Mechanisms of Micro-Fiber Flocculation Due to Hydrodynamic Force, 1997 Engineering Conference Proceedings

Fiber flocculation is a phenomena, mostly concerned by engineers, which may produce local density variations of paper. Mechanisms extracted from fluidization with water of spherical and cylindrical particles falling against gravity are applied to micro-fiber flocculation. There are essentially three mechanisms responsible for this phenomena: drafting, kissing and tumbling. When fluidized, one fiber is drawn into the wake of another, termed drafting. The second fiber quickly accelerates to make intimate contact with the first, called kissing. Once fibers kiss, they quickly become intertwined due to vortex shedding and create a micro-floc that will continue to grow until strong turbulence is encountered. This interaction is responsible for the agglomeration that leads to micro-fiber flocculation in the converging portion of the headbox where turbulence is at a minimum. The turbulence may be generated by a strip placed on the floor of the headbox perpendicular to the direction of flow. The addition of this strip would add turbulence to the lower portion of the headbox reducing the interaction between fibers through drafting and kissing, in turn, reducing fiber agglomeration and micro-fiber flocculation. The turbulence distributions are numerically simulated utilizing FLUENT.