State of the art – camera-based NIR technology for even better sorting results
It is now over 20 years ago that the first near infrared (NIR) detection systems, originally developed for the food industry, found their way into recycling. A lot has happened since then both in terms of the available sensors and the evaluation algorithms being used.
Mobile phones recognise their legitimate users via the built-in camera and vehicles drive autonomously on our motorways. These are just two examples of the rapid development in sensor-based applications.
It was only a matter of time before camera-based systems also became standard in NIR sorting units, given the large number of developers dealing with these issues worldwide. Early in 2012 the first UniSort PR series replaced the point-to-point scanner, which had been usual until then. The UniSort PR from STEINERT uses an HSI (hyperspectral imaging) camera that has a previously unheard of visual/spatial resolution of 3 – 8 mm. A further benefit of HSI technology is its very high spectral resolution.
Greater efficiency using our proprietary STEINERT software
And the application range made possible by HSI technology can be fully exploited since the software used for evaluation is an in-house development and the sorting task can soon be adapted to your individual needs. Long development loops with external suppliers are therefore superfluous.
NIR refers to a spectrum in a range between 760 and 2500 nm that is invisible to humans. Typical patterns for materials based on molecular vibrations can be detected in this wavelength range after excitation with light.
Even the smallest differences in the chemical composition of the detected materials can be assessed since the HSI technology we deploy is able to analyse these typical patterns at very fine resolutions. This has a very positive impact on many applications.
This is how for instance our UniSort PR can detect a difference between the chemical composition of a PET bottle and a PET tray when sorting a PET fraction. The system could for example be used to select the PET tray or other PET multi-layer as active in the sorting process and only the pure PET bottle fraction would then be transferred to the subsequent processing line. The downstream processing line – say a colour sorter or even a density separator – would consequently be less burdened with impurities, which greatly simplifies the sorting task and results in higher extraction and better purity in the PET bottle target fraction.
The high spectral resolution of the UniSort PR makes its detection much more resilient against moisture. Water has a very significant wavelength in the NIR range, so it can slightly overlap the actual signal of the target object at a lower spectral resolution.
In addition to these relatively "complex" applications, the UniSort PR can of course also be used for all typical NIR applications in the field of sorting plastics or plastic mixtures, the sorting of substitute fuels or in the green waste / waste wood sector. The UniSort PR is generally available in working widths of 1,000 mm, 1,400 mm, 2,000 mm and 2,800 mm.
A combined system is also available, which also provides the system with colour information in the visible range (VIS range) in addition to pure detection using NIR. This means for example that PET bottles can be sorted by their colour, or even milk bottles and paper.
As with all our UniSort solutions, the UniSort PR can also be integrated into a control system where all currently collected data like material composition, belt occupancy and material distribution can be delivered.