Deinking Dispersion and Washing, 1996 Pulping Conference Proceedings

Lawrence A. Broeren

Simons Engineering, Inc.

This paper presents the results of a deinking dispersion and washing trial which was conducted by Simons Engineering at the Alfa Laval Celleco (ALC) Pilot Plant, Lawrenceville, GA. The trial consisted of multiple dispersion process steps and two types of washing to determine their effect on TAPPI, sub-TAPPI and total dirt, brightness, and other parameters. The Shinhama kneader was used for dispersion and the ALC Plmdized Drum Washer (FDW) was used for washing. The PDW was used in the Fluidized Drum mode (impingement feed on the exposed drum) and the Gravity Decker mode (normal submerged feed).

The wastepaper furnish was commercial post consumer white and colored ledgers and lottery tickets.

Because of today’s wastepaper contaminants, particularly non-impact inks, most new deinking processes contain the process step of dispersion to assist in achieving a low dirt level. Often this dispersion process step is done with a kneading type of disperser. Some deinking processes have two dispersion process steps; often both done with kneaders. A deinking pilot plant trial was conducted with three dispersion process steps using a kneader for each dispersion step. The individual and cumulative dispersion step results were determined and compared.

Dispersion will reduce dirt levels but it will also reduce brightness. Washing after dispersion will increase brightness. The trial included both the Fluidized Drum (PD) and Gravity Decker (CD) modes of washing the deinked stock after the first disperser process step. The results of the two modes of washing were determined and compared.