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气液环流反应器中宏观混合及微观混合的研究
Alternative TitleInvestigation on macro- and micro-mixing in gas-liquid loop reactor
张伟鹏
Subtype博士
Thesis Advisor杨超
2013-05-01
Degree Grantor中国科学院研究生院
Degree Discipline工业催化
Keyword环流反应器   高径比   宏观混合   微观混合   气泡特性   湍流模拟
Abstract气升式环流反应器作为一种多相反应器,因其结构简单、能耗小、剪切速率均匀、传质和传热效率高、良好的固体悬浮性及混合性能等优点,已广泛应用于石油化工、能源、医药、生化工程、环境工程等领域。但迄今为止,由于气-液两相流动及传质的复杂性,气升式内环流反应器的设计、放大及操作仍主要依赖实验验证和经验关联,缺乏必要的基础数据及理论依据。除此之外,以往对于气升式环流反应器性能的研究,多集中在大高径比反应器上,对于小高径比反应器的性能报道很少见。为此,如何基于此类反应器的流动和混合特性,设计高效的气升式内环流反应器以实现对反应器的科学放大已成为亟待解决的问题。鉴于此,本文应用实验和数值模拟相结合的方法,对短高径比气升式内环流反应器的气液两相流动、宏观混合及微观混合予以考察,主要的研究工作及结论概括如下: 采用电导脉冲技术系统地研究了环流反应器内不同设计参数及操作参数对液相宏观混合时间的影响,通过气含率曲线确定了短高径比气升式内环流反应器的气-液相流型转变气速,并结合双电导探针考察了反应器上升段内局部气泡特性的分布规律,为反应器的设计提供了基础数据。通过求解标准k-ε两流体模型方程,研究了环流反应器内的气-液两相流动过程,计算结果与实验值吻合较好。 微观混合特性对工业生产过程中涉及的快速复杂反应体系的生产能力及产物选择性有很大影响。本文以酸碱中和与氯乙酸乙酯的平行竞争反应为模型体系,首次对环流反应器内的气液两相微观混合特性进行了描述,考察了进料时间、表观气速、静液高度、上升段与下降段面积比等因素对离析指数的影响。反应器内的微观混合性能与湍动动能耗散率的大小和分布密切相关,为此本文利用CFD方法考察环流反应器内不同区域的湍动能耗散分布,对反应器内部微观尺度上的混合与反应机制进行了分析。 研究表明,小高径比气升式内环流反应器具有更宽的均匀鼓泡操作气速范围。表观气速等操作条件以通过改变能量输入的方式影响反应器内宏观及微观混合效果。而诸如静液高度、上升段与下降段面积比及气液分布板等结构参数对混合性能的影响则通过改变反应器内流动阻力及湍动能分布的形式得以实现。结合气泡特性的径向分布及湍动能耗散分布可知,上升管及反应器顶部的中心区域混合效率最高,适宜进料。 关键词:环流反应器,高径比,宏观混合,微观混合,气泡特性,湍流模拟
Other AbstractAs a kind of multiphase reactor, airlift internal loop reactors are commonly used in petrochemical, energy, pharmaceutical, bio-engineering and environmental engineering processes due to their advantages of simple structure, low power consumption, uniform shear distribution, high gas-liquid mass and heat transfer rates and especially good solid suspension and mixing performances. However, due to the complexity of gas-liquid two-phase flow and mass transfer, the design, scale-up and operation of airlift internal loop reactors are still mainly dependent on experimental tests and empirical correlations, lacking in necessary basic data and theoretical support. In addition, most researches about airlift loop reactors are focused on the reactors with high aspect ratios, and reports about the ones with low aspect ratios are rarely found. Thus, how to design this kind of high efficiency reactor based on flow and mixing performances and realize operation optimization are key problems to be resolved. So the gas-liquid flow and macro- and micro-mixing characteristics for airlift loop reactors with low aspect ratio are experimentally studied and numerically simulated in this dissertation. Major research work and conclusions are summarized as follows:
Pages129
Language中文
Document Type学位论文
Identifierhttp://ir.ipe.ac.cn/handle/122111/8282
Collection研究所(批量导入)
Recommended Citation
GB/T 7714
张伟鹏. 气液环流反应器中宏观混合及微观混合的研究[D]. 中国科学院研究生院,2013.
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