Note that the world's annual consumption of plastic materials has increased from around 5 million tons in the 1950s to nearly 100 million tons today.
Therefore, it can be said that the production and use of plastics has a range of environmental impacts.
It is true that, technically, almost all plastics can be recycled. However, as there are about 50 different groups of plastics with hundreds of different varieties, recycling plastics is a bit complicated.
The FLOTTWEG Approach
To recycle plastics, the different components have to be separated according to their specific weight. A simple “sink or float” process can be used to accomplish this task. However, this process takes a long time and the performance in terms of residual moisture content as well as centrate clarity is not adequate for further processing.
So what about looking around for a centrifuge that separates solids according to their specific density and improve separation performance and lower residual moisture content?
The FLOTTWEG SORTICANTER® is a unique solid bowl centrifuge which separates polyolefines from plastics and impurities. The separation efficiency is up to 99.99 %. The FLOTTWEG SORTICANTER® separates the freely drainable moisture, thus the moisture content in the discharged solids is between 2 and 20%.
The FLOTTWEG SORTICANTER® is suitable for sorting plastics such as ABS, PA, PP, PE, PS, PVC, as well as recycling of plastic fibers, cable waste, etc. and also for sorting and washing plastic mixtures such as DSD films, DSD mixed plastics, fibres and films, ground bottles, recovery of pet flakes, granulate from production waste and return materials, granulate from plastics after medical application, cable insulations and carpet fibres.
How the FLOTTWEG SORTICANTER® Works
Plastic materials to be separated in first stage are shredded to an edge length of 12 to 16 mm. Then adhesive impurities are eliminated by friction washers. The plastics slurry is conveyed to a tank with an agitator, homogenized and pumped to the SORTICANTER®.
The SORTICANTER® basically comprises a conical cylindrical bowl provided with a second cone at the end and a scroll tailored to the internal contours. The bowl and the scroll rotate at high speed in the same direction. The scroll rotates at a slightly different speed from the bowl to enable conveying. The mixture of solids and liquid is pumped through the feed pipe and passes through feed ports in the scroll into the rotating bowl. The product is then accelerated to the bowl speed to expose the suspension to centrifugal forces.
Centrifugal force in a solid bowl centrifuge causes solids with a higher specific weight than the liquid phase to settle against the bowl wall. The scroll conveys the separated solids up a conical beach where they are discharged through ports in the solids housing. Solids lighter than the liquid phase float and are carried with the liquid flow to the other end of the centrifuge. Before these floating solids reach the conical end, they are conveyed through a drying zone to a second port. The separation liquid (liquids with different densities can be used to make one solids phase float and one solids phase settle) is drained at the outer diameter of the second cone. The liquid flows into the impeller chamber to be discharged via the impeller.