Study On Displacement Digester Systerms (DDS) Cooking With The Mixture Of Eucalyptus And Bamboo

The process conditions of displacemented cooking with the mixture of eucalyptus and bamboo was optimized by single-factor experiment. The optimal process conditions of displacemented cooking were: the dosage ratio of eucalyptus: bamboo was 3:2, pretreatment time was 60min (total time of the three pretreatment stages), the charge of alkali was 17% (calculated as Na₂O), 25% Cooking the Sulfidity (calculated as Na₂O), the heating up time was 160min, the maximum temperature was 168℃. The fiber morphology of pulp indicated that the average length, width, the ratio of fiber length, fiber width and fiber length distribution of mixed pulp were better than which of the eucalyptus pulp or bamboo pulp. The fiber length distribution ranged between 0.20 and 1.20mm, mainly ranged between 0.50 and 0.80mm. The fiber width distribution ranged between 8.0 and 32.0μm, mainly ranged between 8.0 and 16.0μm.The law of delignification and reaction process of displacemented cooking with the mixture of eucalyptus and bamboo were studied. The results indicated that the reaction process of delignification included three stages during cooking, namely the initial stage of delignification, the main stage of delignification and the stage of residual lignin removal. A part of lignin was removed in the initial stage of delignification, the removal rate was 27.54%. The removal rate of the main stage of delignification was64.66%, and the removal rate of the stage of residual lignin removal was 3.97%.The reaction dynamic of the displacemented cooking with the mixture of eucalyptus and bamboo was studied. It was found that the lignin concentration of the main stage of delignification and the stage of residual lignin removal was the first grade reaction to the reaction of delignification, and the activation energy of the two stages were 51.609 kJ/ mol and 64.955 U/mol respectively.The concentration of NaOH had great impact on the final extent of delignification. In the main stage of delignification, the grade of concentration of NaOH to the reaction of delignification was 0.89, and in the stage of residual lignin removal was 1.49. The concentration of Sulfide also had great impact on the two stages. In the main stage of delignification, the grade was 0.43, and in the stage of residual lignin removal was 0.86. Finally, the dynamic model of the displacement cooking with the mixture of eucalyptus and bamboo was determined as follow:The main stage of delignification: -dL/dt=A₁e^-6208/T[OH^-]^0.89[S^*]^0.43The stage of residual lignin removal:-dL/dt=A₂e^-7813/T[OH^-]^1.49[S^*]^0.86...