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A number of chemical pulp bleaching technology and its prospects in China

Subsequent oxygen delignification to improve the selectivity, has studied the actual pre-treatment used, including acid treatment agent (NO, CI, CIO, O,, acid HO, SO, etc.) and basic treatment agent (NaSO,, NaCIO, Na2s etc.). The effect of acid treatment agent is superior to basic handling agent, acid pretreatment Pi single acid or mixture of acid, studies suggest that the application of the mixed acid can enhance the effectiveness of removal of metal ions. In the pretreatment of various protective agents used, the magnesium is recognized as more effective protective agent, and only a small amount of oxygen that can be seen clearly when the bleaching effect. These magnesium salts include magnesium silicate,[link widoczny dla zalogowanych], magnesium carbonate, magnesium sulfate, magnesium hydroxide and magnesium complexes and so on. Hydrogen peroxide bleaching 3.3 H0 is well known as early as the bleaching agent for bleaching of mechanical pulp and mechanical pulp is quite common,[link widoczny dla zalogowanych], but H0 for chemical pulp bleaching is mainly due to the chlorine bleaching of Environmental Protection agent constraints developed. H0 bleaching depends mainly on the alkaline solution generated HOO dissociation reaction with lignin, lignin destruction in the carbonyl group to alter lignin chromophore in order to improve the whiteness of the pulp, the other part of the dissolved lignin can also. The main disadvantage of bleaching H0 decomposition exists, the decomposition of 0 and H0, and the formation of O. , HO. And HOO. Free radicals, these free radicals and lignin reactions can lead to a new generation of chromophore, which in H20 bleaching, usually have to deal with through the acid and chelating agent to remove metal ions in order to reduce oxygen consumption, thereby enhancing the H0 bleaching efficiency. H0 can be used as bleaching agent and can be used as delignification agents, it is the application of chemical pulp bleaching is divided into the following aspects: (1) the last paragraph for multi-stage bleaching, the main purpose is to further enhance the whiteness and white degree of stability, reducing the consumption of chlorine, a common process for the CEHP, CE. HDP, CEDEPD and so on. (2) for multi-bleaching the middle, replacing the H section and E segments, reduce pollution and improve the pulp quality and reduce the amount of CIO and reduce production costs bleach, a common process has CEPD, CEDPD, CEPDPD and so on. (3) for multi-stage bleaching of the first paragraph, you can play the role of delignification. Preparation of the CIO investment in equipment and high production costs, therefore,[link widoczny dla zalogowanych], to reduce the CIO while the amount of pulp to the production of whiteness and strength of the paper is that the domestic requirements of scientists committed to solving the problem. For some species, such as wood pulp and reed pulp, South China University of paper National Engineering Center has developed a better way to bleach, bleaching method does not use the CIO of the bleaching agent, bleaching agent used and developed can greatly H0 reduction in conventional CEH bleaching three paragraphs the amount of chemicals, bleached pulp with high brightness, high strength, etc.,[link widoczny dla zalogowanych], but also significantly reduce waste water pollution load. This high intensity, high brightness, low pollution bleaching process and related equipment have been several large domestic pulp and paper enterprises in the promotion and application, and achieved good economic and social benefits. 4 Summary tradition, pulp and paper companies focused on pollution control in wastewater treatment in the pulp cooking, because the pungent smell of cooking waste and dark colors reminiscent of the dangers to them. But in essence, with the Environment Protection and enhancement of research, people come to realize: compared with the cooking liquid and waste liquid bleach contained highly toxic, carcinogenic substances in strong human and environmental hazards of larger, more durable, therefore, to change the traditional bleaching process and methods, the use of less polluting and non-polluting bleaching methods and processes is imperative. China's national conditions at this stage, requiring all enterprises to adopt non-polluting pulp and paper bleaching is not appropriate, this is because the business is difficult to raise enough funds, In addition, the existing pollution-free bleaching production costs are too high, so the traditional chlorine bleach to transform and reduce the amount of chlorine and other drugs, on this basis,[link widoczny dla zalogowanych], the oxygen bleaching of pulp and hydrogen peroxide treatment can significantly reduce the formation of chlorinated organic compounds, but also can guarantee the quality of bleached pulp.