Effect of Sulfite, Sulfide and Hydroxide Concentrations in Mini Sulfide Sulfite Anthraquinone Pulping, 2007 Engineering, Pulping & Environmental Conference

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Previous work has indicated that the cost per ton of pulp could be decreased by roughly 30 % for an MSS-AQ process, relative to a conventional Kraft process. The improvements in process operating costs are primarily due to decreased wood demand and the elimination of lime kiln fuel. These cost-savings could readily be achieved as the considered process would not require a lime kiln while creating significant improvements in pulp yield. These values do not reflect potential cost savings related to equipment capital and maintenance costs. Compared to conventional kraft pulps, MSS-AQ pulps provide great benefits with regard to total yield, improved initial brightness and bleachability. Although their burst and tensile strengths have been found comparable to those of kraft pulps, their tear strength has typically been found to be somewhat lower. In an attempt to improve the overall strength properties of MSS-AQ pulps, the relative effects of sulfite, sulfide, and hydroxide concentrations have been explored. Results obtained from high kappa laboratory pulping experiments have shown how pulp yield and strength properties vary with different MSS-AQ liquor compositions and total chemical charge. The chemical charges can be optimized such that the pulps had higher yield and brightness. In addition some of the MSS-AQ pulps refined more easily, and had strength properties comparable to the reference kraft pulp.