Reducing Energy Consumption in Thermomechanical Pulp Production Using Chlorine Dioxide

摘要

Hemlock and pine/spruce high-freeness pulps have been treated with chlorine dioxide over a range of temperatures (25-65 o C), times (10-120 min) and chlorine dioxide charges (0.5-5% w/w). These chlorine dioxide treatments were followed by alkali soaking or reaction with alkaline peroxide. The resulting changes in pulp properties were determined. For the hemlock furnish, a small but rapid increase in tensile strength occurs under mild chlorine dioxide treatment conditions. Treatment with 1% chlorine dioxide for 10 min at 45 o C and 10% consistency increased the tensile index by 3 N·m/g. A subsequent alkali soak at room temperature and 4% consistency with a charge of 0.4% w/w of sodium hydroxide on pulp increased the tensile by another 10 N·m/g giving pulp with a final tensile index around 40 N·m/g. Pulp brightness was lowered by the chlorine dioxide treatment from 55% ISO to 45% ISO and even further to 36% ISO on soaking with alkali. The dark chlorine dioxide treated pulp could be easily brightened with highly alkaline peroxide to give a final brightness of 72% ISO and a high tensile of 42 N·m/g.