Parameter Optimization And Pulp Quality Control Of Lo-solids Kraft Cooking Of Eucalyptus Wood

Nowadays, Lo-Solids cooking system was widly used in the world. Although a fewLo-solids cooking fiberlines have been imported into China in recently years, such as HunanJuntai Pulp&Paper Co., Ltd, but the cooking reaction course, technology parameters andpulp quality control of these Lo-Solids cooking fiberlines are almost copied from oversea.Therefore, it is necessary to systemly study Lo-solids cooking technology according to localconditions, and the study of Lo-Solids kraft pulping of eucalyptus wood by laboratorysimulation is very important.The objective of this study was to optimize the process of Lo-Solids kraft pulping ofeucalyptus wood and evaluate the cooking behavior of Lo-Solids kraft pulping of eucalyptuswood compared with the conventional cooking by laboratory simulation. in addition, thekappa control mathematical model was established based on the delignification kinetics ofkraft pulping and the mechanism of low solids kraft pulping, model asKa=A-BlnH-Cln[OH-]d-Dln[HS-]. The relationship between H-factor, process averageeffective alkali concentration and the initial degree of sulfidity with the kappa number of lowsolids kraft pulping was studied by laboratory simulation. All cooks were based on the factoryactual production and were in duplicate to obtain pulp of16~18kappa number and residualalkali was control in range of6~8. The results were as follows.Wood delignification in whole cooking process was made up of three steps asconventional cooking: the first phase was “initial delignification” occurred in impregnationstep(temperature up to135℃) with15.45%lignin removal; The second phase was “the bulkdelignification” occurred during135℃to155℃at45min with75.53%lignin removal; Thefinal phase was “residual delignification” from155℃at45min to the end of the cooking withover6.10%lignin removal. Overall,97.08%of lignin,33.34%of the holocellulose and49.93%of the pentosan were removed at the end of the cook.The optimum conditions of Lo-Solids kraft pulping by laboratory simulation were asfollows: wood chips steaming time30min, the ratio of stage alkali55%:45%, the active alkalicharge21%(based on NaOH), the extraction temperature135℃, H-factor1200~1300.The kappa control mathematical model of Lo-Solids kraft pulping of eucalyptus wood isstudy from the bulk delignification phase, in addition, used as kinetics index model:-(dL)/(dt)=K’L~a [OH~-][HS~-]The kappa control mathematical model is established based on the delignificationkinetics of kraft pulping and the mechanism of low solids kraft pulping, model as Ka=A-BlnH-Cln[OH-]d-Dln[HS-]. The relationship between H-factor, process averageeffective alkali concentration and the initial degree of sulfidity with the kappa number of lowsolids kraft pulping was studied by laboratory simulation. All cooks were based on the factoryactual production and the constant coefficient A（119.71）, B（5.214）, C（17.550）, D（6.389）of the model were obtained by linear fitting. The results showed that the kappa number of lowsolids kraft pulping can be predicted accurately by the mathematical model and the linearcorrelation coefficient R~2was0.9266.