In the region of three quarters of the waste paper to be processed consists of cardboard pieces and paper packages that are mostly available loose. The balance of the material consists of pasteboard cases and residual reels. With such varied shapes of material being pressed the results are non-uniform bales. This in turn leads to a different weight of the bales. Above all the very stiff pasteboard cases may, if they are supplied to the press without having been reduced in size, lead to a complete obstruction of the press. Moreover, with such irregular bale sizes, subsequent storage by stacking the bales becomes very difficult. Ultimately, there can be a large problem with economically transporting the finished bales as lorries and ship containers will not be filled to capacity.
Universal size reduction machine WLK Super-Jumbo
In order to create economic conditions for storage and transport the waste material therefore has to be reduced in size before being pressed. The requirements to be met by size reduction are very high since the plant used has to cope with the above mentioned material problems and has to achieve an annual throughput of 20,000 tons. For this size reducing task a single-shaft shredder, type WLK Super-Jumbo is used. Material is fed into the large hopper of the WLK shredder with a bin-tipper loading onto a conveyor belt which is mounted at floor level and inclines up into the machine.
The WLK shredder is driven by two powerful and robust electric-motors rated at 55 kW each. The solid single-rotor with a width of 1,800 mm and a diameter of 600 mm is based on WEIMA Maschinenbau GMBH patented V-rotor technology, offering extremely aggressive cutting performance with reduced heat build up in both material and the machine. The 54 cutting tools mounted on the rotor are 80 mm x 80 mm concave cutting blocks. The blades have been produced from special knife steel and can have four cutting corners. The rotor speed is approx. 80 rpm which results in a considerable reduction in the sound level in comparison with high-speed size reducing machines. The hopper opening is approx. 2.20 m x 2.40 m with a volume of approx. 5.8 m³.
Fast material supply
Material feeding to the rotor is carried out by a ram that runs on horizontal guides in the machine frame. This ram presses the material in a load-controlled manner against the rotor. In case of an overload, the ram switches to a reversing mode until the overload has ceased. This ram and the machine floor are fitted with metal strips (segmented ram/floor) to prevent the thin pieces of waste from sticking under the ram and stopping it from operating. Additionally, brass ram guides guarantee a smooth and secure guiding of the ram.
With an adjustable counter-knife that has been particularly designed for the size reduction of paper an exact adjustment of the cutting gap is possible. In conjunction with the cutting blocks used here (with specially designed knife tips) this Super-Cut system guarantees the efficient processing of thin materials that are difficult to be reduced in size with a high cutting quality and a low dust percentage. The counter-blade rail consists of 4 pieces. This means that in case of damage, the complete counter-knife may not have to be replaced, reducing repair costs.
The machine is equipped with a lifting screen housing in front of the rotor. This permits a fast access to the rotor which in turn results in reduced down- time during cleaning and maintenance work and therefore guarantees reduced standstill periods and a high availability of the machine. The cutting blocks in the machine are rotated from one tooth to the next once worn. This procedure results in a blade service life of approx. one year.
Discharge of material
The size-reduced material is discharged without any screen onto a conveyor belt mounted below the rotor. This conveyor belt sidewalls to prevent the material from falling from the belt. With this plant the key is not the final particle size but purely to reduce any large, irregular pieces that contribute to the irregular sized bales. This prevents the problems associated with the pressing process that results in the bales falling apart. The material is conveyed diagonally towards a second conveying belt which runs at a faster speed. This results in further separation and loosening of the material to assist baling.
The size-reduced and loosened material is now a mixture of parts with approximately the same size and composition. It is conveyed into the funnel (1.0 m x 1.3 m) of the downstream press. The funnel of the press may now be filled faster and more consistently than with material that had not been reduced in size. Furthermore, the press can run a higher number of strokes resulting in a higher bale weight because of the better compression. The bales produced possess a uniform size of 1.2 m length, 0.8 m width and 0.6 m height. They have clean edges and a uniform weight of approx. 550 to 600 kg. All in all, the pressed bales are approx. 50 kg heavier than those made of material that has not been reduced in size. In this way, the storage room being available on a truck and/or in a sea container will be optimally utilized. In the course of its further processing, the material may well be treated and processed in the pulper and the bales are capable of dissolving well.
For about 28 years, the Wesendrup-AVU-Recycling GmbH & Co. from Wetter on the Ruhr have been dealing with paper recycling and besides the processing plant for waste paper operate a plant for file and paper shreddering and in 9 cities the local collection and disposal of waste paper in 1,400 deposit containers. Mr. Herr Rudolf Wesendrup, managing partner and the developer of the plant states, 'With the single-shaft shredder of WEIMA Maschinenbau GmbH, we have further rationalized the processing and treatment of waste paper to bales and have made it economic at low operational cost which will result in a fastpay-back of the investment made. The continuous obstruction of the press e.g. through pasteboard cases that had not been reduced in size and which considerably disturbed the operation is now in the past. The absolute reliability of the plant with regard to performance and availability, the short delivery time as well as the comprehensive service which has always been available during commissioning and thereafter, confirm that we have made the right decision in choosing WEIMA Maschinenbau GMBH.'