耦合化学反应的多孔介质内热质传递机理研究

发布时间：2018-03-19 15:03

本文选题：多孔介质　切入点：热质传递　出处：《中国科学院工程热物理研究所》2017年博士论文　论文类型：学位论文

【摘要】：催化反应,例如催化燃烧、催化重整、催化裂解、催化加氢及催化部分氧化等,是能源化工领域最重要的反应类型之一,其在工业生产中具有广泛的应用。大部分催化反应过程中,反应物的转化都同时包含了复杂的热质传递过程。目前,催化吸/放热反应主要利用固定床反应器实现。该反应器内存在不同尺度的流动、热质传递及化学反应过程,而且它们之间存在复杂的耦合作用。其内流动、热质传递及它们与化学反应的耦合协同特性会随多孔介质的形态结构、材料及化学反应类型发生较大的变化。这些因素对反应器运行所需泵功、反应器内反应效率及热效率具有决定性的影响。因此,获得特定多孔结构的结构、流动与热质传递特性,并确定适合特定化学反应类型的最佳多孔结构,以在尽可能小的泵功下,使热质传递与化学反应协同性最好,达到最优的物质转化率与能源利用率具有重要的意义。本课题紧紧围绕能量热化学利用中的复杂热质传递过程,对耦合化学反应的多孔介质内热质传递机理进行系统的研究,解析微纳尺度与大孔尺度多孔介质内热质传递规律,深入剖析热质传递与化学反应的耦合协同性,获得特定多孔结构内的流动与热质传递特性,综合评价比较不同多孔结构内的流动及热质传递特性,明确指出不同多孔结构的适用范围,以期为多孔介质传热传质学的发展以及能源的热化学利用做出一定的贡献。首先基于离散单元法(DEM)-计算流体力学(CFD)对传统颗粒填充床内的流动、热质传递与化学反应等物理现象及它们之间的耦合协同性进行了系统的三维研究。着重对床层内的两个协同进行了分析,一个是床层内颗粒间流动与传热的场协同分析,另一个是催化剂颗粒内热质传递与化学反应的协同分析。揭示了低圆管-颗粒直径比下局部孔隙率、局部颗粒-流体传热系数和局部壁面-流体传热系数沿床层的振荡性分布,并利用场协同原理对流场与温度场进行了分析,提出了壁面-流体传热强化的填充结构。以用于化学热泵的丙酮加氢为例,对颗粒填充床内耦合化学反应的热质传递过程亦进行了三维CFD数值模拟,对床层内与催化剂颗粒内的传热传质阻力进行了分析,获得传热传质阻力最大处,从而指导多孔填充床反应器内热质传递的强化。通过调控催化剂颗粒结构参数(颗粒大小、孔隙率及孔尺寸),研究了催化剂颗粒结构对丙酮转化率及异丙醇选择性的影响规律,为丙酮加氢反应催化剂颗粒的设计提供了指导,并建立了气相催化反应CFD模拟研究的一般性方法。其次通过数值模拟与实验的方法对泡沫金属反应器内涂层泡沫金属的流动传热特性进行了系统的研究,揭示了涂层对泡沫金属有效导热、气固传热及辐射传热特性的影响规律。首先成功构建涂层泡沫金属单元胞的结构,并获得表征其结构的相关参数,利用CFD对不同结构参数、不同基质及不同涂层材料下涂层泡沫金属的纯导热引起的有效导热进行了模拟,获得了催化剂涂层对泡沫金属有效导热的影响规律,建立了涂层泡沫金属的纯导热引起的有效导热系数的关联式;然后,对涂层泡沫金属内的流动及气固传热进行了 CFD模拟,研究得到催化剂涂层对泡沫金属流动压降及气固传热的影响规律,验证了涂层内努森流动的出现对气固传热的强化作用;最后,对泡沫金属及涂层泡沫金属内的辐射传热特性进行了实验研究,获得了泡沫金属内辐射传热特性及催化剂涂层特性对泡沫金属内辐射传热特性的影响规律,得到了涂层泡沫金属的概念性有效辐射导热系数。然后以振荡流回热器为例,对多种填充结构的结构、流动及传热性能进行了评价,综合比较了各种填充结构的优劣。建立了适用于不同填充结构(颗粒、丝网及泡沫)振荡流回热器的流动传热综合控制模型,然后将不同填充结构的特性参数引入流动传热综合模型中,采用C语言编程利用有限差分法对振荡流回热器的回热过程进行了模拟,获得了不同填充结构的结构特性,得到了不同填充结构振荡流回热器的换热效率与综合性能,明确指出各自流动与热质传递的优势与缺陷,即制约不同填充结构传热效率的因素,获得了各种填充结构的普遍性规律。最后建立了传统颗粒填充反应器与新型泡沫金属反应器的一维两相反应器模型,并采用C语言利用有限体积法实现了模拟。泡沫金属反应器的反应器模型考虑了涂层厚度及涂层对反应器内传热特性的影响。以丙酮加氢慢速反应为例,对传统颗粒填充反应器与新型泡沫金属反应器进行了模拟比较。验证了这两种反应器用于慢速反应时的优劣,并对这两种结构的结构、流动及热质传递与化学反应的协同特性进行了进一步的综合研究。
[Abstract]:For example, catalytic reaction, catalytic combustion, catalytic reforming, catalytic cracking, catalytic hydrogenation and catalytic partial oxidation reaction, is one of the most important types of energy chemical industry, has been widely used in industrial production. Most of the catalytic reaction process, conversion of the reactants are also contains complicated processes of heat and mass transfer. At present, the catalytic endothermic and exothermic reactions using fixed bed reactor. The existence of different scale flow reactor, heat transfer and chemical reaction process, and the existence of the complex coupling between them. The flow, heat and mass transfer and their coupling with chemical reaction with synergistic properties of porous media structure the material and the type of chemical reaction change greatly. These factors of pump power required for the reactor operation, has a decisive influence on the reaction efficiency and thermal efficiency of the reactor. Because of this, get special Fixed structure of porous structure, flow and heat transfer characteristics, and to determine the optimal porous structure suitable for a particular type of chemical reaction, the pump power in as little as possible, transfer and chemical reaction, the best synergy to heat, has the vital significance and the utilization rate of energy conversion to achieve the optimal material. This topic closely around the complex heat and mass transfer in the process of using chemical energy, heat and mass transfer mechanism of porous media on the coupling chemical reaction system research, analysis of micro nano scale and large pore scale porous medium heat and mass transfer law, in-depth analysis of heat and mass transfer and chemical reaction coupling synergy, flow and the heat and mass transfer characteristics for specific the porous structure of the comprehensive evaluation, comparison of different flow and heat transfer characteristics of the porous structure, clearly pointed out that the application scope of different porous structure, with a view to the heat and mass transfer in porous medium Make a contribution to the development and utilization of energy chemical. Firstly, based on discrete element method (DEM) and computational fluid dynamics (CFD) to the traditional pellet packed bed flow, heat and mass of 3D collaborative research system transfer coupling between chemical reaction and physical phenomena and their focus on the bed. The two coordinate is analyzed, a synergy analysis of flow and heat transfer of particles in the bed between the field and the other is a collaborative analysis of heat and mass transfer reaction of catalyst particles and chemical. Revealing a low tube particle diameter than the local porosity, the local particle fluid heat transfer coefficient and local wall surface the fluid heat transfer coefficient along the bed oscillatory distribution, and using the field synergy principle of convection field and temperature field are analyzed, put forward to strengthen the heat transfer fluid filled structure wall. For the hydrogenation of acetone chemical heat pump as an example, on a The particle packed bed heat transfer process coupled with chemical reaction were also discussed in three dimensional CFD numerical simulation of heat transfer, mass transfer resistance inside the bed and catalyst particles were analyzed, obtained the maximum heat transfer resistance, so as to guide the porous packed bed reactor with strong heat and mass transfer. By adjusting the structure parameters of catalyst particles (particle size, porosity and pore size), studied the influence of catalyst particle structure conversion and selectivity to acetone and isopropanol, provides guidance for the design of acetone hydrogenation catalyst particles, and a general method for simulation of gas phase catalytic reaction of CFD. The second was studied by numerical simulation method with the experiment on the flow and heat transfer characteristics of metal foam coating of metal foam inside the reactor, reveals the effective thermal conductivity of metal foam coating, gas-solid heat transfer and radiation heat transfer characteristics The influence of structure. First coating metal foam cell was successfully constructed, and get the parameters of the structure, of the different structure parameters by using CFD, the effective thermal conduction of different substrates and different coating materials under the coating of metal foam by simulation, obtaining the effect of catalyst coating on the effective thermal conductivity of metal foam that association has established a pure thermal conductive coating of metal foam effective thermal conductivity caused by the flow of the coating; then, metal foam and the gas-solid heat transfer was simulated by CFD simulation, study effects of flow pressure drop and gas catalyst coating on the metal foam heat transfer, verify the flow of Neinusen appear. The gas-solid heat transfer the strengthening effect; finally, radiation heat transfer characteristics of metal foam and coating in metal foams was studied, obtained the radiation heat transfer in metal foams Effect of regularity and characteristics of the catalyst coating of metal foam radiative heat transfer characteristics of the obtained coating concept of metal foam thermal conductivity. Then the effective radiation heat exchanger to oscillation as an example, the structure of a variety of filling, flow and heat transfer properties were evaluated, comprehensive comparison of various filling structures is established. Suitable for different filling structure (particles, mesh and foam) comprehensive control model of oscillating flow heat transfer back to the heat exchanger, and then the characteristic parameters of different filling structure into the flow and heat transfer model, using C language programming by using the finite difference method of oscillation flow heat exchanger heat recovery process was simulated and obtained different structure the structural characteristics of the filling, thermal efficiency and performance for different filling structure to oscillation heat exchanger, pointed out their advantages and disadvantages and the flow of heat and mass transfer, i.e. Different factors restricting the filling structure of heat transfer efficiency, was filled with various common law structure. Finally, a one-dimensional two-phase reactor model of reactor and reactor model of metal foam filled with traditional particle, and using C language to realize the simulation by using finite volume method. The reactor model of foam metal reactor is considered the thickness of the coating and coating on the heat transfer characteristics of the reactor. The hydrogenation of acetone to slow reaction as an example, the traditional particle reactor filled with new foam metal reactor was studied. The two kinds of reactors for slow reaction when the pros and cons of verification, and the two kinds of structure, collaborative response flow and heat transfer and chemical studied further.

【学位授予单位】：中国科学院工程热物理研究所
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TQ021

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