The Effect Evaluation Of Thermostable Xylanase Pretreatmentand Oxidation Pulping Of Wheat Straw

Recently, Paper-making industry in our country facing two big problems:intensive disparity between supply and demand;energy-saving and ejection-decreasing. Scientific and rational use of non-wood resouces,implement cleaner production process, raise the standard of energy-saving and ejection-decreasing, improve the quality of pulp- and paper-making standard using non wood fiber, all of those methods above can be used to achieve the two major goals: reducing the imbalance between supply and demand energy conservation and emissions reduction.In the present work, we constructed an effcient method to improve pulp and black liquor based on the straw fiber in order to solve problems in paper-making industry.We have analyzed three sections of pressure/temperature hydrogen peroxide pulping process of wheat straw, by increase process and cleaner production process.It was investigated that thermostable xylanase was used for the pretreatment if the raw material of wheat straw, and enzyme treatment effect by Different processing methods.1. The suitable pretreatment condition of thermostable xylanase process was as following, the xylanase charge was 40 IU/g, liquor ratio was 1:9, pH was 7.2, reaction time was 4h and temperature was 95℃ respectively.In this condition, there were had 1.14% reducing sugar in the nzymolysis liquid of wheat straw material after xylanase treatment, and 1.23% reducing sugar content wheat straw pulp. For wheat straw material, reducing sugar amount had increased 0.39% after alkali extraction. For the pulp, it had increased 1.25%.Using the acetone extraction the wheat straw material, we had found that the reducing sugar from 1.14% to 1.21%. Then lignin content in liquid is from 0.35g/L to 0.46 g/L.2. Three sections of pressure/temperature for hydrogen peroxide pulping process conditions: The first section(alkalized pretreatment) 4% of sodium hydroxide dosage, liquid ratio was 1:6, the holding time was 60 min,thread rolling concentration was 20%. The second section, pulp concentration was 15%, 6% of sodium hydroxide dosage, Oxygen pressure was 0.65 MPa, H2O2 dosage 2%, treated for 90 min at 120℃, aslo Na2 Si O3 dosage 2% and 0.5% MgSO4. Three sections(bleaching), pulp concentration was 15%,2% of sodium hydroxide dosage, Oxygen pressure was 0.45 MPa, H2O2 dosage 4%,treated for 60 min at 120℃, aslo Na2SiO3 dosage 2% and 0.5% MgSO4. Finally, the pulp yield was 82.87%, Kappa was 43.5 for the first section. About second section, the pulp yield was 63.62%, Kappa was 12.9. After the third secton, the pulp yield was 54.13%, Kappa was 3.2, pulp brightness was 66.7% ISO.3. Compare with the NaOH、KOH and NaOH-KOH(mole 1:1) used for three sections of pressure/temperature hydrogen peroxide pulping, we analyze yield, delignification rate and brightness. We can find that the KOH also can as alkali for pulp.NaOH-KOH(mole 1:1) have the same result with NaOH. So we can use NaOH-KOH for pulp and bleaching.4. It had different effects with the different point of Hydrogen peroxide, for difference adding point with hydrogen peroxide had better effect than adding point in only one point.