With any single stream sorting system, there is a delicate balance of several factors that all operators try to reach. How do you satisfy fiber quality requirements, make necessary throughput requirements, and reduce sorting labor while minimizing the amount of fiber getting to your container lines?
The fiber that falls off the last screen can adversely affect the plant’s optical sorters, and ultimately falls off the end of the system and is lost into the residue. Why does a large percentage of this fiber end up on the container line? There are several reasons:
Overrunning the system. If your system is rated at 20 tons/hour and you try to process 30 tons/hour over it, fiber will end up on the container line.
Steep screen angles. Steep screen angles are great to help clean up your paper (with fewer people), but there is a potential trade off. The steeper your screens are set, the more fiber may end up on your container lines.
Worn stars. If your screen’s stars are worn, your paper struggles to climb at any angle and your container line will get paper on it.
Non-OEM stars. Stars made with the wrong composite material wear quickly and affect paper climbing ability.
The wrong stars. “Wheel shaped” or “guitar-pick shaped” stars may be good for size separation at low angles, but these style stars don’t help paper climb when your screen is set at a steep angle. The best of bad choices have to be made with this style star. Either operate your screens at low angles (lose less fiber to container line but make dirtier paper) or operate at steeper angles (make cleaner paper but overrun your container line with fiber).
3-D fiber. Your screens are not intelligent enough to distinguish light sheet paper and 3-dimensional boxboard and chipboard that has been balled up. A balled up cereal box has weight, dimension, and acts like a container–thus it falls off the last screen and heads to the container line.
There are several fiber cleanup devices on the market to capture this fiber before it wreaks havoc on your container line. Van Dyk offers three different fiber clean up solutions, all of which can be effective depending on your system throughput, your material composition, your layout and space available for a retrofit, etc.
The Lubo Elliptical is a ballistic separator that separates all light sheet papers, film, and remaining fines from your containers. The grids on the paddles provide a screening on size.
The Lubo PaperMagnet® removes all light sheet papers and film from your containers. It is ideal for a small space. By adjusting the parameters, conveyor speed, and airflow, an optimal adjustment can be achieved for different material inputs and separation qualities for the 2D or 3D fractions. Depending on the size and composition of the material, input recovery rates as high as 98% can be established.