Kraft Pulping with Modified Dissolved Solids Profiles: Effect of Chip Properties, 1998 Pulping Conference Proceedings

The mechanisms by which dissolved organics in kraft liquors interfere with pulping and reduce strength and optical properties of pulps is still not completely understood. The study aimed to determine whether radiata pine pulp strength benefits associated with reducing solids levels in kraft pulping liquors, “the dissolved solids effect”, were greater for chipper damaged chips and/or for high density chips containing thick walled fibres. Although it was confirmed that lowering he level of dissolved organics in kraft pulping liquor increased pulp strength, as indicated by pulp viscosity, WZSTI and tear tensile relationships, there was no conclusive evidence that the greater fibre wall disorder likely to result from chipper damage led to a substantially larger increase in pulp strength due to reduced liquor solids. However, a strong relationship between pulp strength and the number of fibre wall dislocations gives support to the theory that the “dissolved solids effect” is related to the amount of disorder in the fibre wall structure. The results indicate that wood density, and the fibre properties associated with it, may have an interactive effect with chipper damage and pulping liquor solids. A method using confocal microscopy and image analysis of acridine orange stained fibres was used to show that areas of deformation in the fibre wall generally contained less lignin than the surrounding undamaged regions.