The Influence On Refining Energy Of Mechanical Pulping With Microbe And Enzyme

With the intensified consciousness of environment protection and the implement of the environment protection law, bio-pulping and bio-treatment technology have been gradually studied and developed in the pulp and paper industry. And the bio-treated pulp had lower pulping energy consumption, better paper physical properties, less environmental pollution and better subsequent pulp bleachability than the untreated pulp. Therefore, bio-pulping technology has been increasingly paid more attention by more and more experts and professors in China and overseas, and is gradually becoming a way to reduce pulping energy consumption, improve the pulp qualities and reduce environmental impacts. Many researchers have made an extensive and deep studies on utilizing bio-technology to reduce pulping energy consumption and they have got certain achievements. It has been found that Microbe and enzyme, for bio-pulping technologies, had significant effectiveness in reducing energy consumption and improving pulp properties.In this thesis, white-rot fungi and other enzymes treated aspen mechanical pulps were studied. It utilized white-rot fungi to isolate, optimize and inoculate in the feasible temperature and time condition: temperature 28～30℃, time 4～5 days, solid enlarged isolating or grafting white-rot fungi; temperature 28～30℃, time 10 days, isolating crude enzyme solution from white-rot fungi in a constant temperature shaker water bath. The crude enzyme solution from white-rot fungi contained manganese peroxidase-MnP, lignin peroxidase-LiP, laccase and so on. White-rot fungi, white-rot fungi isolating crude enzyme solutions and commercial enzymes including cellulose enzyme (Trichoderma viride cellulase) and hemicellulase (AU-PE89 xylanase) were used to treat triploid aspen mechanical pulp for reducing energy consumption and improving pulp properties and subsequent pulp bleachability. With scanning electron microscopy (SEM) and Fiber quality analysis (FQA), the mechanism and theory of aspen mechanical pulp fibers modification or changes during bio-treatment were researched and discussed. There were many researches on bio-mechanical pulping, but most of the bio-treatments were used to pretreated the fibers or pulps (wood chips and rice wheatstraw) before the refining stage. In this paper, bio-treatments of aspen mechanical pulp were carried out between the first and the second refining stage, which can make microbe and enzyme come into cell wall of fibers easily and react with fibers directly and indirectly to give the resultant pulp better properties. The results indicated that the appropriate bio-treatments can remarkly reduce refining energy consumption. The beating degree of treated pulp can be improved 5 oSR～15 oSR higher than that of the untreated pulp. Additionally, the bio-treatment can improve pulp strength properties such as breaking length, burst index and tear index, especially the burst index was improved by about 100%. Pulp optical properties had been improved, and the brightness depended on the specific treatment conditions, the brightness was remarkly reduced 1%ISO～3%ISO or so with white-rot fungi treatment or white-rot fungi isolating crude enzyme solution treatment. However, the other commercial enzymes obviously improved the brightness 1%ISO～7%ISO or so. Furthermore, the appropriate bio-treatments also can remarkly improve pulp subsequent peroxide bleachability. The resultant brightness can be increased 1%ISO～6%ISO or so as well as improved pulp strength properties. The enzyme treatment had much contributions to burst index improvement, and the burst index can be improved by 50%. It was found that BYBF and Lentinus lepideus white-rot fungi had better treatment effectivness than other white-rot fungi. It also was found that Sdu-4 and Lentinus lepideus isolated crude enzyme solutions had better treatment effectivness than other ones. The best results of cellulase and xylanase treatment were gotten at temperature 60℃and enzyme dosage 20 IU/g, while the best results of mix enzyme treatment came out at temperature 45℃and enzyme dosage 20 IU/g.