Height of the spout of a gas plume discharging from a metal melt
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I. INTRODUCTION
THE spout region where the gas emerges during argon stirring, in a metallurgical ladle, is the most important location for the slag/metal reactions in the metallurgical ladle treatment, and it is the site of undesired side reactions with air. Hence, the hydrodynamic characteristics of this part of the gas-stirred metal melt are of great interest. But, in contrast to the numerous investigations on the bulk properties of the gas/liquid plumes, there are only a few studies of the spout region[1–5] and most of them have been carried out on laboratory setups using water as the liquid. This article deals with the height of the spout in gas/metal systems. Coldmodel experiments using mercury and plant experiments involving 120 and 350 t ladles have been carried out. This article follows a preceding article,[6] which addresses the size and dynamic behavior of the open part of the spout, uncovered with slag, which develops at high gas flow rates. II. EXPERIMENTAL METHODS OF LABORATORY MEASUREMENTS The cylindrical vessel, of 290 mm i.d., is the same as that used previously.[6] The height of mercury was chosen to be 225 mm at rest. All the measurements of the spout height were carried out with a bare metal surface, that is, without coverage by a slag (oil) layer. The nozzle for injection of nitrogen is located at the center of the vessel, and its upper end is flush with the bottom of the vessel. The plume and its spout are highly dynamic. This effect has to be taken into account in the measurement techniques and requires clear definitions of the quantities to be measured. The height measurements were carried out with a fast electrical method, enabling a short time resolution of height variations. The setup is shown in Figure 1. A single Ni-Cr resistance wire of 0.2 mm in diameter, with about 0.32 V cm21, is mounted between two stainless steel plates, one at ¨ KIMITOSHI YONEZAWA, formerly Scientist with the Institut fur All¨ gemeine Metallurgie, Technische Universitat Clausthal, is Manager with the Technical Administration and Planning Group, Nippon Steel Corporation, 6-3 Otemachi 2-chome, Chiyoda-Zu Tokyo, 100-71 Japan. KLAUS ¨ SCHWERDTFEGER, Professor, is with the Institut fur Allgemeine Metal¨ lurgie, Technische Universitat Clausthal, F Robert Koch Str. 42 38678 Clausthal-Zellerfeld, Germany. Manuscript submitted August 13, 1998. METALLURGICAL AND MATERIALS TRANSACTIONS B
the bottom and the other at the top of the vessel. Since the resistance of the mercury bath is much lower than that of the wire, there is practically no resistance between the wire and the counterelectrode below the surface of the bath. That is, the measured resistance is that of the part of the wire above the surface. Its change, caused by the change of meniscus height, is determined with a Wheatstone bridge plus amplifier, yielding a precision of 60.2 mm in the level of a quiet surface in calibration measurements. The radial height profile was determined by changing the position of the wire. Close to the center of the vessel, the data we
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