Effect of green liquor pretreatment on pine wood components behaviour during Kraft pulping

The influence of wood chips impregnation with modelled green liquor at a liquor-to-wood ratio of 0.7:1 and 4:1, marked further by 0.7M and 4M, respectively, on the extended kraft delignification of pine chips has been investigated. It was shown that the dynamics of delignification and hemicelluloses removal after the pretreatment was significantly changed, in comparison to conventional kraft cooking. The lignin, xylan and mannan removal rate constants in the initial, bulk and final phases of the second stage of cooking were calculated. It has been found that, after the pretreatment at 0.7M and 4 M, the delignification rate increased by 12 and 5% at the initial phase and by 10 and 6% at the bulk phase, respectively. The selectivity of delignification was higher in the case of a low liquor-to-wood ratio at the impregnation stage.