热态多相搅拌反应器内传质性能的研究

发布时间：2018-03-01 07:38

本文关键词： 多相流反应器容积传质系数传质模型热态多层桨　出处：《北京化工大学》2015年博士论文　论文类型：学位论文

【摘要】：多相搅拌反应器被广泛应用于生物化工、石油化工、矿物化工、精细化工及环境工程等行业,为生物发酵、石油冶炼、选矿工程、制药、污水处理等多种过程工业中涉及到的催化加氢、卤化和氧化等反应提供一个较为均一的浓度场和能量分布场。在这些反应中,物料应充分接触和混合以避免反应过程中局部反应物浓度过高或过低而引起的反应过快或中止。在快速反应中,传质速率常常成为控制步骤,传质性能直接影响产品质量和产量,是评价、设计和优化搅拌反应器的一个重要参数。目前反应器内传质特性的研究还主要集中在常温下,导致在进行反应器放大和设计时只能借鉴常温研究结果和规律。本实验室己开展的热态操作条件下流体力学性能的研究表明热态和常温的规律有较大差别,这就不可避免地导致使用常温下研究规律做指导的设计和放大与实际的热态生产过程产生偏差。为了更好地指导实际生产中反应器的设计和放大,本文研究了热态操作条件下不同体系的传质性能。首先在以亚硫酸钠溶液为液相的非凝并体系中,使用由六直叶半椭圆管叶涡轮桨(HEDT)和两层上提操作方式的四宽叶翼形桨(WHU)组成的三层组合桨,通过亚硫酸钠氧化法研究了热态操作条件下(50-80℃)非凝并体系中的容积传质系数(KLa)。结果表明,KLa随着单位功耗、表观气速和温度的增大而增大。定量得出表示KLa与单位功耗、表观气速和温度关系的关联式,关联式中温度、单位功耗和气速的指数依次变小,这说明在非凝并体系中升高温度可以明显增大KLa,增大单位功耗比增大表观气速更利于提高KLa。在以水为液相的凝并体系中,研究了热态操作条件下气-液两相体系中的气液分散和传质性能及加入玻璃珠的气-液-固三相体系中的通气搅拌功率及传质性能。结果表明,气-液两相体系中,气含率(sG)随温度升高而明显降低,KLa受温度的影响很小。依实验数据关联得不同温度下的气含率和KLa与温度、功率和表观气速的经验关联式。对比关联式中的指数可以看出,温度、表观气速和功耗对气含率的影响依次减小,对KLa的影响依次增大。功耗对KLa的影响指数分别是表观气速和温度对KLa影响指数的2倍和4倍。在气-液-固三相体系中,固体颗粒的加入改变了温度对KLa的影响规律,KLa随着温度的升高而增大。同时温度的变化也影响固相浓度对KLa的影响,在常温(25℃)下,KLa随着CV的增加而减小,但随着温度的升高,这种减小的幅度减慢；在54℃,CV对KLa几乎没影响；在80℃,KLa随着Cv的增大甚至有些增加；但整体而言,在40-80℃间,KLa随着Cv的变化幅度基本在10%以内。为了满足工业用桨的多样性,本文还研究了多种三层组合桨在不同操作条件下的传质性能。使用桨型为HEDT,抛物线形叶片涡轮桨(PDT),WH和三叶翼形桨(CBY)。研究表明,通气量较低时各种组合桨的kLa差别不大,但通气量较大时差别明显。表观气速较高时(uG=0.016-0.039 m·s-1), PDT+2WHD传质效果最好,而HEDT+2WHU传质效果最差。在相同功耗下,高转速和大桨叶投影横截面积的桨型组合利于传质。得到了不同桨型的功率准数和传质系数的关联式。通过多变量分析方法得到了适用于高温操作条件下凝并体系和非凝并体系的kLa模型kL模型。建立在小涡模型的基础之上的kL模型,可以用来描述高温下kL变化规律。高温凝并体系下,kL模型中DL的指数与小涡模型中的指数0.5相近,但单位能量耗散率的指数却由1/4减小为1/6,这是因为温度的升高削弱了功耗对kL的影响。非凝并体系下的kL模型中扩散系数的指数明显高于凝并体系。通过理论模型计算和分析了影响容积传质系数的气含率、气泡尺寸、溶氧扩散系数、液相传质系数和相界面积在不同温度的变化关系,通过模型的理论计算值与实验值的对比,验证了模型的准确性。
[Abstract]:Multiphase stirred reactor is widely used in chemical, petrochemical, mineral chemical, fine chemical and environmental engineering industry, bio fermentation, petroleum refining, mineral processing engineering, pharmacy, sewage treatment and other industrial processes involved in the catalytic hydrogenation of halogenated and oxidation reaction to provide a more uniform the concentration field and energy distribution. In these reactions, the material should be fully contacted and mixed to avoid local reaction in the process of concentration is too high or too low and cause a rapid reaction or suspension. In fast reaction, the mass transfer rate usually is the controlling step, mass transfer performance affects the product quality and yield, is the direct evaluation. One of the most important parameters for the design and optimization of stirred reactors. The mass transfer characteristics of the reactor is mainly concentrated in the normal temperature, resulting in the design and reference only research reactor at ambient temperature The fruit and regularity. Hydrodynamic performance of the thermal operating conditions of the laboratory has been carried out under the show has a larger difference between the hot and normal rules, which inevitably leads to guide design and enlarge thermal production process and the deviation of the use of room temperature. In order to guide the actual production design and scale-up in the reactor better, this paper studied the mass transfer performance of different thermal system operating conditions. In the first phase of non coagulation system in sulfite solution, used by six straight blade turbine propeller semi elliptical tube (HEDT) and the two layer on mode of operation of the four wide blade hydrofoil impeller (WHU) three layer paddle, by oxidation of sodium sulfite on the thermal operating conditions (50-80 C) volumetric mass transfer coefficient and non condensate in the system (KLa). The results show that KLa with unit power consumption, increase of superficial gas velocity and temperature The quantitative increase. KLa and unit power consumption, table correlation of gas velocity and temperature, the temperature in the correlation unit, power consumption and speed index are smaller, indicating that the temperature in the non coagulation system can significantly increase KLa, increase the unit power consumption than the increase of superficial gas velocity is more conducive to improve KLa. with water as the liquid phase of the coagulation system, researched the thermal operating conditions of gas - liquid two-phase gas-liquid dispersion and mass transfer in the system of ventilation performance and adding glass beads of gas liquid solid three-phase system of stirring power and mass transfer performance. The results show that the gas-liquid two-phase system, gas containing rate (sG) decreased with the increase of temperature, KLa little affected by temperature. According to correlation of experimental data under different temperature of gas holdup and KLa correlations with temperature, power and superficial gas velocity. The contrast in the correlation index can be seen, temperature, superficial gas velocity Power and influence on gas holdup decreases, the impact on KLa power consumption increases. The influence of KLa index are superficial gas velocity and temperature effect on the KLa index of 2 times and 4 times. In the gas liquid solid system, solid particles could change the effect of temperature on KLa the KLa increases with the increase of temperature. At the same time, the temperature change can also influence the solid concentration of KLa, at room temperature (25 C), KLa decreases with the increase of CV, but with the increase of temperature, the decrease slowed; at 54 degrees, CV almost has no effect on KLa in 80; C, KLa increased with the increase of Cv and even some; but on the whole, at 40-80 DEG C, KLa with the range of Cv is less than 10%. In order to meet with the diversity of oar industry, this paper also studies the various mass transfer performance of three layer composite impellers under different operating conditions. The use of paddle type HEDT. Parabolic Linear blade turbine impeller (PDT), WH and trefoil hydrofoil impellers (CBY). The results show that kLa little difference in various combinations of propeller ventilation volume is low, but the difference is obvious. A large amount of ventilation at higher superficial gas velocity (uG=0.016-0.039 m s-1), the best PDT+2WHD HEDT+ 2WHU and the effect of mass transfer, mass transfer the difference in the same power consumption, impeller combination of high speed and high projected blade cross-sectional area for mass transfer. The correlation of different power paddle type number and mass transfer coefficient are obtained. The kLa model kL model is suitable for high temperature operation and coagulation system and coagulation system by multi variable analysis method. KL model based on small vortex model, can be used to describe the change rule of kL under high temperature. High temperature coagulation system, kL model, DL index and the index of 0.5 small vortex model is similar, but the unit energy dissipation rate index has decreased from 1/4 to 1/6, This is because the temperature weakens the impact on power of kL. KL model of non coagulation under the system of diffusion coefficient index was significantly higher than that of coagulation system. Through the theoretical model and the analysis of the impact of the volumetric mass transfer coefficient of gas holdup, bubble size, oxygen diffusion coefficient, liquid phase mass transfer coefficient and interfacial area changes in different temperature. The calculated values were compared with experimental values, to verify the accuracy of the model.

【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TQ021.4

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