Flow characteristics and CFD simulation on a high-efficiency sieve tray with bubble crusher

doi:10.11949/j.issn.0438-1157.20170318

Abstract

Abstract:

A high-efficiency sieve tray with bubble crusher was proposed. A layer of bubble crusher device was added in the height range of the foam layer on the sieve tray. The device could decrease the volume of the bubble and force the interphase to renovate, improve mass-transfer efficiency of trays in the trace distillation, and strengthen the gas-liquid mass transfer. The numerical simulation of gas-liquid two-phase flow field is carried out on the micro-bubble tray and sieve tray by Euler-Euler two fluid model, which was verified by test. The results showed that the bubble crusher device can effectively break the large bubbles, which made the gas distribution in those regions characterized by the small fraction of gas volume and evident back-mixing phenomenon more uniform, the regional area with large bubble content larger, and the gas hold-up distribution was gradient. The bubble crusher device in the foam layer can increase the interfacial area for vapour-liquid contact and residence time, improve the mass transfer efficiency and reduce the gas entrainment. The turbulence intensity near the bubble crusher device was high. The gas sprayed while large bubbles broken will further tear the liquid layer and increase the height of the foam layer, and bubble coalescence was restrained. The quick interphase renovation could enhance mass transfer process. The results can provide guidance for the design and optimization of industrial trays.

Key words: numerical simulation, bubble, sieve plate tower, gas-liquid two-phase flow, gas holdup

摘要：

就痕量精馏中塔板传质效率低、需强化气液传质的问题，研究者提出了新型鼓泡破泡一体化高效精馏塔盘，通过在筛板上泡沫层高度范围内设置一层破泡装置，打破大气泡，减小气泡体积，强制界面进行更新，从而提高传质效率。采用双欧拉模型分别对鼓泡破泡一体化塔盘和筛板进行了气液流场的数值模拟，并对模型进行了验证。对比两种塔板的计算结果可以看出：在相同操作条件下，破泡装置将大气泡破裂成无数小气泡，使高气含率区域面积较普通筛板进一步增大，且气含率梯度变化更均匀；增加破泡装置后，在相同气速条件下气泡上升速度下降，气体在液层中的滞留时间延长，使鼓泡层高度增加，可显著提高传质效率，且降低了气体雾沫夹带量；破泡装置还明显改善了气相的纵向分布，气含率由塔板底部向上逐渐增大且存在明显分界；破泡装置附近湍动较剧烈，气泡破碎喷出的气体会进一步撕裂液膜，气体破碎作用会抑制气泡聚并，促进界面的快速更新更有利于传质过程的进行。研究结果可对工业塔板设计和优化提供指导。

关键词: 数值模拟, 气泡, 筛板塔, 气液两相流, 气含率

CLC Number:

TQ053.5

CHEN Guanghui, ZHU Huateng, GUO Xiuling, WANG Weiwen, LI Jianlong. Flow characteristics and CFD simulation on a high-efficiency sieve tray with bubble crusher[J]. CIESC Journal, 2017, 68(12): 4633-4640.

陈光辉, 祝华腾, 郭秀玲, 王伟文, 李建隆. 鼓泡破泡一体化高效精馏塔盘流动特性与CFD模拟[J]. 化工学报, 2017, 68(12): 4633-4640.

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