Mid Sweden University

Pappersindustrin a r en va ldigt energikra vande bransch och det a r da rfo rekonomisk ha llbart att optimera tillverkningsprocesserna utan att pa verkaslutprodukten. Den process som kra ver mest energi a r raffinering, dvs denmekaniska so nderdelningen av tra flis och det a r o nskva rt fo r fo retag at kunna minska den energi som kra vs att defibrera tra flis. Forskning har visa att en axiell kompression av tra flis ger upphov till uppsprickning parallell med fiberriktningen, vilket reducerar den ma ngd energi som kra vs fo r attdefibrera tra flisen. Med sma a ndringar i flisningsprocessen ga r dt fa dennakompression med hja lp av ra tt insta llda flisningsparametrar. Detta arbetegick ut pa att underso ka en modifierad fliskniv med en modifikation som gerupphov till skjuv- och dragspa nning fo r o kade uppsprickningar. Ensimulering utfo rdes fo r att kunna se hur den modifierade flisknivensspa nningsfa lt spred sig ja mfo rt med en icke-modifierad kniv.Flis tillverkades med Mittuniversitets hydrauliska flisverktyg fo r att utfo rakvasistatiska tester. Knivvinklarna 34° samt 54° studerades med modifieringoch utan modifiering. Proverna sa nktes ned i vatten fo r att kunna se deno kade uppsprickningen med hur mycket vattnet som absorberats.Resultaten visade att den modifierade kniven med vinkel 54° gav signifikant o kning av sprickbildning i tra flis och absorberade 7 % mer vattena n den modifierande knivarna

The pulp and paper industry are a very energy consuming business and it’sin the company’s best interest to optimise their processes to save money.The process that requires the most energy is refining and it’s desirable tofind methods that reduces the energy for defibration. Studies has proventhat axial compression toward the grain direction have led to fractures thatmakes the defibrating for the chip easier. Examining how chipping angleseffect the fractures have shown that the right fitting of edge and spout an-gle separates the grain more and leads to a higher water uptake. In thisstudy a modified knife with a surface that cause shear stress and tension isset to the grain direction with different edge angles to examine how it ef-fects the fractures. Chipping is done with a hydraulic press that does quasi-static tests. Two edge angles are observed, one with 34° angle and the other54°, whilst the spout angle is set to a constant 30°. With help from a videocamera the fractures are recorded from the chipping tests. Later the speci-men is submerged in a water bath to see how fracture has changed thewater uptake in the wood chip. The weight of the wood chip is calculatedbefore and after the water bath to see the percentage uptake of water. A fi-nite element analysis is also created to simulate how the stress is distrib-uted in the cut with and without modification. With the results you couldsee that the modified knife soaks up a lot more water than the non-modi-fied knife. The modified knife with the angle of 54° did 7 % more water up-take than the modified knife with 34° angle. The 54° modified angle knifealso had about 17 % more water uptake than the non-modified ones.Which came to the conclusion that a modified knife would give more shear stress in the chipping process and will generate more fractures.