卧式双轴搅拌釜内流场分析及釜残回收研究

采用SolidWorks软件建立卧式双轴搅拌釜三维模型,应用FLUENT软件进行数值模拟。针对高黏度流体,分析了卧式双轴搅拌釜沿Y轴方向截面上的流场特性。计算结果表明:该卧式双轴搅拌釜中高黏度流体具有较好的流场分布,搅拌效果良好;在导热油为加热介质的实验装置上分别进行了高黏度二价酸酯混合物(MDBE)蒸馏釜残和甲苯二异氰酸酯(TDI)蒸馏釜残中产品的回收实验。实验结果证明将该釜作为蒸馏塔釜残的深度蒸馏再沸器,产品回收率高达99%以上,可以大幅度减少化工固体废物排放。     

合成橡胶聚合釜的技术进展

从聚合反应工程的角度对合成橡胶聚合釜的技术进行了评述,介绍了国外合成橡胶聚合釜搅拌技术的进展概况,并指出我国目前的开发重点为:a.刮壁式搅拌浆的工业化开发,特别是在顺丁橡胶聚合釜中的应用;b.同轴线双轴异浆异速组合式浆,特别是外层带刮板的组合粟的开发;c.适用于特高粘度体系,如本体聚合,聚合物的脱挥发分过程等的卧式单轴或双轴自清洁式搅拌装置的开发;d.沸腾换热技术和搅拌浆叶内通冷却介质技术在聚合釜领域的推广应用。     

应用CFD对D-T型双轴卧式搅拌装置功率特性和传热特性的模拟

针对自主开发的适用于高黏度、高凝固点、强热敏性物料的一种新型带搅拌结构的卧式双轴再沸器的搅拌功率特性和传热及温度分布特性进行了流体力学模拟研究.应用动网格技术计算分析了该卧式双轴搅拌装置的功率特性和传热特性,得出结论:任意一轴的功率准数以及总的功率准数均近似满足N_p·Re=K_p;当1.1 < Re< 20且30 000< PR< 130 000时,总的传热关联式为Nu=2.55 Re~(0.61)Pr~(0.31)Vis~(0.14).     

高粘搅拌聚合反应装置

评述了高粘搅拌混合技术在聚合反应工程领域应用的新进展,分析了宽粘度域搅拌叶轮,卧式自清洁搅拌机构和立式搅拌釜等一系列用于处理高粘液体搅拌混合装置的特点和应用,指出聚合装置的研究开发有助于聚合反应工程的发展,大的有效反应体积,具有自清洁特性的高效高粘流体混合装置是研究开发的方向。     

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。     

卧式双轴搅拌床反应器混合特性研究

本文对卧式双轴气相聚合搅拌床反应器的混合特性进行了实验研究。以三氧化二铝粉体和氯化钾粉体分别为主体物料和示踪物料,用电导法考察了搅拌转速、器内物料的装料高度及通气速率对该搅拌床反应器的混合特性的影响并获得了相应的关联式。结果表明,弗鲁德数、无因次装料高度及通气速率对混合特性有明显的影响。     

立式捏合机捏合间隙影响CFD分析

本文利用计算流体力学(CFD)方法研究捏合间隙对立式捏合机混合性能的影响。首先，根据立式捏合机搅拌桨叶运动特点以及被混物料的流变特性，进行立式捏合机混合流场数值模拟。其次，确定立式捏合机混合性能宏观评价指标。最后，分析了捏合间隙的变化对混合性能评价指标的影响。分析结果表明：间隙越小，立式捏合机的混合性能越好；当空心桨叶两侧的捏合间隙大小相等时，立式捏合机的功耗最小。     

立式压滤机的特点及其在铀矿冶中的应用设想

立式压滤机是固液分离领域的重要设备之一,其主要特点是自动化程度高,滤布再生能力强,应用领域广。列举了立式压滤机的应用情况,并通过对立式压滤机与卧式压滤机的比较,提出了立式压滤机应用于大型铀矿山的设想,从而实现减少设备占地面积、降低滤渣含水率、提高自动化程度、降低劳动强度等卧式压滤机无法实现的效果。     

立式压滤机的特点及其在铀矿冶中的应用设想

立式压滤机是固液分离领域的重要设备之一,其主要特点是自动化程度高,滤布再生能力强,应用领域广。列举了立式压滤机的应用情况,并通过对立式压滤机与卧式压滤机的比较,提出了立式压滤机应用于大型铀矿山的设想,从而实现减少设备占地面积、降低滤渣含水率、提高自动化程度、降低劳动强度等卧式压滤机无法实现的效果。     

多尺度作用的D4/APAEDMS本体共聚过程仿真

引　言本体聚合过程中 ,体系黏度随单体转化率的增加急剧上升 ,从而带来一系列特殊的问题 :宏观层次上 ,黏度增加将导致搅拌功率消耗显著增加与聚合热难于移出 ,影响到聚合过程操作稳定性 ;微观层次上 ,体系黏度增加必然对聚合过程中微观混合和物系传递产生显著影响 ,直接影响聚合体系的动力学特性和分子特性 ,同时动力学特性和分子特性决定了聚合物系黏度 .因此 ,本体聚合的本征动力学参数不能直接应用于高转化率、高黏度的工业聚合过程 ,对本体聚合过程进行动力学模拟考虑本征化学反应及聚合物系扩散过程是必要的有关八甲基环四硅氧烷 (Ｄ…     

Numerical simulation of non-isothermal pressure-driven miscible channel flow with viscous heating

We study the pressure-driven, non-isothermal miscible displacement of one fluid by another in a horizontal channel with viscous heating. We solve the continuity, Navier–Stokes, and energy conservation equations coupled to a convective-diffusion equation for the concentration of the more viscous fluid. The viscosity is assumed to depend on the concentration as well as the temperature, while density contrasts are neglected. Our transient numerical simulations demonstrate the development of ‘roll-up’ of the ‘interface’ separating the fluids and vortical structures whose intensity increases with the temperature of the invading fluid. This brings about fluid mixing and accelerates the displacement of the fluid originally occupying the channel. Increasing the level of viscous heating gives rise to high-temperature, low-viscosity near-wall regions. The increase in viscous heating retards the propagation of the invading fluid but accelerates the ultimate displacement of the resident fluid.     

ONSET OF DOUBLE-DIFFUSIVE CONVECTION IN A HORIZONTAL BRINKMAN CAVITY

This investigation reports on a linear stability analysis of the quiescent state within a horizontal porous cavity subject to vertical gradients of temperature and solute. The fluid motion is modeled using the Brinkman extension of Darcy's law, coupled with energy and species conservation equations. The horizontal boundaries are considered rigid-rigid, rigid-free, or free-free. Mixed thermal and solutal boundary conditions, of Dirichlet and Neumann types, are considered. The thresholds for monotonic and oscillatory convection instabilities are determined explicitly in terms of the governing parameters of the problem. The results for a viscous fluid and the Darcy porous medium emerge from the present analysis as limiting cases.     

Numerical simulation of the flow in an extensional flow mixer. Effect of fluid elasticity on the flow

We discuss the viscoelastic flow of the matrix fluid in an Extensional Flow Mixer (EFM) obtained by a numerical simulation. The effect of the fluid viscoelasticity on the flow state in an EFM was considered by the comparison of the flow states of the purely viscous fluid and the viscoelastic fluid. The mixing performance of the EFM is also considered. The Phan‐Thien Tanner model was used as the constitutive equation of the viscoelastic fluid and the Carreau model was used as that of the purely viscous fluid. Results obtained are as follows: (1) Stagnation flows occur in the converging‐diverging plates (c‐d plates) in the case of viscoelastic fluid. The size of stagnation flow region becomes large when the fluid has a strain‐thickening elongational viscosity. (2) The absolute value of the extensional strain and the pressure drop in the c‐d region increase with fluid elasticity. Meanwhile, the residence time in the c‐d region decreases with that. (3) There is no stagnation region in the c‐d plates for a purely viscous fluid. The stagnation flow has an effect on the estimation value of EFM's performance. The prediction by the purely viscous fluid is not useful for the flow in an EFM because of extremely low accuracy.     

反向旋转卧式双轴捏合反应器混合特性的数值模拟

以差速反向旋转卧式双轴捏合反应器为研究对象,选用高黏牛顿流体糖浆为模拟物料,通过三维有限元数值模拟方法研究了高黏糖浆在捏合反应器中的流动过程,获取了流速和剪切速率的空间分布,进一步结合粒子示踪技术探究了分布混合过程与混合效率,并且考察了搅拌结构对流动与混合过程的影响规律。研究表明,捏合反应器中几乎不存在流动死区,桨叶末端和重叠区域的流速和剪切速率较高,且高流速和高剪切区域均随着捏合杆数目和捏合杆长度的增加而增大。捏合杆可以推动物料在圆周方向上的运动,在重叠区域存在周期性交互作用,进而可以强化分布混合过程。拉伸率随着混合时间以指数形式增加,且随着捏合杆数目和捏合杆长度的增加而增加。时均混合效率大于零,随着捏合杆数目的增大而增大,随着捏合杆长度的增加呈现先增大后减小的趋势。     

Measurement and characterization of mixing time in shake flasks

As yet, investigations on mixing time have been focused on small and large scale stirred tanks. The aim of this study was to develop a new method for characterizing the mixing process and quantitatively measuring the mixing time in shake flasks by introducing a rotating camera for online observation of the fluid flow in combination with a typical colorimetric method using a pH indicator. In this presented scheme, only one drop of sulfuric acid was injected with a peristaltic pump into a bulk solution consisting of either deionized water or a viscous polyvinylpyrrolidone (PVP) solution. In this study, a novel interpretation of mixing time for the colorimetric method was introduced. The macroscopic mixing time is independent of the concentration of added acid. Interestingly, the recorded mixing time was similar irrespective of the shaking diameters (25, 50 mm). In addition, the dimensionless mixing number stayed constant in the regime of high Reynolds number. Our results showed that mixing number of the fluid in the regime of high Reynolds number is independent of the given geometries of flasks.     

Design of Horizontal Vessels Operated as CSTR – Basic Mixing Tasks,RTD, Productivity

Agitator performance in standard vertical vessels with cylindrical shape, dished bottom and zero to four baffles has been the topic of numerous publications. In certain industries, however, horizontal cylindrical vessels with hemispherical ends, divided internally into multiple compartments, are preferred for continuous processes operating at high pressures. Use of standard correlations derived from vertical vessels may lead to incorrect performance predictions for these horizontal vessels, and hence unsatisfactory process results. A number of laboratory trials were undertaken to identify differences in behavior and potential means to improve design for horizontal vessels. Differences with respect to solids suspension, mixing time and residence time distribution were studied. CFD simulations were undertaken and validated against the experimental results.     

油气田开发过程中油气水的运移特征研究

油、气、水在油层中的运移是油气田开发过程中的关键环节。一次采油过程的油气运移与岩石和流体的膨胀作用有关;注水开发过程主要是水驱油的过程,前人从微观机制、前缘推进、重力分异、粘性指进、渗透阻力的垂向不均匀和平面不均匀等方面对水驱油气机制进行了研究。下一步应以盆地为基本单元对油气田开发过程中压力变化和油气聚集进行研究。     

粘稠物系流变特性对螺带桨混合性能影响的研究

选用流变性质不同的三种物系:糖浆、CMC溶液、鲍格流体,在直径为0.286m的釜内,以不同结构的螺带桨进行搅拌,测定了功率、混合时间、速度分布和流型。分析了流变性质如粘度的剪切依赖性、弹性等对这些性能的影响,并在流型观测的基础上对功率、混合时间的变化规律作了解释。     

A CFD model for predicting the flow patterns of viscous fluids in a bioreactor under various operating conditions

Computational fluid dynamics simulation is becoming an increasingly useful tool in the analysis and design of simultaneous saccharification fermentation (SSF) and saccharification followed by fermentation process (SFF). To understand and improve mixing and mass transfer in a highly viscous non-Newtonian system, it was necessary to simulate the flow behavior in this bench scale bioreactor (BioFlo 3000). This study focused on designing a high concentration medium agitation system for such a process using the commercial computational fluid dynamics package Fluent (V. 6.2.20) and its preprocessor Mixsim (V. 2.1.10). The objective of this study is to compare performance of various designs of a bioreactor and identify the flow pattern and related phenomena in the bench scale tank. The configuration of the physical model for simulating a mixing tank with a Rushton impeller consists of an ellipsoidal cylindrical tank with four equally spaced wall mounted baffles extending the vessel bottom to the free surface, stirred by a centrally located six-blade Rushton turbine impeller. Simulations were performed with the original and a modified design in which the lower bottom shaft mounted a Lightnin A200 impeller. The results suggest that there is a potential for slow or stagnant flow between top impellers and bottom of the tank region, which could result in poor nitrogen and heat transfer for highly viscous fermentations. The results also show that the axial velocity was significantly improved for the modified geometry in the bottom of the tank.