【作者】 郭三川；

【导师】 詹怀宇；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2008， 博士

【摘要】 桉树生长快,制浆造纸性能优良,是我国“林纸一体化”工程中重点推广的速生树种之一,发展桉树制浆对促进我国造纸工业的可持续发展具有重要意义。本论文以我国南方的速生桉木为原料,进行了硫酸盐法蒸煮、氧脱木素和无元素氯（ElementalChlorine Free,简称ECF）漂白的研究,并分析了纤维性质对纸浆打浆性质和纸页性质的影响,为速生桉木的清洁制浆提供理论依据和技术支持。采用实验设计与分析软件MODDE对速生桉木硫酸盐法蒸煮进行了实验设计和结果分析,由MODDE数学模型的分析结果可知,有效碱用量、硫化度、蒸煮温度和保温时间对速生桉木硫酸盐浆的蒸煮结果均有明显的影响,且影响的程度各自不一。在某一卡伯值条件下,纸浆的细浆得率、黏度和白度不能同时达到最优化水平。MODDE可以根据蒸煮工艺条件预测蒸煮结果,当蒸煮条件为:有效碱用量17%,硫化度29.5%,蒸煮温度150℃,保温时间135 min时,MODDE预测的蒸煮结果为:卡伯值18.1（上下限分别为21.5和15.3）,细浆得率50.3%（上下限分别为51.2%和49.5%）,白度34.1%ISO（上下限分别为36.1%ISO和32.2%ISO）,黏度1429 mL/g（上下限分别为1627 mL/g和1232 mL/g）。MODDE也具有优化蒸煮工艺的功能,在要求达到的蒸煮指标时,分别设定细浆得率、黏度和白度的最大化权重,在给定的卡伯值范围内,可以制定出合适的蒸煮工艺条件（有效碱用量、硫化度、蒸煮温度、保温时间）;同样,细浆得率、白度或黏度也可作为目标进行蒸煮工艺的优化。在硫酸盐法蒸煮过程中,蒸煮温度、有效碱用量和保温时间对纸浆己烯糖醛酸的含量均有明显的影响,而硫化度则对纸浆中己烯糖醛酸的含量影响不大。较低的蒸煮温度、较低的有效碱用量和较短的保温时间有利于降低纸浆中己烯糖醛酸的含量,且纸浆的细浆得率也较高。研究了用碱量、温度、氧压和时间对桉木硫酸盐浆（卡伯值为17.1）氧脱木素的影响。较为优化的氧脱木素工艺条件为:用碱量2%,温度100℃,氧压0.5 MPa,时间60min,此时氧脱木素浆的卡伯值为9.5,白度为58.4%ISO,黏度为795 mL/g。添加表面活性剂能进一步提高氧脱木素的脱木素率,提高纸浆白度,而纸浆的黏度只略有下降。三种表面活性剂（S1,S2和S3）较适宜的用量均为0.2%左右,其中表面活性剂S3的效果最好。当S3的用量从0增加至0.2%时,氧脱木素浆的白度从58.4%ISO升高至62.3%ISO,卡伯值从9.5降低至8.1,黏度从795 mL/g降低至744 mL/g。木素红外光谱和³¹P-NMR谱的分析结果表明,桉木原料木素中的酯键在硫酸盐法蒸煮过程中易被氧化而断裂,木素被降解:原料木素中的紫丁香型木素单元在蒸煮和氧脱木素过程中溶出较多:在蒸煮和氧脱木素过程中,苯环的侧链断裂溶出,苯环上的甲氧基被脱除。桉木经硫酸盐法蒸煮后,木素结构中侧链上的连接键也发生了断裂,使脂肪羟基的含量增大;蒸煮过程中,木素之间的连接结构发生断裂,使得木素中酚羟基的含量增大;此外,蒸煮也使得木素原料中稳定的内酯或酯发生水解,使木素的羧基数量增加。氧脱木素过程中,木素结构单元发生了开环反应,使羧基含量增加,酚羟基含量减少。此外,木素侧链的氧化也使脂肪族羟基的含量减少,羧基的含量增加。对卡伯值为24.1（CK1）和17.1（CK2）的桉木硫酸盐浆分别进行了ODQP和DQP漂白。CK1浆经氧脱木素后卡伯值降至16.9,在有效氯用量为2.5%,H₂O₂用量为2.5%时,ODQP漂白浆的白度达到86.1%ISO,黏度为783 mL/g;CK2浆在有效氯用量为4.0%,H₂O₂用量为2.5%时,DQP漂白浆的白度为85.4%ISO,黏度为706 mL/g。相同打浆度下,DQP浆的抗张指数和耐破指数比ODQP浆高,而撕裂指数则是后者高;抗张指数相同时,ODQP浆的撕裂指数高于DQP浆;ODQP浆比DQP浆容易打浆。氧脱木素作为硫酸盐法蒸煮的继续可以降低后续漂白药品的用量,改善漂白选择性。CK2浆在有效氯用量为4.0%,H₂O₂用量为2.5%时,DQP和（DQ）P漂白浆均能达到85%ISO以上的白度,且具有较好的白度稳定性。（DQ）段适宜的终点pH值为3.5～4。相同打浆度下,DQP浆的抗张指数和耐破指数都比（DQ）P浆好,（DQ）P浆的撕裂指数高于DQP浆;抗张指数相同时,（DQ）P浆的撕裂指数较高。（DQ）P浆较容易打浆。（DQ）P两段短流程漂白可得到与DQP三段漂非常接近的结果,将D段和Q段合并为一段（DQ）在技术上是可行的。两段漂所需要的设备投资、能耗和运行成本比三段漂少,具有明显的优势和潜在的应用前景。当漂白浆的白度均为84%ISO左右时,与CK2 O（DQ）P漂白浆相比,CK2 O^*（DQ）P（O^*为表面活性剂S3强化的氧脱木素）漂白浆所消耗的漂白化学品的量更少,即氧脱木素段添加合适的表面活性剂能有效降低漂白化学品用量。达到相同打浆度时,O^*（DQ）P浆需要消耗较多的打浆能耗,但其抗张指数、撕裂指数和耐破指数均高于O（DQ）P浆;抗张指数相同时,O^*（DQ）P浆的撕裂指数较高。对白度为85%左右的CK2漂白浆来说,DQP和（DQ）P的强度性能最高,O^*（DQ）P次之,O（DQ）P最低。与桉木漂白浆相比,麦草漂白浆很容易打浆,其主要原因是由于麦草漂白浆中较高的细小组分含量和半纤维素含量。打浆后,桉木纤维润胀并分丝帚化,纸浆的各项强度指标快速增大。麦草漂白浆经打浆后其纸页强度性能的上升幅度较小,其主要原因是麦草浆打浆过程产生大量的细小组分,而主要不是纤维的分丝帚化;打浆度相同时,桉木漂白浆的各项纸页强度性能要比麦草漂白浆的好得多。桉木漂白浆的纤维素含量高,半纤维素含量适中,因而打浆后纸页的强度性质得到较大改善;麦草漂白浆的半纤维素（尤其是木聚糖）含量高,而纤维素的含量相对较低,因而易打浆而强度的上升幅度较小。桉木漂白浆纤维的总电荷比麦草漂白浆高,打浆过程中纤维的总电荷基本保持不变但表面电荷明显增加;麦草漂白浆纤维的表面电荷比桉木浆低,且打浆过程中纤维的表面电荷变化非常少,说明其纤维表面的细纤维化程度没有桉木浆好,故其强度的改善没有桉木浆好。采用位错（dislocation）值可以表征制浆漂白过程中纤维的损伤程度。桉木漂白浆经打浆后,桉木浆纤维的位错值变化不大,而麦草浆纤维的位错值随打浆度的上升而明显增大,这也是导致打浆度相同时桉木漂白浆纸页强度比麦草漂白浆更好的原因之一。纸浆细小组分的性质影响着纸页的各项性质。麦草浆含有大量的细小组分,约为35%～47%,大部分为杂细胞,;筛分除去细小组分后,麦草浆的滤水性能明显改善,强度性质和光学性质也都有所提高。而桉木浆中的细小组分主要是纤维碎片和细小纤维,筛分除去细小组分后,纸页的抗张指数和耐破指数明显降低,而撕裂指数提高。更多还原

【Abstract】 Eucalyptus grows fast and behaves well in pulp and paper making,it is one of the fast-growing trees which are developed emphasisly in the "Forestry-pulp-paper integration" project,and the utilization of fast-growing eucalyptus is important for the sustainable development of China’s paper industry.Researches on kraft cooking,oxygen delignification and elemental chlorine free（ECF） bleaching of fast-growing eucalyptus were carried out in this thesis;the effects of fiber properties on pulp beating and sheet properties were also studied;which will provide the fundamental base and technique support for the clean pulping and bleaching of fast-growing eucalyptus.The modelling and design software（MODDE） was used for the design and evaluation of the kraft cooking experiments of fast-growing eucalyptus.Based on the MODDE mathematic model of kraft cooking,it can be learned that the variations of effective alkali charge,sulfidity, temperature and time affected the pulp properties significantly,for the pulp with a given Kappa number,pulp screened yield,viscosity and brightness could not be maximized simultaneously.Mathematic model is based on the cooking experiments,it could predict pulp properties at a given cooking conditions,at the cooking conditions of effective alkali charge 17%,sulfidity 29.5%,temperature 150℃,time 135 min,the pulp properties predicted by model were:Kappa number 18.1（upper 21.5,lower 15.3）,screened yield 50.3%（upper 51.2%,lower 49.5%）,brightness 34.1%ISO（upper 36.1%ISO,lower 32.2%ISO） and viscosity 1429 mL/g（upper 1627 mL/g,lower 1232 mL/g）.The kraft cooking can also be optimized by model:as the target Kappa number was set up and the weight of screened yield, viscosity and brightness were mamximized with different values（from 0 to 1）,the optimal cooking conditions,including effective alkali charge,sulfidity,temperature and time,could be established.Similarly,screened yield,brightness or viscosity can also be as a target for the technological optimization.During the kraft cooking process,the temperature,effective alkali charge and time affected the pulp HexA content significantly,and the variation of sulfidity did not influence the pulp HexA content.Lower temperature,lower effecitve alkali charge and shorter time resulted in a pulp with lower HexA content and higher screened yield.The effects of alkali charge,temperature,pressure and time on oxygen delignification were studied.For eucalyptus kraft pulp with Kappa number 17.1,the optimized oxygen delignification conditions were:alkali charge 2%,temperature 100℃,O₂ pressure 0.5 MPa, time 60 min;and the oxygen delignifed pulp with Kappa number 9.5,brightness 58.4%ISO, viscosity 795 mL/g was obtained.The utilization of surfactant during oxygen delignification process could improve the delignification efficiency and pulp brightness,and pulp viscosity decreased slightly.The oxygen delignification reinforced with three different surfactants（S1, S2 and S3） were also carried out,the optimized charges of the three surfactants were all 0.2%, and surfactant S3 led to better results than the others.With the charge of S3 increasing from 0 to 0.2%,pulp Kappa number decreased from 9.5 to 8.1,brightness increased from 58.4%ISO to 62.3%ISO and viscosity decreased from 795 mL/g to 744 mL/g.Changes of lignin structure during kraft cooking and oxygen delignification were analysis by means of FTIR and ³¹P-NMR.The results showed that during kraft cooking process the ester links between lignin units were cleaved,more syringyl lignin units were dissolved,the contents of aliphatic OH,phenolic OH and COOH groups in residual lignin increased apparently.The oxygen delignification process resulted in the increase on the content of COOH groups and decrease on the content of phenolic OH groups which indicated that the phenolic rings were partially opened during oxygen delignification process,COOH groups were formed at the same time.The oxidization of lignin side chains led to increase of COOH groups and decrease of aliphatic OH.Two different eucalyptus pulps with Kappa numbers of 24.1（CK1） and 17.1（CK2） were prepared by kraft cooking process,the ODQP and DQP bleaching sequences were applied to these two kraft pulps respectively.After oxygen delignification,the Kappa number of CK1 decreased from 24.1 to 16.9,which was close to that of CK2,meaning that the kraft pulping was extended by the oxygen delignification.The bleaching results showed that ODQP pulp with the 86.1%ISO brightness and 783mL/g viscosity was obtained from CK1 pulp when the active chlorine charge was 2.5%,H₂O₂ charge was 2.5%;the DQP pulp with 85.4%ISO brightness and 706 mL/g viscosity was also obtained from CK2 pulp at the active chlorine charge of 4.0%,H₂O₂ charge of 2.5%.The property testing of the sheets made from the 86.1%ISO ODQP pulp and 85.4%ISO DQP pulp indicated that the ODQP pulp had better tear index and less beating energy consumption at a given beating degree but lower tensile index and burst index compared with those of the DQP pulp.Kraft cooking extended by oxygen delignification can improve pulp bleachability.The DQP and（DQ）P bleaching sequences were applied to CK2 pulp.The bleaching results showed that the DQP pulp with brightness 85.4%ISO and（DQ）P pulp with brightness 85.3%ISO were obtained when the active chlorine charge was 4.0%,H₂O₂ charge was 2.5%. The brightness of the（DQ）P pulp was not sensitive to the variation of the pH value in（DQ） stage in the pH range of 2 to 4,the pulp brightness didn’t change significantly.The property testing of the sheets made from the DQP and（DQ）P bleached pulps indicated that both pulps had very good strength properties,the（DQ）P pulp had better tear index and less beating energy consumption at a given beating degree but lower tensile index and burst index compared with those of the DQP pulp.The experiment results indicate that it is feasible to combine D stage and Q stage into a（DQ） stage.O（DQ）P and O^*（DQ）P（O^*:Oxygen delignification reinforced with surfactant S3） bleachings were carried out with CK2 pulp.With the same final brightness about 84%ISO, O^*（DQ）P pulp consumed less active chlorine and peroxide compared with the O（DQ）P pulp; although O^*（DQ）P pulp needed a higher beating energy,the tensile index,tear index and burst index of the pulp were better than those of O（DQ）P pulp at the same ^oSR value.Generally, the strength properties of DQP and（DQ）P pulps were superior to those of O（DQ）P and O^*（DQ）P pulps.Wheat straw bleached pulps responded to refining more easily than eucalyptus bleached pulps and that the differences were due mainly to the higher contents of fines and xylan in the wheat straw pulps.During the beating process,the strength property of the eucalyptus pulps developed fastly because of the fiber swelling and fiber laminating;in the case of wheat straw bleached pulps,large amount of fines were formed instead of fiber swelling and fiber laminating during beating,which resulted in a very limited increase in pulp strength property. At a given beating degree,the strength properties of eucalyptus bleached pulps were much better than those of wheat straw bleached pulps.The eucalyptus bleached pulps had higher cellulose contents and moderate hemi-cellulose contents,which led to significant progress on the pulp strength properties; although wheat straw bleached pulps were easily beaten,the lower contents of cellulose and higher contents of hemi-cellulose（especially xylan） resulted in limited improvement on pulp strength properties.At a given beating degree,the eucalyptus bleached pulps had higher total fiber charges than those of wheat straw bleached pulps,and the total fiber charges were not affected by the beating;the surface fiber charges of eucalyptus bleached pulps were higher than that of wheat straw bleached pulps at a given beating degree,and were developed by beating.The initial number of dislocation was higher and that the number increased more rapidly during beating for wheat straw fibers than for eucalyptus fibers.These results may explain the lower and slower development of the strength properties of paper sheets prepared from wheat straw pulps than in that from eucalyptus pulps.The fines had a significant effect on sheet properties.Wheat straw pulps had a very high content of fines（35%～47%）.Removal of fines from the wheat straw pulps improved not only the drainability of the pulps suspension but also the mechanical and optical sheet properties,this indicated that the fines in the wheat straw pulps acted mainly as filler with low bonding properties.Removing the fines from eucalyptus pulps led to a decrease on sheet tensile index and burst index,an increase on sheet tear index,and it could be learned that the fines in the eucalyptus pulps was beneficial to the pulp strength properties.更多还原