管式搅拌反应器功率特性研究

以新型管式搅拌反应器为研究对象,在冷态物理模拟的基础上,研究了管式搅拌反应器内的功率特性,以水作为介质,在流量0～3.6 m3/h,搅拌转速100～400 r/min范围内考察了搅拌转速对功率的影响,并对功率准数与雷诺数的关系进行了分析.研究结果表明,在实验范围内,T型桨管式搅拌反应器的搅拌功率P与N1.3～1.4近似成正比;搅拌功率准数与雷诺数满足下列关系式Np=109.79Re1.69.     

搅拌流化床搅拌功率研究

根据在粉体中运动物体受力分析 ,对几种不同型式搅拌桨功率准数表达式进行了推导 ,并对搅拌流化床中的功率准数与通气速率和搅拌速度进行了关联 ,关联结果与实验值吻合较好。     

粉体混合过程及搅拌功率的DEM数值模拟和实验

采用数值模拟与功率测试相结合的方法,研究直叶桨式粉体混合机搅拌过程及搅拌功率、扭矩的变化规律。对粉体混合机内球形颗粒的混合过程进行离散单元法DEM数值模拟,研究直叶桨式粉体混合机内搅拌转速、搅拌桨直径、桨叶数目等特性参数对粉体混合时搅拌功率和扭矩的影响,并拟合得到功率计算公式。搭建粉体搅拌试验台,测试粉体搅拌功率并与模拟结果比较。结果表明,直叶桨式粉体混合机内功率消耗与搅拌桨转速、搅拌桨直径、桨叶数目等特性参数有密切关系。同时,扭矩值和功率值与搅拌桨转速、搅拌桨直径和桨叶数目都呈正相关。实验得到了与模拟类似的扭矩-转速关系以及功率-转速关系,模拟值与测试值具有较好的吻合性,验证了所推导公式的准确性。     

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。     

搅拌反应器内相际传质为：1.反应器操作特性研究

系统地研究了搅拌反应器中通气量，搅拌速率等操作因素及悬浮体系中不同形态颗粒对氧气－水体系功率准数Ｋ和容积传质系数ＫＬａ的影响规律。     

基于CFD模拟的新型径向流搅拌桨设计

用CFD软件模拟了3种传统径向流搅拌桨—平直叶式、半圆管式和非对称抛物线式搅拌桨的功率消耗和泵送能力等搅拌性能,研究了不同桨叶结构和尺寸对搅拌桨功率准数和泵送能力的影响,设计扇环抛物面桨叶结构,比较了新型桨与传统桨的功率准数、泵送效率等搅拌性能和轴向投影面积率的差异.结果表明,桨叶外缘顶点曲率增大可减小功率准数和提高泵送效率,轴向高度减小可使功率准数降低但对泵送效率提升不大.基于空间自由曲面设计的带有新型非对称扇环抛物面桨叶的搅拌桨操作性能最佳,比非对称抛物线式搅拌桨功率准数下降30.8%,泵送效率提高22.6%.新型搅拌桨轴向投影面积率比非对称抛物线式搅拌桨增加21.5%,能用于气液分散操作.     

厌氧移动床生物膜反应器侧伸式搅拌装置的试验研究

选取三种CBY型桨,对厌氧移动床生物膜反应器中采用的侧伸式搅拌装置进行了深入研究.试验考察了三种桨型的功率准数、时间准数,并通过考察其临界转速的方法探讨其最优桨型、最佳安装角度.CBY-3型桨在同样的填充量下临界功率较另两桨型低,混合时间短,优于CBY-2和CBY-1型桨.在水平偏角α为15～20 °,向下偏角β为1～5 °时得到搅拌的最低临界转速.为厌氧移动床生物膜反应器搅拌装置的设计提供了参考.     

卧式双轴T型搅拌器在牛顿流体中的功率消耗

以苯乙烯间规聚合反应过程为背景 ,采用卧式双轴 T型自清洁搅拌反应器 ,研究了它在牛顿流体中的搅拌功率和流型与转速、加料量的关系。实验结果表明 ,在层流区域 ,Np·Re=Kp 关系仍然成立 ,加料量对搅拌流型和搅拌功率影响较大。通过对实验数据关联得到牛顿流体功率准数关联式。     

全氟聚醚聚合釜搅拌转速的设计

研究了全氟聚醚聚合釜的搅拌转速设计问题。根据传热方面的要求选用了卧式釜。依据理论推导并结合试验,获得了全氟聚醚中试釜的搅拌功率与搅拌转速的关系式。     

泛能式搅拌桨搅拌特性研究

在直径为 2 4 0mm的搅拌釜内 ,考察了泛能式搅拌桨的功率、传热特性 ,混合实验在直径为 386mm的搅拌釜中进行。在层流域内 ,建立了功率准数Np 与桨几何尺寸及雷诺准数Re的关联式 ;得到了努塞尔准数Nu与桨几何尺寸、雷诺准数Re、普朗特准数Pr以及体系粘度的关系 ,并采用单位质量流体表示的雷诺准数εD4/ν3 取代雷诺准数关联 ,误差均在 10 %以内。在中低粘度区内相同功耗下 ,泛能式桨的传热系数明显高于螺带桨。当Re >3时 ,泛能式桨的混合效率比双螺带桨要高。     

MIXING IN CLOSED VESSELS - SUSPENSION OF SOLID PARTICLES AND POWER DEMAND

The suspension of solid material in a closed vessel has been studied. The vessel was designed as a pressure vessel having dished ends. Both the impeller speed at the off-bottom suspension point as well as the power demand related to this speed have been determined. In the study, emphasis was placed on studying the influence of both form and position of the baffles

It was found that a new dimensionless number, designed to describe the phenomena related to the suspension of particles, is a function of the impeller Reynolds number at the off-bottom suspension point. The impeller Reynolds number was varied between 10000 and 800000

Based on the results of this study, it can be stated that the design and position of the baffles are of great importance in minimizing the power demand in the suspension of particles. At the off-bottom suspension point, the power demand was lower for solid baffles when compared with baffles constructed of rods.     

Photopolymerization of butyl acrylate microemulsions 1. Post-polymerization

The oil-in-water-type microemulsion polymerization of butyl acrylate initiated by UV light was investigated. The polymerization showed two nonstationary rate intervals with a short rise to a maximum. The rate of polymerization was found to be proportional to the 0·7th power of the incident light intensity. The number of radicals per particle was found to be much below 0·5. The initiating radicals are supposed to be formed by the decomposition of the excited (SDS/BA)^* intermediates (micelles). Desorbed radicals were found to increase the number of new particles after the cessation of illumination. The number of polymer particles increased during the whole polymerization. The micellar mechanism was proved to apply to the present system. The dependence of the molecular weight, or the relative viscosity of the microemulsion versus conversion is described by a curve with a maximum.     

Elucidation of the miniemulsion stabilization mechanism and polymerization kinetics

Styrene/hexadecane miniemulsions were polymerized at 50°C using a redox initiator. The miniemulsions and their corresponding latexes were characterized in terms of size, polymerization rate, and surface properties. The resulting data were analyzed to elucidate the miniemulsion stabilization and polymerization mechanisms. It was found that the free surfactant concentration exceeded the critical micelle concentration when large amounts of surfactant (60 mM sodium lauryl sulfate) were used, resulting in simultaneous micellar and droplet nucleation. Most surfactant was on the surface of the droplets (85%) or particles (95%). The fractional surface coverage was proportional to the surfactant concentration to the 0.55 power. Using a particle diameter equation, the number of particles was calculated to be proportional to the surfactant concentration to the 1.35 power. Through direct particle size measurements, a power of 1.38 was confirmed. The rate of polymerization was determined by reaction calorimetry to be proportional to the number of particles to the 0.59 power, in contrast to classical Smith–Ewart kinetics for conventional emulsions (1.0 power). The average number of radicals per particle was estimated from the rate and number data, and varied with the particle diameter to the 0.97 power. The observed kinetic dependencies were validated through an extension of Smith–Ewart theory. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 3987–3993, 2003     

Emulsion polymerization of styrene in a continuous stirred reactor

The emulsion polymerization of styrene has been carried out in a continuous stirred reactor at 50°C. Polymerization rates were initially very high but declined subsequently. These rates did not always attain a steady value, but sometimes oscillated with time. Size analysis of the polymer particles showed that particle nucleation almost stopped soon after start-up. A new generation of particles appeared later in the process. The average number of radicals per particle was usually, but not always, >0.5. The time-average polymerization rate was only weakly dependent on the initiator concentration but varied with the first power of the emulsifier concentration.     

POWER CONSUMPTION AND SOLID SUSPENSION IN COMPLETELY FILLED VESSELS

Mixing in a completely filled vessel, designed as a pressure vessel, has been investigated. The power demand of two pitched blade turbines of different sizes, and one high flow impeller was studied. The influence of side-mounted and bottom-mounted baffles, as well as the clearance between the bottom and the impeller was investigated. The experiments were carried out in a plexiglass vessel with a diameter of 288 mm. The Power number was calculated from measured data on the power demand and the impeller speed. Furthermore, preliminary studies on the critical impeller speed and power demand at the off-bottom suspension point for one set of glass particles were carried out. The Power number was mainly influenced by the impeller type, while the power demand at the off-bottom suspension point was more dependent of the impeller size and clearance. For bottom-mounted baffles a minimum in the Power number was noticed with increased clearance. It was found the minimum was located at the transition point between two different How patterns. This study shows that the configuration with the lowest Power number is not necessary the most efficient for suspending solid particles.     

A kinetic study of the emulsion polymerization of vinyl acetate

The emulsion polymerization of vinyl acetate was studied at 50°C. It was found that the rate of polymerization was proportional to the 0.5 power of the initiator concentration and the 0.25 power of the number of particles. The number of particles was proportional to the power 0.5 ± 0.05 of the emulsifier concentration, but independent of the initiator concentration. The limiting viscosity number of the polymers produced was independent of the initiator concentration and number of polymer particles. It is suggested that the mechanism of vinyl acetate emulsion polymerization is similar to that of vinyl chloride. The linearity of the conversion-versus-time curve is explained as being due partly to a decrease in the desorption rate of radicals from the polymer particles and partly to a decrease in the termination rate constant.     

具有黏结颗粒的搅拌槽功率特性

功耗是搅拌反应器设计和放大过程的重要参数。在圆柱形搅拌槽内通过实验研究了相对液体体积、转速和物料高度对功耗的影响,采用离散元方法(DEM),用Hertz-Mindlin with JKR模型模拟了不同相对液体体积颗粒的黏结力对功耗的影响。结果表明,随相对液体体积增大,功耗呈先增大后减小的变化趋势,在相对液体体积为0.0162时达到最大值。随转速增大,功耗增长变快,但随相对液体体积增大,转速对功耗的影响指数呈先减小后增大的趋势。不同物料高度的功耗最大值均为饱和颗粒的1.8倍,不同物料高度的单位质量功耗随相对液体体积的增长速率几乎一致。提出了新的间接测量颗粒间黏结力的方法,发现功耗与黏结力呈线性关系。     

用光学微流变研究硅烷偶联剂改性乳胶的流变性及稳定性

光学微流变法是一种直观研究聚合物乳胶流变性和稳定性的新方法,并且通过对微流变因子的分析可以间接反应乳胶粒子微观结构信息.本文在配方相同的情况下,通过改变加料方式合成出不同微观结构的乳胶粒子.采用动态光散射仪、光学法微流变分析仪和圆桶流变仪,研究乳胶的粒径、粒子均方位移、相关弹性因子、粘性因子和流变性能与加料方式的关系....