Low Kappa Kraft, Kraft-SAQ, Polysulfide, and Polysulfide-SAQ Pulping and Physical Properties Comparison.

With the growing environmental concerns facing the pulp and paper industry, there is a need to lower digester kappa to reduce the amount of organics to the bleach plant.There is also a need to maintain a satisfactory yield.To address these concerns, a pulping study comparing polysulfide and polysulfide-SAQ to kraft and kraft plus SAQ was conducted.A western United States softwood mixture was cooked over the range 15 kappa to 30 kappa.The effect of these additives on pulp yield is that the polysulfide and SAQ produce similar yield increases compared to conventional kraft for the kappa range 20 to 30.At 15 kappa the polysulfide pulping results in a superior yield increase compared to SAQ.The combination of SAQ with polysulfide liquor results in a synergistic effect that increases with kappa for the range studied.The pulping results and physical property comparisons of polysulfide, polysulfide-SAQ, SAQ, and conventional kraft are discussed.