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Posted: Aug 08, 2011

Molecular sorting for resource efficiency: new separation and recycling processes

(Nanowerk News) Decreasing supplies of raw materials, rapidly increasing demand in newly industrializing countries and increasingly tough environmental regulations – all these factors have contributed to the soaring price of raw materials. The only way to resolve this situation is through more efficient recycling management and improved separation and sorting technologies.
Researchers from the Fraunhofer-Gesellschaft in Germany will take on this challenge in a pioneering new project, funded as part of the Fraunhofer-Gesellschaft's "Markets Beyond Tomorrow" research programme. On 20th July 2011 the project "Molecular Sorting for Resource Efficiency", coordinated by the Fraunhofer Institute for Chemical Technology ICT in Pfinztal, Germany, was officially started. The opening reception was attended by over twenty Fraunhofer researchers, representatives of the VDMA and of the president of the Fraunhofer-Gesellschaft.
The aim of the project is to close the gaps in material cycles with innovative recycling processes, which will enable resources already present in Germany to be recovered and reused in high-value applications. Starting with low concentrations of finely dispersed materials, or contaminated material flows, the developed processes will recover high-quality materials (of equal value to primary materials) on an industrial level. Examples include highly-transparent glasses, rare metals from slags and gases, and high-quality wood materials from wood scrap. The project will develop techniques for waste streams of glass, wood, composite materials, slags and hot gasses, and by the end of the project the developed processes should also be applicable to other material flows.
"These technologies have a huge application potential", explains project leader Dr. Jörg Woidasky. "We estimate a market of 2 billion € for these technologies by 2020. Germany has taken on a leading position in this field, and in the commercialization of its developments on both a national and international level."
The project will run for 3 years, and has received 4.5 million € funding from the Fraunhofer-Gesellschaft. Beside the Fraunhofer Institute for Chemical Technology ICT in Pfinztal, the other partners in the project are the Institute for Silicate Research ISC (Würzburg), the Institute for Wood Research – Wilhelm-Klauditz-Institut WKI (Braunschweig), the Institute for Building Physics IBP (Holzkirchen/Stuttgart), the Institute for Ceramic Technologies and Systems IKTS (Dresden), the Institute for Interfacial Engineering and Biotechnology IGB (Stuttgart) and the Institute for Systems and Innovation Research ISI (Karlsruhe).
Materials separation at molecular level
The aim of the scientists is to develop new materials separation processes. "In the automobile industry, for example, high-performance lightweight materials are combined to make hybrid components, such as mounting supports and roof structures. At some time in the future they will be available for recycling, but such high-performance materials require new separation and sorting techniques. In the years ahead it will not be possible in many cases to replace primary raw materials economically using conventional recycling and production processes," says project coordinator Dr.-Ing. Jörg Woidasky from the ICT. In contrast to present methods the scientists want to separate the relevant raw materials, in particular those in short supply, at the production plant or in the first stage of processing, and to process them in just a few steps. "The separation processes should take place at the smallest required level, by way of molecular sorting," explains Woidasky. The scientists are focusing on metals and materials flows from the mineral, biogenic, organic and silicate raw materials sectors.
High-transparency glass made from scrap flat glass
What materials separation at molecular level would be like is demonstrated by the ISC's research scientists with the example of glass, a mineral raw material. Technologies of the future, such as photovoltaics and solar energy, require glass which contains only an extremely small amount of iron, because iron reduces light permeability. The dynamic rate of growth of these technologies is so great, however, that demand is outstripping the natural iron-free raw materials available, even when the amount of highly transparent glass provided by recycled photovoltaic modules is included. Scrap flat glass is used as a raw material for making cheap container glass. Its iron content is too high for making high-transparency glass. In present recycling processes its color is chemically removed but this does not improve light transmission. The ISC's experts are therefore developing processes which separate the iron from the glass at molecular level and convert any remaining minute traces of iron so that they do not affect transmission. Material separation is carried out in the glass melt at a temperature of around 1500 degrees Celsius. "Basically, we fish out the iron atoms from the glass melt," says Dr. Jürgen Meinhardt from the ISC. "We use scrap flat glass as the raw material for producing high-transparency glass. Flat glass manufacturers currently use expensive, very scarce iron-free materials which they mix with the mineral raw materials to produce high-transmission glass. At present only 10 to 20 percent of scrap flat glass is recycled for use in the production of new flat glass," explains Meinhardt. A high-transparency pane of glass made using the new separation technique should be available for demonstration purposes in about three years' time.
Smart wood recycling
The research scientists are also looking at scrap wood, which, with a volume of eight million tons per year, makes up one of the biggest industrially produced material flows in Germany. Only about 20 percent of waste wood, however, is used for recycling purposes: Germany's Waste Wood Ordinance prohibits the use of wood which has been coated with organohalogen compounds or treated with wood preservatives. Its use is restricted to the production of synthesis gas or activated carbon. There are hardly any methods available to detect these pollutants in wood, but new separation techniques at molecular level could help: "To detect whether the wood is untreated, contaminated with minerals, treated with organic wood preservatives, or contains heavy metals such as lead or other metals such as manganese, copper, chromium or tin, the wood's surface is scanned and the wood is sorted using various techniques, including near infrared spectroscopy, laser-induced spectroscopy and mass spectroscopy," explains physicist Peter Meinlschmidt from the WKI. "Wood treated with organic wood preservatives for example is then cleaned using supercritical fluids. Combustion and pyrolysis processes are used to remove heavy metals. In cooperation with the other institutes involved in the project, we are also developing new extraction techniques, not only to remove the various pollutants but also to recover valuable materials such as copper." Plastics, adhesives, cellulose, basic chemicals and other products can also be obtained from the cleaned wood. In about three years' time the researchers aim to produce a demonstrator sorting unit for scrap wood which will use a cascading process to recover a large part of the wood that is wasted today .
"This will be followed by further demonstrators over the next ten years. We should then be able to recover rare metals from combustion residues and rare materials from hot gases, for example. Over the course of the project we will put together a complete methods construction kit for recovering and recycling materials to address the needs of a wide range of industries, including automobile manufacture, mechanical engineering and plant construction. Because one thing is certain: resource-efficient production will be crucial to the competitive health of Germany in the years ahead," Woidasky concludes.
Source: Fraunhofer-Institut für Chemische Technologie ICT
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