聚合物高效脱挥技术进展

聚合物中挥发分含量的不同导致聚合物脱挥过程遵循不同的热质传递机理，基于脱挥过程关键机制开发高能效的聚合物脱挥技术与装备具有重要工程意义。本文分别简述了闪蒸脱挥、起泡脱挥以及扩散脱挥3种脱挥方式的传递机理、过程特征以及过程模型，在此基础上从脱挥工艺和装备两个方面综述了近年来聚合物脱挥过程强化的手段与方法，并系统介绍了栅缝降膜脱挥、超重力旋转强化脱挥、超临界流体辅助脱挥、超声空化强化脱挥等过程强化新技术及其应用现状，提出了未来聚合物脱挥理论与工程实践的研究方向：一方面仍需深入研究扩散脱挥与起泡脱挥的耦合作用机制，建立精准、普适的脱挥过程模型；另一方面指出立式降膜脱挥技术因其能效优势，有望成为未来大规模工业脱挥器的重要选择。     

聚合物系的挥发分脱除——起泡脱挥机理及模型

聚合物系的挥发分脱除(以下简称脱挥)是聚合物生产中的关键工艺之一。本文对国外有关聚合物系脱挥领域的文献作了综述,介绍了聚合物脱挥的基本概念,重点描述了起泡脱挥传质中气泡的成核、生长、破裂,气泡合并、凝聚的机理以及它们的表达式,并介绍了几种起泡脱挥的模型。     

二醋酸纤维素塑料生产中挥发分的脱除与利用

分别研究了二醋酸纤维素塑料水分、增塑剂吸收量及生产过程中螺杆转速、喂料量、螺杆组合对脱挥效率的影响。结果表明，水分作为助脱挥剂，有利于脱挥；增塑剂吸收量高，不利于脱挥；高螺杆转速、低喂料量、排气口前高屏障型螺纹元件均有利于脱挥；挥发分的有效脱除可改善产品通透度和热稳定性；挥发分中60 %以上为邻苯二甲酸二乙酯（DEP）成分；通过设计冷凝系统，实现了挥发分中增塑剂的分离，从而实现了DEP的回收利用。     

聚合物系的脱挥发分设备

评述了近２０年来国内外在聚合物制造过程中脱挥发分（简称脱挥）设备的应用和研究概况。重点讨论了塔式薄膜蒸发脱挥器，该类脱挥器具有结构简单，成本低，处理量大等优点。为了使塔式列管式脱挥器中的蒸发器内有较理想的流体分布，介绍了加设在蒸发器内的液体分布器的结构。     

聚合物系脱挥研究进展

综述了聚合物系脱挥中脱挥表征方法、影响因素基本规律、脱挥基本理论和超泡脱挥动力学及脱挥设备等方面的研究现状,指出了今后可能的发展趋势。     

板缝聚合物脱挥作用

P.L.Maffettone 和 G.Astarita 等研究者对最近(1990年)研制的一种新的静态聚合物脱挥技术进行脱挥的过程(这种新脱挥技术是这样的:让聚合物溶液在装配成互相垂直的平板群的壁缝中流过而脱挥.板内设有孔,热油在这些孔内循环流动使板壁保持一个高的温度,平板群置于真空闪蒸室内。)进行了模拟。模型同时考虑了动     

超临界流体增强聚酯薄膜中的质量传递

聚合物中杂质/挥分的存在对聚合物的终端使用将产生负面影响,因此必须将其除去.传统的脱挥方法效率有限,使用超临界流体技术可增强脱挥效率.测定了温度为343 K、压力为30 MPa、CO₂流量为4.0 L•min^-1条件下,PET聚酯薄膜中的乙二醇单体挥分含量与时间的关系,以研究聚合物系超临界流体脱挥过程中的质量传递规律;根据传质理论建立了一个理想的超临界流体脱挥过程的质量传递模型,并用该模型分析处理实验数据,结果表明该模型较好地反映了聚合物系超临界流体脱挥过程的基本特征.     

聚合物搅拌脱挥设备及其CFD模拟研究进展

综述了聚合物搅拌脱挥设备的开发进展,分析了设备开发过程存在的关键问题。指出卧式脱挥设备中的流动特性、混合特性、成膜特性以及表面更新特性等是强化传质的关键因素,具有自清洁搅拌特性的高效卧式脱挥设备是装备开发与研究的主要方向。阐述了计算流体力学(CFD)在研究高黏流体卧式搅拌设备内传递过程机理中的应用。基于网格重叠技术的有限元方法和基于动网格的有限体积方法可以解决复杂几何结构的桨叶和翅片、双轴的旋转运动以及啮合机构非常小的间隙等难题。借助于CFD中VOF多相流模型可以精确地追踪气液相界面,模拟反应器中的成膜过程和表面更新特性,进而可以深入分析设备中的传质过程,为高效聚合物脱挥设备的优化与设计提供了新的思路。     

工业聚合反应装置：Ⅲ.均相本体聚合反应器（下）

论述了聚酯，聚酰胺缩聚反应装置及高粘流体脱挥设备。在简述其选型原理及设备结构的基础上，介绍和推荐了一些新型缩聚反应器和脱挥装置。     

聚甲醛生产中的挥发分脱除北大核心

根据聚甲醛的生产特点,通过研究双螺杆挤出机的脱除挥发分(简称脱挥)机理,结合聚甲醛实际生产的脱挥工艺,从螺杆组合、螺杆转速、进料量、筒体温度、螺杆长径比等方面分析了影响挤出机脱挥效率的主要因素,给出了适合聚甲醛生产的工艺参数:进料量与螺杆转速的比值维持在18~20,筒体温度为180~195℃,真空度维持在0.01 MPa以下。通过对现有挤出机脱挥系统的优化改造,使脱挥后聚甲醛中甲醛挥发量达100μg/g以下。     

旋转填充床内高黏介质脱挥过程的传质模型(英文)

A mass transfer model for devolatilization process of highly viscous media in rotating packed bed(RPB) was developed based on penetration theory and mass conservation.Before establishing the model,some mass transfer experiments of thin film were conducted in a designed diffusion cell including vacuum and feeding system. In this study,acetone was used as the volatile organic compound(VOC) and syrup as the highly viscous media.The thickness of thin film was changed by using different liquid distributor.It was found that bubbling played an important role in the devolatilization.The correlation of diffusion coefficient of acetone in highly viscous dilute solution was proposed.The relative error between predicted and experimental data was within the range of ± 30% for diffusion coefficient of acetone in syrup.A comparison of experimental data of RPB with model indicated that the relative error was within ± 30% for efficiency of acetone removal.     

超重力旋转床微米级粉尘脱除实验研究

以超重力旋转床作为除尘设备,用超细滑石粉模拟工业微米级粉尘,考察旋转床除尘的分离效率和设备压降.在气量500～700 m~3/h、液量0.6～1.0 m~3/h、转速560～1 400 r/min、平面丝网层数为3的条件下,除尘总效率均大于97%,设备总体压降不超过490 Pa.超重力旋转床相对于其他除尘设备,显示了高效除尘和低压降性能.     

旋转填充床内高黏介质脱除有机挥发组分过程强化

The removal of a volatile organic compound (VOC) from high viscous liquid was carried out in a rotating packed bed (RPB) in this study. The mixed liquid of syrup and acetone was used as simulated high viscous polymer solution with acetone as the volatile compound. The influence of the rotating speed of RPB, liquid viscosity, liquid flow rate, vacuum degree, and initial acetone content in the liquid on acetone removal efficiency was investigated. The experimental results indicated that the removal efficiency increased with increasing rotating speed and initial acetone content in the viscous liquid and decreased with increasing liquid viscosity and flow rate. It was also observed that acetone removal efficiency increased with an increasing vacuum degree and reached 58% at a vacuum degree of 0.1 MPa. By the comparison with a flash tank devolatilizer, it was found that acetone removal ef-ficiency in RPB increased by about 67%.     

溶剂回收的新型设备--折流式超重力旋转床

折流式超重力旋转床是一种新型、高效的精馏设备，主要介绍了其结构特点和工作原理，与常用填料式旋转床相比，折流式超重力旋转床可以更方便地实现连续精馏操作所必需的中间进料，并可以同一轴安装多个转子以提高单台设备的分离能力，而在转子之间没有动密封，其在有机溶剂回收精馏过程中成功的工业应用，展示出十分广阔的应用前景。     

超重力法脱除气体中硫化氢

采用超重力设备--旋转填料床替代传统湿法脱硫工艺中的脱硫塔,以PDS为脱硫催化剂,对工业过程中产生的含硫化氢气体进行了脱硫实验研究,考察了气液比、转速、碱废、温度、PDS含量等对脱硫率的影响规律.在适宜的条件下,获得了99.0%以上的脱硫率.与塔式脱硫技术相比,该技术具有脱硫效率高、液气比小、脱硫设备体积小等优点.     

错流旋转填料床脱除细颗粒物研究

细颗粒物对环境和人体都会产生较大危害, 传统除尘设备无法高效脱除。超重力旋转填料床复合了多种除尘机制, 除尘效率高, 能耗低。本文采用平均粒径为2.25μm的粉煤灰模拟细颗粒物, 错流旋转填料床为湿式除尘设备, 搭建了中试规模的实验系统。提出了使用激光粒度分析仪测量粉尘粒度分布并计算分级效率的方法, 通过实验考察了转速、液气比和气量对错流旋转填料床分级效率的影响。研究表明, 分级效率随转速、液气比、气量的增大而增大, PM_2.5的脱除效率可达到96%, 为超重力湿法除尘的工业化推广提供有力的数据支撑。对分级效率曲线进行拟合, 相关系数R=0.9808。对比发现, 错流旋转填料床的分级效率高于一般湿式除尘器, 对微米级粉尘也有很高的脱除率, 可以高效脱除气体中的细颗粒物, 应用前景广阔。     

Devolatilization of large coal particles in fluidized beds

Analysis of devolatilization of predried large coal particles in fluidized beds requires consideration of both the chemical kinetics of coal decomposition and transport processes. Models available either assume the devolatilization particle to be isothermal (whereas it may be shown that, in general, large temperature gradients may exist within the particle) or require extensive numerical integration procedures. This Paper describes a model which permits formulation of analytical and easy-to-use equations for the estimation of the devolatilization history of a large predried coal particle in a fluidized bed. The model predictions are compared with experimental data collected for Mississippi lignite. A correlation is proposed for the estimation of the total devolatilization time. The analytical solutions presented may be used with ease in coupling the devolatilization process to the other phenomena, such as drying and/or combustion of volatiles and residual char, occuring during fluidized bed combustion of coal.     

High-gravity-assisted emulsification for continuous preparation of waterborne polyurethane nanodispersion with high solids content

In this work, we developed a continuous preparation strategy for the production of high-solids-content waterborne polyurethane (WPU) emulsions via high-gravity-assisted emulsification in a rotating packed bed (RPB) reactor. By adjusting the experimental parameters and formula, WPU emulsions with a high solids content of 55% and a low viscosity were prepared. Preliminary applications of the high-solids-content WPU as a thermally insulating material were demonstrated. RPB emulsification is an economical and environmentally friendly production strategy because of the low energy consumption, short emulsification time, and effective devolatilization. This study demonstrated an effective method for preparation of high-solids-content WPU, moving toward commercialization and industrialization.     

超重力旋转床脱除微米级粉尘的实验研究

用超细滑石粉模拟工业微米级粉尘,通过实验研究了超重力旋转床的除尘特性.考察了旋转床在不同的气量q<,G>、液量q<,L>、转速n和轴向放置平面丝网层数n<,m>下的除尘效果,确定了实验室规模下适宜的除尘工艺条件:q<,G>=600 m<'3>/h,q<,L>>0.6 m<'3>/h,N=1 400 r/min,n<,m...