Plastic recycling is a well-established industry that globally processes and resells several million tons of used plastic material each year. Rather than operating merely out of environmental necessity, plastic material recovery services can be both cost-efficient and productive, saving resources for a range of different manufacturing applications. The recycling and reclamation field also encompasses the industrial processes by which plastic materials are separated into their base monomers and made available for further polymerization at secondary and tertiary levels.
While the plastic recycling industry was originally focused on recovering manufacturing scraps and byproducts left over from initial plastic fabrication, present-day recycling services are capable of reclaiming heterogeneous post-consumer goods as well. The methods employed by material recovery systems tend to vary according to the type of plastic being processed, but there are some essential practices common to most recycling services. Stages such as sorting, cleaning, size reduction, separation, and pelletizing can be found in most plastic recycling operations. Likewise, the machinery used to achieve these processes generally falls into a handful of equipment categories called Plastics Recycling Machine.
Plastic Recycling Sorting Process and Equipment
Sorting and grouping plastic materials according to resin type is an important first step in the recycling process because contamination can render a batch of material un-reusable. The most frequently recycled resins, including polyethylene terephthalate (PET), high-density polyethylene (HDPE), and polyvinyl chloride (PVC), must be carefully separated from one another in order to enable further processing. Contaminants within each type of plastic must also be removed from the base resin to ensure stock purity.
Sorting machines must rapidly identify and categorize large volumes of post-consumer plastic, often under continuous input. Although there are varying degrees of technical sophistication and capacity, an advanced sorting machine can be equipped with some or all of the following features:
Sensors: These devices detect specific polymers within a mixed stream of plastic materials. They can be equipped with x-ray or infrared sensing that registers a polymer's unique signature along the spectrum. Some sensors also incorporate color detection technology that sorts material according to tint and transparency.
Ejectors: Mechanical or precision air ejection units physically group different plastic materials according to resin types. Depending on their capacity, ejectors can often handle very high rates of input.
Computing Systems: Computer processing technology supplies the algorithms that are used to identify and sort different materials. These systems provide the controlling parameters for both sensor and ejector operations.
User Interfaces: An operator's interface can provide machine controls and diagnostic tools for technicians. In addition, interfaces can also offer networking abilities to help integrate a sorting machine and make rapid adjustments to its functions.
Size Reduction Machines
Plastic materials usually need to be cut into smaller sizes in order to allow further processing and to provide easier packaging, transportation, and distribution of recycled stock. This cutting presents certain challenges, as many plastics are abrasive to metal blades and can have wide variation in their hardness, weight, and thickness. Most standard size reduction is performed by single or multi-shaft shredders, and granulators. Multi-shaft shredders perform scissor-like cutting with a series of rotating blades that can handle moderately dirty or contaminated material, but are somewhat imprecise in the size of the cuts. Single shaft shredders perform more of a tearing motion, and have slower motors that lengthen blade lifespan. They can also handle dirty or abrasive material and usually have adjustable or replaceable blades.
Granulators are composed of a rotor attached to blades that rotate within a chamber containing a grid floor. Their capacity for processing plastic material depends on the speed of the rotor, angle of the cutting blades, spacing of the grid, and the shape of the rotor. Granulators are usually sturdy machines, capable of relatively rapid cutting rates, and the presence of the grid allows for more precise control over the size of cuts. Granulator blades typically need to be replaced regularly over the course of operations.
