12 VOITH


Getting the best out of OCC stock preparation


What factors determine the quality and efficiency of stock preparation for recovered paper? Voith shows what it takes to create a robust OCC stock preparation process. PPL reports


more than 85 complete OCC (old corrugated container) systems installed, the Voith Group is the world’s leading specialist in OCC stock preparation plants. One of the company’s great


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strengths is its holistic expertise, which enables the manufacturer to develop high-performance systems and components for stock preparation as a full-line supplier. “We consider OCC stock


preparation both at the product level and as an overall process,” explains Andreas Heilig, vice president of product management for Fiber Systems at Voith, based at Heidenheim in Germany. “On the one hand, we consistently look for optimisation potential in each individual process step and for all components used in it. On the other hand, with our cross- component engineering at the process level, we have a keen eye for the big picture, so all process steps are optimally coordinated with each other. “The result is an extremely


robust and seamless process that delivers on efficiency, yield and quality.”


A robust process despite major challenges Unexpected downtimes are one of the worst cases for every paper mill. Therefore, a robust and trouble-free production process


January/February 2020


The TwinPulp system prevents unnecessary shredding of impurities by early and consistently removing coarse contaminants. This relieves the whole downstream process and contributes to cleanliness at this early stage


is one of the most important requirements for OCC stock preparation. Voith machines, for example, eliminate contaminants consistently and at an early stage so that the subsequent process steps are affected as little as possible from the dirt level upstream. The coarsest material is


already sorted out in the pulper using the TwinPulp system or the IntensaDrum. Typical contaminants in this stage include stones, cans, plastic bags, larger plastic parts, adhesive tapes and wood. In addition to the usual suspects, however, frequently larger rejects such as curtains, brick stones, larger metal items and other extremely heavy contaminants that are normally unexpected in recycled paper can also be found in the pulper.


Extremely heavy rejects – such as big stones and metal parts – are sedimented in the Junkomat outside the pulper (TwinPulp system). In the next stage, coarse impurities are separated in the IntensaMaXX pulper detrashing machine. In the IntensaScreenDrum that follows, the remaining fibre material is recovered, and the reject is discharged from the process. In the TwinPulp system, larger and rope-like plastic parts are twisted together by the rotation of the suspension and form a rag with the help of cut bale wires. The rag is continuously discharged using a ragger. A problem arises because if the


rag breaks, so production must be stopped. This is because the broken rag further agglomerates


and impairs pulper operation significantly or makes it even impossible. The broken rag has to be manually removed from the pulper. It not only reduces productivity, but also represents a safety risk for employees. “In order to avoid breakage,


we have designed the ragger in such a way that it changes its contact pressure depending on the pulling efficiency of the ragger wheel. This minimises the risk of the ragger breaking and adds to the robustness of the process,” explains Sebastian Schuster, product manager for OCC Process at Voith.


Fewer chests for increased reliability and efficiency With its intelligent system design, the screening system further adds to the overall robustness


ith more than 120 years of experience in paper production,


Pulp Paper & Logistics


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