The available components are selected to comply with the required purity levels of the end product. Simple structures for simple tasks – complex structures for difficult tasks.
Herbold Meckesheim offers bale separators for compressed bales of different materials, e.g. bottles or plastic household waste, which enable subsequent classification of the material and manual sorting or the mechanical separation of coarse foreign bodies by means of a vibrating screen or screen drum.
The removal of labels and dirt by the Herbold label remover is carried out by friction between the rip-off elements on the rotor and the interchangeable steel pins. The forward feed inside the machine is created by the design and layout of the rotor rip-off elements. A special feature is the design of the working chamber, which ensures even loads and dwell time of the bottles. After going through the working chamber and leaving the machine, the separation of the labels and the removed contamination is carried out by the subsequent process steps.
The addition of water during pre-shredding uses the movement and friction of the material to be shredded for a pre-wash. In this way, relatively large quantities of foreign materials can be removed, e.g. sand from agricultural films. The separation of foreign materials at this early stage of the washing process protects all the subsequent units from wear and tear.
The VWE 600/2 pre-washing unit combines the function of a foreign body separator with a pre-wash of the feed material. In three integrated process steps, the Herbold pre-washing unit separates foreign bodies such as stones, metals, glass, sand and paper from the shredded material, subjects the feed material to an intensive washing process and finally makes any more foreign bodies sink to the bottom.
Material containing foreign bodies is sprayed with water and pre-washed in a drum, part of which has a screen, up to 2 m in diameter and up to 6 m in length.
Herbold granulators using a double cross cutting action guarantee a good cleaning effect. By adding water during the grinding process, the friction created by the shredding can be used for intensive washing. At the same time, the wet grinding prevents blockage of the screen and protects the material during the cutting process.
The material which is simultaneously washed and granulated in the wet granulator falls into a dewatering screw, which separates the dirt dissolved in the water. For plastics containing paper, the friction washer, a high-speed screw, is used, which removes by centrifugal force the paper softened during the pre-washing and wet grinding. In the case of higher contamination, an intensive washer is also used instead of the friction washer.
Swim-sink tanks use the specific weights of the various kinds of plastic to separate them. Examples of typical applications are the separation of PET or PVC (both of which sink) from polyolefins, such as PE or PP (both of which float). The light fraction is transported along the surface of the water by means of paddle drums, whilst the heavy fraction is extracted – depending on its amount – either by pneumatic valves at the bottom of the tank or by a scrape conveyor mounted below the tank.
Separation quality in the ppm range (e.g. for PET bottles) is achieved by a second separation stage, consisting of a heavy particle and hydrocyclone system. Depending on the task, the separation stages – swim/sink tank and hydrocyclone separation system – are used either individually or in combination.
The hot washing stage serves not only for the removal of adhesives, but also for washing out remaining impurities in the flakes, such as sugar, soda residues, etc, under strict control of the various process parameters such as pH-level, detergent, de-foamer, temperature and dwell time. The complete process, together with the dosing of the caustic agent and detergent are controlled automatically.
By cleaning the process water in an ultra-filtration stage, we can ensure a closed water circuit and reduce the consumption of fresh water, heating energy and chemicals to a minimum. The experience with hot washing in PET washing lines also forms the basis for the modified hot washing steps in film washing lines and PP/PE hard plastic washing lines. With the Herbold hot washing process, qualities of the washed products can be achieved, which in combination with the other washing, separation and drying steps of a Herbold system need fear no comparison with the source materials.
The dirty water created by the washing process is collected and cleaned and can be reintroduced into the circuit, which significantly reduces the water consumption. Herbold Meckesheim offers all the elements required for this circuit.
An important component of a treatment system for plastic waste is the silaging of intermediate and end-products. Herbold Meckesheim supplies silo systems for all ground products and very low-flow goods such as film flakes or fibres. Rectangular silos are available for capacities up to 60 m3, and round silos for up to 20 m3.
A mixing silo with capacity up to 20 m3 is available for regrind from hard plastics.