竹浆氧漂预处理和强化的研究

Study of Prctreatment and Intensification of Oxygen-bleaching of Bamboo Kraft Pulp

本文探索了氧漂前硝酸预处理的可行性,发现硝酸用量为3％时,后继氧漂可使硬度降低60％,预处理及氧漂在粘度降低22％的情况下,硬度可降低71.1％。作为氧漂保护剂MgSO_4优于EDTA;添加H_2O_2优于Na_2S;氧漂时加入2％H_2O_2可使白度增值14.1度,在粘度降低15.5％时,氧漂段硬度可降低69.2％。以1.5％H_2O_2进行补充漂白,可使常规氧漂浆和预处理后的氧漂浆白度增值分别为6.2度与15.1度。 HNO_3(NO_2)预处理的竹浆经强化氧漂和H_2O_2漂白,为获得高白度创造条件,在粘度下降29％时,漂浆白度增值达42.1度,高锰酸钾值降低到0.83,为高白度漂白创造条件。

Bamboo pulp is & kind of common pulp in China. In order to carry out bleaching bamboo pulp with oxygen, the basic technological conditiond of kind bamboo pu!p bleaching with oxygen are put forward. The conditions are.-the charge of alkali 4%,pressure of oxygen 0. 8 MPa,consistency 10%,time of bleaching with oxygen 60m. ,in the mean time brigtness of pulp bleached with oxygen is 22% (SBD) ,the KMnO4 number is 12. 01 .viscosity is 990 cm3/g. On the basis of this,the effect of nitric acid pretreatment before bleaching,intensification of the stage of bleaching with oxygen and additionally bleaching with H2O2 on the quality of purp bleached with oxygen is studied in the paper.I . HNO3 pretreatment Busing on instability of nitric acid,being apt to be dissociated and releasing nitrogen dioxide, nitric acid (?) was arried out to study nitrogen dioxide effect. When pretreatment is carried out with HNO3 at 25℃ and with (?) quota of three kinds of pulp bleached with oxygen shows that pulp pretreated with HNO3 at higher (?) as with NO2.(?) HNO3(NO2) in process of pretreatment shows that after pretreatment the characteristics of pulp (?) effecial by the charge of HNO3(NO2). While the charge of HNO3(NO2) is changed in the range of 2%-4.5%,the orightness goes up with the charge and KMnO4 number down, for instance, pretreatment with 4.5% HNO3 results in a 91. 8 4 delignifieation ratio. When the charge of HNO3 is 3 % , KMnO4 number of pulp will lower 71. 1 % , but viscositry can keep 805cm3/g. The optimum charge of HNO3(NO2)is thought to be 3%.Ⅱ . Intensification of oxygen bleaching stage1. EOT A and MgSO4 strengthen the protection of carbohydrate. Results show that under the same conditions when 2 % EDTA added to pulp sample, viscosity reaches 967cm3/g, which is 8.9% higher. When 0.2% MgSO4 is added to the pulp sample, viscosity is 990cm3/g, when is 3% higher than viscosity of pulp sample to which EDTA is not added. When 0. 2% MgSO, is added to pulp sample, viscosity is 11.5% high.2. Strengthening delignification and modification of chromophoric group with H2O2.Test results show that in bleaching with oxygen, H2O2 is added. With the charge of H2O2 increasing from 0. 5% to 3%, the brightness gain gets 14. 5 units after oxygen bleaching. KMnO4 number of pulp bleached with oxygen lowers 70. 2% ,at the same time the viscosity of pulp also drops in some degree,but the best results are thought to be that 2% H2O2 is added to pulp sample bleached with oxygen,brightness gain is 14. 1 unit.KMnO, number drops to 6. 07 and viscosity is 837cm3/g.Ⅲ . Supplement of H2O2 bleaching1.5% H2O2 is used to bleach pulp sample pretreated or nonpretreated by HNO3(NO2). Results show that the brightness of pulp sample pretreated by HNOS(NO2) under the same conditions increases 6. 2 units after H2O2 bleaching. The brightness of pulp bleached with oxygen by means of protection of EDTA and MgSO4 increases 2 units under the same conditions. At the bleaching stage of H2O2 when pulp adding Na2S is bleached,its quality is better than pulp sample adding H2O2.