Study On The Changes Of Hemicelluloses Of Poplar Green Liquor Pretreatment And Its Affects To Pulp Properties

The industry of pulping and paper is faced up with a huge challenge due to the shortage of resources and the crisis of energy, as well that offers opportunities to develop it. Based on conceive of combinations of biorefinery and pulping, the study is mainly about extracting hemicelluloses by green liquor pretreatment of poplar before pulping. that is not only in favor of pulping after pretreatment, but also can use the hemicelluloses to produce production which can be worth more, save resources and improve the benefit.The pretreatment of green liquor in poplar Kraft pulping process and the influences of pretreatment conditions on pentosan extraction have been studied in this paper. Traditional Kraft pulping was used as contrast; we researched the influence of pentosan extraction on pulp and paper properties. At last, we extract hemicelluloses from pretreatment liquor and analyzed the factor of hemicelluloses extraction.At first, the pretreatment parameters on pentosan extraction have been studied in this paper. We designed orthogonal experiment under the condition of the liquor ratio1:4, optimized pretreatment green liquor charge, heat preservation temperature, and preservation time in order to analyze pretreatment parameters on pentosan extraction. The green liquor charge has the most evident influence on the quantity of the hemicelluloses extraction, the pretreatment temperature less and the pretreatment time least. Considering the problem of energy and the actual production efficiency, we got the optimal pretreatment parameters, liquor ratio1:4, green liquor charge1.5L/kg, pretreatment temperature105℃and pretreatment time90min. Conditional experiment was adopt for discussed the affect of the green liquor charge, temperature and time to hemicelluloses extraction. The final results indicate that liquor ratio1:4, green liquor charge1.5L/kg, pretreatment time90min, pretreatment temperature100℃is more suitable to the more pentosan, which reach to l3.81%.The second, we researched the influence of hemicelluloses extraction on pulp and paper properties. The green liquor charge has the most evident influence on the hemicelluloses extraction, so we change the green liquor charge to discuss the influence of hemicelluloses extraction on pulp and paper properties. The pretreatment conditions are liquor ratio1:4, pretreatment time90min, pretreatment temperature100℃, green liquor charge increased form0.25L/kg to1.5L/kg. The wood chips were cooked by sulfate after pretreatment (16%alkali charge, sulfidity24%, temperature165℃, time60min). The result shows that when green liquor charge increased form0.25L/kg to1.5L/kg, the gross stock yield, Kappa number and viscosity decreased gradually, and lower that traditional Kraft pulp. The screened stock yield increased compared with traditional Kraft pulp. Compared with untreated material, the tear index of pretreated paper improved, However the burst, tensile index and folding number decreased.At last, we use the method of ethanol precipitation to extract hemicelluloses from pretreatment liquor. Spin evaporated pretreatment liquor under the temperature90℃and slipped out of the liquid is50mL,60mL,70mL,80mL,90mL. Surplus liquid mixed with ethanol by volume ratio1:4. After precipitate, we centrifugal separated it and the hemicelluloses mixture was obtained.