A consistent supply of raw materials influences the quality and efficiency of the entire process, because fluctuations in the raw material quality or quantity continue throughout the following recycling process. Subsequent corrections are only possible to a limited extent and involve a great deal of effort. Our solution: Voith not only provides conveyors but also control concepts that have proven their good performance in many installations.

The raw material is dissolved and homogenized in the pulper. Already here it is important to remove as many contaminants as possible, for example adhesive tapes, plastics and wires. This is because impurities that are carried along are further and further crushed during the subsequent process steps. These contaminants can only be sorted out with considerable additional effort or are even carried through the process to the paper machine. A double advantage: Efficient cleaning reduces wear on the subsequent machines. At the same time, the machines run safer and smoother, and a wider operating window of the subsequent machines is achieved. This improves the robustness of the whole process.

The main task of the Protector System, the high-consistency (HC) cleaning, is the early separation of highly abrasive contaminants. An efficient disposal increases the service life of all downstream machines and pumps. To achieve this target, Voith uses a two-stage system. A booster pump prior to the second stage ensures the necessary pressure and thus an efficient separation.

In the low-consistency (LC) Cleaner, remaining heavy particles such as sand are selectively removed from the fiber suspension by centrifugal separation. Compared to other manufacturers, the Voith system scores with an excellent separation at significant higher stock consistencies. This is made possible by the EcoMizer technology developed by Voith.

During coarse screening and fractionation, coarse impurities are further removed from the pulp, flakes are defibered, and the reject is washed several times to avoid fiber losses. Clever: The three-stage Voith system requires no vats for intermediate storage of the fiber suspension. This reduces a large number of typical problems in coarse screening. One the one hand, no agitator is required to move the pulp in the vats to avoid a floating layer. This reduces installation effort and energy consumption. On the other hand, agitators tend to spin the impurities, which endanger the downstream pumps and machines. The closed system design with a minimum number of chests and standpipes reduces the risk of clogging in the further course of the process.

During fractionation and fine screening, the accepts contained in the fiber suspension are separated into long and short fibers. Also important is the removal of disturbing small reject particles and stickies. The quality of the fractionation and screening is determined to a large extent by the circuit variants and slot widths. The Voith screening system is optimized for the requirements of the final paper machine.

The task of the thickening stage is to increase the stock consistency and to reduce storage volume. It also provides clean filtrates to be used in the OCC process water cycles. The thickeners are characterized by excellent mechanical robustness and long lifetime of the filter sectors. Outstanding filtrate quality sustainably reduces fiber loss as well as the number of solids that are recirculated.

The dewatering process increases the stock consistency from about 5 to 30 percent or more to prepare for the next process stage and for complete separation of the water cycle. The dewatering machines provide consistent and continuous discharge and thus a homogeneous supply of the dewatered stock to the subsequent systems. This reduces the number of energy peaks in the subsequent processes and thus lowers the overall energy demand of the dispersion system. With our systems, a more rigid and reliably stable operation can be achieved, compared to other machines available on the market.

The dispersing system homogenizes the dewatered stock and shreds dirt specks and stickies to the point of invisibility. The extremely compact dispersion system requires only three machines – the screw press, the high-speed heating system and the disperser. Coming from the screw press, the dewatered stock is then processed and heated with steam in the rapid heating system. If needed, it can also be used to mix in bleaching chemicals. Voith dispersers achieve best optical paper properties with the lowest energy consumption on the market.

High and constant fiber strength enables safe and efficient operation of the paper machine at high speeds. The conditions for this are created in the refiner. An intelligent setting of the gap width is important. This guarantees uniform fiber treatment even with process fluctuations. At the same time, contact between the refiner plates is avoided in order to keep service life of the refiner plates at a high level.

The reject, water and effluent treatment is a very important part of the BlueLine OCC Process. Rejects have to be eliminated efficiently from the system. Depending on the further processing, rejects are dewatered and shredded. Problems in the reject management have a negative impact on the overall system performance and can even lead to a complete shutdown in stock preparation.

No less important is water management. Small impurities accumulating in the water cycle can cause major problems. Further, paper mills pose special challenges to the wastewater treatment, e.g., with regard to calcium deposits. Voith systems are perfectly designed for these often very special conditions to ensure maximum process reliability in the long term. Efficient anaerobic reactors help keep energy requirements to a minimum.