Dispersion of Bubbles and Gas-Liquid Mass Transfer in a Gas-stirred System

• Published in: Transactions of the Iron and Steel Institute of Japan Vol. 28; no. 4; pp. 262 - 270
• Main Authors: TANIGUCHI, Shoji, KIKUCHI, Atsushi, MATSUZAKI, Hitoshi, BESSHO, Nagayasu
• Format: Journal Article
• Language: English
• Published: The Iron and Steel Institute of Japan 1988
• Subjects: effective viscosity; fluid flow; gas holdup; gas injection; mass transfer; steel making; turbulence; volumetric coefficient
• ISSN: 0021-1583; 1881-1183
• DOI: 10.2355/isijinternational1966.28.262

Bubble dispersion and mass transfer between gas and liquid in a gas-stirred system have been studied experimentally and theoretically. Nitrogen gas was injected into water through a nozzle located at the bottom center of a cylindrical vessel. Local gas-holdup distributions were measured by an electrical resistivity probe. The volumetric coefficient in the bubble-dispersion zone for the absorption of CO2-water system was measured. Experimental conditions were as follows: gas-flow rate (qG) =(16.7-167)×10-6m3/s, radius of vessel (r1)=O.055-0.50m, height of water (z1)=0.1-0.4m and diameter of nozzle =6mm. A mathematical model based on the boundary-layer theory is proposed. The model consists of equation of flow with uniform effective kinematic viscosity υe and equations of bubble and solute diffusion with uniform effective diffusivities, De, B and De, S, respectively. Equations were solved numerically assuming υe=De, B=De, S, and the theoretical distribution of local gas holdup, axial velocity, and solute concentration were obtained. By comparing the theoretical distributions of local gas holdup with the measured ones, values of υe could be obtained for various qG, r1 and z1. The values of υe were correlated with qG on the basis of dimensional analysis. This correlation was consistent with related data available in the literature. Volumetric coefficients, calculated by the present model, were in agreement with the observed ones.