Mass Transfer Performance and Hydrodynamics of a Bubble Column Reactor at Offshore Floating Conditions

Abstract

Hydrodynamics and mass transfer characteristics are analyzed in a bubble column subjected to simulated ship motions using a hexapod robot with six-degree-of-freedom motions. Wire-mesh sensors have been used for collecting local gas holdup and flow patterns under nonreactive conditions. Additionally, the electrical conductivity of the liquid phase during CO 2 uptake was extracted to determine hydroxide ion consumption rates as an indicator of mass transfer. The two-phase flow patterns in the bubble column operating under offshore conditions deviate significantly from the stationary ones due to the buoyancy-driven lateral migration of bubbles. The consumption rates of hydroxide ions during the chemical absorption of CO 2 revealed that the amplitude of oscillations imposed on the bubble column is the dominant factor for the mass transfer in moving columns. Contrarily, the effect of the oscillation frequency is negligible, which is attributed to bubble coalescence and bubble flow maldistribution in the bubble column subjected to rotational oscillations. Bubble-free zones are formed in the liquid phase because of the buoyancy effects in the column tilted from the vertical axis, while the frequency of the oscillations does not add any additional effects to the bubble kinematics. The latter is attributed to the low shear rates maintained over the range of frequencies simulating marine swells.

Coalescence of Two Equal-Sized Bubbles with Air Injection

“…Bubble coalescence plays a crucial role in the bubble size and void fraction distribution in gas–liquid two-phase flow systems and thus heat and mass transfer efficiency. , When two bubbles come into contact and merge, a kind of hydrodynamic singularity arises. , Subsequently, an air bridge (often called a “neck”) forms, connecting the two merging bubbles. Finite-approach velocities, arbitrary surface shapes, and fluid properties contribute to the variety. − The neck formation and temporal evolution are critical features in the study of bubble coalescence.…”

“…Bubble coalescence plays a crucial role in the bubble size and void fraction distribution in gas−liquid two-phase flow systems and thus heat and mass transfer efficiency. 1,2 When two bubbles come into contact and merge, a kind of hydrodynamic singularity arises. 3,4 Subsequently, an air bridge (often called a "neck") forms, connecting the two merging bubbles.…”