Thread Content
1. Characteristics of chlorine dioxide pulp bleaching 1. Chlorine dioxide has strong oxidizing ability and high bleaching efficiency.； Easy to discolor dust spots ； Effective in removing resin from hardwood pulp. 2. Selectively remove lignin, resulting in high bleaching pulp yield, high mechanical strength, high whiteness and good stability. 3. It can remove copper, iron, manganese and other heavy metal ions in the pulp, which is beneficial to subsequent bleaching. 4. It has antiseptic and bactericidal effects, effectively reduces the viscosity of white water, and can reduce the acidity, color and sodium chloride content of bleaching wastewater. 5. The BOD5 and CODcr loads in wastewater are low, which greatly reduces toxic and carcinogenic organic halides (AOX), reduces wastewater treatment costs, and reduces papermaking water consumption. 6. Bleaching waste paper pulp requires a small amount and a short time ； And can eliminate fluorescence in waste paper pulp. 7. The main bleaching agent in the ECF pulp bleaching process. 8. Significant economic and social environmental benefits. 2. Characteristics of hydrogen peroxide pulp bleaching 1. It is most suitable for bleaching high-yield pulps such as mechanical pulp, semi-chemical pulp, cold alkali pulp, etc. The high yield is still maintained after bleaching. 2. After mechanical wood pulp is bleached, the whiteness increases, but the opacity does not decrease much. 3. Chemical pulp is bleached with peroxide, which has good stability. Peroxide can be used for final bleaching in the manufacture of special paper. 4. It is too expensive to produce peroxide by electrolysis. Peroxide can be produced by other methods, such as: Using the anthraquinone method can reduce the cost of H2O2, but the investment scale is too large ； Existing paper companies currently have no examples of self-production. 5. Peroxide bleaching is not suitable for pulps that require high whiteness. 3. Comparison of economic conditions in application 1. In the application process of multi-stage bleaching, the dosage of H2O2 (100%) in a single stage is generally: Straw pulp 1.0～2.0%, wood pulp 2.0～3.0%, bamboo pulp 2.0～3.0% ； The total dosage of CLO2 is generally 0.3~1.0% for straw pulp, 1.5~2.0% for wood pulp, and 1.5~2.0% for bamboo pulp. 2. H2O2 is not used for bleaching alone. Generally, in order to remove heavy metal ions such as copper, iron, and manganese, a chelating stage must be added before H2O2 bleaching. The process is complex and there are many adding facilities. ； If the same price of drugs is invested, CLO2 can improve the brightness of pulp much more than H2O2. 2. The pulp bleaching method for household paper directly affects the hygienic indicators of the paper produced and the health of users. Currently, domestic pulp abroad uses chlorine dioxide for bleaching, and other pulp bleaching methods are not allowed. 3. Under normal circumstances, the whiteness of household paper pulp bleached is relatively high, above 90% ISO, which cannot be achieved by H2O2 bleaching.