硫酸盐竹浆两段氧脱木素目标脱木素率的确定

Determination of Target Delignification Rate of Kraft Bamboo Pulp in Two Stages Oxygen Delignification

研究两段氧脱木素工艺参数对硫酸盐竹浆脱木素率和黏度下降率的影响,分析了脱木素率与所得浆料中α-纤维素含量、聚戊糖含量和灰分之间的关系。结果表明,硫酸盐竹浆两段氧脱木素目标脱木素率约为68%较为适宜,其所对应的一段和二段氧脱木素活性碱用量、氧压、反应温度、反应时间分别为3.0%、0.9 MPa、80℃、40 min和2.0%、0.3 MPa、100℃、60 min。超过该脱木素率,尽管浆料中聚戊糖含量随脱木素率的提高有所下降,但α-纤维素含量在该过程中上升不明显,而黏度下降率则显著增加。另外,研究还发现,当两段氧脱木素活性碱总用量超过5.0%时,浆料黏度下降率急剧升高所对应的脱木素率转折点约为64%。在保证浆料黏度没有显著降低的前提下,为尽可能脱除木素(达到68%的目标脱木素率),两段氧脱木素活性碱总用量不应超过5.0%。

The effects of oxygen delignification parameters on the delignification rate and viscosity reduction rate,and the relation between delignification rate and the contents of α-cellulose,pentosan and ash contents of the oxygen delignified pulps were investigated in this paper.It was found that the proper target delignification rate was approximately 68% after optimization of two stages oxygen delignification.The corresponding alkali charge（as NaOH）,oxygen pressure,reaction temperatures and durations for two stages oxygen delignification were 3.0%,0.9 MPa,80℃,40 min and 2.0%,0.3 MPa,100℃,60 min,respectively.Although pentosan content of oxygen delignified pulps decreased once beyond this target delignification rate,the increase of α-cellulose content was not significant while the viscosity reduction rate was obviously increased.Moreover,it was also found that,when the total alkali charge of two stages oxygen delignification was higher than 5.0%,the decrease rate of viscosity would be accelerated correspondingly at the transition point of delignification rate of approximately 64%.Therefore,to avoid the significant reduction of pulp viscosity but simultaneously increase the delignification rate of kraft bamboo pulps in two stages oxygen delignification,the total alkali charge（as NaOH） of two stages oxygen delignification should not be higher than 5.0%.