Quantitative characterization of the blockage effect from dispersed phase on wax molecular diffusion in water-in-oil emulsion
Quantitative characterization of the blockage effect from dispersed phase on wax molecular diffusion in water-in-oil emulsion
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油包水乳液中分散相对蜡分子扩散的堵塞效应的定量表征
DOI：
10.1016/j.petrol.2020.108012
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发表时间：
2021
影响因子：
--
通讯作者：
Kaifeng Fan
中科院分区：
文献类型：
--
作者：
Si Li;Kaifeng Fan
分子扩散是蜡沉积的主要机制，而分散水滴通过限制扩散路径影响蜡在油包水（w/o）乳状液中的扩散，本文采用几何分析方法分析了分散相对蜡分子在w/o乳状液中受限扩散路径的堵塞作用，提出了真实的乳状液中堵塞效果与含水率、分散度和分散相不均匀度的关联式。首先，将水滴视为尺寸和排列方式均匀的球形颗粒，推导了二维和三维理想条件下不同蜡扩散路径的平均曲折度。结果表明，随着含水率的增加，堵塞程度增强。此外，通过显微镜观察不同w/o型乳状液的液滴尺寸分布，并统计总结了一组微结构表征参数。建立了真实的乳状液的三维微结构模型，并考虑了液滴粒径分布对曲折度的影响。增大水滴的分散度和多分散度可以提高堵塞效果，但影响不显著，含水率仍是主要影响因素。在此基础上，提出了堵塞系数与含水率、数均粒径和多分散性的关联式，并用文献中的1H/19 F-NMR测试结果进行了验证，平均相对误差为3.17%。这将为揭示蜡在W/O乳状液中的扩散机理和多相流管道的蜡沉积预测提供支持。
Molecular diffusion is the main mechanism of wax deposition, whereas the dispersed water droplets influence the wax diffusivity in water-in-oil (w/o) emulsion by restricting the diffusion path. In the present work, geometric analysis method was used to analyze the blockage effect from dispersed phase on the restricted diffusion path of wax molecules in w/o emulsion, and a correlation was proposed relating the blockage effect with water fraction, dispersed degree and nonuniformity of dispersed phase in real emulsions. Firstly, regarding water droplets as spherical particles with uniform size and arrangement pattern, the average tortuosity of different wax diffusion paths was deduced in two-dimensional (2D) and three-dimensional (3D) ideal conditions. The results showed that the blockage degree was enhanced with the increase in water fraction. Moreover, the droplet size distribution of different w/o emulsions was investigated by microscopic observation and a set of microstructure characterization parameters were summarized in statistics. A 3D microstructure model of real emulsion was established to derive the tortuosity, taking the effect of droplet size distribution into consideration. The blockage effect was enhanced by the increase in the dispersity and polydispersity of water droplets, but this influence was not significant and water fraction was still the main influencing factor. On this basis, a correlation of blockage coefficient with water fraction, number-averaged diameter and polydispersity was proposed and validated using the1H/19F-NMR test results in literature with the average relative error being 3.17%. This will provide a support to the revealing of wax diffusion mechanism in w/o emulsions and the wax deposition prediction of multiphase flow pipelines.
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