In this treatment plant mixed plastics, such as crisp packets, yoghurt pots, margarine tubs or plastic bags, are refined into an agglomerate which is then used as a reducing agent for iron ore (pig-iron) in the steel industry. Due to its high caloric value, it can also substitute fuels (coal and oil) which are usually needed during steel production.
Delivery and pre treatment
As a first step, bales of mixed plastic are delivered to the plant. These are then opened by removing the steel wires manually. Next, the material is fed into a rotating drum, which loosens up the material on its way to the shredder. After shredding, ferrous and non-ferrous metals like iron and aluminum are separated from the material using magnetic and eddy current separators. An air separator divides the material into heavy plastics and a light fraction consisting mainly of foils and hollow parts.
The plastic mix is heated up in large cylindrical reactors, that center on vertical rotating axles holding numerous fast rotating knives. The heat required for the process is generated by kinetic energy from friction and pressure. The heat leads to the evaporation of water from the plastics and leaves the reactor as steam. The temperature in the reactor remains close to 100°C until nearly all water has evaporated, after which the material is heated up to about 130°C through the action of the rotating knives. The finely shredded plastic reaches a paste-like form and the energy needed to keep the knives rotating reaches a peak, indicating that the process is completed. Next, the pasty material is quickly chilled with cold water and then removed from the reactor as a granular agglomerate.
The entire process is run as a batch operation.
The produced agglomerate material is again sieved and exposed to magnetic and eddy current separators. It is then split into three fractions, varying in size:
a fine fraction (<1mm) can be used in thermal processes
a medium fraction (1 to 8mm) is used for the reduction of pig-iron in steel industries and
a large fraction (>8mm) is shredded again and combined with the medium fraction.
Storage and delivery
Large silos are used to store the finished agglomerate (1 to 8mm), it can be delivered in bigbags or simply filled into trailers.
At the steel mill, the agglomerate is blown into a furnace together with hot air. The material is gasified and utilized to chemically reduce iron ore (pig iron). In the past, heavy oil had to be used for this process, therefore one might reasonably say that our agglomerate successfully substitutes valuable primary resources and contributes to environmental protection.
The agglomerate can also be used to manufacture new recycled plastic items (like garden furniture or window frames). However, this requires high quality agglomerate and refining and not all of the produced agglomerate can be utilized in this way.