Gas holdup, bubble size distribution, and mass transfer in an airlift reactor with ceramic membrane and perforated plate distributor

Abstract

The airlift reactor is one of the most commonly used gas–liquid two‐phase reactors in chemical and biological processes. The objective of this study is to generate different‐sized bubbles in an internal loop airlift reactor and characterize the behaviours of the bubbly flows. The bubble size, gas holdup, liquid circulation velocity, and the volumetric mass transfer coefficient of gas–liquid two‐phase co‐current flow in an internal loop airlift reactor equipped with a ceramic membrane module (CMM) and a perforated‐plate distributor (PPD) are measured. Experimental results show that CMM can generate small bubbles with Sauter mean diameter d32 less than 2.5 mm. As the liquid inlet velocity increases, the bubble size decreases and the gas holdup increases. In contrast, PPD can generate large bubbles with 4 mm < d32 < 10 mm. The bubble size and liquid circulation velocity increase as the superficial gas velocity increases. Multiscale bubbles with 0.5 mm < d32 < 10 mm can be generated by the CMM and PPD together. The volumetric mass transfer coefficient kLa of the multiscale bubbles is 0.033–0.062 s−1, while that of small bubbles is 0.011–0.057 s−1. Under the same flow rate of oxygen, the kLa of the multiscale bubbles increases by up to 160% in comparison to that of the small bubbles. Finally, empirical correlations for kLa are obtained.

Characteristics of Bubbly Flow, Mass Transfer, and CO2 Absorption in a Two-Stage Internal Loop Airlift Reactor Assembly with a Diamond-Shaped Guide Baffle

“…On the other hand, bubbles with d eq > 4 mm are irregularshaped and are called large bubbles in this study. The difference in the bubble shape between large and small bubbles has also been reported by Zhang et al 53 The cumulative frequency curve intuitively shows that with the increase of U g , the number of small bubbles gradually increases, the probability of bubble collision in the bubble swarm increases, and large bubbles are more likely to break into small ones. As a result, the number of small bubbles increases.…”

“…These two ILALRs perform better than the ILALR−DSGB. But it should be pointed out that the superficial gas velocities in the literature 53,56 are much larger than that in this work.…”

“…On the other hand, bubbles with d eq > 4 mm are irregular-shaped and are called large bubbles in this study. The difference in the bubble shape between large and small bubbles has also been reported by Zhang et al…”

“…47 The mass transfer performance of ILALR−DSGB is better than that in the ILALR assembly with screens. The values of k L a in the single-stage ILALR with a perforated ring sparger 56 and ceramic membrane module and perforated plate distributor 53 are 5.0 × 10 −3 − 4.0 × 10 −2 s −1 and 3.3 × 10 −2 − 6.2 × 10 −2 s −1 , respectively. These two ILALRs perform better than the ILALR−DSGB.…”

Local Gas Holdup, Bubble Size Distribution, and Bubble Velocity in a Submerged Rotating Packed Bed Reactor

“…As shown in Figure 10b, the deviations between predicted and experimental v are within ±15%. 47 airlift reactor, 48 stirred tank, 11,38,49 rotating foam reactor, 16 and SRPB. The dimensions of the reactors and energy dissipation rates (δ) were also listed.…”