Gas holdup at dynamic equilibrium region of a bubble column: Effect of bubble generator performance

Gong, Chunkai; Xu, Xiahong; Yang, Qiang

doi:10.1016/j.cej.2022.136382

“…However, it only works within a limited range, as the proportion of microbubbles introduced into the SBCR increases, the probability of collision between bubbles increases, and the bubbles are more likely to coalesce, causing the bubble size to increase. In extreme cases, it may even cause the gas holdup to collapse, weakening the mass transfer promotion of the microbubbles . Thus, when the microbubble-introducing proportion exceeds a certain value, continuing to increase the microbubbles has little enhancement effect on the liquid volumetric mass transfer coefficient k L a , and the specific values vary depending on the microbubble generator selected.…”

Section: Resultsmentioning

confidence: 99%

“…In extreme cases, it may even cause the gas holdup to collapse, weakening the mass transfer promotion of the microbubbles. 42 Thus, when the microbubble-introducing proportion exceeds a certain value, continuing to increase the microbubbles has little enhancement effect on the liquid volumetric mass transfer coefficient k L a, and the specific values vary depending on the microbubble generator selected. In this experiment, taking SVMG as the microbubble generator, the maximum enhancement ratio of α SVMG to gas−liquid mass transfer is 30%, as shown in Figure 20.…”

Section: Liquid Volumetric Mass Transfer Coefficientmentioning

confidence: 99%

Bubble Size “Bimodal” Distribution Enhances Mixing and Mass Transfer in Slurry Bubbling Column Reactor

Wang,

Zhu,

Shuai

et al. 2024

Ind. Eng. Chem. Res.

0

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To meet the needs of industrial installations to enhance mixing and mass transfer, solving the problem that the liquid turbulence caused by the microbubbles is weak and unfavorable for gas−liquid−solid phases mixing, we propose a concept of employing bubbles with a "bimodal" size distribution. Specifically, microbubbles are introduced to enhance mass transfer, while macrobubbles are utilized to promote mixing. Building upon this design philosophy, we developed a comprehensive gas distributor comprising a swirl-venturi microbubble generator and a ring-shaped gas distributor. This combined system aims to optimize the distribution of the bubble sizes. Experimental studies have been conducted to investigate the impact of bubble size distribution on gas holdup, solid holdup, liquid phase mixing, and the liquid volumetric mass transfer coefficient within the slurry reactor. From the experimental findings, we derive essential principles for the design of the "bimodal" bubble size distribution. First, the superficial gas velocity of the macro bubble should exceed the critical value, set at u g,trans-tM , which equals 0.077 m/s in our experiments. Second, the proportion of air intake from the swirling-venturi microbubble generator to the total air intake should not surpass the critical ratio α SVMG,trans established at 30% in this experiment. These principles provide a solid foundation for optimizing the proposed "bimodal" bubble size distribution and improving the overall performance of the slurry reactor.

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“…In response to the sharp contradiction between high titer products and large-scale 5), ( 6)-( 10), ( 11)-( 15), ( 16)- (20) represents 100, 300, 500, 700 g/L xylose broth with 100/300/500/700/900 rpm.…”

Section: Discussionmentioning

confidence: 99%

“…In industry, KL and α are usually combined into one index, the volume transfer coefficient KLα, a significant parameter to simulate the aerobic microorganisms bioprocess' and reactor scale-up 19 . The relationship between α and gas holdup (αg) with fluid/gas volume is given in equations ( 2) and (3) 20 .…”

Section: = ⋅ * −mentioning

confidence: 99%

Threshold effect on whole-cell catalysis of extra hyperviscous biosystem by a sealed oxygen supply biotechnology

XU,

Hua,

Hu

et al. 2024

Preprint

0

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The end-product concentration and productivity are critical issues in economic competition between biotechnological commercials and the chemical engineering industry. The prominent contradiction between high-titer products and the large-scale oxygen demand for aerobic biocatalysis leads to hyperviscosity, mass transport bottleneck in [dynamically changing](javascript:;) polyphase biosystems, and severe foaming problems. In this study, an intensification strategy for the whole-cell catalytic preparation of high-titer xylonic acid by Gluconobacter oxydans in a sealed-compressed oxygen supply bioreactor is propose. Multi-scale control factors are quantitatively studied to determine the biochemical parameter thresholds, and theoretically calculated the optimal production performance based on threshold effect. Finally, 650.8 g/L xylonic acid is obtained with a maximum productivity of 41.7 g/L/h with a catalytic performance of 95.8%, compared with the theoretical calculations. The intensification strategy for the oxygen transfer threshold effect overcome the stubborn obstacles of obligate aerobic catalysis, while providing a sustainable value-added pathway for fermentative lignocellulose.

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“…Finally, in SOS-BR, an intensification strategy for producing XA with high concentration, efficiency, and quality is established by combining theory and practice, breaking through the viscosity limitation in a hypertonic/hyperviscous system. Overall, this intensification strategy provides valuable technical guidance and 5), ( 6)-( 10), ( 11)-( 15), ( 16)- (20) represents 100, 300, 500, 700 g/L xylose broth with 100/300/500/700/900 rpm.…”

Section: Discussionmentioning

confidence: 99%

Threshold effect on whole-cell catalysis of extra hyperviscous biosystem by a sealed oxygen supply biotechnology

Hua,

Hu,

Han

et al. 2024

Preprint

0

View full text Add to dashboard Cite

The end-product concentration and productivity are critical issues in economic competition between biotechnological commercials and the chemical engineering industry. The prominent contradiction between high-titer products and the large-scale oxygen demand for aerobic biocatalysis leads to hyperviscosity, mass transport bottleneck in [dynamically changing](javascript:;) polyphase biosystems, and severe foaming problems. In this study, an intensification strategy for the whole-cell catalytic preparation of high-titer xylonic acid by Gluconobacter oxydans in a sealed-compressed oxygen supply bioreactor is propose. Multi-scale control factors are quantitatively studied to determine the biochemical parameter thresholds, and theoretically calculated the optimal production performance based on threshold effect. Finally, 650.8 g/L xylonic acid is obtained with a maximum productivity of 41.7 g/L/h with a catalytic performance of 95.8%, compared with the theoretical calculations. The intensification strategy for the oxygen transfer threshold effect overcome the stubborn obstacles of obligate aerobic catalysis, while providing a sustainable value-added pathway for fermentative lignocellulose.

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Gas holdup at dynamic equilibrium region of a bubble column: Effect of bubble generator performance

Cited by 9 publications

References 49 publications

Bubble Size “Bimodal” Distribution Enhances Mixing and Mass Transfer in Slurry Bubbling Column Reactor

Bubble Size “Bimodal” Distribution Enhances Mixing and Mass Transfer in Slurry Bubbling Column Reactor

Threshold effect on whole-cell catalysis of extra hyperviscous biosystem by a sealed oxygen supply biotechnology

Threshold effect on whole-cell catalysis of extra hyperviscous biosystem by a sealed oxygen supply biotechnology

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