Manufacturer: Resource id #8
reference number: 2688
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Abfallaufbereitungsanlage Sorting plant Year of construction: 2000-2003 Throughput: 500 t/day approx, 120.000 t/year approx. The sorting plant is suitable for domestic refuse, bulky waste, plastic waste, light-weight fraction from shredders and factories waste. Different waste types are shredded and subsequently screened, sorted and dried. After that the high heat value fraction is turned into fuel pellets. The process includes the following stages: • receipt, pre-sorting and loading of the wastes; • shredding of coarse fraction; • classification; • separation of ferrous and non-ferrous metals; • shredding of middle size grain fraction; • thermal drying; • separation by screening into a coarse and a fine fraction; • sorting; • pelletizing; • utilisation in gasification plants. Receipt of the waste The waste is tilted into a feeding hopper according to their type: domestic refuse, bulky waste or bulky factories waste. A sorting excavator loads the waste that does not need shredding directly onto a channel conveyor belt. The waste that needs shredding is loaded into the primary shredder. After that, the shredded waste and the waste that does not need shredding are loaded onto a high-speed conveyor belt. All the machines are accessible by a wheel-loader. Extraneous materials such as • large pieces of wood; • large pieces of metal; • large pieces of inert materials are removed into special containers. Bulky waste is tilted near the feeding hopper and pre-sorted by the excavator as described above. Separation of potential recyclable and extraneous materials The aim of the separation is to get as much potential recyclable materials as possible from the waste and to liberate the waste flow from the materials that are capable to disturb the process. The input particles involved in conveying and separation processes should not exceed 350 mm approx. A trommel screener separates the waste into three fractions (coarse, middle size and fine fraction) in order to optimize the subsequent separation processes. The coarse fraction > 240 mm is chosen in such a way that big sheets of paper and foils cannot significantly disturb the automated sorting of screen underflows. Screen residues contain mainly paper, foils, big composites, plastic waste, textiles, sheet metal packaging and wood. Sometimes stones and electric gadgets can occur. Overband magnets separate ferrous materials out of the screen residues. Then ferrous materials are loaded into a primary shredder. The primary shredder is equipped by an obstruction flap that protects the equipment from extraneous materials. The shredded material returns into the screening section for screening in order to get middle size and fine fraction. Ferrous metals are separated out of the middle size fraction > 60 - < 240 mm by an overband magnet and a drum magnet. After that, non-ferrous metals are separated. The middle size fraction is processed in a ballistic separator where the waste flow is separated depending on flight curves of different materials. The input material is fed onto an inclined surface rotating at a horizontal axle. This so-called paddle transports the materials in a ballistic flight curve on the inclined surface. Depending on the material properties the parts show different behaviours: lightweight and flat parts like paper or foils move upwards and are discharged at the upper end of the paddle surface. They form the light fraction. The intense mechanical treatment during discharge removes dirt from the components. Heavy, substantial parts roll in the opposite direction. They are collected at the lower paddle end and are discharged as heavy fraction. It concerns stones, bottles and metals that have not been caught by overband magnets, par ex. stainless steel. The third material category (< 15 mm) is the light fraction. It consists of materials falling through the perforated paddle surface. The light fraction gets into the underflow < 80 mm. The light fraction is cut in a shredder into particles < 60 mm and then conveyed into the dryer. In the rotary dryer material is dewatered and its weight is reduced. The dryer supply air is heated in the heating chamber and blown into the drying chamber. The material is dried 10-20 minutes approx. to reduce its moisture to < 10 %. The drying chamber has a form of a drum. Thanks to its rotation, the material is intensively exposed to the hot air. The dryer is driven in such a way that the Cb content in the water vapour cycle is < 10 % after drying. The C^ content is controlled by measuring of O₂ content after the hot gas generator and after the filter. If the O₂ limiting value is exceeded, the O₂ percentage can be lowered through water injection. If the “second alarm” value is exceeded, the heating of the dryer supply air and the material loading are stopped and the unit is automatically inertized by N₂. The dryers are loaded by screw conveyors which also prevent the infiltration of false air into the dryer. The material is discharged from the dryer by a sliding gate that is operated in clocked operation. This sliding gate prevents the infiltration of false air as well. In case of a serious dryer error, the velocity of loading conveyors is reduced and the residual input flow is redirected into the dryer via a gathering conveyor. After separation of ferrous and non ferrous metals, the fine fraction is also conveyed into the rotary dryer. In the rotary dryer, the material moisture is reduced to < 15 %. The separation of ferrous and non ferrous metals ensures an accurate elimination of noxious substances like Cd and Ni contained mainly in batteries. Post-processing After drying, the waste separated from the fine fraction is fed into further procession. Further separation is performed by winnowing. A pneumatic table is set into rotation and is through-flown by air bottom-up. The vibration and the air flow spreads and lifts the entire material bed. The lighter particles are fluidized, float on top of the heavier particles and then drift downhill in the direction of the deck’s inclination where they are discharged at the deck’s lower end. The heavier particles are not picked up by the air flow and move towards the air table. They contact its surface and are flowed off the deck to the discharge end for heavy particles. The sharpness of separation can be optimized if the product stream is divided into two fractions (4/30 and 30/80) and distributed to 2 pneumatic tables. A flip flop screen with cells 4 mm is placed upstream of the pneumatic table in order to avoid the small grain fraction < 2 mm to mix up with the light fraction as dust irrespective of its material. The screened product is incinerated. The heavy particles are conveyed to the inert fraction and the light particles are pelletized. Pelletizing The material suitable for pelletizing is fed into the pellet presses via an intermediate buffer. The rotating pressure rollers press the material through radially arranged holes. The material is compacted thanks to high friction force. The pellets are cooled by convection cooling and discharged. Cooling During the process of pressing the pellets are heated to 90°C through tumbling, friction and shredding. After pressing they are cooled in a pellet cooler to 35°C approx. The pellets are transported into and out of the pellet cooler by rotary feeders. The warm pellets are cooled in a counter current pellet cooler by the waste air coming from the delivery hall. After that the pellets are screened and the particles < 8 mm in the underflow return into the process of pelletizing. |
