【作者】 胡会超；

【导师】 詹怀宇；

【作者基本信息】 华南理工大学 ， 制浆造纸工程， 2010， 硕士

【摘要】 热水预抽提技术作为一种经济、环保的生物质预处理技术,具有对设备腐蚀低、预抽提液中寡糖含量高、单糖降解率低、对纤维素破坏较小和木素溶出较少等优点,已成为结合制浆造纸生物质精炼的研究中应用最为广泛的生物质预抽提技术之一。竹子,作为我国南方一种重要的非木材原料,其结合制浆造纸的高值化利用的研究,对于木材原料匮乏的我国的生物质资源化利用和制浆造纸产业的持续发展具有重要意义。因此,本论文以我国南方的竹子为原料,进行了制浆前的热水预抽提,然后进行硫酸盐蒸煮和无元素氯(Elemental Chlorine Free,简称ECF)漂白,分析了热水预抽提条件对抽提液各主要组分变化规律及后续KP法制浆和ECF漂白性能的影响,为竹子结合制浆造纸的生物质精炼提供理论依据和技术支持。采用热水预抽提技术、离子色谱和高效液相色谱的检测手段,在不同的最高温度和保温时间下,对竹子主要糖组分(葡萄糖、木糖、阿拉伯糖)的抽提得率及其主要降解产物——糠醛和羟甲基糠醛的浓度进行了考察。探讨了木糖、葡萄糖和阿拉伯糖的寡糖、单糖得率,糠醛和羟甲基糠醛浓度随反应温度和反应时间的变化规律。进一步,采用H-因子对数(LogH)做变量,对热水预抽提液各组份的变化规律进行了研究。得到了获得最大量糖组分得率的同时、尽量减少抽提液中糖组分降解产物浓度的合理LogH范围以及热水预抽提的最佳温度范围。为了了解热水预抽提过程糖组分溶出和降解的机理,建立了预测热水预抽提液中糖组分得率及其降解产物浓度的动力学模型,研究了半纤维素在热水预抽提过程中的反应动力学特性。发现竹子中木聚糖和阿拉伯聚糖的溶出、木寡糖、木单糖、阿拉伯糖、糠醛的降解反应速率系数与氢离子浓度呈指数或线性关系,即氢离子对以上各组分的生成和降解具有催化作用。据此,建立了预测热水预抽提液中木寡糖、木单糖和阿拉伯糖得率、糠醛浓度的动力学模型,该模型能很好地对以上四种物质的量进行预测(R2大于0.985)。竹子中总糖的抽提程度对于热水预抽提后续的KP法制浆和ECF漂白具有重要影响,建立戊糖、己糖和糠醛、羟甲基糠醛生成量的预测模型,进而获得总糖溶出量的经验模型具有重要意义。根据动力学特性的研究结果,将抽提液氢离子浓度引入到H-因子计算式得到了H ’-因子。通过修正反应的活化能,建立了竹子热水预抽提过程戊糖、己糖、糠醛、羟甲基糠醛生成量的经验模型。结果表明,该模型能很好地对热水抽提液中的戊糖、己糖、糠醛、羟甲基糠醛的生成量进行预测(R2大于0.965)。选用三种热水预抽提H-因子(0、500和1000)和三个蒸煮有效碱用量(15%、18%和21%),通过对比KP法制浆的有效碱消耗、VOC生成量和KP浆的卡伯值、得率、黏度、己烯糖醛酸含量、打浆性能,探讨了热水预抽提对竹子后续KP法制浆性能的影响。结果表明,热水预抽提可以提高竹片蒸煮脱木素效率,达到相同卡伯值(20),可节省约2%-3%的有效碱用量,得到更高的纸浆黏度,更低的VOC和HexA生成量;然而,纸浆的得率下降较多,打浆性能也显著下降。选取卡伯值相近(20)的三种热水预抽提后竹片制得的纸浆,采用DQP漂序,通过变化二氧化氯用量和过氧化氢用量,对比漂白浆的白度、返黄值、卡伯值降低率、黏度和相同白度(85%ISO)纸浆打浆性能、相同打浆度(450SR)纸浆的物理强度(撕裂指数、抗张指数、耐破指数),探讨了热水预抽提对竹片KP浆ECF漂白性能的影响。发现热水预抽提可以提高纸浆漂白过程的卡伯值降低率;相同总有效氯因子下,漂后浆的白度较高,返黄值较低,黏度相近;达到相同白度(85%ISO)可节省约1.4%的总有效氯用量,然而返黄值略高、打浆性能下降,且纸浆的物理强度降低。对比不同热水预抽提条件,抽提液糖组分得率和对后续KP法制浆和ECF漂白的正面和负面影响。发现相对于H-因子500的热水预抽提条件,H-因子1000可获得更高的糖组分得率(约为H-因子500的2.5倍);但是,未漂KP浆的得率损失仅由7%增至10%,打浆转数提高了约0.3倍;漂白浆的返黄值未变化,打浆转数提高约0.35倍,纸浆物理强度下降变缓。所以,热水预抽提的强度更高,单位糖组分得率对后续KP法制浆和ECF漂白所造成的不利影响越低。因此,本实验条件下的最佳热水预抽提条件为H-因子1000。更多还原

【Abstract】 The technology of hot water pre-extraction, as an economical and environmentally friendly pretreatment technology, has the advantages of lower corrosion to equipment, higher content of oligosaccharides, smaller damage to cellulose, lower degradation rate of monosaccharides and less dissolving rate of lignin. It has been extensively studied in biorefinery integrated with pulp and papermaking. Bamboo is a non-wood raw material in south China. The research of bamboo biorefining integrated with pulping and papermaking is important for the resource utilization of biomass and sustainable development of pulp and paper industry in China. Hence, this dissertation studied on the bamboo hot water pre-extraction, kraft pulping and elemental chlorine free bleaching of the pulp. The effect of the hot water pre-extraction conditions on the changing behaviors of main components in extracts and the following kraft pulping and ECF bleaching were analysed. This research will provide the fundamental base and technology support for the biorefinery integrated with pulping and papermaking of bamboo.The yields of main saccharides (glucose, xylose and arabinose) extracted from bamboo and its degradation products (furfural and HMF) were studied at different maximum temperature and holding time of hot water pre-extraction, using HPAEC and HPLC as detection apparatus. The variations of yields of monomers and oligomers of xylose, glucose and arabinose and the concentrations of furfural and HMF as reaction temperature and time were discussed. Furthermore, the changing behaviors of the above components as the logarithm of H-factor (LogH) during hot water pre-extraction were analysed. The reasonable range of LogH and the optimal range of reaction temperature were established for maximizing yield of saccharides and minimizing the concentrations of degradation products from saccharides.The kinetic characteristic of hemicellulose hot water pre-extraction was studied for understanding dissolution and degradation of saccharides, and the kinetic models of the saccharides and its degradation products were built. It was found that there was a relationship (exponent or lineal) between hydrogen ion concentration and the dissolving and degradating reaction rate coefficient of xylan, arabinose polymer, xylose oligomer, xylose, arabinose, furfural and HMF. The kinetic models for predicting the yields of xylose oligomer, xylose, arabinose, and the concentrations of furfural and HMF were set up. The relative coefficients (R2) of the models for the four compounds are above 0.985.The extraction extent of saccharides from bamboo has an important influence on following kraft pulping and the pulp ECF bleaching. Thereby, there was concernment significance to build an empirical model of the formation of pentose, hexose, furfural and HMF. Hydrogen ion concentration was introduced to the calculating formula of H-factor , obtaining H ’-factor, according to the dynamic characteristics. The models for predicting the formation of pentose, hexose, furfural and HMF using modified activation energies were built. The results show that the models are precise, the R2 are greater than 0.965.Three hot water pre-extraction H-factors (0, 500 and 1000) and three cooking effective alkali dosages (15%, 18% and 21%) were selected. The effect of hot water pre-extraction on the kraft pulping performance of bamboo was researched by comparing the consumption of effective alkali, formation of volatile organic compounds and the Kappa number, yield, viscosity, hexenuronic acid content, beating performance of the resulted pulps. The results show that hot water pre-extraction of bamboo could improve the delignification efficiency of pulping, save about 2%-3% of the effective alkali, obtain higher pulp viscosity, lower VOC and HexA content based on the same Kappa number (20). However, there are obvious decrease in the yield and beating performance of pulp.The bamboo pulps with similar Kappa number (20) after hot water pre-extraction and kraft pulping was chosen as unbleached pulp for DQP bleaching. The effect of hot water pre-extraction on the ECF bleaching performance of bamboo pulp was studied, through comparing brightness, PC number, decreasing rate of Kappa number, viscosity and beating performance of bleached pulp, and handsheet’s strength properties of bleached pulp with same brightness (85%ISO) and beating degree (450SR) under different dosages of chlorine dioxide and hydrogen peroxide. The results indicate that hot water pre-extraction before kraft pulping could obtain higher decreasing rate of Kappa number, higher brightness, lower PC number, similar viscosity of bleached pulp at the same total active chlorine factor. For the same brightness bleached pulp(85%ISO), hot water pre-extraction could save 1.4% bleaching chemical, but the PC number was slightly higher, beating performance and strength properties of bleached pulp were also lower.The saccharides yield in extracts and the positive and negative influence of pre-extraction on subsequent kraft pulping and ECF bleaching were compared under different conditions of hot water pre-extraction. It was found that H-factor 1000 of hot water pre-extraction could obtain higher yield of saccharides (2.5 times as that of H-factor 500), however, the yield loss of kraft pulp increased from 7% to 10%, PFI revolutions to beat the kraft pulp to the same 0SR increased about 0.3 times, the PC number of bleached pulp has no much difference, the loss of the strength properties of bleached pulp was not obvious. Forasmuch, the higher the intensity of hot water pre-extraction, the lower the negative effect of unit saccharides yield in extracts on subsequent kraft pulping and ECF bleaching. Consequently, the optimal H-factor of hot water pre-extraction is one thousand under the experimental conditions.更多还原