NaOH-AQ/O₂两段蒸煮中氧段硅转移特性的模拟研究

【作者】 曹海峰；

【导师】 翟华敏；

【作者基本信息】 南京林业大学 ， 制浆造纸工程， 2008， 硕士

【摘要】 麦草是中国造纸工业最重要非木材纤维来源。但是硅干扰是麦草制浆中存在的重要问题,硅溶入黑液中,对黑液碱回收系统造成严重的“硅干扰”,严重影响着整个碱回收系统的稳定运行。NaOH-AQ/O2两段蒸煮是非常有前景的环境友好的麦草制浆方法。本论文通过利用在漂白针叶木浆中人为添加二氧化硅并模拟氧碱蒸煮段工艺,探索硅在氧碱蒸煮过程的转移规律和特性,并通过添加助留剂研究在氧脱木素后硅的留着机理,为在工业生产中推广应用NaOH-AQ/O2两段蒸煮这种环境友好的制浆方法发挥作用。氧碱蒸煮段,浆料除硅的影响因素主要有:pH值、氧压、温度等。本论文主要的研究结果有:(1)氧碱蒸煮体系的碱度对硅转移有重要影响。在氧压、温度等反应条件固定下,随着pH的降低,浆料中硅含量在升高,当pH为5时,浆料中硅含量最高,水相中硅含量最低;(2)氧碱蒸煮体系的氧压对硅转移有影响。在相同pH和温度的条件下,在一定的压力范围内,随着氧压的增加浆中硅含量提高,而水相中的硅含量下降;(3)氧碱蒸煮体系的温度对硅转移有较大的影响,在相同的pH和氧压等条件下,随着氧碱蒸煮的温度提高,浆料中的硅含量在提高,而水相中的硅含量在下降;通过模拟试验,发现浆中硅含量在氧压为pH为5,0.5MPa,温度100℃,得到最高浆中硅含量为1.49%,水相中的硅含量为0.05g/l,此时硅的转移率达到12.4;(4)氧碱蒸煮后,PEO对蒸煮后体系中硅转移产生较大的影响。pH、PEO用量和浆浓对硅转移产生影响,较好的硅在纤维上保留条件是:pH为9,PEO用量为0.06%,浆浓为3.0%,此时浆中的硅含量高达3.8%;(5)经过SEM扫描发现纤维细胞壁表层发生了细纤维化,并且纤维细胞表层的微纤丝和纤维细胞表层吸附有硅颗粒,证明了模拟试验的可行性。更多还原

【Abstract】 Wheat straw is one of most important non-wood fiber raw materials for China’s papermaking industry. Silicon in the wheat straw black liquor is a key obstacle to the chemical recovery of the black liquor. NaOH-AQ/O2 two-stage cooking process is a potential process for environmental friendly wheat straw pulping. This paper deals with the silicon transferring properties between the fibers and water phase in simulation alkaline O2 cooking by adding given Na2SiO3 to the O2 cooking system. The purpose is to guide the NaOH-AQ/O2 two-stage cooking process toward industrial application.The main factors that influence the transfer between fibers and water phase during the oxygen-alkali cooking are pH, oxygen pressure, temperature and so on. The main results obtained are following:1. The pH value has an important influence on silicon transferring between the fibers and water phase in the oxygen-alkali cooking stage. Under the fixed oxygen pressure, temperature and other conditions, the silicon retention on the fibers increase with the decrease of alkalinity in the system.2. The oxygen pressure has impact on silicon transferring between the fibers and water phase in the oxygen-alkali cooking stage. Under the given pH, temperature and other conditions, the silicon retention on the fibers increased with the increase of oxygen pressure in the system3. The temperature has an obvious impact on the oxygen-alkali steam boiling stage. Under the fixed pH value, oxygen pressure and other conditions, the silicon retention on fibers increase with the increasing of temperature while the silicon concentration in the water phase decrease.The simulation test indicated that high silicon content in the fibers was 1.49%, a low silicon concentration was 0.05g/L in the water phase when the oxygen pressure was 0.50 MPa, pH was 5 and the temperature was 100℃.4. After O2 cooking, the addition of PEO has an important impact on the silicon transfer between the fibers and water phase. The beneficial parameters to the silicon retention on the fibers, up to 3.8% silicon based on the fibers (o. d), were pH, 9; PEO dosage, 0.06%; the pulp concentration, 3.0%.5. It is observed that there are silicon gels on the fiber surface by SEM and showed that the silicon can be transferred onto fibers from cooking liquor by oxygen-alkali cooking.更多还原