The Research On High Consistency Ozone Bleaching Technology And Mechanism For Kraft Bamboo Pulp

With the rapid development of economy, the demand for paper and paper products isgrowing,and China is a country with poor forestry resources，these restrain the developmentof papermaking industry in our country.In addition, the emissions of toxic and harmfulchlorine bleaching wastewater have became one of the main aspects of environmentalpollution in pulp and papermaking industry.As for rich bamboo resources and favorablepulping properties, bamboo resources make up for the shortage of the wood pulp raw material.The development and utilization of the abundant bamboo resources in our country promotesustainable development of papermaking industry. New bleaching technology without anychlorine is found, such as ozone, which is adopted to achieve totally enclosed pulping andbleaching process and to realize clean production in the first place.Based on reducing pollution and improving the quality of the bleached pulp, ozone as ableaching agent is selected, ozone can effectively remove lignin and improve the whiteness ofpulp. Based on this, self-made high efficiency and consistency ozone bleaching device wasused to study the ozone bleaching of kaft bamboo pulp. The orthogonal experiments weredesigned to explore the effect of the pulp consistency, ozone consistency, reaction time on theproperties of sulfate bleached pulp.The optimized ozone bleaching was carried out under pulpconcisistency of35%~40%, ozone consistency of125g·Nm–3,the reaction time of3min.Thepulp whiteness was69.4%ISO, viscosity was700mL·g-1, kappa value was5.1.On thisbasis, the effects of different additives on the protection of carbohydrates were studied. Theselectivity of ozone bleaching were significantly increased, bleaching whiteness improved,the range of viscosity loss reduced, pulp properties improved. The whiteness of the resultedpulp improved2.1%ISO, viscosity increased80mL·g-1, selective increase by1.3.Optimization of the subsequent hydrogen peroxide bleaching bleaching after ozonebleaching was studied. On the basis of single factor bleaching,.The optimized hydrogenperoxide bleaching was carried out under H2O2dosage2.5%with the temperature90℃for112min by response surface methodology.The whiteness of the result pulp bleaching was88.8%ISO, viscosity was763mL·g-1.Finally the TCF bleaching process of sulfate bamboopulp based on ozone bleaching was studied. Compared to the traditional CEH bleaching,the brightness reversion of the bleaching section (OAZP) and physical properties wereresearched. Tensile index, tear index, burst index and folding number after TCF bleachingprocess was respectively61.43N·m2·g-1,10.47mN·m2·g-1,5.01Kpa·m2·g-1,53times.Theeffect of TCF bleaching was better than the CEH bleaching.Microscope and scanning electron microscopy (SEM) and fiber quality analyzer wereused before and after ozone bleaching to observe fiber morphological changes under theoptimum condition of ozone bleaching. The results showed that most of the fibers becameshorter and coarser.The phenomenons of broom, bur and tear on fiber surface were showed.And a lot of fines and debris were generated. FTIR, X-ray diffraction were used in studyingthe mechanism of high consistency ozone bleaching.The results showed that the benzenewere damaged and hydroxylated to increase the possibility of ozone contacted with the lignin.And hair color groups such as Carbonyl on the benzene ring were damaged to improve pulpwhiteness. The degree of crystallinity before and after ozone bleaching was40.68%and38.79%respectively. The diffraction peak positions before and after ozone bleaching didn’tchange,and reduction in strength was small.These showed that effect on the degradation ofcarbohydrates after ozone bleaching was small.Finally, the differences between board type ozonizer equipment and tubular ozonegenerator was studied as well as the technology about high consistency ozone bleaching. Andthe performance parameters of tubular ozone generator was studied.The results fully showedthat the stability of the tubular generator. Compared with the plate type ozone generator,ozone consistency tubular ozone generator produces is larger and stabler.What’s more, thebetter effect of bleaching is obtained, and more close to the actual production.