Paper Pulp Mixing

The Colorful Fluid Mixing Gallery

Shown here is a paper pulp drop tank. Paper stock is added on the top of the vessel. Near the bottom there is a side entering impeller, an inlet and an outlet. Water is injected at the inlet just above the impeller. The impeller mixes the water with the paper stock, diluting the stock and breaking down the fibers. The diluted pulp leaves the vessel through the outlet all the way at the bottom. The bottom of the vessel has a horseshoe shape, to minimize dead zones where pulp might build up. Paper pulp has a complex rheology and has a yield stress. A special model was used to allow for stagnant regions, laminar regions and turbulent regions. The image shows the velocity magnitude at the vessel wall.

Shown here is the flow pattern in a stock chest for mixing and storage of paper pulp. The image on the top shows the flow pattern with a solution of 1% pulp. The image on the bottom shows how the flow pattern changes when the concentration is increased to 5%. The impeller was modeled as a simple straight jet with no swirl. These images were created in cooperation with Dr. Richard D. LaRoche at SGI/Cray.

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Last Updated April 10, 1998 by André Bakker