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My closing statement read: "There is only one real effective and incentive method to encourage environmentally sound collecting of beverage one-way containers and it is deposit in combination with High-Tech R&D resulted Reverse Vending Machines! |
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Zdroj/Source: RECYCLING m@gazine No. 10/2008 -  , 6.98 MB, 24 pages)
 p. 6 |
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HOME
Archiv 2008
10.11.2008 Integrated Plastics Waste Management System – Austria |
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Plastics are produced from crude oil and prices for this raw material have been rising continuously for years. Up to the 1970s, you had to pay less than $5 for one barrel. Today it is close to the $120 mark. This fact plus the growing mountains of waste are two reasons why the subject of recovery is becoming ever more important.In Austria some enterprises already started testing various methods for plastics waste recovery in the mid-1980s. Today there are several systems for recovery of almost all types of end-of-life plastics. A shortage of waste plastics is forecast within the next few years. New for oldThe majority of recycled used plastics come from the wide field of packaging. Out of the 130,000 tonnes which are collected in this branch each year, about half is converted to granulates and new products. PET bottles are well suited for this, for which over 40,000 tonnes were used in 2007. About 60 per cent thereof were able to be processed in recycling plants and mechanically recycled. Plastics foils from trade and industry are the second group of products which it is worth recycling. Much more than 30,000 tonnes are collected, mostly only slightly contaminated and easily recyclable. New foils can be produced from the secondary raw material, and mostly consumers don‘t even realise that they are using a product which is produced from waste plastics.Another 10,000 tonnes of bottles, cups, cans, buckets and packaging foams are collected each year and mechanically recycled – altogether no small amount for only 8.2 million people. Mechanical recycling of small and heavily polluted plastics waste would not make sense, neither ecologically nor economically, as the efforts needed for sorting and cleaning are too high. At the same time, such waste is in very great demand in Austria for alternative fuel within industry. It is also used as hydrocarbon providers for chemical processes – something which is also utilised by the Austrian steel industry. Plastics replace fuel oil or coal, and so fossil energy resources are conserved. Additionally, emissions of greenhouse gases are reduced.Cement Industry uses Plastics FuelIn modern cement works, the use of conditioned plastics waste for production of energy is getting more and more common. Cement production is very energy-intensive. Flame temperatures of 2,000 °C are needed. The energy costs of cement production count for about one third of the overall production costs. This is the main reason why the industry is currently improving energy efficiency, on the one hand, and reducing the specific need for fuels, on the other hand. Currently in Austria, 49 per cent of the energy input in the cement industry is alternative fuel, half of it gained from plastics waste.
Plastics Waste reduces Greenhouse GasesAn investigation by the Institute for Energy Research of JOANNEUM RESEARCH Forschungsgesellschaft mbH (Graz, Austria) has proven that the input of used plastics for heat generation in cement works offers not only economic but also ecological advantages. The main aim of this investigation was to qualify the effects of this new form of alternative fuels utilisation in cement works with respect to investments in energy and greenhouse gases emissions. The study compares the current situation – which is characterised by waste land filling with subsequent use of the landfill gas and by the supply of process heat in cement works from hard coal – to new production technology: creation of conditioned alternative fuels from waste and the use of these for process heat generation. Conclusions:
Alternative Energy for Fibre ProductionThe pulp and fibre factory Lenzing AG/Austria, in connection with its partner AVE, one of Austria’s leading disposal companies, is another positive example of the use of treated waste as a source of energy in industrial manufacturing. The raw material for the production of textile fibres is cellulose, generated from wood. This process requires a lot of energy and led to the decision to build a residue recovery plant, which incinerates high-calorific waste and as a result produces electrical power, heat and steam. The circulated fluidised bed boiler has a capacity of 110 MWth and an output of 130 t/h steam with a temperature of 500 °C and pressure of 79 bars. Only 15 per cent of the bulk energy consumption of 12 million GJ has to be generated from fossil fuels (gas, coal and oil); 85 per cent are produced from the site’s own waste wood, bleaching liquors and about 230,000 tonnes of plastics waste annually. The fuel preparation unit is based on state-of-the-art bio fuel handling technology, with a process capacity of between 18 and 36 tonnes per hour of mixed plastics waste. Balled plastics are delivered on the tipping floor and fed to the primary shredder. The desired particle size is described as ‘hand-sized’, approximately 80 mm in side length. After leaving a screening drum, smaller material than the above size is accepted, whereas larger material passes to a secondary shredder. Prepared waste is then fed into two rectangular, 4,000 m3 flat-bottomed bunkers. They are filled and discharged in such a way that a fully homogeneous mixing of the fuel is ensured.A discharge screw moves over the entire bottom surface and feeds the mixed fuel to a 400 m-long pipe belt conveyor for transport to small day-silos at the combustion plant. Using conventional fuels, such as coal and natural gas, and also dry waste-derived fuels, the net energy efficiency of the RVL plant (PDF) exceeds 80 per cent. Thermal efficiency was checked in several tests. They showed that for all of the fuels used, combustion of a single fuel fraction did not reduce plant efficiency – either for combustion or for energy recovery. Boiler efficiency using the plastics- derived fuel was as good as or even better than with a normal fuel mix. A blast furnace, in which iron ore is transformed to iron work, is about 30 to 40 metres high and has a volume of up to 4,000 m3. Iron oxides are fed in from the top. Shredded or palletized plastics are fed in at the lower side of the blast furnace. The plastics gasify and in this process the reduction gas carbon monoxide is generated. This gas reduces the iron oxides to form pig iron on its way down the blast furnace, extracting oxygen. The reduction gas has a temperature of 900 to 1,200°C and consequently the iron melts. Liquid pig iron gathers at the bottom of the blast furnace and is poured out at regular intervals. In a blast furnace you may get up to 10,000 tonnes of pig iron per day. Pellets from Waste PlasticsSo far, carbon monoxide has been produced as a reduction agent by gasification of heavy oil, coke and coal. Instead of this, the new and resource-saving procedure of substituting feedstock by waste plastics is a method for recovering used plastics and thereby saving natural resources. For manufacturing of these pellets, plastics waste is utilised from separated collections of packaging from households, from commercial waste and shredder residues, from waste electrical and electronic equipment and end-of-life vehicles. Waste plastics are shredded to a size of a few millimetres or palletised by pressing them through perforated plates to a size of 6 to 10 millimetres. 220,000 tonnes of plastic are able to replace and save 150,000 tonnes of heavy oil. This form of waste recovery is called ‘feedstock recycling’. Waste plastics are utilised to save new resources – in this case heavy oil. The main benefit here is not to generate heat by incineration, but to produce chemical base materials like carbon monoxide. This represents a forward-looking strategy to save natural resources. There are various alternatives for recycling of waste plastics. Which one of these methods is better now? Material recycling or mechanical recycling – the remelting and transforming of plastics into new products – is considered time and again the best method. However, only around 20 per cent of waste plastics qualify, namely those which are collected clean and sorted (e.g. PET drinking bottles or large foils from industry).Energy recovery has a lower standing – for unjustified reasons. After all, in doing so, you utilise plastics originating from crude oil to generate heat, and 1 kilogram of plastics waste incorporates the same heating value as 1 litre of fuel oil. Therefore you utilise mixed plastics waste above all, for which sorting for separate types of plastics would be too cost- intensive. In order to estimate and compare the value of feedstock recycling within blast furnaces, this method was measured against other recycling strategies. The environmental benefit of various plastics recycling processes can easily be quantified by the amount of energy resources saved, because these processes mainly result in energy resource savings. This parameter includes effects on greenhouse gas emissions as well: less energy use means less environmental pollution. The benefit of resource savings for material/mechanical recycling of plastics waste is within a range of 0 to 60 GJ/t of recycled plastics waste for different processes.60 GJ/t are realised in recycling processes where homogeneous plastics waste fractions are transformed to granulate, which is a valuable secondary raw material. In many material recycling processes for mixed plastic waste (producing palisades, roofing tiles, etc.), the recycling benefit is actually very small. The energy needed for recycling is equal to the energy credit from the substitution, because the materials substituted by recycling (concrete, wood, roofing tiles, etc.) do not need much energy for production. The benefit of feedstock recycling in blast furnaces is approximately 47 GJ/t, which is undoubtedly higher than the benefits of material recycling processes for mixed plastic waste.Plastics for heating Vienna‘To combine the necessary with the useful’ could have been the slogan for construction of the waste incineration plant Spittelau in 1971, right in the heart of Vienna. During transformation to an architectural piece of art by the renowned artist Friedensreich Hundertwasser at the beginning of the 1990s, it became above all a cult-symbol and a tourist attraction for the city of Vienna. The Spittelau waste treatment plant (PDF) is one of three combustors in the city of Vienna. Municipal solid waste accumulates to more than 600,000 tonnes each year. With an incineration capacity of 260,000 tonnes, the Spittelau plant disposes of more than one third. Two boilers manage a volume of 15 tonnes per hour of waste each. In the process, 60 MW of heat capacity and 6 MW of electrical power are generated. During the reconstruction after a fire in 1987, in which a big part of the plant was destroyed, an ultra-modern flue gas purification plant was integrated. The fraction of plastics in Viennese municipal solid waste is about 10 per cent by weight. Out of the 260,000 tonnes treated each year in the Spittelau incineration plant, plastics waste is between 23,000 and 26,000 tonnes. The calorific value of plastics is very high: around 43,000 MJ per tonne on average. The contribution of these plastics alone to heat release is therefore roughly 1,000 billion MJ per year. At the usual 7,900 hours of operation per year, this amounts to an annual heat output of 32 to 36 MW. The total power of the boilers in Spittelau is 66 MW. This means that the 10 per cent of plastics waste account for 50 per cent of the heat output of the plant. The use of combustion heat from plastics waste from the Spittelau plant alone allows the following energy sources to be saved per year: 35,000 tonnes of coke, or 35 billion m3 of natural gas, or 25,000 tonnes of oil. Two more waste incineration plants and seven caloric power stations together with the Spittelau facility produce heat for the community of Vienna. The base supply is covered by the waste combustors. According to need, the power stations deliver additional heat quantities. Within the next several years, construction and connection of further operations is planned. This useful way of sustainable energy recovery will help the city of Vienna to extend its heat supply of this kind from 34 per cent at present to 50 per cent in the near future. Even now, the District Heating of Vienna (‘Fernwärme Wien’) is among the ten biggest municipal suppliers in Europe. Large parts of Vienna are supplied by district heating. Since 1969 the 40 km conduction grid at that time has been enlarged to more than 1,000 km today. For comparison: the total road length of the city of Vienna is around 2,800 km. More than 250,000 flats and 5,200 major customers are connected to the Viennese district heating grid.Right BalanceWithin an integrated waste management system, it is important to distribute all material flows to the best qualified plants respectively. The ongoing distribution of the Austrian plastics waste flows can still be optimised, and plastics bound for landfills must be reduced towards the zero mark.Anyone who is starting to develop a modern waste management system has the chance to design a special concept, fitting precisely to their specific situation. They are able to create a strategy to reach an ecological and cost-effective ideal level of utilisation of plastics waste. As a secondary raw material, it is perfectly qualified to substitute primary resources. The expert knowledge for this purpose is available. The ecological optimum, and the realisation of achievable revenues and economical benefits for all parties can become a reality through careful and sustainable planning. So, it’s up to us to find the right balance.CONTACT:
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