System changes filter continuously: impurities in the production of post-consumer plastic granules has become an interesting challenge

As we have had the opportunity to deal with in other articles, the quality of the plastic input from separate waste collection has undergone a general deterioration in recent years, also due to the closure of imports on the Chinese market in late 2017.

The increase in the presence of mixed plastics , such as coupled poles, PVC or contamination of other plastics inside the post-consumer waste bale that arrives at the plastics processing plants, puts the polymer producer in difficulty on the maintenance of a suitable quality of the polymers to be produced.

Never as in these periods has the quality of waste washing systems been a fundamental fact for selecting, cleaning and limiting parts that cannot be easily processed in extruders.

The less material incompatible with the main material to be processed, such as HDPE, PP, LDPE, MDPE, PS and others, the more the production gains in terms of speed, quality and costs.

The washing process must be well designed according to the input to be processed and its use must not be pushed to maximize production, as the waste processing cycle inside the tanks provides for correct material passage times , movement and a sufficient length of the path in the water for the right decantation of the material.

It is not always possible to have the correct washing systems and, not always upstream of these, it is possible to have modern optical selection systems for incoming plastic materials, which can divide plastics by homogeneous families of products.

When the technical combination, efficient automatic selection and properly dimensioned washes are not available or are undersized, the use of post-consumer material for the production of recycled granules could lead to many difficulties in the production of granules.

There are impurities filtration systems on the market that match the extruders and that can replace traditional cassette filters, allowing production to be given help in terms of quality of the granule produced, reduction of waste and production speed.

We are talking about the automatic filter changers that provide a continuous self-cleaning system of the residues on the filters, expelling the waste parts, maintaining the pressure of the extruder, with losses assessable in 5-10 Bar and a modularity on the capacity of filtration up to 50 microns.

The automatic filter changers can also be used for plastics with fluidity instability within the extrusion, such as PET and Naylon .

Although they are excellent tools for improving the production process of post-consumer plastics, it should not be forgotten that this type of waste, as it comes from a heterogeneous mix of mixed plastics, would need a careful processing chain that covers all the steps related to mechanical recycling.