Numerical simulation of liquid-liquid two-phase flow in tubular mixer-settler

doi:10.11949/0438-1157.20200928

Abstract

Abstract:

The tubular mixer-settler has a broad application prospect in industrial production. A tubular mixer settler was simulated by using computational fluid dynamics (CFD). The effects of dispersed phase droplet size (d₃₂ = 100—500 μm), oil-water ratio (O∶A = 1∶1—1∶5), inlet baffle position on the mixing and settle performance of tubular mixer-settler were systematically investigated. The simulation results were compared with those of traditional square mixer-settler. The results show that the flow field distribution in the tubular mixer chamber is better than that in the square mixer chamber, in which the flow dead zone is not easy to generate. In the tubular mixer chamber, a lower pressure zone is formed above and below the impeller, and the turbulent kinetic energy of the fluid is higher. The mixing performance can be improved by reducing d₃₂ of dispersed phase and oil-water ratio of feed. In the tubular settler, increasing the dispersed phase d₃₂ and reducing the feed oil-water ratio can improve the clarification performance, and the inlet baffle can effectively improve the clarification performance.

Key words: numerical simulation, computational fluid dynamics, extraction, two-phase flow

摘要：

管型混合澄清槽在工业生产中具有广阔的应用前景。通过计算流体力学分别对管型混合澄清槽内的混合室和澄清室进行数值模拟，系统地探究了分散相液滴尺寸（d₃₂₌100~500 μm）、进料油水比（O∶A = 1∶1~1∶5）、入口挡板及入口位置对混合澄清效果的影响，并将模拟结果与传统方型混合澄清槽进行对比。结果表明，管型混合室内的流场分布更合理，不易形成流动死区。管型混合室内搅拌桨上方和下方形成压力更小的低压区，流体的湍动能更大，搅拌性能更好。在混合室中，降低分散相d₃₂和进料油水比能够提高混合性能。在澄清室中，提高分散相d₃₂和降低进料油水比能够提高澄清性能，入口挡板能够有效提高澄清性能。

关键词: 数值模拟, 计算流体力学, 萃取, 两相流

CLC Number:

TQ 027.2

LAN Minle, TAN Boren, XU Dongbing, WANG Yong, QI Tao. Numerical simulation of liquid-liquid two-phase flow in tubular mixer-settler[J]. CIESC Journal, 2021, 72(4): 1965-1974.

蓝敏乐, 谭博仁, 许东兵, 王勇, 齐涛. 管型混合澄清槽内的液-液两相流的数值模拟[J]. 化工学报, 2021, 72(4): 1965-1974.

Figures/Tables 16

Fig.1 Schematic diagram of tubular mixing-settler

Fig.2 Geometry of mixer (the unit is mm)

Fig.3 Geometry of settler and baffles (the unit is mm)

Fig.4 Generation and quality of structured grid

Fig.5 The flow field distribution in the mixer chamber

Table 1 Volume fraction of dead zone in the two mixers

最大流速的百分比/%	死区体积分数/%
最大流速的百分比/%	管型混合澄清槽	方型混合澄清槽
5	1.23	2.42
7.5	4.13	4.88
10	7.72	8.84
12.5	16.2	18.7
15	32.4	33.7

Fig.6 The pressure distribution in the mixer chamber

Fig.7 The distribution of turbulent kinetic energy in mixer chamber

Table 2 Average turbulent kinetic energy, average organic phase holdup and variance of organic phase holdup in tubular and square mixer

混合澄清槽	平均湍动能/(m²/s²)	平均有机相相含率	有机相相含率方差
管型混合澄清槽	0.004145	0.2449	0.009062
方型混合澄清槽	0.003566	0.2400	0.007507

Fig.8 The distribution of dispersed phase holdup in mixer chamber

Fig.9 Distribution of dispersed phase holdup under different d32

Fig.10 Distribution of dispersed phase holdup under different oil-water ratio

Fig.11 Distribution of dispersed phase holdup in settler with different d32

Fig.12 Distribution of dispersed phase holdup in settler with different oil-water ratio

Fig.13 Effect of baffle on the settle performance in tubular settler

Fig.14 Effect of baffle on flow field distribution of tubular settler

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