| In this paper, the extended delignification of reed NS cooking and the TCF bleaching of reed NS pulp were comprehensively studied based on the practice of Dandong Paper Mill to find out the technology suitable for the reality of pulp mill, and also to provide the oretical foundation for pulp production.The additive-enhanced extended delignification of reed NS cooking was studied. The additives i.e. Lvyang, CT-1 and 2282 were supplied respectively by Daochun Chemical Company of Henan Province, Xiantao Chemical Company of Hubei Province and Buckman Company. The experimental results indicate that Lvyang is the best one of the three additives used for extended delignification. The optimum technological conditions for reed NS-Lvyang cooking are as follows: Na2SO3 dosage 28% (based on Na2SO3), Na2CO3 dosage 6% (based on Na2CO3), Lvyang dosage 0.15%, liquor ratio 1:5, max temperature 165 C and time at max temperature 3 hours. Under the above cooking conditions, pulp yield is 55.8%, the Kappa number of pulp is 17.1 and the pulp viscosity is 1144 ml/g. The Kappa number of reed NS-lvyang pulp is 8 units lower than that of reed NS pulp.In reed NS-Lvyang cooking, the dilignification process can be divided into three stages. The initial delignification stage corresponds to the period of increasing cooking temperature from 50 CC to 105 C and the lignin remove ratio is 10%; the period from 105 C to keeping max temperature for 30 minutes corresponds to the bulk delignification stage with the lignin remove ratio of 71% and the period from 30 minutes at max temperature to the end of the cooking process correspond to the residual delignification stage with the lignin remove ratio of 11%.Comparing the IR spectra of Lvyang and CT-1 with that of AQ, it was found that Ivyang, CT-1 and AQ have the same characteristic absorption peak and thus it can be concluded that the three additives have similar structure. The surface-active agents are added in Lvyang, and they can't be confirmed by IR spectrum analysis.It appears that increasing cooking chemical dosage can accelerate delignification, but extreme cooking chemical dosage results in the sharp decrease of pulp viscosity. Enhancing cooking temperature can speed up delignification. Prolonging the time of delignification can improve the brightness of pulp, however, the poor selectivity of delignification brings about the obvious decrease of pulpviscosity. The optimum conditions for oxygen delignification of reed NS-lvyang pulp are NaOH dosage 4%, oxygen pressure 0.6MPa, MgSO4 dosage 0.05%, max temperature 100 C, keeping 100 C for 60 mins and pulp consistency 12%. Under the conditions, the brightness of pulp increases from 50.2 %ISO to 62.3 %ISO, the Kappa number of pulp decreases from 17.1 to 10.5 and the viscosity of pulp decreases from 1144 ml/g to 1123ml/g. 1% hydrogen peroxide can effectively enhance the oxygen delignification and reduce pulp Kappa number by 5.8. After the peroxide-enhanced oxygen delignification, the brightness, Kappa number and viscosity of pulp are 69.7%ISO, 9.5 and 1111 ml/g respectively.Acidic peroxide bleaching catalyzed by sodium molybdate can effectively remove the residual lignin. The dosage of sodium molybdate mainly affects the speed of delignification. The viscosity and brightness of pulp are mainly impacted by the pH value of bleaching. The optimum bleaching conditions obtained are as follows: pretreating the pulp with 0.4% DTPA at normal temperature for 30 mins, bleaching pH value 5.0, peroxide dosage 1.5%, sodium molybdate dosage 0.1%, pulp consistency 12%, temperature 60 C and time at 60 C 120 mins. Under the above conditions, the brightness of pulp can be increased from 39.0%ISO to 53%ISO, a brightness gain of 14%ISO can be achieved, the viscosity of pulp decreases from 1317ml/g to 1127 ml/g and the Kappa number of pulp decreases from 17.9 to 8.1.As reed NS-Lvyang pulp is pretreated by PAc, temperature is the key factor that affects the bleaching results at the suitable PAC dosage. With the temperature increasi...
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