Abstract
This paper discusses the effects of the liquid velocity and the liquid phase properties on the gas holdup and the flow regime transition in a large-diameter and large-scale counter-current two-phase bubble column. In particular, we compared and analysed the experimental data obtained in our previous experimental studies. The bubble column is 5.3 m in height, has an inner diameter of 0.24 m, it was operated with gas superficial velocities in the range of 0.004–0.20 m/s and, in the counter-current mode, the liquid was recirculated up to a superficial velocity of -0.09 m/s. Air was used as the dispersed phase and various fluids (tap water, aqueous solutions of sodium chloride, ethanol and monoethylene glycol) were employed as liquid phases. The experimental dataset consist in gas holdup measurements and was used to investigate the global fluid dynamics and the flow regime transition between the homogeneous flow regime and the transition flow regime. We found that the liquid velocity and the liquid phase properties significantly affect the gas holdup and the flow regime transition. In this respect, a possible relationship (based on the lift force) between the flow regime transition and the gas holdup was proposed.
Highlights
Two-phase bubble columns are equipment used for bringing one or several gases into contact with a liquid phase
We have experimentally investigated the influence of liquid phase properties on gas holdup and flow regime transition in a large-scale counter-current bubble column
We found that the liquid velocity and the liquid phase properties significantly affect the gas holdup and the flow regime transition
Summary
Two-phase bubble columns are equipment used for bringing one or several gases into contact with a liquid phase. The transitions between the three prevailing flow regimes depend on (i) the operation mode, (ii) the design parameters and (iii) the gas/liquid phases of the bubble column. The many relationships between the bubble column fluid dynamic parameters and the various variables characterizing the system make it difficult to find general correlations for the precise design of bubble columns (i.e., the correct estimation of the gas holdup) [7]. The large variation of gas holdup values presented in the literature leads to the development of a large number of correlations for the gas holdup To this end, we have set up a large-scale and large-diameter bubble column to study the global and local bubble column fluid dynamics and, to provide rational basis for bubble column design and scale-up [2].
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