Method used in the manufacturing of heavy mechanical and chemi-mechanical pulp

摘要

During the manufacturing of heavy mechanical and chemi-mechanical pulp the chips are led to a chip washer (1), an impregnation device (2), defibration (4), cleaning (5), screening (10) and water extraction (11). Waste (6) from the cleaning process (5) is divided in a semi-permeable membrane device (7) in a concentrate (8) containing highly molecular substances and a permeate (6) containing low molecular substances as well as chemical remains. The concentrate (8) is led away and destroyed while the permeate (9) is re-circulated to the process, appropriately to the chip wash (1) impregnation (2) and/or defibration (4). The surplus of back water from the water extractor (11), back water drain (14), can also be led to the membrane device (7) and the permeate to be partially used from there as a replacement for fresh water.