【作者】 王丽雅；

【导师】 李希；

【作者基本信息】 浙江大学 ， 化学工程， 2006， 硕士

【摘要】 精对苯二甲酸(PTA)是聚酯工业的重要原料，目前主要采用对二甲苯(PX)的空气氧化法生产，国内PTA生产企业的现有技术及设备全部依赖进口。为了获得具有自主知识产权的PTA核心技术，我课题组开发了以鼓泡塔为特征的新型氧化反应器。与传统的搅拌釜相比，鼓泡塔结构简单，加工成本与难度较低，设计与制造均较容易国产化。本论文针对自主开发的鼓泡塔氧化反应器进行相关的冷模实验研究。本文的主要内容包括：1、针对PX氧化反应所特有的高气速、高固含率和大塔径等特点，采用电导探针、Pavlov管和亚硫酸钠氧化法等测定了气液两相和气液固三相体系下，不同直径的鼓泡塔反应器中流场分布和质量传递的相关参数，为鼓泡塔反应器的反应器模型化和工业应用奠定了基础。研究发现：(1)随着表观气速的增加，局部气含率明显增加；塔径的增加使径向上的气含率分布更平坦；随着固含量的增加，局部气含率减小。(2)随着表观气速和塔径的增加，液速分布更为陡峭；固体的存在阻碍了气液相运动。在液体流动转折点r／R=0.7的位置湍动最剧烈；随着气速和塔径的增加，湍流脉动强度增强；在高固含量下，湍流脉动加剧。(3)塔内存在接近于塔内径的最大涡旋，塔径的增加使含能尺度的涡旋尺寸增加，而气速对涡旋尺寸的影响不大；高频和低频尺度的能量随着气速和塔径的增大而增加，含能尺度区间的能量占总能量的97％以上。(4)随着表观气速和塔径的增加，液相体积传质系数明显增加；固含量对传质系数的影响可以忽略。2．鉴于鼓泡塔反应器在工业放大过程中，将出现轴向液速径向分布更为陡峭，塔中心处气含率过高等不利于传质和反应的特点，提出了在鼓泡塔内设置阻尼内构件的方法来抑制塔中心过高的流速，根据这一思路开发出带阻尼内构件的新型鼓泡塔专利技术。结论包括：(1)阻尼内构件可有效的改善轴向液速的径向分布；采用一维拟均相模型可较好的描述内构件的阻尼作用。(2)内构件的加入也使局部气含率的径向分布更为平坦；气速和塔径对带内构件的鼓泡塔中局部气含率分布的影响与空塔中一致。(3)提出了表观气速、鼓泡塔的塔径、内构件的无量纲阻尼面积和固含率等因素对传质系数影响的关联式。更多还原

【Abstract】 Purified terephthalic acid (PTA), one of the important feedstocks of polyester, is produced by p-xylene (PX) liquid phase oxidation. Industry processes of PTA are all controlled by foreign companies, so domestic companies import all of the existing technology and equipment from them. For improve the market competitive power of domestic companies and break through the patent barrier of foreign companies, it is nessessary to develop domestic industry techonology.Compared with traditional agitated tank, the patent on bubble column as the main reactor of PX oxidation is rare. Further more, Bubble column reactor has its own strong points such as simple structure, low construction and operating cost. So bubble column has been chose as main reactor of new-type industry process.The paper included the following aspects:1. Conductivity probe, Pavlov tube and oxidation of sodium sulfite has been used to measure the parameters about flow field and mass transfer in gas-liquid and gas-liquid-solid bubble columns with different diameters. Experiments are based on the feature of PX oxidation, such as high superficial velocity, high solid content and large equipment. The results are as follows(1).With the increasing of superficial gas velocity, local gas holdup remark increases. The radial distribution of local gas holdup becomes flatter with the increasing of column diameter; the addition of solid makes local gas holdup decrease.(2) . With the increasing of gas velocity and column diameter, the radial distribution of liquid velocity become steeper; the addition of solid disturbs the movement of gas-liquid phase. In the inversion point of liquid flow, root-mean-square fluctuation velocity is maximum value. Turbulent intensity increases with superficial gas velocity, column diameter and solid content.(3). The biggest eddy size approaches to column diameter. Eddy size increases with column diameter, while gas velocity almost has almost no influence on it. Power distribution for varying wavelet scale that fine scale and large scale power became larger with the increasing of gas velocity and column diameter.(4). With increasing of gas velocity and column diameter, liquid phase mass transfer coefficient increases. The addition of solid has no influence on mass transfer coefficient.2. The damping internal had been placed in bubble column reactor to solving the problem caused by the scaling up of equipment, for example the ununiformity distribution of liquid velocity and gas hold-up caused gas short pass in the centre of column, then influenced mass transfer and reaction. The results are summarized as follows(1). The damped internal could effectively improve the radial distribution of axial liquid velocity. In small bubble column, the liquid velocity distribution curve is flatter. Quasi- homogeneous model could indicate the effects of internal well.(2). The radial distribution of local gas holdup is flatter when internal is placed in the column.(3). The relating formula about the influence of gas velocity, column diameter and internal front face area on mass transfer coefficient is presented.更多还原