The specificity of plant fiber disintegration in the knife milling process

The refining of plant fibre, particularly wood fibre, in a disc refiner involves changes in its geometric parameters and fraction proportions in the general semi-finished material mass. Fibre disintegration nature and intensity largely depend on the loads and forces occurring at the intersection of the rotor disc knives and the refiner stator. This research presents data confirming the possibility of regulating both normal and tangential forces by modifying the discs operational part design. It assesses the efficiency of the developed disc design compared to the traditional design used in fibreboard production. The redistribution of knives on the disc surfaces reduced the knife crossing angle (to approximate to 0-15 degrees) and the number of (contacts) points formed from their intersection (to approximate to 528 pcs.), thereby increasing the main process parameters of the refining process (length of cut per second, cyclic elementary length, working refining surface) and the share of the normal components of the applied force (to approximate to 75%). An experimental study of mixed softwood fibre refining was carried out; the dependencies and optimal process conditions for regulating the gap (0.08-0.1 mm) between the refiner discs and the pulp concentration (2.5-3%) were determined taking the fibre properties into account. The new refiner disc design ensures a more intense fibre diameter reduction compared to the length. As a result, the longer and thinner, and therefore more flexible, fibres prevail in the wood pulp (to 50%), ensuring better inter-fibre interaction and improving the strength properties of the finished products (for 20-25%) without the use of binding resins.

Automated summary

This research focuses on refining plant fibre, especially wood fibre, in a disc refiner by modifying disc design to regulate forces for improved efficiency in the refining process. Experimental studies on softwood fibre refining determined optimal process conditions and dependencies for regulating gap between refiner discs and pulp concentration. The new disc design ensures more intense fiber diameter reduction, leading to better inter-fiber interaction and improved strength properties in finished products without the use of binding resins.