Enhanced photo bio-reaction by multiscale bubbles

Abstract

Based on experimental and computational fluid dynamics simulations, the scale effect between the bubbles and the algae for different sizes in the culture process were investigated in a photobioreactor column under single and combined gas intake conditions, including factors such as the bubble distribution, gas holdup and mass transfer coefficient of different scale bubbles (500 μm microbubbles and 5 mm bubbles). In general, microbubbles could improve mass transfer and photo bio-reaction. For microalgae cultures with large particle sizes or high biomass concentration, the mixing ability of microbubbles was weakened, and therefore, the culture efficiency decreased. However, this can be improved by using millimeter bubbles with the strong turbulent characteristic. Therefore, a multiscale bubble combination intake method was proposed. This method can significantly strengthen both the multiphase mixture and mass transfer vm F Virtual mass force, N•m -3 lift F Lift force, N•m -3 I Unit matrix S S , User-defined source terms g U Superficial gas velocity, m•s -1 Q g Gas flow rate, L/min M Y Contribution of the fluctuating dilatation in the compressible turbulence to the overall dissipation rate v D C C , Interphase forces coefficients Re Reynolds number g Gravitational acceleration, m•s 2

Scale‐up of the cross‐flow flat‐plate airlift photobioreactor

“…A series of images were taken at the center of the CFA‐PBRs at a fixed interval of time. The image batches include image enhancement, image segmentation based on the curvature calculation and circumferential fitting, image morphological processing, and particle measurement 17 . The time and space average BSDs were obtained by the statistical method, and the Sauter mean diameter was calculated by the following calculation formula 18 : …”

Experimental Study on Slug Flow Characteristics and its Suppression by Microbubbles in Gas-Liquid Mixture Pipeline

“…Based on the characteristics mentioned above, microbubbles are introduced into the suppression of slug flow. The microbubbles will affect the back-mixing flow in the boundary layer during the movement of slug flow (Zhao et al 2018;Mashhadani et al 2011;Li et al 2016), which is expected to play a role in slug flow suppression.…”

Continuous formation of microbubbles during partial coalescence of bubbles from a submerged capillary nozzle

“…As the bubble size decreases, its surface area for a given gas volume increases and its residence time in liquid becomes longer. Thus, the use of microbubbles has attracted the attention of many researchers and engineers in chemical engineering fields covering absorption and chemisorption, bioreaction and electrochemical systems 4,5 . The most common way to generate millimeter‐sized bubbles is to inject gas direct into a liquid through a submerged nozzle, but microbubbles cannot be generated by that way because the diameter of produced bubbles is considerably larger than that of the injection orifice 5 .…”

“…Thus, the use of microbubbles has attracted the attention of many researchers and engineers in chemical engineering fields covering absorption and chemisorption, bioreaction and electrochemical systems 4,5 . The most common way to generate millimeter‐sized bubbles is to inject gas direct into a liquid through a submerged nozzle, but microbubbles cannot be generated by that way because the diameter of produced bubbles is considerably larger than that of the injection orifice 5 . To decrease the bubble size, many additional techniques are used, such as adding an outer liquid stream or using acoustic fields, electric fields, and porous media 6‐11 .…”

“…4,5 The most common way to generate millimeter-sized bubbles is to inject gas direct into a liquid through a submerged nozzle, but microbubbles cannot be generated by that way because the diameter of produced bubbles is considerably larger than that of the injection orifice. 5 To decrease the bubble size, many additional techniques are used, such as adding an outer liquid stream or using acoustic fields, electric fields, and porous media. [6][7][8][9][10][11] Partial coalescence is a special coalescence process with the generation of smaller satellites.…”