Influence of wood chips quality on kraft pulp's yield and properties

The influence of wood chips quality on the pulp yield and properties of unbleached kraft pulps was investigated. Four sorts of wood chips, namely pine pins, sawmill chips from pine and spruce, and screen reject from pine young wood, were tested under laboratory conditions. Two pulping procedures, conventional and with extended delignification, simulated in batch digesters, differed as to the charge of active alkali, hydromodulus and cooking temperature. Batch cooking was controlled by the H factor method. Results obtained confirmed that both the pulp yield and the amount of rejects are strongly influenced by wood's quality. Pulp fibre properties, such as coarseness and sedimentation velocity, depend on wood species, as well as on the degree of delignification.