A micro‐jet array for economic intensification of gas transfer in bioreactors

Abstract

Bioreactors are of interest for gas‐to‐liquid conversion of stranded or waste industrial gases, such as CO, CH4, or syngas. Process economics requires reduction of bioreactor cost and size while maintaining intense production via rapid delivery of gases to the liquid phase (i.e., high kLa). Here, we show a novel bioreactor design that outperforms all known technology in terms of gas transfer energy efficiency (kLa per power density) while operating at high kLa (i.e., near 0.8 s−1). The reactor design uses a micro‐jet array to break feedstock gas into a downward microbubble flow. Hydrodynamic and surfactant measurements show the reactor's advanced performance arises from its bubble breakage mechanism, which limits fluid shear to a thin plane located at an optimal location for bubble breakage. Power dissipation and kL are shown to scale with micro‐jet diameter rather than reactor diameter, and the micro‐jet array achieves improved performance compared to classical impinging‐jets, ejector, or U‐loop reactors. The hydrodynamic mechanism by which the micro‐jets break bubbles apart is shown to be shearing the bubbles into filaments then fragmentation by surface tension rather than “cutting in half” of bubbles. Guided by these hydrodynamic insights, strategies for industrial design are given. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2710, 2019

Structural Design and Performance of a Jet-Impinging Type Microbubble Generator

“…The comparison of the k L a per power density between our measurements in this work and those reported from previous literature ,,− is listed in Table , where the k L a and demonstrated k L a per P / V in this work is calculated according to the result of σ = 63.7 mN/m and P L / V L = 0.146 shown in Figure (d). As can be seen from the table, the jet-impinging type bubble generator offers a better energy efficiency than many bubble generating systems but cannot operate at a higher k L a compared with an array of downward microjets.…”

“…In this work, the liquid volumetric mass transfer coefficient ( k L a ), which is determined through the dynamic dissolved oxygen method, is adopted as an index to evaluate the efficiency of the microbubble generator. The change of the k L a with the liquid input power per unit volume ( P L / V L ) under different gas input power per unit volume ( P G / V L ) is shown in Figure .…”

Dispersion Characteristics in a Counter-Current Microstructured Slurry Bubble Column and Its Analysis Based on the Turbulence and Circulation

“…In the co-current flow, the rising bubbles are pushed toward the wall, while in the counter-current flow, the bubbles are pushed away from the column wall . In the absence of a surfactant or salt in the liquid, the turbulence intensity in the axial direction reduces, and as a result, the bubble diameter increases . The presence of particles reduces the turbulent intensity of the continuous phase if the ratio of the particle size and turbulence scale is less than unity .…”

“…48 In the absence of a surfactant or salt in the liquid, the turbulence intensity in the axial direction reduces, and as a result, the bubble diameter increases. 49 The presence of particles reduces the turbulent intensity of the continuous phase if the ratio of the particle size and turbulence scale is less than unity. 50 It indicates that the turbulence in the liquid phase is weak in the presence of small particles.…”

Three-Stage Shear-Serrated Aerator Broke CO2 Bubbles To Promote Mass Transfer and Microalgal Growth

“…Several key metrics were proposed to analyze the energy efficiency of bubble generating systems of gas–liquid contacting reactors quantitatively, such as interfacial area density of the output dispersion and the energy necessary to create interfacial area . A micro-jet array bioreactor for gas transfer intensification outperformed all published technologies in relation to energy efficiency while operating at high k L a (near 0.8 s –1 ) . Fluidic oscillator-mediated microbubble generation was applied to wastewater treatment plants .…”