Multi-level sulfide content.

摘要

Paper pulp (e.g. kraft pulp or sulfite pulp) is produced utilizing at least two different supplies (35, 41) of cooking liquor (e.g. white liquor), having different percentages of lignin reaction enhancing or carbohydrate degradation slowing chemicals (e.g. one having low sulfide content, and the other high sulfide content). The high sulfide content supply is typically used to impregnate the pulp (in 37), while the second supply is used in other cooking stages (e. g. digester 12), whether co-current or countercurrent. At least 60% of the sulfide of the cooking chemicals may be provided in the first supply (35). Some of the sulfide in the first supply is desirably provided in the form of polysulfide or elemental sulfur. When about 2% polysulfide on wood is utilized yield is significantly increased. Utilizing multiple chemical (e.g. sulfide) content supplies results in an optimum viscosity/kappa ratio and/or pulp strength properties for the pulp produced. <IMAGE>