ASR - FROM WASTE TO PRODUCTS

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Silas Randall
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1 ASR - FROM WASTE TO PRODUCTS Sattler, H.-Peter and Laage, Bernd LSD Umwelt- und Recyclingtechnologie GmbH, Hanau and R-plus Recycling GmbH, Eppingen Germany The paper will explain WESA-SLF, a dry-mechanical process to treat ASR with the aim to achieve usable products, mainly organic materials, metals, and minerals. Detail information will be given about the first plant for processing 4 tons per hour ASR which had its start up end of The experience with the first months in operation as well as with the quality of the products and the influence on their properties/composition by changing specific plant parameters/adjustments are discussed. The German regulation for end-of-life vehicles (ELV), effective since April 1998, demands for scrap cars a recycling quota o f85 % from the year The today's quota is roughly 75 %, i.e. about 25 % of the ELVs are waste - known as automotive shredder residue (ASR) - and go to landfill. Therefore, to reach the goal for 2002, the ASR must be processed and its components recycled as products. The most innovative technique capable to do that is the WESA-SLF process. It is a drymechanical processing method, intended to completely separate out the organic and inorganic components of the ASR. As separation criteria the specific density of the components is used, which guarantees an adequate selectivity of separation between the organic and the inorganic components as shown in Fig ,8 7, ,7 2, Cu Fe Al Glass PVC 1,4 1,2 1,1 1,1 1,1 0,9 0,8 0,7 PUR PA Rubber ABS PP Wood Paper Fig. 1 Specific densities of the ASR Components

2 In order to reliably achieve this goal, however, the ASR must be completely disintegrated, that is even the smallest parts such as wires must be reduced in size, so that, for example, the insulation is stripped off the copper wire. This is achieved when all of the ASR is reduced to a particle size of less than 7 mm. Since cutting /crushing is the most expensive step in processing, because of costs due to wear and energy, extensive investigations have been undertaken to determine an optimal procedure. The result has been the development of selective 2-step comminution (see Fig. 2). After screening the fine components of the ASR < 7 mm, which must not necessarily be subjected to comminuting and the fraction < 1,2 mm, which consists mainly of sand and is transported directly to the final product "minerals + metals", the remaining material is cut in a socalled rotary shear to a particle size of about < 20 mm. The rotary shear operates without a sieve, so material which is already small, mostly the abrasive mineral products, drop through the rotary knives. All the magnetic components are then separated out from the coarse-cut fraction. This is done mostly to reduce the rate of wear in the subsequent main comminuting stage, executed by a double-shaft cutter. In this machine the required particle size of < 7 mm and thus the necessary degree of disintegration is achieved with an integrated slide-in sieve. Since the ASR may contain between 5 and 25% moisture, depending on its origin and the time of year, and moist material a) is difficult to screen and b) separation cannot subsequently be guaranteed due to adhesion between moist organic and inorganic material, all the material, after comminuting, is dried in a through-put belt dryer to a moisture level below 2%. Drying is deliberately carried out on the crushed product, since on one hand a crushed product with a very large relative surface area can be most effectively dried, and on the other no moisture can remain in the cutted foam and textile particles. Since experience has shown that during subsequent handling of the disintegrated material individual components may often adhere to each other again thus, for example, copper wire can stick in particles of foam preliminary air classifying is carried out immediately after drying via a special designed so-called cone sifter. The heavy material from the preliminary sifting is now screened into 3 fractions of differing particle sizes via a multi-level sieve. Screening into narrower particle categories is necessary to achieve the highest possible degree of separation with the zigzag air sifter at the final separating stage. A zigzag air sifter is a flow separation device, which consists of a series of conduits connected to each other angularly. The metered sifting air volume flows upwards through the separating device, and the feed material is transported to the top half of the sifter via a cellular wheel sluice. Particles with a downward velocity greater than the separation downward velocity cannot remain in the flow and are to the heavy material extraction at the bottom end of the device. Particles with less than the separation downward velocity are carried by the sifting air and separated as light material in a post-connected cyclone separator via cellular wheel sluices.

3 ASR PRE SCREENING < 1,2 mm < 7 mm PRE CUTTING FERROUS MAGNETIC SEPARATION MAIN CRUSHING DRYING AIR CLASSIFYING FOAM, FLUFF SCREENING SIFTER 1 SIFTER 2 SIFTER 3 ORGANIC FRACTION COPPER MINERALS + METALS Fig. 2 WESA-SLF-PROCESS

4 The following products are obtained from the ASR processing - a magnetic fraction with approximately 95% iron, - copper granulates / chaff - a mixture of mineral materials with some metals and - the organic fraction, whose contents and caloric properties (based on previous lab tests) are stated Metal, each < 0,5 % Carbon ~ 50 % Hydrogen ~ 6 % Oxygene ~ 12 % Chlorine 1-2,5 % Ash content % Caloric value > 23 MJ/kg Variations in the quality respectively the composition of the 4 products can be achieved for example by changing the particle size category, i.e. smaller size bands, and/or the air flow velocity of the zigzag sifters. By doing that, it should be possible the separate even vinyl (PVC) from the other organic material, as Fig. 1 indicates, and such lower the chlorine content of the organic product. The extracted iron scrap and the copper are sold to steel plants respectively secondary smelters. The mineral fraction with the metals can be further treated in well established processes in the recycling industry and in this way win the metals, mostly copper and aluminium. These products have a guaranteed outlet, which provides a more or less contributory profit margin for the process. The optimal recycling methods for the organic fraction have not yet been found. The highly homogenous organic products, as a result of their high carbon content and high caloric value, may be used - only thermally as fuel, for example in gasification systems, heating and power stations, etc. - or material-thermally, e.g. as a carbon provider in steel works. - or for the production of methanol Furthermore, as the result of their extremely high absorbency, the organic fractions may also be used as a binding agent for mill scale-, sewage- or coal sludge. Freely selectable particle sizes may be determined via simple mixing and conditioning procedures, and the material handled in this way may be recycled in a circulating fluidised-bed-reactor, or in a rotary kiln, cupola oven, or blast furnace.

5 Some details regarding the costings of the WESA-SLF prototype plant: - Investment : approx 4 m DM / 2,04 m EUR / 2,1 m $ - Capacity : 4 t/h = approx. 16,000 tons per year in 2 shifts - Processing costs : approx. 150,- to 120,- DM/t / 76,- to 61,- EUR/t 79,- to 63,- $/t. Because of the great interest of the automotive industry and it's suppliers to solve the above mentioned year 2002 recycling problem, the pilot plant located in Eppingen in the southern part of Germany is financially sponsored by the "ARGE-Altauto", the German working committee for ELVs.

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