Study On Efficient Oxygen Delignification And Clean Bleaching Of Kraft Reed Pulp

In the "Eleventh Five-Year" period, resource conservation and environmental protectionhad been put on the important strategic position of paper industry in china, which has madegreat achievements in the reduction of pollutant emissions. The future of the "12th Five-Year"period, the environmental policy will be more stringent. In this situation, the pace to solve theshortage of resources and environmental pollution problems must be speed up for the paperindustry. Rational use of good non-wood fiber, such as the use of reed, bamboo, bagasse andother grasses, will still be a way to solve the shortage of papermaking raw materials. Andclean bleaching is also a development trend of the pulp industry.In the thesis, kraft reed pulp was selected for raw material, the optimum of two-stageoxygen delignification boosted by hydrogen peroxide and the subsequent TCF and ECFbleaching were studied, which will offer more important research and application of value inreducing bleaching costs and pollution load.Firstly, the study on oxygen delignification boosted by hydrogen peroxide of kraft reedpulp showed that the delignification effect of two-stage oxygen delignification could beimproved by the addition of H2O2, and when added in the first stage, better delignificationefficiency and whiteness would be gotten. The optimum conditions of oxygen delignificationwere as follows: for the first stage: NaOH charge2.5%, H2O2charge0.3%, oxygen pressure0.6MPa, MgSO4charge0.5%, temperature85°C, reaction time45min, pulp consistency10%;for the second stage: NaOH charge1.2%, oxygen pressure0.4MPa, temperature100°C,reaction time45min, pulp consistency10%. After oxygen delignification, the pulp kappanumber decreased to6.9, the viscosity was1046.6mL·g^-1, brightness was57.5%ISO,delignification rate was62.3%.Then, TCF bleaching sequences of kraft reed pulp were studied after the oxygendelignification. The study on the activating pretreatment before hydrogen peroxide bleachingshowed that it could improve the beaching effect protect the liquid intensity. The combinationof pretreatment and atmospheric pressure or high temperature and high pressure hydrogenperoxide bleaching was a highly effective bleaching sequence, and MP₁MP₂, MPPo or MPMPo was good among them. Paper brightness of three kinds could reach up to85%ISO,and among them, MPPo bleaching had the best bright stability and the lowest viscosity. To thepaper strength properties, MP₁MP₂bleaching gotten the best while MPPo bleaching the worst.And then, ECF bleaching sequences of kraft reed pulp were studied after the oxygendelignification, including （Op-O） DMP,（Op-O） HMP and （Op-O） DED₂. The results showedthat, the brightness was （Op-O）DMP＞（Op-O）HMP＞（Op-O）DED₂＞85%ISO, the viscositywas （Op-O）DED₂＞（Op-O）DMP＞（Op-O）HMP, and the bright stability was （Op-O）DED₂＞（Op-O）HMP＞（Op-O）DMP. According to the comparison of the optical qualities, the strengthproperties and the wastewater load,（Op-O） DMP was the best sequence among the threekinds of ECF bleaching.Finally, the comparison of results among ECF, TCF and CEH bleaching was studied inthe experiment. For the ECF and TCF bleaching, the paper qualities had no big difference, butthere was less environmental influence for the TCF bleaching. And among the ECF bleaching,（Op-O） DMP was the best sequence of efficiency. But regardless of the ECF or TCFbleaching, was better than CEH bleaching on the paper qualities, comprehension cost andenvironmental influence. The results also showed that, the following bleaching load could bereduced greatly by the highly effective oxygen delignification, and the ECF/TCF bleachingstudied in this experiment had important research and application value.