At a meeting in Hamburg, 200 waste experts discussed how the coveted metals can be recycled. Pilot plant planned for 2014.
Hamburg / Berlin. Cer, lanthanum, neodymium, ytterbium - hardly anyone was interested in rare earth metals until the 1950s. The last substance from this group, promethium, was not discovered until 1947. It was not until the electronics age that the 17 chemical elements became sought-after raw materials. Rare earths are also indispensable for the chemical industry. Cerium is found in catalysts, lanthanum in batteries, neodymium in computer hard drives and generators in wind turbines, and ytterbium in high-power lasers.
China supplies 95 percent of the metals in demand. Although there are also large deposits in Australia, Russia, the USA and India, the first stages in the processing of rare earths mainly take place in the Middle Kingdom. Ever since the country restricted its exports, it has slowly become clear to the West that a further shortage could have serious consequences - and that in future it will have to be all the more important to use raw materials sustainably.
The recycling is in this country but still in the beginning, as a meeting of 200 waste experts showed that met on Tuesday and Wednesday in Hamburg. No recycling system has yet been established, said Prof. Martin Faulstich from the Technical University of Clausthal. The reason: Regardless of the rise in commodity prices, rare earths have been too cheap to have a significant impact on product prices. For a laptop, raw materials accounted for only two to ten percent of production costs. For the industry, therefore, it has not been worthwhile to invest in recycling systems.
But with a view to the future, there seems to be a rethinking now, especially as it becomes increasingly clear which treasures are slumbering in electronic waste. Experts at the Öko-Institut in Freiburg estimate that in the 2010 PC sold in Germany alone around 15 tons of the neodymium, which was valued for its magnetic properties, and two tons of praseodymium were processed. It is recycled so far: nothing. After all, 25 percent of the precious metals used in electronics gold, silver and palladium would be recovered, the experts said.
The latter happens because, according to estimates, half of the electrical appliances discarded in Germany end up properly at recycling centers. Specialized companies then break down the scrap into its individual parts. A further part of the garbage, however, ends up abroad. And Germans keep throwing smartphones, hair dryers and electric toothbrushes in the general waste, although this is prohibited. So it happens that in addition to precious metals, iron, copper and aluminum, rare earths also end up in waste incineration plants and end up as bottom ash, whereby they bake into crumbs like slag when bathed in cold water. In this form they are worthless - still.
Under the direction of the Federal Institute for Materials Research and Testing in Berlin, researchers nationwide are working on methods with which more metals can be recovered than before - and also rare earths. For this purpose, the Berlin company Tartech in Damsdorf near Hamburg is expected to put a 2014 million euro pilot plant into operation in April 2,5, which is to be supplied with 40.000 tons of slag by Stadtreinigung Hamburg, another partner of the project. The Berlin city cleaning company also wants to have slag tested there.
So far, around ten kilograms of aluminum and copper have been extracted from one ton of slag, explained Dr. Stefan Lübben from city cleaning. With this conventional method, magnets and eddy current separators would pull ferrous and non-ferrous metals out of the ash mass. This works with slag particles up to 15 millimeters in size. In the future, the proportion of recovered metal should be doubled by including particles that are smaller than one millimeter. The result should then be 20 kilograms of metal per ton of slag instead of ten. That doesn't seem like much. A mistake, so Lübben. You have to see the entire dimension: “In Hamburg alone, 200.000 tons of slag are produced each year, and 4,8 million tons nationwide. That is why it is very worthwhile if we extract one percent more metal. It's about many millions of euros. "
This is to be made possible by a new process that Tartech intends to test in the pilot plant near Hamburg. The ash particles are thrown onto a rotor at a speed of up to 1000 km / h, causing the mineral buildup to break off. This would leave the metallic core. If one then extracts the iron and non-ferrous metals from the mass of such particles, rare-earth metals should be left over. According to estimates, these are only present in the slag in a concentration of about 25 ppm (parts per million, ie 25 of one million particles), but in a nationwide or international application, the technology would pay off, explained Tartech chief engineer Claus Gronholz. Whether all this actually works as intended, should probably be determined only from 2016.
It will take considerably longer before the rare earth metal neodymium can be recovered from magnets in wind power generators. Prof. Jörg Woidasky from the Pforzheim University told the conference in Hamburg that it had already been tested how, for example, the fiber-reinforced plastics from the huge wind turbines could be crushed and then reused as an admixture with concrete. But neodymium? "Research is being carried out on this, but nothing more."
An unexpected contribution to solving the shortage could come from Saxony. At the end of January, Seltenerden Storkwitz AG, a subsidiary of Deutsche Rohstoff AG, presented the report of an Australian consulting firm. According to this, the upper part of a deposit under the Storkwitz district could contain 600 tons of rare earth oxides at a depth of 20.100 meters. Estimates in the 1980s had predicted 38.000 tons; however, there was no dismantling at the time. The company is currently examining the costs at which the raw materials can be extracted - and whether more is being stored at greater depths. The aim is to detect at least 80.000 tons of rare earth oxides.
