A model study was carried out to elucidate bubble and liquid flow characteristics in the reactor of metals refining processes stirred by gas injection. Wood's metal with a melting temperature of 70 ЊC was used as the model of molten metal. Helium gas was injected into the bath through a centered single-hole bottom nozzle to form a vertical bubbling jet along the centerline of the bath. The bubble characteristics specified by gas holdup, bubble frequency, and so on were measured using a twoneedle electroresistivity probe, and the liquid flow characteristics, such as the axial and radial mean velocity components, were measured with a magnet probe. In the axial region far from the nozzle exit, where the disintegration of rising bubbles takes place and the radial distribution of gas holdup follows a Gaussian distribution, the axial mean velocity and turbulence components of liquid flow in the vertical direction are predicted approximately by empirical correlations derived originally for a water-air system, although the physical properties of the two systems are significantly different from each other. Under these same conditions, those turbulent parameters in high-temperature metals refining processes should thus be accurately predicted by the same empirical correlations.
MANABU IGUCHI and HIROHIKO TOKUNAGAInvestigation was made of the heat-transfer effect on the motions of cold bubbles and molten metal in a bottom-blown bath. The heat transfer between the bubbles and the molten metal finished at an axial position near the nozzle exit. The bubble and liquid-flow characteristics measured above this position were in good agreement with those in a bath agitated by isothermal gas injection of the same mass flow rate. A simplified mathematical model was proposed to describe the two characteristics. The experimental results of gas holdup and mean liquid-flow velocity were satisfactorily predicted by it. The accuracy of the prediction became higher as the distance from the nozzle exit increased, due to disintegration of bubbles.
In refining processes such as the AOD process cold gas is blown horizontally into the molten metal bath of the processes. The spatial distribution of bubbles in the bath is one of the important factors influencing the efficiency of the processes. In this study, a water model study was carried out to understand the characteristics of bubbles and liquid flow generated by horizontal gas injection. The bubble and liquid flow characteristics were measured using an electro-resistivity probe and a laser Doppler velocimeter, respectively. In the flow field near the nozzle the bubble characteristics for the horizontal cold gas injection can be predicted by empirical equations derived for isothermal gas injection systems. The liquid flow characteristics could not be measured in this region. On the other hand, in the region far from the nozzle the two characteristics for the cold gas injection became different from those for the isothermal gas injection because of enhanced buoyancy force acting on expanding cold bubbles due to heat transfer.
Blasen-und Stromungscharakteristika beim horizontalen Einleiten von kaltem Gas in einWasserbad. Beim Frischen, z.B. nach dem AOD-Verfahren, wird kaltes Gas horizontal in die Schmelze geleitet. Die raumliche Verteilung der Blasen ist ein wichtiger Faktor fOr die Effektivitat des Verfahrens. An einem Wassermodell wurde daher die Blasen-und Stromungscharakteristika, die durch das horizontale Gaseinleiten hervorgerufen werden, studiert. Die Messung erfolgte mit einer Widerstandssonde und einem Laser-Doppler-Velocimeter. 1m Stromungsfeld nahe der DOse laBt sich die Blasencharakteristik beim horizontalen Gaseinleiten mit empirischen Gleichungen, die fOr isothermes Gaseinleiten abgeleitet wurden, vorausberechnen. Die Stromungscharakteristik lieB sich in diesem Bereich nicht messen. DemgegenOber andert sich das Verhalten in groBer Entfernung von der DOse. Die Verhaltnisse fOr isothermes Gaseinleiten konnen nicht mehr herangezogen werden, da erhohte Auftriebskraft auf die kalten Blasen, die sich infolge WarmeObergangs ausdehnen, wirkt.
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