Deinking of Recycled Pulp by the Cross Flow Filtration Method, 1997 Recycling Symposium Proceedings

Cross-flow filtration is used in process stream filters in order to remove oversized contaminants and clean up a liquid stream. This project examines the possibility of using this method in order to deink a pulp slurry with minimal effluent water. A large quantity of water is used to deink wood pulp by conventional washing methods. The vessel constructed for this project allows pulp to flow through the inner part of a cylindrical screen while removing water, ink, and filler from the slurry and thus deinking the pulp with a minimum of water usage.

Pulp slurry at 3%, 2.5%, 2%, 1.5%, l%, and 0.5% consistency are pumped at 100 GPM at varying pressure drops through the vessel. The 100 GPM flow through a 2 inch schedule 40 pipe line results in an approximate velocity of 10 ft/sec. This velocity will ensure a turbulent flow through the vessel and prevent the screen from binding.

Inlet, accept, and effluent streams from the vessel are tested for fiber length, spec scan ink distribution, brightness, ash, consistency, and flow. From these tests, the deinking efficiency of the screen is determined.

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