Pulp Paper & Logistics


VALMET 23


3 “More consistent pulp quality is one of the major benefits of the new digester,” explains Andreas Vikström, head of the cooking and fibre department of the SCA liner mill


of the ImpBin technology for impregnation and a steam/liquor phase digester for cooking wood chips. “We had an incredible start-up and beat the previous production record after only five days. We also very quickly produced a pulp of significantly higher quality than before,” says Vikström.


Cleaner pulp and lower maintenance costs One major difference is that there has been a considerable reduction


in the amount of gravel and sand in the pulp. “You always get a little bit of


gravel and sand together with the wood chips, and if you don’t manage to separate it, they are carried along in the process. Ultimately, they end up in the kraftliner as stains when the grains are crushed in the paper machine,” explains Vikström. “We now have a much better cleaning process, and the number of complaints about these kinds of stains has reduced dramatically.” The improved pulp cleanliness has also resulted in significant wear reduction in several departments, which has resulted in much lower maintenance costs. “In the subsequent washing


area, for example, the lifetime of the refiner segments has doubled, and we can also see an increased lifetime of the screen baskets in the screen room following the refiners,” says Vikström. The cleaner pulp also results


in fewer deposits on the paper machine. The result is that it runs better.


Built-in washing The pulp from the digester also contains a lot less soap than before. The reason for this is that the new digester is equipped with a counter-current washing zone in the lower part of the vessel, which means that the pulp washing process starts there earlier. “In the past we have had a lot


of issues with soap in the pulp causing operational disturbance in the subsequent washing area, but those problems have disappeared completely,” explains Vikström.


It has also been possible to


reduce the dilution factor in the washing line by about 50 percent without reducing the overall washing efficiency, thus reducing the energy consumption in the evaporation by 15 percent.


Less chemicals needed due to more consistent pulp quality


Another major benefit of the new cooking system is that the quality of the pulp is higher and has become more consistent.


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A safe and lean way of working resulted in this sample station, where several sampling points are found in the same area May/June 2018


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