CHANGE OF THE CONCENTRATION OF COMPONENTS IN THE COOKING LIQUOR DURING KRAFT PULPING

In the present paper, change of the main components (NaOH, Na2S and AA ) in the cooking liquor during kraft delignification of spruce wood ha s been studied. It was found out that, with the active alkali input of 16% Na2O on o.d. wood, the respective concentrations of Na2S and NaOH in the cooking liquor decrease to 1/2 and 1/6 of those used at the be ginning of pulping. Due to that fact, the initial 25% sulphidity of th e cooking liquor increases in kraft pulping to 33 - 35%. Furthermore, the work evaluates concentration change of the main components in the cooking liquor during initial, bulk and residual delignification. Thou gh delignification kinetics is different, whether it occurs in initial , bulk and residual phases of delignification, it is constant in each individual phase and not proportional to the kinetics of change of alk ali concentrations in the cooking liquor.