【作者】 季伟；

【导师】 李十中；

【作者基本信息】 天津大学 ， 材料学， 2006， 硕士

【摘要】 木糖是一种重要的工业原材料,在医药、食品、化工等行业中已得到广泛的应用。木糖主要以富含半纤维素的植物资源,如玉米芯、棉籽壳、秸秆和稻草等为原料,经过一定的处理制得。玉米是我国三大粮食作物之一,大量的副产品玉米芯目前除少量进行初加工外,绝大部分作为农家燃料被燃烧掉,并未得到充分的利用,既浪费了资源又污染了环境。因此,开展以玉米芯为原料,生产木糖方面的理论与生产技术的研究是十分必要的。工业中制取木糖是将植物中的多缩戊糖(即半纤维素类物质)进行高温酸水解,然后经过中和、活性炭脱色处理,再经过阴阳离子树脂交换过滤,得到纯净的木糖溶液,最后经过蒸发浓缩、结晶、分离干燥,获得木糖晶体。该工艺操作复杂,成本较高。膜分离技术是一种新型的化工分离技术,具有多方面的优点。本试验将膜超滤技术引入,研究了贯膜压力、流量、温度等因素对木糖液超滤处理过程的影响,证明超滤处理能较好地截留色素胶质等杂质,提高木糖纯度。超滤能代替一次脱色工艺和提高并优化其它工艺性能,达到简化操作,降低成本的目的。浓差极化和膜污染严重限制了膜的应用和发展。在本试验中使用气体鼓泡法来改善浓差极化和膜污染对膜性能的影响。超滤操作过程中在膜组件内人为形成两相流,气泡的扰动作用能增强液体的湍流程度,改善浓差极化和膜污染。试验研究了气液两相流操作对膜渗透通量的影响,结果表明气液两相流操作能有效提高膜渗透通量,透量提高率随气体鼓泡压力和流速的升高而增大。鼓泡能在一定程度上提高木糖液纯度。这些结果对于未来的木糖工业生产应用有重要的意义。试验取得了较好的效果,超滤处理工艺能应用于改善木糖生产。更多还原

【Abstract】 Xylose is an important crude material which has been widely used in many fields such as medicine,food and chemistry industries.Xylose can be prepared byβ-xylanase reaction with corncob, cotton seed hull or rapeseed hull. Maize is one of the three main foodstuff plants in China and the average yield of corncobs is about 40 million tons every year. Most of the corncobs are burnt, although a few are used .Then it is very important to do the theoretic and the processing technologies researches about the xylose preparation with corncobs. In order to get the xylose crystal,people hydrolysis theβ-xylanase containing in corncobs, after with the processes of neutralizing ,activated carbon treating, filtering, then gain cleaned xylose solution. After the xylose solution is being evaporated ,crystallized , divided, and dehydrated. the xylose is prepared.In the current industry, twice activated carbon treatments, twice ion-exchange treatments are needed. The traditional manufacturing processes are costly and complex.As a novel and effective separation technique ,membrane process has many advantages. This experiment proposes ultrafiltration into the research. We study the relationship between the effect of ultrafiltration treatment and factors such as trans-membrane pressure, flux and temperature. The result shows the ultrafiltration treatment can cut down impurity and purify the solution. It can take place of activated carbon treatments and simplify the manipulation. So the cost can become lower .However concentration polarization and membrane fouling in the membrane process severally limit its application and development . In the study, we use gas sparging to deal with the tricky problems——concentration polarization and membrane fouling. The effects of gas sparging in liquid i.e two-phase flow operation on ultrafiltration are studied. In application of two-phase flow operation ,the permeation flux can be enhanced. Experimental results show that the increase rate of flux is concerned with trans-membrane pressure(TMP) and gas velocity. Gas sparging can also purify the xylose solution. The work will exert innovative influences on the future industry application of xylose production.After a lot of tests, it has been proved to have a good effect. So, the process of ultrafiltration has highly economic potentiality.更多还原