Parameters Affecting Bubble Formation and Size Distribution From Porous Media

Abstract

This paper describes the experiments designed to control bubble size during gas injection through porous media into liquid cross flow. A parametric study examined the effect of control variables on average bubble size and standard deviation. Results showed that for a given air and liquid flow rate, changing liquid channel height at the air injection site had the largest effect on bubble size and size distribution while varying porous media grade and electrolyte concentration had smaller, though significant, effects. In this study, the channel height was varied from 0.8 to 8 mm, porous media grade from 0.5 to 100 and salt concentration varied from zero to 3%. The resulting average bubble diameters were 0.085–2.5 mm.

Applying Imaging Technique to Investigate Effects of Solute Concentrations and Gas Injection Rates on Gas Bubble Generation

“…However, as for increasing NaCl concentration from 10 g/l to 20 g/l, the standard deviation can be further decreased by 100-300 μm. When NaCl concentration 16 Geofluids 18 Geofluids reaches 20-30 g/l, there is no significant decrement of standard deviation (<100 μm). Overall, the CCC of NaCl for mean bubble size could be identified at 20 g/l, although the original definition of CCC only refers to mean bubble size.…”

“…However, due to the different air diffuser and gas injection rates that they applied, there seems less possibility of conducting any comparison against those experimental outcomes. Other studies, including Shepard et al [16], Alam et al [5], Pan et al [8], all studied BSD changing with solute concentrations. Nevertheless, any comparison can still hardly be conducted due to various bubble generating apparatus, different selections of surfactants, fine particles in the fluid, slurry conditions, etc.…”

“…Moreover, microbubble dispersion can improve in situ bioremediation because of its advan-tages over air sparging, surfactant injection, and bioventing [12][13][14][15]. Microbubble dispersion technology has been well studied for various floatation/separation processes and enhanced aeration systems [10,12,15,16].…”

“…The intrusive methods include electroresistivity [43][44][45][46], ultrasound reflection [47][48][49][50][51], and optical techniques [52][53][54][55][56][57][58], which inevitably cause instrumented interference on bubble samples. In comparison to those approaches, the imaging technique as a nonintrusive method has been primarily adopted for both academic and industry bubble size measurement due to lower cost and ease of operation [5,9,15,16,28,30,59]. Nevertheless, the densely binding bubbles in the observing chamber bring challenges for image analysis.…”

“…According to Puleo et al [64], Moruzzi and Reali [65], Shepard et al [16], and Nguyen Hai Le et al [30], BSD is dependent on several influential factors: hydraulic pressure in the viewing chamber, the temperature of water solution, solute concentration (surface tension), pH of the aqueous environment, type of injected gas, type of gas bubble generator, gas injection rate, etc. Even though most previous works have investigated multiple factors on BSD, they separately studied and analyzed a single factor of many individually influencing BSD [5,8,9,15,16,30,64,66,67]. By far, the significance of combining factors on BSD has not often been investigated.…”