Washing
Today chip washing is seen as being a compulsory step in order to
remove the bark, soil, sand and other abrasive contaminants (Figure 1.52).
In this way the life time of the refiner discs is increased and doubled in
some cases. The water can be heated to better clean species with high
resin or gum content and to defrost chips stored outdoors in winter. In this
way also conveyer, screws and dryers are protected and energy saved.
The water is kept in a closed loop and cleaned in the same circuit as the
water emanating from the chip plug screw. The surface wetting caused by
washing is thought to improve steaming and refining.