Gas-liquid mass transfer coefficients in the gas-liquid-solid micro-fluidized beds

doi:10.11949/0438-1157.20220166

Abstract

Abstract:

Gas-liquid-solid micro-fluidized bed combines the advantages of microfluidic system and macro-fluidized bed, and has potential industrial application value, but its application basic research is very lacking. The effects of several conditions including superficial gas velocity and liquid velocity, bed diameter, size of solid particles on the volumetric and liquid-phase gas-liquid mass transfer coefficients of CO₂ absorption by NaOH solution were studied by using the three-phase micro-fluidized bed made of 1.6, 2.0, 2.4 mm capillary tubes and solid particles with diameters of 160, 190 and 220 μm based on the investigations of gas-liquid-solid flows. The results show that the gas-liquid volumetric mass transfer coefficient increases with the increase of the superficial gas velocity and liquid velocity, in which the change of superficial gas velocity mainly affects the gas holdup and phase interface area, while the change of superfrical liquid velocity mainly affects the gas-liquid liquid-phase mass transfer coefficient. The mass transfer performance of the micro-fluidized bed with smaller bed diameter is the better, and its interface area and total gas-liquid mass transfer coefficient are enhanced. When solid particles are added into the gas-liquid mini-bubble column with solid holdup of 0.15—0.30 at three-phase bubbling flow regime, the gas-liquid volumetric mass transfer coefficient of this three-phase micro-fluidized bed is 1.1—1.5 times of that in gas-liquid mini-bubble column. Compared with the macro-fluidized bed, the interface area of micro-fluidized bed is 5—10 times of that of macro-fluidized bed under the same conditions, which is the main factor influencing the larger volume mass transfer coefficient of micro-fluidized bed.

Key words: gas-liquid-solid, micro-fluidized bed, gas-liquid, mini-bubble column, mass transfer coefficient, fluidization

摘要：

气液固微型流化床兼具微流控系统和宏观流化床的优点，具有潜在的工业应用价值，但是，其应用基础研究十分缺乏。采用床径为1.6、2.0、2.4 mm的微型流化床，平均粒径为160、190、220 μm的玻璃珠，以NaOH水溶液吸收CO₂气体为气液传质研究物系，在三相流动研究的基础上，考察了表观气速、表观液速、床径、粒径等对三相微型流化床气液体积传质系数的影响。结果表明：给定其他条件，增加表观气速和表观液速，均使气液体积传质系数增大；表观气速主要改变气含率和气液相界面积，而表观液速主要改变液相传质系数；床径减小，气液相界面积和气液体积传质系数都有所增加；在气液两相微型鼓泡塔中加入固体颗粒，形成三相分散鼓泡流型，当其固含率在0.15~0.30范围内，可显著增强气液传质，其气液体积传质系数是气液微鼓泡塔的1.1~1.5倍；与宏观流化床相比，相同条件下微型床的相界面积为它的5~10倍，是微型流化床具有更大体积传质系数的主要影响因素。

关键词: 气液固, 微型流化床, 气液, 微鼓泡塔, 传质系数, 流态化

CLC Number:

TQ 021

Kaiyue WANG, Yongli MA, Chen LI, Mingyan LIU. Gas-liquid mass transfer coefficients in the gas-liquid-solid micro-fluidized beds[J]. CIESC Journal, 2022, 73(8): 3529-3540.

王凯玥, 马永丽, 李琛, 刘明言. 气液固微型流化床的气液传质系数[J]. 化工学报, 2022, 73(8): 3529-3540.

Figures/Tables 18

Fig.1 Experimental setup and flowchart of mass transfer in the gas-liquid-solid micro-fluidized bed

Fig.2 Image processing process

Fig.3 Variation of volumetric mass transfer coefficient with superficial gas velocity in gas-liquid-solid micro-fluidized bed

Fig.4 Flow patterns of gas bubbles in gas-liquid-solid micro-fluidized beds at different superficial gas velocities (D=2.0 mm, dp=190 μm)

Fig.5 Changes of gas-liquid phase interface area, bubble diameter and gas holdup with superficial gas velocity in gas-liquid-solid micro-fluidized bed

Fig.6 Changes of liquid-phase mass transfer coefficient with superficial gas velocity in gas-liquid-solid micro-fluidized bed

Fig.7 Changes of liquid-phase mass transfer coefficient with bubble diameter in gas-liquid-solid micro-fluidized bed

Fig.8 Variation of volumetric mass transfer coefficient with superficial liquid velocity in gas-liquid-solid micro-fluidized bed

Fig.9 Flow patterns of gas bubbles in gas-liquid-solid micro-fluidized beds at different superficial liquid velocities(D=2.0 mm)

Fig.10 Changes of phase interface area, bubble diameter and gas holdup with superficial liquid velocity in gas-liquid-solid micro-fluidized bed

Fig.11 Changes of liquid-phase mass transfer coefficient with superficial liquid velocity in gas-liquid-solid micro-fluidized bed

Fig.12 Changes of liquid-phase mass transfer coefficient with bed diameter in gas-liquid-solid micro-fluidized bed

Fig.13 Flow patterns of gas bubbles in gas-liquid-solid micro-fluidized beds at different bed sizes(dp=190 μm)

Fig.14 Volumetric mass transfer coefficient between gas-liquid bubbling micro-column and gas-liquid-solid

Fig.15 Effect of particle diameter on volumetric mass transfer coefficient in gas-liquid-solid micro-fluidized bed

Fig.16 Liquid-phase mass transfer coefficients of gas-liquid-solid micro-fluidized bed with different particle sizes when superficial gas velocity changes

Fig.17 Liquid-phase mass transfer coefficients of fluidized beds with different particle sizes when superficial liquid velocity changes

Fig.18 Effect of fluid velocity on the ratio of bubble diameter to particle diameter in gas-liquid-solid micro-fluidized bed

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