Mechanical Plastic Recycling

Plastic waste has become an integral part of our daily lives—whether in packaging, textiles, or technical products. Yet it is precisely this plastic waste that poses a major challenge to our environment. Many plastics end up in landfills or in the natural environment because they are not properly sorted and recycled. However, the recycling of plastic waste is crucial for conserving resources and reducing environmental impact.

A key problem in plastic recycling is the sorting of different types of plastic. Only when plastics are cleanly separated can they be reused and processed into high-quality products. This is where separation by density comes into play: Many plastics differ in weight, which allows for separation using a so-called sink-or-float process. In this process, the materials are separated in a medium with a specific density, so that lighter plastics float to the surface and heavier ones sink.

However, the conventional method of performing this separation purely by gravity is only feasible if a large area is available and the purity requirements are not too high. With its Sorticanter®, Flottweg offers a modern solution to make this process significantly more efficient. By utilizing centrifugal force (up to 1500x g), the Sorticanter® separates plastics faster and more precisely, resulting in drier and more homogeneous plastic fractions. Additionally, disruptive effects such as air bubbles or dust are reliably removed.

The Flottweg Sorticanter® efficiently and precisely separates plastics using an innovative centrifugation process that takes advantage of the different densities of the plastic fractions. Before the sorting process, the raw material is crushed to a particle size of 2 to 16 mm and thoroughly washed to remove any adhering contaminants, such as paper labels. The pre-washed material is then mixed in specially developed homogenization tanks with a carrier liquid, the so-called liquid separation medium (e.g., Epsom salt solution).

The homogenized suspension is fed via a static feed line into the rotating bowl of the Sorticanter®, where it is accelerated by centrifugal force. In the process, the heavier materials are pressed against the bowl wall and, as solid components, are transported by an internally rotating scroll at a differential speed toward the conical end of the bowl. In the conical section, dewatering takes place, during which the separation medium is separated from the solids by centrifugal force. The dried solids are discharged as the heavy phase through outlet openings.

The plastic fraction, which floats on the surface of the separation medium, is gently transported toward the light material discharge—similar to leaves drifting on a river. There, separation from the liquid occurs via a special cone, whereby the light material is mechanically dried and exhibits minimal residual moisture. An additional dehumidification step is therefore unnecessary, making the process particularly efficient and resource-conserving.

Mechanical processes using the Flottweg Sorticanter® enable high-precision separation of plastic fractions, even in complex mixtures. A prerequisite for the separation process is that the individual plastics are not present as composite materials, as their complex composition can complicate separation and impair the quality of the recycled fractions. Additionally, the density of the carrier liquid must fall between the densities of the plastic mixes to be separated.

Plastics Recycling with the Flottweg Sorticanter

The Importance of Plastic Recycling for the Environment and the Economy

Plastic recycling is of great importance from both economic and environmental perspectives. Through the efficient separation and recycling of plastic waste, valuable raw materials can be recovered, which reduces the need for new plastic production and thus conserves resources. Economically, this leads to cost savings, as less energy and material are required to manufacture new products. At the same time, environmentally friendly recycling reduces freshwater consumption and minimizes waste and emissions. Furthermore, waste prevention and the return of plastics to the production cycle reduce the burden on landfills and the release of pollutants into the environment. Overall, plastic recycling supports resource conservation and promotes a sustainable circular economy.

The Flottweg Sorticanter® offers an efficient, reliable, and environmentally friendly solution for plastic processing in chemical recycling. The combination of crushing, cleaning, homogenization, and precise centrifugation ensures optimal separation and product quality. In this way, the technology supports the sustainable use of plastic waste and promotes the circular economy through the recovery of valuable raw materials.