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麦草低温碱氧两段蒸煮及其全无氯漂白

Alkaline-oxygen Pulping of Wheat Straw at Low Temperature and Tcf Bleaching of Akaline-oxygen Pulps

【作者】 陈双双

【导师】 曹云峰;

【作者基本信息】 南京林业大学 , 制浆造纸工程, 2012, 硕士

【摘要】 麦草是我国造纸工业最丰富的非木材纤维原料。然而,由于麦草制浆废液黏度大,碱回收困难,使得传统制浆技术受到一定的限制。NaOH-AQ/O2两段蒸煮是一种适于麦草且环境友好的制浆方法。本论文主要研究麦草碱-氧碱两段蒸煮及其全无氯漂白技术。通过对麦草进行一段碱法蒸煮后,所得浆料不经洗涤,直接通入氧气进行第二段氧碱蒸煮。对麦草氧碱蒸煮段用碱量、氧压、温度和时间四因素三水平进行方差分析,在用碱量02%(NaOH计)、氧压0.20.6MPa、温度70100℃和时间3090min内,得到用碱量对得率的影响最大,时间对其影响最小;麦草氧碱蒸煮后,浆料黏度下降并不明显;用碱量对浆料卡伯值的影响最大,氧压对其影响最小。由此得到较适宜的工艺条件为:用碱量1%(NaOH计),氧压0.6MPa,温度85℃,时间60min。在较适宜的工艺条件下氧碱蒸煮结果为:浆料得率52.6%;浆料黏度为1042mL/g,比单段碱法蒸煮后浆料黏度(1099mL/g)降低5.2%;浆料卡伯值17.9,比单段碱法蒸煮后浆料卡伯值(20.3)降低11.8%;黑液黏度为3.4mPa.s,比单段碱法蒸煮黑液黏度(5.1mPa.s)降低33.3%。对麦草进行碱-氧碱两段蒸煮,所得草浆在较低温度(80℃)下进行压力过氧化氢漂白。漂白后浆料卡伯值从17.9降至9.411.9;H2O2用量在0%5%范围内,纸浆白度从37.1%ISO升高至45.6%ISO60.6%ISO,且与卡伯值之间具有一定的线性关系:︱白度增加︱=︱卡伯值降低︱х1.57;浆料得率在86.6%89.5%之间,同时,得率降低与卡伯值减少之间具有较为标准的线性关系:︱浆料得率降低︱=︱卡伯值降低︱х0.19。麦草氧碱浆压力H2O2(Ppt)漂白,在NaOH用量4%,Na2SiO3用量3%时的脱木素及漂白效果较好,卡伯值从17.9下降至6.7,下降了62.6%,白度从36.2%ISO上升至73.6%ISO。表明Ppt漂白的脱木质素及漂白效果明显。对压力过氧化氢漂白后的浆料不经螯合直接进行H2O2补漂,以及螯合处理后漂白的对比试验,均可将麦草氧碱纸浆漂至白度80%ISO左右,而采用Ppt-Q-P漂白比Ppt-P漂白的纸浆的白度高4.0%ISO左右,且浆料黏度在929.6mL/g1025.0mL/g。

【Abstract】 Wheat straw is one of the most abudant non-wood fiber raw materials forChina’s papermaking industry. However, the difficulties of alkali recovery due to thelarger viscosity of wheat straw pulping waste liquid which restraint the developmentof traditonal pulping technology. NaOH-AQ/O2two-stage cooking process is asuitable method for wheat straw pulping and environmental friendly. This papermainly study on the wheat straw alkali-oxygen alkali two stage low temperaturecooking and TCF bleaching technology.Wheat straw after alkaline-AQ pulping was disposed with oxygen directlywithout washing.An L9(34)orthogonal test was designed to study the effects of alkali charge,oxygen pressure, cooking temperature and holding time on wheat straw alkaline-oxygenpulping. The result showed alkali charge had the maximum influence on yield, while holdingtime had the minimum influence but the declined of viscosity was not obvious. Alkali chargehad the maximum influence on kappa number, while oxygen pressure had the minimuminfluence. The optimal conditions were determined as follows: alkali charge on oven dry pulp(as NaOH)1%, oxygen pressure0.6MPa, the maximum temperature85℃and holding time atthe maximum temperature60min. At this optimal condition, kappa number decreased11.8%.The wheat straw alkaline-oxygen pulp was obtained with yield52.6%, viscosity1042mL/g,the kappa number17.9, black liquor viscosity3.4mPa.s. Compared with the first stage alkalinepulping, viscosity decreased5.2%, kappa number reduced11.8%, and black liquor viscositydecreased33.3%.Alkaline-oxygen cooking of wheat straw at low temperature (85℃).Akaline-oxygen pulps were bleached through pressure hydrogen peroxide at lowtemperature(80℃), Kappa number was reduced from17.9to9.411.9; when theH2O2dosage range between0%and5%, brightness increased from37.1%ISO to45.6%60.6%ISO, and have certain linear relationship with Kappa number:︱brightness increment︱=︱decreased Kappa number︱х1.57; the yield between86.6%89.5%,meanwhile there is a standard linear relationship between decreasedyield and reduced Kappa number:︱lessened yield︱=︱reduced Kappa number︱х0.19.Wheat-straw soda/soda-oxygen pulps were bleached through pressurized H2O2(Ppt). Kappa number of pulp decreased with increasing of H2O2and Na2SiO3charge.Kappa number was reduced from17.9to6.7, the removal of remaining lignin up to 62.6%, Brightnesses increase from36.2%ISO to73.6%ISO. That is to say that Pptbleaching had highefficiency of delignification and bleaching properties.Brightnesses of the bleached wheat straw soda-oxygen pulps by oxygenpretreatment-pressurized-H2O2bleaching (Ppt-Q-P) and pretreatment-pressurizedH2O2-H2O2bleaching(Ppt-P) both reached to about80%ISO, while brightness of thepulp bleached by sequence of PptQP was4.0%(ISO)higher than that by the PptPsequence, the viscosity of bleached pulp reached about929.6mL/g1025mL/g.

  • 【分类号】TS745
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