The Influence Of Hemicellulose On Bagasse Pulp Elemtetail-Chlorine-Free Bleaching And Aox Generation

In this paper, the influence of bagasse pulp hemicellulose on ECF bleaching process and AOX generation is studied.First,The conditions of xylanase pretreatment on bagasse pulp are studied.Then with the optimization of different Xylan content bagasse pulp D0EpD1bleaching process,study the effect of Xylan content to ECF bleaching effluent and AOX production. Results are as follows:1.By optimizing of xylanase pretreatment process for bagasse pulp, the optimal enzyme treatment conditions are enzyme dosage2.5IU/g,pulp consistency6%,50℃,pH7.5,90min. With xylanase pretreatment,the pentosan content of bagasse pulp most reduces to37.4%.2.Based on the analysis of the effects of different dosage chlorine and time on bleaching propertities of bagasse pulp, optimal D0EpD1bleaching conditions are studied. The optimum conditions shows below. Pulp dense10%,ClO2total volume (active chlorine)1.6%.D0:ClO21.3%(active chlorine),60min,60℃. Ep:NaOH2.0%, H2O20.8%,65℃,90min.D1:ClO20.3%(active chlorine),70℃,75min.Compared with untreated bagasse pulp bleaching, the total amount of ClO2can be reduced by20%achieving the same brightness.3.Based on the analysis of the effects of different dosage chlorine and Xylan content on AOX production,study the relation between them. With the increase of the content of hemicellulose and the dosage of ClO2, The AOX generation in bleaching wastewater also increases.When the pentosan content reduces37.4%than the original pulp content,the total AOX contained in bleaching effluent can be reduced to29.6%with the same chlorine dosage.4.By means of fiber quality analyzer, X-diffraction, IR and SEM, study the mechanism of xylanase pretreatment of bagasse.The results are as follows:(1) Through the analysis of fiber quality analyzer, xylanase pretreatment of bagasse pulp can increase the proportion of long fiber pulp and decrease the average fiber width ratio, resulting in the increase of fiber length to width ratio. At the same time, fine fiber content decreases, which improves the physical strength of the paper.(2) X-diffraction results show that after xylanase pretreatment of bagasse pulp, bagasse cellulose crystalline degree increases,which is conducive to the physical properties of pulp increasing.(3) Demonstrated by UV treatment of bagasse pulp xylanase pretreatment waste liquid, xylanase pretreatment can destroy part of xylan and lignin-cellulose complex structure in bagasse pulp, also makes parts of lignin dissolved. After bleaching, it will make lignin better touch bleaching agent, and thus improve the bleaching efficiency.(4) Infrared spectrum analysis shows, after xylanase pretreatment, bagasse hemicellulose have certain degradation, and lignin content decreases,Parts of lignin dissolve out.(5) In the scanning electron microscope observation, the surface of bagasse pulp after xylanase pretreatment is rough and the surface of the fibers also appear more holes. With the increase of xylanase pretreatment concentration, the probability of occurrence of damage and fracture is greater.