Study of Plume Eye in the Copper Bottom Blown Smelting Furnace
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TRODUCTION
THE plume eye, which was firstly observed in steel-making,[1–16] describes the phenomenon of exposure of the lower level liquid because the upper level liquid is pushed away by the injected gas.[3] Due to the inherently transient flow phenomena[17] and stochastic nature of the bubble rise in the bath,[4] the dynamics of a liquid–gas interaction system in a vessel agitated by gas is highly complex. A few studies of the nature of plume in ladle or tundish associated with steel refining process are found in the literature.[1–16] In the steel ladle, a large plume eye is not desired as it leads to nitrogen and oxygen pick up, which is harmful to the steel quality.[4] In the tundish, the gas injection technique is through ladle shroud, the gas bubbles coming from the ladle shroud move downward.[2] A large plume eye is also not desired in the tundish because it results in slag entrainment and inclusions may be formed due to the metal-liquid re-oxidation reactions.[2] Small plume eyes are preferred in the ladle and tundish to avoid the interactions between refractory and plume eye and reduce the refractory erosion.[4]
XU JIANG, MAO CHEN, and BAOJUN ZHAO are with the School of Chemical Engineering, The University of Queensland, Brisbane 4072, Australia. Contact e-mail: [email protected] ZHIXIANG CUI is with Dongying Fangyuan Nonferrous Metals, Dongying 257000, P.R. China. Manuscript submitted August 24, 2018.
METALLURGICAL AND MATERIALS TRANSACTIONS B
In the bottom blown oxygen copper smelting technique, which was developed in China and has been commercialized for just a decade,[18] understanding the nature of the plume eye is vital to its production efficiency. During the operation, copper concentrates are added from the top of the furnace through the feed mouth. Oxygen-enriched air is injected into the smelting furnace from the bottom of the furnace through the lances with injection angles of 7 and 22 deg, and the gas bubbles move upward right after the gas injection. The injection of gas not only provides oxygen for reactions, but also promotes the mixing of the bath inside the furnace.[19,20] The upwelling gas bubbles, generated by the injection of oxygen-enriched air into the bath, rise in the bath and create a wake of matte that can push the slag layer away, as a result the matte is exposed. In the present study, the exposed matte surrounded by the slag is called the plume eye. With a large plume eye present in the bath, the copper concentrate added through the feed mouth, located at the top of the gas-blowing zone, can be added into the matte layer directly without passing through the slag layer. Consequently, the reaction rate can be accelerated[21] and the entrained matte in the slag can be reduced. No literature has been found to understand the nature of the plume eye generated in the bath of the horizontal vessel by the bottom blown gas. The experimental results of plume eye in both ladle and tundish cannot be directly transferred for the study of plume eye in the horizontal vessel due to the differences
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