Extrusion Asia Edition 1-2022

39 Extrusion Asia Edition 1/2022 输送将物料带到空气分级器（型号SZS 630/212 ），空气分级 器有一条曲折形通道，用于筛选出轻质材料，例如箔、纺织 品、纤维或灰尘。 最后，一个双工位大袋站可用于装袋。在这里，轻质材 料和清洁的 PP 片这两种产品被以风力方式装入大袋中。为了 方便用户，可通过舒适的触摸屏（西门子 S7-1500）自动控制 整套设备。材料的波动通过对设备的组件进行有针对性的控制 来处理，从而保证了最高的性能。智能和自动控制系统确保了 高效率的运行，人力需求也较低。 High purity of recyclates Herbold Meckesheim has developed a new washing plant for shredding and cleaning hard PP plastics, which is used very suc- cessfully to produce re-granulates. Both, the high purity of the recyclates and the high throughput, plus the resilience and ease of maintenance, as well as the elevated level of automation, are praised. Designed for high capacities and a 24-hour continuous operation, two tons of PP flakes can be produced per hour with a residual moisture of less than one percent and a flake size of twelve millimeters or less. What does a model plant look like in detail? First, at a big bag emptying station, the PP shredded material passes through the bottom outfeed of the big bag into a funnel with a volume of 0.5 cubic meters. From here, the material is discharged via a screw conveyor onto a conveyor belt. A large buffer hopper (Type SB2) of around two cubic meters ensures an even feeding of the material flow to the downstream coarse material separa- tor. This is important in the case of a direct upstream shredder that discharges unevenly. Heavy-duty cutting mill The reliable coarse material separator (Type SAS 50/430) segre- gates heavy foreign materials such as metals, stones or glass to protect the downstream units such as the cutting mill and the friction washer. To minimize loss of PP, upward flow by pump is integrated. The heavy-duty cutting mill (Type SML 60/145) car- ries out wet chopping of the PP bottles pre-shredded to 30 mil- 分离罐、螺旋脱水器和机械干燥机 Separation tank, dewatering screw and mechanical dryer 用于 PP 片和筛选后的轻质材料的双工位大袋站（前景中心位置） Double big bag station for PP flakes and sifted light materials (in the foreground) ➠ Herbold Meckesheim GmbH Industriestr. 33, 74909 Meckesheim, Germany www.herbold.com limeters. Due to high friction, the mill achieves an excellent cleaning effect and, thanks to the addition of water, shows low wear on the blades, housing, and screen. The rotor has replace- able knife supports and the wear plates are exchangeable, which, combined with the optimal accessibility, makes the ma- chine completely wear protected. During the next step, the friction washer (Type FA 3000) inten- sively cleans the PP flakes. In the process, it separates dirty water as well as fine particles and paper fibres and conveys the product further to the separation tank. The rotor of the washer requires little maintenance thanks to exchangeable wear plates. In the separation tank (Type SSB 4000/1800) – using water as medium for density separation – the flakes are transported as floating material with a dewatering screw to the downstream mechani- cal dryer. Particles with a density beyond one gram per cubic centimeter, such as PVC or PET, are discharged by a chain scraper conveyor. Low cleaning effort The mechanical dryer (Type T 1015 PA) removes moisture from the washed PP flakes and evacuates residual impurities like paper fibres. Embedded in a hot-dip galvanized housing, the machine is equipped with a pneumatically operated mechanical cleaning with a rinsing appliance for the screen surface and exchange- able wear plates on the rotor blades for low cleaning effort. Pneumatic conveying takes the material to the air classifier (Type SZS 630/212), which has a zigzag channel for sifting out light materials such as foils, textiles, fibres or dust. Finally, a double big bag station is available for bagging. Here, the two products, light materials and cleaned PP flakes, are pneumatically packed into the big bags. The entire plant can be controlled automatically for the convenience of the customer with a comfort touch panel (Siemens S7-1500). Fluctuations in the material are handled by targeted control of the plant com- ponents, guaranteeing a maximum performance. The smart and automatic control system ensures an efficient operation with low manpower requirements.