多相反应体系的微界面强化简述

加氢、氧化等气液慢反应过程广泛存在于现代过程工业之中,这些反应过程一般受传质速率控制。因此,对这类多相反应体系的传质强化一直是研究热点之一。但总体而言,除外场和微通道(微流控)强化等一类强化反应器外,以往的研究大多集中于界面尺度为毫-厘米级的传统反应器的搅拌与混合方式、气泡分布状态、流体流型、构效关系等方面,而鲜有将研究视角投放到传统以米为直径计量单位的反应器平台上如何构建尺度为微米级的界面体系及其特殊效应方面。探讨了多相反应体系的微界面反应强化理念,并简述了微界面的涵义、微界面反应强化与构效调控方法、微界面反应器的结构与形成原理、微界面体系的微颗粒测试与相界面表征技术、微界面反应强化面临的问题与挑战等,以与本领域同行共同研讨。     

亚硫酸铵微界面强化氧化特性研究

以亚硫酸铵水溶液的空气氧化为研究对象，考察了微界面强化对该体系传质与氧化过程的影响。在同一实验平台和操作工况下，对微界面强化与传统鼓泡塔氧化过程的传质和反应性能进行了实验研究。利用高速摄像与压差测量技术，分别对反应过程的空气气泡分布与气含率变化进行了测定。结果表明，相较于传统鼓泡塔空气氧化反应器，微界面强化氧化反应器以微界面体系取代了传统毫-厘米级宏界面，在不同盐离子浓度与氧化气量工况下均表现出了良好的强化效能。在微界面体系强化下，亚硫酸铵氧化过程气含率大幅提升，相界面积增加十余倍，反应速率平均提升56.8%，实验结论为微界面强化反应器的多相反应体系工业应用提供了一定的数据支撑。     

微流控双水相贴壁液滴流动强化酶促反应研究

以微流控双水相液滴流技术为基础,开发了一种酶促反应平台,将微流控贴壁液滴流快速传递、高效混合的特点与双水相反应分离耦合过程优化结合。本体系克服了传统宏观双水相体系传质传热慢以及耗时耗能的问题,并建立了贴壁液滴微反应器,产生更大的内环流,进一步增强传质效果。探究了双水相液滴界面的分子限域能力、对酶和产物的选择性分配能力。通过比较贴微通道壁和未贴微通道壁两类液滴微反应器的酶促反应效果,发现贴微通道壁液滴微反应器仅6 min转化率即可达到40%,其反应速率可达未贴微通道壁液滴微反应器9.4倍。本文通过微流控双水相贴壁液滴流实现了酶促反应的强化,为微尺度下的酶催化反应过程强化提供了一种新的思路。     

气液反应体系相界面传质强化研究

气液反应界面传质的强化是当今高效和节能反应器研究的重要课题,弄清反应器内的气液传质机理是对气液反应器进行数学描述的关键。反应过程的能效和物效与体系中的传质系数k_G,k_L,k_S以及相界面面积a等参数直接相关,这些参数受气泡尺寸、分布、表观气速和气含率等因素的制约。就确定的体系和反应条件而言,这些因素会因反应器的结构尤其是搅拌和混合方式的变化而异。文章从理论上分析了影响气液界面传质的各因素,建立了较为详细的理论模型。理论计算结果表明:气泡大小是影响气液界面传质和最终反应速率的重要流体力学参数,微米级气泡对反应过程的强化作用明显。能量耗散率是决定体系气泡大小的深层原因,强化气液反应器设计时应重点考虑。     

微尺度下非均相反应的研究进展

微结构反应器(微反应器)是微化工系统的核心装备之一,是实现化工过程强化的重要技术基础。从微尺度非均相反应过程的基本原理出发,系统综述了近十年来微尺度下多相流动、分散和传递等方面的相关报道,系统地介绍了一些典型微尺度非均相反应过程,分析总结了微尺度反应技术的优势和特点,并对未来微尺度反应技术的发展方向提出了展望。     

微反应器内聚合物合成研究进展

微反应器作为化学工程学科的前沿和热点方向,逐渐成为聚合物合成的新装备、新工艺与新产品开发的重要平台,得到学术界和产业界的广泛关注。微反应器可实现可控的多相微尺度流动,能够强化聚合反应中的混合、传质和传热过程,严格控制反应时间,实现反应单元的模块化组合。与传统搅拌反应器相比,这些特点使得微反应器在控制聚合物分子量分布,简化反应环境,提高反应选择性,调节聚合物分子结构和宏观形貌等方面展现出了一定优势。本文全面综述了聚合物合成微反应器理论和技术的研究进展,并在新过程和新产品开发、反应动力学测量、微尺度基础研究和反应器放大等方面进行了展望。     

微反应器内聚合物合成研究进展

微反应器作为化学工程学科的前沿和热点方向,逐渐成为聚合物合成的新装备、新工艺与新产品开发的重要平台,得到学术界和产业界的广泛关注。微反应器可实现可控的多相微尺度流动,能够强化聚合反应中的混合、传质和传热过程,严格控制反应时间,实现反应单元的模块化组合。与传统搅拌反应器相比,这些特点使得微反应器在控制聚合物分子量分布,简化反应环境,提高反应选择性,调节聚合物分子结构和宏观形貌等方面展现出了一定优势。本文全面综述了聚合物合成微反应器理论和技术的研究进展,并在新过程和新产品开发、反应动力学测量、微尺度基础研究和反应器放大等方面进行了展望。     

声化学微反应器——超声和微反应器协同强化

微反应器和声化学技术都是化工过程强化的重要手段,但都有优缺点。阐释了“声化学微反应器”的理念--微反应器和声化学技术相互集成,利用超声强化微通道内的混合、传质和预防堵塞等,同样借助微反应器实现声场和气泡场的有效调控并解决声空化过程的放大难题,实现协调强化的目的。同时,深入剖析了声化学微反应器内的声空化行为、声场和气泡场调控规律,以及多相流动体系中的混合与传质强化机制。最后展望了该领域的发展方向,并指出超声空化过程中表界面时空尺度现象和理论是实现并优化超声强化的基础。     

超声微反应器内气液传质过程的介尺度强化机制

采用CFD方法对超声微反应器内的Taylor气液两相流的传质过程进行了模拟。针对传质过程中主要的介尺度结构,包括气泡表面波、空化声流、液相内的局部浓度,分析了其空间分布和时间演化规律。模拟结果有效捕捉了实验难以观测的液膜区域,并将液膜厚度与气泡表面波振动进行了关联,阐释了气液界面附近的空化声流对传质过程的强化作用。根据超声微反应器内Taylor流的传质特点,分别研究了不同流动和超声条件对液弹内和液膜处传质过程的影响,比较了各局部传质对整体传质效率的贡献。通过分析整体/局部Sherwood数与Peclet数间的关系,研究了超声效应对气液传质速率的影响。分析结果从介尺度角度验证了文献关于超声微反应器传质系数的计算,完善了超声微反应器内气液传质过程的强化理论。     

微反应器在重整制氢系统中的应用与进展

微反应器在传质、传热、反应效率等方面都明显优于传统反应器,具有微尺度、节能、安全、稳定等诸多优点。从微制氢系统组成、微制氢反应器的加工、催化剂装载和连接密封等方面对微反应器在重整制氢系统中的应用进行综述。     

Microinterface intensification in hydrogenation and air oxidation processes

Hydrogenations and air oxidations usually have low apparent reaction rate, generally controlled by mass transfer rate, and widely exist in the modern chemical manufacturing process. The key to increase the mass transfer rate is the reduction of the liquid film resistance 1/k_La. In this work, the original concept of microinterface intensification for mass transfer and then for these reactions has been proposed. We derived the regulation model and set up the mathematical calculation method of micron-scale gas-liquid interface structure on mass transfer and reaction, designed the mechanical energy exchange device that can produce gas-liquid microinterface system on a large scale, and established the OMIS system which is able on line to measure the diameter and distribution of millions of microbubbles, interface area a and mass transfer film thickness δ_M, as well as developed a series of microinterface intensified reactor systems (MIRs) for the applications of hydrogenation and air oxidation processes. It is believed that this research will provide an up-to-date development for the intensification of hydrogenation and air oxidation reactions.     

Study on the characteristics of micro-interface intensified oxidation of ammonium sulfite

The process intensification of interfacial area and reaction conditions in multi-phase systems are important issues in industrially scaled reactors. In order to investigate the intensifying effect of micro-interface system on gas-liquid mass transfer and reaction rate, the ammonium sulfite oxidation was selected as the research object. A systematic air forced oxidation experiment was carried out through the micro-interface intensification reactor (MIR) and the traditional bubble column reactor (BCR) under the same experiment platform and operating conditions. The bubble size distribution and overall gas holdup were measured by high-speed camera technology and differential pressure measurement, respectively. The experimental results showed that MIR obtained higher gas holdup because of the micro-interface structure, the interfacial area was increased by more than 10 times, the reaction rate increased by 56.8% averagely compared with BCR. The experimental conclusions provide certain data support for the industrial application of the multiphase reaction system of the micro-interface intensification reactor.     

Intensification principle of a new three-phase catalytic slurry reactor. Part I: Performance characterisation

This paper presents the concept and the performances of a mini horizontal stirred tank reactor, used for hydrogenation reaction. A simple analytical model based on characteristic times of heat and mass transfer illustrates the intensification principle and shows that the relevant intensification parameter is the mass to heat transfer characteristics times ratio. The proof of concept is made through a small scale reactor named RAPTOR^® (French acronym for Reactor with Polyvalent Rectilinear Stirred Reactor with Optimised Transfer). The mass transfer performances are measured and compared to conventional stirred tank reactor and other multiple impeller continuous reactors. In a following second paper, a comparative study is proposed to evaluate the eco-efficiency and the techno-economic advantages of a continuous process involving a RAPTOR^® versus a classical batch process based on a stirred reactor.     

A review on computational fluid dynamic simulation for rotating packed beds

A rotating packed bed (RPB) is one of the cutting-edge process intensification technologies due to its high mass transfer and mixing efficiency. Nevertheless, owing to the complex structure and hydrodynamic characteristics of RPBs, valuable data inside the reactor is hard to obtain by conventional experimental methods. Computational fluid dynamics (CFD) owing to its unique advantages of low cost, completeness of data and ability to simulate real and ideal conditions, has been adopted by many researchers to carry out fundamental research and practical application of RPBs in recent years. This paper therefore elaborates on the research progress on CFD simulation of RPBs. The building of a physical model of these reactors as well as selection of mathematical models are described, then applicability and accuracy of these models are compared and discussed. Simulation results for gas and multiphase flow in reactors are also presented. Additionally, the application of CFD to mixing and mass transfer between phases and processes in rotating packed beds is introduced. Optimum designs of reactors by the CFD method are also described. Finally, problems remaining with CFD simulation of rotating packed beds and future development directions are discussed. © 2018 Society of Chemical Industry     

微孔射流毛细管反应器内液-液两相传质和反应选择性

微反应技术在化工过程强化领域已得到广泛应用,尤其适用于快速复杂竞争反应体系。对于液-液两相快速竞争反应,反应过程受传质限制,显著影响反应转化率和收率。本文开发了一种新型的微孔射流毛细管反应器（MJCM）,采用微孔射流强化进口处液-液两相传质性能,分别采用水-苯甲酸-煤油体系和水-氢氧化钠-甲苯-苯甲酸-氯乙酸乙酯体系研究了不同操作参数（流量、流量比、表面活性剂浓度、温度）和结构参数（孔径、管长）下液-液两相传质特性和反应选择性,并获得了舍伍德数Sh的关联式。结果表明：随着两相流量的增加,传质效率E呈下降趋势,总体积传质系数k_La呈增加趋势,反应选择性指数X_s则先减小后增大;孔径的增大则会减弱液液传质和反应选择性;随着毛细管长的增加,E和X_s逐渐增大,k_La则逐渐减小;水相-有机相流量比的变化对E和k_La会产生不同影响,而温度的适当升高则可以提升反应选择性,表面活性剂的加入降低了传质和反应选择性。与其他液液传质设备对比,MJCM在液-液两相传质、反应选择性方面性能良好,可以用于工业生产进行液液传质与反应过程的强化。     

Characterization of the performances of an innovative heat-exchanger/reactor

The use of heat exchanger/reactors (HEX/reactors) is a promising way to overcome the barrier of poor heat transfer in batch reactors. However to reach residence time long enough to complete the chemistry, low Reynolds number has to be combined with both a plug flow behaviour and the intensification of heat and mass transfers. This work concerns the experimental approach used to characterize an innovative HEX/reactor. The pilot is made of three process plates sandwiched between five utility plates. The process stream flows in a 2 mm corrugated channel. Pressure drop and residence time distribution characterizations aim at studying the flow hydrodynamics. Identified Darcy correlations point out the transition between laminar and turbulent flow around a Reynolds number equal to 200. Moreover the flow behaves like a quasi-plug flow (Pe > 185). The heat transfer and mixing time have also been investigated. The ratio between the reaction kinetics and the mixing time is over 100 and the intensification factor ranges from 5000 to 8000 kW m⁻³ K⁻¹. As a consequence, no limitations were identified which allows the implementation of an exothermic reaction. It has been successfully performed under severe temperature and concentration conditions, batchwise unreachable. Thus, it highlights the interest of using this continuous HEX/reactor.     

Intensification of hydrodesulphurization process with a structured bed spiral mini-reactor

The procedure followed for the study of the characteristics of the intensification of catalytic hydrodesulphurization process with a structured bed spiral reactor is presented in the current work. This procedure consists of two parallel experimental methods investigating the mechanisms involved in the operation of the reactors. The first method aims at the study of the process mechanisms with mock up experiments at ambient conditions using systems with inorganic or organic liquids, water or heptane, and oxygen or nitrogen as gas phase. The second one focuses on the mechanisms at reaction conditions using simple model reactions, like benzene hydrogenation. The studied mechanisms with the methods followed are the fluid dynamic characteristics of the operation of spiral reactor, flow regime, axial dispersion and mass transfer limitations. The mass transfer limitations were also studied with desulphurization experiments taking into account the impact of the inhibitors hydrogen sulphide and ammonia on the desulphurization reaction.     

微尺度内液-液传质及反应过程强化的研究进展

微化工技术作为一种高效的过程强化技术获得了广泛应用。本文从流动、传递及反应三者之间的耦合机制出发,系统综述了近十五年以来关于微尺度内液-液两相流动与传质过程特征、强化传质的微反应器、评价标准及其在化学品合成与材料制备中的应用等方面的研究进展,并对其未来发展方向进行了展望。