The purpose of an efficient pulping process is to break down recovered paper as completely as possible into individual fibers and cleanly remove contaminants. To simplify the process of separating them from the fibers, the contaminants need to remain as intact as possible.
In industrial paper production two processes have become established that meet these requirements: LC (low consistency) pulping systems and drum pulpers. The system used by paper manufacturers will depend largely on the quality of the raw material, the production volume, and the proportion of contaminants.
This is why Voith’s customers have the option, with IntensaDrum and IntensaPulper, of choosing a stock preparation system of the highest technical standard that is best suited to their needs, regardless of the kind of raw materials they are processing. The two systems are from a comprehensive, high-caliber range that no other supplier offers its customers and that allows the economic efficiency of the entire plant to be improved.
Parameters for an efficient pulping process
Due to an efficient, technologically optimized solution, the downstream stock preparation machines are also exposed to fewer influences like stock density fluctuations, raw material variations and contaminant loads. If all key process parameters have been coordinated with one another and with the automation system, the reject in the recovered paper is not shredded unnecessarily and can therefore be easily separated.
The stock consistency remains almost constant and the flake content in the accepts is minimal. This creates the basis for a robust pulping process without unscheduled downtimes. In order to select the ideal pulping technology option it is therefore important to know which raw material is to be processed and how high the reject content in the raw material is.
Minimal stock density fluctuations for more efficiency
Voith Paper aims to offer its customers a pulping process that removes all coarse rejects and in which all fiber constituents end up in the accepts. Moreover, the accepts should be free of flake and should not exhibit stock density variations. The quality of the raw material, i.e. its ash content and fiber composition, should also be equally consistent. Variations in the raw material and feeding are compensated by the fact that all pulping systems on the market have built-in tolerances.
On the other hand this means that the whole stock preparation system cannot be operated at its optimum and the efficiency of the system is impaired. Voith is constantly working on solutions for minimizing such fluctuations during the pulping stage to further increase the efficiency of the entire paper production process as a result. “This gives our customers the opportunity for significant savings potential,” emphasizes Hannes Mauz, Director Global Product Management Fiber at Voith Paper.
By now there are more than 200 IntensaPulper installations worldwide. The picture shows an IntensaPulper that is part of the stock preparation unit for the Schoellershammer PM 6.
IntensaDrum the right choice for high proportion of rejects
If the recovered paper has a high proportion of contaminants and the raw material is relatively easy to pulp, the advantages of the IntensaDrum technology come into play. In this case the pulping process is done gently by rubbing the fibers against one another.
To this end, bars lift the suspension in the first section of the IntensaDrum, the pulping area, and drop it onto the drum body. As – unlike an LC pulper – there is no rotor, contaminants like plastic bags, cans or glass are mostly not shredded to pieces and can be removed easily. In the screening area, the second part of the IntensaDrum, the process is similar to that in the pulping area: The fiber suspension is raised and dropped onto the drum body which is perforated in this area.
To guarantee an efficient separation of the fibers from the contaminants pulp consistency must be diluted at the beginning of the screening area to lower consistency. As this cannot be achieved by conventional dilution by water from spray pipes via the perforation, an additional concentrated stream of water shoots directly through the open reject outlet into the first part of the screening area.
As a result, fiber loss with the rejects and flake content in the accepts are very low. However, the IntensaDrum not only enables an efficient pulping process with very uniform stock densities and low flake content. Thanks to the simple principle of the technology and the wear-free inlet chute the system is virtually maintenance-free. The high stock density during pulping also allows the specific energy consumption and use of chemicals to be reduced. The IntensaDrum is a proven technology with numerous references, especially for pulping short-fiber OCC, as well as for graphic papers.
Up to 20 percent less energy consumption using IntensaPulper
In the case of a low reject in the recovered paper grades, the IntensaPulper from Voith is the better option. Excellent pulping efficiency, high reliability and low maintenance requirements are the basis for enabling paper manufacturers to significantly lower their running costs. In addition, the IntensaPulper product family consumes significantly less energy than comparable systems, saving up to 20 percent in the pulping process. This is due to the special geometry of the vat and the asymmetric arrangement of the rotor, which creates an optimized flow pattern that converts flow energy into pulping performance.
“In the LC pulping system the robustness of the ragger, Junkomat, IntensaMaXX and IntensaScreenDrum ensure trouble-free contaminant treatment with minimal fiber loss,” adds Wolfgang Mueller, Global Product Manager Pulping at Voith Paper. These features have made the IntensaPulper and the complete TwinPulp system the benchmark for LC pulper systems worldwide.
Part of the BlueLine product family
IntensaDrum and IntensaPulper belong to the BlueLine product range, in which Voith combines various technologies for modern stock preparation that meet the requirements for an environmentally friendly paper industry. As well as sustainability in respect of quality and reliability, the products allow customers to significantly reduce costs for energy, fibers, water and maintenance.