 euros per tonne. The guardians of the treasure are, amongst others, DEUMU site manager Marko Klickermann and head of production and process engineering Uwe Mauersberger. These two know exactly what can be recycled – and what cannot. “A car made of steel is recycled by more than 95%”, Marko Klickermann says. Uwe Mauersberger adds: “On the other hand, with respect to carbon parts for instance, nobody knows how to recycle this material.” Marko Klickermann gives an approving nod. “Moreover, in steel recycling, there is no down-cycling as is the case with paper and plastic. Steel remains steel – after recycling, the quality is still the same as it was during production.”
Scrap is and remains a valuable and important secondary raw material in steel production
Without steel scrap, the German steel industry could not survive as it covers 43% of its demand. Globally, the share is just a bit more than one third – this is also due to the fact that in China, where almost half of the globally produced raw steel is manufactured, the share of steel scrap in production amounts to only 10%. At this moment another lorry rolls onto the DEUMU site. It comes from Bad Harzburg, which is only 40 kilometres away from Salzgitter. Scrap is a regional product, just like apples from the farmer in the neighbouring village. “Half of our scrap comes from within a radius of 150 to 200 kilometres”, Marko Klickermann says. Steel scrap rarely travels very far; only small quantities are imported from neighbouring countries such as the Czech Republic or Poland. Long transportation routes lead to a too drastic increase in prices. However, the lorries are not allowed to just drive onto the premises and unload their scrap. Every delivery is closely inspected by the DEUMU experts. Although the material is always declared, everything is still checked - including for radioactivity. Even the grippers of the excavators have sensors installed, which would emit an alarm immediately. Weak radiation is only very rarely recorded though.
A distinction is also made according to the type of further processing: What is to be processed by the shredder or cutter, what is processed by the stamp and what is even manually cut with a cutting torch, such as a train tank wagon? “We differentiate between twelve different types of finished scrap and classify these according to their size, physical characteristics and chemical composition,” explains Uwe Mauersberger. The most precious type of scrap is single-origin scrap since mixed and contaminated types of scrap need to be processed and separated. Single-origin material mainly comprises scrap which is directly returned from production, e.g. leftover pieces of coils and slabs from the company’s own steel production. Additionally, sheet metal scrap from the automotive industry is high quality scrap.
This “scrap” is returned in exactly the same material quality in which Salzgitter Flachstahl GmbH (SZFG) has delivered the steel to their customers - however, it is then pressed into cubes, which sparkle in the sun. “With respect to our own production residues, we differentiate between 15 types of scrap; therefore, we analyse every piece of the slabs and coils”, says Uwe Mauersberger. Here, the characteristics of the types of scrap are decisive for its further use in the melting process. “However, we also process slags and extract the iron from them. For this purpose, we comminute the slag, grade it and sort out the contained iron by means of magnets.”
High steel qualities are a question of accurate analysis, sorting and dosing of scrap
The results of the checking and sorting processes are clearly visible on the premises. Everything is in strict order. The scrap piles clearly differ from each other but are also very intrinsically homogeneous. Here, steel plates, which are covered with a red rust film and from which machine components for the processing steel industry have been cut out, are stacked. Right next to them is a pile of production scrap from the automotive industry - a pile of silver shining cubes. Not far from them, large machine parts are piled up, with the remains of a complete bus on top of them, from which steel arms are stretched out into the void: The early robotic armies of industrial automation have already begun to be recycled here.
The premises are reminiscent of an apothecary cabinet. Here, accurately sorted, DEUMU stores the high-quality and single-origin ingredients for their mixtures, for which precise compositions are to be strictly observed. This is due to the fact that every “scrap medicine” must be accurately adjusted and dosed for steel production. Not far from the DEUMU premises, raw iron is produced from iron ore, coking coal and other ingredients in the furnaces of SZFG. In the steel works, this raw iron is then fed to the converters, where any undesired accompanying elements and excessive carbon are burnt with the help of pure oxygen. Here, an extreme heat of more than 3,000 degrees would occur.
To keep the temperatures between 1,700 to 1,740 degrees, steel scrap is added to the converter. Since this “medicine” must not add other undesired substances to the raw iron, the DEUMU employees must know exactly which mix of scrap material they can deliver to the converter. This is no problem but routine. “We have in-depth knowledge of the production processes and know our systems very well”, states Marko Klickermann. To be certain, an analysis and check are carried out after each melting process to avoid degradations of the steel qualities. When purchasing the scrap, DEUMU already knows what SZFG requires. “Through our discussions with the production department, we already know what types of scrap we require before we buy scrap”, explains Marko Klickermann.
Almost 98% of the scrap delivered to Salzgitter is processed back into crude steel
Approximately 35,000 tonnes of the externally delivered scrap is thus fed to the production process of SZFG every month. Added to this are approximately 65,000 tonnes from the company-internal production. However, the largest part of the purchased scrap is delivered to Peiner Träger GmbH (PTG): Approximately 100,000 tonnes per month. The electric steel plant in Peine converts the scrap steel into new steel with a ratio of 1:1. PTG covers 100% of their own demand with scrap. With each load, an electric arc furnace melts 115tonnes of scrap at a temperature of 3,000 degrees. Additionally, DEUMU regularly sends old carriers and sometimes the embossing indicates that this carrier was produced in Peine many years ago. This is the moment in which the cycle closes, the best allegory for “the cycle is running smoothly”.
In the long term, more and more of such closed cycles will develop. Currently, in foundries and other electric steel plants, the rate is as high as 90 to 95% already. In Peine, where steel scrap is the only raw material, it is even at 100%. Things are running smoothly for DEUMU as well: The 2.4 million tonnes of recycled scrap per year is offset by only 50,000 tonnes of foreign material adherence, which is thermally recycled or disposed of. This equals mere 2.1%. In other words: Almost 98% of the delivered quantity is returned to the production process. This is an impressive recycling rate. It is above average; according to a two-year-old study by Fraunhofer-Institut für Umwelt-, Sicherheits und Energietechnik (UMSICHT), the average is 93%. In the “closed cycles” discipline, the steel industry can thus be regarded as world champion – and Salzgitter AG is a top performer.
Further improving the rate in the future will not be an easy task. Scrap is increasingly bonded to foreign material such as plastic. Additionally, more complex products include new undesired accompanying substances. For the steel recycling industry, this represents a great challenge, which is countered by means of new analysis methods and sorting technologies. For DEUMU, this development represents a task but not an obstacle: Marko Klickermann and his colleagues are sure that they will continue to be able to provide Salzgitter and Peine with high-quality steel scrap in the future.