UniSort sorting equipment makes significant increases in capacity possible

Since 2004, Brantner Walters has operated an automated recyclable materials sorting plant in Wölbling, Austria. In May 2012, a pre-sorting facility was put into operation at the facility in order to effectively respond to growing throughput and increasing requirements for product quality.

From the very beginning, Brantner has relied on products made by RTT Steinert, a subsidiary of Steinert Elektromagnetbau, which has its headquarters in Cologne, Germany. The original facility incorporated two UniSort PX, two UniSort CX and one UniSort C when it was first commissioned. The facility’s typical products were clear PET, green PET, blue PET and PE.

The basic idea behind the pre-sorting facility was to increase the capacity of the existing plant components by ensuring that only a portion of the flow of the bottle fraction to be sorted would be conveyed to the appropriate section of the plant. To accomplish this, Brantner made use of the fact that approximately 50% of the PET bottles are clear.

The latest generation of UniSort equipment was used to effectively separate the clear fraction of the bottles from the input material. The UniSort colour recognition system was combined with a HSP NIR camera for the first time. Both cameras view the same point, which simplifies the evaluation and thus reduces the amount of bottles incorrectly ejected (due to rolling objects).

The technology from RTT Steinert functions completely without the need for any obtrusive rotating mirrors or other moving optical elements. Furthermore, the latest generation of the NIR camera utilises an image sensor that enables the simultaneous imaging of all of the objects within the field of view (with the same high spectral resolution of less than 3 mm). This eliminates any losses of objects due to observing points only within individual areas. The spatial resolution of the HSP NIR camera is <5 x 5 mm; a sampling rate of more than 300 Hz means that it can detect even very small objects.

The first stage of the pre-sorting facility consists of two UniSort PC 2000 R machines. These sort the bottles by type of plastic and simultaneously by colour. The high-value clear bottle fraction is sorted positively in order to achieve maximum purity. The fraction that has passed through this stage is then sorted by type of plastic in the pre-existing plant section.

The UniSort C 1400 is used in a second stage. This is purely a colour-sorting stage using transmitted light. The fraction that has passed through the first stage (clear PET bottles) is once again sorted here. Due to a spatial resolution of better than 1 x 1 mm, the finest nuances of colour can be reliably detected and removed. The transmitted light camera is even capable of distinguishing weakly coloured (light blue) PET bottles from clear bottles.

Coloured bottles are ejected and further processed together with the product from the first stage. The use of the latest UniSort machines ensures both very high purity and minimal over-sorting. As 50% of the PET input is already gated out in the pre-sorting facility, the pre-existing facility with its NIR colour sorting stages can continue operating without modification.

Sensor solutions from the Steinert UniSort family are capable of recycling 95% of the materials in the raw materials industry. The UniSort sensor sorting systems with inductive recognition, colour and X-ray sorting systems make it possible to achieve a material purity of 98%.