Specific types of metals and alloys are needed to manufacture high quality – and especially dishwasher-safe – cutlery. But where can we get these metals from if we don’t want to steal Nature’s supplies? One example: from new scrap from stainless steel production processes.
We not only recover large quantities of metal at our facilities, we also achieve the highest levels of purity.
International imports have prompted both the European and German high grade steel markets to focus on producing special quality steels with particularly high quality alloying elements. This means that valuable components – such as nickel, chromium and molybdenum – are being added to the steel. These, however, are not only in the final product but also in the production residue: in the metal slag and spent refractories. It is, therefore, well worth its while to recycle these two material streams to recover these valuable raw materials so that they can be returned and reused by the high grade steel and copper industry. This is exactly what we do at REMONDIS’ Lippe Plant – to be precise, at our LEGRAN business division.
High grade steel is produced in so-called electric arc furnaces. These use a combination of electrical and chemical energy to melt down alloyed high grade metal scrap. The whole process takes place using electrodes which are lowered into the material and create temperatures of up to 3,500°C. Besides high grade metal scrap, alloying elements are also added to the furnace during the secondary metallurgy process in order to produce high grade steel that meets the required specifications. A homogenous layer of slag forms on the surface of the hot liquid high grade steel during the production process. This is discharged from the furnace together with the liquid high grade steel at the end of the production process and then separated from the steel before being left to cool.
Inside an electric arc furnace
The metal slag floats on the surface of the liquid high grade steel and is removed from the furnace together with the liquid steel
Both the high temperatures and the thermal process result in residual materials sticking to and drying on the surface of the furnace. The refractory material must, therefore, be replaced at regular intervals to prevent the furnace being permanently damaged. The material – known as spent refractory – is effectively broken off the furnace walls. It contains large amounts of mineral residue as well as traces of the alloying elements used to produce the high grade steel.
The special feature of LEGRAN’s metal slag processing system at the Lippe Plant is the way the material is treated. The slag and spent refractories need to be pulverised before they can be processed and this job is carried out by a rod and ball mill which dates back to the time when the site used to produce aluminium. The quality and level of purity of the recovered metals are second to none thanks to the combined use of this system and the subsequent separation methods. This intelligent reuse of the site’s existing technology, therefore, not only benefits us but our customers as well. What’s more, we are able to offer customer-specific and material-specific solutions whenever they’re needed – thanks also to our years of know-how and the ongoing improvements we have made to the technology we use.
Metal trapped in the slag
The metal slag processing operations at the Lippe Plant are able to handle huge volumes of materials. There are two reasons for this: firstly, the company uses old facilities that were converted for this new purpose and secondly because it used to serve numerous major customers. The facility’s workload, however, has decreased as the number of steelworks in Germany has declined – which means we can now offer our metal slag processing services to smaller smelting and foundry businesses. They, too, can now make the most of our recycling facility so that the metal in their residual materials is no longer wasted. What’s more, they no longer have to handle the process of sending their residue to landfill. Talking about landfills: we have some innovative ideas in this area, too, at the Lippe Plant. We have, for example, developed technology that removes practically all of the water from the remaining finely powered mineral so that less landfill space is needed. Our medium-term goal, though, is to stop sending material to landfill at all. At the moment, we are working on finding ways to enable it to be used as a recycled building material.
One of the highlights of our metal processing system is the way the process water is sourced and treated. The plant uses the rainwater that falls on the landfill. This rainwater collects in the leachate treatment facility where any pollutants are removed. Once cleaned, the water is used in the mills for grinding the slag and spent refractories before being pumped back to the leachate facility after the dewatering stage so that it can be cleaned again. A closed water cycle in other words. Any excess water is pre-treated and neutralised and then transferred to the Emscher wastewater treatment facility.
31,000t is the same amount of carbon emitted by a car travelling around the world five times
LEGRAN’s metal slag processing not only benefits steelworks and other metal processors, it also protects the environment. In other words: it is vital as it helps curb climate change. Every gram of metal that is recovered and returned to production cycles reduces energy consumption and environmental pollution. How? The alternative – i.e. using ore to produce metals – is extremely energy-intensive and generates large volumes of carbon emissions. To say nothing of the negative impact that the mining and transport of the natural resources have on the environment.
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