Study On The Short Clean Bleaching Sequence Of Sulfate Bagasse Pulp

With the continuous development of our national economy and the improvement of people's living standard,the demand for paper products is increasing as well.It is one of the characteristics of China's papermaking industry to develop and utilize non wood fiber resources as raw materials of pulping and papermaking since China's timber resources are relatively short of supply.As agricultural waste,bagasse is abundant in South China.The previous study showed that bagasse has excellent properties of being pulp and paper raw materials.Therefore,the efficiently development and utilization of bagasse plays a positive role in promoting the sustainable development of China's paper industry to alleviate the current situation of wood fiber raw material shortage.Research and production practice has been confirmed that kraft pulping is appropriate for bagasse raw material in cooking methods.The kraft pulping,which is not part of the focus of this paper,was chosen as the cooking method.And the focus of this paper is the bleaching of bagasse Kraft pulp.Generally speaking,pulp bleaching methods can be divided into chlorine bleaching?chlorine,hypochlorite,chlorine dioxide?and oxygen bleaching?oxygen,ozone,hydrogen peroxide?,and pulp bleaching process is a combination of a series of these methods.The bleaching of bagasse Kraft Pulp include CEH,CEHP,ODED process in production practice at present.Due to the use of elemental chlorine,the CEH and CEHP bleaching process will be eliminated.So the typical bleaching process is ODED,which is composed of oxygen delignification and chlorine dioxide.It is a typical ECF bleaching process for wood fiber raw material and developed by USA and Europe countries last century.For bagasse Kraft pulp's characteristics of low lignin and hemicellulose content,easily swelling under the alkaline conditions and poor drainage,combined with the actual situation of the important progress of the manufacturing cost of nearly ten years of domestic ozone generator manufacturing technology decreasing greatly,based on preliminary exploration,this essay abandoned the traditional bleaching process of using oxygen delignification as the first stage and choose ozone bleaching as the first step,combined with the efficient hydrogen peroxide bleaching,composition of the ZP TCF short sequence bleaching process of bleaching of Bagasse Kraft pulp,and the process parameters,the process of ozone bleaching protection,the viscosity,fiber morphology and physical properties change of pulp before and after bleaching were systematically studied.The single-stage high-concentration ozone bleaching sequence was systematically studied in this paper.Single factor experiment was designed.The effects of key factors such as pulp concentration,reaction time,pH value and ozone concentration on the bleaching effect of ozone were discussed.The optimum conditions of single stage ozone bleaching were obtained.The optimum sequence conditions were:At room temperature?25??,the pulp consistency was 39%,the pH was 2,the ozone concentration was about 120g/Nm³,and the reaction time was 3min,the O₃ dosage is 0.85%o.d.p.The resulting pulp had brightness of51.1%ISO,viscosity of 580 ml·g^-1 and Kappa value of 4.5 under this condition.The main factors affecting the bleaching of hydrogen peroxide are:the dosage of hydrogen peroxide,the reaction temperature and time and the pH.The optimum conditions were as follows:the dosage of hydrogen peroxide was 3%,the reaction time was 120min,the reaction temperature was 90?,and the dosage of NaOH was 0.8%.Under these conditions,the resulting pulp had brightness of 85.6%ISO,a viscosity value of 559 ml·g^-1,a Kappa value of 3.21.Bagasse is easy to cook and easy to drift,the color is relatively shallow compared with wood pulp,Z-P process can significantly improve the pulp brightness and can be a good solution to the problem of serious loss of viscosity at the same time.the value of the slurry back after P is only 0.8,after-bleached pulp's brightness is of good stability.The physical proprieties of pulp is excellent after Z-P process,the tensile index after P stage is 49.89 N·m²·g^-1,the breaking index is 4.02 Kpa·m² G^-1,tear index is 7.99mN·m²·g^-1,and folding resistance is 36.On the basis of above,the effects of different additives on carbohydrate were studied.V additives can significantly improve the selectivity of ozone bleaching,improve bleaching brightness,reduce viscosity loss and improve the performance of bleached pulp.Compared to the pulp without the addition of additives,the V promoter increased the viscosity by 21%,the increase value is 122ml·g^-1;the Kappa value decreased by 6.7%,the decrease value is 0.3;the brightness increased by 2.9%ISO,and the bleach selectivity increased by 0.48.The optimum amount of V aid is 0.3%.The microscopic morphology of the fibers was observed by optical microscope after ozone bleaching.The surface of the fibers began to be divided into silk threads,fully expanded and became uneven after ozone bleaching.SEM observation of the fiber morphology showed that there were obvious holes and a lot of gullies or bulges on the fiber surface.Compared with the blank sample,the surface of V treated fiber is more smooth,which shows that V can protect the structure of cellulose and prevent the degradation of cellulose.The infrared spectrum showed that the ozone bleaching caused the ring opening of the benzene ring,and destroyed the conjugated structure.The crystallinity of the fiber was improved after V treatment,which indicated that the V promoter could protect the crystalline region of cellulose.