The Possibilities to Apply Polysulphide-Aq Pulping in Kraft Mills

Abstract

Developments in polysulphide pulping during the last 35 years are reviewed with emphasis on the successful PSpulping experience at the Peterson kraft mill in Moss, Norway. New and economical PS generation technology not disturbing the Na/S-balance in kraft mills will enhance application of PS-pulping world wide. Multi-stage PSpulping may improve the yield increase for a given PSsulphur charge to a digester system. Especially PS-black liquor impregnation followed by kraft cooking with conventional white liquor is interesting. Drying of fresh wood chips before PS-AQ pulping has a negative effect on obtainable yield increase. The paper and board making properties of polysulphide-AQ pulps are comparable to kraft pulps from a given wood source. PS-AQ paper grade pulps seem to preserve their paper making properties by recycling better than kraft pulps containing less hemicelluloses.