On the Design of Bubble Columns Equipped with a Fine Pore Sparger: Effect of Gas Properties

Abstract

Abstract:In our previous works we have proposed design equations that can predict with reasonable accuracy the transition point from homogeneous to heterogeneous regime as well as the gas holdup and the mean Sauter diameter at the homogeneous regime. The validity of the proposed correlations was checked with data obtained using different geometrical configurations and several Newtonian and non-Newtonian liquids as well as the addition of surfactants. However, in all the experiments the gas phase was atmospheric air. This work investigates the effect of gas phase properties by conducting experiments employing various gases (i.e., air, CO 2 , He) that cover a wide range of physical property values. Experiments revealed that only the use of low-density gas (He) has a measurable effect on bubble column performance. More precisely, when the low-density gas (He) is employed, the transition point shifts to higher gas flow rates and the gas holdup decreases, a fact attributed to the lower momentum force exerted by the gas. In view of the new data, the proposed correlations have been slightly modified to include the effect of gas phase properties and it is found that they can predict the aforementioned quantities with an accuracy of ±15%. It has been also proved that CFD simulations are an accurate means for assessing the flow characteristics inside a bubble column.

Bubble characterization and gas–liquid interfacial area in two phase gas–liquid system in bubble column at low Reynolds number and high temperature and pressure

“…It is observed on Fig. 13 that the mean Sauter diameter, gas holdup and interfacial area are slightly affected by the type of gas employed, but significantly affected by the liquid phase, in agreement with Kanaris et al (2018) (Kanaris et al, 2018). The Sauter mean diameters of He in water and ethanol/water mixture are generally slight higher than those of N 2 under similar operating conditions (Fig.…”

“…Table 1 summarizes available literature studies on the influence of operation parameters on bubble characteristics in bubble columns. Many research reported that with the increase of gas superficial velocity, the gas holdup enhanced, inducing an increase in bubbles number, turbulence and collision frequency, resulting in the increase of bubble size (Behkish et al, 2007;Clark, 1990;Kanaris et al, 2018;Lau et al, 2004;Luo et al, 1999;Majumder et al, 2006;Wilkinson et al, 1992). However, Mohagheghiana and Elbing (2018) and Akita and Yoshida (1974) both observed a decrease in Sauter mean diameter of bubbles with increasing gas superficial velocity.…”

“…Bubble columns are widely used in many industrial gas-liquid operations (e.g. wet air oxidation, gas/liquid reactions, fermentations, agitation by gas injection) in chemical and biochemical industries due to their simple construction, no mechanically moving parts, low operating cost, high thermal stability, high-energy efficiency and good mass transfer capabilities (Kanaris et al, 2018). Most research for bubble columns focused on ambient conditions, while many industrial bubble columns are operated at extreme conditions with high temperatures and pressures (Pohorecki et al, 2001 ;Léonard, 2015).…”

“…In all above processes, bubble size distribution and gas holdup are important design parameters, which have been often used to define the gas-liquid interfacial area available for mass transfer (Akita and Yoshida, 1974;Kanaris et al, 2018;Majumder et al, 2006;Pohorecki et al, 2001;Stegeman et al, 1996). The operation of bubble columns can be affected by several parameters.…”

Bubble-Size Distribution and Hydrogen Evolution from Pyrolysis of Hydrocarbon Fuels in a Simulated Ni0.27Bi0.73 Column Reactor

“…The BSD is shifted from smaller-sized bubbles to larger-sized bubbles, as shown in Figure . The reported increasing trend of d avg , with respect to u 0 , is consistent with literature data. − However, as mathematically expressed in eq , increasing the u 0 substantially results in large We number flows, which, in turn, minimizes the probability of coalescence. This is attributed to the lower time for the film drainage to complete as bubbles collide.…”