Relative Effect of Additional Solid Media on Bubble Hydrodynamics in Bubble Column and Airlift Reactors towards Mass Transfer Enhancement

Abstract

Many researchers have focused on multi-phase reactor development for improving mass transfer performance. However, solid particle addition in gas–liquid contactor for better oxygen mass transfer performance is still limited. Hence, this study aims to analyze the relative effect of different types of local solid media on the bubble hydrodynamic characteristics towards mass transfer enhancement in bubble columns (BCR) and airlift reactors (ALR). This was investigated by varying solid media types (ring, sphere, cylinder, and square), solid loadings (0%–15%), and superficial gas velocities (Vg) (2.6–15.3 × 10−3 m/s) in terms of the bubble hydrodynamic and oxygen mass transfer parameters. The result showed that bubble size distribution in BCR and ALR with additional plastic media was smaller than that without media addition, approximately 22%–27% and 5%–29%, respectively, due to the increase of the bubble breaking rate and the decrease of the bubble rising velocity (UB). Further, adding media in both reactors significantly decreased the UB value. Since media increased flow resistance, resulting in decreased liquid velocity, it can also be the moving bed to capture or block the bubbles from free rising. Therefore, oxygen mass transfer performance was investigated. The oxygen transfer coefficient (KLa) in BCR with solid media addition was enhanced up to 31%–56% compared to a non-addition case, while this enhancement was greater at higher solid loading due to its higher effective surface, resulting in a higher bubble break-up rate compared to the lower loading. In ALR, up to 38.5% enhanced KLa coefficient was archived after adding plastic media over the non-addition case. In conclusion, ring and cylinder media were found to be the most significant for improving KLa value in BCR and ALR, respectively, without extra energy.

Effective Analysis of Different Gas Diffusers on Bubble Hydrodynamics in Bubble Column and Airlift Reactors towards Mass Transfer Enhancement

“…As discussed by Bun et al ( 2019) [10], the performance of the multiphase contactor is not only related to the gas-phase dynamic, but the liquid phase also has a significant effect through mixing behavior. Hence, the experiments were conducted to understand the liquid flow pattern.…”

“…2.4.2. Specific Interfacial Area (a) and Gas Hold-Up Specific interfacial area (a) was calculated through the ratio of total air bubble surface and total reactor volume [10]. Hence, the interfacial area determination formula is expressed in Equation ( 4),…”

“…Sastaravet et al (2014) [9] indicated that the bubbles in BCR were basically associated with the balance of surface tension and buoyancy force; however, it may not govern in ALR. [10] discussed that it can be influenced by the geometric effect. Hence, another factor besides bubble size distribution, the gas-liquid mixing behaviors in ALR may cause the back-mixing resulted from higher superficial gas velocity in the riser compartment and circulated flow from the downcomer to the riser.…”

“…Learning from this mass transfer theory and literature from recent reviews, bubble size distribution (BSD) is the local variable to be considered in order to investigate the gas-liquid contact development as well as mass transfer enhancement. For this purpose, our recent publication examined the effect of additional solid media on bubble hydrodynamics for intensifying the oxygen mass transfer [10]. Adding plastic media into BCR and ALR resulted in enhancing the K L a coefficient up to 31-56% compared to the non-addition cases.…”

Hydrodynamics and Mass Transfer in a Concentric Internal Jet-Loop Airlift Bioreactor Equipped with a Deflector

“…8% for the superficial gas velocity higher than 0.034 m/s. Sastaravet et al [47] investigated the effect of polypropylene particles of different shapes and solid loading on the bubble hydrodynamics and mass transfer in a bubble column and internal-loop airlift reactor with a splitting baffle. The enhancement of the k L a coefficient up to 38.5% was achieved in the airlift reactor when the solid particles were added.…”