WET METHOD OF PREPARING FIBERBOARD PRODUCTS IN A SUBSTANTIALLY CLOSED AND BALANCED WHITE WATER SYSTEM

摘要

WET METHOD OF PREPARING FIBERBOARD PRODUCTS IN A SUBSTANTIALLY CLOSED AND BALANCED WHITE WATER SYSTEM Wet method of making fiberboard products in a substantially closed white water system by applying one or more layers of separately prepared surface pulp to a layer of base pulp at the wet sheet forming stage, which layers are subsequently hot pressed into the final product, while the volume of white water is maintained substantially constant. The base pulp is produced by treating the chips in a defibrator under generation of steam of predetermined superatmospheric pressure and corresponding elevated temperature. A major portion of the base pulp is diluted with white water drained off and recycled from the base layer wet sheet forming stage to form a base layer suspension, which is transported by the white water to the wet sheet forming stage, where the white water is drained off and recycled to the base layer suspension stage to form a new base layer suspension. A smaller portion of the base pulp is further diluted with white water recycled in a separate closed circuit from the surface layer forming stage to form a surface layer suspension which is transported to the surface layer stage by the white water which is drained off to form a surface layer sheet and recycled to the surface layer suspension stage to form new surface layer suspensions.