不同类型搅拌器的气—液分散和混合特性

在通气式搅拌槽内研制了直叶圆盘涡轮、直叶桨式涡轮、４５度折叶圆盘涡轮、４５度折叶桨工涡轮、凹弧叶圆盘涡轮、锥形涡轮和布鲁马金式搅拌器的临界分散转速、分散状态、搅拌功率、气含率、气泡停留时间、排量准数和输出效率，并获得了适用上述种类搅拌器的临界分散转速、搅拌功率、气含率和气泡停留时间关联式。     

非标准釜中双层桨的搅拌功率和气含率

在装有单层或双层蛇管换热器的搅拌釜中，分别以六直叶圆盘涡轮（ＤＴ）、四叶（４５°）折叶桨（４ＩＢＴ）或六叶（４５°）折叶桨（６ＩＢＴ）为上层桨，ＤＴ为下层桨，测定了不同双层桨的搅拌功率和气含率。结果表明，搅拌功率随蛇管层数、液位高度和桨间距的增加而增大，但气含率随液位的上升而下降。在装有双层蛇管换热器的搅拌釜中，ＤＴ与６ＩＢＴ双层桨的通气搅拌功率Ｐａ和气含率α的关联式为Ｐａ＝２．４９（Ｐ０２ＮＤ３／ＱＧ（０．５６））（０．３７）及α＝０．０２９Ｐ＿ｖ￣（０．４８）ｕ＿ｓ￣（０．４７）。     

牙膏化胶搅拌器设计初探

本文对牙膏化胶搅拌提出了采用高速折叶式圆盘涡轮搅拌器来解决粘合剂CMC在山梨醇中的分散性问题，并就高速折叶式圆盘涡轮搅拌器的振动和偏摆问题进行了专门的论述。     

6种常规搅拌器的剪切性能研究

不同搅拌工况下剪切性能的需求是选用搅拌器的一个重要指标,文中基于对常规的6种搅拌器流场的CFD模拟,计算了搅拌器各自的剪切性能量纲一数C_3,分析了搅拌流场中剪应力的累计概率分布及统计平均结果。二者对比发现:从宏观平均效果上看,搅拌器剪切性能满足直叶桨>斜叶桨,圆盘涡轮>开启涡轮>桨式;而剪应力极大值影响作用则是直叶圆盘涡轮>斜叶圆盘涡轮>直叶桨式>斜叶开启涡轮>直叶开启涡轮>斜叶桨式。因此,对剪切作用敏感的搅拌过程,在采用常规的搅拌器剪切性能评价的基础上,还需要充分考虑搅拌流场中剪应力极大值的影响,合理选用搅拌器。     

不同组合桨煤浆搅拌槽混合特性的数值研究

采用ANSYS15.0软件的多重参考坐标系、标准k-!湍流模型及多相流模型,针对单层平直桨、双层45°折叶涡轮桨、平直桨叶-45°折叶涡轮桨叶组合桨这三种型式,分别研究了煤浆搅拌槽内的流体混合特性。结果表明,平直桨叶-45°折叶涡轮桨叶组合桨煤浆搅拌槽内流体湍动剧烈,其出口截面上示踪剂体积分数的最大波动幅度为1.24%,表明搅拌槽内的煤浆和石灰石添加剂已混合均匀。     

折叶涡轮桨搅拌器流型及温度分布数值模拟

采用MIXSIM对折叶涡轮桨搅拌器搅拌槽内流体流型及紊流状态下的温度分布进行模拟.结果显示:随Re数的增大,流体流型由径向流逐渐向轴向流发展;在温度变化趋于稳定时,温度在搅拌轴两侧基本呈对称分布,且分别存在一个低温区域.     

三相搅拌器叶片数和安装高度对搅拌效率的影响

采用Ansys CFX 12.0软件建立了涡轮式中心龙卷流型搅拌器实体模型,采用计算流体动力学方法对搅拌器内气液固三相的搅拌效果进行了数值模拟,并运用Origin将数据进行拟合,得出搅拌器内某一点的气相和固相的体积分数及速度矢量图等,重点研究了搅拌桨不同叶片数和安装高度对搅拌效果的影响。结果显示:在同一工况下,搅拌桨叶片数为22、安装高度为160mm时搅拌效果最佳。     

液体性质对翼型轴流桨气液分散特性的影响

EFFECTSOFLIQUIDPROPERTIESONGAS-LIQUIDDISPERSIONOFHYDROFOIL1前言在气液搅拌系统中，搅拌桨的气液分散特性直接关系到体系的分散效果，从而对相际间的混合与传质构成影响。影响搅拌桨气液分散特性的因素很多，除桨叶结构、搅拌器和搅拌糟的几何条件外，液体性质亦是一个非常重要的因素，它对体系的初始分散和二次分散有显著的影响。有关圆盘涡轮桨的气液分散特性研究，国内外众多学者已作过较为详细的报道。由于涡轮桨自身的缺陷，自80年代初期一种新型的搅拌器．翼型轴流桨问世以来，其良好的搅拌性能已在许多行…     

低密度聚苯乙烯微粒子的制备

研究了在悬浮聚合法制备粒径小于50μm,表观密度小于0.5g/cm3的聚苯乙烯微粒子过程中,搅拌器的位置、搅拌速度、分散剂及交联剂对产品粒径和密度的影响。结果表明搅拌桨接近或稍高于液面时有利于生成小粒径产品;搅拌器最佳搅拌速度为500～620r/min;使用明胶和聚乙烯醇（PVA）混合分散剂体系能得到粒径小、密度低的产物;随二乙烯苯（DVB）的加入,产物粒径和密度均减小,当DVB/St>1时得到平均粒径小于50μm的产物。     

粉体搅拌扭矩的试验及关联式

在直径为480mm的平底搅拌槽内,采用平均直径为4.89μm的氢氧化铝粉体进行搅拌扭矩的试验。通过扭矩传感器测量3种不同型式（开启涡轮XCK、二叶直桨PJ和管形桨GXJ）的6个搅拌器（XCK348、XCK290、PJ348、PJ232、GXJ348和GXJ232）的扭矩。试验结果表明：针对不同的搅拌器型式,搅拌器的扭矩增加幅度从高到低的排序是XCK348＞GXJ348＞PJ348＞XCK290。随着粉体高度的增加,GXJ348搅动效果相对较好。相同工况下搅拌的扭矩随着转速增加而有所下降。搅拌的扭矩大小主要是和搅拌器离粉体表面的高度和搅拌的Froude数有关。对于搅拌器组合,当间距较大时各层搅拌器互相不影响;当层间距与搅拌器直径之比小于0.32时,各层搅拌器存在相互作用。通过扭矩的量纲分析和搅拌粉体的受力分析,分别获得了3种搅拌器型式的扭矩关联式。     

Impact of impeller type on methyl methacrylate emulsion polymerization in a batch reactor

The emulsion polymerization of methyl methacrylate (MMA) was carried out in a lab‐scale reactor, which was equipped with a top‐entry agitator, four wall baffles, a U‐shaped cooling coil, and a temperature controller. Potassium per sulfate and sodium dodecyl sulfate as were used as the initiator and the surfactant, respectively. The experimental investigation demonstrated the impact of the impeller type (45° six pitched‐blade turbine and Rushton impeller), number of impellers (single and double impellers), and impeller speed (100–350 rpm) on the monomer conversion, polymer particles size, molecular weight, and glass transition temperature. The results revealed that the effect of the impeller speed on the characteristics of the polymer attained using the pitched‐blade turbine was more prominent than that for the Rushton turbine. It was also found that the impact of the impeller speed on the polymer characteristics was much more pronounced for the double pitched‐blade turbines rather than for the double Rushton turbines. However, more uniform size distribution was achieved with the Rushton turbine. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40496.     

Experimental Study of Influence of the Impeller Spacing on Flow Behaviour of Double‐Impeller Stirred Tank

The flow fields in the stirred tank with three different kinds of combined double‐impeller agitators: disc turbine + disc turbine (DT‐DT, radial impeller), pitched blade turbine + pitched blade turbine (PTD‐PTD, axial impeller) and pitched blade turbine + disc turbine (PTD‐DT), were investigated in detail by using laser Doppler anemometry. The two‐dimensional mean velocity field and the distribution of turbulence intensity were obtained for different impeller spacings. The experimental results show that the impeller spacing has a significant influence on the flow field. To improve flow homogeneity and agitator efficiency, the appropriate impeller spacing should be in the range of 1/2 to 2/3 of the tank diameter.     

Emulsification in batch emulsion polymerization

Dispersion of liquid–liquid systems is often applied in industrial processes such as extraction, suspension, and emulsion polymerization. The influence of emulsification of the monomer in the aqueous phase on the course and outcome of the batch emulsion polymerization of styrene has been studied. A visual criterion was applied for determining the lowest impeller speed for sufficient emulsification (N*). It appeared that in polymerization experiments under the same conditions, N* was the critical value above which no further increase in polymerization rate was observed. Using a turbine impeller instead of a pitched blade impeller as well as using a larger impeller diameter provides better emulsification at constant power input. The results indicate that scale‐up with constant impeller tip speed is most appropriate in case of a turbine impeller. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3225–3241, 1999     

不同流场状态对球形氢氧化镍生长粒度的影响

在相同的搅拌桨线速度、晶化时间、化学条件下,采用化学沉淀法分别应用八斜叶涡轮圆盘桨、推进式螺旋桨、Intermig桨分别制备球形氢氧化镍晶体。采用SEM技术考察各个样品的微观形貌,并结合PIV物理模拟技术分析不同桨型状态下反应器内的流场特性,研究表明:采用八斜叶涡轮圆盘桨是样品的球形度最佳,采用Intermig桨时样品的粒度d0.5最大。讨论了不同桨型对球形氢氧化镍晶体松装密度的影响。     

Vortex depth in mixed unbaffled vessels

An experimental investigation of vortex depth in an unbaffled cylindrical vessel with co-axial agitation was made. Five types of impellers: standard six-blade disc turbine, flat six-blade turbine, pitched six-blade turbine, pitched three-blade turbine and anchor agitator were tested. Turbine impellers were investigated in two positions (H₂ = d and H₂ = d/3). On the basis of theoretical analysis, the dimensionless vortex depth was statistically correlated as a function of Froude and Galileo numbers and a relative impeller size. Liquid viscosity and impeller size variations were reflected in the value of the Galileo number which was within the range 4 × 10⁵ – 5 × 10¹⁰. The vessel diameters used in the experiments were, D= 0.15, 0.20, 0.30, 0.40 and 0.64 m.     

Emulsification in batch‐emulsion polymerization of styrene and vinyl acetate: A reaction calorimetric study

Dispersion of liquid–liquid systems is commonly applied in industrial processes such as extraction, suspension, and emulsion polymerization. This article describes the influence of the quality of emulsification on the course and outcome of a batch‐emulsion polymerization of styrene and vinyl acetate. From visualization experiments and polymerizations in combination with reaction calorimetric studies, a critical impeller speed, N*, can accurately be determined for a particular reactor setup and a given recipe. The results show that styrene–water emulsions are more difficult to emulsify than vinyl acetate–water emulsions. In general, a large turbine impeller appears to be more effective in emulsifying monomer–water dispersions than a pitched‐blade impeller. In addition, for vinyl acetate emulsion polymerization, the possibility of premixing the reaction mixture has been investigated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 944–957, 2001     

双层斜叶涡轮搅拌桨特性研究

利用冷模实验装置对双层斜桨的特性进行了研究,分析了功率准数的变化规律,研究了单桨、组合桨通气情况下功率的变化和稳定性。获得了气含率与通气量、搅拌功率的关联式。     

搅拌槽中酯化反应热失控的CFD模拟

热失控是化工过程中常见的安全风险之一。在间歇釜式反应器中,桨叶的机械转动可以增强流体的循环流动、湍流强度、混合程度以及传热,进而有效防范热失控。防控效果与反应器结构和搅拌桨型密切相关。针对丙酸异丙酯酯化反应,采用计算流体力学模拟研究了桨型(Rushton桨、30o PBT桨及60o PBT桨)、转动方向和挡板对釜式反应器内温度演化的影响,从流动结构方面分析了原因。基于散度的失控判据比较了三种搅拌桨抑制热失控的能力,抑制能力为Rushton桨＞30° PBTD桨＞60° PBTD桨。本研究可为搅拌反应器热失控的优化设计提供一定的理论依据。     

高效带钩圆盘和带钩窄叶桨的优化

通过固体颗粒和水的混合物在搅拌器中进行搅拌 ,使固体颗粒粉碎至一定粒度 ,研究了搅拌桨的形状、宽度、是否采用流线型以及桨径与槽径比、桨叶层数对粉碎效果和搅拌功率的影响 ,得出了减小桨叶宽度并采用流线型叶片可以节省能耗和适当加大搅拌叶轮的直径和层数可以省时的结论。介绍了优化后的带钩圆盘桨和带钩窄叶桨的形状、尺寸比例关系和在湍流状态下全挡板时的搅拌功率准数和功率准数修正系数。     

Effects of the Stirred Tank's Design on Power Consumption and Mixing Time in Liquid Phase

The influence of the stirrer type and of the geometrical parameters of both tank and agitator (clearance of an impeller from tank bottom, impeller diameter, draft tube and geometry of the tank bottom) on power consumption and mixing time in liquid phase under turbulent regime conditions (Re > 10⁴) have been studied. Different types of agitators have been used, namely Rushton turbine, 45° pitched‐blade turbine, MIXEL TT and TTP propellers and 1‐stage or 2‐stage EKATO‐INTERMIG propellers. All these stirrers were tested with the same power consumption per unit mass of liquid. On the basis of measured power consumption per unit mass, which is required to achieve the same degree of mixing, the results obtained in the present work show that the TTP propeller is the most efficient in liquid phase. Recommendations on the optimum geometric configuration have been made for each type of stirrer.