IMECH-IR  > 流固耦合系统力学重点实验室
油滴在油水两相强旋流场中的聚并性能研究
英文题名Investigation into droplet coalescence in strong oil-water two-phase swirling flow field
梁楚楚
导师吴应湘
2018-05-23
学位授予单位中国科学院大学
学位授予地点北京
学位类别硕士
学位专业工程力学
关键词含油污水处理 聚并 群体平衡模型 柱型旋流器 分离效率
摘要

随着我国油田普遍进入了石油开采的中后期,原油含水率逐年增加,含油污水的处理问题已经成为了制约油田发展的关键因素。柱型旋流器因其体积小、无运动部件、能耗小等优点,在含油污水处理领域具有良好的应用前景。由柱型旋流器的工作原理可知,分散相液滴粒径的大小直接影响着其分离效率的高低。而前人涉及到液滴聚并和破碎现象的研究,多数情况下是为了解决搅拌罐、转盘塔等这类工业萃取设备中分散体系的相间传质及液滴粒径演化问题。只有少量的实验和数值模拟研究在研究水力旋流器的性能时,会考虑液滴间的相互作用及液滴粒径的变化,而关于柱型旋流器在这方面研究更是少之又少。因此本文基于柱型旋流器里的两相流场理论和群体平衡模型,采用实验和数值模拟相结合的方法,探究了柱型旋流器内的油滴粒径分布规律及其对分离性能的影响。

本文通过实验考察了同一入口含油率下,不同入口混合流速和分流比对柱型旋流器入口和溢流口油滴粒径分布、索特平均粒径变化量、进出口压降的影响。在数值模拟中,将欧拉多相流模型和群体平衡模型相互耦合,使用了四个聚并模型来预测溢流口处的油滴粒径分布,发现简化的Prince-Blanch模型的预测结果和实验数据的吻合度较高。在此模型的基础上,研究了操作参数(入口油滴粒径、离心加速度、分流比)、结构参数(内溢流管插入深度)对油滴粒径分布规律、柱型旋流器分离效率的影响。模拟结果表明,入口油滴粒径越大,旋流器的聚并、分离效果越好。对于粒径较大的油滴而言,分流比、离心加速度的增大不利于油滴的聚并;但旋流器的分离效率和分流比呈现正相关关系,并对应着一个最优离心加速度。增加内溢流管的插入深度,可以有效提高旋流器分离效率,油滴聚并性能则会先增强后减弱。

基于Prince-Blanch聚并模型,分析了柱型旋流器里的旋流聚并物理机制,发现入口油滴粒径和湍流耗散率是两个影响旋流器里液滴聚并的重要可调因素。并用该理论解释了旋流气浮技术、柱型旋流器结合沉降罐等除油技术在现场的应用。

英文摘要

As most oil fields in China have gone into interim period or late period of oil exploration, the water content of crude oil has been increasing year by year. Thus the treatment of oily wastewater has become a key factor constraining the development of oil fields . The cylindrical cyclone has a good application prospect in the field of oily wastewater treatment due to its advantages of small volume, no moving parts and low energy consumption and etc.. According to the working principle of the cylindrical cyclone, the size of droplets in the dispersed phase directly affects the separation efficiency. Previous studies on droplet coalescence and breakup have, in most cases, been done for addressing the problems of interphase mass transfer and droplet size evolution of dispersion system in industrial equipments such as the stirred tank. When predicting the separation performance of hydrocyclones, only a few experimental and numerical simulation studies have considered the interaction between droplets and the change of droplet size distribution. Furthermore, there is less research on this problem in the cylindrical cyclone. Thus, based on the two-phase flow field theory and population balance model in a cylindrical cyclone, this paper explores the oil droplet size distribution and its influence on the separation performance by combining experimental and numerical simulation methods together.

We investigate the effect of inlet flow rate and split ratio on the oil droplet size distribution of at the inlet and overflow of the cylindrical cyclone, the Sauter mean diameter variation, and the pressure drop at inlet and outlet under the same inlet oil content. In the numerical simulation, the Eulerian multiphase flow model and the population balance model are coupled to each other. Then we make use of four different coalescence kernels in order to predict the droplet size distribution at the overflow, and find the simulation result of simplified Prince-Blanch model more consistent with the experimental data. Based on this verified model, we studied the influence of not only the operational parameters( oil droplet size distribution at the inlet, centrifugal acceleration and split ratio), but also geometry parameters( insertion depth of internal overflow tube) on droplet size distribution and separation efficiency of the cylindrical cyclone. The numerical simulation results show that the larger oil droplets at the inlet are, the better the coalescence and separation effects are. For larger droplets, the increase of split ratio and centrifugal acceleration do not benefit coalescence, yet there is a positive correlation between the separation efficiency and split ratio .And the separation efficiency corresponds to an optimal centrifugal acceleration. Increasing the insertion depth of the internal overflow tube can effectively improve the separation efficiency, while the oil droplet coalescence shows the trend of strengthening first and weakening later.

Based on the Prince-Blanch coalescence model, the physical mechanism of coalescence in the cylindrical cyclone was analyzed. It was found that the inlet oil droplet size and the turbulent dissipation rate are two important factors affecting droplet coalescence in the cylindrical cyclone. Then this theory was used to explain the application of oil removal technology such as cyclone combined with flotation technology, and cylindrical cyclone combined with sedimentation tank.

语种中文
文献类型学位论文
条目标识符http://dspace.imech.ac.cn/handle/311007/73152
专题流固耦合系统力学重点实验室
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梁楚楚. 油滴在油水两相强旋流场中的聚并性能研究[D]. 北京. 中国科学院大学,2018.
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