MODIFIED POLYSULPHIDE (AQ)-PULPING OF SOFTWOOD

A review of the polysulphide (PS) liquor generation methods has been made. By preparing some PS liquors which simulate future possibilities, pilot scale PS-(AQ) pulping studies were conducted. The studies were carried out in a recently acquired pilot plant which can simulate both conventional cooking techniques as well as the latest pulping developments. Two types of pulps were made, type 1 were liner board grade pulps and type 2 were bleachable grade pulps. Type 1 pulps were made by using up to 20 % green PS-liquor in conventional PS-AQ pulping. Type 2 pulps were made by adding all PS in the impregnation stage of ITC simulated cooks and applying either NaOH (Soda liquor) or kraft liquor (WL) as the major alkali source. The pulping experiments to produce liner board grade pulps showed that, addition of PS-green liquor could save up to 9