【作者】 周建国；

【导师】 林炳鉴；

【作者基本信息】 北京化工大学 ， 化工过程机械， 2001， 博士

【摘要】 本文首次利用自行研制的可视化天然高分子用单、双螺杆挤压机，采用统计学手段进行试验设计和数据分析，较详尽地考察了棉籽饼粕挤压脱毒的工艺和设备参数对脱毒效果的影响。此外，本文首创地运用控制容积法以及作者与课题组成员实验建立的蛋白质物料本构方程经验式对单螺杆挤压这种高含水率、高粘度物料的流场进行了数值模拟，讨论了不同流动模型及工艺参数对挤压过程的影响。 挤压脱毒试验结果表明，采用螺杆挤压法脱毒，简便易行、且能取得优良的脱毒效果，但各挤压加工参数间需良好匹配。而且，单、双螺杆挤压机和棉籽粉、棉籽粕上的脱毒规律也存在着差异。捏合盘的加入可降低棉籽饼粕中的游离棉酚含量，但宜适当放置，捏合盘长度、位置及交互效应的作用十分显著，间距的影响则不显著。此外，捏合盘参数对脱毒效果也存在着一定的影响。从挤压产品组织结构看，尽管存在差别，经挤压后的棉籽蛋白可以获得与大豆蛋白挤压产品相类似的组织化纤维结构；实际挤压脱毒中，游离棉酚可能同多种氨基酸及其盐类发生化学反应并存在着多个反应点，赖氨酸则是其中重要的反应成分。 挤压流场模拟结果表明，影响棉籽饼粕挤压过程的各加工参数中，含水率的影响最为显著，螺杆转速次之，且两者间存在交互作用：无量纲产量主要影响沿流向速度分布形态，而对其它量影响不大：螺槽截面上的粘度沿螺槽深度方向呈近壁面处小、中间位置处大的分布特性。本构方程则是决定上述这些挤出响应变量反应的关键因素。而棉籽饼粕属天然高分子物料，其挤压改性过程中的本构方程十分复杂。模拟中采用作者及其课题组成员实验得出的蛋白质物料本构关系经验式进行计算，结果也表明不同流动模型处理得到的结果并不相同。牛顿流体处理尽管数值上与非牛顿流体存在差异，但也能大致反映出挤出加工的实际情形；非牛顿、非等温且温度沿流向非充分发展情形则存在一个各变量从初期显著波动到逐渐趋于稳定，最后与充分发展情形一致的发展过程。 从脱毒结果看，螺杆挤压脱毒法效果明显，值得进一步研究和应用；从数值模拟结果看，本文采用的计算方法、处理及程序实现是成功的。更多还原

【Abstract】 Effects of varying screw speed, moisture content and feed rate on cottonseed meal de-gossypol process were studied using both single-screw and twin-screw extruder. Experimental results indicated that difference in . detoxification rule could arise between single-screw and twin-screw extruder or cottonseed flour and meal. Effects of screw configuration, mainly kneading blocks (KB) indicated that incorporation of KB, if appropriately set, could considerably reduce the residual free gossypol (FG) content. The length and position of KB significantly affected the de-gossypol results, while the spacing effect was marginal. KB parameters take effect as well. As for the de-gossypol mechanism, FG might react with several kinds of Amino Acid and with more than one binding site, ε -Amino Acid possibly the most important. In addition, the extrusion product fibrous texture of cottonseed protein was similar to that of soy protein.Through an experiential rheological model of protein product extrusion, flow simulation of single-screw extrusion indicated that different flow models led to different results. Isothermal and Newtonian flow model could reflect the true extrusion process to some degree though numerically different from the non-Newtonian, while the non-Newtonian, non-isothermal and temperature-undeveloped model experienced a fluctuation of extrusion variable at the beginning and stability as well after enough length of development zone, with values the same as those fully developed. In addition, effects of moisture on extrusion process were shown to be dominant, screw speed the less and dimensionless volumetric flow rate mainly affected the velocity distribution along the channel. With the viscosity, a distribution of small value near the wall and great in the midst of channel depth was assumed.Seen from the detoxification and flow simulation result, the screw extrusion de-gossypol method and numerical flow simulation of this extrusion process were proved to be effective.更多还原