Chemical Treatment in Mechanical Pulping - Part 3. Pulp Yield and Chemical Pretreatment, 1998 Pulping Conference Proceedings

In the first part of this report, a method was developed to measure and calculate the pulp yield for a large scale pilot tudy of chemical pretreatment in mechanical pulping. The method, using dynamic material balance at process teady state, takes into account not only process solid losses but the amount of chemicals applied as ell. A omparison of pulp yield using the method at the Andritz Pilot Plant with actual yield at a mill operation is also iscussed.

The second part of this report investigated how different chemical treatments affect the pulp yield when compared on he basis of similar pulp properties (freeness, tensile and brightness). Both low and high density hardwoods were sed, and the chemical treatments were: alkaline peroxide, alkaline sulfite and cold caustic soda. It was found that, or a high density hardwood such as Acacia mangium, the alkaline peroxide, or APMP process, gave a higher yield nd required less amounts of overall total alkali and energy consumption than the other two. Possible mechanistic explanations were discussed in terms of different chemistries involved in the different pretreatment.