open access

https://hdl.handle.net/2115/75025

Gas-Liquid Mass Transfer in Simulated Turbulent Wake Flow

英語

gas-liquid mass transfer

2002-01-15

日本鉄鋼協会

ISIJ International

42(1)

112-114

In materials engineering, gas injection processes are frequently adopted to remove impurities such as oxygen and carbon. There are two types of gas dispersion patterns formed above the nozzle; bubbling and jetting. The former is realized when the gas velocity at the nozzle exit vn, is lower than the speed of sound, c, while the latter is realized for vn≧c and a gas column is formed on the nozzle. This column disintegrates into many bubbles with different diameters above a certain distance from the nozzle exit. Many bubbles are therefore generated in the molten metal bath regardless of the bubbling and jetting. The removal of impurities is closely associated with the dissolving rate of the gas into the bath. However, under such a highly turbulent condition it is difficult to evaluate the mass transfer coefficient between the bubbles and molten metal because the precise evaluation of the interfacial area is actually impossible. As the gas flow rate increases, mass transfer at the gas-liquid interface increases. However, it is not clear whether the mass flux at the gas-liquid interface is attributed to the enhancement of the interfacial are A or to the enhancement of the mass transfer coefficient k. Accordingly, previous researchers introduced the volumetric mass transfer coefficient defined as kA/V, where V is the bath volume. In a series of studies on gas injection, the authors have tried to elucidate the contributions of the interfacial area and the mass transfer coefficient to the volumetric mass transfer coefficient. The mass transfer coefficient at a gas-liquid interface exposed to two types of liquid jets shown in Figs. 1(a) and 1(b) were measured. CO2 gas was supplied with a syringe into a top lance to form a gas-liquid interface at the exit of the top lance. Accordingly, the gas-liquid interfacial area can be measured with sufficient accuracy. The flow fields around the gas-liquid interface thus exposed to the two types of jets are models for the flow fields around the top and side of a bubble rising in ha highly turbulent flow field. In this study the gas-liquid interface was exposed to a turbulent wake flow, as shown in Fig. 1(c). This study therefore is intended to clarify the mass transfer coefficient at the rear part of a bubble.

学術雑誌論文

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0915-1559

1347-5460

AA10680712