Effective recycling relies on effective sorting. With a wide range of sorting technologies on the market today, WMW reviews the options and looks at the issues that are driving the development of new technology.
by Claudine Capel
European citizens will not have failed to notice that the sorting of waste, particularly at a household level, is becoming increasingly important. While the various EU countries currently take different stances on how and which waste to separate, the trend will be to separate as much useful waste as possible and deal with it in the most appropriate manner.
Separating the different elements found in waste streams is essential for enabling the recovery of useful materials, minimizing the amount of material sent to landfill and allowing recyclable materials to find a new incarnation. Companies sort and recycle materials in order to extract value, but those operating in EU Member States are also bound by EU rules and regulations relating to the environment.
UniSort Flake Click here to enlarge image
In June 2008 MEPs voted to reshape the waste framework directive and the new rules are that each country will have to set and adhere to its own targets on waste. In terms of recycling, the new legislation states that 50% of all household waste and 70% of all construction waste must be re-used or recycled by the year 2020, so the need to make sure sorting processes are as effective and economical as possible is of paramount importance.
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Waste disposal companies dealing with the sorting of materials will commonly use one or more of these five methods:
• Trommel separators/drum screens These separate materials according to their particle size. Waste is fed into a large rotating drum which is perforated with holes of a certain size. Materials smaller than the diameter of the holes will be able to drop through, but larger particles will remain in the drum.
• Eddy current separator This method is specifically for the separation of metals. An ‘eddy current’ occurs when a conductor is exposed to a changing magnetic field. Put simply, it is an electromagnetic way of dividing ferrous and non-ferrous metals.
• Induction sorting Material is sent along a conveyor belt with a series of sensors underneath. These sensors locate different types of metal which are then separated by a system of fast air jets which are linked to the sensors.
• Near infrared sensors (NIR) When materials are illuminated they mostly reflect light in the near infrared wavelength spectrum. The NIR sensor can distinguish between different materials based on the way they reflect light.
• X-ray technology X-rays can be used to distinguish between different types of waste based on their density.
It should also be mentioned that manual sorting of waste is still very much a technique that is used in the world today. Danish company M&J says many of its shredders are bought by companies that want to use them prior to material being sorted by hand on so-called manual picking lines. M&J has shredders that can produce large-sized particles, making it easier for those hand-sorting the waste to do their jobs effectively.
The S+S Varisort Compact Click here to enlarge image
Those companies paving the way in the sorting of waste use the aforementioned technologies, but are also constantly developing new and more effective methods. In sorting there is a multitude of ways to get the job done. This article aims to provide a flavour of the most common, as well as the most innovative, methods of sorting being used by European waste disposal companies today. We do not have the space to go into detail on every method currently available and in use, but hope this article serves to give an overall impression of the technologies employed in today’s market and their value to society.
With today’s recycling culture, sorting is surely set to increase. Not all companies can transport the waste to their own plants in order to separate it sometimes this work needs to be done on site. Mobile sorting machines are therefore a must, and one company that is leading the way in this field in waste screening is Doppstadt with its SM series of mobile sorters.
The SM series uses drum screens and is adaptable to a variety of uses. There are four different machines to choose from depending on the type and size of waste to be sorted, and each of them includes features designed to make them easy to maintain, keep clean and transport. The rotating drums have rotating brushes to keep them from getting clogged up and are capable of dealing with heavy materials. They employ a patented load-sensing technology which optimizes the flow of material through the drum and the machines benefit from short set-up times as they have hydraulically-folding discharge conveyors. The SM series can sort anything from compost to construction waste and soil to materials excavated from landfill.
Just one example of a use for mobile sorting technology is a plant set up by Cesaro Mac Import in Italy using Doppstadt machinery. As well as a shredding machine this plant makes use of a screening station, SST 1025, with a 40 mm trommel screen. The plant processes waste that is the by-product of paper recycling. This waste comprises paper rejects and sludges. These rejects or foreign fibres can be processed once they are separated and their calorific value is useful so it is important to use effective technology that can remove this matter from the sludge. The Doppstadt screens in Italy process 550 tonnes of rejects each day.
One of the key features of companies leading the way in today’s market is the ability to sort the increasingly diverse range of materials coming through, and deal with them appropriately. Titech, a global company with its headquarters in Norway, has long been aware of this issue and has been spearheading technologies which have now been adopted across the industry. The 15-year-old company sorts a huge range of materials; everything from plastic bottles and WEEE to construction and industrial waste. It places a great deal of importance on research and development. It knows that new materials will be created, but the need to dispose of them correctly will also be paramount. In light of this it uses a diverse range of sensor technology in order to get the purest fractions from every waste stream.
UniSort P Click here to enlarge image
The sensor technologies applied at Titech include: NIR (near infrared), which recognizes different materials based on their spectral properties of reflected light; CMYK (cyan, magenta, yellow, key) sorts paper or carton that has been printed using CMYK; VIS (visual spectrometry) recognizes all colours that are visible and works for both transparent and opaque objects; EM (electromagnetic) sorts metals with electromagnetic properties, as well as sorting metals from non-metals and recovers stainless steel or metallic compounds; RGB sorts specifically in the colour spectrums of red, green and blue for specialized applications and X-ray sorts by recognizing the atomic density of materials. This enables Titech to achieve a high purity level regardless of size, moisture or pollution level.
Another emerging technology is MIR (mid infrared) which works on a similar principle to NIR, but projects light in the mid infrared range onto materials to be analyzed. French company Pellenc ST has been piloting this technology in 2008 as a more efficient way to separate paper and cardboard. Traditionally machines have employed the same technology used to sort plastics, i.e. colour sorting methods, to sort paper and cardboard but this results in a much lower level of efficiency. Pellenc ST says its new MIR method brings efficiency levels up to 90% which is an improvement of around 30%.
Completely installed EuRec waste treatment plant in China Click here to enlarge image
The range of sensors used at Titech gives us a good indication of the direction the European, and indeed global, sorting market is taking. The company’s flagship machines at the moment are the Titech Finder, which can take a high throughput of material and achieve excellent purity, and the Titech Polysort Flake, which can sort smaller particles at extremely high resolution. As many readers will know, Titech has recently expanded its operations by forming a partnership with leading German company CommoDas, which has further increased the range of materials that it is capable of sorting.
German company RTT has been operating since 1990 and is famous for its trademarked Unisort machines which have been tailored to specific waste streams. The Unisort CB, for example, salvages circuit boards from WEEE, while the Unisort P can sort a wide range of polymers, papers and more using NIR technology.
Plant connected interim storage facility with bales in China Click here to enlarge image
The company has always been ahead of the game and its response to the demand for high resolution has been another of its successes. The Unisort Flake deals with waste at a fraction size of 350 mm and can be programmed with specific criteria for every waste stream. As with most sensor sorting machines, the waste is fed in on a conveyor belt under the sensors which then instruct the high-pressure air jets to separate the waste into the appropriate containers.
So, with the high level of variation in waste streams it usually takes a combination of technologies to separate it all successfully and the stream may also need more than one run through the filtering machine. But these days, customers are increasingly demanding. They want a machine that can separate as much waste as quickly as possible and, with the size of machines also a factor, they are looking for something that takes up the least amount of space.
Enter S+S Separation and Sorting technology GmbH and its Varisort Compact system, which had its grand unveiling at the 2008 IFAT show. This Bavarian company focuses on the detection and separation of contaminants from material streams, and has worked hard to produce a machine that industry professionals would see as a good investment. S+S obviously knows its market. The Varisort machine combines inductive, optical and NIR sensors which can run simultaneously, and its accuracy of detection is impressive sorting up to 500,000 parts per second. It also includes high-speed valves which can process up to 500 switching cycles per second.
The EcoTowerSort can be adapted to deal with a number of different waste streams, for example ASR and WEEE, and is able to recover even very fine-hair copper wires Click here to enlarge image
Its modest size means it appeals to those companies for whom space is a factor. And it is also impressive to note that its lack of stature has in no way compromised its ability to separate waste. S+S has simply made its shorter conveyor belt faster and the compressed air blasts even more precise in order to make sure the job is done properly. Peter Mayer, Sorting Sales Manager at S+S says ‘Because of its outstanding flexibility the Varisort Compact system is ideal for sorting electronic waste. Irrespective of the type of electronic waste that needs to be sorted, the Varisort Compact can always optimally perform the sorting task by employing different sensors.’
For companies that deal with large-scale waste such as WEEE, a compact sorting machine like this can be a godsend. With any recycling technology one must consider that it is only ever one part of a larger processing system, which usually comprises several machines and takes up a large amount of space.
One cog in a larger wheel
Sorting is, of course, just a single element of the waste disposal/recovery process. But it is a vital part and can come at almost any stage in the life of the waste stream once the material has been discarded. With this in mind the big players in the sorting market have to remain flexible and provide technology that can cope with literally any type of waste. Obviously, technology which is designed to deal with small scale flakes cannot also cope with large scale WEEE or wet agricultural waste, but companies are trying to get as close as they can to developing machines that are multi-purpose and combine technologies to do several different jobs at once.
Toratec’s EcoTowerSort® is designed for separating metal fractions, but sorts its waste stream in several different stages using different types of technology. This means it is able to combine different waste processing methods which would have previously required more than one machine. Its combinations of eddy currents, inductive metal sensors, optical camera sensors and NIR enable it to give the purest resulting waste streams possible. Customers looking to buy an EcoTowerSort are able to specify the waste streams they usually deal with and purchase a machine with the exact combination of technologies they need.
From Europe to China
German company EuRec Technology GmbH is particularly noteworthy as a company which is versatile in its handling of waste. As part of its offering a complete line of processing technologies, EuRec favours inclusion of a disc separator to provide solutions for a number of mixed waste streams. The disc separators can screen crushed waste, compost and brown coal, process reclaimed material from landfill, process waste incineration ash and separate inert materials from incineration plants as well as sewage sludge and other cohesive materials.
The ability to deal with both wet and dry materials makes this technology ideal for taking on large-scale mixed waste disposal operations.
One such project EuRec has recently embarked upon is a waste treatment plant in China. The plant deals with municipal solid waste from a district of Beijing. The multi-component domestic waste goes through the mechanical treatment process and is then separated into useful materials. This may be a relatively new approach in China, but is commonplace at established mechanical-biological treatment plants in Germany and Europe.
The limits on the amount of organic or biodegradable waste imposed by the European Landfill Directive means that technology such as EuRec’s disc separators have even more value in today’s marketplace. Technology that can cope with organic and solid waste together enables waste disposal companies to fulfill these requirements in an efficient and cost-effective way.
An increasingly global market
Eurec’s move to China shows that the demand for effective and efficient sorting is becoming increasingly global. And another German company which has now spread its reach into Asia is sorting giant Steinert GmbH which specializes in the separation of metals.
At the company’s global sales conference in April 2008 it signed contracts with its Japanese partners in order to establish Steinert Japan, a joint venture for which Steinert GmbH has the majority share. Discussions at the conference also covered the various global marketing methods for recycling and recovery (and therefore sorting) of waste. Each area of the world approaches its waste differently and therefore Steinert GmbH will be applying different strategies in its worldwide marketing. The company felt that its global sales meeting provided a great platform to discuss these different opportunities and optimize the benefits it is able to provide to its customers.
On a global scale the opportunities for waste handling companies are increasing alongside increased global awareness of environmental issues, and recovery is set to become all the more important in areas such as minerals processing, electronic scrap, metal recycling, refuse and the food industry.
Claudine Capel is associate editor of Waste Management World
To mingle or not to mingle?
To get the most from a waste stream, and decrease the chances of residuals going to landfill, companies need to know what is in it so they can select the best methods of sorting. Local authorities in particular are open to criticism when collecting household residual waste if they don’t have the access to appropriate technology to make the best use of the waste streams coming in.
This point highlights that issues concerned with effective sorting (and subsequent recycling) cannot be addressed by manufacturers of sorting equipment alone.