反应性固体颗粒增强气液传质研究

发布时间：2018-04-12 17:10

本文选题：气液固传质 + 增强因子　；参考：《天津大学》2014年博士论文

【摘要】：化工过程强化是实现化工生产过程高效、节能与减排等目标的重要手段,也是传统化工发展的重要方向之一。本文对反应性固体颗粒增强气液传质过程进行了实验和理论研究。对反应釜内含有瞬时化学反应性微溶固体颗粒增强气体吸收过程进行了理论分析,在溶质渗透模型基础上,结合cell模型建立了一维传质模型,考虑反应固体颗粒尺寸以及固体颗粒溶解速率对传质过程的影响,对模型进行了解析求解,得到了传质系数和传质增强因子的数学表达式。考虑颗粒位置及颗粒间相互作用对传质的影响,采用数理统计的方法,建立了二维界面传质模型,并采用复合网格技术对二维传质模型进行了数值求解。结果表明,增强因子随固含率的增大而增大,并逐渐趋于一个恒定值,然而增强因子随气相分压、固体颗粒粒径、固体颗粒与界面距离的增大而减小。将鼓泡塔模型和二维界面传质模型相结合,对鼓泡塔内伴有化学反应的气液固三相传质过程进行了数值求解。结果显示增强因子随着固含率和气体流量的增加而增大,随气相分压和颗粒粒径的增大而减小。对鼓泡塔中伴有瞬时化学反应气液两相传质过程进行了理论研究。考虑了湍流和对流传质,基于表面更新理论,对气体吸收过程建立数学模型,并进行了解析求解。考察了气相溶质分压、气相流率、气液界面浓度、扩散系数和表面更新率等因素对气液传质增强因子的影响。结果表明,增强因子随液相反应物浓度的增加和气体流率的增大而增大,随气相溶质分压的增大而减小。采用反应釜对Mg(OH)_2浆料和Ca(OH)_2浆料吸收SO_2及CO_2的传质过程进行了实验研究,并采用鼓泡塔对Mg(OH)_2浆料和Ca(OH)_2浆料及NH_4HCO_3水溶液吸收SO_2的传质过程进行了实验研究。对传质模型进行了实验验证,模型预测值与实验结果吻合良好。
[Abstract]:Chemical process strengthening is an important means to achieve the goals of high efficiency, energy saving and emission reduction in chemical production process, and is also one of the important directions of traditional chemical industry development.In this paper, the process of gas-liquid mass transfer enhanced by reactive solid particles has been studied experimentally and theoretically.The process of gas absorption enhanced by micro-soluble solid particles with instantaneous chemical reaction in the reactor was analyzed theoretically. Based on the solute permeation model and cell model, a one-dimensional mass transfer model was established.Considering the effect of particle size and dissolution rate of solid particles on the mass transfer process, the mathematical expressions of mass transfer coefficient and mass transfer enhancement factor are obtained.Considering the effect of particle position and particle interaction on mass transfer, a two-dimensional interface mass transfer model was established by mathematical statistics, and the numerical solution of the two-dimensional mass transfer model was carried out by using composite grid technology.The results show that the enhancement factor increases with the increase of solid holdup and tends to a constant value. However, the enhancement factor decreases with the increase of gas phase partial pressure, particle size and the distance between solid particle and interface.The gas-liquid-solid three-phase mass transfer process with chemical reaction in the bubble column was numerically solved by combining the bubbling column model with the two-dimensional interfacial mass transfer model.The results show that the enhancement factor increases with the increase of solid holdup and gas flow rate and decreases with the increase of gas partial pressure and particle size.The gas-liquid mass transfer in bubble column with instantaneous chemical reaction was studied theoretically.Considering turbulence and convection mass transfer, a mathematical model of gas absorption process is established based on surface renewal theory, and the analytical solution is given.The effects of gas solute partial pressure, gas phase flow rate, gas-liquid interface concentration, diffusion coefficient and surface renewal rate on the enhancement factors of gas-liquid mass transfer were investigated.The results show that the enhancement factor increases with the increase of the concentration of liquid phase reactants and the gas flow rate, and decreases with the increase of the partial pressure of solute in the gas phase.The mass transfer process of Mg(OH)_2 slurry and Ca(OH)_2 slurry absorbing SO_2 and CO_2 was studied by using a reactor, and the mass transfer process of Mg(OH)_2 slurry, Ca(OH)_2 slurry and NH_4HCO_3 aqueous solution absorbing SO_2 was studied by using bubbling column.The mass transfer model is verified by experiments and the predicted values are in good agreement with the experimental results.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TQ021.4

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