Enhancement of gas-to-liquid oxygen transfer in the presence of fine solid particles for air-exposed multiphase system

• Interfacial entrainment of particles should be initiative step for “particle effect”.
• Particulate specific gravity and interfacial turbulence control particle-entrainment.
• Interfacial-cleaning for “particle effect” is dictated by particle-entrainment.
• Supernatant conductance of Graphite may reflect interfacial entrainment of particles.

To investigate “particle effect” promoting gas-liquid mass transfer for a better process control, nine species of fine particle (d32 = 1-–15 μm), divided into Group 1 (SSA > 65.4 m2/g, termed PAC, SiO2, Al2O3 and MnO2) and Group 2 (SSA < 9.8 m2/g, termed Biochar, Graphite, Mg(OH)2, CaCO3 and BaSO4), were comparatively introduced for oxygenation tests in an air-exposed stirred system. Group 1 particles with interfacial-cleaning effect facilitated oxygen transfer better than their counterparts of Group 2. For all the particles employed, however, the “particle effect” interestingly presented under control of solid specific gravity, since enhancement factor (Ef) globally performed to grew up either when particulate density decreased or liquid density increased (Pb(NO3)2 as solute). Moreover, the strength of “particle effect” depends largely on interfacial turbulence, because proper agitation allowed optimal acceleration of oxygen transfer (700 rpm for this work), while either more sluggish or turbulent flow regime would hinder or even eliminate “particle effect”. Consequently, interfacial liquid-entrainment of particle entities was assumed to have played an initiative role for induction of “particle effect”, and this hydrodynamic process was elucidated to be subject to particulate specific gravity as well as interfacial turbulence.

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