Fpinnovations

Yujun Sun

Richard M Berry

Theodore Radiotis

Richard Mckinnon Berry

Impregnating or spraying softwood chips in a solution containing an appropriate concentration of alkaline earth metal ions selected from the group consisting of calcium ions, barium ions and strontium, preferably calcium ions, at room temperature before a reductive alkaline pulping process, for example kraft pulping, significantly increases pulp yield. Using an agent that complexes with the metal ions, such as hydroxyethylidene diphosphonic acid (HEDP) allows this benefit of metal ions to be achieved during the pulping process rather than in a separate impregnation step.

Increasing alkaline pulping yield for softwood with metal ions

Polysulphide produced by oxidizing white liquor includes both active and inactive components. 'Active' polysulphide is the only component that increases pulp yield. The amount of active polysulphide formed when manganese oxides are used as catalysts in the generating process is increased by adding a co-catalyst. Adding bismuth compounds and, in particular, bismuth oxide as a co-catalyst increases the total amount of polysulphide formed with all the manganese oxides and increases the amount of active polysulphide produced particularly when using the lower manganese oxides. The co-catalyst also increases the number of cycles in which the most active catalyst, manganese dioxide, can participate before losing efficiency. Other elements in the same group and adjacent groups in the periodic table are active but these other elements are more soluble than bismuth and are toxic.

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Beaconsfield, Canada

Yujun Sun