Characteristics of alkaline and neutral sulfite pu

2022-08-08
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Characteristics of alkaline and neutral sulfite pulping of oak

key words: oak; Pulping; AS-AQ; Ns-aq oak is the main wood species in the natural secondary forest in the eastern mountainous area of Liaoning Province, accounting for 51% of the wood volume. Among them, the amount of decayed wood in over mature forests can be saved 1.6 million m3 [1] per year by means of harvesting. As the leftover material of commercial wood processing, if it can be chipped for papermaking, the yield can be increased by 35%, and another 1million m3 [2] of papermaking material can be provided every year. Therefore, without affecting the forest resources of existing forest steel after cold deformation, a total of 2.6 million m3 of wood raw materials can be provided for papermaking every year. However, oak wood is dense and hard, the fiber length width ratio is small, and the softness coefficient is low, so it is considered to be low-quality papermaking material. At present, only a small amount of oak wood is used to produce alkaline semi chemical pulp as the pulp for the production of packaging paperboard. In order to effectively develop and utilize this part of resources, the author and others have studied the preparation of scmp[3], apmp[4] and sulfate chemical pulp from hard miscellaneous wood such as oak. The results show that the above qualified pulp species can be prepared from oak. This paper introduces the experimental results of oak AS-AQ and ns-aq pulping and the beating and papermaking characteristics of the pulp

1 on Pulping and bleaching characteristics

tussah wood chips used in the experiment were taken from Xinbin paper mill in Liaoning Province. The bark and super thick chips were removed and placed in plastic bags to balance the water for standby. The chemical composition of raw materials is:

oak hot water extract 5.34%

oak 1% NaOH extract 19.59%

oak benzene alcohol extract 2.23%

oak clarson lignin 17.98%

oak holocellulose 84.36%

oak pentose 22.96%

oak ash 0.38%

oak and poplar belong to broad-leaved wood, and the content of their main chemical components is similar.It's just that the oak wood is hard and dense, and the cooking liquid is not easy to soak. Therefore, we can refer to the cooking conditions of poplar [6] and give appropriate strengthening as the cooking conditions of oak. The strengthening measures are to appropriately increase the dosage and extend the heating time to facilitate the soaking of the liquid medicine. The specific technological conditions of ns-aq cooking of oak wood, whether grade B1 EPS or grade B2 EPS, are as follows:

total dosage of oak wood (NaOH, for wood) 25%; Alkali ratio [na2co3/(na2co3+na2so3), NaOH meter] 15:85; Heating time 150min; Maximum temperature 170 ° C; Holding time: 300min; The liquid ratio is 4:1. In the medicinal liquor of oak AS-AQ cooking, NaOH is used instead of Na2CO3, so the cooking liquor is strengthened, and the total amount of alkali is no longer increased. Other conditions are the same as above. The specific cooking results are shown in Table 1

it can be seen from the data in Table 1 that both kinds of pulps have achieved good digestibility. Pulp residue

Table 1 cooking results of the two methods

pulp type

crude pulp

rate%

fine pulp

rate%

pulp residue

rate%

kappa value unbleached pulp white

degree% d/o

as-aq

ns-aq

53.50

53.64 50.81

52.24

5.03

lightweight Not easy to destroy 2.61

34.2 32.8

43.7

49.4

the rate is less than 5%. The high and low temperature universal material testing machine of Jinan experimental machine factory is used to test the tensile strength, compressive strength, elongation and elongation of all kinds of materials, semi-finished products and finished products at different temperatures. It can be used for peeling, tearing, bending, bending, shrinkage and other experiments, which is in line with the indicators controlled in actual production. The crude pulp yield is about 53.5%, and the fine pulp yield is more than 50%. The kappa number of both is similar, which belongs to the range of bleachable pulp, indicating that the process conditions are reasonably determined, and the alkali consumption of ns-aq cooking is appropriately increased, which effectively compensates for the relatively weak reaction capacity of ns-aq cooking liquor. Compared with the two kinds of pulps, ns-aq has a better degree of vaporization, so the kappa number is low, and the pulp residue rate is also low. When the yield of crude pulp is similar, fine pulp

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