陶瓷原料振动流化床干燥过程模型及模拟

发布时间：2018-04-08 08:30

本文选题：振动流化床干燥　切入点：陶瓷原料　出处：《景德镇陶瓷学院》2015年硕士论文

【摘要】：陶瓷工业是一个耗能高、污染大的行业,主要体现在陶瓷粉料制备、烧成等环节。随着国家节能减排战略的大力实施,新型节能的陶瓷粉体造粒干燥技术研发势在必行。相比于现有的湿式球磨喷雾干燥造粒制粉工艺,陶瓷干法造粒干燥制粉技术具有节能环保优势,在陶瓷工业有重要的应用前景。振动流化床干燥是陶瓷干法造粒干燥制粉过程的一个重要操作单元,然而其干燥机理复杂,陶瓷原料颗粒物性参数多,现有干燥机理模型还不能实现对陶瓷原料颗粒振动流化床干燥这一过程的定量描述、特性分析和优化控制。本课题以陶瓷原料颗粒振动流化床干燥过程为研究对象,结合陶瓷颗粒物料特性实验,基于计算流体动力学方法,采用双流体模型对干燥过程中热空气相和陶瓷原料颗粒相的流动特性进行了数学描述,分别推导出了恒速干燥阶段和降速干燥阶段中气固两相间热质传递方程,建立了由基本控制方程组、颗粒动力学模型、湍流模型、曳力模型及气固两相热质传递模型等组成的振动流化床干燥过程非稳态二维数学模型,实现了对陶瓷颗粒振动流化床干燥过程中干燥室内两相湍流运动、传热与传质过程的定量描述。通过有限体积法对干燥过程的控制方程组等进行离散和数值计算,并运用SIMPLE算法对双流体模型进行了数值迭代求解。利用C语言编译了振动模型,并通过UDF模块引入到计算流体动力学求解器中,分别模拟分析了振动频率为0 Hz、10 Hz、15 Hz、20 Hz和进口热空气速度为0.5 m/s.1 1m/s、1.5 m/s时干燥室内颗粒相流动特性,确定了最佳操作参数。在此基础上,分别模拟分析了床层高为75 mm、100 mm、125 mm及进口热空气温度为393 K、413 K、433 K、453K时陶瓷颗粒振动流化床干燥过程的传热传质特性,模拟结果表明：1)当振动流化床振幅A=3 mm、振动频率户15 Hz、进口空气速度va=1m/s时,干燥过程中颗粒相流化质量较好,颗粒体积分数分布较均匀,床层较稳定,未出现较大的波动或腾涌和“气栓”现象;2)通过气固两相传热传质特性模拟分析发现干燥过程明显存在恒速干燥和降速干燥两个阶段,且床层高度和入口空气温度对干燥速率有较大的影响；3)在约360s时,整个床层中的陶瓷颗粒相湿含量下降缓慢,在0.05～0.07kg/kg之间,颗粒相温度较高,约为453 K,此时陶瓷原料颗粒相湿含量已符合压砖机的工艺要求。
[Abstract]:Ceramic industry is a high energy consumption and pollution industry, mainly reflected in ceramic powder preparation, sintering and other links.With the implementation of the national strategy of energy saving and emission reduction, it is imperative to develop new energy-saving ceramic powder granulation and drying technology.Compared with the existing wet ball milling spray drying technology, ceramic dry granulation drying technology has the advantages of energy saving and environmental protection, and has an important application prospect in ceramic industry.Vibratory fluidized bed drying is an important operation unit in the drying process of ceramic dry granulation. However, its drying mechanism is complex, and there are many parameters of particulate matter of ceramic raw material.The existing drying mechanism model can not realize the quantitative description, characteristic analysis and optimization control of the drying process of ceramic particles in vibrating fluidized bed.In this paper, the vibrating fluidized bed drying process of ceramic raw material particles is taken as the object of study, combined with the experiment of ceramic particle material characteristics, based on the computational fluid dynamics method.The two-fluid model was used to describe the flow characteristics of hot air phase and ceramic raw material particle phase in the drying process, and the heat and mass transfer equations between the two phases in the constant drying stage and the decreasing drying stage were derived, respectively.A two-dimensional unsteady mathematical model for the drying process of a vibratory fluidized bed is established, which consists of basic governing equations, particle dynamics model, turbulent model, drag model and gas-solid two-phase heat and mass transfer model.The two-phase turbulent motion, heat transfer and mass transfer in the drying chamber during the drying process of ceramic particles in vibratory fluidized bed are described quantitatively.The governing equations of the drying process are discretized and numerically calculated by the finite volume method, and the two-fluid model is solved numerically by SIMPLE algorithm.The vibration model was compiled by C language and introduced into the computational fluid dynamics solver by UDF module. The particle phase flow characteristics in the drying chamber were simulated and analyzed when the vibration frequency was 0 Hz / 10 Hz / 15 Hz and the inlet hot air velocity was 0.5 m/s.1 / s / 1.5 m / s, respectively.The optimum operating parameters are determined.On this basis, the heat and mass transfer characteristics of ceramic particles during the drying process of vibratory fluidized bed were simulated and analyzed, when the bed height was 75 mm / 100 mm ~ (125) mm and the inlet hot air temperature was 393 K ~ (13) K ~ (413) K ~ (433) K ~ (453) K ~ (453K), respectively.The simulation results show that when the vibration fluidized bed amplitude is 3 mm, the vibration frequency is 15 Hz and the inlet air velocity is va=1m/s, the fluidization quality of particle phase is better, the particle volume fraction is more uniform, and the bed is more stable.Through the simulation analysis of gas-solid two-phase heat and mass transfer characteristics, it is found that there are two stages of constant speed drying and slow drying obviously in the drying process.And the bed height and inlet air temperature have a great influence on the drying rate. When the drying rate is about 360s, the wet content of ceramic particles in the whole bed decreases slowly, and the temperature of the particle phase is higher between 0.05~0.07kg/kg.It is about 453 K, and the wet content of ceramic particle has met the requirement of brick press.
【学位授予单位】：景德镇陶瓷学院
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ174.6

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