New Correlations of Volumetric Liquid-Phase Mass Transfer Coefficients in Gas-Inducing Agitated Tank Reactors

Abstract

Volumetric liquid-phase mass transfer coefficient (kLa) is one of the most important parameters for the evaluation of the performance of a gas-inducing agitated tank (GIAT). In this paper, two equations in terms of power input per unit liquid volume (P/VL) and relative gas dispersion parameter (NI/Ncd), respectively, are developed according to data in literature. They can correlate existing kLa values within ±20% of measured ones for bladed impellers with different impeller submergence to tank diameter ratios in the range of 0.5 -1.23. In order to validate these equations, the liquid phase mass transfer coefficients in a continuous GIAT equipped with a 4-blade straight impeller were measured by removal of oxygen from water. It was found that the equation in P/VL criterion could correlate kLa values within ±12% of the experimental data, and the equation in NI/Ncd criterion could correlate kLa values within ±15.6% with an exception of 26.8% for NI = 16.7 Hz.

Self-inducing Reactors for Bioengineering

“…Similar to the research on critical speed and suction rate, modifying the impeller type, impeller combination form, and geometric dimension also affects the volumetric mass transfer coefficient. In their study, Yu et al examined the relationship between impeller diameter, immersion depth, and mass transfer coefficient in a self-inducing reactor: k L a = 1.212 true( P V q true) 0.0816 normalv 0.692 true( h 0 d true) − 0.390 …”

Mathematical Modelling and CFD Simulation for Oxygen Removal in a Multi-Function Gas-Liquid Contactor

“…The nitrogen gas cannot be induced into the tank until the impeller speed reaches the critical speed, N cr , below where there is no evident degassing effect [39]. N cr is often greater than the minimum impeller speed for the complete dispersion of the gas phase, N cd [15,17]. Thus, it is deemed reasonable to treat the two phases as perfectly mixed when the rate of agitation is above N cd .…”

“…The k L a T depends on the reactor type. For the GIAT type, the k L a GI can be calculated using Equations ( 26)-( 29) [15] when no nitrogen gas is added.…”

“…The main body of the degassing system becomes a BC when the mechanical agitator is off. Many researchers [15,40,41] have demonstrated that a square BC has the same mass transfer performance as a cylindrical column whose inner diameter equals to its side length. The complete mixing model and axial dispersion model (ADM) are two well-accepted models to predict the performance of a BC [19].…”

“…Many researchers have proposed different correlations for the overall k L a in diverse reactors by associating its value with numerous parameters. For example, Yu [15] put forward two correlations for GIAT by compiling 44 data points in the literature and validated the correlations by their experiments. Comparatively, the correlation based on power input per liquid volume outperforms the other.…”